Long story short if I remember the video well after watching it a while ago: while sand is cheap for thermal energy storage, storing it with reasonable efficiency requires a massive unit (much higher capacity than one home would reasonably need; can't be scaled down well) held underground (immediately incurring massive costs).
They're saying that storing it underground could mitigate the size issues. Though I query if we'd need these if we simply installed ground source heat pumps everywhere?
Err... you're not wrong. My initial comment would have made more sense if this had been the post I was intending to reply to. Not sure how I managed to screw THAT up.
