Some of the approximately 2.000 termite species that have been described are considered engineers of the ecosystem in a sense. Some of the world's largest biological structures are found in the mounds formed by various genera such as Amitermes, Macrotermes, Nasutitermes, and Odontotermes. These mounds can reach heights of up to eight meters. Over tens of millions of years natural selection has improved the 'design' of its mounds.
What can human engineers and architects learn from termites by studying their behavior?
In a new paper published in Frontiers in Materials, researchers show how termite mounds can teach us how to design comfortable indoor temperatures for our homes without the carbon footprint of air conditioning.
Lund University's Dr. David Andréen said: “We show here that the 'exit complex', an intricate network of interconnected tunnels found in termite mounds, can be used to promote the flow of air, heat and moisture in new ways in human architecture.
Macrotermes michaelseni termite mounds in Namibia, Andréen, and co-author Dr. Reviewed by Rupert Soar. More than a million people can live in a colony of this species. Symbiotic mushroom gardens, where termites grow for food, are at the center of the mounds.
The exit complex, a dense lattice-like tunnel network connecting wider channels inside to the outside, was the study area for the researchers. This includes the north-facing surface of the mound, which is exposed to direct midday sun during the rainy season (November to April) when it grows. Termite workers keep their exit tunnels closed to the outside during this season. The complex needs to provide adequate ventilation while allowing excess moisture to evaporate. So how does it work?
Andréen and Soar examined how oscillating or pulse-like flows are made possible by the design of the outlet complex. As a basis for their research, they used a 2005D-printed copy of a scanned part of an output complex part taken from nature in February 3. This piece had a volume of 1,4 liters, a thickness of 4 cm and a 16% tunnel.
Using a loudspeaker to mimic the wind, the researchers sent vibrations of the CO2-air mixture through the part while using a sensor to monitor mass movement. They discovered that airflow was highest between 30Hz and 40Hz oscillation frequencies, middle between 10Hz and 20Hz oscillation frequencies, and least between 50Hz and 120Hz oscillation frequencies.
Turbulence Assistance to Ventilation
The researchers concluded that the tunnels of the complex interact with the wind blowing over the mound, improving the mass transfer of air for ventilation. As a result of internal turbulence caused by wind oscillations at certain frequencies, exhaled gases and extra moisture are carried away from the center of the mound.
“When ventilating a building, it is important to maintain the delicate balance of temperature and humidity that occurs inside without blocking the inflow and outflow of fresh air. Most HVAC systems have trouble doing this. Here, a structured interface allows the exchange of respiratory gases only due to concentration changes between the two sides. Soar noted that this maintains the conditions inside.
The output complex was then reproduced by the authors using various 2D models of varying complexity from simple straight tubes to a lattice. Using an electromotor, they tunneled an oscillating body of water and filmed the mass flow as it progressed. Surprisingly, they discovered that for the tide to reach the entire complex, the engine only had to push air back and forth a few millimeters (equivalent to modest wind oscillations). More importantly, the layout must be sufficiently lattice-like for the necessary turbulence to occur.
According to the authors, the ascent complex could provide wind-powered ventilation of termite mounds at low wind speeds.
“We anticipate that future building walls built with the latest technology, such as powder bed printers, will have networks similar to the outlet complex. According to Andréen, these will keep the air moving thanks to embedded sensors and energy-efficient actuators.
Soar concluded: “Construction-scale 3D printing will only be possible when we can design structures as complex as those found in nature.” The exit complex is an example of a complex structure that can simultaneously address several issues such as maintaining comfort inside our homes and controlling the passage of moisture and breathing gases through the building envelope.
We are about to make the transition to building what nature does: for the first time it may be possible to create a real structure that breathes, lives.
📩 28/05/2023 23:43