Tag Archives: buildings

Revolutionary Cement Prevents Heat Build-Up in Buildings

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Concrete buildings absorb heat in hot climates

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Cement can self-cool by reflecting light outward and dissipating heat from its surface, offering a comfortable indoor climate without reliance on air conditioning.

Traditional cement often absorbs infrared light from the sun, trapping heat and causing indoor temperatures to rise along with the surrounding air.

To tackle this challenge, Fengyin Du from Purdue University in Indiana and her team developed a unique cement that features tiny reflective mineral crystals called ettringite on its exterior.

This innovative cement releases infrared light instead of retaining it, allowing for rapid heat loss. “It acts like a mirror or radiator, reflecting sunlight and releasing heat into the atmosphere, enabling the building to remain cool without needing air conditioning or power,” Du explains.

Initially, the researchers create small pellets from commonly found minerals like limestone and gypsum. These are ground into a fine powder, mixed with water, and poured into silicon molds that contain small perforations. Air bubbles moving through these holes form slight indentations on the surface, where the reflective ettringite crystals can develop. The aluminum-rich gels in the set cement permit infrared rays to traverse the material.

Du notes the process is easily scalable and enables cement production at lower temperatures, making it $5 less expensive per tonne than conventional Portland cement.

Du and her team evaluated the temperature regulation of their cement on the hot roof of Purdue University’s campus and observed that its surface temperature was 5.4°C (9.7°F) cooler than the surrounding air and 26°C (47°F) lower compared to Portland Cement.

Surface dimples of cement viewed under an electron microscope

Guo Lu/Southeast University

“It’s a valuable material,” states Oscar Brousse from University College London. “You enhance the material’s ability to reflect and emit energy, thus efficiently releasing energy that the material has absorbed.”

However, gauging just the surface temperature of a material does not convey its real-world performance. “A surface temperature reduction of 5°C translates into a 5°C decrease in air temperature, which can significantly impact local conditions.”

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Source: www.newscientist.com

Using fungi-based living materials to create sustainable buildings

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The bacteria Neurospora Crassa formed a scaffold for living construction materials

Wim Van Egmond/Science Photo Library

Fungi and bacteria could one day become part of living building materials that can grow and repair.

When we try to reduce waste and greenhouse gas emissions, one of the major challenges facing the world is finding more sustainable building materials. Concrete-only production accounts for more than 5% of total human-induced greenhouse gas emissions.

Some researchers want to develop engineered biological materials generated from cells, which have desirable attributes such as self-assembly, repair, and photosynthesis. Many powerful, mineralized structures exist in organisms such as bones and corals.

Chelsea Heberan Montana State University and her colleagues tested whether similar mineralized structures could be created around scaffolds of fungal mycelium. Mycelium is a network of microscopic, branching filaments that make up part of most fungi.

Heberan and her team grew mycelial scaffolds using fungi called Neurospora Crassa, After that, I applied bacteria Sporosarcina pasteurii On the scaffolding.

As fungi and bacteria metabolize urea in the growth medium, they formed a cured structure consisting of calcium carbonate, the same compound found in eggshells and shells.

She says the team drew inspiration from the bones. Bone has biological ninerals formed on scaffolds for collagen and other proteins. “The bones are very strong and tough considering how light it is,” Heberan says.

Although other biological materials created in the lab only lived for a few days, the structure developed by Heberan and her colleagues was viable for at least a month.

“We are excited by the outcome and look forward to engineering more complex and larger structures,” Heberan says. “If survival rates are high enough, we can actually convey persistent biological properties to materials that we care about, such as self-healing, sensing, and environmental repair.”

“Proposing mycelium as a scaffolding medium for living materials is a simple but powerful strategy,” he says. Aysu kuru At the University of Sydney.

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Source: www.newscientist.com

Cooling fabric reduces heat transfer from pavements and buildings in urban areas with high temperatures

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A scorching hot day in Bucharest, Romania, June 2019

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In the future, city dwellers could beat the heat with clothes made from new fabrics that keep them cool.

Made from plastic material and silver nanowires, the fabric is designed to keep you cool in urban environments by using the principle of radiative cooling, a natural process in which objects radiate heat back into space.

The material selectively emits a narrow band of infrared light that allows it to escape the Earth’s atmosphere, while at the same time blocking radiation from the sun and from surrounding structures.

Jo Bo-jun, a researcher from the University of Chicago, Illinois, and his team say the material “is more than half [the radiation]” from buildings and the ground,” he says.

Some cooling fabrics and building materials already use this radiative cooling principle, but most of their designs don’t take into account radiation from the sun or infrared radiation from structures like buildings and pavements, and they assume the materials are oriented horizontally against the sky, like roof panels, rather than vertically like clothing worn by a person.

Such designs “work well when they face something cooler, like the sky or a field,” Su says, “but not when they face an urban heat island.”

Xu and his colleagues designed a three-layered fabric: the inner layer is made from common clothing fabrics like wool or cotton, and the middle layer is made up of silver nanowires that reflect most of the radiation.

The top layer is made of a plastic material called polymethylpentene, which does not absorb or reflect most wavelengths and emits a narrow band of infrared light.

In outdoor tests, the fabric remained 8.9°C (16°F) cooler than regular silk fabric and 2.3°C (4.1°F) cooler than a broad-spectrum radiation-emitting material. When tested against the skin, the fabric was 1.8°C (3.2°F) cooler than cotton fabric.

Su said this slight difference in temperature could theoretically increase the amount of time a person can comfortably be exposed to heat by up to a third, but that this has yet to be tested.

“It’s always been difficult to make this material practical as a fiber.” Aswath Raman, the UCLA researcher added that the study is a good example of applying the physical principles of radiative cooling to a practical material. Other materials with similar properties could also be used on vertical surfaces in buildings, he said.

Science
DOI: 10.1126/science.adl0653

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Source: www.newscientist.com

Scientists Develop New “Cooling Glass” to Combat Climate Change by Channeling Heat from Buildings into Space

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Innovative “cooling glass” developed by researchers at the University of Maryland provides a groundbreaking, non-electrical solution for reducing indoor heat and carbon emissions, and significantly advances sustainable building technology. It shows great progress.

Applying new coatings to exterior surfaces can reduce air conditioning usage and help fight climate change.

Researchers at the University of Maryland have developed an innovative “cooling glass” designed to reduce indoor temperatures without using electricity. This revolutionary material works by harnessing the cold air of outer space.

New technology, microporous glass coating, described in paper published in the journal sciencecan lower the temperature of the material beneath it by 3.5 degrees. Celsius According to a research team led by distinguished professor Liangbing Hu of the university’s School of Materials Science and Engineering, it has the potential to reduce the annual carbon dioxide emissions of mid-rise apartments by 10%.

Cooling mechanism with two functions

This coating works in two ways. For one, it reflects up to 99% of solar radiation, preventing buildings from absorbing heat. Even more interestingly, this universe emits heat in the form of long-wave infrared radiation into the icy universe, whose temperature is typically -270 degrees Celsius, or just a few degrees warmer. absolute temperature.

In a phenomenon known as “radiative cooling,” spaces effectively act as heat sinks for buildings. They use new cooling glass designs and so-called atmospheric transparency windows (the part of the electromagnetic spectrum that passes through the atmosphere without increasing its temperature) to dump large amounts of heat into the infinitely colder sky beyond. Masu. (Although the emissions are much stronger than those from the new glass developed at UMD, the same phenomenon causes the Earth to cool itself, especially on clear nights.)

State-of-the-art durable materials

“This is an innovative technology that simplifies the way we keep buildings cool and energy efficient,” said research assistant Xinpeng Zhao, lead author of the study. “This could help us change the way we live and take better care of our homes and the planet.”

Unlike previous attempts at cooling coatings, the new glass developed by UMD is environmentally stable, withstanding exposure to water, UV light, dirt, and even flame, and withstands temperatures up to 1,000 degrees Celsius. can withstand. Because glass can be applied to a variety of surfaces such as tile, brick, and metal, the technology is highly scalable and can be adopted for a wide range of applications.

The research team could use finely ground glass particles as a binder, bypassing polymers and increasing long-term durability outdoors, Zhao said. We then selected a particle size that maximizes the release of infrared heat while reflecting sunlight.

Climate change solutions and global impacts

The development of cooling glass is in line with global efforts to reduce energy consumption and combat climate change, Hu said, adding that this year’s Independence Day could have been the world’s hottest day in 125,000 years. He pointed out recent reports that it was a day of sex.

“This ‘cooling glass’ is not just a new material, it’s an important part of the solution to climate change,” he said. “By reducing the use of air conditioners, we have taken a big step towards reducing energy usage and reducing our carbon footprint. This is because new technology is helping us build a cooler, greener world. It shows how it can help.”

In addition to Hu and Zhao, Jelena Srebric and Zongfu Yu, professors of mechanical engineering in the University of Wisconsin-Madison’s Department of Electrical and Computer Engineering, are co-authors of the study, each contributing expertise in CO2 reduction and structural design. There is. .

The team is now focused on further testing and practical application of the cooled glass. They are optimistic about its commercialization prospects and have formed a startup company, CeraCool, to scale and commercialize it.

Reference: “Solution-processed radiatively cooled glass” Xinpeng Zhao, Tangyuan Li, Hua Xie, He Liu, Lingzhe Wang, Yurui Qu, Stephanie C. Li, Shufeng Liu, Alexandra H. Brozena, Zongfu Yu, Jelena Srebric, Liangbing Written by Hu, November 9, 2023, science.
DOI: 10.1126/science.adi2224

Source: scitechdaily.com