feb 09 | Riscaldamento Climatizzazione Idronica

Biomimicry in building design

by Fabrizio Corbe

Some examples of cutting-edge designs are created according to the principles of biomimicry: an applied science that studies the principles and forms of environmental adaptation found in the natural world and uses them to design objects and systems capable of meeting the needs of human society. Modern cities, much more than old cities, are notable for their power to change the local environment: heating and air-conditioning systems installed in buildings not only impact on air quality but also on the dynamics of air movement at the lowest levels of the atmosphere. As a result, building design takes on an aerodynamic importance that opens the exciting possibility of using wind systems for the production of electricity with low environmental impact.

Wind shape
The phenomena linked to air movement in cities are influenced by the "shape factor" of buildings: urban design, even when it reflects important factors such as solar exposure, rarely takes into account the aerodynamic effects of the materials used for the building itself. These effects are particularly noticeable where buildings are extremely tall compared to the size of their base: a multitude of high-rise buildings usually increases wind flow, the strength of which is further increased by the turbulence created by the angular shapes of their exterior surfaces. The exterior appearance of a high-rise building is hardly ever considered in respect to wind loads: the problem is usually resolved at a structural level, by introducing sufficient load coefficients into the dimensions of the load-bearing framework. It is only recently that some designs with wind turbines more or less integrated into the building's fabric have included external surfaces specifically designed to channel wind flow in order to produce electricity.

The Eastgate Center was designed by the architect Mick Pearce with the aim of providing optimum comfort conditions for all internal spaces and maintaining their stability in terms of heat and humidity without the need for mechanical air-conditioning.

The Bahrain Trade Center, designed by Atkins Architects, is one such example. It has three integrated 95-ft diameter wind turbines generating a total of 1000 MWh of electricity a year. That is equivalent to about 10% of the building's total energy needs. The twin towers, connected by bridges for people to cross between the two, were designed to create a Venturi effect capable of increasing the wind speed. The effects on the surroundings are yet to be evaluated. Skidmore, Owings & Merrill LLP have taken a different approach in their design of the Pearl River Tower in Guangzhou, China: it is a thin, wide, parallelepiped-shaped structure with the main façade facing head-on to the prevailing wind. The tapered shape of the façade channels the wind towards two air-permeable intermediate floors, where wind microturbines are located. Combined with integrated photovoltaic panels which take advantage of direct sunlight, the microturbines can provide 100% of the building's operational energy needs. In both cases--and we could mention many others--we are looking at a design approach that, regardless of the remarkable results achieved in terms of energy, opposes the work of man to the forces of nature; it aims to maximize the output of systems designed to harness natural resources but without bringing, on a wider scale, positive effects to the urban ecosystem. These designs therefore show a significant disregard for the local and global effects on the environment.

The power of the method
Biomimicry is an applied science which has only recently become established: it studies the principles and forms of environmental adaptation found in the natural world and uses them to design objects and systems capable of meeting the needs of human society. The potential applications of biomimetic research concern almost all sectors of human activity. Furthermore, the strategies, processes and synergies employed will be more effective the more we are able to make the most of local features through specifically devised solutions and technologies. Human transformation of space is undoubtedly one of the areas of major interest: examples of efficient forms of adaptation to inhospitable environments abound in the building traditions of all cultures but there are also recent cases of interest. The Eastgate Center in Harare, capital of Zimbabwe, is a shopping center and office block of about 344,500 sq. ft. intended as a multifunctional public building. Its design emulates the climate adaptation strategies found in termite mounds, which are able to maintain a constant internal temperature and humidity level despite the high external temperature range--from 2 °C at night to 42 °C during the day--that occurs in sub-Saharan Africa. Preliminary studies on the way the ventilation systems of termite mounds work were carried out by the TERMES (Termite Emulation of Regulatory Mound Environments by Simulation) project. 3D scans were taken of termite mounds in their natural habitat and the way in which these insects regulated the climate of their homes was also studied. Designed by the architect Mick Pearce in conjunction with Arup Associates, the Eastgate Center was built with the aim of providing optimum comfort conditions for all internal spaces while maintaining stable levels of heat and humidity without the need for mechanical air-conditioning. The complex consists of two parallel blocks divided by a central hall with a glazed roof and open to the circulation of breezes through the external and internal green walls. Simple, low-energy ventilators are positioned to allow for air movement: the air is taken in and let out by opening and closing air vents located on the external surface of the building and channeled into narrow flues--the surface of which allows convective heat transfer to take place with the solid concrete structure--that connect the cool lower part of the building with the hotter and more exposed upper part.

The Eastgate Center, Harare, is a shopping center and office block of about 344,500 sq. ft consisting of two parallel blocks divided by a central hall with a glazed roof and open to the circulation of breezes through the external and internal green walls. An extremely complex ventilation system of air flues--which has only ten hourly air changes--uses the nocturnal cooling of the building's thermal mass. The Eastgate Center in Harare replicates the climate adaptation strategies used in termite mounds to maintain constant internal temperature and humidity levels.

The Eastgate Center consumes about 10% of the energy needed for the heat regulation of a building of equal size in the same location by using a complex continuous air circulation system based on an extremely effective reversal of low-speed aerodynamics. In this example of biomimicry applied to a public building, a methodological approach open to design cross-over with the natural sciences is at the heart of genuinely sustainable solution, not necessarily based on complex technologies, but definitely informed by their intelligent and appropriate use.

Clean technology
Clean Technology Tower is a design project that was submitted in April 2008 by the Chicago-based American architectural firm Adrian Smith + Gordon Gill Architecture LLP. The two founders contributed to the design of the Pearl River Tower and the new concept has continued in the same vein, using information from a biomimicry study into the aerodynamic shape of flying animals. The main aim is the establishment of a symbiotic relationship between the high-rise building and the surrounding environment, and in particular with the element in which the building is immersed: air. The result is a "zero energy building", i.e. a building capable of producing its entire operational energy needs. In this case, it uses only wind turbines strategically placed to make the most of the aerodynamic flows generated around the exterior surfaces.

Clean Technology Tower is a design project produced by the Chicago-based American architectural firm Adrian Smith + Gordon Gill Architecture LLP, which has developed the biomimetic concept of previous designs.

The Clean Technology Tower's shape is designed to direct air currents through special flues positioned along the edges of the building; this is because whenever it encounters an obstacle, air naturally increases its speed as it flows around it. The shape of the surface allows flows from all directions to hit the turbines, which, properly channeled, maximize output in terms of air capacity and operational continuity; their density along the external surfaces increases as the building rises, making the most of the greater wind speeds found at higher levels. A veritable wind farm with vertical-axis turbines is located on the roof (where wind speed is at its highest) in order to capture air for generating the depression required to ventilate the internal spaces. Photovoltaic panels keep these spaces shaded (especially the dome situated at the top) and are installed in the lining of the external windows along the entire south face of the building. Among the positive effects on the surroundings, two results are particularly marked: - the pressure placed on the turbines means that the outgoing air returns its original speed before it was intercepted by the tower; - the aerodynamic shape of the building and the absence of sharp edges along the borders minimizes the speed of the wind not channeled into the turbines. The tower is designed to accommodate shop spaces at street level, a sports and health center, a 323,000 sq. ft hotel and around 2,152,000 sq. ft. of office space, located on higher floors to take maximum advantage of natural light; the large space under the dome on the top floor is designed to host public events, which will enjoy a panoramic view of the city. Situated in downtown Chicago, Clean Tower Technology uses design principles and technologies that can be extended to the majority of urban sites with a high population density. "We consider each building as an instrument that can limit the impact of human activity on the environment," explains Gordon Gill. "As architects, the shape of a building represents the main area in which we can optimize performance." Adrian Smith emphasizes the potential of this approach: "The basic idea has global applicability but only if we ensure our designs are in harmony with the environment will we be able to reduce the environmental impact locally and to optimize the production of clean energy: for this reason, every Clean Technology Tower we build will be different from another."

The Clean Technology Tower's shape is designed to direct air currents through special flues positioned along the edges of the building; this is because whenever it encounters an obstacle, air naturally increases its speed as it flows around it.. A veritable wind farm is located on the roof (where wind speed is at its highest) in order to capture air for generating the depression required to ventilate the internal spaces. The shape of the Clean Technology Tower is inspired by the outline of animals in flight. The turbines are hit by the rapid air flows that are generated along the surface.

Imitating nature
Biomimicry (bios: life; mimesis: imitation) is a relatively new science in which studies natural phenomena related to life--elements, models, processes and systems--to provide the inspiration for solving human problems of sustainability. As Janine M. Benyus--author of Biomimicry: Innovation Inspired by Nature--maintains, life forms on Earth have been patiently evolving and perfecting themselves over 3.8 billion years, transforming a mass of rock and water into a hospitable planet: what better models are there? The innovation of the biomimetic approach does not lie in the simple observation and replication of natural phenomena on an industrial scale. Indeed, from Newton's apple onwards, science and technology has always demonstrated that it is capable of taking ideas from the laws of physics and chemistry and using them for widely differing purposes. What they have not been able to do, however, is to adapt--the main driving force behind the survival of existing species--to the natural environment, the origin of these very same laws. In fact, the continual transformation by man of the Earth's surface has gone hand in hand with the conflict between natural and artificial environments, the consequences of which have begun to manifest themselves quite clearly. Biomimicry, on the other hand, is seen as an eminently sustainable discipline. The first question to whatever problem arises is: how do living species behave in this situation? Let's take a leaf as an example: if we consider the conversion factor of solar light into energy, it is definitely less efficient than a photovoltaic cell. However, contrary to the cell, a leaf only needs water, carbon dioxide and a few grams of minerals, which are in abundance in all soils. It grows relatively quickly, uses very little energy and does not produce waste, pollution or noise. In addition to transforming water, minerals and solar energy into chemical energy, during its lifetime it emits oxygen and provides its own independent means of sustenance. Finally, at the end of its productive life, it is 100% recyclable, that is, ready to start a new cycle. Natural life forms--including humanity--have fairly closed life cycles: from this perspective, a leaf is vastly more efficient than any photovoltaic cell.