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  • 1/2", 600' for $120. [1]


  • Internal volume - 6 gal [2]. 1 gal per 100 feet.

Lessons Learned

  • Large bed of sand to store heat, or even pulverized, dry soil - is sufficient to store large amounts of heat. Even for seasonal storage.
  • It is easier than having to maintain a large pool of water.
  • Specific heat of water - 1 cal/gram/C vs rock at 0.2 cal/gram/C. Need 5x rock to water. But Void Ratio may be 50%, so one would need 10x the sand compared to water.
  • Insulated basement with sand would be ideal.