 Solar Power
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Photovoltaics (Solar Power)
Solar cells, also called photovoltaics (PV) by solar cell scientists, have been used economically to power everything from watches and calculators to individual homes where it is expensive or impossible to send electricity through power lines. As consumers become more interested in this technology, an increasing number of power companies are now experimenting with using PV to meet some of their power needs.
PV technologies produce electricity directly from sunlight. When sunlight strikes a solar cell, its semiconductor materials absorb a portion of that light. If the energy from the absorbed light strikes electrons in the outer shell of an atom, these electrons are freed from their parent atoms. Free electrons can then travel into a circuit in the form of electricity.
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The most common PV device available today is made from rigid, crystalline silicon solar cells (although other materials can also be used). About 40 of these cells are typically combined to produce a flat module, and about 10 of these modules are mounted to form a PV array, which can measure up to several meters on a side. 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.
Where It's Available
The solar resource across the United States is ample for PV systems because they use both direct and scattered sunlight. However, the amount of power generated by a PV system at a particular site depends on how much of the sun's energy reaches it. Thus, PV systems, like all solar technologies, function most efficiently in the southwestern United States, which receives the greatest amount of solar energy.
While renewable energy systems are capable of powering houses and small businesses without any connection to the electricity grid, many people prefer the advantages that grid-connection offers.
A grid-connected system allows you to power your home or small business with renewable energy during those periods (diurnal as well as seasonal) when the sun is shining, the water is running, or the wind is blowing. Any excess electricity you produce is fed back into the grid. When renewable resources are unavailable, electricity from the grid supplies your needs, thus eliminating the expense of electricity storage devices like batteries.
In addition, power providers (i.e. electric utilities) in most states now allow net metering, an arrangement where the excess electricity generated by grid-connected renewable energy systems "turns back" your electricity meter as it is fed back into the grid. Thus, if you use more electricity than your system feeds into the grid during a given month, you pay your power provider only for the difference between what you used and what you produced.
For many people, powering their homes or small businesses using a small renewable energy system that is not connected to the electricity grid—called a stand-alone system—makes economic sense and appeals to their environmental values.
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