Comparative assessment of Organic Rankine Cycle integration for low temperature geothermal heat source applications

Present study deals with the comparative assessment of three different configurations of ORC (Organic Rankine Cycle) system including basic ORC, recuperated ORC, and regenerative ORC system for low temperature geothermal heat source. The comparison of the performance of each cycle is carried out at their optimum operating condition using Non-dominated Sorting Genetic Algorithm-II for minimum specific investment cost and maximum exergy efficiency under logical bounds of evaporation temperature, pinch point temperature difference and superheat. Objective functions are conflicting, therefore, optimization results are presented in the form of a Pareto Front Solution. Thermal efficiency and the exergy efficiency for recuperated and regenerative are higher than basic ORC but with an additional average specific investment cost of 3% for basic and 7% for regenerative cycle. Working fluids with critical temperature in the same range of heat source results in better thermal performance. R245fa has highest Exergy efficiency of 51.3% corresponding to minimum specific cost of 2423$/kW for basic cycle, 53.74% corresponding to 2475$/kW for recuperated, and 55.93% corresponding to 2567$/kW for regenerative cycle. (C) 2016 Elsevier Ltd. All rights reserved.