AOH :: SUNPRIME.TXT
Solar energy primer
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June 23, 1991
SOLPRIME.ASC
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This file courtesy of Ron Barker.
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A Solar Energy Primer
Solar Energy can be converted for use on earth in several ways. The
Sun is of course our closest star, upon which we are dependent for
life. The sun is estimated to be at least 4.5 billion years old and
it has an average distance from earth of about 92,000,000 miles.
Its core temperature is 15,000,000 degrees centigrade. Its total
energy output is 3.83 x 10^23 KW. It is the source of energy for
oil, natural gas, coal, hydro, wind and an argument could be made
that even nuclear fission owes its existence to the sun.
Sunlight is a form of Radiant Energy that is manifests as heat in
any object that is exposed to it. Heat is the result of excited
molecules in the object, not the sunlight itself. This is analogous
to when you get sunburned on a relatively cool day and don't realize
it, which is a result of too many ultraviolet rays.
The technology involved in capturing this solar energy for man's use
goes back thousands of years. There are several methods of
utilizing Solar Energy.
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PASSIVE SOLAR is the design of structures to efficiently use solar
energy without mechanical devices. A building can be so designed as
to become a solar collector. This is done by having large window
areas placed on the south side of the home which capture solar
energy in tile floors that absorb, store and re-radiate the heat.
Overhangs can also be provided in the design to block the sun in
summer months.
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Passive Solar Design usually requires that these concepts are
incorporated into the structure when it is built since a retrofit is
difficult, but not impossible.
Obviously a design that is appropriate in Montana is inappropriate
in Mississippi, where for a good portion of the year, solar heat
gain is not advantageous.
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ACTIVE SOLAR is the process of using mechanical devices to capture
and store solar energy. Most people are familiar with the flat
plate solar collector, they were becoming popular during the late
1970's and early 1980's.
The flat plate collector consists of a box typically 8" high by 5'
wide by 10' long that had a copper absorber plate and tubing. A
glass cover is placed over the box and the greenhouse effect creates
temperatures up to 200 degrees F inside the collector.
A pump circulates a heat transfer fluid through the collector, then
through a heat exchanger. A separate pump circulates water from a
hot water tank through the heat exchanger transferring heat from the
collector to the storage tank.
A properly designed solar thermal system provides 70% or better of a
family's hot water in a climate like Mississippi.
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A variation of the flat plate system that is very popular in
Australia and Israel is the thermosyphon system that does not use
pumps or controls.
The storage tank is placed above the collector and as the water is
heated in the collector, it rises to the storage tank and cooler
water enters the collector. Thermosyphon systems are extremely
efficient for domestic hot water uses and have been used in
Australia for 40 years.
The design life of a properly designed active solar thermal system
is at least 20 years. Thermal systems can also be used to heat
homes using heat exchangers such as baseboard heaters. Usually
there is a backup source such as gas or electric to provide for
extensive over-cast periods.
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Solar air collectors do not use water but rather air as the heat
transfer medium. This system uses blowers to circulate air through
the collectors and directly heat a home. Heat can be stored in rock
bins or transferred using water as the heat carrier medium.
One of the interesting uses for solar air systems is drying grains
such as wheat, rice etc.
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FOCUSING CONCENTRATOR COLLECTORS are very high temperature and
pressure systems that are applicable to industrial and large scale
power generation. They work in a similar fashion to a magnifying
glass in the sunlight. Solar Energy is concentrated using lenses or
mirrors onto a central "receiver".
Fluid is circulated through the receiver where temperatures of 7,000
degrees have been generated. The heat converts water to steam which
then drives a steam turbine. The largest system currently on line
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is in the Mohave Desert of California, and is generating
approximately 300 megawatts of electricity.
The largest single unit is SEGS 8, rated at 13.8 KV 5000 Amps or 80
Megawatts. Each system is (1) Square Mile in Area with linear
"trough" collectors that track the sun. Currently there are four
additional units under construction rated at 80 Megawatts each.
Concentrating collectors operate more efficiently in a desert
environment, as intermittent cloud cover can produce temperature
differentials in the array. This in turn produces physical stress
from expansion and contraction of the material. Concentrators
are not efficient at converting diffuse solar energy, an advantage
that flat plate collectors have over the concentrating.
In other words on a partly cloudy day the concentrator would be
practically useless, where a flat plate system generates heat even
on overcast days due to the greater surface area.
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PHOTOVOLTAICS is the direct conversion of sunlight to electricity.
This is achieved by layering a semiconducting material, usually
silicon, into at least two layers consisting of a P and N layer
separated by a Boron barrier layer.
To make a very long story extremely short, sunlight "knocks"
electrons from the silicon that then follows the path of least
resistance onto "grids" that have been mounted onto the surface and
back of the solar cell.
These "cells" are then connected in a manner similar to flashlight
batteries, that is, positive to negative, and are configured to
provide the appropriate power desired. The cells are mounted in an
aluminum frame with a glass cover.
The first use of solar cells for power, was space satellites.
Another common use is for "solar" calculators which have become
popular during the last few years. There are larger applications
for "terrestrial" use that are coming into use.
It is already economically competitive to use PV (Photovoltaic) if a
home is to be powered at a distance of 1/2 mile from the closest
utility service.
The choice becomes one of paying a utility company to construct a
line to the home and then paying a monthly bill or constructing a PV
System and being self sufficient.
Other practical applications include small panels for keeping the
batteries charged on tractors, bull dozers, etc. that spend hours
outside and are used intermittently. Recreational Vehicles are an
additional use that is becoming increasingly popular. The PV RV
works very well due to the 12 Volt System for which the RV is wired.
The Photovoltaics can provide a means of reducing the use of the
Generator, extending its life and reducing the associated noise.
PV's have also become practical for pumping water in remote
locations using submersible pumps. Also PV powered pump jacks are
available that can pump up to 5000 gallons a day with out using gas
or utility connections.
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Telecommunications is also a practical application of PV and there
are many Microwave repeaters powered by sunlight. In fact wherever
a remote location needs electricity, PV is the hands down winner for
providing it.
A diesel or gas generator needs constant fuel and attention, where
PVs operate without fuel and the only maintenance is occasional
checking of batteries.
Photovoltaics for residential use can be achieved in two ways.
First is the utility inter-tie in which excess electricity is sold
to the utility. The homeowner pays the difference in what is
consumed and produced.
The utility however is only obligated to pay the "avoided" cost for
the electricity which is usually considered to be about 60 cents on
the dollar on what the utility charges.
Other drawbacks are that when the utility goes offline, the PV
system must also go offline to prevent shock to line workers. The
utility inter-tie would not require battery storage however, which
is a significant cost of PV Systems.
The second type of system could be considered a Solar Powered
Uninterruptable Power Supply for the home. A battery bank provides
power for the home which is charged by PV when solar is available,
when solar is not available the batteries are charged by the
utility. This system offers several advantages including backup
power for utility loss and substantial savings on electrical bills.
Should these savings be reinvested into the system, eventual
disconnect from the utility would be possible. As utilities
increase rates, the construction of these systems will be
inevitable. An additional benefit to the United States would be the
decentralization of the electrical supply.
Currently a concerted terrorist attack could bring down the entire
electrical network, with the attack of a relatively few power
transformers and transmission lines. PV would be a way of not
having all of our eggs in one basket.
If you have questions concerning Photovoltaics or Solar Thermal,
please feel free to contact me on The Continental Divide or at
the following address:
Southern Solar Electric
c/o Charlie Brister
514 Plainview Circle
Richland, MS 39218
(601) 939-5976
Compuserve 72527,1677
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Vangard note....
An average modern home uses up to 10,000 Watts of power while
an apartment will use up to about 8,000. Of course, this
varies depending on the size of the dwelling, whether or not a
climate controlled system is used to maintain a stable
temperature and how many appliances are used.
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Many people are not aware that most modern equipment is
partially ON all the time. The practice of designing this
feature into modern equipment began because older Television
sets required a warmup time before the picture would come on.
When the newer circuitry was first introduced, it was
advertised as "instant-on" to lure the buyer into selecting the
new models since they would not have to wait until the picture
tube heated up.
A modern dwelling therefore usually has at least one TV, at
least one VCR, one or more refrigerators and a host of
electronic appliances which require some form of idling power.
So it is very easy to total up the watts necessary.
Inductive devices are not generally on all the time, but they
are the ones which use the greatest amount of energy, usually
because they drive heavy loads, such as refrigeration units,
air conditioners, washer/dryers, generally speaking, most
motors.
An interesting observation in relation to the so-called free
energy devices is that they will ONLY power RESISTIVE devices
and NOT INDUCTIVE devices. One of the reasons cited for this
is that the free energy usually depends on a tuned circuit
which can be considerably loaded by any inductive components.
It would make an interesting study to see just how much energy
was used when all the devices which use this idling current
were PHYSICALLY DISCONNECTED from the power lines when not in
actual use. We would probably be amazed as to how our power
bill would diminish were we to implement such a simple
procedure.
We have a friend who suggested making giant versions of thermo-
electric converters using P/N junctions. He says he and a
group of friends made one of these giant thermocouples and
planted it in the ground where it would experience a
temperature differential between the coolness of the earth
(averaging about 68 degrees at 6 feet year round) to that of
the above ground air.
Of course, there are also multiple thermodynamic systems which
use very sensitive refrigerants to successively tap into any
heat/cool temperature differential.
It would be nice to have some bucks to investigate the various
methods and make a kit which anyone could build and use to
furnish power for their home or transport.
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If you have comments or other information relating to such topics
as this paper covers, please upload to KeelyNet or send to the
Vangard Sciences address as listed on the first page.
Thank you for your consideration, interest and support.
Jerry W. Decker.........Ron Barker...........Chuck Henderson
Vangard Sciences/KeelyNet
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If we can be of service, you may contact
Jerry at (214) 324-8741 or Ron at (214) 242-9346
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