Blue Cat wrote:
I imagine that a solar puddle would do the job as a quick and dirty
water heater. The plastic doesn't last long though.
There is the beer bottle collector, but it seems like a lot of work.
Batch water heaters, in general, are about as simple as you're going
to get. They're basically a tank, or some kind of container, of water
painted black, enclosed in an box (insulated if possible) with a glass
front that generally faces the sun.
Plans for batch heaters can be found for free on the web. Here is one.
I imagine you could construct something like a longer lasting solar
puddle using more durable materials. Scrap metals and glass would
seem to be the cheapest stuff you'll likely to find.