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  • While the weather in Iceland is often cold, wet, and windy,

  • a nearly endless supply of heat bubbles away below the surface.

  • In fact, almost every building in the country is heated by geothermal energy,

  • in a process with virtually no carbon emissions.

  • So how exactly does this renewable energy work?

  • Between the Earth's core and its crust is a mixed layer

  • of solid and partially molten rock called the mantle.

  • Temperatures here range from 1,000 to 3,500 degrees Celsius.

  • Some of this heat comes from the radioactive decay of metals.

  • But much of it comes from Earth's core,

  • which has been radiating energy since the planet formed

  • over four billion years ago.

  • While the mantle moves slowly,

  • circulating roughly 40 kilometers below the Earth's crust,

  • there are places where it surges closer to the surface.

  • Here, the magma forms pockets and veins in the ground,

  • heating underground rivers and pools to temperatures reaching 300 degrees.

  • Controlling heated water is at the heart of harnessing geothermal energy,

  • and there are two primary models for how to do it.

  • One is to build a geothermal power plant

  • which uses these hot, deep pools to produce electricity.

  • First, engineers drill a well several kilometers into permeable rock

  • like sandstone or basalt.

  • As the hot, highly pressurized groundwater flows into the well,

  • the rapid change in pressure and temperature

  • produces huge amounts of steam.

  • This steam then turns the blades of a turbine to generate electricity.

  • Finally, the remaining cooled water and condensed steam

  • are injected back into the ground to create an open loop

  • that provides electricity without losing water.

  • However, we don't have to drill this deep to take advantage of the planet's heat.

  • Thanks to solar radiation,

  • dirt just 1.5 meters deep can reach temperatures over 20 degrees Celsius.

  • Geothermal heat pumps pipe water or antifreeze liquid

  • through this layer of earth to siphon its energy.

  • These liquids are then pumped through local infrastructure,

  • dispersing their heat before moving back through the ground

  • to absorb more energy.

  • While external electricity is needed to operate the pumps,

  • the energy provided is far greater than the energy used,

  • meaning this process is also a sustainable loop.

  • In fact, geothermal heat pumps are both cheaper to operate

  • and at least two times more energy efficient than fossil fuel equivalents.

  • Whether geothermal energy is radiating just below our feet,

  • or heating water several kilometers deep,

  • the planet is constantly radiating heat.

  • Averaged across one year,

  • Earth gives off roughly three times more energy than humanity consumes.

  • So why does geothermal only account for 0.2% of humanity's energy production?

  • The answer has to do with heat, location, and cost.

  • Since geothermal heat pumps rely on the consistent heat

  • found in shallow earth,

  • they can be implemented almost anywhere.

  • But geothermal power plants require tapping into

  • high-temperature geothermal fields;

  • regions hotter than 180 degrees and typically several kilometres underground.

  • These high temperature zones are hard to find,

  • and drilling this deep for just one of the several wells a plant will need

  • can cost up to $20 million.

  • There are regions with shallower geothermal fields.

  • Iceland and Japan are near active volcanoes and tectonic plate boundaries,

  • where magma rises up through the crust.

  • But these same factors also make those regions prone to earthquakes,

  • which can also be triggered by intensive drilling.

  • Furthermore, while geothermal energy is clean and renewable,

  • it's not entirely harmless.

  • Drilling can release vapors containing pollutants

  • like methane and hydrogen sulfide.

  • And drilling tools that use pressurized water can contaminate groundwater.

  • Fortunately, new technologies are emerging to meet these challenges.

  • Emission control systems can capture pollutants,

  • and electromagnetic monitoring can help detect seismic risks.

  • We're also uncovering entirely new sources of geothermal energy,

  • like pockets of magma in mid-ocean volcanoes.

  • So if we can safely and responsibly tap into the heat sustaining our planet,

  • we might be able to sustain humanity as well.

While the weather in Iceland is often cold, wet, and windy,

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B2 US TED-Ed geothermal energy heat drilling magma

Iceland's secret power - Jean-Baptiste P. Koehl

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    shuting1215 posted on 2022/01/04
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