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Comment by nostromo | Hacker News Reader

These surfaces at scale will be a game changer for fighting climate change. They seem like magic. Here’s a key quote from Wikipedia:

> 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.

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Cover 1-2% of the Earth's surface with solar panels and you have so much spare energy that you can do all kinds of crazy stuff, like sucking carbon dioxide out of the air and turning it to diamonds for fun.

Solar panels are limited by cost. If this cooling ceramic is a better version of the barium sulfate thing (i.e. just an extremely cheap-to-produce material that's very white) then this is viable because it doesn't cost hundreds of dollars per square metre to manufacture.

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).

"hundreds of dollars per square meter" not true anymore.

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.

A quick calculation on Wolfram Alpha: to cover 2% of the world's surface at 50EUR/m2 would cost roughly 540 trillion euros, or 5.5 years of current world GDP.

Quoting the GP:

> 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.

If I'm not mistaken 510 millions square kilometer earth surface, 2% of that 10 millions square kilometer, at 200 Wp/m2 gives 2 PW peak.

Current peak electricity production capacity is about 7.5 TW according to:

https://www.statista.com/statistics/267358/world-installed-p...

There are many open bare places on Earth where solar panels are useless because there are no electricity users nearby: any desert.

If all it takes is to truck the ceramic panels around and dump them to the ground, then it's probably not that expensive.

How long will they last in the desert though? My intuition say they would be covered with sand in a few weeks tops.

There are rocky deserts.

70% of Sahara is rocky, not sandy, for example.

Sure. But even there there is a ton of mobile dust and sand in the air.

So in order to save the environment we plan on covering it with white sheets?

Just because we don't want to tell Africa and China to stop burning and polluting and dumping it all in the rivers?

Just to point out, but it's not Africa, and it's mostly not China that are burning and polluting.

Where I live solar panels are limited by regulations. They pay for themselves after a couple of years so people would plaster them literally everywhere the sun shines if they were allowed to. White paint otoh probably has worse ROI.

The "white paint" parent is referring to can passively cool the surface a few degrees below ambient temperature 24/7 (yes, even at night). I could imagine worse investments.

White paint (if cheap) on a building you are actively trying to cool would seem to have a very good roi.

I think white shingles for the roof would probably be even more effective. IIRC, a lot homes in hotter climates have started using them.

Adding bifacial solar panels is probably a fantastic combination as well.

A lot less than 1% of the earth‘s surface is buildings.

A negative ROI (return on investment) suggests it won't pay for itself ever, be that in cash or carbon.

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.

Seriously. 1-2% of Earth's surface is a _lot_ of surface.

As a term of comparison, here's a back of the envelope calculation estimating that 0.18% of the surface is covered by roads and parking areas.

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.

Cover that much of the Earth and you've got a good start on making a Trantor.

Deep cut

Indeed; at 9.2 trillion m^2, the Sahara desert sits right in that range at 1.8% of Earth's 510 trillion m^2.

Yup. We have more than enough harnessable solar power to allow every single person a clean energy budget higher than a typical American, offset all other industrial carbon production, and start to unwind the last century of humanity's carbon impact.

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.

Using less energy makes perfect sense until we achieve this desirable future state of abundant excess energy. That state is not right now, however.

Nope, because all the carbon production until that point can be unwound.

The shitty uncomfortable life that the "use less" camp wants me to live, cannot.

But currently we aren't on a course to actually unwind that carbon production in time.

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.

"can be" is very far from "is going to be" and even further from "is going to be paid for".

Also, we have a lot of solar energy .. during the day. The storage/transmission problem is solvable but not solved.

Who’s gonna pay for the unwinding though?

Whatever you we use that energy on will probably create heat though.

To put that in perspective, in 2014 the estimate was artificial structures covered 0.6% of the Earth's surface. It might take a while to double the amount of buildings, roads etc. and cover it all with PDRCs

Are artificial drivable and walkable surfaces counted?

Quoting https://science-atlas.com/faq/how-much-of-the-earth-is-inhab...: "According to the FAO Global Land Cover SHARE database, produced in 2022, 0.6% of Earth’s land surface is defined as ‘Artificial surfaces’. Artificial surfaces include any areas that have an artificial cover as a result of human activities such as construction (cities, towns, transportation), extraction (open mines and quarries) or waste disposal. This figure gives us an estimate of roughly 900,000 km2 of human-covered land worldwide."

You can't run tires on a reflective surface and expect it to remain reflective.

Thas wasn't quite what I was implying, but actually, figuring out economical high albedo roads would be fantastic.

Iron fertilization of equatorial oceans would make for very high albedo algae blooms. The ocean absorbs the vast majority of absorbed solar radiation. It has been pointed out that at low angles it reflects almost all light, but that is when the energy has gone through the most atmosphere and the water or land would absorb much less anyway. Napkin math scaling up previous fertilization experiments indicates about 1.5 billion USD per however long the blooms last, to trigger a snowball earth. We'd stop when it got cold enough.

Easily verified from ice core data. The UN Convention on Biological Diversity banned large-scale iron fertilization experiments in 2008. Cynically, I don’t think anyone’s figured out how to make money on it either.

If the 1.5 billion USD per event estimate is correct, it has to be banned because it's cheap enough that people don't need to make money on it — it's about what Oxfam raises every 18 months.

> UN Convention on Biological Diversity

I really wish people would stop inferring financial motives when other, far more obvious motivations are right there.

I think in the grand scheme of things we are more likely to start making asphalt and concrete out of basalt, for the CO2 absorption.

Until you drive on them on a sunny day...

Or a winter day at high latitudes. I'm convinced the Illuminati (it's in the name, no?) arranged the roads so you're always driving into the sun wherever and whenever you're going.

Does that figure include the ocean?

No. It is the percentage of land surface. Earth is cosmically insignificant and incomprehensibly large, both.

> These surfaces at scale will be a game changer for fighting climate change.

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).

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