The global solar PV industry continues to undergo various innovations with a race to improve solar cell and module efficiencies, and improvement in the materials that go into making a panel, all with the aim to drive down the levelized cost of electricity (LCOE); however, the crux ultimately boils down to one thing – reliability.
A module that's going to work under extreme weather conditions day in and day out, and still expected to work non-stop, comes with a typical performance warranty of 25-30 years, technically ensuring its reliability. So how is the industry making sure the end product serves the purpose?
To discuss this, TaiyangNews brought together solar PV manufacturers, to backsheet suppliers and even equipment makers to our Virtual Conference on Reliable PV Module Design on October 26, 2023.
In his keynote speech, Board Member of SOLYCO Solar AG, Dr. Lars Podlowski spoke about the reliability testing of various commercial TOPCon PV modules.
Reflecting on concerns about reliability of TOPCon solar modules vis-à-vis the industry workhorse PERC, Podlowski shared results of reliability tests, mainly damp heat (DH) on dual-glass and glass-backsheet versions.
While dual-glass TOPCon modules are at par with PERC, glass-backsheet modules show a huge variation in product quality regarding DH stability. With further investigation of individual parameters revealed that the power degradation is mainly due to the losses in fill factor, which can be routed to increase in series resistance, meaning the moisture ingression corroding the aluminum-silver contacts on front side, with no dip in Voc, indicate that the passivation stack is intact. Having said that, Podlowski emphasized that not every glass-backsheet module failed, implying TOPCon as a technology still compatible with the glass-backsheet configuration; however, special care needs to be taken when selecting the BOM.
LONGi's Senior Product Manager Dongxia Ni discussed how the company ensures supreme module lifecycle quality from design to end-of-life. Referring to the global temperature rise and the world facing extreme weather events, Ni said reliability becomes all the more important to ensure return on investment for solar investors.
According to the IEA, most solar module related faults range from J-box/diode failures, cell cracking, hotspots, glass breakage, mechanical load failure and PID degradation. LONGi, as Ni shared, is focused on optimizing quality and reliability across the life cycle of modules.
While the existing basic IEC standards are necessary, these are not enough to ensure the modules have long-term reliability, opined Ni. She said along with ensuring quality raw material supply from qualified vendors, AI-powered manufacturing and QR-code encoded traceability for each panel it produces, LONGi conducts several simulation and failure studies for real-world application scenarios to minimize the possibility of failure/degradation for its modules in the field.
Stressing on managing total quality control to ensure high reliability for the company's 210 Vertex modules, Trina Solar's Senior Product Manager Zhou Yangyang said that the company's in-house State Key Lab is central to these efforts. Here, the manufacturer conducts extensive research and development on new energy, PV advanced technology and its industrialization.
For its flagship 210 Vertex modules, Trina Solar conducts 5 rigorous tests to prove its high mechanical reliability. The test results show that the modules can withstand uneven snow load of 2.8 m, can operate safely under 40 °C, can withstand 35 mm hail impact, have passed ±1500Pa Dynamic Load Test @ 20000 times, and also cleared 17 hurricane wind tests.
While the IEC test standard requires modules to withstand 25 mm hail impact, Trina says its Vertex panels can power through 35 mm hail size under its own in-house test standard.
By the end of 2023, the company targets its total silicon wafer production capacity to grow to 50 GW, cell capacity to 75 GW including 40 GW of TOPCon, and module capacity of 95 GW.
Currently holding the record of industry leading 24% solar module efficiency for its all back contact (ABC) modules, Aiko Solar's Senior Product Manager Dr. Jimmy Melskens said these panels outperform PERC in various common reliability tests such as DH, thermal cycling, PID and LID.
As the name suggests, ABC modules from Aiko have all their contacts at the back of the panel, thus doing away with all possibility of optical loss on the front. Since the cell structure replaces the use of expensive silver with copper, it also provides a cost advantage, according to Melskens.
He shared that the single-side soldering for the ABC modules lowers the crack risk on edge between connected solar cells to zero, while triple welding strength vs. traditional technology substantially reduces the risk of detachment and micro-cracks.
Aiming to continue on the path, Aiko plans to launch bifacial ABC modules in Q1/2024 with 188-54 cell and 188-72 cell configurations. Melskens admitted that the bifaciality of its modules will be modest as compared to PERC but argued that it will be worth it in the long run. The bifacial module will be followed by a lightweight module next year.
When you focus on improving quality of a solar module, you automatically contribute to its reliability, according to JA Solar's Senior Technical Manager Ignacio Espinosa. He stressed that solid quality is the key for solar module while entering high efficiency n-type era.
While its n-type PV modules score well on various reliability tests, Espinosa said the manufacturer found degradation in high-temperature and high-humidity tests with glass-backsheet n-type products. It found encapsulation layers like the EVA easily hydrolyse, causing the film to become acetic acid, thus leading to the corrosion of the TOPCon silver-aluminum paste.
The solution is to optimize encapsulation layers and improve the aluminum paste for glass-backsheet n-type modules. Espinosa said the company is working on the same for last several months and is confident of finding a 100% reliable solution soon, expected in the beginning of 2024. Till then, it will stick to the production of glass-glass n-type products.
Talking about the backsheet component at the conference was Endurans Solar's Commercial Manager & Sustainability Lead Imco Goudswaard who discussed the importance of reliable and sustainable backsheets for high-performance modules.
Compared to the fluorine-based backsheets that abound the market today, Goudswaard said Endurans Solar's HP backsheet uses polyolefin technology that has high moisture and UV resistance and is designed for circularity. It gives 'glass-like protection'.
Since most traditional backsheets follow a linear model, they don't have an option of low-cost mechanical recycling and lead to fluorinated waste with a complex material recycling. By 2050, the world is expected to have installed 30 billion solar modules while end-of-life backsheet waste can grow to as much as 500 kt/year. Hence, for the industry working on a renewable energy source, it is important to make the right backsheet material choices that will have a big impact 30 years down the line.
Citing Endurans' polyolefin backsheets, Goudswaard said these have a longer lifetime with a high-water barrier and acetic acid permeability. Built with mono-layer consistency of co-extruded films, the backsheets have excellent UV and hydrolysis as well as abrasion and acid resistance, he added.
Touching upon supply chain concerns along with trade barriers in some markets like the US and India, Goudswaard said the industry must be wary of dependency on any single market. Endurans is hence expanding in the US. It is also developing backsheets engineered for bifacial modules, high-performance encapsulants and rear perforated insulator for back-contact modules, building on its HPO platform.
Speaking about the company's own initiatives to recycle its products, Goudswaard shared being able to reuse the backsheet edge trims during the production process. For end-of-life, it is currently doing some trials with partners for recyclability.
Beyond TOPCon, it is the heterojunction (HJT) module technology that's fast catching up. Huasun Energy's Director of Business Development Europe Christian Comes is confident that despite the cost factor, just like TOPCon, HJT too will see quick acceptance in the global markets thanks to its high efficiency advantage.
In fact, as he shared, the lowest efficiency HJT modules are at the level of the highest efficiency TOPCon modules. Calling it reliable by design, Comes stressed that HJT is a proven technology with its thin wafer, symmetrical structure, silver contacts and no TCO surface.
Comes said that the company is currently using 120 um wafers and in 2024 it plans to reduce the same to 100 um or 90 um. Such thin wafers, when used in the manufacture of HJT cells (low temperature of 200ºC), are very flexible. The result is excellent mechanical endurance without microcracks, he stated.
As per its technological roadmap, Huasun targets to grow its cell efficiency of 26% to 26.5% in 2024 with a G12-132 module having 750 W output. Further on, by 2025 the aim is to venture into tandem structure using the HJT and perovskite combination. The target module output for this one is 800 W with a cell efficiency of 28%.
Autowell Technology's Overseas Sales Director Paulo Rocha discussed innovative interconnection solutions from a stringer equipment manufacturer's point of view to avoid soldering failures.
He discussed the current trend of various cell sizes, including rectangular wafers, as posing demands on the equipment's stable production capacity output.
The Chinese manufacturer has been working on innovative interconnection solutions to avoid soldering failures. For instance, to deal with stringing issues in rectangular wafers, ribbon flattening was achieved with 0.1 mm thickness, but that's not enough since the overlapped cell will suffer higher pressure during lamination and the breakage rate will increase.
As an equipment company, Rocha said Autowell (or ATW) developed a system to insert a pressure absorber on each single overlapped cell edge, thus successfully eliminating breakages on lamination process for negative cell gapped modules.
The other steps ATW has undertaken include development of multiple step soldering, reduced temperature overshooting, actual lower temperature at set point. Single cell soldering is done to improve cell gap tolerance, among others.
As for HJT, Rocha argued that 0BB is a cost reduction solution that is particularly urgent for HJT. It is applicable to both HJT and TOPCon technologies. Given that HJT demands low-temperature interconnection methods, the 0BB comes as a dual advantage solution, providing adhesive usage instead of high temperature soldering and eliminating the Busbar and so reducing the consumption of silver paste, which makes cost reductions particularly significant for HJT.
In the future, ATW said it aims to reduce cost and improve efficiency through the innovative 0BB technology and novel soldering approaches. There will be increased use of artificial intelligence (AI) which will be unsupervised to ensure uninterrupted production.
Executive Panel
Moderated by TaiyangNews Head of Technology Shravan Chunduri, the panel discussion revolved around how to ensure a solar panel's high performance for decades.
When it comes to reliability, Huasun Energy's Christian Comes believes the onus also falls on the customers to be cautious with what they end up buying. With price pressures coming in along with extreme competition, manufacturers may end up compromising the quality of materials to bring down their costs. This, borne out of an instinct to survive, can cost reliability of the end product.
At the same time, not all companies are at the same level of technological efficiency, hence the market may also have some not-so-reliable products. This needs to be watched out.
Defending the glass-backsheet modules against the general perception of these not being as reliable and long-lasting as their glass-glass counterparts, Endurans Solar's Imco Goudswaard said transparent backsheets have a significant role to play in installations that require lightweight modules.
For instance, distributed generation applications where aesthetics are more important, as well as building integrated PV (BIPV) segment.
To deliver on reliability, Autowell Technology's Paulo Rocha said that an equipment manufacturer needs to have a high production volume to be able to warrant consistent, quality manufacturing. What's good is that newer developments in terms of technology are coming up, so if there is enough volume, companies can deliver equipment worthy of the efforts put in.
Rocha added that it is good to see all players using various quality standards for their products and remain open to changes.
The trio unanimously voiced that platforms such as the TaiyangNews conference offer a platform for the industry to come together and exchange information about technology, demand and markets, which wasn't the case earlier. Even big players are open to finding solutions to make the industry more competitive.
Moving on, TaiyangNews plans to host its Special Focus Webinar on Solar Getting Smart—How Digitalization Boost Energy Efficiency in PV Power Plants with TrinaTracker on November 14, 2023. Registrations to the event are free and can be done here.
Further up, block your dates from December 4 to 8, 2023 for our annual flagship event TaiyangNews High Efficiency Solar Week. Registrations will open soon!