Will the electricity grid cope with the switch to EV charging?

electricity grid
© Tom Wang

Emma Chetwynd Jarvis, Electrical Connections Manager at Rock Power Connections, discusses if the electricity grid will be able to cope with the transition to electric vehicle charging

The Government’s Road to Zero strategy includes the challenging goal that all new cars and vans should be ‘zero emission’ by 2035. There are a variety of modelling scenarios around the adoption of Electric Vehicles (EVs), forecasting over 3 million EVs to be on the road by the end of 2030.

Despite these large numbers, the Distribution Network Operators (DNOs) appear calm and confident that the network will cope with this increase. They are continuing to publish their EV strategies and all seems to be on track. An example of this can be seen from Western Power Distribution (WPD) who predict that their current substations are up to the job.

The Department for Transport’s National Travel Survey reported the average annual mileage for cars is following a declining trend. WPD forecasts that the majority of their larger local transformers will be able to accommodate a weekly charge for each customer connected to it.

Northern Powergrid (NPG) are also confident, predicting very little impact on the network from EVs in the next ten years. Even after this, depending on the growth of EV use, less than 3% of NPG’s primary and secondary distribution substations would require reinforcement. A key factor contributing to this confidence is that the NPG have seen a reduced demand in the overall load on their network due to distributed generation and increased energy efficiency. This reduction in the net peak load has offset the increase in load that would come from EV charging.

What is clear amongst the DNOs is that optimal charging, encompassing a flexible approach and smart technology is the key to balancing future demand. However, there are a few things that need to be considered when evaluating whether the grid would be able to cope with this increase in EV charging.

Optimal charging

If the majority of EV owners charge their vehicle as soon as they arrive home from work, this could cause a demand peak on the network. Considering a wide window for the plug-in (around 5 pm-8 pm) and a mix of top-up to full charges (ranging from 1 hour to 6 hours), even if only a small proportion of the UK’s 27 million households owned an EV, a big impact would be made on the network demand. This is also a time when electricity is already at its peak, as people return to their homes for the evening.

This is where smart chargers and vehicle-to-grid (V2G) chargers can add huge benefits to help balance supply and demand. Smart chargers modulate the time or rate at which an EV charges, whereas V2G charging allows a two-way flow between the grid and the battery, using the EV as a static energy store. Both can help relieve pressure on the electricity network, negating the peak if used on a mass scale.

Getting electricity where it is needed

Although WPD and NPG have confidence in their switchgear, it is arguably the underground cable network that is not as prepared for the introduction of mass EV chargers. Both mains and services cables may require upgrading to cope with this new demand.

The emerging changes in building regulations now requires charge points to be included for each parking space in all new residential developments. To establish an electrical connection to these new developments, the DNO can specify the need for a greater minimum cable size which ensures that it is future-proofed for any additional EV chargers.

Likewise, upgraded supplies to existing properties would benefit from the installation of new larger cables as part of the works. Although this would produce additional costs, it will be more cost-effective in the long run than replacing the cable if the site then requires EV charging in the future.

Urban areas

In simple terms, connection of EV chargers should be much easier in urban areas where there is a greater density of substations and underground cable networks. For the majority, home chargers could be powered from the existing distribution board. Faster, rapid chargers could simply require a new connection form the local Low Voltage (LV) or High Voltage (HV) cable network.

In areas where the capacity of the network is restricted, WPD has plans to offer alternative connections where businesses can only charge at specific times of the day. For example, a commercial fleet at a depot could charge overnight using local capacity that is in place for daytime industrial usage to overcome the need for network reinforcements.

Many of the DNOs have started to offer ‘heat maps’ that illustrate the available capacity for EV chargers at each substation. This is extremely helpful when assessing site feasibility or EV charging requirements on a city-wide basis.

Capacity, however, isn’t the only issue. As an electrical network has an increasing number of EV chargers connected to it, harmonics will become an issue.

EV chargers use power electronics which can cause interference and, in some cases, damage to the electricity network. This is often referred to as harmonic disruption. Certain population demographics are likely to be early adopters of EV, therefore we will see geographical clusters which will have more home chargers and a greater demand for chargers at the workplace. In addition, urban areas with higher forecast rates of EV-owners will have more EV charger destination locations such as supermarkets, gyms, cinemas, retail and leisure parks.

The local distribution network will only be able to handle the harmonics from a certain number of EV chargers. If numbers increase beyond this, the network will require reinforcement or the EV chargers will need to be supplied from a different network, requiring longer cable runs. In either case, there will be increased costs.

Rural areas

It can be far more challenging to get power to rural areas. Taking into account that many en-route locations (such as motorway service stations) may be in remote locations, well away from the grid, these sites will also need the largest loads to power banks of rapid and super-rapid chargers. In extreme cases, this can involve kilometres of cable across public highway and private land, as well as crossing motorways and railways. Not only is this costly, but is much more labour intensive and would require longer timescales to get power where it is needed.

Transport Secretary, Grant Shapps, has plans to tackle this problem. Announced in May, the £500M Rapid Charging Fund aims to have at least 6 high power chargers at every motorway service station by 2023. By 2035, the aim is to have part-funded 6,000 rapid power points besides the UK’s major roads.

Whilst the overall outlook for connecting EV chargers to the distribution network is very positive, especially in the immediate future, undoubtedly there will be very different experiences on a project-by-project basis, and is dependent on a variety of factors. To meet the Government’s Road to Zero strategy, optimal charging encompassing smart technology whilst adopting a flexible approach will be key to balancing the increase in demand.

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