WILL THE ELECTRICITY GRID COPE WITH THE SWITCH TO EV CHARGING?
The Government’s Road to Zero strategy includes the challenging goal that all new cars and vans should be ‘effectively zero emission’ by 2035. There are numerous modelling scenarios around the adoption of Electric Vehicles (EVs) and the higher forecast suggest up to 3,064,000 EVs by the end of 2030.
Despite these large numbers, the Distribution Network Operators (DNO) who are proactively publishing their EV strategies appear calm and confident that the networks will cope.
As a prime example, Western Power Distribution (WPD) predict that their 33kV and 11kV 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 and was 7,8000 miles in 2017. This translates to 150 miles a week and WPD forecast that the majority of their larger local transformers will be able to accommodate the equivalent weekly 35kWh charge for each of the customers connected to it.
To be precise, they stated once every five days based on optimising charging events.
Northern Powergrid (NPG) are similarly confident, predicting very little impact on the network from EVs in the next ten years. Even after 10 years, depending on the EV growth prediction used, less than 3% of NPG’s secondary and primary distribution substations would require reinforcement.
A key component of this confidence is that NPG have seen a reduced demand in the overall load on their network over the past ten years. This reduction in the net peak load, due to distributed generation and increased energy efficiency, has so far offset the increase in load from EV charging.
National Grid has also stated that the decarbonisation of transport and energy are symbiotic. As renewables increase their dominance in power generation, EV batteries have a critical ability to take excess generation and help balance the grid.
What is clear amongst the DNOs is that optimal charging, encompassing smart technology and a flexible approach will be key to balancing future demand.
If all EV owners plug their vehicle in when they arrive home, this could cause a demand peak on the network. Considering a wide window for plug-in (say 5pm to 8pm) and a mix of top-up to full charges (1 hour to 6 hours), even if only a small proportion of UK households (of which there are 27 million) own an EV and follow this behaviour it will cause a big impact on the network demand.
And this impact will occur when electricity demand is already at its peak.
This is where smart chargers and Vehicle-to-Grid (V2G) chargers can add huge benefits to help balance demand and supply. Smart chargers modulate the time or rate at which an EV charges whereas V2G charging enables a two-way flow between the battery and the grid, using the EV as a static energy store. Both can relieve pressure on the electricity network, negating the peak if used at scale.
Using an Active Network Management approach will also ease the charging burden from commercial fleets.
GETTING ELECTRICITY WHERE IT IS NEEDED
Whilst WPD and NPG have confidence in their switchgear, it is the underground cable network which is less ready for the onslaught of EV chargers. Both mains and services cables may need upgrading to cope.
Emerging changes in the Building Regulations will require charge points to be included for each dedicated parking space in new residential and every 1 in 5 for commercial developments. For electricity connections to these new developments, the DNO can specify a greater minimum cable size to ensure that it is future-proofed for any EV charger requirements.
Likewise, for any upgraded supplies to existing properties, new larger cables could be installed as part of the works. Whilst this network reinforcement will incur additional costs, it will be more cost-effective than replacing the cable if the site requires EV chargers in the future.
What can be more problematic is the retro-fitting of EV chargers in homes, workplaces, destination and en-route locations. The ease with which the local network can accommodate EV chargers will depend upon the availability of electrical load and whether the network can cope with the harmonic fluctuations that EV chargers cause.
In simple terms, connection of EV chargers should be much easier in urban areas where there is a greater density of substations and an underground cable network (as opposed to overhead lines). For the large part, home chargers could be powered from the existing distribution board and faster, rapid chargers could simply require a new connection from the local Low Voltage (LV) or High Voltage (HV) cable network.
In areas where network capacity is restricted, WPD has said it plans to offer alternative connections where businesses can only charge at certain 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. This would overcome the need for network reinforcements.
As a handy tool, many of the DNOs are offering 'heat maps' showing available capacity for EV chargers at each substation. This is a great help when assessing site feasibility or EV charging requirements on a city-wide basis.
But capacity isn't the only issue: as an electrical network has an increasing number of EV chargers connected to it – in homes, workplaces and destinations - harmonics will be an issue.
EV chargers use power electronics which can cause interference and damage to the electricity network, known as harmonic disruption. Certain population demographics are likely to be early adopters of EVs; these will be in geographic clusters which will have more home chargers and a greater demand for workplace chargers.
Likewise, the location of destination chargers will be determined by the Public Network Operators making an investment based upon footfall and the ability to get a power supply to that location. Urban areas with higher forecast rates of EV-owners will have more EV chargers in 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. Beyond this, the network will require reinforcement or the EV charger will need to be supplied from a different network which would require a longer cable run to site. In either case, there will be increased costs.
But what about rural areas, where the network tends to be overhead lines?
It can be far more challenging to get power to rural areas. Taking into account that many en-route locations (motorway services and fuel 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 the extreme cases, this can involve kilometres of cable across public highway and private land, crossing of motorways and railways and the establishment of new primary substations. Not only costly, but a much more labour intensive and longer timescales to get power to where it is needed.
The costs of getting power to site may be prohibitive, yet these locations will be critical to EV drivers.
Transport Secretary Grant Shapps has plans to tackle this very 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.
One of the questions raised is how much power capacity do you bring to these areas? Is it a case of building the capacity incrementally as the nation adopts electric cars? Or do you bring in a huge load now knowing it will be under utilised for the immediate future?
WPD has developed a 'prefab' solution as part of its Take Charge project which can provide up to 20MVA capacity at a site. Likewise, Electricity North West is investing £25m over three years in eight schemes as part of their Leading the North West to Zero Carbon plan, all designed to create new capacity in the area through new electrical infrastructure.
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 dependant 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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