Gasoline Or Batteries For Robo-taxis? It Depends.

It seems inevitable that whenever automated cars are referenced, they're assumed to be electric vehicles, i.e. EV-AV. This fits the image of a utopian future of ubiquitous mobility which doesn't pump out tailpipe emissions and hasten the end of human civilization.

From an engineering perspective, there are some specific advantages offered by electric drive, particularly the ability to directly control individual wheel motors for acceleration and braking. If you're starting from scratch and building your own vehicle, basic electric platforms are readily available; you don't have to work with a traditional car manufacturer. This is why we've seen the rise of low speed automated shuttles based on simple but effective electric platforms, as well as custom-built parcel delivery bots.

For robo-taxis in particular, when it comes to scaling up mobility services, the choice of vehicle platform must include a wide array of factors. Customers will typically value being served by zero emission vehicles, and this can be important to the mobility provider's relationship with the host city (especially if the city is leveling fees based on factors including emissions, as I wrote about recently).

One dominant factor in deploying robo-taxi services is the duty cycle of the vehicles, specifically how the energy source affects the availability of the vehicle to make money for the operator. What is up-time versus down- time with regard to propulsion? The tried and true choice for taxis is gasoline, with many taxi and ride-hailing drivers choosing hybrids to enhance fuel economy as far as possible while ensuring the ability to re-fuel during a quick stop at a gas station. Contrast this with using an EV, whose range and re-charging time could make or break a robo-taxi service in which the vehicles need to be in nearly constant operation.

What types of robo-taxis are on the road now? In 2018 Waymo placed an order for 20,000 Jaguar I-Pace all-electric vehicles. But they started with and are still using Chrysler Pacifica hybrid minivans which don't require charging. Cruise is using Chevy Bolts for their developmental fleet but are not yet offering services and trying to make a profit purely via mobility services. The Lyft-Aptiv partnership operating since 2018 in Las Vegas has logged more than 50,000 individual trips with its fleet of 30 BMW 5-Series sedans, powered by internal combustion. The cars, which have an automated driving stack and enhanced electrical system provided by Aptiv, can be hailed by any Lyft user in Las Vegas. This is a revenue producing service, therefore duty cycle is key.

In an ideal world, a vehicle which is not moving would not consume energy. From the early days of the gasoline-powered automobile, the car has consumed energy during an entire trip, whether idling in traffic or moving. Electric drivetrains offer the advantage of burning no energy when not moving, but internal combustion engines (ICE) now have start-stop technology which reduces or eliminates energy use when stopped (depending on whether the humans on board are wanting air conditioning).

You can see that the nature of use determines the choice of powertrain. If you're moving goods there may or may not be a time component. If time is not critical, charging time may be less of an issue.

As with virtually all things engineering, there are trade-offs between the various factors. As I've said, the biggest negative for EV's is charging time and range. What about an electric vehicle that doesn't depend on a battery? Recently Hyundai Executive Vice Chairman Chung Euisun commented that since self-driving vehicles consume significant amounts of power for computing, Hyundai's hydrogen-powered cars, which can go more than 600 kilometers on a single charge, would be a great match since these fuel cell electric vehicles can travel longer range without the negatives of charging time. "Self-driving cars will be interlinked to development of hydrogen-powered cars. Hydrogen vehicles are a good platform for autonomous cars," he said. Hydrogen still has significant challenges in terms of fueling infrastructure, as well as energy costs to produce and distribute it. This makes it a potentially better fit for geo-fenced fleet services than privately-owned vehicles which roam freely and therefore need a far-flung re-fueling infrastructure.

To sum up, no matter which robo-taxi development programs or customer trials you look at, their choice of vehicle does not necessarily represent the type of powertrain that will be used at scale in the future. The key is high up-time. Because EV technology is evolving rapidly as the auto industry moves strongly in this direction, EV's will likely become increasingly attractive for these mobility services. But for companies that are going for profit in the first wave, ICE is still a strong contender. But to what degree? I'd be pleased to hear from my more knowledgeable colleagues and may provide an update based on that discussion.