Hydrogen fuel cell cars: How do they work?

Libby Plummer Read more August 4, 2017

The race is on to replace the current generation of gas-guzzling vehicles, with the UK government recently pledging to halt the sale of all new petrol and diesel cars by 2040.

While plug-in electric cars and hybrid vehicles are in the running as their replacements, many believe the future lies in cars powered by hydrogen fuel cells. And a number of auto firms have already made inroads in this area.

What is a fuel cell?

Fuel cells generate electricity from a chemical reaction and were first developed way back in the 1830s. They were used commercially by NASA more than a century later to generate power for satellites and space capsules.

Unlike conventional batteries, which rely on chemicals stored within the cell to maintain power, fuel cells use a constant flow of fuel into the cell. Most fuel cells use hydrogen and oxygen.

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A single fuel cell has about the same amount of power as a single-cell dry battery, which can’t even power a laptop. In order to power cars, fuel cells are stacked and linked together.

Rather than relying on petrol or diesel, Fuel Cell Vehicles (FCVs) combine hydrogen with oxygen in order to produce electricity to drive the motor.

How do fuel cells work?

Fuel cell-powered cars, like Toyota’s Mirai or the Honda Clarity FCV, combine the features of an internal-combustion engine-powered and battery-powered car. Power is made from fuel in a tank, but the fuel is hydrogen instead of liquid gasoline or diesel. Typical engines burn fuel, though, while fuel cells chemically fuse with oxygen in the air, producing water — the only waste product resulting from this process.

There are different kinds of fuel cells but those commonly seen powering cars are called polymer exchange membrane, or proton exchange membrane. They have a similar structure to a battery with a positive terminal, negative terminal and an electrolyte separating the two.

So, like a rechargeable battery, as long as the fuel cell has a power source, it can run. The power for these comes from an electrochemical reaction between hydrogen and oxygen, which is always available in the air. As long as hydrogen is available, the cell can run.

Why are fuel cells good for cars?

Unlike combustion engines, which release harmful carbon dioxide into the atmosphere, fuel cells only produce water and heat as byproducts, making them more environmentally sound.

They also produce less sound than those running on engines, meaning naps in the passenger seat can be much more peaceful.

What’s the catch?

While fuel cells themselves don’t produce any carbon dioxide, the production of the hydrogen used can cause pollution as most of it is currently produced using fossil fuels, giving off carbon dioxide.

Hydrogen can also be produced by the electrolysis of water and, while this process can be fuelled by renewable energy sources, such as wind power, most hydrogen is still made using pesky fossil fuels.

Also, habits die hard. Society is used to producing cars with gasoline engines, meaning they’re generally cheaper, better tested and more reliable. It’s also much easier to repair your petrol-fuelled car — how many garages have you seen advertising discounts on fuel cell check-ups?