pv magazine Roundtables Europe Address PV Quality Concerns

View the original recording at pv magazine here.

One of the key developments in the PV marketplace in 2021 is the emergence and deployment of large-format and high-powered modules. Power outputs of 400, 500 and even 600 Wp and beyond are reshaping notions of power plant design. However, given the rapid shift, concerns have been raised about the longevity of high-powered modules, and their susceptibility to a range of failure modes.

As a participant in pv magazine’s Roudtables Europe 2021, CEA’s Director of Technology and Quality, George Touloupas, discusses what issues to the BoM these newer Large Format Modules pose.

Transcript:

George Touloupas - Roundtables Europe 2021 Cornerstone 1: Quality

Jonathan Gifford:

Well, moving forward with our quality pitches, our third pitch comes courtesy of Clean Energy Associates. With headquarters in both Denver and Shanghai, CEA has worked on more than $70 billion worth of projects since its founding in 2008. From CEA today, as the company's Director of Technology and Quality and solar and storage, he has 11 years experience in both project development and manufacturing and currently leads projects on internal quality standards, new production technologies, and new services. From Clean Energy Associates, George Touloupas. It's my pleasure to see you again, as part of one of our quality events here at PV magazine.

George Touloupas:

Hey Jonathan, very nice to meet you.

Jonathan Gifford:

Nice to see you again. Thanks for joining from Athens. Please take us through another aspect of quality when it comes to these large format modules. And I understand, related more to the BOM, the bill of materials.

Tempered Glass Leads to Hail Issues

George Touloupas:

Yeah, absolutely. And what the previous speakers presented is very familiar to our day-to-day experience in the factories, but also in the field because we also do EL inspections. So, while Jay showed there was a recent case in Europe, with V-shape cracks. And you can actually see the V-shape cracks right here in the image on the right-hand side, and of course cold soldering and wiring misalignment, and a host of other issues.

So, we are currently in the process of auditing all new production lines. And most importantly, let's say production lines for new designs. We have paving, tiling, and of course shingling, which is less popular, and all this bundled with bigger wafers and cut cells, etc. We also have very thin glass, so it's a host of new technologies, let's say, that haven't been tried.

Everything gets optimized, absolutely, to have a higher yield and lower cost. One example is the glass; so tempering very thin glass, 2mm glass, is not feasible at least with mainstream production processes. So it gets strengthened or half-tempered, which is exactly the way it sounds. It's half the strength, well roughly half with reduced strength. So its ability to bear impact back from hailstone is reduced.

We have a big problem in the US, it's very well known, there’s a lot going on now. It's not mature yet. Everyone realized the IEC standard is not great. But we also have hail in Europe, as you can see in the map here. So overall the BOM, the new BOM and processes are creating a lot of new risks.

Ranking Solar Manufacturers Based on R&D Maturity and Capacities

Now, another view of the changes. So basically now we have the two new wafer size four months, the M10 and G12 or 182 and 210. And gigantic plans for multi-10 of gigawatt capacities rolling out now and next year. All this is brand new lines, brand new processes, well, different processes and new BOMs.

What you see on the right is a chart of maturity for each technology field. So, we have devised a system to rank from 0 to 10, according to the R&D maturity, capacity scaling up. So, after reaching 5GW, do you get a 10 and then shipment after you reach 5GW, you get another 10. So, the maximum score is 30. So you can see jumping from Q4 2019 to 2020, from the blue to the orange – huge change - everybody's jumping to the new technologies.

These are anonymized suppliers, but you know, all the big names are in here. So that's another very bird's eye view of the very fast and sweeping pace of change.

PV Module Risk of Defects Increasing with New Technologies

Now this is reflected on the factory floor, as we've seen from previous presenters. EL defects. Basically, let me explain what you see here.

So, there are several defect categories. This is based on the pre-shipment inspection, step four, which is the last step, so inspecting a sample of modules. Of course, you have to do a lot more of that, but this is a very good statistical view of the quality of the products. Of course, when the defects get too high, you reject the shipment. But this is what can be seen on the factory floor from 2018 to 2020.

Overall, there's the ability, there are some improvements, so, the cell quality that's fed in is better. So these are visible cell defects, not EL defects. But the EL defects themselves have risen, and this is mainly due to soldering - cold soldering, or weak soldering; introduction of multi-busbar plays a big role, half cut also, and cracks.

And this is very important. So, what you see here is not really a defect rate, it's a risk score. So the defect rate itself has not increased so much, but the risk of the defects has increased, so more severe cracks. Before a few years, we had one standard width size; full cells, 72 cells, big gaps between the cells, and this has changed dramatically. And that's exactly what you see here. 

Solar PV Quality Control from Pre-Production to Pre-Shipment Testing

Now, in terms of what we do; we do everything we saw before. As Jay said, for responsibility, you need to do from the factory gate down to pre-installation and post-evaluations so that you can have the chain of custody of the quality and accountability - it's very important. But this is like a very schematic, high-level map of CEA's [quality control and testing] approach. But as I said, it includes everything that was recommended before, but at a more high level.  

Pre-Production Product and Production Qualifications and Requirements

So the first step is to check the product. We have a set of technical requirements that we call the golden standard. It checks the product qualification, but also the production interior requirements. The areas that are marked in red are especially pertinent for the new generation modules. So reliability testing, and then go to have the new IEC standard 63209-1 that is codifying all these fresher PQP, etc. standards. So this is a good tool. Of course IQC, IPQC, all the QA requirements are very critical.  

PV BOM (Bill of Materials) Review and Technical Due Diligence

And then the BOM review, which is basically a review of the documentation, reliability test reports. Uh, we receive and review several sets of reliability test reports on a daily basis. When I say reliability testing, I mean, testing that lasts for several months.  

Pre-Production Factory Audit

And of course the factory audit is very important because we have brand new facilities and brand new processes. And it's very important to do that before going to production.

Inline PV Production Process Monitoring

And then inline production monitoring is basically a mini factory audit on a daily or even nightly basis, where we're checking the material. For example, EVA - it's the same type, is it the same thickness? Because thickness is very important.

Pre-Shipment Inspection and Batch Testing

And pre-shipment inspection, as we discussed, that's where you can really block bad shipments and reject them and have the work. But the thing is always important. For hail, we see more pronounced interest, because the glass can have a very big glass tempering process. So there is some concern here, also DML sequence or SML not so frequently. Definitely LID, LETID, they are there. But these are like cell level, not module level technology.

So that's, that's a high level methodology of the risk in the project, especially in this era of cost of new multimodal technologies.

Simplest Method for On-Site Solar EL Inspections

Jonathan Gifford:

Great. George Touloupas, Director of Technology with CEA thank you very much for those insights. One question from our audience - what's the simplest method, like well, we've heard about the importance of EL testing, both from Jay, from Frederick and yourself, but what's the simplest method for EL inspection at on-site, so when you're actually on the field?

George Touloupas:

So yeah, we do a lot of that. The simplest is to do a nighttime EL inspection. You can also do it during the day, but you need very expensive equipment to do that. So we have done the biggest, probably biggest project, over 50 MW of 90% EL inspection a couple of years ago. So we have a pretty big track record. We have our own equipment.

I think this is very effective, so you can do it on a sampling basis and have a very good statistical overview of the status. But of course, you know, you start with the lower bar. So IR inspection thermography is very effective, it’s very low cost, so that's the first thing that should be done. And of course, monitoring, and IV tracing. EL is more like focused, expensive, electro-magnetic resonance. First you do the x-ray and then you go to the most expensive diagnostics, but it's very effective. You can really see where it's going. And even if you monitor, for example, monitor cracks, you see how they develop.

Jonathan Gifford:

Yeah. Okay. So you can actually scale it up if things become a problem over time. George Touloupas, thank you very much for joining us today at Roundtables Europe.