Numerical modeling and thermoeconomic optimization of PEM fuel cell assited cogeneration system

In this research, it is aimed to design a power plant that produces electricity, produces hydrogen and as a heating system. Geothermal water at 130°C in the Afyon Ömer Gecek geothermal field and the solar potential of the region were used as sources. While the water flow rate in the region is 85 kg/s, the average solar radiation is accepted as 600 W/m2. Three different model designs were used to make the most efficient use of these resources. In the first model, energy from parabolic trough solar collectors and energy from geothermal water were transferred to an Organic Rankine Cycle (ORC). Electricity is produced here. The resulting electricity was converted into hydrogen and electrical energy was produced again with a fuel cell. While similar sources are used for similar purposes in Model 2, a double-stage heat exchanger system is used, unlike Model 1, in order to increase efficiency. R-134a heated by geothermal in ORC was reheated with Therminol VP-1 from solar energy. In the third model, a flat plate solar energy system was used due to economic concerns. Water was used instead of Therminol VP-1. In this model, R-134a in ORC was preheated and then heated with geothermal. After the energies from solar and geothermal sources were transferred to ORC, the remaining heat was transferred to residential heating in all three models. ORC produced 2.67 MW in Model 1, 2.87 MW in Model 2 and 2.56 MW in Model 3, respectively. ORC electricity unit cost is 0.0108 $/kWh, 0.0098 $/kWh, 0.0111 $/kWh for Model 1, Model 2 and Model 3, respectively. Then, the cost of hydrogen produced from electricity by electrolyzer is $1,585/kg, $1,551/kg, and $1,585/kg, respectively. Then, the cost of generating electricity from the fuel cell again is 0.06748 $/kWh, 0.06607 $/kWh, 0.06822 $/kWh. Finally, the systems were optimized and the results were presented. The energy and exergy efficiencies of the systems are 27.65% and 34.56% for Model 1, 23.22% and 33.88% for Model 2, and 25.85% and 32.66% for Model 3, respectively.