Karolyn lives in Minnesota where the winters are COLD and built this very efficient solar heated stock tank.
The design is based on the earlier solar heated stock tanks, but incorporates better and more complete insulation and a carefully designed drinking opening with a canvas shield that goes well down into the tank and reduces heat loss from the opening.
The performance of the tank has been very good through the very tough 2013 - 2014 winter.
Details on the construction and performance below.
Thanks very much to Karolyn for sending this material in!
I built a solar tank for my horses this winter 2013-2014.
I used some of your suggestions/plans, and added a few of my own ideas.
The tank is a 100 gal galvanized tank.
The box is made from 1/2" plywood, and 2 x 4 's throughout.
I used 4" insulation, top, bottom and sides. The insulation was brought out to the full box. This insulation is rated at R14. I used fiberglass insulation to fill the gap between the metal tank and the R14 sidewall insulation so there are no "dead" spaces.
The south side of the tank has two clear panels, both sealed, and with a 4" space between them. Then another about 4" space between the inner clear panel and the flat black painted tank wall. The sun shines through these glazed panels onto the black metal tank heating it.
From the front two curves of the metal tank on the sun/collector side, there is sealed insulation that does not allow any heated air to escape the front heating space. The top in this area is 4" insulation, as well as the sides and bottom, and they are all sealed (caulked).
I covered the clear panel outside with a 8" square wire panel to protect the clear panels from hooves and teeth.
All wood edges are protected with metal edging as well.
The top has an opening that measures 10" x 15" and is edged with a 2 x 4 frame with metal edging. The 2 x 4 frame holds the canvas that lines the water hole and hangs into the water within 3" of the bottom of the tank. This is to keep the cold air/wind from cooling the whole tank, only the exposed water (the opening) and the rest of the tank stays warmer.
More on the general internal construction of this type of tank...
I am in Minnesota, and we have had a very cold, snowy, winter this year.
I installed a floating thermometer and recorded all tank temps for the frigid winter, and they were all above freezing -- no ice.
The lowest temp was 41 degrees, with an overnight outside temperature that read -25F the night before. Daytime temperatures were in the 50's all the way to 62 degrees on many occasions on sunny days with highs on those days of 10 to 25 degrees.
One year update from Karolyn:
"I couldn't be happier with it. It has proven to be a very efficient tank with no need for an electrical heater. It never has had ice in it, so I think that says a lot about Solar built to work and be successful."
October 9, 2014