Climate control is one of the key issues when it comes to the future of construction. On the one hand, global warming is increasing the demand for intelligent systems to control the temperature of buildings, and on the other, the construction sector is one of the main sources of energy consumption worldwide - both for the construction of buildings and for their operation with increasing cooling loads. This is where the innovative ADAPTEX solar shading concept comes in, whose mode of action is based on smart materials.

The research project of the same name was developed jointly by university and industry partners as part of smart³. The result is textile-based façade elements that have already been tested as prototypes for use in practice. This sun protection is installed in front of large glass surfaces and can adapt its degree of opening and therefore also its efficiency to the current climate conditions. Shape memory alloy wires (SMA wires) are incorporated into the permeable structure and serve as actuators for the shading elements.

SMA technology on a large scale

The mechanism for ADAPTEX is based on textile logic: the SMA wires are interpreted as 'fibres' integrated into the textile surface structure. This enables an unusual leap in scale, as SMA wires have previously only been used as actuators in object-based applications such as mechanical engineering or medical technology. In the ADAPTEX project, the technology will be applied to large surface elements for use in facades. If the 'smart' SMA wires are interpreted as part of a textile that can be produced in endless lengths from a roll, the smart technology can now be used to activate surfaces as high as a building.

The temperature dependency of the SMA material is ideal for use as a climate control element. The SMA wires contract as the temperature rises and relax as it cools. This effect is used for the movement mechanism of the surface structure. Only when a high degree of shading is required - during the day when the sun is shining and it is warm - does the surface close as a result of the rising temperature. When the temperature drops, the panel opens again automatically. The principle works entirely without an external power supply: the concept is to use the sun's energy to protect against its effects. The result is a self-sufficient system that can shade and modulate the climate without using electricity. This saves energy during operation compared to conventional automated shading systems such as motorised blinds. SMA wires are ideal for façade applications because they are wear-free, durable and maintenance-free.

SMA wires are wear-free, durable and maintenance-free, making them ideal for façade applications.

As products available on the market, they are designed in different configurations and thicknesses for specific activation temperatures. The ADAPTEX solar shading system can be adapted to a specific temperature range by integrating the appropriate SMA wires for different climate zones. As well as being activated by the outside temperature, the wires can also be activated by a single short current pulse. This additional control option can therefore increase individual user comfort. The system can also be integrated into double skin façade systems to create solar shading elements that can be easily integrated into conventional building processes and construction methods.

Adaptex in use under real conditions

The research team was particularly interested in the development of self-sufficient operation and retrofitting of buildings, as energy efficient refurbishment of existing buildings is one of the most pressing issues in the construction industry. An important aspect of this was the realisation of a 1:1 demonstrator façade to validate the concept and learn from real-world implementation. A location with large climatic variations between day and night was chosen as the demonstration site: Muscat in the Sultanate of Oman. In summer, temperatures can reach up to 40 degrees Celsius during the day for weeks on end, only cooling down at night.

Air conditioning and solar shading is a ubiquitous problem, which in recent decades has mostly been addressed by conventional, energy-intensive air conditioning systems, whose waste heat adds to global warming. The Eco House test building is located on the campus of the German University of Technology in Muscat, where the prototypes were installed and tested externally over a period of one year. Construction took place during a joint assembly week in August 2022, in collaboration between the ADAPTEX research team and professors and staff from the university. Due to the high temperatures during the day, work could only be carried out in the evenings and at night.

Multiple award-winning development

The result is impressive not only for its technical innovation, but also for its high-quality design. The interdisciplinary collaboration between façade planners, material specialists and designers resulted in two different functional principles. The 'Wave' system is based on a steel cable mesh with integrated textile bands made of glass fibre fabric, which deform their geometry and close when activated. The 'Mesh' system combines glass and basalt fibre structures arranged one behind the other, allowing different degrees of opening by moving one of the layers. This variant proved to be a 'local hero' for local visitors, as it is reminiscent of the patterns of Arabic 'mashrabiya' façade elements. These are perforated, open wooden lattices used in traditional construction to provide privacy, shade and ventilation.

From prototype to demonstrator

Design and technology have been developed together from the start of the project. In this way the technology becomes an integral part of the design and the design an integral part of the technology. The development process began with countless experimental design prototypes, which were continually refined and analysed throughout the project. This 'hands-on' process and the 1:1 samples and prototypes enabled an intensive and creative exchange between the nine partner institutions from different disciplines and working cultures right from the start. The fact that this kind of interdisciplinary work promotes innovation is also reflected in the international recognition the project has received, such as the 'Award of Excellence 2022' in the Innovation category from the Council on Tall Buildings and Urban Habitat CTBUH, Chicago, or the 'Special Prize for Innovation' from the Zumtobel Group Awards, 2022. The next step will be to develop the project to market maturity so that this innovation can soon make a concrete contribution to the building revolution.