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Ventilation

Crystalline modules

In addition to orientation, ventilation of photovoltaic modules also impacts on yield. The electricity yield of the PV system decreases the more the modules heat up. For each degree of temperature increase relative to the standard module temperature of 25 °C, crystalline modules lose an average of 0.4 to 0.5% of their nominal output. Ventilation is an advantage, but not essential. A comparison of the electricity yield of PV modules with and without ventilation shows that the yield of non-ventilated PV modules is only around 10% less.

Good ventilation cools the modules and thus ensures optimum electricity yield. On façades and roofs, a ventilation layer of approx. 10cm should be planned in order to increase yield.
Figure 1: Decrease in yield due to increased module temperature depending on ventilation

Source: WM Baden-Württemberg

Thin-film modules

The decrease in output at higher temperatures is less with thin-film modules than with crystalline. Thanks to the lower temperature coefficient, the decrease in output in summer – at high module temperatures – is up to 10% less than with crystalline modules (Bächler). However, because of their lower efficiency, thin-film modules need more area than poly- or monocrystalline modules in order to achieve the same output.

Last page update: 08.02.2011