Sweating Gyroid Cubes, TU Graz 3D-Prints Ceramic Coolers That Work Without Power

Photo credit: TU Graz
In a hot attic on the Graz University of Technology campus, air next to one water-soaked ceramic block measured nearly seven degrees Celsius cooler than the space around it. Kristijan Ristoski, who built the water supply into a full cooling wall for his master’s thesis, said the drop was easy to feel across the room. That block is a cube about 23 centimeters on each side, printed from clay, fired at low heat so it stays open and thirsty, then loaded with water.

Milena Stavric, Julian Jauk, and Ristoski, three innovators from the Institute of Architecture and Media, designed the cubes to combat metropolitan heat without using energy-intensive compressors or refrigerants. Water naturally rises up into the clay by capillary action and spreads through a maze of small pores, and when it evaporates off the interior surface, which is massive, it draws all of the heat out of the surrounding air. It’s the same principle that has been employed in clay jugs and traditional wind towers for millennia; they simply couldn’t develop the shapes required to make it operate efficiently and effectively.

Nowadays, with the emergence of additive manufacturing, the team can construct forms that would be nearly difficult to make with traditional molds and presses. Each cube has a triply periodic minimum surface made of the gyroid lattice, which has been around for a long time yet is easier to print into a piece of material than you might imagine. One of the best features of this lattice is that it has no dead ends or air pockets, making it simple to print without supports and allowing it to carry a disproportionately large amount of evaporative surface area, and hence cooling power, in a small volume of material.

They’ve also developed a variant that includes fungal mycelium and wood chips, which burn away in the kiln and leave behind a network of fine thread-like capillaries and larger pockets, allowing water to move about and evaporate off. The end product is a highly effective cooling system that can be adjusted by supplying water to the cubes.

The fruits of their labor can already be seen at Campus Neue Technik, a two-meter square wall installation on Stremayrgasse, and another at Graz’s Museum of Perception. To top it all off, they’re experimenting using sediment dredged from Lake Neusiedl, which would otherwise be discarded as garbage, as a substitute for traditional clay.

Milena’s ultimate goal is to develop cooling systems that may be used where they are most needed, in cities where all those trees cannot always be counted on to keep things cool. The cubes are versatile and can be used indoors or outdoors, as long as water is available and the air is dry enough for evaporation to occur. Of course, there are still a few issues to work out before they can be considered a full replacement for air conditioning, such as scaling, mineral buildup, frost, cleaning, and hygiene, but for the time being, the results are quite impressive: nearly seven degrees cooler just next to a single cube, and no need to plug anything into the wall.
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