You've got to have the whole fuel production, storage and transportation system ready to go 100% of the time. Raises costs if you do it honestly, if you try to skimp it might not work when you need it.
It might be okay if production and transportation only work some of the time if you can store up enough fuel to ride out the outages. That's how it works today for fuel transportation; gas stations commonly go without deliveries for days or weeks at a time when roads are snowed out, for example, and oil tankers and LNG tankers make their deliveries even less frequently.
In particular, solar and wind won't produce any fuel at night when no wind is blowing, and may not produce enough fuel during the rainy season or winter.
Right now it is solar and wind electricity that is cheap. E-fuel [1] and other forms of chemical storage [2] are a thing but might not be so cheap. Seasonal storage might use methane and avoid the legendary boondoggle that is Fischer–Tropsch [3] but methane is itself a powerful greenhouse gas. A really good methane handling system loses much less but if you lose 1% of it you might as well be burning fossil fuels. Even hydrogen isn't completely benign [4] as it depletes those "negative ions" that were a fad in the 1970s and as a result prolongs the life of other greenhouse gases.
TCES is extremely cheap (megajoules per dollar of rechargeable capacity, compared to tens of kilojoules per dollar for batteries) and will likely be critical to the energy transition, but it won't run your servers overnight or your airplanes over the Atlantic. Things like cycle life are still an issue for TCES. And you need electric power to run your TCES system, so efficiency is still a concern.
I feel like oxidizing methane to methanol shouldn't be rocket science, especially if you have an unlimited amount of energy to use. NADPH does it at scale already. A few more cheap process steps would give you nontoxic ethanol instead.
