The ballast structures, in which the load is applied, are a solution for the installation of photovoltaic systems on roofs, such as membrane roofs, for which the preservation of warranty and tightness is an important aspect. In this case, the support structure for the photovoltaic panels is not screwed permanently to the roof. For this reason, the structure requires additional loading with concrete blocks, as shown in Fig. 1 and Fig. 2.

Figure 1: PV installation installed on a flat roof using SolTech Service's ballasted mounting system. Photo used by permission of SolTech Service.

Figure 2: Scheme of installation structure for flat roofs with ballast – installation systems of KENO Sp. z o.o. Photo used by permission of KENO Sp. z o.o..

When a ballasted structure is used, the steps for mounting the PV modules to the support structure are similar to those for an unballasted installation. The weight of the load per PV module depends on the wind zone, the angle of inclination of the panel, as well as the height of the building. For one panel with standard dimensions (about 100 cm x 164 cm), this load is about 60 kg. For this reason, an important limitation for the use of this type of fixing system is the roof load capacity.