How Solar Systems Work
Solar electric systems, also known as photovoltaic (PV) systems, convert sunlight into electricity.
Solar cells—the basic building blocks of a PV system—consist of semiconductor materials. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms. This phenomenon is called the "photoelectric effect." These free electrons then
travel into a circuit built into the solar cell to form electrical current. To see a simulation of the photoelectric effect, please view our animation. Only sunlight of certain wavelengths will work efficiently to create electricity. PV systems can still produce electricity on cloudy days, but not as much as on a sunny day.
The basic PV or solar cell typically produces only a small amount of power. To produce more
power, solar cells (about 40) can be interconnected to form panels or modules. PV modules range in output from 10 to 300 watts. If more power is needed, several modules can be installed on a building or at ground-level in a rack to form a PV array.
PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a
day.
Because of their modularity, PV systems can be designed to meet any electrical requirement, no matter how large or how small. You also can connect them to an electric distribution system (grid-tied), or they can stand alone (off-grid).
Grid-Connected Small Solar Electric Systems
A grid-connected small solar electric or photovoltaic (PV) system receives back-up power from a utility's grid when the PV system is not producing enough power. When the system produces excess power, the utility is required to purchase the power through a metering and rate arrangement.
Net metering is the best arrangement. Under this arrangement, the power provider essentially pays you retail price for the electricity you feed back into the grid. See Estimating Energy Cost Savings for a Net-Metered Photovoltaic System.
Stand-Alone Small Solar Electric Systems
A stand-alone small solar electric or photovoltaic (PV) system operates "off-grid"—it isn't connected to a electricity distribution grid operated by a utility.
A stand-alone PV system makes sense if any of the following apply:
*You live in a remote location where it's more cost effective than extending a power line to a grid
*You're considering a hybrid electric system—one that uses both a PV system and a small wind electric system.
*You need minimal amounts of power; e.g., irrigation control equipment and remote sensors.
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