Feasibility Assessment of Underground Cooling for Geothermal Power Cycles

Abstract

Geothermal heat sources offer significant potential for electricity generation in Australia by Hot Fractured Rock, HFR, technology and other approaches. However, all of the sites of greatest geothermal potential are situated remote from any significant surface water source, which poses a significant challenge to the method by which the working fluid in the power cycle will be cooled. The need for cooling in any thermal power cycle has driven many conventional power plants to be located close to a river, lake, or ocean to provide an environmental heat sink (Department of Environment, 2001). Where this is not realistic, cooling towers are almost invariably used to provide greater cooling than is possible by aircooling alone, utilising the evaporation of water, much like a large evaporative air cooler. However, the water consumption due to evaporation and fouling losses, even for a conventional power station with comparatively high efficiency, is typically 1363 L/MW.h per day (Ricketts et al., 2006), and will be greater for typical geothermal plants owing to their low thermodynamic efficiency.