Using solar energy to heat underground water. Starting small, but real potential
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The GeoTES project occupies a dusty patch of ground nestled between well-plumbed oilfields with hundreds of wells — some idle, some still pumping. Just 1,200 feet below its surface — shallow by drilling standards — are pockets of permeable sandstone, now emptied of oil, into which highly brackish water has seeped.
Like the oil it is replacing, GeoTES begins with the sun. At the surface, parabolic mirrors gather solar energy, which is used to heat a silicon oil flowing through an aboveground loop to 700 degrees Fahrenheit. Comparatively cold groundwater is pumped up, heated by the oil, then sent back down. As long as the sun is shining, the system heats the water in the reservoir. At night, the water continues circulating, maintaining a temperature of about 500 degrees. When called upon to make electricity, the groundwater is brought to the surface through an extraction well, where its heat spins a turbine.
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