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An A-frame solar water heater concept - Page 3

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Posted by News on July 21, 2005, 10:32 pm


I read the first paragraph and there was nothing to tell me what all this
was about, so I stopped reading.  What is the function of the A frame?  Then
I may read the rest of it.

Posted by Ranieri on July 21, 2005, 10:46 pm


SAT: 780 math / 410 verbal

Posted by Harry Chickpea on July 22, 2005, 4:57 pm
 nick@acadia.ece.villanova.edu (Nick Pine) wrote:


Gotta laugh.  Note the concept of putting water near the peak of a
triangular prism to absorb and store heat.  This wonderous idea is
presented by the same Nickie that pooh-poohed the idea of
inexpensively preheating water for a domestic water heater via the
simple expedient of placing a 4" pipe underneath and along the
ridgeline of a roof.  IIRC, his comments were along the lines of what
if it leaks, what if it freezes?  Yet, he has no comment or solution
for the same questions about his own Nickie special design.

Nick would have people construct a special A-frame greenhouse instead,
to attempt to capture enough heat to warm an entire house, making the
cost/benefit ratio of heating water to the same temperature totally
impractical, especially on those cold winter days when 90% cloud cover
can be common for weeks at a time.  Maybe if Nick hurries, he can
still get a job for NASA designing a solar powered outhouse to be
towed behind the shuttle.

Now - half tongue-in-cheek, and half-serious, I present an
alternative. Cost-wise, a more simple alternative to A frame plan "A"
might be the less pretentious plan "b," where a b shape holds a tank
or pool at the base (on the ground), contained within strawbales, and
a more or less vertical wall of inexpensive construction grade 2" x4"
lumber forms the staff of the b, partly braced by the tank and
strawbales.  This structure would be on the south side of a house,
with a vegetable garden just south of the structure.

1 clear plastic
2 clear plastic
3 black shadecloth
4 black plastic
5 insulation and frame
6 winterime tempered herbs cloche
Sun > >
                       /////                        I
                      /////                         I
                     /////                          I
                    /////                           IHouse
                   /////                            I
                  /////                             I
                 ///// plastic pla                  I
                ///// straw straw stic p            I
               // 6/ pool or tank straw l           I
              //  /straw straw straw    astic       I
garden south //  /ground ground ground north house

The southern side of that b wall would be double glazed with plastic,
while the north side of the wall would have black plastic and black
shadecloth over insulation and a simple frame. The wall might even
tilt, like an italic letter b for a better solar angle.  Cold water
from the bottom of the tank would be pumped by a low volume pump
(bilge pump?) to the top manifold and allowed to trickle down through
the shadecloth (which would spread and even the flow) and over the
black plastic, underneath the first closely-spaced layer of plastic
glazing.  Since the pump would be controlled by a thermostat or solar
sensor at the top of the b, it would only run when it could accumulate
heat energy, and no water would be exposed to the cooling effects of
night air or have to be drained or pumped without benefit.  The heated
water drips into and is allowed to accumulate on the top of the tank,
thus preserving a greater delta T between the pumped water and the
solar collector, increasing efficiency.

Hot water for the house is taken from the top of the tank, and the
return pipe enters below mid-level in multiple low-flow horizontal
outlets to help preserve the stratification.

The staw bale insulation for the pool or tank could be seeded with
fertilizer or dried manure during the fall in preparation for the
coldest part of the winter.  During that period a small amount of
water would be allowed to saturate the inner layer of straw, setting
up an exothermic composting process underneath the pool that would be
buffered by, and add to the heat of, the pool of water during those
cloudy and short days that Nick's design fails to address.

With this design, the weight of the large amount of water safely rests
on straw which is on the ground, without requiring an expensive and
possibly dangerous permanent structure.  The covered pool or tank is
simply enshrouded in hay and leaves for the winter, and an outer
covering of plastic prevents that material from being blown away or
saturated with water from late fall rains or melting snow.  The issue
of freezing is avoided with the simple expedient of a small drainback
hole in the pipe or hose from the pump to the top of the frame.

When spring arrives, the plastic, shadecloth, and insulaton are
removed from the frame, the hay from the south side of the tank is
spread as compost and mulch, and a layer of clear plastic replaced to
form a low tent along the south side of the tank, for use as a
cloche/greenhouse in starting seedlings for the garden.  (A smaller
cloche is shown in the diagram, where a shelf allows midwinter growth
of herbs in the area beneath where the water has to drain back into
the tank.)  Once the spring seedings are safely started, the plastic
is again removed.  The plastic might be used during the summer for
water catchment or to solar sterilize parts of the garden.  In early
summer, the frame is used to support pole beans, the bulk of the straw
is spread, and the tank or pool allowed to cool and supply water to
the garden during parched periods.  The outflow of the gutters of the
house are redirected to keep this pool as filled as possible and
reduce watering costs.  After the August/September dry spell, the pool
will be empty, and the final remaining straw and manure can be removed
and set out as winter mulch for the garden.  The pool is then
remounted on fresh straw, and any rainwater from the roof again
channeled into it to help fill it.

Come fall, the vines are removed, the plastic is remounted and the
process is repeated.

This design is superior to Nicks in that it has
1. far lower cost
2. far greater safety
3. far simpler and easier construction
4. year around use compared to seasonal use
5. no problems with freezing
6. secondary heat source for cold cloudy days
7. lower pumping costs per unit of useful heat
8. no structural permits and inspection required
9. less impact from vandalism
10. less environmental impact
11. portability
12. lack of acompanying psuedomath justification

Posted by Derek Broughton on July 22, 2005, 6:00 pm
 Harry Chickpea wrote:

And your problem is???  In a stand-alone greenhouse, you don't have a
serious problem if it springs a leak.  If it's in your house, you sure do.

Posted by Harry Chickpea on July 22, 2005, 6:38 pm

It isn't my problem.  As I pointed out to Nick at the time, a 4" pipe
contains enough thermal mass, and the location is inherently warmer
than the rest of the attic, to preclude freezing in all but the most
extreme climates, and allowing a small cushion of air at the top for
expansion would resolve the issue even if it did freeze.  The pipe
would be no more or less likely to spring a leak than any other pipe.
I suggest that you and Nick might want to remember that people have
plumbing and even <gasp!> bathtubs on the second floors of their
homes, and condos and apartments and office buildings have plumbing
that reaches to the sky.  Somehow, they survive.

Compare the likelihood of standard pipe leaking in a properly designed
and protected tempering tank system to the potential for catastrophic
leaks in "a 4'x12' shallow pond at the top and 2 poly film water ducts
along the north and south edges to avoid wind sliding and
overturning.." contained in a minimally protected A frame covered in
plastic.  Can you say "BB gun?"  Can you say "mouse nibble?"  Mice
would find such a structure a nice winter home.  Poly film - pipe.
Poly film - pipe.  Hmmm.

Nope.  I don't have a problem.


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