Net ZEB Design Processes and Tools - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 204

primarily the computational time rather than increased user input, there is
little practical reason to use decoupled HVAC models to support Net ZEB
design.
4.3.3.3 Photovoltaics and Building-Integrated Photovoltaics
Photovoltaic systems are among the most common renewable energy
systems in Net ZEBs because they consistently generate electricity during
daylight hours, require relatively little maintenance, have considerable
flexibility in capacity and surface area, are not highly angularly dependent,
and can be installed on the near-south-facing façades and flat or near-south
facing roofs. While numerous tools are available for the prediction of
stand-alone PV system performance, there is significant value in explicitly
modeling PV modules within the main building model. Self-shading of PV
(i.e., when BIPV modules are shaded by the building structure) is avoidable
and should be minimized wherever possible. Beyond the much lower
performance for shaded modules (which can be proportionally worse than
the fraction of shaded area), PV modules can be damaged if they are not
properly wired with a bypass diode (GSES, 2004). Microinverters can
partially alleviate this problem because each module is operated
independently and does not affect the others' performance. As shown in
Table 4.3 , complex roof geometries (e.g., a cross-gable) can significantly
reduce PV performance. Many BPS tools neglect individual module
geometry, and instead, treat BIPV as continuous surfaces. Thus, care during
design must be taken to avoid self-shading and other geometrical
compatibility issues.