[Greenbuilding] [BULK] Solar thermal with sand storage

[Keith Winston]

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.

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...

Keith



Speireag Alden wrote:
> On 2008, Jan 28, at 12:40, Morgan McDonald wrote:
>
>   
>> Thanks for the idea, Speireag.
>>
>> Only problem is that we don't want moisture in the warm sand  
>> because it
>> may lead to bacteria growth (stinky and possibly unhealthy for  
>> humans).
>>     
>
>      Understood, but I'm not advocating a slow drip out of a line.   
> The supply of water would be finite, and the bottles would be  
> designed not to leak.  Since the sand would pretty much always be  
> warmer than the ambient temperature, and sometimes considerably  
> warmer, I would not be worried about bacteria.
>
>      I was just pointing out that in the event of a bottle failure,  
> the system would not fail catastrophically.  In fact, the operator  
> would probably never be aware that the bottle was leaking.
>
>      I think I'd set the bottles cap-upward, since the most likely  
> failure point is probably where the cap seals to the neck of the bottle.
>
> -Speireag.
>
>
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