My solar heated stock tank, I hope it works!

I've been wanting to build one of these for a few years now and finally decided to just do it. I basically followed the plans on this site, http://www.builditsolar.com/Projects/WaterHeating/SolarHorseTank/SolarHorseTank.htm, but modified the box to fit my tank. I have a wider, lower, black plastic stock slready so I built the box to fit my tank. I also used 2" blueboard insulation on the side because we already had some laying around. Ditto for the 1" foam board with foil backing for the lid. I would really prefer to use thicker insulation on the lid, but didn't have enough to use two layers and didn't really want to buy another board. We'll see how this works this winter and make any modifications, if needed, next spring.

I didn't think to take pics of the whole building process, but here's the box. The original plan called for thinner blue board that would fit in the gap between the corner 2x4's and the plywood outside. I only had 2" board, so I filled those gaps with spray foam. I also used the spray foam on all the gaps and seams between blue board and wood, wherever needed. There's the 2" blue board all around the sides and two layers of it on the bottom.

Here it is with the tank in it. You can see the foil backed insulation on the lid. The cloth lines the drinking hole to hopefully help with the wind sucking heat out of the tank.

Here's the finished product. The board on top is help with the seam where two pieces of OSB meet. Didn't have enough, unfortunately, to use one whole piece.

A close up of the oilcloth around the drinking hole.

Here it is in place. As you can see, it's shaded, I have to move my haystack. :(

Oh, well.

This is to water the goats and a couple of cows. I'm hoping to drastically reduce the use of the stock tank heater. That sucker uses a lot of electricity. I will try to remember to update on how it's working over the winter. If it does work well, I am going to make a smaller version for the 'girls', the dairy does.