Solar energy is often classified as either active or passive. Active solar technology refers to electric or mechanical devices that draw on the energy of the sun to produce electricity and/or provide heating or cooling. Passive solar energy involves intelligent building design to leverage the sun's power to light, heat, and even cool.
Photovoltaic (PV) solar technology generates electricity by converting solar radiation into direct electrical current, and photovoltaic panels have achieved success in residential, non-residential, utility-scale, and off-grid applications.
Solar Thermal Electric (STE), or concentrating solar power (CSP), technologies use mirrors and lenses to focus a large area of sunlight into a concentrated beam. The beam heats a source, most commonly water, thereby producing steam to rotate a turbine. STE systems are often utility-scale, and through efficient storage of thermal energy, a plant can continue to generate electricity after dark. STE technologies exist in four common forms, including parabolic troughs, solar power towers, parabolic dishes, and Fresnel reflectors.
Concentrating Photovoltaic (CPV) technology also uses mirrors and lenses to concentrate sunlight. However, instead of using the sunlight's thermal energy to produce steam, the concentrated beam is directed at high-efficiency photovoltaic cells.
Solar Heating and Cooling (SHC) technology traps and stores the sun's energy for controlled use in homes, offices, pools, and other spaces. Solar water heating is an example of a SHC technology.
For more in-depth information about solar energy systems, see the National Renewable Energy Laboratory's solar research page.
- The cumulative installed photovoltaic capacity in the U.S. exceeded 4,400 MW in Q1 2012. (Solar) Energy Industries Association (SEIA) and GTM Research
- Total U.S. installations were 506 MW in first quarter of 2012 (up 85% from Q1 2011) and are forecast to reach 3 GW by the end of 2012. (SEIA)
- 2011 saw an annual growth rate of 109% for PV installations, coupled with a 20% decrease in the weighted average of PV system prices. (SEIA)
- Solar energy will grow faster than any other renewable source, averaging an annual growth rate of 11.7% through 2035. (The Energy Information Administration (EIA))