Thermodynamic analysis of a geothermal energy-basedORC cycle to produce power, freshwater and hydrogen

In this study, a trigeneration system, including a geothermal fluid as the heat source, the ORCcycle as the power generation unit, the RO unit as the unit for the freshwater production and a PEMunit for the hydrogen production, is presented. The system is studied from an energy and exergy pointof view. The simulation was performed by using the EES software. Different parameters were studiedto investigate their effects on the performance of the proposed system. Validation was done to be surethat the written code was correct. For the initial analysis, five different geothermal fluids werecompared. After comprehensive analysis, it is found that the ORC cycle can produce ۸۲.۴۲ kW ofpower. The energy and exergy efficiency of the system are ۶.۶۲ % and ۱۶.۵۶ %, respectively. Byconsidering the initial assumptions, the amount of freshwater production rate and the amount ofhydrogen production rate are ۲.۲۱۵ kg/s and ۰.۰۰۱۱۸۸ g/s, respectively. Among the different subsystems,the PEM unit has the highest amount of exergy destruction rate. When the geothermal fluidtemperature rise, both energy and exergy efficiencies decrease while the freshwater and hydrogenproduction rate increase. When the ambient temperature rises, both energy and exergy efficienciesincrease.

Keywords:

Geothermal fluid , ORC cycle , PEM unit , RO unit , thermodynamic study