An innovative “cooling glass” developed by University of Maryland researchers offers a groundbreaking, electricity-free solution for reducing indoor heat and carbon emissions, marking a significant advancement in sustainable building technology.
A new coating, when applied to exterior surfaces, can reduce air conditioning usage and combat climate change.
Researchers from the University of Maryland have created an innovative “cooling glass” designed to reduce indoor temperatures without using electricity. This groundbreaking material functions by tapping into the chill of outer space.
The new technology, a microporous glass coating described in a paper published in the journal Science, can lower the temperature of the material beneath it by 3.5 degrees Celsius at noon, and has the potential to reduce a mid-rise apartment building’s yearly carbon emissions by 10%, according to the research team led by Distinguished University Professor Liangbing Hu in the Department of Materials Science and Engineering.
Dual-Function Cooling Mechanism
The coating works in two ways: First, it reflects up to 99% of solar radiation to stop buildings from absorbing heat. More intriguingly, it emits heat in the form of longwave infrared radiation into the icy universe, where the temperature is generally around -270 degrees Celsius, or just a few degrees above absolute zero.
In a phenomenon known as “radiative cooling,” space effectively acts as a heat sink for the buildings; they take advantage of the new cooling glass design along with the so-called atmospheric transparency window—a part of the electromagnetic spectrum that passes through the atmosphere without boosting its temperature—to dump large amounts of heat into the infinite cold sky beyond. (The same phenomenon allows the earth to cool itself, particularly on clear nights, although with much less intense emissions than those from the new glass developed at UMD.)
Cutting-Edge, Durable Material
“It’s a game-changing technology that simplifies how we keep buildings cool and energy-efficient,” said Assistant Research Scientist Xinpeng Zhao, the first author of the study. “This could change the way we live and help us take better care of our home and our planet.”
Unlike previous attempts at cooling coatings, the new UMD-developed glass is environmentally stable—able to withstand exposure to water, ultraviolet radiation, dirt, and even flames, enduring temperatures of up to 1,000 degrees Celsius. The glass can be applied to a variety of surfaces like tile, brick, and metal, making the technology highly scalable and adoptable for wide use.
The team used finely ground glass particles as a binder, allowing them to avoid polymers and enhance its long-term durability outdoors, Zhao said. And they chose the particle size to maximize emission of infrared heat while simultaneously reflecting sunlight.
Climate Change Solution and Global Impact
The development of the cooling glass aligns with global efforts to cut energy consumption and fight climate change, said Hu, pointing to recent reports that this year’s Fourth of July fell on what may have been the hottest day globally in 125,000 years.
“This ‘cooling glass’ is more than a new material—it’s a key part of the solution to climate change,” he said. “By cutting down on air conditioning use, we’re taking big steps toward using less energy and reducing our carbon footprint. It shows how new technology can help us build a cooler, greener world.”
Along with Hu and Zhao, mechanical engineering Professor Jelena Srebric and Professor Zongfu Yu from the Department of Electrical and Computer Engineering at the University of Wisconsin-Madison are co-authors of this study, contributing their expertise on building CO2 savings and structure design, respectively.
The team is now focusing on further testing and practical applications of their cooling glass. They are optimistic about its commercialization prospects and have created the startup company CeraCool to scale up and commercialize it.
Reference: “A solution-processed radiative cooling glass” by Xinpeng Zhao, Tangyuan Li, Hua Xie, He Liu, Lingzhe Wang, Yurui Qu, Stephanie C. Li, Shufeng Liu, Alexandra H. Brozena, Zongfu Yu, Jelena Srebric and Liangbing Hu, 9 November 2023, Science.
DOI: 10.1126/science.adi2224
There seems to be problem with these claims. Kirchhoff’s Law basically says that “For an arbitrary body emitting and absorbing thermal radiation in thermodynamic equilibrium, the emissivity is equal to the absorptivity.” That means, materials with high reflectivity generally have low absorptivity, and therefore, low emissivity. Polished silver has a very high reflectivity and an emissivity of about 0.02. How do the authors expel heat efficiently if their material has a high reflectivity?
The material is highly reflective in the light spectrum. The material is highly absorptive/emissive in a narrow band of the infrared spectrum. However, this is kind of a bizarre claim of a “solution”. Carbon dioxide is also highly active in the same band of the infrared spectrum, the so-called “atmospheric window”. Mankind is releasing carbon dioxide to close that window! So, how is this glass a “solution” if it is designed to send radiation through a window we have already begun closing?
ok – great -when will this be available as a paint – and can we have a transparent version to paint on our glass windows? The market is HUGE – we are all waiting for something simple we can all do for a reasonable price !
This “solution” is really silly. The glass is supposed to selectively transmit infrared radiation through the narrow spectral band of the so-called “atmospheric window”. Any IR radiation emitted by the glass in an upward direction will pass through the atmosphere efficiently and be lost to space, helping the local surface lost energy and remain cool. However, the “atmospheric window” is partially closed now and continues to close more due to carbon dioxide emissions. Mankind is closing this natural energy “window” while glass designers are counting on the radiation pathway to remain open. It’s like our left hand does not even care what the right hand is doing. They just want to market glass, even if it has no importance. BTW, making glass requires high temperatures generated (typically) by burning fossil fuels! Yay! More sad irony! Let’s just keep rearranging the ship’s deck chairs and assuring passengers that things are OK while the ship catches fire and sinks.