Why PHEVs could be a greener solution for fleets than EVs
Plug-in hybrid vehicles could help the automotive industry achieve more ambitious climate goals than battery electric vehicles, according to research by Swedish scientists.
They investigated the lifecycle greenhouse gas emissions and found that PHEVs have greater potential to shrink their carbon footprints than BEVs because of the significantly lower carbon intensity of their production and manufacturing process.
Carbon footprint of batteries
The key difference is the size of the battery pack – the larger the batteries the bigger the carbon footprint of a vehicle. Each kWh of battery capacity produces somewhere between 61-106kg of CO2 per kWh, which gives PHEVs an important environmental advantage over BEVs as they leave the factory.
Despite most PHEVs having a zero emission range 10 times shorter than a BEV equivalent, this is still enough to cover typical daily driving distances, say researchers at Lund University in Sweden. They cited a study of 73,000 PHEVs in the USA and Germany, which found that an electric range of 60km would be sufficient to drive 75% of journeys without resorting to the car’s internal combustion engine.
“This means that the major portion of a BEV’s battery is seldom used and, during most trips, effectively only adds weight to the vehicle,” said the report, published in the journal Applied Energy.
PHEVs must maximise electric km
To minimise the life cycle greenhouse gases of PHEVs, however, requires them to be run whenever possible on electric power generated from renewable sources, and to be fuelled by renewable biofuels if they have to resort to their internal combustion engines.
Bio-fuels such as an ethanol-petrol mix or a diesel based on hydrotreated vegetable oil (HVO), are widely available at filling stations in Sweden, but not throughout the EU.
PHEV vs EV
To create a real world example, researchers modelled the greenhouse gas emissions of a Kia Niro PHEV and BEV (with 64kWH battery) over a 200,000km life cycle. Their findings found that the Niro PHEV had a smaller carbon footprint than the Niro BEV in 2020, even when it was powered with petrol. When the researchers ran the same model using a cleaner electricity mix (based on EU-28 forecasts for 2050), the gap between the PHEV and BEV narrowed, but the PHEV still held the advantage if it were fuelled by HVO biofuel or E85 petrol (assuming it could cover at least 52% of its journey distances in electric drive).
Electrification will not meet EU carbon targets
With the EU looking for a 90% reduction in transport emissions by 2050, the researchers warn that even if a BEV is powered by a relatively clean, green renewable energy mix, it will not come close to delivering the 90% carbon savings required.
“Electrification is not sufficient in itself to achieve a 90% reduction of the car fleet’s greenhouse gas emissions, even in a scenario when the greenhouse gas intensity of the electricity mix has been significantly reduced from the current level,” they said.
“It also indicates that PHEV technology combined with renewable fuels has greater potential for GHG reduction than BEV technology. Plug-in hybrid electric vehicles, rather than being viewed as transitional, can be seen as an enabling technology for meeting ambitious climate goals. This is because their moderately sized battery packs reduce production phase greenhouse gas emissions compared to battery-electric vehicles. They also enable a limited supply of battery minerals to electrify a larger fleet, reducing the sustainability concerns around extracting sufficient amounts of minerals for a large fleet of battery-electric vehicles. If mainly driven in electric mode, a fleet of plug-in hybrids also reduce the need for fuels to the point where it may be possible to meet the demand with sustainably produced renewable fuels that have low life cycle greenhouse gas emissions.”