Electricity Production by Geothermal Hybrid – Plants in Low-enthalpy Areas

In Central Europe, the utilization of low enthalpy reservoirs for electricity production has not yet fully developed. Reliable technological experience will only be obtained from future projects. Currently, the utilization is still at an experimental stage and the failure of only a single project could easily have dramatic consequences for the continuation of other projects due to limited public interest and funding. Due to the imponderability of pure geothermal production we propose a new hybridization concept. Herewith, the probability of a success will be increased and geothermal energy can become attractive for private funding. In contrast to existing hybridization plants using geothermal to preheat working fluids of conventional plants we consider a superheating from additional fuels of a geothermal vapor cycle. Therewith, an optimum temperature can be adjusted that is less dependent on the geothermal source temperature but that is generally considerably higher than most geothermal plants. Such hybridization offers the advantage of a smooth transfer from conventional systems and allows a nearly arbitrary combination of different energy fuels. On the basis of existing data from the European EGS location in Soultz-sous-Forêts, economic estimations have been performed. Based on proper thermodynamic evaluation, our quantitative analysis demonstrates the advantage of such utilization, if already pure water is superheated. Such hybrid combination would produce electricity to an overwhelming part from geothermal resources. Using even organic working fluids, such plants even start to become economic at T~100°C under typical legal European conditions. INTRODUCTION