re: solar water heating component selection advice needed
28 jan 2001
george estep wrote:
> thanks for your "outside the box" thoughts on this issue...
you are welcome.
>i like the fact that you keep us all from existing within the limits
>of today's conventional approaches.
the pioneers are the ones with the arrows in their backs :-)
> i like the greywater approach, in general. i do have a place to put
>such a storage tank, but i will have to look at what will be required in
>terms of plumbing, etc. if i could get the greywater from the dishwasher,
>that would be quite hot.
i'm thinking of rearranging some plumbing to make a such a greywater heat
exchanger that feeds another unpressurized 55 gallon steel drum with three
hdpe liners on top of a woodstove. the rv pump would empty the stove drum
into the electric water heater drain, with the cold water input shut off.
i'll need a small hot water pressure tank, which might not have been needed
if i'd been able to leave the cold water input open, but i've been told that
might allow some hot water to migrate into the well pressure tank, which has
a bladder that can't take hot water. a larger distance (say 20' more pipe)
between the well tank and water heater might prevent this. adding more pipe
seems simpler than adding another pressure tank.
> i'm generally inclined to buy these items and assemble the system,
>rather than build the individual pieces.
i can relate to that, eg with cars and circuit breakers...
>i don't believe i have the skills or tools to build a storage tank which
>would provide leak-free performance for decades.
you might. a stout plywood shoebox inside some 2x4 studs with some bolts
and a single piece of epdm rubber roofing material folded up like a chinese
takeout box. pp&l had an ap note describing how to home-build these for
customers who wanted to heat their houses with off-peak power.
> clearly thermomax collectors are very expensive. they seem to have two
>main advantages: high efficiency in cold weather and a single, short,
>straight water path, which should minimize pump requirements.
a $75 4'x24' epdm rubber bladder on a plywood shelf over the garage ceiling
might outperform these collectors. as an alternative, you could lay 24' of
30" poly tubing ($12) on top of some pv panels instead of the plywood shelf.
a 24' garage (north to south) with an 8' ridge would focus the sun 4' from
the north wall at dawn with 2:1 aperture concentration. the focus would move
towards the north as the sun rose, until the peak shadowed the south edge of
the shelf collector at a 45 degree sun elevation, which would still make
lots of hot water in summertime...