Control strategy for the dynamic shutdown of the charging process of an advanced adiabatic compressed air energy storage

Advanced adiabatic compressed air energy storage (AA-CAES) requires frequent startups and shutdowns when the component works under off-design conditions with interaction and performance reduction. This study examines the influence of shutdown control strategies on energy consumption and safety to address these challenges. To this end, a detailed charging process comprising three series of centrifugal compressors with intercoolers was constructed within the framework of UniSim (R) Design. The safety measures were meticulously considered by integrating anti-surge circuits, vent valves, and check valves. PI controllers were allocated to the primary component to govern the shutdown procedure. Energy consumption, air injection flow rate, inlet flow rate of compressor, and inlet and outlet pressure of compressor were evaluated under a control strategy involving compressor operation and operation time. Our results show that, on the one hand, the shutdown strategy of increasing the inverter motor speed of the high-pressure compressor (HP) in the load shedding stage and ensuring that the inlet guide vane of the middle-pressure compressor (MP) is not less than that of the low-pressure compressor (LP) at the termination in the load shedding stage performs better energy efficiency. On the other hand, the shutdown strategy can avoid harmful abnormalities, such as that the inlet pressure of the HP is higher than the outlet pressure of the MP and the outlet pressure of the MP gradually increases. The results also show that delaying the time while lowering the compressors' operating limit helps the air injection flow rate gently decrease to zero. These results indicate that the control strategy affects the safety and energy efficiency of the charging process during the shutdown. In addition, these results reveal that the components in the charging process interact with each other during the shutdown, so the control strategy requires comprehensive consideration. Furthermore, the findings can guide a similar charging process of AA-CAES.