ENERGY- SOLAR FACTS

         By: Chan Eddy/KA1OU

 Solar power is often touted as a solution to our energy needs, and it can
be a useful addition to our means of producing electrical power. But it is not
'the answer' to all of our problems. Let's take a look at some facts and I will
let you decide.
 The solar constant (the amount of energy from the sun striking the Earth) is
approximately 1.37 KW/Square Meter. That means that if we had a means for
converting sunlight to electricity at 100% efficiency, we would be able to
get 1.37 KW for every square meter of collector we were using. However, our
most efficient means available (cost wise) appears to be photovoltaic solar
cells. Efficiency runs approximately 7 percent, but for our discussion, let's
use 10 percent (makes the math easier!). We will figure the requirement for
an average home (here in northern New England) as well as for a large
manufacturing facility I am familiar with.
 Most homes built in the last 20 years come wired for a 200 amp service which
means that, theoretically, that home would be able to draw up to 22 KW. But
most homes draw no more than a fourth of that at any time. So let's use 5 KW
as a baseline. 5 KW divided into 137 W/square Meter (remember 10% eff.) gives
us approximately 36.5 sq. m. of solar panels to meet the average demand. Double
that if you really want to make sure you have enough reserve to charge storage
cells if you run the house 24 hrs a day (why anyone would want to, I have no
idea). 36.5 sq meters of solar panels isn't too bad, so it may be practical
for residential use. Industrial is another matter.
 The facility where I am employed uses approximately 1.1 MW of power on
average during a 24 hour period. 1.1 MW divided into 137 W/sq meter gives an
answer of approximately 8030 sq meters! Again, double that if you want reserves
to charge storage cells for the dark hours. Not too practical!
 The arguement has been brought up for the use of solar farms to generate power
in large amounts, and it will work in areas with a large number of days of
sunlight- desert areas in the southwestern US. Not practical in chilly, cloudy
New England. Also takes up lots of land area.
 There are other types of solar cells under development that use a
photochemical reaction and have the potential to be more efficient than solid
state solar cells, btu they are still under developement, and to my knowledge
are not yet available commercially.
 I mentioned storage of solar generated power and I will have a message
covering that topic later.

KA1OU @ WA1WOK.NH