Back to the source: reducing the carbon cost of EV production

April 30, 2012 § Leave a comment

When assessing how ‘green’ electrified vehicles really are, much emphasis is usually placed on the source of the electricity which powers them, and whether the use of non-renewable juice can negate the benefits of zero emissions from a – metaphorical – tailpipe. But this  doesn’t tell us the whole story either; to fully assess the carbon footprint of electrified vehicles, it’s necessary to go back to the source and look at their production as well.

A study by Ricardo last year for the UK’s Low Carbon Vehicle Partnership (LowCVP) set out to develop an understanding of a vehicle’s whole-lifecycle impact, and found that for a typical battery EV, 46% of its total carbon footprint was generated in its production before it even hit the road. This compares to 35% for a plug-in hybrid, 31% for a hybrid and 23% for an average petrol-engined car, based on data projections for 2015-specification vehicles and predicted fuel and electricity supplies.

The study concluded that over a typical 10-year or 150,000km lifespan electrified vehicles would give an overall carbon saving – due to their lower in-use emissions – and that a typical medium-sized ICE family car would create around 24 tonnes of CO2, compared to an equivalent EV’s 18 tonnes (the lifecycle impact of a diesel was found to be roughly similar to that of a petrol-engined car). However, it was clear that “the introduction of battery packs, electric motors and power electronics into a passenger car increases the embedded CO2 emissions associated with the vehicle’s production.” Embedded carbon (CO2e) for the ICE was around 5.6tCO2e, but 8.8tCO2e for the EV, 43% of which arose from the battery.

A follow-up piece of research, presented in February 2012, assessed a popular mid-market SUV in standard, electric and range-extended EV forms, and took into account revised projections on factors including embedded emissions for battery pack production, carbon intensity of electricity and lifetime mileage. Again, a lower proportion of the ICE vehicle’s lifetime embedded carbon was in its production – 21%, compared to 35% for the EV and 29% for the RE-EV – but the EV still came out ahead overall, and crucially, the ‘payback time’ – the point at which its in-use carbon savings compensated for its higher-carbon production – was around 65,000 km, well within the predicted vehicle lifetime.

Yet there are improvements which can be made in production too, from zooming in on each stage of the supply chain and individual processes, to installing solar panels (such as SEAT’s extensive array at Martorell) or wind turbines like those at Nissan’s LEAF plant. Such measures are becoming more common as manufacturers update, extend or otherwise upgrade their facilities, and this can of course ultimately be of benefit to production of all vehicles, not just EVs and hybrids. Likewise, targeted improvements to reduce embedded carbon in specific components, and detail-changes to improve fuel efficiency, can apply to ICE and hybrid vehicles as well as EVs. This could entail using (and finding new) low-carbon alternatives to steel or aluminium, such as composites, as well as greater use of recycled materials – which could also be of benefit in reducing vehicle weight.

Economies of scale are not necessarily an issue for mainstream manufacturers such as Renault, who can produce their EVs and hybrids alongside ICE vehicles, but low-volume car-makers and small start-ups building niche vehicles do have the benefit of flexibility. They can also take a more radical approach in developing their production processes. Most notably, Gordon Murray Design’s patented iStream design and production process  is “a complete re-think on high volume materials and the manufacturing process, and will lead to a significant reduction in CO2 emissions over the lifecycle of the vehicles produced using it”, claims the company. Reducing vehicle weight is key, but also a design around a basic platform which is easy and cheap to manufacture, easily-modified, and highly-scalable; in the assembly process, pre-painted composite panels are bolted onto a near-complete chassis, with no need for a paint shop.

Reducing the number of necessary components enables quicker, less energy-intensive construction and installation. Suppliers are also developing compact, lightweight powertrain solutions in easily-integrated modules. Solutions reducing battery dependency can also play a role: KERS, other flywheel energy storage technologies and supercapacitors can enable the use of smaller batteries with a lower embedded carbon content.

Yet when developing a vehicle for production, the end of its useful working life must also be considered: the potential for recycling and reuse of its constituent parts and materials, especially the materials which go into batteries. Honda claims to be the first OEM to extract rare earth elements in a mass-production process at a recycling plant, with an 80% recovery rate from its end-of-life nickel-hydride hybrid batteries. Renault, meanwhile, is particularly concerned about battery reuse, not least because its EV-leasing programme (in which the batteries are leased on a separate contract to the cars or vans themselves) puts it in a potentially costly position; along with partner firm Nissan, it is looking at a number of ‘second life’ solutions such as home energy storage.

Ultimately, lowering the impact of vehicle production will be driven as much by financial concerns as environmental – saving energy and carbon, by achieving efficiencies, means saving money.

*Full version of this article to be published in Electric & Hybrid Vehicle Technology International magazine.

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