Solar Thermal Power Plant Technologies
Three types of technologies are used in solar thermal power plants:
1) Solar thermal plants using parabolic trough: In these solar thermal plants a parabolic trough is installed. It consists of the long array of curved mirrors that form the trough and focus the sun’s rays on pipe through which the fluid, usually water, flows. Due to focused sunrays the fluid gets heated and its steam is formed. The steam flows through the conventional generators to produce electricity. The solar thermal plants using parabolic troughs are the most commercialized of the lot. As per the estimates, at present there is more 350MW of produced by the parabolic trough plants in California.
2) Solar Power Towers: The Solar Power One was the first project in US that began in 1982 aimed at producing electricity from solar energy on a large scale basis. In the solar power tower a field of mirrors is used to reflect the solar energy towards the central tower in which there is a fluid, usually water. The fluid gets heated and converted into steam, which turns the turbine as is done in conventional power plants.
See figure: Solucar PS10, the first solar thermal power plant based on tower in the world that generate electricity in a commercial way.
3) Solar thermal power plants using solar parabolic dish: The parabolic solar dish comprises of the parabolic shaped concentrator that has a similar shape to a satellite dish. The reflectors are installed on their inner surfaces that reflect the solar energy at the focal point at the center where the receiver is mounted. In the receiver the heat engine is installed that generates the electricity.
The only problem with solar thermal power plants is that they can produce electricity only during daytime and when the skies are clear. Some of the solar thermal power plants are based on hybrid technology. During daytime and clear sky days sunrays are used to heat water and generate steam. During night time and cloudy sky days natural gas is used to boil the water so that non-stop electricity is generated.