Geothermal energy comes from the earth’s heat, generated by magma and radioactive decay. It’s not as abundant as solar energy but is harnessed by 20+ countries, notably Iceland. Extracting energy involves boiling water to drive turbines, but current technology only reaches pockets of heat near the surface. It’s not strictly renewable, but slowly renews itself thanks to radioactive heating. Deeper pockets of heat could provide a prodigious source of energy, but the deepest hole drilled is only 8 miles deep. Geothermal energy will join solar and nuclear energy in providing clean energy.
Geothermal energy is the energy that emits from the earth. It comes from magma and the radioactive decay of uranium, thorium and potassium. Magma is hot due to the enormous amount of friction and pressure found in the area of the earth’s subsurface.
While geothermal energy is massive in total, it doesn’t fare very well when compared to the amount of energy we get from the sun, which wins out by a factor of about 20,000. However, this energy is harnessed by more than 20 countries, most notably Iceland, which gets 17% of its electricity from geothermal energy. The largest geothermal power plants produce a couple of hundred MW (megawatts).
The process of extracting energy from the earth’s heat is quite simple. Water is pumped through pipes to the heat source and allowed to boil, the flow drives a turbine that harvests energy, then the water is recondensed and sent back into the cycle. If we had pipes strong enough and deep enough, we could send them down into the Earth’s mantle and have a virtually inexhaustible source of electricity. But with today’s technology, we can only reach pockets of heat near the surface.
Geothermal energy is not a strictly renewable energy source like wind or hydroelectricity, because the ground cools slowly as energy is extracted from it. However, it slowly renews itself thanks to radioactive heating. Molten rock at temperatures between 1,200 and 2,200°F (650-1,200°C) is thought to be found in pockets 50 to 60 miles (about 80-97 km) below the Earth’s surface, just below the tectonic plates. This would provide a prodigious source of geothermal energy, but the deepest hole humanity has drilled extends only about 8 miles (13 km) below. As we move towards independence from fossil fuels, geothermal energy will join solar and nuclear energy in providing clean energy to the world’s offices, industries and homes.
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