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Expert claims: Hybrids offer most effective strategy to real world CO2 emission reduction

Emissions Analytics, a leading independent specialist for the scientific measurement of real-world emissions, says that hybrid vehicles offer the most effective route to overall emission reduction at present, even more effective than battery electric vehicles.

“One of our biggest challenges is fleet turnover, with vehicles staying on the road typically for up to 12 years,” explains Nick Molden, CEO of Emissions Analytics. “It means that refreshing the entire fleet is a very slow process. Given reservations about current BEVs, we require an alternative that will have a more immediate impact. Due to CO2’s long life in the atmosphere, a small change now is far better than a large change in the future. We need to optimise the use of the industry’s available battery capacity to facilitate a critical early reduction.”

Through extensive real-world testing of electrified vehicles, Emissions Analytics found that hybrids, whether in gasoline or diesel form, offer the highest CO2 reduction per kWh across all electrified powertrains.

Using mild, full and plug-in hybrid real-world emissions test data, from both European and US vehicles, Emissions Analytics compared hybrids with its internal combustion engine equivalents. Using the company’s standardised on-road cycle, it determined the average CO2 reduction from hybridisation was 23 per cent for the EU and 34 per cent for the US, with an average of 30 per cent across all pairings.

Emissions Analytics then calculated the distance-specific CO2 reduction per unit of battery size (capacity), in g/km/kWh, for mild, full, plug-in hybrids and BEVs. The results indicated that mild hybrids are the most efficient way to reduce CO2, given limited global battery capacity. With a reduction of 73.9g/km/kWh, the technology was a clear favourite, with full hybrids coming in second at 50.5g/km/kWh.

Due to their disproportionately large batteries, BEVs were the worst of the available options, with a mere 3.5g/km/kWh reduction. The size of BEV batteries tends to be large to accommodate infrequent, extreme use cases – like high-mileage trips, not often undertaken by average drivers – and do not make the best uses of limited supply.
The calculations did not take into account the upstream CO2 in fuel extraction, refining and transportation, or the production and distribution of electricity. Some studies suggest the upstream CO2 of electricity is greater than for gasoline, but the relative efficiency calculations here implicitly assume they are equal.

Improving the air quality in cities is another popular reason for those championing BEVs. It is, however, a false assertion that they are needed to fulfil this purpose. Existing technology is more than capable of bringing European cities within compliance, the primary polluters being vehicles with older internal combustion engine technology.

Molden outlined two potential paths that are immediately available. One is a switch from gasoline to diesel, reducing CO2by 11 per cent, coupled with a mild hybrid system, providing a further six per cent reduction. A final swap to full hybrids would deliver an addition 16 per cent reduction for a 34 per cent total. Alternatively, switching directly from gasoline to gasoline mild hybrids provides an 11 per cent reduction, with a further 23 per cent from the move to full hybrid.

The EU’s post-2021 CO2 reduction target for passenger cars is 37.5 per cent by 2030. Emissions Analytics tests clearly shows that, even with current technology, widespread hybridisation would achieve over three-quarters of that target.

Given a decade of further advances and innovations, it is possible that the goal could be met without the need for BEVs at all. Beyond the 37.5 per cent reduction target, more extensive electrification would be required to bring whole fleet emissions down.

“The ideal solution is an immediate transition to petrol and diesel hybrids, with a further decade spent refining the technology, infrastructure and battery supply chain to allow the adoption of BEVs,” concluded Molden. “By 2030, the EU and the US would have had another decade to develop expanded, cleaner electricity generation capacity, improving the lifecycle emissions of BEVs.

“Alternatively, by 2030 the availability and price of renewable energy may well fall to a level at which hydrogen fuel cells could be economically viable. These avoid the environmental and geopolitical issues caused by largescale battery production and would likely offer even lower lifecycle emissions. The overall message is this though: it is paramount that governments and industry take into consideration real-world data when promoting technologies to efficiently reduce CO2.”