So, how does the solar water bottle work in practice?
All one needs is a small square of corrugated iron sheet. With a saw blade one cuts a hole into it the size of a Coke bottle. The hole must fit the bottle snuggly and have holding teeth cut by pliers so the 2 kg bottle cannot fall inside.
Then the bottle is filled with water and some bleach against algae. Some silicone goes around the bottle and some to the sheet before it is sunk into a hole in the roof just a bit smaller than our construction. The hole in the actual roof is best cut with a grinder. Some rivets make it perfect.
After a couple of years one just changes the bottle and on it goes as a free 60 watt light bulb.
For detailed installation instructions, click here.