Direct sunlight can be converted to electricity using photovoltaic (PV) converters, solar energy concentration process (CSP) and many other experimental methods. Photovoltaic converters are mainly used to supply small and medium appliances with electricity, from a calculator that is powered by a single solar cell to homes without electricity grid and which are supplied with electricity by a group of photovoltaics. Electricity was widely generated by solar radiation concentrators, but now photovoltaic matrix stations that produce a large amount of electricity such as solar power generation systems are more common. In 2007 the 14-megawatt power plant in Clark County, Nevada, as well as the 20-megawatt plant in Benixama, Spain, became the two clearest signs in the trend towards building giant solar PV plants in the United States and Europe.
As a renewable energy source, solar energy requires a supportive source, which can be partially wind energy. This support is usually obtained from batteries, but devices usually use hydroelectric energy that is stored by pumping. The University of Kassel's Solar Energy Technology Institute is testing a virtual power station connected to an energy storage system, where energy can be generated from solar, wind, or organic gas and hydropower that is stored by pumping, to provide sufficient energy for continuous use; the project relies on Renewables only.
