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Josef Hargrave

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Bioreactive façades: cultivating algae for energy

Bioreactive façades

Cultivating algae for energy

Focus Area

Cities, Sustainability

Discipline

Advanced Technology and Research, Building Envelope Design, Building Performance and Systems, Façades, Sustainability

Region

Europe

Year

2014

The façade of a building is a key element in reducing energy consumption. Intelligent façades can control light, shade, temperature and ventilation. As designers strive to create buildings with zero net energy, a new breed of façade – which actually generates energy – is emerging.

Our research team has developed a façade system that harnesses the power of algae to create heat energy and biomass. The system uses flat-panel photobioreactors (PBR), which are transparent glass containers for cultivating micro-algae. Carbon dioxide emissions from conventional combustion processes are fed into the panels. The algae photosynthesise in the sun, consuming carbon dioxide and producing biomass. The solar thermal effect also generates heat.

The system is integrated with the building services, so that the generated  heat can be used for hot water. The biomass is harvested periodically and either transformed into methane off-site or made into pharmaceutical products.  The system was piloted at BIQ House in Hamburg, a 4-storey, 15-apartment residential building designed by architects SPLITTERWERK to derive its energy from renewable sources. The façades included 200 m² of PBR panels, as well as an energy control system. The panels take the form of louvres, supported on central vertical axes, which can track the path of the sun. As well as producing energy, they shade the building, meaning less air-conditioning is needed.

Following the successful launch of the pilot scheme, the German government commissioned Arup to monitor its performance and users’ acceptance, and to optimise the façade system over a two-year period. This provided data on the effectiveness of the system and showed that it can be optimised for maximum efficiency.

Key Findings

The BIQ House showcased the world’s first operating algae-based bio-responsive façade system integrated into conventional building system services.

The panel photobioreactors (PBRs) are 8% to 10% efficient at transforming solar energy into biomass. The system can be fully automated. Carbon dioxide can be fed into the system from boilers in neighbouring buildings, or other nearby combustion processes. The façade system shows a net energy gain.

Application

Following the pilot at BIQ House, our research partners Colt International GmbH have made the system commercially available under the brand name SolarLeaf.

The technology is most suitable for large-scale projects in moderate climate zones. As a façade system the cultivation of the biomass requires no additional land use and is suitable for both new buildings and retrofitted older buildings.

The advantages of algal biomass as an energy source are that it can be used flexibly for power and heat generation, and that it can be stored with virtually no energy loss.

The system implements a short carbon cycle and prevents carbon emissions from contributing to climate change. Because microalgae absorb daylight, bioreactors can also be used as dynamic shading devices. The cell density inside the bioreactors depends on available light and the harvesting regime. When there is more daylight available, more algae grows – providing more shading for the building.

Impact

As local and decentralised energy generation schemes are becoming more common, Arup is investigating the potential for using bioreactive façades on an urban scale. Future urban planning concepts will look for ways of connecting mass flows of heat, electricity, water and CO2 between buildings and within communities.

Designers are increasingly seeking to create closed-loop systems for smart cities and to provide ecosystem services through the built environment. Bioreactive façades offer opportunities to link the production of heat and high-quality biomass with reducing carbon emissions. As well as a fuel, algal biomass is a valuable resource and we are looking to explore this urban value chain in ongoing collaborations.