I love solar energy and making things out of trash. This project combines the two loves into a solar water kettle made from old plastic bottles.
This kettle will heat 16 oz of water in full sun to a nice hot/warm temperature for some sun tea or washing hands, but you'll have to wait a few hours or less depending on outside temperatures. I've only recently made this during the winter and have achieved 95 degree water temps during 30 degree outside temps. Someone in a warm area of the world will have to make one and tell me how hot it can get during summer-like temperatures.
(Instructables member Kopomeroy built a few versions of this; they achieve 140-160 F during 80 F outside temps. See comments below.)
This takes three plastic bottles to build, one 2-liter, one 16 oz, and one 20 oz. Also needed are flat black spray paint, 5/8" (16mm) rubber heater hose, aluminum foil tape. The outer 2-liter bottle should preferably be clear.
After making this I realized a major problem when using a plastic bottle core; the breakdown of the plastic from heat and UV rays which could leach plastic chemicals into the water. This hot water might be useful just to wash your face or something but not to drink. An alternative to this design is to use a glass or aluminum bottle for the center bottle.
This kettle will heat 16 oz of water in full sun to a nice hot/warm temperature for some sun tea or washing hands, but you'll have to wait a few hours or less depending on outside temperatures. I've only recently made this during the winter and have achieved 95 degree water temps during 30 degree outside temps. Someone in a warm area of the world will have to make one and tell me how hot it can get during summer-like temperatures.
(Instructables member Kopomeroy built a few versions of this; they achieve 140-160 F during 80 F outside temps. See comments below.)
This takes three plastic bottles to build, one 2-liter, one 16 oz, and one 20 oz. Also needed are flat black spray paint, 5/8" (16mm) rubber heater hose, aluminum foil tape. The outer 2-liter bottle should preferably be clear.
After making this I realized a major problem when using a plastic bottle core; the breakdown of the plastic from heat and UV rays which could leach plastic chemicals into the water. This hot water might be useful just to wash your face or something but not to drink. An alternative to this design is to use a glass or aluminum bottle for the center bottle.
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Signing UpStep 1: Clean, prep, and paint
If your bottles held contents other than water, you'll probably want to wash out all the sticky drink residue. Mmmmmm....sticky drink!
Peal off all the labels.
Give the 16-oz bottle a light spray with the flat black so it drys fast, a second coat may or may not be necessary.
Peal off all the labels.
Give the 16-oz bottle a light spray with the flat black so it drys fast, a second coat may or may not be necessary.
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Aluminum has become a major suspect for Alzheimers and I suppose if not so much of our dishes were made out of it this would have been made popular in a much broader sense already.
As rule of thumb, it might be best to not use anything that doesn't occur naturally on the surface of the earth. Clay, Glas, Wood, Stone, you get the idea, no matter how much of a hippie this makes you look. ^^
- all of the energy comes from the electro-magnetic rays of the sun, (hence, this will not work unless it is a sunny day), yes?
- the absorption of the heat is augmented by the black paint, yes?
- the retention of the heat is effected by the greenhouse effect where sunlight passes freely through glass or clear plastic, but hot gasses do not effectively pass their heat back out readily - so the heat is largely retained, yes?
- you have augmented the amount of heat collected by the addition of a somewhat parabolic reflector made of tape, yes?
- the net effect is that the temperature of the tank (the black-painted bottle) is 95 Fahrenheit after 2 hours.
If I understand the principles involved and the numbers, this could scale to provide 55 gallons of 95 F water on demand in 35 degree sunny weather simply by doing the same thing with a 55 gallon tank and surrounding air-trapping plastic, no?Additional bottles (aka layers) act as insulation and help prevent energy loss to the outside.
As for scaling up -- a 55 gallon tank doesn't have enough surface area to heat up in a reasonable amount of time. You'd be better off insulating it without bothering to limit yourself to transparent insulation, and then use a separate solar thermal collector.
Separate but related rant: I hate the plastic taste in take-out coffee cup lids, who knows what is leaching into that hot drink. Why don't they make paper lids like the paper cups?
Maybe even a couple of wraps of the bubble-wrap material, unless it would interfere with the heating of the inside bottle.
Seems like it would help, actually ... but I'm not sure of the optics involved here.
http://www.twobowlbirdbath.com/photos.shtml
Check this one out http://www.instructables.com/id/Parabolic-solar-ray-gun-a.k.a-solar-death-ray/
I saw a similar idea by Steven Jones on Solarcooking.org Solar Pressure cooker
He used a glass canning jar for the inner container and a plastic bag for the outer one.
If there was some way to make a even a partial vacuum between the two bottles (without collapsing the outer one, it would insulate even better. I remember they used to make thermoses out of mirrored glass with a vacuum between the inner and outer bottle. Those were not very forgiving of over-pressurizing.
It's a very tight fit and the friction holds everything together.
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