As buildings undergo a smart evolution in sensors, communication, HVAC, energy management and so on, the building façade is no exception. Intelligent building and research firms around the world are creating innovative and multi-faceted building skins.
Much like human skin, a building’s outer layer needs to be weatherproof, insulating and, ideally, maintain an attractive appearance. Also like a human skin, a building’s façade has the potential to provide essential sensory input, allow regulation of temperature and air circulation, adapt to its environment and derive important elements from the sun’s rays.
Dutch architects and engineers Jon Kristinsson and Andy Dobbelsteen have released details on a new ‘smart skin’ system for zero-energy buildings, conceived by Dr Noor van Andel and Mr Peter T Oei. Tests on prototypes have shown promising results.
Smart skin is a thin translucent skin for buildings instead of walls. Groundwater is used to buffer the temperature difference between night and day and even between summer and winter. Technicians often think that using thick or high-performance insulation is the only way to reduce energy losses. Smart skin is a concept designed for the Netherlands; a wet country with an averagely mild climate and high groundwater level. Smart skin is not a well-insulated wall, but uses the thermal mass of groundwater for heating or cooling.
While at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Dresden they've teamed up with the Department of Textile and Surface Design at Weissensee School of Art in Berlin to create a smart façade, incorporating bio-mimicry.
They have created a thermally reactive blind made up of individual fabric components shaped like flowers. Each component contains an integrated shape-memory actuator made of a nickel-titanium alloy that returns to its original shape when exposed to heat. When the wires are warmed by sunlight they contract to open the textile components, covering the façade and preventing solar gains. When the sun disappears the flowers close and the façade becomes transparent once again.
[contact-form-7 id="3204" title="memoori-newsletter"]
Maintaining a fashionable transparent glass façade is desirable and start-up company Oxford Photovoltaics has developed a technology that “prints” organic solar cell materials directly on to glass without the need for visible wires or cells. The super-thin layer of transparent, organic dye-sensitised cells is applied to conventional glass, and when hit by sunlight creates a potential difference, or voltage, that is collected by receptors running around the edge of the pane.
Impressively, the system can convert about 12% of solar energy received into electricity, which is just 3% less efficient than conventional PV panels currently on the market, but it costs significantly less to manufacture, says Rick Wheal, a consultant at Arup who is helping Oxford Photovoltaics to develop the product for construction.
Bio-mimicry has been taken to another level in Germany, where unicellular algae is being grown in facades to create biofuel. A team of engineers from Arup working in cooperation with Germany’s Strategic Science Consult, installed a bio-adaptive microalgae facade on to a four-storey residential block in Hamburg. The BIQ house, designed by Austrian firm Splitterwerk Architects, incorporates 64 “double-glazed” rainscreen panels, each one filled with water and a species of algae that grows rapidly in response to direct sunlight.
A series of pipes connecting the panels circulate the algae and pump it to a plant room where, through the process of anaerobic digestion, it will be "eaten" by bacteria to produce methane gas that can be either stored locally or used to help fuel the building.
The clever part is how the process of photosynthesis in the algae also drives the building’s dynamic response to the amount of solar shading it requires. As sunlight speeds up the rate of algae growth, so the glass becomes increasingly cloudy, blocking direct sunlight from entering the building. The level of opacity can also be controlled, removing algae with the pump to adjust the amount of solar shading.
The facade is expected to create 15g of biomass per square metre of glazing, given that as a unicellular organism algae is 30-50% efficient at converting the sun’s energy into usable energy, the technology has great potential, says Arup’s Wheal.
“Skyscrapers have huge south-facing facades and algae could have very positive benefits in terms of reducing a building’s cooling energy requirement without the need for expensive chillers. The energy produced, in the form of methane, could be used to run a combined heat and power plant to generate electricity and heat”.
The potential for noise and vibration problems have held back the development of facade-integrated wind energy, but in Sweden there’s a proposal to harness piezoelectricity, an energy source that’s still at the research stage but is being taken increasingly seriously. Design firm Belatchew Arkitekter has proposed retrofitting a landmark residential tower in Stockholm with thousands of tiny "hairs" that generate electricity by simply swaying in the wind.
Piezoelectricity is an electric charge that accumulates in certain solid materials, such as crystals, when they are deformed. Compared with traditional wind turbines, the straws would be almost silent, have no moving mechanical parts prone to malfunction, and could operate at low wind velocities as only a light breeze would be needed to cause them to sway and generate power.
Belatchew Arkitekter claims that if sufficient straws are attached to the building it would become carbon neutral. The concept of hairy energy-producing facades is also being explored by Max Fordham and Make Architects, says Max Fordham’s Watts: “I like the idea of having a hairy building, using thousands of needles that vibrate in the wind might create enough energy to drive internal sensors or LED lights and it overcomes problems related to mechanical systems where parts need maintenance or fall off”.
Be it through algae, hair, groundwater or PV glass, future smart buildings seem set to benefit from bio-mimicry incorporated into their natural environment facing skins, improving the building’s internal functions and creating positive impact for society. Learning from organisms that live in relative harmony with the environment appears, perhaps unsurprisingly, to be the best way to construct sustainable buildings.