Useful lessons in ventilation provided by insects' mounds

Oct 22, 2010 By Alvin Powell
During a presentation sponsored by Harvard’s Wyss Institute for Biologically Inspired Engineering, biologist J. Scott Turner debunked some 50-year-old assertions that termite mounds’ complex tunnel structure works to circulate air in an orderly manner from a nest chamber low in the mound, up a central chimney away from the nest, and, as the air cools, down small outer tunnels to the bottom of the nest. Credit: Rose Lincoln/Harvard Staff Photographer

While some power companies scour the globe for steady winds to drive giant turbines, a biologist is turning to lowly termites and their lofty mounds to understand how to harness far more common intermittent breezes, seeking ideas that could drive nature-inspired building systems whose “sloshing” air movement could provide ventilation and cooling.

J. Scott Turner, a biology professor at the State University of New York, brought his termite-mound studies to Harvard’s School of Engineering and Applied Sciences Wednesday (Oct. 20) in a talk sponsored by Harvard’s Wyss Institute for Biologically Inspired Engineering.

Turner’s topic, “New Concepts in Termite-Inspired Design,” presented the results of years of research into the structure of termite mounds in Namibia, including an extraordinary effort to fill a mound’s tunnels with plaster and then slice off millimeter-thick layers to create a cross-sectional map of the insides.

Turner’s work debunked some 50-year-old assertions that termite mounds’ complex tunnel structure works to circulate air in an orderly manner from a nest chamber low in the mound, up a central chimney away from the nest, and, as the air cools, down small outer tunnels to the bottom of the nest.

That understanding of termite mound function has already inspired human architecture -- including a building in Zimbabwe designed without air conditioning that instead uses wind energy and heat-storing materials to maintain a moderate temperature. The only problem with these sorts of termite-inspired designs, Turner said, is that his studies show that the mounds actually don’t work that way.

Deploying temperature and humidity gauges, and armed with tracer gases, Turner found that a termite mound does not regulate interior temperature. The temperature inside the mound was not appreciably different from that of the surrounding ground, rising during some parts of the year and then falling. In addition, he found that the air in the nest didn’t really circulate. Instead, it was stable, with cooler air in the nest low in the mound and hotter air in the mound’s upper portions and chimney.

The same fluctuation wasn’t found with humidity, which was maintained at roughly 80 percent year-round. But it isn’t the mound or its design that does that job, Turner said. Instead, actively move water within and out of the mound as they transport water-soaked earth. In addition, the symbiotic fungi that live in the mound with the termites also help to regulate humidity. The fungi, which help the termites digest tough cellulose in the plant material the insects bring into the nest, form complex, folded bodies that absorb excess humidity during wet months and release water during dry months, Turner said. This helps to maintain a stable humidity, dry enough to keep moisture-loving fungal competitors at bay.

“They actively regulate nest moisture, but not through design of the mound,” Turner said.

So, if the mound itself doesn’t regulate heat or humidity, Turner and his collaborators wondered, what does the elaborate branching system of tunnels do?

The answer came on further investigation, when researchers found that the tunnels work as an air exchange system. The smaller tunnels on the mound’s surface, used by workers to move in and out of the mound, also serve to mute the gusty, turbulent air outside the mound. Those high-energy gusty breezes are blocked in the surface tunnels, allowing more gentle air movements to penetrate the mound in a pulsing, in-and-out process akin to a breathing human lung. Through this process, fresh air is exchanged into the deepest part of the mound, “sloshing” in and out in a tidal movement that refreshes the mound’s air.

“We think these mounds are quite efficient manipulators of transient energy in turbulent wind,” Turner said. “That’s how the mound breathes.”

That in-and-out sloshing, Turner said, provides a model for building design. Though most people would refuse to live in a building resembling a termite mound, the tunnel structure could be replicated in building materials used in exterior surfaces, saving energy through passive air exchange systems in everyday, ordinary buildings.

“There might be some really interesting architectural opportunities,” Turner said.

Explore further: Lifting the brakes on fuel efficiency

add to favorites email to friend print save as pdf

Related Stories

Termites foretell climate change in Africa's savannas

Sep 07, 2010

Using sophisticated airborne imaging and structural analysis, scientists at the Carnegie Institution's Department of Global Ecology mapped more than 40,000 termite mounds over 192 square miles in the African ...

Satisfying job leads to better mental health

Oct 14, 2010

(PhysOrg.com) -- If you want to have good mental health, it’s not enough to just have a job, you should also have a job that satisfies you, according to new research from The Australian National University. ...

Redirection reduces impact of erosion

Oct 06, 2010

The life expectancy of cooling plates in heat exchangers at Rio Tinto Alcan’s Yarwun alumina refinery has increased from a few days to as long as 12 months with help from CSIRO’s slurry erosion researchers, ...

Recommended for you

Lifting the brakes on fuel efficiency

Apr 18, 2014

The work of a research leader at Michigan Technological University is attracting attention from Michigan's Governor as well as automotive companies around the world. Xiaodi "Scott" Huang of Michigan Tech's ...

Large streams of data warn cars, banks and oil drillers

Apr 16, 2014

Better warning systems that alert motorists to a collision, make banks aware of the risk of losses on bad customers, and tell oil companies about potential problems with new drilling. This is the aim of AMIDST, the EU project ...

User comments : 0

More news stories

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

A homemade solar lamp for developing countries

(Phys.org) —The solar lamp developed by the start-up LEDsafari is a more effective, safer, and less expensive form of illumination than the traditional oil lamp currently used by more than one billion people ...

UAE reports 12 new cases of MERS

Health authorities in the United Arab Emirates have announced 12 new cases of infection by the MERS coronavirus, but insisted the patients would be cured within two weeks.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...