A sentence virtually never spoken concerning my attempts at improvised infrastructure is “It works too well.” In this case it originally worked so well it destroyed itself, repeatedly, so really didn’t work at all – at least never for very long.
There’s been a lot of simplification since the beginning, because every “improvement” I originally thought up turned out to be a disadvantage. But the biggest problem was that I was using a real proper solar collector box that a neighbor gave me, and…
…it just got way too hot in there. Hot enough to melt epoxy. Hot enough to melt PVC, for heaven’s sake*. Rubber gaskets couldn’t survive it. And anyway, when you open the hot water tap in your house you don’t want live steam. Which is what I was getting.
So the final and probably the most effective simplification has been to just not close the glass cover. This had a dramatic effect: Water temperature went from way too hot to barely hot enough. It’s been a cool May and I expect later summer water temperature to increase.
Overall, simplifications continued until my water heater was just a bunch of black hose in a fiberglass box…
…terminating at a bit of pipe stub and a faucet. And so far it’s working…adequately, but only just. I have hottish water in the afternoon, basically. Which saves me some propane for dish washing but is nothing to get excited about. With no cover on the box, the water temperature goes cold immediately at sunset.
This would all be more disappointing if not for the irony that my finally getting around to trying a solar water heater happened almost simultaneously with the appearance of a real shower at Ian’s place – after almost fifteen years of sponge baths at my kitchen sink. So the most important reason for wanting quantities of hot water disappeared just as I was getting some.
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*Yes, I did try to replace it with CPVC but ran into the “no available fittings” problem. Ended up just running the hose down to a bit of galvanized pipe.
Joel – keep an eye out for an older hot water heater unit, one that is still water tight but might have a failed heating element,. Plumb it into your system such that it fills up and keeps the water hot. Somehow also have to allow circulation back to the hot box. This might allow you to draw out the bottom outlet while the hottest water rises to the top. Has to be a way to store hot/warm water such that you get what you need any time. Just a thought to kick around.
Okay think of this: Make your collector less efficient when the sun is hot. Mount 12 volt muffin fan in the side of the box and then replace the lid. Control the fan with an auto thermostat. It will maintain 180-200 degrees in the box and only use power when the sun is out.
https://smile.amazon.com/gp/aw/d/B092M99DLQ/ref=sspa_mw_detail_1?ie=UTF8&psc=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWwp13NParams
Just block the dang thing with a piece of cloth, or a piece of plywood, or anything. Clearly your heat input is vastly greater than your need.
Also, increase the amount of water mass that is being heated. You need 100+ gallons of water in this loop. If you mounted the tank high, and the collector low, convection would heat the tank. Then draw the water from the tank.
I experienced the power of an insulated box in the sunshine many long moons ago. You can make pizza in an oven made that way…
To me, the fact that you can generate that much heat with the box would be driving me nuts figuring out what ways it could be used. It would be like free money if you could effectively use it to heat either water or the cabin. Keep thinking about it – you’ll figure out something yet.
“…when you open the hot water tap in your house you don’t want live steam. Which is what I was getting.”
Two words: Solar Still.
You’ve got the heating coils, now just attach the condensing coils and a collector. The sun can supply your distilled water needs throughout the day while you go off and do other stuff.
I’d second the Neon Madman’s though, but I’m not a plumber or an electrician (I hear “steam” I think “generator”…but you’ve already got solar electric). Seems like that power should be usable somehow. Good luck with whatever you decide to do with it:-).
A variation of Ben’s suggestion, what if you put some of those circular dampers you see on charcoal grills on opposite sides of the case, and use bimetallic strips from old thermostats to turn them, with physical stops so they can only go from full close to full open.