Abstract This review presents a comprehensive and comparative analysis of four prominent bottoming cycles: the Steam Rankine Cycle (SRC), the Supercritical CO₂ Brayton Cycle (s‐CO₂), the inverse Brayton cycle (IBC), and the Air Bottoming Cycle (ABC) integrated with proton exchange membrane (PEM) electrolyzers for hydrogen production. The study evaluates each cycle through a multi‐criteria 4E framework (energy, exergy, economic, and environmental performance). The SRC system emerges as the most promising, achieving an exergy efficiency of 21. 93% and a hydrogen production efficiency of approximately 57. 4%. In comparison, the IBC lags with an exergy efficiency of 13. 72% due to higher irreversibilities. Hybrid configurations employing thermoelectric generators (TEGs) further enhance low‐grade heat recovery, adding up to 1. 2–2. 4% to the overall system efficiency. The exergoeconomic analysis reveals a cost rate of 32. 8/GJ for SRC‐based hydrogen systems compared to 25. 58/GJ for IBC, suggesting a trade‐off between cost and performance. The integration of bottoming cycles with PEM electrolyzers presents a viable route to reduce fossil fuel dependency and greenhouse gas emissions, potentially cutting lifecycle CO₂ emissions by 12–20%. This review highlights technology synergies crucial for transitioning toward a hydrogen‐enabled circular energy economy.
Ugli et al. (Mon,) studied this question.