In the last few months, leading module makers have been in a race to offer higher power modules raising the bar for utility-scale panel power to 500 W and more. Acknowledging the trend, TaiyangNews organized a first virtual conference on the topic: 500W+ Solar Modules - How to Boost PV Panel Power to the Next Level (see TaiyangNews Virtual Conference on 500W+ Solar Modules). All leading module producers that had announced 500W+ modules in H1/2020 took part in the event and presented details of their technologies. We are summarizing the company presentations at the event and include also the Q&A parts – here, for JinkoSolar.
Amy Liu, product manager at the world's largest solar module supplier JinkoSolar, presented details of its new Tiger Pro module series at the TaiyangNews 500W+ Conference end of July. While Dany Qian, vice president of JinkoSolar, outlined key features of the TigerPro series in an interview with TaiyangNews in June (see Targeting Utility Scale Market With Tiger Pro Modules), Liu presented insights into the Tiger Pro technology platform. The rationale behind the Tiger Pro is that increasing module power reduces tracker and cables costs, while the gain in module efficiency lowers costs for land. Tiger Pro is designed to gain on both fronts.
Key features of Triger Pro
The Tiger Pro modules are built on the same platform as the earlier Tiger series, which according to Liu registered 3 GW of orders since its introduction last year. The key difference of the Pro to the earlier released Tiger platform is its design based on the larger 182 mm (M10) wafer format. Tigers Pro is offered in two series: A 72-cell configuration, which comes as a bifacial product with 535 W and a monofacial panels with 540 W. The other series is a 78-cell based model that also comes in monofacial and bifacial variants with 585 W and 580 W output power. respectively. The main 'advanced module technologies' used are – multi busbars (MBB), half cells and Tiling Ribbon (TR). While the first two are well known, TR is a cell interconnection method specially developed by JinkoSolar. Here, the circular copper ribbon is pressed flat at the overlap region and encapsulation material is used as a filler to provide extra protection to the cells.
Making of Tiger Pro Modules
The first important step of the module production process is soldering – and the preparation process starts with pressing the circular ribbon flat and thin at the overlap region. In JinkoSolar's TR process the ribbon thickness in the overlap region is same as for the circular ribbons in the cell region to avoid the risk of creating microcracks. A detailed inspection of the soldering region including EL inspection is conducted during the production process to ensure high soldering quality.
Lamination is the next important production step in TR design as the encapsulant fills the overlap region to provide a buffering effect. JinkoSolar is using thicker encapsulants to improve protection and release stress from the cells. As for MBB, Triger Pro employs 10 busbars, which decreases the current path by 50% compared to 5-busbar design and results in a 0.4% gain in cell efficiency, said Liu. The design also benefits from the generic advantages of MBB such as reduced risk of microcracks and improved light utilization.
JinkoSolar offers 25-year power warranties for its monofacial Tiger Pro panels, and 30 years for bifacial products. The rated degradation assumption of this module series in the first year is 2%, while the following warranted linear degradation differs for bifacial compared to monofacial panels. According to Liu, the linear degradation is reduced from 0.6% /year for earlier products to 0.55% for monofacial and 0.45% for bifacial modules of the Tiger Pro series. JinkoSolar is offering its bifacial product in two variants – with transparent backsheet and as glass-glass modules –, whereas the warranty length for both is 30 years.
The Triger Pro will be in mass production in Q3/2020 and JinkoSolar anticipates to reach 13 GW capacity in 2021.
System level
JinkoSolar is promoting the two variants of the bifacial module for different applications. The light weight transparent backsheet is said to be ideally suited for countries with high labor costs. Since the dual glass product has a better wind load property, this product is highly compatible for power plants in areas with high wind speeds, according to Liu.
At the system level, the Tiger Pro is compatible with both 1P and 2P trackers as well as central inverter. As for the compatibility with string inverters, Liu said that when modules are installed in locations with high irradiance and very hot ambient temerature, the typical 26 A string inverters may cause inverter losses of 0.1% due to high input current. However, Liu emphasized that leading inverter manufacturers Huawei, Sungrow and SMA are planning to come up with next generation inverters capable of handling 30 A in the second half of this year.
Benefits
According to JinkoSolar, the 535 W variant of its Tiger Pro enables connecting one additional module per string compared to a 500 W product, which along with high the power attribute increases the net string power by 11%. As to the ultimate benefits of the Triger Pro in savings in BOS and LCOE, Liu presented the results of a simulated project located in Vietnam with 120 MW size that uses trackers and string inverters. Compared to a 500 W module, the monofacial Tiger pro 540 W installation resulted in a 3% reduction in BOS costs, while the LCOE could be reduced by 2.5%.
The presentation was followed by a Q&A with the conference attendees, which we have listed below (selected questions, edited & summarized):
Question: Why is the degradation lower with transparent backsheet based bifacial modules compared to the monofacial?
Amy Liu: We use a Tedlar based backsheet that has better water vapor resistance than non-Tedlar based products we use. However, in reliability tests we found that the transparent backsheet product has similar degradation rates as the dual glass product.
Question: What is the reason for stacking the cells in the module using TR technology as cell-to-module (CTM) losses are high?
Amy Liu: First, we want to eliminate cell gaps, so that we can increase the module efficiency. Of course, CTM losses are higher than for typical half cells, but there are other methods to increase both power and CTM. As we want to strike the right balance between efficiency, power and reliability, we have opted for tiling ribbon.
Question: What is the unique advantage of Tiger Pro among the M10 based module products?
Amy Liu: We have the highest efficiency among the M10 modules. And high efficiency saves costs for land. Just in case, someone wants to keep the land costs at the same level, Tiger Pro enables having a wider pitch that increases the energy yield.
Question: What is the reason for having 72-cell and 78-cell configurations?
Amy Liu: According to our analysis, we found out that a system with 78-cell modules has the lowest LCOE in fixed tilt systems compared to 72-cell modules. It also leads to the lowest LCOE with trackers in low wind regions. In high wind locations, 78-cell modules, due to their larger size, increase project costs. In low wind locations, systems with large module sizes increase the trackers costs only a little, which at the end is beneficial. 78-cell based modules with their high power saves on BOS costs.
Question: What diode design you are using for your high-power Tiger Pro products?
Amy Liu: The fuse current is 25 A. JinkoSolar has designed a new junction box for the Tiger Pro that has little higher current than the normal product. If the location of the bifacial installation has high bifacial gain, we can also set it to 30 A. Here we are flexible according to customers needs.
Question: What is the LID for bifacial and monofacial:
AIt is 1.5% for both monofacial and bifacial. We use backsheet and encapsulation materials that keeps it low.
Question: What is the reason for opting 182 mm as the wafer size for Tiger Pro?.
Based on our investigation, the optimal width of the module is between 1.13 m to maximum of 1.14 to load into a container. Based on this analysis, we found M10 is the best cell size. The M10 can support high power and also offer convenience in transportation. We can strike a right balance between these two.
Question: Since JinkoSolar has also worked on n-type cell technology; do you have any plans to use such cells for Tiger Pro?
Amy Liu: Yes, we do have plans to integrate n-type technology. Jinko has 0.8 GW n-type capacity. Earlier it was PERT, which has been upgraded to TOPCon. We call it HOT technology. We will have a n-type Tiger Pro product next year. It will be exhibited during SNEC (see JinkoSolar Launches 610 W TopCon Module at SNEC).
The power will be higher for the n-type module over p-type. The warranty terms will be also better: first year degradation will be 1% and linear degradation will be 0.4%. The bifaciality is also higher. It will be our premium product.
TaiyangNews: Thank you for your presentation at the TaiyangNews 500W+ Solar Module Conference.
The JinkoSolar presentation of Amy Liu can be viewed on the TaiyangNews YouTube Channel here.