> A team of engineers at Stanford University has found a way to cool buildings by using interplanetary space as a heat sink.
LOL. Yes. I’ve actually done some calculations of using interplanetary space as a heat sink for buildings as part of my CSIRO work.
And no, we’re not talking white paint, we’re talking black paint.
Radiation from a building can be intercepted by other objects on the ground, by the atmosphere and clouds, or be emitted straight to outer space. When I mathematically switched off thermal convection in the air, the resulting “undercooling” at night of building surfaces would drop the building surface temperatures to about 20 degrees C below that of the local atmosphere. When thermal convection in the atmosphere was mathematically switched back on the building surface becomes 1 to 2 degrees C cooler than the atmosphere. This is known as “undercooling”.
For the work I was doing this undercooling due to radiation to space was bad news. At times of high humidity the local drop in temperature results in condensation, and the thin layer of water formed is the worst possible situation with regards to rusting – there’s not enough water to oxygen and salt electrolytes block the access of . Most of the rusting of Australia’s galvanised iron roofs is due to this undercooling created by radiation to space. Ditto for rusting of tools inside sheds and factories.
Another view on this is seen in Frank Herbert’s book Dune, where “dew collectors” are thermoplastics that turn white during the day to keep cool and turn black during the night to radiate excess heat to space to collect as much dew as possible.
A maximum undercooling material that does not rely on colour change would be one that is reflective at short wavelengths (350 to 750 nm) and completely non-reflective a long wavelengths (longer than 3 micrometres).
Anyway, if following the strategy proposed in the article, BEWARE OF CONDENSATION.
