*2.2. Energy Yield and Aesthetics*

When designing the BIPV system, a trade-off needs to be made between the aesthetics and the energy-yield of the installation. A different approach exists between BAPV and BIPV. For BAPV, the electrical installation is typically done on an existing structure. A high energy yield is of primary importance as the motivation to place it can be found in reduced electricty costs. For BIPV, the energy yield is of secondary importance, whereas aesthetics and building regulation standards are primary factors to take into account [54]. Neglecting the importance of the energy yield could, however, lead to a less favourable position of BIPV compared to other measures that are used to reduce the energy consumption and ecological footprint of the building [55].

As compared to conventional PV systems, partial shading due to adjacent structures, building elements (e.g., pipes and ducts), frame edges, or the curvature of the installation is more prevalent in BIPV installations [36,47–49]. As a consequence, the power output of the shaded modules and, more importantly, the unshaded modules will be reduced, depending on the electrical configuration. The mismatch losses due to partial shading are specific for each installation, though studies indicate losses ranging from 5–25% [53,56–58].

This impact can, however, be limited by implementing the MPPT on smaller scales, e.g., per panel and not per string. To increase the power output, it is advisable to do the MPPT per module (distributed MPPT) and not per string. A micro-inverter (DC/AC) or power optimizer (DC/DC) solution is, thus, preferred to the traditional string inverter approach.
