Page 363 - Handbook of Energy Engineering Calculations

h/2.4/0.8)(1.2) = 316.3 peak Watts. Using 50-W modules, we have 316.3/50
= 6.32 modules; seven would be chosen.
For precise accuracy in module selection, designers suggest using month-
by-month averages for average W-h for a location. Then the lowest monthly
average is actually used in the calculations.

Related Calculations. Today, the most common applications for
photovoltaics are remote or stand-alone systems. A stand-alone system is not
connected to the local utility and is used in remote areas of the world where
there are no nearby power lines. Thus, some 50,000 homes, worldwide, are

powered by photovoltaics. Connecting such remote homes to a utility costs
much more than generating electricity from the sun.
Developing nations use photovoltaics to refrigerate medicines, pump
water, or light villages. Developed countries use photovoltaics to light roads,

billboards, and road signs. Recreational vehicles and boats also use solar
energy to operate various devices.
Other uses of solar power include railway cabooses, airport emergency
lighting systems, marine buoys and coastal markers, and electric carts for

transporting sightseers.
Hybrid photovoltaic systems use two or more power-generating sources
connected together. The secondary source for the solar modules can range
from gas or diesel generators to wind generators or hydroelectric generators.

However, the most common secondary source is the gas or diesel generator.
In the hybrid system, the secondary generator automatically starts when the
battery voltage of the photovoltaic array drops below a safe level. By using a
hybrid system, the solar energy array can be reduced in size. This allows the

secondary source to supply the remaining needed energy during times of
minimal sunshine caused by seasonal or weather factors.
Currently, the price of a peak Watt is in the $3 to $5 range. As greater use
is made of photovoltaics, the price per peak Watt is expected to decline.

Since this source of power is more expensive than conventional sources,
photovoltaics is still confined to specialized uses.
Data in this procedure are from the U.S. Department of Energy
Conservation and Renewable Energy Inquiry and Referral Service.

As the prices of various fuels—oil, coal, gas, etc.—continue to rise, solar
energy increases in importance as an alternative energy source. Coupled with