Considerations for Replacement of Field-Installed Photovoltaic (PV) Modules

Have you ever faced issues with finding replacements for solar modules on your PV generating systems? NAES Renewables has extensive experience in identifying and sourcing replacement modules for sites of all ages. In this discussion, Project Engineering Manager Frances Plourde provides an overview of the present status of the issues facing module replacement evaluations and provides insight on how to address this growing industry issue.

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Transcript

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Welcome to Power Bank, sponsored by NACE Renewables, where big ideas, bold conversations, and unstoppable energy collide. We're your hosts, Ann mc Broome and Francis ppl, and we're diving headfirst into everything you need to know, want to hear, and can't stop talking about in renewable energy. Let's get into it. Hello, welcome to the Power Bank Podcast, sponsored by NACE Renewables. My name is Frances Lrd and I'm a project engineering manager here at NACE Renewables and I'm very excited to talk about some considerations for replacement of field installed photovoltaic modules. This is an issue that we at nace renewables believe is going to significantly impact the photovoltaic energy industry, especially in the years to come. It is something that we have experience in addressing for large scale photovoltaic systems, especially aging and distressed assets. Before we begin, I'd like to present some of the context behind the need for photovoltaic module replacements. The United States added an estimated 50 gigawatts of photovoltaic generating capacity in 2024. This represents thousands and thousands of modules that were installed in the United States to provide clean and efficient electricity generation. We're obviously incredibly excited about that. This continues an upward trend of rapidly increasing utilization and installation of photovoltaic power capacity installed in the United States in the past few years. However, this means that the amount of PV generating capacity and the number of PV modules that will need to be replaced in the coming years is also rapidly increasing. As we know, photovoltaic modules do degrade over time or need to be replaced for other reasons after their lifespan has concluded and so because of the rapid increase in utilization of photovoltaic modules, the number of those modules that need to be replaced is also rapidly increasing the National Renewable Energy Laboratory or NRL estimates that roughly 27 gigawatts of PV generating capacity that has been installed as of 2020 will be decommissioned as of 2030. Again, this represents thousands of solar modules that will need to be removed from installation. Hopefully the majority of these modules will be replaced by new modules, hopefully the generating capacity of these systems will remain, they will just need new modules in order to continue to generate. This represents thousands of modules that will eventually need to be replaced. As I mentioned before, many of these modules will need to be replaced simply because they've hit their expected lifespan. Most PD modules have a warranty that extends for between 20 and 25 years It's assumed that modules will be able to maintain up to 80% of their initial nameplate efficiency for that lifespan. So once you start hitting 20 to 25 years after the modules were installed, you're hitting the end of that warranty time. And it may be time to retire those modules and to replace'em with new ones. The primary mechanism for this loss in performance is what we call age-related degradation. This is a phenomenon we notice in photovoltaic modules where prolonged exposure to the elements leads to material degradation and loss of performance capacity. Aside from this normal age related degradation, modules can also exhibit under performance due to other issues as well. There may be issues impacting those modules that are leading to more intense under performance or rapidly increasing cases of under performance that can necessitate those modules being replaced. This can include what we call serial defects, which we discussed on a previous podcast in the Power Bank, if you wanna go back and listen to that. But this is where there is, a. Flaw that is noticed repeatedly throughout modules of the same model or within the same biding group that has a severe impact on module performance, as well as long-term safety and efficiency of a photovoltaic system. So as we discussed in that previous podcast, some of these issues can include separation of solder paste. It can include failure in the module, back sheet separation in those back sheet layers. And this can lead to things like hotspots, which can lead to arc faults and thermal issues as well. So aside from just the under performance, these modules need to be replaced due to the safety issues that they can pose to the systems. An additional reason for module replacement that we're beginning to see with more and more regularity is that of impact damage. The primary mechanism for this, for photovoltaic modules is that of hail impact damage. This is something that we're becoming increasingly aware of in the photovoltaic industry because as we're seeing large amounts of photovoltaic generating capacity be installed in areas of the country that have high occurrences of hailstorms, we're seeing increased instances of severe damage to PV systems caused by severe hailstorms. So this is something that the industry is aware of. Many module manufacturers are working to design modules to be more hail and impact resistant, but this is another reason why modules may need to be replaced, especially older models of modules that aren't as impact resistant. Now that we've gone into the context behind why PV modules may need to be replaced and why this is such a pressing issue for the industry as a whole, we get to a major question, which really grounds our discussion, and that is. Why are module replacements so complicated? Why can't we just go back to a manufacturer or the original supplier of the modules where we purchased them and request replacement modules? And the reason for that is because the PB industry is so rapidly developing, it's very rare for modules to be available from the manufacturer even a few years after their initial development and sale. Manufacturers continue to rapidly develop new technologies, new materials, different sizes and configurations of modules. And so after five to 10 years that a module has been on the market, it becomes very difficult to find replacement modules that are of that exact same model and same manufacturer. At that point, it becomes necessary to identify how you can replace those modules with similar modules that you may be able to find on the market that may not be the exact same type. So there are several considerations that we take into account when we're performing a module replacement evaluation. We begin our investigation by looking at the supply chain of the modules that we're trying to source. We look at the available inventory that suppliers have, the available sizes, electrical and physical sizes of modules that are presently available for sale. And we also look at the quality of that inventory, especially as we're seeing such an increase in the amount of PD modules that are removed from service. We're also seeing the rise of a very large secondhand photovoltaic module market many of those modules that are removed from service are still safe and efficient to use. They might just be older. They might not be within their warranty term but they are still functioning. And so there are an increasing number of secondhand module resellers popping up that offer older modules that. It may not be available elsewhere that are older, that may not be under warranty, but that can fit perfectly into an existing system if you use that same type of module. So all of those are things to consider when you're looking for a replacement module to make sure that the module you're looking for is actually available in the quantity, the quality, and the price that you're looking for. After we've established that the modules are available for purchase, it's important to look at the structural and the physical. Characteristics of those modules. Primarily, this focuses on the module size, so the length and the width of the module that it can actually fit into the existing installation system without significant retrofitting. Another consideration is module thickness Most PV modules tend to be between 30 millimeters and 45 millimeters thick, and this can have implications as to how those modules are affixed to the rack. The mounting method is also very important to pay attention to if the existing modules are mounted to the racking system using the mounting holes that are present in the module frame, it's important to try to ensure that those mounting holes are in the same spacing. On the replacement modules, it usually voids a module warranty to drill new mounting holes into the module frame. Because of the physical shock it introduces into the system, it severely damages the module to do so If you are still planning on using the mounting holes as the way of mounting the module. To the racking structure, you need to make sure that the replacement modules have the same spacing in the mounting holes, or you need to consider drilling new holes into the z purlin or whatever other portion of the racking structure you're using to mount the modules to accommodate the new modules. You can also consider using external mounting clamps or clips, and these will allow you to attach. The modules to the racking structure externally without needing to worry about the spacing between the mounting holes. So that's a common solution to mounting issues caused by replacing modules. We now take a look at the electrical characteristics of the replacement module. Primarily, this involves making sure that the power output of the replacement modules is sufficiently close to the power output of the original modules in order to make sure that the power output of the system isn't gonna be significantly impacted by the module replacement. We also have to look at the voltage and current outputs of the replacement modules specifically to make sure that the replacement modules will work well with the systems inverter. It's important to make sure that replacement modules will be able to meet the maximum power voltage range of an inverter. And it's also important to make sure that the short circuit current limit of the inverter will not be exceeded by those replacement modules. It is also important to pay attention to the way that the replacement modules will be grounded to the rest of the system. Mounting a PD module through the mounting holes usually provides sufficient grounding if you use external clips or clamps. Those do not provide sufficient grounding, and so an additional grounding wire may need to be installed. At this point it's also important to mention that we don't recommend installing modules of different types in the same string if the voltages of those two module types are different, doing so can introduce voltage imbalances within the string that can lead to overall under performance and potentially electrical load imbalance, which can cause issues to your system later down the line. So for any module, any modules that need to be replaced on site, we recommend removing all of the modules that need to be replaced, consolidating all of the remaining original modules within all of the same strings, and then installing full strings of replacement modules in order to mitigate these potential voltage imbalance issues. As you can probably tell from our discussion, the modular replacement process is more of an art than a science. It requires consideration of several different factors simultaneously, and it's not without its challenges. As I mentioned before, the PV module industry is evolving and changing so rapidly. So because of that, and because module manufacturers are constantly trying to utilize the newest technologies for the most efficient and most productive solar modules, this has led to an industry where there is almost no standardization. There are almost no standardized module characteristics within the PV module industry at the present time. This means that there's almost no standardization. For any PV module characteristics, this includes physical size, dimensions, length, width, thickness. It includes electrical output, so not just the power output, but also the voltage in current output, as well as the mounting considerations. The mounting hole spacing is also a characteristic that's not standardized. This makes replacement of modules very difficult because it's almost impossible to find replacement modules that have exactly the same characteristics as the original modules. This is why replacing modules is such an arduous process because you have to weigh all of the different module characteristics in order to find the best available module for your particular use. As the PV module industry continues to rapidly develop, the available supply of older and smaller modules continues to dwindle. So by the time you hit five to 10 years past when modules were manufactured, it becomes almost impossible to find those modules or modules of similar power output, or physical characteristics. This makes module replacement of older modules significantly harder because it can become nearly impossible to find modules of lower power output or smaller physical footprint. In addition to the process that we discussed earlier, there are several other considerations that should be mentioned when you're pursuing a module replacement evaluation. The first is set of warranty considerations. So as we discussed before. Many of the cases of PDV module replacement occur in the context of a module warranty claim or a serial defect claim. As we mentioned before, many times those claims are resolved by the manufacturer providing new modules to install in place of the old ones. This can lead to the same issue that we discussed previously where newer modules can't fit easily into systems that were built to accommodate older modules, because the newer modules tend to be physically larger and have larger power, voltage and current outputs. So you're left with having to reconcile the older existing system with the newer modules that are provided by the manufacturer. At the same time, installation configurations of replacement modules may not necessarily. Fit those replacement modules module warranty. So for example, if you're trying to install a replacement module into an existing system that necessitates that mounting clamps are placed at certain spacing on the module that mounting clamp spacing may be outside of the replacement modules warranty. In that case, there may be little recourse if a module warranty claim is needed on those replacement modules in the future. So these are all things to consider, especially when you're evaluating a module warranty prior to purchasing an original or replacement module, and make sure that that warranty is actually going to serve your needs in the future. Additionally, the costs of actually performing that module replacement should be considered when deciding whether or not a module replacement evaluation should be performed for a given site. Aside from the additional expense to procure the replacement modules, you have additional expenses in terms of labor costs for the. Replacement. So to actually remove the old modules and replace them with the newer ones. Additionally, you may need res stringing of parts of the array in order to consolidate the original modules into all of the same strings, and then install the new modules into the empty strings in the array. There may also need to be structural changes to the existing system. You may need to retrofit the racking structure in order to accommodate the. Replacement modules, or you may need to purchase new mounting clamps. You might need to perform electrical changes to the system by installing new wiring or changing connectors, or changing fuses in order to accommodate the new modules. All of these costs, in addition to the material costs of the replacement modules should be considered when performing a module replacement evaluation because the costs associated with the module replacement may not necessarily outweigh the financial loss caused by the modules that need to be replaced. So that's something that we highly recommend considering before you begin a module replacement evaluation. Additionally, it's very important to consider aesthetic considerations when you're performing a module replacement evaluation, especially if the modules are going to be installed in a public facing configuration. You need to pay attention to the size and the color of the modules that you're replacing in order to make sure that they look consistent with the surrounding modules. For example, if you've ever driven on the freeway past Eagle Stadium in Philadelphia, you'll notice that there are several pV modules that are installed parallel to the exterior wall of Eagle Stadium. They look very cohesive. They're all of the same size and color. And so if any of those modules needed to be replaced, it would look very out of place for the replacement modules to be drastically different in terms of size and color. So those are considerations that, especially public facing PB installation should pay attention to. Additionally, if the system is intended to provide a certain amount of ground coverage, if it's for a solar carport or shade structure, it's important to make sure that the size of the replacement module will be able to provide sufficient ground coverage in that structure. So you wanna make sure that you're not installing a smaller module in those instances that can potentially lead to gaps that can defeat the purpose of having a shade structure. To summarize our discussion today, I wanna leave you with some recommendations that we at NACE Renewables always provide to our clients when pursuing module replacements. First of all, if you're in the process of designing or building a PV system, we highly recommend that you keep a good number of spare modules. On hand and available for replacement. It's much easier to purchase extra modules at the time of the site being built or commissioned than to try to find those modules at a later date. Depending on the size of your system and the availability of storage space that you have on hand, we recommend between five and 20% of the modules that are installed at your system be kept as spares in order to enable more efficient module replacement in the future, and to forego the need for performing module replacement evaluations in the future. We do recommend that any new PV systems are designed to accommodate whatever standard module characteristics currently exist. So within the last few years, nine of the world's major module manufacturers, have agreed upon a set of standard module characteristics, including the physical size, the dimensions of the module, as well as the mountain hole spacing. Obviously, this standard will only start affecting modules that are installed in the future past this point, so it doesn't necessarily. Alleviate the complications of replacing modules that were installed up until this point, but hopefully this signals a change in the industry towards more standardization of module characteristics, which will hopefully lead to more efficient module replacements in the future. In cases where large numbers of replacement modules are required, so for example, if you're replacing modules at a utility scale photovoltaic site, there are options for custom made PV modules that can help accommodate these needs these are usually only available in very large quantities, so if you need more than 1000 replacement modules, but this may be a very good option, especially in cases where large numbers of replacement modules are needed that are proving very difficult to find due to the module age or size. We hope this discussion has given you an overview of the process for performing a module replacement evaluation, and has given you an insight into how NACE renewables has approached these issues in the past. If you have any questions about module replacements or would like to reach out to us. To discuss these projects further, please send us an email at Power bank@nace.com. We look forward to hearing from you. Thank you so much for joining us on today's episode of The Power Bank, sponsored by NACE Renewables. If you have any questions regarding the topic of our discussion today, or you would like to reach out to us about special projects for photovoltaic sites, we would absolutely love to talk with you. You can send us an email at Power bank@nace.com. Thank you and keep powering on.