Dynamic Modeling of California Grid-Scale Hydrogen Energy Storage

The variability of renewable energy sources, specifically for large scale integration into the electricity sector, has brought increased attention to the requirements for energy storage systems. To mitigate the intermittency of renewable energy, many different energy storage technologies, such as pumped hydro, compressed air energy storage, batteries, flow batteries, hydrogen energy storage, capacitors, and flywheels are available. Some of these energy storage systems (e.g., batteries, flywheels) are best suited for short-term storage and highly dynamic operation, while others (e.g., pumped hydro, flow batteries, hydrogen) can accomplish massive and seasonal storage of renewable electricity sources. The integration of high levels of renewable power will require the features of both of these types of energy storage systems. The current work focuses upon hydrogen energy storage as it may contribute to large capacity and seasonal energy storage. Studies show that hydrogen energy storage in areas like California, where the viability of very high levels of grid connected renewable energy generation is promising can highly increase the solar and wind market penetration. Hydrogen energy storage systems generate hydrogen from water using an electrolyzer dynamically powered by using inexpensive or otherwise curtailed renewable energy, storing the hydrogen, and subsequently using the hydrogen for various purposes (e.g., to produce electricity via a fuel cell for power generation or transportation applications). In this work, the dynamics of hydrogen energy storage (HES) integrated with large-scale renewable power using the capabilities of the existing California natural gas infrastructure were investigated. The dynamics associated with the grid demand, renewable power, temperature, pressure, and HES capacity for one week of November and August were analyzed in detail while an aggregated analysis of the entire state for the whole year were simulated in MATLAB/Simulink. First, the solar and wind resources, considering spatially resolved resource availability at each hour during the year, were analyzed to simulate large-scale implementation of combined solar and wind power resources sufficient to meet the entire annual California electric energy demand. At each hour the excess power from the renewable sources is directed to a model solid oxide electrolyzer (SOE) system to produce hydrogen. The hydrogen is pressurized through two stages of compressors and then stored in