[pfdietz]

Hydrogen burning could have a place in an all-renewable grid: it could be much more economical for very long duration storage than using batteries. The last 5-10% of the grid becomes much cheaper to do with renewables if something like hydrogen (or other e-fuels) is available.

A competitor that might be even better is very long duration high temperature thermal storage, if capex minimization is the priority.

[crote]

> it could be much more economical for very long duration storage than using batteries

Yes, but that's not the only option you have. With the absolutely awful efficiency of burning hydrogen you'd need to be building a massive amount of additional wind and solar - which in turn means you'll also have additional capacity available during cloudy wind-calm days, which means you'll need to burn substantially less hydrogen to generate power.

This leads to the irony that building the power-generation infrastructure for generating enough hydrogen means you won't even need to bother with the hydrogen part: you're basically just building enough solar that their overcast supply is enough to meet the average demand. As a bonus, you've now got a massive oversupply during sunny winter days and even more during summer days, so most of the year electricity will essentially be free.

[pfdietz]

Efficiency is not very important for very long duration storage. What's important is minimizing cost, which is dominated by capex, not by the cost of the energy used to charge the storage system. Paying more to charge it can make sense if that greatly reduces capex.

So, yes, more input energy is needed. So what?