The crust stretched, thinned, and broke into tilted blocks, forming mountains at high elevations while filling and flattening basins with sediments and water, as John McPhee memorably described in his 1981 book , Basin and Range. From a geothermal perspective, the important thing is that all this stretching and tilting brings hot rocks relatively close to the surface.
There’s a lot to like about geothermal energy: it offers an almost limitless, constant source of emission-free heat and electricity. If the US could capture just 2% of the thermal energy available two to six miles below its surface, it could produce more than 2,000 times the country’s entire annual energy consumption.
But due to geological constraints, high capital costs and other challenges, we hardly ever use it: today it accounts for 0.4% of US electricity production.
Until now, developers of geothermal power plants have largely been able to tap only the best and most economical locations, such as this part of Nevada. They must be able to drill into porous, permeable, hot rock at relatively low depths. Rock permeability is essential for water to move between two man-drilled wells in such a system, but it is also the part that is often missing in otherwise unfavorable areas.
Beginning in the early 1970s, researchers at Los Alamos National Laboratory began to show that we could engineer our way around that limit. They found that by using hydraulic fracturing techniques similar to those used today in the oil and gas industry, they could create or expand cracks within relatively solid and very hot rock. Then they can add water, mainly in underground engineering radiators.
Such an “enhanced” geothermal system basically works like any other, but it opens up the possibility of building power plants in places where the rock is not yet hard enough to allow hot water to flow. to circulate easily. Researchers in the field have argued for decades that if we lower the cost of such techniques, it will open many new areas of the planet for geothermal development.
A famous 2006 MIT study estimated that with a $1 billion investment over 15 years, improved geothermal plants could create 100 gigawatts of new grid capacity by 2050, putting it on par with league of the most 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 get heat out of the ground in places that don’t have a naturally circulating geothermal system, then we have access to a tremendous resource,” said Susan Petty, a contributor to that report and founder of Seattle-based AltaRock Energy, an early-stage geothermal startup.