Porous ceramic cubes produced by a 3D printer utilise energy-efficient evaporative cooling and significantly lower the temperature. A prototype of the cooling wall made from ceramic cubes is already on display on the TU Graz campus.
In light of rising temperatures and more frequent heatwaves, the Institute of Architecture and Media at Graz University of Technology (TU Graz) is presenting an energy-efficient solution to urban heat islands: 3D-printed cubes made from highly porous ceramics, combining centuries-old knowledge of passive cooling with state-of-the-art additive manufacturing. The ceramic cubes are suitable for cooling both indoor spaces and ambient air outside.
The cubes make use of a physical principle that is particularly well known in hot and dry regions of the world: evaporative cooling. When water evaporates, it absorbs heat from its surroundings and the air cools down. “This has been working for centuries, both in clay jugs and in traditional wind towers,” explains Milena Stavric from TU Graz. “The key technological advance here lies in the use of 3D printing, which enables us to produce highly complex, porous and functionally optimised geometries from clay mixtures. These special structures store water particularly efficiently and, despite their small volume, create an enormous evaporation surface.”
Clearly noticeable cooling effect
The cubes, with sides measuring around 23 centimetres, are digitally designed and 3D-printed from a ceramic clay mixture. The printed clay objects are fired at low temperatures to achieve a highly porous consistency. The specially developed minimal-surface geometry (TPMS) provides a very large surface area while using minimal material. Water is absorbed into the porous ceramic by capillary forces and distributed evenly throughout its complex geometry. This creates a large evaporation surface, over which the water continuously evaporates, drawing heat from the surroundings.
To further increase cooling performance, the team is experimenting with bio-inspired approaches in the institute’s own Shape Lab. Fungal cultures and sawdust are added to the clay as a nutrient medium. A mycelium – the thread-like network of fungal filaments – grows into the material and forms a fine network. The clay-fungus mixture is 3D-printed and fired. Fungal mycelia and sawdust burn, leaving behind a network of micro- and macro-pores through which water can spread particularly well inside the cube.
Indoor test
A field test carried out in a hot attic at TU Graz showed a significant effect. In a controlled experimental setup, a temperature drop of almost seven degrees Celsius was measured in the immediate vicinity of the water-filled cube. “The cooling effect was clearly noticeable throughout the room,” says Kristijan Ristoski, who wrote his Master’s thesis on integrating the cubes and water supply into the cooling wall.
The team is also trying out other newly developed material blends. One area of focus is the sediment from Lake Neusiedl, which has to be dredged regularly to slow down the silting up of this shallow body of water. Until now, most of the lake sediment has been disposed of without being put to any use. In future, these sediments could be integrated into resource-efficient construction processes as a sustainable building material produced by 3D printers.
Natural cooling principle instead of energy-intensive air-conditioning technology
Ceramic walls offer a resource-efficient alternative to energy-intensive cooling systems and are suitable for residential and office buildings as well as for schools, public spaces and waiting areas. “Our aim is to provide cooling where people suffer particularly from the heat – for example, in cities where trees are sometimes unable to provide sufficient cooling. To achieve this, we rely on natural cooling principles rather than energy-intensive air-conditioning technology,” says Milena Stavric.
Cooling demonstration wall in Graz
Anyone interested can take a look at the technology at the Museum of Perception in Graz. And in Stremayrgasse, at TU Graz’s Campus Neue Technik, a free-standing demonstration wall made of clay, measuring two by two metres, was recently erected. There, you can experience the cooling effect first- hand.
Planners and interested companies who see potential for applying the technologies involved are welcome to contact the project team directly.
The project “3D-Printed ceramic cooling walls for sustainable urban architecture” was carried out in close collaboration with TU Graz’s Institute of Building Physics, Services and Construction and was funded by Austria Wirtschaftsservice GmbH (aws) as part of the proof of concept programme.