There are three types of geothermal energy. In a few places, high temperatures from within the earth are naturally concentrated near the surface—a fantastic resource. Elsewhere, we’re experimenting with drilling deeper wells, fracturing the rock, and then circulating water to bring up heat. Finally, there’s ‘low temperature,’ using the constant temperature just below the surface to heat or cool a building. These last two are more widely available, but cost prohibitive today.

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