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Self-driving cars could save energy

Posted by Alex Barrett on 23 November 2016 at 11:30 am

In 2014 transport accounted for 38% of the UK’s final energy consumption [1]. The majority of this was due to the use of road vehicles, both for private transport and for business. Cars account for a considerable fraction of the greenhouse gasses we emit.

As roads get more congested the fuel efficiency of cars drops as they idle in heavy traffic, requiring more energy and emitting more pollutants. However new developments in transport technology could fundamentally change the way we use cars, and result in a considerable reduction in the amount of energy they require.

Self-driving cars have been in development for some time, with companies like Google [2] and Tesla Motors [3, 4] working on systems that will let an on-board computer do the driving, without input from a human. Self-driving cars are being trialled on American roads, and there are plans to test autonomous lorries on UK motorways in the near future. [5].

Less idling, less congestion

Much of the inefficiency associated with cars comes from the way in which they are driven, and the traffic conditions on roads. In a perfect world traffic would flow perfectly, with cars moving at their most efficient speeds for the majority of their journey. Anyone who has ever been in a car knows that this is far from the case. Cars spend a lot of time braking and accelerating, or idling in traffic on city streets or congested motorways. Cars are driven in circles while drivers try to find a parking space, and all of this requires more fuel and emits more exhaust.

Platoons of lorries

Once all vehicles become interconnected this all changes. Traffic lights will tell a car that they are about to change, cars will tell the vehicles behind them when they spot a parking space, and computers will control traffic flow along roads so that as many cars as possible maintain a constant speed. It has been estimated that these small changes could provide fuel savings of as much as 15 percent [6, 7]. For heavy goods vehicles it will be possible to create “platoons” of lorries where numerous vehicles drive in close formation to reduce drag, and so improve their fuel efficiency. This isn’t practical with human drivers, as driving close enough to the vehicle in front to gain an aerodynamic advantage is difficult and dangerous. If the lorries are constantly communicating their positions then a computer can safely drive them in such a formation.

Increased use of renewables

Many self-driving cars will also use electric and hybrid fuel systems. A switch to electrical cars has many benefits. Cars will be powered from the grid, rather than by burning their own fuel supplies. This means that pollutant emissions will not be as spread out along our roads, but concentrated at a few power stations where they can be more effectively controlled. At present renewable sources hardly contribute to transport, but this could rapidly change once electric vehicles become more convenient than a diesel fuelled alternative.

Electric car batteries can actually help to balance electricity supply from intermittent sources like wind and solar. Batteries can be charged during periods when electricity is plentiful, and store it for use later on. This process can be done with privately owned cars, but will be far more efficient if the owners of large fleets of robotic taxis coordinate with the electricity suppliers to charge their vehicles at the optimum times.

Many of these developments may seem a long way off, but some are already on the horizon. Many cars already have cruise control systems that improve their fuel efficiency, or an “Eco” button which can be used to make them drive in a more energy efficient fashion. If you have these features in your vehicle then t is well worth using them to reduce the amount of energy you use on transportation.

References

  1. UK energy consumption statistics (links to pdf)
  2. Google self-driving car project
  3. Tesla Motors
  4. Clean Technica
  5. BBC news
  6. Ensia.com
  7. Brown, A., Gonder, J., & Repac, B. (2014). Road Vehicle Automation. In G. Meyer & S. Beiker (Eds.), (pp. 137–153). Cham: Springer International Publishing.

Image Credit: Roman Boed via Flickr

 

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