What is a SolarLeaf Bioreactive Façade?

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SolarLeaf bio-reactive façade is a system that uses microalgae and solar thermal heat to generate renewable energy for a building. The façade cultivates algal biomass for generating electricity, which incidentally also acts as a shade for the building. The system can be integrated with new as well as existing buildings, offsetting 2.5 tons of carbon dioxide emissions each year.

Its installation involves the creation of a secondary façade by providing a second outer layer of flat panel glass bioreactors to the sides of the building facing the sun. These panels are designed to rotate along their vertical axis for tracking the sun and can close together to form an outer layer creating a thermal buffer.

The flat panel glass bioreactors cultivate the micro-algae and make up the façade’s bio-skin. The inner panes of the bioreactors have a cavity to enable the growth of the algae. These bioreactors can produce 4,500kW/h of electricity from 200m² of integrated photobioreactors algae façade.

How does SolarLeaf work?

1. The cavities in the vertical glass louvers are filled with water containing nutrients that convert daylight and CO₂ to algal biomass through the biochemical process of photosynthesis; at the same time, the water is heated up by solar-thermal effects. This phenomenon is depicted by the apparent greenness on the outside of the façade.
2. The generated biomass and heat are transported to the building’s energy management center by a closed-loop system. The energy management center controls the bioreactors, thus controlling all the processes for the operation of the SolarLeaf and its integration with the building’s energy management system.
3. The surplus heat, which is unused by the algae, is utilized for solar water heating or stored by using geothermal systems. 
4. Compressed gas is given to the bottom surfaces of the bioreactors in the form of large bubbles. This creates an upstream water flow and instability in the system, facilitating the intake of carbon dioxide and light by the algae. Simultaneously, a mixture of water, air, and small plastic scrubbers washes the inner surfaces of the panels. All the service pipes for the inflow and outflow of the culture medium and the air are integrated into the frames of its elements.
5. The energy management center is also responsible for regulating the temperature in the culture medium and algal-cell density.

The technology was first implemented at the Bio Intelligent Quotient (BIQ) house in Hamburg, Germany, in 2013. The building uses sunlight to produce all the energy needed for electricity and heat, hence reducing its carbon footprint.

The construction industry can execute this system on a wider scale by establishing coordination between stakeholders and designers, as it combines several facets of construction, such as design, materials, services, simulations, structural engineering, and control systems.

Benefits

1. The SolarLeaf system can be operated throughout the year. It has an efficiency of 10% for light to biomass conversion and 38% for light to heat. This is more economical compared to photovoltaic and solar thermal systems, which have an efficiency of 12-15% and 60-65%, respectively.
2. Biomass can be used flexibly to generate electricity and heat, with the option of having it stored virtually without any loss of energy. Cultivation of microalgae needed for the process does not require additional land, and the power generation remains consistent irrespective of weather conditions.
3. Carbon required to feed the algae can be sourced from any combustion process, thus shortening the carbon cycle and prohibiting the emissions from entering the atmosphere.
4. The bioreactors can also serve as dynamic shading devices as the growth of the algae depends on the availability of daylight. More shading can be received for the building by growing more algae.
5. The bioreactors can produce biomass and also trap solar thermal heat, therefore capable of powering the building in two ways. Besides, they provide noise insulation to the building.
6. After attaining a certain growth rate, some of the algae are harvested and processed to produce biogas for generating electricity as well as heat for the winters. The CO₂ released after burning the biogas is fed to the algae. This creates a cycle of solar thermal, geothermal, condensing boiler, local heat, and capture of biomass using a bioreactor façade.

FAQs

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