In general yes, grid solar + grid batteries are cheaper than any peaking power plants. So now 24/7 batteries + wind + solar generally outcompetes nuclear, coal, or natural gas on price as long as there’s no tariffs involved.
This isn’t enough to make batteries + solar viable in Alaska but long distance transmission lines could solve that issue cost effectively.
Communities in the north will use diesel generators in the winter (nothing else is viable). Again, I assume you are talking about off grid communities, which is basically all of them except a few cities (and most cities have their own grids disconnected from the rest, especially Southeast Alaska).
Rather than building 10x as much solar in the north + battery systems + winter hydrogen storage etc long distance HVDC to cities and the surrounding grid just makes so much more sense. Even better because the state is huge and the population is tiny they can go nearly 100% hydro.
Where batteries could be useful is operating those long distance power lines at nearly 100% 24/7 then load shifting via batteries to match local demand.
For seasonal storage, round trip efficiency is mostly irrelevant; the relevant metric is capex per unit of stored energy.
A panel in Alaska only collects so much sunlight over the summer before considering efficiency losses from Hydrogen. It would require buying panels that effectively get ~1 month of use over the entire year due to efficiency losses + limited gathering period, and solar isn’t that cheap.
So in Alaska you’re just better off only using panels directly in the summer which at least provide several months of electricity per year. In say Texas on the other hand you get energy from a panel year round so a marginal panel purchased to generate hydrogen at say 20% round trip efficiency gets 30% * 9 months + say 70% of average production for the 3 winter months = 4.8 months of winter electricity per year. Of course you also need to pay for the hydrogen generating machine and the hydrogen burning device, but that’s not necessarily problematic.
It is certainly the case that hydrogen would be better than batteries for this storage use case in Alaska.
In 20 years it might make sense but today green hydrogen is several times more expensive than gas even when you can use cheaper electricity, can make use of the equipment year round, and have the benefit of larger economies of scale. Even if the goal is completely about climate change locating that same equipment in the lower 48 states is just a much better idea.
If the basement rock is close to the surface and is crystalline, it probably involves deep mining to form cavities, which would raise the capex by maybe an order of magnitude. Other options could become cheaper then, say storing ammonia.
This is for large scale storage, of course, not for individual residences.
Having energy cost related scheduled (winter) downtime gives the plants proper maintenance windows.
With free power but only during surplus peaks in summer when the grid can't transmit a large utility solar farm's entire production, and the day/night/weekday time shifting batteries are also already fully active, you could (looks like the math checks out) electrolytically refine iron ore into iron metal (for later smelting in an arc furnace) just about cost-competitively with (coal-fired) blast furnace operation. The key is to skip most overhead by operating them only to eat otherwise-curtailed production and connecting them to the DC bus between the MPPT and the grid inverter (same as the day/night shifting battery).
For example, last Sunday Germany covered more than 100% of its own power load with renewables even though winter is approaching. Only a small part of that was solar power, most electricity was generated by wind turbines: https://www.energy-charts.info/charts/power/chart.htm?l=en&c...
As I said elsewhere I'm thinking ultra low capex thermal storage will edge out hydrogen here, though.
Half of Germany is north of the straight part of the US/Canada border...
I’ve got an usually good location for small scale hydro, there was even a mill on the property, but it just doesn’t seem worth it to me.