We need technologies to store electricity generated by renewables. If anyone has a better idea than hydrogen to do this in a scalable way, congratulations, you made the world a better place.
I mean the simplest one is gravity; the most scalable version of that is pumping water up into a reservoir behind a hydroelectric power plant. There's others that propose heavy trains going uphill or weights down a hole, but that doesn't scale very well and has additional maintenance costs.
But yeah, that would be electrical into mechanical energy (pumps), the cost would be flowing water up against gravity. Of course, it also requires a source of water downhill and a reservoir uphill. I was going to quip about Lake Mead being empty, but that would be huge distances to cover. Maybe something close to sea, or else a purpose built closed loop system.
Pumped hydro is great where it works, but we have used most of the best places for it. We also know it is an environmental disaster for the local area which needs to be balanced against the gain.
If you are gone make hydrogen, just right there turn it into methanol and use and transport that around.
Or just make airplane fuel right on sight.
But the problem with all those theories is that investing in electricity consuming plants that will only have a very low utilization is generally not a great plan.
Maybe not trying to build your whole grid out of renewables would be the better plan.
Given how annoying H+ ions are to handle, rather than sticking them together as H2 it may be easier to leave them in the electrolyte from whence they came, in the form of a "battery".
Unless there's some magic breakthrough in catalytic chemistry for water electrolysis, the capital cost of all the platinum required is going to be a problem.
