Posted by Iain McClatchie on November 11, 2005, 8:14 pm
4500 gallons, swinging between 170 and 100 degrees F, will store
25 therms, or about $0 worth of heat. If you're paying just $500
for that capacity, you'll have to use it 3-5 times a year to get
your money back. Seasonal storage ain't gonna do it. But the
tank will do nicely for < week storage, for runs of cloudy days.
I looked at SIP panels, they're expensive. I can see they might
make sense up in Washington.
GoSolar> If you look around, possible to by big logs of EPS that
GoSolar> you can cut for cheap Like 4'x4'x20' etc for a hundred
GoSolar> bucks or so. Cut with a hot wire, that will go a long way.
It's $/ft^3 at Lowe's, so this is a fabulous price. Can you please
tell me where to buy such blocks, I can really use this information.
GoSolar> A big ferocement tank looks really cool as well.
That's the way we're going, but we're planning on cycling the tank
several times a year.
Posted by gosolar23 on November 11, 2005, 9:11 pm
$0 bucks? Well there goes my dreams of large storage. I don't think
I could every get to those kind of temperatures with a trickle
collector. Back to the drawing board. Maybe just a 400 gallon tank in
a bin of rocks.
Iain. All sip manufactures essentiall make big foam 'loafs' I think
8'x8'x28'. Not only can they sell these in cut up logs, they also
have tons of scraps. My SIP manufacture offered to give me the foam I
SIPS seem to make the most sense to me. Fast, straight, much stronger
than sticks. Also, much, much tighter and bettered insulated then
sticks. Stick bays are hard to insulate well and tend to grow mold
And you are not cutting down a bunch of trees. If designed well, they
are free of dimensional lumber. I like ICF's, but they become an
engineering problem up high in earthquake country (like Seattle).
How big a tank you building and where you putting it?
Posted by Iain McClatchie on November 15, 2005, 8:12 am
Eric> All sip manufactures essentiall make big foam 'loafs' I think
Eric> 8'x8'x28'. Not only can they sell these in cut up logs, they
Eric> have tons of scraps. My SIP manufacture offered to give me
Eric> the foam I need.
Wow. I need to get on the phone with these folks again. Can you
tell me who made that offer?
Eric> SIPS seem to make the most sense to me. Fast, straight,
Eric> much stronger than sticks. Also, much, much tighter and
Eric> bettered insulated then sticks. Stick bays are hard to insulate
Eric> well and tend to grow mold when wet.
Yep. But it appears to me that plumbing with SIPs is expensive.
SIPs themselves are expensive; although I don't remember the details,
when I looked at it my impression was that a SIP wall was going to
cost noticeably more than a normal wall after the plumbing and
electrical were installed in both.
For our house, wall insulation isn't where we're losing most of our
I think something like 15% of the heat goes through the walls. It
wasn't enough to spend extra money on.
Eric> And you are not cutting down a bunch of trees.
Yep, that's nice too. I had considered doing the roof with SIPs,
since they're strong and thin and have no plumbing and only small
amounts of electrical, but I had a hard time finding SIP vendors
willing to do curved sections. Most of our roof is barrel sections,
except the portion supporting the glazed collectors.
Eric> How big a tank you building and where you putting it?
Between 4,000 and 10,000 gallons, depending on cost (we have a
budget of $0k for the tank). We're putting it in the ground, below
a deck. The current, not-certified-by-a-civil-engineer-yet plan is a
shotcrete tank inside R40 XPS foam. The tank will probably be
sealed with some sort of painted-on sealant, and the top will be
sealed by an EPDM liner across the top below the insulation.
House loses ~800k BTUs on a cold January day, so we need
about 2000 gallons a day for storage. With between two and
ten days of storage, we cycle the storage about five to seven
times a year, so it almost works out. I want the big storage
because it nearly pays for itself and it's always nice to have a
little extra margin, in case you, for instance, throw a big outdoor
party in October and end up heating the patio for six hours.
I assume there is some sort of foam I can shoot between the
XPS panels to fill the gaps, but I'm not aware of anything yet.
Maybe I should talk to the SIP vendors about that, too.
For a while our solar system was looking like a money loser,
but then gas prices went up and California Title 24 rev 2005
went into effect, and it appears we can use less expensive
windows and save more than the cost of the solar system. So
I'm happy, but I probably would have built it anyway, if perhaps
a bit smaller. You do what makes you happy.
Posted by nicksanspam on November 11, 2005, 12:55 pm
Why not try cogen instead of a BAD EXAMPLE of solar house heating? :-)
Sure, for the same thickness. Try numbers. It won't rust, for starters.
But the polycarbonate may not last long.
Try looking for "roofing."
Posted by Jeff Thies on November 12, 2005, 6:51 pm
That's the bulk of his cost. Will the the lifespan be much less as a
trickle collector than one where the fluid is is sealed in tubing? Would
he be better converting from a trickle collector to maybe something with
pex tubing on the underside?