Zero-Carbon Technology | Zero-Energy Bionic Building Facades Cool and Insulate Buildings

 

FlectoLine is an intelligent facade developed by the University of Stuttgart and the University of Freiburg in Germany. As a prototype, this architectural solution has been installed in the greenhouse at the Freiburg Botanical Garden, enabling passive and automatic control of solar radiation based on climatic conditions.

 

 

The prototype covers the exterior of a greenhouse window on one side and has an area of 83.5 square meters (899 square feet). It consists of a series of shading elements, each of which comprises two fiber-reinforced thermoplastic flaps that can be opened independently or folded together.

 

Overall, these elements evoke the traps found on Venus flytraps; however, the actual inspiration comes from the predatory appendages of another carnivorous plant—the waterwheel plant (Aldrovanda vesiculosa). The pneumatic “hinge zones” at the base of each flap are inspired by the veins on the modified wings of the striped bug (Graphosoma italicum). When air is pumped into the flexible, elastic hinges, the structure expands, causing the stiffer primary flap to fold over to one side.

 

 

Since the two flaps in each component fold simultaneously to either side, they can block sunlight from passing through the windows, helping to keep the interior of the building cool. On hot days, this action can significantly impact how much air conditioning is needed.

 

 

In cool weather, the flaps fold inward, causing them to meet in the middle—this action is triggered simply by shutting off airflow in the hinge area. Once deployed, these elements maximize the amount of sunlight entering the room from the warm interior through the windows, thereby reducing the building’s reliance on its heating system.

 

 

The entire facade can be set to operate automatically, responding to weather conditions, time of day, and ambient temperature; it can also be manually adjusted as needed. As an added benefit, the facade is powered by photovoltaic cells installed on the outer surfaces of its components.

 

Integrated drive

 

FlectoLine consists of fiber-reinforced composite panels with built-in hinge zones, which have been specially developed for use in conjunction with integrated pneumatic actuators. The pneumatic actuators are directly embedded into the composite material in the form of pads. The material structure of the composite can be divided into a harder section beneath the actuator and a more flexible section above the actuator.

 

 

When pressure is applied, the pad deforms more intensely in the direction of the more flexible board, causing the entire composite board to bend in that direction. By clamping one side adjacent to the hinge region, free bending motion can be achieved at the unclamped end. Since the drive system is directly integrated into the composite board, no mechanical linkage is required between the folding elements and the actuation mechanism. The flexible hinge region requires only low pressure—between 0.3 and 1.5 bar—to achieve angular positions ranging from 0° to 90°. During the folding process, elastic energy is stored in the flexible hinge region, enabling the module to immediately rotate back to its original position as soon as the pressure is released.

 

Material System

 

Two distinct material systems have been developed for the technical implementation of exterior walls. First, the bio-inspired material system is abstracted into elastic and stiffer material layers and transferred into a hybrid composite material comprising elastomeric components and thermoset fiber-reinforced composites. Similar to wing veins, the actuator chamber is enclosed by an elastomeric layer, which ensures interlayer adhesion within the driving plane. The direction of motion during the actuation process is determined by the asymmetric distribution of glass-fiber-reinforced materials above and below the driving plane.

 

 

The first material system has already been tested in previous demonstrations and proven effective, demonstrating its reliability and adaptability for large-scale applications. However, to optimize the manufacturing process in terms of time and cost, a second alternative material system has been developed. To explore an even simpler alternative, a material structure based on thermoplastic plastics has been engineered, which operates in a similar manner: two layers of thermoplastic glass-fiber-reinforced polyamide-6—with differing stiffness levels—are bonded together using an elastic adhesive.

 

 

Both systems are equipped with a protective outer layer that boasts excellent weather resistance, making them suitable for use in facade elements. Each system has undergone weathering and fire-resistance testing to ensure that its mechanical performance and appearance remain stable at a minimum. 15 years Moreover, the components must meet at least fire rating B2 requirements. Given the varying weather conditions on exterior walls, the components were also subjected to wind-tunnel testing, with maximum anticipated wind loads applied from different directions. To ensure the longevity of the curtain wall elements, each material system was cyclically tested under pneumatic actuation for at least 20,000 test cycles, with bending up to 90°.

 

Control system

 

 

To effectively control the performance of responsive facades, a digital twin has been developed that can simulate in real time thermal and lighting behavior as well as energy production from integrated photovoltaic (PV) panels.

 

The digital twin collects real-time data through embedded sensors, including indoor illumination levels from light sensors, outdoor illumination levels from solar exposure sensors, indoor temperature readings from distributed temperature sensors, and wind conditions from facade anemometers.

 

 

Forecast data—such as detailed weather forecasts (including solar radiation, cloud cover, temperature, wind speed, and precipitation) obtained from meteorological application programming interfaces (APIs), as well as energy demand forecasts based on previous usage patterns—are also integrated into the system. Using this data, a decision-tree-based control algorithm optimizes three key aspects of indoor comfort—adequate lighting levels, minimized glare, and thermal regulation—while simultaneously maximizing photovoltaic energy generation. By continuously analyzing both real-time and forecast inputs, the system calculates the optimal panel angle, ensuring efficient operation throughout the day and striking a balance among occupant comfort, energy efficiency, and renewable energy production.

 

Large responsive facade

 

 

As a proof of concept, the FlectoLine facade demonstrates the potential of creating large-scale responsive facades using fiber-reinforced plastic laminates equipped with compliant hinge zones and integrated pneumatic actuators.

 

The FlectoLine facade covers an area of 83.5 square meters and consists of 101 components, with dimensions along the x- and y-axes ranging from 0.81×0.86 meters to 1.50×1.31 meters. These modules require a pressure of just 0.4 bar to fully deploy to a 90° angle, demonstrating their exceptional motion efficiency. The design incorporates thin-film organic photovoltaic (PV) cells to harness solar energy, ensuring that the responsive facade can independently meet its own energy demands.

 

In addition, the FlectoLine facade explores the possibility of fostering direct interaction between the built environment and its occupants through an active control system—made possible by the seamless integration of computational design, advanced simulation, and manufacturing processes.

 

Summary

 

Thanks to its adaptive design, FlectoLine significantly reduces the need for artificial climate control, thereby enhancing energy efficiency and indoor comfort. Its operation relies on a low-pressure pneumatic system that can extend or retract the shading modules, maximizing solar gain in winter and minimizing overheating in summer.

 

 

This responsive facade represents a cutting-edge approach in architectural design, enabling the building envelope to actively respond to environmental and user stimuli. By integrating programmable material deposition, advanced actuators, and sensor networks, these dynamic systems can adapt in real time to optimize energy performance, enhance occupant comfort, and foster new forms of interaction between users and their built environment.

 

Their ability to regulate solar gain, ventilation, and thermal performance makes them a key component in reducing energy demand and supporting sustainable urban development. As the emphasis on sustainable design continues to grow, these façades will play a pivotal role in shaping the architecture of the future, embodying the seamless integration of technological innovation and architectural functionality.

 

This innovation marks a promising step forward in integrating bioclimatic strategies into building envelopes, aligning with the goals of enhancing energy efficiency and climate resilience.

 

Source: Youlv.com