Utvärdering av V2G : Lönsamhet och miljöpåverkan med N(D)-baserad degraderingsmodell för elbilsbatterier

Sammanfattning: The transition from combustion engine vehicles to electric vehicles (EV) is an important step in achieving a carbon neutral society, but poses future difficulties in energy production. This is an issue in sustaining sufficient net energy, as well as providing sufficient power during hours of high demand. Vehicle to grid (V2G) may serve as a means of mitigating the power related issues. The main restraints are that battery state of charge (SoC) must be high enough when transportation is desired, and that the added energy flux through the battery causes additional wear. Furthermore, the production of batteries is heavily energy demanding, and the supply chain prompts environmental concerns. This study examines V2G profitability and environmental impact through modelling and simulation using Python. A battery degradation model is constructed based on life cycle versus depth of discharge, a N(D)-function. A V2G-system for one vehicle is simulated with t = 8736 h. Profitability is determined applying parameter optimization of maximum SoC and minimum difference in price of bought and sold energy. Evironmental impact is assessed with GWP100, and presented in terms of g CO2e per discharged kWh of energy from the battery. The results show that battery degradation is an important factor in determining profitability, but do indicate that profit is possible. However, the N(D) based modelling involves a risk of underestimating battery degradation due to insufficient model complexity. Calculated environmental impact is low, which is partly a result of low battery degradation, but there is a lack of similar studies on other energy storage methods, leading to difficulties in making useful comparisons.