*3.4. Spatial Relations of Buildings and PV Panels*

Photovoltaic panels are installed on buildings in two basic configurations with respect to building components [29] (p. 59):


These relations between building components and photovoltaic array mounting systems can be also classified as BIPV and BAPV. BIPV is considered a functional part of the building structure as it is architecturally integrated into the building's design. This category includes designs that replace the conventional roofing materials, such as shingles, tiles, slate, and metal roofing. BAPV is considered an add-on to the building, not directly related to the structure's functional aspects (Figures 10–12). It relies on a superstructure that supports conventional framed modules. Standoff and rack-mounted arrays are the two subcategories of BAPV systems. Standoff arrays are mounted above the roof surface and are parallel to the slope of a pitched roof. Rack-mounted arrays are typically installed on flat or pitched roofs. In the second case, the tilt is either parallel to or different from the roof inclination to be more suitable to the angle of solar incidence. From the above definition, the main difference between BIPV and BAPV is the extent of tightness of the integration of photovoltaic systems and buildings [9] (p. 3593). The multitude of possible relations between these two components is illustrated in Figure 10.

**Figure 10.** Types of relations between the photovoltaic solar systems and building forms and components (diagram by W. Celadyn, P. Filipek).

**Figure 11.** Solar electricity generating thin-film system independent of the building (photo by W. Celadyn).

**Figure 12.** PV modules installed on a structure added to an office building (photo by W. Celadyn).

An analysis of a building demonstrated the direct link between the functional requirements and external appearance. The drastic changes in the energy sector have had a lasting impact on this traditional link. The relationship between local conditions and their impact on the built environment is mostly nullified [29] (p. 38). Contrary to collectors that are mounted onto the building skin, these systems allow for a full integration both in terms of construction and design [32] (p. 262).
