Over the past few years, the question of hydrogen power has never been far from motor manufacturers’ lips.And it has been given a boost in the wake of the Government’s professed aim — now looking increasingly challenging — of banning the sale of all new pure petrol and diesel cars from 2030.For while electric cars charged from batteries remain the biggest automotive growth area, some experts believe hydrogen gas is the real longer-term solution to environmentally friendly car travel. Munich marvel: BMW has just started production of its iX5 Hydrogen that uses zero-emission fuel cell technologyThis is despite the huge shadow that has loomed since the disaster on May 6, 1937, of the Hindenburg airship which used the lighter-than-air gas for lift, but which exploded in a fireball on landing at Lakehurst airfield, New Jersey, in the U. S.Yet hydrogen’s supporters insist it is no more dangerous than petrol.How it worksWith fast refuelling taking just seconds, there are two ways to use tankfuls of hydrogen to power vehicles.The first is to burn the hydrogen gas in a converted internal combustion engine — and I have driven a prototype hydrogen BMW 7-series limousine around Berlin that did just that.The other, in which Korea’s Hyundai has been a practical pioneer, is to use fuel-cell technology in which the gas is used in a chemical reaction to generate electricity, which in turn powers a motor.Fuel cells simply act as a mini onboard power station….