|
HISTORIC NOTE
The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
of Florida
September, 1932
COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30. 1914)
AGRICULTURAL EXTENSION SERVICE, UNIVERSITY OF FLORIDA
FLORIDA STATE COLLEGE FOR WOMEN,
AND UNITED STATES DEPARTMENT OF AGRICULTURE,
COOPERATING
WILMON NEWELL, Director
SOLAR WATER HEATERS
By
FRAZIER ROGERS,
Professor of Agricultural Engineering,
Florida College of Agriculture
Fig. 1.-Solar water heater on the College of Agriculture farm.
Bulletins will be sent free upon application to the
AGRICULTURAL EXTENSION SERVICE,
GAINESVILLE, FLORIDA.
Bulletin 68
BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola
A. H. BLENDING, Tampa
FRANK J. WIDEMAN, West Palm Beach
RAYMER F. MAGUIRE, Orlande
GEO. H. BALDWIN, Jacksonville
J. T. DIAMOND, Secretary, Tallahassee
STAFF, AGRICULTURAL EXTENSION SERVICE
JOHN J. TIGERT, M.A., LL.D., President of the University
WILMON NEWELL, D.Sc., Director
A. P. SPENCER, M.S., Vice-Director and County Agent Leader
J. FRANCIS COOPER, M.S.A., Editor
R. M. FULGHUM, B.S.A., Assistant Editor
E. F. STANTON, Supervisor, Egg-Laying Contest
RUBY NEWHALL, Secretary
COOPERATIVE AGRICULTURAL DEMONSTRATION WORK
W. T. NETTLES, B.S., District Agent
H. G. CLAYTON, M.S.A., District Agent, Organization and Outlook Specialist
J. LEE SMITH, District Agent and Agronomist
R. W. BLACKLOCK, A.B., Boys' Club Agent
HAMLIN L. BROWN, B.S., Dairyman
E. F. DEBUSK, B.S., Citrus Pathologist and Entomologist
N. R. MEHRHOF, M. AGR., Poultryman
WALTER J. SHEELY, B.S., Agent in Animal Husbandry1
J. E. TURLINGTON, Ph.D., Agricultural Economist2
FRANK W. BRUMLEY, M.S.A., Agricultural Economist, Farm Management
W. R. BRIGGS, B.S.A., Assistant Agricultural Economist, Farm Management
D. E. TIMMONS, M.S.A., Agricultural Economist, Marketing
CARLYLE CARR, B.S., Specialist in Rodent Control1
COOPERATIVE HOME DEMONSTRATION WORK
FLAVIA GLEASON, State Agent
LUCY BELLE SETTLE, B.S., District Agent
RUBY MCDAVID, District Agent
MARY E. KEOWN, M.S., District Agent
VIRGINIA P. MOORE, Home Improvement Agent
ISABELLE S. THURSBY, Economist in Food Conservation
ANNA MAE SIKES, B.S., Nutritionist
NEGRO EXTENSION WORK
A. A. TURNER, Local District Agent
ROSA J. BALLARD, Local District Home Demonstration Agent
lIn cooperation with U. S. D. A.
2Part-time.
Solar Water Heaters
By FRAZIER ROGERS
A supply of hot water is needed in every household. In Florida
there should be little difficulty in utilizing the rays of the sun as
a means of heating water for domestic purposes. In the penin-
sular section of the state many solar heaters are operating satis-
factorily at the present time. Some of the heaters have been
installed for more than 10 years and are still functioning to the
satisfaction of their owners. Many of these heaters are "home-
made", although many commercial heaters are to be found in
the state.
The basic information for this bulletin was obtained from a
solar heater constructed on the College of Agriculture farm by
the Department of Agricultural Engineering of the University
of Florida. Temperature of the water in the storage tank is
recorded constantly by a recording thermometer. Records of the
temperatures have been kept for 18 months. The highest tem-
perature recorded during that period was 1910 Fahrenheit, which
was reached on September 19, 1931. There were very few days
during the entire year when the temperature of the water in the
storage tank did not reach 120 Fahrenheit.
The design of the heater is very simple. It consists of an
absorber and a storage tank, with connective pipes. The water
circulates through the coils in the absorber due to thermo-siphon
action. That is, water upon being heated becomes lighter and
will rise to a higher level if a circulating system is provided.
The storage tank is placed higher than the heating element
(absorber) so that the cold water will replace the hot water
from the absorber when circulation begins. The water will con-
tinue to circulate in the system as long as there is a difference
in temperature between the water in the absorber and that in
the storage tank.
ABSORBER
The absorber is the heart of the solar heating system. The
heating of the water will depend upon the efficiency of the ab-
sorber. The utmost care should be exercised to see that the
absorber is properly constructed.
Figure 4 gives a front view of the absorber coils with the tank
Florida Cooperative Extension
connections for both solar absorber and auxiliary heater. The
auxiliary heater is not a part of the solar system but may be
desired in event the solar heater does not supply an ample quan-
tity of hot water. This would be especially desirable where the
water demands were variable. The storage tank must be higher
than the absorber. The cut-off valve as shown in Fig. 4 may be
of the globe type and operated by hand or may be of the auto-
matic type. This valve is necessary to prevent the backward
movement of the water through the circulating system during
the night, thereby cooling it. If operated by hand it should be
conveniently located so as to make its operation less troublesome.
Fig. 2.-Diagram of end of absorber, showing angle at which the absorber
should be set.
The absorber is usually placed on the roof on account of the
protection afforded by being above the ground out of the reach
of children who might damage the glass. So far as operation is
concerned it might be placed on the ground. The angle at which
the absorber is placed to the horizontal or ground surface is very
important. Higher temperatures are secured when the rays of
Solar Water Heaters 5
the sun strike the absorber at right angles. Since the sun's rays
strike the earth at different angles during different seasons of
the year, and since it is fairly easy to heat the water during sum-
mer, the absorber should be so arranged that the sun's rays will
strike it at a 90 degree angle about the first of March and the first
of October each year. For the latitude of Florida, placing the
absorber at an angle of 40 degrees to horizontal will permit the
sun's rays to strike it at an angle of 90 degrees during October
and March, and has proven satisfactory. Figure 2 shows the
position of the absorber and also the pipe connections leading to
and from the storage tank.
Figure 3 gives a cross-sectional view of the absorber. The
bottom of the absorber is constructed of tongue and groove ma-
terial on which is placed two inches of insulating material. Care
toI jut ____""____ __ i________\ ___ ini .. ..
'ie c-
/o/?or <. it's h '
Secr on or A
.. -- .... ..:,- ~ i Ii ...--- -1
Fig. 3.-Cross-sectional diagram of the absorber, concrete, pipes, coil and sash.
should be exercised to waterproof this insulating material, if it
is absorptive. Coal tar and roofing paper may be used for this
purpose.
To increase the absorption material as well as to hold the coils
in place, about 2 inches of concrete of a 1-2 mixture is placed on
the insulation. While the concrete is still soft the coil should be
imbedded to 1/ of the diameter of the coil pipes. In constructing
the absorber it has been found convenient to place the coil on the
insulating material and support it with 2" blocks until the con-
crete can be placed. Thick sheet metal has been used in place of
concrete with very good results, the coil pipes being fastened on
the sheet metal instead of being imbedded in the concrete. The
coil is.made of 3/4" black or galvanized wrought iron pipe. The
Florida Cooperative Extension Solar Water Heaters 7
SLAR H L A T R.
;. 4.-Complete diagram of solar water heater, showing absorber, tank and auxiliary heater, with connections. Connecting pipes from absorb +" tank are only indicated by breaks in the pipi
L L
Solar Water Heaters 7
Florida Cooperative Extension
8 Florida Cooperative Extension
joints should be well leaded so as to prevent leakage. The inside
of the absorber should be painted a dull black to increase its
efficiency.
The glass used is ordinary window sash. Some of the glass
substitutes have been used with good results. The area of glass
needed will depend upon the amount of hot water wanted per day.
The general practice is to have one square foot of glass surface
for each gallon of hot water wanted per day. Then for a 30-gallon
capacity system one would need an absorber about 4x71/2' or 5x6'.
These are the most common dimensions for that capacity tank.
It is essential that the absorber be constructed as nearly air-
tight as possible, to prevent the loss of heat by radiation.
STORAGE TANK
An insui .ced storage tank is necessary in a solar hot water
system on account of the necessity of keeping the water hot over
night as well as maintaining the heat for two or three days in
event of no sunshine. The tank used in most solar systems is the
same type tank used in other hot water systems. Figure 5 shows
the most common method of insulating tanks. Build a square
box so that the tank when placed in it will have at least 2 inches
of clearance on all sides. The tank is then placed in the box and
insulation poured around it. Ground cork, dry sawdust or shav-
ings may be used. Be sure that there are no leaks in the tank
that will keep the insulation wet, for these materials lose most of
their effectiveness as insulators when they become wet. Asbestos
may be used as an insulator but is usually more expensive than
the other materials mentioned. If the absorber is any great dis-
tance from the storage tank the pipes connecting these should be
insulated. For short distances this is not necessary.
If the absorber is to be used where there is danger of the water
freezing, provision should be made for draining the water from
the system. It would require several days of low temperatures
to result in any damage from this cause. "
Solar Water Heaters
=2i Cole/ wa/er
cZCd w7 soTr
SC T 7i oN S f#. Ro UG TA A'/4
Fig. 5.-Cross-sectional diagram of storage tank, showing connections and
insulation.
llot' rWate.-
Florida Cooperative Extension
BILL OF MATERIAL FOR A 30-GALLON TANK CAPACITY HEATER
The following bill of material will give an idea of the require-
ments for a 30-gallon tank capacity heater.
Absorber
5 18"x48" single window light sash
2 pieces 2"x4"x10' lumber
2 pieces 2"x2"x 4' "
12 pieces 1"x4"x10' tongue and groove flooring
36 sq. ft. 2" insulation
5 pieces %1"x3"x4' batteries
8 pieces %"x4"x4' cleats
2% dozen No. 12 wood screws
6 lbs. assorted nails
/2 sack Portland cement
3 cu. ft. sand
1 qt. black asphalt paint
1 qt. lead and oil paint
Coil
18 pieces %4" black pipe 6' long
2 pieces 3/" 8' "
19 pieces %" close return bends
40 pipe straps for / pipe
1 /" tee
1 %" ell
1 cut-off valve
1 %" gal. pipe and cap 1' for vent
Tank
1 30-gal. range boiler
20 pieces 1"x4"x8' tongue and groove flooring
1 bbl. insulation (ground cork, sawdust, etc.)
|
RSS
HIDE
