By Nigel Bean Chair of Applied Mathematics, School of Mathematics, University of Adelaide & Josephine Varney Ph.D. Candidate, University of Adelaide
The recent push to reduce carbon emissions from the electricity sector encompasses common, immediately available approaches such as increasing power plant efficiency and increasing the deployment of renewables. The opportunity now exists to accomplish these goals simultaneously through the use of geothermal energy to increase the power output, and decrease the carbon intensity, of thermal power plants.
This technology is referred to here as geothermal assisted power generation (GAPG). Basically, GAPG employs hot geothermal fluid to heat the boiler feedwater at a thermal power plant. The steam that would otherwise be taken from the turbines to heat the feedwater is allowed to run through the turbines, thereby generating extra power and increasing plant efficiency. Here we use efficiency to mean “fossil fuel efficiency”, as more power is generated per unit heat (MMBtu) of fossil fuel, because of the addition of the geothermal heat.
Unquestionably, greater deployment of GAPG has major implications for geothermal developers. GAPG allows them to focus on what they do best, getting hot geothermal fluid from the ground to the surface, and does not require the expertise or capital to produce and sell electricity. Further, the power plant is able to generate up to three times as much power per kilogram of geothermal fluid as a stand-alone geothermal power plant.
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