I wonder if ammonia might be doable at residential/DIY scale. Then you have to (a) store it safely, and (b) have a way to use it - not many people have a personal marine application.
I'm in favour of home PV and community batteries | larger area "peak" use industries - it's a sensible long term use of cyclic energy production.
What are the challenges to incline rail lifting a lot of material up a mountain to roll down later?
Water freezes, slopes with snow can be unstable, cold weather is hard on gears, etc.
Large (in old mine shafts and chambers?) thermal mass storage has potential, not dissimilar to "heavy" (not suitable for EV) recent battery technologies.
Are there any serious tidal races in Scandy lands that can be tapped?
It's a poser alright.
OTOH there's mines, but oddly enough I've seen no discussion in the media of using them.
So.. there's no simple land/geographic features worth exploiting. OTOH some storable liquid/gas is more realistic. There's also sand batteries - Helsinki city has one - but they're maybe not so easy to do residentially/DIY, I would expect the neighbors to complain.
The GP comment mentioning "Scandanavia" seemed like a good excuse to spitball ideas with mountains - but as outlined they're no easy fix either - you can't just put a big dam anywhere without potential dangers and cold climates have issues with freezing, expansion, contraction, etc.
Where I'm at we're more concerned with overnight power for massive 24/7 continuous operation than with longer nights and less light in winter .. that's simply not a thing here.
So AFAICT mass PV is a distinct possibility, and if it can be leveraged to reduce the cost of wintertime energy usage, it will find a firm foothold.