I haven't heard any reasonable immediately implementable numbers or solutions from the renewable proponents how affordably store enough energy to heat cold countries during months long winter.
The technologies I like provide solutions to the hard problems.
In Finland, the coldest weather is experienced when, during winter months, there is a persistent anticyclone parked overhead. Those can cover the entirety of the country, and inside them there is negligible wind. For example, on 8th of December it was -20°C, and the average output of wind power (nominal installed capacity ~2800MW) over the day was 330MW. The average output of grid-connected solar was <1MW (It's December in Finland, what did you expect?).
Anticyclones can remain in place overhead for weeks. The value often used to calculate the cost of renewable+storage is 3h. This is a reasonable value for California, where solar production correlates well with use. If you built the grid in Finland based on that, we would just die when it gets cold.
There are no renewables that work well in Finland. Water power is fully built out. Solar only produces power when we don't need it. Wind reliably does not provide power when we need it. Compared to renewable with enough storage, even with all it's overruns, OL3 is remarkably cheap.
But how much of the heating is, or needs to be, electric?
Many current heating fuels are fossil and not great either, but they can be replaced with renewable fuels which solves storage vs renewable-produced electricity.
That does seem to head for electricity based heating. But a web search lead to some (admittedly 6 yrs old) graphs that have electricity being in in 3rd place after fuel based heating solutions by energy use: https://www.stat.fi/til/asen/2014/asen_2014_2015-11-20_tie_0... - and hopefully those new houses are better insulated and use proportionally much less energy than the average housing stock, eg passive houses.
Do you propose to build so many nuclear plants that you can provide peak electricity including heating in cold winter months? Do you have numbers for that? (I imagine that'd be the most expensive solution ever, as nuclear plants are high in capital costs and you're basically proposing to have lots of nuclear plants that only run on very cold winter days.)
I guess what many nuclear proponents seem to forget is that you need flexibility no matter what source of electricity you have - because even if your plant runs 24/7 (which it doesn't), energy needs aren't constant.
Storing heat is not difficult. You just heat up water and put it in an insulated tank. Either steel, or dig a hole in the ground and insulate that, with a floating insulated lid. Once it's big enough, the losses are so low that you can use it for seasonal storage, and with solar to heat it up in the summer, it's cheaper than natgas. At least where I live.
Next year, I think, they're building a storage not far from where I live with 200.000 m³ capacity.
Nobody is using gas to heat anything in Finland. District heating is pretty much all some combination of waste heat from some other industrial process (including electricity production), coal, wood or peat. Some district heating scale heat pump and storage projects are in prototype phase but are meaningless % of actual usage.
For individual house heating it is some combination of pure electric, heat pump, wood and oil.
Gas in general is used very little for electricity here (only ~7% of total energy production) and gas cooking stuff is also relatively rare.
