This is how the bioenergy facade works

What makes the bioenergy facade so productive?
Two aspects are key in allowing the facade to be highly efficient in leveraging sunlight for production of heat and biomass: The optimized blending process in the culture medium enables 8% of the incident light to be efficiently converted into biomass. For the heat, the multilayered construction of the glass elements ensures thermal insulation, leading to a heat conversion efficiency of 38%, comparable to established solar thermal devices which approach 45%.

How do you ensure the facade’s reliable and optimal functionality?
A fully automated control system (programmable logic controller) manages the facade’s entire technology with custom control software which ensures the optimal production of heat and biomass, while seeing to it that the house is supplied with hot water and heat throughout the year.

How much energy is needed to run the bioenergy facade?
The electrical energy required to run the facade is approximately 25 % as much energy as it produces in return. This is the only cost charged to you in our operator model, if cellparc is allowed to harvest and market algae biomass.

Does the bioenergy facade produce any noise?
The circulation of water and the rising gas bubbles produce a mild gurgling during the daytime. At night, the bioenergy facade is turned off and remains completely quiet.

This is how the bioenergy facade works

What happens with the algae in the bioenergy facade?
Microalgae are plants that use light, CO2 and nutrients (N , P) for growth – creating biomass in the process. Because microalgae are unicellular, they do not grow by becoming larger but instead by dividing and thus increasing in numbers. Each cell is its own little power station – which is why microalgae grow faster than higher plants.

Where do the microalgae grow?
The algae grow in a space of about 1 cm thickness between two transparent glass panels.
This space is filled with water containing nutrients (N, P, CO2). Periodically, gas bubbles are introduced at the bottom of the panel, turbulently mixing the water as they rise to the surface. In cycles measured in milliseconds this turbulence exchanges the algae facing the sunlight at the front of the panel with those in shade at the back, an oscillating movement that ensures that the incident light is used optimally and that all the algae are provided with enough light at all times, creating biomass in the process.

How are the panels cleaned?
The inner surfaces of the panels are constantly being cleaned by small particles whirling around in the turbulent flow of water. This allows the glass to remain perfectly clean for months on end. That is why the bioenergy facade can remain in operation continuously and without interruption.

This is how the bioenergy facade works

How is heat produced?
The heat is produced solely by the physical process of sunlight absorption into the water (culture medium). Using a heat exchanger, it is then extracted from the warm culture medium to be used for heating and warm water. The heat obtained this way has a temperature between 20 and 25 °C which can be increased to 50-70 °C as desired, using a heat pump.

This is how the bioenergy facade works

How are the algae supplied with nutrients?
All elements of the bioenergy facade are connected through a tubing system which allows for continuous recirculation of the culture medium. Nutrients (N, P and CO2) are then added at a central point of this system whenever the concentration of nitrate is measured as falling below a certain threshold.

How much CO2 is bound by the microalgae?
Per gram of dry biomass, approximately 2g of CO2 is consumed, using a saturation device under 2 Bar pressure. The CO2 is added in a dissolved condition, to fully saturate the medium. This is to avoid that the CO2 is emitted from the culture medium before it is consumed by the microalgae.

This is how the bioenergy facade works

How are the algae harvested?
Using the method of ultrafiltration, algae are harvested automatically, whenever the cell density meets a set threshold (approx. 4 times daily). The harvesting process takes place in a filter system which allows to separate particles of a size of 32 nm and to accumulate these in the retentate up to a density of 100 g d.w./L with little input of electricity of only 2.5 W/l. Thus, the filtrate is free of any particles and can be reused for cultivation.

What happens with the algae after harvesting?
Microalgae can be marketed in various forms, including fresh, dried or as an extract of biomass. Its richness in bioactive substances, such as antioxidants, vitamins or anti-inflammatory compounds makes them attractive for use in cosmetics, animal feed or various health foods.

Benefit from
a superior technology

Automated process engineering for an optimal functionality

Additional functionalities

Noise protection

The bioenergy facade provides noise protection both through its mass as well as by the shell structure of the single elements. From an acoustic point of view there are three shells, optimized to keep resonance frequencies below 100 Hz und thus below the frequency of human audible sensibility. The sound reduction index reached is about 50 dB classifying the bioenergy facades as class 6 according to DIN 2719, the highest protection class.

Sun protection

Depending on the cell density established in the culture medium, the transmission of light through the bioenergy facade varies. This means, the degree of sun protection and light transmission can be controlled to fit custom needs, simply by harvesting the algae. In addition to this, the panels may be turned, to cause selective shade in the rooms as desired.

Thermal insulation

The bioenergy facade consists of four layers of heat insulating glass. Combined, they exhibit a heat transmission coefficient similar to a three layer insulating window.

Because the bioenergy facade also produces heat, the thermotechnical quality of a building with a bioenergy facade is significant – a unique duplicate effect, which has yet to be taken into account in standardized assessments based on the energy Saving directive (EnAV).

Water recycling

In addition to the aforementioned benefits of the facade, it further opens the opportunity to recycle treated waste water through direct coupling to a decentralized waste water plant. Coupling it to an anaerobic plant is recommended over direct aerobic treatment, as the coupling not only enables biogas to be produced, but also plant nutrients (nitrogen and phosphor) to be released, which can then be reused for the production of the algae. A single person’s waste water can this way be fully recycled, using just 10 sqm of the biofacade.

Are you planning a project and would like to learn more?

Assess the viability of a bioenergy facade for your project in 3 simple steps.

What type of project is it?

Is decentralized water recycling part of your plan?

What is the surface area of your project’s facade?


0 foot² 30,000 foot²

What is your project’s estimated demand for heat?


0 MWh/a 1,000 MWh/a

Calculated output

(Site: Karlsruhe, Germany; southern exposure)
Heat production (MWh/a): HEAT_PRODUCTION
Coverage of heat demand (%): COVERAGE_OF_HEAT_DEMAND
CO2 savings (t/a): CO2_SAVINGS
Production of microalgae (cwt/a): PRODUCTION_OF_MICROALGAE

Production of biogas (m³/a): PRODUCTION_OF_BIOGAS
Recycling of X m³/a of waste water equivalent to the water consumption of Y number of persons.


Preliminary analysis of the frame conditions indicate that your project is viable for a bioenergy facade.

Want to learn more? Please contact us.


Preliminary analysis of the frame conditions indicate that the facade area may be too small for a bioenergy façade to be economically self-sustaining as part of the operational model. The rich functionality of this facade and the value it provides however still make it an attractive solution to consider.

To learn more, please contact us.

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