Accumulative energy storage systems in electric grids with renewable energy sources

Abstract

Renewable energy technologies are increasingly recognized as viable solutions to the persistent energy deficits in developing countries. In India solar energy is particularly promising due to its high solar insolation and geographical advantage. The country receives average solar radiation of approximately 200 Mw/2/day and experiences 250-300 sunny days annually, with solar irradiance levels ranging from 4 to 7 kWh/2/day and annual sunshine hours between 2300 and 3200. India also hosts the world’s largest solar installation, the 2.25 GW Bhadla Solar Park in Jodhpur. The expanding deployment of photovoltaic (PV) microgrids in rural and semi-urban regions, such as Barmer in Rajasthan, reflects both the significant potential and the implementation challenges associated with decentralized sustainable energy systems. Batteries are crucial in off-grid renewable energy systems to help to balance load demand with energy production. Small-scale systems generally show this imbalance more clearly since the averaging effect usually observed in bigger power systems is absent there. Under such conditions, storage systems have to allow fast changes in power and provide continuous supply to end users. Among their many benefits are excellent durability and expandable energy capacity of vanadium redox flow batteries (VRBs). When employed as the only storage technology, their efficiency falls at low charge/discharge rates, though, due to parasitic losses connected to electrolytic circulation-posing constraints. Using their complimentary properties in terms of power density, energy storage capacity, and operational robustness, this work investigates a hybrid energy storage method combining VRBs with lithium-ion batteries (LIBs) [1]. This work attempts to solve a challenging optimisation problem introduced by the interaction between VRB parasitic losses and LIB degradation by system modelling and performance evaluation. A thorough vanadium redox flow battery (VRB) model 2 was constructed to assess the performance of the proposed system including both electrochemical stack dynamics and related mechanical components. After that, it was planned to put together a standard EMS that would keep track of energy flows in the HESS. The multi-objective optimisation was carried out using MILP together with real-world solar irradiation and load demand profiles. To examine different ways of operating, the weighting of objectives was varied in a sensitivity analysis process. In addition, a detailed physical model was made in MATLAB/Simulink to analyse how the control strategies reacted to sudden changes in the system.