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Best Of Both Worlds: Geothermal Energy That Sucks CO2 From The Atmosphere

Clean power from the Earth used to use a lot of water. But a new discovery means that water can be replaced with CO2, which gets left in the ground and doesn't alter the climate.

Work by scientists at the University of Minnesota could result in a new way to capture heat from underground geothermal sources, which lets us generate clean electrical energy for our own uses while simultaneously disposing of some of the CO2 that's responsible for global warming. Though it sounds implausibly positive, it actually all lines up in terms of science, and best of all, this piece of lateral thinking was achieved in a flash of inspiration during a road trip—the best type of idea.

The way geothermal energy is usually tapped for power generation is by drilling a couple of shafts deep into the earth, and pumping high-pressure water down one shaft. This makes its way through a hot rock layer (which gets its heat from the essentially inexhaustible energy of nearby plumes of hot lava) to the second shaft, picking up heat en route. The resulting steam is used to push a turbine, and generate power.

Except that two scientists pondered: What if the water in this equation was replaced with high-pressure carbon dioxide? Because it's a gas rather than a liquid, CO2 can ferret its way into more and tinier cracks in the sub-surface hot rocks than water—making the new system more feasible in areas water-based geothermal sources aren't deemed practical.

Water-based geothermal plants also suffer from blockages, where the water dissolves the rocks (or parts of them, like the mineral content) around it and prevents reliable flow of water through the loop. Water can also be hard to truck in to where the geothermal power plants are located. CO2 systems don't suffer the same issues. And if your geothermal system is also an oil well—as some of them are—the pumping in of CO2 can help push out the crude you're trying to extract.

The CO2 gas in question is sucked from the atmosphere, and is thus safely "trapped" in closed-loop systems in the geothermal plant, and partly dissolved into sub-surface materials. Exactly as proposed by some CO "burial" schemes.

Essentially, it's a win-win, and the team behind it has already received grants to develop the idea. They're planning a spin-off firm, so we may see the principle tested in real life sooner than you think.

[Image: Flickr user billward]

Chat about this news with Kit Eaton on Twitter and Fast Company too.

Read More: Volcanic Magma Could Provide Geothermal Energy

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  • Robert Schreib

    ??If the CO2 can compress oil out of the earth, then could this CO2 be used for 'Fracking' where they inject toxic chemcial-laden water deep underground to extract natural gas? Maybe if they could put a layer of fracking water at one lower-most stratum and pump liqufied CO2 underneath it, like a layer cake, the CO2 could indirectly proel the natural gas upward to be collected. And if that works, it could be another way to sequester the CO2 from our coal-burning electric power plants deep in subterrean stra layers, so that it does not cause global warming.