Photovoltaics are the solar panels used to harness the suns energy, and turn it into electricity that can be stored in batteries and used to power a building's electrical systems. Solar cells are thin rectangular wafers, typically made of silicon. A four-inch silicon cell can produce about one watt of DC electricity. A number of cells form a module or a module array.
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Silicon is a material known as a ‘semiconductor’ as it conducts electricity and it is the main material for photovoltaic cells. Impurities such as boron or phosphorus are added to this base material. These impurities create the environment for electrons to be freed when sunlight hits the photovoltaic panel. The freeing of electrons leads to the production of electricity. The blue represents the main material, silicon. The black round and irregular shapes represent the impurities of boron or phosphorous. As the sun/light strikes the cell the impurities free up electrons which ‘bounce’ around at incredible speeds. This creates an electrical charge. |
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This is a large arrangement of Photovoltaic Panels in Arizona
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This a much smaller arrangement of Photovoltaic Panels on a single residence
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This is a simple drawing of the basic components needed to build a photovoltaic based full feed or back-up system for residential or commercial needs. What is not shown in this drawing is a connection to the grid (local electric utility company). Some full systems are grid tied and others are stand alone systems. It is only your personal desire that will help to define the system that is best for you. Some people want a system that will power the basics if there is a power failure of the grid. Others want to be totally independent of any power company. And still others want to use the sun's energy when they can, and sell some extra power to the power company. |
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All of the PV (photovoltaic) systems are quiet, and operate automatically using solar electric technology. Because there are no moving parts, PV systems are virtually maintenance free.
The typical grid-tie system with a battery back-up operates 24/7. During daylight hours, the solar array delivers power to the main electric panel and also stores energy in the battery bank. The power you don’t use is sent into the utility grid, spinning your meter backwards (if allowed by your utility company) and lowering your electric bill. During power outages, the solar array provides power for daytime loads and the batteries provide power for nighttime loads. This type of system will provide security and safety for your family during periods of extended power emergencies, as well as creating a large portion, or all of, your electric needs while making some money by selling power to the local utility. |
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Another type of system is a grid-tie with no battery back-up. The thought process here is that most of the power being used by a home or business is during daylight hours, and since the usage of power at night is minimal, the PV system pays for most of the electric usage. |
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Another system is that of the independent family, where the system is a stand alone with no grid-tie, and a battery bank. Very often this type of system will also use a wind powered generator in conjunction with the PV array. It has been found that during daylight hours, there is often less wind, so the PV supplies the power. Then at night and during cloudy or stormy weather, when there is less of the sun’s power, the wind picks up and supplies the power. If a wind system is not used, then a larger bank of batteries is required. |
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Here's the bottom line. Solar space heating and solar water heating systems are fairly simple and straight forward. A PV system has many more variables in its design and a much larger assortment of parts and connecting materials. PV panels / modules / arrays and the inverters, chargers, controllers etc, are much more expensive than the main components of the other systems. One of the reasons we have provided you with plenty of links regarding solar PV and geothermal is that they are systems that should be thoroughly researched before making a decision to add them to your residence. There is no question that they pay for themselves, but it is a longer payback time than the simpler systems. There is also the question of whether or not our utilitiy companies will be able to continually maintain the grids and keep us from the brown-outs and black-outs. That is where the decision to be independent of all of that becomes more important. So do some good research, and call us when you are ready to have a system designed.
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