This study considers how flexible vehicle charging could affect the adoption of renewables, backup capacity requirements and CO2-emission reduction costs. The study analyses three different charging strategies representing the different EV flexibility levels, which, from low to high flexibility, are: dumb charging, smart charging and smart charging in combination with bidirectional charging (vehicle-to-grid or V2G). The researchers conclude that smart charging systems could reduce overall energy system costs and, if coupled with ambitious emissions reduction targets, increase investment in variable renewable energy sources.
The European transition to climate neutrality relies on several simultaneous transitions. These include increasing use of renewable energy in electricity supplies and decarbonisation of transport, in particular through increasing proportions of electrically powered vehicles and vessels in the mid and near term. These two processes necessarily interact as growing use of electric vehicles may particularly affect overall electricity demand. This interaction is complex and depends not only on numbers and use of electric vehicles, but also on the deployment and geographical distribution of charging infrastructure and its coupling with the grid – as European energy markets interact with one another.
A significant limitation of some key renewable energy sources is their variability over time. For example, wind power is highly dependent on weather conditions, while solar power only functions during daytime at levels that are also affected by weather and geographical location. This can lead to substantially reduced supply in periods of low wind and low sunlight.
This study considered the potential impacts of electric vehicle expansion on the adoption of variable renewable energy across Europe from 2025 to 2050. The researchers used an electrical-systems model that minimises overall costs to project the outcome of three electric-vehicle charging scenarios. In the ‘dumb charging’ scenario, all vehicles charge at maximum rate from when they are plugged in; in ‘smart charging’ the charge is drawn flexibly at times of optimal availability; and in ‘vehicle-to-grid charging’ smart charging is combined with the potential for electric-vehicle batteries to discharge energy to the grid to help meet supply deficits. While the study considers the efficiency of charging-discharging battery cycles1, it does not allow for the effects on the lifetime of batteries. The researchers point out that the latter is both complicated in terms of modelling and say that empirical evidence is limited – especially for future decades2.
The researchers based their projections on country-level analyses using a model of electric vehicle uptake which projected a total of 159 million cars across Europe by 2050 consuming 347 terawatt hours of electricity per year3.
The researchers find that increased flexibility in electric vehicle charging strategies leads to reduced overall costs compared to the dumb-charging scenario. When applying a CO2-emissions reduction target in the power and heat sectors, of 95% (compared to 1990) in the model, greater charging flexibility leads to a greater share of renewable energy in the power mix. This is due to a substantial increase in the use of variable renewable power, especially solar, they say, partially offset by a small reduction in the share of controllable renewable sources. Higher use of variable renewables also means less curtailment (deliberate reduction in energy output) mainly driven by better integration of solar energy, according to the researchers.
However, when the model uses a less ambitious emissions reduction target of 80%, flexible charging does not lead to an increase in variable renewable capacity, they say.
In the 95% reduction scenario, say the researchers, increases in variable renewables are accompanied by increased capacity from conventional controllable power plants (largely natural gas)4. These plants are required to provide backup supply when renewable sources cannot meet demand, which can potentially result in substantial shortfalls. However, as these situations rarely occur, the overall use of this fossil-fuel supply steadily decreases over the period and the 95% emissions-reduction target is maintained. The researchers point out that due to the greater flexibility of electric vehicles, both electricity and CO2 prices (or CO2-emission impact) can be significantly lowered5 – even though a higher amount of backup capacity is needed at the same time. However, the use of energy storage is now becoming more prevalent.
The researchers argue that electric-vehicle policy frameworks should encourage the use of more flexible charging strategies to reduce overall costs and promote the adoption of renewable energy sources. They suggest that policy approaches could include market mechanisms such as tax breaks, research into smart-charging co-ordination systems and provision of necessary technological infrastructure. They also recommend that investment incentives are provided for controllable fossil-fuel power plants to ensure that this backup capacity is available.
The researchers point out that the model includes some assumptions about factors such as vehicle-owner behaviour, optimal market responses and independence of different effects. They suggest that the results should, therefore, be interpreted as a basis of what might be achieved through optimal use of flexible charging. They add that any incentives for EV owners should include rewards for charging behaviour that responds to the energy systems’ needs.
They also highlight potential areas for future research, including infrastructure requirements for smart charging and business models, variable costs of renewable energy production and more detailed modelling approaches.
- Smart charging is a topic covered in the EU’s alternative fuels infrastructure regulation (AFIR) proposal: https://eur-lex.europa.eu/legal-content/en/TXT/?uri=CELEX%3A52021PC0559
- The EU’s Sustainable Transport Forum is currently examining the policy needs of smart and bidirectional (V2G) charging.
- The researchers suggest that it is preferable to accept the losses of battery charging-discharging cycles than to opt for increased ‘shedding’ of renewable generation demand (i.e. distributing demand for electric power when demand for electricity is greater than the primary power source can supply).
- The researchers point out that the lifetime of batteries is less of a problem than it was in the early days of electromobility. This is linked to the increasing size of batteries – which implies that, at constant annual kilometrage, fewer charging cycles per year are necessary – and that deep discharging occurs much less frequently since daily kilometrage (~40 km in Germany) is on average considerably lower than the EV range (~400 km with 80 kWh battery), which is available for the majority of currently purchased EVs). It is worth noting that deep discharge cycles degrade batteries quickly.
- The researchers say that they only analysed the mid-trajectory scenario, because the impacts of EVs on the energy system are similar in all three trajectories.
- Currently, storage is actually used to reduce dependence on, and further increase of, gas plants. Both stationary storage (including batteries) and EV flexibility need to be considered.
- For further detail on this point, please see the study’s Figures 10 and 11. Fig. 10 shows that in the 95% reduction scenario, CO2 prices drop from about 1 000 euros per tonne (€/t) to about 480 (€/t) – when moving from the ‘Dumb charging’ case to the ‘Vehicle-to grid’ charging case. The left part of Fig. 11 indicates that mean power prices drop from €130 /MWh to about €95/MWh at the same time.
Blumberg, G., Broll, R., and Weber, C. (2022) The impact of electric vehicles on the future European electricity system – A scenario analysis. Energy Policy 161: 112751. Available from: https://doi.org/10.1016/j.enpol.2021.112751
To cite this article/service:
“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.
Notes on content:
The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.
- Publication date
- 26 October 2022
- Directorate-General for Environment