## A hypothetical machine (fluid expansion)

Hello,

Imagine that we have a fluid heated up by solar energy (every day during sunlight). Due to higher temperature it would undergo thermal expansion and do some mehanical work while expanding, right? And during night it would cool down and hence compress and do some negative mechanical work. Now, my friend has an idea of constructing a shading system (practically a set of "shading units" that cover people from sun and open at day and close at night). What are the possible complications that might arise?
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 Recognitions: Gold Member Your friend is obviously thinking, which is always a good thing. In this case, however, his approach would be counterproductive. The most efficient use of solar energy would be based upon accumulating all heat or light available, which "shuttering" would decrease.
 Perhaps that's the point. Perhaps this invention is intended to keep houses cool by automatically closing shutters on windows in strong sunshine? I think it might work but I suspect it would be hard to control the exact time at which the shutters open or close. Sunshine isn't allways a good measure of temperature either. Many countries have a lot of sunshine in winter when it's cold with snow on the ground. Do you want the shutters open or closed then? Open to allow heat in but closed if the sun is too bright?

## A hypothetical machine (fluid expansion)

Also, the coefficients are thermal expansion (volumetric coefficents) are small numbers. Let's take for instance ethanol (which expands quite a lot) whose β=750*10^(-6) K^-1.

Do you agree that thermal expansion will be too negligible to produce any significant work, like closing/opening the shutters?

Recognitions: