If you'd asked me a year ago if I would be posting to the "Water" section, I would have answered "no".
How things change!
Here's an interesting project that I took on this month. With winter here, and water troughs needing heat to stay thawed, I've put up with exposed steel troughs long enough. Why these things don't just come from the manufacturer with insulation wraps is a mystery to me. Three years ago, I built an insulated box for a water trough, and it is still effective. Now that we have more horses we need more water troughs. Into the old water trough, I never built into it provisions for putting in insulation. I decided that the second cover would be better and have insulation.
To insulate mine, I had plenty of particle-board and 2x4's lying around, so building a box to cover the trough was easy. I built this carefully, however, to ensure room for the insulation and not much wasted space around the trough walls.
To capture some heat from the sun, I found a great idea from Build-It-Solar, and added a solar collector to one side. Here is the page from Build It Solar that inspired me. There were some limitations in the Build-It-Solar water trough, most relating to the need for ruggedness. Worse, the water was held in only by walls of plywood lined with plastic pool-wrap. Horses are like little bulldozers with teeth. Leaving a solar collector within reach of their hooves invites disaster. And if it isn't possible to throw in a floating water heater on seriously cold days, then there's no point in doing this project. A piddly solar collector will not melt water when it's -30! So using a metal trough to hold the water was essential.
For the solar collector to heat the water, the sunlight must be absorbed efficiently. I painted the water trough black. It turned out that the black paint was glossy, but I had a bit of matte left in a spray can, so I lightly sprayed that on the side that would be in the sun. Sun entering the clear panel hits the black metal water tank and passively warms the water. I have no idea how strong the effect will ultimately be, but I'll never find out if I don't try.
So far, I've used only left-over materials from other projects (building a new barn, tearing down an old one, etc.). When it came to covering the solar collector, I had some translucent panel materials, which also happened to fit perfectly. Looking at them realistically, though, I realized that the fiberglass panels would not let much light through directly to the trough. A lot of energy would be absorbed into the fiberglass sheets themselves, defeating the purpose. I went to the hardware store and picked up a clear corrugated polycarbonate sheet instead ("Suntuf"). It was easy to work with, and is very transparent.
I packed foam insulation into the walls, including making an insulated base with a sandwich of plywood and foam insulation. The insulation in the walls is R=7.5, and the double thickness in the bottom would be about R=15. More insulation on top of the trough does two things. First, obviously, insulates the water from radiating heat through the top surface. Second, the top sheet of insulation blocks air circulation between the sun collector area and the air above the water. Why?
Because you have to cut a hole in the lid! The horses are getting thirsty! (another mystery of the Build-It-Solar tank, they carefully tested their tank, but there was no drinking hole in it) With a hole cut out, the air above the water will almost always be cold. Wind will make that air circulate in and out of the hole. If the air circulation also cools the air in the solar collector, then the solar effect is diminished.
Here it finally is, facing south (it was sunset when I took the picture, so no more sunshine into the collecter). The cut-out in the top is 12"x12"; just enough for the horses to poke their noses through. They aren't too keen on doing that yet, but they are getting used to it. Pieces of metal trim around the edges of plywood to prevent chewing.
Well, there it is. Hope it interests someone. Not a lot of farmers visit a site like this one, I know, but I thought it was germane to the topics of saving energy and collecting it from the sun.
Steven