Energy and exergy-economic performance comparison of wind, solar pond, and ocean thermal energy conversion systems for green hydrogen production

The necessity of energy solutions that are economically viable, ecologically sustainable and environmentally friendly has become fundamental to economic and societal advancement of nations. In this context, renewable energy sources emerge as the most vital component. Furthermore, hydrogen generation systems based on renewable energies are increasingly recognized as the most crucial strategies to mitigate global warming. In the present study, a comparative analysis is conducted from an exergy-economic perspective to find the most efficient configuration among three different systems for renewable-based power to hydrogen production. These renewable sources are wind turbine, salinity gradient solar pond (SGSP), and ocean thermal energy conversion (OTEC). SGSP and OTEC are coupled with a hydrogen production unit by a trilateral cycle (TLC) to improve the temperature match of the heating process. The heat waste energy within these systems is recovered by a thermoelectric generator (TEG), and a proton exchange membrane electrolyzer (PEME) is used for hydrogen production. Under base case input conditions, the net power input of PEME is estimated to be approximately 327.8 kW across all configurations. Additionally, the 3E (energy, exergy, and exergy-economic) performance of the three systems is evaluated by a parametric study and design optimization. The results of the best performance analysis reveal that the best exergy efficiency is achievable with the wind-based system in the range of 5.8–10.47% and for average wind speed of 8–12 m/s. Correspondingly, the most favorable total cost rate is attributed to the wind-based system at a wind speed of 8 m/s, equating to 66.08 USD/h. Subsequently, the unit cost of hydrogen for the SGSP-based system is estimated to be the most economical, ranging from 42.78 to 44.31 USD/GJ.