Design of Geothermal Energy Conversion Systems with a Life Cycle Assessment Perspective

The development of Enhanced Geothermal Systems (EGS) for the cogeneration of electricity and district heating has recently gained interest, and is expected to know an important development in the future. Major research questions on the design of the energy conversion system concern the increase of the efficiency in the usage of geothermal resources, as well as the increase of their economic profitability. The quantification and the minimization of the generated life-cycle environmental impacts is as well a key point for the public acceptance of geothermal energy and for the choice of both the conversion technologies and the depth of EGS by the engineers. This paper presents a systematic methodology for the optimal design and configuration of geothermal systems considering environomic criteria. Process design and process integration techniques are used in combination with life cycle assessment and multiobjective optimization techniques. It is illustrated by an application to the design of geothermal cogeneration systems in the context of Switzerland.