As old diesel trains are phased out around the world, the UK has unveiled a new type of engine aimed at decarbonizing railways. The hydrogen-powered train is called HydroFLEX and this week it has completed a first round of tests.

Stuart Hillmansen, who heads the team designing the system at the University of Birmingham, said the key is that it can be "retro-fitted" to older trains and existing rolling stock.

"Our prototype shows how hydrogen-powered technology can be incorporated within existing trains, without needing to modify the drive's control," he told CGTN Europe.

CLICK: WHY NEW TECHNOLOGY COULD BECOME THE DIFFERENCE BETWEEN LIFE AND DEATH IN RURAL AREAS 

Hillmansen also believes it won't be just trains that will be hydrogen-powered. "It's an exciting advance because it shows how this technology could be adopted into the mainline system to deliver emissions-free public transport," he said.

The HydroFLEX concept has three parts: large tanks store the element at an extremely high pressure, which is then fed through a regulator into a fuel cell where a catalyst is added, so it can bond to oxygen. The by-products are electricity and water.

The main drawback is that it takes up more room to store hydrogen than fossil fuels. 

Watch the interview in full above 

Want to know more about how hydrogen power works? Read this: Could hydrogen power be the sleeping giant of green energy?