Picture of Solar Water Heater
This is basically what the name says, it's a water heater.

Tests: For the tests I used the water heater vs a regular bottle, each had one cup of water in it
The starting temperature of the water was 20C(68F)
The outside temperature was 10.5C
After half an hour the regular bottle was at 18C(64.4F), and the heater was at 26C(78.8F)
I would have done a longer test but the sun went down.
*There was a large amount of moisture on the walls of the heater wich reduces the amount of sunlight that can heat it. I poured some salt into it which will hopefully dry it out.
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Step 1: Supplies

Picture of Supplies
-A glass bottle
-A can of spraypaint
-Two clear 2 liter bottles
-Electrical tape
-A rubber hose and a small plastic tube(or a slightly smaller rubber hose that fits properly into the glass and plastic bottle)
-A vacuum pump
-A piece of plastic or cardboard

Step 2: Preparing Your Bottles

Picture of Preparing Your Bottles
Cut the bottoms off both of the plastic bottles, make this cut as smooth as possible.
Take one of the pieces from the bottom and either cut or drill a hole in the bottom large enough to it over the mouth of your glass bottle. If you drill this, make sure you get it right the first time.
Put your bottle on a stick and spraypaint it black. Now wait for it to dry...
Put the bottom of your plastic bottle over the mouth of the glass bottle.
jj.inc4 years ago
how can those 2 liter bottles hold any vacuum at all.
Magnelectrostatic (author)  jj.inc4 years ago
Even though they're just plastic bottles they do have some amount of strength...
Well, I mean, When I go suck the air out of my 2liter bottle I have sitting here it just collapses, do you even need a vacuum pump for this.
Magnelectrostatic (author)  jj.inc4 years ago
no...(well, depends on what you mean) I used one of those wine sealer things.
If you want a stronger vacuum I would suggest putting some cardboard rings inside the bottles, they'll add strength without cutting down much on the light intake.
Honestly the vacuum idea is a good concept but I didn't really give the actual build enough attention.
I know the vacuum is a great benefit to solar heaters and this cardboard Idea is good.
very cool idea i have been planning a big thing like this On my front Garden wioth pumps for Mopcving water and i like the reflector idea