Alamir H. Hassan

Integrating the exergy and economic analyses of water electrolyzers is the pivotal way to comprehend the interplay of system costs and improve system performance. For this, a 3D numerical model based on COMSOL Multiphysics Software (version 5.6, COMSOL, Stockholm, Sweden) is integrated with the exergy and exergoeconomic analysis to evaluate the exergoeconomic performance of the proton exchange membrane water electrolysis (PEMWE) under different operating conditions (operating temperature, cathode pressure, current density) and design parameter (membrane thickness). Further, the gas crossover phenomenon is investigated to estimate the impact of gas leakage on analysis reliability under various conditions and criteria. The results reveal that increasing the operating temperature or decreasing the membrane thickness improves both the efficiency and cost of hydrogen exergy while increasing the gas leakage through the membrane. Likewise, raising the current density and the cathode pressure lowers the hydrogen exergy cost and improves the economic performance. The increase in exergy destroyed and hydrogen exergy cost, as well as the decline in second law efficiency due to the gas crossover, are more noticeable at higher pressures. As the cathode pressure rises from 1 to 30 bar at a current density of 10,000 A/m², the increase in exergy destroyed and hydrogen exergy cost, as well as the decline in second law efficiency, are increased by 37.6 kJ/mol, 4.49 USD/GJ, and 7.1%, respectively. The cheapest green electricity source, which is achieved using onshore wind energy and hydropower, reduces hydrogen production costs and enhances economic efficiency. The growth in the hydrogen exergy cost is by about 4.23 USD/GJ for a 0.01 USD/kWh increase in electricity price at the current density of 20,000 A/m². All findings would be expected to be quite useful for researchers engaged in the design, development, and optimization of PEMWE.

Specific heat is a vital characteristic of nanofluids. The present work is an experimental assessment for the isobaric specific heat measurements for the Al₂O₃ nanoparticle dispersed in a base fluid of different mixture ratio of ethylene glycol and water at 30, 40, 50, and 60 vol%. The experiments were conducted over temperature range from 35 to 105 °C with nanoparticle concentrations of 0.5 to 2.5 vol%. The results indicated that the specific heat of nanofluid decreases as the nanoparticle volume increases and EG ratio increases but increases as the temperature increases. This characteristic demonstrates that the use of nanofluids should be at as high temperature as possible to fulfill a good beneficial effect. A new correlation from the measurements with maximum deviation of 2.2% was found to estimate the specific heat for these nanofluids.