Exergy and exergoeconomic analysis of geothermal assisted high temperature electrolysis

In this thesis, energy, exergy, and exergoeconomic analysis of a geothermal assisted high temperature electrolysis process is performed. Energy and exergy analysis is applied to each component of the system for three environment (dead state) temperatures: standart environment temperature (25°C), summer temperature (11°C) and winter temperature (-1°C) at a given location. Energy and exergy performance parameters such as heat, power, exergy destruction, and exergy efficiencies are determined for three dead state temperatures. Heat exchanger network and high temperature electrolysis unit are primarily responsible for exergy destructions in the system. Cost analysis is applied to each component of the system. The cost functions of each stream in the plant are obtained using specific exergy costing (SPECO) method. Cost relations at the component level are related with certain exergoeconomic variables in the system. The capital investment cost, the operating and maintenance costs and the total cost of the system are found to be 422.21 ?/kWh, 2.04 ?/kWh and 424.25 ?/kWh, respectively. The net electrical power input to the system is 122,129 kW for high temperature electrolysis. The specific unit exergetic costs of the power input to the system are 0.17 ?/kWh, 0.20 ?/kWh, and 0.24 ?/kWh at 25°C, 11°C, and -1°C, respectively. Cost of hydrogen production is determined to be 1.6 ?/kWh for 1 kg of hydrogen production. The cost of steam entering the system is obtained as 2.73 ?/kWh.Key words: Geothermal Energy, Hydrogen, High Temperature Electrolysis, Energy, Exergy, Exergoeconomic Analysis.