This would combine well with another low-tech battery solution, stacked weight, which would store without loss or reliability worries for those few days in the year you need them.
Edit: Actually, while this idea sounds good, a fridge requiring 1 million joules for a rainy day would need 10,000kg @ 10 meters, even before considering efficiency losses.
Edit: Actually, while this idea sounds good, a fridge requiring 1 million joules for a rainy day would need 10,000kg @ 10 meters, even before considering efficiency losses.