Researchers are developing a new type of geothermal power plant which is claimed to lock away unwanted carbon dioxide (CO2) underground – and use it as a tool to boost electric power generation by at least 10 times compared to existing geothermal energy approaches.
The technology to implement this design already exists in different industries, so researchers are optimistic about the marketing prospects of this approach, aimed mainly at enhancing the use of geothermal energy not just by efficiency but also as scale. The new power plant design resembles a cross between a typical geothermal power plant and the Large Hadron Collider: It features a series of concentric rings of horizontal wells deep underground. Inside those rings, CO2, N and H2O circulate separately to draw heat from below ground up to the surface, where the heat can be used to turn turbines and generate electricity.
Jeffrey Bielicki, co-author of the study and assistant professor of energy policy in the Department of Civil, Environmental and Geodetic Engineering says about the new approach to enhancing the potential of geothermal resources uses CO2 and another fluid, to partly replace some of the water which is recycled in the system. This approach — using concentric rings that circulate multiple fluids — builds upon the idea to use CO2 originally developed by Martin Saar and others at the University of Minnesota, and can be at least twice as efficient as conventional geothermal approaches, according to computer simulations.
Scientists involved in this research believe that the resulting multifluid design will enable geothermal power plants to store energy away – perhaps hundreds of GWh – for days or even months, so that it is available when the electricity grid needs it. The underground geothermal formation could store hot, pressurized CO2 and N, and release the heat to the surface power plant when electricity demand is greatest. The plant could also suspend heat extraction from the subsurface during times of low power demand, or when there is already a surplus of renewable power on the grid.
In computer simulations, a 16-km-wide system of concentric rings of horizontal wells situated about three miles below ground produced as much as half a GW of electrical power – an amount comparable to a medium-sized coal-fired power plant — and more than 10 times bigger than the 38 MW produced by the average geothermal plant in the United States. The simulations also revealed that a plant of this design might sequester as much as 15 mil tons of CO2/year, which is roughly equivalent to the amount produced by 3 medium-sized coal-fired power plants in that time.
The information hereby provided comes out partly from an article published on RenewableEnergyWorld blog, for which one should chew it with a grain of salt. Technologic enhancements to existing energetic systems are good news, only that they usually apply to a handful of sites; which is also the case with the CO2 storage in geothermal reservoirs. Surely on a global scale the number of coal power plants outbids the number of geothermal sites in exploitation. That and the fact that the combination of the two technologies is unlikely to be found in a reasonable proximity to one another, would make the applicability of the above described technology rather unlikely to be shrink by much the anthropogenic CO2 cloud.
In conclusion, the enhanced method to extracting energy from geothermal reservoirs is welcomed and might turn out beneficial. The more positive aspect of this development is the possibility of using the reservoir as battery with limited losses on reasonably large time scales. This in turn would incur the deployment of financial resources to build the required infrastructure, which would add up to the existing overcrowded system. Maybe it is time for a drastic change in the way we look at energy systems.