Investigation energy, exergy and electricity production performance of an integrated system based on a low-temperature geothermal resource and solar energy

Abstract

In this work, energy, exergy and electricity generation performance of an integrated system was conceptually investigated by using Engineering Equation Solver (EES) under 200-1000 W/m(2) solar irradiation interval. The system comprises evacuated tube solar collectors (EVTSCs) with the surface area of 100 m(2), an organic Rankine cycle (ORC) and a low-grade geothermal resource. The EVTSCs were used to enhance the temperature of the low-grade water coming from the geothermal source. The calculations were carried out for three geothermal sources in Kula (63 degrees C), Saraycik (74 degrees C) and Turgutlu (86 degrees C), respectively. N-hexane, n-pentane and n-butane were selected as a working fluid in the ORC. It was determined that the selection of the working fluid affected the performance of the ORC. And also, the waste heat is extracted from the ORC were used efficiently for space heating. As a result, the overall energy and exergy efficiencies of the system and power generation of the ORC were seriously affected by enhancing the water temperature of the geothermal resources by EVTSCs. The maximum overall energy and exergy efficiencies of the system were calculated as to be 6.92% and 21.06% by using n-butane for the source in Turgutlu, respectively. The minimum overall energy and exergy efficiencies of the system were calculated as 0.32% and 2.19% by using n-hexane for the source in Kula, respectively. The maximum and minimum generated electricity were calculated as to be 19.46 kW and 0.6168 kW for the sources in Turgutlu and Kula, respectively. It was seen that the best performance of the system was found for n-butane compared to n-pentane and n-hexane.