Introduction: In the first two articles, the author mainly expounded the design methods of traditional strings, pointed out the shortcomings of the traditional methods and put forward personal improvement ideas. Today, the author carried out further analysis on improving traditional design methods. 1. What restrictions are imposed on 24 string solutions? Through the above calculations, it can be found that the design of the serial number is affected by three parameters. 1) Extreme low temperature of the project site If 260W components are used, When the extreme low temperature = -30°C, 24-string designs can be used. When the extreme low temperature is -40°C, 23 string designs should be adopted. Therefore, in the southeastern region where the temperature is relatively high, a 24-string scheme is feasible; however, in many places in the northwestern region (Inner Mongolia, Xinjiang, Gansu, Qinghai, etc.), extreme cold temperatures may reach -40°C and 24 clusters. The plan is not feasible. 2) The nominal power of the component The greater the nominal power of the component, the greater the open circuit voltage. The same as TRW 60 pieces, when extreme low temperature = -30°C, When using 260W components, 24-string designs can be used. When using a 290W monocrystalline module (Voc=39.5V, even under NOCT conditions, Voc=36.6V), 23-string designs should be used. 3) Component temperature coefficient The temperature coefficients of the components of different manufacturers are different. The larger the absolute value of the temperature coefficient, the smaller the number of series connections. If a 260W component is used, extreme low temperature = -35°C, When the temperature coefficient is -0.32%/°C, a 24-string solution can be used; When the temperature coefficient is -0.33%/°C, theoretically 23 strings should be used. 2. What are the benefits of using 24-string solutions? Compared with the design scheme of 22 components per string, the 24 component solution can reduce project investment to a certain extent and reduce line loss. 1) Reduce project investment The same 265W component is used, When each array uses a 22*2 block solution, 86 arrays of 172 branches can form a power unit with a capacity of 1.00276 MWp; When each array uses a 24*2 block solution, 79 arrays of 158 branches can form a unit with a capacity of 1.00488 MWp. Each unit saves 7 arrays. The amount of steel used for the brackets does not change much, but the basic investment will be reduced by about 8%. Each unit saves 14 branches and saves 1 combiner box. 2) Reduce line loss On the one hand, as the number of branches is reduced by 8%, the amount of cables from the assembly to the combiner box is reduced and the line loss is reduced; On the other hand, the number of components per series branch increased by 9.1% and the voltage per branch increased by approximately 9.1%. Since the line loss is proportional to the square of the voltage, the line loss from the assembly to the combiner box can be reduced by approximately 17.4%. If the DC line loss from the component to the combiner box accounts for 1% of the total power generation, the overall system efficiency brought about by the adjustment of the plan will increase by approximately 0.14%. summary Photovoltaic modules adopt a design scheme of 24 modules per string, which has a certain positive effect on the increase of power generation and cost reduction of the project. However, the number of strings in each string is affected by factors such as the extreme low temperatures of the project site, the nominal power of the components, and the component temperature coefficient. Therefore, not all conditions apply to this scheme. In actual application, it is necessary to use calculations according to the conditions of the location of the project. Heat Proof Pvc Roof Tile,Heat Proof Pvc Roof Sheet,Pvc Plastic Translucent Tile,Heat Resistance Roof Tile ZHENHAO BUILDING MATERIALS CO.,LTD , https://www.zhpvctile.com
Reflections on the Series Design of Photovoltaic Modules (Part 2) - In-Depth Design Improvements