What are the latest developments in low carbon vehicles?

Every year I try to get to the Cenex Low Carbon Vehicles show at Millbrook. Now ten years old, this exhibition gives me a chance to see where we are up to on our journey to zero-carbon transportation. You get a very good idea of the key issues of the moment. Where progress is rapid, and where progress is stuttering. It includes a conference, a technology and commercial exhibition, and an opportunity to try out some of the vehicles on the Millbrook test tracks.

This year I was able to get a train to Milton Keynes and pick up a shuttle bus to Millbrook. More pleasant than spending time on Britain’s motorways, and more in keeping with the low-carbon transportation theme.

The overwhelming impression was of a maturing sector. Fewer radical breakthroughs, at least from the consumer perspective, and more solving problems in a drive for commercialisation. That fits with a recent survey showing that 40% of European drivers expect their next vehicle to be an electric car.

Electric cars are no longer quirky; they are mainstream. The target market is no longer just environmentally conscious early adopters.

You can see this in the central exhibit in the showcase; a cutaway shell of the new Aston Martin Rapide E. An electric supercar. Parked outside the exhibition, the Jaguar Land Rover i-Pace SUV attracted a lot of interest. Both these cars show European manufacturers taking on the Tesla to attract performance enthusiasts.

Batteries and range

But expensive performance cars are not everyday transport. To get mainstream acceptance, the industry has to solve two problems; range and charging time. A lot of the technology exhibition was around batteries.

The first stand I visited was ABB. They were showing 350 kW chargers that will give an electric car a 200 km range in 8 minutes. These are designed for the Ionity network, a collaboration of German car manufacturers aiming to make long-distance travel with EV’s a practical reality. They will be installed on the motorway network where fast charging brings greatest benefits. They are unlikely to be used in cities and shopping malls, as people generally spend a lot more time there and you can tolerate slower charging.

The superfast chargers need special equipment and infrastructure. 50 kW and 100 kW chargers drop into the current grid. 350 kW chargers need their own substation.

As a chemist, my first thought was just how much and how fast energy was being stuffed into an electrochemical process. How hot would things get, and how dangerous could it be? I was not surprised to find that the cables from the charger to the vehicle needed to be liquid cooled, as well as cooling the battery itself.

It is the battery that controls the rate of charging and not the charger. ABB said that there were no cars yet that could take that fast a charge, but the next generation of batteries would. Intrigued I asked several other battery and powertrain engineering companies what they made of the goal of a 200km charge in 8 minutes.

Most were sceptical. Hyperdrive Innovation said there was always a trade-off. Faster charging means higher temperatures and heavier buses to carry the current. You increase cost and weight and reduce battery life. Is it commercially viable?

Others suggested that new solid-state battery chemistries could operate at higher temperatures so needed less cooling. In principle, they can reach higher energy densities and are safer. But even here there are difficulties. If you use polymer separators, you can’t operate at such high temperatures, and if you use a garnet film made through chemical vapour deposition, the ohmic losses are higher, and the temperature goes up again.

Prof David Greenwood suggested that the currently favoured solution is to go to higher voltages to reduce charge and discharge currents. The Rapide E has an 800V battery.

Hydrogen has not gone away

Although most of the exhibition focus was on battery vehicles, and the problem of range and rapid charging, hydrogen has not disappeared. Using hydrogen in fuel cells to generate electricity is well established, and the Toyota Mirai is an example of a passenger car that runs on hydrogen, but the lack of infrastructure has been holding them back.

At LCV 2018 the real interest was in commercial vehicles that operate ‘back to base’ routes. Like buses and refuse collection trucks. Since these always come back to a depot, it simplifies and cuts the cost of providing the hydrogen gas supply. One of the vehicles on display was a hydrogen-powered bus with a range of 180 miles. That’s enough for reliable use in most cities.

The other advantage of ‘back to base’ vehicles is that you refuel them regularly. Hydrogen is the smallest gas molecule and can leak through the smallest gap. It is hard to contain in a lightweight pressure vessel.

One expert said, “the key problem with hydrogen in a private passenger car is that when you go on holiday and leave it in the airport car-park for two weeks, there will be no hydrogen left when you return”.

Connected Autonomous Vehicles

Autonomous vehicles were another focus of the event, with a showcase of research projects and smaller innovative companies.

One of the interesting exhibits was Streetdrone; a small electric vehicle designed as a platform for testing autonomous systems, hardware and software. Streetdrone believe there is a market for people who want to try out new ideas in vehicle autonomy

There are various levels of autonomy no automation at all (level 0) to vehicles that operate completely without human intervention, such as a robot taxi or delivery vehicle (level 5). The general view of the exhibitors is that we have all the systems for level 2. Things like smart cruise control that keeps you a defined distance from the vehicle in front, or automatic parking and lane changing.

Level 2 assumes that there is a driver, and they are paying attention to what is going on and can take control if necessary. I can see the value in that; it is an extension of the driver assistance tools now available in some passenger cars.

Level 4 is the target, where safety is always assured even if the driver’s attention is elsewhere.

Level 3 is the weird one, where the driver does not have to pay attention (they can be reading or watching a movie), but they have to take back control if there is a problem the system can’t handle. That sounds like a very bad idea to me. I am not sure I would want to be in ‘control’ of a vehicle that might suddenly dump control back into my lap when I was busy with something else. And I can’t see me being able to focus on the road and what is going on around me if I have nothing to do.

Key messages

The key messages I picked up:

• The focus in battery electric vehicles is solving the range/charging time challenge. We are not there yet, but we can see solutions.
• Hydrogen is a viable fuel for high usage ‘back to base’ vehicles like buses.
• Autonomous vehicles are definitely on the way, but there are some tricky steps from driver assistance to allowing the ‘driver’ to spend their journey time on other tasks.