[Greenbuilding] [BULK] Solar thermal with sand storage

[Speireag Alden]

On 2008, Jan 28, at 22:24, Keith Winston wrote:

> The problem is heat transfer in and out. Coils of plastic/copper/??
> That's where wet sand changes things, since conductivity is extremely
> improved, and in fact the flow through the sand can utlized for
> exchange. But then you have to have a watertight tank... Actual
> conductivity of dry sand isn't so great, and you don't get convective
> loops like in water. But it's an interested idea, it would be
> interesting to experiment with it.

     I'm thinking multiple runs of PEX, plumbed such that it's a sort  
of contra-flow heat exchanger.  The line from the solar collector  
runs one way, and the line from the cold water supply toward the hot  
water heater runs the other way, and they're taped together.  You  
could even split the line from the solar collector into two or three  
lines and surround the domestic water line.

     So the cold-to-hot water line would circulate around the  
perimeter to get an initial charge, and then move in between three  
other lines and coil with them for awhile, and then off to the heater  
to bring the water up to correct temperature, if it's not there already.

     What do you think?

> For those interested, this kind of gory solar talk is all we do on the
> solarheat group at yahoo. You can join if you want...

     If I join another group, or add anything to my activities in the  
face of all the house building which is waiting for me to do it, my  
loving and patient spouse would have good reason to be very upset...

-Speireag.