Harvesting energy from hot, dry rocks

Oilfield technology captures geothermal energy from a wider range of areas

Spotted: Geothermal energy is a clean, renewable source of power, but its availability is limited to certain areas, such as volcanic regions or places with deep drilling. Now, however, Sage Geosystems has developed a way to make geothermal energy available almost anywhere using oilfield technology.

Most existing geothermal energy comes from a relatively small number of rock formations that sit close to the Earth’s surface and produce large volumes of water or steam. Sage, on the other hand, is targeting the plentiful hot, dry rock formations that are hot enough to produce energy, but don’t have the necessary volumes of water or steam to bring that heat and energy to the surface.

Sage’s system, which relies on proven oilfield technology, involves drilling a fracture into the ground that acts as a chimney, efficiently capturing heat from deeper and hotter rock formations. These underground fractures serve as artificial reservoirs to store pumped, pressurised water. Energy is provided both by the pressure of this stored water once it’s released back to the surface and the heat the water has absorbed from the surrounding hot rocks.

In Sage’s HeatCycle well design, multiple wells are drilled next to each other and alternate between injecting fluid and producing energy. This approach optimises energy generation efficiency. The system can also be paired with intermittent renewable energy sources, including wind and solar, to create a form of efficient energy storage. When surplus green energy is generated, such as during sunny and windy periods, that energy powers Sage’s HeatCycle wells. Because the hot, dry rocks will also heat the pressurised liquid, it means that the system will actually store and release more energy than was initially expended to pump the fluid down.

Earlier this year, the company closed a $17 million series A funding round. The proceeds will fully fund the first-of-its-kind, three-megawatt commercial Geopressured Geothermal System (GGS) facility in Texas, which will use Sage’s technology to harvest energy from pressurised water stored deep underground. More recently, the company announced a new partnership with Meta that will see Sage deliver up to 150 megawatts of new geothermal baseload energy to power Meta’s data centres.

Written By: Lisa Magloff and Matilda Cox