Title: Appropriate technology for mechanized agriculture
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Title: Appropriate technology for mechanized agriculture lecture notes
Physical Description: 1 v. (unpaged) : ill. ; 28 cm.
Language: English
Creator: University of Florida -- Agricultural Engineering Dept
University of Florida -- Agricultural Engineering Dept
Publisher: University of Florida, Agricultural Engineering Department
Place of Publication: Gainesville, Fla.
Publication Date: 1985?
Copyright Date: 1985
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Subject: Agricultural innovations -- Study and teaching -- Florida   ( lcsh )
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Summary: Contains 35 lectures used in the course "Appropriate Technology for Mechanized Agriculture" given in the Fall of 1985 at the University of Florida, Agricultural Engineering Department.
Statement of Responsibility: Agricultural Engineering Department, University of Florida.
Bibliography: Includes bibliographical references.
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General Note: At head of title: Agricultural Engineering Department, AGE 6933.
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Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 1
Definition of Appropriate Technology and Related Ideas

Choices abound whenever technology is selected. The
description of certain technologies as "appropriate" suggests
evaluation of alternative technological choices based on one or
more criteria. Jequier's (1979) definition of appropriate
technology indicates several of these criteria:

By 'appropriate technology', we mean new types of
technology which can be characterized by any one, or
several, of the following features: low investment cost per
workplace, low capital investment per unit of output,
organisational simplicity, small-scale operations, high
adaptability to particular social or cultural environments,
sparing use of natural resources, and very low cost of
final product. They may also be of an intermediate level
of technological sophistication (i.e. somewhere between a
traditional and a modern technology) or particularly easy
to operate and maintain by unskilled people.

There may be many additional criteria also upon which
%appropriateness' may be judged (Ekhaus, 1976): avoidance of
unemployment or labor absorption, maintaining a favorable trade
balance, economic development, output maximization, cost
minimization, etc. Betz (1984) added reducing population flow
to urban centers, providing an adequate national food base,
being as consistent as possible with the indigenous social
structure, and building upon and preserving the indigenous
cultural continuity and heritage. In fact, most of the possible
goals of appropriate technology in agriculture, IIB on the course
outline, can be restated in a more general context and each can
be a possible criterion for appropriateness.

With so many possible criteria, it is inevitable that some may
conflict with others. A single example of technology may meet one
or several criteria but not others, or it may meet a number of
criteria but to varying degrees; some well, some not so well.
The many possible criteria upon which appropriateness may be
determined are often in conflict. The characteristics which
enable a technology to meet one criteria may automatically exclude
it from meeting another desirable criteria.

Further, a technology which meets a given criterion in one
situation may not meet that criterion in another situation.
And, a technology which meets a criterion at one time may not
meet that criterion at another time due to changed circumstances.

Therefore, we can say that what constitutes appropriate technology










varys with the circumstances peculiar to each individual situation.
Whether a technology is appropriate is not dependent only on the
technology itself.

This complexity of the idea of appropriate technology has surfaced
in Bhagavan's (1979) assertion that "There is nothing approaching
even a rough and ready definition of appropriate, intermediate,
low-cost, alternative and soft technologies that is universally
applicable." One common element, however, in these many related
ideas and criteria, is the social aspect. Criteria of technology
should not be limited only to economic criteria of efficiency, for
instance, but should be expanded to include additional criteria
not traditionally granted major importance in capitalistic
systems. De Forest (1980) summarized "appropriate technology as
process has generally been defined as a fundamental alteration in
the procedures whereby technologies are selected and implemented
in order to give greater weight to social values such as
decentralization and individual control and less weight to the
relatively unimpeded operation of market forces."

There are a number of related ideas closely akin to appropriate
technology. Jequier (1976) described several of these as "a set
of overlapping but nevertheless distinct areas": appropriate,
intermediate, soft, and low-cost technologies. Intermediate"
infers a position between extremes on some scale, perhaps
complexity, level of technology or between traditional and modern.
"Soft" seems to have been popularized by Lovins (1977) as a
descriptor of energy technologies which are flexible, resilient,
sustainable and benign". "Alternative" refers to technologies
which are different from the conventional or modern.
"Traditional" refers to technologies which have been used for a
considerable time in a given situation. "Modern" and "small-
scale" are self explanatory.


References

Betz, Matthew J., Pat McGowan. and Rolf T. Wigand, eds. 1984.
Appropriate Technology: Choice and Development. Duke Press Policy
Studies, Durham, N.C. (T, 185, .A7, 1984 in Library East), pp.
3-7.

Bhagavan, M.R. 1979. A Critique of "Appropriate" Technology for
Underdeveloped Countries. Res. Rpt. No. 48, The Scandinavian
Inst. of African Stud., Uppsala. (DT, 1, .N64, No.48 in Library
East), pp. 7-11, 19.

De Forest, Paul H. 1980. Technology Choices in the Context of
Social Values A Problem of Definition. Chap. 1 in Appropriate
Technology and Social Values A Critical Appraisal, Franklin A.
Long and Alexandra Oleson, eds. Ballinger Pub. Co., Cambridge,
MA. (T, 14.5, .A67 in Library East), pp 11-13.

Eckaus, Richard S. 1976. Appropriate Technologies for










Developing Countries. National Academy of Sciences, Washington
(HC, 59.7, .E25 in Library East) pp. 5-18.

Evans, Donald D., and Laurie Nogg Adler, eds. 1979. Appropriate
Technology for Development: A Discussion and Case Histories.
Westview Press, Boulder, CO. (HC, 59.7, .A823 in Library East)
pp 42-46.

Jequier, Nicholas, ed. 1976. Appropriate Technology, Problems
and Promises. Development Centre of the Organisation for Economic
Cooperation and Development. (T, 49.5, .A66 in Library East) pp.
16-20.

Jequier, Nicholas. 1979. Appropriate Technology Directory.
Development Centre of the Organization for Economic Cooperation
and Development, Paris. (T, 49.5, .J44 in Library East) p. 8.

Lovins, Amory B. 1977. Soft Energy Paths. Ballinger Publishing
Co.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 2
History of Appropriate Technology


Appropriate technology has been described as a cultural movement,
and well it may be. With the end of Colonialism and the
conclusion of World War II, came realization of the extent and
degree of worldwide poverty. Many countries and organizations
came to the aid of needy Lesser Developed Countries (LDC'S), both
with outright gifts of food and other materials and with various
efforts to transfer their technology to the LDC'S. Many of these
earlier technology transfer efforts were just that; direct
transfer with little or no attempt to adapt the technology to
local conditions. This approach led to technology
misapplications, in which hardware was imported, used for a short
time, and abandoned due to some problem. Typical problems
included lack of proper maintenance, lack of support
infrastructure and inadequate operator training.

Development of these former colonies proceeded with some success
during the 50's and beyond, but the magnitude of human needs
prevailed over what could be accomplished during the 60's.
Failures of some projects, African drought, unstable governments,
and inflation all took their toll (Eckhaus, 1977). Unemployment
became a major problem in many underdeveloped countries. The
"Green Revolution" failed to meet everyone's expectations, foreign
aid programs suffered some well-publicized failures, the energy
crisis occurred, and many underdeveloped countries incurred severe
balance of payments problems. The "appropriateness" of certain
aspects of development of the underdeveloped countries came to be
deservedly questioned.

A primary source of ideas leading to the development of a
philosophy of appropriate technology was the Indian leader,
Mohandas "Mahatma" Gandhi, 1869-1948 (Bhatt, 1980). He lived
in an India with severe poverty and was determined to improve
the plight of his countrymen. His development ideology for India
emphasized full employment through an emphasis on agriculture and
on cottage industries. These traditional industries were to be
aided by, but not dominated by, modern industries. Ghandi's
approach contrasted with that of Nehru, India's first Prime
Minister after independence from Britian, who encouraged heavy
industrialization through the use of several Five-Year Plans.

Ernest F. "Fritz" Schumacher (1973) is usually considered the
father of the appropriate technology movement, though he seemed to
favor the modifier "intermediate" over "appropriate". On a 1963
visit to India (Hoda, 1976) he was "influenced by the Gandhian
ideas of industrialization and technology (and) adapted them to










modern needs and turned intermediate technology into a worldwide
movement." His book, Small is Beautiful, Economics as if People
Mattered, popularized a worldwide appropriate technology movement.

Today the appropriate technology movement is represented by the
work of more than 100 organizations worldwide, many of which
include the term "appropriate" in their title (Jequier, 1979).



References

Bhatt, V.V. 1980. The Development Problem, Strategy, and
Technology Choice: Sarvodaya and Socialist Approaches in India.
Chap. 8 in Appropriate Technology and Social Values A Critical
Appraisal, Franklin A. Long and Alexandra Oleson, eds. Ballinger
Pub. Co., Cambridge, MA. (T, 14.5, .A67 in Library East), pp. 151
-155.

Eckaus, Richard S. 1976. Appropriate Technologies for
Developing Countries. National Academy of Sciences, Washington
(HC, 59.7, .E25 in Library East) pp. 6-9.

Hoda, M.M. 1976. India's experience and the Gandhian tradition.
Chap. IV in Part 2 of Appropriate Technology, Problems and
Promises, Nicholas Jequier, ed. Development Centre of the
Organisation for Economic Cooperation and Development. (T, 49.5,
.A66 in Library East) pp. 144-150.

Jequier, Nicholas, ed. 1976. Appropriate Technology, Problems
and Promises. Development Centre of the Organisation for Economic
Cooperation and Development. (T, 49.5, .A66 in Library East) pp.
24-27.

Jequier, Nicholas. 1979. Appropriate Technology Directory.
Development Centre of the Organization for Economic Cooperation
and Development, Paris. (T, 49.5, .J44 in Library East) pp.
29-313.

Schumacher, E.F. 1973. Small is Beautiful. Blond & Briggs, Ltd.,
London. Also Harper & Row, Pub. Inc., New York.

Winner, Langdon. 1980. Building the Better Mousetrap:
Appropriate Technology as a Social Movement. Chap. 2 in
Appropriate Technology and Social Values A Critical Appraisal,
Franklin A. Long and Alexandra Oleson, eds. Ballinger Pub. Co,
Cambridge Mass. (T, 14.5, .A67 in Library East) pp. 27-51.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 3
Case Studies


Several collections of case studies of specific examples of
technology transfer exist (Betz, 1984; Evans and Adler, 1979;
Jequier, 1976). It is useful to examine a number of these to
obtain an idea of what is considered to be appropriate technology,
to gain an understanding of the range of factors which bear on the
application of technology in a new setting, and to see the types
of technologies which have been considered successful in an
appropriate sense.

We will read and discuss four case studies. They are: 1) a
historical recounting of development in the People's Republic of
China since World War II, 2) regional development projects on a
Korean island, 3) a hydroelectric power project on Papua New
Guinea, and 4) the Lorena cookstove. The first of these is taken
from the first reference and the others are taken from the second
reference.


References

Betz, Matthew J., Pat McGowan. and Rolf T. Wigand, eds. 1984.
Appropriate Technology: Choice and Development. Duke Press Policy
Studies, Durham, N.C. (T, 185, .A7, 1984 in Library East), pp.
67-143.

Evans, Donald D., and Laurie Nogg Adler, eds. 1979. Appropriate
Technology for Development: A Discussion and Case Histories.
Westview Press, Boulder, CO. (HC, 59.7, .A823 in Library East)
pp 81-431.

Jequier, Nicholas, ed. 1976. Appropriate Technology, Problems
and Promises. Development Centre of the Organisation for Economic
Cooperation and Development. (T, 49.5, .A66 in Library East) pp.
156-344.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 4
Technology: Sources and Transfer


The dimensions of technology are many and broad. Technology
originates in many various ways; for example, by garage tinkerers,
university laboratories, and multi-million dollar industrial
research and development programs. Technology takes many forms;
for example, a new material, a chemical process, a machine.
Technology is disseminated in many ways; for example,
entrepreneurs in commerce, agricultural extension agents, word of
mouth among individuals, returning foreign-educated technologists,
private sector direct investment by the industrialized nations.
Technology is available, often for any individual application, in
a bewildering array of choices. Ekhaus (1979) reminds us that
technology often varies over a range of input requirements, i.e.,
variations between labor and capital requirements in a typically
inverse relationship.

Jequier (1976) distinguishes between the hardware and the software
of technology. Hardware is the "factories, machines, products or
infrastructures (roads, water distribution systems, storage
facilities, etc.)" Software is the "knowledge, know-how,
experience, education and organisational forms" or the development
and delivery system. Both are important. Jequier suggests that
software may be more important for developing countries since it
is often lacking and since it relates more closely to culture.
However, the importance of software is more easily overlooked
because it tends to be invisible.

The development of new technology occurs in various ways and from
various sources. Much technology is in the "public domain" in
that patent protection, if any, has expired. This includes much of
the older technology often found to be more appropriate for
applications in LDC'S. Some technology is protected by patents
which in some cases may limit its application but in others may
make the technology available where it otherwise would not have
been. Some technology is withheld from general knowledge by
secrecy (military information, for example). Some technology is
owned, is considered proprietary information this includes
technology protected by patents and is available for a
consideration. On the other hand, much technical information is
widely and easily available and often requires little on the part
of the acquirer to obtain. It is available through institutions
and agency seeking to help LDC'S, through philanthropic
foundations, through low-cost educational programs and literature.
Another alternative may be for the beneficiaries of the technology
to be the innovators; acceptance occurs more readily under these
circumstances.











Development of new technology is encouraged if proper incentives
exist. These include a reward system; for instance, a patent
system or another system of financial rewards.

Dissemination and acceptance of technology are other issues.
Jequier (1976) discusses how community innovators test the waters
of new technology and serve as "gatekeepers", depending on their
experiences with the technology. In disseminating some types of
technology, particularly those involving groups of people, it may
be useful to identify and work with the community leaders or power
structure. Risk is a very significant reason why many people are
reluctant to adopt new technology, until it is well proven to
them. Lack of capital, even in very small amounts, is a
compelling reason for many in LDC'S to avoid new technology.

Jequier (1976) presented a useful distinction between three types
of technology:
1. Private technology, consumer goods whose introduction depends
on individual or family decision.
2. Community technology, infrastructures and production
technologies.
3. Public technology, large industrial firms and national
institutions.
Innovation efficiency varies with type; Jequier suggests that
community technology is the most difficult in which to innovate
in LDC'S, because of ineffective pricing mechanisms, difficulties
in decision making, and the relative importance of software.

Organizations involved in appropriate technology needs
identification and development can be categorized (Jequier,
1976).
1. "Higher education institutions, or rather, small groups which
originated from and are closely linked with such institutions,
like Kumasi University in Ghana, Mindanao State University in
the Philippines, the University of the Andes in Colombia, or
the Technische Hogeschool Eindehoven in the Netherlands."
2. "Governmental, private or semi-public organizations specialized
in intermediate technology and working primarily on a national
basis, like the Appropriate Technology Cell of the Ministry of
Industry and the Gandhian Institute of Studies in India, or the
Appropriate Technology Centre in Pakistan."
3. "Multinational groups or research centres, like the London-
based Intermediate Technology Development Group (ITDG),
Volunteers in Technical Assistance (VITA) in the United States
or the International Rice Research Institute (IRRI) in the
Philippines."


References

Eckaus, Richard S. 1976. Appropriate Technologies for
Developing Countries. National Academy of Sciences, Washington
(HC, 59.7, .E25 in Library East) pp. 53-66.











Evans, Donald D., and Laurie Nogg Adler, eds. 1979. Appropriate
Technology for Development: A Discussion and Case Histories.
Westview Press, Boulder, CO. (HC, 59.7, .A823 in Library East)
pp 24-35.

Jequier, Nicholas, ed. 1976. Appropriate Technology, Problems
and Promises. Development Centre of the Organisation for Economic
Cooperation and Development. (T, 49.5, .A66 in Library East) pp.
21-24, 43-61.










Agricultural Engineering Department


ABE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 5
Farming Systems of the World


The farming systems of the world vary immensely in many different
characteristics. Efforts have been to type them into groups
having similar characteristics. Norman (1979) briefly reviews
this effort and provides a definition of farming system: The
pattern of resources and processes of resource use in a farming
unit. "Farming unit" is purposely imprecise so as to accommodate
shifting agriculture or the farmer who farms at two different
locations and in two different fashions. "Resources" include
natural resources, human resources, capital resources, and
incipient products. The evidences of mechanized agriculture we
are concerned with, fit of course into the capital resources
category, but the appropriateness we are concerned with relates
heavily to the human resources and also to the natural resources.
The "processes of resource use" refer to the manipulation of
resources for production and include energetic, hydrologic,
biogeochemical, and socioeconomic. Norman further subdivides the
capital resources into permanent (including cleared land and
established irrigation systems), semi-permanent (including barns,
fences, draft animals, and implements), operational (fertilizer,
herbicides, etc.) and potential (bank credit, owed labor, etc.).

Categorization of an example farm into a farming system type is
useful in that different candidate technologies are associated
with different farming system types. A permanent irrigation
system is not going to be considered as a possible technology for
a shifting cultivator, for example.

There is not yet, however, agreement on what constitutes a listing
of world farming systems types. Therefore this list (derived in
part from Norman, 1979, Spedding, 1975, and Duckham and Masefield,
1971) will serve only to approximately describe the various
possibilities and is not claimed to be exhaustive or non-
overlapping. Overlapping seems inevitable because of the several
different means of differentiation between types. A single
farming unit could have portions fitting into more than one of
these types. This list is laid out in order of generally
increasing intensity. Therefore, the types we are most concerned
with in the application of appropriate technology to (generally)
the LDC'S are nearer the beginning of the list.

1. Shifting or alternating cultivation systems (also known as
"swidden" and "slash and burn": Rainfed cropping with
annuals, biennials or short-lived perennials for a cropping
period up to perhaps several years followed by a longer
fallow period in forest or grassland. Typified by mixed










cropping (see # 4 for definition) with many species. Food
production, particularly in the tropics, may be essentially
continuous year-round. Now largely confined to the tropics.
Tools may be limited to ax, hoe, digging stick and fire. Soil
fertility is renewed during fallow. Any livestock are
typically non-ruminants.

2. Pastoral nomadism: Livestock (ruminants) herding on usually
unimproved rangeland. Sheep and goats common in many areas of
the world, reindeer in Finland, cattle in Africa.

3. Ranching: Livestock raising on either unimproved or improved
rangeland, but with a fixed farmstead of buildings. Cattle
and sheep predominate.

4. Rainfed annual cropping systems: Includes monocultures and
complex cropping, the latter including mixed cropping (more
than one crop simultaneously, no geometric pattern),
intercropping (more than one crop simultaneously in a
geometric pattern) and relay cropping (more than one crop
simultaneously, planted and harvested at different times).
Soil fertility declines gradually to a stable level unless
replenished. Main non-solar work energy sources may range
from human through draft animal to internal combustion
engines.

5. Mixed cropping and livestock: Cropping (non-irrigated or
irrigated) and livestock usually complement each other through
mutually beneficial interactions. Crops provide livestock
feed and livestock wastes provide plant nutrients for crops.
Livestock provide higher quality food products than crops
and/or higher-valued cash commodities.

6. Irrigated annual cropping systems: Norman (1979) defines
irrigation as the controlled supply of water to a field,
additional to the (precipitation) that falls on it, and the
controlled disposal of surplus water from the field. Crops
can be flooded (rice, jute) or non-flooded and supply can be
by gravity or by lifted water. Scale of irrigation system can
be small or large. Irrigation is generally more intensive
than non-irrigation (labor, capital, management), but yields
are higher and multiple cropping (more than one crop per
season) may be enabled.

7. Perennial fruit, nut and other shrub, vine and tree crops:
This includes plantations for such crops as bananas, oil palm,
and rubber. Incidence of irrigation varies with crop and
location.

8. Vegetable, small fruit, ornamentals, and other specialty
crops: Intensive, usually with irrigation.

9. Confinement livestock operation: Includes beef feedlots,
broiler and egg production, hog farming, and other species.












Aquaculture can be fit into this type. Characterized by high
animal densities, most feeds being produced on other farms.

10. Greenhouses: Used for vegetables and ornamentals. A very
intensive form of agricultural production. Multiple cropping
common.

There are certainly farming systems which do not fit into one
of these ten types. However, these types probably represent the
bulk of the world's current farming systems.


References

Duckham, A.N., and G.B. Masefield. 1971. Farming Systems of the
World. Praeger Publishers, New York (281.02, D835f in Hume Lib.)

Norman, M.J.T. 1979. Annual Cropping Systems of the Tropics.
Univ. Presses of Fla., Gainesville (Hume Library). pp. 1-15,
86-102, 136-162, 190-206.

Ruthenberg, H. 1971. Farming Systems in the Tropics. Oxford:
Clarendon Press. (Hume Library).

Spedding, C.R.W. 1975. The Biology of Agricultural Systems.
Academic Press, New York. pp. 14-24.











Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lectures No. 6 & 7
Goals for Appropriate Technology in Mechanized Agriculture


There are numerous possible goals which can be considered whenever
choosing an appropriate technology for mechanizing agriculture.
These are, typically, the same possible goals that can be followed
in agricultural development in general, but many are discussed
here in the context of mechanization. Some of these goals are
interrelated with others. Following is an enumeration and
explanation of a number of the goals which more likely should be
considered.

1. Labor employment. Many of the LDC's have high labor
unemployment. High population growth rates have resulted in
excess labor availability in rural areas; migration to urban
areas occurs despite their inability too to absorb the overflow.
It is often desirable to maintain or even to increase jobs in
agriculture to give employment opportunities. The goal to
maintain or increase employment in agriculture is directly
opposite that usual in industrialized agriculture, where
technologists are conditioned instead to reduce labor inputs, as
labor is a relatively high priced production input. On the other
hand, it may be very reasonable to attempt to reduce labor inputs
to those farming operations, if there are any, during which a
shortage of labor exists. Operations in which labor availability
is limiting are most likely to be the critical operations of
primary tillage, planting, weeding and harvesting. The
performance of operations in a timely manner so as to optimize
production quantity and quality is called timeliness, and it is
this concept which helps justify much mechanization technology.
Total labor employment per unit land area can even be increased
with the initiation of irrigation or with mechanization which
enables increased cropping intensity due to improved timeliness.

2. Simplicity. Educational levels of agricultural labor and
of those who repair and maintain farm machinery in many of
the LDC's are low by Western standards. Complex machinery is
foreign to most. Without proper maintenance, many machines will
not perform as well or as long. If misused, life and performance
may also suffer. Johnston (Chap.2 in Ahmed and Kinsey, 1984)
recommends a "blacksmith" level of technology as appropriate for
many LDC's for repairing machinery and for developing, with farmer
input, simple machines. A strategy mainland China has followed
successfully is a policy of gradual change, so that the changes in
technology have not outpaced the ability of its people and
resources to track.










3. Minimization of capital requirements. Technology must be
affordable. Many farmers in LDC's have little capital and/or
little access to credit. New technology of a mechanical
nature is often capital intensive, whereas new technology of a
bio-geochemical nature, such as improved varieties, usually
requires little additional capital. Capital investment per
worker, or, as Schumacher termed it, investment per workplace,
seems an appropriate measure to consider. We need to keep in mind
also the fact that agricultural investment per worker, at least in
industrialized agriculture, is among the largest of all
industries.

4. Superiority. New technology must be superior to, not just as
good as, the currently used technology, or there will be no
incentive for the farmer to change. Superiority can be terms
of one or many of the goals herein enumerated. Without clear!
superiority, farmers will be exposed to a higher level of risk in
order to adopt new technology. Risk is something the LDC farmer
can stand little of. His sometimes seemingly irrational clinging
to traditional methods may be a result of his aversion to risk
even though the potential rewards of new technology may be great.

5. Sustainability. A major concern of many is whether our food
production systems are sustainable over a long period of time.
The fossil fuel dependency of industrialized agriculture
strongly suggests that within a few decades it will be forced to
undergo significant changes with respect to energy sources in
order to continue. More generally, it appears that a sustainable
agriculture must consume only renewable and recycled resources.
Fossil fuel energy consumption is anticipated to gradually
decrease as increasingly higher prices signal the end of the
fossil fuel era. Perhaps then draft animals will make a comeback
or perhaps we will have harnessed the sun for cheap electric
power. Another area of concern is the possible long-term effects
of agricultural chemicals on the environment. A major concern is
ground water quality. Also, maintenance of our arable land
resources, including controlling soil erosion to a level
acceptable over the long term and maintaining soil fertility, is
necessary.

6. Improved quality of life and increased income. Most farmers
in LDC's are very poor. Most have little opportunity to
improve their standard of living. If new technology can
enable the farmer to increase his income or to break out of the
entirely subsistence mode and initiate the transition to the
production of cash commodities, then he can increase his standard
of living and begin to finance improvements in his technology. He
can accumulate capital. Alternatively, even a subsistence former
may, with new technology, be able to improve his quality of life
through greater or more varied production.

7. Reduced drudgery. This has been a standard reason for
agricultural mechanization in the industrialized countries.
Making work easier is just as much a reasonable goal also for










the LDC farmer. Implications for a longer, healthier and
happier life with reduced drudgery are important.

8. Increased production. Though the main effect of mechanization
in industrialized agriculture has been to substitute for
labor, it is recognized (Giles, 1975) that another often
important result of mechanization can be to increase production.
Certainly irrigation generally increases yields as compared with
rainfed farming. If multiple cropping is facilitated by improved
timeliness, production can be sharply increased.

9. Increased productivity of various inputs. The "yield
mechanization", as Giles termed increases in production due to
mechanization, results in increased productivity of other
inputs, particularly labor and land. When output is increased
due to changes in one input factor, say mechanization, and other
input factors remain constant; the ratios of output to these other
input factors, also known as productivities for those respective
production factors, also increase. Serendipity.

10. Profit maximization. This is a standard goal or measure of
success in industrialized agriculture and is given here for
comparison and because it may likely be a goal in some LDC
farm systems too. A significant weighting of other goals also,
however, is what makes appropriate technology appropriate.

11. Compatibility with existing culture or "way-of-life". New
technology should, generally, disrupt as little as possible
the existing culture. Changes in culture otherwise only occur
over time measured in terms of generations. Sudden changes may
cause much disruption and anguish, which can be directed, with
negative results, toward the new technology. New technology can
cause problems by sharply increasing labor productivity or
combining many jobs into few, creating unemployment. Technology
which is "scale-neutral", or can be used even on the smallest
farms, has distinct advantages. It prevents the larger or
better capitalized farmers from taking competitive advantage and
forcing the smaller farmers out. Another factor which must not
be overlooked is that use of modern machinery is usually
considered prestigious by LDC farmers (they're no different from
industrialized farmers in that respect), giving it a favorable
bias over less fashionable technology which may otherwise be more
appropriate.

12. Utilization of locally available resources. Such a goal
not only minimizes transportation requirements and reduces
dependency on foreign sources, but serves to increase
self-sufficiency and self-reliance, increase local employment, and
build up a support infrastructure. However, it may increase total
costs due to diseconomies of small scale production, and forego
all other benefits of mass production.

13. Environmental preservation, or improvement. Likely no
technology has zero effect on the environment, but it is










desirable that new technology have as little negative effect
on the environment as possible. Certainly there are examples of
new technology which result in improvement of the environment as
compared with existing technology.

14. Diversification. Among the advantages of diversification are
an increase in self-sufficiency, an improvement in standard
of living for the subsistence farmer, and a smoothing of
labor requirements throughout the year.

15. Self-sufficiency. and self-reliance. In addition to
instilling pride and confidence, attainment of these goals
provides a greater measure of individual and local control,
and less dependency and reliance on others.

16. Regional development. Often a political goal, to make the
area a contributing rather than a dependent entity, and to
improve the living conditions of the population.

17. Income redistribution. Perhaps a goal if the existing income
distribution is seen as undesirable, as it might be if there
are the extremely wealthy, few middle class and many in
poverty. The redistribution of wealth is a more extreme possible
goal, but one that may be considered if there are very large
landholdings as well as large numbers of poor who own no
or too little land.

18. Minimization of cost of agricultural products. A not unusual
political goal, to satisfy the urban population. However, too
low food prices are a chronic problem of agriculture and may
stifle development.

19. Political development. Improvement in the human situation is
a usual way by which political fortunes are made and therefore
policies which help agriculture to develop may thus be
supported by politicians. Governments are usually larger and
stronger and can encourage development more when economies are not
distributed and weak.

20. Improved balance of payments. Improvement of agricultural
exports with a commensurate smaller increase in imports of
agricultural inputs results in an improved balance of
payments. Balance of payments is a perennial problem of LDC's.

It is the individual circumstances peculiar to each individual
situation which determine whether a technology is appropriate.
Decisions are made largely by the farmer, based upon his
perceptions and weighting of a number of potential goals.
Hopefully, a significant portion of such goals are identified and
discussed above, though it is obvious there are some included
which are corporate rather than individual goals.










References


Ahmed, Iftikhar, and Bill H. Kinsey. 1984. Farm Equipment
Innovations in Eastern and Central Southern Africa. Gower Pub.
Co., Brookfield, VT. pp.1-88.

Asian Productivity Organization. 1983. Farm Mechanization in
Asia. APO, Tokyo. pp. 1-17.

Crossley, Peter, and John Kilgour. 1983. Small Farm
Mechanization for Developing Countries. John Wiley & Sons, New
York. pp. 171-176, 180-184.

Eckaus, Richard S. 1976. Appropriate Technologies for
Developing Countries. National Academy of Sciences, Washington
(HC, 59.7, .E25 in Library East) pp. 37-52.

Esmay, Merle L., and Roy E. Harrington, eds. 1979. Glimpses of
Agricultural Mechanization in the People's Republic of China.
American Society of Agricultural Engineers, St. Joseph, MI.

Food and Agricultural Organization of the United Nations. 1969.
Smaller Farmlands Can Yield More. FAO, Rome. pp.1-13, 33-40.

Giles, G.W. 1975. The reorientation of agricultural mechanization
for the developing countries, Part I, Policies and attitudes for
action programs. Mechanization in Asia 6(2): 1-16.

Intermediate Technology Publications Ltd. 1985. Tools for
Agriculture, A Buyer's Guide to Appropriate Equipment. 3rd ed.
I.T. Pub. Ltd., London.

Knorr, Dietrich. 1983. Sustainable Food Systems. AVI Pub. Co.
Inc., Westport, CT. pp. 1-47.

Usherwood, Noble R. 1981. Transferring Technology for Small-Scale
Farming. ASA Spec. Pub. No. 41. American Society of Agronomy.
Madison, Wis. pp.1-14, 36-52.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 8
The Farming Systems Research and Extension Approach


A recent approach to rural development is the farming systems
approach. It responds to deficiencies experienced in more
conventional approaches, in that recommended technology was often
not accepted by farmers. Altieri (1984) says: "the basic premise
of this 'farming systems approach' is that appropriate
technological changes for small farmers must emerge from
agro-socioeconomic studies that identify the conditions
influencing traditional farming systems, so that the new
recommended practices are adopted to the farmers' real needs and
circumstances." In practice, research and extension are combined
as the researchers identify, in consultation with farmers, their
needs, and from this identify researchable problems, the results
of which lead to improved technology the farmers more readily
adopt. An essential element of the farming systems approach is
that the process begins with the farmer. Another is that the
research is of an applied nature (Andrew and Hildebrand, 1982),
often conducted on the farm rather than on an experiment station
or in a laboratory and often under adverse conditions, but with a
view toward quick results as well as early adoption. Another
aspect is that the approach is of a holistic nature, involving the
entire farming system including the household rather than only
production of a single commodity, as well as incorporating both
research and extension. Another aspect is the interdisciplinary
character necessitated by the diversity of interrelated problems
encountered. The entire approach has now come to be called
farming systems research and extension (FSR&E), or farming systems
applied research (FSAR) or simply farming systems research (FSR).

Four stages of the FSR&E approach are identified:

1. Descriptive and diagnostic stage. Study of the current
farming system, usually by an interdisciplinary team, to
understand its operation, constraints, and the goals and
motivations of its participants. Questionnaires are a
commonly used tool to determine what are perceived problems as
well as opportunities for improved production.

2. Design stage. Derivation of improved technologies to address
problems identified in the first stage. Technologies are
usually not reinventionss of the wheel" but are instead
variations of technology existing elsewhere applied to
local circumstances.










3. Testing stage. On-farm testing is common, first with
managerial input by the research team, then under farmer
management.

4. Extension stage. Taking the improved technology to additional
farmers, with perhaps another round of the process.

The farming systems approach seems quite compatible with the
development and application of appropriate technology since it
incorporates the human element, the farmer and farm household,
and their goals, and therefore accounts for the cultural as well as
the technical aspects of technology.

Farming systems research and extension is therefore characterized
as including a holistic systems approach, "bottom-up" farmer
involvement, applied research of an interdisciplinary nature, and
an orientation toward improving farmer welfare.


References

Altieri, Miguel A. 1984. Towards a Grassroots Approach to Rural
Development in the Third World. Agr. and Human Values 1(4):45-
48.

Andrew, Chris 0., and Peter E. Hildebrand. 1982. Planning and
Conducting Applied Agricultural Research. Westview Press,
Boulder, CO. (S, 540, .A2, A53, 1982 in Hume Library)

Norman, David W., Emmy B. Simmons, and Henry M. Hays. 1982.
Farming Systems in the Nigerian Savanna: Research and Strategies
for Development. Westview Press, Boulder, CO. (S, 473, .N5, N67,
1982 in Hume Library) pp. 5-7, 15-35.

Shaner, W.W., P.F. Phillipp, and W.R. Schmehl. 1982. Farming
Systems Research and Development: Guidelines for Developing
Countries. Westview Press, Boulder, CO.











Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture
Lecture No. 9
Mechanized Agriculture Development in Industrialized Countries

For most of the history of agriculture, inventions of a physical,
as opposed to a biological or chemical, nature have occurred
sparcely. However, within about the past 200 years the pace has
quickened markedly. Table 1 lists a number of these "physical"
inventions and when they occurred:

Table 1. Significant agricultural inventions
--------------------------------------------------


Invention


Date


Wooden plow
Hand sickle
Hand ax (cast bronze) 2500-
Cart with solid wooden wheels
Shaduf (first water raising machine)
Oxen yoke
Bag-type fruit press
Horizontal water mill (vertical axle)
Screw pump ("Archimedes")
Donkey-powered mill for grinding grain
Vertical undershot ("Vitruvian") water wheel
Water raising wheel
Comb-type reaping machine ("Vallus")
Overshot water wheel
Windmill
Steam engine
Cotton gin
Cast iron plow
Vertical shaft water turbine
Grain cradle sythe Early
Steel moldboard plow (John Deere)
Reaper (Cyrus McCormick)
Threshing machine
Mowing machines
Steam traction engine
Barbed wire
Internal combustion engine (Nicholas Otto)
Cream separator
Binder (reaper which ties bundles of grain)
Gasoline tractor (John Froelich)
Combine
All-purpose tractor (Farmall)
Rural electrification
Pickup balers
Cotton picker
Center pivot irrigation system


3000
3000
-3000
2500
2200
2000
2000
600
300


B.C.
B.C.
B.C.
B.C.
B.C.
B.C.
B.C.
B.C.
B.C.


100 B.C.

100 A.D.
500 A.D.
1100 A.D.
1769 A.D.
1793 A.D.
1797 A.D.
1800 A.D.
1800's
1837 A.D.
1834 A.D.
1837 A.D.
1850's
1855 A.D.
1874 A.D.
1876 A.D.
1877 A.D.
1877 A.D.
1892 A.D.
1920's
1924 A.D.
1930's
1930's
1941 A.D.
1949 A.D.


---------------------------------------------------------------


------------------------------------------------------------











Using the United States as an example of industrialized
agriculture, we note that early Colonial agriculture was quite
primitive. The first settlers had and used primarily hand tools;
ax, shovel, sythe, hoe, fork, etc. Draft animals, when used, were
used mainly for plowing and harrowing with crude implements and
hauling with carts. Sources of tools were blacksmiths and
imports; many were homemade of locally available materials, just
as the early settlers made most everything else they used;
housing, furniture, clothing, etc.

Westward expansion and the beginnings of industrialization led to
labor shortages in the early 1800's. Farmers began to mechanize
as technological advances enabled them to do so. The several
decades before and after the Civil War (which also contributed to
the labor shortage) were punctuated by repeated significant U.S.
agricultural mechanization developments, so much so that the
technology lead was taken from Europe. Most of this technology
was dependent on draft animals, whose numbers increased greatly.

Even draft animal power proved limiting, however, and new sources
of greater power were found in the latter part of the nineteenth
century and the first part of the twentieth century; the steam
engine, and later the gasoline engine. Application of the latter
power source countered the labor shortages of World War I.

Continued mechanization after World War II has related both to
increasing scale and to facilitating new non-mechanical technology
such as improved fertilization, hybrid varieties and pesticides.

American agriculture has been shaped indelibly by the relative
costs of its inputs. Labor has been relatively expensive whereas
land, energy and capital have been relatively cheap. Therefore,
mechanization has centered highly on replacing labor. Very
appropriate, given the circumstances.

References

Blandford, Percy W. 1976. Old Farm Tools and Machinery. Gale
Research Co., Fort Lauderdale, FL. (58, B642o in Hume Library)

Loomis, R.S. 1984. Traditional agriculture in America. Ann.
Rev. Ecol. Syst. 15:449-478.

Rasmussen, Wayne D. 1982. The mechanization of agriculture.
Science :77-89.

United States Department of Agriculture. 1960. Power to Produce.
The Yearbook of Agriculture, 1960. USDA, Washington.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 10
Mechanized Agriculture Development in LDC's


Mechanized technology for agriculture in the LDC's also began with
only primitive hand tools. The machete and hoe are yet the common
tools of many subsistence farmers. Development of agriculture in
LDC's generally languished until after World War II except for
large scale plantation agriculture, which was typically financed
and managed by foreigners to produce export crops. Progress since
then has been slow in some areas, fast in others. It is not
usual that labor shortages in LDC agriculture spur mechanization
as it did in some industrialized agriculture, though that does
occur in some cases. Much of the mechanization which has occurred
relates to the Green Revolution.

The Green Revolution is the name which has been given to the
diffusion of modern agricultural technology throughout numerous
LDC's and which is centered upon dwarf varieties of wheat and
rice. These varieties respond better to additional inputs of
fertilizer and irrigation than do the traditional varieties.
Mechanized technology is therefore an integral part of the Green
Revolution, not only to provide irrigation water but also to
perform operations in a more timely manner and thereby permit
multiple cropping. Day and Singh, in describing the effect of the
Green Revolution on Indian Punjab agriculture say that "Large-
scale mechanization has not been confined to land preparation. It
is also extensive for the tasks of irrigation, harvesting, and
threshing. Part of the mechanization has been due to an increase
in the average size of holdings, part to the seasonal shortage of
family labor."

Day and Singh (1977) also describe more in general the changes
wrought by the Green Revolution upon the Punjab:

"...a state in rapid transition from age-old production
methods to modern technology, a state experiencing a rapid
growth in farm output and a drastic change in the seasonal
work pattern of farmers. The transformation clearly involved
extensive investments and the substitution of capital for
labor as individual tasks were being mechanized and as wholly
new methods and materials were being adopted. New markets
and roads were in evidence everywhere. Where villages had
once stood, towns were evolving; where market towns had stood
essentially unchanged for decades, cities circumnavigated by
burgeoning industries were now in evidence; where bullock
carts still plied the dusty roads, buses and trucks swept
past, overloaded with people and produce, leaving a choking
mixture of dust and diesel fumes; beside the closely











clustered flat-topped mud houses, plastered with cow-dung
patties drying for fuel, one saw new, modern brick houses,
each connected to the high-tension electric wires ubiquitous
in every developed country; where blindfolded camels still
strode their endless rounds drawing water with ancient
Persian wheels, one saw squat huts under shady bamboos
emitting the throb and hum of tubewells emptying water for
irrigation connected by water and electricity all the way to
the remote Bhakra Dam."

Thus it is suggested that Green Revolution development has
brought about a compendium of diverse effects; some good, some
bad. This seems true whenever there is change.

A very significant aspect of LDC agricultural development over the
past quarter century has been the development of International
Agricultural Research Centers (IARC's). Beginning with the
Mexican center to work on wheat and maize (1943, later known as
CIMMYT), under whose leadership of Norman Borlaug was developed
the short stemmed wheat varieties which lead to the Green
Revolution, the Rockefeller and Ford Foundations also established
the International Rice Research Institute (IRRI) in Los Banos,
Philippines in 1959. Successes at these led to the establishment
in 1967 of CIAT near Cali, Colombia and IITA in Ibadan, Nigeria.
The need for additional funding resources led to the formation of
Consultative Group on International Agricultural Research (CGIAR)
in 1971, an "association of countries, international and regional
organizations, and private foundations dedicated to supporting a
system of agricultural research centers and programs around the
world. The purpose of the research effort is to improve the
quantity and quality of food produced in the developing
countries." Co-sponsers of CGIAR are World Bank, Food and
Agricultural Organization of the United Nations, and United
Nations Development Program. There are 48 members in 1985 and a
budget of $180 million. Nine new IARC's have been begun since
1971 (Table 1).

Table 1. International Agricultural Research Centers

Name Location Founded Responsibilities

CIMMYT Londres, Mexico 1943 Wheat, maize, barley,
triticale
IRRI Los Banos, Philip. 1959 Rice
CIAT Cali, Colombia 1967 Cassava, rice, corn, field
beans, forages, beef
IITA Ibadan, Nigeria 1967 Sweet potato, yam, corn,
cocoyam, cowpea, lima
beans, soybeans, rice
CIP Lima, Peru 1971 Potatoes
WARDA Monrovia, Liberia 1971 Rice
ICRISAT Hyderabad, India 1972 Groundnuts, chickpeas,
pigeon peas, pearl millet,
sorghum










ILCA Addis Ababa,
Ethiopia
ILRAD Nairobi, Kenya
IBPGR Rome, Italy


IFPRI
CGIAR
ISNAR


Washington, D.C.
Aleppo, Syria
The Hague,
Netherlands


1974

1974
1974

1975
1976
1979


Pastoral and mixed farming

Livestock diseases
Plant germ plasm
collections
Food policy
Foods for dry subtropics
Improvement of research
and extension services


It appears that the IARC's have been, are now and will continue to
be an important source of appropriate technology for agricultural
development of the LDC's.


References

Bayliss-Smith, Tim P. and Sudhir Wanmali, eds. 1984.
Understanding Green Revolutions. Cambridge Univ. Press, New York.
(HD, 2065.3, .U52, 1984 in Hume Library)


Consulting Group on International Agricultural Research.
International Research in Agriculture. CGIAR, New York.
(R13.030, 161 in Hume Library)


1974.


Day, Richard H. and Inderjit Singh. 1977. Economic Development
as an Adaptive Process. Cambridge Univ. Press, New York. pp.
119-138. (281.155, D274e in Hume Library).

Esmay, Merle L., and Roy E. Harrington, eds. 1979. Glimpses of
Agricultural Mechanization in the People's Republic of China.
American Society of Agricultural Engineers, St. Joseph, MI.


Jennings, Peter R. 1976.
production. Sci. Amer.


The amplification of agricultural
(Sept. issue)


Plucknett, Donald L., and Nigel J.H. Smith. 1982. Agricultural
research and third world food production. Science 217:215-220.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 11
Power Requirements for Agricultural Mechanization


Energy and power is required to perform any agricultural operation
which involves moving materials, whether it be soil, agricultural
produce, agricultural wastes, inputs for agricultural production,
equipment, or personnel. That energy must be provided in a
mechanical form as opposed to thermal, chemical or other form. In
primitive and subsistence agriculture that energy tends to be
provided by renewable sources, including manual human labor and
draft animals, and in some cases water power, wind power and other
sources. Limitations of capacity and extent of these renewable
sources may be a limiting factor on agricultural production. In
order to evaluate the suitability of and to size energy sources
we need an understanding of the nature of energy and power and how
to make necessary calculations.

Several definitions are basic to an understanding of the nature of
energy, work and power in mechanized agriculture:

(1) Force (push or pull): A vector (a quantity having both
magnitude and direction) tending to produce change in the
motion of (to accelerate or decelerate) objects. Measured in
units such as pound force, kilogram force, dyne and Newton.
Draft is the force required to pull (or push) an implement.

(2) Work: Product of force (or draft) and distance. Measured in
units such as foot-pound and Newton-meter (Joule).

(3) Energy: Capacity to perform work and is equivalent to work.
Forms of energy include mechanical, heat or thermal, chemical,
electrical, radiant and nuclear energy, etc. Measured in
units such as British thermal unit (btu), kilocalorie (kcal),
Joule (J), kilowatt-hour (kWh), footpound (ft lb) and
horsepower-hour (hph).

(4) Power: Time rate at which work is done or energy is expended
or generated. Power is energy per unit time. Measured in
units such as watt (J/s) and horsepower (550 ft lb/s or
33,000 ft lb/min), where s = second. Energy is the product of
power and time.

Conversions of energy from one form to another are never made
without losses into undesirable energy forms, usually thermal.
Efficiency is the quotient of desirable output to total input:
therefore more energy (and power) must be supplied to a device
producing a conversion of energy forms than is needed as
output. Efficiency varies with method of conversion.











How to calculate energy and power requirements:


(1) Lifting.
Energy is product of force (weight) and height. A lifted
object has its potential energy increased by the amount of
energy ideally (minimum amount possible) expended.
Power is energy per unit time or force times vertical
velocity.

(2) Pulling or pushing:
Energy is the product of force (or draft) applied and distance
moved. The force is the sum of as many as several components,
including friction, rolling resistance, soil reaction, lifting
(if going up a slope).
Power is energy per unit time or force times velocity.
Draft and power requirements for various agricultural
equipment operations; tillage with various types of tools,
planting, cultivating, etc. are detailed in ASAE Data: ASAE
D230.3, Agricultural Machinery Management Data, now published
in ASAE Standards (1985). Equations and procedures are
applicable as well to small scale equipment.

(3) Accelerating or decelerating:
Energy expended in accelerating an object equals 1/2 its mass
times its increase in velocity squared. Then its increase in
kinetic energy due to the increase in velocity equals that
same amount.
Power is energy per unit time.

(4) Pressurizing a fluid (liquid or gas):
Energy is the product of quantity of fluid and increase in
pressure.
Power is the product of flow rate (quantity per unit time) and
increase in pressure.

(5) Rotating a shaft:
Energy is torque (force times lever arm) times angle rotated
(in radians).
Power is torque times angular velocity (in radians per unit
time).
ASAE (1985) also gives rotary power requirements for numerous
harvesting machines.

Attempts have been made to quantify an appropriate level of energy
and power to apply to agricultural production. Giles' (1967)
showed that a relationship existed between power available per
unit of cultivated land and level of production (Fig. 1); he











































suggested a minimal power range of 0.5 to 0.8 horsepower of
mechanical power, whether human, animal or tractor, per hectare
(0.37-0.60 kW/ha) in order to achieve "respectable" yields of
2000-3000 kg/ha. Note that of course that such power level is not
continuously applied, but rather that as much as this power level
is available for application whenever needed for at least some
operations. The APO (1983) reports that some of their delegates
thought a more accurate parameter to determine adequacy of
mechanical power or energy would be energy, rather than power, per
unit area; however, no suggestions were made for amount of
energy or methodology of measurement.

Revelle (1976) recommended India increase energy use in
agriculture for "irrigation, chemical fertilizers and additional
draft power for cultivating the fields" in order to increase food
production and reduce food costs. Chancellor (1977), in relating
the use of supporting resources to climate-driven photosynthesis
agreed: "...one of the most important roles of fuel and electrical
energy flow to agricultural production systems, is that of a
catalyst which permits activation of otherwise underutilised
dormant resources so that they may serve to a greater extent as
production inputs." Makhijani (1975) recommended a power
availability of 1/2 to 1 horsepower (0.38 to 0.76 kN) for a few











hundred hours per hectare for LDC agriculture.

Stout (1979) presented data (now about 10 years old) on available
power (Table 1):

Table 1. Distribution of Agricultural Power in Developing Nations

Region kW/ha Percent


S


Africa
Asia (excluding China)
Latin America

Percent of Total


0.07
0.16
0.19


Human Animal Mechanical

35 7 58
26 51 23
9 20 71

24 26 50


References

American Society of Agricultural Engineers. 1985. ASAE Standards
1985. ASAE, St. Joseph, MI.

Asian Productivity Organization. 1983. Farm Mechanization in
Asia. APO, Tokyo. pp. 6.

Chancellor, William J. 1977. The role of fuel & electrical
energy in increasing production from traditionally based
agriculture. East-West Food Inst., East-West Ctr., Honolulu.

Giles, G.W. 1967. Agricultural power and equipment. In The
World Food Problem, Vol. 3, Rpt. of President's Sci. Adv. Comm.,
White House, Washington, D.C.

Makhijani, Arjun. 1975. Energy and Agriculture in the Third
World. Ballinger Pub. Co., Cambridge, MA. (HD, 1417, .M34 in
Library East)

Revelle, Roger. 1976. Energy use in rural India. Science
192:969-975.

Stout, B.A. 1979. Energy for World Agriculture. FAO, UN,
Rome.


--------------------------------------










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 12
Humans as Mechanical Energy Sources


The power and energy that a human can produce is limited when
compared with other power sources used in agriculture. The "rule-
of-thumb" human power output is approximately 0.1 horsepower or 75
watts, or 0.25 MJ/h. That power level can be sustained for
several hours per day so that daily mechanical energy output or
useful work can be as high as 1 horsepower-hour or 0.75 kilowatt-
hour or 2.5 MJ. It typically however is less, 0.5 to 1.5 MJ/d
(Fluck, 1981). Smil (1979) suggested annual useful work by a
human to be in the order of 300 to 500 MJ. This annual useful
work is about the equivalent of a one horsepower motor working
full time for one to two weeks, or the equivalent of only a few
gallons of liquid fossil fuel. The economic value of this
relatively small amount of mechanical energy as supplied by other
energy sources is obviously quite small. Despite these low
individual values, the power and energy which can be produced by
4.3 billion humans is considerable, as evidenced by the lasting
evidences of human labor on the face of this planet.

Much of the energy expenditures by humans is reported in terms of
the food energy metabolized rather than the mechanical energy or
useful work expended, which is a much smaller value. One must
therefore be careful whether reported data is in terms of food
energy input or mechanical energy output; most are the former.
Man, just as the other animals, converts chemical energy in food
to mechanical energy with a rather low efficiency, typically in
the order of only a few percent of total food energy consumption
when working or 20-30% of the added food consumption expressly
required for working.

Total daily food energy consumption for an adult human varies with
sex, size, climate, physical activity, etc. and generally ranges
from somewhat less than 2000 kcal to over 4000 kcal (3.12-6.24
hph, 8.37-16.75 MJ, or 2.33-4.65 kWh). Much of this energy, in
the order of 6-8 MJ/d, is required for basal metabolism of the
body and normal non-work activities and is not available to
produce mechanical energy. Metabolism of food energy when
sleeping is in the order of 0.20 to 0.25 MJ/h; that during the
most leisurely awake activities about 0.4 MJ/h.

Additional energy requirements for various tasks (in terms of food
energy intake), vary from about 0.25 MJ/h upward to above 5.00
MJ/h depending on the severity of the work. Passmore and Durnin
(1955) in a standard source for such data. Stout (1979) gave a
number of examples (Table 1). These values are total food energy
expenditure; about 0.4 to 0.5 MJ/h should be subtracted from these










values to obtain the added effect of the labor involved over light
non-sleep activities. Mechanical work done, if any, is only a
portion of the net difference. The remainder must be discarded to
the environment by the worker as heat. Environmental factors of
temperature, humidity and radiant energy control the amount
discarded and therefore also control the amount available as work
output (Raeburn, 1984).

Table 1. Total Food Energy Requirement When Performing Various
Tasks
-------------------------------------------------------------------
Activity Energy
MJ/h
-------------------------------------------------------------------
Sitting 0.41
Walking
Asphalt 1.41
Grass 1.56
Stubble 1.73
Plowed field 1.91
Shovelling 1.51-2.64
Pushing wheelbarrow 1.26-1.76
Mowing with a scythe 1.71
Weeding 0.83-1.33
Loading shocks onto carts 1.41
Clearing bush 1.53-1.78
Hoeing 1.11
Plowing with horse 1.28-1.48
Plowing with tractor 1.05
Milking by hand 1.18
Tree felling 2.06


Norman's (1978) partitioning of human metabolic and work energy
relationships is convenient: In terms of food energy consumption,
he generalized that total or gross work energy expenditure is 1.00
MJ/h and that basal metabolic energy expenditure is 0.25 MJ/h;
therefore net work energy expenditure is 0.75 MJ/h. To carry his
analysis a step further, the portion of net (food) energy
expenditure converted to mechanical energy is about one third that
or 0.25 MJ/h.

It is probable that, beginning from a low power output level,
overall efficiency of food energy conversion to mechanical energy
increases as work load and output power level increase, at least
to some level. Then, energy conversion efficiency probably
decreases as power level continues to increase.

Norman (1978) emphasized the fact that in many subsistence
agricultural systems the energy output in produced food is
approximately equal to the energy required and consumed by the
human farmers in growing the food. That is, the system is
operating in equilibrium with neither subsidies nor surpluses.











References


Fluck, Richard C. 1981. Net energy sequestered in agricultural
labor. Trans. ASAE 24(6):1449-1455.

Freedman, Stephen M. 1982. Human labor as an energy source for
rice production in the developing world. Agro-Ecosystems
8:125-136. (S, 601, .A37 in Hume Library)

Norman, M.J.T. 1978. Energy inputs and outputs of subsistence
cropping systems in the tropics. Agro-Ecosystems 4:355-366. (S,
601, .A37 in Hume Library)

Passmore, R., and J.V.G.A. durnin. 1955. Human energy
expenditures. Physiol. Rev. 35:801-840.

Raeburn, J.R. 1984. Agriculture: Foundations, Principles, and
Development. John Wiley & Sons Ltd, New York. pp. 113-115.

Smil, Vaclav. 1979. Energy flows in the developing world. Amer.
Scientist 67(5):522-531.

Stout, B.A. 1979. Energy for World Agriculture. FAO, UN,
Rome. pp. 211-221.












Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 13
Draft Animal Force, Power and Energy


The force, energy and power available through the use of draft
animals exceeds considerably that available from a human being.
Humans using draft animals can therefore amplify their own
capabilities, thereby increasing human labor productivity. Power
outputs of draft animals range from about 0.3 to 0.75 kW, compared
to a human's 0.075 kW. Force or draft which a draft animal can
exert over a long period of time range from about 10 to 15% of
body weight; body weights range from 80 (donkey) to 900 (bullock
and buffalo) kg.

Useful work performed by draft animals depends upon species, size
and height, speed, environmental conditions, and time worked.
Speed when performing field operations ranges from 0.5 to 1.0 m/s.
Time worked ranges to in the order of 2000 h/yr but is typically
only a few hundred hours per year.

A "rule-of-thumb" for work performance of draft animals is that
the animal can exert a tractive force (draft) of 10% of its body
weight at a speed of about 1 m/s for up to 10 h/d (Brody, 1974;
FAO, 1972). A good sized horse can thus produce one horsepower
continuously for a day's work.

Sustainable draft force exerted by draft animals varies from about
0.10% of their weight for some oxen to about 0.25% of their weight
for donkeys. Draft forces exertable depend upon the surface on
which the animal walks. Maximum draft force which a draft animal
can exert over a short time interval can be considerable. FAO
(1972) indicates oxen can exert up to their weight, and that
donkeys and horses can exert up to twice their weight.

Animals are also used by man for their load carrying capacities.
Spedding (1975) cited load carrying capacities ranging from 40 kg
for reindeer to 250 kg for the camel, and they may be as much as
half the animal's weight in the case of the donkey. If roads and
freight vehicles permit, however, draft animals can transport much
larger loads by pulling them, even by sled and particularly by a
wheeled vehicle, than by carrying them.

Draft animal power varies with species. Stout (1979) gave values
(Table 1):










Table 1. Estimated Normal Draft Power of Various Animals

Species Weight Avg. Speed Power
(kg) (m/s) (kW)

Light horse 400-700 1.00 0.75
Bullock 500-900 0.60-0.90 0.56
Buffalo 400-900 0.80-0.90 0.56
Cow 400-600 0.70 0.34
Mule 350-500 0.90-1.00 0.52
Donkey 200-300 0.70 0.26


Annual power output of draft animals ranges (Guyol, 1977) from 150
kWh for asses, 450 kWh for mules, 550 kWh for oxen, to 600 kWh for
horses, buffalo and camels.

Norman's (1978) partitioning of draft animal metabolic and work
energy relationships is convenient: In terms of feed energy
consumption, he generalized that total or gross work energy
expenditure is 6.0 MJ/h and that basal metabolic energy
expenditure is 1.5 MJ/h; therefore net work energy expenditure is
4.5 MJ/h. To carry his analysis a step further, the portion of
net (feed) energy expenditure converted to mechanical energy is
about one third that or 1.5 MJ/h (0.42 kW).

The energetic efficiency of draft animals is a subject of
considerable interest and some complexity. Brody (1974) defined
several efficiencies:

Work accomplished
Gross eff. = ----------------
Energy expended

Work accomplished
Net eff. = ----------------------------
Energy expended above that expended at rest

Work accomplished
Absolute eff. = --------------------------------------------
Energy expended above that of walking sans load


He observed maximum efficiencies for horses of 25%, 28% and 35%
respectively; typical efficiencies were considerably less.
Efficiencies increased with speed to a maximun at 5-6 km/h
(1.4-1.7 m/s). Efficiencies also increased asymptotically with
increasing power output to the maximums indicated above. Gross
efficiencies vary with portion of time the horse is worked (Table
2) (Spedding, 1975).











Table 2. All-day Gross Efficiencies for Horses
---------------------------------------------------------------
Hours Worked Work Output Energy Expended Efficiency
(MJ) (MJ) 7.
------------------------------------------------------------------
12 32.2 195.1 16.5
10 26.9 172.9 15.5
8 21.5 150.3 14.3
6 16.1 128.1 12.6
4 10.8 105.5 10.2
2 5.4 83.3 6.4
0 0.0 61.1 0.0
------------------------------------------------------------------

The time per day which draft animals can be worked varies from 3
to 6 hours in tropical climates to 8 to 10 hours in temperate
climates (FAO, 1972), thereby affecting the daily energy output
obtainable.

Draft animals and beasts of burden have served man well in the
past and seem to be in many cases appropriate technology for
agriculture today.


References

Brody, Samuel. 1974. Bioenergetics and Growth. Hafner Press, a
Div. of MacMillan Pub. Co., new York. pp. 898-917.

Food and Agricultural Organization of the United Nations. 1972.
Manual on the Employment of Draught Animals in Agriculture. FAO,
UN, Rome. pp. 23-32.

Guyol, Nathaniel B. 1977. Energy Interrelationships. Federal
Energy Adm., Washington, D.C.

Norman, M.J.T. 1978. Energy inputs and outputs of subsistence
cropping systems in the tropics. Agro-Ecosystems 4:355-366. (S,
601, .A37 in Hume Library)

Smil, Vaclav. 1979. Energy flows in the developing world. Amer.
Scientist 67(5):522-531.

Spedding, C.R.W. 1975. The Biology of Agricultural Systems.
Academic Press, New York. pp. 166-168.

Stout, B.A. 1979. Energy for World Agriculture. FAO, UN,
Rome. pp. 211-221.

Ward, Gerald M., Thomas M. Sutherland, Jean M. Sutherland. 1980.
Animals as an energy source in Third World agriculture. Science
208: 570-574.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 14
Manual Tools and Equipment for Field Operations


Among man's first agricultural tools may have been a pointed stick
for digging, for tilling the soil and planting seeds. Other tools
also came into use to serve several other functions in field
operations. These primitive hand tools evolved independently and
to many different forms in different geographical areas in order
to meet local conditions. Among the functions met by hand tools
are primary tillage, planting, cultivation and weeding, crop
protection and harvesting. Manual tools for non-field operations;
irrigation, crop processing and transportation; will be treated in
subsequent lectures rather than here.

The importance of manual tools is evident from statistics such as:
84% of Kenya's arable land is cultivated with hand tools, 12% with
animal power, and 4% with tractors (Ahmed and Kinsey, 1984, mid-
1970's data).

Manual tools for primary tillage include a wide assortment, but
most can be classified as either digging hoes, shovels or spades,
and digging forks. Boyd (1976, pp.21-22) shows examples of each.
Many are manufactured in LDC's. He suggests the digging hoe, a
large and heavy hoe, remains most popular in LDC's. It is the one
of these tools which is swung to enter the soil rather than simply
being pushed into the soil at low velocity, thereby transferring
significant stored kinetic energy upon impact. Increased weight
in the head of the hoe used in this manner is advantageous. The
digging hoe is not dissimilar in general configuration and use to
the mattock (Boyd, 1976, pp.149), another tool used for digging,
especially in land with roots and stumps, and one which is likely
more familiar to Westerners.

Crossley and Kilgour (1983, pp. 59-60) show how the digging hoe is
used. The hoe is swung over the head and downward with a power
stroke to enter the soil, then the farmer tilts the handle upward,
leveraging the severed chunk of soil back towards him. Shovels
and spades and digging forks are used by inserting the tool into
the soil and tilting and/or lifting the soil to break or turn it.
Force is applied with hands and/or feet (Blandford, 1976, pp.86-
89). The digging hoe may be a more suitable tool for primary
tillage, especially in dry soil. Boyd suggests work rates of 0.01
to 0.033 ha/d for manual primary cultivation, depending on
cultivation depth and soil conditions.

Another manual tool, which is widely used in many variations for
cutting of vegetation, both in clearing and in harvesting, is the
machete, cutlass, or bill hook (Boyd, pp. 105-106, 149-150).











These two tools, the hoe and the machete, are widely considered
the most basic of manual tools, ones which many subsistence
farmers could not do without.

Manual tools for cultivating, including weeding, are found in
several general types. Hoes, either with a solid blade or with
tines, are widely used (Boyd, pp.21-22; Green River Tools, 1985,
pp.5) with a chopping or pulling motion. Push-type hoes (Boyd,
pp.21; Green River Tools, pp.6) and stirrup hoes (Green River
Tools, pp.6) are pushed, or pushed and pulled, so that weeds are
severed at or just below the soil surface. Wheel hoes (Boyd,
pp.22-25; Green River Tools, pp.10) are pushed by rolling the
two-handled cultivator through the field; various types of soil
contacting tools are used, including sweeps, tines and stirrups.
Rice paddy weeders (Boyd, pp.25) aerate the soil in addition to
weeding. Manual weeding methods remain appropriate in many
circumstances because of their low power requirements and despite
their large time requirements.

Manual seeding devices include dibblers, jab planters, wheeled
seeders, and "cyclone"seeders. Dibblers are used to make holes
in which seed are subsequently manually placed (Blandford, pp.
74-77). Jab planters (Boyd, pp. 43) are walking stick type
planters which combine the functions of dibbling a hole and seed
placement, with total flexibility of seed placement Wheeled
planters (Boyd, pp.43-49; Blandford, pp.75-80; Green River Tools,
pp. 9) are manually-operated wheeled seeding devices which meter
seed by various methods and usually place seed in a straight line
at regular intervals. "Cyclone" seeders (Green River Tools, pp.9;
Boyd, pp.53), having their origins with the seed fiddle
(Blandford, pp.74-75), are useful for broadcast seeding of small
seed. Manual methods of seeding remain appropriate in many
circumstances due to their low power requirements.

Manual harvesting devices take several basic forms. The sickle
(Boyd, pp.105-106; Green River Tools, pp. 29) was one of the
earliest agricultural tools; it is used for cutting small grain
and forage in a crouching, squatting or kneeling position. The
scythe (Boyd, pp.105-106; Green River Tools, pp.30) allows the
harvester to stand; cutting rates are 0.2 to 0.8 ha/d. The cradle
(Blandford, pp.113-114; USDA, pp.23), a scythe with a catching
surface added, catches the falling cereal grain until the proper
amount is collected and dumped for tying. Manually operated,
2-cycle air-cooled engine powered brush cutters/reapers (Boyd,
pp. 107-108) allow less drudgerous cutting of forages and weeds.

Other manual tools associated with harvesting include the rake and
the fork. Blandford (pp.122-124) terms these as hand gathering
tools, but forks find function in materials handling and rakes in
seedbed preparation as well.

Manual equipment for pesticide application takes several forms and
is widely used. Boyd (pp.53-60) details various granule











applicators, plunger and bellows dusters, and rotary fan dusters.
Sprayers seem to be more widely used than dusters, with types
including slide action sprayers, continuously pumped knapsack and
shoulder-carried sprayers, compression type sprayers, and engine-
powered knapsack sprayers. Application rates (area covered per
unit time) are set by human walking speed, and seem generally
suitable for LDC agriculture.


References

Ahmed, Iftikhar, and Bill H. Kinsey. 1984. Farm Equipment
Innovations in Eastern and Central Southern Africa. Gower Pub.
Co., Brookfield, VT. pp.2.

Blandford, Percy W. 1976. Old Farm Tools and Machinery. An
Illustrated History. Gale Research Co., Fort Lauderdale.

Branch, Diana S., ed. 1978. Tools for Homesteaders, Gardeners,
and Small-Scale Farmers. Rodale Press, Emmaus, Pa.

Crossley, Peter and John Kilgour. 1983. Small Farm Mechanization
for Developing Countries. John Wiley & Sons, New York.

Green River Tools. 1985. Catalog of the Green River Tools
company. Brattleboro, VT.

Intermediate Technology Publications Ltd. 1985. Tools for
Agriculture, A Buyer's Guide to Appropriate Equipment. 3rd ed.
I.T. Pub. Ltd., London.

Raeburn, J.R. 1984. Agriculture: Foundations, Principles and
Development. John Wiley & Sons, New York. pp. 113.

United States Department of Agriculture. 1960. Power to Produce,
The Yearbook of Agriculture. USDA, Washington, D.C.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 15
Draft Animals and Associated Implements


A first consideration in the use of draft animals is the method of
harnessing the animals' efforts can be productively utilized. FAO
(1972) provides perhaps the best current and most comprehensive
treatment of harnessing draft animals, though Crossley and Kilgour
(1983) also treat this subject. Harnessing methods and equipment
or gear vary widely with species and geographical area. Forces
generated by the animals' traction against the ground must be
effectively and efficiently transferred from the body of the
animal to a pulled implement or to support a carried load and
without undue restriction or irritation to body surfaces. Thus
harnesses have demanding specifications. Smith (1981) examples
oxen yoke inefficiency (an uncomfortable yoke when redesigned
allowed a steer to increase its pulling load from 30 to 50 kg) and
cruelty.

Horses are generally harnessed with some combination of collar
around the neck, breast strap across the chest, and weight
suspended from the back; these elements are tied together by the
entire harness assembly from which force is applied to the
implement with trace chains and, with tongued implements, a
breasttree. Horses are controlled by reins attached to a head
bridle and a mouth bit and by voice commands. Oxen are generally
harnessed with yokes, either neck yokes or head yokes (the latter
not recommended by Crossley and Kilgour, 1983). Implements
are attached to the yoke with chains or ropes. Oxen are
controlled with reins or rope attached to their horns or ears
and/or to a nose ring and by voice commands.

Implements for use with draft animals follow the same functions as
tools for human use, with some additions. FAO (1972) lists
several criteria important for implements for draft animals: light
weight, simple, robust, and low cost. It is obvious that design
compromises are frequent.

Plows for primary cultivation with draft animals vary considerably
(ITS, pp. 17-20; FAO, pp. 79-105). Plowing methods and equipment
vary considerably with rainfed versus irrigated farming, with
whether or not organic matter is incorporated, with whether or not
the soil is inverted, etc. Moldboard plows may or may not have
support wheels. It seems that few for use in LDC agriculture have
provision for the farmer to ride. Additional seedbed preparation
and weed control may be accomplished with a wide variety of
cultivators; toothed, tined and disc harrows; and miscellaneous
other devices (ITG, pp. 21-24, 42-44; FAO, pp. 106-135, 160-172).
Some of these implements allow the farmer to ride rather than










walk. Wheeled toolcarriers for use with draft animals to which
various tools can be attached have been the subject of
considerable research and are gaining some popularity (ITS,
pp. 45-55; FAO, pp. 116-124).

Seeders, planters and transplanters can be animal drawn as well as
manually operated; ITS (pp. 65-68) and FAO (pp. 140-151) showed
several examples FAO (pp. 151-156) examples fertilizer and
manure distributors and spreaders. It appears that animal powered
harvesting devices, such as reapers, mowers, etc., are not widely
used in LDC agriculture, despite the fact that the technology is
old and well known. A number of various plow-type devices for
peanuts and root and tuber crops are used, however (FAO, pp. 178-
183).

Working rates for draft animals vary with species, condition,
size, environment, implement and other factors. Clark and Haswell
(1970) example plowing rates for a pair of oxen or buffalo ranging
from 0.12 to 1.0 ha/d; this with the animals working as much as 7
h/d. CAST (1977) suggests a team of horses could plow about 0.8
ha/d. Working rates for draft animals are governed by the same
equation as tractors and their implements: C = SWE, where C is
field capacity, S is forward speed, W is width of implement, and E
is field efficiency. A team of draft animals plowing with a 0.30
m wide plow at 1 m/s and a field efficiency of 75% will plow 0.082
ha/h.

Total draft animal time over a season to perform the various field
operations necessary to produce a crop was documented by Leach
(1976) in various agricultural systems to range from 120 to 642
h/ha and averaging 302 h/ha. Norman (1978) gave values from India
ranging from 60 to 210 h/ha and averaging 108 h/ha.

Animal diseases are a hindrance to increased draft animal usage in
LDC agriculture (Crossley and Kilgour, pp. 70-77) Trypanosomiasis,
transmitted by the tsetse fly, infests tropical lowland Africa.
Rinderpest, foot and mouth disease, and anthrax are some of the
other important diseases limiting draft animal use.


References

Branch, Diana S. 1978. Tools for Homesteaders, Gardeners, and
Small-Scale Farmers. Rodale Press, Emmaus, Pa.

Clark, Colin and Margaret Haswell. 1979. The Economics of
Subsistence Agriculture. MacMillan and Co Ltd, London.

Council for Agricultural Science and Technology. 1977. Energy
Use in Agriculture: Now and for the Future. Rpt. No. 68. Ames,
Iowa.

Crossley, Peter and John Kilgour. 1983. Small Farm Mechanization
for Developing Countries. John Wiley & Sons, New York. (pp. 61-










78).

Food and Agricultural Organization of the United Nations. 1972.
Manual on the Employment of Draught Animals in Agriculture. FAO,
UN, Rome. pp. 23-32.

Intermediate Technology Publications Ltd. 1985. Tools for
Agriculture, A Buyer's Guide to Appropriate Equipment. 3rd ed.
I.T. Pub. Ltd., London.

Leach, Gerald. 1976. Energy and Food Production. IPC Science
and Technology Press Ltd., Guildford, England.

Norman, M.J.T. 1978. Energy inputs and outputs of subsistence
cropping systems in the tropics. Agro-Ecosystems 4:355-366. (S,
601, .A37 in Hume Library)

Smith, A.J. 1981. Draught animal research; A neglected subject.
World Animal Rev. 40:43-48.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 16
Single Axle Tractors


Small tractors in the power range of about 2 to 12 kW (2.7 to 16.1
hp or 7.2 to 43.2 MJ/hr) and having only one axle are known by
several names, including single axle tractors, two wheeled
tractors, walking or walk-behind tractors, pedestrian tractors,
hand tractors and power tillers. This type of tractor is not
normally treated to any extent in the standard tractor textbooks;
Liljedahl, et al., (1984) recognize power tillers as a tractor
type but ignore it in their treatment of such important topics as
tractor statics and dynamics and human factors engineering. In
fact, SAE's (Society of Automotive Engineers') definition of
agricultural tractor excludes single axle tractors on the basis of
their having less than 15 kW net engine power. The Nebraska
Tractor Tests, the standard for tractor testing in the United
States, do not include tractors with power outputs this low. The
ASAE Book of Standards does not include any standards specifically
applicable to single axle tractors.

The single axle tractor may have had its origin with the 1915
Elbert-Duryea (Gray, 1974), a 12-16 hp tractor which had two large
drive wheels, one small wheel for balance and no provision for the
farmer to ride. The 1917 Allen Water Ballast and the 1917 Moline
were similar. The single axle tractor was commonly used for
several decades in industrialized countries as a garden tractor,
but was adapted for use in LDC agriculture after World War II.
It seems ironic that the single axle garden tractor once popular
for industrialized country garden use has now mainly been
supplanted by rotary tillers and four wheel riding lawn and garden
tractors. APO's 1979 survey of member countries showed numbers of
tractors (Table 1). The total number of power tillers in these
countries exceeded 3 million.

In 1978 Peoples' Republic of China had 1.37 million walking
tractors in use and 0.557 million riding tractors (Esmay and
Harrington, 1979). This is 1.07 walking tractors and 0.44 riding
tractors per 100 hectares of arable land.

The advantages of single axle tractors which make them appropriate
technology in many LDC agricultural applications include:
1. Increased power availability compared with humans and draft
animals.
2. Low cost compared with four wheel tractors. Less power,
weight, and complexity leads to lower costs.
3. Energy inputs are required only when working. Draft animals
and human laborers eat daily and year round.
4. The single axle tractor is the right size, in terms of power










per unit area, for the farmer who tills a few hectares of
land.
5. Small size leads to increased manuverability in small fields
with less land dedicated to headlands or endrows as well as
ability to travel on narrow roads.

Table 1. Number of tractors on farms in 1979 in APO (Southeast
Asia) Countries per 100 hectares of arable land

Country Power Tillers 4-Wheel Tractors

Japan 50.4 26.9
Korea, Rep. of 13.2 0.1
China, Rep. of 7.3 0.3
Thailand 1.4 0.3
Philippines 0.9 0.3
Sri Lanka 1.0 1.8
Indonesia 0.017 0.012
Nepal 0.015 0.11
India 0.01 0.23
Pakistan 0.36


Disadvantages of the single axle tractor are several. Operation
of single axle tractors can be very tiring and require
considerable skill. Traction (draft forces generated) of tractors
is limited to a portion of tractor weight, typically in the order
of half the weight. Single axle tractors, weighing only up to a
few hundred kilograms, can therefore develop only a couple of
hundred kilograms or a couple of kilonewtons force. This mostly
limits plows to one moldboard and secondary tillage tools to one
meter width. Fuel consumption of properly loaded single axle
tractors per unit of land area worked is typically greater than
that of properly loaded larger tractors; energy productivity is
less with smaller equipment.

Two variations of the single axle tractor exist; the rotary
tiller, whose wheels, if it indeed has wheels, provide little if
any traction force (ITS, pp. 26-30), and the motor mower, a single
axle tractor with an integral sickle bar mower (ITG, pp. 125-126).
Some rotary tillers can be fitted with drive wheels and other
attachments and are therefore essentially identical with single
axle tractors. Others have two axles, one for wheels and the
other for the rotary tiller.

The single axle tractor is typified as having an air-cooled engine
of 2 to 15 or more kW, usually diesel for larger engines with
gasoline available in smaller sizes, handlebar steering with
controls integrally mounted, multiple forward and rear speeds,
attachment for pulled implements and often a power takeoff for
rotary tillage and stationary power needs, and implements designed
and sized for the tractor. Some implements, especially carts,
have provision for the operator to ride. Manufacturers seem to be
centered in Southeast Asia and Western Europe, and use seems to be










centered in softer soils such as rice paddy and in market
gardening in Europe.

Crossley and Kilgour (1983, pp. 162-165) provide a basic static
analysis of the single axle tractor, showing how the farmer's work
and traction characteristics can be made easier with proper
balancing and implement adjustment.


References

Asian Productivity Organization. 1983. Farm Mechanization in
Asia. APO, Tokyo. pp. 6.

Branch, Diana S. 1978. Tools for Homesteaders, Gardeners, and
Small-Scale Farmers. Rodale Press, Inc., Emmaus, PA.

Crossley, Peter and John Kilgour. 1983. Small Farm Mechanization
for Developing Countries. John Wiley & Sons, New York. (pp. 61-
78).

Esmay, Merle L., and Roy E. Harrington, eds. 1979. Glimpses of
Agricultural Mechanization in the People's Republic of China.
American Society of Agricultural Engineers, St. Joseph, MI.

Gray, R.B. 1974. The History of the Agricultural Tractor.
American Society of Agricultural Engineers, St. Joseph, MI

Intermediate Technology Publications Ltd. 1985. Tools for
Agriculture, A Buyer's Guide to Appropriate Equipment. 3rd ed.
I.T. Pub. Ltd., London.

Liljedahl, John B., Walter M. Carleton, Paul K. Turnquist, and
David W. Smith. 1984. Tractors and Their Power Units. AVI
Publishing Co., Inc., Westport, CT.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 17
Riding Tractors


Riding tractors range in power from as low as about 5 kW in the
smallest lawn and garden tractors to over 300 kW in the largest
4-wheel drive agricultural tractors. Manufacturers are located in
most of the larger countries of the world, LDC's as well as
industrialized. The larger tractor manufacturers are
international in scope and their tractors are now mostly assembled
in several countries from components manufactured in many
countries. Most agricultural tractors are now rubber tired;
crawlers are less important now than they once were, though they
are yet used on very soft soils. Diesel engines now predominate.
Most tractors have power takeoffs for power transfer to implements
and integral hydraulic systems for power transfer to and control
of implements. Several types of implement connections are used:
drawbar for towing, 3-point hitch for mounted or semimounted
implements, and frame mounting.

The evolution of tractors has occurred over about 125 years since
the first steam traction engines. Advances have occurred rather
steadily during this interval and continue (Liljedahl, et al.
1984; Gray, 1974). Current directions of continued tractor
development include increased fuel efficiency, increased power
levels, increased speeds, increased power to mass ratio, greater
operator controlthrough improved instrumentation as well as
automatic control of some functions, better operator environment,
etc.

With such a broad range of tractor sizes available, an important
issue is the determination of appropriate size. Now-traditional
methods of optimizing tractor size, i.e., of selecting the best
size for a given farm, fall within the area termed farm machinery
management. Techniques are given by ASAE (1985) and Hunt (1983).
A typical approach is to derive an equation expressing total costs
of owning and operating the tractor and which includes the power
level of the tractor, take the first derivative of that equation
with respect to power, equate it to zero, and solve for the power
level which minimizes costs. The optimum power is the square root
of a complex collection of cost-related factors. Factors in the
numerator under the radical and which when increased lead to
larger tractors include land area, labor cost, and timeliness
costs. Factors in the denominator under the radical and which
when increased lead to smaller tractors include fixed cost
percentage, a factor which includes depreciation and interest.
Experience has proven riding tractors of about 20 kw and larger
to be restricted to cultivated land areas of about 20 hectares and
larger in order to prove economical. Riding tractors of about 20










to 30 kW seem to be the most widely used of all sizes of riding
tractors in LDC agriculture. The availability and acceptance of
riding tractors contributes to consolidation and increased average
size of land holdings.

Singh and Chancelor (1975) investigated Northern India farms with
a range of levels of mechanization, from human and draft animal
power only to tractor and electric or diesel irrigation. They
found that as level of mechanization increased, energy inputs and
yields per unit land area increased, and labor input and costs per
unit of production decreased. This was on farms on which the
levels of mechanization were pre-established and therefore likely
at least somewhat appropriate, i.e., the larger farms (9 and 10 ha
average) had riding tractors. Balis (1974) reviewed several
studies and found similar results. In addition he reported that
the Tractor Evaluation Project found that a power level of 0.4 to
0.5 kW/ha to be adequate under Northern India conditions. Further,
farmers who received tractors as part of the project's research
quickly increased their farming intensity (crops/yr) from about
1.2 to 1.5, and projected increases to 2.0 within five years.

A major advantage of riding tractors is that operating speeds are
not restricted to normal walking speeds of the farmer. Speeds are
instead limited to those proven practically limiting, which
generally range from about 3 to 10 km/hr or about 0.8 to 2.8 m/s,
depending on the operation. Tractor moldboard plowing speeds are
typically 6 to 9 km/hr or 1.6 to 2.5 m/s. Another major
advantage is that increased power availability enables increased
widths of implements to be used. Both factors lead to increased
field capacities and increased labor productivity. A third major
advantage of larger tractors is that, since field capacity is
sharply increased, timeliness of critical field tasks is enhanced,
enabling increased quantity and quality of production. A fourth
advantage is that drudgery of work is decreased with comparison to
human powered, draft animal powered or single-axle tractor powered
field operations.

Numerous efforts have made to develop a small, inexpensive riding
tractor suitable for LDC agriculture. Crossley and Kilgour (1983)
show several examples. A thrust for their attempted development
is presumably to reduce costs below commercially-available small
tractors. Another may be to achieve better visibility and control
over field operations. Inadequate power and traction, lack of
dependability, and lack of manufacturer interest seem to have
dampened such efforts. Though there are a number of smaller
riding tractors manufactured in several countries, they do not
seem nearly as popular as 20 to 30 kW tractors.


References

American Society of Agricultural Engineers. 1985. ASAE Standards
1985. ASAE, St. Joseph, MI.










Asian Productivity Organization. 1983. Farm Mechanization in
Asia. APO, Tokyo. pp. 6.

Balis, John S. 1974. The utilization of small tractors in
integrated agricultural development: The tractor evaluation
project applied. Cornell Agr. Econ. Staff Paper No. 74-15.
Cornell Univ., Ithaca, N.Y.

Crossley, Peter and John Kilgour. 1983. Small Farm Mechanization
for Developing Countries. John Wiley & Sons, New York. (pp. 61-
78).

Esmay, Merle L., and Roy E. Harrington, eds. 1979. Glimpses of
Agricultural Mechanization in the People's Republic of China.
American Society of Agricultural Engineers, St. Joseph, MI.

Gray, R.B. 1974. The History of the Agricultural Tractor.
American Society of Agricultural Engineers, St. Joseph, MI

Hunt, Donnell R. 1983. Farm Power and Machinery Management, 8th
Ed. Iowa St. Univ. Press, Ames.

Liljedahl, John B., Walter M. Carleton, Paul K. Turnquist, and
David W. Smith. 1984. Tractors and Their Power Units. AVI
Publishing Co., Inc., Westport, CT.

Singh, Gajendra, and William Chancellor. 1975. Energy inputs and
agricultural production under various regimes of mechanization in
Northern India. Trans. ASAE 18:(2):253-259.











Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 18
Processing Equipment: Threshers, Shellers,
Cleaners, Grinders, Mills


Post-harvest processing of food, feed and other agricultural
products is as necessary in LDC's as in industrialized
agriculture. Among the ways by which we can examine available
and potential equipment are function which the equipment performs
and power source for the equipment.

Functions performed by agricultural processing equipment can be
generalized and identified by such names as: reduction or
comminution (grinding, milling), disassociation (threshing,
shelling), separation (cleaning), mixing, and classification
(sizing, grading). Often there are similarities among various
machines which perform a particular function, irrespective of the
agricultural commodity.

Power sources for agricultural processing equipment may range from
human through draft animal to internal combustion engines and
electric motors, and include a few others in addition. Many
processing operations require a known amount of energy to process
a given quantity of material and the equipment can be scaled up or
down or the throughput adjusted dependent upon the power available.
Processing machines which are human powered may be hand cranked or
pedal or treadle driven. Processing machines which are draft
animal powered are usually driven by a gear arrangement which
allows the animals to walk a circular path while pulling a
suspended shaft.

Crossley and Kilgour (1983, pp. 30-32) illustrate the principles
of small threshers and indicate energy requirements of 8 to 16
Wh/kg of threshed rice for engine driven and 1 Wh/kg for human
power (at 75 W/hr; the seeming discrepancy is not explained).
ITG (1985, pp. 127-132) show numerous examples, many powered by
engines or motors. Power requirements range from 1.5 to 11 kW
and output of threshed grain ranges from 60 to 4000 kg/h. This
compares to capacities of 5000 to 20,000 kg/h for the threshers
used in America in the late 1800's and early 1900's. Power
requirements average 16.9 W per kg/h of capacity. ITS also
shows several threshers for rolling grain on a threshing floor.
Darrow and Pam (1981) show additional examples of appropriate
technology threshers on pp. 95 to 97.

Winnowers are used for blowing chaff and low quality grain from
good grain; ITG (1985, pp. 137) shows several examples,
including human powered.










Seed cleaners and graders (Crossley and Kilgour, 1983, pp. 32;
ITS, 1985, pp. 148-149; Hall, 1963, pp. 71-91; Henderson and
Perry, pp. 152-176) are used to provide high quality seed and
grain.

Shellers for corn (maize) are shown and described by Crossley and
Kilgour (1983) on pp. 30-31. ITS (1985, pp. 133-137) shows
numerous examples. Manual corn sellers have outputs from 30 to
150 kg/h, inferring a human energy requirement of 2.5 to 5 Wh/kg.
Engine and motor driven corn sellers have outputs to several
thousand kg/h and power requirements averaging 2.6 W per kg/h of
capacity.

ITS (1985, pp. 158) shows several peanut decorticators,
sellerss or threshers), especially important in African
agriculture. Both manual and engine powered versions are shown.

Grinding mills for size reduction of grains are based on several
principles. Hammer mills have swinging weights (hammers) rotating
at high velocity; power requirements start at 2.5 kW for 75 kg/h
capacity (Crossley and Kilgour, 1983, pp. 25-26; Henderson and
Perry, 1955, pp. 128-130; ITS, pp. 154) and they thus require
motor or engine power. Plate mills or burr mills (Crossley and
Kilgour, pp. 25; ITS, pp. 150-152; Henderson and Perry, pp. 131-
132) are suitable for hand cranking (capacities of 5 to 50 kg/h)
as well as motor or engine power (50 to 600 kg/h and power
requirements ranging from 3 to 25 watts per kg/h of capacity).
Henderson and Perry (1955, pp. 138) show energy requirements for
both hammer mills and plate mills; total range is from
approximately 4 to 12 Wh/kg, with the plate mill requiring less
energy than the hammer mill. Roller mills (Crossley and Kilgour,
pp. 26-27; ITS, pp. 152-153) are used for flaking grain (4 to 8
Wh/kg) and removing rice husks (2.5Wh/kg).

Among the other available processing equipment suitable for LDC
agriculture are rice hullers (Crossley and Kilgour, pp. 28-29,
ITS, pp. 115-157), coffee hullers (Crossley and Kilgour, pp. 30;
ITS, pp. 159), chaff cutters (ITS, pp. 162-163), root
cutters (ITG, pp. 161), coffee pulpers (ITS, pp. 159), and
cane crushers or squeezers (ITS, pp. 161-162).


References

Branch, Diana S. 1978. Tools for Homesteaders, Gardeners, and
Small-Scale Farmers. Rodale Press, Inc., Emmaus, PA.

Crossley, Peter and John Kilgour. 1983. Small Farm Mechanization
for Developing Countries. John Wiley & Sons, New York. (pp. 61-
78).

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook: Vol. 1. Volunteers in Asia, Stanford, CA.










Hall, Carl W. 1963. Processing Equipment for Agricultural
Products. Agr. Engr. Assoc., Inc., Reynoldsburg, OH.

Henderson, S.M., and R.L. Perry. 1955. Agricultural Process
Engineering. John Wiley & Sons, Inc., New York.

Intermediate Technology Publications Ltd. 1985. Tools for
Agriculture, A Buyer's Guide to Appropriate Equipment. 3rd ed.
I.T. Pub. Ltd., London.











Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 19
Driers for Grain ond Other Agricultural Commodities


Both grains and numerous other agricultural commodities are dryed,
primarily to enhance preservation. Among the non-grain
commodities are fish and other meats, fruits and vegetables,
copra, coffee, and tea. Primitive methods of drying consisted of
simply exposing the product to the sun and air, in some cases on
frames or racks and in others simply spread out on the ground or
another surface in a thin layer. Current low technology driers
are not much more complex than that, though they may provide
protection from insects and other pests as well as enhancement of
air movement and multiple layers of product.

Drying or dehydration consists of the removal of moisture from a
product. In order to evaporate moisture, heat is needed
(approximately 2.50 to 2.67 MJ/kg of water evaporated, depending
upon the water temperature). Further, air flow is useful in
removing the water-laden air surrounding the product and in
replacing it with low humidity air to continue further
evaporation. Finally, low humidity air is helpful both in
effecting faster evaporation and in preventing re-wetting of the
product.

In low technology drying, the heat source is most often the
sun, whether the product is directly exposed to sunlight or whether
air is heated by sunlight and passed over or through the product.
However, other sources of heat may also be used: wood, charcoal,
crop residues, etc.

The maximum temperature to which the product is exposed is
important for some products. Seeds for germination should not be
exposed to temperatures above about 35 to 40 C. Products for
human consumption should not be exposed to certain products of
combustion in order to minimize off-flavors, carcinogens, etc.

Final moisture content for most agricultural products, to enable
long-term storage, should be about 12 to 14% moisture by weight.
Since initial moisture content can be much higher, up to about
95%, considerable size and weight reduction can occur upon
drying.

NAS (1976) reviewed solar crop drying, noting that it "is perhaps
the most ancient and widespread of all the direct uses of solar
energy". Crops are spread on the ground in a thin layer for
direct exposure to the sun and wind, as well as to wind-driven
dirt, rain, insects, vermin and birds! Periodic stirring by
manual means speeds drying and prevents overdrying. Stout (1979)










reported on IRRI trials of several surfaces; rice dried fastest on
asphalt, followed by concrete, woven matting, synthetic jute
sacking, and clear polyethylene sheeting. Moisture content of
a 3 cm deep layer was reduced from 23-24% to 14% or less with all
surfaces in 4-5 hours.

Numerous designs have been developed for small solar dryers (NAS,
1976). Some have a stack or chimney to enhance air flow utilizing
the natural buoyant effect of heated air. Solar dryers may
include a glass or other transparent surface through which the
solar radiation passes before it heats the product, air or another
material. Solar dryers can be locally constructed of mostly
locally produced and locally available materials. The use of
solar energy in this manner is both simple and cheap.

Larger scale but yet low technology solar dryers may take the form
of an air-inflated plastic tube or tunnel to collect the solar
energy with heated air being forced through the collector and the
stored product by a fan powered by a motor or engine. A low
energy dryer of perhaps appropriate technology is that developed
by Shaw and which consists of a producer gas powered motor-
generator set and fan to force air over all components to extract
most all waste heat which is forced through the product to be
dried.

Darrow and Pam (1981, pp. 118-126) reviewed several sources of
dryer information and designs, including simple racks, the use of
sulfur as a preventative against discoloration and some insects,
various solar dryers or cabinets, and others. One unique grain
dryer they describe consists of a horizontal 16 foot diameter
sheet metal surface over a fire pit with an animal-pulled stirrer
to prevent overheating of the grain. This dryer can dry 450 kg of
rice from 24% moisture to 14% in 4 hours using 75 kg of straw as
fuel.


References

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook: Vol. 1. Volunteers in Asia, Stanford, CA.

National Academy of Sciences. 1976. Energy for Rural
Development. NAS, Washington, D.C. (pp. 79-81)

Stout, B.A. 1979. Energy for World Agriculture. FAO, UN, Rome.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 20
Manually Operated Pumps and Other Water Lifting Devices


Human powered pumps are suitable for irrigating small areas of
land and for providing water for livestock and human consumption.
The quantity of water lifted by a manually operated pump is
limited by the energy available from the persons) powering the
pump. Water flow rate is further limited by the height the water
is lifted, the amount per unit time being inversely related to
lifting height. Water sources for irrigation may be either wells
or bodies of surface water. Once lifted with human power, water
for irrigation is distributed by gravity in furrows or simply by
basin irrigation.

The shaduf, shadoof or well sweep (Israelson and Hansen, 1962, pp.
56-57) "makes use of the principle of the lever with a suspended
fulcrum and a counterweight. The bucket, suspended from the long
end of the pole, is sometimes made of leather, stiffened near the
top with a wooden hoop. The operator throws his weight on the
sweep, the bucket fills, and the counterweight raises it to the
next higher channel into which the water is poured. A single
shaduf is operated by one man, and with it he can lift water only
5 or 6 feet, but the devices are sometimes installed in series of
three or four, thus raising the water 20 feet or more. With the
shaduf one man can raise approximately 20 gpm from 5 to 6 feet."
Stern (1979, pp. 116) shows the Indian "Dall" or "Auge", a
variation of the shaduf.

Water wheels can be used to lift water as well as to extract power
from falling water. Darrow and Pam (1976, pp. 41) show a simple
bamboo water lifting wheel. Maximum lifting height is limited to
somewhat less than the diameter.

The reciprocating or pitcher pump (ITG, 1985, pp. 101-107; Crouch,
1983, pp. 17-47; Stern, pp. 118-121; Darrow and Pam, 1981, pp.
203) is a familiar fixture on many wells. It has a hand-operated
lever which actuates a rod to a piston in a cylinder. If the
cylinder and the handle are in the same mechanism, suction lift
can be as much as about 8 m. If the handle is connected by a pump
rod to the piston located near water level in a cased well, lift
can be more. Manual pumping rates example by Boyd average 3100
1/h. The Spangler pump shown by Crouch is a variation of the
reciprocating pump. Stern (pp. 120) discusses energy
relationships of hand pumps; typical pump efficiency of 60% limits
available human power to about 0.037 kW which must equal the
product of flow rate and lift.










The inertia pump (Crouch, pp. 49-55, Congdon, 1977, pp. 93; VITA,
1970, pp. 97-100) is an extremely simple pump; the pump itself
moves up and down as actuated by the handle, lifting water as it
rises and holding and releasing it as the pump is lowered.

The Archimedes screw, said to have been invented by Archimedes
about 200 B.C. (Stern, pp. 116; Crouch, pp. 77-80) is an auger in
a cylinder which, when set at an incline with the lower end in
water and turned, will raise water. Dimensions of Crouch's
example are 0.46 m dia. and 1.80 m long. Manually operated
Archimedes screws can lift water up to 0.8 m (15,000 1/h) and up
to up to 33,000 1/h (0.25m).

The diaphragm pump exists in several variations (ITG, pp. 113;
Crouch, pp. 1-16). It can be actuated by a reciprocating handle
or the IRRI double diaphragm pump can be stood on and rocked back
and forth to operate (Darrow and Pam, pp. 103). The diaphragm
pump can be built simply using locally available and low cost
materials.

The chain pump (VITA, pp. 92-96; Darrow and Pam, pp. 203-204)
consists of a series of balls or washers on a continuous
recirculating chain which passes through a tube and lifts water
on the side which is rising.

The bucket pump is a series of water lifting buckets on a
continuous recirculating chain (Stern, pp. 117-118). Its
operating characteristics should be similar to those of the chain
pump.

The semi-rotary pump (Stern, pp. 122-123; Boyd, pp. 97) and
helical rotor pumps (Stern, pp. 122-123; Boyd, pp. 96) are
additional types of manufactured hand operated pumps.

The bucket and windlass, another familiar type of water lifting
device, is slow. Lifts are limited only by rope diameter and
windlass capacity.

Table 1. Manual water pumping and lifting devices

Max. rate Max. Lift
Device 1/h m

Shaduf 4500 1.8
Pitcher pump 3500 60 (?)
Archimedes screw 33000 0.8
Diaphragm pump 11000 7.6
Inertia pump 17000 4.0
Chain pump 30000 6.0
Semi-rotary pump 6600 7.5
Bucket and windlass 500 (?) 60 (?)










References


Congdon, R.J. 1977. Introduction to Appropriate Technology.
Rodale Press, Emmaus, PA.

Crouch, Margaret. 1983. Six Simple Pumps. Volunteers in
Technical Assistance, inc. Arlington, VA.

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook. Volunteers in Asia, Inc. Stanford, CA.

Intermediate Technology Publications Ltd. 1985. Tools for
Agriculture, A Buyer's Guide to Appropriate Equipment. 3rd ed.
I.T. Pub. Ltd., London.

Israelson, Orson W., and Vaughn E. Hansen. 1962. Irrigation
Principles and Practices. John Wiley and Sons, Inc., New York.

Stern, Peter. 1979. Small Scale Irrigation. Intermediate
Technology Pub., Ltd., London.

VITA. 1970. Village Technology Handbook. Volunteers in
Technical Assistance, Mt. Rainier, MD.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 21
Draft Animal Powered Pumps and Other Water Lifting Devices


Many of the pumps and other water lifting devices operated by
human labor can be or are also powered by draft animals. The
differences are; 1) that animals can supply higher power rates and
energy levels than can humans, and 2) animals are limited in the
ways in which they can work.

The animal powered chain pump is shown by ITG (1985, pp. 108) and
Crouch (1983, pp. 57-76). Both examples utilize a draft animal
treading a circular path around the chain pump mounted over a
well. ITG's examples are commercially-available units which
incorporate a large gear arrangement to convert direction of the
rotary motion, whereas Crouch's example is a homemade unit which
makes use of an automotive-type differential for that purpose.
Both can be used in dug wells of diameter greater than about 1 m.
Maximum lifts are 13 and 6 m and maximum flow rates are 15,000
and 34,000 1/h respectively.

An animal-powered bucket pump is shown by Darrow and Pam (1981,
pp. 32). Gearing is used to convert the direction of rotary
motion so that the draft animal walks a circular path around the
pump and well.

The Persian wheel or Saqia (Stern, 1979, pp. 123-124) is an
ancient method of lifting water using animal power. It consists
of a water lifting wheel powered by a draft animal treading a
circular path transmitted through a gear arrangement. Lift height
is limited to somewhat less than the wheel diameter. Revelle
(1976, pp. 970) indicated that in India bullocks were used (prior
to 1972) to lift 4 to 6 million hectare meters of water for
irrigation using approximately 4 million Persian wheels and other
unmotorized wells. Working time for lifting water was 7 to 10 %
of total working time. He said that one pair of bullocks can lift
1 hectare meter in 600 hours; no indication was given of lift.
This is an average flow rate when working of 16,667 1/h. Singh
and Chancellor (1975, pp. 252) show a picture of a Persian wheel
in which the gear is connected to the wheel via an underground
shaft enables the water source to be outside the circular animal
path. Further, this Persian wheel is in fact a bucket chain
rather than a water wheel, suggesting that the term "Persian
wheel" applies to perhaps several specific water lifting devices,
all animal powered through a geared arrangement.

The Indian mot (Stern, pp.124) appears to be a rope-pulley-bucket
in well arrangement which is lifted as tha animal walks forward
away from the well, but with which the animal must walk backward










in order to lower the bucket back into the well.


References

Crouch, Margaret. 1983. Six Simple Pumps. Volunteers in
Technical Assistance, inc. Arlington, VA.

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook. Volunteers in Asia, Inc. Stanford, CA.

Intermediate Technology Publications Ltd. 1985. Tools for
Agriculture, A Buyer's Guide to Appropriate Equipment. 3rd ed.
I.T. Pub. Ltd., London.

Revelle, Roger. 1976. Energy use in rural India. Science
192:969-975.

Singh, Gajendra, and William Chancellor. 1975. Energy onputs and
agricultural mechanization under various regimes of mechanization
in Northern India. Trans. ASAE 18(2): 252-259.

Stern, Peter. 1979. Small Scale Irrigation. Intermediate
Technology Pub., Ltd., London.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 22
Wind for Pumping and Lifting Water


Windmills with a vertical axis have been used since the seventh
century in the Middle East, perhaps earlier. Dorf (1978, pp. 265)
claims vertical axis windmills were used in Persia as early as 250
B.C. Horizontal propeller-type windmills dating from the twelfth
century in Northern Europe were used for pumping water and milling
grain. NAS (1976, pp. 113) claims Egyptians used windmills "as
early as 3600 B.C."

Wind is a solar-energy-derived renewable energy source of
relatively low intensity or density. Shepherd (1983) gives a
global flux density of 2.5 W/m2 for wind energy density, but
considerable variations from this average value occur with
location. The power available from wind is proportional to the
rotor area swept perpendicular to the wind direction, to the third
power of wind velocity, and to air density.

P = 1/2 A V

This available power must be reduced by multiplying by a
coefficient of performance, c which varies with specific
equipment but can be no more than 0.593. Multi-bladed windmills
of the horizontal axis wind turbine (HWAT) type can approach
about half the theoretical maximum coefficient of performance.

Wind velocity increases with height above the earth. Therefore
windmills are often mounted on towers to take advantage of the
higher velocities and larger amounts of power available. The
ratio of wind velocities at two heights varies as the ratio of the
heights raised to the 0.17 power.

Advantages of wind power are that the user is taking advantage of
a renewable, non-polluting and "free" energy source.
Disadvantages include the significant capital investment, the
variability of wind, the possibility of damage due to high winds,
and the possible need of a storage system (water tank for pumped
water or batteries for electric power). Wind velocities useful
for extracting energy are in the range of about 10 to 50 km/h.
Lower velocities have too little power and higher velocities can
damage equipment. Damage in high winds is prevented by feathering
the blades, braking, or turning the windmill perpendicular to the
wind.

The familiar fan or turbine windmill used for pumping water was
built and sold by the millions in the U.S. in the late 1800's and
early 1900's. Both this application and that of generating












electric power with small generators of up to 2 kW capacity were
replaced by rural electrification which provided a more reliable
and more economical energy source. The large number of slow-
turning blades typical of water pumping windmills is to provide
the higher torque necessary to start a reciprocating cylinder
water pump. Typical coefficients of performance of water pumping
windmills are 0.10 to 0.25, with values being higher at low but
usable wind velocities. Table 1 shows typical water pumping
capabilities of a 4.9 m (16 ft) diameter windmill. For instance,
in a 24 km/h (15 mph) wind this windmill could lift 40 m (131 ft)
4.58 m /h (4575 1/h) of water (40 x 4.58 = 183). The output (lift
times flowrate) increases linearly rather than to the third power
of wind velocity due to the coefficient of performance decreasing
with increasing velocity. Davidson and Chase (1908, pp. 298-316)
give an historic perspective on the windmill.

Table 1. Typical Pumping Capability of a 4.9 m Windmill

Wind Speed Lift x Flowrate
km/h m m /h

8 61
16 122
24 183
32 244
40 305


Sail windmills are reviewed by Darrow and Pam (1981, pp. 140-143).
They are used in several LDC's for pumping water for irrigation
and other purposes. Sail windmills are made of bamboo spars, rope
or wire, and rush or split bamboo for woven triangular sails and
are connected to traditional low lift pumps. They reported that
one Cretan sail windmill (the original design is attributed to the
island of Crete) with dacron sails with a 4.9 m diameter wheel
pumped almost 5000 1/h at a 2.7 m lift in a 23.3 km/h wind. NAS
(1976, pp. 114) describe and depict the "water ladder" used with
sail windmills; the water ladder is an inclined trough with
closely fitted flights attached to an endless chain powered by the
windmill.

Another device reported by Darrow and Pam (1981, pp. 146) is a
Savonius rotor windmill constructed of two oil drums and other
materials and connected to a diaphragm pump. It lifted 822 1/h
4.6 m in a 16 km/h wind.

References

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook. Volunteers in Asia, Inc. Stanford, CA.

Davidson, j.Brownlee, and Leon Wilson Chase. 1908. Farm
Machinery and Farm Motors. Orange Judd Co., New York.










Dorf, Richard C. 1978. Energy, Resources, & Policy. Addison-
Wesley Pub. Co., Reading, MA.

Fraenkel, Peter. 1979. The Power Guide. Intermediate Technology
Publications Ltd., London. (pp. 43-46, 56-64).

National Academy of Sciences. 1976. Energy for Rural
Development. NAS, Washington, D.C. (pp. 79-81)

Shepherd, Dennis G. 1983. Wind Power. Chap. 19 in Handbook of
Energy Technology and Economics. John Wiley & Sons, New York.









Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 23
Human Powered Transportation Equipment



Human powered transportation equipment can range from simple
containers which allow carrying some type of material to more
complicated equipment which through some type of mechanical
advantage allow moving heavier loads or moving at higher speeds.

In order to transport a load from one location to another a
human will have to exert energy in two ways. First there is the
energy required to lift the object (from ground level to carrying
height) and then there is the energy required to move the load
to the desired location.

It has been documented that porters in Nepal can carry
anywhere from 75 to 120% of their body weight (up to 120 kg)
while covering a distance of 18 miles in 24 complete walking
hours (0.75 mph) (Oli, K.P.). This is probably higher than what
a typical person can carry.

Simple transportation equipment usually reduce the drudgery
of carrying by placing the load on areas of the body which can
tolerate heavier weights such as the head, back, or shoulders.
Another consideration is that there sometimes exists a need for
the hands to be free either to preform other operations or to
maneuver through rough terrain. The size and shape of the load
being moved can also influence the method of carrying. An
example of such equipment is the shoulder yoke (figure 1) which
allows the load to be placed on the shoulders. Another example
is large trays which are balanced on the head which allow for
freedom of the hands.

More complex transportation equipment, on the other hand,
usually remove all or part of the load from the operator and
place it on one or a set of wheels, trading the heavy load for a
smaller friction or rolling resistense (Barwell, 1976). The
degree to which this can be successful depends on the material
and technology available to make the transportation equipment,
and the terrain one is working on. The drudgery of pushing or
pulling inadequately built equipment through rough terrain might
outweigh the benefits of not carrying the load. Given the
correct equipment and terrain the friction and rolling resistance
can be small enough to allow for movement of greater loads and/or
at higher speeds.

The choice of the number of wheels in transportation








equipment depends on the material being moved and the terrain one
is working on. In general it can be said that as the number of
wheels increases, the satbility of the equipment and the weight
it is able to carry increases, while the manuverability of the
equipment decreases (Kidd 1976, Barwell 1976).

The wheelbarrow is one popular device used extensively all
over the world. The conventional wheelbarrow has the wheel
located in front of the load carrying container, while the
operator is located behind the load. In this design the weight
of the load is devided between the wheel and the operator by some
ratio. One variation on the wheelbarrow is one that has an
engine mounted on the wheel which assists the operator in moving
the load. Another variation is the chinese wheelbarrow (figure
2) which locates the wheel directly under the load. In this case
all of the weight is placed on the wheel, but it is harder to
keep everything in balance. Yet another design is the handcart
(figure 3) which is similar to the chinese wheelbarrow but has
two wheels. This allows for greater stability and greater loads
but requires fairly flat surfaces and cannot get through the
narrow paths that the wheelbarrows can.

Another popular transportation equipment is the bicycle.
The bicycle is popular for many reasons. It is fairly cheap
because it is mass produced. It is highly manuverable in narrow
and rough paths. One can travel at high speeds while pedaling or
move heavy loads while walking alongside the bicycle and pushing
on the handlebars. The Transport Bicycle (figure 4) is a
modification of the bicycle which allows carrying heavy loads.

Adding and extra wheel to the bicycle yields much higher
stability. This design has been used in many vehicles such as
the rickshaw, padicab, and the chinese pedal cart (figure 5).
Wilson, 1977, has proposed a stronger built, better designed
tricycle with a variable gear ratio called the Oxtrike (figure
6).

Figures 7 and 8 display some interesting designs in human
powered transportation equipment which have yet to be
commercially produced.



References

Barwell, I.J. 1976. Chinese Handcarts and Wheelbarrows.
Appropriate Technology vol. 3 no.3. (p.p 20-22)

Congdon, R.J. 1977. Introduction to Appropriate Technology.
Rodale Press, Emmaus, PA. (p.p. $2-91)

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook: vol. 1. Volunteers in Asia, Stanford, CA. (p.p,
194-195)








Kidd, David. 1976. Appropriate Technology vol.3 no.3. (p.p.
14)

01i, K.P. Load Carrying Abilities of Porters in the Hills.
Draught Animal News no.3. (p.p. 7-10)

Papanek, Victor. 1973. Design for the Real World. Bantam
Books, New York, N.Y. (p.p. 198-205)

Wilson, S.S. 1976. The Oxtrike. Appropriate Technology vol. 3
no. 4. (p.p. 21-22)






















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Mock-ups and working models of two
vehicles designed and built under the
authors direction at KonsMockukolon
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were explorations in transporting ma-
iaom over rough terrain by muscle
power tone. One of them (designed
by James Hennessey and Tillmon
Fuchs) s a proposal for an inner-ey
mrnabout and shopping vlhide.
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Agricultural Engineering Department


ABE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 24
Other Water Lifting and Pumping Devices

There are some, but not many, water lifting and pumping devices
which are not powered by manual labor, draft animals, wind, or by
engines or motors. In the latter category, there are of course
numerous pumps which are powered by internal combustion engines
fueled with liquid or gaseous fossil fuels and electric motors;
these mainly non-renewable energy consuming devices are not the
topic of this section. Rather, the subject of this section is
those water lifting and pumping devices which are powered by
"other" renewable energy sources.

The hydraulic ram (or hydram) is one such device. The hydraulic
ram utilizes the kinetic energy in a large part of a stream of
water descending through a pipe to elevate a small part of the
stream to a height which can be above the source. The water flows
into the hydraulic ram through a pipe into a water chamber. There
are two exits from the water chamber for the water flow; 1)
through a check valve into an air-cushion chamber (containing air
at various degrees of compression and water) and 2) through a
waste valve, also called an impulse valve or a clack valve. Water
flowing through the inlet pipe into the water chamber and out the
waste valve, under significant fall, gains momentum until it
closes the waste valve. The momentum causes additional water to
then flow through the check valve instead and into the air-cushion
chamber, compressing air to store energy and simultaneously
forcing water out the air chamber through the delivery pipe until
the pressure in the air-cushion chamber exceeds that of the water
supply, at which point water flow into the air-cushion chamber
ceases. Lower pressure in the water chamber then allows the waste
valve to close, and the cycle repeats periodically.

Waste valves are commonly adjustable by adjusting a weight on
the valve or the spring loading on the valve, affecting
hydraulic ram cycle frequency. VITA (1970, pp. 104-106) gave
operating frequencies of 25-100 cycles per minute.

Fraenkel (1979, pp. 74-76) gave several examples of commercially
available hydraulic rams with specifications, though Darrow and
Pam (1981, pp.206-209) also show examples of easily constructed
rams of mainly common pipe fittings. Fraenkel's data indicates
hydraulic rams can operate under as little as 0.5 m supply head
and elevate water as much as 125 m. The portion of the total
water flow elevated ranges from as little as 1-2% at high lifts
to about 40% at low lifts. NAS (1976, pp. 155-160) suggests the
efficiency of the hydraulic ram is about 60%, and Clegg and VITA
present formulas for calculating elevated water flow which assume
67% efficiency:











2HF

3L

where Q is flow rate of elevated water,
H is head of supply water,
F is flow rate of supply water
and L is lift of elevated water.

NAS also examples a ram utilizing a vertical water fall of 3.7 m
elevating 5 or 6% of its flow 38 m; at a lift of only 7.6 m, 22%
of its flow will be elevated.

Advantages of the hydraulic ram include its relatively low cost,
its simplicity and very low maintenance requirements, its zero
operating costs, and its use of only renewable energy.

The Plata Pump (Fraenkel, pp. 76) is a plastic tube with a series
of propellers mounted on a shaft inside the tube. The shaft
drives a small pump. A 57 1/s input flow with a 0.38 m head will
lift 0.07 1/s 3.05 m or 0.02 1/s 91.5 m. Efficiencies of less
than 10% are calculated using this example data.

According to a sketch in an old advertising brochure by
International Harvester, an ancient Grecian method of irrigating
consisted of a waterwheel powered by flowing water in a stream;
the center area of the waterwheel was filled with a series of
spiral troughs which filled with water and gradually wound the
water toward the center and therefore lifted the water upward as
the wheel turned. When the water reached the center there was
evidently an escape route for it to pour out and onto the field.

It would appear that there has been ample opportunity for the
development of many other water powered devices to lift water; why
there is so little evidence of such devices is somewhat of a
mystery. For instance, a device comprised of a waterwheel to
extract power from a stream coupled with a water-lifting wheel
would appear to have rather wide applicability. What is more
obvious, however, is that there are few renewable energy sources
which readily provide shaft power with low or intermediate levels
of technology and which can therefore utilize renewable energy
other than muscular or wind to lift water.


References

Clegg, Peter. 1975. New Low-Cost Sources of Energy for the Home.
Garden Way Pub., Charlotte, VT. (pp. 141-143).

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook. Volunteers in Asia, Inc. Stanford, CA. (pp.
206-209).











Fraenkel, Peter. 1979. The Power Guide. Intermediate Technology
Publications Ltd., London. (pp. 43-46, 56-64).

National Academy of Sciences. 1976. Energy for Rural
Development. NAS, Washington, D.C. (pp. 79-81)

Ramsower, Harry C. 1917. Equipment for the Farm and the
Farmstead. Sinn and Co., Boston. (pp. 195-206).

Stern, Peter. 1979. Small Scale Irrigation. Intermediate
Technology Pub., Ltd., London. (pp. 126-127).

VITA. 1970. Village Technology Handbook. Volunteers in
Technical Assistance, Mt. Rainier, MD.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 25
Animals for Transportation


Draft animals serve as one source of energy for transportation.
They can be used with a wide variety of devices to facilitate the
transport of freight or people: wagons, carts, trailers, sleds,
sleighs, saddles, etc. They can be used singly, or they can be
hitched together in teams of two or more to pull larger loads.
They have the advantages of depending on renewable energy (for the
most part; manufactured transportation devices, veterinary
supplies, and even feed produced with fossil fuel input to the
contrary), being self-reproducible (with the exception of the
mule), being able to use very poor or almost nonexistent roads,
etc. Draft animals also have disadvantages working time is
limited to a portion of total time; limited power capabilities;
susceptibility to accidents, diseases, etc.; relatively low
efficiency of energy conversion; training requirements; speed;
etc. Barwell and Ayers (1982) estimate the number of draft
animals in LDC's at 400 million, and a significant portion of
their available work is devoted to transportation.

Animal-powered transport is used to move agricultural inputs to
the farm (though this function is rather limited in traditional,
non-green-revolution agriculture), to move materials and people on
the farm, to move agricultural produce from the farm to the
market, and to move people to and from the marketplace.

The limited distances which animal-powered transportation can
traverse per unit time is a major limiting factor to their use.
Most draft animal species move at speeds in the range of 0.6 to
1.0 m/s; daily distances travelled seldom exceed 40 km and more
typically run 10 to 20 km. This characteristic is obviously
limiting to the use of animals for transporting perishable
agricultural produce, especially for long distances.

Pack animals carry much of the world's freight in rugged areas
where the terrain is unsuitable for improved roads and in other
areas where roads are not adequately improved for wheeled
vehicles. Donkeys, horses, mules, camels, llamas, reindeer, yak,
oxen and elephants are among the species most familiar for this
use. Freight is usually attached to the animal with the aid of a
saddle-like device or baskets or rack of some sort which is
attached to the animal. Spedding (1975, pp. 166) gave examples of
load carrying capacities by several species; the donkey can carry
as much as half its weight.

In some applications of animals for moving freight, the animal or
animals simply drag the freight on the ground. Skidding logs in










forestry operations is an example. In most such applications,
however, the animals) pull a vehicle or other device upon which
the freight is loaded. The ability of the animal to produce draft
power is an important characteristic in both cases. Also, the
harness through which the animal transfers draft force to the load
is another major consideration (Barwell and Ayers, 1982).
Sustainable draft force generated by an animal ranges from about
10% of their weight for bovines to 15% of their weight for
equines, but up to 25% for donkeys. This available draft force
must be adequate to exceed the summation of resistance forces or
total draft of the load: rolling resistance, friction (mainly axle
friction which typically is only a few kg/t of load) (Davidson and
Chase, 1912, pp. 249-250), and lifting of the load and vehicle up
any incline.

Rolling resistance is characterized by the coefficient of rolling
resistance, which is the ratio of rolling-resistance force to the
vertical load on the wheel. It is affected by several factors
roadbed (the harder the road, the less the rolling resistance),
diameter of tires or wheels (the smaller the diameter of wheels,
the more they are always climbing uphill out of the depression
they continually make) width of tires or wheels (the wider the
tire the less it sinks into the road). The appropriateness of
3 m and larger diameter wheels for ox carts, as used in some LDC's
on poor roads, is apparent. Davidson and Chase reported draft of
three size wheels on several surfaces (Table 1):

Table 1. Approximate coefficient of rolling resistance with 15 cm
wide wagon wheels with iron tires

Front-rear wheel diameters (m)
Surfaces ---------------- ------------------
1.12-1.42 0.91-1.02 0.61-0.71

Paved (macadam) 0.028 0.030 0.035
Dry gravel road 0.042 0.045 0.055
Earth road, dry and hard 0.034 0.038 0.050
Earth road, thawing mud 0.050 0.060 0.070
Brass sod, dry 0.066 0.072 0.090
Brass sod, wet and soft 0.086 0.101 0.140
Corn field, dry 0.089 0.100 0.132
Plowed ground 0.126 0.152 0.187


ASAE's (1985) standard equation for calculating coefficient of
rolling resistance for pneumatic tires is

C = 1.2/C + 0.04

where C varies from 15 for soft sandy soils to 50 for hard soils,
giving C from 0.120 to 0.064.

Draft required to lift a load up an incline is easily determined










D = W sin


where D = draft to pull load up incline,
W = weight of load,
and = angle of incline.

Two-wheeled carts pulled by a single draft animal, some by a pair
of draft animals, are a common means of transport over much of the
lesser developed world. Ramaswamy (1981) said that in India two
thirds of the freight transportation in rural areas is by 12
million animal-drawn carts; reasons include low cost, rough roads,
short hauls, and small quantities. Cart technology has not
changed very much for several thousand years, though materials now
used include salvaged automotive components. Freight transport
with carts is significantly more efficient than with pack animals.
Carts generally weigh 100 to 200 kg and can haul 500 to 1000 kg.
Shaft spacing and length must vary for donkeys (0.50 m and 1.40 m
respectively) versus oxen (0.65 m and 2.0 m). A cart for a pair
of animals has a single shaft. FAD (1972) suggests practical
loads are 800 kg for a pair of oxen and 400 kg for a donkey.

Wagons, four-wheeled animal drawn vehicles, are not used
extensively in most LDC's, perhaps due to their high cost. Wagons
have been used historically in the developed countries (McKinley,
1980) and which carried loads up to 7000 kg. Most wagons are
pulled by teams of an even number of animals though some small
wagons are designed to be pulled by a single animal.

The braking of wheeled carts and wagons when descending slopes or
slowing is accomplished through wheel or axle brakes on heavier
vehicles. Lighter carts depend on the draft animal for braking,
possibly a problem for bovines as their shoulder yokes do not
provide for application of a forward force.


References

American Society of Agricultural Engineers. 1985. ASAE Standards
1985. ASAE, St. Joseph, MI.

Barwell, Ian, and Michael Ayre. 1982. The Harnessing of Draught
Animals. Intermediate Technology Publications, London.

Davidson, J. Brownlee, and Leon Wilson Chase. 1912. Farm
Machinery and Farm Motors. Orange Judd Co., London. (pp.
241-257).

Food and Agricultural Organization of the United Nations. 1972.
Manual on the Employment of Draught Animals in Agriculture. FAO,
UN, Rome. pp. 184-198.

McKinley, Marvin. 1980. Wheels of Farm Progress. American
Society of Agricultural Engineers, St. Joseph, MI. (pp. 97-102).











Ramaswamy, N.S. 1981. Notes towards the management of animal
energy uyilization in India. In Energy and Environment in the
Developing Countries, Manas Chatterji, ed., pp. 255-274. John
Wiley & Sons Ltd, Chichester.

Spedding, C.R.W. 1975. The Biology of Agricultural Systems.
Academic Press, New York. pp. 166-168.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 26
Engine Powered Transportation Equipment



Transportation is an essential component of many production
systems. Food that remains on the farm can not be considered as
having entered the market and therefore has little value other
than for the farm household's personal use. Many of the
developing countries have put substantial emphasis on increasing
small-scale farming yields as a way to increase the country's
self sufficiency and well being. Such excess yields, however,
have little value if they can not be introduced into the
marketing system. Introduction of a product into the marketing
system usually consists of two phases. The first phase may
involve a short trip to a small town or a main road pickup point.

The second phase of introduction to market involves
distribution of the product into the market using larger scale
transportation equipment such as trucks, trailers, buses, trains,
boats, etc. This phase is usually better developed in most
countries. Table 1 shows some typical values for energy
intensiveness of different modes of transportation. Although
energy is an important factor in many countries, other factors
such as terrain, cost of construction (for example rails vs.
roads), and available technology are also important
considerations.

Table 1. Energy intensiveness of various modes of freight
transportation

Energy intensiveness, Btu/ton mile
Mode -----------
Range Average

Air 11,000-70,000 12,000
Truck 690-6200 2,500
Rail 275-1400 800
Water 70-2000 470
Pipeline 275-4200


Local transportation, on the other hand, is much less
developed in many developing countries. Local roads at the farm
and village level are usually of low priority compared to the
country's main roads and transportation facilities.
Transportation usually involves short distances (up to 3 miles if
on the farm and up to 20 or 30 miles if off the farm) over rough






terrain with inadequate or no roads available.


The use of engines as opposed to human or animal power can
have many benefits. One of the major benefits of engine powered
transportation equipment is their ability to move at higher
speeds than that of humans or animals in most cases. Although
engine powered transportation equipment can carry very large
loads, within the limits of a small farm, draft animals probably
have adequate load carrying capabilities. However, at lower
speeds. Other considerations such as ease of use, comfort,
dependability, and so on can be and are important considerations
to take into account.

In agricultural processes speed can be a very important
consideration in transportation equipment. Farmers often face a
time limit in which they must get their produce either to market
or storage facilities. This limit is created by perishable crops
which must be sold or stored immediately after harvest or by
falling market prices after the beginning of the harvest season.
Jusification for the purchase of transportation equipment (as
with any other piece of machinery) involves the price of the
vehicle and the extra income that is generated by the use of that
vehicle.

Examples of engine powered transportation equipment are
fairly obvious. They include trucks, pick-up trucks, tractors
with wagons behind them, and walking tractors (figure 1) with
small wagons behind them. In general, however, tractors are
designed for off road use and are not intended for high speed
movement on paved roads. However, in many countries the small
multi-purpose tractor is very popular. Over 1,370,000 walking
tractors are presently in use in China (Harrington, 1979).

Another area of engine powered transportation equipment is
stationary transportation equipment. These equipment are
porbably better known as materials handling equipment. These
equipment include: flight conveyers, augers (screw conveyers),
belt conveyers, and blowers. Some general features of each of
these equipment are as follows:

1. Flight conveyers: Inexpensive, versatile, noisy, slow.

2. Augers: Inexpensive, simple, compact, for short
transfers.

3. Blowers: High capacity, high power requirements, short
distance transfer.(Hunt, 1893)

Materials handling equipment can be powered by electric
motors, combustion engines, or tractor PTO shafts.

Flight conveyers (figure 2) have.chain carried scrapers for
flat conveying of formed buckets for vertical work. The
capacity, CAP, of a flight conveyer can be measured by knowing
the demensions of the flight, the chain speed, the flight








spacing,,and the angle of lift from the horizontal. The
following equations are used to measure the capacity (use figure
3 as a reference).

'When shaded area is triangular:

2 3 3
wh S m ft
CAP =--------- ----- I ---- 3
cs tan 0 min min

When area Is trapezoidal:

2 3 3
2wSh(s-t) wS(s-t) tan 0 m ft
CAP = --------------------------- ----- E ----- 3
cs min min
Where:
w = width of flight, cm [in.]
s = center to center spacing of flights, cm Cin.3
h = hight of flight, cm [in.3
t = thickness of flight, cm Ein.3
0 angle of conveyer, rad Edeg3
S = speed, m/s Eft/s3
c = 333.3 [4.83

An auger (figure 4) is a screw like device contained within
a metal tube which moves material forward as the screw turns
within the tube. The capacity of an auger is given by the
following equation:
2 2
(D d )
CAP = ---------- X P X rpm X F
36.6
Where:
CAP = capacity, cu ft per hour.
D = screw diameter, in.
d = shaft diameter, in.
P = screw pitch, in.
rpm = auger rotation speed, revolutions per minute.
F = Auger % fill from table 2 (express as a decimal value).

Table 2. Auger percent fill at different rotation speeds and
inclines.

% Fill at given rpm
Incline -------------------------------------------------
rad Edeg3 100 300 500 700

0 03] 85 84 69 54
0.35 [203 82 70 54 40
0.70 E403 74 59 43 33
1.00 [57.33 65 49 36 28
1.22 E703 47 36 29 22









Blowers usually have higher capacities than other farm
conveying equipment but have higher power requirements. Blowers
operate by floating grain in a high velocity air stream. In
general it takes 2-3 cubic meters to float 1 kg of grain (Hunt,
19@3)

References

Crossely, Peter, and Kilgour, John. 1983. Small Farm
Mechanization for Developing Countries. John Wiley and Sons, New
York, NY. (p.p 36-39)

Esmay, Merl E. 1979. Glimpses of Agricultural Mechanization in
China. American Society of Agricultural Engineers.

Fluck, Richard C. Energy Conservation in Agricultural
Transportation. Circular 616, Florida Cooperative Extension
Service.

Henderson, S. M., and Perry, R. L. 1955. Agricultural Process
Engineering. John Wiley and Sons, New York, NY. (p.p. 179-209)

Hunt, Donnell. 1983. Farm Power and Machinery Management. Iowa
State University Press, Ames, IA. (p.p. 182-191)











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Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 27
Solar Thermal Energy Equipment and Processes


Solar energy, radiant energy from the sun, has several uses as a
source of thermal energy. Of course, its main use is in the
production of carbohydrates through photosynthesis. And, it is
perhaps unfortunate that solar energy cannot yet be easily and
cheaply converted to mechanical or electrical energy. One
disadvantage of solar is that the energy density is low. The
solar constant, 1.395 x 10 MJ/m s, the solar radiation at the
outer limits of the earth's atmosphere, is reduced by hours of
darkness, atmospheric absorption, and cloudiness so that solar
insolation ranges from 0.09 x 10 MJ/m s at polar regions to 0.29
x 10 MJ/m s in desert areas. A typical U.S. location receives
during a summer day 20 to 30 MJ/m or the equivalent of 5.5 to 8.3
kWh/m of low-grade thermal energy. Another disadvantage of solar
energy is its intermittency; this necessitates energy storage if
solar energy is to be depended upon for nighttime or cloudy day
energy needs.

NAS (1976, pp. 23-26) mentioned several current applications of
solar energy appropriate in rural areas:
1. Water heating (for both domestic and commercial use);
2. Heating of buildings;
3. Cooling of buildings;
4. Drying of agricultural and animal products; and
5. Salt production by evaporation of seawater or inland
brines.
The unfortunate circumstance is that there are so few real
applications in agriculture for so prevalent and inexpensive a
source of energy.

Flat plate solar water heaters have been used for over 50 years to
heat water for domestic and other purposes. The technology is
proven, well-known, and simple: it is also relatively expensive.
Applications are therefore limited to areas where competing fuel
costs are high, such as Israel, Japan, parts of the U.S., etc.
Capital costs typically run in the order of $100/m of collector
area, although less expensive, albeit less durable and less
efficient, collectors are available. Solar heated hot or warm
water can be used for space heating, and has the advantage that
heat storage can be achieved through storage of heated water.
Flat plate collectors can achieve temperatures of 50 to 150 C.

Solar ponds, brine water reservoirs exposed to the sun, can
collect and store solar thermal energy. Multiple layers of brine
water with a gradient of salt concentrations from more
concentrated and heavier at the bottom to less concentrated and










lighter at the surface capture, store and insulate from the
atmosphere the stored solar energy. The thermal energy is used
as such or in engines to produce mechanical power. Relatively
complex technology, cost and ease of contamination are
liabilities of this technology.

Air can also serve as the fluid to transfer heat with a solar
heating system. Storage of heat can be through heating crushed
rock, masonry structural components, or phase-change salts. Even
without heat storage, solar heating may be useful for daytime
livestock housing in winter. This technology is in fact being
used by some U.S. farmers for poultry and hog housing.

Focusing and concentrating solar energy collectors can achieve
higher temperatures than can flat plate collectors. Various
curved and multiple surfaces such as curved troughs, parabolic
shaped surfaces, etc. are used. Costs and complexity are
increased, but higher temperatures (500 to 3500C) are more easily
converted to mechanical work. Fraenkel (1979, pp. 24-26) example
several turbines and engines to convert higher temperature solar-
derived energy to mechanical or electrical energy. Such
technology is not yet in general cost competitive with fossil fuel
energy sources. Coleman et al gave plans for constructing a solar
food dryer which took advantage of these higher temperatures.

Solar energy can, through the use of a thermal energy storage
system, be used to provide nighttime heat for greenhouses. The
currently more successful examples utilize water under the plants
to store heat, also enabling lower and therefore more energy
conserving air temperatures inside the greenhouse.

Solar energy can be used to provide refrigeration or cooling
through the absorption refrigeration cycle and using ammonia or
lithium bromide as the working fluid (TNSRC, 1978, pp. 107-111).
Cost, complexity, and required maintenance skills are deterrents
to this technology, despite its use of a "free" energy source.

Solar energy used to evaporate water is technology useful for
producing salt and distilled water. TNSRC (1978, pp. 38-41)
reviewed technology for solar water distillation, which can
produce drinking water from impure or salt water. With solar
energy of 5 kWh/m d, 2.5 1/m d can be distilled.


References

Coleman, Richard L., Charles J. Wagner, Jr., Robert E. Berry, and
J. Michael Miller. (No date) Building a low-cost, solar food
dryer incorporation a concentrating collector. U.S. Citrus and
Subtropical Products Lab., Winter Haven, Fl.

Duffie, John A., and William A. Beckman. 1974. Solar Energy
Thermal Processes. John Wiley & Sons, New York.










Fraenkel, Peter. 1979. The Power Guide. Intermediate Technology
Publications Ltd., London. (pp. 26-42).

National Academy of Sciences. 1976. Energy for Rural
Development. NAS, Washington, D.C. (pp. 23-26)

Stout, B.A. 1979. Energy for World Agriculture. FAO, UN,
Rome. (pp. 87-114).

Tanzanian National Scientific Research Council. 1978. Workshop
on Solar Energy for the Villages of Tanzania. TNSRC, Dar es
Salaam.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 28
Solar Photovoltaic Energy


Direct conversion of solar energy to electricity is very appealing
to us for its use of a major renewable energy source and its
provision simply and cleanly of a very valuable energy commodity.
Solar photovoltaic cells convert solar energy directly to electric
energy. Semiconductor materials; silicon, cadmium sulfide, and
gallium arsenide doped with minute quantities of impurities;
convert typically 8 to 15% of the incident solar energy to an
electric current flowing through the solar cell and an external
circuit. Electric power production per unit area is therefore
currently limited to about 100 or 150 W/m^2 of photovoltaic cell
area. Cost is the main limiting factor to the application of
solar cells. Prices have fallen from in the order of $2000 per
peak Watt of capacity in the late 1950's to $7-10 per peak Watt
today, but that is yet much more expensive than $0.40-1.00 per
Watt of generating capacity for conventional electric power
plants. The fact that fuel costs are zero, and that operating
costs are only maintenance and (perhaps) the cost of land rental,
makes solar photovoltaic currently cost competitive in certain
markets. In particular, photovoltaic is proving competitive where
electric power line costs must be incurred over long distances
with the prospect of small electric loads and where it replaces
small diesel generators (Usmani, 1985).

Early photovoltaic (PV) solar cells were single crystal silicon,
and it is yet a commonly used material. However, cast
polycrystal, thin film and ribbon silicon cells have a portion of
the market and amorphous (non-crystalline) cells are gaining
market share and promise further reductions in cost.

Disadvantages of solar photovoltaic include, in addition to high
first cost and the solar "catching area" requirements, the need
for a backup or electric power storage system for nighttime and
cloudy day needs, the high technology necessary for manufacturing,
the D.C. rather than A.C. output and the corresponding necessity
for inverters, and pollution resulting from manufacturing
operations.

Advantages include low maintenance, lack of moving parts, long
life, choice of voltage output by choice of number of solar cells
connected in series, safety, lack of environmental pollution
during electric power generation, possible independence from power
grid, light weight, high efficiency (among the possibilities for
conversion of solar energy), quietness, and modularity (size of a
total system can vary greatly and malfunction of one cell only
results in a minimal reduction in power output for the entire










array).


Electric power cost from solar photovoltaic is almost a linear
function of interest rates on the capital investment. A 1 kW
array costing $8,000 and financed at 12% will produce 3.5kWh/d
costing $0.75/kWh even if it has no other costs. Costs must drop
to in the order of $1000/kW or less for PV to be competitive with
fossil-fuel generated electric power for the bulk of applications.
Prospects for reducing the cost of photovoltaic include advances
in manufacturing technology, increases in solar cell efficiency,
and concentrating techniques to increase the amount of solar
radiation impinging on the solar cell. Hitney (1985) cited a
popular residential PV system with 10 to 12 44 W modules,
batteries, regulator and 2.5kW inverter as selling for $8-9000,
or about $17,000/kW of peak generating capacity.

Flat arrays of solar cells are usually tilted toward the equator
at an angle approximating the latitude for highest efficiency and
are effective even with diffuse radiation. Concentrating systems
use Fresnel lenses, mirrors, or parabolic troughs, etc. to
concentrate solar energy impinging on larger areas to smaller
areas of solar cells. They often track the sun's diurnal path,
and may even require cooling to prevent solar cell temperatures
from getting too high to reduce cell efficiency.

A current favorite application of photovoltaic is water pumping
for irrigation, as it offers a built-in storage mechanism.
Research has been conducted at the University of Nebraska
(Sullivan, et al., 1980) with a 25 kW peak output 520 m^2 PV
system irrigating 32 ha of corn.

Another agricultural PV product is the solar fence charger,
costing in the order of $200. Usmani (1985) also suggests PV
be used for grain milling, lighting, and crop drying.

World production of photovoltaics totalled 21.7 MW in 1983
(Maycock, 1984) and is rapidly increasing. It is predicted to
reach 500 MW by 1990, with prices of $3.00/W at the factory.
Maycock cited over 6000 off-the-grid PV residences and several
hundred PV-powered irrigation systems in the U.S. The Dinh Co.
in Alachua, FL is manufacturing a solar powered pump which is
equipped with two 38 W PV modules and batteries which with 6 to
9 hours of charge will lift 000 gal. of water the equivalent of
105 feet.


References

Fraenkel, Peter. 1979. The Power Guide. Intermediate Technology
Publications Ltd., London. (pp. 21-24).

Hitney, Gene. 1985. Remote homes. Photovoltaics International
3(3):27.










Maycock, Paul D. 1984. Photovoltaics: 1983 status report 1990
forecast. In Energy Technology XI, Richard F. Hill, ed.
Government Institutes, Inc., Rockville, MD. pp. 1447-1452.

Maycock, Paul D., and Edward N. Stirewalt. 1985(?). A Guide to
the Photovoltaic Revolution. Rodale Press, Emmaus, PA.

National Academy of Sciences. 1976. Energy for Rural
Development. NAS, Washington, D.C. (pp. 27-29, 87-109)

Usmani, Ishrat H. 1985. Power for the rural poor of Africa, Asia
and Latin America. Photovoltaics International, 3(1): 11-15.









Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 27
Hydropower (Water as a Source of Energy)


Similar to wind, the power of moving water is an indirect
result of solar energy. The sun heats water which evaporates
from oceans, seas, lakes, etc. The evaporated water is then
carried over upland areas by wind currents where it percipitates
back to the earth. The forces of gravity return the water to the
oceans and seas from which it evaporated and the cycle begins all
over again. Dorf, 1978, estimated that the world wide power
available from this downward flow of water is about 4 X 10
watts form which only a small fraction (274.7 gigawatts in 1969)
is now being used by man.

In general the power of flowing water is harnessed by some
means and transformed into the movement of a rotating shaft. The
devices used for such a transformation in historical sequence
are: the water wheel, the tub or flutter wheel, and the turbine.

Water wheels generally rotate in the vertical plane. They
can be distinguished from turbines by the fact that no change in
water pressure occures across their vanes or buckets. Water
wheels can be of three types: overshot, undershot, and breast.

In the overshot water wheel figuree 1) buckets are filled
at the top of the wheel and emptied as they approach the bottom of
the wheel. An overshot water wheel requires about 8 feet of head
and can work well in up to 30 feet of head. Overshot water wheels
can achieve efficiencies of up to 80%, but they are slow and
generate little power for their size.

The undershot water wheel receives its power from the impact
of a flowing stream (passing under the wheel) with the flat or
curved vanes of the wheel. The maximum efficiency that can be
achieved with an undershot water wheel is only about 20%. This
design is often used where no.other choice exists. That is, the
terrain is too flat to bring the water over the water wheel.

The breast wheel is similar to the overshot water wheel with
the only difference that water enters the buckets about half-way
up the wheel. This means that it requires only about 4 or 5 feet
of head. Efficiencies of about 60% can be achieved with this
design.

The tub or flutter wheel differs from the water wheel in
that the wheel rotates in the horizontal plane. Water travels
down an inclined slope from about ten feet above and impacts with







the inclined blades of the wheel which are set up to have a 90
degree angle with the direction of the water flow. The tub or
flutter wheel operates at efficiencies of about 20%.

In turbines, a steady flow of water passes through the
buckets or blades of the turbine and leaves with a minimum amount
of velocity and energy having transmitted most of its kinetic
energy to the rotor. Turbines can have efficiencies of about
95%. There are three basic types of turbines: Francis, Pelton,
and propeller.

The Francis turbine (figure 2) allows water to enter the
rotor around its complete circumference and is therefore called a
full-admission turbine. It is also called a pressure turbine
indicating a change of pressure across the rotor. The Francis
turbine is normally used for heads of 100 to 1000 feet.

The Pelton turbine (figure 3) differs from other types of
turbines becuase it is a pressureless turbine. There is no
pressure change across the runner. All of the water's
pressure/potential energy is converted to kenetic energy in a
nozzle. The high-speed stream of water is then directed towards
the buckets on a wheel. The impact of the water transfers its
kinetic energy to the rotating turbine. The Pelton turbine is
normally used where heads exceeding 1000 feet are available.

The propeller turbine (figure 2) is similar to the Francis
turbine in its operation. Propeller turbine can operate in heads
of 10 to 1000 feet, but require high flow rates at low heads.

Although water wheels are simple enough to be constructed
locally with simple tools, turbines generally require high
accuracy and must be commercially developed.

In the past hydropower has been used to run grain mills, saw
mills, and other similar operations. Figures 4 and 5 show some
of the traditional uses of hydropower. Today, however,
hydroelectric power generation is by far the most popular form of
power generation from flowing water.

Water wheels and tub wheels are generally not used for
hydroelectric power generation due to their inefficiency and slow
rotation speeds. If the use of such devices is desired, the best
choice is the overshot water wheel because of its high
efficiency. The advantages of using the water wheel over the use
of turbines are its simple design and low maintenance costs. The
speed of rotation of an overshot water wheel is about 2 to 12
revolutions per minute which is much lower than the speed
required for a generator. The added gears and belts needed to
bring the water wheel's speed up to generator requirements will
reduce the water wheel's efficiency.

Turbines are almost always used for hydroelectric power
generation. A typical layout of a hydroelectric generating unit
is shown in figure 6. The potential energy that water at an







elevation has stored in itself can be represented by the
following equation:

E = mgh
where
E = potential energy, joules
m = mass of water, kg 2
g = acceleration due to gravity, 9.8 m/sec
h = water head, meters

We, however, are interested in the power generating capacity
of a source of flowing water rather than total energy stored.
Power is expressed as energy per unit time. Thus, if we know the
time over which this mass of water is going to move from the
higher to the lower elevation we will be able to find the
potential power generating capacity by the following equation:

E
P = -----
t
where
P = power, watts
E = energy, joules
t = time to move from higher to lower elevation, sec

Combining the two equations we get the following:

P = (m/t)gh

As you can see the rate of water movement (m/t) in the above
equation is in units of kg/sec. We are, however, more used to
expressing such flows in terms of volume per unit time. Since
water weighs 1 kg per liter we can substitute to get the
following equation:

P = Qgh

where
P = power, watts
Q = flow rate, 1/s
2
g = 9.8 m/s
h = head, meters

This equation represents the theoretical power generating
capacity of a source of flowing water. As it has been mentioned
before turbines can achieve efficiencies of about 95%.
Generators also have about 95% efficiency. This gives a combined
efficiency of about 90% for a hydroelectric power generating
unit. There are additional losses due to friction in the
penstock (see figure 6) and at the entrance and exit of the
penstock which reduces the actual efficiency of the combined unit
to about 75 to 80%. Therefore, the actual power generation
capacity of a flow source can be represented by the following
equation:








P = (eff.)Qgh
where
eff = .75-.80, hydroelectric power generating unit efficiency

Thus, in order to estimate the potential power generation
capacity of a water flow source we need to know the flow rate of
water (m/s) and the head elevation (m). The potential power
generation capacity must justify the cost of the unit.

Ritchie, 1983, has suggested gathering the following facts
and consulting a qualified engineer before deciding to build a
hydroelectirc power generating unit:

1. Maximum and minimum flows of the stream
2. Head or fall of water
3. Length of pipe (penstock) needed to get the needed head
4. Water condition (clear, muddy, acid, alkaline)
5. Soil condition
6. Minimum tailwater elevation (below the plant)
7. Area and depth of storage pond behind the dam, if any
8. Horizontal distance from water source to power site
9. Distance from power plant to point of use of the electricity

References

Clegg, Peter. 1975. Energy for the Home. Garden Way
Publishing, Charolette, Vermont. (pp. 134-161)

Darrow, Ken and Pam, Rick. 1981. Appropriate Technology
Sourcebook, volume one. Volunteers in Asia, Inc. Stanford, CA.
(p. 160)

Dorf, Richard C. 1978. Energy, Resources, & policy. Addison-
Wesely Pub. Co., Reading, MA. (pp. 201-212)

Frankel, Peter. 1979. The Power Guide. Intermediate Technology
Publications Ltd., London. (pp. 65-76)

National Academy of Sciences. 1976. Energy for Rural
Development. NAS, Washington, D.C. (pp. 137-155)

Ritchie, James D. 1983. Sourcebook for Farm Energy
Alternatives. McGraw-Hill Book Company, New York. (pp. 20-1 to
20-10)

VITA. 1970. Village Technology Handbook. Volunteers in
Technical Assistance, Mt. Rainier, MD. (p. 117)






























Fic. L Ow.,SHOT


kAmP 1h4EE,.


ALSO B: MOUNTED HORIZONTALLY


FLrTOM/ 7pp/A/I"


PROPELLER
TURBINE


VALVE


.3


. 4J **


TURBINE


Ge 3-.


- *. *-
'-

























Wooden Water Wheel used to
Mill Rice In Sumatra


As the wheel turns, the main axle turns
with it. Each pole is slowly lifted and then
dropped on the rice below. The poles can
be suspended to enable the operators to
empty and load each pounding basin. The
unit is built entirely out Of wood. As shown
here, the eight flat sides on the main axle
are not necessary.


s\ \


POLES WITN CHAINS SUPPORT
WIBE AT INTERVALS


UND6URS4T
WAYTft WHEEL111


F7-e.5 khu WRE Pk'cRZ 7kA/s/v. 1n ui oAl




















66reo- 7,y-) "crrcI& 6&1/4p LA 17(/Mr


E > -* Pointed side upstream


Stream
depth
reading


Water surface


Current

Streambed
Step 1

t Broadside to current








*- Current

Streembed
Step 2
How to use a velocity head rod: Step 1, mea-
sure stream depth with pointed side of the rod upstream;
step 2, turn the rod perpendicular to current flow and read
turbulent water at highest point on upstream side.


Stream Velocities from Head Rod
Head, in 0 1/2 1 2 3 4 5 6 7 8 9 10 11 12 15 18
Velocity, ft/s 0 1.6 2.3 3.3 4.0 4.6 5.2 57 6.1 6.5 6.9 7.3 7.7 80 9.0 9.8







Approlimate Flow over 90* Triangular Weirb
Head. in Flow, gpm Flow, ac-in/h
3 36 0.08
4 74 016
5 12b 0.28
6 200 0.44
7 294 0.65
8 405 0.89
9 548 1.21
10 714 1.58
II 895 1.98
1., 1118 2.48
11 1365 3.05
13 5 1495 3.34
14 1630 3.63

Approximate Flow over Rectangular Weirs
Crest length
1 I 21f 3ft 4ft
Head, Flow, Flow, Flow, Flow, Flow Flow, Flow, Flow,
m gpm ac-in/h gpm ac-in/h gpm ac-in/h gpm ac-in/h
2 98 0.22 198 0.44 298 0.66 398 0.88
3 181 0.40 366 0.81 552 1.22 738 1.63
4 278 0.62 560 1.24 852 1.88 1140 2.52
5 772 1.70 1164 2.58 1560 3.45
6 1010 2.22 1535 3.40 2055 4.54
7 1270 2.80 1980 4.27 2590 5.75
8 1540 3.40 2330 5 18 3120 6.90

Approdmtate Flow over Trapezoidal Weirs
Crest Length
1ft 2ft 3ft 4ft
Head, Flow, Flow, Flow, Flow, Flow, Flow, Flow, Flow,
in gpm ac-in/h gpm ac-in/h gpm ac-in/h gpm ac-in/h
2 101 0.22 202 0.45 302 0.67 404 0.89
3 190 0.42 376 0.83 560 1.24 750 1.66
4 296 0.65 580 1.28 864 1.91 1160 2.56
5 802 1.77 1196 2.66 1500 3.52
6 1062 2.34 1580 3.50 2100 4.64
7 1350 2.98 2000 4.42 2660 5.88
8 1638 3.62 2430 5.38 3220 7.14


Weir crest




S Streambed


Measuring head on the weir.










Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 30
Wind Power


Power extracted from the wind can be used for numerous purposes.
Since it is rotating shaft power it can of course substitute for
engines or motors in any of their many applications. Historically
windmills have been used for pumping water, grinding grain, sawing
lumber, and other such jobs. One characteristic which wind has,
however, makes its suitability as an energy source for many jobs
imperfect at best: that is its variability. However, if some type
of storage can be easily included, there are some applications
that can tolerate this variability. One is the provision of heat
or cooling with storage of excess for times of deficiency. Wind
energy has been used to heat water, both for dairys and for
livestock housing and residences (Soderholm, 1981). The wind
energy is converted into thermal energy simply by mechanically
agitating water. In structural space heating it is advantageous
that more energy is generated with higher wind velocity, which
also coincides with increased heating needs. An insulated tank
stores heated water to connect supply and demand. Another
application is to connect the turbine to a refrigeration
compressor to cool a produce storage structure; energy in excess
of current needs is stored for future use in the form of ice or
phase change of eutectic salts. Yet another application is to
compress air, for which storage is normally included as a
compressed air tank. Finally, pumped water can serve to store
energy whether or not the fundamental objective is to pump water.

Wind turbine electric power generators appear to be the main way
in which wind will be utilized in the near future. The technology
is well and widely known and has been used for nearly 100 years.
Wind turbines for generating electric power are designed for
higher velocities than windmills for pumping water; they often
have only 2, 3 or 4 blades. Storage of electric power is with
batteries, which are expensive and require considerable
maintenance. High capital costs are another major consideration.
The most important site characteristic is average annual wind
velocity, with about 19 km/h currently necessary to be competitive
with commercial electric power. Wind powered electric generators
may be built with capacities varying from as low as approximately
500 W to many kilowatts. Darrow and Pam (1981, pp. 145-152)
abstract a number of publications including a new periodical, Wind
Power Digest. These example the low technology approach as much
as possible with the utilization of used automobile generators and
alternators, etc. Fraenkel (1979, pp. 47-56) example numerous
available wind-electric systems, most of powers up to a few kW.
Power coefficient, the overall efficiency of a wind-electric
system, is the portion of the intercepted wind energy converted to










electric energy; typical values are 0.3 to 0.4. Rated power
outputs are stated for a particular wind velocity, say 25 or 40
km/h; what is important to the customer is the power output at
winds prevailing at the proposed site, of course. Ritchie (1983,
Chap. 19) reviewed other components of a typical wind-electric
system, including batteries, voltage regulators, inverters and
power grid tie-ins.

Larger wind-electric turbines, 20 to 500 kW and even as large as a
megawatt or larger, are now finding economic feasibility in
certain circumstances. California has over over 200 MW of
installed capacity to generate electric energy for commercial
electric power companies in the Altamont Pass, Techachapi
Mountains, and San Gorgonio Pass locations and the amount is
increasing rapidly.

Costs of wind turbine systems for generating electric power are
as low as $500/kW for 15 kW sized systems, and may typically run
from $1000 to $2000 per kW in 5 to 15 kW systems and as high as
$6000 per kW for fractional kW size systems (NAS, 1976).


References

Darrow, Ken, and Rick Pam. 1981. Appropriate Technology
Sourcebook. Volunteers in Asia, Inc. Stanford, CA.

Fraenkel, Peter. 1979. The Power Guide. Intermediate Technology
Publications Ltd., London. (pp. 43-56).

National Academy of Sciences. 1976. Energy for Rural
Development. NAS, Washington, D.C. (pp. 33-36, 113-136)

Ritchie, James D. 1983. Sourcebook for Farm Energy Alternatives.
McGraw-Hill Book Co., New York. (pp. 19-1 to 19-12)

Soderholm, L.H. 1981. Wind energy for agricultural heating.
pp.262-265 in Agricultural Energy, Vol. 1, Solar Energy, Livestock
Production. Proc. 1980 ASAE National Energy Symposium. ASAE, ST.
Joseph, MI.









Agricultural Engineering Department


AGE 6933
Appropriate Technology for Mechanized Agriculture

Lecture No. 31
Anaerobic Methane Generation


The fact that organic material, rotting under anaerobic
conditions, can produce a flammable gas has been known for
centuries. This had been observed in the phenomenon of marsh gas
and the occasional dancing of flames on marshes. However, it was
not until later dates that the process of decomposing manure,
human and agricultural wastes under anaerobic conditions was
thought of. It has been documented that in the late 1800's and
early 1900's England had developed successful designs for the
purpose of methane generation from septic tanks. Many countries
such as France, Algeria, and Germany produced methane by similar
processes which was used to run automobiles during and after
World War II.

In many of the developing countries which have a small
sources or inadequate distribution of energy supplies, methane
generating units have been developed to meet rural needs. In
India, where cow dung was used for cooking, concern over the loss
of the fertilizer capabilities of the cow dung prompted the
Agricultural Research Institute in New Delhi to begin a series of
experiments concerning anaerobic digestion of cow dung in 1939.
Taiwan also conducted similar experiment using pig manure
starting in 1955. It is estimated that about 7500 anaerobic
digesters have been built in Taiwan of which half are in
operation. The People's Republic of China (PRC) has promoted
similar systems since 1970. It is estimated that tens of
thousands of anaerobic digesters are now in operation in the PRC.
Korea installed 24000 rural methane generators between 1969 and
1973.

Methane is a colorless, odorless gas that has a heat value
of about 1000 Btu's per cubic feet. It can be used to heat
homes, power engines and perform many other household and
industrial energy requiring tasks. The gas produced by anaerobic
digestion is only about 50 to 70 percent methane. 25 to 40
percent is carbon dioxide and small amounts of other gases
including hydrogen sulfide constitutes the rest. Hydrogen
sulfide has the smell of "rotten eggs" and the intensity of its
odor is directly proportional to its amount in the gas mixture.
Many people prefer to use the term biogas rather than methane as
the product of anaerobic digestion because of the gas'
impurities.

In the anaerobic digestion process organic material is
converted to methane and carbon dioxide by specific fermentation







bacteria. The basic reaction in the digester convert carbon plus
water (2C + 2H 0) to methane plus carbon dioxide (CH + CO ).
This process occures in two stages. In the initial stage the
volatile solids in the organic wastes are broken down by
bacteria to a series of fatty acids. In the second stage methane
forming bacteria digest the fatty acids to produce methane,
carbon dioxide and other minor gases. Of the two types of
bacteria the methane forming type is more sensitive to
environmental factors such as temperature, relative acidity, and
minerals in the organic matter and grows at slower rates.

Almost any type of organic wastes can be used in anaerobic
digestion for methane generation. The gas production rates are,
however, influenced by the quality of the wastes used. Table 1
lists some potential organic wastes suggested by the National
Academy of Sciences, 1977, for use in anaerobic digesters. The
degree to which any of these wastes are used depends on local
availability and cultural acceptability. For example, many
cultures are reluctant to use methane that was created from human
wastes to cook food.

Table 1. Organic Mater with Potential for Methane Generation

Crop Wastes Sugar cane trash, weeds, corn and related
crop stubble, straw, spoiled fodder

Animal Wastes Cattle-shed wastes, poultry litter, sheep
and goat droppings, fishery wastes,
leather, wool wastes, slaughterhouse
wastes

Human Wastes Feces, urine, refuse

Industrial Wastes Oil cakes, bagasse, rice bran, tobacco
wastes, wastes fron fruit and vegetable
processing, tea waste, cotten dust, press-
mud from sugar factories

Forest Litter Twigs, bark, branches, leaves

Aquatic Wastes Marine algae, seaweeds, water hyacinths


An anaerobic digestor can produce about 8 to 9 cubic feet of
gas (containing 50 to 70 percent methane) per pound of volatile
solids added to the digester, when the organic matter is highly
degradable (night soil, poultry, pig or beef fecal mater). Table
2 lists average methane yields and energy production for various
animals suggested by Ritchie, 1983.







Table 2. Average Methane Yield and Energy Production of Various
Animals

Methane yield, Energy production,
Animal cu. ft./day Btu/hour

Cow, dairy (1200 lb) 23 568
Steer, beef (1000 Ib) 31 775
Swine (150 lb) 4 103
Poultry (4 lb) 0.21 5.25


Figure 1 shows the schematic of a basic anaerobic digester.
As can be seen from that schematic, wastes entering the digester
are watered down to about 10% solids and 90% water. The slurry
is then heated by some means. Although it is recommended to heat
the slurry or digester, the cost of heating might be a problem in
many areas. A simple design using solar energy for heating the
digester can be a good solution. In many of the tropical and
warmer climate countries it might be possible to get away with
not heating the digester. Although in these cases the production
of the digester is somewhat inhibited (especially at night), the
savings might still outweigh the decreased output. Figure 2
shows the effect of temperature on biogas production. As you can
see biogas production peaks at two different temperatures. This
is due to the two types of methane forming bacteria that exist.
Mesophilic bacteria produce at optimum rates at about 35 degrees
(Centigrade) while thermophilic bacteria have optimum production
at about 55 degrees. Although thermophilic bacteria can produce
biogas at higher rates, they are more sensitive to temperature
changes.

Figures 3, 4, and 5 represent some typical digester designs.

There are a number of considerations that must be taken into
account in order to have a successful anaerobic digseter. Size
of the digester is an important decision in the digester design.
Either the amount of wastes available to use in the digester or
the desired rate of gas production can determine the size of
digester needed. This brings us to the concept of retention
time. Retention time is the amount of time that the waste will
be in the digester. When waste is put into the digester, gas
production is high at first but then begins to slow down. The
longer the retention time the larger the size of the digester.
Correct design involves the selecting the best trade-off between
gas yield and digester construction cost. In general, 12 to 18
days of retention time are used for mesophilic systems, while 5
to 6 days are used for thermophilic systems, Stout, 1984. The
minimum volume of the digester can be determined by multiplying
the detention time by the volume of material that must be added
each day (loading rate) to produce the desired volume of gas
daily.

Another consideration is the stability of the digester.
Sudden changes in the environment of the digester can disrupt the







bacterial breakdown and methane generation. Digester loading
rates and temperatures should be kept fairly stable and at the
recommended levels. Inert wastes, such as sand or rocks should
be removed before putting wastes into the digester so as not to
harm its mechanical parts.

A minor impurity of the biogas produced by anaerobic
fermentation is hydrogen sulfide, a toxic gas that is highly
corrosive in water solution. However, this gas can be safely
removed from the biogas by bubbling through lime water.

Table 3 shows some of the advantages and disadvantages of
anaerobic digestion suggested by the National Academy of
Sciences, 1977.







References

Darrow, Ken and Pam, Rick. 1981. Appropriate Technology
Sourcebook, volume one. Volunteers in Asia, Inc. Stanford, Ca.
(pp.. 182-188)

National Academy of Sciences. 1977. Methane Generation from
Human, Animal, and Agricultural Wastes. NAS, Washington, D.C.

Ritchie, James D. 1983. Sourcebook of Farm Energy Alternatives.
McGraw-Hill Book Company, New York. (pp. 16-1 to 16-14)

Stout, B. A. 1984. Energy Use and Management in Agriculture.
Brenton Publishers, North Scituate, Mass. (pp. 206-222)
f
















Fertilizer


Fertilizer Livestock feed
F7~~io I-/~h~fT~cop A~ ic*o;c die Ent


*1



0





S2


FIGURE 2..


Temperature, *C

Effect of Temperature on Biogas Production (69)







bacterial breakdown and methane generation. Digeister loading
rates and temperatures should be kept fairly stable and at the
recommended levels. Inert wastes, such as sand or rocks should
be removed before putting wastes into the digester so as not to
harm its mechanical parts.

A minor impurity of the biogas produced by anaerobic
fermentation is hydrogen sulfide, a toxic gas that is highly
corrosive in water solution. However, this gas can be safely
removed from the biogas by bubbling through lime water.

Table 3 shows some of the advantages and disadvantages of
anaerobic digestion suggested by the National Academy of
Sciences, 1977.






TABLE 3 Advantages and Disadvantages of Anaerobic Digestion


Advantages


Disadvantages


Produces large amount of methane gas.
Methane can be stored at ambient tempera-
ture.
Produces free-flowing. thick, liquid sludge.
Sludges are almost odorless, odor not dis-
agreeable.
Sludge has good fertilizer value and can
be used as a soil conditioner.
Reduces organic content of waste materials
by 30-50 percent and produces a stabilized
sludge for ultimate disposal.
Weed seeds are destroyed and pathogens
are either destroyed or greatly reduced in
number.
Rodents and flies are not attracted to the
end product of the process. Access of pests
and vermin to wastes is limited.
Provides a sanitary way for disposal of
human and animal wastes.
Helps conserve scarce local energy resources
such as wood.


Possibility of explosion.
High capital cost. (However, if operated
and maintained properly, the system may
pay for itself.)
May develop a volume of waste material
much larger than the original material.
since water is added to substrate. (This
may not be a disadvantage in the rusa'
areas of developing countries where farm
fields are located close to the village, thus
permitting the liquid sludge to be applied
directly to the land, serving both for irriga-
tion and as fertilizer.)
Liquid sludge presents a potential water-
pollution problem if handled incorrectly.
Maintenance and control are required.
Certain chemicals in the waste, if excessive,
have the potential to interfere with digester
performance. (Howevet, these chemicals
are encountered only in sludges from in-
dustrial wastewater and therefore are not
likely to be a problem in a rural village sys-
tem.)
Proper operating conditions must be main-
tained in the digester for maximum gas pro-
duction.
Most efficient use of methane as a fuel re-
quires renmuAl of impurities such as C02
and H2S, particularly when the gas is to be
used in internal-combustion engines.













































N\ Cross section
6t
Gas utilization system
m


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