A solar power plant is based on the conversion of sunlight into electricity, either directly using photovoltaics (PV), or indirectly using "concentrated solar power" (CSP). Concentrated solar power systems use lenses, mirrors, and tracking systems to focus a large area of sunlight into a small beam. Photovoltaics converts light into electric current using the photoelectric effect. The largest photovoltaic power plant in the world was the 354 MW installation located in the Mojave Desert, California. Other large CSP plants include the 250 MW Agua Caliente Solar Project in Arizona, the Solnova Solar Power Station (150 MW, 250 MW when finished), and the Andasol solar power station (150 MW), both in Spain.