Assessment of additional aging on electric vehicles batteries in the framework of vehicle to building services

The energy transition implies a progressive loss in grids inertia. Energy storage systems can contribute to enhance the flexibility of electric systems, even if their penetration in the grid at the European level currently amounts to only a few percentage points of the overall generation capacity. In this framework, the use of electric vehicles (EVs) as multiple decentralized mobile energy storage when interconnected to a bidirectional charging column for performing Vehicle-to-X services is widely proposed. In this work, as pioneering approach, the additional aging of 50-kWh BEVs and 10-kWh PHEV batteries performing Vehicle-to-Building (V2B) operation is experimentally assessed in reference to a grid-connected renewable Micro-Grid (MG). A MG dynamic model including suitable stochastic real-time power management is developed to minimize i) the instantaneous grid power exchange and, ii) the PHEV power fluctuations. Simulations outcomes provide batteries State of Charge evolutions, subsequently implemented in the design of experiment to perform accelerated aging tests. Four 18,650 NMC Li-ion cells are tested over 9 equivalent years of operation. This allows to quantify the V2B additional degradation for the investigated case study. As results, State of Health (SoH) value achieves 84.8 % for the PHEV battery (compared to 95.8 % when V2B is not performed), while it stands at 92.9 % for the BEV (slightly lower than 95 % SoH for V2B absence). These outcomes could contribute to pave the way in the awareness of V2B impact on renewable-based Micro-Grids, while reducing stressful conditions on PHEV batteries that could yield to faster degradation.