Practical Uses of Solar Energy

June 1992
Energy Efficiency & Environmental News:
Practical Uses of Solar Energy1
Florida Energy Extension Service and Mike West2
PRACTICAL USES OF SOLAR ENERGY
electricity (heat pump) or natural gas for a 24’ by 20’
pool.
You can put solar energy to work for you and save
energy and money.
Switching to solar helps protect
A solar system for a 24’ by 20’ pool costs $3200 to
Florida’s beautiful and delicate environment, and reduce
$4200. The installed cost of a solar system is about the
our dependence on fossil fuels. Today, there are three
same as a heat pump, or about twice the cost of a natural
practical uses of solar energy for the homeowner: pool
gas heater ($1500 to $7000, depending on the desired
heating, hot water, and electricity for remote locations.
pool temperature and the size of the pool). Solar heater
maintenance costs are much less than either type of
conventional heater. An additional advantage of solar is
Less use of electric power generated from fossil
quiet -- solar pool heaters are almost silent.
fuels means less greenhouse gas and acid rain emissions.
Every kWh saved eliminates 1.5 pounds of carbon
The best type of pool heater collectors are the rubber
dioxide, 0.2 pounds of sulfur dioxide, 0.25 pounds of
mat type, according to FEES specialist Gary Cook. The
carbon monoxide, and 0.01 pounds of nitrogen oxide
mats are virtually indestructible, and if damaged, are
emissions.
easily repaired. Gary has had this type of collector on
his roof for over 12 years. The mats heat his 700 gallon
To purchase solar systems, consult a local contractor.
hot tub from 75°F to over 100°F in less than one hour
Many communities are served by an energy conservation
(two hours in winter). His swimming season is extended
or solar contractor. Check the yellow pages under "Solar
three months (Gary lives in Gainesville).
Energy Systems."
Follow up on each potential
contractor’s list of references.
Solar Water Heating
Solar Pool Heating
Today, there are thousands of solar water heating
systems installed in Florida. They put the sun to work
The most practical and popular use of solar energy
heating water for showers, hot tubs, and dish washing.
for the homeowner is solar pool heating. A solar pool
Reliable solar water heating systems are economical
heater extends the swimming season from May through
where natural gas is unavailable. Modern systems can
October to February through November (in Central
supply at least 70% and up to 90% of a
Florida, water temperature at least 75 degrees).
This
amount of heating is equivalent to $1500 worth of
1.
This document is the June 1992 issue of Energy Efficiency and Environmental News, the newsletter of the Florida Energy Extension Service, Florida
Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: June 1992.
2.
Florida Energy Extension Service, University of Florida, P.O. Box 110940, Gainesville, FL 32611-0940; Mike West, Mechanical Engineering MEB
237, UF, Gainesville, FL 32611, phone 904-392-5886, suncom 622-5886, fax 904-392-1071, vax GNV::MKW, Cooperative Extension Service, Institute
of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.
The Florida Energy Extension Service receives funding from the Florida Energy Office, Department of Community Affairs and is operated by the University
of Florida’s Institute of Food and Agricultural Sciences through the Cooperative Extension Service. The information contained herein is the product of the
Florida Energy Extension Service and does not necessarily reflect the views of the Florida Energy Office.

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Energy Efficiency & Environmental News: Practical Uses of Solar Energy
Page 2
family’s hot water needs.
This can cut the typical
company.
Some farmers use PV powered pumps for
Florida home electric bill by 10% to 13%. In this sense,
watering of livestock on remote grazing areas.
PV
a solar hot water heater is a good economic investment.
systems power street, billboard, bus stop, and highway
The return on investment is the cash saved on utility
sign
lights,
navigational
buoys,
and
emergency
bills. This corresponds to an annual rate of return of 7-
telephones throughout Florida.
Small PV systems
9%, very respectable for such a safe investment. Quality
provide
portable
power
for
camping
equipment,
systems last as long as the home they are installed in.
computers, fans, pumps, and test equipment. PV cells
The Florida Solar Energy Center can provide their
are used in calculators and watches. Photovoltaic power
ratings of solar collectors and systems (see References).
is practical where access to utility company lines is
costly, and for low power/portable needs.
Solar water heating systems range in price from
Industry improvements have reduced the cost of PV
$1600 for a small system serving two people, up to
systems to 25-50¢ per kWh. This is still
$5000 for a system that serves a family of eight.
A
considerably more than the 7-10¢ per kWh of utility
quality system sized for a family of 4 costs $3000 to
power. The U.S. Department of Energy (DOE) goal is
$3500.
A solar water heater could save the average
PV power at 12¢ to 20¢ per kWh before 2000.
Florida family around $300 per year, and help protect
the environment by reducing the pollution caused by
To take advantage of the economies of large scale
generating electricity from fossil fuels.
production, the DOE announced a new strategy to
accelerate the use of PV power. The DOE Solar 2000
Be aware of a few important details when selecting
plan calls for an increase in PV use by a factor of ten by
a solar water heating system. A system
the year 2000. Use of PV power is increasing by over
sized for a typical Florida family uses two 4’ by 8’
25% each year, and has been for the past few years.
collectors. Look for a system that uses a solar powered
pump. According to Tom Lane* of Energy Conservation
PV power systems range in price from $75 to
Services, most Floridians should select closed-loop
$40,000 depending on how much electricity the user
systems that use antifreeze to protect the system from
needs. The box below shows how system cost varies.
freezing. Drain-back systems are another option. (Open-
PV systems are a poor economic investment if power is
loop systems are suitable in South Florida and the Keys).
readily available: the annual rate of return is around 1%.
The storage tank should hold at least 20 gallons of water
However, in outlying or isolated locations, connecting to
per
family
member.
Extra
storage
capacity
is
faraway power lines can cost more than a complete PV
recommended, and is inexpensive.
power station!
*
Licensed
solar
contractor,
Gainesville
FL.
Table 1. Cost Comparison. High Capacity Solar
(904)373-3220.
FEES does not endorse brands or
PV Systems Cost Considerably More Than Low
contractors.
Capacity Systems.
Solar Electric Power Generation
Appliances Powered By Solar PV
System
Cost
Today, solar photovoltaic (PV) systems are at work
converting the suns radiation directly to electricity. PV
Outdoor/Path lighting
$75
generated power has three main advantages over all other
types of remote power generation:
DC power for computer or TV only
$800
TV, VCR, stereo, lights, computer
$7000
Free Inexhaustible Power
-- above plus refrigerator
$12,000
Simplicity
-- above plus well pump (home)
$15,000
Low Maintenance
-- above plus ventilation fans
$17,000
-- above plus central A/C
$31,000
PVs provide electricity to rural homeowners,
ranchers, and farmers for TV, VCR, stereo, landscape
and security lighting, pumps, electric fences, and
livestock feeders, without connection to the power

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Energy Efficiency & Environmental News: Practical Uses of Solar Energy
Page 3
As Table 1 shows, even modest increases in
Simplified Sizing Procedure for Solar Domestic Hot
electrical capacity increases the price considerably.
Water Systems. Florida Solar Energy Center #GP-
When using PV power, it is especially cost effective to
10. ERD #417.
replace inefficient appliances with modern energy
efficient ones -- allowing selection of a less costly PV
Thermal Performance Ratings of Solar Collectors.
system. Since PV cells produce DC voltage, the use of
Florida Solar Energy Center #’s GP-14 and GP-16.
DC
(instead
of
conventional
AC)
pumps,
fans,
refrigerators, lights, etc. makes sense.
Use of DC
FSEC Approved Solar Energy Systems: Domestic Hot
appliances reduces the cost of the PV system since they
Water and Pool Heating.
Florida Solar Energy
are typically more efficient and require no invertor
Center #GP-15.
capacity. (The invertor is the part of the PV system that
changes the PV cells DC voltage to AC.) In most cases,
Measurement of Solar Radiation.
IFAS publication
it is not yet economical to power cooling and heating
#CIR-827, ERD# 214.
equipment with PV power since these are seasonal loads.
Heating and cooling accounts for over half the
Solar Water Heating: A Question and Answer Primer.
residential energy use of a typical Florida family.
Florida Solar Energy Center #EN-5. ERD #426.
PV power systems are modular, so they easily grow
Solar Heating of Swimming Pools: A Question and
with the users budget and electricity needs. PV system
Answer Primer. Florida Solar Energy Center #EN-6.
size is measured in watt-hours per day (WH/D). Typical
ERD #422.
system cost is around $3 per WH/D of system capacity.
The smallest systems (around 200 WH/D) can cost up to
Solar Swimming Pool Heating in Florida: Collector
$5 per WH/D, while very large systems (10,000 WH/D)
Sizing and Economics. Florida Solar Energy Center
cost less than $3 per WH/D.
Storage batteries are
#GP-13. ERD #423.
required for power at night and on overcast days. The
required size and cost of a PV system can be estimated
Solar Water Heating Options in Florida. FSEC #EN-9.
using the Sizing Worksheet given in Table 2.
ERD #425.
Utility bills can be used to determine the WH/D of
Sources of Solar Consumer Protection.
Florida Solar
electricity currently consumed. Most bills give "average
Energy Center #FS-29. ERD #428.
kWh used per day," simply multiply this number by
1000 to obtain WH/D. Or, (1) take the total kWh on the
Global Climatic Change Primer.
Florida Energy
bill, (2) divide by the number of days in the billing
Extension Service # EES 72.
period, and (3) multiply by 1000 to obtain WH/D.
Using this method, one can see that a conventional small
The Greenhouse Effect. FSEC #EN-16. ERD #431.
home, with a $65 monthly electric bill, would require
25,000 WH/D of PV capacity to go completely solar
The worksheet in Table 2 will aid in estimating the
using the same appliances and lighting. The great cost
required size of a solar photovoltaic electric power
of such a system emphasizes the importance of using
system. In the first block, list all the appliances which
efficient lighting and appliances, natural gas for cooking
are to be powered by the PV system.
Check the
and heating, and fans for cooling.
appliance label or nameplate for its rated wattage. Next,
estimate the number of hours per day each appliance is
References
"on". Then, follow the calculation instructions in lines
A through G to arrive at the estimated cost of a
Solar Photovoltaics: Out of the Lab and onto the
complete PV power system.
Production Line. Mechanical Engineering, January
1992 by Steven Ashley.
Solar
Equipment
Standards:
some
Questions
and
Answers.
Florida Solar Energy Center #GP-9.
Energy Rescource Directory #421.
Contact the
Center at 407-783-0300.

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Energy Efficiency & Environmental News: Practical Uses of Solar Energy
Page 4
Table 2. PV Sizing Worksheet. Check Appliance Labels For Wattage. For Ratings in AMPS, Multiply AMPS x
VOLTS (120 or 240) to Obtain WATTS. HOURS/DAY is Hours Used Per Day.
List All Appliances to be PV Powered
WATTS
HOURS/DAY
WH/
D
A. Load: Sum of all WH/D above
LOAD WH/D =
B. Battery and Invertor Losses: 25% of line A.
LOSSES WH/D =
C. Net energy needed per day: Add lines A and B.
NET WH/D =
D. Desired number of days of storage capacity.
STORAGE DAYS =
E. Total required system size: Multiply line C by line D.
TOTAL WH/D =
F. System unit cost. (typically $3 to $5)
$ per WH/D =
G. Total system cost. Multiply line E by line F.
TOTAL COST =
$
When using PV power, it is especially cost effective to
Solar Pool Heating
replace inefficient appliances with modern energy
efficient ones.
The most practical and popular use of solar energy
for the homeowner is solar pool heating. A solar pool
SIMPLY SAVING
heater extends the usable swimming season from May
through October to February through November (in
Energy Efficient
Central Florida, water temperature at least 75 degrees).
This amount of heating is equivalent to $1500 worth of
Economical
electricity (heat pump) or natural gas for a 24’ by 20’
pool.
Environmentally Sound
Solar Water Heating
Practical Uses of Solar Energy
Today, there are thousands of solar water heating
You can put solar energy to work for you and save
systems installed in Florida. They put the sun to work
energy and money.
Switching to solar helps protect
heating water for showers, hot tubs, laundry, and dish
Florida’s beautiful and delicate environment, and reduce
washing.
Reliable solar water heating systems are
our dependence on fossil fuels.
Less use of electric
practical where natural gas is unavailable.
Modern
power generated using fossil fuels means less greenhouse
systems can supply at least 70% and up to 90% of a
gas and acid rain emissions.

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Energy Efficiency & Environmental News: Practical Uses of Solar Energy
Page 5
family’s hot water needs.
This can cut the typical
feeders, without connection to the power company.
Floridians home electric bill by 10% to 13%.
Some farmers use PV powered pumps for watering of
livestock on remote grazing areas. PV systems power
Solar water heating systems range in price from
street, billboard, bus stop, and highway sign lights,
$1600 for a small system serving two people up to
navigational
buoys,
and
emergency
telephones
$5000 for a system that will serve a family of eight. A
throughout Florida. Small PV systems provide portable
quality system sized for a family of 4 will cost $3000 to
power for camping equipment, computers, fans, pumps,
$3500.
A solar water heater will save the average
and test equipment. PV cells power calculators, watches,
Florida family around $300 per year, and help protect
and battery chargers.
our environment by reducing greenhouse gas and acid
rain emissions from electric power generating plants.
Photovoltaic power is practical where access to
utility
company
lines
is
costly,
and
for
low
Solar Electric Power Generation
power/portable needs. PV power systems range in price
from $75 to $40,000 depending on how much electricity
Today, solar photovoltaic (PV) systems are at work
the user needs.
converting the suns radiation directly to electricity. They
provide electricity to rural homeowners, ranchers, and
farmers for TV, VCR, stereo, lighting, pumps, electric
fences, and livestock

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