Energy and Exergy Analyses of a New Combined Cycle for Producing Electricity and Desalinated Water Using Geothermal Energy

A new combined cogeneration system for producing electrical power and pure water is proposed and analyzed from the viewpoints of thermodynamics and economics. The system uses geothermal energy as a heat source and consists of a Kalina cycle, a LiBr/H2O heat transformer and a water purification system. A parametric study is carried out in order to investigate the effects on system performance of the turbine inlet pressure and the evaporator exit temperature. For the proposed system, the first and second law efficiencies are found to be in the ranges of 16%-18.2% and 61.9%-69.1%, respectively. For a geothermal water stream with a mass flow rate of 89 kg/s and a temperature of 124 degrees C, the maximum production rate for pure water is found to be 0.367 kg/s.