Written evidence submitted by the Energy and Power Group, Department of Engineering Science at the University of Oxford (GRD0024)


Welsh Affairs Committee—Call for Evidence: Grid capacity in Wales


Executive summary




Question 4: What can be done to incentivise investment in grid flexibility, in particular vehicle to grid technology and ‘smart’ charging?

1         In the coming decade, we expect rapid electric vehicle (EV) adoption in Wales. If not properly managed, this change will increase grid congestion problems. If properly managed, this change can create the opportunity for grid support services from vehicle to grid and smart charging. By 2030, EVs belonging to residents of Wales could add up to 1.7 GW of demand to the Welsh electricity system, which had an average demand of 1.6 GW in 2020. This number is expected to nearly quadruple to 6 GW by 2030. For comparison, the Hinkley Point C reactor will be able to provide up to 3.26 GW of electric power once completed.

2        However, this rapid growth in EV adoption will be unevenly distributed across different geographic regions of Wales. Areas with large shares of EVs will experience an increase in electricity demand for charging, which can exacerbate grid congestion in those areas. Unless flexibility measures are implemented, these early EV adopter areas are likely to experience grid congestion problems soon. Figure 1 shows the maximum charging demand from EVs by Local Authority in 2030 and 2035. Areas in South East Wales, along with the Isle of Anglesey and Wrexham, will lead Wales in EV adoption. These areas are expected to have EV-related power demand increases that are 5 to 10 times larger than other areas of the country: for example, in 2030, Bridgend could have up to 360 MW of extra demand from EV charging, and by 2035, this figure could nearly double to 638 MW. By comparison, 1 MW of power is how much 300-500 kettles would draw when turned on simultaneously. Our projections for EV adoption in Wales are created using the S-Curve Adoption Tool for EVs (SCATE)[4],[5].




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Figure 1. The potential increase in electricity demand from EVs could be 5 to 10 times higher in some Welsh local authorites than in others. Areas with large increases in electricity demand for charging are likely to face grid congestion. Figures are given in megawatts (MW)-- 1 MW of power is how much 300-500 kettles would draw when turned on simultaneously.


3         The number of EVs in an area determines the potential for smart charging and vehicle to grid flexibility. Smart charging can reduce grid congestion and provide other benefits by strategically shifting the time of day when EVs use electricity. Vehicle to grid technology allows electricity to flow from the EV battery back to the grid and can improve the grid resilience in case of extreme weather or network outages. By 2030, Welsh residents’ EVs will store enough energy when half-charged to power 436,000 Welsh households for one day. By 2035, this figure is expected to exceed the number of households in Wales. For comparison, the Dinorwig Power Station in Gwynedd can store enough energy to power 467,000 Welsh households for a day.




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Figure 2. Vehicle to grid potential represented as the number of Welsh households that could be powered for a day using half the energy stored in electric vehicle batteries, per local authority. By 2030, each local authority is projected to have enough EVs to power thousands of households for one day, but vehicle to grid potential is distributed unevenly across local authorities.


4         In Figure 2, we show the potential for the vehicle to grid technology in Welsh local authorities as the number of households that could be powered for one day using half the energy stored in residents’ EV batteries. These maps were created assuming the total number of vehicles in Wales remains unchanged from now to 2035. By 2030, all local authorities are projected to have enough EVs to power thousands of households for one day using vehicle to grid technology: Blaenau Gwent can power the fewest at 1,500 households, and Bridgend can power the power at 90,800 households. By 2035, local authorities have enough EVs to power a number of households ranging from 9,400 in Blaenau Gwent to 181,600 in Rhondda Cynon Taf—a number that exceeds the number of households in the local authority.

5         We measured the potential for energy storage under a vehicle-to-grid scheme in terms of households’ energy consumption for illustrative purposes; however, the flexibility potential we identified could be used for any electric load. For example, flexibility from the large number of EVs projected around Neath Port Talbot could help reduce grid congestion caused by additional electric loads from the Port Talbot Steelworks, possibly following the envisioned emission-reducing measures involving electrification and carbon capture and storage.


Question 5: What should be done to ensure that the grid, particularly in rural areas, can cope with the extra demand that will be generated from the transition to electric vehicles?

9         In rural areas, tourists driving electric vehicles (EVs) are likely to increase electricity demand significantly and have the potential to overwhelm the grid in some areas. Tourist destinations in North East and Mid Wales could drive significant EV traffic in the coming years. Compared to residential EV users discussed in the previous question, tourists are more likely to prefer rapid charging and be inflexible about when they charge, making them more likely to strain the grid and less likely to contribute to flexibility. Despite projections of slow EV adoption in rural areas, these areas are likely to face increased demand from tourists driving EVs, particularly during the holiday season. Achieving the Electric Vehicle Charging Strategy goal of installing rapid (43+ kW) EV charging points every 20 miles on the strategic trunk road network, including the A55 and M4, by 2025 may be a challenge with current grid capacity.


March 2022

[1] Based on simultaneous 7 kW slow charging of all projected EVs.

[2] Subnational electricity consumption, Great Britain, 2005-2020. Department for Business, Energy & Industrial Strategy.

[3] Average daily domestic electricity use per Welsh household was 9.9 kWh in 2019, according to InfoBase Cymru Domestic energy consumption. We assume a typical EV battery size of 35 kWh.

[4] Collett, K. A., Bhagavathy, S. M., & McCulloch, M. D. (2021). Forecast of electric vehicle uptake across counties in England: Dataset from S-curve analysis. Data in Brief, 39.

[5] This tool uses an S-curve model of technology adoption, which represents the acceleration from slow initial uptake of a technology to widespread adoption and slowdown as market saturation is reached. This model allows us to project how small differences in the share of EVs between local authorities are likely to grow in the next 13 years. However, this model assumes a business-as-usual growth in EV adoption across the local authorities and does not account for policies that could accelerate this transition. This model also does not account for diffusion of EV adoption across the boundaries of local authorities, that is, we do not account for how the number of EVs in one local authority could affect the growth in EV adoption in neighbouring local authorities.