How do you decide how green a car is? Do you look at its miles per gallon? If so, what about electric cars? – as they don’t have a miles per gallon figure. What about the energy that goes into the manufacture of batteries in hybrids and EVs? How do you account for that?
All these questions, and many more, were debated at the 2013 Low Carbon Vehicle Partnership (LowCVP) Conference, with the aim of finding a solution to compare how green all vehicles really are on a like-for-like basis.
The problem – the current NEDC fuel economy test
Increasing numbers of motorists are becoming angry with the current New European Driving Cycle (NEDC) fuel economy test because it doesn’t give an accurate indication of the levels of fuel economy that they are achieving in real-life driving.
A number of independent studies have shown that the average car returns fuel economy that is 25% worse than its NEDC figure. Green-Car-Guide.com has found that in many cases, the greener the car, the worse its real-life fuel economy will be relative to its official figure. Why is this?
In our view, which is supported by talking to experts at organisations such as Ricardo, most cars today are engineered to perform well in the official NEDC test – which is a very low load, short driving cycle – and the manufacturers have a number of opportunities to ‘optimise’ the test car to perform well, for instance, by over-inflating tyres, etc.
When the car is driven in the real world, it is virtually always driven outside of this driving cycle, and the powertrains that are the most optimised to do well on the test usually deteriorate most on the road. In our experience, this means that hybrids and downsized engines have the greatest discrepancy from the NEDC figures. The powertrains that are closest to their official consumption during real-life driving, especially when spending more time at motorway speeds than in the NEDC test, are 2-litre turbodiesels, especially in cars that have good aerodynamics.
At a time when we’re seeing the majority of car manufacturers develop vehicles with some ‘plug-in’ capability (not necessary pure EVs), perhaps the greatest problem is the official miles per gallon figures of plug-in hybrids. For example, the Volvo V60 Plug-in Diesel Hybrid has an official combined fuel economy figure of 155mpg. This sounds amazingly appealing, but motorists will never achieve anything close to this figure unless they drive on the NEDC cycle all the time, which is impossible.
In typical real-life driving, a V60 Plug-in Diesel Hybrid owner is likely to achieve an average of around 50 miles per gallon over a year, or 12,000 miles. Why the huge difference? Because the NEDC test is conducted mostly on charged batteries rather than using diesel, whereas in real life it’s likely that the car will be driven more than 50 miles between charges, and so many more miles will be driven on the diesel engine than in the NEDC test. Are people likely to always drive less than 50 miles between charges in a V60 Plug-in Diesel Hybrid? No. If they did they’d buy a pure EV.
As well as not taking into account the likely ‘real’ use of the car, the current NEDC test doesn’t take into account the energy generated from the national grid to charge the batteries of a plug-in car. Plugged in cars are basically pushing emissions away from the vehicle to the national grid.
A pure electric car doesn’t use any petrol or diesel, so it has no tailpipe emissions, and no miles per gallon figure. Yet CO2 is still produced, usually at a power station, to generate the energy to charge the battery.
So, the current NEDC test, which is used as a baseline for comparing how green cars are, may have been seen as a good solution when it was introduced, when only internal combustion-engined cars existed, but it now doesn’t work with the range of alternative powertrain options on offer.
Debating the solution – the LowCVP Conference
All this resulted in the need for the LowCVP in its annual conference to discuss the issue around future CO2e metrics for passenger cars needing to go beyond the tailpipe measures, and take into account whole life cycle CO2e emissions to more fully account for environmental impacts, especially when comparing different vehicle technologies.
This involved a debate about how to replace the NEDC test figure with a calculation that takes into account all the energy used in the entire life of the car – covering the raw materials in its body and powertrain, its manufacture, the energy it uses during its life, to its end of life recycling.
This sounds like a great idea, and some work on this has already been done, with the results showing that low and ultra low emission cars may have more emissions associated with their manufacturing phase, but overall they have a lower carbon footprint throughout their entire life due to them using less energy in their use phase.
However there are a number of problems with developing a standard whole life carbon footprint comparison.
Challenges of moving to ‘beyond the tailpipe’
Firstly, although there is an established way to calculate the lifecycle carbon assessment of products, there are so many complex variables involved in the manufacture of different types of vehicles by a wide range of manufacturers that no agreed ‘level playing field’ methodology is accepted by all car manufacturers.
For example, it’s a complex assessment to compare the relative environmental impacts of extracting lithium for batteries from lakes in Bolivia compared to extracting oil from some of the world’s most ecologically sensitive areas. And if batteries from electric cars are re-used at the end of their vehicle life in houses as energy storage systems, as expected, how does that impact upon the overall ‘green’ calculation?
Another issue is the carbon emissions associated with the energy generation for plugged in cars. This is vastly different all around the world, depending upon the energy generation in each country. For example, an electric car charged in France would have much lower carbon emissions than the same car in the UK, as France has a large nuclear power station ‘fleet’, whereas the UK has more of an energy generation mix, but one that is still mostly reliant on coal and gas. The same electric car in Poland would have huge carbon emissions due to the massive reliance on coal-fired power stations. Car manufacturers aren’t likely to want to quote CO2 figures for their cars that include CO2 from electricity grids that are completely out of their control.
Of course, nuclear power has a massive problem in the area of waste – how would that be factored in to the overall environmental impact of an electric car charged in France?
There’s also the issue of what emissions should be included in any new system. A link may be agreed between carbon dioxide emissions and climate change, but cars also produce other emissions that have a negative impact upon local air quality – which is a huge issue in countries such as China, as well as in UK cities such as London.
Another issue revolves around the information that the consumer wants. When buying a car, does a consumer want a figure that reflects the overall carbon footprint of a car from cradle to grave? The answer is no; they would probably prefer a miles per gallon figure, even if they know they should downgrade it by 25%.
Rather than the conference coming up with any form of clear solution to the problem of replacing the current tailpipe emissions measurement, it instead showed that the whole area is extremely complex.
It was agreed that the current system isn’t working, and that we need to move to a better system to compare different cars in a like-for-like, holistic way. However so many issues were raised with the whole life carbon footprint comparison that it seems that such a system will be many years away. And all the complex issues mean that legislators need to think very carefully before deciding on new regulations.
A ‘half way house’ between a tailpipe emission figure and a full carbon life cycle calculation would be to have a ‘well-to-wheel’ figure. This would provide a CO2 figure for different types of cars and fuels from the generation of the energy – in an oil well or at a power station – to the point where it powers the wheels. To put this into context, an EV today may emit around 89 g/km CO2 well-to-wheel based on the UK’s current energy generation mix compared to zero g/km at the tailpipe – although this is likely to reduce as the UK’s electricity grid is due to be decarbonised over the next 20-30 years.
The key issue for consumers is fuel economy – and associated cost – rather than emissions – either tailpipe or whole life emissions. However a fuel economy figure can’t be quoted for plugged in cars. A good system for consumers could be similar to that used in the United States – which focuses on two ‘metrics’ – a miles per gallon equivalent (MPGe) figure, and a cost for the energy that the car uses over a certain distance/time period – a monetary cost being a metric that can be calculated for any powertrain, and compared like-for-like.
As long as the MPGe calculation can be agreed, and the associated energy cost, then this would provide consumers with the information that is most important to them – an easy way to compare different cars based on a figure in pounds (or dollars etc) that they are familiar with, and the real cost of running a car over a much longer time and distance than the current NEDC test.
In the meantime the industry can work its way through a whole life cycle carbon footprint measuring system, but that is ultimately more likely to be of interest to the industry than the majority of consumers.
If you want to read more about the detail of all this, then the LowCVP issued a report on the day of the conference, entitled ‘Life Cycle CO2e Assessment of Low Carbon Cars 2020-2030’. Prepared for the LowCVP by PE International and validated by Partnership stakeholders, the report shows how total life cycle CO2e emissions will change for different vehicle technologies in the future and estimates how the balance of emissions will alter for different stages in the life cycle for the varying technologies.
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