Technical Envelope

Yamanashi, as the small water pump is activated using electricity generated by solar cells installed on the building’s south-facing eaves. In addition, the capital cost, including plumbing and computer timer control, was just 0.02% of the building’s total construction cost. Nikken Sekkei is currently designing

two unnamed buildings in Japan to incorporate a modifi ed version of Bioskin, and is looking for other suitable projects in Southeast Asian countries where the climate is similar. “Bioskin is very sensitive to the specifi c

environmental conditions and as such is not well suited to mass-production like solar photovoltaics,” says Yamanashi. “The technology must go through many computer simulations and redesigns based on the environmental and contextual situation of each project. “The world of sustainable architecture

is currently too focused on big technical innovations, which when talking about environmental matters is quite dangerous. Bioskin is a low impact biomimetic system and I hope we can develop it to change the world mildly through some projects.”

“We are harvesting algae every day, depending on the amount of sunlight, and gaining much more heat from the system than we expected” Martin Pauli, Arup

Plant life: microalgae inside glass panels are harvested to produce biogas to help meet the building’s energy requirements

Hamburg’s power plants

NATURAL PROCESSES are also the inspiration behind the world’s fi rst bioreactive facade, installed as part of an exemplar housing project at Hamburg’s International Building Exhibition in January 2013, which is now yielding positive results that could signal a paradigm shift in intelligent envelope design. The four-storey apartment block,

known as BIQ, is fi tted with a secondary facade designed to cultivate microalgae inside glass shading louvres fi lled with circulating water and nutrients. This “solar leaf” technology has been pioneered by consulting engineer Ove Arup in collaboration with Germany’s Spitterwork Architects and biotech company Strategic Science Consult. The tiny plants, most no larger than bacteria, grow inside the panels in response to direct sunlight and are harvested and fermented to produce

42 | SEPTEMBER 2014 | CONSTRUCTION MANAGER

biogas to help fuel the building’s energy requirements. The system also acts as form of adaptive shading — as the level of sunlight increases, so the algae multiplies, makes the panels more opaque and provides more shade.

Positive results The two-year research project is gathering data on performance from multiple sensors and is due to publish its results at the end of 2014. The concept has proved effective so far, explains Martin Pauli, project architect at Arup: “Overall performance is quite good, we are harvesting algae every day, depending on the amount of sunlight, and gaining much more heat from the system than we expected at the start. “During design we were unable to

simulate the amount of algae that might be produced, so every gram we harvest is good news and I have a feeling effi ciency is already quite good.” The amount of algae harvested is subject to varying weather and

environmental conditions, although Pauli was unable to confi rm whether a target to create 15g of algae biomass per sq m of glazing has been met. In principle, the effi ciency of the conversion of light to biomass is 10% and of light to heat 38%. By comparison, solar photovoltaic systems have a conversion effi ciency of 12-15% and solar thermal systems 60-65%. As the experiment progresses, a

series of “process variations” are being introduced every two months in an effort to identify ways to improve performance and move the system from concept to reality. Different water temperatures have been tested and during the winter a form of Arctic algae was introduced into the louvres in the hope that it would thrive in the cold. “The aim is to create a harmonious

‘comfort zone’ to enable the algae to thrive in different conditions,” says Pauli. “The Arctic algae would have been a perfect story because being able to vary the algae in different seasons avoids the need to heat or cool the

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Photograph: Colt International GmbH