A systematized framework to optimize grid-interactive charging process of electric vehicles integrated with buildings and distributed renewable sources

Integrating intelligent charging stations with building energy systems not only meets the charging requirements of electric vehicle (EV) users but also alleviates the burden of electrified transportation imposed on the utility grid and enhances building energy flexibility. While, stochastic and urgent vehicle-charging demands bring large challenges to the above-stated integrated energy system due to the difficulty of simultaneously achieving high user satisfaction with vehicle charging, grid stability, and building energy flexibility. This study proposed an optimization framework encompassing office buildings, distributed renewable energy systems, charging stations, and EVs to cover dynamic building energy loads and meet diverse vehicle charging demands, and meanwhile maximize distributed photovoltaic (PV) utilization and reduce utility grid burden. An intelligent order-charging strategy, which manages vehicle charging behaviors according to the charging urgent level, was incorporated in the above-stated framework. The research results indicate that Case 3, which operated under the aforementioned framework, exhibited superior energy performance compared to Case 1, which involved a single charging station with traditional charging control, and the EV charging satisfaction increased from 94 % to 100 %. Moreover, the onsite-renewable penetration of the charging station's total energy consumption reached 26 %. Notably, during the periods with limited sunlight (from 7:00 a.m. to 8:00 a.m. and from 4:00 p.m. to 6:00 p.m.), the energy system would reduce about 60 % energy supply of the charging stations to let the utility grid to prioritize meeting the building load demand, thereby significantly enhancing the energy flexibility. This study's work contributes to achieving low carbon and high flexibility of building-charging-station energy system.