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Photovoltaic (PV) systems use solar electric panels to directly convert the sun's energy into electricity. This conversion of sunlight to electricity occurs without moving parts, is silent and pollution free in its operation. The solar electricity fed through electronic equipment is converted to utility grade electricity for use directly in the home.The solar electricity can be used to offset the need for purchased utility electricity or, if the PV electricity exceeds the home's requirements, the excess electricity can be sent back to the utility, typically for credit.
 Different types of photovoltaic products are available today from numerous manufacturers. The supply of PV collectors worldwide has increased from 20 to 30 percent annually to keep up with the demand for this renewable energy technology. PV modules (or solar electric collectors) are different from solar thermal collectors (that convert the sun's energy into thermal (typically hot water) energy. Photovoltaic modules are usually rigid, rectangular devices ranging in size from 2’ by 4’ to as large as 4’ by 8’. Some PV module technologies are flexible and as large as 2’ by about 20’ or even larger. Rigid PV modules typically have a glass cover while the flexible modules have a very durable film cover. Both types of PV module construction have been rigorously tested to survive storm and hail damage and are resistant to degradation from ultra-violet rays.
Most residential PV systems are used in conjunction with utility-supplied power. Excess power produced during daylight hours can be fed back into the utility's lines, while utility electricity is used in the home when the house demand is greater than can be supplied by the PV roofing. Typical residential PV systems commonly have a peak power production of between 1,200 and 5,000 watts, AC - requiring from between 150 to over 1,000 square feet of installed area depending on the efficiency of the PV technology used.
Most often, PV panels are installed on roofs, but they can also be installed as free-standing units, on a pole on the ground, or even on complex tracking structures that change with the sun's angle during the day.
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PV systems reduce the amount of electricity purchased from the utility.
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Electricity produced using the sun’s energy reduces the amount of energy used from non-renewable resources such as coal, gas, oil and nuclear. In addition, there are significant environmental benefits resulting from reductions in air pollution from burning fossil fuels, reductions in water and land use from central generation plants, reductions in the storage of waste byproducts. In addition, the solar technologies produce energy with little noise and few moving parts.
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PV panels and systems are available through distributors of solar energy products or directly from the manufacturer. Some "Big-Box" stores are beginning to distribute solar electric systems.
One of the greatest barriers to the widespread adoption of PV systems is their high initial cost. Photovoltaic panels require an unobstructed exposure to sunlight to obtain their maximum efficiency. Most PV panels are tested to meet both electrical and environmental performance criteria. Experience with existing photovoltaic products over the past 20 years has shown that they have excellent reliability with very little maintenance required.
Expected cost of electricity produced from a PV system is equal to about 25 to 50 cents per kilowatt-hour (kWh) when considering initial cost spread over the lifetime of the system, plus maintenance costs. This compares with an average rate of now over 9.53 cents per kWh for utility supplied power.1 However, many states and the federal government have active programs to reduce the capital cost and/or the installation cost of PV systems by providing tax credits, tax deductions and rebates for PV systems. Some of the state benefits are significant enough to make the PV electricity nearly competitive with utility supplied electricity.
For homes not in proximity of electric power lines, PV systems may be less costly than extending power lines to the home. Unlike gas generators, they operate silently and require maintenance primarily for the battery storage.
http://www.neo.ne.gov/statshtml/115.htm
Because reliability has proven good thus far, PV systems actually reduce the cost of powering homes and other buildings. The amount varies depending on the size of the system, the building's location, and the building's energy needs.
Most PV products have undergone extensive testing and certification for fire, wind uplift, and electrical safety performance. Some have obtained evaluation reports from major model building codes to assure their acceptance. Many PV products are listed through a testing laboratory such as Underwriters Laboratory.
John Wesley Miller Companies: Armory Park del Sol, Tucson, Arizona
Shea Homes: San Diego, California
The efficiency of PV will depend on the maximum sun exposure, so the house location is important. Panel photovoltaic systems are ready to install and supplied by distributors. PV installations require a portion of the roof to be exposed to direct sunlight. Depending on the PV product, they can be installed by either a roofing professional, an electrician, or both. They must be wired to the house power supply by an electrician.
Manufacturing warranties vary from 10 to 25 years for workmanship and defects. However, many companies also guarantee a minimum power produced by the PV system for a certain number of years. The percentage depends on the technology and the rated peak power of the PV system and is generally about 80% of the rated power.
Panel PV products provide environmental benefits because they do not produce pollution or carbon dioxide emissions like fossil fuel-based utility power. They are also more attractive than many other solar systems, which increases consumer acceptance. Unlike utility supplied power, once purchased, the cost of producing PV electricity remains constant over the life of the system since the only fuel used is sunlight.
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