Anyone have a solar water heater? Planning for cold...

Hi All:
I have a new coop/run and no electricity. Will have a solar electric fence charger, so am wondering if anyone has tried a solar water heater. Maybe just use a black rubber tub for water in a sunny place and diligence when it's freezing. Am in N. VA and water freezes regularly around here in the winter.
Cheers,
N. VA.

PS am hoping to keep the food/water outside the coop (underneath, actually, as the coop is up on concrete blocks) so I'd want something that could conduct the heat from the roof or fence post down to the waterer.