These days when people talk about electric cars they are almost invariably referring to and thinking of battery electric vehicles, or BEVs.
These are the Tesla Model Y and their ilk we hear so much about. These are vehicles powered by at least one and as many as three electric motors fed by large onboard high-voltage batteries that are usually slung low between the axles.
They are recharged predominantly via the existing electricity grid that has long been established to power many facets of our lives.
But there is another form of electric vehicle that sources its electricity from hydrogen, the most common element in the universe.
Hydrogen is stored under high-pressure onboard as a highly compressed gas and is converted into electricity onboard within what’s called a fuel cell stack.
That electricity is used in exactly the same way as it is in a battery electric vehicle to power the e-motor (or motors) that drive the vehicle.
It also stores energy including regenerated electricity from braking in a high-voltage battery. BEVs also do this but use much larger battery packs.
Like BEVs, fuel cell electric vehicles (or FCEVs) release no harmful emissions into the environment, just water produced by electrolysis that exits via a tailpipe.
One of the great advantages of an FCEV compared to a BEV is that refuelling times for a hydrogen tank are roughly equivalent to that of filling a petrol tank. And the range they contain is also similar to a petrol-fuelled car.
That means it takes much less time than recharging the large battery in BEVs and an FCEV can go further on a tank. The downside is that unlike the electricity grid there is only tiny network of hydrogen refuellers in Australia.
That’s an obvious limitation for the take-up of FCEV by private vehicle buyers locally, as well as the fact only a couple of them are supplied to selected customers in Australia, being the Toyota Mirai and Hyundai Nexo.
Many more brands are investigating FCEV globally, but only in a couple of places such as Japan and South Korea are proper refuelling networks being established.
Toyota imported just 20 Mirais to Australia in 2021 as a test exercise. They were handed out on three-year/60,000km leases costing $1750 per month, or $63,000 all-up. After that the cars will have to be handed back.
Underneath the Mirai’s handsome exterior and well-appointed interior is a drivetrain totally alien to most of us.
It stores hydrogen in three tanks which feed a fuel cell stack located up-front under the bonnet where an internal combustion petrol or diesel engine would sit in an orthodox car.
The 128kW fuel cell stack sends electricity to a 134kW/300Nm e-motor located on the rear axle. The total range is claimed to be about 650km.
To drive the Mirai is pretty much like any other EV. It accelerates strongly and is quiet to sit in when rolling along. But when you’re running low on juice there’s no point pulling up at a petrol station or trying to plug in. They aren’t going to help.
That basic issue means widespread application of hydrogen is more likely to happen in commercial heavy and public transport before it expands to become a buying option for you and me.
Buses and trucks often run on set routes, many times returning to a central depot at the end of the day. A hydrogen refueller at a bus depot or on a popular heavy truck route such as the Hume Highway between Melbourne and Sydney makes a lot of sense.
Imagine the impact converting an inner-city bus or delivery van fleet from diesel to hydrogen would have on air cleanliness.
When fuel cell electric vehicles do eventually become part of the offer to private buyers, they are most likely to begin in heavy-duty 4x4s and utilities that are currently diesel-fuelled.
That’s because the bigger and heavier a battery electric vehicle is the bigger, heavier, more powerful and more expensive its battery pack becomes. That extra weight also restricts potential range and towing capabilities.
A fuel cell electric vehicle does not have that impediment. The stacks are not heavy, the batteries are not large and, as mentioned, the hydrogen tanks can be big enough to achieve a decent range.
That’s why Toyota has already dropped solid hints off-road icons like the LandCruiser will become FCEVs in the future. Land Rover is also developing a Defender FCEV.
Some brands are also playing mix and match, adding a plug-in battery to the FCEV set-up that can act as a range extender.
However, as a battery electric vehicle decreases in size, cost and weight so an FCEV’s advantage decreases. Small cars will long remain the preserve of battery electric technology.
Toyota has also taken its experimentation in another direction, advocating the use of hydrogen as a fuel in orthodox internal combustion engines.
Toyota global boss Akio Toyoda boss argues it’s a low-emissions solution (note not zero as it still produces NOx) that would ensure more than 100 years of ICE development has an ongoing purpose and many auto industry employees could stay in their jobs, rather than be turfed out if EV drivetrains take over completely.
One issue with this plan is efficiency. Estimates suggest only 30-40 percent of the energy in the hydrogen goes into moving an ICE car. That’s only a about half as efficient as an FCEV, which in turn is only about half as efficient as a BEV.
Then you start getting into bigger picture hydrogen challenges like storing it in useable quantities and how it has to be compressed at up to 700bar – 10,000psi in round figures – or refrigerating it to minus 253 degrees. That requires energy. It also has to be transported to refuelling sites. More energy costs.
And just as putting electricity in a battery electric vehicle that is produced by a coal-fired power station is of debatable environmental benefit, hydrogen production can vary from horribly dirty to every clean.
That’s why you’re seeing different forms of hydrogen production touted – be it blue or green. The latter is the cleanest and means it’s been refined using renewable energy.
So much to consider. Essentially, despite hydrogen’s appeal, there are enough hurdles to ensure we’re a long way from the mass adoption of FCEV tech for passenger vehicles in Australia.