Lowering the levelized cost of energy (LCOE) has been the key driver of PV developments. However, making solar sustainable and ecologically viable by minimizing the carbon emissions from the solar manufacturing process is also a key. Risen strongly believes that HJT technology can help achieve both of these goals simultaneously. Risen also believes that the HJT structure with TCO as the top conducting layer is more compatible to become the bottom layer of next-generation tandem cell architectures. For all of these reasons, Risen is a strong proponent of HJT technology.
Risen started its journey with HJT in 2019 with G1 solar cells. Soon after entering the larger wafer regime, the company launched its G12-based product. In 2022, the company officially launched its Hyper-ion module, which is based on G12 and HJT. The company has expanded its production capacity to 5 GW in the first half of 2023. In the same year, the company achieved a record module efficiency of 23.9% for its 741 W module. Risen is now in the process of commercializing its Hyper-ion product lines, and Jiajun Ye, product manager at the company, presented the details of this latest product group at the TaiyangNews PV System Technology Trends 2023 Conference.
Ye emphasized that the company faced several challenges during the R&D and industrialization of HJT, mainly improving reliability and efficiency, while reducing costs. Within the costs, silicon related, non-silicon, and equipment costs are major contributors. The major hurdles of the technology are lowering the silver consumption and realizing reliable interconnection without affecting the performance. The company was able to reach its goals through continuous efforts and cooperation with partners from different parts of the supply and value chain. "We have minimized costs to a very competitive level and expect it to be at the same level as PERC or TOPCon soon," says Ye.
One of the major cost optimizations was to adapt to thinner wafers of 100 μm, which reduces the silicon costs compared to 130 μm with TOPCon and 150 μm with PERC. This also reduces the carbon footprint and energy consumption of the technology. To address edge losses due to slicing the cells into 2 pieces, Risen adapted its manufacturing process to half-cut wafers.
To reduce the silver consumption and related metallization costs, which are at the top of non silicon costs, Risen has adopted a silver-coated copper based paste. Chosen after evaluating different compositions, this paste was found to be an optimum one that reduces costs without affecting reliability and efficiency. The Hyper-ion series uses 3rd generation HJT technology with microcrystalline doped layers present on both sides of the cell, which helps in enhancing the absorption spectrum of the solar cells.
As for optimization at the module level, Risen has developed a special interconnection process called Hyper-Link that operates at 25 °C. The process addresses low-temperature concerns associated with the interconnection of HJT cells. Another aspect of Risen's interconnection technology is that the method eliminates the busbars on cells in a socalled 0-busbars or busbar-free design. At the same time, it uses a high number of busbars (24) at the module level, which helps reduce resistance losses. The top layer of heterojunction solar cells has a TCO film, which has poor adhesion with standard module encapsulation materials such as EVA and POE. This can cause delamination in the event of high operating temperatures and hot spots. To address this, Risen has developed a HJT-specific encapsulation material with high adhesion of 40 N, compared to 10 N with POE and 12 N with EVA.
Ye says that the Hyper-ion has achieved 4 firsts in the segment: using thin wafers of 90 μm, mass production of patented busbar-free cells, silver consumption reduced to less than 10 mg/W, and Hyper-Link interconnection technology that does not induce any stress and interconnects busbar-less cells. Based on all these advancements, Risen is promoting 2 modules. One is based on 66 cells for the utility scale. It shares the same platform as the world-record module with close to 742 W and 23.9% efficiency. However, the commercial offering has a module efficiency of 22.1% to 22.5% and 685 W to 700 W power range. It is a double-glass bifacial module measuring 2,384 x 1,303 mm that can either be opted with a typical aluminum frame or Risen's proprietary steel frame. The other product in the series is a 55-cell module with 22.4% efficiency, 585 W power, and dimensions of 2,384 x 1,096 mm, promoted for C&I applications (see Risen Energy's Jiajun Ye's presentation on Very Large 700+W HJT Modules For Utility Applications).
These modules come with a product warranty of 15 years and a power warranty of 30 years. While the first-year degradation is 1%, the annual degradation for the rest of the warranty period is 0.3%, which accounts for 90% power retention after 30 years. These modules have a bifacial factor that is 15% higher than PERC modules and 5% higher than TOPCon modules. The Hyper-ion module has a low temperature coefficient of -0.24%/°C, which means it produces more power in hot weather. The thinner wafer and low-temperature process of HJT also leads to the lowest carbon footprint of 400 kg eq CO2/kWc.
Ye presented a global power generation map for its Hyper-ion HJT solar panels. The map shows that Hyper-ion panels have 5-7% higher energy yield than PERC panels in a variety of climatic conditions. This is supported by the results of 5 pilot projects, which showed that Hyper-ion panels generate 6% more energy than PERC panels. Factoring all benefits, Risen estimates that its HJT module can command a price premium of 1.9 cents/W over TOPCon panels. Risen also has ambitious expansion plans with its HJT technology to increase the production capacity of its HJT panels to 15 GW by the end of 2023, out of a total target of 45 GW. The remaining 30 GW will be split between PERC (24 GW) and TOPCon (6 GW).
The text is an excerpt from TaiyangNews New Solar Products Overview H1/2023, which can be downloaded for free here.
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