Environmental and thermal benefits of linking Brayton, absorption chiller, and organic Rankine cycles with low-enthalpy geothermal source at an arid-zone area of Libya

Abstract

A combined system which consists of Brayton, LiBr/H2O absorption chiller, and HFC 245fa organic Rankine cycles has been developed and linked to a high potential low-temperature geothermal source of energy. Situated in an arid-zone area at Waddan City Libya, the geothermal source could provide sufficient energy for the City and surrounding villages and satisfy their full electrical demand of 100 MW in an uninterrupted and stable way. The system could also supply district heating and hot water. The simulated results show that the output power and thermal efficiency of the combined cycles were improved by 5 per cent and 1.5 per cent, respectively, compared to a standalone gas turbine and it also reduced carbon emissions by 55.7 per cent (291 g/kWh instead of 649 g/kWh). Incorporating district heating to the electrical energy raised the energy utilization factor to 55.1 per cent.