In the drive to reduce buildings’ energy consumption and environmental impact, designers and engineers are jettisoning tried-and-tested facade materials to experiment with innovations inspired by nature.
The practice of biomimicry or bioinspiration, whereby designers try to reflect the structure or function of a biological entity, is centuries old, but only recently has it progressed into adaptive technological systems.
Recent cutting edge examples include Bioskin, developed in Japan, whereby water evaporates from the surface of leaves to create a cooling effect.
Meanwhile, in Germany, engineers have grown algae inside the walls of a residential block.
And in the Netherlands, a cladding made entirely out of plant-based bioresin and hemp fibre has been designed for a future when oil-based construction materials become difficult and expensive to produce. Stephen Cousins reports on a whole new world of “natural” construction.
Tokyo’s pipe dream
The world’s first evaporative cooling facade, installed on Sony’s 25-storey Osaki Home Entertainment HQ in Tokyo, is proving so effective it is being adapted for use on two new Japanese buildings and other possible projects in Southeast Asia.
Bioskin comprises a network of porous ceramic pipes, similar to horizontal railings, arranged across the east elevation of the Osaki building, through which rain water, collected from the roof, is circulated and which heats up under sunlight. The system was invented by Japanese architectural practice Nikken Sekkei, which collaborated with its in-house engineering team.
The water penetrates the ceramic and evaporates from the pipe surface, cooling the surface of the envelope by up to 12.6oC and the surrounding air by around 2-3oC. Its main purpose is to reduce the “heat island” effect, seen in cities like Tokyo, by cooling the environment around the building. It is designed to work best in high temperature, high humidity climates, although Nikken Sekkei says the technology could be adapted for other climates.
Pipes on Sony’s Osaki Home Entertainment HQ release water to cool the building’s facade by up to 12.6degC and the surrounding air by 2-3degC.
The system is based on the phenomenon of transpiration, whereby water moves through a plant and is evaporated from the leaves, stem and flowers, as well as the Japanese concept of “Uchimizu” — the sprinkling of water on gardens and streets to lower ambient temperatures and keep dust at bay.
“Using this fundamental physical phenomenon as the base, and adding the latest design technology using computer simulations, the Bioskin was born,” explains Tomohiko Yamanashi, principal executive officer at architect Nikken Sekkei, who invented the system with three architect colleagues, and developed it in collaboration with an in-house engineering team.
“Conventional facade suppliers were unable to manufacture the system because it is based on plumbing and ceramics, so we asked the leading toilet bowl manufacturer, Toto, to realise our idea,” he adds.
This decision proved key as Toto’s ceramic incorporates photocatalyst technology, developed to keep the surface of toilet bowls clean, and prevents moss and fungi from forming without the need for chemicals. The photocatalyst also breaks down nitrogen oxides in the air, equivalent to the effect of 1,300 poplar trees.
Rainfall collection
Rainwater pumped through the Bioskin is taken from a 30-tonne capacity storage tank installed in the building’s basement between footing beams, which is roughly equivalent to 50% of the capacity needed to run the system at full capacity during the summer. Sourcing water isn’t a problem as Japan has some of the highest rainfall in the world, but the system is also designed to be topped up with tap water, which is very cheap in Tokyo, although so far this hasn’t been necessary.
“Conventional suppliers were unable to manufacture the system, so we asked a leading toilet bowl manufacturer to realise our idea.”
Tomohiko Yamanashi, Nikken Sekkei
The cost of running the system is negligible compared to the Osaki Building’s total energy usage, says 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 modified 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 specific 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.”
Hamburg’s power plants
Natural processes are also the inspiration behind the world’s first 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 fitted with a secondary facade designed to cultivate microalgae inside glass shading louvres filled 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.
Microalgae inside glass panels are harvested to produce biogas to help meet the building’s energy requirements
The tiny plants, most no larger than bacteria, grow inside the panels in response to direct sunlight and are harvested and fermented to produce 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 efficiency is already quite good.”
The amount of algae harvested is subject to varying weather and environmental conditions, although Pauli was unable to confirm whether a target to create 15g of algae biomass per sq m of glazing has been met. In principle, the efficiency of the conversion of light to biomass is 10% and of light to heat 38%. By comparison, solar photovoltaic systems have a conversion efficiency 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.
“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
“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 system to create a comfort zone.”
Unfortunately, the Arctic algae died, in part because it was being attacked by algae already in the system. “Nevertheless, we are confident that in future we will find a species that can survive, which is one of the next steps in terms of process variation,” Pauli adds.
Thermal energy absorbed by the water in the facades is also being harnessed to heat the building. This is being used for hot water and heating, and is stored 80m below ground inside borehole heat exchangers filled with brine. The protracted hot summer means a much greater amount of heat has been generated than expected.
“We are considering the idea of applying the algae concept to data centres, which have a lot of heat available as a result of internal loads, so we could use that in winter to create a comfort zone [to counteract low external temperatures,” says Pauli.
The team is now planning to refine the structure of the bulky louver system, which, though effective at supporting loads created by the water inside, is limiting from an architectural perspective, says Pauli. “I expect the louvers to evolve in a similar way that solar PV cells are moving away from being standardised rectangular panels to organic materials that can be applied to different shapes and surfaces, to enable architects to incorporate it seamlessly into their design concepts,” he concludes.
Netherlands’ fibre future
Organic matter has been applied in a more literal sense to create the facades of a new gas receiving station, built for the sustainable development firm Tuinbouw Ontwikkelings Maatschappij, in New Prinsenland, near Rotterdam in the Netherlands.
The one-storey cube-shaped structure, designed by local architect Studio Marco Vermeulen, is clad in panels made from Nabasco, a composite of bioresin and hemp fibre produced by manufacturer NPSP Composites. The panels’ surfaces are shaped into 3D lettering showing the chemical composition of natural gas in terms of numbers of hydrogen, carbon and nitrogen atoms.
The panels are made of a composite of bioresin and hemp fibres
The concept was inspired by the idea of a transition to a “bio-based economy” in which oil-based construction materials could soon become scarce, triggering the development of plant-based materials. “[In the future] green materials will largely be based on organic residues from agriculture and horticulture,” Marco Vermeulen told CM.
“[In the future] green materials will largely be based on organic residues from agriculture and horticulture.”
Marco Vermeulen
He added: “This development is still in its early days, but will be significant for the construction industry. In the future, bio-based economy these biomass residues will first be processed into usable raw materials. The remaining organic material is available for renewable energy. The industry in the Dutch region of West Brabant seems to achieve a pioneering role in this development.”
He is referring to the building’s location in a 600 ha development site called the Agro & Food Cluster in New Prinsenland, part of West Brabant. The site is a sustainable intensive food production area where energy, water and waste streams are designed to be closed cycles, in which energy is recirculated. For example, waste heat and CO2 produced by a sugar factory will be re-used on the site. In addition, organic residues taken from agriculture and horticulture will be used to manufacture green materials, and as a source of biomass used to generate renewable energy.
