In today’s eco-conscious climate you’d be hard pressed to find a fleet manager who isn’t aware of alternative fuels.

Most are familiar with the concepts of hybrids and bio-fuels.

A number of publicly-funded fleets have seriously invested in electric vehicles and some drivers can fill up with bio-ethanol at their local supermarket.

But none of these technologies is completely green.

Some strains of bio-fuels take a considerable amount of resources and CO2 to process and produce; more than is actually saved in emissions.

Hybrid batteries are expensive to produce and have a limited lifespan.

Rechargeable plug-in hybrids are under development but who wants to wait three hours to charge up their car?

The Holy Grail for fleets is the emission-free vehicle, and the ultimate power source is hydrogen.

When chemically combined with oxygen, hydrogen produces electric power or can be used to run a combustion engine.

It emits only water as a result.

Though abundant as a natural gas it can be industrially created by electrolysis – splitting water molecules with electricity to produce hydrogen and oxygen.

The theory goes that if hydrogen can be created from a renewable source and used globally as an automotive fuel, carbon emissions become a thing of the past.

Potentially, hydrogen is the perfect green fuel.

Ambitious car manufacturers have been heralding the onset of the hydrogen age for decades, although the goal posts have been constantly shifting.

But as the global society increases its focus on the environment, the world’s car manufacturers have redoubled their efforts into developing hydrogen-powered vehicles.

Among a slew of vehicles making the leap from concept to production reality – albeit in very limited numbers – are the BMW Hydrogen 7 and the Honda FCX Clarity.

California dreaming

The FCX Clarity – being produced and leased to businesses in California – is powered by a hydrogen fuel cell.

Compressed hydrogen is stored in tanks and pumped through the fuel cell, which contains oxygen.

The two elements react to create electricity.

This powers an electric motor which runs the car.

The car has a range of more than 300 miles and a top speed of 100mph.

BMW’s Hydrogen 7 works along more familiar lines, using an internal combustion engine.

As with the FCX, liquid hydrogen is stored in tanks.

It is released along internal pipes, changing into a gas before it reaches the engine.

The hydrogen is injected into the engine, where it is mixed with air and ignited.

The car can also be run on conventional petrol, making it a hybrid.

John Kingston, environmental manager at Honda UK, says the Clarity represents the future.

“Without a doubt hydrogen is the way forward,” he says.

“We’ve been investing in this technology for 20 years and we have a commitment to it. It is the ultimate long-term fuel solution.”

So hydrogen technology is here. But it will still be some time before you can fill up your hydrogen car at your local garage.

“There’s definitely the potential for hydrogen motoring to happen,” says John Evans, technical manager at the Society of Motor Manufacturers and Traders, “but there are a lot of things to overcome.”

Currently most of the world’s hydrogen is collected from breaking down fossil fuels and reforming methane, with both methods generating CO2 – hardly a good start.

The efficiency of electrolysis is also under question, says Mr Evans.

“It takes about six to eight times more energy to make hydrogen than the energy you actually get back from it.”

Fuel cells are made of precious metals and are incredibly expensive to produce.

Refuelling network

Storing hydrogen is also a problem.

At the moment it is transported via lorry though manufacturers are working to develop lightweight high capacity storage tanks.

The most obvious barrier is the lack of refuelling infrastructure, which explains BMW’s decision to run their hydrogen model with a petrol tank.

However, manufacturers are optimistic that now that they have shown the way, a global infrastructure can be developed.

“Most educated guesses are at 18 years – by that time we hope to have a hydrogen filling network in place,” says Duncan Forrester, media relations manager at BMW UK.

In its most recent study the HyWays EU research project calculated that if €60 billion were to be invested into infrastructure over the next 20 years, around 16 million hydrogen vehicles could find their way on to Europe’s roads by 2030.

However, Jamie Beevor, data manager for transport at the Energy Saving Trust, says advances in electric vehicle technology could easily eclipse the green panacea that is hydrogen.

“Future energy for vehicles is likely to be a combination of the fuels and technologies available – there is unlikely to be a silver bullet,” he says.

“The widespread uptake of hydrogen-fuelled cars is still a long way off and with battery and electric vehicle technology rapidly progressing, battery electric vehicles could steal a march on hydrogen.”