It's an idea that's been in the back of my mind for a while, and while some people have told me that similar ideas already exist, I haven't found them on the Internet yet.
This idea for a prototype follows on from a number of reflections on the management of heat flows in our human buildings. The catalyst for these reflections was a discussion with a thermal engineer, who confirmed my intuition by explaining me that our current management of thermal flows is catastrophic and that there is a great deal of progress to be made in this area.
The idea is to use reversible blinds capable of absorbing or reflecting solar light energy on demand. These have a non-conductive white side and a conductive black side. As a first approach, I propose that the white side be achieved by applying a white gloss paint to a layer of cork, and that the black side be achieved by applying a matt paint to an aluminum upright, as follows:
The role of aluminum is to conduct heat well, while cork is intended to limit heat capture. The advantage of cork is that it is easy and non-polluting to produce from cork oaks.
The position of these curtains should be adjustable to some extent, with a 40 cm gap, for example. The purpose of this system is to bring the white side as close as possible to the window, so as to reflect the maximum amount of sunlight and suffer as little as possible from its thermal effects when this is not desired. On the other hand, if we need to maximize heat capture, it is important to be able to leave a substantial gap between the window and the curtains, so that we don't heat the window itself (which would dissipate the recovered heat too quickly to the outside) but the air gap between it and the curtains. As the warm air rises, we can also install silent, solar-powered fans above the windows, pulsing the warm air towards the floor of the room:
A partial angle can be given to the curtains if we wish both to take advantage of the sunlight and recover some of its light energy converted into heat (or reflect it, depending on what we need):