> Ideally I can build some giant container of sand with some cinderblock, run some copper through the sand, and heat both using the wood being burned. Then, I

> Ideally I can build some giant container of sand with some cinderblock, run some copper through the sand, and heat both using the wood being burned. Then, I could pump water through the copper which is being passively heated from the sand into my existing hot water baseboard, but it's unlikely to be hot enough - oh well. Is that a similar idea to the sand battery in Finland? It was on HN last year. https://news.ycombinator.com/item?id=32006791 https://news.ycombinator.com/item?id=32006791