Hydrogen Honda arrives in the UK
A fuel cell car claimed to be the world's first to come off a production line has come to the UK.
The Honda FCX Clarity uses hydrogen to generate electricity, which then powers the car.
The carmaker sees it as the future of motoring, insisting hydrogen is better than batteries that need to be very heavy to supply enough electricity.
But it is likely to be many years before the infrastructure is in place to make these cars practical.
As such, Honda's hydrogen car could be seen as a brave move; previous models made by other carmakers in the past, often as derivatives of conventional models, have not been put into production.
One of the big problems with electric cars is providing enough power to help a car accelerate up to a decent speed, while at the same time having enough capacity for a decent range.
Honda thinks the future development of batteries is limited, and that they will never be able to satisfy motorists wanting to use their cars for longer journeys.
But there is another way to power an electric car - hydrogen.
The car is still electric, in that it has an electric motor which turns the wheels.
The difference is in how the electricity for that motor is generated.
How it works
In cars with batteries, the electricity comes from the national grid, with owners plugging their cars in.
In a hydrogen fuel cell car, the power is stored in the form of gaseous hydrogen.
The gas - stored under pressure in a tank behind the rear seats - flows forward to the fuel cell.
In the Clarity, that sits between the front seats.
In the fuel cell a controlled reaction takes place between hydrogen and oxygen from the atmosphere.
That produces two things: water, which is the waste product and comes out of the exhaust, and electricity that is sent to the electric motor at the front of the car.
The big advantage, according to the car maker, is that hydrogen is a much more efficient store of energy than batteries - so the car can be used just the way you would a petrol or diesel version.
The Clarity, for example, has a top speed of 100mph (160km/h) and a range of 270 miles.
"Ever since the car has been around we've been dependent on fossil fuels," says Professor David Bailey from Coventry University Business School.
"What we need to do is to move on to electric power and in the long term, hydrogen.
"This is the seismic shift in terms of technologies under-pinning how we power our cars."
But he has a warning too.
"There's a long way to go yet because it's expensive, because consumers need to be educated, because the infrastructure needs to be put in place."
Hydrogen tanks can be filled much more quickly than batteries can be charged.
But filling up is still one of the things that are holding them back.
Honda's Clarity is in production in Japan, but is only being leased to customers - often government officials and celebrities - in that country and California.
They have the infrastructure in place for drivers to fill up with hydrogen - but in the UK such facilities are not widespread.
At the moment there are only about 10 places across the UK where you could fill up your hydrogen car
Honda admits it will be many years before a suitable network exists.