Form and Function in Harmony - Wacker Chemie AG

Form and Function in Harmony

Makrolon® for the Roof's Inner Ring

Makrolon® was chosen for the stadium roof’s inner ring. This crystal clear and rigid plastic retains its shape and is impact resistant. CDs, DVDs and airplane windows, for example, are made of this material, as is the roof glazing of Cologne’s main rail station. A lightweight yet rigid twin-wall sheeting of this highquality material serves as the carrier plate for the roof panels, whereas a solid Makrolon® plate forms a covering that shields the panels from the elements. This results in a solar panel that weighs less than half of what a comparable glass/glass panel would.

Silicone Gel

In a silicone gel, the individual polymer molecules are interconnected to form a loosely crosslinked network. The silicone chains between two crosslinking nodes retain their mobility and are able to yield whenever they encounter a hard surface. This characteristic makes silicones unusually resilient and flexible. Expressedin figures, the Young’s modulus (a modulus of elasticity measuring the resilience of an elastic material) for silicones is around 0.005 megapascal; ordinary silicone elastomers, in contrast, have a Young’s modulus between 1 and 10 megapascals. The smaller the value, the more resilient the material and the better it can alleviate mechanical stress.

Because they are elastic and resilient, create a barrier for moisture, do not react with semiconductors and display the chemical stability typical of silicones (see box on p. 11, SILICONES), silicone gels are utilized for the encapsulation of electronic chips and solar cells. Silicone gels durably protect sensitive components against mechanical damage, prevent leakage currents and short circuits, and provide a non-corrosive environment.

A silicone gel is created by the vulcanization of a silicone formulation that, unlike a conventional silicone rubber, contains absolutely no fillers. This workable, as yet unhardened form of the gel is also referred to as a silicone gel.

The Secret to Sucess: a Silicone Gel

Within the stadium roof, solar cells of monocrystalline silicon convert the sunlight into electrical energy. These cells are well protected inside the panels. The ight-permeable space between the opaque solar cells can be treated more or less exactly as the client or architect wants. In this way, the transparency of the plastic panels can be adjusted.

Painstaking accuracy and expertise are required to manufacture these panels.

The manufacturing process consists of several steps. First, the individual solar cells are fixed upon the carrier plate and electrically connected in series with thin contact strips. Then, the carrier and cover plates are sandwiched together by means of a special, permanently elastic adhesive strip that runs along the edge of the plates and seals them together. Finally, the sandwich is embedded in a liquid silicone gel – a tricky process requiring in-depth expertise. The SUNOVATION employees take special care to ensure that the encapsulant is completely free of bubbles. After the silicone has hardened, the panel is tested and packaged. It is absolutely necessary to encapsulate the solar cells, which are highly fragile. The encapsulant protects them from mechanical and chemical damage and ensures that they are electrically insulated. Because of their chemical, physical and technical characteristics, silicones are ideal for this purpose and contribute considerably to the solar panels’ high quality and durability.