EVs: Are they really more efficient?
They have been hailed as a new breed of vehicle that could surpass petrol-driven cars on safety, running costs, performance and design. However there has been increased attention on electric vehicles (EV) recently, with some questioning if they are more efficient than internal combustion engine (ICE) vehicles given their use of coal-fired power. The debate has also raised opinions around the emissions created during the manufacturing process of EV batteries.
However are these claims true? We take a look…
Electric cars rely on charging from the local electricity network, and while coal-fired power plants are not emission-free, research by BloombergNEF finds that carbon dioxide emissions from battery-powered vehicles were around 40 per cent lower than for internal combustion engines last year. This benefit will grow as generators transition away from coal and draw more energy from wind and solar farms – a transition that is already underway around the world, almost everywhere except Southeast Asia.
According to the International Energy Agency’s (IEA) 2019 Global EV Outlook: Scaling up the transition to electric mobility[i], an increase in electric transportation on the world’s roads has anticipated a projected decrease in CO2 equivalent-emissions through to 2030. EVs globally emitted around 38 Mt CO2-eq during 2018, compared to 78 Mt CO2-eq that an equivalent internal combustion engine fleet would have emitted during the same timeframe. According to the IEA, the world’s EV fleet consumed around 58 TWh of electricity in 2018, with China accounting for around 80 per cent of world electricity demand for EVs.
However the electricity source of EVs has to be considered when determining overall vehicle efficiency, and while powering an EV via coal is not as environmentally friendly as using electricity from renewables, it doesn’t mean coal-fired charged EVs are not as efficient as ICE vehicles. Bloomberg’s analysis shows that while the biggest difference in vehicle efficiency gain was seen in the UK, which has a large renewable industry, EVs were still more efficient in China, which is more dependent on coal[ii].
An EV motor is around 85 - 90 per cent efficient when converting coal-fired energy to power. It’s estimated that technological improvements will see emissions from combustion engines falling by about 1.9 per cent a year through to 2040, according to Bloomberg, while EV emissions are anticipated to fall between 3 per cent and 10 per cent annually.
“EVs convert over 77 per cent of the electrical energy from the grid to power at the wheels. Conventional gasoline vehicles only convert about 12 per cent – 30 per cent of the energy stored in gasoline to power at the wheels,” according to the US Department of Energy[iii].
The difficulty for ICE vehicles is by providing driving flexibility; they sacrifice thermodynamic efficiency. As The Driven points out, “petrol and diesel cars are very inefficient in converting the energy in their tanks into motion at the wheel ... over 60 per cent of the energy is wasted as heat.”
Particularly in city driving, engines waste fuel while idling or operating at very low outputs compared to their design capacity, and engines at low output achieve very low efficiencies. However fossil-fuelled power stations are designed and operated to maximise thermodynamic efficiency, typically achieving between 40 - 55 per cent. In fact, an EV charged by a gasoline-powered generator would consume less gasoline in total than a conventional vehicle.
And, unlike EVs, most conventional vehicles do not recover the energy wasted to heat by braking for traffic lights.
There is also the emissions associated with exploring for oil and gas, transporting and converting it into fuel, and transporting it to local distributors before trucking it to petrol stations.
According to the US Department of Energy’s Office of Energy Efficiency and Renewable Energy, “Hybrid and plug-in electric vehicles can help increase energy security, improve fuel economy, lower fuel costs, and reduce emissions.[iv]” The Department further states that “EVs emit no tailpipe pollutants, although the power plant producing the electricity may emit them. Electricity from nuclear, hydro-, solar-, or wind-powered plants causes no air pollutants.”
Battery emissions vs lifetime benefits
The sourcing of raw-materials (covered here in a previous article) and the production process required for the manufacturing of EV batteries have also raised arguments around their emissions.
A recent study published by ScienceDirect shows that while the pollution created through the extraction and production of batteries remains the same or slightly higher than the manufacturing process of petrol or diesel-based engines – where a battery is manufactured has a large impact on the emissions generated during this process.
With just under half of the globe’s electric cars, China continues to have the world’s largest electric car market with almost 1.1 million sold in 2018. Around 45 per cent of electric cars on the road in 2018 were in China (2.3 million total), followed by Europe which accounted for 24 per cent of the global fleet, and the United States at 22 per cent.[v].
Due to the country’s market size, the ScienceDirect study compares China’s manufacturing process of EVs and ICE vehicles, and shows that efficiency increases in the manufacturing and infrastructure process are vital to reducing emissions during EV production. Chinese battery manufacturers produce up to 60 per cent more CO2 during fabrication than ICE engine production, but according to the report, the country’s manufacturers could cut their emissions by up to 66 per cent if they implemented American or European manufacturing techniques - China is also expected to make rapid progress towards the uptake of EVs as its renewable industry further grows[vi].
As the manufacturing techniques of Li-ion batteries and other alternative batteries grows and the recycling and re-use techniques of the EV industry and retired EV batteries further develops (previously covered here), there is the potential for a large reduction in CO2 emissions in China, as well as other key manufacturing markets.
However while EVs produce the bulk of their emissions through the manufacturing process and the sourcing of their energy, the lifetime between EV and ICE vehicles gives EVs a clear advantage.
“recent studies that include the complete life cycle of different types of vehicles, as well as their well to wheel data have revealed that even with fossil fuel-based electricity generation and power losses during transmission from electricity generation to filling the battery, electric cars were found to have lower levels of greenhouse gas production … even on the coal rich Australian grid, EVs produce 40 per cent less GHG when compared with equivalent ICE vehicles. In fact, their well to wheel calculations show that to drive 1km in an average petrol vehicle uses 1.36kWh/km while the average figure for electric cars is just 0.28kWh/km – an energy use figure close to five times less than for petrol cars.”
And as EVs become more common, battery recycling will increase in efficiency and reduce the need to extract raw materials, meaning that EVs have considerably lower emissions over their lifetime, regardless of the source that generates the electricity that powers the vehicle.
The future is looking to be increasingly electric: more electricity grids are now moving towards increasing their renewable energy production, EVs are producing fewer emissions through their lifetime regardless of the energy source, and car manufactures are looking to produce more EV alternatives for the mass-market, with many carmakers announcing plans to bring electric versions of their vehicles to market in the next few years.
Transport presently contributes 19 per cent to Australia’s total emissions, a share that is growing in absolute and percentage terms[vii]. It is crucial that this be addressed to de-carbonise the economy. Moving to EVs need not wait until electricity is decarbonised: the facts are clear that the sooner we move to EVs the sooner environmental benefits are achieved.