210 VS 182, what is the truth?

Recently, the industry has once again been arguing over size, with the controversy over 166, 180, and 210 continuing from research and development to mass production. In fact, in the history of the photovoltaic industry's technological development, there has always been controversy over technology, but MBB, which was previously criticized by relevant technical personnel, has become the mainstream of the industry. Looking at the current size dispute, from the perspective of new production capacity, 210 compatible with 182 has become the standard for new production capacity in the industry, and 182 is just an effective component of 210 new production capacity, a low-efficiency model of new production capacity. The entire industry is voting with action, and the advantages of 210 and the tide of the times are unstoppable.

Through objective and detailed calculations, this article analyzes the inverter matching, cable selection, bracket cost, floor space, and installation and transportation of 210 component products one by one, revealing the technical truth behind the use of 210 component and 182 component systems.

Next, we compare the application side and select three 210 and 182 mainstream products for a comparative analysis. The product parameters can be publicly queried online, as shown in Table 1.

Table 1 Main parameters of components

Note: M10-72-540 is a 540Wp module using 182 cells and 72 cells in a package, M10-78-580 is a 580Wp module using 182 cells and 78 cells in a package, and G12-60-600 is a 600Wp module using 210 cells and 60 cells in a package. Same as below.

1. Inverter matching

1Centralized inverter:

Since the centralized inverter uses a DC busbar wiring method, the number of connected strings and the current of each string can be flexibly configured, so the matching of 210 components and centralized inverters is basically not affected by large currents; as shown in Figure 1, the centralized inverter system solution topology shows that when the short-circuit current of the component increases, it is only necessary to replace the combiner box fuse and the inverter DC fuse to achieve the adaptation of the high-current component, and it can be flexibly selected for different short-circuit currents of the components. At the same time, according to the actual power station situation, different combiner box input routes are selected and different combiner boxes are configured to meet the capacity ratio requirements of different projects.

Figure 1 Centralized inverter system solution topology

As shown in Table 1, the 600Wp 210 series modules have a maximum power point operating current Impp of 17.28A and a short-circuit current of 18.6A. According to the relevant IEC62548 standard requirements, the corresponding input fuse of each combiner box is selected to be 30A, and it can adapt to the bifacial gain of the bifacial modules.

2 sets of string inverters:

At present, major inverter manufacturers such as Sungrow and Huawei have launched products with a single string input current of 15A. After a simple line modification, this type of inverter is fully applicable to the 210 series of high-current components. Taking the Sungrow SG225HX product as an example, the maximum input current of each MPPT is 30A. After connecting two MPPTs in parallel, three components can be connected (as shown in Figure 2), which is highly suitable for the current use of 210 bifacial components.

The newly developed high-current string inverters of these mainstream inverter manufacturers will also be available on the market by the end of this year or in the first half of 2021.

Figure 2 SG225HX string inverter system topology

2. Cable Selection

There are two types of photovoltaic dedicated cables: PV1-F 1x4mm2 and PV1-F 1x6mm2. The current carrying capacity of PV1-F 1x4mm2 cable can reach 40A, which meets the maximum operating current requirements of 210 product 600Wp components as shown in Table 1. Even when using 210 bifacial components, it can fully meet the use of its maximum operating current greater than 20A.

Regarding the line loss issue that everyone is concerned about, the following analysis can be used to explain it to you.

A simple calculation method for photovoltaic module cable loss is shown in the following formula. The magnitude of line loss is related to the cable cross-section, length, and current.

in,

Im is the working current of the component, in A;

L is the length of the DC cable, in meters;

r is the line resistance of the DC cable, in Ω/m;

Pm is the power of the module under STC conditions, in W;

N is the number of components.

The PVSYST software was used to simulate the power generation of 182 and 210 bifacial modules. The 182 modules used 4mm2 DC cables, and the 210 modules used 4mm2 or 6mm2 DC cables. The line loss difference between the two modules was compared. The simulation location was Hami, a Class I region in China. The module height was 1 meter above the ground, and the surface reflectivity was 30%. The simulation results are shown in Table 2:

Table 2. PVSYST simulation of two types of component line losses and comparison

From Table 2 we can see

1) If 4mm2 DC cables are used, the line loss of 210 modules is slightly higher than that of 182 modules by 0.16%. There are many factors that affect the power generation of photovoltaic power stations. Among them, the power generation loss caused by factors such as shadow obstruction, dust accumulation, and low irradiation of modules is about 1% to 2%. The difference of 0.16% in line loss has a relatively small impact on the power generation. At the same time, the amount of DC cables used in 210 modules can be reduced by about 14% compared to 182 modules, which can reduce BOS costs. Comprehensively considered, 210 modules use 4mm2 cables, even if the line loss is slightly higher than that of 182 modules, but in the end it has almost no impact on the cost per kilowatt-hour;

2) If the 210 module uses 6mm2 DC cables, the line loss is reduced by 0.11% compared to the 182 module. The reduction in the use of 6mm2 cables can basically offset the increase in cost per meter, and the total cable cost remains basically unchanged. Comprehensively calculated, the use of 6mm2 cables for 210 modules can reduce the system LCOE. In actual projects, 4mm2 or 6mm2 cables can be flexibly selected according to the actual situation of the project.

3. Cost of bracket

1. Fix the bracket

Generally speaking, the cost of a fixed bracket = material cost/installed capacity. The conventional calculation method is to take a bracket unit (usually 2 strings of components), refine the components of each part of the bracket, calculate the theoretical weight, and then calculate the total material cost based on the corresponding market price. The material cost is mainly determined by the amount of steel used, and the amount of steel used depends on the length and cross-sectional dimensions of the main components of the bracket. For example, under the same bracket form, the larger the component installation area, the larger the windward area of ​​the array, and the larger the length and cross-sectional dimensions of the corresponding main components.

Taking a 20MW fish-solar complementary project as an example, the mainstream M10 and G12 bifacial modules on the market are used. According to the mainstream installation method of bifacial modules, four horizontal rows are installed, and the single column bracket form is used. Two strings are placed in a single array, and the bracket designs are carried out separately, as shown in Table 3:

Table 3. Two product bracket designs

Compared with M10 modules, G12 modules have a much larger number of strings and a much larger single array power due to their low voltage characteristics. At the same time, because the modules are wider, the cross-sectional area of ​​the main components such as beams and columns also increases accordingly. In order to accurately compare the three arrays, we follow the principle of consistent stress values ​​of the components of the arrays and check the bearing capacity of the brackets of the three arrays. As shown in Figure 3

Figure 3. Stress cloud diagram of each component of the bracket

Table 4. Cross-section of each component:

Table 5. Stent cost breakdown:

The cross-sections and cost details of each component determined by calculation are shown in Tables 4 and 5 (in order to ensure the same stress value, this article quotes some unconventional cross-sections, which have no effect on the theoretical calculation results). The G12 module has a wider module and a corresponding increase in the cross-section of the main components, but due to its array power advantage, it still has an advantage of nearly 1 cent compared to the M10-72-540W module, and compared to the higher voltage M10-78-580W module, the bracket cost advantage is even greater.

2. Tracking bracket

Tracking brackets mainly include mechanical parts and electrical control parts. The mechanical part is similar to the fixed bracket. The main components (such as main beams and connectors) usually have unchanged cross-sections, and the length is adjusted according to the component specifications. The electrical control part is usually a standardized design. A set of electrical control parts can usually control arrays within a certain length range. This means that within the range allowed by the electrical control part, adjusting the mechanical part to maximize the installed capacity is a shortcut to reduce the cost of tracking brackets.

According to a leading tracking bracket company, taking into account the bracket vibration, overall stiffness and wind tunnel test conditions, the maximum length of components that can be installed on a common 2P flat single-axis bracket is 2.4 meters.

Taking a project in the Middle East (the lowest temperature at the project site is about 25°C) using a mainstream manufacturer's 2P flat single-axis conventional product as an example, the cost of M10 and G12 components is compared (the length of the M10-78-580 component has exceeded the maximum length and does not affect the theoretical comparison results). See Table 6.