"Beer Bottle Solar Collector"
In July of 1979 the "Beer Bottle Solar Collector" by David E. Cowlishaw made the front page of the Springfield Gazzette in the Eugene Oregon area. The editorial commentary said "He's betting at least a six pack on it." The inventor didn't have editorial rights, the bottles are used as storage rather than collecting, and the "green" concepts of today were perhaps a little early for this concept. Obviously this concept is now public domain.
Below is a suggested construction for an externally mounted collector comprised of double glazed windows over black painted metal (such as aluminum siding or metal roofing), with an insulated back, such as foil faced rigid foam insulation.
Resealable recycled bottles contain water with a few drops of bleach, and are stacked on suitable sheet material, arranged to force a serpentine path for the air flow. A one way valve at the top (such as rigid foam insulation flap or slightly overbalanced butterfly), will prevent nightime counterflow of heat to the outdoors. Large air passages will accomodate thermosiphon circulation, eliminating the need for fans or electricity.
For a home with ceilings above the top of the heat storage closet, thermosiphon circulation can also be accomplished, for an electricity free heating system.
With a captured air bubble in a metal container, and a hydraulic line to open and close the interior valve, expanding hot air in a simple mechanical thermostat will close the valve when suitable temperatures are achieved, and contracting cold air will open the valve for demand heating. A means to adjust the captured air volume (such as a large hypo from your local farm supply) will give you an adjustable temperature control.
Clearly this is not a set of plans, but a concept that will allow a builder to make an inexpensive, long service life solar heating system using bottles that would ordinarily be destroyed in the recycling waste stream. To start yours, make arrangements with your local grocers to save the big bottles (quarts, 40 ounces, etc.), and pay them a premium for caps included.
If you pay them 8 cents per bottle with caps, 400 quart bottles for water containment (and heat exchanger surfaces) will cost you $32.00 per 100 gallons of water heat storage. Plus you'll have emergency water if ever needed (don't forget the bleach)!
This is offered in the spirit of getting this information out, and utilized. If you build it, and don't take into account possible overtemperatures (and exploding bottles), weight support requirements, and good construction and insulation techniques, don't try this at home, hire a professional!
Submitted to Solar Oregon, Monday, 29 November 2010 by David Cowlishaw firstname.lastname@example.org
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