[Strawbale] Free energy

[Speireag Alden]

On 2007, Nov 30, at 11:58, Michele O'Malley wrote:

> Actually, your timing may work out well for me since I am actually  
> 4 years from building. What I am doing now is the research so I  
> know what I want and can budget accordingly. Free heat would be  
> great. Can you give me some of the specifics on how you are  
> building your AGS system. I've read a couple articles on AGS but  
> some of the terminology is confusing to a novice. What kind of  
> costs would a DIYer be looking at?


     I have put in three 3/4-inch runs of PEX pipe, buried such that  
they are about ten feet as the worm burrows from the corner of my one- 
story, no-basement house.  At some points, they are five feet down,  
but at others they are only two feet down and about ten feet out from  
the edges.  What the pipe was doing at any given point depended on  
the plan and the topography.

     Because I'm a belt-and-suspenders type, I also buried some 4- 
inch flexible pipe for air.  But water or coolant can transport far  
more energy, far more quietly, than air can, so the air pipes are  
there in case the water pipes spring a leak and I have to go to the  
backup plan.  All of these pipes are now pretty nearly impossible to  
get at for repair.  There is only one buried joint, and I know just  
where it is, and I can get at it, but don't want to have to.

     Then, I built a berm against the north wall of the house, which  
is designed as a retaining wall for that purpose.  That put an  
additional... roughly 300 cubic yards of additional mass in place.

     All the grade around the house was sloped away from the house,  
and then I put down a layer of insulation and plastic, with drainage  
pipe at the edges.  Over all that, I put down silt mixed with horse  
manure and planted our lawn, which is now far more lush than it was  
(trying to grow in the decomposed granite we have here after you  
scrape the topsoil off was pretty difficult).

     Most of my cost has been in earth moving.  We have very rocky  
ground, where any trench over two feet is likely to turn up rocks  
over a cubic yard large, and we have some that are on the order of 6  
cubic yards.  We re-used most of them in the earth berm on the north  
side of the house, but it still took time and money to dig them out  
from where we didn't want them and then put them back where we did  
want them.  Also, in order to cover the umbrella with good growing  
soil with no sharp edges, we had to bring in fill from closer to the  
river, which cost.

     There's the cost of the solar collectors, pump, and other  
plumbing (P/T valve, flow meter, ball valves, and so on).

     Then there was the cost of the insulation and the plastic.  I  
have not broken out the cost of the AGS system from the general  
expansion costs, but it's in the thousands of dollars, certainly.   
Some people on this list believe that this will be wasted money, but  
I'm hoping not.  I'm very fortunate in having a well-known  
professional efficient designer as a nearby neighbor, and he and I  
have kicked numbers around and talked about design.  He's making no  
predictions, because he's a careful fellow and doesn't know enough  
about expected perimeter losses from such a system.  However, he did  
teach me to use water as my transport medium.  He does not see how  
Don Stephens can possible get the performance he claims by using air  
as a transport medium.

     Don Stephens says that it varies depending on circumstances, but  
in general you can get something like 20-30% of the energy back out  
that you put into the storage around the house.  If we can get 20%  
back out, and it comes back out at the rate we need, then I know that  
we can put enough heat into the mass around the house to get us  
through the winter.

     I freely admit that it's an experiment, and that I'm an  
optimist.  However, I like to think that I'm a reasonably cautious  
optimist.

     I hope this is useful; I'm probably not at my clearest, because  
I've been out roofing all day today in freezing, windy weather.  Feel  
free to ask specific questions, and I'll answer as I can.

-Speireag.