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Charge of the electric carPublished on 1 June 2009

By Anne Harris

The ability of the UK power grid to support the growth of electric cars has been called into question, but as E&Tdiscovers there ismore than enough electricity to go around.

One of the key future technologies to green the emissions from car tailpipes is the battery electric vehicle (EV). At present the EVenjoys a niche appeal, but that is set to grow. All the big players are dipping their toes in the water of what is an already crowdedpool with offerings such as the Chevy Volt and the iQ PHEV from Toyota. But it is cars from small manufacturers bearing names suchas Tango, Kewet, Kurrent and the bizarre looking three-wheeled NmG (no more gas) that are holding sway.

While the maturing technology, battery and drivetrain, is allowing these vehicles to move into mass production there have beenconcerns raised about the ability of the UK power grid to accommodate a huge explosion of EVs. The results of simulation studies bya consortium including Ricardo, Jaguar-Land Rover, E.ON and Amberjac Projects, have appeased those fears somewhat, indicatingthat a substantial medium-term rise in the number of electric and plug-in hybrid vehicles would have a much lower impact on the UKnational power grid than the earlier, more anxious estimates.

Four vehicle-fleet charging scenarios were simulated, comprising uncontrolled domestic charging, uncontrolled off-peak domestic

charging, smart domestic charging and uncontrolled public charging throughout the day for example, by commuters who rechargetheir vehicles while at work. Charging was assumed to be single phase AC as this is the most likely near-term solution, but the studyalso considered fast charging scenarios as for a large number of vehicles the energy demanded over a time period is likely to be thesame and distributed evenly.

Assuming a 10 per cent market penetration of plug-in hybrid electric vehicles and pure electric vehicles in the UK, the study showed adaily peak increase in electricity demand of less than 2 per cent (approximately 1GW) for the scenario of uncontrolled domesticcharging the worst case in terms of peak power demand.

Other scenarios are less challenging: off-peak domestic charging, for example, increases electricity consumption throughout the night,but has no impact on the peak daily demand. Since it will be a number of years before a 10 per cent level of market penetration isachieved, even with the recently announced UK government incentive plans, grid capacity at a national scale should be adequate forthis significant electrification of the vehicle fleet.

I was reassured because it is not as bad as people think, apart from the more localised regional effects, Corrin Wren, Ricardo chiefengineer, says. I think that is where the challenge is and, not only that, its making sure that the vehicle technologies are there tosupport it; its a blended and coordinated development; thats where the challenge is. I wasnt too surprised but reassured. There areplenty of challenges ahead, and those lie both on the vehicle and the infrastructure side.

Supporting demand

While the national impact is shown to be manageable, as Wren alludes, the research team emphasises that local improvements maynevertheless be necessary for example, where local network capacity is marginal or where particularly high concentrations ofelectric or plug-in vehicles occur.

We have concluded that the grid is capable of supporting that demand, Wren continues. The issue is about more localised regionaleffects, so if you can imagine if London in particular took on a massive amount of electric vehicles compared to the whole of the UK,then the localised effect is going to be rather profound. There could be quite a demand on a particular section of the grid.

Further work is ongoing to look at the timeline for reduced power station CO2 emissions, which is the key enabler for electric andplug-in hybrids to reach true ultra-low carbon status. Future reports of the Range Extended Hybrid Electric Vehicle project will look atfast charging infrastructure which would offer significant consumer benefits in the use of electric and plug-in hybrids.

The importance of EVs was established by a pair of government reports late last year. The study undertaken by Arup and Cenex onbehalf of the Department for Business Enterprise and Regulatory Reform investigated the scope for the transport sector to switch to

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vehicles powered through electricity from the grid in the period until 2030. Road-based transport currently accounts for approximately22 per cent of the UK CO2 emissions and therefore reducing the reliance on carbon-based fuels in this sector is seen as a priority.

The second report, the King Review of Low-Carbon Cars, highlighted the fact that road-based CO2 emissions reductions will comefrom a number of different sources. However, it concluded that battery EVs and plug-in hybrid electric vehicles (PHEVs) cancontribute to the long-term reduction of the UKs CO2 emissions.

My report has a very positive message, Professor Julia King says, that major reductions of CO2 emissions from road transport in theyears ahead are possible.

But seizing these opportunities will require action from everyone, with government playing a leading role. Government mustcoordinate efforts in an international context and provide the leadership to allocate responsibilities among vehicle manufacturers, fuelcompanies and consumers.

Both studies agree that EVs have the potential to offer significant carbon dioxide and greenhouse gas emissions reductions comparedto conventional petrol/diesel fuelled internal combustion engines.

This applies over a full life-cycle, taking account of emissions from power generation and emissions relating to production anddisposal. Based on the current UK grid mix there are already significant benefits of the order of approximately 40 per cent reduction;these benefits have the potential to become much greater with further decarbonisation of the UK power mix.

Charging up

At present, most EVs will slow-charge using single-phase power from either home sockets or specially erected charging points in carparks and parking bays the slow charge will take around six hours.

It is difficult to say how everything is going to be rolled out and adapted but single-phase is clearly the first point because clearly thegrid covers single-phase almost everywhere, Wren says. Three-phase is more difficult because there is a limited number oftransformers that support three-phase, but in terms of fast charging it is considered to be the solution because it runs at a muchhigher power capability.

For ease of deployment, the short-term solution appears to be single-phase, restraining a daily drive to the distance achieved with abattery charge.

As the industry grows and battery chemistry improves, expect to see fast-charging points spring up at motorway service stations.

Comments

I agree to some extent with some of the comments from Corrin Wren of Ricardo and others. However even if the power demand maynot be an issue I feel that we must look at and consider the Harmonic pollution created by EV's the single phase rectifiers plugged inthe utility network. Even if each charger meets the IEC64000 set limits, it is the number of chargers that may impose problems on thelocal transformers which are not suitable for high level of Harmonic loading. Transfomers need to be 'K' rated to meet the Harmonicloading otherwise we may face overheating of traditional installed transformers and also may be some major failures. It is assumedthat all such problems will come only when the EV growth reaches a respectable volume on our roads. Regards. Shri Karve

Mr Shri Karve,06 Oct 2009

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