Sandia National Laboratories

Photovoltaic Technologies at Sandia

Sandia's Work in Photovoltaics
Sandia's mission in photovoltaic technology is to accelerate the commercial use of photovoltaics and complementary renewable energy technologies as sustainable sources of electrical power. Photovoltaics -- the physical phenomenon that converts sunlight to electricity -- is viewed as a potential cost-effective, environmentally friendly means of producing much of America's future electricity needs. Photovoltaics was first observed in 1839 by a French physicist and its development advanced significantly in the mid-1900s. But it was the energy crisis of the 1970s that stimulated research into improving existing solar-cell technologies and developing new solar-cell materials and designs.

Sandia's effort in photovoltaics focuses on improving the cost-effectiveness, performance and reliability of its products, thus helping industry to achieve and maintain a strong position in the global renewable energy market. Sandia coordinates its photovoltaics work with the Department of Energy, other national laboratories, and other users of photovoltaics technology. Sandia provides technical assistance to those other organizations in areas that include system design and specification, improvements in fabrication processes, component development, and evaluation of systems and components. Sandia also provides education and dissemination of information to organizations that accelerate the growth of sustainable markets for renewable energy systems.

As part of the DOE's National Photovoltaic Program, Sandia:

Works with the crystalline silicon solar cell industry to improve the processing of solar cells, to develop new designs, and to reduce cost by increasing their level of performance.

Works with manufacturers on design, materials, and processes to improve the performance, reliability and lifetimes of photovoltaic modules.

Collaborates with industry to develop and evaluate controller, power processing and other balance of systems components.

Sandia's work with the photovoltaic systems integration industry and with agencies that use photovoltaic power systems consists primarily of technical support for applications and activities targeted at expanding international applications. Sandia also provides education and training to qualified domestic and international agencies, and offers technical support for systems applications.

Sandia established the Photovoltaic Design Assistance Center in 1984 as part of the DOE's National Photovoltaic Program. The center assures the transfer of photovoltaics technology and provides contact between potential users of photovoltaic systems, suppliers of systems and components, and qualified engineers, who evaluate needs and available equipment. The center's engineers provide information about the cost effectiveness and reliability of photovoltaic systems, and its resources also can be used by outside entities -- such as state and federal agencies, international funding agencies, the photovoltaic industry, designers, utilities and architects -- seeking information on whether photovoltaics can fill their needs.

Sandia's Photovoltaic Device Fabrication Laboratory, which houses a Class 100 clean room, fabricates solar cells from high-quality semiconductor materials.

Fundamentals
The basic power element of a photovoltaic system is the solar cell. Although many semiconductor materials can be used to make solar cells, the most common is crystalline silicon. Light striking the solar cell liberates electrical charge carriers within the cell. The internal voltage separates the electric charges, producing an electric current. Metal contact lines or grids on the top and bottom surfaces of the cell enable the current to flow through an external circuit to produce electric power.

A single crystalline silicon cell produces a small amount of power -- about a watt or two. More power is produced by interconnecting several solar cells and encapsulating them in a single package -- the photovoltaic module.

The technology of photovoltaic systems is simple and quiet and requires no moving parts. Batteries store energy for use when the sun isn't shining. Photovoltaic systems come in many different sizes, ranging from a single solar cell to power a calculator, a single module (containing multiple cells) to power a light, to multiple modules to power a water pump or a home, to large arrays of modules to provide industrial-scale power. The technology is now well established and field proven, and many sizes and types of modules are commercially available from a number of different companies.

Applications
Photovoltaic systems are especially suited to remote locations where standard electricity sources aren't available or are too expensive to provide. Lighting is a common use for these systems. Cost-effective applications of lighting powered by photovoltaics include small garden lights, street lights, lighting for recreational areas, highway signs, warning signs and signals, and for businesses and homes both in the developed and developing world. Photovoltaics also is ideal and commonly used for water pumping because water can be pumped into a storage tank during daylight hours, then distributed by gravity whenever it is needed. Some U.S. utilities offer photovoltaic systems to customers for remote livestock watering tanks, and in the developing world, entire village water supplies are powered by photovoltaics. Other uses include remote monitoring, refrigeration, and energy for small commercial ventures. Virtually any power need can be met with photovoltaics, although some are more cost-effective than others.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy.

Media Contact
Chris Miller
cmiller@sandia.gov

Last modified: August 6, 1997

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