The purpose of this study is thermoeconomic performance evaluation of alkaline water hydrogen production assisted by geothermal energy. In this study energy, exergy and cost balances of combined systems of each component for hydrogen production assisted by geothermal energy will be written. Exergy of each involved stream will be calculated and the exergetic balance of each subsystem will be assessed, as well as the global system, identifying and quantifying losses. This will allow thermodynamic performances of combined systems and each component. This information will be relevant to optimize the system performance from an economical point of view.

We consider a geothermal resource at 230°C available at a rate of 230 kg/s. Under realistic operating conditions, 21545 kW power can be produced in a power plant. The produced power is used for the electrolysis process. The electrolysis water can be preheated to 67.6°C by the geothermal water leaving the power plant and hydrogen can be produced at a rate of 0.1125 kg/s. Also, combine flash binary geothermal power plant energy and exergy efficiencies are calculated to be 12.1% and 57.4% at this condition. Electrolysis system energy and exergy efficiencies are calculated to be 71.4% and 60.7% of geothermal water temperature at 230°C and geothermal water flow rate at 230 kg/s. We evaluated at unit exergetic cost of electricity combined flash binary system is 10.1$/GJ (0.0364 $/kWh) and unit exergetic cost of hydrogen is 34.6$/GJ (4.16 $/kg H2).

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