We don't have production facilities for that much clean hydrogen either (about 350.000 tons would be needed for 8 days' worth of Germany's needs. World production of green hydrogen was about 1 million tons between 2015 and 2018[1]).

As I said earlier, the theory may exist, but solving scaling problems isn't trivial, and is going to take some time.

[1]: https://www.statista.com/statistics/859104/hydrogen-producti...