Nestled in the Wilhelmsburg quarter of Hamburg and cradled by the River Elbe, lives a building like no other. Shrouded in 129 ‘leaves’, the emerald exterior of the building lives, breathes and grows.

A pioneering project from engineering giants, Arup, the building houses the world’s first photobioreactor façade, using photosynthesis to heat and power the homes inside.

Ove Arup, a trailblazer in engineering and architectural collaboration, is responsible for bringing some of the world’s most iconic structures to life. Examples of his work include the beautifully art deco, if biologically impractical, penguin pool at ZSL London Zoo; the world-famous overlapping sails of the Sydney Opera House; and the inside-out Centre Pompidou in Paris.

After his death in 1988, his firm continued to lead the way in the built environment, furnishing over 160 countries with now-famous landmarks. The company has grown to over 14,000 people with offices in more than 90 countries worldwide.

In 2013, the engineers at Arup turned their attentions to nature, borrowing a simple biological process to inspire the energy efficient ‘BIQ House’ in Hamburg. Designed for the International Building Exhibition, the block features glass bioreactors hung on the building’s southeast and south-western faces, generating its own heat and energy from the sun.

Getting it going

The ‘SolarLeaf’ itself is a remarkably simple innovation. Each bioreactor or ‘leaf’ is made up of four panels of glass, sandwiched together. The innermost cavity holds 24 litres and is filled with water, the ‘growing medium’, and micro algae. The two cavities surrounding the water-algae mix are filled with inert argon gas to prevent heat escaping.

On the outside, the glass is white and non-reflective, absorbing as much light as possible. Inside, facing the building, decorative glass can be installed for the benefit of tenants. Built into the frame of each bioreactor is an integrated plumbing system, delivering essential nutrients and harvesting the micro algae biomass.

Just like its regular-sized counterpart, micro algae absorb sunlight and carbon dioxide to produce energy. Each tiny plant is made up of a single cell, no larger than bacteria. With the right nutrients, and a little sunshine, the micro algae can quadruple in number in a single day. This material is siphoned out of the bioreactor and is converted into methane gas to be burned as fuel.

Once up and running, the SolarLeaf façade is low-maintenance and almost entirely self-sustaining. Compressed air is injected into the bioreactor ‘leaves’ at regular intervals, forcing big air bubbles up through the water to keep the algae moving. At the same time, the bubbles, water and small plastic scrubbers suspended in the mixture, wash the inside of the panels.

Additionally, the cladding cuts noise pollution from the street; delivers a thermally controlled microclimate; and provides residents with ‘dynamic shading’. Stronger sunshine during the heat of the day stimulates algae to grow faster, providing more shade inside the building when it is needed most.

How it helps…

The system can be operated throughout the year, even during cool winter months. Currently, the bioreactors can convert around 10% of light energy into biomass, while 38% is collected as heat energy.

Heat is transported to the building’s plant room, where it can be used directly to heat water and feed into the central heating system. Any excess heat energy can be stored underground and drawn up with heat pumps when needed.

The SolarLeaf cladding around the BIQ House provides around a third of the total heat demands of the 15 housing units inside.

The micro algae biomass that has been siphoned off is sent to a processing plant nearby and is converted into biofuel for use across Germany. In a similarly collaborative fashion, the building even helps its neighbours to reduce their carbon footprint. In order to keep the micro algae reproducing efficiently, a stream of carbon dioxide must be readily available. This can be obtained from a source of combustion, such as a boiler in a building next door. By harvesting another buildings outputs, the bioreactors can cut carbon emissions that would otherwise be released into the atmosphere.

In order to successfully introduce photobioreactors at a wider scale, designers, architects and building owners would need to work closely together. This technology thrives on strong interdisciplinary collaboration, bringing together engineering, environmental design and material science with simulations, services and building control systems. If properly undertaken, the façade can benefit the user, the building, and the environment.