Posted by phillip on November 23, 2006, 11:36 am
It's been a while since PAHS (Passive Annual Heat Stoarge) and AGS
(Annualized Geo-Solar) have been discussed in this newsgroup, so I was
wondering if there is still any interest in this area. NIck seemed to
give a somewhat tentative endorsement of the ideas in John Hait's book
but in nearly a decade, very little has been heard about PAHS, so I'm
still wondering if an entire's summer worth of heat can actually be
stored under the insulation cape. Likewise, with AGS, I have not seen
any actual measured data to determine if heat is really being stored
underneath the house, below the slab.
The latest development in seasonal heat storage for homes appears to be
the planned Drake Landing Solar community project, in which an entire
neighborhood aggregates heat collected from dozens of homes and stores
the heat in a large thermal borehole for seasonal use. Assuming that
Drake Landing can successfully build their thermal borehole and are
able to heat their neighborhood for an entire winter with it, is there
any reason to think that a thermal borehole might not work to heat a
single home? That is, can the Drake Landing system be scaled down to
store sufficient heat underneath a house or a garage?
If so, then this thermal borehole scheme strikes me as the most
practical means of achieving a zero-energy house, using standard parts
and components, namely closed loop hydronic heat collection, storage
and delivery. Even drilling a borehole field does not strike me as
being very expensive, compared to hiring a backhoe and digging 20-40
feet underground to install an enormous water tank, or to lay down
insulation for a giant rock pit.
In searching for news about Drake Landing, I've found an article
written in March of this year, stating that people have already
purchased and moved into the Drake Landing homes, which are still
hooked up to gas and electricity but already have functional solar
panels on top of the roofs. It's not clear if the boreholes have been
So the question remains, does this system work, and can it be scaled
down for a single home?
Posted by SJC on November 23, 2006, 1:17 pm
Here is a page that has a large thermal store labeled E on the diagram.
Posted by nicksanspam on November 23, 2006, 4:26 pm
I like PAHS, but it seems to involve lots of foamboard and digging,
and storing heat for 5 cloudy days seems to work almost everywhere
except near the poles, with months of shade. I hadn't heard of AGS.
What I can find on the web seems a little vague about how it works.
I think so. I've heard John Hait is not in good health.
Heat stores without much insulation seem to work best if they are really
big, with a small surface to volume ratio.
That's an interesting picture. A 1200 m^3 cube would have 10.6m edges and
a 113 m^2 cover, and they plan to use 116 m^2 of solar thermal panels and
another 54 m^2 of PVs with heat exchangers. Why not just paint the 500mm
foamboard cover black and put a plastic film greenhouse over it and pump
water up and over the cover during the day and let it drain down at night?
I suggested a 20' diameter x 20' tall tank for a new Irish house to store
solar heat for November through March, because the client liked towers, but
a rectangular tank would have been simpler. We might lay plastic film on
the ground and dig a 5' deep x 20' wide x 30' long hole and push the soil
up into a wide perimeter berm on top of the film and cover the berm with
EPDM rubber to keep the soil dry and put a greenhouse over it all to make
a 6000 ft^3 integrated collector/store.
Posted by SJC on November 23, 2006, 6:06 pm
They did more than plan to do it, they DID it and they have data to show
the performance. I was impressed with how much it stored after it got going.
Why not just paint the 500mm
Posted by nicksanspam on November 23, 2006, 7:45 pm
I was impressed that it took 3 years to get going and
wondered why they didn't use the cover as the collector.