Photovoltaics

(The following text is derived from NREL's description of photovoltaic technology.)

Photovoltaic Panels

Solar cells, also called photovoltaic (PV) cells by scientists, convert sunlight directly into electricity. PV gets its name from the process of converting light (photons) to electricity (voltage), which is called the PV effect. The PV effect was discovered in 1954, when scientists at Bell Telephone discovered that silicon (an element found in sand) created an electric charge when exposed to sunlight. Soon solar cells were being used to power space satellites and smaller items like calculators and watches. Today, thousands of people power their homes and businesses with individual solar PV systems. Utility companies are also using PV technology for large power stations.

Solar panels used to power homes and businesses are typically made from solar cells combined into modules that hold about 40 cells. A typical home will use about 10 to 20 solar panels to power the home. The panels are mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight. Many solar panels combined together to create one system is called a solar array. For large electric utility or industrial applications, hundreds of solar arrays are interconnected to form a large utility-scale PV system.

Traditional solar cells are made from silicon, are usually flat-plate, and generally are the most efficient. Second-generation solar cells are called thin-film solar cells because they are made from amorphous silicon or nonsilicon materials such as cadmium telluride. Thin film solar cells use layers of semiconductor materials only a few micrometers thick. Because of their flexibility, thin film solar cells can double as rooftop shingles and tiles, building facades, or the glazing for skylights.

Third-generation solar cells are being made from variety of new materials besides silicon, including solar inks using conventional printing press technologies, solar dyes, and conductive plastics. Some new solar cells use plastic lenses or mirrors to concentrate sunlight onto a very small piece of high efficiency PV material. The PV material is more expensive, but because so little is needed, these systems are becoming cost effective for use by utilities and industry. However, because the lenses must be pointed at the sun, the use of concentrating collectors is limited to the sunniest parts of the country.

Education about Solar Photovoltaic Cells

• Solar Photovoltaic Open Lectures -- This is a series of five fully annotated Power Point presentations created for the solar energy community to assist in the dissemination of information about solar photovoltaic (PV) cells in 2006. They have been updated by students in MECH820, a graduate engineering course in photovoltaic materials, devices, and systems in 2010.
• Solar Power Naturally in the classroom - The curricular materials created for the School Power...Naturally program include 64 lessons that meet learning standards for New York State students in grades 5 through 12.
• Solar Power Beginner - An online resource that provides a basic understanding of photovoltaics and how they work. Features information on crystalline and thin-film solar panels as well as interviews with experts in the field.

Related Links

List of Photovoltaics Incentives

Interwiki Links

• Appropedia Photovoltaics

External Links

- Web sites for current information on PV

• Solar charge controllers
• Solar PV System design discussion forum
• Solar Buzz
• PV Portal
• Solar Access
• Home Power Magazine
• Photovoltaics World
• PV Tech
• Thin Film Today
• pvXchange
• PV Performance Modeling Collaborative