Study and hydraulic modeling of an energy storage system by dynamic control of a pump-turbine-valve circuit
Abstract:
A new method of compressed air energy storage at sea developed by SEGULA technologies is presented. REMORA is a storage system based on the quasi isothermal compression of air carried out by liquid pistons in the compression chambers. The latter are supplied by reversible centrifugal pumps which also act as turbines. The global system consists of elements forming a reversible energy cascade that can store energy in the form of compressed air in the underwater
reservoirs or to return energy in the form of electricity in the electricity grid. To optimize the operating range, a low-pressure pump and a high-pressure pump will have to take turns to supply the compression chambers. In addition, the pumps operate at variable speed to continually approach its rated operating point. Hydraulic valves are present at the inlet of each compression chamber and are connected to each pump by pipes. These valves open and close successively over a very short time depending on the state of compression or expansion of the air in each chamber. These valve switching events occur at the same time as rapid accelerations and decelerations of pump rotation speed that can induce transient flow into the system. ODySEA, a laboratory demonstrator of this storage system with a few kW average power was constructed. An analysis of the experimental results is carried out in order to observe transient phenomena. CFD modelling of the BP pump is performed on STAR CCM+ to predict pump behaviour in both modes. Finally, a transient model of ODySEA hydraulic system is developed on 20-sim with Bond Graph method. The results will allow to know the flow’s behaviour and to optimize system’s operation especially during transient period.