It's actually remarkable how much heat a simple "soda can solar panel" or "downspout solar panel" can inject into a room. Add a photovoltaic panel to run a 12v brushless 100CFM fan to stir the air and inject the hot air into the room, and you have a "free" source of 120F air to heat a few hundred square feet. Add a south-facing window shining sunlight onto a dark grey slate tile floor (which acts like heat sink) and the floor will release that heat well into the night. So with two very simple passive elements, one can, to a large degree, supplement a traditional heat source (heat pump, gas furnace, etc.). I've seen this approach work with vacation cabins in the mountains, and RVs, a well as the traditional house-on-the-cul-de-sac.
These heat collectors are cheap and simple to make (<$500), and should be quite reliable, giving a +50 degree F delta with almost zero maintenance and no utility consumption. The only moving part is the inexpensive and reliable fan.
These heat collectors are cheap and simple to make (<$500), and should be quite reliable, giving a +50 degree F delta with almost zero maintenance and no utility consumption. The only moving part is the inexpensive and reliable fan.
* https://www.pinterest.com/jayhike/soda-can-solar-heater/ and https://lifehacker.com/build-your-own-soda-can-solar-heater-...