Solar energy systems use an electrical (photovoltaic) principle
to convert sunlight into electricity. This power can either be sold
back to the utility company, or stored in lead-acid batteries much
like the one that starts your car.
|PV system (without battery backup)
An inverter/controller sits between the PV (photovoltaic) panels
or shingles and the batteries. This device performs several crucial
- Regulates the electricity flowing from the panels to the batteries
- Converts battery power (direct current, or DC) to standard AC
(alternating current) for your home appliances and electronics.
- Sells power back to the electric company when the batteries
are fully charged (i.e. spins your power meter backwards).
- Charges the batteries from the power company during long periods
of no sun.
|PV Panel (left) and Shingles (right)
The actual light-gathering part of a PV systems comes in two basic
forms: panels and shingles. Photovoltaic panels are commonly about
2 feet by 5 feet in size, and usually mount on the roof of a house
or in an unobstructed area on the ground. PV panels are found in
most photovoltaic systems.
|Solar shingles on roof
PV shingles are roughly the size and shape of a standard shingle,
and are meant for roof-top use only. Mounted in a flexible strip
roughly seven feet long, PV shingles are great for adding a solar
system to new construction.
|Small and large solar systems
The amount of power put out by a photovoltaic system is proportional
to its size. Like a larger sail catching more wind, a larger panel
array captures and converts more of the sun's energy to electricity.
Larger systems cost more, but will allow you to run more appliances,
lights and electronics in your home for a longer time.
The output of a solar system is measured in kilowatts (kW), or
thousands of watts. A 1 kW solar array, for example, puts out enough
electricity in full sun to power 10 100-watt lightbulbs.
Batteries store up electricity from the PV array, making it available
day or night. Batteries also "insulate" your house from
the inconsistent output of the panels or shingles, which can vary
greatly with weather conditions (cloud cover, for example). A larger
battery array costs more, but stores more power. Systems that don't
have a battery backup system won't offer power to your home during
utility company blackouts, but they will sell power back to the
utility company and lower your electric bills.
Depending on power usage in your home, a PV system may cut anywhere
from 10% all the way up to 100% of your electricity bill. Coupled
with a practical energy conservation plan, a solar system can greatly
reduce your utility bills.
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