Advanced organic rankine cycle for geothermal application

Abstract

Exploitation of geothermal sources based on advanced Organic Rankine Cycle (ORC) is studied with respect to energetic, plant-specific and economic aspects. Three natural andfive synthetic refrigerants are investigated as pure fluids within a sub- and transcritical ORC. Furthermore, a zeotropic mixture of R227ea/R245fa is analysed under subcritical conditions. It is shown that transcritical ORC is a promising way to optimize geothermal power plants. The gross power can be increased by >15% compared with standard subcriticalprocesses. Economic analysis indicates that transcritical ORC as well as zeotropic mixtures lead to significantly lower payback periods and, even when taking into account higher specific investment costs and higher mean cash flow. © The Author 2013. Published by Oxford University Press. All rights reserved.