Thermodynamic and performance evaluation of an integrated geothermal energy based multigeneration plant

Abstract

In this study, a new integrated geothermal energy-based plant is proposed for multigeneration purposes such as hydrogen, electricity, hot water, drying, cooling and heating. Therefore, this proposed integrated system is consisted of proton exchange membrane electrolyzer, hydrogen compression unit, organic Rankine cycles, single effect absorption cooling cycle, hot water storage tank and a drying unit. Thermodynamic analyses including of energy and exergy analyses have been performed for general evaluation of the proposed system. Energy and exergy efficiencies of whole plant are found as 37.65% and 39.26%, respectively. Exergy destruction rate is one of the important indicators to improve system performance. The largest three exergy destruction rates occur in organic Rankine cycle 1 with 3076 kW, single effect absorption cooling with 2816 kW and hydrogen production and compression with 2658 kW. In addition to these analyses, parametric analyses have been carried out to see how some variables affect system performance and useful product generation. For this reason, the impacts of dead state temperature, geothermal mass flow rate, geothermal source temperature and pinch point temperature of heat exchanger 1 are investigated. Any increase in dead state temperature, geothermal mass flow rate and geothermal source temperature has positive impact on system performance and useful product generation. Increase in pinch point temperature of heat exchanger 1 decreases the system performance. Hydrogen production rate reaches maximum point (0.0024 kg/s) when geothermal mass flow rate is 8.125 kg/s or when geothermal working fluid temperature is 168 °C for this paper.