13 Jan 2022
1. Background
1.1 The technology market trends of Tiger Neo
N-type module
Most are familiar with traditional P-type cell technology. With large-scale manufacturing of monocrystalline silicon wafers, P-type mono PERC cell technology has been deployed on a large majority of projects since 2017. Mainstream module manufacturers have used mono PERC due to a simple manufacturing process, low cost, and cell conversion efficiency improvements.
However, the efficiency of PERC cells has approached a limit of 24.5%, and cost reduction has also slowed. Meanwhile, new cell technology is developing rapidly, and N-type cells are most likely to replace P-type cells to become the next-generation mainstream technology.
The current technical roadmap for N-type cells is shown below. Among the options, TOPCon and HIT are the primary focus of the current N-type technology.
The traditional P-type cell uses a boron-doped silicon wafer substrate, which easily forms a boron-oxygen pair after initial illumination. It will lead to light-induced degradation after a recombination center is formed by trapping electrons in the silicon wafer substrate. In contrast, the N-type cell silicon wafer substrate is doped with Phosphorus, so there is almost no loss of recombination center formed by the boron-oxygen pair, which greatly reduces light-induced degradation. For example, in TOPCon technology, the structure of the tunnel oxide layer further reduces the sub-surface recombination rate, which greatly optimizes the cell conversion efficiency, and the upper limit can reach 28.2%~28.7%.
The TOPCon cell applies cutting-edge and high-efficiency passivation contact technology, and uses a micro-nano tunneling oxide layer and a carrier-selective microcrystalline silicon film laminated functional structure on the back. This innovative structure demonstrates a two-way improvement in passivation performance and electrical conductivity, which brings significant improvements in cell conversion efficiency and power generation performance. The highest efficiency of N-type HOT2.0 cell is close to 25% in mass production, showing broad application prospects.
In short, TOPCon and HIT achieve efficiency improvements through passivation to reduce the number of sub-surface recombination rates. The former uses tunneling oxide layers and HIT uses intrinsic amorphous silicon film. The differences in the methods lead to the respective manufacturing processes, resulting in the difference in the commercial cost between the two.
1.2 Effect of High-efficiency module on LCOE
With the rapid development of renewable energy around the world, land resources for projects are becoming increasingly scarce in many regions. Optimizing profitability and land resource by selecting the highest efficiency module is an important topic.
The LCOE drives market demand, so high-power and high-efficiency modules have become a trend, and the N-type module has an obvious effect on reducing project costs. JinkoSolar adheres to a philosophy of high power and high efficiency, and the company realizes the simultaneous enhancement of module power and efficiency by integrating large silicon wafers, multiple form factors (including 78 cell specification), multiple busbars, and stitch welding technologies. JinkoSolar's high-efficiency N-type monocrystalline silicon single-junction cell technology has been calibrated by JET testing laboratory, an authoritative third-party testing and certification organization in Japan, to achieve a maximum conversion efficiency of 25.4% for the full-area cell, creating a new world record for the conversion efficiency of large-area N-type single crystal passivation contact ( TOPCon) cell. At this moment, N-type TOPCon has an obvious advantage in mass production efficiency, cost control, and market share.
In the long run, as TOPCon cells develop, the constant improvement in efficiency will continue to increase the power difference between N and P-type modules. The process optimization and new technology application will also continuously reduce costs.
2. Technical highlights
2.1 Technical advance—M10 silicon wafer
The size of M10 silicon wafer is uniform to 182mm*182mm
Industrial end: the industrial chain includes silicon wafers, cells, modules and auxiliary materials to reduce resource waste and promote benign development;
Customer end: the module size is nearly uniform, the system design is simplified and the upstream and downstream collaboration are improved.
2.2 TOPCon technology
TOPCon cell technology is a new passivated contact solar cell developed by the Fraunhofer Solar Energy Institute in Germany. Passivation is a key technology in determining maximum efficiency of the cell, as shown in the picture below.
2.3 Tiger Neo module with high efficiency
2.3.1 Temperature coefficient
The temperature coefficient of a similar P-type module is -0.35%/?C while that of N-type is modified to -0.30%/ ?C. This means the power generation performance is particularly outstanding at high temperature. The bifacial factor or traditional PERC module is 70% while that of TOPCon module is modified to 85%. The corresponding power gain is around 2.03%. According to the formula, the power gain of traditional PERC module due to the rear side power gain is 9.45% while that of a TOPCon module is 2 % more due to the 15% bifacial factor increase (under STC condition and average ground reflectivity).
Tiger Neo’s power output will increase with the bettertemperature coefficient (0.75% higher compared with PERC).
Under the same external environment, Tiger Neo’s operating temperature is lower ( >1 % compared with the same specification P type ) and the heat loss is greatly reduced.
Under high temperature condition, the advantage will further expand (~2% higher than P-type).
2.3.2 Bifacial factor
The bifacial factor or traditional PERC module is 70% while that of TOPCon module is modified to 85%. The corresponding power gain is around 2.03%. According to the formula, the power gain of traditional PERC module due to the rear side power gain is 9.45% while that of a TOPCon module is 2 % more due to the 15% bifacial factor increase (under STC condition and average ground reflectivity).
Power gain contrast due to the increase of bifacial factor
PERC: BSI*Bifi(70%)≈9.45%
TOPCon: BSI*Bifi (85%)≈11.48%
P*=Pfront*(1+BSI * Bifi)
*Bifi:The module bifacial factor
*BSI:Bifacial stress irradiance coefficient (depending on real irradiance & ground reflectivity).
2.3.3 Better warranty
The power warranty can achieve 30 years comparedto a traditional P-type module. The first year degradation is lower than 1% which means the power output at year 30 is guaranteed to be at least 87.4%.
3. System design
3.1 The combination of inverters
Inverter upgrades for high-current modules continue, and as of Q2 2022, the vast majority of inverters are compatible with existing Tiger Neo high-current modules.
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