Solar Window Heater at Night

Question

I have been thinking for a long time about building a Passive Solar Window Heater similar to this:

I live in northern - North America which during the winter ranges from 30°F during the day to 0°F at night (on average).

I am note sure if it will help but it seems like an easy and inexpensive project I can do but the thing holding me back is this; what happens at night? How much heat will I loose out this "open window" during the 16 hours the sun is not shinning on it?

I was wondering if someone else with similar conditions could weight in on how it has worked for them. The last thing I want to do is take it out every night and back in every morning. I know that won't last long. The other option I thought of was a way to close/seal/insulate the opening at night. That twice a day task might be possible.

Answer 1

The trick is to capture the heat in a fluid that circulates through the system only when the sun is heating the fluid. That way, you get the heating with very little cooling. It makes for a more complicated system, but it's worth it; otherwise, your daytime heat collector will become a night-time heat radiator.

Domestic solar thermal panels are a well-established technology: there's a lot to be learnt from how they're designed and operated. There's no need to ignore all that experience and learning - make the most of it.