Solar cells usually operate more efficiently under concentrated light. This has led to the development of a range of approaches using mirrors or lenses to focus light on to specially designed cells and use heat sinks, or active cooling of the cells, to dissipate the large amount of heat that is generated. Unlike conventional flat plate PV arrays, concentrator systems require direct sunlight (clear skies) and will not operate under cloudy conditions. They generally follow the sun's path through the sky during the day using single-axis tracking. To adjust to the sun's varying height in the sky through the seasons, two-axis tracking is sometimes used.
Concentrators have not yet achieved widespread application in photovoltaics, but solar concentration has been widely used in solar thermal electricity generation technology where the generated heat is used to power a turbine.