With the rapid increase in the photovoltaic (PV) installations, the intermittency and the variability of the solar energy sources will lead to the frequent and steep ramping operation of conventional fossil generation. Consequently, energy storage is required for efficient use of the renewable energy source. Hydrogen production via electrolysis can provide both short and long duration capacity as a controllable load to reduce grid fluctuations and improve the resilience of the energy system. Once the hydrogen is produced, it must be stored before it is consumed. High pressure gaseous hydrogen storage is the most popular and mature hydrogen storage technology due to the technical simplicity, reliability, energy efficiency as well as affordability [1]. Compressed hydrogen storage with a fast filling-emptying rate can be used as a hydrogen multiple-purpose station for both stationary fuel cell and fuel cell electric vehicle (FCEV) applications. Although hydrogen electrolyzers, stationary fuel cells, and FCEV refueling stations have been extensively studied, little work has been done integrating these hydrogen technologies with a utility PV field to ensure electric grid stability, maximize PV utilization and efficiently produce and consume hydrogen. A model for a complete system of hydrogen production via electrolysis and high-pressure hydrogen storage was developed. The dynamic performance of different hydrogen storage filling and emptying operations with electrolyzer, stationary fuel cell and FCEV shows the feasibility and flexibility of the integrated hydrogen system.

A high-fidelity dynamic model of a Proton Exchange Membrane (PEM) electrolyzer was developed for hydrogen production from PV electricity. A parallel multi-stage hydrogen compression system with cascade tanks for filling/emptying was designed and modeled. A non-adiabatic lumped dynamic model was developed for the storage tank with heat transfer from the tank to ambient air. The Soave-Redlich-Kwong equation of state was adopted to account for the non-ideal gas response of high-pressure gaseous hydrogen [2]. The 1 MW electrolyzer under full load produces hydrogen at 200 Nm³/hr (17.7 kg/hr) and the hydrogen can be compressed up to the maximum pressure of 45 MPa suitable for heavy-duty fuel cell vehicles.

The storage tanks can be filled with constant/varied hydrogen flow from the electrolyzer depending on the PV power. The compressor and heat exchanger duties as well as the storage tank pressure and temperature are monitored and controlled. The tanks can be discharged to the stationary fuel cell and/or FCEVs. The dynamic performance of integrated hydrogen system for PV smoothing (filling with varied hydrogen flow in short time-scale), peak shaving (filling and emptying with constant hydrogen flow in long time-scale) and FCEV refueling (cascade filling and emptying) will be presented. The feasibility and flexibility of integrated hydrogen production and storage system for grid operation will be shown.

[1] Li, Mengxiao, Yunfeng Bai, Caizhi Zhang, Yuxi Song, Shangfeng Jiang, Didier Grouset, and Mingjun Zhang. "Review on the research of hydrogen storage system fast refueling in fuel cell vehicle." International Journal of Hydrogen Energy 44, no. 21 (2019): 10677-10693.

[2] Xiao, Lei, Jianye Chen, Yimei Wu, Wei Zhang, Jianjun Ye, Shuangquan Shao, and Junlong Xie. "Effects of pressure levels in three-cascade storage system on the overall energy consumption in the hydrogen refueling station." International Journal of Hydrogen Energy 46, no. 61 (2021): 31334-31345.