Fascination Technology With Cooling Ceramics from the 3D Printer Against Urban Heat 

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In our section "Fascination Technology," we present impressive research and development projects to engineers every week. Today: how a ceramic wall from the 3D printer cools indoor and outdoor spaces through evaporation without energy-intensive air conditioning technology.

Rising temperatures and more frequent heat waves exacerbate the problem of urban heat islands. Researchers at the Institute of Architecture and Media at TU Graz (Austria) are therefore developing a passive cooling solution: 3D-printed cubes made of highly porous ceramics. They can cool both indoor spaces and outdoor ambient air. 

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Well-Known Principle Technologically Optimized

The principle has been known for centuries: When water evaporates, it extracts heat from its surroundings. This lowers the temperature of the adjacent air. Clay pots and traditional wind towers have been utilizing this effect for a long time. "The technological advancement lies in the use of 3D printing. With it, we can produce complex, porous, and functionally optimized geometries from clay mixtures," explains Milena Stavric from TU Graz. The structures store water and provide a large evaporation surface with minimal material usage.

Water enters the ceramic through capillary forces and spreads evenly over the complex geometry. It continuously evaporates on the large surface, extracting heat from the surroundings.

The approximately 23-centimeter cubes are first digitally designed and then 3D-printed from a ceramic clay mixture. Firing at low temperatures preserves the porous material structure. The applied minimal surface geometry—so-called TPMS structures—enlarges the surface area while maintaining low volume. Water enters the ceramic through capillary forces and spreads evenly across the complex geometry. It continuously evaporates on the large surface and extracts heat from the surroundings.
To further enhance the cooling performance, the team at the "Shape Lab" is investigating bio-inspired material concepts. Mushroom cultures and wood shavings are added to the clay as a nutrient medium. The mycelium, the thread-like fungal network, grows into the material and forms a fine lattice. During the subsequent firing, the fungal mycelium and wood shavings are burned away. What remains is a system of micro- and macropores, intended to improve water absorption and distribution within the cubes.

Temperature Reduction in Practical Test

In a controlled experiment in the hot attic of TU Graz, a significant cooling effect was observed. In the immediate vicinity of a water-filled cube, a temperature drop of nearly seven degrees Celsius was measured. "The cooling effect was clearly noticeable throughout the entire room," reports Kristijan Ristoski.
As part of his master's thesis, he combined the cubes with a controllable water circuit to create a cooling wall. The researchers are also testing additional material mixtures, including sludge from Lake Neusiedl, which must regularly be dredged to prevent the silting up of the shallow body of water. The sediments could potentially serve as raw material for 3D printing and thus for resource-efficient construction processes in the future.

Cooling without High Energy Demand

The ceramic walls are intended to offer a resource-efficient complement to conventional cooling systems. Possible areas of application include residential and office buildings, schools, public spaces, and waiting areas. "Our goal is to provide cooling where people particularly suffer from heat—such as in cities where trees cannot provide sufficient cooling everywhere," says Milena Stavric. Instead of relying on energy-intensive air conditioning technology, the concept leverages a natural physical principle.

Our goal is to provide cooling where people particularly suffer from heat.

Milena Stavric, TU Graz

Demonstration Wall in Graz

The technology can be seen at the Museum of Perception in Graz. Additionally, TU Graz has erected a freestanding demonstration wall made of clay at the Neue Technik campus on Stremayrgasse. The two-by-two-meter wall makes the functionality and cooling effect of the ceramics directly tangible.

The project "3D-Printed Ceramic Cooling Walls for Sustainable Urban Architecture" was realized in close cooperation with the Institute of Building Physics, Building Technology, and Design at TU Graz and funded by Austria Wirtschaftsservice GmbH (aws) as part of the "Proof of Concept" program.

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