Watt-peak
From Wikipedia, the free encyclopedia
(under construction) Watt peak (symbol Wp )(User friendly definition): Is the Direct Current output in Watt (Joule per second)of a Solar Module as measured under an Industry standardized Light Test before the Solar Module leaves the Manufacturers facility.
Watt peak (technical definition): The Watt Power output of a Solar module is the number of Watts Output when it is illuminated under standard conditions of 1000 Watts/meter2 intensity, 25°C ambient temperature and a spectrum that relates to sunlight that has passed through the atmosphere (AM or Air Mass 1.5).
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[edit] Can also be used for wind electricity generators
[edit] Not the most important number
Although Watt-peak is the standardized number in the PV industry on which prices, sales and growth numbers are based; the watt-peak number is not the most important number. Since a Solar Panel's job is to generate electric energy; the amount of energy that it generates should be the most important number to evaluate.
It can happen that a panel from brand A and a panel of brand B give exactly the same Watt-peak in a laboratorium test; but in a real installation the energy output can be different. This difference can be caused by the fact that in real conditions the temperatures are different and the photovoltaic cell temperature will go up. Photovoltaic cells have a different characteristic at different temperatures; a low efficiency cell will become hot and with higher temperature the efficiency will go down and produce less energy.
For this reason it is always recommended to measure (or demand from manufacturer) real energy output of a PV panel
