While an autonomous car uses more electricity due to all the electronic components, its economical driving style may still be more environmentally friendly. That is the conclusion of American research into the life cycle of autonomous vehicles.

What is the environmental impact of the autonomous car? Are there benefits, or do all those extra components pose an extra burden? Research by the University of Michigan and the Ford motor company has mapped out the environmental burden of autonomous vehicles by using a life cycle analysis.

There are a number of clearly negative effects when cars become autonomous:

  • Extra components are needed, which increase the weight of the car
  • Those extra components use extra power
  • Sensors are needed, for example a lidar on the roof, which has a negative effect on aerodynamics
  • Data must be exchanged, which once again requires power

The computer required for autonomous driving has the greatest effect of all, as it contributes most to the extra weight of the car and also uses the most power. In turn, this extra weight, the disrupted aerodynamics and the external communication are the main factors in the extra energy consumption.


The combustion engine loses out

The extra energy consumption depends very much on the type of autonomous system applied. It can vary from 2.8 to 4% in smaller systems, and can increase up to 20% in larger systems. The distinction lies mainly in the use of radar and the laser scanner on the car roof (lidar).

The researchers compared the negative effects for both a combustion engine and a fully electric vehicle. The combustion engine then clearly loses out, as the generation of electricity is marked by a mere 20% efficiency. The combustion engine was also disadvantaged in propulsion of the extra weight. In the case of the electric car, the way in which the power is produced in order to charge the battery, is what counts. All in all, the environmental burden of the autonomous system for an electric vehicle is half that for a combustion engine.
 

The effect of components of the autonomous system from left to right: on the weight, the direct energy consumption and the energy consumption of the car as a whole.


Eco-driving

In autonomous driving, the researchers assumed a system in which the driver leaves all driving tasks to the car, until the point in time that the driver resumes control (so-called level 4 autonomy). The driving style of the autonomous car can offer a number of environmental benefits:

  • Eco-friendly driving, i.e. gradual acceleration, coasting, no extreme braking when not necessary, etc.
  • Platooning, i.e. driving in close succession, resulting in less air resistance between the cars
  • More gradual merging (gearing of cars on the road, removing the need for the merging car to brake)
     
The environmental balance for an electric car (BEV) with an autonomous system (CAV). End of life (EOL) refers to the environmental costs of waste processing.

These driving style improvements have such a considerable impact that this alone accounts for autonomous driving having a more favourable environmental burden, at least when using a smaller system (computer, radar, lidar, communication) for autonomous driving. However, this driving style improvement must be part of the algorithm with which the autonomous car drives. The benefit for the user lies in the costs saved. If the improved driving style is not deployed, an autonomous car will always have a greater environmental burden. When larger systems for autonomous driving are used, the environmental impact is always negative.

Opening photo: Photo University of Michigan.

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