This geothermal startup has shown that the wells can be used as a giant underground battery.


The crust stretched, thinned, and broke up the inclined blocks, forming mountains on the high side, filling and flattening the basins with sediment and water, as John McPhee so vividly described in his 1981 book. basin and region. From a geothermal perspective, the important thing is that all this stretching and tilting brings the hot rocks relatively high.

There’s a lot to like about geothermal energy: it provides a nearly limitless, almost always emission-free source of heat and electricity. If the United States could capture just 2 percent of the thermal energy two to six miles below the Earth’s surface, it could produce more than 2,000 times the nation’s total annual energy consumption.

But because of geologic constraints, high capital costs, and other challenges, we barely use it: Today, it accounts for 0.4% of America’s electricity generation.

Until now, developers of geothermal power plants have mostly been able to tap only the most promising and economical areas like this one in Nevada. They must be able to drill at relatively shallow depths into porous, malleable, hot rock. In such a system, the fertility of the rock is important to allow water to move between two man-dug holes, but it is also a characteristic that is often lost in favorable locations.

Beginning in the early 1970s, researchers at Los Alamos National Laboratory began to show that we could engineer our way around that limit. They now find that they can create or expand cracks in relatively hard, very hot rock using hydraulic fracturing techniques similar to those employed in the oil and gas industry. Then you can add water, basically engineering radiators underground.

Such an “enhanced” geothermal system works essentially the same as any other, but opens up the possibility of building power plants in places where the rock does not provide enough water to allow hot water to flow easily. Researchers in the field have argued for decades that if we can reduce the cost of these techniques, it will open up vast new stretches of the planet for geothermal development.

In the year A 2006 MIT study estimated that with an investment of $1 billion over 15 years, improved geothermal plants could produce 100 gigawatts of new grid capacity by 2050, putting it in the same league as popular renewable sources. (By comparison, about 135 gigawatts of solar capacity and 140 gigawatts of wind have been installed across the US.)

“If we can figure out how to extract heat from the Earth in places where there’s been no natural circulation geothermal system before, we have a tremendous resource,” said Susan Petty, Seattle-based co-author and co-founder of that report. Based on AltaRock Energy, an early enhanced-geothermal startup.


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