Green algae wall
For professionals.
“Green walls” filled with algae suspension are photobiorectors – they are among the latest bioengineering solutions that we can use as part of urban adaptation to climate change.
The algae used here are microscopic in size – microalgae that use light and carbon dioxide as a source of energy for their functioning – they produce oxygen and organic carbon through photosynthesis. What is important is that low-quality water, e.g. sewage, can be used for their cultivation, as the water is purified by the algae and can thus be reused for other purposes. In order for the algae to grow properly it is necessary to provide them with optimal access to light and a certain temperature – ideally between 16-27 degrees Celsius. Another important element will be to ensure that the suspension can move continuously, so that even each individual algae has adequate exposure to light. These organisms grow very quickly, they can double their mass in one day .
Example of use
The BIQ building is located in Hamburg and was built in 2013. 120 panels – photobioreactors (flat cubes with dimensions of 2500 mm x 700 mm x 90 mm) – were placed on the façade of a small multi-family building. In addition to generating energy, this façade also shades the building, not allowing its walls to heat up. (The greater the intensity of the sun’s rays, the greater the mass of the algae and therefore the less the building façade heats up). This suspension, together with the thermal energy produced by the façade, is then transported to the heat exchanger where water, algae and thermal energy are separated, which can then be used for the day-to-day running of the building. Movement of the algae in the bioreactor is ensured by compressed air supplied to each photobioreactor (in the form of a large gas bomb) in appropriate time sequences. Water movement is from the bottom up. This facade removes up to 6 tonnes of CO2 per year from the air supplied by the system described above. The mature biomass is converted to methane up to 80% in the biogas plant, which is used to generate energy for the building but also to heat it.
The algal suspension can have different colours depending on the species of microorganisms used, some of which have fluorescent capabilities
