Green hydrogen production and liquefaction using offshore wind power, liquid air, and LNG cold energy

Coastal regions have abundant off-shore wind energy resources, and surrounding areas have large-scale liquefied natural gas (LNG) receiving stations. From the engineering perspectives, there are limitations in unstable off-shore wind energy and fluctuating LNG loads. This article offers a new energy scheme to combine these 2 energy units, which uses surplus wind energy to produce hydrogen, and use LNG cold energy to liquefy and store hydrogen. In addition, in order to improve the efficiency of utilizing LNG cold energy, and reduce electricity consumption for liquid hydrogen (LH2) production at coastal regions, this article introduces the liquid air energy storage (LAES) technology as the intermediate stage, which can stably store the cold energy from LNG gasification. A new scheme for LNG-LAES-LH2 hybrid LH2 production is built. The case study is based on a real LNG receiving station at Hainan province, China, and this article presents the design of hydrogen production/ liquefaction process, and carries out the optimizations at key nodes, and proves the feasibility using specific energy consumption and exergy analysis. In a 100 MW system, the liquid air storage round-trip efficiency is 71.0% and the specific energy consumption is 0.189 kWh/kg, and the liquid hydrogen specific energy consumption is 7.87 kWh/kg and the exergy efficiency is 46.44%. Meanwhile, the corresponding techno-economic model is built, and for a LNG-LAES-LH2 system with LH2 daily production 140.4 tons, the shortest dynamic payback period is 9.56 years. Overall, this novel hybrid energy scheme can produce green hydrogen using a more efficient and economical method, and also can make full use of surplus off-shore wind energy and coastal LNG cold energy.