This Chesapeake, Virginia, home takes advantage of both solar water heating and photovoltaics. The solar pool-heating system, located over the front porch, keeps the pool temperature in the 80º range from March to October. The solar collectors, located over the garage, face east, but still produce 75% of the annual hot water needs for this family of four. The PV modules are on the highest part of the roof, and they produce 1 kilowatt of electricity.
The U.S. Department of Energy's Solar Program encompasses three major types of solar energy technologies: photovoltaics, concentrating solar power, and solar heating and lighting. These technologies are introduced briefly below, but you can learn much more about them in the Technologies Section.
Concentrating solar power (CSP) systems concentrate the thermal energy of the sun to drive a steam turbine or heat engine. The turbine or engine then drives a generator to produce electricity. The three distinct CSP technologies are parabolic troughs, power towers, and dish-engine systems. The troughs and towers are applicable to large utility-scale projects in the megawatt range, but dish systems have been demonstrated at the 10-25-kilowatt scale.
Photovoltaics (PV) is the direct conversion of light energy into electricity using semiconductor materials. PV systems are composed of groups of solar cells wired in series to form modules, which can then be interlinked to form arrays. This modular nature allows PV to be used for applications ranging from a fraction of a watt, such as for handheld calculators, to large-scale, multi-megawatt power plants containing millions of solar cells. The most common type of PV device is the flat-plate module, which consists of flat sheets of glass or other materials containing the solar cells. Concentrating PV systems use lenses or mirrors to focus sunlight onto the solar cells, which enhances the light-to-electricity conversion efficiency of the solar cell.
Solar heating includes solar thermal systems that heat a working fluid for various applications. Solar collectors can provide thermal energy for direct use in the form of hot water for domestic water heating, space heating, and process heat, and in the form of hot air for space heating and process heat. Higher-temperature collectors can drive absorption and desiccant air-conditioning systems and can provide low-temperature steam.
Solar lighting is a newly emerging field. The Solar Program is also investigating hybrid lighting, which uses small solar concentrators and fiber optics to bring daylight into building interiors.
Parabolic troughs are currently the most proven of the concentrating solar power technologies. Nine commercial-scale solar-electric generating stations, the first of which began operating in 1984, produce electricity in the California Mojave Desert.
Evaluating Research Progress
Annually, all program research activities are formally reviewed at the National Center for Photovoltaics (NCPV) and Solar Program Review Meeting. Researchers from the national laboratories, universities, and industry present the latest developments for photovoltaics, concentrating solar power, solar thermal, solar lighting, and building technologies. Program managers present status report for their technologies and outlooks for the future. Invited speakers from outside the Solar Program offer fresh perspectives, which help to energize the meeting and those who attend. The Program Review Highlights describe the presentations and activities of the 2003 meeting.
More about the Program Areas
Under the Solar Program's Deployment section you'll see how Solar Program research is being put to practical use. Financial Opportunities features links for consumers who are interested installing solar energy and research professionals who may want to partner with the Solar Program. Information Resources is the place to link to solar energy information generated within the United States and around the world.