solar power

Solar power is the capture and conversion of electromagnetic radiation from the sun into electrical current. Unlike fuel-based generation, it produces no combustion byproducts and requires no moving parts once installed. Two fundamental technologies dominate: photovoltaic (PV) cells that generate electricity directly when photons strike semiconductor material, and concentrated solar power (CSP) systems that use mirrors to focus heat for thermodynamic conversion.

Photovoltaic systems operate through the photovoltaic effect: when light strikes a silicon or other semiconductor junction, it dislodges electrons, creating a voltage across the layer. Modern crystalline silicon cells achieve 15 to 22 percent efficiency under standard test conditions (1000 W/m² irradiance, 25 degrees Celsius). Thin-film technologies like cadmium telluride operate at 10 to 18 percent efficiency but cost less per watt and perform better in diffuse light. Arrays are wired in series for voltage and parallel for current, with inverters converting DC output to AC for grid or load connection.

Concentrated solar power and system integration

Concentrated solar power uses parabolic troughs, heliostats, or Fresnel lenses to focus sunlight onto a receiver, heating fluid (oil, molten salt, or water) to 300 to 700 degrees Celsius. This heat drives a turbine for electricity generation, or stores thermal energy for generation after sunset. CSP scales to 50+ megawatts and operates where direct normal irradiance exceeds 2000 kWh/m² annually, typically in arid latitudes.

Real-world solar output varies with season, cloud cover, panel temperature, and soiling. Photovoltaic systems generate peak output around solar noon and zero output at night, requiring battery storage, grid connection, or hybrid systems for continuous supply. Temperature derating is significant: silicon cell efficiency drops roughly 0.4 to 0.5 percent per degree Celsius above 25 degrees, meaning summer peak irradiance is partially offset by heat loss. Dust, pollen, and salt accumulation can reduce output by 5 to 25 percent depending on climate and cleaning frequency.

Installation depends on available space and sun exposure. Rooftop systems suit residential and commercial buildings in regions receiving 3 to 6 peak sun hours daily. Ground-mounted arrays require southern-facing (Northern Hemisphere) orientation, minimal shading, and structural support rated for wind and snow loads. Utility-scale farms occupy 5 to 10 acres per megawatt for photovoltaic installations, with tracking systems that follow the sun's path improving output by 20 to 35 percent at significant mechanical cost.