Does the UK have the distribution networks and power plants to cope with demand if there is a rapid take-up of electric cars? James Hunt reports.

On 27 October the government's drive to put the UK at the forefront of a green motoring revolution was given a boost when international experts gathered in London to discuss how to kick-start the mass market production of low carbon and electric vehicles.

Energy, automotive, planning experts and government representatives from more than 15 countries debated many of the technological challenges, key barriers and opportunities that could be created from the low carbon and electric vehicle market, and discussed industry standards.

According to business minister Ian Pearson, "currently, less than 0.1 per cent of the UK's 26 million cars are electric", so the push for green power has some way to go. But if the revolution does take off, the question is, can the electricity demand be met?

Most plug-in electric vehicles use battery packs to drive electric motors that are controlled by the driver via electronics. They need frequent, often daily, recharging. Another type of car is the hybrid electric vehicle, which uses electric motors in conjunction with a conventional internal combustion engine, plus a generator. Toyota's Prius is the most notable example.

Hybrids that can also be charged externally are called plug-in hybrid electric vehicles. Toyota has recently started trials of a plug-in hybrid that combines mild hybrid and pure electric vehicle benefits. EDF Energy is installing charging points across London for it.
Hybrid vehicles are more energy-efficient than conventional vehicles powered by petrol or diesel engines, but pure electric vehicles are much more so, and carbon dioxide emissions are greatly reduced. Many conventional vehicles will have to be replaced with electric vehicles if the government is to meet its target of cutting emissions by 26 per cent by 2020.

Grid power
Of course, the electricity to power them must come from another source, the electricity grid. As sales of electric cars grow, driven by environmental concerns and high fossil fuel prices, this could become a problem.

So, how much electricity will be needed, and can the country's existing infrastructure cope, both in terms of power plants and distribution grids? To answer that question, we need to know how many electric cars are likely to be on the road by 2020, as well as what proportion of them will be hybrids.

This is not easy to predict. Electric vehicles still rely on emerging technologies, and could change significantly over the next few years, and nobody knows at what point various groups of consumers will be convinced enough to make the switch. It is also necessary to be able to take an educated guess about how battery technologies (lead acid, lithium ion, lithium polymer or other) will develop, because these affect charging rates and costs.

Battery charge or discharge efficiencies (typically 80-85 per cent) have to be considered. In addition, some electric vehicles use regenerative braking to extend range. This can affect charging. Charging time is currently mainly limited by 13A sockets allowing 3kW output, so new 10kW charging points may be necessary.

EDF Energy has made a start. London mayor Boris Johnson has vowed to start rolling out charging points, and the government is keen. A few workplaces are starting to provide dedicated vehicle parking bays with chargers. Even Google is getting in on the act, promoting the use of electricity for personal transportation. So while the projections of the take-up of electric vehicles are uncertain, and a conservative estimate is 500,000 by 2020, the actual number could be many times this.

2GW peak
What effect might these vehicles have on the current transmission and distribution system? Assuming that the cars charge from 3kW mains sockets, that batteries have standard outputs of 16-22kWh, and that charging will be overnight, then National Grid estimates 2GW would be required to meet peak demand, equivalent to around 4TWh annually. However, Eon UK thinks this estimate of demand might be too high - it all depends upon the assumptions.

To power all 30 million cars in the UK with electricity could require a 27 per cent increase in generation output (about 90TWh a year). The UK's existing portfolio of generation capacity might be able to meet this admittedly worst case (best case?) scenario, but charging would have to be done at night.

National Grid's 4TWh estimate is modest compared with the UK's 350TWh annual consumption. The company puts this figure in context further by pointing out that by 2020 it is assumed it would take 4TWh to power the nation's tumble dryers, were they all switched on at the same time. A World Cup-sized sporting event would be expected to generate a surge in demand of 2GW, so such a figure is within current capacities, as long as the country's power stations are on standby to meet it.

Smart metering
However, it would be better if the country's electric vehicles were not charged simultaneously, and evening charging was minimised. For this reason, National Grid would like to see smart metering accompanying the rollout of electric vehicles. This would help optimise the use of national electrical infrastructure and also provide appropriate price incentives for car owners. Smart metering could even automatically switch charging on at night, but good data handling would be crucial.

Can generating companies cope? It will be important to maximise energy and emissions advantages by recharging electric vehicles using renewable sources, or at least from highly fuel-efficient (to 90 per cent) cogeneration plant. National Grid believes that the incremental electricity demand from electric vehicles up to 2020 will be satisfied by combined cycle gas turbine plant.

John Bateman, Eon UK's research and development programme manager, says: "As a network company and a power producer, Eon has to look at both aspects. We've estimated that plug-in vehicles could potentially represent 5-7 per cent of current total UK vehicle miles by 2020. Based on a typical electrical vehicle output of 30-40kW, this will be equivalent to 7.5TWh electrical energy, or 2.2 per cent of our current generating capacity. Our networks will cope."

However, Bateman says Eon will still have to plan new power plant "very carefully".
"Nuclear power is baseload and wouldn't be flexible enough for unpredictable electric vehicle charging. We have many windfarms, but the wind doesn't always blow at the right time. That leaves thermal plant.
"One reason for wanting to build the 1,600MW Kingsnorth cleaner coal-fired unit, and new gas-fired plant, is to meet future power requirements flexibly. These could cater for demand spikes when electric car owners plug in. We could reduce such spikes by using smart metering and tariff incentives, but first we need to conduct realistic trials to establish what electric car users want."

Growing impact
After 2020, he says, the impact will grow as plug-in vehicle numbers rise.
"Grids will respond, but slowly because of their size and complexity, although with good forecasting and proper planning, capacity can be made available to suit demand," he says.

If Eon UK's and National Grid's views are typical - and there is evidence that they are - then up to 2020, anticipated electric vehicle power demand should be met. On the other hand, most of the UK's remaining nuclear power plants are contending with technical problems and there is concern in some quarters that the country could run dangerously short of electricity this winter, even without a significant fleet of electric vehicles to power.

As things stand today, many owners of electric cars are likely to start charging in the early evening, potentially putting grids at risk, so some vehicle manufacturers are reported to be developing sophisticated integrated information and charging systems.

They will need to discuss with network providers how best to optimise charging regimes.
Demographics may be important too, since electric vehicles are likely to be more common in cities because of their limited range. Local tax differentials and electricity infrastructure differences may have local impacts that have yet to be fully considered.

Again, co-ordinated planning with local authorities, distribution network operators and vehicle manufacturers will be essential to get optimum results.

No constraint
It is unlikely, then, that existing electricity generation and transmission is a constraint to the development of electric vehicles in the short to medium term. However, it will be important to consider carefully potential local constraints and to provide solutions to them, both short-term operational solutions and longer-term investment.

There is a new and very interesting possibility. Because most vehicles are typically parked 85-90 per cent of the time, vehicle batteries could be used to let electricity flow from the vehicle to the grid as well as from the grid to the vehicle. This is vehicle-to-grid (V2G). In this way, electric vehicles could, theoretically, be used as distributed energy storage.

V2G possibilities include balancing loads by "peak shaving" (sending power back to the grid when demand is high) or buffering during power outages. Electric vehicles could also be used to buffer wind turbines, effectively stabilising wind variability. Therefore, V2G could, in principle, add highly desirable flexibility and redundancy. Bearing in mind that Scottish and Southern Energy has recently warned that centralised fossil fuel-fired generation will have to give way to energy efficiency and generation diversity, V2G could be part of the solution.

"V2G is a very interesting concept but there are technical, practical and economic challenges in terms of connection to the grid, feed-in tariffs, battery capacity and life, and other impacts, such as customer behaviour," says Eon UK's Bateman. "Very careful battery management will also be required. We will be looking at it."

The only low carbon alternative to electric vehicles is hydrogen-powered vehicles (which in actuality would be electric vehicles with on-board power generation). Apart from the technical problems to be overcome, this would also require the building of an enormous, and hugely expensive, hydrogen infrastructure.

For the foreseeable future at least, the future is electric.

James Hunt is a freelance journalist

Comment on this story

Screen name

Email (For verification only. Your details will not be retained or passed on. Not for publication)

Comment

Report Abuse

Sign up to our free email newsletters