阿特斯_NP_IEC_TC82_WG8_guidelines-testing-and-sorting-bifacial-cells_V5

CSIQ NASDAQ Guidelines for I-V measurement and sorting of bifacial photovoltaic cells in production line 2018.10.25 2Canadian Solar Inc. Contents Background Draft Proposal of Standard Appendix Deviation Analysis of Bifacial Fitting Method 3Canadian Solar Inc. Background The market share of bifacial cells has increased rapidly in 2008, particularly for PERC bifacial PV cells. The ongoing standard IEC 60904-1-2 DTS is mainly for I-V measurement of bifacial PV modules, not suitable for bifacial PV cells. It is of great urge to legislate standard for I-V measurement of industrial bifacial PV cells, especially for inline production. 4Canadian Solar Inc. Draft Proposal of Standard Guidelines for I-V measurement and sorting of bifacial photovoltaic cells in production line 5Canadian Solar Inc. 1. Scope This part of IEC 60904 describes procedures for the measurement of the current-voltage I-V characteristics of bifacial photovoltaic solar cells in simulated sunlight and guidelines to the sorting of bifacial PV cells in production line. It is applicable to single bifacial PV cells. The requirements for measurement of I-V characteristics of standard monofacial PV devices are covered by IEC 60904-1 and the additional requirements for measurement of I-V characteristics of bifacial PV devices are covered by IEC 60904-1-2 DTS. The purpose is to provide bifacial PV cells with precise I-V measurement and proper binning for bifacial module fabrication, in order to reduce mismatch loss and mitigate reliability risk. 6Canadian Solar Inc. 2. Normative references IEC 60891, Photovoltaic devices – Procedures for temperature and irradiance corrections to measured I-V characteristics IEC 60904-1, Photovoltaic devices – Part 1 Measurement of photovoltaic current-voltage characteristics IEC 60904-1-2, Photovoltaic devices – Part 1-2 Measurement of current-voltage characteristics of bifacial photovoltaic PV devices CDV IEC 60904-2, Photovoltaic devices – Part 2 Requirements for reference solar devices IEC 60904-3, Photovoltaic devices – Part 3 Measurement principles for terrestrial photovoltaic PV solar devices with reference spectral irradiance data IEC 60904-4, Photovoltaic devices – Part 4 Reference solar devices - Procedures for establishing calibration traceability IEC 60904-7, Photovoltaic devices – Part 7 Computation of the spectral mismatch correction for measurements of photovoltaic devices IEC 60904-8, Photovoltaic devices – Part 8 Measurement of spectral responsivity of a photovoltaic PV device IEC 60904-9, Photovoltaic devices – Part 9 Solar simulator performance requirements IEC 61836, Solar photovoltaic energy systems – Terms, definitions and symbols 7Canadian Solar Inc. 3. Terms and definitions Bifacial fitting coefficient Bifacial fitting coefficient is used to fit I-V characteristic of bifacial cells under double-side illumination by the measured I-V characteristics of bifacial cells under single-side illumination, typically at Standard Test Conditions STC unless otherwise specified. It contains a series of fitting coefficients ✓ the short-circuit current fitting coefficient 𝑘𝐼𝑠𝑐 ✓ the open-circuit voltage fitting coefficient 𝑘𝑉𝑜𝑐 ✓ the maximum power fitting coefficient 𝑘𝑃𝑚𝑎𝑥 Overall efficiency Overall efficiency is the compositive efficiency in consideration of front side efficiency and rear side efficiency for bifacial cells. It is a parameter which would assess the power generation capacity of a bifacial cell in bifacial illumination. 𝜂𝐵𝑖𝐹𝑖𝑁 𝑃𝑚𝑎𝑥𝐵𝑖Fi𝑁𝑆 1000𝑊 𝑚−2 ✓ 𝑆 is the area of the cell. ✓ 𝑃𝑚𝑎𝑥𝐵𝑖Fi𝑁 is the overall maxim power at bifacial illumination condition 𝐵𝑖𝐹𝑖𝑁, which is STC on front side and 𝑁 on rear side. ✓ 𝑁 can be 0, 100, 200, 300, etc, corresponding to rear illumination conditions of 0𝑊 ∙𝑚−2、 100𝑊 ∙𝑚−2, 200𝑊 ∙𝑚−2, 300𝑊 ∙ 𝑚−2 etc. In these cases, illumination condition could be marked as 𝐵𝑖𝐹𝑖0, 𝐵𝑖𝐹𝑖100, 𝐵𝑖𝐹𝑖200, 𝐵𝑖𝐹𝑖300, etc. 8Canadian Solar Inc. 4. Apparatus 4.1 For measurement by double-side simultaneous illumination A solar simulators system, as defined in IEC 60904-9, with the capability to provide illumination on both sides of the bifacial PV cells simultaneously and illumination on each side of the bifacial PV cells separately; Front illumination must be able to provide irradiance levels above 1000 Wm-2. Rear illumination must be able to provide adjustable irradiance level from 0 to 1000 Wm-2. The spectra of rear illumination should be the same as front illumination. Optional simultaneous simulator systems are showed as below Front simulator Sample Rear simulator Front simulator Sample Rear reflective light source Double simulator system Single simulator and reflector system 9Canadian Solar Inc. 4. Apparatus 4.2 For measurement by double-side sequential illumination A solar simulators system, as defined in IEC 60904-9, with the capability to provide illumination on single side of the bifacial PV cells separately; Front illumination must be able to provide irradiance levels above 1000 Wm-2. Rear illumination must be able to provide adjustable irradiance level from 0 to 1000 Wm-2. The spectra of rear illumination should be the same as front illumination. Optional sequential simulator system is showed as below Front simulator Sample Rear simulator Sample Sequential simulator system Flipper 10Canadian Solar Inc. 5. Measurement method Due to the mismatched spectral responses between front-side and rear-side of the bifacial PV cells, separate calibrations to both sides of the bifacial PV cells are necessary. The measurement by double-side simultaneous illumination is preferred, especially for inline measurement in production line. Alternatively, the measurement by double-side sequential illumination and determining overall I-V characteristics by fitting can be used. Alternatively, if the variation in bifaciality of to-be-test bifacial PV cells is within 5 range, the measurement by single-side STC illumination and determining overall I-V characteristics by fitting can also be used. 11Canadian Solar Inc. 5. Measurement method 5.1 Measurement by double-side simultaneous illumination Procedure Step 1 Measure the front STC I-V characteristics 𝑃𝑚𝑎𝑥𝑓, 𝐼𝑠𝑐𝑓, 𝑉𝑜𝑐𝑓. Step 2 Measure the rear I-V characteristics 𝑃𝑚𝑎𝑥𝑟, 𝐼𝑠𝑐𝑟, 𝑉𝑜𝑐𝑟. Step 3 Measure the overall I-V characteristics, under STC illumination on the front side and 𝑁 𝑊 ∙ 𝑚−2 on the rear side 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁, 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁, 𝑉𝑜𝑐𝐵𝑖𝐹𝑖𝑁. Typically, 𝑁 is 200. 𝐵𝑖𝐹𝑖200 means STC illumination on the front side and 200𝑊 ∙𝑚−2 on the rear side. Step 1, step 2 and step 3 can be conducted in any sequence. Example of an irradiance and measurement procedure Step A Rear-side STC irradiance, measure the rear STC I-V Step B Bifacial irradiance, measure the overall I-V Step C Front-side STC irradiance, measure the front STC I-V 12Canadian Solar Inc. 5. Measurement method 5.2 Alternative measurement by double-side sequential illumination Procedure Step 1 Measure the front STC I-V characteristics 𝑃𝑚𝑎𝑥𝑓, 𝐼𝑠𝑐𝑓, 𝑉𝑜𝑐𝑓. Step 2 Measure the rear I-V characteristics 𝑃𝑚𝑎𝑥𝑟, 𝐼𝑠𝑐𝑟, 𝑉𝑜𝑐𝑟. Step 3 Calculate the overall I-V characteristics equivalent to double-side simultaneous illumination 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁, 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁, 𝑉𝑜𝑐𝐵𝑖𝐹𝑖𝑁, 𝐹𝐹𝐵𝑖𝐹𝑖𝑁 as below Step 1 and step 2 can be conducted in any sequence 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁 𝑃𝑚𝑎𝑥𝑓 𝑃𝑚𝑎𝑥𝑟 𝑁1000𝑘𝑃𝑚𝑎𝑥 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁 𝐼𝑠𝑐𝑓 𝐼𝑠𝑐𝑟 𝑁1000 𝑘𝐼𝑠𝑐 𝑉𝑜𝑐𝐵𝑖𝐹𝑖𝑁 𝑉𝑜𝑐𝑓 𝐿𝑛1𝐼𝑠𝑐𝑟𝐼𝑠𝑐 𝑓 𝑁1000𝑘𝑉𝑜𝑐 𝐹𝐹𝐵𝑖𝐹𝑖𝑁 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁𝑉𝑜𝑐 𝐵𝑖𝐹𝑖𝑁 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁 ✓ 𝑘𝑃𝑚𝑎𝑥, 𝑘𝐼𝑠𝑐 and 𝑘𝑉𝑜𝑐 are bifacial fitting coefficient of maximum power, short-circuit current and open-circuit voltage. 13Canadian Solar Inc. 5. Measurement method 5.3 Alternative measurement by single-side STC illumination Alternatively, if the variation in bifaciality of to-be-test bifacial PV cells is within 5 range, the measurement by single-side STC illumination can be used. Procedure Step 1 Sample the front STC and rear STC I-V characteristics of bifacial PV cells in the production line. Sampling rate greater than 1 is recommended. Then calculate the average maximum power bifaciality 𝜑𝑃𝑚𝑎𝑥 and short circuit current bifaciality 𝜑𝐼𝑠𝑐. Step 2 For the to-be-test bifacial PV cells, measure the front STC I-V characteristics of to-be-test bifacial PV cells 𝑃𝑚𝑎𝑥𝑓, 𝐼𝑠𝑐𝑓, 𝑉𝑜𝑐𝑓. Step 3 For the to-be-test bifacial PV cells, calculate the rear STC I-V characteristics of to-be-test bifacial PV cells 𝑃𝑚𝑎𝑥𝑟, 𝐼𝑠𝑐𝑟, 𝑉𝑜𝑐𝑟, using the sampled 𝜑𝑃𝑚𝑎𝑥 and 𝜑𝐼𝑠𝑐 as below 𝑃𝑚𝑎𝑥𝑟 𝑃𝑚𝑎𝑥𝑓 𝜑𝑃𝑚𝑎𝑥 𝐼𝑠𝑐𝑟 𝐼𝑠𝑐 𝜑𝐼𝑠𝑐 14Canadian Solar Inc. 5. Measurement method Step 4 For the to-be-test bifacial PV cells, calculate the overall I-V characteristics equivalent to double-side simultaneous illumination 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁, 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁, 𝑉𝑜𝑐𝐵𝑖𝐹𝑖𝑁, 𝐹𝐹𝐵𝑖𝐹𝑖𝑁 as below 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁 𝑃𝑚𝑎𝑥𝑓 𝑃𝑚𝑎𝑥𝑓 𝜑𝑃𝑚𝑎𝑥 𝑁1000𝑘𝑃𝑚𝑎𝑥 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁 𝐼𝑠𝑐𝑓 𝐼𝑠𝑐𝑓 𝜑𝐼𝑠𝑐 𝑁1000 𝑘𝐼𝑠𝑐 𝑉𝑜𝑐𝐵𝑖𝐹𝑖𝑁 𝑉𝑜𝑐𝑓 𝐿𝑛1𝜑𝐼𝑠𝑐 𝑁1000𝑘𝑉𝑜𝑐 𝐹𝐹𝐵𝑖𝐹𝑖𝑁 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁𝑉𝑜𝑐 𝐵𝑖𝐹𝑖𝑁 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁 ✓ 𝑘𝑃𝑚𝑎𝑥, 𝑘𝐼𝑠𝑐 and 𝑘𝑉𝑜𝑐 are bifacial fitting coefficient of maximum power, short-circuit current and open-circuit voltage. ✓ These bifacial fitting coefficients are calculated by minimizing the deviation from the fitted overall I-V characteristics and the directly measured overall I-V characteristics by double-side simultaneous illumination. 15Canadian Solar Inc. 6. Sorting suggestion The overall I-V characteristics is more relevant to the actual outdoor operation of bifacial PV cells and modules with both side illumination. Sorting the bifacial PV cells by overall I-V characteristics is recommended in production line. Alternatively, sorting the bifacial PV cells by front-side I-V characteristics only can be used. Alternatively, sorting the bifacial PV cells by both front-side and rear-side I-V characteristics can also be used. 16Canadian Solar Inc. 6. Sorting suggestion 6.1 Sorting by the overall I-V characteristics Sorting the bifacial PV cells by overall efficiency 𝜂𝐵𝑖𝐹𝑖𝑁 is recommended in production line. The binning by overall efficiency with 0.1 gap or 0.15, 0.2 etc. is recommended. Sub-binning by short-circuit current 𝐼𝑠𝑐 or current at maximum power point 𝐼𝑚𝑝𝑝 in the same efficiency bin is highly desirable in order to reduce the mismatch loss in bifacial module fabrication. In the case of rear illumination condition 𝑁 is 0 𝑊 ∙𝑚−2 , the bifacial PV cells are sorted only by front STC I-V characteristics. The choose of rear illumination condition 𝑁 is determined by the manufacturer and customer needs. 17Canadian Solar Inc. 6. Sorting suggestion 6.2 Sorting by front-side I-V characteristics only Sorting the bifacial PV cells by front-side I-V characteristics only. The binning by front-side STC efficiency with 0.1 gap is recommended. The sub-binning by 𝐼𝑠𝑐 or 𝐼𝑚𝑝𝑝 in the same efficiency bin is highly desirable. The choose of efficiency gap for binning and sub-binning is determined by the manufacturer and customer needs. 6.3 Sorting by both front-side and rear-side I-V characteristics Sorting the bifacial PV cells by both front-side and rear-side I-V characteristics. The binning by front-side STC efficiency with 0.1 gap and also rear-side STC efficiency with 0.5 efficiency gap is recommended. The sub-binning by 𝐼𝑠𝑐 or 𝐼𝑚𝑝𝑝 in the same efficiency bin is highly desirable. The choose of efficiency gap for binning and sub-binning is determined by the manufacturer and customer needs. 18Canadian Solar Inc. 7. Report Report should include at least ✓ Specifications of the tested bifacial PV cells; ✓ Measurement method, i.e. double-side simultaneous illumination or single-side STC illumination; ✓ Rear illumination condition 𝑁, i.e. 0, 100, 200 or 300 𝑊 ∙𝑚−2. ✓ Measurement results, i.e. the front STC I-V characteristics 𝑃𝑚𝑎𝑥𝑓, 𝐼𝑠𝑐𝑓, 𝑉𝑜𝑐𝑓, the overall I-V characteristics 𝑃𝑚𝑎𝑥𝐵𝑖𝐹𝑖𝑁, 𝜂𝐵𝑖𝐹𝑖𝑁, 𝐼𝑠𝑐𝐵𝑖𝐹𝑖𝑁, 𝑉𝑜𝑐𝐵𝑖𝐹𝑖𝑁, 𝐹𝐹𝐵𝑖𝐹𝑖𝑁, bifaciality coefficient 𝜑𝑃𝑚𝑎𝑥 , 𝜑𝐼𝑠𝑐. ✓ Sorting information, i.e. average efficiency, average power and bifaciality coefficient of each binning. ✓ In case of measurement by single-side STC illumination, the RMSE deviation Root Mean Square Error between the fitted overall I-V characteristics and the measured overall I-V characteristics by double-side simultaneous illumination should be provided. ✓ Other measurement details, i.e. personnel, equipment, data. 19Canadian Solar Inc. THANKS QA 20Canadian Solar Inc. Appendix 1 Validation of fitting by single-side illumination A Deviation Analysis 21Canadian Solar Inc. 1st round Canadian Solar mono-PERC and multi-PERC bifacial cells, 1200 cells each. The front STC, rear STC and bifacial illumination STC on front side and 200 𝑊 ∙𝑚−2 on rear side I-V characteristics are measured by the HALM bifacial I-V tester at AIKO Solar. 0 .7 7 00 .7 5 60 .7 4 20 .7 2 80 .7 1 40 .7 0 00 .6 8 60 .6 7 2 L S L U S L L S L 0 .6 6 3 目标 * U S L 0 .7 6 3 样本均值 0 .7 1 3 1 8 样本 N 9978 标准差（组内） 0 .0 0 7 4 4 0 3 1 标准差（整体） 0 .0 1 1 5 9 7 4 过程数据 Cp 2 .2 4 C P L 2 .2 5 C P U 2 .2 3 C p k 2 .2 3 Pp 1 .4 4 PPL 1 .4 4 PPU 1 .4 3 P p k 1 .4 3 C p m * 整体能力 潜在（组内）能力 P P M U S L 4 0 0 .8 8 P P M 合计 5 0 1 .1 0 实测性能 P P M U S L 0 .0 0 P P M 合计 0 .0 0 预期组内性能 P P M U S L 8 .7 0 P P M 合计 1 6 .2 7 预期整体性能 组内 整体 单晶双面电池实测效率双面率分布（7 1 .3 5 ）的过程能力 Mono-PERC bifacial cells Average bifaciality 71.3 STDEV 1σ 1.16 Multi-PERC bifacial cells Average bifaciality 73.6 STDEV 1σ 1.34 22Canadian Solar Inc. Step 1 Measure the I-V characteristics of 1200pcs sampled bifacial cells. Step 2 Calculate the overall I-V characteristics BiFi’ of the cells 1-600 by front STC, rear STC and initial fitting coefficient k. Step 3 Determine optimum fitting coefficient k by minimizing RMSE_1 for cells of 1-600 Step 4 Calculate the overall I-V characteristics BiFi’ and RMSE_2 of the cells 601-1200 by front STC, rear STC and optimum fitting coefficient k. Step 5 Sample the bifaciality by average of cells 1-50 4 sampling rate, to present the bifaciality of 1200pcs of cells. Step 6 Calculate the overall I-V characteristics BiFi’’ and RMSE_3 of the cells 1-1200 by front-side STC, sampled bifaciality 𝜑, and optimum fitting coefficient k. Front STC 𝑃𝑚𝑝𝑝 𝑓 , 𝑉𝑜𝑐 𝑓 , 𝐼𝑠𝑐 𝑓 , 𝐹𝐹 𝑓 Rear STC 𝑃𝑚𝑝𝑝 𝑟 , 𝑉𝑜𝑐 𝑟 , 𝐼𝑠𝑐 𝑟 , 𝐹𝐹 𝑟 BiFi 𝑃𝑚𝑝𝑝 𝐵𝑖𝐹𝑖 , 𝑉𝑜𝑐 𝐵𝑖𝐹𝑖 , 𝐼𝑠𝑐 𝐵𝑖𝐹𝑖 , 𝐹𝐹 𝐵𝑖𝐹𝑖 𝑃𝑚𝑝𝑝 𝐵𝑖𝐹𝑖′ 𝑃𝑚𝑝𝑝 𝑓 𝑃𝑚𝑝𝑝 𝑟 ∗0.2∗�