Concentrated solar power (CSP), also known as solar thermal electricity, has been around since the 1980s. Instead of converting sunlight directly into electricity like photovoltaics (PV) do, it relies on the core technology of fossil-fuel generation: steam turbines. The difference is that rather than using coal or natural gas, CSP uses solar radiation as its primary fuel—free and clear of carbon.
Mirrors, the essential component of any CSP plant, are curved or angled in specific ways to concentrate incoming solar rays to heat a fluid, produce steam, and turn turbines. Because CSP relies on immense amounts of direct sunshine, it is best suited to hot, dry regions where skies are clear.
A critical advantage of CSP is energy storage. Unlike PV panels and wind turbines, CSP makes heat before it makes electricity, and heat is easier to store. When equipped with molten salt tanks for heat storage, CSP plants can continue to produce electricity well after the sun goes down.
As of 2014, CSP was limited to just 4 gigawatts worldwide. As the technology becomes more effective and less expensive, the central benefit of reliability will hasten its growth.