Automotive: Should speed be limited to make electric vehicles more attractive?

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Electric vehicles travel long distances more slowly than internal combustion vehicles. Can reducing traffic speeds improve their attractiveness and moderate the rush to large batteries?

This article was not written by the editorial staff of La Dépêche du Midi, but taken from the partner site The Conversation.

Society is increasingly aware of the consequences of the intensive use of thermal vehicles, particularly as regards oil supply, climate change and air quality. To solve these problems, different strategies targeting mobility practices and transport offer need to be implemented.

As far as technological leverage is concerned, fleet electrification is an interesting prospect, because electric vehicles have several advantages over their thermal counterparts. However, their diffusion is associated with risks and limitations, in particular related to issues of range, speed of recharging and sizing of batteries and recharging stations.

In this context, I study here the consequences of a reduction in traffic speed to 110 km/h on the performance and attractiveness of electric vehicles (here referring only to fully electric vehicles, thus excluding hybrids). I build on my work analyzing the uptake of electric vehicles in the context of long-distance travel.

The electric vehicle: a zero-emission vehicle?

Electric vehicles are sometimes referred to as “zero emission” vehicles. This expression means that no pollutants are emitted to the exhaust during circulation.

This concept, on the other hand, excludes all indirect emissions, such as those associated with the production of electricity needed to recharge the battery, or even with the manufacturing and end-of-life treatment of the vehicle. The concept of “exhaust” emissions also excludes some pollutants linked to the use phase of the vehicle, in particular that caused by wear on the brakes, tires and road surface.

Despite these nuances, electric vehicles generally emit fewer pollutants than internal combustion vehicles. On the one hand, they emit fewer air pollutants during the use phase and thus reduce the damage caused to health, especially in densely populated areas.

On the other hand, even considering the entire life cycle (from procurement of materials to end of life), an electric car generates less greenhouse gases on average than its thermal counterparts. For example, an electric vehicle charged in France and traveling 225,000 km generates 74% less greenhouse gases than a petrol car.

Travel time, a major barrier to acceptability

In 2022, only 13% of new passenger car registrations in France were all-electric models.

Despite their advantages, EVs struggle to replace internal combustion vehicles, particularly as acceptability is limited by range and recharging time constraints for long-distance travel.

Let’s take the example of a vehicle with a battery with a capacity of 50 kWh (this energy corresponds to the “volume” of electrical energy it can store), used in a range of state of charge between 10 and 80%, and which can be recharged at a maximum of 100 kW (this power corresponds to the maximum “speed” at which the battery can be recharged; the average power of a recharge is generally lower than the maximum power, typically 82 kW for a vehicle that can be recharged at 10 0kW maximum). These characteristics correspond to those of a Peugeot e-208, representative of the average vehicle registered in 2021.

Based on the actual fuel consumption supplied by the manufacturer, the driver can make journeys at 130 km/h alternating between 55-minute traffic phases and 25-minute breaks to recharge.

Due to charging needs, electric vehicles therefore make long journeys at high speed much slower than internal combustion vehicles. By way of comparison, drivers of internal combustion vehicles who follow road safety recommendations travel at 130 km/h with a 20-minute break every 2 hours.

Improving the attractiveness of electric vehicles

To make EVs more attractive, journeys in an EV should be as long as in an ICE. Two strategies are then possible.

The first is to greatly increase the battery capacity and charging performance of electric vehicles. Batteries of the order of 110 kWh, rechargeable at about 320 kW peak, would be needed to carry out cycles of 2 hours of circulation at 130 km/h and a 20-minute break.

The second strategy is to reduce the speed of traffic on the motorway to the detriment of internal combustion vehicles. For electric vehicles, cycles of 2 hours of driving at 110 km/h and 20 minutes of rest would require 60 kWh batteries, rechargeable at around 170 kW peak.

On the highway, charging stations are mostly high-power terminals that enable fast charging. They are connected to the electricity grid via large switchboards which supply strong electric currents. These cabinets are more or less isolated from users, here they are hidden by black fences. ionization

These two scenarios pose different implementation challenges and risks.

The scenario where batteries are doubled in size does not seem feasible in the short term given industrial constraints, nor desirable in the long term.

First, this strategy would have a direct effect on the supply voltages of battery-producing materials. However, dependence on oil must not be replaced by dependence on lithium, cobalt or graphite, materials considered critical by the European Commission.

Furthermore, oversizing the batteries would increase the economic and environmental cost of the vehicles, while autonomy is only a constraint for long motorway journeys, which generally represent only a marginal part of the actual use of a vehicle.

The second scenario, involving the generalization of traffic to a maximum of 110 km/h, is technically feasible by 2030. First, it would be highly relevant to the attractiveness of electric vehicles and would limit the rush to high-capacity batteries.

Furthermore, it would reduce the need for charging infrastructure on highways, allowing for a reduction in spending and consumption of raw materials. In fact, the installation of a 150 kW ultra-fast charging station costs around 130,000 euros, of which 45,000 are subsidized with public funds, and its construction, including the electrical cabinet, requires around 1.2 tons of materials (according to the EVBox, ABB and Efacec product sheets).

Finally, this scenario is also recommended to limit greenhouse gas emissions or energy dependence on Russia.

A collective responsibility for the controlled development of electric vehicles

Limiting the maximum authorized speed on motorways and promoting the adoption of “energy-efficient” electric vehicles would make the electrification process more robust, but also more equitable.

For long-distance travel today, there are already large inequalities between the performance of various new electric vehicles. For example, more urban vehicles (like the Twingo ZE) don’t allow for long journeys. Additionally, a high-end vehicle (such as a Tesla Model S) is approximately 15% faster at completing a long journey on charges than a mid-range vehicle (such as the Peugeot e208).

This new form of travel-time inequality could be accentuated by the emergence of new vehicle models with high-capacity batteries on the one hand and an obsolete electric vehicle fleet on the other. Furthermore, this would constitute a dangerous form of obsolescence of old vehicles: new vehicles with ever higher performance will appear on the market, while the fleet will still include many older vehicles. The desire to renew one’s electric vehicle will therefore be exacerbated and lead to overconsumption, with the associated impacts.

Even if the electrification of vehicles is one of the levers for making mobility more sustainable, user practices and the transport system must adapt to the constraints of this process. Then there is a collective responsibility to be developed by all the actors: every user, builder and public decision-maker is called to contribute.

The temporary reduction in the speed of motorway traffic is a controversial measure. It therefore requires a personal commitment to adapt the way we move and travel, a political commitment to carry this project forward and ensure that speed limits are respected, as well as a duty of coherence with our European neighbors to harmonize regulatory speeds on motorways.

Similarly, limiting the maximum speeds achievable by vehicles would also reduce excesses and market more fuel-efficient vehicles.

Finally, the emergence of electric vehicles shows the need for a global vision to guide an environmental transition: betting on purely technological hopes risks not being enough to solve the great environmental challenges and also risks giving rise to new resilience problems and increasing the fragility of the most vulnerable.

Julien Baltazar, PhD student in mobility and environmental management, CentraleSupélec – University of Paris-Saclay

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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