Pilot system: the test facade was installed on an industrial building owned by Ritter Energie- und Umwelttechnik in Langensteinbach near Karlsbad.
© Universität Stuttgart, IBK 2
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Lighting studies and the efficiency of the system

In order to assess the sun protection and daylight properties, two facade modules at floor height were produced without a cover panel, and were installed in the test station at the TU München at the department for shell structures, where they were then studied for lighting properties. The results showed that the collector facade has high, storm-resistant sun protection potential, prevents additional cooling loads, and can replace conventional sun protection. The costs for complex sun protection appliances or glazing are therefore redundant.

The gross collector heat yields were determined using simulation calculations in Oslo, Frankfurt, Würzburg, Madrid, Athens and Doha. Depending on the location, up to around 70 % of the yields from roof-mounted solar energy systems with a pitch angle depending on the latitude could be achieved at the facade level. However, these yields are distributed more evenly throughout the year. From an energy perspective, a cover panel on the collector should be avoided if possible. If an additional cover panel is required, for example for safety reasons, the yield losses are lower with toughened safety glass.

According to the scientists, the typical energy payback time is 10 months. Compared with conventional on-roof collector systems, the facade systems have economic advantages due to their triple use for energy recovery, daylight use and protection against the sun and heat. The solar thermal concept, which is integrated into the facade, has won several awards, including the “Intersolar Award” (2010), the “European Aluminium Award 2010”, at the Essen aluminium fair, and the “Design Plus Award” at the ISH.

Planning aspects and the pilot system

When planning a solar thermal facade, any possible obstacles which may reduce the yield should be taken into account. A free-standing building without roof projections, porches or vegetation close to the property is ideal. These quickly cause shading and therefore impair the output. When mounted on a south-facing facade surface, the facade collector makes a greater contribution to the heating in the winter when the sun is low than a comparable collector which has been mounted on the roof. Due to the lower level of irradiation in the summer, it can be larger in size without the solar energy system frequently coming to a standstill.

The facade elements were installed in a pilot system as a curtain facade system on an industrial building owned by Ritter Energie- und Umwelttechnik in Langensteinbach near Karlsbad (see Fig.). The facade elements consist of eight collectors without cover panel, and are each 1.6 m wide and approx. 2.8 m high. The aperture surface of an individual collector is 4.21 m², with a total surface of 33.68 m². In each collector, 24 tubes are arranged one on top of the other, and are south-facing with an 8° westwards deviation.

The aim was on the one hand to gather initial experience in mounting under realistic conditions, while at the same time to test the functioning and safety of the system during daily operation. It became clear that when integrated into the facade, a larger number of collectors (compared to roof installation) are switched in series with the same pressure loss, and that as a result, the amount of casing required can be minimised. The functioning of the hydraulic components in the collector and its parts was measured and studied while the system was in full operation. The test facility met expectations with regard to operating behaviour, and ran smoothly.

According to the staff working in the building, the perforation of the CPC mirror panels guarantees pleasant protection against the sun, while offering a view to the outside. The indoor area remains comfortably cool, which significantly improves the working atmosphere.

Projektinfo 07/2013:
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Measurement of the prototypes and 0 series of the facade collector
Universität Stuttgart, ITW

Simulation and yield assessment

Industrial partner for collectors, test collector facility Langensteinbach
Ritter XL Solar GmbH

Industrial partner for facade

Industrial partner for facade construction

Industrial partner for facade construction
Metallbau Früh GmbH