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.

In the countries willing to follow an energy transition towards decarbonization, a strong emphasis is put on electrification. Carbon-free power production tends to rely more on intermittent renewable energies, bringing many uncertainties on the electricity output to the grid. The transportation sector aims to reach a high penetration of electric vehicles (EVs) on the road to overcome its fossil fuels dependency, adding an important load to charge their batteries. The V2G technology intends to alleviate these new issues by allowing the fleet of EVs to act like a storage system for the grid. This concept was proven to be mature but requires more pilot projects to build a greater consensus. The energy community BRF Stenberg, under construction in Hudiksvall, is willing to integrate V2G in its energy system. In this paper a model of the energy system for the whole community is built. Different types of V2G application are simulated and compared to a baseline. The constraints are formulated as a quasi-linear optimisation, where the cost from electricity purchase is minimized. A direct DCDC connection between PV production and EV charging is investigated, as well as the impact on the degradation of the batteries. The results show that it is necessary to integrate frequency regulation services to build a profitable project. The DC connection does not bring a significant benefit to the system. The battery degradation is proven to be a critical parameter that must be accounted for in the design of the system. / I de länder som är villiga att följa en energiomställning mot en koldioxidfri utveckling läggs stor vikt vid elektrifiering. Kolfri elproduktion tenderar att vara mer beroende av intermittenta förnybara energikällor, vilket medför många osäkerhetsfaktorer i fråga om elproduktionen till elnätet. Transportsektorn strävar efter att uppnå en hög penetration av elfordon på vägarna för att övervinna sitt beroende av fossila bränslen, vilket ger en viktig belastning för att ladda deras batterier. V2G-tekniken syftar till att lindra dessa nya problem genom att låta fordonsflottan fungera som ett lagringssystem för nätet. Konceptet har visat sig vara moget men kräver fler pilotprojekt för att skapa ett större samförstånd. Energisamfälligheten BRF Stenberg, som håller på att byggas i Hudiksvall, är villigt att integrera V2G i sitt energisystem. I den här artikeln byggs en modell av energisystemet för hela Energisamfälligheten. Olika grader av V2G-tillämpning simuleras och jämförs med en baslinje. Begränsningarna formuleras som en kvasilinjär optimering, där kostnaden för elinköp minimeras. En direkt DC-DC-anslutning mellan solcellsproduktion och fordonsladdning undersöks, liksom effekten på batteriernas nedbrytning. Resultaten visar att det är nödvändigt att integrera frekvensregleringstjänster för att bygga ett lönsamt projekt. Likströmsförbindelsen ger inte någon betydande fördel för systemet. Batteridegraderingen visar sig vara en kritisk parameter som måste beaktas vid utformningen av systemet.