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Technology Quarterly: Borrowing from nature
[September 06, 2007]

Technology Quarterly: Borrowing from nature

(The Economist Via Thomson Dialog NewsEdge) Clean technology: Architects believe that biologically inspired designs can help to reduce the environmental impact of buildings

ARCHITECTS have long taken inspiration from nature. In ancient Egypt columns were modelled on palm trees and lotus plants, and building designers have borrowed the shapes and proportions of natural forms ever since as they strived to achieve aesthetic perfection.

Some architects now believe that such biomimicry has more to offer than simply making buildings look good. They are copying functional systems found in nature to provide cooling, generate energy and even to desalinate water. And they insist that doing these things using biomimetic designs is not just a gimmick, but makes financial sense. "It's often the case that green technology is considered to be commercially unattractive," says Michael Pawlyn, an architect at Grimshaw, the firm behind the Eden Project, a highly acclaimed biome structure in England. That perception, he says, is wrong--and he has the designs to prove it.

So far, the use of biomimetic features in buildings has been driven as much by aesthetics as by function, and has been limited to relatively simple, passive systems. The Arab World Institute in Paris, for example, has an array of mechanical, eye-like irises on its south-facing faade. These open and close to control the amount of light entering the building, thereby regulating the internal temperature.

Similarly there are now several buildings that have ventilation systems based on those found in termite mounds. The Eastgate Centre, a shopping centre and office block in Harare, Zimbabwe, has a mechanical cooling system made up of vents and flues that help hot air out of the structure. "It's the same principle as the chimney effect, but a bit more controlled," says Professor George Jeronimidis, director of the Centre for Biomimetics at the University of Reading. As hot air rises and flows out through vents at the top of the building, cooler air is drawn in at ground level.

Dr Jeronimidis is now taking this concept further by using adaptive materials that flex in response to the level of moisture in the air--an idea borrowed from the way pine-cones open and close. Using a cellulose-like fibre composite, he has created a vent that changes from one curved shape to another, depending on the relative levels of moisture inside and outside a building. When warm, moist air builds up inside the building, the vent opens to allow it to escape. But when the air inside is dry, the vent stays shut and moist air from outdoors is kept out. "In principle it can be made to respond naturally, without any additional power," says Dr Jeronimidis.

Intelligent designs

Architects have become more interested in this sort of thing in recent years, he says, as greater attention is paid to the energy consumption and sustainability of buildings. Biology offers solutions to a range of problems. "Nature has had the benefit of a pretty long R&D period," says Mr Pawlyn, who hopes to take the exploitation of natural designs to a completely new level. His firm has borrowed a trick used by fog-basking beetles and in the nostrils of camels for a novel desalination plant.

When Grimshaw was given the brief to regenerate the Santa Catalina Isthmus, a narrow stretch of land on the coast of Las Palmas in Grand Canaria, the firm came up with the concept of a 3km (1.9 mile) promenade with a theatre and botanic garden as its focus. But rather than creating yet another drain on local resources the architects wanted the structure to be cooled and irrigated by natural means. "We decided to put forward a scheme that showed how the island could move towards self-sufficiency in water and energy, without relying on fossil fuels," says Mr Pawlyn.

This meant finding a way to turn seawater into clean drinking water without expending too much energy. Fog-basking beetles, which are found in Namibia, have an ingeniously simple way of doing this. They hide underground during the day so that when they come out at night, their dark backs are relatively cool compared with the ambient night air. As moisture-laden breezes roll in from the Atlantic, the water in the air condenses on the beetles' backs (just as a cold bottle of beer left on a table causes water in the air to condense on its surface). The beetles simply have to tilt their bodies to make the water trickle into their mouths. A similar trick is also used by camels to prevent them losing moisture as they exhale. Moisture secreted through the nostrils evaporates as the camel breathes in, cooling the nostrils in the process. When the camel breathes out, moisture within the air then condenses on the nostrils.

Inspired by this, Mr Pawlyn and his colleagues have designed their theatre around the same principles. A series of tall, vertical evaporation "gills" are positioned so that they face towards the sea and the incoming coastal breeze. Warm seawater, taken from close to the surface, is pumped so that it trickles down these units. As the breeze blows through the gills some of the seawater evaporates, leaving salt behind. The clean, moist air then continues its journey until it encounters a series of vertical condensing pipes. These are kept cold by pumping deep-sea water, from 1,000 metres below the surface, through them. As the moist, warm air hits the pipes the water condenses and trickles down to be collected.

"You get a very powerful desalination effect," says Mr Pawlyn. This system is able to supply enough water for the 70,000-square-metre complex. A traditional flash-distillation desalination plant consumes between five and 12 kilowatt hours (kWh) of energy per cubic metre of water. The biomimetic approach, however, requires just 1.6 kWh per cubic metre. And since the water pumps will be mostly powered by a wind turbine, driven by the same prevailing winds that provide the plant's airflow, the overall energy consumption of the site is reduced even further. In the process, the same system can also help to cool neighbouring buildings, says Mr Pawlyn.

Build me a rainforest

Although it is unclear whether this innovative project will go ahead, the principles have already been tested by Charlie Paton, an engineer who collaborated in the scheme. His organisation, Seawater Greenhouse, has built pilot greenhouses that show this idea really works. The catch is that it will only work in certain climates, says Mr Pawlyn. "If you have a very dry and hot environment, the water readily evaporates."

Nonetheless, Mr Pawlyn and his colleagues believe that biomimetic principles can be taken even further, to generate new income as well as reduce running costs and resource use. Natural ecosystems are restorative, notes Mr Pawlyn. "They operate in a closed loop made up of quite complex webs of different organisms," he says. "Man-made structures tend not to do that." Instead, man-made systems tend to be linear, consuming raw materials at one end and producing waste at the other. The result is a gradual depletion of natural resources.

In an effort to reproduce a closed-loop system, Grimshaw has developed a design for an indoor tropical rainforest. This botanical garden is designed to sit on an existing landfill site and be a completely carbon-neutral structure. For most of the year, heat to maintain the hothouse will be provided by solar heating through a glazed roof. During the colder months additional heating will come from landfill biomass. The building is designed to be flanked by a number of large vertical vessels into which biodegradable waste, originally intended for the landfill, will be tossed. As the waste breaks down in these large composting units, it reaches temperatures of up to 75C, and this heats the indoor garden.

This building will not only be carbon-neutral but will also generate income, by providing the service of waste disposal. Some countries impose landfill taxes of as much as 20 ($40) per tonne of waste. The designers reckon that their proposed building could generate as much as 7m ($14m) a year by acting as a substitute for a landfill site. And in the true spirit of restorative closed-loops, the resulting compost can be sold for agricultural use.

"Buildings should be able to pay for themselves," says Professor Julian Vincent, director of the Centre for Biomimetics at the University of Bath in England. At the moment, he says, most biologically inspired systems used in architecture are simply morphological. "This seems to me to lose the point of biomimetics," he says. There is huge potential, but architects are only just beginning to learn how to apply biomimetics in a more functional way, says Michael Weinstock, director of the Architectural Association School of Architecture in London. Not only large projects but smaller homes and offices can benefit from the same principles, he insists. "One of our ambitions is to ensure that every building ought to be able to generate its own energy," he says.

Bringing biomimetics home

This need not require elaborate new structures like Grimshaw's theatre or indoor rainforest. Biomimetics can be applied in simpler ways, too. Smart paints which use a self-cleaning principle borrowed from lotus leaves are now being tested. Once applied, the surface of the paint takes the form of densely packed ridges or bumps, just like the microscopic bumps found on lotus leaves. A property of such tiny bumps is that they prevent drops of water from spreading out: the drops simply roll off the surface instead, taking dirt with them. (Self-cleaning glass relies on a similar principle.) And organic solar cells, which mimic photosynthetic processes to capture light and convert it into electricity, are arguably a form of biomimetic technology, too.

"Part of the challenge, I believe, is to reconnect people with resources," says Mr Pawlyn. He makes a strong case that borrowing architectural ideas from nature can help to reduce the environmental impact of buildings. In the process, it may also encourage people to view natural systems with greater respect, in more ways than one.

SOURCE: The Economist

Copyright 2007 Economist Newspaper

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