Posted by nicksanspam on February 21, 2005, 5:34 pm
That version would use 4 sheets of plywood and 35 8' 2x4s, about $43 with
the double poly film liner. Welded wire fence on the bottom with a 2x4 hoop
inside the box at the top and bottom and 26 4' vertical studs on 1' centers
would lower the materials cost to $02 and reduce the labor required.
A wall might look like this, viewed in a fixed font, with a few wires across
the top to hold it together:
| |screw eye + wire--- - - -
| | film
| |pp - p
| |ol|2|o |
| | ofilm |
| | op
| | do
| | pl |
| | ly
| | yf
| | wi
| | ol
| | om |
| | dp
| | po
| | llyfi |
|2x4| y - l
| | w|2|m
| |wo|x|p |
| |io 4|o
| |rd - lyfilm...
--- efencewirefence... - - -
A tank like this could be much larger, with little increase in materials cost.
Posted by BobK207 on February 22, 2005, 3:45 am
by the time you buy & build a wooden one & line it with plastic plus
the hassle with fittings (if you penetrate the wall) you'll be money &
headache ahead to just buy one
I'd go with plastic. I'd also take another lookat the used plastic 55
gal food grade drums
Posted by Jonathan Mau on February 22, 2005, 1:46 pm
I have been giving consideration to a big water thermal store also. The
55 gallon plastic drums can be had for CAN$0. What I don't know is the
temperature characteristics. I think these are HDPE. The tanks I have
found in HDPE are only rated at 120 degrees F with a liquid of S.G. 1.7 I
think. I wonder if one could get a few more degrees with a S.G 1 liquid?
I suspect this is an issue of wall thickness, temperature, and pressure
and not an absolute limit of the material.
I am still considering these 120 degree tanks too, so if anyone had an
idea of upper temperature limit with water, I's like to hear it.
My calculations show so far that the lower cost of 55 gallon drums
outweighs the higher cost of insulation as compared to one large tank only
considering the cost of tank(s) and insulation. Throw in all the bits and
pieces to run piping into say between 4 and 18 55 gallon drum tanks and things
might change. I assumed 21 inch thickness fibreglass insulation for about
R 72. My tanks will be in an outbuilding subject to winter temperatures.
Any ideas on low cost insulation? Straw bales maybe? When I looked for a
R value on straw bales there did not seem to be the same consensus that
one finds with 3.5 inch fibreglass (grin). I think for 18 inches thick I
found a lower number of 28 and an upper number of 45.
Posted by nicksanspam on February 22, 2005, 2:49 pm
Sure. Then again, maybe that rating only applies for rail or truck transport.
You might wrap a drum with chicken wire.
You might arrange plastic drums in a square or hex grid and connect them with
short threaded nipples through adjacent holes in the walls near the bottoms
or bulkhead fittings with barb or garden hose adapters. If the drums are
cylindrical, a single PVC bulkhead fitting might connect two of them.
Low-pressure ag applications use "push plumbing"--drill a smooth hole
in a drum with a step bit, and push some smooth tubing into the hole.
Posted by iain-3 on March 1, 2005, 8:06 am
I've been looking at this problem as well. My current best plan is to
fill an insulated, EPDM-lined hole in the ground with drain rock, then
cover that with EPDM and insulation and bury the thing under my patio.
The point of the drain rock is that it's cheap, available and
in bulk, and takes vertical stresses without any engineered structure.
This last bit is important: HDPE/fiberglass tanks seem to be about
$/gallon, and have maximum recommended temperature limits of 140 F /
In case it's not clear, this is a water tank, not a rock tank :).
The rocks fill about 2/3 of the volume of the store, and store a little
less heat per unit volume than water. So the overall tank has to be
upsized a little.
I'm thinking of using "blueboard" extruded polystyrene insulation,
probably the 30 psi variety. From Lowe's this is about 7 cents per
ft^2-R. I've read that it can be had for 3 cents, which would improve
my economics a bit.
Drain rock is about $1/yd^3, delivery is about $3/yd^3.
Even including the geotextile felt between the EPDM and the drain rock,
this is about $.30/gallon, and has no size restriction, shape issue,
or safety problem with overheating.
I do have some reservations about the idea though:
- the drain rock, even if prewashed, will be dirty. Just dumping it
out of the truck will create fines, which will end up plugging my
solar collectors if I can't figure out how to get them out of that
tank. I'm assuming I'll have a cheap spa-type cartridge filter on
the tank exit to stop expensive damage from fines, but my guess is
that without some clever idea, I'll end up plugging up and changing
that filter every twenty minutes :).
- Maintenance will be a bitch. The tank I'm planning is large (125
cubic yards). Digging 200 tons of wet drain rock out to get to a
leak would be very bad. I'm wondering what I do to make sure
there are never any leaks.
- The top of the (unpressurized) tank to the bottom of the rooftop
solar panels will be 23 feet. I'd like to have a drainback system,
- I am pumping up a 23 foot head, and that'll cost $$ for
- I'm going to get burbling noises in the down pipes from the roof,
as falling water pulls a partial relative vacuum at the top of
the panels and opens the air vent. Alternatively, I can have a
23-foot head restriction near the ground in the flow back to the
tank, a loss of energy requiring a bigger pump.
- Even if I don't have a drainback system vented at the top, the low
pressure near the top of the panels will create steam bubbles which
will make noise which will piss me off.
- Pressurizing the tank puts a lot of reliance on field-glued seams,
which sounds like a lead-in for disappointment.
- I am imagining the EPDM liner falling into the hole when the drain
rock gets poured in. Securing this thing is going to be a major
pain. I will probably fill the hole halfway with water before
dumping any drain rock in, to cushion the blow on the bottom