Novel small-scale bio-hydrogen liquefaction assisted by dual-loop Rankine cycle and absorption refrigeration: Thermodynamics and techno-economic analyses

Most bio-hydrogen production facilities are located in remote plantations, necessitating self-sufficiency in its energy demand. To enhance the energy efficiency, heat integration must be conducted internally, independent of any external processes and energy supply. The objectives of this study are to propose a novel systemthat combines the utilization of waste heat from a bio-syngas-fueled gas turbine and internal waste heat generated by a hydrogen liquefier using a dual-loop Rankine cycle for a remote bio-hydrogen liquefaction plant and analyze its exergo-economic performance. This system serves as both a power and heat source for the hydrogen liquefier and an ammonia absorption refrigeration pre-cooler. The results are compared to a traditional combined cycle power plant andpower plant (CCPP) hydrogen liquefaction system. The findings indicate that the heat recovery system of the Joule-Brayton cycles increases the coefficient of performance from 0.1236 to 0.1649, and reduces the specific energy consumption from 10.6 to 7.55. Additionally, the proposed system boosts power and heat generation by 12.9% compared to the conventional one. Consequently, when a low-temperature gas turbine is adopted, the overall exergy efficiency increases from 54.73% to 64.06%, and when a high-temperature gas turbine is applied, it rises from 62.16% to 69.17%. Despite the added complexity, economic analysis shows that normalized capital investment is reduced by 21.7%, and the levelized cost of liquid hydrogen (LCOH) decreases by 12.42%. Achieving an LCOH below 3 USD/kg-LH2 is feasible in the proposed system, assuming a feed gas price of 1 USD/kg and an escalation rate of 1%. This study underscores that the proposed system offers high energy efficiency and low LCOH, and is well-suited for remote hydrogen liquefaction plants utilizing biohydrogen and bio-syngas feedstock. The study contributes to the development of small-scale hydrogen transportation in remote areas and a sustainable hydrogen production supply chain in the future.