Can Nanotechnology Make the World’s Largest Buildings More Sustainable?By Daniel Husserl, LEED®-AP, Senior Sustainability Specialist, NELSON
Fast forward 50 years to 2057. Sustainable architecture is ubiquitous, and the tallest building in the world now stands at more than 1000m with over 200 floors of residential and commercial space. Prudent planning by the world’s top design firms has facilitated the development of an organic building which Frank Lloyd Wright once defined as being “bred by native character to environment [and] married to the ground.” This building, which for irony’s sake we shall call Napoleon, also happens to be the most energy and water efficient structure per square foot on the planet. We owe this super-efficiency not to a newly developed graywater or LED lighting system, but rather to progress in microscopic materials science – better known as nanotechnology.
Now we return to 2007, where Taipi 101 is gracefully handing its “tallest building in the world” title to the Burj Dubai. The Burj Dubai will be an astounding structure when completed, but one cannot help but wonder what alternatives could have existed had more progressive sustainability technologies been at our disposal. Of the technologies that have advanced sustainability in our built environment, it seems those of the microscopic ilk have had the most significant positive impacts. These technologies, though, have been generally focused on materials within a building (i.e. recycled content in carpets and VOC levels in paints) and have not been gratuitously applied to a building’s core and shell. Recent innovations in nanoscience have brought us nascent technologies which could potentially be adapted to support super-efficient (beyond USGBC’s LEED®Platinum rating) building design.
These tiny technologies are only between 1 and 100 nanometers – about one onehundred thousandth of a millimeter – but they promise to play a key role in a new sustainable design revolution. Once financially and commercially viable, this revolution will perhaps provide cost-effective technologies to support superstructure sustainability. Though there are many tiny technologies currently in development, the following three would likely play a noteworthy role in the new sustainable design revolution, if not be the chief protagonists:
Carbon nanotubes are still far from commercial production but no doubt have promising sustainable design applicability. A carbon nanotube is a one-atom thick carbon sheet rolled into a one nanometer thick cylinder. Nanotubes have previously unseen strength to weight properties with bonds stronger than those found in diamonds. Through microscopic in their own right, nanotubes can be combined into larger structures that fall into a variety of forms, or allotropes, depending on the intent of their use. The impressive property of carbon nanotubes is that each nanotube allotrope bares its own electronic, thermal, and structural properties, making each feasible for a multitude of design applications. Napoleon’s designers would be faced with the challenge of utilizing the unique properties of carbon nanotubes without sacrificing the structural or environmental integrity of the building. One potential application for this nanotechnology would a hybrid structural steel with carbon nanotubes integrated throughout. This hybrid steel could be employed as a reinforced, lightweight structural steel frame with the goal of greatly reducing the amount of materials required to make Napoleon stand tall. This technique, without nanotubes, was in fact recently used to build the steel exoskeleton frame of the Hearst Corporation tower in New York City at a significant material savings. The superior strength of this hybrid skeleton would also add to the building’s disaster resilience and allow greater design flexibility. Additionally, carbon nanotubes are remarkable heat conductors. Though no such system has been tested, Napoleon’s designers could possibly utilize the carbon nanotube-steel frame as the integral part of a revolutionary, super-efficient radiant heat and cooling system.
Solar nanocrystals promise to greatly increase the efficiency of energy capture from the sun’s rays. Whereas existing solar panels only transfer light to energy from the visible range, solar nanocrystals absorb both visible and infrared light. They achieve this greater level of efficiency by incorporating inorganic nanorods into organic semiconductor films in a plastic-based polymer. As it turns out, the plastic film (hopefully recycled) enables the nanorods to be aligned in any number of ways which maximizes light absorption by the crystal itself. The polymer-based nature of these solar crystals offers a world of opportunity for flexible applicability in architectural design. Although solar nanocrystals have had a restricted commercial life due to their higher cost, market data has shown that costs will significantly decrease over a 10 year period as they did with traditional solar panels. Given their higher efficiency and flexible applicability, one could guess that this solar nanotechnology will eventually be the prominent solar energy technology. Now back to Napoleon. This solar polymer can be applied to any surface that a traditional polymer can be and by using any method currently used for polymer application. Napoleon’s designers would have innumerable options (cost notwithstanding) including integrating translucent solar nanocrystals into the building’s shell, spraying them on Napoleon’s roof or any other surface, and even weaving them into solar fabric parasols programmed to flex and follow the sun’s path to maximize efficiency. One could even provide an mp3 and mobile device charging solar sweater or t-shirt to tenants as a perk after lease signing. Obviously the options associated with this nanotechnology are infinite, with human imagination and cost being the only constraints.
This fascinating nanotechnology is 95 percent composed on something we have no shortage of – as the name suggests, air. Formed by extracting the liquid from gels through supercritical drying, Aerogel is often made from highly porous silica, alumina, chromia and more recently, carbon. Often called “frozen smoke,” it is already produced commercially but can be cost-prohibitive in its pure form. It is therefore typically incorporated into other materials such as glass, polycarbonate or composites to reduce its cost while retaining its beneficial qualities. Aerogel is a translucent, hydrophobic, ultra-lightweight material that also happens to be the best insulating solid in the world at up to R-8/2.5cm. With pore diameters of about 30 nanometers, it also demonstrates greatly reduced solar heat gain and improved energy efficiency. The small pore size literally traps nitrogen and oxygen to prevent air flow-through. Aerogel also reduces sound transfer to 5dB/1.57cm. Centimeter for centimeter, Aerogel is a much more environmentally efficient material than Argon gas windows or fiberglass wall insulation. It is, though, currently more expensive than these alternatives. Aerogel’s numerous desirable qualities suggest that this nanotechnology would be abundantly used in a building such as Napoleon. Napoleon’s designers would likely utilize the transparency and insulation properties of Aerogel to maximize natural light in the building while reducing heat gain and loss of translucent surfaces. Additionally, the unique properties of Aerogel potentially would enable Napoleon to have a partially translucent building core, which could allow building tenants to view plush atriums up to the 200th floor. An added environmental benefit of these translucent walls would be the reduction of fiberglass used for wall insulation. Many other promising nanotechnologies are in development, and some, such as translucent concrete and self cleaning glass, are only years away from becoming financially viable commercial products. As the sustainable design movement continues to blossom, I am reminded of one of the greatest “blind leaps” humankind has made in the past 100 years: former United States President John F. Kennedy once set a goal to put a man on the moon in 10 years without the assured technical or financial means of doing so. We are beginning to see a similar building owner and designer goal-driven approach to achieve sustainable design without a clear idea of how far we can push. The technologies to build a super-efficient Napoleon may not exist or be cost-effective in 2007, though by exploring the potentialities of up-and-coming nanotechnologies we are reaching into the future. Who knows…with a little luck and innovation, we may soon end up on a 200th floor green roof resting our legs on a bamboo bench.