PV doesn't work in cloudy conditions
PV does not stop functioning, just because the skies turn cloudy. The so-called perfect conditions would be blue skies, sunshine, vertical rays on the modules and cool temperatures. PV modules are usually tested at Standard Test Conditions, however real conditions vary largely. Hence, power generated by modules under cloudy conditions is also tested. This is known as low-light condition performance.
Solarpraxis' PV+Test recognizes that panels generate less power in low light conditions. The question, then, would be how much less? There are naysayers who believe that PV completely shuts down under low light conditions, during days in winter or under extensive cloud cover. That’s just not the case. When the 1,000 watts per square meter fall to about a fifth, then it is safe to assume that the output also falls below a fifth of its nominal output.
Low-light performance, as the PV+Test reveals, is highly dependant on the cell and module technology utilized. The relative efficiency reduction at low light levels of 200 Watts per square meter of solar irradiance reveals the deviation from the performance norm. When efficiency falls by less than one percent, or when modules perform better in such light and display a positive percentage, then they are suitable for climates with more cloud cover – or alternatively in dusty conditions, or when the air is full of mist or smog.
When a solar power plant is built, professionals do an analysis not just of the cost of development and potential performance data, but they also take into account the area’s irradiation figures. Simulations are used to gauge the efficiency of a standard module under different light conditions and planners can then decide on the modules they wish to install. Thus, modules are tested under low-light conditions as well and if the right ones, with the lowest performance dips under cloudy conditions are selected, then PV power is still produced on grey days.
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