Façade technology continues to advance, with Arup at the forefront of its evolution. One major area of development is the conservation and generation of renewable energy from bio-reactive facades, as demonstrated by our SolarLeaf façade.

A world first

Unveiled as a pilot project at the International Building Exhibition (IBA) in Hamburg in 2013, the world´s first bio-reactive façade design generates renewable energy from algal biomass and solar thermal heat. The integrated system, suitable for new and existing buildings, was developed collaboratively by Strategic Science Consult of Germany (SSC), Colt International and Arup. 

The biomass and heat generated by the façade are transported by a closed loop system to the building’s energy management centre, where the biomass is harvested through floatation and the heat by a heat exchanger. Fully integrated with the building services, excess heat from the photobioreactors (PBRs) can help supply hot water, heat the building, or be stored for later use. 

The BIQ House
The BIQ house in Hamburg, Germany, becomes the world's first real world test apartments for green facades using microalgae. This video by Arup explains the history of the project and the development of this groundbreaking technology.

Multiple benefits from biomass

Biomass can be used for power and heat generation and can be stored with virtually no energy loss. Cultivating microalgae in flat panel PBRs requires no additional land-use and isn’t unduly affected by weather conditions.

Carbon to feed the algae can come from any combustion process (such as a boiler in a nearby building), giving a short carbon cycle and preventing carbon emissions from entering the atmosphere and contributing to climate change.

Because microalgae absorb daylight, bioreactors can also be used as dynamic shading devices. Cell density inside the bioreactors depends on available light and the harvesting cycle - with more daylight, more algae grows and provides more shading for the building.

Full-scale pilot project

The first SolarLeaf façade was installed on the BIQ house at the IBA in Hamburg in 2013. 129 2.5m x 0.7m bioreactors were installed on the south-west and south-east sides of the four-storey residential building. Working as a secondary façade, SolarLeaf provides around one third of the total thermal demand of the 15 residential units in the BIQ house.

How the SolarLeaf façade works

The flat photobioreactors are highly efficient for algal growth and need minimal maintenance. Made of four layers of glass, the two inner panes form a 24-litre cavity where the growing medium circulates. Either side of these panes, insulated argon-filled cavities help minimise heat loss. The front glass panel consists of white antireflective glass, while the glass on the back can include decorative glass elements.
Compressed air is introduced to the bottom of each bioreactor at regular intervals, creating bubbles for upstream water flow and turbulence that stimulate the algae to absorb CO2 and light. At the same time, a mixture of water, air and small plastic scrubbers wash the inner surfaces of the panels. SolarLeaf integrates all servicing pipes for the inflow and outflow of the culture medium and air in its frame.

Year-round operation

The system can operate all year round, with a light to biomass conversion efficiency of 10% and light to heat 38%. In comparison, photovoltaic systems have an efficiency of 12-15% and solar thermal systems 60-65%. The maximum temperature that can be extracted from the bioreactors is around 40 degrees Celsius, as higher levels affect the microalgae.

SolarLeaf Mashable video
Watch: Mashable film on the world's first bio-reactive facade, where glass panels cultivate microalgae to produce renewable energy, unveiled in 2013.

Future synergies

Our bio-responsive façade creates synergies by linking building services, energy and heat distribution, diverse water systems and combustion processes.

The key to successful implementation of photobioreactors on a wider scale is cooperation between stakeholders and designers. The technology benefits strong interdisciplinary collaboration, combining skills in environmental design, façades, materials, simulations, services, structural engineering and control systems.

The key to understanding this integration is to have a complete perspective of the systems’ benefits for user, building and environment.