X-rays reveal termites' self-cooling, self-ventilating, self-draining skyscrapers

X-rays reveal termites' self-cooling, self-ventilating, self-draining skyscrapers
Multi-scale 3D X-ray tomography of termite nests reveals the secrets of their architecture which plays a significant role in ventilation, thermal regulation and water drainage after rainy periods. Credit: Kamaljit Singh

Many species of termites, whose societies are built on hierarchies of kings, queens, workers, and soldiers, live in towering nests that are ventilated by a complex system of tunnels.

The nests, also known as mounds, protrude from the ground like skyscrapers and can grow as tall as seven metres. They are also self-cooling, self-ventilating, and self-draining—but until now the mechanisms behind these climate control features has remained unknown.

A group of engineers, biologists, chemists and mathematicians lead by Imperial College London, the University of Nottingham, and CNRS-Toulouse have looked closer than ever before at how these nests work using 3-D X-ray imaging. They found small holes, or pores, in the walls of termite mounds which help them stay cool, ventilated, and dry.

Lead author Dr. Kamaljit Singh, from Imperial's Department of Earth Science & Engineering, said: "Termite nests are a unique example of architectural perfection by insects. The way they're designed offers fascinating self-sustaining temperature and ventilation controlling properties throughout the year without using any mechanical or electronic appliances."

In their new study, published in Science Advances, the researchers sourced termite nests from the African countries Senegal and Guinea and studied them using two types of 3-D X-ray imaging.

First, they scanned the nests at a lower resolution to measure the nests' larger features, like walls and corridors known as channels.

From the images they calculated the thickness of the nests' inner and outer walls, as well as the structural details of inner channels which termites use to get around the .

The researchers found that networks of larger and smaller pores in the nest walls help exchange carbon dioxide (CO2) with the outside atmosphere to help ventilation. Larger micro-scale pores are found to be fully connected throughout the outer wall providing a path across the walls, and by using 3-D flow simulations, the authors showed how CO2 moves through the nests to the outside.

The simulations showed that the large micro-scale pores in nest walls are useful for ventilation when the wind outside is faster, as CO2 can leave freely. However in slower wind speeds, the larger pores can also help to release CO2 through diffusion.

Multi-scale 3D X-ray tomography reveals the secrets of termite nests. Credit: Kamaljit Singh

Dr. Singh said: "This is a remarkable feature that lets the nest ventilate regardless of the weather outside."

Nests are usually found in hotter regions, which means they must stay cool. Indeed, the authors found that the larger pores also help regulate temperatures inside nests. The pores, which lie in the outer walls of the nest, fill with air which reduces heat entering through the walls—similarly to how the air in double glazed windows helps keep the heat inside.

Considering the crucial role the pores play, the team also wondered what happens when it rains and the pores become blocked by water.

They found that the nests use 'capillary action' - where liquid flows through small spaces without external help from gravity—that forces rain water from the larger pores to the smaller pores. This ensures the larger pores keep stay open to keep ventilating the nest.

Dr. Singh said: "Not only do these remarkable structures self-ventilate and regulate their own temperatures—they also have inbuilt drainage systems. Our research provides deeper insight into how they manage this so well."

The scientists say the newly found architecture within could help us improve ventilation, temperature control, and drainage systems in buildings—and hopefully make them more energy efficient.

Co-author Professor Pierre Degond from Imperial's Department of Mathematics said "The findings greatly improve our understanding of how can help control ventilation, heat regulation, and drainage of structures—maybe even in human dwellings. They also provide a new direction for future research, and will eventually bring us one step closer to understanding mechanisms that could be useful in designing energy efficient self-sustaining buildings."

Co-author Dr. Bagus Muljadi from the University of Nottingham said: "We know that nature holds the secrets to survival. To unlock them, we need to encourage global, interdisciplinary research.

"This study shows that there is a lot more to learn from mother nature when it comes to solving even the most important 21st century problems."

Explore further

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More information: K. Singh el al., "The architectural design of smart ventilation and drainage systems in termite nests," Science Advances (2019). advances.sciencemag.org/content/5/3/eaat8520
Journal information: Science Advances

Citation: X-rays reveal termites' self-cooling, self-ventilating, self-draining skyscrapers (2019, March 22) retrieved 17 September 2019 from https://phys.org/news/2019-03-x-rays-reveal-termites-self-cooling-self-ventilating.html
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Mar 23, 2019
What is the difference in size?
O2 molecules versus CO2 molecules
phys.org> The researchers found that networks of larger and smaller pores in the nest walls help exchange carbon dioxide (CO2) with the outside atmosphere

Simulations showed that the large micro-scale pores in nest walls are useful for ventilation when the wind outside is faster, as CO2 can leave freely. However in slower wind speeds, the larger pores can also help to release CO2 through diffusion

there is a feeling O2 molecles are smaller than CO2 molecules
which meaneth
what ever the size of the simulated ventilation holes
The O2 molecules flow freer than CO2 molecules

Mar 23, 2019
Molecules are orders of magnitude smaller than the pores and ventilation holes discussed here.

Mar 23, 2019
The size of the holes makes no never mind
Ojorf> Molecules are orders of magnitude smaller than the pores and ventilation holes discussed here.

Is like saying
the size of the holes
compared to the size of the O2 and CO2 molecules
is so great
there is no distinction which flows freer
O2 or CO2 molecules

Mar 23, 2019
Yes, exactly like that.
You've got it!

Mar 23, 2019
Weak wind sends 02 out main pathway holes and pushes C02 out smaller branch pathways. C02 comes out slower but is more diffused.

Strong wind blows it all out. In that case, momentum overcomes the sizes of the holes.

Mar 23, 2019
if i remember correctly, CO2 masses heavier than O2 ?
& that is why a cloud of carbon dioxide can be so dangerous in large concentrations.
As it shoves the oxygen away?

Mar 23, 2019
Yes, and I assume the fungal farms the termites grow would suffocate if this C02 concentration wasn't vented out. The pores and the overall enclosed structure of the mound allow for the low internal temps in the hot African sun. Open spaces act as insulation and a place for the gas to drift into when the breeze is low.

Mar 23, 2019
Atmospheric Cooling

So why this interest in CO2
humans live at ground level
where we breath O2
which is lighter than CO2
as the air
ground level is a mixture of O2 and CO2
in point of fact
20% O2
0.03% CO2
what is this interest in CO2
as the only atmospheric gas
apart from 79% nitrogen is 20% oxygen
as yet
it is not obvious
What relevance, 0.03% CO2 has anything to do with air cooling circulation?

Mar 23, 2019
Ambient C02 from incoming air isn't the issue. It's from the fungal farms which are fed wood paste by the termites. The fungus eats the wood paste and produces C02 in the process. In an enclosed chamber this would build up over time and suffocate the fungus, therefore making the termites go hungry who harvest and eat the fungus. It is synergetic relationship between fungus and arthropod that has developed over millions of years. How you may ask? Gradual steps of building nests over millennia and finding things to eat. Eventually some how, some way, the termites learned to do agriculture.

Mar 24, 2019
CO2 has no part in ventilation

If termite farming
the fungal farms, builds up CO2
suffocating the fungus
this meaneths
this fungus is converting O2 and Carbon
to CO2
it is the nitrogen and oxygen that is ventilating this termites abode
and in the process removing the stale air over the termites fungal farms
what relevance CO2
As CO2 has no part in ventilation

Mar 24, 2019
Because C02 is part of the cycle of life on Earth.

Even plants respire and produce C02 on the cellular level. They just don't emit as much as they consume when they photosynthesize during daylight hours.

And since the current percentage of oxygen in the atmosphere is largely attributed to photosynthesis (a process that uses photons, water, and CO2), one could say that CO2 has a hand in making the oxygen percentage side of the ventilation gases.

Mar 24, 2019
I wonder if the researches have considered releasing a "MineCraft" version of this data for educators?

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