太阳能发电峰会资料Accurate_measurements_in_PV.ppt

,Accurate measurements in photovoltaics,Pasan SA Pierre-Ren Beljean, CTO Shanghai, May 10, 2008.,What are the needs for accurate measurements ?,Pasan SA www.pasan.ch,Page 3,An accurate measurement will lead to better :,Manufacturing control Cell match in modules Overall efficiency Money return Prediction of in-site performance,Pasan SA www.pasan.ch,Page 4,Parameters affecting measurement accuracy in PV :,Electrical : Electrical calibration accuracy Dynamical behaviour Electro-optical calibration : Confidence to calibration laboratory Optical : Light ununiformity Spectral distribution Calibration of Ref. Cell Light stability Environnment : Temperature,Pasan SA www.pasan.ch,Page 5,Electrical errors :,Calibration of each channel (Straightforward !) Dynamical behaviour Time response of each channel Time response of cell to electrical stimulation Time response of cell to light stimulation,Pasan SA www.pasan.ch,Page 6,Electro-optical calibration errors :,Calibration of Ref. Cell or module Must be done by recognized laboratories. Tedious procedure needing to know spectral response of the cell. Proper use needs to know spectral response of the module to be tested and the spectral content of light from Sun Simulator. Difficult to obtain better than 3 % certified accuracy.,Pasan SA www.pasan.ch,Page 7,Optical errors 1 / 2 :,Light ununiformity Current generated by module determined by the least illuminated cell Difference in illumination between Ref. Cell and module directly imputable on global performance measurement. Light spectral content, mismatch factor Different response of module under test and Ref. Cell Varies with module technology and quality of light Critical for multilayer cells, GaAs, etc. due to the disposition of several cells in series, each of them using a part of the spectrum.,Pasan SA www.pasan.ch,Page 8,Optical errors 2 / 2 :,Light stability The least important parameter. Light usually monitored in real-time by Ref. Cell. Software allows automatic correction.,Pasan SA www.pasan.ch,Page 9,Temperature :,IEC 60904-3 stipulates STC to be 25 C 2 C, but 2 C means, for typical silicon, 0.8 % of power variation. Temperature should be measured as accurately as possible. No possible matching of Ref. Cell and module, as Isc measurement used in Ref. cells is quite not sensitive to temperature.,How to minimize measurement errors ?,Pasan SA www.pasan.ch,Page 11,Minimizing electrical errors,Calibration accuracy. Periodical check. Fast responding load and acquisition Proper software to eliminate transient effects in cells and/or in loads.,Pasan SA www.pasan.ch,Page 12,Minimizing electro-optical calibration errors,Calibration of Ref. Cell or Ref. module Use recognized laboratory service for calibration (PV World Scale). Periodically check your calibration.,Pasan SA www.pasan.ch,Page 13,Minimizing optical errors,Light uniformity Use simulator with high uniformity Periodically check for uniformity and perpendicularity. (1 cm at 5.5 m corresponds to 0.3 % error). Light spectral content Use simulator with accurate spectral distribution Know exactly your spectral content to calculate mismatch factor Light stability Use stable simulator,Pasan SA www.pasan.ch,Page 14,Minimizing temperature errors,Use temperature-controlled test area Allow modules or cells to stabilize