Strategic charging of electric vehicles in public parking areas: Optimized charging strategies of electric vehicles from a parking area operator perspective

Typ
Examensarbete för masterexamen
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Publicerad
2022
Författare
Björklund, Filip
Ekström, Jonathan
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As part of current climate change, with focus on the reduction of green house gas emissions, the automotive industry is shifting from internal combustion engines (ICEs) to electric motors. As of 2021, in Sweden, around 45% of all newly registered vehicles are electric vehicles and it is expected that this share will increase in the future [1]. The electrification that society faces also creates challenges to the current electricity systems in place as new loads are introduced. This will not only mean there is a need to expand the current electricity generation and grid, but also that electricity has to be used smarter. This master’s thesis investigates possible advantages with implementing smart charging strategies in parking areas. A linear programming model was developed to evaluate the aggregated EV charging load in a parking garage located in central Malmö, Sweden. Real parking data on incoming and outgoing vehicles, i.e. over 8000 registered parking events in September 2021, is used as a case study allowing for one month of parking need to be analyzed. There are four cases that are compared, each with a distinct objective. The first case is a reference case in which charging is undertaken as quickly as possible, i.e. restoring the state of charge (SOC) as soon as possible directly upon arrival. Remaining cases optimizes economical aspects, where the second case minimizes the cost of grid connection capacity and the third case minimizes the cost of electricity given the spot prices on the electricity market for the investigated period. The fourth and final case is a combination of cases two and three with the purpose of minimizing the total cost. These cases were also subjected to different scenarios; a base scenario that reflect the parking garage today, a scenario with an assumed integrated solar PV system, and a scenario with Vehicle-to-Grid (V2G) implemented. Finally, a scenario investigating the impact from electricity prices in terms of grid connection capacity and value of solar PV. Results show that smart charging may reduce the peak capacity of this parking garage by just over 70%, given a suitable governing algorithm. Given the assumptions on entrance and target SOC levels the parking area should be able to be operated in an off-grid mode without grid power supply, i.e. all charging is made from incoming EVs that have higher entrance SOC than target SOC. Avoided grid costs could in such case be used to reimburse vehicle owners for discharging some electricity to other vehicles and get free parking or even make money from parking. Case 4, minimizing the total cost, resulted in a large transferable capacity. The large capacity was used to turn a profit from arbitrage transactions and the selling of excess electricity stored in EVs entering the parking garage. A PV system can be introduced to reduce the cost of purchased electricity and peak demand, with greatest effect on the cost of purchased electricity. In current economical pricing model there are larger potential savings in using electricity in-house than selling it to the grid, which means that the savings found in this study should be larger with increasing electricity prices.
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Electric Vehicles, Charging Strategy, V2G, PV, Smart Charging, Peak Shaving, Aggregated Charging
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