Solar Energy

There are two basic types of solar electric technology - photovoltaics and solar-thermal electric.

1. Photovoltaics

Photovoltaic (PV) is the technical word for solar panels that create electricity. Photovoltaic material, most commonly utilizing highly-purified silicon, converts sunlight directly into electricity. When sunlight strikes the material, electrons are dislodged, creating an electrical current which can be captured and harnessed. The photovoltaic materials can be several individual solar cells or a single thin layer, which make up a larger solar panel.

Photovoltaic cells power many of the small calculators and wrist watches in use every day. More complex systems provide electricity to pump water, power communications equipment or highway construction signs, and a myriad of other small, off-grid uses, which almost always provide electricity for small and/or intermittent electricity needs that are cleaner and cheaper to operate than extending a power line or using liquid fuels. Rural solar electrification in the developing world, away from the electric grid, can also provide much needed electricity to replace or reduce the use of kerosene lamps, diesel generators, and wood fires for lighting, refrigeration, communication, etc.

Photovoltaics are also making inroads as supplementary power for utility customers already served by the electric grid. In the last two years, grid-connected solar systems are now a larger market than off-grid applications. Currently, compared to most conventional fuel options, photovoltaics are still a very small part of the energy make-up of any country. However, more and more individuals, companies, and communities are choosing PV for a variety of environmental, economic development, emergency back-up, fuel and risk diversification, and now, economic reasons. The economics of a photovoltaic system for your home or business is not just the solar resource (see map below), but rather a combination of the solar resource, electricity prices, and local/national incentives.

Photovoltaic technologies are being developed that can be built right into building roofs, facades, canopies and windows. Thin-film technologies that don`t use any silicon at all are the focus of large amount of research, as well as concentrating photovoltaics (CPV), which uses lenses or mirrors to increase the sunlight`s intensity, thus increasing the amount of electricity produced.

For more information on photovoltaics:

* U.S. DOE`s Office of Energy Efficiency and Renewable Energy

* Consumer`s Guide to Buying a Solar Electric System (pdf file)

* State and Local Incentives (DSIRE database)

* FindSolar.com

2. Solar Thermal Electricity

Solar thermal electricity technologies (also called concentrating solar power, or CSP) produce electric power by converting the sun`s energy into high-temperature heat using various mirror configurations, which is then channeled to an on-site power plant and used to make electricity through traditional heat-conversion technologies. The plant essentially consists of two parts: one that collects solar energy and converts it to heat, and another that converts the heat energy to electricity.

Concentrating solar power systems can be sized for village power (10 kilowatts) or grid-connected applications (hundreds of megawatts). Some systems use thermal storage during cloudy periods or at night to produce electricity outside of the traditional solar daytime window. Others can be combined with natural gas and the resulting hybrid power plants provide high-value, dispatchable power. These attributes, along with high solar-to-electric conversion efficiencies, make concentrating solar power an attractive renewable energy option in the southwest United States and other sunbelt regions worldwide.

There are three basic types of CSP technologies:

* Stirling engines

* Solar troughs

* Solar towers

For more information on concentrating solar power:

* Sandia National Laboratory

* National Renewable Energy Laboratory

Back 05.10.2008.