Thermodynamic Analysis Of Organic Rankine Cycle Using Geothermal Energy To Produce Hydrogen, Fresh Water And Electricity

The Organic Rankine Cycle (ORC) is named for the use of a high molecular mass organic fluid, whose liquid-vapor phase change or boiling point occurs at a temperature lower than the water-vapor phase change temperature. The fluid allows the Rankine cycle to recover heat from low temperature sources. In this study, a trigeneration system, including a geothermal fluid as the heat source, the ORC cycle as the power generation unit, the RO unit as the unit for the freshwater production and a PEM unit for the hydrogen production, is presented. The system is studied from an energy and exergy point of view. The simulation was performed by using the EES software. Different parameters were studied to investigate their effects on the performance of the proposed system. Validation was done to be sure that the written code was correct. For the initial analysis, five different geothermal fluids were compared. After comprehensive analysis, it is found that the ORC cycle can produce ۸۲.۴۲ kW of power. The energy and exergy efficiency of the system are ۶.۶۲ % and ۱۶.۵۶ %, respectively. By considering the initial assumptions, the amount of freshwater production rate and the amount of hydrogen production rate are ۲.۲۱۵ kg/s and ۰.۰۰۱۱۸۸ g/s, respectively. Among the different sub-systems, the PEM unit has the highest amount of exergy destruction rate. When the geothermal fluid temperature rise, both energy and exergy efficiencies decrease while the freshwater and hydrogen production rate increase. When the ambient temperature rises, both energy and exergy efficiencies increase. In every heat engine, there is a thermodynamic cycle, which is called a power cycle because of the production of useful work in the cycle.

Keywords:

Organic Rankine cycle , PEM unit , RO unit , Electricity production , geothermal