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Dictionary

Global Solar Market

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.

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. There are 4.8 GW of installed capacity (2016) 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).

Ouarzazate
The Ouarzazate Solar Power Station, Morocco, will generate 580MW when completed

Global Deployment of CSP

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 experienced a boom from 2010 (0.97GWp) to 2014 (4.3GWp), and is now at 4.8GWp (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.

Power Generation extended by Heat Storage

Molten salts are proving an efficient way of storing the heat for use after direct solar radiation is no longer available. This can extend power generation several hours after sunset, and represents a major advantage of CSP over PV panels.

In many cases PV has out-performed CSP. This is due to falling costs of panels. PV can continue to generate power with cloud cover, while CSP needs to maintain a high level of concentrated light. This has restricted its application to desert regions. Globally, in 2017 CSP still only accounts for 2% of world installed solar power generation capacity. Falling prices for CSP plants are now bringing the performance to the point of presenting a serious competitor to conventional fossil and nuclear power plants. Chile has a CSP plant in the Atacama region providing baseload at less than 5c per kWh.

CSP Plant types

Trough Systems

The USA SEGS (Solar Energy Generating Systems) were the world's first commercial parabolic trough plants (Nameplate capacity 354 MW = 474,799 HP, 539 GWh in 2015, 19.2% capacity factor, 75MWe). Other examples: Nevada Solar One (Nevada). Andasol (Europe's first). Plataform Solar de Almeria SSPS-DCS (Spain) test facilities.

The parabolic trough focuses light from a linear reflector onto a central tube along the focal line (receiver) containing a working fluid, usually molten salt or water. The reflector can follow the sun by rotating through a single axis. The working fluid can be heated to 150-350°C, and flows to a central power generating system.

Solar Power Tower

The solar tower uses an array of dual-axis tracking reflectors called heliostats to concentrate light to a central receiver located on a tower. An example is the PS10 (Planta Solar 10) in Andalucia, Spain (11MW from 624 heliostats). The working fluid can reach temperatures of 500-1000°C. Solar towers can have higher efficiencies than trough systems, and provide better energy storage capability.

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Ivanpah, Mojave Desert, California. Its gross capacity is 392 MW, provided by 173,500 heliostats, focusing light onto central solar power towers.
Other Designs

Fresnel reflectors use flat mirrors rather than parabolic. This reduces the cost and allows more mirrors to be used, making more use of the available sunlight.

The Dish Stirling is a single array of mirrors and a mounted receiver. The main advantage is high efficiencies, reaching 30-34%.