Now that environmental and energy issues have become popular topics and the roofing industry continues to become more environmentally aware, many roofing contractors are trying to find ways to integrate energy efficiency into roof systems. And one way to do this is by using photovoltaic roofing materials.
Most photovoltaic systems are not roofing products; they are stand-alone photovoltaic arrays mounted onto racks on rooftops. A photovoltaic system converts solar energy into electricity by turning the direct current power generated by the arrays into the alternating current power used by standard electrical appliances and provided from the electrical grid.
During the late 1970s, the installed cost of a photovoltaic system was more than $50 per watt of rated capacity, or about $2 per kilowatt hour (kWh). A photovoltaic system's rated capacity is its ability to generate a specified number of watts during one hour of full sunlight. During the 1980s, several thin-film photovoltaic technologies were developed that promised cost reductions as demand for high-volume automated manufacturing increased.