By Malinda Geisler, content specialist, AgMRC, Iowa State University, malindag@iastate.edu.
 
Profile revised June 2011.


Overview
Solar energy is a clean, renewable energy that may be used to supplement or replace existing power sources. Solar energy has many applications; a few include heating water, generating power to operate remote equipment and helping to reduce the reliance on overhead, electrical light sources.
 
The “solar cell” or photovoltaic (PV) cell technology was discovered in 1954 by Bell Telephone researchers. Just a few years later, PVs were already being used to power U.S. space satellites. The success of PVs in space created opportunities for commercial applications that continue to grow 50 years later.
 
Sales and Market Share
Even with successful applications in the space program, the solar industry did not experience rapid growth until the oil embargos of 1973 and 1979. With support from Federal and state tax incentives, the solar industry grew slowly over the next 10 years. Through consolidation of companies and restructuring of tax credit programs, the number of firms has decreased since 1990, yet the growth rate of solar collector equipment sales continues to grow.

Solar thermal collectors are divided into low-, medium- and high-temperature collectors. Low-temperature collectors that collect less than 110 degrees Fahrenheit are used to heat swimming pools and low-grade water and space heaters. Medium-temperature collectors (greater than 110 degrees F, generally 140 to 180 degrees F) are mainly used for hot water heating. High-temperature collectors (180 degrees F or higher) are used primarily by utilities and independent producers to generate electricity for a grid. Total revenue of all solar thermal collector shipments was $96.7 million in 2009, up from $81.3 million in 2008.

Domestic shipments of solar thermal collectors were 12.2 million square feet (sq. ft.) in 2009. The residential market is the primary market for solar thermal collectors, accounting for 10.2 million sq. ft. of solar thermal collectors and 84 percent of total shipments, with swimming pool heating being the most common application.
 
Usage and Demand
In 2009, total U.S. net generation of all electricity was more than 3,950 billion kilowatts. Coal generated 44.5 percent, nuclear generated 20.2 percent and natural gas accounted for 23.3 percent. Hydroelectric accounted for 6.8 percent and petroleum was 1.0 percent. Other renewables combined accounted for 3.6 percent. Solar energy accounted for 0.5 percent of the non-hydroelectric renewable energy. 

H.R. 1424 passed into law on Oct. 3, 2008. It was an eight-year extension of the 30 percent solar tax credit. It removed a monetary cap for residential solar electric installations.
 

Sources
American Solar Energy Society

Electric Power Annual, Energy Information Administration.

Solar Thermal Collector Manufacturing Activities, Energy Information Administration.