A solar tower, also known as a solar power tower, is a way to concentrate solar power to make it a more powerful energy source. Solar towers are sometimes also called heliostat power plants because they use a collection of movable mirrors (heliostats) laid out in a field to gather and focus the sun at the tower.
By concentrating and collecting solar energy, solar towers are considered a type of renewable energy. Solar towers are one kind of solar tech (including parabolic trough or dish-engine systems), all of which can make up a concentrated solar power (CSP) system. According to the Solar Energy Industries Association, CSP plants in the United States have about 1,815 megawatts of energy capacity.
As the sun shines down on a solar tower’s field of heliostats, each of those computer-controlled mirrors tracks the sun’s position on two axes. The heliostats are set up so that over the course of a day, they efficiently focus that light towards a receiver at the top of the tower.
In their first iteration, solar towers used the sun’s focused rays to heat water, and the resulting steam powered a turbine to create electricity. Newer models now use a combination of liquid salts, including 60% sodium nitrate and 40% potassium nitrate. These salts have a higher heat capacity than water, so some of that heat energy can be stored before using it to boil the water, which drives the turbines.
These higher operating temperatures also allow for greater efficiency and mean that some power can be generated even on cloudy days. Combined with some kind of energy-storage device, this means solar towers can produce reliable energy 24 hours a day.
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