Lowest DAYTIME temp records [RE-wrenches]

[Joel Davidson]

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Should PV systems be designed using nighttime temperatures when it is 
obvious that voltage is not present in the dark? Should climate data from a 
weather station be used because it is available even if the system location 
has a different microclimate? Does this seem reasonable? SMA's string sizing 
tool has the right idea. They ask you to select the coldest record low 
ambient temperature when sunlight will be on the array.


www.weather.com only lists record high and low temperatures. NEC 690.7(A)
specifies the lowest expected ambient temperature which implies sunlight on
the array to cause voltage. Except in rare situations record low
temperature occurs at night or before sunrise when no voltage is present.

Does anyone know a source for the lowest expected ambient temperature when
sunlight will be on the solar array?

Joel Davidson




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