The environmental impact of electric vehicles
Vehicle electrification offers a huge opportunity for innovation in everything from transport choices and car design to smart infrastructure and business models. The rapid development of the sector also promises plenty of opportunities to build multiple iterations of enabling products as the underlying technology evolves. What isn’t entirely clear is whether a wholesale shift to electric vehicles (EV) now will, in all cases, be good for the environment. Understanding the issues involved, and hence the steps that designers can take to further reduce EV’s climate impact, demands a nuanced comprehension of the EV ecosystem and how it is likely to develop over time. The good news, though, is that in the mid-term, the shift to EVs should benefit the environment.
The challenges of assessing the environmental impact of a shift to EVs include 1) taking a holistic view of the situation, and 2) finding valid comparisons between EVs and internal combustion engine (ICE) cars.
To address the first challenge, here’s a simple winners-and-losers example of the possible effect of EVs on the environment. Using regenerative braking should reduce the amount of polluting brake dust an EV produces, which is good for the environment, but the high torque of EV motors may cause more rapid tyre wear that throws off more particulates, which is bad for the environment. So, are we for or against EVs based on this analysis?
On the second issue of finding fair comparators with which to assess an EV’s impact on greenhouse gas emissions, we can look at the way that solar energy, either locked up in hydrocarbon fuels or produced by photovoltaic processes, is exploited in both the EV and ICE. We find that an EV converts, on average, 77% of the energy in its battery into motion, while an ICE car only converts between 12% to 30% of the energy in its fuel into motion.
The EV is more efficient at converting the energy it is provided with than the ICE, which is great, but if that energy comes from a hydrocarbon-powered generator instead, then its climate superiority is less obvious.
An analysis of these trade-offs by Carbon Brief finds that EVs driven in Europe have considerably lower emissions over their lifetime than ICE equivalents and that the climate benefits of EVs are much smaller in countries where grid electricity is generated from coal. In this case, the emissions of EVs are more like those of the most efficient hybrid electric vehicles. The analysis goes on to argue that the climate advantages of EVs will grow as countries reduce the amount of hydrocarbon fuel they use to generate grid electricity.
A wider analysis of EVs and ICE vehicles breaks down the constituents of a vehicle’s emission into four categories: exhaust emissions (for ICE cars); emissions from the fuel cycle, including in oil production, transport, refining, and electricity generation; emissions from manufacturing the non-battery components of the vehicle; and emissions from manufacturing the battery.
If we say that the energy used to make the non-battery parts of an EV and ICE car are roughly equivalent, then the spotlight falls upon battery manufacturing. This is energy intensive since it involves mining, transporting, and processing raw materials, often extracted in unsustainable and polluting ways, and then forming them into highly sophisticated battery packs. If this is done in a country where electricity is generated from hydrocarbon sources, the resultant vehicle will carry a ‘carbon deficit’ that will take a long time to pay off through the reduced carbon impact of the vehicle in use. Again, it’s hard to develop true comparators, but one analysis suggests that the average driver would take three to four years to ‘pay down’ the carbon cost of building the battery pack. If you’re one of those people who likes a new car every three years, choosing an EV each time could just be increasing your carbon footprint.
The good news for electronics designers is that it is now widely understood how important it is to use the energy that EV batteries store carefully. For example, sophisticated battery management systems can help extend the life of battery packs, and hence reduce the lifetime climate impact of an EV. They do this by protecting batteries from excessive charging and discharging, balancing the charge between cells so that they wear evenly, and managing the way that they are heated in cold weather and cooled under heavy load to ensure optimal performance.
Vehicle designers are also moving to higher voltage battery architectures in order to reduce I2R losses, and this demands innovations in the DC/DC converters that turn the battery’s voltage (of up to 800V in some cases) into the 12V or 48V needed to drive the auxiliary electronics in the car.
Traction inverters, which convert the battery’s DC into AC to drive the motor(s), are being updated with silicon carbide semiconductors that can withstand higher voltages and temperatures. They also switch more quickly than silicon equivalents, boosting conversion efficiency while allowing denser circuits with lower cooling needs. Onboard chargers are benefiting in similar ways. They are also being updated to allow vehicle-to-grid (V2G) applications whose uptake will rely, in part, upon the round-trip efficiency with which energy can be stored by the battery and then fed back into the grid.
It turns out that the environmental impact of EVs can only be properly assessed in the widest possible context. For example, city dwellers may like the reduction in pollution that EVs bring, but no one is winning if it is just being shifted to the area around a coal-fired power plant. On the other hand, concerns about climate change and rising interest in EVs have prompted people to rethink their travel habits. We see this in the way that people are replacing car, bus, and rail journeys with trips on electric scooters, bicycles, and mopeds. There’s also an argument to be made that widespread uptake of V2G strategies will reduce the climate impact of travel by allowing greater use of renewables, as well as avoiding the need to build new generating capacity – whose construction alone would have its own carbon impact.
Although the environmental advantages of EVs are open to nuanced debate at the moment, the direction of travel is clear. We need to decarbonize our transport and shifting to EVs is one important way to do it. Electronics engineers can play a significant role in making it happen by taking advantage of the latest technologies, and the opportunities for multiple iterations that the market currently allows, to make a difference.
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Michael Pochmann
Michael Pochmann is Segment Manager Automotive EMEA at Avnet Silica. With over 20 years’ experience,...
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