Reddit mentions of EZ-37 Solar Water Heater Panel by Heliatos

As promised here is a follow up on collecting solar thermal energy (heat) to use in a off grid chicken coop. If you can collect the heat of the sun all day, and find a way to store it, then you can use the collect heat while the sun is shining or for hours after dark.

There are several solutions for collecting heat from the sun. The simplest way is to use a coil inside of a panel. A coil is a continuous tube that a fluid can pass though. A panel is a box to hold the coil. The coil zig-zags back and forth across the panel. On one end of the panel is an inlet to the coil. At the other end of the panel is the coil's outlet. The panel should have a clear face allowing for the maximum amount of sunlight to reach the coil. The inside of the panel can be painted black to hold as much heat as possible.

There are commercial units a plenty some have unique designs.

https://www.amazon.com/EZ-37-Solar-Water-Heater-Heliatos/dp/B007F54PUY/ref=asc_df_B007F54PUY/

https://www.alibaba.com/product-detail/Domestic-stainless-steel-high-efficiency-non_60440911805.html

Energy can be extracted from the sun when the panel and coil is exposed to sunlight. A fluid passed through the coil will be warmed by the sun. A pump can be used to recirculate the fluid though the panel to increase the temperature of the fluid by way of multiple passes through the coil.

Moving a hot fluid around in a circle will not get you anywhere. You want the heat of that fluid for your own purposes. It maybe to keep a water bucket from freezing in winter, it maybe to provide warmth for your chickens. It may be tempting to use water as the fluid in your coil, but it would be wiser to use an oil or possibly antifreeze. This will give you a reliable heat source that you can tap for what you need.

To harness the heat from the panel connect a secondary coil between the panel outlet and the pump. A cylindrical copper coil placed into a bucket of water will transfer heat. The fluid in the coil will warm the water in the bucket. With each pass of the fluid through the coil heat will be gained from the sun and lost in the water. If the total amount of heat gained from the sun is greater than the heat dissipated by the system then the bucket of water will heat up.

The easiest way to store the energy harnessed from the sun is to use an insulated tank. Place a secondary coil into an insulated water tank. You can mix this water with cold water to give to your flock. Or you can pass this water (with a second pump) through a radiator to warm your coop.

To make this work you will need a power source, in most cases a 12v battery. There are many 12v pumps available on the market. When the sun is not shining the pump should be shut off to prevent loss of heat.

EZ-37 Solar Water Heater Panel by Heliatos https://www.amazon.com/dp/B007F54PUY/ref=cm_sw_r_cp_apa_UKoDzbCA7TG1A

Just use one of these water heater panels.