Driverless cars spark fuel economy headache

Judging from General Motors’ test cars and Elon Musk’s predictions, the world is headed toward a future that’s both driverless and all-electric. In reality, autonomy and battery power could end up being at odds.

That’s because self-driving technology is a huge power drain. Some of today’s prototypes for fully autonomous systems consume 2kW to 4kW of electricity — the equivalent of having 50 to 100 laptops continuously running in the boot, according to BorgWarner. The supplier of vehicle propulsion systems expects the first autonomous cars — likely robo taxis that are constantly on the road — will be too energy-hungry to run on battery power alone.

In an industry where the number of LEDs in a brake light are scrutinised for their impact on fuel efficiency, processing data from laser, radar and camera sensors will be an enormous challenge for engineers trying to power vehicles efficiently. Car makers and their suppliers will also have to find ways to offset emissions produced by feeding the car’s increasingly intelligent brain.

“We’ve been battling all the time because the governments are always pushing for a few percent improvement every year,” Scott Gallett, vice president of marketing at BorgWarner, said of fuel-economy standards. “This just amplifies that challenge,” he said.

The autonomous features on a some cars use so much power that it makes meeting fuel economy and carbon emissions targets 5% to 10% harder, according to Chris Thomas, BorgWarner’s chief technology officer.

Those calculations are based on prototype cars with sensors rigged on the roof, and the power demands of electronics inside the car will inevitably fall as the technology improves. But even if chipmakers pull off promises to reduce power consumption by as much as 90%, car makers will still need to make fuel efficiency gains elsewhere to compensate for all that computing, Mr Thomas said. “They’re worried about one watt, and now you’re adding a couple thousand,” he said.

A fully autonomous small car like a Honda Jazz, for example, will get 54.6 miles to the gallon in 2025 in the best-case scenario, more than five miles below the US emissions target. A small pickup or SUV would be at 45.8 mpg, versus a target of 50. However, engineers don’t have much time to resolve this, as companies are planning to deploy their first fully self-driving cars in the next couple of years.


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