Conference article

In this study a thermoeconomic analysis of combined heat and power generation (CHP) for geothermal applications is presented. Different working fluids and power plant concepts are investigated for power generation by Organic Rankine Cycle and additional heat generation. For geothermal conditions in Germany; process simulations of series; parallel and hybrid circuits compared to sole power generation are performed. The results show that for power generation fluids with low critical temperature; like R227ea or isobutane; are suitable. In general; an additional heat generation decreases the averaged costs of electricity generation. In case of a source temperature of 120 °C the costs can be reduced from 25 ct/kWh to 16 ct/kWh compared to power generation. For CHP applications fluids with higher critical temperature and series or hybrid circuits are the most efficient concepts. With increasing temperature of the geothermal water an increase of supply temperature of the heating system has less influence on the costs of electricity generation. A doubling of mass flow of the geothermal water decreases the averaged costs of electricity generation in the range of 28 % and 43 % depending on power plant concept and boundary conditions.

Geothermal energy; Organic Rankine Cycle; cogeneration; thermoeconomic analysis