Concentrated solar power (CSP)

Concentrated solar power plants are so-called because they use a large array of mirrors focusing the sun’s light onto a small area. The resulting heat is used to turn a steam engine to generate electricity, or to power a thermochemical reaction.

Some plants store heat in molten salts, which permit the power generation day to be extended by several hours.

Although PV remains dominant, due to falling costs in the production of PV panels, CSP can have a higher efficiency than PV, and can store heat in molten salt to extend power generation after dark. In 2016, there were 4.8 GW of installed capacity worldwide, producing electricity in sun-rich areas, such as Spain, the USA and Morocco, at economically viable rates.

In February 2014, the world’s largest concentrated solar thermal plant was the Ivanpah Solar Electric Generating System in the Mojave Desert, California. Its gross capacity is 392 MW, provided by 173,500 heliostats, focusing light onto 3 central solar power towers. Along with $300m from NRG Energy, Google provided $168m investment. The Ouarzazate Solar Power Station, Morocco, uses parabolic-troughs, and will be the world’s largest CSP plant when it is completed (580 MW).

Global capacities: in 2005 there were 0.354 GW of CSP, and in 2016 this had grown to 4.815 GW, of which Spain boasted 2.3 GW total capacity, followed by the USA with 1.74 GW.

Concentrated solar power plants have expanded rapidly, from less than 1GW in 2010 to 4.8GWp in 2016. Growth has tailed off due to competition with falling PV prices, concentrator photovoltaics (CPV), and lack of policy support. Interest in CSP remains primarily only in developing countries with high solar insolation levels.

In 2016, only 2 countries had more than 1GWp installed capacity: Spain (2.3GWp) and USA (1.7GWp). Other countries with CSP: India (225 MWp), South Africa (200 MWp), Morocco (180 MWp), and UAE (100 MWp). China and Australia have a mere 10 MWp and 12 MWp respectively.

In 2017, SolarReserve in Chile bid $63/MWh, or 6.3c per kWh, for a CSP plant that could operate 24 hours a day.