In 2011 ENERTRAG had a constructed a system to use a windpark to produce hydrogen and burn this in a gas/fuelcell plant. But since a change in the EEG Umlage Gesetz made them pay for their own energy produced by wind, it became unprofitable to do so.

If that sounds idiotic to you, that's because the change in the EEG was created to make exactly this impossible.

I think your information is out of date. It appears the wind park with hydrogen production is still active [1].

[1] https://enertrag.com/produkte/windgas