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)

Inverter/Controller

An inverter/controller sits between the PV (photovoltaic) panels or shingles and the batteries. This device performs several crucial roles. It:

• Regulates the electricity flowing from the panels to the batteries for charging.
• 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.

Deep-cycle battery

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.

Copyright (c) 1999-2006 Energy Alternatives
(530) 899-1835