Earlier this month, a corner of the internet turned a little greener thanks to the first geothermal power project in the northern Nevada desert. Project Red, developed by a geothermal startup called Fervo, has begun pumping electrons into a local grid that includes data centers run by Google. The search company invested in the project two years ago as part of its efforts to run all data centers on green energy 24/7.
Although Project Red will produce two to three megawatts, or enough to power thousands of homes, it is an important demonstration of a new approach to geothermal power generation. You can harness the earth’s natural heat anywhere in the world.
Hot rocks are everywhere, increasing temperatures by hundreds of degrees Fahrenheit within the first few miles of the earth’s surface, yet geothermal power plants provide only a small portion of the world’s electricity supply. That’s mainly because they’re built in locations where naturally heated water, such as hot springs or geysers, is easily available. Hot water is pumped to the surface, where it produces steam that powers turbines.
The Nevada site, which is an “enhanced” geothermal system (EGS), operates differently. Instead of drilling into a natural hydrothermal system, Ferbo effectively created an artificial hot spring by drilling into bone-dry rock and returning hotter water to the surface.
This strategy piggybacks on hydraulic fracturing technology developed by the oil and gas industry. Furbo said he drilled two wells, each of which he extended down more than 7,000 feet before becoming completely level. They then connected them using hydraulic fracturing, creating a crack in the rock connecting the two boreholes. Water enters one borehole cold and exits the other at a temperature sufficient to drive a turbine and generate electricity.
As a result of the month-long test period, Furbo says temperatures at the bottom of the borehole reached 375 degrees Fahrenheit (191 degrees Celsius) and enough water passed through the system to generate an estimated 3.5 megawatts of electricity. It was confirmed that the experiment was successful this summer. According to Fervo CEO Tim Latimer, these operational numbers have remained relatively stable since then, suggesting the project was ready to be connected to the grid for a long time. The Nevada wells are being drilled close enough to traditional geothermal power plants that the project can utilize existing turbines and power lines to power the grid.
Latimer said the power output is less than the 5 megawatts the company originally estimated in its announcement with Google, but further adjustments should produce more power in the future. As it stands, this project is the first to achieve such a high level of performance, he points out. His two power stations in northeastern France currently generate electricity from dry rock, but they operate at much lower temperatures and take advantage of the rock’s natural fault system. Latimer said Fervo’s results show the strategy can be scaled up.
