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This sounds like a waste of energy to me. I think all roofs should be covered in solar power generating equipment. Reflecting all that sun energy back into the

This sounds like a waste of energy to me. I think all roofs should be covered in solar power generating equipment. Reflecting all that sun energy back into the air just heats up our planet, better to convert that into electricity

orev 6y ago
Light turns into heat when it is absorbed by a material. Reflecting it back into the air sends it (and the heat) back out into space, and since air is mostly clear it does not get absorbed so doesn’t “heat up the planet”, at least not in any significant way. Sure, using the energy for solar would be nice too, but that’s far more expensive per square meter, so paint is a fine solution that’s cheap.
- ping_pong 6y ago
  I guess everyone is forgetting about the "Greenhouse effect" where that theoreticaly light/heat is reflected back into the Earth? Or do you not believe in the Greenhouse effect?
dredmorbius 6y ago
Both have their merits. It depends on what's needed in a specific location, how much incident sunlight there is, and what the effects on other cooling loads are. By reflecting white light back through the atmosphere, rather than absorbing light and re-radiating heat (infrared) wavelengths, more energy can be transmitted back through and out of the atmosphere into space. Air, and specifically the CO2 and other greenhouse gasses in it, are relatively opaque to infrared light, so that is trapped. In areas with high cooling loads, offsetting heat before it can enter into structures has benefits. This is reflective rather than insulative blocking, and is quite effective. Solar panels are of course useful, though expensive compared with even specialty paints. They also convert most of the incident sunlight to heat (only about 10-20% is typically converted to electricity), which is re-radiated into surroundings. Again, typically this isn't a major factor, but it could well be worthwhile painting surfaces not covered with PV arrays white, especially in warm climates and high-solar-incidence regions. I have my doubts whether this specific paint's characteristics are all that meaningful in a real world with dust, dirt, grime, and bird droppings. But the underlying idea is valid and has been used in similar technologies and deployments.

orev 6y ago

Light turns into heat when it is absorbed by a material. Reflecting it back into the air sends it (and the heat) back out into space, and since air is mostly clear it does not get absorbed so doesn’t “heat up the planet”, at least not in any significant way. Sure, using the energy for solar would be nice too, but that’s far more expensive per square meter, so paint is a fine solution that’s cheap.

ping_pong 6y ago
I guess everyone is forgetting about the "Greenhouse effect" where that theoreticaly light/heat is reflected back into the Earth? Or do you not believe in the Greenhouse effect?

dredmorbius 6y ago

Both have their merits. It depends on what's needed in a specific location, how much incident sunlight there is, and what the effects on other cooling loads are. By reflecting white light back through the atmosphere, rather than absorbing light and re-radiating heat (infrared) wavelengths, more energy can be transmitted back through and out of the atmosphere into space. Air, and specifically the CO2 and other greenhouse gasses in it, are relatively opaque to infrared light, so that is trapped. In areas with high cooling loads, offsetting heat before it can enter into structures has benefits. This is reflective rather than insulative blocking, and is quite effective. Solar panels are of course useful, though expensive compared with even specialty paints. They also convert most of the incident sunlight to heat (only about 10-20% is typically converted to electricity), which is re-radiated into surroundings. Again, typically this isn't a major factor, but it could well be worthwhile painting surfaces not covered with PV arrays white, especially in warm climates and high-solar-incidence regions. I have my doubts whether this specific paint's characteristics are all that meaningful in a real world with dust, dirt, grime, and bird droppings. But the underlying idea is valid and has been used in similar technologies and deployments.