How do you install your PV on a flat roof? Vertically.

Easy Solar AS vertical PV (source)

Installing strategies for PV modules on flat roofs has gone through several generations.

The first generation, I will call optimal local. In this strategy, the PV modules incline approximates their location latitude to maximize performance. With optimal local strategy, except for very low latitudes, successive rows of PV modules must spread apart to avoid inter-shading (see figure 1).

Figure 1: Example of optimal local PV system (source)

The higher the latitude, the larger the distance between the rows of PV modules. Higher latitudes combine in both lower solar altitudes and steeper PV module inclines. The sun’s position in the sky stays closer to the horizon while the PV module angle to the horizontal increases. The shadows between successive rows of PV modules lengthen, forcing the rows to be further apart. The total roof area covered with PV modules decreases.

A trade-off ensues: wining on the generation of each PV module versus losing on the total area of PV installed.

Realizing the trade-off, I think around the 2000s, the second-generation strategy appeared: I will call it optimal area. The objective is to maximize the rooftop area covered with PV modules…