NINGBO, China, Oct. 24, 2022 -- With the rapid development of PV technology from p-type to n-type, the difference in power generation of different cell technology products are drawing more and more attention. Nowadays the mainstream cell technologies are PERC, TOPCon and HJT. Each of them has its own advantages and disadvantages, but the comparative research on power generation is still lack of systematic whole-life cycle comparison based on the perspective of global application scenarios.

To this end, the core parameters of above mentioned three technologies are collected and the power generation of utility-scale power plants with these three different cell technology panels over a 25-year life cycle in 21 typical countries and regions with different climatic environments around the world are measured by Risen Energy Co., Ltd to create a comparison map of global power generation gains.

I. Global power generation gains Map（HJT vs PERC/TOPCon）

Globally, HJT technology products have higher power generation, which is 4.37%-6.54% higher than PERC and 1.25%-3.33% higher than TOPCon. and its power generation performance is more outstanding especially in high temperature regions (e.g. the Middle East, Australia and the southern US), with  6%+ gain compared to PERC and 3%+ gain compared to TOPCon. As shown in Figure 1.1.

Figure 1.1 Map of global power generation gains

Figure 1.1 Map of global power generation gains

II. Technical analysis of modules

Based on the characteristics of the modules, the power generation gap between different cell technologies in each region on the map is mainly caused by three factors: temperature coefficient, bifacial factor and power degradation, which is why the HJT modules can deliver higher power generation gains and more stable power yield for the PV system with its extremely stable temperature coefficient, higher bifacial factor and higher power retention.

2.1 Extremely stable temperature coefficient

Compared to the power temperature coefficient of -0.35%/°C for PERC and -0.32%/°C for TOPCon, HJT modules have a more stable power temperature coefficient of -0.24%/°C, which means the HJT modules are of lower power degradation compared to PERC and TOPCon modules as the module operating temperature rises, thus reducing the power generation loss, and this power generation gain advantage will be especially in case of high operating environment temperature, as shown in Figure 2.1.

  • At an operating temperature of 60°C, the relative power of HJT modules is 2.8% higher than that of TOPCon modules and 3.5% higher than that of PERC modules.
  • At an operating temperature of 65°C, the relative power of HJT modules is 3.2% higher than that of TOPCon modules and 4% higher than that of PERC modules.

Figure 2.1 PERC/TOPCon/HJT power and temperature correspondence curves

Figure 2.1 PERC/TOPCon/HJTpower and temperature correspondence curves

2.2  Higher bifacial factor

With natural symmetrical structure, the HJT cell is inherently a bifacial cell and is the cell technology with the highest bifacial factor at present, as shown in Figure 2.2. Under the same application scenario, the higher the bifacial factor, the greater the backside power generation gain. The HJT modules' bifacial factor is around 85%, which is about 15% higher than PERC modules and approximately 5% higher than TOPCon modules, as shown in Table 2.1.

Figure 2.2 Structure of HJT cell

Figure 2.2 Structure of HJTcell

Table 2.1 Bifacial factor of PERC/TOPCon/HJT modules

Table 2.1 Bifacial factorof PERC/TOPCon/HJT modules

In the same utility-scale ground-mounted power plant application scenario, the higher bifacial factor of HJT modules brings high power generation gain compared to that of PERC and TOPCon modules.

2.3 Higher power retention

Based on the power degradation curves of the three different cell technologies, it is clear that by the end of year 25, the power retention rate of HJT modules is 92%, while that of PERC modules is 87.2% and that of TOPCon modules is 89.4%. This means HJT products is of the best power output retention in the whole life cycle of utility-scale power plants, which can lead to more stable and relatively higher power generation, as shown in Figure 2.3.

Since the above discussed results are reckoned with the current 2% first-year degradation, the power generation gain advantage will be more remarkable as the improvement of cell and module encapsulation technology and materials can lead to less first-year degradation of the HJT products.

Figure 2.3 Product warranty of PERC/TOPCon/HJT module

Figure 2.3 Product warrantyof PERC/TOPCon/HJT module

Above is a brief analysis of the performance of HJT cells and modules. However, what are the main factors that affect the power generation of the modules? How significant is the impact? Risen Energy tried to carry out further parsing by PVSYST. 

III. PVSYST analysis

In terms of influence factors for power generation, a typical high and low temperature application scenarios will be selected for analysis respectively.

3.1 Low temperature application scenarios

Harbin is chosen as a typical example for low temperature application scenario, which is located near 45.9°N with an average annual temperature of 4.7°C and a total horizontal radiation of 1347 KWh/m2. The power plant is designed with a DC/AC ratio of 1.25 and an installed capacity of 4MW (with slight variations in the actual design), using fixed bracket with optimal tilt angle and suitable string inverters. By year 25, TOPCon's power generation gain is 3.94% and HJT's power generation gain is even higher at 7.73% compared to PERC's power generation, as shown in Table 3.1.

Table 3.1 Comparison of PERC/TOPCon/HJT power generation gain

Table 3.1 Comparison ofPERC/TOPCon/HJT power generation gain

According to the loss comparison, the most important factor affecting power generation in low temperature applications is power degradation. At the end of year 25, the power degradation is 12.86% (1.6% + 11.26%) for the PERC modules, 10.6% (0.6% + 10%) for the TOPCon modules and 7.87% (1.6% + 6.27%) for the HJT modules. See Figure 3.1.

Figure 3.1 Comparison of the main losses of PERC/TOPCon/HJT in low temperature

Figure 3.1 Comparison ofthe main losses of PERC/TOPCon/HJT in low temperature

3.2 High temperature application scenarios

Abu Dhabi in the Middle East is chosen as a typical example for high temperature application scenario, which is located near 24.4°N with an average annual temperature of 28.5°C and a total horizontal radiation of 2015.1 KWh/m2. The power plant is designed with a DC/AC ratio of 1.05 and an installed capacity of 4MW (with slight variations in the actual design), applying the optimum tilt angle for fixed bracket and suitable string inverters. By year 25, TOPCon's power generation gain is 4.52% and HJT' power generation gain is even higher at 9.67% compared to the PERC' power generation, as shown in Table 3.2.

Table 3.2 Comparison of PERC/TOPCon/HJT power generation gain

Table 3.2 Comparison of PERC/TOPCon/HJTpower generation gain

According to the loss comparison graph, in addition to power degradation, operating temperature loss is another major factor which affects power generation in high temperature scenarios. At the end of year 25, the power degradation of PERC modules is 12.86% (1.6% + 11.26%), while that of TOPCon modules is 10.6% (0.6% + 10%) and that of HJT modules is 7.87% (1.6% + 6.27%); the operating temperature loss of PERC modules is 8.31%, while that of TOPCon modules is 7.26% and that of HJT modules is 5.81%, as shown in Figure 3.2.

Figure 3.2 Comparison of the main losses of PERC/TOPCon/HJT in high temperature

Figure 3.2 Comparison ofthe main losses of PERC/TOPCon/HJT in high temperature

The above analysis shows that in low temperature application scenarios, module power degradation is one of the main factors affecting the product's power generation; and in high temperature applications scenarios, the operating temperature is another major factor. Due to the extremely stable temperature coefficient, higher bifacial factor and higher power retention of HJT modules, the power generation gain advantage of HJT is obvious in high temperature areas, and in low temperature areas, HJT also shows a relatively high power generation gain, which will bring higher power generation gain and more stable power yield to the PV system.

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