*2.4. Modularity*

This criterion relates to the ease of the practical construction of the installation. A modular system can easily be built and is the most plug-and-play option. This modularity aspect needs an evaluation for both the mechanical and electrical installation. The main focus of this paper, however, is on its electrical aspect. Modularity in its ultimate form would mean that the mechanical and electrical installation of the building

can be carried out simultaneously by the same person. This person is preferably a construction worker with a minimal amount of extra training such that no skilled electrician is required to wire up the electrical installation after the façade itself has been placed. Relating to the previous aspects of flexibility, modularity does not mean that every BIPV module will be the same. The mechanical dimensions of a curtain wall BIPV module will be the same over a certain area of the building, e.g., one floor level, for the easiness of constructing the façade. Part of the BIPV module will be glass; the other part will be PV. The ratio glass/PV is, however, a parameter that can differ over different panels. This concept is illustrated in Figure 2 where BIPV modules are shown with 50% and 100% PV penetration. Furthermore, the glazing could also be changed to transparent PV modules which further increases the variety of electrical parameters in the system.

**Figure 2.** The zoom on a small part of a typical apartment or office building façade where building-integrated photovoltaic (BIPV) curtain wall modules can be used. To illustrate the modularity principle, the size of the curtain wall element remains the same but the ratio glass/photovoltaics (PV) can be changed.

Cabling is another factor that strongly influences the modularity of the system. Ideally, a preinstalled AC or DC bus structure would run inside the BIPV modules. By doing so, the BIPV modules can be directly interconnected at the moment of their installation. At the corners of the building, the cables of the BIPV modules of the same floor level can then be connected to the main AC or DC backbone.
