FAÇADES RENEWABLE ENERGY
For commercial and industrial buildings and the retrofitting of existing structures, the integration of PBR has great potential for the future of energy and carbon reduction
Harvesting biomass A key development in PBR technology in recent years is the ‘flat panel uplift bioreactor’. This has been designed and tested by a German research consortium, exploring technologies for exploiting microalgae resource as a resource. The first prototype of the system
features 2.5m by 1m panels made up of two transparent deep drawn skins of 100% recyclable polyethylene terephthalate (PET) welded continuously along the edges to enclose a 20 mm-deep cavity. Pressurised air periodically introduced to the cavity on the underside of the panel generates turbulences inside the bioreactor, leading to an increased mixing of the water-based medium with CO2, that is continuously fed to the cycle. The algae cell division rate is directly
A computer image of a building with a photobioreactive façade. A full-scale prototype façade is scheduled to be installed by 2013, says Arup
linked to exposure to sunlight; in ideal conditions during summer the biomass will duplicate in periods of about seven hours. With an algae content of up to 15g per litre, the bioreactors fully absorb the daylight. To maintain high production
rates, the inputs and outputs of the closed- loop system have to be closely monitored and controlled by the building energy management system. Heat generated through solar thermal
effect needs to be dissipated to prevent the system overheating; for a stable production rate, the temperature needs to be kept below 40C. If this is done through a heat exchanger, the thermal energy can be recovered and used for heating – the bioreactor performs like a solar collector with a level of efficiency of about 40%.
Bioreactive façades Material and façade specialists at Arup GmbH and Strategic Science Consult in Germany have investigated the potential of integrating flat-panel bioreactors into the building skin. A number of key findings have emerged from this work, summarised
as follows: l Independent energy generation through production of biomass: The algae can be harvested, dried and stored automatically in the plant room of the building. The
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CIBSE Journal October 2011
www.cibsejournal.com
Arup GmbH
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