Could highly reflective paint that acts as passive cooling count as a maxwell's demon?

[GrahamF]

Xiulin Ruan, a professor of mechanical engineering at Purdue University, and his students came up with a white paint that reflects 98.1 percent of solar radiation. The white paint actually emits more infrared heat than it absorbs. For example, previous experiments showed this paint cooling a surface by 8 degrees Fahrenheit versus the surroundings under noon sunlight. At night, the ultra-white material can keep things 19 degrees Fahrenheit cooler. Wouldn't this functionally be a form of Maxwell's Demon?

[exchemist]

1 hour ago, GrahamF said:

Xiulin Ruan, a professor of mechanical engineering at Purdue University, and his students came up with a white paint that reflects 98.1 percent of solar radiation. The white paint actually emits more infrared heat than it absorbs. For example, previous experiments showed this paint cooling a surface by 8 degrees Fahrenheit versus the surroundings under noon sunlight. At night, the ultra-white material can keep things 19 degrees Fahrenheit cooler. Wouldn't this functionally be a form of Maxwell's Demon?

Something odd here. An efficient emitter of thermal radiation is a black body, not a white one. Do you have a link describing what they did in more detail?

As for Maxwell’s Demon, no. The surface of the ground at night will often be cooler than the air, if there is no cloud cover. That’s because from a radiation point of view the ground is trying to get towards thermal equilibrium with space - which is very cold.

[exchemist]

4 hours ago, GrahamF said:

Xiulin Ruan, a professor of mechanical engineering at Purdue University, and his students came up with a white paint that reflects 98.1 percent of solar radiation. The white paint actually emits more infrared heat than it absorbs. For example, previous experiments showed this paint cooling a surface by 8 degrees Fahrenheit versus the surroundings under noon sunlight. At night, the ultra-white material can keep things 19 degrees Fahrenheit cooler. Wouldn't this functionally be a form of Maxwell's Demon?

OK, I may have found the basis of this: https://pubs.acs.org/doi/10.1021/acsami.1c02368

Translating the jargon into normal language, this is based on barium sulphate, which the authors say has a high band gap - which makes it non-absorptive, i.e. white, in the visible region of the spectrum, while having a "9μ phonon resonance", i.e. vibrational excitation of the crystal lattice, making it a good absorber and emitter in the infra red. 

In effect, this paint is white in the visible but "black" in the IR! Very clever. 

But no Maxwell's Demon.  Thermodynamics continues to rule. 

 

 

[TheVat]

Phoenix, your paint has arrived.

[Endy0816]

NiteHawkInLight released a great video on this recently, including his work and process to make a home kitchen version.

Interesting stuff.