We've certainly heard a lot less from the car industry about hydrogen power in recent times as makers scramble to compete with new products in the here-and-now world of plug-in powerplants.
Hydrogen is still happening. It's a massive step beyond plug-in technology because it requires completely new technology and new infrastructure, but many of the world's carmakers are still investing heavily in the concept.
Toyota is about to launch what is arguably the world's first production hydrogen fuel-cell car, the FCV.
The Honda FCX Clarity, which was launched in 2008, will cease production this year.
Toyota powers ahead on hydrogen
Just as it did with Prius, the Japanese maker has persisted with what seemed an impossible task and taken a huge step towards making an alternative fuel viable for the mass market.
It's "arguably" the first because many makers have had hydrogen fuel-cell cars on lease programmes in limited numbers for many years (Toyota included). The best-known is the Honda FCX Clarity, which was launched in 2008 and will cease production this year.
But after seven years on the market, there are still fewer than 50 on the road in the US, Japan and Europe, and it was never offered for outright purchase. Honda claims to have been first to market with a functional hydrogen fuel-cell car, the original FCX of 2002.
Hyundai has just launched a hydrogen version of the Tucson/ix35, which is also only available on lease. Like the Honda, its primary market is the US and also like the Honda, the monthly lease price includes all the fuel you can drink - from the handful of hydrogen filling stations, most of which are in California.
Hyundai claims that this is the world's first "series production" fuel-cell car - reasoning that it's built on the same production line as regular ix35 models, although initial production is capped at 1000 units.
Hyundai has just launched a hydrogen version of the Tucson/ix35, which is also only available on lease.
Mercedes-Benz, too, has a model called F-Cell available in Europe. It's a hydrogen-powered version of the previous-generation B-class, out on limited lease programmes.
So what makes the Toyota FCV different? Toyota is pitching it as a bespoke production model from the start and it's thought that customers will be able to buy one.
Toyota claims to have been perfecting the FCV for over a decade. It says that the cost of the hardware in the car has been reduced by 95 per cent compared with early prototypes and that the car will offer Prius-like performance: 0-100km/h in under 10 seconds.
Range will be more than 600km.
The FCV has stirred Honda into creating a rival, building on the technology of the FCX Clarity.
The FCEV concept previews this new model, which Honda claims is 60 per cent more efficient than the FCX and good for a range of 500km. Expect to see it next year.
Toyota's determination to establish FCV as a viable car choice is reflected in its partnership with the University of California's Advanced Power and Energy Program (APEP), with a project which aims to address one of the biggest problems with hydrogen power: the need for a dedicated refuelling infrastructure.
Toyota and APEP have mapped out a variety of locations for new filling stations in California (although the car will also be sold in Japan and Europe) and the government has committed funds to build 20 new stations by the end of next year, 40 by 2016 and as many as 100 by 2024.
The APEP calculates that just 70 stations could serve 10,000 hydrogen cars, with owners no more than six minutes away from a refuelling station.
There are fewer than 300 hydrogen stations in operation worldwide. Countries that have committed to the concept of building "hydrogen highways" with networks of filling stations include Japan, Germany, Italy, Norway, Sweden, Denmark, Spain and of course the US.
Why do so many carmakers and governments see potential in hydrogen cars? Because hydrogen is clean and because it's an energy-dense fuel rather than simply stored power (as in a battery), a tankful will get you a similar distance to a petrol-powered car. So no anxiety about running out of gas and no long wait to power-up: Toyota claims the FCV can be refuelled in three minutes.
A hydrogen car is ultimately an electric car, except that the powertrain creates its own electricity as you drive. Hydrogen is forced into a fuel cell and a chemical reaction creates electricity, with water as the byproduct. Fuel cells are relatively light and small, hence the term "fuel cell stack": many are grouped together to generate sufficient power for a vehicle.
Downsides?
The cost of designing bespoke hydrogen-powered cars, that infrastructure and also the argument put forward by sceptics that this fuel is not as clean as it seems. Hydrogen can be created by electrolysis, but that requires power - which comes primarily from burning fossil fuel in some countries (a similar argument can be applied to plug-in electric cars).
Hydrogen can also be created from natural gas - but that's a fossil fuel.
It's true that hydrogen fuel-cell cars are decades away from becoming truly mainstream. But remember: 30 years ago the thought that your family car could be plugged in and recharged each night would have seemed like fantasy to most people.
