Energy/Exergy Conversion Factors of Low Enthalpy Geothermal Plants

Abstract

A geothermal heat plant is a not only a source of heat, but, in general, also a sink for relevant amounts of electricity, consumed mainly by the pump(s). This electricity demand is usually not given much attention although being decisive for operation costs, but also offering chances for demand side management as a variable consumer. From the perspective of an integrated energy system, geothermal installations basically move energy from the electricity sector into the heat sector, similar to compression heat pumps. The main heat pump performance indicator is the ratio between invested energy and useful heat, the COP. This paper transfers the COP concept to geothermal sites, by defining and determining the quantity for a selection of mostly German geothermal sites.