The views expressed are those of the author and do not necessarily reflect the position of FORESIGHT Climate & Energy

Fleets can provide significant flexible storage capacity for city-wide usage
The transition to a sustainable energy system is crucial for avoiding catastrophic climate change and establishing a zero-carbon economy. A major challenge is the need for large-scale power storage capacity to integrate variable renewables and stabilise transmission and distribution grids. Experts anticipate that following the widespread introduction of battery electric vehicles (BEV), it will be possible to use the batteries of grid-connected cars and heavy vehicles as a distributed power storage network. While the outlook for such a solution depends on multiple factors, a 2030 scenario for the city of Munich already sheds light on the potential of vehicle-to-grid (V2G) capabilities. The capital of Germany’s southwestern state of Bavaria has a population of over 1.5 million and a hub of science, research, high tech, and industry. Munich has a finely meshed distribution grid paired with high electricity consumption, making it an interesting test bed to explore the potential for V2G energy supply. Little solar photovoltaic (PV) energy supply means it does not have to deal with bottlenecks of electricity in-feed to the grid, nor does it struggle to shift excess PV electricity to off-peak periods. Therefore, the main use case for V2G in Munich is the adaptation of the overall load profile to spot prices and renewable generation in the German power market.

POTENTIAL CAPACITY
The estimated power demand of electric vehicles by type, demonstrating the variable load (source: Siemens)

COMPLEMENTARY VEHICLES
Private and commercial EVs complement each other well as far as V2G power is concerned: While private vehicles are often parked during working hours and can provide flexibility during the day while loads are high, many commercial vehicles can do the same with their bigger batteries when out of use during nights and on weekends. The cumulative charging power of private and commercial vehicles adds up to about 200 megawatts (MW) in 2030 representing a significant share of Munich’s peak load of 1000 MW during summertime. Consequently, V2G provides a valuable buffer for peak shaving in our specific scenario. Looking into the different vehicle types, we see that V2G power of private vehicles adds up to almost 140 MW during workdays, including about 90 MW of private EVs parked at home and 35 MW of private EVs parked at work. At 11 kilowatts (kW) per vehicle, this is sufficient to cover around three hours’ worth of power consumption. A preferable use case, though, would be to spread out this capacity over time to flatten loads equitably during peak hours from 8 am to 8 pm. Commercial passenger cars and small vans could contribute up to 50 MW during the day and 190 MW at night. Our scenario indicates a potential V2G capacity of 10 MW at daytime to 90 MW at nighttime for trucks, and up to 20 MW at night for buses. Trucks and buses are particularly attractive due to their large battery capacities, high-powered charging facilities and predictable travel schedules. Overall, commercial vehicles might provide between 60 MW during the day and 300 MW overnight. The latter will be of particular interest when more renewable generation comes online and electricity use needs to be shifted. These projections for V2G capacities are based on current data for power consumption and supply, the number of EVs in Munich, as well as battery capacities, state-of-charge ranges and charging behavior. Current trends and regulatory guidelines were also taken into consideration.

BATTERY CITY
The potentially available power from V2G could provide significant flexibility to Munich’s energy system in 2030. It could be used to balance the city’s load profile and to store excess renewable energy generated in the surrounding region, for instance, to compensate for weather changes affecting solar and wind power. Given the strong differences between the metropolitan area and its rural hinterland, Munich is an interesting test case for using V2G to manage renewable generation and load on a regional rather than local scale; indeed, the scenario suggests that in the future, cities could serve as “batteries” for the surrounding regions. Load balancing with V2G has the advantage of reducing the need for conventional peak load generation capacity, which would reduce CO2 emissions as well as the overall cost of electricity generation. It would also help planners avoid building oversized renewable generation assets, could enhance demand-side flexibility and would reduce the need to build additional storage facilities. Finally, for EV drivers and fleet operators, V2G activities can optimise costs over the lifetime of BEVs. The ability to store surplus electricity produced from renewable sources would help avoid further waste due to throttling or shutting down of generation capacity. In 2021, Germany’s energy system had to throttle about 5.8 terawatt-hours’ worth of wind power in order to ensure grid stability. Clean electricity stored in distributed BEV batteries could also compensate for renewable generation shortfalls if weather patterns deviate from forecasts, making conventional supply reserves obsolete.

PROFILE MATCH
EV use and solar PV production have complimentary profiles (source: Siemens)

ECOLOGICAL AND FINANCIAL
Significant emissions could be avoided through peak shaving. We would use more renewable energy by adding V2G storage capacity for excess generation, which in turn would allow us to compensate for theoretical in-feed and the integration of additional zero-carbon electricity sources into the grids. By harnessing V2G’s full potential and avoiding losses from intentional throttling, we would need to build less storage capacity in other forms and avoid oversized solar PV and wind farms, preserving finite resources and materials. Both individual and corporate vehicle owners would stand to gain by connecting their BEV storage capacity to the grid, not only ecologically, but also in financial terms. They can reduce the overall cost of electricity generation by eliminating the need for conventional peak-load generation capacity and by adding demand-side flexibility. The study shows that the potential of V2G is there for the taking; now, it is up to the regulators to seize the opportunity by creating the legal framework as well as incentives that foster the development of this technology. Then, operators will develop business models to offer tariffs on V2G and sell the aggregated power on spot markets.

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