Best transparent material that allows infrared to pass through?

In summary: The main concern is allowing the infrared to get out while keeping the cool air in.In summary, the goal of the conversation is to create mass producible radiative cooling panels that require no electricity and can reduce global warming and energy usage by 10%. The cover needs to block airflow and use air as an insulator while allowing infrared passthrough. Materials like cling wrap made of polyethylene have been suggested, but durability is a concern. The panels also need to have an aluminum shroud to block infrared from angles that are not directly above, and other optical properties such as visible light and UV do not affect the efficiency of the paint cooling. The main focus is allowing infrared to escape while keeping cool air in.
  • #1
practicalphysicsnoob
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TL;DR Summary
I'm working on building panels that reflect heat trying to create sub ambient temperatures. I need to create a cover out of something transparent that allows IR passthrough
Trying to create a version of mass producible radiative cooling panels
At first I want to start off with something able to be created at home relatively cheaply as I dive further in I will start trying to find more durable materials with the same capabilities
In order for the system to work the cover needs to block airflow and use air as the insulator but allow infrared passthrough.

I have seen cling wrap used because it is made out of polyethylene which does a decent job at it and its cheap, the only problem is durability. You can use more layers because it begins to absorb and block the passthrough of more IR.
If anyone has any ideas or suggestions that would be awesome.

My end goal is to create mass producible panels that require no electricity to passively cool, and if scaled big enough could reduce global warming and reduce energy usage across the globe by roughly 10%. Not only would that reduce the green house effect and pollution purely based on usage of fossil fuels, it would also relieve some of the pressure on energy grids across the world especially during summer months with the population getting more dense in big cities. (side note the greenhouse effect is part of the reason more methane is being released from the glaciers that are now melting which in turn is rapidly increasing the rate they melt. The panels I am working on reflect part of the radiation and instead of making the surrounding areas warmer and cooling the target area it gets reflected out into space instead of getting caught in the ozone layer.)

All credit for any of these ideas goes to Tech Ingredients and Nighthawkinlight they have already made videos on how to do this from home my goal is to come up with prototypes create a company and be able to sell them at scale while being cheap enough that almost everyone can use them.
I want to be absolutely transparent I do want to patent the prototype but the only reason I want to patent it is so a huge company doesn't come along and do it first causing artificial inflation and charging to much for the end product.

This can be made relatively cheaply, I do not care for profit margins when a product like this could do a huge part to help our earth. Every dollar I make from this idea will go back into being able to spread it far and wide. All the ingredients in making the panels are non toxic besides the polyethylene which is very little. Also if you want to reach out to me privately or ask any questions you can send an email to me [Personal information redacted by the Mentors]
Link to the original video where I got the idea
 

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  • #2
Welcome to PF.

practicalphysicsnoob said:
I do want to patent the prototype but the only reason I want to patent it is so a huge company doesn't come along and do it first
But if we help you, you won't be able to patent it without naming us all as co-inventors... :wink:

Can you give an example of where this would be used? What other optical properties do you want from this layer? What about UV? What about visible light?
 
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  • #3
berkeman said:
Welcome to PF.But if we help you, you won't be able to patent it without naming us all as co-inventors... :wink:

Can you give an example of where this would be used? What other optical properties do you want from this layer? What about UV? What about visible light?
"But if we help you, you won't be able to patent it without naming us all as co-inventors... :wink:"
Haha any help I can get would get a huge shoutout if this thing kicks off!
So far what I understand the layer between the radiative paint just needs to allow IR passthrough. The cold air at the bottom then transfers its heat to the heat exchanger layer underneath at that point it works as a normal radiator. So far the panels are going to have an aluminum shroud to block infrared from angles that are not directly above, as far as the material goes visible light passthrough and UV don't affect the efficiency of the paint cooling. The main concern is allowing the infrared to get out while keeping the cool air in.
 
  • #4
practicalphysicsnoob said:
So far what I understand the layer between the radiative paint just needs to allow IR passthrough. The cold air at the bottom then transfers its heat to the heat exchanger layer underneath at that point it works as a normal radiator. So far the panels are going to have an aluminum shroud to block infrared from angles that are not directly above, as far as the material goes visible light passthrough and UV don't affect the efficiency of the paint cooling. The main concern is allowing the infrared to get out while keeping the cool air in.
It sounds like you are describing a physical system that you haven't posted a diagram of (or a link to) yet...?

You can use the "Attach files" link below the Edit window to upload PDF or JPEG diagrams.
 
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  • #5
berkeman said:
It sounds like you are describing a physical system that you haven't posted a diagram of (or a link to) yet...?

You can use the "Attach files" link below the Edit window to upload PDF or JPEG diagrams.
just attached some pictures I'm working on how to use CAD right now I can upload some designs later on in the week!
 
  • #6
practicalphysicsnoob said:
just attached some pictures I'm working on how to use CAD right now I can upload some designs later on in the week!
Thanks. I'll try to watch the video tomorrow sometime. BTW, it's best in discussion forums to add new information in new replies, not by editing your Original Post (OP). Modifying the OP can make subsequent replies very confusing for folks reading the thread later. :smile:
 
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  • #7
berkeman said:
Thanks. I'll try to watch the video tomorrow sometime. BTW, it's best in discussion forums to add new information in new replies, not by editing your Original Post (OP). Modifying the OP can make subsequent replies very confusing for folks reading the thread later. :smile:
came across a thread talking about the use of polymethyl methacrylate in a sort of plexiglass or lexan. Gonna be doing a deeper dive into that ill link articles as I read them.
 
  • #8
Slick presentation in the videos.
He seems to have created an embodiment of Maxwell's Demon.
 
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  • #9
It isn’t a Maxwell’s demon, it is just a clever use of gray body emissivity. If you can have a gray body that is nearly “black” in an atmospheric window and nearly “white” at all other wavelengths then it can exchange heat with cold space instead of with the warm atmosphere.
 
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  • #10
Dale said:
It isn’t a Maxwell’s demon, it is just a clever use of gray body emissivity. If you can have a gray body that is nearly “black” in an atmospheric window and nearly “white” at all other wavelengths then it can exchange heat with cold space instead of with the warm atmosphere.
..., and "space" is at CMB, yes? "Smoke and mirrors" fool people, not Maxwell's demons.
 
  • #11
practicalphysicsnoob said:
TL;DR Summary: I'm working on building panels that reflect heat trying to create sub ambient temperatures. I need to create a cover out of something transparent that allows IR passthrough

My end goal is to create mass producible panels that require no electricity to passively cool
Have you searched low absorption and high emissivity coatings? There are materials that absorb little and radiate a lot to create exactly the effect that you are describing. Here's one list from that search: http://www.solarmirror.com/fom/fom-serve/cache/43.html. The best radiative heat transfer will be with the panel exposed without a cover. In that case, your heat transfer surface would be the rear surface of the panel.

Another search using search terms radiative cooling found a number of good hits. One of those hits has a good summary of the theory: https://onlinelibrary.wiley.com/doi/10.1002/advs.201500360. You might find the section in that paper titled Solar Reflectors and IR Transparent Convection Cover Materials interesting reading.
 
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  • #12
Bystander said:
..., and "space" is at CMB, yes?
Yes, although many of these coatings emit strongly in a window that is not that cold.
 
  • #13
jrmichler said:
Have you searched low absorption and high emissivity coatings? There are materials that absorb little and radiate a lot to create exactly the effect that you are describing. Here's one list from that search: http://www.solarmirror.com/fom/fom-serve/cache/43.html. The best radiative heat transfer will be with the panel exposed without a cover. In that case, your heat transfer surface would be the rear surface of the panel.

Another search using search terms radiative cooling found a number of good hits. One of those hits has a good summary of the theory: https://onlinelibrary.wiley.com/doi/10.1002/advs.201500360. You might find the section in that paper titled Solar Reflectors and IR Transparent Convection Cover Materials interesting reading.
"Without any insulation for the nonradiative heat gain, the cooling power of the radiator is limited. In most of the experimental demonstrations, the radiators were insulated by polystyrene foam to suppress the conductive heat gain from the back surface and side walls and highly IR transparent low-density polyethylene film was used as convection cover on top of the radiator with sufficient air gap." that is the part I'm trying to over come I have to have the insulated area be covered by something that wont tear from a piece of hail or a bird landing on.
 
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  • #14
This is an interesting approach, and is not too different from the way that the temperature of most orbital spacecraft is managed. A combination of reflective surfaces and modulated radiation (louvers, etc) allow good thermal control. The absence of atmosphere is important. This is not (even slightly) a new idea; It simply isn't worth much in a terrestrial application. It works best when least needed (clear cool/dry nights) and doesn't work (at all) when most needed (solar noon). In those situations where it will work, there is usually a more capable solution (swamp cooler, etc). Reflectors / radiant barriers / shade can prevent the gain of most/all+ of the heat that could be removed in this manner. You have to climb past a lot of low-hanging fruit to get to this solution.

In my experience: If a 'new' global-scope idea isn't based on some new information (or a significant recent change in economics / requirements / materials) and you don't see it 'out there' anywhere, 1 of 2 things are true:

1. You're a lot smarter than everyone else.
2. Smart people have already looked at it and discarded it for some reason

It's never #1 (for me). Good luck.
 
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