Hello, welcome to the webinar, Innovative Approach to Assess Solar Plant Health and the Role of Technology in Protecting Assets. I'm Luke Brett from Reuters Events. This is one of several pieces of work we're doing on optimizing the operational phase of the solar life cycle. Do get in touch if you're interested in participating in any of our digital content over the coming months. My email is luke@luenergyupdate.com. There are over 1,000 of you signed up today, thanks very much for the great response, thank you in advance to our panelists for their time. Just a brief bit of housekeeping before we begin. This webinar will last an hour and is being recorded. We will send you all the audio recordings and presentations within a week.
You have the facility to ask questions through me as an organizer, so make sure you have access to your computer. The purpose of today's session is really to take a closer look at the barriers when operating and maintaining solar parks, and to discuss which technologies are being used to optimize this. Joining me today to address some of the issues, Jacqueline from Allianz Global Investors, Andrea from JinkoSolar, and Lucie from DuPont Photovoltaic Solutions. If at any point you want to ask panelists a question, simply enter this into a text box and we will try to get to it during the Q&A. Without further ado, Jacqueline, who will be moderating the session, do fire away.
Thank you, Luke. I'm very happy to be here today. I would like to introduce this session with a quote from our founder CEO, Andreas Utermann, who once said, "People go where they feel welcome, but they stay where they feel included." This is my motto today. There is no cluster, silo. We are all part of a value chain, and each of us has a role to play. Bear with us, contribute, and let's start a constructive discussion on how we can all together as an integrated entity, deliver quality and performance. Welcome on board, everybody, and let's start with a presentation from Andrea from Jinko Solar.
Thank you very much, Jacqueline and Luke, for the very nice introduction. Also very happy to participate in this webinar today. Going to start with our presentation. As Jacqueline mentioned, I think the topic is really related to how to make sure that PV plants operate and perform in the best possible conditions. Of course, to reach that, the journey starts from chunk of silicon material, probably, to produce some technology that's then put in the ground, can really perform at best of the condition and put in the condition to perform in a very reliable and durable way for a very long time. You know that modules are really supposed to stay in the field for a long time.
From the manufacturing point of view, it's really challenging to make sure that, of course, the modules will perform according to expectations, and not only because of the warranty, says that, but because, of course, we need to have technologies reliable and able to sustain the business plans and the development of competitive cost of electricity and energy generation in general. From the manufacturing point of view, of course, Jinko is since ever focused on keeping high quality components, high quality technology, reliable, of course, and mature. Historically, Jinko, of course, had a very strong evolution on technology, starting since the beginning from R&D. Historically, of course, we remember Jinko was producing, of course, cost-effective polycrystalline technology.
Along the years, especially in the last three, four years, we really managed to increase dramatically the efficiency of the cells and the modules, thanks also to our R&D investments and effort, even at large-scale production. We are talking about the production volume of Jinko planned for this year of almost 20 GW, focused on mono PERC high-efficiency cells, with, for instance, one of the world records last achieved, already above 24.5% cell efficiency. Of course, this is a target, of course, to increase performance of modules, starting from clearly the efficiency and the nominal power class of the PV modules. That's, again, just the tip of the iceberg when talking about quality , reliability and performance of a PV plant.
The journey starts much far away, as I was telling, because especially in a vertically integrated production like the one from Jinko, we start focusing on technology and quality since when we cast ingots for production, then cutting them into wafers, producing cells and modules, finally as a finished product. These vertical integration, of course, give us the possibility to control not only the price of the cost of the production, but also the quality of production. This is where the quality value chain starts. Because, again, having a module that, let me stress out again, had to perform for 25- 30 years in the field.
Of course, this fulfillment is achieved since when the modules are produced with high-quality components and when production is really controlled from A to Z to make sure that the modules do not degrade, for instance, further than what it's normally expected. Again, not because only the warranty says that. In terms of technology, just for instance, in technology and innovations, we saw in the industry and in the market, not only driven by Jinko but in general, driven by the fact that the size of the PV cells is really increasing right now. The target is to go towards even larger PV cells. Clearly, this sets a challenge in terms of reliability and not only in terms of performance, which is, for instance, the fact that a larger cell produces more current. This is, of course, very good from the performance point of view.
The module power class can really increase because the losses at module level are really significantly decreased. Just to compare, the same module made with the same cell efficiency in a format of a full cell or a half-cut cell can really have a gap of two power classes, even. So, we are talking about between eight and 10 W per module difference, again, using the same cell efficiency.
Of course, in terms of reliability, this can be a challenge if the, for instance, the current or the energy dissipated on a module or on a cell because of a hot spot, for instance, happens, and in a full cell format, we have the potential risk of overheating the cell to a critical limit, which could be somehow dangerous for not the cell itself necessarily but, for instance, the encapsulating material, the polymers used for the backsheet or the encapsulating, of course, in general, of the encapsulation in general of the module. Talking about numbers, for instance, and hot spots. A module with a full cell configuration can really develop easily hot spots. Well, not easily, unfortunately, but in some situation, in some scenario, can really have developed hot spots far beyond 100 degrees Celsius.
This is really, really dangerous because, of course, you can imagine the stress, the thermal stress that is induced on the polymers, on the plastic materials, and this is potentially a threat if we have this situation. In a half-cut cell configuration, the modules, of course, the cell have a different shape, a different format, a different interconnection, and a different area. The energy dissipation that happens on a half-cut cell module is significantly lower and enough to protect the module, even in this, of course, unwanted or dangerous scenario that unfortunately happen actually often and more than what we would like to see.
We will see later also in which cases, and that's also related to the operation and maintenance side, which is, of course, the topic of today, how the hot spots can really develop from really unexpected or underestimated situations and why is it important to have, for instance, as in this case, half-cut modules configuration to really significantly mitigate the risk that we have on not only on performance, but more importantly on the reliability of the modules. One more innovation that was introduced in the last years, of course, apart from half-cut cell, is in the increased number of busbars to not only increase the power class of the modules and the low light performance, for instance, but also to mitigate, in terms of reliability, the potential impact of microcracks.
On a half-cut cell module, it's very straightforward, understandable by the fact that the geometry of the cell changes, and the potential developments or a path of a crack is reduced by 50%. This potentially decreases the disconnected portion of the cell surface by 50% accordingly. Potentially, the impact on performance reduction that we have on a half-cut cell is also reduced thanks to this configuration and to this different cell interconnection. In terms of multi-busbar, for instance, technology or multi-wire, as the technology is going towards, like in our Tiger series, newly developed and launched very recently, is the fact that by moving from five busbars, for instance, up to nine busbars or nine multi-wire interconnections, this also significantly reduces the potential impact of microcracks.
Again, this is not only for power class of modules and the efficiency of power class of modules in terms of nominal values, but in terms of operation of the modules in the field, because the majority of microcracks, as we know, are unfortunately not produced, or fortunately for us, not produced during production or during transportation even, but many, many cases during the operation and because of the vibrations or mechanical stress or thermal stress that the modules have to go through during the operation and lifetime. Talking again about our new Tiger series and the developments, not only in terms of technology but also in terms of reliability, the special shape of the wire, which is not a normal round shape, clearly is focused to increase the reliability of the modules and to decrease the potential damages that could happen on cracks.
Clearly, on cracks that could happen on the cells, sorry. Clearly, the fact that there is a metal connected to a silicon material creates some mechanical stress, for instance, caused by the different thermal expansions or thermal behavior of the two materials into the laminate, which could, for instance, very simply generate possible cracks on the cells, which are all fragile or very thin materials, thin slices of silicon, which can be significantly impacted by a thermal stress induced by a metal wire or a metal busbar, metal ribbon. The fact that the ribbon, in this case, is much thinner, in terms of mechanical stress, of course, helps to reduce this potential impact on the cell.
The technology development is not, of course, only focused on the increase of power class of modules or efficiency of the modules, but especially also on the reliability of the interconnection and ultimately of the module overall. For instance, even the fact that at the overlap of the Tiger modules, the overlap cell area, where the cells are slightly almost touching each other, there is a cushion or a buffer, where the EVA is playing this role of protecting not only the cell in terms of encapsulation, but also in terms of mechanical resistance or protection against stress, against cracks or possible damages. Of course, if we talk about reliability and long-term durability of modules, we know or how important is the role of the encapsulation and especially of the backsheet.
Of course, the fact that there is a possibility to use many different components and many different materials for a backsheet, of course, opens a very wide range of scenarios and behavior of the modules in the field. We will see that later during Lucie's presentation and analysis that DuPont did in the field of the module's behavior. This is just summarizing, here in this slide, how the fact that Tedlar-based backsheet actually do have really the lowest possible failure rate measured in the field, which is, of course, the reason why we use that material, in particular, for the production of PV modules. All, of course, it aims to increase the profitability of the PV plants. As I said, the fact that the modules have a high-power class or high efficiency is just the tip of the iceberg.
Downstream, the modules have to operate reliably and durably for a very long time. Again, in terms of value chain or quality value chain, we try, of course, to cover as long as possible the chain, but of course, there is a limitation as a manufacturer, that there is steps that are not in our control. Of course, we always try to cooperate with the downstream market to guide EPCs , investors, or installers in a way to make sure that the modules really are put in the condition and even stored or handled or installed, operated, maintained in the best possible way, in the appropriate way, to reduce possible damages that might occur. Even a very simple aspect in terms of storage, we saw, unfortunately, in many cases, even distributors still stocking three boxes of modules, for instance, one on top of the other.
This is a possible damage for, of course, the box that is at the bottom. Of course, despite even the manuals or any guidelines clearly states that, there is still, of course, unfortunately, distributors or somehow parties not really probably underestimating the potential impact that this generates on the modules. Even in terms of handling or care of the modules during the operation, for instance, we all know that we don't have to step on modules. We will see later a couple of pictures showing that actually not everyone is really doing that.
Again, this is not to blame or not to point a finger against someone that is probably not doing things right, but it's just to state how important it is also to keep the manufacturer involved even during the operation of the sites, to make sure that the modules really perform according to expectations, and to follow the guidance and the suggestions that the manufacturers of the modules, like in our case, can give to the operators to make sure that the modules really perform in a reliable and durable way. I was talking about cracks before and how important it is to mitigate cracks on the modules. I mentioned that cracks happen during operation on the modules. We know that, of course, even the wind pressure, the vibrations on modules generate cracks because of the mechanical stress that it's induced on the silicon wafers on the silicon cell.
Clearly, if we step on the modules, and in this picture, I think it's clear that someone clearly didn't follow the rules there that I was showing in the previous slide. This directly induced cracks on modules, and it's even visually possible to spot this kind of damages, even with a simple infrared inspection. Not really necessary, even in some cases, to go for a better electroluminescence when the problem is so high that the interconnections of the cells are really damaged, for instance, and the cells are so cracked that can be really developing hotspots. Even during operation and maintenance, we will see later also in terms of cleaning, how important it is to pay attention on the way and the systems and the processes that we apply for the cleaning of the modules to make sure that the modules are not damaged.
In terms of the installations, we all know there is an IEC standard that says that, for instance, the connectors of the modules should not be plugged with different type or, different shapes or different brands of connectors. This is a regulation that is clearly not probably mandatory from the manufacturing point of view. Of course, it is required to have an IEC certification for the installation. It's not rare to see in the past, installations made with even MC4 and MC4 connectors together, which is clearly not working well. We see at the center of the pictures here what happens if that is done. Clearly because the connectors, if they're not plugged properly or plugged with different type of connectors, can really melt. This is a very simple thing to do and very easy, actually, rule to follow during installation of PV sites.
Clearly can create potential losses on the PV operation and operation of the sites and, can really increase losses on the sites if it's not followed. Talking about hot spots. Clearly, we know that modules have to be cleaned. Now, the question is how often, many times we also have questions from customers, EPCs, or operation and maintenance companies, how often the modules have to be cleaned and how can we clean the modules with a dry system, with a water system, and so on and so forth. Of course, every case, every site, every installation is different. There is not a general rule, but it's clear that when an installation is put in condition to develop hot spots, like shown in this chart, above 100 degrees, we are not only reducing the performance of the installation, but we are significantly hampering the reliability.
These modules were, of course, on a very dusty area, where work roads were done very beside the big installation. The modules were completely covered by dust, and the modules, as you see here, were really developing hot spots above 110 degrees Celsius. This is really dangerous. The modules were already bubbling. The EVA was already bubbling and creating some kind of start, delaminating the modules. Again, the problem is that it's not only losing power and energy and yield of the plants, but really potentially damaging the performance of the reliability of the module. I was making jokes about the fact that we don't have to step on modules. In my experience, it happened also that, for instance, of course, we suggested to clean the modules to the customer because they were dirty because of some dust accumulation.
Of course, clearly cleaning them carefully, so we said. I think the operators probably took our words a little too strict way, because they were so careful that the operator were really jumping on the modules to clean them centimeter by centimeter. Clearly, the problem is that, yes, the modules were spotless, really brilliantly cleaned, but we didn't do any electroluminescence test, but for sure the cells were most likely damaged because of this operation carried out in this way. In terms of cleaning, its interesting many times, and it happens also in our experience, to see how modules can be looking perfectly clean.
The surface maybe it's really looking clean and homogeneous. But, in reality, the thin layer of dust that sits accumulated is potentially not visible by eye or not so obvious, that it's like shown here in top right picture, visible by eye. If we go for an X-ray, sorry, for an infrared inspection, for instance, in this case, the customer was, if I remember well, as in this case, probably thinking of potential damages of the modules or underperformance or problems with the modules. With an infrared inspection, we clearly identified the fact that they, of course, confirmed that they cleaned the modules with a water jet. The water jet traces were really clearly visible on the infrared images here.
This is clearly not a good way of cleaning modules, for instance, because the water jet high pressure can really generate strong vibrations on the modules, which can really potentially damage the cells. Clearly, again, it's important also when cleaning or operating the sites or doing any modification to the installation or operation activity, maintenance activity, it's really important to keep the suppliers of the components involved or to ask for confirmation if any doubts, to make sure that the operations is really carried out in the proper way, if there is no indications in the manuals or guidelines that the manuals are giving or the component suppliers are giving.
To summarize, clearly, we all talk about LCOE, IRR, and how important is, of course, to make sure that the energy production is high and the modules and the BoS costs are reduced as much as possible, and the module efficiency is high. Of course, we always have to keep in mind that the quality value chain is much longer than what the manufacturers can do in the factory and how much efficiency we can put into a module. Of course, we always have to keep in mind how important is the operation and maintenance activities and to follow the guidelines and to ask for support to the manufacturers as well when needed, to make sure that the modules really perform in a durable and reliable way for a long time, to make sure that the system performance is the highest possible.
Thank you very much, and I give back the floor to you, Jacqueline.
Thank you, Andrea. Personally, I find it very bold. I mean, that a module manufacturer comes on stage and not only acknowledge the defects coming from modules, but they do address them and how they do address them. I think it's exactly what I like about the presentation from Andrea, that it highlights the complexity in the PV industry. There is this common belief that if the sun shines, the power plant is producing, but it's not that easy. There are so many factors and components which have to come together in order for those modules to properly function and deliver their promised output. When it does not happen, every technical interface can be a source of underperformance. I can tell you, everything that Andrea showed in his presentation, I have seen it. I think it's something maybe we should reflect on.
I think now it's the perfect transition to Lucie's presentation on sharing DuPont's experience and expertise. I'll leave it to you now, Lucie.
I'm trying to do things in the right order. Unmute, present. I hope everybody can now see my screen. I'm going to talk to you a little bit about some innovative approach to assess solar plant health. Before I get to that, I need to turn the page, and it's not doing it. Let's do it that way. It looks like I have no control. Luke, I might need your help because I have no control there.
Hi. Please just try again quickly. You are the presenter, so it should be working smoothly as practiced. Just try one more time on full screen.
There we are. They appear now. Thank you, Luke.
Okay.
When I meet somebody, first of all, I'd like to know where they're coming from, so that I can understand better where they're going. This is where we come from, and in particular, where I come from. I started in the PV industry in 2009. I spent about three years doing prototypes, making prototype modules. You would never believe what I've done. Then I went to the field and did some panel inspections to understand the degradation process on panels. Our field partners were developers, utility companies, universities, O&M companies, service providers, and so on. They allowed us to collect statistics on about 1.8 GW of panels spread over 355 installations. What we learned from this actually surprised me. About one-third of the panels we inspected showed a visual defect. That's a pretty high number.
Amongst the visual defects you see, for example, broken panels, water ingress, EVA yellowing, delaminations at various interfaces, some solder ribbon corrosion, and I probably miss a couple. There are also some invisible defects, such as PID, which is only visible with thermal IV testing. You have also some problems with defective diodes and so on. Now, the potential impact of all those defects is you may lose power, and that's notably what hotspot will do, PID, LID, light and temperature induced degradation, and various types of cell degradation involving shunt resistance and series resistance. You have also some safety implications. In particular, when you have backsheet cracking, then you will suffer from a major safety problem. I was trying to think about what tools I had in my toolbox, and in which case I should use which tool.
I'll take an example there to illustrate the multimodal approach. Say you have thermal imaging, you can even do a visual inspection, some limited lab analysis. You can do IV testing in the field, and then you can, of course, look at your historical trends from the archive data in the monitoring system. I take the example of PID. What do I need to have so that I know I've got PID? When you give me a thermal camera, I'll be able to tell you if you've got PID. That's all I need to tell you you've got PID. However, if you want to put a system fix in place, then I need to also see the panels, and then I will tell you if you can recover your PID or if you can recover only part of your PID.
To know the extent of the problem, really, you need to do IV testing. This will give you how much power you've lost. IV testing only gives you the data for today. It doesn't give you the data for a month ago or a year ago. To determine how much power I've lost over a period of time, I will need to look at your historical trends. Then I've used every tool in my toolbox to diagnose the problem , quantify the problem, and determine the potential for recovery. That's where the multimodal approach is born. This multimodal approach doesn't apply to every type of defect. You might actually use one or two or three of your tools in your toolbox according to what you really want to do. I'll give you another example of a portfolio assessment we performed last year.
We had 40 plants, and the basic assumptions was that the plants were performing. Question is, are they really? Are they performing okay, or are they underperforming? First of all, we need to set an expectation. How much is a normal degradation? Even that is a pretty tricky point. I decided to base myself on an NREL publication, and this NREL publication said that panels between 0- 10 years tend to suffer from 0.7% degradation per year. I wanted to be compared to my peer group in the 0-10 year group. Now 0.7% degradation is my expected degradation. After performing several measurements, various types of measurements, this is the picture we get. We've got a total power loss, and we've got the number of years of operation. Your dotted black line there is your expected degradation.
We can see that only four installations perform to our degradation criteria of 0.7%. Now, there are various reasons where we might have got to that stage. First of all, soiling and vegetation growth. We applied some corrections to our data to make sure we didn't take into consideration any soiling or any vegetation growth. This data is clean of soiling and vegetation. Now, you may also suffer from system losses. System losses include ground faults, inverter problems, cable problems. Sometimes you will suffer curtailment and network availability. The scope of our work was really to determine the power loss at the panel-level. We also eliminated the system losses. The picture you have there is only linked to panel-level losses. I have highlighted some of the losses in the previous slide, so I will not go through them again.
Now we look a little bit more in detail where our losses are coming from. Well, we performed some thermal imaging, and we were able to determine the amount of disconnected panels here. You see some installations here suffer from high degree of disconnect. Potential reasons for disconnected panels or strings are blown fuses and faulty connectors. These two reasons are pretty easy to fix. Then on top of that, you might have ground fault problems, the famous resistive problems. On a couple of installations, we saw some fire damage, and of course, you've got the reasons that are beyond your control, like weather damage, and finally, some faulty panels. We decided to discount the disconnected strings here and really get to how are the panels performing from those that are connected, how well are they performing. There we are.
We get from the graph on the left-hand side to the graph on the right-hand side, where we exclude the disconnected strings and panels. The picture is much better, but only a quarter of our installations are performing to our expectation of degradation. That's a lot of degradation. Amongst the causes for degradation, this was a very wide portfolio, so we saw very wide problems on this portfolio. Some of the causes, we had a couple of installations with many broken cells, and the power loss from there was obvious. We had also a couple of installations with early PID problems. Early PID problems can be spotted very easily with thermal imaging. Like at the end of the string, you see a very mild thermal signature, which is very indicative of early PID. In some installations, we also had pretty high optical losses.
The optical losses may come from delamination problems in front of the cells, but they may also come from EVA yellowing and other types of optical transformation in front of the cell. What did we learn? Well, actually, these installations delivered revenue. They were under a pretty good feed-in tariff for that time. The installations were also reported as having backsheet problems. Be careful, backsheet problems usually do not yield power losses. The reason for that is you may suffer late inverter starts or tripping in bad weather, and these are all times of minimal production. In fact, at the system level, when you look at your production data, it's fairly rare that you will see an increase in your power loss due to backsheet problems or cracked backsheets. You might have to put more effort into maintaining your operation with this type of problem.
Still, having a cracked backsheet will mean that you're leaving potentially bare wires exposed. You have a duty to make your installation safe. Why didn't we detect this power loss before? We did detect it before. We were called to investigate on this portfolio because there was an inclination that this portfolio was not operating properly. Our data is a little bit skewed. It wasn't a complete surprise that it was underperforming. The reason why it's difficult to assess the amount of underperformance is first, the performance ratio. Everybody knows the performance ratio, but it relies on accurate assessment of irradiance and temperature. Weather stations tend to suffer from misalignment, soiling, breaking, degradation, and drift, and they usually don't get the tender loving care that the panels are getting, or even the same TLC as your inverters. We've got a complex system.
We've got multiple components, and each of them may dysfunction or malfunction. We also have a system of optimization on-site . The maximum power point tracking is an optimization system. You might even interlink your inverters so that one of them will capture all the energy produced for all the others at the beginning of the day. That's an optimization system. All these malfunctions and the optimization system mean that you've got a very complex system to analyze. This is all done in multiple conditions and ever-changing conditions of vegetation , soiling, and shading. Indeed, we measure a lot of data, but how to analyze this data is very complex. Last point, these plants were between six and 11 years old. They had a monitoring system, but the quality of the data was fairly poor.
I would say the quality of the data for those plants was actually not out of line compared to other plants of that age. There are some challenges for those times that were pretty difficult and complex to solve. I've got a couple of minutes, I think. I'll leave you with a little story. Many years ago, I wasn't working in PV, and one of my customers had a production problem with our product. I had to go and see him to check what the problem was and solve it. We started production, and the problem didn't show, and we waited all day watching production, and the problem didn't show.
With the customer, we decided, okay, what is the information that you need to send me when you have this problem, how fast, and which kind of lot number and clear descriptions and photos, and I'll come back when the problem reappears. I went into the office and I thought, okay, my product was in spec. It wasn't borderline spec. It was well in the spec for every parameter that I was measuring. That product still created a problem at the customer. That means that somehow I was not measuring something that was crucial for my customer to be operating. That's what KPIs are about, like key performance indicator, is that how do you assess the performance of the product? It might be something that is touchable that you sell. It might be a service that you sell.
Your KPIs will help you along the way to determine the health of your plant and maybe how to make it work better. Diagnosis is part of the cure. I want to leave you with those thoughts, and I hope there will be some questions. Back over to you, Jacqueline.
Thank you, Lucie. I find the presentation from Lucie interesting. I agree with her. We have accumulated over time a huge amount of data. It's true that we do not always take the time to look at them, to run analysis in order to detect eventually defaults or maybe potential optimizations. I think it's the next milestone in our industry, the digitalization topic. I would like to come back on the introduction from Lucie. She explained where she came from, where she was heading to from the laboratory to the PV fields. It's exactly what I would like to come back on, that how did DuPont develop its expertise in the PV industry? Originally, they provided components for the production of backsheets. Actually, they just need to know how their backsheets with the matches they imagined would behave compared to other materials.
They started to ask customers. They directly talked to end users, and they went on field, they inspected PV plants, and over time, they accumulated data, which thankfully they are sharing with us today on all the defects that they observed. My takeaway from what Andrea and Lucie have presented is really following. You purchase a module over 20 years, 25 if not more, and if you want it to age well, take care of it, maintain it properly, and perform a health check. The same way you do it for any other asset, could it be your car or your house? Now, I think we will start the Q&A session. I think there were already some interesting questions about how to detect the micro cracks with the different instruments, different methodology. I don't know. Lucie, do you want to take it over from here or?
Yes. Andrea will be able to answer that one as well. Micro cracks are pretty tricky, and the wording of the defect is important there. A micro crack means that you've got a crack in the cell, but you haven't disrupted the connection on your cell. Basically, your very thin finger lines there are not interrupted. Micro cracks pretty much amount for no power loss. You can detect them with electroluminescence. You cannot detect them with thermal imaging, because for thermal imaging, you need to have full-blown cracks. That means finger line interruption, that will generate some hot spots. Yes, you can detect them with electroluminescence.
Mm-hmm. Thank you, Lucie. There is another question on the correlation between hot spots and soiling. Andrea, would you like to answer that one?
Yes. Thank you. Yeah, of course. It doesn't happen always clearly that, of course, modules develop hot spots, and the soiling is one of the causes, well, probably one of the most common causes of hot spot development, unfortunately. It happens when, of course, modules or cells are not homogeneously or somehow partially shaded or partially soiled.
The heavy soiling clearly tends to develop hot spots on cells, on the modules because of the current dissipation or energy dissipation, because of the lower activity of the shaded cells. That's something that has to be normally avoided, and it's normally tolerated in a normal soiling scenario, in a normal tolerable soiling losses scenario that is affecting naturally most of the installations. When happened in a heavy way, like in the pictures I shown during my presentation, clearly the risk is there, and the interest from all is clear to avoid or to solve those problems, in the fastest possible way to reduce possible damages to the modules.
Thank you, Andrea. I personally have a question for Andrea. You showed us the different kind of defects on the modules and how you mitigated them, and I was just wondering, how do you get this information from the operation field? Since you said yourself, once you sell the module, everything is out of your, how do you get access to those data on field, and how do you actually integrate them to two things, to your production lines and to your commercial processes, to your contracts, basically, how you sell them?
Very broad topic and how to build. Probably a short answer, let me try. There are clearly, of course, the influence or the control that the manufacturer have on the PV modules operation is very limited downstream. Of course, let's say that in general, if module is transported, operated, I mean, installed and operated properly, the potential failures are really low. We are talking about historical data that we have from our mass production of below 0.1% of failure rates on PV modules. We are really talking about small volumes of general failures that can happen on mass production. Of course, that's when modules operates in a proper way or modules are operating appropriately. That's why it's important to keep us or to keep the manufacturer somehow involved when something seems to go wrong with the PV modules in our case.
Of course, we also learn from that. The solution of the half-cut cell was just an example, for instance, to see how nicely the technology development had also to mitigate, for instance, the hot spots phenomena that might happen during the lifetime of the PV modules. Even in the next generation of PV modules, we are continuously learning and improving also the materials and, again, also the history that we have on backsheets material that was used in the past or polyamide or PET. We learn a lot about how to prevent or avoid failures or to increase the durability of the PV modules by selecting the correct components for full production.
Thank you, Andrea. I also have a question for Lucie, because as an asset manager, of course, I'm extremely cost-conscious. I was just wondering, you presented this 360 approach. Do you have any idea of which costs are involved here? Could you come up with a figure or just a range? What would be your recommendation on this 360 approach? Is there a good time to start doing this health check, or what is overall your approach on this?
It's a hard question to answer, Jacqueline, because it actually depends on the scope of your project. If you want to go on all-round health check, you might be more detailed in the case where, for example, you want to purchase a plant. The level of investigation will vary according to the scope of the project. No, it's difficult to give you a price. This is a project-based price, and basically, we need to talk more about value, in terms of trying to put some kind of financial numbers on this activity. Value of the asset. This value of the asset, if you underestimate the value of the asset, you have a problem. You should always try to acquire a health check with every change of ownership, and I take change of ownership in the broad context.
When you change, for example, when you do the acceptance test, for example. When you go from an EPC contract to an O&M contract, it's useful to know the health of your plant. Even with cases where even a change in the insurance contract, it is useful to know the health of your plant. Your old insurer will insure a certain number of things, but if you have potentially preexisting problems and then you change your insurance, your new insurer will not insure you for the preexisting problems. It might be that you only purchased a couple of panels with a cracked backsheet, and this seemed to be a sporadic problem, so you didn't think it was a widespread problem.
Your new insurer will say, "Well, it may not have been widespread, but it's the same defect, so we will not insure this defect." Then you run into problems. Any change of ownership, whether it is contract-based or whether it is really owning the asset, it's useful to know the health of your plant.
Yeah, that makes sense. Thank you, Lucie. There is an interesting question here. How do you detect and quantify PID loss in an operational plant? Could you expand on the thermography? Would you like to answer this one as well?
Yes. PID is actually now become a pretty simple problem to diagnose and quantify. If you stay in the field, it's easy to quantify and diagnose. Basically, diagnose is just, you've got the disease, but I can't tell you how serious it is. You do that with thermal imaging, and you will tend to compare your strings, the start of the string with the end of the string, and you will derive a pattern of heating with thermal imaging.
That's the diagnosis. At that stage, I can't tell you how serious it is. I can only tell you how serious it is with IV testing, and this will tell you how serious it is now, okay? Not how serious it's been for how long. Your historical trend will give you another clue about how long you've lived with this problem and potentially on the evolution of the problem in the coming years.
Thank you, Lucie. I think there is another question for you, and it comes to my questions as well. Ravi is asking, for a 100 MW peak portfolio, what is the time and effort to conduct a full 360?
It depends. It depends if you've got 10 plants, 10 MW, the turnover could be fairly fast because we've tried to automate the process as much as possible. Depending on the value you want to get, but also on the circumstances you want to get the data under, you might decide to do only a sample test of IV, for example, which could make sense. You would do 100% thermal imaging, and then you would do, say, only 50% or even 10%, depending on your thermal imaging or the IV testing. You can actually turn around this type of data, 10 plants, 10 MW, a portfolio of 100 MW in a pretty short time. If you've got only one plant at 100 MW, it's even easier. It's more boring for me, but it's easier. I guess you could work that one around.
Let's take the two scenarios. You could work around some data in about a month on 100 MW on one plant. If you need to manage several assets there and do the 360 on several assets, it might take you two or three months. It depends how many assets you're talking about.
Mm-hmm. Yeah, that makes sense.
The logistics is very important also in assessing how long it's going to take.
Thank you, Lucie. I have another interesting question here from Constantine. I think it's going to be rather for Andrea. What is your view on a UV fluorescence test versus EL tests?
Interesting one. The first one is, yeah, somehow probably starting to be used more commonly, in the last period. The information we can have from the two tests or two methodologies are clearly not exactly the same. There is, of course, advantages or disadvantages on using fluorescence or electroluminescence, also in terms of feasibility of the test or speed of the test. I think the interesting thing of fluorescence is that it can tell somehow part of the story of the cracks. It can tell in some cases when a crack happened, which is not possible to tell from electroluminescence tests. Probably, again, when it's probably necessary or possible to understand a little more about the history of the crack's developments, it can be more effectively used for this kind of analysis.
I think electroluminescence is probably more common because just it was mostly used in the last years compared to fluorescence. Clearly, it's also a very good and useful tool to use even on-site . I think the limit of electroluminescence was in the past that it was not possible to use it in the field, but now there is really portable tools, even with drones or portable machines that can really enable to do electroluminescence very easily and quickly, also in the field.
Thank you, Andrea. I have a very interesting question from Carine: How do you detect backsheet problems during the preventive maintenance? Lucie, would you like to answer that one?
Yes, sure. Backsheet problems are usually in three categories. You might see backsheets yellowing either when you look through the glass or when you look at the back of the backsheet. That's a pretty easy visual problem to see. Not easy to photograph, so you need a white sheet to try and show the amount of yellowing. You've got two other problems which are serious problems. These are backsheet delamination. They look a little bit like bubbles trapped when you look at the backside of the panel. You've got backsheet cracking. Now, the cracking, you could see directly from looking at the back of the backsheet, or you might have to have a backlight behind your field of observation.
You would put a torchlight behind at the front of the panel, and you will look from the other side to see inner layer cracking, which will lead to water ingress also. Yeah, backsheet problems are pretty visual problems. When you have them, you can see them. In an operational phase, you may be able to see your backsheet problems if you've got ground faults on your inverters and inverter tripping.
Thank you, Lucie. I think we will take one last question, from Christian, and it's going to be for Andrea. Does shading cause hotspot PV modules, and to which extent?
Sorry, I didn't hear the first part. Can you repeat that, please?
Does shading cause hotspots? Yeah.
Oh, yeah. Of course. Yeah, got it. Yeah, clearly, yes.
To which extent?
Fortunately.
Yeah. Mm-hmm.
It depends on what kind of shading we are talking about. Normally, far shading, like, caused by multiple row shading on shed installation or a normal ground-mounted installation is in the order of a few degrees. We are talking about probably a general condition between five and 10 degrees Celsius hotspot, which is totally tolerable for a PV module. If we talk about very near shading, caused by, for instance, leaves on the modules or bird drops or even soiling itself, it can be, of course, considered a kind of shading. We see that those scenarios really or obstacles very close to the PV modules, for instance, on rooftops, like chimneys or poles, et cetera. These kinds of shades can really increase the temperature of the cells quite a lot.
Especially if it is a small area which is not triggering the bypass function of the diodes that are installed in the junction box. This transition part of functioning of the module, when the diodes are not acting to protect the cells, and the modules and the cells are partially shaded in a very near shade scenario, then that's probably one of the most difficult situations, and when the modules can really develop hotspots of tens of degrees Celsius, unfortunately.
Thank you, Andrea. I think we have reached our limit. Luke, do you want to close the presentation?
Absolutely. Thanks a lot, guys. Excellent job , all presenters and panelists. Jacqueline, you did a great job steering the conversation. Andrea and Lucie, fantastic job, too. Plenty of questions were coming in. Unfortunately, yes, that's all we have time for. I'm sure you found all the insight very useful, stimulating, and certainly food for thought. You will all have access to the full audio replay and presentations within a week from now. Do share them with your colleagues, clients in the broader solar community. The aim of these discussions is to act as a catalyst for operational change in the solar industry. Big thank you again for tuning in and enjoy your weekend. Bye-bye.