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re: plans to make pool solar heater
13 apr 1998
andrew mckegney wrote:
>nicksanspam@ece.vill.edu wrote:
>>mark main wrote:
>>>bourque@microtec.net wrote in message
>
>>>>i am looking for a plan to make my own solar system to heet my pool...
>
>>pool heeting is easy. keeping the heet in isn't, unless you...
>
>>>1. cover your pool at night to retain the heat of the day.
>
>>you might make a foamboard + concrete cover that automatically floats at
>>night (with some air pumped into pvc pipes) and sinks during the day
>>(water in pipes), with a "solar pool cover" over that, to reduce heat
>>loss by evaporation, and surround the pool with asphalt or a 20' skirt
>>of pebbles over black plastic to keep rainwater from washing the heat
>>out of the surrounding soil...
>come on nick - you're not still telling people to float concrete in
>their pools are you ?!!
sure. a square foot of water 2" deep displaced by 2" of foamboard weighs
about 10 pounds, like 1" of gravel or concrete or slate. some almost
bouyant 4x8' panels, might be floated by displacing 130 lb of water with
air in 24' of 4" perimeter pvc sewer pipes, or a 600 pound 3.5"x32ft^2
air cushion underneath. an arched plastic film greenhouse on top with
a reflective north wall might be a nice place to play bridge on a winter
afternoon. i also use arithmetic for solar pool heating in december:
>where i live, in december, a 70 f 24x36x8' deep pool with us r20 sides
>and bottom would lose about 24h(70f-54f)1824ft^2/r20 = 35k btu/day to
>the soil, and another 18h(70f-23f)24'x36'/rc = 731k/rc btu/day through
>a us rc cover at night, and 6h(70f-38f)24x36/r1 = 166k btu/day through
>the "solar pool cover" during the day, and gain about 620x0.9x24x36
>= 482k btu/day of solar heat through the cover, so if the solar energy
>that flows into the pool equals the heat energy that flows out during
>an average december day, 482k = 35k + 731k/rc + 166k, so rc = 2.6.
where's your arithmetic, andrew?
>an inch of beadboard (r4) or styrofoam (r5) insulation might be enough,
>or more, if the cover is in 4x8' modular rafts tied together with
>uninsulated gaps between them.
let's see... the aforesaid pool with an r10 cover would lose about
24h(70f-30f)24x36/r10 + 35k = 118k btu on a cloudy december day. with
c = 442k btu/f of water and an equal thermal soil capacitance, the
temperature would decrease 118k/884k = 0.13 degrees f on a cloudy day.
>a pool cover is absolutely necessary to keep a pool warm in any climate...
agreed...
>pool covers made of semi-transparent plastic, with bubbles moulded in, are
>made specifically for the pool industry and are very inexpensive.
those pool covers are miserable insulators, us r1 at best,
vs. a common r20 house wall. very poor thermal band-aids.
>forget trying to float rigid foam boards, they are much too cumbersome...
these would automatically sink to the bottom for swimming or solar
collection. swimming under the concrete/foam covers is inadvisable,
in the sunken position.
>your best bet for solar pool heating is to purchase pre-manufactured
>plastic solar panels from a company like fafco, or solar industries,
>and install them yourself.
bailing buckets for bottomless boats...
nick
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