I have seen quite a few people talk about using solar to heat water. I haven't seen any that made it work. The problem is that it takes too much power to do it at a remotely reasonable cost. You might consider insulated waterers instead.
I don't know about solar capacity for infrared heat. Let us know how that goes if you try it.
I understand wanting to add heat on the coldest nights; I worried too for the first winter here in the upper midwest. Then I experienced how effective feathers are as insulation by playing with some loose feathers and down in a bag and by feeling how warm my chickens were and watching how they acted. With good ventilation in the coop, and enough food and water, and being acclimated, it really is unnecessary.
