How about keeping the tank on the roof and using a thermosiphon [1] or, better still, a passive vapor heat pipe [2] to transfer heat to the tank from a collector below? The height difference between the collector and the tank would only have to be a foot or two and you'd want the tank on the roof anyway to provide pressure when using the hot water.
[mg] [1] http://en.wikipedia.org/wiki/Thermosiphon [2] http://en.wikipedia.org/wiki/Heat_pipe On Tue, Sep 18, 2012 at 4:42 PM, <[email protected]> wrote: > I know of a few locations where it would be nice to have passive solar hot > water in the summer. I have noted that a black garden hose in the sun > produces hot water. The hose could be placed on a roof. The problem is > getting this heat into a storage tank passively. The hot water tank > would have to be mounted higher than than the hose. I would like > to employ the ordinary basement hot water tank. Hot water rises and will > not go down to the basement tank. > > Is there any fluid that sinks when heated? Can a dissolved gas be > somehow employed to make hot water sink? > > Any ideas? > > Frank Znidarsic >
