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Concentrating Solar Power Basics

Jul 17

Concentrating solar power systems harness the sun's heat to generate electricity for large power plants.

Today, many power plants use fossil fuels to heat water. The steam produced by boiling water drives a large turbine that generates electricity. A new generation of power plants uses concentrating solar power systems as well as the sun to heat their energy. There are three types of concentrating solar power systems: the linear concentrator, dish/engine, and power tower.

Linear Concentrator Systems

Linear concentrators collect sunlight's energy by using long rectangular or curved mirrors. The mirrors tilt toward the sun and focus sunlight onto tubes or receivers that run the lengths of the mirrors. The heat from the reflected sunlight heats the fluid that flows through the tubes. To produce electricity, the hot fluid is used to heat water in a steam-turbine generator.

There are two main types of linear concentrators: Parabolic trough systems where receiver tubes are placed along the focal line for each parabolic mirror, and linear Fresnel systems where one receiver tube is placed above multiple mirrors in order to give the mirrors greater mobility when tracking the sun.

Dish/Engine Systems

Mirrored dishes are used in dish/engine systems. However, to reduce costs, the dish is often made up of several smaller flat mirrors that have been shaped into a dish shape. The dish-shaped surface directs sunlight onto a thermal receiver which collects heat and then transfers it to an engine generator.

Today, the Stirling engine is the most popular type of heat engine in dish/engine systems. The receiver heats the fluid to create mechanical power by moving pistons. This mechanical power can then be used to start a generator or alternator that produces electricity.

Power Tower Systems

The power tower system utilizes a large number of sun-tracking, flat mirrors called heliostats to concentrate and focus sunlight onto the receiver at the top of a tower. The receiver heats a heat-transfer fluid, which is then used to create steam. This is then used in a traditional turbine generator to make electricity.

Some power towers use steam/water as the heat-transfer fluid. Because of its superior heat transfer capabilities and energy-storage capabilities, advanced designs also use molten sodium salt. Thermal storage or energy storage allows the system's ability to continue sending electricity even in cloudy conditions.

 

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