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Could I build a sand battery to store energy for winter?

3 min readJun 23, 2024

One of the biggest energy requirements in my house in Bavaria (Germany) is heat. My wife and I needed about 24,000 kWh ( 2450 L of oil) per year . About 1,900 kWh (194L of oil) per year is for warm water.

Let’s say a sand battery becomes interesting if it can cover at least 10%, so 2,400 kWh.

I assume that we can extract heat until it’s about 15°C and we could heat it up to about 100°C. That is a temperature change of 85°C.

Energy = 840J/kg°C × 2.7×10–7 kWh/J × mass × temperature change

2400 kWh = 0.22 kWh/ ton °C × m ×85°C

m = 128 tons

Dry sand has a density of 1602 kg/m3. So 77m³ of dry sand would be required, e.g. 5m x 6m x 2.6m. That hole would need to be insulated and have pipes within it.

That is gigantic.

1m³ of sand is about 20€/m³. It’s astonishingly cheap, but it would still be 1540€ just for the sand. No digging, no insulation, no pipes.

Including the sand storage into the buildings construction

Obviously, it does not work in my case of an old house with a comparatively small garden. But maybe it’s interesting for new homes? I wonder if the foundation of the house could…

Interesting idea. I think the biggest challenge is the thermal insulation - you’d need a way to keep a box of sand at 100 ° C for half a year without losing much of the heat to its surroundings.

Also speaking of the material - sand has a pretty…

This is all wrong. With solar panels you can heat up sand up to 800C . You need to recalculate the needed size , it will be much smaller for sure. Due to high temperatures it need to be put in its own isolated compartment. In house from the picture you would literally die in the summer, and your house too :D