Hydrogen is regularly described as the environmentally friendly fuel of the future but industry experts say the road will not be easy.

Representatives of vehicle manufacturers at the National Hydrogen Association convention in Texas say hydrogen technology is feasible, but there are significant hurdles to it becoming commercially viable.
$quot;We all have our homework to do in the coming years,$quot; said Klaus Bonhof, manager of the alternative fuels division of DaimlerChrysler. $quot;We must produce technology viable in volume, and that technology must be commercially applicable.$quot;

BMW, Toyota, Honda, GM, DaimlerChrysler and Volkswagen have hydrogen-powered vehicles on display at the conference, but all have similar technological challenges. For example, a hydrogen car can travel 45 to 50 miles (72 to 80 km) on a gallon, but a normal-sized fuel tank will only provide a range of 125 to 150 miles (200-240 km), experts said.

The problem arises from the fact that although hydrogen is put in a car as a liquid at very low temperatures, it reverts to being a gas as it warms. It dissipates into the air even when the vehicle is not being used. $quot;You have boil off, you are ventilating hydrogen,$quot; said BMW vice president of clean technology Frank Ochmann. $quot;After a certain time, after a week, say, the tank will be empty. This is a certain headache that we still have, but we're working on this.$quot;

Ochmann said BMW is testing an insulated tank that would keep hydrogen cold and liquid. $quot;If you put a snowman in this tank, it would take about thirteen years to melt down,$quot; he said. Ochmann also says BMW estimates it will be 2025 before hydrogen powered vehicles are commonly produced and sold.