Optimal Charging and Discharging Strategies for Electric Cars in PV-BESS-Based Marina Energy Systems

Abstract

The emerging concept of integrated community energy systems (ICESs) proves its suitability for improving the operation of local grids—increasing self-consumption from local generation, enhancing the load factor, and reducing energy cost. In Ballen marina—located on the Danish island of Samsø—the battery energy storage system (BESS)’s action can be possibly complemented by the flexibility of boats and electric cars. With the greater involvement of energy consumers, the energy system’s performance may become more efficient—from both technical and economic perspectives. Within this framework, the optimal charging and discharging strategies of the marina’s electric cars were developed and evaluated. The car usage profile was generated, utilising a stochastic approach to resemble daily variations in the driving pattern. The optimal charging strategy was established, subsequently integrating this action with boat flexibility. As a future scenario, the benefits of vehicle-to-grid (V2G) technology implementation were examined, proving significant enhancements of the future marina’s grid—with increased photovoltaic (PV) generation capacity and the number of electric cars. The economic benefits of bidirectional charging were proven, with ample advantages for the marina and the rental company, leading to cost savings of up to 51.7% and minimising the energy export by 21.3%. Therefore, increasing the integration level of Ballen marina’s flexible units—electric cars and boats—was concluded to be an important goal for the coming years.