New technology cools down 'feverish' cities
2024-09-04
Last year, the Earth experienced its hottest year on record. However, the scorching heat of 2024 is even more intense, with four consecutive days in July breaking the record for the hottest day in Earth's history. Research has shown that extreme high temperatures not only exacerbate water scarcity and strain the power grid, but also cause nearly 500000 deaths annually. Faced with this' heat wave challenge ', scientists have come up with ingenious solutions. In a recent report, the UK's "Nature" website showcased some "cooling secrets": from ultra cold materials that can release heat, to phase change materials that intelligently regulate heat, and to new high-efficiency air conditioners, scientists are actively exploring new strategies for cooling cities. Several regions in Italy have experienced high temperatures this year, including the capital city of Rome, which has issued consecutive red heat warnings. The picture shows tourists passing by the outdoor cooling facilities of a hotel in Rome, Italy. Developing electric cooling equipment, leading a new trend of coolness. Most air conditioners and refrigerators absorb or release large amounts of heat by compressing or expanding fluids. Although these methods are cost-effective, they emit greenhouse gases and consume a significant amount of energy. According to data from the International Energy Agency, air conditioning and electric fans account for approximately 20% of the total electricity consumption of buildings worldwide. The organization predicts that by 2050, the global energy demand for air conditioning will triple. What is even more worrying is that the coolant used in air conditioning is harmful to the environment. Scientists are searching for new methods to replace traditional air conditioning. In November last year, the Emmanuel Defy team from the Luxembourg Institute of Science and Technology published an article in the journal Science, stating that they had successfully developed a refrigeration device made of lead, scandium, and tantalum metals, with a theoretical maximum efficiency of around 60%. The core of this innovation lies in the clever use of the principle of electric heating cooling. When an electric field acts on a material (ceramic) and changes the direction of charge, it can temporarily increase the temperature of the material. When the electric field is removed, the material will rapidly cool down. The entire system does not require any moving parts and does not use refrigerants that are harmful to the environment. Its working efficiency is twice that of a standard air conditioning system, which can significantly reduce energy consumption. The Delphi team collaborated with Murata Corporation in Japan to manufacture a prototype device. DeFei pointed out that this special ceramic produced by Murata Company is widely used in devices such as mobile phones and computers, laying the foundation for the widespread application of new refrigeration devices. However, it will take time to transform this cutting-edge technology into a universal product. Ultra cold and phase change materials provide new cooling solutions. In addition to developing cooling systems, scientists have also developed some new types of ultra cold materials and phase change materials, aiming to provide new solutions for urban heatstroke prevention and cooling. All materials will reflect some sunlight and release energy in the form of heat. But ultra cold materials can not only reflect most of the solar radiation, but also release a large amount of thermal radiation, which can achieve cooling without electricity. In 2014, Professor Fan Shanhui and research assistant Asworth Roman from Stanford University published an article in the journal Nature stating that they had developed an ultra cold surface. This ultra-thin multi-layer material can not only 'unload' infrared heat inside buildings, but also reflect and heat the building's sunlight, as if putting a 'cooling coat' on the building. The new material is composed of 7 alternating layers of silicon dioxide and hafnium dioxide, and when installed on the roof, it can cool down up to 5 ℃ during the day. The field of ultra cold materials has developed rapidly in recent years. Scientists have developed various ultra cold materials using plastics, metals, paints, and even wood. In July this year, Professor Zhao Haibo and others from the National and Local Joint Engineering Laboratory of Environmental Friendly Polymer Materials, Sichuan University, China, published a paper in Science magazine, saying that they had developed a whole biomass radiant cooling gas gel with high solar reflectance, which can be prepared on a large scale and recycled. The aerogel is prepared from gelatin and DNA. The results show that the surface temperature of the aerogel is 16 ℃ lower than the ambient temperature under the outdoor conditions of high solar irradiance, showing excellent refrigeration performance. A team from the University of Melbourne in Australia described a "phase change ink" composed of suspended nanoparticles in the journal Materials Chemistry in 2023. When this material is heated and turned into metal, it forms a linear structure and can reflect excess heat, thereby cooling the surrounding environment. When it is cooled, it has a serrated structure that allows heat to enter and keeps the surrounding environment warm. The team hopes to use this ink as a window coating and design different coatings according to the season to make the building warm in winter and cool in summer. From laboratories to cities, there is an urgent need for standardized development. It is currently unknown which cooling technologies will ultimately stand out in the competition with heat waves. Numerous ideas are still "hiding" in the laboratory, waiting for the right moment; Some are "trial and error" and deployed in small projects. For example, some scientists have suggested that in cloudy or humid weather conditions, ultra cold materials may find it difficult to exert their "skills". This is because water vapor captures infrared radiation, preventing it from dissipating into space. In January of this year, the team of physicist Mathias Santamoris from the University of New South Wales in Australia proposed a strategic action: they transformed buildings in Riyadh, the capital of Saudi Arabia, with ultra cold materials, while doubling the number of irrigated trees, expected to reduce the city's temperature by 4.5 ℃. Professor Zhao Haibo stated in an interview with Science and Technology Daily that "ultra cold materials have the unique advantage of achieving refrigeration without the need for additional energy input, and are expected to play an important role in multiple fields in the future. Intelligence and multifunctionality are also important trends in the development of such materials." However, Professor Zhao Haibo also reminded that "currently, most of these materials are in the academic research stage, with less consideration given to factors such as cost and construction conditions, and need to be combined with engineering needs to achieve practical goals. In addition, the performance evaluation methods of ultra cold materials are not yet unified, and there is a lack of relevant standards internationally. It is urgent to develop a reliable set of standardized research standards to promote the healthy development of this field
Edit：Xiong Dafei Responsible editor：Li Xiang
Source：Stdaily
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