They invented cooling ceramics that would air condition buildings without the need for electricity.

Material known as cooling ceramics offers high-performance optics for cooling production no power or coolant. Its cost-effectiveness, durability and versatility make it well-suited for commercialization in many applications, especially building construction.

This ceramic reduces the thermal load of buildings and provides stable cooling performance even in a wide range of climates. “It increases energy efficiency and can fight global warming”The researchers said in a statement.

Passive radiative cooling, or PRC, is considered one of the most promising green cooling technologies to curb the growing demand for air conditioning, reduce environmental pollution and combat global warming, according to Professor Edwin Tso Chi-yan from CityU, one of the corresponding authors of the paper. article.

Although similar materials have existed before, these use nanophotonic structures, so they are limited by their high cost and poor compatibility with current end uses; Polymeric photonic alternatives, on the other hand, lack weather resistance and effective solar reflection.

Improved optical properties and applicability

“But our quenching ceramic achieves improved optical properties and has strong applicability,” said Professor Tso. “Color, weather resistance, mechanical strength and Ability to reduce the Leidenfrost effect (a phenomenon that prevents heat transfer and neutralizes liquid cooling on a hot surface) are key properties that ensure the durable and versatile nature of cooling ceramics.”

The extraordinary uniqueness of cooling ceramics, Hierarchically porous structure as bulk ceramic material easily fabricated using highly accessible inorganic materials such as aluminaBy a simple two-step process involving phase inversion and sintering. No precision equipment or expensive materials are required, making scalable production of cooling ceramics highly possible.

Optical properties determine the cooling performance of PRC materials in two wavelength ranges: solar range (0.25-2.5 µm) and mid-infrared range (8-13 µm). Efficient cooling requires high reflectivity in the former range to minimize solar heat gain and high emissivity in the latter range to maximize radiative heat dissipation. Due to the high band gap of alumina Cooling ceramics keep solar absorption to a minimum.

96.5% solar reflectance rate

Not only that, by mimicking the biological whiteness of a species of insect called cyphochilus and optimize the pore structure based on the Mie distribution, The cooling ceramic efficiently scatters nearly the entire wavelength of sunlight, providing a near-optimal solar reflectance rate of 99.6%. and reaches a high thermal emission of 96.5% in the mid-infrared. These advanced optical properties exceed those of today’s next-generation materials.

“Ceramic cooling It is made of alumina, which provides UV resistance to degradation, this is a typical concern of most polymer-based PRC designs. It also exhibits excellent fire resistance, withstanding temperatures in excess of 1,000°C; this exceeds the capabilities of most polymer- or metal-based RPC materials,” said Professor Tso.

Excellent weather resistance

Beyond its outstanding optical performance, cooling ceramics exhibit excellent weatherability, chemical stability and mechanical durability, making it ideal for long-term outdoor applications. At extremely high temperatures, the quenching ceramic exhibits super hydrophilicity, allowing instantaneous droplet dispersion It facilitates rapid impregnation due to its interconnected porous structure. This superhydrophilic property prevents evaporation and prevents the Leidenfrost effect, which is a typical feature of traditional building envelope materials. Therefore, the new material allows efficient evaporative cooling.

“The beauty of quenching ceramics is that it meets the requirements of both high-performance PRC and applications in real-life environments,” said Professor Tso. It can be colored with a double-layer design, thus improving its aesthetics to the consumer’s liking.

“Our experiment shows that applying cooling ceramics to the roof of a house Can obtain more than 20% electricity“, He claimed.

“For space cooling, the great potential of ceramic cooling has been confirmed, reducing dependence on traditional active cooling systems and Provides a sustainable solution to prevent grid overload, greenhouse gas emissions and urban heat islands“said Professor Tso.

Based on these findings, Tso added that the research team plans to develop more passive thermal management systems. It aims to explore the application of these strategies to improve energy efficiency, promote sustainability and increase the accessibility and applicability of RPC technologies in various sectors, including textiles, energy systems and transportation.

Reference work: DOI: 10.1126/science.adi4725

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