Over the last few years we have spent a lot of time researching new ways to produce green hydrogen using renewable energy – it is a very promising clean fuel with all kinds of applications. Stored as a cryogenic liquid or compressed gas, it can be burned as a hydrocarbon fuel substitute with relatively little modification to normal internal combustion engines. It can also be run through a fuel cell to produce electricity, which acts as a type of liquid/gas battery.

But in general, you need a lot of fresh water to produce it—about 9 L (2 gallons) of water for every 1 kilogram (2.2 lb) of hydrogen you produce. And the electrolysis process, although improving, is still lossy. So every time you divert precious renewable energy from the grid to produce hydrogen, you're throwing away a percentage. This is somewhat redundant given the massively increasing energy demands that power grids around the world have to meet while also getting rid of the cheap, simple and dirty energy sources of the past. (Loz Blain, more at newatlas.com)