• HydroFlex was developed by Porterbrook and the University of Birmingham
• A prototype version of has been tested out in Long Marston, Warwickshire
• Its manufacturer now hopes to attract purchase orders from UK train operators  
• It is virtually silent, emits no greenhouse gases and water vapour is its exhaust

Britain looks set to return to the age of the steam train, with locomotives fuelled by Hydrogen.

These virtually silent marvels emit no greenhouse gases and produce water vapour as their only exhaust. 

A prototype version of the vehicle, dubbed HydroFlex, has been tested out in Long Marston, Warwickshire.

Carriage space in this proof-of-concept version is currently taken up with the equipment needed to power the train.

The firm behind its creation will now create a working version that has this installed beneath and on top of carriages, freeing up space for passengers.

It is not yet known when HydroFlex will go into full service, but its manufacturer hopes to attract purchase orders from train operators across the nation.

Up to 45lbs of hydrogen is stored in four high pressure fuel tanks. The fuel cell combines hydrogen fuel with oxygen from the atmosphere to form pure water and electricity. This electrical energy can be stored in two lithium ion battery packs

HOW DOES IT WORK? 

Up to 45lbs of hydrogen is stored in four high pressure fuel tanks.

The fuel cell combines hydrogen fuel with oxygen from the atmosphere to form pure water and electricity.

This electrical energy can be stored in two lithium ion battery packs.

Energy is used to power an electric motor and drive the train forward.

HydroFlex was developed by railway rolling stock lease firm Porterbrook, based in London, with the University of Birmingham (UoB).

Initial tests involved system checks of each piece of equipment separately and working together.

The technology has been added to existing Class 319 trains in the prototype version, but theoretically can be fitted to any train, old or new. 

This means that no new trains will have to be built to specifically incorporate the hydrogen drive system - meaning existing trains can be recycled, further conserving precious resources. 

The UK government is currently developing the infrastructure to get hydrogen from renewable energy such as windfarms, which would make it a completely green source of fuel in the future.

Dr Stuart Hillmansen, senior lecturer at UoB's Centre for Railway Research and Education, said: 'Our prototype shows how hydrogen powered technology can be incorporated within existing trains, without needing to modify the drivers' controls. 

'It's an exciting advance because it shows how this technology could be adopted into the mainline system to deliver emission-free public transport.'

Hydrogen fuel cells create electricity to power a battery and motor by mixing hydrogen and oxygen.

The only emissions are steam and water and excess energy is stored in ion lithium batteries on board the train.

However, their deployment on trains has been delayed because they are currently more expensive to build than their traditional fossil fuel counterparts.

Only two are currently in active service worldwide and both are in Germany. 

Hydrogen fuel cells are stored on the roof of the locomotive carriages on Germany's trains, but narrow tunnels and tight stations - many built by the Victorians - make that unfeasible on the UK's rail network.

Carriage space in this proof-of-concept version is currently taken up with the equipment needed to power the train

The firm behind its creation will now create a working version that has this installed beneath and on top of carriages, freeing up space for passengers

It is not yet known when HydroFlex will go into full service, but its manufacturer hopes to attract purchase orders from train operators across the nation

Porterbrook is not the only firm working on delivering hydrogen trains for use in the UK. 

More than 100 of the eco-friendly locomotives are currently thought to be in development by French firm Alstom, ahead of a roll-out in two years time.

The trains, which are virtually silent, have been dubbed 'Breeze' and can travel at speeds of up to 87 mph (140 km/h).

A fleet of electric trains built in 1988 by British Rail will be the first to undergo the conversion.

Alstom is working alongside Eversholt Rail on the initiative and unveiled a prototype earlier this year when it carried passengers in Germany.

The trains can run for around 620 miles (1,000km) on a single tank of hydrogen, similar to the range of diesel trains.

Alstom claims the trains will be operational by 2021 in some regions of the UK, but the race is on to beat them to this deadline.

HydroFlex was developed by railway rolling stock lease firm Porterbrook, based in London, with the University of Birmingham

The technology has been added to existing Class 319 trains in the prototype version, but theoretically can be fitted to any train, old or new. Initial tests involved system checks of each piece of equipment separately and working together

This means that no new trains will have to be built to specifically incorporate the hydrogen drive system - meaning existing trains can be recycled, further conserving precious resources

HOW DO HYDROGEN FUEL CELLS WORK?

Hydrogen fuel cells create electricity to power a battery and motor by mixing hydrogen and oxygen in specially treated plates, which are combined to form the fuel cell stack.

Fuel cell stacks and batteries have allowed engineers to significantly shrink these components to even fit neatly inside a family car, although they are also commonly used to fuel buses and other larger vehicles.

Oxygen is collected from the air through intakes, usually in the grille, and hydrogen is stored in aluminium-lined fuel tanks, which automatically seal in an accident to prevent leaks.

These ingredients are fused, releasing usable electricity and water as byproducts and making the technology one of the quietest and most environmentally friendly available.

Reducing the amount of platinum used in the stack has made fuel cells less expensive, but the use of the rare metal has restricted the spread of their use.

Recent research has suggested hydrogen fuel cell cars could one day challenge electric cars in the race for pollution-free roads, however - but only if more stations are built to fuel them.

Fuel cell cars can be refueled as quickly as gasoline-powered cars and can also travel further between fill-ups.

Fuelling stations cost up to £1.5 million ($2 million) to build, so companies have been reluctant to build them unless more fuel cell cars are on the road.

The U.S. Department of Energy lists just 34 public hydrogen fuelling stations in the country; all but three are in California. 

According to Information Trends, there were 6,475 FCV's worldwide at the end of 2017.

More than half were registered in California, which puts the U.S. (53 per cent) at the forefront for FCV adoption.

Japan takes second place with 38 per cent, while Europe is at nine per cent.