Walking past the BIQ apartment building in Hamburg, Germany, you’ll see a variation on solar power not found anywhere else in the world. Inside 129 bubbling bioreactors attached to the façade, algae grow through photosynthesis, creating a source of biomass to help heat the building.
It’s an early example of something that may become more common in the future: façades made partially or entirely out of natural materials. Today’s typical urban street canyon consists of acres of steel and glass; it may eventually be green.
The algae advantage
As the algae grow in a solution contained within flat glass panels mounted on BIQ’s southwest and southeast façades, they are periodically collected and incinerated to create energy. The water solution containing the algae, meanwhile, is passed through a heat exchanger to send heat produced to occupied spaces. Together, these sources provide around one-third of the total heat used by the building’s 15 residential units.
BIQ
The algae also provide passive temperature control. “When the algae grow, normally in the summer, the panel works as a shading device for the building, so it reduces the solar gain. During the winter photosynthesis is low, so the solar radiation can pass through the solution and heat the building,” said engineer Guglielmo Carra, who leads the materials consulting team in Arup’s Milan office. (The firm helped design the algae panel system, which is known as SolarLeaf, and has been monitoring its performance since the building was completed in 2013.)
Although SolarLeaf is approved for use in Germany, its relatively high price tag has held it back from widespread implementation on commercial projects there. “Cost, both related to construction and maintenance of the system, is the biggest issue,” Carra said. “But the system itself can be used. It works with existing technologies. It increases and expands the opportunity of renewable energy integrated into a building.”
SolarLeaf functionality
In its current form, the system is detached from the main façade of the building, thus creating the need for an additional layer to ensure acoustic and thermal insulation.
As the technology advances, algae bioreactors could eventually be integrated into a single-skin façade, significantly lowering the overall price tag. This will likely lead to additional work around aesthetic issues — developing ways to allow visual variety for algae-containing façades without compromising performance, for example.
BIQ façade
Other investigations hold out the promise of additional functionality in the system. Another Arup team has studied whether algae could be used to clean greywater and recirculate it back into the building.
All-natural, locally sourced
But can an entire façade be made of natural materials? Arup and others are experimenting with biocomposites, which combine biopolymers — resins obtained from processing plants that offer alternatives to petroleum-based products — with natural fibers from fast-growing plants like jute, flax, and hemp. The BioBuild project, a sprawling research initiative funded by the European Commission, proved that urban gardens filled with native plants could one day provide an endless source of raw materials for nearby construction sites.
Self-supporting BioBuild façade panel
Interior and façade biocomposite systems could significantly lessen construction waste, as panels could be recycled at the end of their lifecycles. Another advantage: a huge reduction in weight, which could lower transportation and installation costs. “Through proper engineering, the strength of the material could be comparable to aluminum while cutting its weight in half,” Carra said.
After bringing the BioBuild project to a mock-up stage, Carra and his colleagues are now working to refine the technology further. “At the moment, we’re working on identifying which plants and natural resources — including agricultural waste — could become a future resource for construction,” he said. “We’re assessing the potential benefits in terms of carbon dioxide reduction and economic returns for the industry.”
Working with nature, not against it
For Carra, the advances being made in building materials parallel those in the energy sector. Rather than digging for coal, we can now harness the power of the sun and the wind; similarly, instead of relying on steel and concrete, we can grow construction materials from renewable sources. “In materials there’s a similar shift into what nature gives,” he said. “We can really use nature and not waste nature.”
For more information about green façade innovations, check out Cities Alive: Green Building Envelope.
Questions or comments for Guglielmo Carra? Email guglielmo.carra@arup.com.