Is this a battery?

I read ‘On demand’ (Design Engineering, 9 April) but would like to know if I am missing something.

Here is a device full of water with two electrodes made of different alloys with different work functions; consequently a potential difference exists between the two electrodes. When they are joined together a current flows.

This sounds like a battery. If you want electricity why not use the output from the battery directly instead of feeding the evolved hydrogen gas to a fuel cell and going through another conversion process with its attendant losses?

Admittedly the process sounds different in that it evolves hydrogen from both electrodes but since it is generating electricity by the consumption of the two electrodes it still sounds like a battery.

Do the inventors have figures comparing its total power output when used as a battery with what you get if you use the hydrogen to power a fuel cell?

Denis Sharp

Arundel, West Sussex