excess output was turned to hydrogen on site then used to power jet turbine generators during the evenings to stretch their input to the grid beyong the 'sunny bit' ... makes far more sense than batteries to me.
The major problem that hydrogen has is in efficiency, especially if you burn it.
If you take electricity, use it to crack water to get hydrogen, and then burn it in an ICE engine the efficiency is really low, about 25%. It's better if you use Fuel Cells, it can get up to 40 to 60%, but then fuel cell life is much lower than electric motors. When you add in the costs of transporting hydrogen to fuelling points the cost/benefit analysis gets even worse.
The efficiency of putting electricity into batteries and then powering EVs is much higher, at around 80 - 90%, which is why they are attracting more development investment than hydrogen vehicles.
There are use cases where the efficiency argument doesn't count for so much, most notably Heavy plant/earthmoving and heavy goods transport, but for personal transport the sums don't add up for most people. Imagine having to pay 4 times as much per mile for a hydrogen vehicle over a BEV.
