The designer may well use building elements such as canopies and shading systems to integrate PV systems, but will need to look in detail at shading and PV technology to understand the details of how to design this PV integration. One of the first things that the designer will discover is the fact that an efficient PV system is not automatically a good shading system. In general, a PV system on louvres will need a certain mutual distance between the louvres to prevent shading of the cells, which may let too much sun through at a lower sun angle in spring and fall (Figure 23.15).
Heat load and daylight control systems can be combined with the integration of PV systems. Moreover, the designer who studies these aspects in detail, will discover that PV systems can also
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Figure 23.15 Daylight control at the Kaiser fashion house in Freiburg (Germany). This 4kWp PV system on louvres is mounted in front of the glass facade and prevents glare inside. The PV louvres are in the center of the figure. Reproduced with permission by BEAR Architecten T. Reijenga |
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Figure 23.16 South facade of ECN Building 31 in Petten (The Netherlands). The shading structure supports the 35kWp Shell Solar modules. Reproduced with permission by BEAR Architecten T. Reijenga |
be part of the thermal envelope or thermal system [18]. Another example is the refurbishment of Building 31 in Petten (NL) [19]. In this project, the PV system is integrated into a louvre system that supports the 35kWp Shell Solar modules, to keep out the summer heat and give less glare, and improve daylight conditions inside. To prevent shading of the modules by the upper louvre, the dimensions of the louvers have to be almost twice the size of the modules (Figure 23.16) [20].
Orientation is a major design issue for (green) buildings. The heat load of a building, the need for shading and the design of facades all depend on the orientation. Orientation is also important for PV systems. Facade systems might be suitable in certain countries, especially at a northern (above 50 °N) or a southern (below 50 °S) latitude. When shading of the facade cannot be prevented, and for the countries in between these latitudes, sloped surfaces facing the sun or even horizontal surfaces might be more suitable. The designer’s final choice will be based on orientation, amount of total annual (sun)light on the PV module, shading from surrounding buildings and the aesthetics of the design (very usable tools for estimating and calculating the yields under various orientations and slopes have been developed by amongst others the Dutch consultancy firm Ecofys and the Polytechnics of Lausanne, Switzerland). An important issue for the designer is to appreciate the blue, grey or black cells and to become familiar with finding integration opportunities in the first draft design. Ideally, a PV system should not be added to a building but designed as part of the building.
