Active cooling Cryo paint on decks?

[JBP-PA]

Has anyone tried active cooling cryo paint on their decks? Seems ideal for boats. I've ordered their 4 oz sample and will try it somewhere. A gallon is $250!

Cryo X Co - What Will You Cool?

CryoPaint cools outdoor surfaces up to 15°F below the air temperature.

cryox.co

 

[dLj]

Sure looks like snake oil. Nothing in their technical justification looks like it supports their claims... But what do I know???

dj

 

[Ralph Johnstone]

Sure looks like snake oil.

Dunno about that. They could be charged with false advertising for giving snake oil a bad name it's so hokey.

I'm still willing to put the search for perpetual motion as one notch closer to reality than this stuff. I'd even look at UFO's before trying this stuff. Teleportation, time travel, flat earth too for that matter.

 

[Davidasailor26]

Sounded like free energy / perpetual motion to me too, but maybe it's real? This from Purdue seems to suggest it's possible - The whitest paint is here – and it’s the coolest. Literally.

 

[dLj]

Sounded like free energy / perpetual motion to me too, but maybe it's real? This from Purdue seems to suggest it's possible - The whitest paint is here – and it’s the coolest. Literally.

I would get behind that it doesn't transmit or absorb heat as other paints will, but there is no mechanism to create cooling that I can see. Hence the "15 degrees less" claim seems to defy to laws of physics - at least via the mechanisms defined in the first post. The Purdue post does not make that claim, rather it claims much great reflectivity and less absorption. That could very well be true. That could allow much less cooling needs for a building - but creating a surface that is 15 degrees less? I'm not seeing it.

dj

 

[Davidasailor26]

Hence the "15 degrees less" claim seems to defy to laws of physics - at least via the mechanisms defined in the first post. The Purdue post does not make that claim, rather it claims much great reflectivity and less absorption.

The Purdue article does say “the researchers demonstrated outdoors that the paint can keep surfaces 19 degrees Fahrenheit cooler than their ambient surroundings at night. It can also cool surfaces 8 degrees Fahrenheit below their surroundings under strong sunlight during noon hours.” And the research abstract they link to says “During field tests, the BaSO4 film stays more than 4.5 °C below ambient temperature or achieves an average cooling power of 117 W/m2.”

It makes no sense to me either, even after reading explanations of how it’s supposed to work, but I googled the phenomenon some more and couldn’t find anything that says it’s fake.

 

[Rick Webb]

Sounds like Chroma Kinetic Energy Augmentation

 

[dLj]

The Purdue article does say “the researchers demonstrated outdoors that the paint can keep surfaces 19 degrees Fahrenheit cooler than their ambient surroundings at night. It can also cool surfaces 8 degrees Fahrenheit below their surroundings under strong sunlight during noon hours.” And the research abstract they link to says “During field tests, the BaSO4 film stays more than 4.5 °C below ambient temperature or achieves an average cooling power of 117 W/m2.”

It makes no sense to me either, even after reading explanations of how it’s supposed to work, but I googled the phenomenon some more and couldn’t find anything that says it’s fake.

I guess I didn't read far enough.

These two lines can be interpreted differently: “the researchers demonstrated outdoors that the paint can keep surfaces 19 degrees Fahrenheit cooler than their ambient surroundings at night. It can also cool surfaces 8 degrees Fahrenheit below their surroundings under strong sunlight during noon hours.” If you read those clearly, they are not necessarily claiming a cooling effect.

Now, that said - this statement certainly does “During field tests, the BaSO4 film stays more than 4.5 °C below ambient temperature or achieves an average cooling power of 117 W/m2.”

@Rick Webb -what the heck is this? "Sounds like Chroma Kinetic Energy Augmentation" - I'll have to look - never heard of it...

dj

p.s. just did a quick search - it must be late - I don't get it... I'm going to bed and maybe in the morning look at this again... LOL

 

[Ralph Johnstone]

@Rick Webb -what the heck is this? "Sounds like Chroma Kinetic Energy Augmentation" - I'll have to look - never heard of it...

Don't bother @dLj or @Rick Webb will have caught two of us .

 

[pgandw]

The Purdue article does an excellent job of conflating 2 distinct phenomena - reflectivity and black body radiation. I expected nothing less from mechanical engineers.

The reflectivity using barium sulfate is about a 10-15% improvement in reflectivity - if you can make the paint with normal other paint qualities. On a boat deck, IF the coating can stand up to the environment, the reflectivity will promote sunburn even more and be harsher on your eyes. Just sayin'.

The majority of heat radiated by the barium sulfate is in an atmospheric "window". These are wavelengths where the atmospheric absorption of electromagnetic waves is low in comparison to other wavelengths. Theoretically, heat radiated at these wavelengths goes mostly out into space. However, if you stand in front of the wall or deck that is emitting, you will feel the radiated heat - just like standing in front of a brick wall after sunset. Your body does not have a window at the same wavelengths, naked or clothed. Nor do other buildings and structures. So the radiated heat that is not oriented at the clear sky (clouds reduce the window significantly) does not escape into space. But that's where the claim for "cooling" comes from.

Science lecture over. An improvement in some conditions? Yes. World changer? No.

Fred W
MSEE (Purdue U no less)

 

[thinwater]

Tricky wording. Right now it is 15 degrees warmer outside than inside my house, No AC yet. Thermal mass. Insulation. No magic way around the rule of thermodynamics. It's about time to turn the AC on, though.

The claim that you can radiate heat from cooler to warmer ... that's perpetual motion machine stuff. LOL. What's sad is when anyone believes any of it. These magic paints come out every few years. PT Barnum. Politics. People want to believe.

----

This is a real product category, just not these guys or their claims.
Cool Paints

 

[JBP-PA]

Yea, it's black body radiation combined with a highly reflective paint. I've seen it a couple places, and there are a couple YouTube experimenters who claim they made some and it works. Up until now I've only seen it offered for large scale commercial projects, but I'm willing to risk $30 to test it.
My current plan is to paint half of some white canvas, lay it on the deck when it's clear and hot, and see what happens. It's not really a fair test, since the unpainted portion will not be as reflective, but it will be fun to see what happens. I might rig the same canvas as a boom tent.

Not sure what kind of canvas to use.

 

[rgranger]

Tricky wording. Right now it is 15 degrees warmer outside than inside my house, No AC yet. Thermal mass. Insulation. No magic way around the rule of thermodynamics. It's about time to turn the AC on, though.

The claim that you can radiate heat from cooler to warmer ... that's perpetual motion machine stuff. LOL. What's sad is when anyone believes any of it. These magic paints come out every few years. PT Barnum. Politics. People want to believe.

----

This is a real product category, just not these guys or their claims.
Cool Paints

Strictly speaking, the paint doesn’t have to violate thermodynamics to work...but it would have to overcome extremely unfavorable statistics.

In principle, any pigment capable of two-photon absorption could luminesce at a higher frequency. We’ve observed this using high-powered lasers as the light source. In fact, it was purely theoretical until high-flux lasers became available. Under ambient photon flux, however, excited-state lifetimes are too short and photon density too low for a realistic statistical hope for a second photon to arrive while the molecule is still excited.

The statistics are somewhat more favorable for phosphorescence. I’ve spent some time wondering whether it might be possible to design a phosphorescent molecule with a sufficiently long-lived excited state to enable two-photon absorption of ambient IR radiation. In principle, this could allow excitation from the triplet state to an even higher electronic state, which could then relax by emitting a higher-energy photon...effectively converting absorbed IR into visible or UV light. At the time I was wondering if a pigment could be engineered to absorb IR and act as a kind of “night-light” paint (e.g., for a bathroom). I was not thinking about the pigment as a cooling agent. I was only thinking about IR radiation because (presumably) if you need a nightlight, the lights would be off in the bathroom and IR radiation is all you could count on. I even sketched out the a possible Jablonski diagram.

If one could create a long-lived triplet state capable of absorbing a second IR photon, then such a mechanism could, in principle, achieve what this “paint” claims to do.

Something similar (but in reverse) has already been developed. Early in my career, I was an intern in a lab developing DayGlo pigments (the super bright yellow and orange you see on highway worker vests and even in bingo markers).

The dayglo pigments work by pairing a fluorescent dye with a conventional pigment of similar color. The fluorescent component absorbs UV light and re-emits it as visible light near the frequency of the conventional pigment, while the regular pigment reflects that light as usual. The result is that more light of a particular color is leaving the surface of the paint than what struck the paint. This is why those pigments seem so bright.

 

[JBP-PA]

Here are my first test results. The manufacturer said canvas was not a good idea as the paint would crack so I laid up a couple of thin panels of one layer of 1708 with a hinge between them. One I painted with ordinary flat white house paint, the other with the BaSO4 Cryo-X cooling paint.

On my car on a partly cloudy day, which is not ideal for cooling paint, the result was still noticeable. After a half hour, the bare window is 111F, flat white house paint on the left is 101, and the cooling paint is 94.

Sorry for the blurry pictures, my arms aren't long enough. Next week I'll try them on my boat.

 

[JBP-PA]

Here are a couple of journal articles on how the BaSO4 paint I'm using works (referenced in the Purdue article) and cooling paints in general work. Ca3(PO4)2 calcium phosphate aka Acrylic nanorods look amazing as soon as someone makes a paint from them.

https://pubs.acs.org/aamick/article-abstract/13/18/21733/368635/Ultrawhite-BaSO4-Paints-and-Films-for-Remarkable?redirectedFrom=fulltext

https://www.sciencedirect.com/science/article/pii/S0038092X2500355X

Acrylic nanorods - calcium phosphate

https://pubs.acs.org/aaemcq/article-abstract/5/4/4117/448619/Calcium-Phosphate-Paints-for-Full-Daytime?redirectedFrom=fulltext

 

[Davidasailor26]

Pretty interesting. I wonder what the temperature readings are on the underside of the panel with the two different paints. That might be a good indication of how much heat would actually be transmitted into the boat. Plus it would eliminate any variation from the emissivity of the different surfaces that could affect the IR gun readings.

 

[JBP-PA]

Pretty interesting. I wonder what the temperature readings are on the underside of the panel with the two different paints. That might be a good indication of how much heat would actually be transmitted into the boat. Plus it would eliminate any variation from the emissivity of the different surfaces that could affect the IR gun readings.

This was "Hey the paint is dry, let's throw it on the car and see what happens." An IR gun is pretty unreliable, especially on paint that is designed to radiate IR heat. My primary temperature sensor was my Direct Information Gathering & Interpretive Thermal System, aka DIGITS, but photos of me touching it would be pretty boring. The IR gun is what I had handy. The windshield felt much hotter than 111 degrees. The panels felt consistent with the IR gun. I didn't get in the car because it was hot. The only meaningful test is whether the boat feels cooler inside, which I've yet to try.

 

[thinwater]

Here are my first test results. The manufacturer said canvas was not a good idea as the paint would crack so I laid up a couple of thin panels of one layer of 1708 with a hinge between them. One I painted with ordinary flat white house paint, the other with the BaSO4 Cryo-X cooling paint.

On my car on a partly cloudy day, which is not ideal for cooling paint, the result was still noticeable. After a half hour, the bare window is 111F, flat white house paint on the left is 101, and the cooling paint is 94.
View attachment 238995

View attachment 238996

View attachment 238997
Sorry for the blurry pictures, my arms aren't long enough. Next week I'll try them on my boat.

You can't accurately measure temperature using an IR gun...

• In the sun. You will read reflected IR.
• A white area. The test area needs to be black (read the manual).

You could read the temperature from the back side, using black-painted spots. I've used an IR thermo in industry a lot to measure temperatures on refinery equipment, and for example, if you want to measure stainless steel accurately, you have to paint a black spot. The difference can be many degrees. Reading glass accurately in the sun is just difficult, because black paint won't work, so I would skip that one.

Once you get a temperature on the back side, compare that to a shaded block spot in the same area. The difference in heat flux can then be estimated using convective heat loss equations. It won't be accurate, but it will be something. Roughly, in the range we are considering, the difference in heat transmission will be proportional to the difference between the backside temperature and the air temperature (if the air temperature is read from a shaded black surface).

Remember, the IR meter is reading IR emissions, not the actual temperature.

 

[JBP-PA]

You can't accurately measure temperature using an IR gun...

• In the sun. You will read reflected IR.
• A white area. The test area needs to be black (read the manual).

You could read the temperature from the back side, using black-painted spots. I've used an IR thermo in industry a lot to measure temperatures on refinery equipment, and for example, if you want to measure stainless steel accurately, you have to paint a black spot. The difference can be many degrees. Reading glass accurately in the sun is just difficult, because black paint won't work, so I would skip that one.

Once you get a temperature on the back side, compare that to a shaded block spot in the same area. The difference in heat flux can then be estimated using convective heat loss equations. It won't be accurate, but it will be something. Roughly, in the range we are considering, the difference in heat transmission will be proportional to the difference between the backside temperature and the air temperature (if the air temperature is read from a shaded black surface).

Remember, the IR meter is reading IR emissions, not the actual temperature.

see my previous post....

 

[colemj]

Looking at those linked articles, it appears that these paints are designed for radiative cooling as well as normal reflecting (blocking) of sunlight. The radiative cooling aspect is what mostly sets them apart from any normal reflective paint (bright white), with increased reflection a minor difference.

So measuring the temperature of their surface isn't the correct way to judge them. This would only, at most, show any difference due to reflection. At worst, it will show increased temperatures due to radiative cooling.

The correct measurement seems to be measuring the inside temperature of something coated with the paint. Maybe paint a fiberglass or metal container with a temp sensor inside?

Mark