With the transformation and upgrading of the photovoltaic power generation technology in China, the innovative photovoltaic power generation solutions with both efficiency and reliability are emerging endlessly, including the bifacial solar cell photovoltaic module technology developing rapidly in recent years, and simultaneously such photovoltaic companies in the forefront of technological changes as JOLYWOOD are committed to promoting the further decline in the cost of this breakthrough technology and the large-scale applications, so as to inject new momentum for photovoltaic module manufacturing industry.
The bifacial solar cell photovoltaic module is such a device that can generate current and voltage with both sides accessible to the sunlight. Compared with single-side modules, the bifacial solar cell photovoltaic module integrating the bifacial cell technology can have its back generate power and its total power generation can achieve a significant increase with more gain obtained.
The I-V test of the traditional single-side solar cell modules follows the IEC 60904 series standards in such standard test conditions (STC: irradiance = 1000W/㎡, cell temperature = 25℃, AM = 1.5). However, due to the characteristics of the bifacial power generation, it is rather difficult to test the output power of the front and rear sides and there has been no uniform standard test method so far in the world. Therefore, how to accurately calibrate the power of the bifacial solar cell modules has become a difficult problem urgently to be solved, firstly the significant differences between buyers and sellers in power calibration have seriously restricted the commercialization of the product; on the other hand, the ultimate nominal value of the bifacial module power will directly affect the system design of the terminal power station.
In order to solve this problem and standardize the test methods and power calibration of the bifacial solar cell photovoltaic modules, recently, TUV NORD, National Photovoltaic Testing Center and JOLYWOOD have joined hands in strength to hold the Seminar on Test Methods of Bifacial Solar Cell Modules in Wuxi. Based on the long-term outdoor testing, laboratory research validation and collection of enough firsthand data, the I-V test method has been preliminarily confirmed after discussion for bifacial solar cell modules, including the test conditions, test methods and processes, nominal requirements for module nameplates, test reports and other relevant contents. At the same time, the corresponding recommended values of the standard also have been proposed in accordance with the installation sites in different background.
The rear reflectivity R has its recommended value of 10%, and if converted to the STC conditions, it indicates the front and rear irradiation intensity of 1000 W/m2 and 100 W/m2 respectively. The bifaciality (BiFi) is defined as follows: BiFi = Iscrear/Iscfront, used to evaluate the power generation capacity of the module rear relative to its front and usually expressed in percentage; Iscfront It indicates the short circuit current value measured on the front in the STC conditions with the module rear effectively sheltered; Iscrear It indicates the short circuit current value measured on the rear in the STC conditions with the module front effectively sheltered.
After testing is completed in accordance with the recommended test scheme, we can work out the reflection compensation current Isccomp and the reflection compensation irradiance Gcomp. Isccomp=Iscfront +R*Iscrear=Iscfront+0.1*BiFi*Iscfront=(1+0.1*BiFi)*Iscfront。
Adjust the solar simulator to have irradiation intensity satisfy the irradiance Gcomp of bifacial photovoltaic modules, and test the photovoltaic I-V characteristics of the bifacial photovoltaic modules in case of the irradiation intensity Gcomp and temperature of 25℃.
This test method has such characteristics as follows:
1. In view of the methods for calibrating Level-1 on-gauge plates of the modules in a third-party laboratory and for calibrating Level-2 on-gauge plates during the process of factory production, the test requirements mutually matched have been applied, which has not only guaranteed the accuracy of the Level-1 on-gauge plates and simultaneously ensured the production efficiency of the Level-2 on-gauge plates on the premise that the actual mass production has been effectively used.
2. The current test has shown such test information as the bifaciality, rear reflectivity R, test conditions, compensation irradiance, electric performance parameters and test uncertainty, standardized the requirements for test reports and nameplate nomination and presented the details more comprehensively, so it boasts more reference values.
3. Based on the difference of the installation background, this scheme has accordingly regulated the reflectivity R of different rears.
This test scheme has been proposed based on the relevant IEC standards and a large number of verification data, aiming to serve as one of the effective solutions on how to accurately calibrate the power of bifacial solar cell modules.
Jolywood (Taizhou) Solar Technology Co., Ltd. is dedicated to the development and large-scale manufacturing of N-type monocrystalline bifacial solar cells. It has built up the production line for the world’s largest 2.1GW N-type monocrystalline bifacial solar cells and 5600 square meters’ efficient solar cell research and development center, with annual sales of nearly 5 billion yuan. Its parent company Jolywood (Suzhou) Sunwatt Co., Ltd. (SZ300393), founded in 2008, succeeded in listing of the GEM (growth enterprise market) in 2014 as the world’s largest professional manufacturer of photovoltaic back panels and has been making great efforts to establish itself as the global first-class product integration and manufacturing operator leading in the field of photovoltaic modules.
The National Center of Supervision and Inspection on Solar Photovoltaic Product Quality (CPVT for short) is China’s first national-level statutory photovoltaic product inspection institution approved by AQSOQ. The Center laboratory has been recognized by the CB laboratory of the IEC Conformity Assessment for Electrotechnical Equipment and Components (IECEE) and the national laboratory CNAS, the test results boast mutual recognition in the international market, third-party impartiality and sufficient legal effect and CPVT will always be committed to actively serving enterprises for quality enhancement, efficiency improvement and industrial transformation and upgrading and actively boosting the healthy and rapid development of the photovoltaic industry in China.
TUV NORD Group is a global leading technology provider for evaluating the safety, performance and quality of photovoltaic products. It is not only dedicated to providing the comprehensive testing and certification services of the whole supply chain from the solar photovoltaic modules and spare parts to the photovoltaic power generation system for manufacturers, installers, service providers and investors, but also to broad cooperation with the electric power companies, insurance, banking, funds, investors and EPC etc. So far, the global market access service of TUV NORD has covered 16 countries in Asia, Europe, Africa, Oceania, North America and South America.