You know what also cools houses down super efficiently?
Trees
this post was submitted on 14 Nov 2023
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Excellent - how many trees can I grow on my roof? Can they be retrofitted?
/s
Trees? Not many. Grasses, herbs, wildflowers, and shrubs? Tons of them. And you can pretty easily retrofit over an existing sloped roof. And the weight is no more than a tiled roof.
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You know what cools roofs and generates electricity? Magic!
Another trick: bifacial panels oriented to pick up the reflected light from highly reflective roofs
What about Ultra white ceramic trees?
True though this is still practical for folks who live in deserts and other treeless places
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NightAHawkinLight on youtube has been working on something similar. same kind of snow-like nanostructure to reflect light away, but with the added benefit of a paint that emits light in a wavelength that travels through the atmosphere without interacting with any of it.
so if you point a painted tile at the sky it will actually cool below ambient temperature, it's pretty wild https://www.youtube.com/watch?v=N3bJnKmeNJY
Tech Ingredients did a video about it as well. https://www.youtube.com/watch?v=dNs_kNilSjk
The biggest problem with making stuff white and using fancy materials is the amount of crap they get exposed to.
Moisture is one issue, both in the form of water vapor / condensation as well as rain. But there's also smallish animals, like birds and cats that crawl around on roofs. Not to mention all the insects. Then there is the normal sand and dust in the air, plus all the pollution. Depending on where you live, white stuff gets really dirty within weeks or months.
I work in a white office building and they have it cleaned with pressure washers twice a year, it takes a whole climbing team a good two weeks to clean the whole thing and it looks dirty again after a few months. And that's just a white form of plastic (HPL) you can blast away on, without causing damage. With these fancy meta materials often they are really fragile and any damage undoes the special properties.
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They could just put a layer of something like Teflon over it. That's why crosswalk stripes feel so slick.
If you put something over it, it loses it's reflective properties. Something is only as reflective as it's upper most layer. Unless you use something transparent, but even things we would commonly think of as transparent usually are only transparent at specific wavelength. And even then it's probably not really transparent, more like translucent. Not to mention things like internal reflections and wavelength lengthening.
This is a super complex subject with many people all over the world working on it and lots of money being put into it. It likely everything people can think of has been thought of and we need some real effort to get to a workable solution. Since no commercial application has been found, it's not certain this is a fixable problem.
Too often we see innovative ideas and they are marketed as this is just the first version. We can work out the kinks, extrapolate and get to something real special. In reality this is often not the case, actual limitations apply and not all problems are fixable.
Those are slick from the added glass powder for reflectivity.
Who’s putting Teflon on road stripes…?
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Super awesome. Not only is it white and shiny aluminum oxide, it uses a nanostructure, as observed on beetles, to maximize reflection, minimizing heat retained.
What's the gains in contrast to regular white bathroom tiles? (Not a joke question)
But what about it getting dirty and how well does it resist having its nano structure getting damaged? Like, there's that spray that can make sneakers or clothes virtually stainproof....until you wear them several hours or rub your hand against them.
Probably illegal here because of the high reflective value. Depending on the sun's position, it could dazzle and blind people, e.g. people driving cars or riding bikes. I know that for this reason, shiny metal roofs are not allowed.
There is a difference between mirror like reflection and diffuse reflection. Mirror reflection is what you get with metal roofs which beam the sun directly to a target resulting in one spot being blinded. Diffuse reflection will spread it around, resulting in more light all around which is what we can handle as humans.
Can mostly handle. Snow blindness is a thing, and that's all diffuse reflection too, not specular. But it's unlikely a roof would be such a problem.
The reason for snow blindness is the fact the snow fills such a high portion of the visual field.
Yeah, hence it's unlikely a roof would fill it to the same extent and wouldn't be a problem.
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It's not visibly reflective. Yes, it's white, but it's cool to the touch because the majority of the energy is radiated out into space via non-visible wavelengths. Someone has already posted a great YouTube video from Night Hawk In Light in a comment where he explains how this tech works and makes his own paint!
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Scotland here. Does this come in black?
Would we ever be able to use a material like this to reflect a significant enough portion of the light falling on Earth to reduce the total heat imparted by sunlight in a meaningful way? Could we use this as defacto ice caps to perhaps reduce global temperatures in any real way?
The only feasible plan we have for increasing the albedo of the planet overall is atmospheric engineering. Basically you can make a reflective cloud that’s millions of square miles in area, many orders of magnitude more cheaply than any other kind of structure.
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Imperial March begins to play
My thoughts exactly at first glance! At least, now we know why some people think storm troopers are so cool.
Why ceramic and not just paint?
The article addresses that. It is because ceramics are durable while paints and coatings are not.
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Most coatings like paint that have this effect include ceramics to do most of the reflection, but the other paint stuff the ceramic substrate is emulsified in does not have near the reflectivity, so you're impairing yourself if reflectivity/heat rejection is the only goal.
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So there’s gotta be a downside to reflecting all this heat though?
I know windows sometimes can focus and reflect the sun setting your neighbours house on fire, birds aren’t going to affected, bugs?
It looks like this reflects and scatters the light, rather than reflects and focuses it. Otherwise it would look like a mirror, not a ceramic.
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