Procedure for determining the uncertainty of photovoltaic module outdoor electrical performance‡

This paper sets forth an uncertainty estimation procedure for the measurement of photovoltaic (PV) electrical performance using natural sunlight and calibrated secondary reference cells. The actual test irradiance should be restricted to values between 800 and 1000 W/m 2 in order to assume that maximum power varies linearly with irradiance. Only the uncertainty of maximum power at standard test conditions (STC), i.e., 1000 W/m 2 plane‐of‐array irradiance and 25°C cell temperature, is developed in its entirety. The basic uncertainty analysis principles developed herein, however, can be applied to any electrical variable of interest (e.g., short‐circuit current, open‐circuit voltage and fill factor). Although the equations presented appear cumbersome, they are easily implemented into a computer spreadsheet. Examples of uncertainty analyses are also presented herein to make the concepts more concrete. Published in 2001 by John Wiley & Sons, Ltd.