Yesterday I finished disassembling the whole solar water heater system in preparation for moving it up on the roof, inside a new (yet to be built) breadbox.
I've pondered several design ideas, with teh simplest being essentially a framed-up version of the same "tent" that I already had down on teh ground.
The ground version was just taped together--the one on the roof would have a wooden frame the plex pieces would all be screwed into, and a metal base frame that the tank would be strapped to and evertying else bolted down to, and styrofoam sheets layered between just under the tank and the roof itself, to help keep heat inside it instead of escaping down thru the roof into the house.
It'd have clear plastic east and west ends, made out of smaller thinner pieces of plex and sheet plastic I had salvaged from the remodels at work and from Mark, double-layered with an air gap. That should help trap heat inside at the ends, including when it has no sun on it. Both north and south tent sides would be the large thick plex panels from Mark. I have found some of my gate hinges that can be used to allow opening the unit up; they'd go on the bottom end of the south face of it, so I can fold the south face panel down and out, to access the tank and plumbing and pump and wiring when necessary (which will hopefully never have to be used).
Above the ends of the tent would be a pair of tubes following the shape of the tent itself, but with a big radius curve at the apex, to hold an insulation sheet (probably a blanket or set of layered blankets, with a plastic cover to help keep rain off of them), that I can pull over the whole thing at night or when it's raining, to help hold in the heat better when no sun is on it (so that when it gets sun again it doesn't have to heat it up as much, since less heat would be lost from it).
Also considering two insulation-covered thick "endcaps" that would hinge from the bottom, and fold up against the east and west ends of the tent, with a pull of a cord. Weighted or sprung against that cord so that when the cord is not being pulled down they'll lay back down against the roof and allow heat into the sides. Painted flat black on the inside so they get more heat when they are open, and make the roof hotter there in that area to help the tank heat more too.
Possibly do the same thing (instead of the frame and blanket layers) for the north and south tent faces. Then I only open the north face for wintertime, spring, and fall, and open both for summer because the sun will be overhead and north of the unit then, and having it all clear will let more heat in.
The "tent" shape is probably the most stable without bolting to the roof, with most of it's mass well below the halfway point in it's height, and most of it's surface area below that as well, so ti'd be harder for winds to tip over even if they got as high as earlier this season when trees were uprooted around town.
The other shapes I've considered are less like an isoceles triangle the tent would be, and more like a rigth triangle, with the perpendicular sides beign the base and the north side whcih would also be tall, with the tank held vertically (instead of horizontally like in the tent), and the tank leaning with the top toward teh north and the bottom toward the south, at something like a 45 degree angle, or possibly even closer to parallel with the roof surface. However, this would get less efficient during summer, though as hot as it is then that would not really affect it's usefulness. :lol: It would possibly make it better at heating in the early morning and evening, though, if the sides of the tank were facing east/west instead of north/south.
But it *would* make ti much more susceptible to winds, so perhaps simply turning the tent so it's large sides are east/west and ends are north/south would be a better compromise.
The roof angle is very shallow where it would go, but does still make it face more north if I do that with the tent perfectly parallel with the roof. If I build the tent so that ti's north end is raised up, however, I can make it so it is iether completely level, or actually faces south a little, without making it quite as vulnerable to winds as the other version would be.
I've just about convinced myself the tent is the simplest to build and the most wind-resistant, so input from others with any experience in this is appreciated.
Also, I think the "petal" style of hinged-base insulation covers for all four sides would be the best and certainly easiest to operate method of covering it when there's no sun on it, and is also the most wind-tolerant (or can be made so, much more than blankets on a pipe frame, which will act like a sail or parachute in the wrong wind conditions).
If my descriptions are not sufficient, I can post drawings. HAvent' made any yet as I'm still playing in my head with the ideas.