Capacity Optimization of a Renewable Energy System Coupled with Large-Scale Hydrogen Production and Storage

Hybrid renewable energy and hydrogen energy systems have been proved to be a reliable and cost competitive option for power generation and hydrogen supply. However, the inappropriate capacity of hydrogen production and storage may result in out-of-balance of the power supply side and the hydrogen consumption side. In this paper, a simplified mathematical modeling of the hybrid energy system, including power generation, hydrogen production and storage has been presented to optimize the capacity of alkaline electrolyzer and hydrogen storage tank. Multi-objective functions are adopted in the capacity optimization model, including abandoned rate of renewable power, hydrogen supply fluctuation, and utilization efficiency of electrolyzer and hydrogen storage tank. A meta-heuristic algorithm (i.e., improved multi-objective particle swarm optimization algorithm) is chosen to solve the model. A hybrid energy system with a distributed photovoltaic power station with the rated power of 7000 kW has been designed to satisfy the hydrogen demand of 720 kg/d of a chemical plant. The results reveal that the optimal capacity configuration of the hybrid energy system is 4971 kW for the alkaline electrolyzer and 937 Nm(3) for hydrogen storage tank during a period of 8760 h. Compared with the empirical model and single-objective optimization model, the proposed multi-objective optimization model is found helpful to optimize the capacity of hybrid energy system and gives better results regarding renewable energy utilization rate, equipment usage rate, and hydrogen supply stability.