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How EV Charging Could Compromise Grid Reliability

The rollout of low carbon technologies including electric vehicles and electric heating will be key to the UK achieving its strict net-zero deadline. If the most ambitious predictions of EV take-up play out, they will play a significant role in a potential 50% increase in the UK’s peak demand. By the late 2030s, the UK’s total annual energy demand is forecast to increase from around 300TWh currently to nearly 600TWh.

How EV Impacts Peak Demand

Peak demand for electricity in the UK typically falls between 6pm and 8pm during the week. This is particularly prominent in winter, as people return home from school or work and turn on electrical appliances for heating, cooking, and entertainment.

If most people swap out their petrol or diesel car for an electric model, this could deliver a huge increase to peak demand. With the majority of drivers expected to use home charging stations, many would return home and plug in their car to charge within the peak demand period. With a forecast 21 million EVs by 2035, this could deliver a spike in peak demand of as much as 100GW.

As it stands, the grid wouldn’t be able to withstand such a sudden change in demand. One figure from research by National Grid ESO estimates that by 2035, if just 2% of installed EV chargers were to be switched on at the same time, it would result in a larger disruption event than the power cut experienced in August 2019. In that incident, triggered outages at Little Barford power station and Hornsea windfarm at the same time, saw almost a million homes and businesses left without power for around an hour.

The increase in peak demand is just one way that electric vehicle charging represents a risk to grid stability. Too many chargers turning on or off either at the same time or in quick succession could destabilise the grid and result in a power outage, as well as impacting on voltage stability by adding a significant, constant additional power load to the grid.

In the event that there is a major power disruption, EV charging has the potential to extend the disruption by further constraining the grid. The recovery from a prolonged outage could be much slower if it created a long-lasting ‘cold load pickup’ as EV drivers seek to charge vehicles that have run out of power as soon as the supply is restored.

Intelligent Solutions

Much of this potential for disruption is a worst-case scenario, assuming that National Grid takes no steps to control and manage this significant increase in peak demand. Fortunately, National Grid ESO is already exploring ways to mitigate the risk of disruption and to most efficiently manage vehicle charging. There are a number of ways of doing this, but the most important in terms of balancing demand is likely to be smart charging.

As opposed to traditional charging devices, EVs charged using smart charging share a data connection with the wider electricity system, allowing the charging operator to remotely monitor, manage and restrict charging to optimise energy consumption. This could include throttling the charging of EVs during peak demand, or even tapping into the potential of Vehicle to Grid storage to use existing EV charge capacity to bolster grid supply.

Increasingly, many commercial EV charging providers are turning to battery-buffered charging systems to minimise their impact on the grid, as well as to more efficiently provide the large amounts of power needed to charge a vehicle when required. EVs charged from a battery energy storage system don’t risk contributing to spikes in peak demand as they don’t draw directly from the grid, helping to reduce the stress on the system. Similarly, they can draw energy from the grid during periods of low demand or cost, then using it to charge EVs or elsewhere in a home or site to power electrical equipment.

The Uninterruptible Power Supply (UPS) capabilities of some battery energy storage systems also protects a site from the risk of disruption that could come from the rapid, improperly managed rollout of EVs. In the event that your power supply is disrupted, a battery can keep your site running as normal during small disruptions or buy valuable time to switch to backup generation or safely shut down equipment and computers.