Supercritical Rankine Cycle Coupled with Ground Cooling for Low Temperature Power Generation

Abstract This paper presents an application of an earth-air-heat-exchanger (EAHE) as condenser in low to medium temperature power generation plants. A supercritical Rankine cycle (SRC) utilizing organic refrigerants as working fluids was used as the power cycle for the plant. The heat source temperature was varied from 125-175 0 C. The condenser was coupled to an EAHE system buried at a depth of 2 m under the surface of the earth. Its effect on the power cycle efficiency over a period of six months has been studied. It was observed that the soil temperature 10 cm from the surface (horizontal direction) of the underground pipe increased by almost 2 0 C during this time. This temperature change decreased with distance from the pipe. The soil temperature profile varied with time, distance from the pipe and location along the length of the pipe. The efficiency of the SRC increased by 1% and the daily fluctuations were reduced when EAHE was used.