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Posts: 98
Reply with quote  #1 

Hi guys,

been very busy with other stuff but now I'm back to solar.

This summer I want to build a scalable heatbank. I need your thoughts on this project. I plan to make a 1 cubic meter (35 cubic foot) big insulated below grade heatbank and above that an insulated 1 cubic meter big air filled empty space.
I want to deploy temperature sensors within and outside the heatbank, the empty space above and the outside and log them.

My main question is: How scalable would that be? Let's say instead of 1 cubic meter I use 8m3 (2mx2mx2m) for both heatbank and empty space,
that means in my example with a dirt wall to the north (for simplicity I will ignore that area) the surface exposed to the surroundings would increase from 5 square meters to 20 square meters, the surface directly exposed to the elements of the space above grade would increase from 4 square meters to 16.

So it looks the bigger I make it the better the performance should be? Frankly I "tried" to calculate the whole thing but... you know :-)

The effort even for 1 cubic meter is considerable, so this is what I would like to go with, not bigger. 

Your thoughts?

See the attached picture please for reference


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Posts: 1,074
Reply with quote  #2 
Why dirt as the storage medium? Not sure what the specific heat of dirt is but "... water stores about 5 times as much heat per lb as sand ..." from the following link:

Both temperature rise and airflow are integral to comparing hot air collectors

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Posts: 98
Reply with quote  #3 

the idea is to build the house on top of the dirt that's already there, just insulate it. Such a house would have no basement, just like an Earthship. I can't imagine a huge watertank underneath the house, the price would be prohibitive I guess.

It has been done by this guy in Michigan (even though he still uses an additional heater for the last winter months):

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Posts: 2,952
Reply with quote  #4 
The general idea has been around for years. I think the biggest issue is cost.

Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay

Posts: 269
Reply with quote  #5 
This guy used a sand bed that he heats all summer to help in winter.  


It's been years since I went through his entire journal but I believe in the end it only worked for a few days before running out of stored heat and adding almost nothing to the house in the winter.

Dry dirt/rock/... just can't store much heat. 
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