Thanks so much for all the ideas and links!
In this case, "camp" means a 1920's one-room building 24x24 - something like what 'ghurd' posted a photo of. I have a small solar panel that currently gives me light and water pumped up from the lake.
I am trying to strike a happy medium between a black tank on the roof (no hot water in the morning for a shower, need to reinforce the roof), and the more complex systems. I was originally looking at building a system with a circulating pump, but the thermosiphon seems so much more elegant, and no sensors or drain on the PV system.
I have a nice 2' x 4' piece of thermopane glass from an old skylight, a bunch of miscellaneous 1/2" copper pipe, and a beer keg (that someone converted to an electric water heater a long time ago, but I'm reforming it).
My idea is to build a pressure treated wood box to hold the glass and the copper pipe, mount that box low on the roof, and pipe it to the beer keg in the attic (liberally insulated with fiberglass). I should be able to get it easily 2 feet above the top of the collector. I imagine I will need to insulate the pipe from the collector to the tank (distance will be about 10 feet or so).
1) Am I on the right track?
2) What do I use economically for a backing plate, and how do I bond the pipes to it?
3) Where do the various inlets and outlets go to? It seems like the cold supply and the cold out to the collector should go in the bottom of the tank, and the hot from the collector and the hot out of the tank should come out the top, but the various diagrams are not so clear on this point.
Most of the diagrams I have seen are for using a thermosiphon system as a preheater for another system, not on their own, and they use more complicated plumbing and diffusers.