Passive radiative cooling ceramic with high solar reflectivity
cityu.edu.hk
cityu.edu.hk
The region around Almeria is covered by greenhouses that use white plastic sheets to protect their crops. The region has effectively cooled by 0.3 degrees whereas other areas have increased 0.5.
https://www.agroberichtenbuitenland.nl/actueel/nieuws/2019/0...
> Some estimates propose that if 1–2% of the Earth's surface area were dedicated to PDRC that warming would cease and temperature increases would be rebalanced to survivable levels.
Solar near people and PDRCs away from people (where solar is impractical) along with a reduction in Carbon is a feasible plan today.
I really wish people would stop inferring financial motives when other, far more obvious motivations are right there.
https://www.reddit.com/r/theydidthemath/comments/zwni88/requ...
Approximately 1% is covered by any kind of construction: https://www.quora.com/What-percentage-of-Earths-land-is-used...
Almost 15% of land area (not total surface) has been "modified" by humans: https://www.weforum.org/agenda/2021/10/human-impact-earth-pl... This includes agriculture, mining and, somehow, pollution.
Its main limitation would likely be construction costs, which is a problem solar panels are already starting to run into. Although construction of solar requires setting up cables and not e.g. accidentally snapping hundred-dollar solar panels in half (which would be a non-issue for barium sulfate, since it's dirt-cheap and basically just white paint anyway).
Adding bifacial solar panels is probably a fantastic combination as well.
If you're actively trying to cool the building then painting it in something that lowers the energy needed to cool it. And as were just talking about paint, carbon and cash cost is likely to be low relative to savings.
So no, painting all houses in this stuff might not reverse global warming, but that wasn't what we were talking about.
If all it takes is to truck the ceramic panels around and dump them to the ground, then it's probably not that expensive.
70% of Sahara is rocky, not sandy, for example.
Just because we don't want to tell Africa and China to stop burning and polluting and dumping it all in the rivers?
https://allo.solar/panneau-solaire-410w-noir-mono-p-type-tw-...
104.08 EUR tax (20%) included for 410Wp gives 0.254 EUR/Wp
1722 x 1134 x 30 mm = 1.92 square meter gives 53.38 EUR/m2.
Some wooden floor are more expensive than PV per square meter.
People forget that PV, battey, wind costs are still decreasing.
> People forget that PV, battey, wind costs are still decreasing.
Some insist on forgetting it. And the decrease has been exponential, with no reason to believe it will stop at the next order of magnitude.
Anyway, covering 2% of the world with anything is a huge undertaking.
Current peak electricity production capacity is about 7.5 TW according to:
https://www.statista.com/statistics/267358/world-installed-p...
But instead of working towards that end-state, a lot of people (even people on this site) seem to be more interested in shaming others into using less energy, and attacking others for "immoral" uses of energy.
The shitty uncomfortable life that the "use less" camp wants me to live, cannot.
It's like saying there's an oasis 2 days walk from here, so don't worry about having a shower and possibly using all your drinkable water. You still need to save enough water to actually get to the oasis, and at the moment, we're kinda sorta having a conversation about whose job it is to actually make the trek, so in reality it's going to be at least another day before everyone decides that they need to start marching, and as we only currently have 2.5 days of drinking water. That shower is really irresponsible.
Also, we have a lot of solar energy .. during the day. The storage/transmission problem is solvable but not solved.
Aren’t the materials just reflecting heat into the atmosphere, which due to human activity has greater heat carrying capacity?
The materials would be good for reducing energy consumption (cost-benefit ratio tbd).
As always, the technology is promising but I’ll only really believe it when I can buy it at Home Depot.
Nobody has come up with a DIY "paint" or coating that is durable.
This is not entirely true. It's not because your thermal energy is radiated to something colder, but rather because clouds contain and reflect the thermal energy that would otherwise be lost to space.
I’d buy two: one for hot and one for cold!
Thermodynamics does not permit a thermal diode to exist.
This thermos would only keep your coffee hot if you dropped it into a furnace.
A perfect black surface on a spacecraft can do more than charcoal black paint, but only by a matter of degrees. If memory serves its less than a 2x multiplier between off the shelf and exotic materials. But when ounces cost thousands of dollars, you’re going to go exotic.
[0] https://www.science.org/doi/full/10.1126/science.adi4725
[1] https://www.sigmaaldrich.com/US/en/product/aldrich/667420
Maybe it would be better to cover with something deadly to algae. Preferably not toxic. If there are such things. Silver nanoparticles?
Aluminium plate painted with this paint is cooler when exposed to the sun not only than unpainted plate but also ambient air which feels really magical for me.
I can see my neighbor's roof. If I can see it, that means that it's radiating in all directions, not just into space.
It’ll expel that fraction to space regardless of its neighbors.
This is cool stuff, but it’s just stuff. It’s not a silver bullet. We here are all old enough, many of us by half, to no longer get sucked in by magic thinking.
Sunlight that is scattered off the roof can scatter back off other roofs before heading into space. Likewise radiation that is emitted by the roof can be absorbed and then re-emitted by other roofs before heading off into space. Neither of these preclude the roof from doing its job.
At the end of the day, the roof will effectively reflect back sunlight from the high temperature sun, while radiating infrared radiation into the low temperature sky, and have a neutral energy balance with the surrounding earth / houses / trees / objects which are at a similar temperature to it.
… but that's not what they're asking about?
Imagine you're standing in a second story window, looking out. Out the window, you're seeing your neighbor's roof, coated with this stuff. A lot of sun is hitting that roof — How much heat is coming in through that window, off that roof?
There have been stories in the past of reflective surfaces cooking nearby apartments, so I get the concern. I think in this case it boils down to it not being reflective, mostly, so it's fine.
Two pieces of this material in an overlapping field of reflection are putting out exactly the wavelength the other will absorb. I can’t defend my building from being baked by yours by coating it with the same stuff. I am simply going to return the favor in the process.
Not to mention the big problem of creating a new case of the haves versus the have-nots.
That depends on what you mean by "see". If you paint a square on a white paper with a magical paint that absorb 100% of the light, you can still see that there's a black square, because it's sitting on a contrasting background.
Even if the material is perfectly radiating everything to space, i.e., the roof sends no light to your eyes, it's still just a patch of blackness among normal things, and you can see the shape of it, just like a puddle on the road at night, as you walk with your back to the moon.
The first portion of that equation is hot: roofs have a lot of sq. ft.'age, and a fair bit of sunlight strikes them. But the second part is well the other direction: the window probably doesn't occupy a whole lot of the field of view of the roof: i.e., mostly, any ray emitted randomly from any point on the roof is likely going to be skyward, so assuming it emits the heat/light out equally in all directions, your window only gets a small fraction.
The portion coming in your window doesn't go back out to space but I don't think that's a big deal?
Most of the light hitting the roof will be reflected back up into space. Some small percentage of it will scatter and disperse into all other directions.
If you were in a plane at exactly the right angle between the roof and the sun, you'd see a glare much stronger than you'd see at street level.
The infrared radiation will indeed go out in all directions. The way I understood it there will be less of it, because the roof is cooler. So if this material replaces a traditional surface, you will get more visible light scattered your way, and less infrared light.
Things do not radiate uniformly, neither behave like mirrors (specular). The truth for most objects is somewhere in between.
You can see it with a plastic object as well, when it is positioned so that the angle to the normal vector (a vector perpendicular to the surface) of the light source and to your eye are the same (as in, you would be able to see the light source if it were a mirror), you see much more light than when you are simply looking at it "from the side".