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The electric vehicle balance sheet

18/10/2011

When comparing emissions between EVs and vehicles that use conventional internal combustion engines, the well-to-wheel approach is often used to gauge the overall impact of each form of mobility on the environment. This looks at the emissions released when getting a fuel from the ground (in most cases) to the tank of a vehicle – well-to-tank – and then those released when the fuel is used in the vehicle to provide kinetic energy – tank-to-wheel.

When driving an EV, the emissions come from the well-to-tank phase, and it is generally accepted that, while not quite the ‘zero emission’ performance that some manufacturers spin to potential customers, EVs emits less CO2 than conventional vehicles – even if the electricity comes from coal-fired power plants.

But what about the entire lifecycle emissions of the vehicles, from manufacturing through to use and then disposal?

A recent report from the Low Carbon Vehicle Partnership (LowCVP) looks at this issue, taking a more holistic view of lifecycle emissions rather than just a vehicle’s performance on the road.

An EV will produce around 18 tonnes of CO2 over its lifetime, compared to the 24 tonnes produced from a conventional vehicle.

The report, a joint project between the LowCVP and technology provider and consultant Ricardo, found that some of the carbon savings made during the use of EVs are offset by increased emissions created during their production. Amazingly, the report states that 46% of a battery EV’s overall carbon footprint is generated at the factory, before it has travelled a single mile. The reason is to do with embedded emissions, and these are particularly high in an EV’s battery.

However, when everything is taken into account, EVs still come out favourably on lifecycle emissions. An EV will produce around 18 tonnes of CO2 over its lifetime, compared to the 24 tonnes produced from a conventional vehicle.

The LowCVP report demonstrates the usefulness of comparing lifecycle emissions between different types of vehicle. There is, however, something that has so far failed to make it onto the balance sheet for EVs.

Electric vehicles, as well as being a silent mode of city transport, could also be thought of as a parc of electricity storage potential on wheels, with each vehicle capable of storing excess electricity from the grid. Ricardo has also produced a report with National Grid which shows that EVs could fill a niche in the future to help balance the grid, and also reduce emissions.

Amazingly, the report states that 46% of a battery EV’s overall carbon footprint is generated at the factory, before it has travelled a single mile.

The report states that, using demand-side management alone (using current charging capabilities at no significant infrastructure cost), the projected UK fleet of plug-in EVs in 2020 (600,000 units, it estimates) would be able to provide an average of 6% of daily UK network balancing service requirements. This would rise to a maximum of 10% in the evening and overnight. This ‘free’ storage capacity could result in less additional electricity generating plant needed on standby to smooth out the peaks and troughs of the daily toils on the grid. Peaking power plants are, by their nature, expensive to operate.

Not only this, the balancing services for the grid from EVs could be provided on a commercial basis, which, alongside improving the carbon efficiency of grid operation, could return value to vehicle owners.

So EVs may not be quite as ‘green’ as once thought, since the battery does have some considerable environmental costs. But – if used strategically – they have some ancillary benefits that conventional vehicles cannot provide, meaning that grid operators, as well as certain environmentalists, should be pleased to see more EVs on the roads.

Fuente: Euroinnova

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