Radiative Cooling And Carbon Capture: New Technologies For An Overheated World

October 8th, 2020 by  


Some of you may have been absent the day your high school science teacher gave a lesson on how ancient people living in hot climates made ice without refrigeration. According to the Washington Post, at sunset they would pour water into shallow earthen pits or ceramic trays that were insulated with reeds. All through the night, the water would radiate heat into the air  around it and eventually turn to ice even though the ambient temperature never dropped below freezing.

SkyCool radiational cooling panels

SkyCool radiational cooling panels. Credit: SkyCool Systems

Scientists know this phenomenon as radiative cooling. Outside the thin layer of atmosphere that surrounds our planet, the temperature is perilously close to absolute zero — 457.87 degrees Fahrenheit to be exact. The atmosphere acts like a thermal blanket around the Earth, protecting it from such intense cold. The problem today is that all the crud humans have pumped into the atmosphere — mostly carbon dioxide and methane — prevent the heat below from radiating back into space. The balance between heating and cooling has been disrupted by human activity and so far, humans seem oddly unconcerned about how out of whack things are getting here on our tiny blue lifeboat out at the edge of the universe.

Researchers at the University of California at Los Angeles want to take advantage of the physics that allows water to turn to ice in the desert to help the Earth shed some of that excess heat. Led by Aaswath Raman, they have developed a thin, mirror-like film engineered to maximize radiative cooling at the molecular level. The film sends heat into space while absorbing almost no radiation, lowering the temperature of objects by more than 10 degrees even in the midday sun. When incorporated into buildings, it can help cool pipes and panels and may even replace air conditioning in some instances. It requires no electricity and no special fuel — just a clear day and a view of the sky. “It sounds improbable,” Raman says,“but the science is real.”

Most researchers say the phenomenon is an interesting physical fact with few practical applications because radiative cooling is only measurable at night when objects emitting heat but receive none in return. When daylight comes, the warmth of the sun cancels out any cooling effect. “Every paper made some kind of statement to the effect of, ‘Well, it’s usefulness is kind of limited because … you most need cooling during the day,’ ” Raman says. “Then I thought, well, why can’t we make this work during the day?”

The path forward involved developing a material so perfectly reflective it absorbed almost no energy even when exposed to full sunlight. In addition Raman and his team wanted to maximize the amount of radiation the film sent into space. Heat is just another part of the electromagnetic spectrum, like radio waves and light, but at lower frequencies on the infrared portion of the scale. The Earth’s atmosphere blocks some infrared radiation naturally but even more infrared energy is blocked now that the air is loaded with carbon dioxide.

Yet there are some infrared wavelengths that do pass through. Ramen’s quest was to tune the reflective material to radiate energy at those specific wavelengths so it could pass through the atmosphere and on into space. Working with scientists at Stanford’s department of engineering led by professor Shanhui Fan, he began crafting a film from many microscopic layers. The thickness and composition of these layers were designed to interfere with the way different wavelengths of light travel. Incoming solar radiation would rebound right back into space but outgoing thermal radiation would bounce around between the layers with only the desired infrared wavelengths able to escape.

Ramen and his collaborators created a new company called SkyCool to commercialize their technology. Today, people and businesses around the world rely on air conditioning to cool their personal spaces but the electricity needed to run all those billions of air conditioners accounts for about 7% of all carbon emission. As the world gets  hotter, more air conditioning will be needed, which in turn will create more emissions and more heat. SkyCool’s mission is to break that cycle and allow the people of the world to cool off in a way that is efficient and affordable.

[Note: Ramen is the same fellow who created a super white reflective roof paint to help keep commercial buildings cool. And it should be pointed out that he and most of his colleagues are immigrants or children of immigrants who today would be excluded from the US by Tyrannosaurus Trump and his Nazi sympathizer adviser, Stephen Miller. Food for thought for those who are still able to function outside the bubble of lies, distortions, and deliberate misinformation that is the stock in trade of the failed Tramp administration.]

Chris Atkinson is a former program director for ARPA-E. When asked to fund Ramen’s early work, “my initial response was, if this was so good, why hadn’t it been done before?” he tells the Washington Post. But what Ramen and his colleagues had going for them is something prior generations of scientists did not — nanotechnology. With it, they could manipulate their materials, molecule by molecule, until they behaved exactly the way they wanted them to. “I was struck by the elegance and simplicity of it,” said Atkinson, now a professor of mechanical engineering at Ohio State University. “The fact that you can get something for nothing is remarkable, especially in the energy realm.”

The quest now is to make the materials more efficient and less expensive so they will be accessible to more people and businesses. The work continues and the SkyCool team is planning to replace all the air conditioners used by one building in the California State University system and cool it solely with advanced radiative cooling equipment. The system is already in use by a grocery chain in Stockton, California. The owner says he has no idea how the system works but is pleased it has saved him over $3,000 in energy bills over the summer. That’s the sort of endorsement that makes other business owners sit up and take notice, regardless of where they fall on the political spectrum.

Carbon Capture Is Still In The Mix

Last month, the International Energy Agency said that removing carbon dioxide from the atmosphere — a process known as carbon capture — will be an essential part of lowering average global temperatures so humans can continue to survive on planet Earth. Renewable energy won’t be enough for the world to hit climate targets without capturing and storing emissions generated from factories, power plants, transportation and other sources. The transition to renewable energy, such as solar and wind, simply cannot cut emissions in time. Climate scientists like Michael Mann say the world must slash emissions 50% by 2030 to have any hope of avoiding a climate catastrophe.

Many carbon capture system installed at thermal generating sites have failed to be commercially viable even though they can remove as much as 92% of the carbon dioxide in the exhaust stream. However, a new company called CarbonCure Technologies based in Canada is focusing on lowering carbon emissions for making concrete. Concrete produces lots of emissions, so much that if the cement industry was a nation, its emissions would surpass those of all other nations except for the US and China says The Guardian.

The company has received a major investment by a consortium headed by Amazon and Microsoft and is working with 300 concrete and cement producers around the world to inject captured CO2 into their products. The injected gas chemically transforms into limestone, reinforcing the concrete, which Amazon will use for the buildings at its new headquarters in Virginia. CarbonCure’s goal is to reduce carbon emissions by 500 million metric tons a year by 2030. In 2019, global carbon emissions were 33 gigatons, according to the International Energy Agency. It’s safe to say the company’s goal will be important but hardly sufficient to forestall a climate crisis.

According to the IEA, there are only about 20 projects in commercial use worldwide,  yet billions of dollars in investment are flowing into the sector. Microsoft has announced a “moonshot” climate plan that will involve direct air capture of carbon dioxide with the resulting carbon injected into rock formations.

Norway is launching a full scale carbon capture and storage project, named Longship in honor of the iconic Viking vessels which one crossed the oceans to many parts of Europe and North America. A direct air capture project for the Permian Basin in the southwestern US is doubling in size and aims to remove 1 million tons of carbon dioxide a year. The US government is getting in on the act. It recently awarded $72 million to two dozen different carbon capture initiatives.

“We are at a tipping point and no one knows quite how it will tip,” Klaus Lackner, an Arizona State University expert in the field who invented “mechanical trees” that remove carbon dioxide from the air, tells The Guardian. He says the world is likely to surge beyond the 1.5 C global heating limit called for by the Paris climate agreement. “We are living in an overshoot world where 1.5 C will be missed. We are going to have to step harder on the brakes and we are going to have to get carbon back.”

Not everyone is convinced that carbon capture is the way to go. “Carbon capture and storage is not a solution to the climate crisis, it is part of the problem,” said Karen Orenstein, the climate and energy program director at Friends of the Earth. “This extraordinarily expensive pipe dream is just false rhetoric propagated by the fossil fuel industry in an attempt to save itself.”

Klaus Lackner puts a fine point on the discussion. He tells The Guardian the industrial capacity for widespread carbon capture exists but requires political will to make it happen. “Much like … sewage in the 18th century, we don’t see the value of cleaning up a mess until it hurts us. There’s going to be irreversible harm, Species are going to go extinct, seas will rise and we won’t be able to unmelt glaciers. We will get there, the question is how much collateral damage we will do on the way.” That is indeed the question. 
 


 


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About the Author

Steve writes about the interface between technology and sustainability from his homes in Florida and Connecticut or anywhere else the Singularity may lead him. You can follow him on Twitter but not on any social media platforms run by evil overlords like Facebook.