Assessing and mitigating potential hazards of emerging grid-scale electrical energy storage systems

Abstract Electrical energy storage (EES) systems consisting of multiple process components and containing intensive amounts of energy present inherent hazards coupled with high operational risks. Although the thermal hazards of batteries have aroused widespread attention, the safety issues of emerging large scale EES technologies persist. This study aims to begin to fill this gap by examining the hazards of typical 100 MWh or more EES systems which are used for grid applications. These systems include compressed and liquid air energy storage, CO2 energy storage, thermal storage in concentrating solar power plants, and Power-to-Gas. Hazard assessments are performed using a hybrid method to consider and evaluate the EES systems’ potential hazards from three novel aspects: storage, operability, and connectivity. Results reveal that for a similar energy storage capacity, cryogenic liquid systems have the least severe accident consequences while thermal energy storage using synthetic oil exhibits the largest. Concerning the operations in many cases, extreme operating conditions, complicated heat exchanger networks involving multiple flammable working fluids, and system operation intermittency present the major challenges to the safer operation of EES systems. Lastly, these systems themselves form one of many components of the power supply, each of which needs to accommodate fluctuations in supply and demand but also should be prevented from transmitting hazards to each other. Considering both engineering and administrative controls, this paper concludes with a discussion on the four grouped strategies from inherent to procedural for the elimination and mitigation of the identified hazards. Representative solutions and research perspectives including inherently safer design, operation uncertainty management, resilience analysis, energy barriers design, and life cycle safety assessment are suggested for the overall safety enhancement of industrial EES systems.