Real Green Heat
When viewing photos of the BIQ apartment complex in Hamburg, Germany, one might question whether or not it’s real. The futuristic-looking, gleaming green facility was officially put into operation at the end of April, and its makers claim it is the world’s first photobioreactor (PBR) facade.
Hosting 200m² of integrated photobioreactors, the five-story, 15-unit apartment complex grows algae on its surface and produces heat and power as a result. The microalgae used in the facades are cultivated in flat panel glass bioreactors, according to designer Arup’s European research leader Jan Wurp. “In total, 129 bioreactors have been installed on the south-west and southeast faces of the four-story residential building. The heart of the system is the fully automated energy management center where solar thermal heat and algae are harvested in a closed loop to be stored and used to generate hot water,” says Wurp.
The innovative facade system is the result of three years of research and development by Colt International, based on a bioreactor concept developed by SSC Ltd. and design work led by Arup. Funding support came from the German government’s ZukunftBau research initiative.
How It Works
The photobioreactors positioned on the southwest and southeast sides of the building grow algae not just for energy production, but also for controlling light and shade in the building. Each is 70 cm wide, 270 cm tall and 8 cm thick, and is mounted on a steel frame and arranged within a group.
Photobioreactors are filled with an aqueous solution and CO2 is constantly added as a nutrient, which enables the algae to flourish. It is supplied to the algae via a saturation device that directly introduces flue gas from a micro-CHP (combined-heat-and-power) system into the water circuit. The use of CHP is controlled as needed for the desired growth of algae, and a monitoring network continually checks all parameters relevant to the process, which is almost fully automated.
The culture medium in the photobioreactors is constantly stirred by supply of compressed air through an airlift to prevent the microalgae from sinking and settling. Small, lattice-like beads serve as scrapers and are enclosed within the photobioreactors, and prevent algae from depositing on the glass. The photobioreactors are all connected in a series, so algae and its medium circulate through all of them when the system is operating, according to concept designer IBA-Hamburg.
The photobioreactors may reach a temperature of 35 degrees Celsius (95 degrees Fahrenheit) during the day when facing sunlight, thus acting as solar thermal absorbers. As the medium is heated, it is circulated through the building service center. At a central location, algae biomass is filtered out from the culture medium and collected, which takes place in a flotation system, specially developed by IBM-Hamburgh together with company AWAS International GmbH.
After the liquid is separated from the algae, most is returned to the photobioreactors, with a small amount being removed from the system and discharged into a public sewer. The harvested algae is fed to an external biogas plant, which sends power to the grid, and powers the micro-CHP.
On the thermal side of the equation, heat demand by the building is relatively low, and needed on a seasonable basis, so several components are in place to store and make use of heat when necessary.
Heat is drawn off the algae-filled medium through a heat exchanger, and thermal energy is distributed throughout the building for several uses, including heating the air and preheating hot water. Excess heat is stored 80 meters deep in geothermal boreholes, from which energy is drawn with heat pumps as needed in periods of low heat generation by the bioreactors.
At the same time, waste heat from the flue-gas production process—the nutrient for the photobioreactors—is captured and also used to heat water, and surpluses are stored.
According to IBA-Hamburg, although it wasn’t implemented, the original plan used photovoltaics on the roof. Though it could easily be done in the future, in the meantime, electricity will be drawn from the grid.
While the initial photobioreactor facade design was implemented at an apartment, IBA-Hamburg believes it is a good fit for several other applications, including industrial and commercial constructions, buildings for public infrastructure, trade, or residential buildings.
Rainer Mueller of IBA-Hamburg points out that this is an example of algae production technology leaving the lab and being brought to real life, as a piece of architecture. “So now we have to survey the bioreactors,” Mueller says. “We do this monitoring together with renowned universities, and we also use the feedback of the residents. As for now, everything is running smoothly from the operational point of view. Some of the people who moved in told us that in the beginning, they just had to get used to the occasional bubble sound made inside the water panels.”
Boiled down to a very basic idea, IBM-Hamburgh’s vision behind the energy concept is the connection of different energy sources working together, thus bringing together, in one circuit, solar energy, geothermal energy, a condensing boiler, district heating, and the production of biomass in the bioreactor facade.
Author: Anna Simet
Managing Editor, Biomass Magazine