Solar Energy Balanced Facade project: Schenker Storen’s innovation for a new kind of thermal efficiency

Schenker Storen teamed up with the Institute of Civil Engineering (IBI) at the Lucerne School of Engineering and Architecture and made a pioneering blind for a thermal facade test to help with the “Solar Energy Balanced Facade” project. The two project partners are using this system to explore a promising alternative to conventional building facades in Switzerland.

When travelling by train from Lucerne to Horw, from the tracks you can see a very special blind mounted on a large angular box with a high window front looming out from a wooden frame. This is the thermal test bench for the Solar Energy Balanced Facade project, SEBF for short, which the researchers have affectionately dubbed the “bird’s nest” as it looks like a bird house.

Within the context of the SEBF project, the Institute of Civil Engineering (IBI) used the thermal test bench built specifically for the project, to research a new way to store heat in a double-skin facade that would passively adapt itself and have a positive impact on the energy balance of a building. More specifically, in the winter, the material in the parapet area of the windows absorbs and stores the heat from the sun and then releases it into the airtight space between the double-skin facade at night.

Essentially, it is the solar heat energy stored in the building that is released to the exterior via the window pane, not the heat energy from within the building. As a result more heat remains within the interior rooms, reducing the amount of energy needed for heating the building and improving its energy balance.

Based on the measured data collected and analysed, Thomas Wüest, research associate at the IBI and creator of this project, can proudly confirm that it works. Furthermore, it turned out that this system contributes even more substantially to the efficient cooling of the interior rooms in the summer than originally assumed. The storage system ensures that the double-skin facade does not heat up too much in the summer as it captures and stores the sun’s heat, explains Mr. Wüest. As a result, the interior rooms do not need to be cooled down as much, which in turn has a positive effect on the energy balance of the building.

These encouraging results were attained after three and a half years of research. The team working on the SEBF project had to overcome numerous different obstacles along the way. The fact that modern double-skin facades are usually ventilated is one such challenge. For this test facade to work though, it could not be ventilated in any way. Consequently, the team used a very new facade system at the beginning of the project, the so-called Closed-Cavity-Facade (CCF), as it creates an airtight cavity between the two skins of the facade. They also had to find a way to regulate the light incidence and therefore the transfer of heat to the storage area, which the system needs to function. The idea of an upward-moving blind came about because in an SEBF, the heat is stored in the parapet area and the area where the light infiltrates is controlled separately and independently from the rest of the window surfaces. This covers the storage area while the rest of the window pane continues to provide a view to the outside. Conversely, the blind at the top provides privacy and glare protection, while the storage unit below continues to absorb the solar heat. However, a blind that could meet all the requirements of the project was not readily available. That is why the team was looking for an innovative blind manufacturer who could gather the necessary resources and had the grit to take on this special challenge.

"Schenker Storen was just such an innovative blind manufacturer,” reports Mr. Wüest.

A blind for the solar energy balanced facade

Fuelled with pioneering determination, the innovators working in Schenker Storen’s innovation department grabbed this special challenge by the horns. Not only was it necessary to develop a blind system that could be used with the relatively new and specific Closed-Cavity-Facade (CCF), which has completely different requirements to conventional facades and windows, it also had to be as straightforward as possible with a very quick turnaround. Not to mention that it is one of the first blinds ever built that works in opposite directions and can be closed from both above and below.

In order to create a shading system solution as easily and quickly as possible, existing components were used for the more demanding environmental conditions. The technical approach was discussed in various brainstorming sessions and in consultation with the IBI, says Mr. Thomas Stöckli, Head of the Innovation Department at Schenker Storen. Ultimately, the solution was to construct a prototype that would build on our proven economy slat blind 70. The difference being that the new one has two blinds, not just one. The top one works completely normally, while the one below is pretensioned with a spring. The spring balancer is redirected via rollers so that the top slat, i.e. the head rail, is permanently retracted upwards. This takes over the work of gravity, but the other way around, upwards not downwards. The motor then moves the top slat up and down against the spring force, which makes all the slats move up and down via the mounting straps.

That is how a new prototype came to be: a bi-directional blind that shades the heat storage area and the remaining window surfaces independently of one another. Two versions were installed in the thermal test bench on site and tested continuously, together with the entire heat storage system, for almost a year. The results speak for themselves.

“We were intrigued by how Mr. Wüest produced his measurements and that he was able to identify an additional area where energy could be saved using his SEBF”, stressed Mr. Stöckli.

Innovations of the future

The innovation team at Schenker Storen was already knowledgeable on the subject of CCF and components that could be moved upwards from the bottom. They were able to contribute a lot of valuable experience gained in the field to drive this project forward. As Mr. Stöckli points out, the experience gained from the SEBF project will also be potentially applied to future developments. Because Schenker Storen is unwaveringly invested in the subject of energy and the difference sun shading has on the energy balance of buildings.

Sun shading devices already ensure that the amount of energy and light let in through transparent components, such as windows and glazing, adapts to the respective weather conditions. This is all the more important nowadays with the growing trend for wall-to-wall windows and large-scale glazing. Purposefully designed systems can lower heating costs in winter and reduce the need for active cooling in summer. Numerous Schenker Storen products are Minergie-certified and available with Smart Home solutions for efficient and convenient control. Schenker Storen considers itself to be a driver of innovation for the sun shading technology of today and the future with the firm intention of providing improved energy efficiency and sustainability.

That is why Schenker Storen supported the IBI’s innovative and promising SEBF project free of charge, Mr. Stöckli explains. Schenker Storen will of course continue to contribute to Mr. Wüest’s project.

Efficient, more fault-proof and affordable – High Impact with Low Tech

According to Mr. Wüest, many researchers focus more on new technologies, leaving the development of existing technologies rather “neglected”. With the SEBF project and blind prototype, they relied as much as possible on the low-tech methods of tried and tested technology.

"Complex and, in some cases, error-prone technology, must be avoided, or if it has to be used, to do so in an intelligent and controlled manner,” says Mr. Wüest. The experimental heat storage tank we installed, is just an aluminium tank painted black and filled with thickened water. The experiments are already yielding impressive results, states Mr. Wüest with a smile.

The blind prototype from Schenker Storen embodies and supports Mr. Wüest’s efficient and economical low-tech approach. That is why the team drew on the proven and simple technology of the economy slat blind and developed it further where necessary.

The SEBF project provides proof, both in theory and in practice, of the beneficial impact this passively adaptive heat storage system can have in a double-skin facade. Its success is testament to the “High Impact with Low Tech” approach. Mr. Wüest remains optimistic. “Lots of research projects are now working in a similar vein, moving away from complicated high-tech solutions towards more reliable and smart low-tech applications; even with grey energy.”

The Minergie-certified sun shading products from Schenker Storen meet the highest requirements for optimum heat insulation and contribute to the construction of energy-efficient and sustainable facades. You can read more about this here.