Ensuring Safety in Grid-Scale Battery Systems | EP243

In this episode of the Clean Power Hour, Tim Montague engages with industry leaders Dr. Zhehan Yi and Ryan Mayfield to discuss the critical topic of safety in grid-scale battery systems. As the demand for renewable energy surges, understanding the safety protocols and standards surrounding battery storage has never been more essential. The conversation delves into the rapid growth of battery installations across the United States, which have skyrocketed from approximately one gigawatt to nearly 17 gigawatts in just four years. With projections that BESS capacity could exceed 100 gigawatts in the US by the end of the decade, addressing safety concerns becomes paramount.

Dr. Yi emphasizes the importance of integrating safety measures early in the design process, particularly regarding thermal runaway risks associated with lithium-ion batteries, which dominate the market. He discusses how engaging with authorities having jurisdiction (AHJs) and adhering to fire codes can mitigate potential hazards and foster the successful adoption of these transformative technologies. The episode also covers fundamental safety standards and testing protocols, such as UL 9540 and UL 9540A, shedding light on how companies like CPS America are innovating to enhance reliability and safety.

Ryan Mayfield brings over 25 years of experience in solar PV and energy storage to the table, sharing insights from his work with developers and EPCs (engineering, procurement, and construction firms). He highlights the need for ongoing education within the industry to ensure all stakeholders—from facility owners to grid operators—are informed about the risks and best practices associated with battery systems.

For more information about Mayfield Renewables, visitors can check out https://www.mayfield.energy/, about CPS America check out https://www.chintpowersystems.com/, or follow Clean Power Hour at cleanpowerhour.com.

Social Media Handles
Dr. Zhehan Yi
Ryan Mayfield
CPS America
Mayfield Renewables

Transcript

Zhehan Yi: 0:50

To be honest, from manufacturer standpoint, passing or getting the certificates or passing those tests is actually the minimum requirement of your product, right? But you gotta do much, much more for your product, you know, to improve the safety, not just passing it. So we do have a lot of, actually, I'd say, measures that were taken in terms of, you know, CPS battery.

intro: 1:15

Are you speeding the energy transition? Here at the Clean Power Hour, our host, Tim Montague, bring you the best in solar batteries and clean technologies every week. Want to go deeper into decarbonization. We do too. We're here to help you understand and command the commercial, residential and utility, solar, wind and storage industries. So let's get to it together, We can speed the energy transition.

Tim Montague: 1:42

Welcome to the Clean Power Hour live. I'm Tim Montague, your host today, ensuring safety in grid scale battery systems, expert insights and best practices, featuring Dr Zhehan Yi from Chint Power Systems, America's number one three phase string inverter manufacturer, and now featuring a five megawatt hour battery solution, and Ryan Mayfield of Mayfield Renewables, grid scale battery systems have seen remarkable growth in the United States, with installed capacity jumping from around one gigawatt just four years ago to approximately 17 gigawatts today. This rapid adoption is expected to continue with projections that the US could exceed 100 gigawatts of battery storage capacity by the end of this decade, as deployment accelerates, so do safety concerns. The acceptance and understanding of these systems by authorities having jurisdiction and utilities are crucial for their successful integration. Ahs often focus on safety aspects, particularly the risk of thermal runaway in lithium ion batteries, which dominate the market, engaging with the HJ early in the design process and adhering to fire codes are essential steps in addressing these concerns and ensuring the safe widespread adoption of this transformative technology. Today, we're going to explore explore some of the fundamental safety standards and testing protocols like UL 9540 and you UL 9540 a and learn how CPS and others are addressing safety and reliability. A few housekeeping notes, please do ask questions by entering them in the Q and A tab in the Zoom interface. We will do our best to get to all of your questions and note that this event is being recorded. We will be posting the recording on the Clean Power Hour website and our YouTube channel in about a week. So look for that, and please share it with your colleagues. As I was saying in the pre show, there's a tremendous need for more education of ourselves as energy professionals, of authorities having jurisdiction of customers. These are facility owners, landowners, grid operators. So much need for education. So I'm really grateful for our speakers today, and with that, I'm really pleased to introduce our expert panelists. Dr Zhehan Yi is the utility and ESS Product Solutions director for Chint Power Systems America. He focuses his efforts in leading CPS utility and ESS product roadmap and strategy. Dr Yi graduated from Georgetown University, sorry, George Washington University, with a PhD in electrical engineering. He holds six patents and is the author of more than 30 peer reviewed articles and conference proceedings. Dr Yi is an IEEE senior member, Associate Editor for IEEE access and co chair for IEEE Task Force on Internet of Things and for power systems. His research interests includes artificial intelligence and power systems and renewable energy integration. Dr Z is joined by Ryan Mayfield, founder and CEO of Mayfield renewables. Ryan brings 25 plus years of solar PV and energy storage experience to the industry. Since founding his engineering consultancy in 2007 he's been instrumental in advancing industry standards through his role on NEC code making panel 13, and as former PV systems technical editor for solar pro magazine an environmental resources engineering graduate, Mayfield is widely recognized for developing best in class technical training and engineering solutions across the renewable sector. He's the author of PB design and installation for dummies and a regular contributor to home Power magazine. What. Welcome Dr Z and Ryan. I would love to hear some brief introductory comments from both of you. Why don't we start with you? Dr Z tell us why this is such an important topic, and how CPS has been working to bring grid scale batteries to the US market.

Zhehan Yi: 6:07

Yeah. Thank you, Tim Ryan, for this opportunity. It's great to join the webinar today. Yeah, I think battery has been a the increasing interest topic in the past couple years, and I believe you'll still be a like a hot topic in the next couple years, as the attaching rate of battery to solar, larger scale solar project increase, and also the needs for renewable energy, as we know for So energy is really, I would say, the patch goal, because it depends on how well the solar irradiation is generating the power. So to make those more stable, or to make those more usable for the better utility, any storage is a good tool to smooth out the solar generation and to store the excess energy in the solar and from the solar so you can use it later, when it's needed. So it's a good tool. As more and more that we're hearing from safety concerns, especially from HJ we noticed that there's some gaps between the understanding of the solar battery safety, especially fire safety, and also the protocol or the emergency response needed to eliminate it or to reduce the risk of those safety issues. I believe this is a good topic that we can open the discussion here with you, Tim and Ryan, and also discuss with our attendees today as well to have questions.

Tim Montague: 7:40

Great. Thank you. And Ryan Mayfield, tell us a little bit about your recent experience serving developers EPCs and asset owners of battery storage systems and why this topic is near and dear to you,

Ryan Mayfield: 7:54

sure. Thanks, Tim, thanks for having me on this. Is thrilled to be here and appreciate the opportunity, and for us, so at Mayfield, we do a lot of design engineering work, and so working with, as you mentioned, EPCs developers, and that also puts it puts us in touch with a lot of ages, and for those people, very interested in safety, very interested in how the systems are going to work, what are the risks associated with it? Because honestly, there are risks, and we need to identify those, and we need to be realistic about those and mitigating against what those risks are. So I think that's always one of the big things where we are in an industry that's rapidly evolving. We're learning things in real time. We are having issues. We're seeing things, and we're responding to those. And so trying to gather that information, collect it, and then turn around and educate the industry. That's a big part of you know who we are, what we're doing, what we want to do for the industry. This is another great opportunity to do that. And you mentioned CMP 13. So I am on code making panel 13. I'm an alternate and just recently got back from a set of meetings. Very interesting. That's for the National Electrical Code. And so National Electrical Code trying to think about all the other codes as well, fire code, 855, and how we're going to make these systems as safe as possible. So thrilled to be here and share some of these insights and hear from the folks out there.

Tim Montague: 9:21

Awesome. Thank you. If you're just joining now, please do put your questions in the Q A tool there at the bottom of the Zoom interface. We really want to hear your questions, and we'll do our best to get to all of those today. And don't worry if a colleague couldn't be here today, you can share the recording with them in a week's time, this will be on the Clean Power Hour website and our YouTube channel, and I'll make sure that CPS promotes the recording as well, so you can look for that. So let's talk a little bit about this foundation that we have established here in the US, one of the main certification bodies for equipment, electrical equipment, batteries, solar, is UL, and we have something called UL 9540 and UL 9540 a, what are and this is for both of you, what are the general requirements and limitations of 9540

Zhehan Yi: 10:25

Yeah, maybe I can start from manufacturers perspective for their product, especially valid product for large scale battery that to be able to prove that is safe from fire propagation perspective, you have to pass the 9540 a test. And 9540 A is mature majorly for, just for the fire propagation, our thermal runaway test for the battery. Itself, and 9540 is more like a standard, or like a certificate for a system level, including battery and PCs, to see how the system work together to ensure the safety. Yeah, it provides a lot of actually guidance on how you design your battery to prevent fire propagation or thermal propagation. It's it's a good foundation and understanding ground for the majority of the users, also the manufacturer, on how they can design the system and how people use the system. But I'm pretty sure there are still limitation in there, because for a system that passed this test, we're still seeing fires, whether in the warehouse or whether they're in operation. So there must be something that is missing, or, let's say, missing, but something more that we can do to to increase the safety or prevent such kind of events or eliminate it. I would say, if we start from 9540 a it's called a thermal runway propagation test. I would say one of the limitation of it is it does not have a, like a four visibility of the large scale file behavior of the system. Thermal propagation is solely just heat up or, like intentionally put test the cells or from cell level, from pack level, from module, rack unit level, to see how, if one of the cell or get hit up and start to smoke, provide some thermal runaway events, how it's going to propagate through the cells and through the packs, how it working in that way. And it's all these tests are done in the lab, to be honest. So one limitation is that does not have the full scale feasibility of how the battery will behave if it's really on fire in reality. So that's one I can think of. The second, I think, is more site specific, because it's done in the lab. So a lot of case battery, most of the case actually battery are installed in the environment, are different than the lab. So there are a lot of other protocols or other measures needed to be done to improve the safety of the battery itself. I'll

Tim Montague: 13:07

just reiterate. UL 9540 is a safety standard for energy storage systems. It's a comprehensive safety standard that governs the integration operation and maintenance of energy storage systems. And and then 9540 A is the test method for thermal runaway evaluation at the cell module, unit and installation level. Ryan, do you have any comments about 9540 and 9540 A Yes,

Ryan Mayfield: 13:34

I was, that's a great recap on that, Tim, and that's exactly what I was going to reiterate some of the things that doctors you said. So what you just said is exactly right. And so the important, the thing that I always reiterate or talk about when I'm talking about these two, is 9540 is the standard. So manufacturers will go and test to that standard, and they will get a listing to 9540 9540 A is a test method, and exactly as you just laid it out. So they start at the smallest unit level, or excuse me, small, smallest portion of the battery, so that's the cell level. And then they move. They go larger and larger in terms of the testing protocol. And as Dr Z noted, there's, there is a real, I guess discrepancy is the way to put it, in terms of what the test is doing versus what this large scale fire test would be producing. So per 9540 a the to properly do the test, the manufacturer has to initiate thermal runaway in a cell that that has to propagate to an adjacent cell within the module, and at that point, the manufacturer can actually contain that propagation and not have it go to any other cells. And that would be considered a passing test, and you would get the data from that, and that would be able to inform you, as a installer, as a, h, j, what the propagation risks are. As Dr Z noted, there's no requirement to light that on fire, though. So as part of the 9548 test, as it stands right now, there is no need to, there is no requirement to, to actually light it on fire. And as we know, we are seeing fire. So even units that are going through the 9548 testing, there are still external events happening that could start the units on fire. And that's actually what we've been seeing most often from the when we go and look at the fires that have happened, it's these external events. It's water that got into the battery container. It's a it's a lightning event or something like that. That actually is what caused the fire. It wasn't the batteries themselves, but nonetheless, they caught on fire. So as an industry I mentioned earlier, we're learning in real time, we're making adjustments. And the things I would just point out is CSA, the. CSA group is going to introduce they they have it written now. They're going through public comment 2025, they have something called CSA TS 800 and that is a large scale fire test procedure. And so this will be a procedure that manufacturers can follow actually light the gasses on fire and see what happens. And so this is, in my opinion, a good, big step for our industry, because we're going to actually be able to see what happens at that point, and folks like CPS are going to be able to understand much better hJS will understand, and so we'll be able to mitigate our risk better.

Tim Montague: 16:26

Your comments remind me of Mike Tyson, who's in the news because he has a fight this week, which is amazing. The guy is coming back in his 60s, I think, but he's famous for saying, everybody has a plan until they get punched in the face. And this is how, this is what we're talking about, though, right? Because the actual real life circumstances are always different than the laboratory testing that goes on. But I'm curious if either of you could tell us a little bit about what are the paces that UL is putting these systems through to achieve 9540 or 40 a you both have said they're not actually catching the battery on fire or forcing you to catch the battery on Fire and but what are they doing? They're just putting it in an oven. Are they discharging and charging it super fast? What all are they doing?

Ryan Mayfield: 17:20

Doctor Z, do you want to as a manufacturer? You've gone through it. I'm sure you've been part of all that.

Zhehan Yi: 17:27

Yeah, so for the 9548 specifically, Ryan mentioned that there are multiple levels, from the cell level, which is the smallest building block of the battery, and then go up to module level, which is like a package of multiple of the cells. And then go up to the rack level, unit level, which can be like a container, like a 20 D container. The tests are the tests were divided into multiple phases at the very beginning, for example, for the pet level, your attention intentionally heat up one of the cells by putting some of the heating films internally of your the pack. And then, you know, hitting up and see how the cell will perform. The cell will heat up and release some gas, like, usually it's like, frameable gas, and then it can start to smoke. And you will see when the point is start the thermal event. You can see how it goes with all the smoke coming out of the pack. And there will be monitor, monitoring of the different cells inside the module. Then you see how the thermal runway can propagate from one to one consecutively, and eventually, how it goes, does the the module cut fire, or does the module just safely release the gas without any explosion or any fire? So basically, that's a procedure, and it's really interesting that we're talking about pass and fail for this type of application, because it's hard to understand what pass means, and what fail means. Because this, this test require you to do thermal runway propagation. I believe the best practice, or the best design of the battery, is no propagation, just limited content, it into one cell without any propagation, right? That's the ideal condition. But that never happened. That's why we want to see what if it escape, and then what if it propagates to another one? And what's going to happen? This is at the cell level, that is the smallest level. Then we have the pet level, multiple pack together and see how they propagate, and also the unit level, which have multiple racks of the batteries inside. So

Tim Montague: 19:26

let's talk about by thinking how he was. Let's talk about this from the H J perspective. What are the concerns? When an HJ is looking at a site plan, they see, okay, there's going to be three battery containers, or 300 battery containers, and they're thinking, Okay, what if so? I'm curious, what are the concerns, and what are the realistic concerns, and what are perhaps the unrealistic concerns that HJ might have? Yeah, I

Ryan Mayfield: 19:54

think it's a great question. And as Dr Z was saying, this is a test, and it's hard not to use Pass Fail language when we start talking about tests, but it's really, it's gathering data is really what it is. And so to say pass fail, I think is. And I even heard myself say it just a couple minutes ago, so I know it's, I'm not perfect about it, so it's more about collecting the data and understanding what will happen to the system under these when these events happen. And so as far as an h j goes, You're you as an H J, want to see that 9548 test report and understand what will happen if there is thermal runaway at those different levels. And so on our larger scale, we're talking about here our utility scale systems, we're going to see full containers of batteries, and they're going to be separated some distance from each other. And what you really want to know is, what if we do have a thermal runaway event, what will happen inside that container, and how will it prop. From a container, one container to the next. Those are the questions really, that need to be asking. And that really helps inform how far apart do we put these where, how far from a property line, how far from a building? Those kinds of things. Helps understand that the data reports are they're dense, quite honestly, and very often it's going to be working with the manufacturer to understand, here's what it was, or with the testing lab to understand, here's what the data is telling us. Because there's gonna be a lot of numbers, there's gonna be a lot of talk about volatile chemicals and those kinds of things that are being released. Can't expect hJS to be chemists and understand all that and be able to come up with a good answer. So working with the manufacturer and the testing agency, I would say, is a big part of it. Yeah,

Tim Montague: 21:36

and then often the HJ is going to engage the local fire department and get their comments, because they're the ones who's who are potentially cleaning up the mess. And let's face it, it's early days in battery storage, of course, in California, many jurisdictions have now seen grid scale batteries, but in most other parts of the country, these are very one off facilities, and we have literally 1000s and 1000s of jurisdictions. And these guys, no pun intended, but they're drinking from a fire hose, right? And you can't blame them for being skeptical or cautious, and so this is why, this is one of the reasons we're here today to put good information out there, on the internet, on YouTube, that these first responders can see. And traditionally, they're taking care of building fires or car fires on a daily basis, but they're not taking care of battery fires. And if you pour water on a lithium battery, bad things can happen. Right? Lithium is extremely reactive, so I guess I would love to hear, what are your What are your comments for H, j's and first responders about lithium iron phosphate, then the main grid scale technology that we're talking about, and how do you quell their fears?

Ryan Mayfield: 23:01

Sure, I can try and jump on that one. First one of the things we've been at Mayfield, we've been doing a lot of research on this. We've been doing putting a lot of our own content together and putting it out there. So part of that is talking with fire officials, talking with people who are doing this work day to day. And one of the early on, and when we started these discussions, one of the things that got pointed out to us by fire officials is they will risk a lot to save a lot. They'll risk a little to save a little. And so what I mean by that is, if this is a battery system inside of a building where there are people, they will they being the firefighters will risk a lot in terms of what their procedures are in order to save that building, to save lives. If this is a remote location, and it's a couple dozen containers full of batteries out in the middle of a field, they'll probably pour water around this perimeter of it and do a defensive mechanism of letting it extinguish itself. And so I think there's a really important thing of working with the firefighting community as well to understand what is, what's in if you're putting it inside a building, what's inside the building? What are the real risks, what are and how should such a fire? Because you're right. Tim, the approach of dumping water on it may not be the best, most effective way. May not result the end result of what they want on that. Unfortunately, at this point, we're still in a lot of education mode and working with those age days on that. And

Tim Montague: 24:26

we have a question from the audience, from Corey, could you please define a thermal runaway event. What exactly are we talking about here? Either of you thermal

Ryan Mayfield: 24:36

so in, in the context of what we were talking about with the testing thermal runaway, as Dr Z said, is part of the testing process, they will they being the testing lab, will heat up a cell, will heat up one of the cells of the inside the battery, inside the battery, inside the module, depending on the level of test you're doing, but they're putting heat onto it, and they're going to raise that heat until at some at a certain point of a temperature, that cell will not be able to do anything but go into thermal runaway, which means it the it will consume itself. It's there's chemical energy there, it will consume itself. And it will do that by burning itself up, for lack of a better way of saying it, so that would be a thermal runaway event in the testing process. At the cell level, you have to you a manufacturer, you a testing agency, you have to initiate a thermal runaway event. So you have to heat a cell up enough to make that happen. And at that point, you're collecting gasses. You're collecting information about what happened in that situation. Then when you move into the larger the module level, the unit level, you're doing the same thing, but there are different requirements, as I mentioned before. At the module level, you have to propagate from one cell to another in order to collect the data, in order to be considered a test that has gas. The proper data,

Tim Montague: 25:52

The Clean Power Hour is brought to you by CPS America, the maker of North America's number one three phase string inverter with over six gig Watts shipped in the US. The CPS America product lineup includes three phase string inverters ranging from 25 to 275 kW. Their flagship inverter, the CPS 252, 75 is designed to work with solar plants ranging from two megawatts to two gigawatts, the 252, 75 pairs. Well with CPS America's exceptional data communication controls and energy storage solutions. Go to chintpowersystems.com to find out more cool. I think we should move on to risk mitigation strategies. And you can keep your questions coming, these are good questions. But what are strategies that not only the manufacturer, and we want to hear from you, Dr Z on this, but also the developer, designer, engineers of these systems do to minimize the risk of a thermal runaway event. Nobody wants these events. They're not good for anyone. They're dangerous. They can spiral out of control. Sometimes they can burn for days and days. It's not easy to put out a lithium battery fire. The H days are low. The first responders are slowly but surely learning different techniques. I heard of one fire where they encase the fire in concrete because they couldn't get it to go out using traditional methods. But what are some of the risk mitigation strategies that battery manufacturers are using? Dr Z? That's

Zhehan Yi: 27:24

a great question. To be honest, from manufacturer standpoint, passing or getting the certificates or passing those tests is actually the minimum requirement of your product, right? But you gotta do much, much more for your product to improve the safety, not just passing it. So we do have a lot of actually, I would say, measures that were taken in terms of CPSS battery. Tim, not sure if you will be able to share screen. I did have some slides visualization that I can sure have to explain the concept. Yeah, yeah. So, just real quick, CPS America, we're a subsidiary of the bigger group. Our parent company, Chint Group, is a public company, and CPS America is the number one market share in the US for three phase string builders in the past, I guess, eight of nine years. And we have people servicing all of our projects and a customer all over the US. We have more than 20,000 projects in the US and office up in multiple locations, just some housekeeping items. Yeah, yeah. We have this five megawatt hour liquid cool battery, and our pair with our 2.4 string ESS skid, which is essentially a PCs or inverter. So CPS will provide the rounded solution, like everything is coming from CPS, except for the cell of the battery. So the cell will only pick the top one cell. So we do have a lot of strategies, or like safety concerns that we are taking in our our design just not only passing the test, but more of these considerations are beyond the test standards, and from what we learn from reality, what we learn from those incidents to improve our product, CPS with globally, will deploy roughly two people hour of battery, and we have non thermal events So far, let's say our methods so far have been proved in a lot of cases that it would work. So there are multiple perspective, for example, to eliminate the rigs or the manager rigs. The best way is to prevent it. So you will have to start from the design, for example, mechanical design, electrical design. So in our case, specifically, for example, for our strategy, we don't put PCs or the inverter together with the battery in one container. Because, although you can argue that PCs or the inverter itself is very safe, but you cannot, 100% say that product Chinese can't fail, because product Chinese can fail over the years, and it can be a point of hot spot that can heat up anything in the container, if you put it in there and cause castigated failure of your battery cells, if they are like close to each other. So our strategy is we separate the electrical, you know, compartment and chemical compartments, and we put the PCs or the inverter into a separate container to manage the electrical safety. And we have by doing that, you can add more protections, because you are not limited to the space of the battery container itself. You can add a lot of more for example, OCPD sensors and other strategies needed to bring more safety protection for your system. And in our case, specifically, we're using a screen structure, which give us more flexibility, because for central you have the four megawatt, five megawatt PCs connected to one battery. And if one fail, you're talking about four or five megawatt fail of energy that can cause a larger impact. In our case. When using the modularized string structure, we have a two kilo, 200 kilowatt as a unit, totally 12 of the 200 kilowatt inside our PCs container to manage each of the rack we can do rack level monitoring of the cells and the modules, how they work, how where they work, and how we can monitor the state of health of the cells immediately from all these PCs we have, I would say we have more granularity of this management from the rigs, and eliminates a lot of bricks that central structure cannot do mechanically. We we've done more like, of course, you have to have like, anti sesame design, right? Because a lot of these projects are installed in the California where earthquake can happen, and these are like external factors that can lead to other damages to your to your system. So mechanical design is one of it. And fire suppression. Of course, we mentioned 9540 a. One thing I didn't mention here is NFPA, 69 for for, for first responder, if they see the battery on fire and it's completely on fire, let's say, let's take an example of a grid scale battery in the middle field, nowhere on main area. And if the battery is fully on fire, the first responder know exactly what they can do, because they are, they're trained to deal with fire. I think the most dangerous case is you see no fire by smoke. In that case, you really don't know what's going to happen. It can start explosion because it's have the flammable gas getting concentrated inside the tank, and you don't know at one point when it's higher than the limits it can get into the explosion. So there are a lot of considerations of this design that way take actions in our manufacturing of the battery. For example, we have a anti explosion system, which with the help of gas detectors and also data driven algorithms, multiple sensors inside the container. When it detects such kind of rigs, we can start earlier prevention of explosion event. For example, we have exhausting system to get a gas out of the container, to keep the concentration of the flammable gas to be lower than the L E, L, which is the lower limit level for explosive and also we have pet level early fire suppression, meaning we have in the pack, in a battery module, we have a distinguish inside a module, so When it detects some, you know, overheating or flame like inside the module, ex equal plastic self, to distinguish the fire early inside the module, before it get escape out of that and continue to propagate into other units. Yeah, these are considerations that we are like taking when we designed a system, and we have all these reports available, happy to share with the audience here, if you have any questions.

Ryan Mayfield: 33:57

Actually, before we leave aside, I just want to, I just want to reiterate. Dr Z, you touched on it, but that in a PA 69 six, there's a 68 and a 69 anti explosion design. That's a really big part of this, and something that folks really should be looking at. That's HJ should be paying attention to, how are you? I'm the question that people should be asking is, how is the unit we're specifying? How is it going to mitigate against exactly that explosion risk? There's might be louvers in the top of the unit that allow gasses to escape and things like that. And the comment you made about firefighters and explosion versus fire. I've had them tell me exactly the same thing. They would 100% rather have a known fire hazard than an unknown explosion hazard. So they see flames, they see fire. Yep, we've got this. We know how to deal with this. We see a bunch of gasses and unknown things that that's when things get really scary, and that's when the fires that we have seen historically, that's where we've seen the biggest damage, and we've had firefighters hurt because of these unknowns. And so this is definitely a big part of it. So I wanted to make sure that we I highlighted that because that in a PA 69 is a big deal. I

Tim Montague: 35:07

wonder if we could walk through too as the system ramps up in let's just say temperature, so as you're charging and discharging the battery, it can heat up. And then, of course, there's the environment. And so there is a there's this cooling system in the container to run fluid past the batteries, to pull heat off of them and keep the system running at a stable temperature, which the batteries want. But let's say the cooling system were to fail for some reason, and then the batteries are going to heat up. What is the cascade of events Dr Z that the system does in order to prevent a thermal runaway? That's

Zhehan Yi: 35:48

a good question, and that's what I mentioned earlier. Fear that prevention is always the best, and you need to prevent it not only from just when the fire starts, it's from, I think, electrical protection, because a lot of time, like you mentioned, the failure is not from the cell itself, make, maybe from other components, for example, the PCs, or any other like circuits in the system, the cooling system. The best way is you would have to have a BMS that is smart enough to monitor systems, state of health and the conditions of situational awareness of your system. What we're doing here that we, like I mentioned, we have a string structure so we have a better granularity than like essential structure to monitor the rack level, state of health and the situation of those racks in case, for example, if the cooling system get down, the system BMS would first know again, then you pass up to the EMS, the EMS will be able to shut down the entire system to prevent the battery from being discharging and charging, to continue to heat up the cells and get out of control. Yeah, I think most of this can be prevented from battery management system and also in energy management system level.

Tim Montague: 37:04

Got it. Thank you. Yeah, this, I

Zhehan Yi: 37:06

already mentioned, we have a string structure, meaning that each rag is connected to a one 200 kilowatt PCs, or the battery inverter, so you have a better isolation from the rack to rack, because if one rack fell, the unit 200 KW will isolate itself or turn itself off, and instead of just keep running with The thoughts and feeding the thoughts, and eventually can cofad And yeah. And also, I would say the maintenance, like long term service agreement, or like maintenance of the battery, is very important. And there's something that also missing from from the current 9548 standard is it does not really consider the long term degradation of the battery when doing the test, because those tests with the battery usually are like the new batteries. But over time, battery characteristic can change. Internal resistance can change it, dissipation characteristic can change as well. So those are all risk factors that we need to be considered in terms of, you know, fire safety. This way install the system, it's going to be there for 20 years. It's not like first year, no problem. Second year, no problem. And it's good. We have to make sure that when the system is there, it's going to be safe. So I would say maintenance is a very important point to ensure fire safety. And for string structure is very easy for maintenance, because you have the string level monitoring and a situational awareness to know, okay, which string I need to get into the service earlier than the others, instead of doing all over for the tank, like every time

Tim Montague: 38:42

I have a question regarding that, if you have a five megawatt hour container, for example, but let's say you're regularly discharging one megawatt hour, and so only a fraction of those cells are directly going to be impacted. Does the system try to mix up which strings are being used on a daily basis so that all of the packs will age at approximately the same age? Or does it try to age a specific pack first. And, yeah, I'm just curious, how does the algorithm for that work?

Zhehan Yi: 39:16

Yeah, good question. Usually you would charge it. It's charged entire container instead of just a specific rack. So all of the container will be charged discharge at the same rate, even if, for example, you have a five megawatt system, and you only need one megawatt. Most of the case, you would let them charge, discharge the entire system, but you degrade your power down for all of the racks I see. And this is something that I mentioned earlier, that I think we should also consider it, because using battery in the US is really not having a really long history, but also, battery has been used all over the world, not only the US. Maybe we can locally some of the experience we can borrow from other markets to improve the safety here, for example, this is the job test that we've done, and it's this is required in Asian markets that for the battery to pass the safety test, you have to do this job test. In this case, we're lifting the battery up to four meter, which is slightly over 13 feet, and let it just free fall down to the ground to see what it happened. What would happen? Would that be any kind of fire get ignited from the pack? Or would that be explosion or anything in there this, I think are some considerations that as the market or the industry is learning and moving forward, maybe we'll have more standard all this test procedures getting in their standards that require the manufacturer to do this test. And if you move on the next slide, yeah, this. Is exactly what we've been doing with the cell level propagation, thermal propagation, test like hitting up the cells inside and see how it goes with the, you know, thermal runaway. And if you go to the next slide, our battery actually, not only using the US, but also, you know, all around the world, like the IEC markets, Asian markets. So by the benefit of that is, when you're doing the design for a battery, you have to consider all the standards, not just for the ego health standards, so you have more considerations of the safety and measures of the safety they have to implement into your battery. And this is an interesting case battery installed over the water. And if you look closely, you will see the firewall between the battery containers. What we are seeing here in us is because land is limited, so a lot of case you want to put battery as close as possible, but even back to back. So a lot of battery design with just one door open because they want to put a battery back to back. But this is in Asia markets, they will require a like a firewall between the batteries. You You won't be able to put the battery back to back. And this would, you know, help prevent the fire escape from one container to the other propagation. So it's interesting to see. You know, all the markets are taking different measures to improve the fire safety, and I believe, where the battery technology is developing and where our first responder and the manufacturer are learning from this process, we'll have more and more of these methods or protocols or technology that we can implement to, you know, further improve the safety of the battery, especially the fire safety, yeah. Now, last

Ryan Mayfield: 42:39

slide was very interesting to me, with the with those separators, and I think I will be curious to see once we have these large scale fire tests that I mentioned earlier, CSA is putting this document together, once we start to see what those actually are, what the results are. We may see something. I wouldn't be overly surprised to see something similar coming out of those, because we will be seeing these containers lit on fire and understand what the true distance is, to keep them safe from each other. Essentially.

Tim Montague: 43:06

All right, we only have a few minutes left, and we've got a couple questions. We will get to those, but I think we should talk a little bit about and we've already addressed some of this like we were talking about the firewall. But what are some of the installation best practices that developers and designers need to be thinking about

Ryan Mayfield: 43:29

for us when we think about that. Spacing is a big one. And so just right along the lines of what we were just talking about, what, how close or how far apart can these, or should these be the location, if they're indoors versus outdoors, what does that fire suppression system look like? For me, that's one of the biggest ones, of just understanding what are, what can we or can't we do, as the case may be, and what are, how are the what mitigation methods are being taken so for me, that's the, probably the number one thing I think about when I'm looking at these is distance, not only from unit to unit or container to container, but to property lines, to buildings to Tim. You have a nice array there in the back of your and there's some trees there. And so there's a vegetation that could be considered as part of if there was a batteries in that situation. So, you know, looking at this system holistically, and understanding where we're putting these units, and trying to project into that. And

Zhehan Yi: 44:24

also, I think the selection of the sites in in the weather and the environment of the site, for example, is a high humidity, or is it getting pretty, pretty hot in in the summer, constantly, about 110 this, I think, are all risk factors that need to be considered when designing the battery and selecting the batteries operating environment requirements. And also, I think, Ryan, you mentioned that the clearance between the batteries, safety distance between the battery and also between battery and other objects. If there's building nearby, or if there's like other trees or solar farm usually nearby, that would be the most important items. And actually, a lot of case batteries are installed near the substation, if you're looking at like solar plus storage. Solar are usually spread out and so and solar plus storage, where storage is really like more put in a central place near the substation. So there's some considerations, I believe, like between substation and battery safety distance, for example, we

Tim Montague: 45:26

have a couple questions about O and M, and of course, these systems are going to be out there for 20 plus years, so you will have to do O and M of various flavors. But what is the recommended base level of O and M, and then what can asset owners expect in terms of frequency of having to swap out modules or even. Larger systems in the field,

Zhehan Yi: 45:55

yeah, I can start for O and M. It's always best for their manufacturer to do the O M first, because we know, for example, CPS, we are the manufacturer, not only for the battery, but also the for PCs. So we provide the entire system, so we know how they work each other, and the schedule for each of the components to be maintenance during the over the course of 20 years. We do have a like a checklist, if customer work with us on the long term service agreement, we have a checklist of every you know, components, battery cells or battery packs especially, and the PCs that need to be serviced over the time, like every year, every for example, half year we need to be serviced. We have a full list of the check full list of the items that need to be checked up. And one other thing I want to mention is we have our flexible and system, which is special the CPS. We have the system that is providing the remote monitoring of the system of the batteries, PCs and other you know, components in the system, or preventive control, for example, if you notice something happen, we can do remote diagnosis to nail down if we can find out the main cause of it and Do some preventive actions to correct it or to repair it in case something happened, and to prevent further damages to the system. Ryan,

Tim Montague: 47:19

do you have any comments about O and M? Yeah,

Ryan Mayfield: 47:21

the thing I would add to all that, and that's great input that Dr Z had, I think the thing that I when my mind goes to O and m1, of the things I encourage people to go do is look at NFPA 855 and there's actually an O and M section within that, and so it's referenced in the National Electrical Code and and given in great detail in 855 a lot of it is going to be working with the manufacturer to understand what those exact procedures are. But I think the first and foremost for me having an O and M plan even before you commission the system will set you off on the right path, because once it's done, once you've commissioned it and it's operating, it's going to probably be harder to get back and make that plan, that O and M plan, and make it as effective as you can if you were to do it in the design or upfront stage. And so that would be my the thing that I really encourage people to look at and think

Tim Montague: 48:12

of, I'm curious, Ryan and Dr Z, are there boiler plate safety plans out there that our listeners can get a hold of to see examples of what a safety plan looks like for grid, scale batteries.

Ryan Mayfield: 48:24

I mentioned 855, and it has a very detailed list of what is, what goes in there, but it doesn't, it's, it's, there's no it's not a boiler plate. It's not going to hand it over to you, really, it's working with the manufacturers. And maybe Dr Z you can speak to this if CPS has something that is more readily available than what is just a list of items. Yeah, I

Zhehan Yi: 48:43

think it's hard to have the boiler plan, because every project is different, and especially report for battery is very customized. And every HJ may have their own requirement, I think one good practice is to work with Astra, get more feedback on that from them, to understand the requirements, because they are especially the first responder they would be the one dealing with if there's something happened. Fire to understand those requirements always beneficial for the manufacturers and also for the installers of the battery, especially, for example, some of the I know, for example, San Jose County, those, they have a good, very good guy live for as far as safety installation of batteries. And those, I believe that public available, yeah, would be. They have the PDF published on the website that you can search. And those would be good guidelines to understand in terms of installation of batteries and ensure safety.

Tim Montague: 49:39

And of course, we have dedicated storage conferences happening around the country now in the US, so you can attend those and run into these guys there. I think we should wrap up. I want to make sure our listeners know that they can find all of our content at Clean Power hour.com, and reach out to me on LinkedIn. I love hearing from our listeners. I want to thank you all for being here today. And how can our audience reach you? Ryan Mayfield, yeah,

Ryan Mayfield: 50:09

so I'm on LinkedIn as well. You can find me. Can find our business, Mayfield renewables on LinkedIn, and then also, folks are welcome to contact me directly. Email is always the best way for me, and that's my emails. Ryan at Mayfield, dot energy,

Tim Montague: 50:22

wonderful and Dr Z, how can our audience find you?

Zhehan Yi: 50:26

I think email will be the pretty the best way and straightforward way. So my email is my full name, zhehan@chintpower.com so you'll be able to send me email directly. And also, if you have LinkedIn, you can also send me message on LinkedIn.

Tim Montague: 50:44

Great. And of course, you can find much more at the Chint Power Systems website. That's Chintpowersystems.com or on LinkedIn. I want to thank Ryan Mayfield and Dr Zhehan Yi for joining us today. Thank you so much. I'm Tim Montague, let's grow solar and storage. Take care, everybody.

Unknown: 51:06

Thank you. Thanks, Tim. You.