In an effort to curb global warming engineers have created the whitest paint yet | Hacker News Reader

In an effort to curb global warming engineers have created the whitest paint yet

purdue.edu

> The paint's solar reflectance is so effective, it even worked in the middle of winter. During an outdoor test with an ambient temperature of 43 degrees Fahrenheit, the paint still managed to lower the sample temperature by 18 degrees Fahrenheit.

That statement is confusing to me, by ambient temperature do they mean surface temperature? I thought it was impossible to cool something below ambient without adding energy into the mix?

Actually, it's not. There are materials that are both generally highly reflective and also have blackbody emissions with strong peaks in frequencies that the atmosphere is transparent to. Such materials can radiate enough energy into space to passively self-cool below nearby ambient temperature, even during the day.

Depends on what you use as "ambient". Those panels and paints emit radiation in frequencies where atmosphere is transparent, so they use "coldness of outer space" as ambient.

Yes I think they simply misured the surface temp of a nearby panel not painted with this white paint.

This is cool (ha) but won’t its reflectance be substantially diminished the moment it gets dirty? Feels like that might end up being an issue if you’re aiming to paint a roof with this.

Still likely better than painting a roof with anything else, I suppose.

Could a paint like this be used to further increase the efficiency of solar panels?

Yes, if you painted the mounting surface with it, and used bifacial panels.

You'd still be better off just increasing your surface area of the normal type though.

Hmmm no, it’s not trasparent. Maybe you can paint the borders/frame of a solar panel and keep it a bit cooler but not over the panel.

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