Sunlight is earth’s most ubiquitous form of energy. It is clean, inexhaustible, and the United States boasts one of the largest solar resources of any industrialized country. In the last decade, both distributed generation (small-scale installations located close to where the energy is ultimately used) and utility-scale generation have grown rapidly, and this expansion has brought solar energy into new realms of competitiveness. With effective support, solar energy can help to address some of the United States’ most pressing energy concerns, including energy security and climate change.
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.