Page 102 - Applied Photovoltaics

3. Array V oc > 120 V—in addition to the above conditions for arrays exceeding
50 V, an insulation monitor is required for floating, isolated arrays.

5.10 MECHANICAL PROTECTION
Solar modules must have adequate strength and rigidity to allow normal handling
before and during installation. If glass is used for the top surface, it must be tempered,
since the central areas of the module become hotter than areas near the frame. This
places tension at the edges, and can cause cracking. In an array, the modules must be
able to accommodate some degree of twisting in the mounting structure, as shown in
Fig. 5.23, as well as withstand wind-induced vibrations and the loads imposed by
high winds, snow and ice (IEC, 1993).

Figure 5.23. Possible module twisting on a distorted mounting frame (JPL, 1981).

The points most sensitive to such mechanical damage are the module corners, edges,
cell edges and any substrate supports.

5.11 DEGRADATION AND FAILURE MODES
The operating life of a solar module is primarily determined by the durability of the
encapsulation (Czanderna & Pern, 1996), although there are light-induced
degradation mechanisms in boron-doped silicon cells (Schmidt & Cuevas, 1999).
Field results indicate that, over an anticipated 20–30 year life, solar modules can be

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