Ive been wondering the same for a couple years now.I think this may be uncharted territory.Ive played with the idea of thermovaltic pet bowls in the winter.Just plain gathering heat during the day and it continues to keep the water above freezing at night.I will do some searching too and let you know if I find anything.Take care:Dan
Thanks Dan.......I've been looking into DIY solar lately, and I'm thinking that the reason solar heating bowls are absent is that I imagine it takes alotta energy to power a heated bowl. A panel outside a window can power an LED light, but maybe not a heating coil.
Perhaps the solution is to figure out another method of heating the bowl which wouldn't require as much energy that could be powered by a small solar panel?
I've looked into those solar horse troughs, but they start at $500, and they're much bigger than what I'm looking for. I'm thinking of a smaller water bowl that I would put in the wall of the barn, which I could attach to a battery and solar panel outside the barn.
Converting the sunlight to electricity and back to heat is very inefficient and unnecessarily complicated (more expensive).
What you want to do is collect it directly as heat.
That is easy enough to do. It is just an insulated box with a water line coiled up inside and a window to let some concentrated sunshine in. Add some mirrors to concentrate the sunshine and mount the box below the water bowl. Insulate the lines between the bowl and box and the heated water will flow up into the bowl and pull cooler water back down into the box.
The same basic idea can be scaled up to make enough hot water for bathing or even to heat your house.
This is a really interesting topic and one that I'm having fun looking into!
I couldn't find solar-powered bowls on the market for your specific purpose -- though, there are lots of birdbaths and koi ponds that heat water with solar energy -- but Build it Solar, a great resource for all things solar-powered, provides some fantastic information, photos, projects and examples of solar-powered water bowl/troughs for on-farm use! There are full construction details and lots of information on efficiency of each model! Most are pretty easy to construct and seem to have a low return rate on cost!
Here are the links:
Here's another idea - generating (small-scale) solar power from a soda pop can!
Another option might be to purchase a solar hot water pump (or make one!) and attach it to the barn:
Good luck! Keep us posted!