Photo: Stefan Schweihofer/Pixabay | Edited
Houston-based Fervo Energy has discovered a new way of storing energy in geothermal layers under the surface. The surplus energy is used to pump water underground, which can be kept under pressure for days without significant losses. The water is released when needed, flowing for extended periods to generate electricity.
Storing surplus energy becomes increasingly crucial as solar and wind power become an important grid part. Traditionally, batteries are used for this purpose, but not all are the traditional batteries we use daily. Any system that can store energy in one form or another is a battery. An accumulation lake high in the mountains can be used as a storage battery if water is pumped upstream using energy surplus and then released to generate electricity. Other storage systems use sand to store heat for extended periods, but really, any form of energy storage would do.
Fervo Energy, a startup involved in geothermal power generation, has discovered a new energy storage method. The company operates several geothermal power plants in Nevada, using underground heat to generate electricity. This setup circulates water between two wells through hot rocks deep beneath the surface. The water emerges from underground hot enough to convert refrigerants or other fluids into vapors that propel a turbine. This is the traditional way, but the startup thinks its wells could also be used for energy storage.
Creating fractures in rocks with low permeability can work as underground reservoirs where natural conditions don’t allow the establishment of geothermal plants. This is no different than what natural gas fracking works, only it’s not used to release the gas. The low permeability rocks ensure water doesn’t leak into other areas, so the pressure builds within as the fractured rock sections push against the earth.
If the water they pump into the ground has nowhere to go, the pressure builds up and gets high enough to flex the rocks, which act like a balloon. The water can be released hours or even days later, and the pressure is sufficient to keep it flowing for long periods. Their first experiments indicate that Fervo can create flexible geothermal power plants capable of ramping electricity output up or down as needed.
Most importantly, the water pumped into the ground can be stored for long periods. It flows back for similar periods when released, acting like a giant and long-lasting battery. The power plant could thus shut down production when solar and wind generation is peaking and then kick in to provide electricity when those energy sources wane. This is only an experiment for now, but Fervo Energy wants to see if it can work safely and reliably at scale.
The company still needs to demonstrate that this storage system can work continuously within large-scale commercial plants operating in various regions and geologies. The geothermal industry suffered a huge setback in 2009 when an early commercial effort in Switzerland triggered a series of earthquakes that caused several million dollars in damages. Induced seismicity remains an issue in the geothermal industry, as in other fracking projects.
Fervo Energy, a startup involved in geothermal power generation, has discovered a new energy storage method. The company operates several geothermal power plants in Nevada, using underground heat to generate electricity. This setup circulates water between two wells through hot rocks deep beneath the surface. The water emerges from underground hot enough to convert refrigerants or other fluids into vapors that propel a turbine. This is the traditional way, but the startup thinks its wells could also be used for energy storage.
Creating fractures in rocks with low permeability can work as underground reservoirs where natural conditions don’t allow the establishment of geothermal plants. This is no different than what natural gas fracking works, only it’s not used to release the gas. The low permeability rocks ensure water doesn’t leak into other areas, so the pressure builds within as the fractured rock sections push against the earth.
If the water they pump into the ground has nowhere to go, the pressure builds up and gets high enough to flex the rocks, which act like a balloon. The water can be released hours or even days later, and the pressure is sufficient to keep it flowing for long periods. Their first experiments indicate that Fervo can create flexible geothermal power plants capable of ramping electricity output up or down as needed.
Most importantly, the water pumped into the ground can be stored for long periods. It flows back for similar periods when released, acting like a giant and long-lasting battery. The power plant could thus shut down production when solar and wind generation is peaking and then kick in to provide electricity when those energy sources wane. This is only an experiment for now, but Fervo Energy wants to see if it can work safely and reliably at scale.
The company still needs to demonstrate that this storage system can work continuously within large-scale commercial plants operating in various regions and geologies. The geothermal industry suffered a huge setback in 2009 when an early commercial effort in Switzerland triggered a series of earthquakes that caused several million dollars in damages. Induced seismicity remains an issue in the geothermal industry, as in other fracking projects.
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