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The following is a brief explanation of how solar electric technology works. Good information about other solar technologies is available at www.solarboston.org. For detailed technical information, consult our educational resources page, or feel free to contact us.
Solar electric (photovoltaic) systems convert sunlight directly into electricity with no moving parts. A typical system consists of modules (or panels) that are mounted on a rooftop, an inverter to interface the modules with the existing power grid, cabling and switches. Sometimes systems include batteries, which are used to provide backup power when the electrical grid goes down. Sometimes the photovoltaic modules are integrated into other building materials (BiPV) and not roof-mounted, as at The Solaire in Battery Park City.
Whenever sunlight strikes solar electric (PV) modules, they produce electricity. The amount of electricity produced by a system will vary according to a number of factors, including: size and electrical characteristics of the modules, amount of available sunlight, and angle of sunlight to the modules. The maximum amount of electricity is generated when the light is most intense (a sunny day) and strikes the solar modules directly (when the sun’s rays are perpendicular to the modules).
Power output from modules ranges from 10 to 300 watts. A number of modules are installed as part of a typical solar electric system. The modules are connected to an inverter that changes the Direct Current (DC) produced by the modules into Alternating Current (AC) - the same that comes out of standard electrical outlets.
The vast majority of solar electric systems in NYC are connected to the utility grid. If you own a grid-tied system, you still have an account with Con Edison and you buy power from them when the solar system doesn’t supply enough - like at night or on a cloudy day. But you can also send surplus power produced by your system back to the electric utility, spinning your electrical meter backwards and giving you a credit to use at some time when the sun isn’t supplying all your power needs (this is called net metering - currently in NYC it is only applicable on residential systems).
If you are interested in backup storage in case of a power outage, you can add batteries to your solar electric system. Stand-alone systems (not connected to an electric utility) always incorporate batteries in order to provide power at night and on cloudy days. An examples of very small stand-alone systems are the muni-meters for parking, which dot many Manhattan streets.
Solar electric systems shouldn’t be confused with solar water-heating systems that operate by using the sun’s rays to heat water. Rather, solar photovoltaic technology produces electricity from the flow of electrons that are freed when sunlight interacts with the semiconductor material in the modules.
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