An effectivity of 23.9% and energy output of 741 W are numbers which are worthy of consideration. These outcomes have been offered by Chinese language photo voltaic producer Risen Vitality for its newest, Hyper-ion module sequence, which deploys “G12” (210 mm), HJT half-cut cells in a big format for big scale photo voltaic functions. Risen can be producing a “55-cell” model of the identical module, for industrial and industrial utility. At a hefty 41 kg, the “66 cell” model of the module is not any light-weight.
In mass manufacturing, the Hyper-ion doesn’t fairly attain the lofty figures of its champion of the sequence. The modules obtainable available on the market have an influence output of 680 W to 705 W with a module effectivity of 21.9-22.7%. Risen’s outcomes nonetheless rival the best-performing modules, nonetheless, and communicate to the potential of HJT.
Behind the dual-glass encapsulation there’s a trace of the way forward for HJT within the Risen product. The corporate has deployed a notable innovation – busbarless cell interconnection, which it calls Hyper-Hyperlink. The strategy replaces conventional busbars with a wire mesh that bonds and types {an electrical} contact with the cell with out the usage of standard high-temperature soldering.
Hyper-Hyperlink makes use of 24 metallic wires for cell interconnection, past the 18-20 multi-busbars used within the newest high-performance merchandise. Whereas Risen has revealed a number of the technical methods behind its Hyper-Hyperlink busbarless know-how, it’s removed from being an open guide.
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Session 3 | Dec 5, 12:15 pm CET |Subsequent era cell and module tech
What does life-after-PERC appear to be? Excessive-efficiency n-type applied sciences have surged into the mainstream with TOPCon clearly the entrance runner. However HJT and xBC applied sciences are additionally being superior and bringing distinctive worth to the market. Within the present oversupply market, how will high-efficiency applied sciences compete, and what’s the pathway for future price reductions? Moreover, can these next-generation applied sciences overcome materials provide challenges?
Busbarless extra typically is termed zero-busbar or “0BB.” In a single sense the strategy is novel, in one other it’s well-known. What is evident is that it’s rising at a scale not seen earlier than in PV manufacturing. Risen alone needs an annual manufacturing capability of 15 GW of its heterojunction modules by the tip of 2023.
“There may be very robust and invaluable IP [intellectual property] being developed for particular implementation of the busbarless know-how,” mentioned George Touloupas, director of know-how and high quality at photo voltaic technical advisory Clear Vitality Associates (CEA). “There’s a super quantity of secrecy. Actually, there are obstacles in entrance of the stringers [on production lines] and you aren’t allowed to see them. Internally, they make folks signal very strict NDAs [non-disclosure agreements] and non-compete [agreements] – as a result of it’s so essential.”
As Touloupas notes, there are numerous methods being explored for busbarless cell interconnection. The one with the longest observe document entails wires embedded right into a plastic movie, with electrical contact occurring in lamination. Different approaches use an epoxy resin to carry the wires in place, with an encapsulation layer added in a secondary course of.
“In China, virtually all of the HJT markers try and testing this know-how,” mentioned InfoLink chief analyst Corrine Lin. “There are a number of zero busbar options,” see desk under.
Zero-busbar know-how below growth
| Resolution | SmartWire Connection Expertise (SWCT) | Built-in movie overlaying (IFC) | Shelling out | Welding-dispensing |
| Description | Copper-coated ribbons are positioned by a clear foil. This foil-wire meeting (FWA) interconnects cells. Copper-coated ribbons and cells are firmly mixed by lamination. | Interconnecting cells by inserting ribbons to their entrance and rear sides by IFC. Ribbons and cells are firmly mixed by lamination. | Between fingers. Place ribbons to cells by meting out. Ribbons and cells are firmly mixed by lamination. | Welding ribbons to cells (cell interconnection and ribbon-cell mixture happen concurrently). Stick ribbons to cells utilizing meting out. |
| Shelling out methodology | N/A | N/A | Display printing | Shelling out |
| Ribbon tabbing methodology | Foil-wire (ribbon coated with copper) meeting | IFC | UV/epoxy adhesive (meting out/display printing) | Infrared welding adopted by meting out on the 2 ends for additional fixation |
| Ribbon-cell connection | Lamination | Lamination | Lamination | Infrared welding |
| Encapsulant | Service-film. Foil-wire (metal) meeting plus encapsulant. | Pores and skin movie plus encapsulant | Pores and skin movie plus encapsulant. Service-encapsulation movie (modified commonplace encapsulant)/polyvinyl butyral (PVB). | Normal encapsulant |
| Execs | Robust adhesive power between ribbons and cells Extra conductive |
Robust adhesive power between ribbons and cells No want to mix ribbon manufacturing stage |
Simpler | No want for pores and skin movie and provider movie. Robust adhesive power between ribbons and cells Superior hot-spot resistance |
| Cons | Mix ribbon and movie in earlier manufacturing stage – extra sophisticated Electroluminescence (EL) testing for defects solely works after lamination |
Should add pores and skin movie EL testing for defects solely works after lamination |
Wants pores and skin movie modified commonplace encapsulant Two-layer encapsulation prices extra, whereas carrier-encapsulation movie is tougher Common adhesive power between ribbons and cells EL testing for defects solely works after lamination |
Breaking attributable to ribbon shrinking after welding Requires extremely exact meting out which is tough and time-consuming Fingers and ribbons welded immediately, mass-production (MP) is tough |
| Corporations | Meyer Burger | XN Automation, Maxwell | Autowell, AUTO-ONE, XN Automation, Autowavs, Lead Clever | Maxwell |
| Progress | Meyer Burger: MP | REC: MP; Astroenergy: R&D | Risen: MP; Tongwei, Jinko: R&D | Huasun: R&D |
| Word | The foil-wire (ribbon coated copper) meeting is created with a clear insulant optical movie, adhesive, and ribbons which are positioned above the floor of the meeting and embedded within the adhesive | Putting ribbons to the entrance and rear sides of cells by IFC on one manufacturing line Pores and skin movie weight roughly 100 g/m² |
Repeated lamination could also be wanted attributable to common adhesive power between ribbons and cells. Some producers attempt to use PVB and autoclave for two-time lamination | Ribbons have to be thicker or shaped right into a harpoon-like form at their intersection with fingers, affecting silver consumption discount |
Supply: InfoLink
Again to the long run
As is so usually true in PV know-how, what’s outdated is new and this additionally applies to busbarless know-how. The strategy was first developed by now-defunct Canadian producer Day4 Vitality in 2003 and was promoted, below the SmartWire label, by Meyer Burger after its acquisition of the know-how, when the Swiss firm was a pure-play manufacturing tools provider.
“When Meyer Burger began creating heterojunction know-how round 2010, the corporate instantly snapped up an IP from Day4,” mentioned Touloupas. “Meyer Burger noticed it as an ideal match for heterojunction know-how.”
A evaluate by analysis institute Fraunhofer ISE – commissioned by Meyer Burger and revealed in 2020 – famous that “Meyer Burger has intensive patent households on HJT and SmartWire manufacturing processes, techniques and merchandise; a few of these patent households is not going to expire till 2039.”
Whereas HJT was a pure match to SmartWire, Meyer Burger offered some 500 GW of its busbarless strains to HJT and non-HJT producers in 2016-2017, in line with the corporate’s then chief industrial officer, Michael Escher. On the time, Escher spoke to SmartWire’s potential to scale back silver consumption, “to solely 80 mg, as a substitute of 300 mg per cell.”
Each silver consumption and busbar know-how have come a good distance within the interim interval. Silver paste and screen-printing know-how have made nice strides in lowering the quantity of silver utilized in metallization, delivering price financial savings with out the usage of busbarless interconnection. Multi-busbar (MBB) know-how, of which the most recent era has been badged “tremendous multi-busbar,” has moved into mainstream manufacturing with alacrity.
“When Day4 developed the know-how, the benefit versus two- or three-busbar modules would’ve been far larger,” mentioned Tristan Erion-Lorico, vp for gross sales and advertising at PV Evolution Labs (PVEL). “With some producers now going to a 20-busbar module, the efficiency hole isn’t so large.”
Silver discount
The efficiency increase delivered by SmartWire, which will be prolonged to different busbarless approaches, is partly that there’s diminished shading of the cell floor each by the busbars themselves and by the metallization paste. It’s doubtless within the implications for metallization the place the busbarless and HJT mixture really shines.
By lowering “ohmic losses,” SmartWire facilitates “fine-line metallization” and subsequently “a drastic discount in silver utilization by 85% or extra,” in line with researchers from the Centre Suisse d’Electronique et de Microtechnique (CSEM), in a 2014 paper offered on the EUPVSEC convention in the identical 12 months.
The CSEM was a long-running associate within the HJT tools and course of growth of Meyer Burger and hosted a pilot line on its campus in Neuchâtel, Switzerland. The paper, “SmartWire photo voltaic cell interconnection know-how,” concluded that the cell interconnection strategy represents a “key enabling know-how for aggressive silicon heterojunction modules because it permits to decrease the constraints on cell metallization conductivity.”
Chinese language producers echoed the curiosity of the Swiss researchers. “The Chinese language have been engaged on this for years and every little thing is best [with busbarless technology] – decrease price and better effectivity,” mentioned Alex Barrows, head of PV at photo voltaic manufacturing consultancy Exawatt. “The fee is decrease due to diminished silver utilization and there’s increased effectivity due to much less shading. If a producer could make it work, it’s a very neat answer and in the long term it’s virtually inevitable that we are going to transfer to one thing comparable for HJT.”
Barrows famous that the implementation of silver-coated copper paste, for HJT cell metallization, dilutes a few of this benefit, “and due to that possibly there was much less of a rush to undertake zero-busbar because it already did a number of the work in taking the associated fee out of HJT,” he mentioned. The advantages stay sizable nonetheless.
Risen claims that by deploying its Hyper-Hyperlink together with silver-coated copper paste, it may possibly obtain a silver content material of 10 mg/cell in its Hyper-ion modules. By comparability, the 14th version of the “Worldwide Expertise Roadmap for Photovoltaics,” revealed in March 2023, concluded that in 2022, common positively-doped “p-type” silver consumption stood at 11 mg/cell.
“I’ve seen within the roadmaps that zero-busbar might convey the HJT silver price all the way down to [that of tunnel oxide passivated contact] TOPCon [solar],” mentioned CEA’s Touloupas, noting that HJT isn’t a competitor with p-type passivated emitter rear contact (PERC) photo voltaic, however slightly with n-type TOPCon.
Bismuth hassle
There may be, nonetheless, a fabric problem. The know-how’s growth was enabled, partly, by means of bismuth in interconnection wires.
“One of many predominant improvements achieved by Meyer Burger 10 years in the past, was to exchange the lead on the ribbon coating with bismuth, as bismuth-tin alloy is low-temperature,” mentioned Touloupas. “That implies that the soldering is occurring within the laminator at round 150 C when the alloy melts and achieves contact.”
Bismuth consumption is doubtlessly problematic. In a 2021 research, researchers from the College of New South Wales, in Australia – alongside Amrock Consulting and Trina Photo voltaic – concluded that obtainable bismuth would restrict manufacturing to 330 GW – far larger than Risen’s focused 2023 consumption however a possible bottleneck as the worldwide photo voltaic trade quickly expands towards terawatt scale.
The paper is titled “Design issues for multi-terawatt scale manufacturing of present and future photovoltaic applied sciences: challenges and alternatives associated to silver, indium and bismuth consumption.” It concluded that “vital materials consumption reductions are required to fulfill the goal manufacturing price for sustainable multi-TW scale manufacturing in about ten years from now.”
Maintaining cool
Low temperature processing is a necessity for HJT cells, as commonplace firing or soldering can injury delicate passivation layers. “MBB know-how sometimes makes use of infrared soldering, which is simply too scorching for HJT,” says PVEL’s Erion-Lorico. Whereas busbarless interconnection achieves contact within the lamination course of at far decrease temperatures, challenges stay.
“One thing we’ve talked about within the PVEL Scorecard is that we’re nonetheless seeing some struggles with thermal biking outcomes for some HJT producers, in that the vary of thermal biking outcomes is increased for HJT than for PERC – some are doing it properly and a few are struggling,” mentioned Erion-Lorico. “The low temperature soldering will be a difficulty.”
Regardless of the nice progress that’s being made, the adoption of any new materials or processes in PV manufacturing at vital scale is one thing that would manifest new dangers.
“No matter answer is chosen, and there are a number of, an important factor is reliability,” mentioned Touloupas. “We hope to have the instruments – prolonged assessments – that may establish the losers amongst busbarless know-how implementation. We have to perceive the failure mechanisms and hopefully they’re the identical as these present in standard soldering.”
Meyer Burger didn’t reply to requests for an interview concerning the corporate’s SmartWire know-how. It’s at the moment deploying SmartWire in its module manufacturing in Germany.
This text was amended on 30/11/2023 to take away reference to the Day4 Vitality patent.
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