The Role of Energy Storage in Decreasing Life-Cycle Carbon Emission and Increasing Renewable Energy Usage of Electric Vehicle Charging: A Case Study for the Hungarian Energy System

This case study investigates the potential of energy storage to reduce CO2 emissions and increase the share of renewable electricity used for electric vehicle (EV) charging in Hungary, a climatically diverse country with strong prospects for renewable energy expansion. Using national electricity generation and demand data, together with life-cycle CO2 emission factors, we evaluated the impact of storing solar energy in industrial storage systems, specifically sodium–sulfur (NaS) batteries. Based on the amount of energy stored, we estimated the variability in the number of EVs that could be operated. Life-cycle CO2 emissions were assessed and compared across three scenarios: (1) direct charging from the grid, (2) grid charging supported by large-scale energy storage, (3) charging directly from local NaS battery storage. The results show that, during winter, even if 100% of available solar generation is stored, often less than 300,000 EVs can be charged. In contrast, during spring and summer, sufficient solar energy is available to charge up to two million vehicles on many days, resulting in daily CO2 emission reductions of several kilotons. The analysis further indicates that EV operation can achieve the lowest life-cycle emissions when the EVs are charged directly from the NaS batteries.