What is a fuel-cell vehicle?

Land Rover has recently revealed it plans to bring hydrogen fuel-cell vehicles (FCEVs) to market by 2025, and companies like Hyundai and Toyota have been quietly working away on cars like the Hyundai Nexo and the Toyota Mirai over many years.

But fuel-cell technology remains a mystery to many car enthusiasts. How does it work, what are the benefits, what are the pitfalls, and will there ever be a time when fuel-cell vehicles are as common as internal-combustion vehicles?

The fuel-cell electric vehicle (FCV) is at its most basic level an electric vehicle (EV). It has at least one electric motor powering the drive wheels. Like a battery-electric vehicle, it also has a big-ass battery – most likely a lithium-ion job, although the Toyota Mirai makes do with Toyota’s favourite battery technology, nickel-metal hydride.

The battery may not be as large in capacity as the battery of a pure-electric vehicle, due to the juxtaposition of packaging and energy density. An FCEV doesn’t need to be “all ate up with” battery pack if some of the energy needed for a practical range can be stored in a higher density, more compact receptacle such as two to four gas tanks.

While the drive (torque) for the powertrain is converted from electrical energy, that electricity can be supplied either from the battery itself, or from what’s called a fuel-cell stack, which can also recharge the battery while the car is on the move.

Simple answer is it’s a stack of fuel cells. A fuel-cell is a kind of battery, but with the fuel (hydrogen) pumped into the fuel-cell to create an electric charge dynamically. A battery, in contrast, is self-contained, with all the materials necessary to produce electric current already present.

By itself a single fuel-cell typically holds less than one volt of electricity, which isn’t even enough to recharge the battery in a wristwatch. But ‘stack’ the cells together in one big array and the combined output can be enough to drive a vehicle.

The Toyota Mirai’s fuel-cell stack is rated at 650 volts and the stack generates 114kW, which is one kiloWatt more than the electric motor can use.

Electricity is defined as the flow of electrons through a conductive material. The trick with a fuel-cell is to liberate an electron from each hydrogen atom and collect those electrons as electric charge that can be stored in a battery or used immediately to drive the car’s electric motor.

Hydrogen is the commonly preferred fuel for FCEVs because it combines with oxygen to form water molecules, which are harmless to the environment.

Fuel-cells take hydrogen atoms, rip off an electron in a catalytic process and send the hydrogen on its way as an ion.

The very definition of an ion is a stable atom (hydrogen, in this case) that has given up an electron. This process takes place at the fuel-cell’s anode, one of the fuel-cell’s three basic components.

The second basic component of the fuel-cell is the electrolyte, which is a material that allows ions to pass through, but not electrons. Trapped by the electrolyte, the electron has nowhere to go other than into a conductive material as electric current.

Meanwhile, the ion has passed through the electrolyte boundary, meeting with oxygen molecules at the cathode, the third component of the fuel-cell. Here, another reaction takes place, with hydrogen ions combining readily with oxygen to form water – a non-toxic ‘waste’ material that’s emitted from the car.

The oxygen molecules are freely available in the air we breathe, so no special process is required to supply oxygen to the fuel-cell stack, other than a compressor to deliver the air to the cathode.

An FCEV offers key benefits for everyday use and the environment. As it’s only emitting water, it’s far and away a better choice for personal transport than internal-combustion cars, which will always be saddled with CO2 and other emissions that are collectively harmful for the environment.

FCEVs can provide a longer range than battery-electric vehicles, more often than not, so you will be able to undertake that journey to a holiday destination with kids and recreational gear on board without worrying you might be stranded along the way.

And unlike battery-electric vehicles, FCEVs don’t leave you standing around for hours waiting for the battery to recharge.

At present there are very few places where you can fill the car’s tank(s) with hydrogen, but if a hydrogen bowser should ever come to be as commonplace as LPG, diesel or petrol, the convenience factor will rocket away, leaving electric vehicles wrong-footed.

It takes three to five minutes to refill an FCEV with hydrogen – about the same time as it would take to refill a petrol or diesel car.

Hydrogen fuelling stations are already rolling out in large numbers across the USA and Europe, but they’re very rare in Australia for the moment.

Hydrogen has a bad name for its highly combustible nature, as we know from the airship, the Hindenburg, but unlike fossil fuels in a liquid state, hydrogen’s lighter weight ensures that in the very unlikely event it should explode, the flame front will shoot straight up into the air, mostly away from occupants of the vehicle. To that extent, it’s a safer fuel than petrol or diesel.

If you thought EVs were expensive, prepare yourself for the sticker shock of buying an FCEV. They are bound up with the expensive lithium-ion battery like a battery-electric vehicle, but there’s the rare-earth metals of the fuel-cell stack on top of that cost. But manufacturers are working hard to find cheaper materials for the fuel cells.

Environmentally, like EVs and in fact any new car, the FCEV results in a lot of CO2 emissions during the manufacturing process, and each car will likely take tens of thousands of kilometres and years on the road before it pays back the CO2 ‘debt’ and crosses over into ‘carbon neutral’ territory.

As already mentioned, there’s practically nowhere in Australia where you can pull in and refuel your FCEV. That is likely to change over time, but it has to be driven by automotive brands like Hyundai and Toyota before it’s likely to become reality here.

Hydrogen isn’t an easy element to produce on an industrial scale or transport to remote locations, although different organisations are finding new ways of overcoming those hurdles.

Hydrogen atom enters the fuel-cell and reacts with the anode,
Reaction converts the atom to an ion by removing its negatively-charged electron,
Ion passes safely through the electrolyte, which is a barrier to the electron,
The electron is transferred by a conductive wire to a storage battery,
The ion reacts with the cathode and bonds with oxygen to form harmless water molecule.

People know it as the most common element in the universe, but hydrogen is hard to capture in its natural state. It’s a very light element, so you won’t find it floating around freely at sea level.

But it’s the essential ‘fuel’ for a fuel-cell vehicle.

There are many ways in which hydrogen can be produced in commercial quantities, but many of those methods demand more energy than the energy produced by the hydrogen in a fuel-cell stack.

Some methods produce hydrogen as a by-product of an industrial process, which is fine as long as you were using the energy for some purpose other than just producing hydrogen, and provided also that you’re not producing mega-tonnes of carbon dioxide (CO2) as well. Sadly, that’s usually not the case.

The ideal way to produce hydrogen is by a process named electrolysis. Only electrolysis – currently providing just four per cent of global hydrogen production – holds out any real hope for clean, sustainable hydrogen production.

Hydrogen hived off from fossil fuels usually leaves behind carbon dioxide (CO2), which is one greenhouse gas the world doesn’t need in higher quantities.

With electrolysis, however, the only by-product from the process – splitting water molecules into the constituent atoms – is oxygen. Oxygen is not a greenhouse gas and we need it to breathe anyway, so all good...

The question arising though, is how to produce industrial quantities of hydrogen from water without using megaWatts of electrical energy which has been traditionally supplied in Australia by coal-fired power stations.

There is a way, and it’s not complex, but it could be expensive. Somehow, the trick would be placing a large water supply near a sustainable energy source, such as a large photo-voltaic (solar power) array. The electric power converted from the sun would supply enough energy to split the hydrogen atoms from the water molecules, leaving just oxygen behind.

As if producing hydrogen isn’t hard enough, the little matter of transporting it to places where it can be used effectively is at least as challenging. It’s a sneaky gas, escaping at every opportunity, but one way to keep it stored is by chilling and compressing it.

Another way to transport it is by combining it in a stable chemical like ammonia, a process that the CSIRO has been developing in recent times.

As a planet, we’re still lagging behind where we should be, weaning people off internal-combustion vehicles and fossil fuels.

Electric vehicles are beginning to gain ground, as they achieve higher levels of practicality, but it’s expected internal-combustion engines will carry on for some years yet, albeit increasingly so in hybrid and plug-in hybrid applications.

The projected timeframe for fuel-cell vehicles is even further in the future. They’re here right now, but not in truly viable forms.

The price has to come down, the refuelling infrastructure has to improve drastically, and the nexus of those two trends must occur before development of electric vehicles and the rollout of charging stations proceeds too far and too fast for FCEVs to reel in that head start.