July 27, 2022

060 - How PV panels change the fire behaviour of roofs with Jens Kristensen

060 - How PV panels change the fire behaviour of roofs with Jens Kristensen

[March 2023 update] The Thesis PDF is finally available! Check it here: https://www.researchgate.net/publication/369141515_Fire_risk_associated_with_photovoltaic_installations_on_flat_roof_constructions_-_Experimental_analysis_of_fire_spread_in_semi-enclosures

If a PV panel is fire safe, and the roof is fire safe, what is the outcome of a panel placed on the roof? Not a great surprise that merging two things that meet their requirements within their respectable eco-systems gives a not such a fire-safe outcome after all... This is the difference between considering systems versus product characteristics, and in relation to the fire safety of PV panels, something truly unique to my today's guest - dr Jens Steemann Kristensen.

Jens has gone a long way from burning PV panels in a cone calorimeter to trying to understand the holistic behaviour of panels placed on the roof. Join me in learning about his journey, his doubts and findings, and most importantly - some really interesting findings in how the issue of fire-safe PV roofs can be solved.


[00:00:00] Wojciech Wegrzynski: Hello, everybody. Welcome to the Fire Science Show session 60. Today I have a topic that I would classify. Under interesting, relevant, and maybe even sexy. It's a topic of fire safety of photovoltaic installations on flat roofs. Certainly a very, very irrelevant issue. And we've seen lots of large fires of such installations.

[00:00:20] Wojciech Wegrzynski: Going through the U S and in Europe as well. And regardless of this fires happening, there's not that much research going into this subject. So certainly the efforts of my today's guests are very much. Appreciated where maybe not that much appreciated by the PV industry, but the certainly appreciated by the fire industry. My guest today is, uh Jens Kristensen, Doctor Jens Kristensen

[00:00:43] Wojciech Wegrzynski: he just defended his PhD. at the university of Edinburgh with his research being performed, , both at the Edinburgh end. At the DTU in Denmark where he's currently. it was great effort on investigating why. Or how [00:01:00] such a roof installations could burn. And they really appreciate that. SUNY into his early research. He realized the very specific complexity in the system and pursued that until he got his PhD. Researching this complexity. And trying to understand how this complexity changes the behavior. Of the roof and panel system. Considering them both together, not separately, which is a huge distinction from how our industry often operates. And this podcast episode.

[00:01:31] Wojciech Wegrzynski: We'll tell you a lot. About the safety of photovoltaic systems. But also a lot about how our systems operate so without further ado please join me with Jens and uh, now let's spin the intro and get into the episode [00:02:00]

[00:02:10] Wojciech Wegrzynski: Hello, everybody. Welcome to Fire Science Show I'm today with Dr. Jens Steeman Kirstensen congratulations on your Viva

[00:02:18] Jens Kristensen: thank you very much. And thanks for invitation to your fantastic show.

[00:02:22] Wojciech Wegrzynski: really happy to have you here. And we are gonna discuss surprise, surprise your PhD topic, which is, photovoltaics and fires and that's uh, I must say you, you have a very interesting twist on the. Flammability or, or fire behavior of photovoltaic panels. I really like your approach and the way how you studied, but we'll reach that point.

[00:02:45] Wojciech Wegrzynski: Why is so interesting from my perspective soon, first, uh, please tell me like, uh, what made you start incinerating photovoltaic panels? Like, is this a hobby from childhood to burn things up?

[00:02:58] Jens Kristensen: No, no. Ah, [00:03:00] maybe, maybe I was one of the students in physics who tried to ignite everything, but I was probably not one, one behaving the best either, with the photo voltaics it started when I was a master student at, at DTU, the technical university of Denmark where had my. Current supervisor Grunde Joomas, master of studies, no head of studies it's called, and also he was one of the guys teaching fire safety engineering.

[00:03:25] Jens Kristensen: So, um, there was only three courses at teach here in fire safety engineering. So I went to him and asked, Hey, do you have more courses within fire safety engineering? Uh, and he said, yes, we can do individual courses. So I had an individual course, which went well. And then at some point, If insurance, who is an insurance company of Ikea contacted contact to ask, Hey, do you wanna be a third party on some experiments related to photo panels on, flat roof constructions, which Ikea have a lot of, uh, and, uh, yeah, I was the third party on that.

[00:03:55] Jens Kristensen: And Ikea was happy with those experiments or my report, and that [00:04:00] turned into master thesis afterwards with some large scale experiments, and. They were quite happy with that as well. So, so we continued with, with a PhD and got the two insulation companies, Kingspan and Rockwell, uh, on board as sponsors as well, the project.

[00:04:15] Jens Kristensen: So it's been a long journey. now I read the, finish the PhD and it looks like our continue, working on the topic.

[00:04:22] Wojciech Wegrzynski: Oh, that's cool.

[00:04:22] Wojciech Wegrzynski: usually people after their PhD, they don't want to see the subject of the matter and

[00:04:28] Jens Kristensen: Yeah. You know, to be honest, I think, I think, the subject is still interesting. I did not answer all the questions. I still think it's, it's a very extremely relevant topic. and I do know that that. I'm one of the few people working on the topic. and if I'm able to continue raising awareness, of the issues related to the installations, on roof construction or in the built environment, I think it's some extent necessary, to continue,

[00:04:58] Wojciech Wegrzynski: um, I think what makes your work [00:05:00] really unique, and this is obviously, your. advantage or your achievement as well as achievement of your supervisors, GDA and, the whole project is that you look at the holistic setup of the PV panel and the roof,

[00:05:15] Jens Kristensen: Mm. Mm,

[00:05:16] Wojciech Wegrzynski: the manufacturers of, PV panels or many other bodies

[00:05:20] Jens Kristensen: yeah, yeah,

[00:05:21] Wojciech Wegrzynski: would look solely on the, on the fire performance of the panel itself,

[00:05:26] Jens Kristensen: yeah,

[00:05:26] Wojciech Wegrzynski: look only on the roof itself.

[00:05:28] Jens Kristensen: yeah.

[00:05:28] Wojciech Wegrzynski: you try to understand what makes the way, how the panel is placed on the roof, change the, the fire conditions. And I, I

[00:05:36] Jens Kristensen: Yeah. Yeah.

[00:05:36] Wojciech Wegrzynski: it, it also places your research in this universal area. you are not really connected to any PV panel manufacturer. The insulation of, of course you did research on certain types of insulation cuz that's what you had access to.

[00:05:54] Wojciech Wegrzynski: But it's also, fairly universal in terms of, of the properties of the, this materials. So, I think it [00:06:00] makes it really interesting. Like what was the point when you. It would be interesting to look at the problem from this perspective of the, this semi enclosure as you name it, uh,

[00:06:12] Jens Kristensen: Yeah. Yeah. Yeah. Uh,

[00:06:14] Wojciech Wegrzynski: panel, instead of just going simply, let's put a, shit load of PV panels into cone rank them by flammability or

[00:06:21] Jens Kristensen: yeah, well, well that's, I guess almost what I started doing. you know, that's the risk, it's been lot long journey. I remember, some of the first stuff I did was, was taking a PV panel, trying to cut it up into, 11 by 11 centimeters of, uh, And cutting a glass panel is, is quite tough. I can tell, it all, uh, cracks, but I did it.

[00:06:41] Jens Kristensen: I put it in a cone. I tried to ignite it, but, but I also realized that the back of, a PV panel mostly is a flu polymer, which has a very high thermal stability, uh, and a very low, heat of combustion when it's finally ignited. and the amount of combustible materials in a standard [00:07:00] panel is extremely limited.

[00:07:03] Jens Kristensen: Uh it's it's around 10%. so, so at that point I started considering is the PV model actually a file.

[00:07:09] Wojciech Wegrzynski: Mm.

[00:07:10] Jens Kristensen: Or what is it actually that's burning. so what we did then was, uh, steady state experiments where I had a gas burner and then I measured the heat flux as the function of distance to the gas burner without the panel.

[00:07:21] Jens Kristensen: And of course the, the heat flu is, is reduced as a function of distance, uh, which is quite obvious. But then we installed the PV panel above it and played around with, with the inclinations and the gap height. Uh, and we only published a limited amount of that. Cause I did. Continue with, with, you know, I didn't do that many experiments as it was powerful master thesis, but at that point realized that, okay, the deflection of the flame below, the PV panel actually increas the heat significantly towards the surface below.

[00:07:52] Jens Kristensen: and because I only had access to few panels and wanted to, I repeated the same experiments with a panel, which had been [00:08:00] used for one experiment. Uh, and then I reused the same panel. So I used the panel where a part of the backside membrane was burned away and thus there was no combustible materials left on, on the back seat.

[00:08:14] Jens Kristensen: And, and at that point I realized the panel itself is probably not a fuel load. So I have to look at the, the system behavior rather than just individual components. And, and that's how we ended up continuing, or looking at the system rather than, The individual components.

[00:08:29] Wojciech Wegrzynski: Because is the panel? a bunch of glass, Silicon plastics.

[00:08:35] Jens Kristensen: Uh, yes, it's a glass, mostly in general. but it is, glass panel, two to three millimeters thick, uh, then there's that frame to on most panels to stabilize, uh, the construction. And then you have the Silicon, cells with C combustible. uh, then there are some metals, relatively limited as well.

[00:08:54] Jens Kristensen: Then you have the back, which is you have the, the cells encapsulated in EBA. Uh, [00:09:00] and then you have the back, which is often the, at that it, then you have a junction box and you have some cabling, of course, the whole

[00:09:07] Jens Kristensen: infrastructure.

[00:09:08] Wojciech Wegrzynski: how, how heavy is the square meter of a panel? is it,

[00:09:11] Jens Kristensen: Uh, yeah, stand, more or less standup panels. One meter times 1.7 and weight is 18 kilogram. So it's, it's tens per square.

[00:09:22] Wojciech Wegrzynski: That's not that that even if you consider that all of it goes into fuel load, that that's still not very much of, of a fuel load. And if, if you say that it's approximately 10% of it, which

[00:09:33] Jens Kristensen: Yeah. It's it's

[00:09:35] Wojciech Wegrzynski: extent that's not a very big, uh, fuel factor. And, and then. On contrary, we see this large fires this roof, installed facilities.

[00:09:43] Wojciech Wegrzynski: There was the famous case of Walmarts in us. It was

[00:09:46] Jens Kristensen: oh yeah.

[00:09:47] Wojciech Wegrzynski: it was a very metal case where, I think it led to the removal of, of some of the affordable systems from their

[00:09:54] Jens Kristensen: Yeah.

[00:09:54] Wojciech Wegrzynski: or at least that was the, the intention at that

[00:09:56] Jens Kristensen: Yeah, yeah, yeah.

[00:09:58] Wojciech Wegrzynski: So. Indeed. [00:10:00] We, even though it's such a small fuel source, there is, in the public space, some risk associated with that.

[00:10:07] Wojciech Wegrzynski: And I, I assume your, uh, research was, was going into the system approach into looking how the panel changes the fire dynamics of, of the roof itself, not just treating it as an additional fuel that's, that's pretty smart. And what about ignition?

[00:10:24] Jens Kristensen: Yeah,

[00:10:25] Wojciech Wegrzynski: because you've mentioned you put the fire underneath the panel, so, you did care about the fires that are within the roof.

[00:10:32] Wojciech Wegrzynski: And then the panel is as, as additional factor or fires that could originate in the panel. And then what was the

[00:10:40] Jens Kristensen: Yeah, we, we had several, you know, There's several sources of ignition. there is of course, an external source of ignition, which we cannot control or missed. There was a large fire in Norway and I thinking facility it's named as the fire, a. [00:11:00] The largest cooling facility in Norway, but there was a forklift catching fire inside, uh, the cooling facility and the fire broke through the roof.

[00:11:08] Jens Kristensen: But, but what happened afterwards was that the fire propagated, along below the solar, along the roof, and then spread into a different, fire compartment. So certainly the compartment section of the, facility was, was, uh, breached, due to the installation of the PV panels. but mostly you. Of course the external, cases of ignition.

[00:11:28] Jens Kristensen: And then you have, the PV system itself, which is a direct current system, which you can discuss whether the installation practice and standardization, uh, is good enough, because the, the standardization of the PV module itself is, is, is quite good. It's it's the electrical Institute international.

[00:11:47] Jens Kristensen: I can't remember. It's called,

[00:11:50] Wojciech Wegrzynski: mm.

[00:11:51] Jens Kristensen: And, then you have all the infrastructure. One of the main issues, there are several issues. one of them is the connectors. So the connectors [00:12:00] that you use to connect each panel, but also to connect, series of panels into, parallel, system or connect them to a combiner box, because there is a lot of, connectors with. There are several manufacturers, but there is no standard. So you have, the defecto or default standard, which Isly, which is a company, multi fi MC four connector. But you have a lot of connected from different companies, which can be assembled with that connect.

[00:12:30] Wojciech Wegrzynski: Mm-hmm

[00:12:30] Jens Kristensen: But it's not designed to be assembled. It can be exampled, but it's not designed to.

[00:12:34] Jens Kristensen: So that means with time, resistance will build up and such a system. And with resistance, you'll have production of heat and reproduction of heat. You'll have more resistance. And at the end you'll, uh, have an electric failure, and you'll have a direct current docking.

[00:12:47] Wojciech Wegrzynski: so, at the moment you can commission your, roof. It's a certain performance because it just works. But after time, it can, uh, build up this, failure, uh,

[00:12:57] Jens Kristensen: Yeah. And then you can look at who. Yeah. [00:13:00] Then you can look who allowed to install the PV systems in the different countries. If, if you look at Denmark where I'm at, I am right now, you do not even need to be an electrician to, install, uh, large direct current system on, on a roof construction. Uh, it's only, uh, electrician.

[00:13:15] Jens Kristensen: Certified tion who have to connect it to, the AC side of the building, all of the rest of the system, you know, you don't need anything

[00:13:23] Wojciech Wegrzynski: and what about the roof itself? Like roof is to some degree combustible. It just has to pass a certain, uh, test to

[00:13:32] Jens Kristensen: Yeah. Yeah, yeah,

[00:13:34] Wojciech Wegrzynski: Can you bring me in line, like how we test roofs and what we expect from roofs, at least in

[00:13:39] Jens Kristensen: Yeah. So, so in Europe we have the, uh, E N 1 3, 5 0 1 dash five it's it's called B roof. and as long as it's what is it called compliant with B roof? then you allow install our roof construction, Be roof, there's four different test methods because it's Euro and we do not really agree on how [00:14:00] to test stuff.

[00:14:01] Jens Kristensen: So, so there is test 1, 2, 3, 4, which are different from to country. so France have their test system, uh, Germany, Denmark, I think Norway, Sweden have system, the UK of course, a different, so they have a different test system. but in general, All of these tests, designed to verify that a fire not spread along a little roof, propagate along a roof.

[00:14:26] Jens Kristensen: That's also what we see in the experiments is if we have a roof construction, we have a roof construction in general. I can go to the nearby here. I can start a decent bonfire because the roof is designed not to facilitate spread of fire,

[00:14:41] Jens Kristensen: but.

[00:14:42] Wojciech Wegrzynski: does doesn't mean it does not burn at all.

[00:14:44] Jens Kristensen: You know, it burns because mostly it's plastics, uh, mostly it's PVC or, uh, Beto or, TPO or E P DM. There is different. The two loss were also plastics. so all of these materials [00:15:00] are plastics. There's just decent amount of flame charts in it. and does the fire are not able to properly, you will have ignition, but, the amount of heat that's necessary to heat up, the next part of the roofing membrane, to release a certain amount of paralyzes gases, cannot be released from the burning, uh, paralyzer After burning roof from my brain.

[00:15:19] Wojciech Wegrzynski: So eventually the fire dies out because

[00:15:21] Jens Kristensen: Exactly. Exactly.

[00:15:23] Jens Kristensen: Yeah. It's just quid. Yeah,

[00:15:25] Wojciech Wegrzynski: and now, and now comes to you with your

[00:15:27] Jens Kristensen: yeah,

[00:15:28] Wojciech Wegrzynski: a PV panel on top of that.

[00:15:30] Jens Kristensen: yeah,

[00:15:30] Wojciech Wegrzynski: the font starts.

[00:15:31] Jens Kristensen: yeah. Then, then the whole system changes because you have what is called, uh, a heat feedback rope. so because of the, the barrier, which is above, certainly, which could be some extent, it's a vertical barrier, which either, deflects the flame. So you have, deflective, flame, that's almost similar to, you know, a concurrent flame.

[00:15:49] Jens Kristensen: Uh, if you talk about concurrent or a post claim spread, so you suddenly have a higher amount of, heat flock, radi. Towards the roof below and thus you have a, [00:16:00] a significantly higher heat flow towards the area, and thereby the, the sign of the roofing membrane. If, it's designed based on with, with the flame towers, uh, of retardants, cancel loud, the whole do system just doesn't matter. Yeah.

[00:16:14] Wojciech Wegrzynski: Um, but In your legal systems, you are not obliged to repeat, like, be roof with the PV panel. No, it's just, you are putting a thing on the thing. It doesn't.

[00:16:23] Jens Kristensen: two different things.

[00:16:24] Jens Kristensen: You know, first of all, first of all, the fire safety in Europe, when it comes to, to the PV panel or building applied PV panel, which this is, uh, that means you have an existing building and you come with your technology and it's just add on technology. And that add on technology has in most countries, nothing to do with the roof.

[00:16:41] Wojciech Wegrzynski: Hmm.

[00:16:42] Jens Kristensen: you don't have to consider it for fire safety here in, in Denmark, we had the, the issue, it it's been asked to like the ministry have been asked, what do we do about this. Well, it's not a part of the building. It's not our problem, and different places. And as far as I understand in Europe, they have different point of view.

[00:16:59] Jens Kristensen: [00:17:00] but it's not real standardized anywhere, how to design it or how to consider it with respect to the design.

[00:17:05] Wojciech Wegrzynski: On the opposite side, the people doing the PV panels, they would be responsible for the PV panel itself

[00:17:12] Jens Kristensen: Yeah.

[00:17:12] Wojciech Wegrzynski: can show it's low flammability. It's

[00:17:14] Jens Kristensen: Yeah. That.

[00:17:15] Wojciech Wegrzynski: uh, we're not adding fuel to the roof. You're good.

[00:17:19] Jens Kristensen: Yeah, it's a perfectly fine, uh, panel itself. Uh, and that's what they're saying. so they, first of all, they don't want to hear the word fire. you know, I don't have, many friends, within the TV industry. Um, and, and the funny thing is, I, I honestly think I'm trying To ensure long term sustainability of their product. So we also install them in 30 years from now, because that's what I'm honestly, uh, afraid of. If, if we do not do, or act right now, we will have an issue in the future. and then we might have politicians who are doing what politicians are best at when it comes to, not understanding the issue.

[00:17:59] Jens Kristensen: Uh, and [00:18:00] that will be Bann. And the product from the environment and, utilizing the roof construction from PV systems is the way to.

[00:18:09] Wojciech Wegrzynski: Yeah, it's a very well exposed, surface. So, so give me the technicalities, like, uh, give, give me the meat so, so what exactly did you find? Like what's the number one finding of, your extensive research in, beer burning the semi enclosures.

[00:18:29] Jens Kristensen: I think, first of all, it is the definition of the, what we call the semi-enclosure, what Guillermo Rein and then Ricky, during my viva said, like, it's just a cavity and SIM closure, no one understands what its, but I calling until I finished the, of my Jesus. So, first of all, it is the, the identification of the, , SIM enclosure, uh, and the importance of the reradiation, the whole system behavior, which is, crucial for, the fire safety on the roof instructions.

[00:18:59] Jens Kristensen: then [00:19:00] we identify for. The specific setups that we had experimental setups, we identified a critical gap height where if the gap height is above a specific gap height. So the gap height is defined as, as the distance from the roof construction to the PV module. At the point of ignition, if the gap part is, let's say, uh, 13 centimeters in the specific specific setup, the fire do not propagate at all, but if we lower the module one centimeter.

[00:19:29] Jens Kristensen: Certainly Def fire starts to propagate, to the whole roof construction. so it's very, very small details with, uh, define the difference between, no flame spread and flame spread.

[00:19:40] Wojciech Wegrzynski: This gap height also relates to the, Hite straight of the, of the source, right?

[00:19:45] Jens Kristensen: Sure. Sure. so to some extent we need to define what is, what is the worst case scenario? Source of ignition. cause of course, if, if you have, a low heat release rate, you'll also have a low flame height and, and thus the distance to [00:20:00] the panel itself, the panel above, uh, might be larger and thus the flame does not deflect below and the cannot propagate.

[00:20:07] Jens Kristensen: So there is some relation there, uh, but screen flames, but no flames, but yeah.

[00:20:12] Wojciech Wegrzynski: well, that's an elegant solution. If there's a critical gap height allows you to fully benefit from, from this

[00:20:20] Jens Kristensen: Yeah. Yeah. but the issue is, as some people said, it's a deal with the be, right. Because if we then have a, a relatively high gap height on a flat roof construction, we'll have issues with, wind load, or, uh, load from snow or so, so there is it's, it's a whole. system. We also talked, I talked with, with Ikea, my contact person there.

[00:20:39] Jens Kristensen: About how about adding more flavor, tons, or how about, using, thinner, uh, roofing membrane? The problem, if it's a thinner roofing, because if it's a thinner roofing membrane, the fuel load, the smaller. So certainly you don't need such a high G height because you have such a limited amount of fuel that you cannot heat up.

[00:20:56] Jens Kristensen: You don't have enough time to heat up the material

[00:20:59] Wojciech Wegrzynski: But [00:21:00] based on my own experience as a wind engineer, I, I'm not sure if the wind issue be so significant when you raise the panel, like 10 centimeters higher. you see the, let me give you background.

[00:21:15] Jens Kristensen: Yes you

[00:21:15] Jens Kristensen: perception. Yeah.

[00:21:17] Wojciech Wegrzynski: I know this because we've built wind tunnel.

[00:21:19] Jens Kristensen: Mm,

[00:21:20] Wojciech Wegrzynski: And when we build a wind tunnel, we've started having customers

[00:21:24] Jens Kristensen: mm. Mm.

[00:21:25] Wojciech Wegrzynski: and tell us guys, I am selling PV panels, or I'm selling this PV installation somewhere, or I'm doing, small car park buildings covered with PV panels.

[00:21:35] Wojciech Wegrzynski: And I need to tell my customers that this product safe in case of wind, or it does not is resistant to wind. So can you put my PV panel in the wind tunnel, like blow 20 meters per second

[00:21:51] Jens Kristensen: Yeah. Yeah. Yeah.

[00:21:52] Wojciech Wegrzynski: and then tell me that it's saved. And we were like, You see you have, again, it is very similar case to what you've [00:22:00] realized.

[00:22:00] Wojciech Wegrzynski: You've taken the product out of the context of the building. So when you have wind blowing on your PV panel, the walls of the PV panel are sealed like the large surface where you have the PV panel

[00:22:17] Jens Kristensen: Mm.

[00:22:18] Wojciech Wegrzynski: is like, is not porous. And you block the other, uh, wall.

[00:22:22] Jens Kristensen: Okay. Yeah.

[00:22:22] Wojciech Wegrzynski: wind cannot go from the other side.

[00:22:24] Jens Kristensen: Yeah.

[00:22:25] Wojciech Wegrzynski: It's gonna push your panel into the roof, and even in a very, very strong wind

[00:22:31] Jens Kristensen: Mm,

[00:22:32] Wojciech Wegrzynski: It will not create enormous forces on the panel.

[00:22:35] Jens Kristensen: mm.

[00:22:36] Wojciech Wegrzynski: destruction forces.

[00:22:37] Jens Kristensen: Oh, okay.

[00:22:38] Jens Kristensen: Okay.

[00:22:38] Wojciech Wegrzynski: you, if you frame the same thing on a flat roof, like you have a, have a giant warehouse, which can be like few hundred meters

[00:22:47] Jens Kristensen: Mm,

[00:22:48] Wojciech Wegrzynski: You put a flat wall added,

[00:22:51] Jens Kristensen: mm,

[00:22:51] Wojciech Wegrzynski: you have a corner of that.

[00:22:53] Jens Kristensen: mm,

[00:22:53] Wojciech Wegrzynski: What happens when the wind is attacking that building a huge VTIs form [00:23:00] at the edges

[00:23:00] Jens Kristensen: mm, mm.

[00:23:01] Wojciech Wegrzynski: like a giant VTIs. And because it's a verti it's it's rotating. So at one point it's pushing down on the other

[00:23:10] Jens Kristensen: it's lifting. Yeah, yeah,

[00:23:12] Wojciech Wegrzynski: be sucking your panels.

[00:23:14] Wojciech Wegrzynski: now the force created by this.

[00:23:16] Jens Kristensen: Mm,

[00:23:17] Wojciech Wegrzynski: is at the complete different level, or it can be times 10 of what the panel would feel

[00:23:25] Jens Kristensen: yeah, yeah, yeah,

[00:23:26] Wojciech Wegrzynski: so it's not really a problem of the panel.

[00:23:28] Jens Kristensen: Mm.

[00:23:29] Wojciech Wegrzynski: matter if your panel is 10 centimeter taller or, or not, it matters like where versus this vortice it will be on your

[00:23:36] Jens Kristensen: Mm. And that's also like, like such things. That's one of the reasons it would be like ideal to have the P industry involved in the project, as well as collaborator, rather than someone, not really a fan of what we're doing. I've tried, I've applied for some of their conferences and accepted, so far.

[00:23:55] Jens Kristensen: but I really hope that they do understand that that. That's helped them.

[00:23:59] Wojciech Wegrzynski: [00:24:00] Yeah, if you have a solution for the flammability, maybe you don't have a complete solution, but you have a pretty good idea where the solution may be and how to significantly reduce the added complexity that comes from this system. And wind engineering has very good answers why this can be actually done,

[00:24:18] Jens Kristensen: Hmm.

[00:24:18] Wojciech Wegrzynski: contrary to the popular belief that it cannot be

[00:24:21] Jens Kristensen: Mm. Mm.

[00:24:22] Wojciech Wegrzynski: of wind or some

[00:24:23] Jens Kristensen: Yeah. Uh, and, and the issue is all the different ways you can install them. So, so on a flat roof construction, you can have them like mechanically fixed, but you can also just have them BA it on the roof.

[00:24:34] Jens Kristensen: Uh, Yeah. yeah, yeah,

[00:24:37] Wojciech Wegrzynski: layers of bricks.

[00:24:38] Jens Kristensen: exactly. I don't know. I don't know. It depends on, on the owner, but I I do understand why they prefer just to balance the, because then they don't have to penetrate your roof construction, with, with metal screws and thereby your, the roof is

[00:24:50] Jens Kristensen: intact. Yeah, yeah,

[00:24:51] Wojciech Wegrzynski: and the, the roof is there to protect against the elements water, especially.

[00:24:56] Jens Kristensen: yeah, yeah,

[00:24:57] Wojciech Wegrzynski: want to make holes in

[00:24:58] Jens Kristensen: exactly. exactly. [00:25:00]

[00:25:00] Jens Kristensen: Yeah.

[00:25:00] Wojciech Wegrzynski: Of course. that's, It's interesting that, we are, seeking the solutions. And I believe that what you have found through your research is a very elegant way.

[00:25:11] Wojciech Wegrzynski: I also saw in some other papers, of yours

[00:25:14] Jens Kristensen: Mm.

[00:25:14] Wojciech Wegrzynski: with, the Malaysia colleagues, you have been, investigating, how often this fire

[00:25:19] Jens Kristensen: Yeah. Yeah, yeah.

[00:25:19] Wojciech Wegrzynski: I also found it very, very interesting. Can you comment on that

[00:25:22] Jens Kristensen: Yes, yes, so it's even Malaysia actually started with, with a paper manuscript and asked of us if we wanted to participate on that. And, and we, you know, adjusted it here and there and recalculated it. so as it says in the paper itself, it it's quite the amount of data is sparse and the quality of the data is limited, but it is all the data we have access.

[00:25:44] Jens Kristensen: And someone have to do the first analysis. So we analyzed those five sets of data in total and realized, or, or found out calculated that an annual, frequency, of fires would be around 29 fires per Gigawatt [00:26:00] capacity. , so that's equivalent, in a country like Denmark, 29 fires per year. if you look in, then you multiply that with 300, 320, you have the amount of fires in, uh, the European union.

[00:26:13] Wojciech Wegrzynski: How much, is the gig out of panels as like a field, not a building, right.

[00:26:18] Jens Kristensen: that's like the whole gig. What is the whole capacity in Denmark? So, a large, roof construction, commercial roof construction could be one mega. Two megawatts, if, it's like extremely big. so that's, that's the, that's the scale, installations iswas as, as

[00:26:36] Wojciech Wegrzynski: so that would mean for a like large building. The, fire, uh, frequency would be like one every like 25

[00:26:44] Jens Kristensen: Yeah. Yeah,

[00:26:45] Jens Kristensen: yeah.

[00:26:46] Jens Kristensen: And,

[00:26:46] Wojciech Wegrzynski: and for household installation, like one in a 500

[00:26:49] Jens Kristensen: yeah, yeah. But then again, you know, we have to remember, first of all, the, the quality of the data, some of the data. comes from the Italian, fire and rescue services. if you look at the, Italy, [00:27:00] have a significantly higher amount of fires per year than any other country, but that's cause the Italian fire and safety, services are actually looking for those fires.

[00:27:10] Jens Kristensen: They actually reporting those fires. So you have more or less the actual. Whereas there is other countries. if you look in the states, they have maybe 20 fires a year because it's not really possible to, report these fires. Uh, there is the, um, the report by McNamee and, Brian Meacham on pre-owned green attributes, to buildings and then build environments.

[00:27:34] Jens Kristensen: and it's, It's really highlighted that, well, it's just not possible to report this kind of virus. , then there is also different systems in Germany or the Netherlands, uh, the amount of fires which are actually, reported is just based on surveys and media or social media. So it's just, if there's suddenly fire in the media, they write it down.

[00:27:55] Jens Kristensen: So the different of fire here is. Very large [00:28:00] fire, then it's, then it's actually reported, whereas smaller fires are not repoed. So, so what we look at might actually only be the tip of the iceberg, whereas all of these smaller fires are not really, highlighted anywhere. it would be ideal to, get some data from the insurance companies of course, because they will have, uh, they probably

[00:28:21] Jens Kristensen: have all the, yeah, they probably have all data.

[00:28:23] Jens Kristensen: then it's just a question. Of sharing that data and, and their willingness to share that data. and since they have not shared or, or mentioned the data or, or Christian, the numbers that we came out with, some one could think that they are lower. but, but we don't really know. so collaborating with them and, and having actually.

[00:28:42] Jens Kristensen: Access to that data or, just feedback based on that data would be a huge benefit for understanding the risk related to PV systems, in the environment

[00:28:52] Wojciech Wegrzynski: uh, going back to your, study, you've mentioned gap height, being

[00:28:56] Jens Kristensen: Yeah.

[00:28:56] Wojciech Wegrzynski: the variable that, that you found like really important. [00:29:00] Uh, any other things, you, you found it influenced this, this behavior. I know inclination

[00:29:05] Jens Kristensen: Yeah, inclination surely, uh, affected it as well. We didn't do that many experiments with inclination because we had too many parameters, but when we inclined the panel, the critical gap height. became larger, the flame spread rate was higher. so that was also quite, uh, interesting to see.

[00:29:22] Jens Kristensen: then we had some limitations with the width of the, which limited the flame, unfortunately. but I, to rebuild that experimental and do it a big, uh, locker, and then we might be able to, to see. Verifi verify the behavior. but in general, we verified the behavior during my, my master thesis.

[00:29:44] Wojciech Wegrzynski: And, uh, you, you've also mentioned you've worked with, manufacturers of, of installation. So I guess you were, changing the roof membrane, uh, itself a bit. Was it important variable for

[00:29:56] Jens Kristensen: Uh, the membrane, the membrane was, was the same. So the insulation was, the variable [00:30:00] because there were insulation companies, Ikea, no, uh Kingspan and Rockwell two huge competitors, but they were quiet during the, uh, the whole thesis

[00:30:08] Wojciech Wegrzynski: congratulations on working

[00:30:10] Jens Kristensen: yeah, yeah, yeah, yeah, yeah, yeah. But, but, but they were really, uh, great to work with because. I think they, uh, to some extent, except that there they were on the same project, uh, and, and kept quiet. So that was great. so, there was no significant difference in my opinion, between the materials I worked with. I did not test them at the same thickness. You know, one could say, I should test them at the same thickness.

[00:30:33] Jens Kristensen: One could say, I should test them for the same R value. so the insulation capacity or how well the conductivity, uh, and of course the connectivity of the pion from king is lower than the productivity for the mineral. And in addition, the, the Kingspan product does also have aluminum fall and chop.

[00:30:52] Jens Kristensen: So during the experiments, That actually benefited the, the P insulation. but the issue with the P [00:31:00] insulation is that it, it swelled when it was exposed to heat and, and that part of the insulation would swell, did not have any, uh, connectivity or it had a very high conductivity. So the, the connectivity tested for the material, Know, in the standout test methods where not representative when the material was exposed to heat, but in these experiments, we had 60 millimeters of, of pation and, and the fire did not penetrate.

[00:31:27] Jens Kristensen: Uh, and for the mineral wall, we had 50, it should have been the same, but yeah, that was what they supplied me.

[00:31:34] Wojciech Wegrzynski: and, the differences in, in panels, how are we testing different PV models?

[00:31:38] Jens Kristensen: , I tested a few different pure models which were supplied, and they more or less behaved similar all them, one of them or two of them actually, was dripping. so when it exposed the heat, it started dripping, uh, was burning droplets and droplet continued to burn, when they hit the surface or hit the floor.

[00:31:56] Jens Kristensen: Uh, of course that would be an issue if it was. [00:32:00] Vertical installation. But right now, when it's a horizontal installation, it's, it's not such a big issue also. Cause the not spread outside the array.

[00:32:08] Jens Kristensen: So an array is like a group.

[00:32:12] Wojciech Wegrzynski: that, that segments me to the region where we're gonna start, start hypothe.

[00:32:17] Jens Kristensen: Yeah. Yeah.

[00:32:17] Wojciech Wegrzynski: and what if the roof was inclined?

[00:32:20] Jens Kristensen: Uh, yeah, that's a good issue because also what, what kind of materials will you have on a roof, which is inclined, if it's tile, then it's probably not such a big issue. Uh, but if it's still a material which can burn, you know, then of course it would be an issue also because you'll have flame spread.

[00:32:36] Jens Kristensen: Even to a high extent, uh, be similar to concurrent flame spread. Uh, so you'll have flame spread and panel, so yes

[00:32:50] Wojciech Wegrzynski: And, it's a big trend, you know, photo

[00:32:52] Wojciech Wegrzynski: are, are a huge

[00:32:53] Jens Kristensen: yeah, yeah.

[00:32:54] Wojciech Wegrzynski: you, you see them everywhere and, it's not only roofs now being covered. I, I see

[00:32:59] Jens Kristensen: Yeah. Yeah.

[00:32:59] Wojciech Wegrzynski: with, [00:33:00] PV panels and in the facade setting. This brings us to good old, cavity issue, like, like it was framed by your, by your examiners in your Viva.

[00:33:10] Wojciech Wegrzynski: so we, we're technically creating, system with, somewhat combustible, cladding and,

[00:33:16] Jens Kristensen: And not to mention an increased probability of addition,

[00:33:18] Wojciech Wegrzynski: Yeah. as if Cav fires were not a big problem, we, we now have one that can ignite

[00:33:23] Jens Kristensen: Yeah. .Yeah. Yeah. And, and the issue here is, that these, facade amount of PV modules is different from the, building applied systems, which I've worked with. So what I work with is you have an existing building, which is a building itself, and you, apply a system, but when you use it in the facade, it's, what's called a building integrated PV. So certainly the PV module replaces a component of the building. If you remove the, the PV module from the facade, you have to replace it with an other, construction, product.

[00:33:56] Wojciech Wegrzynski: I'm pretty sure I saw, uh, at least in here [00:34:00] PV models that were literally glued to existing facades

[00:34:03] Jens Kristensen: Okay. Okay. Then it can be a different system.

[00:34:05] Wojciech Wegrzynski: And for started would be amended with, PV panels. So I guess that brings us to a complete new set of unknown challenges

[00:34:13] Jens Kristensen: Yeah. Yeah.

[00:34:14] Wojciech Wegrzynski: and, risks. We may not even be And in this case, the spread rates may be com. They will be completely different then

[00:34:22] Jens Kristensen: But

[00:34:23] Wojciech Wegrzynski: what you've reported. And so, but also hopefully the membrane is also than on, on the

[00:34:30] Jens Kristensen: it.

[00:34:31] Wojciech Wegrzynski: of the standards we have,

[00:34:32] Jens Kristensen: But mostly it's. Yeah, mostly it's like ventilated facade, you know, in, in most of these systems. and the interesting thing here is because it has to, in most cases has to be replaced with a construction product. If you remove it, it's tested as a construction product. So there is existing test methods.

[00:34:50] Jens Kristensen: It's accepted to be part of, of the whole, fire safety, system or regulation. The issue now is how do you put a PV module into [00:35:00] the existing test systems

[00:35:01] Wojciech Wegrzynski: it's really interesting. So you would consider, uh, facade in a very different way than you consider the roof or

[00:35:07] Jens Kristensen: Yes, yes, yes, yes.

[00:35:08] Wojciech Wegrzynski: put a thing, you, you put the thing in it. You could be okay, because you just put the thing on the

[00:35:12] Jens Kristensen: Yeah.

[00:35:12] Wojciech Wegrzynski: on the facade. You've, with the facade itself, which is a system,

[00:35:16] Jens Kristensen: Hmm.

[00:35:16] Wojciech Wegrzynski: that's an interesting point of view

[00:35:17] Jens Kristensen: but then you can question does, does, does the test methods, are they representative of the real world, and especially when you include the module into test system, are you able to, uh, Tabulate or are you able to, can you actually fit that PV module in, or will do it differently from test, center to test center?

[00:35:38] Jens Kristensen: Because no one really knows how to fit the PV module into test method or into that existing framework. but you know, if it's approved and it it's compliant with the standards, then there is no issue.

[00:35:50] Wojciech Wegrzynski: Fantastic.

[00:35:50] Jens Kristensen: yeah.

[00:35:51] Wojciech Wegrzynski: that's a whole world that, that opens and if we want a sustainable future, these, these are the issues as fire engineers and, uh, [00:36:00] listeners of the podcast will, uh, we will face as if there was not enough issues around. and my last one, I also saw these interesting solutions where, the photovoltaic panels would be, put.

[00:36:10] Wojciech Wegrzynski: Inside the glass tiles that you would put, on the roof. are your feelings about that?

[00:36:17] Jens Kristensen: Oh,

[00:36:18] Jens Kristensen: no,

[00:36:18] Wojciech Wegrzynski: it's interesting, but then you, exponentially increased the number of disconnections that you've, mentioned previously as, as to ones that worry you the

[00:36:26] Jens Kristensen: Mm. Yeah. Yeah. If, you know, with time you're able to implement it, most cases, you'll soon be able to implement it in, in a standard window, more or less transparent. Uh, and of course we should do that. We just have to figure out these years, uh, related to that technology. and what. Unexpected consequences are, I'm not sure at the moment that I, that I understand the complexity, of such systems right now I'm working with one specific system.

[00:36:53] Jens Kristensen: And, and of course with time, hopefully I'll be able to, to understand more complex things. So I guess that's one of [00:37:00] why I enjoy, uh, if I'm able to continue with which I'm quite sure I'll so yeah, there is a lot of, uh, unanswered questions.

[00:37:07] Wojciech Wegrzynski: that's, uh, that's, gonna be a lot of work for us. I, I say that in almost

[00:37:12] Jens Kristensen: Yeah. Yeah.

[00:37:13] Wojciech Wegrzynski: but that's, that's a, that's a, that's a good career

[00:37:15] Jens Kristensen: Some, some point you, I really hope someone will join me just trying to understand issues. So I'm not just, you know, working with folks. So there is actually. More. Yes. And I don't matter if it's just, you know, if they're group with me or if they're somewhere else, it would actually be nice if they're at a different university course, then you'll have some, you know, constructive feedback and criticism saying, yes, you're not right.

[00:37:39] Jens Kristensen: Yes. Thank you. Thanks for criticizing my work. that would be great.

[00:37:44] Wojciech Wegrzynski: I, I hope you'll get a lot of messages after this episode. Maybe someone will significantly disagree with you

[00:37:52] Jens Kristensen: That would be perfect. Yes.

[00:37:54] Wojciech Wegrzynski: yeah. In, in like two weeks, you're having your public, presentation of your PhD thesis, will [00:38:00] there, there be a stream or

[00:38:01] Jens Kristensen: Uh, that's the plan. Yes. Yes. I'm not sure if people following the stream will be able to ask questions, uh, or not at the moment, I'll have to figure out, but, but I'm quite sure it'll be stream, because,

[00:38:13] Wojciech Wegrzynski: What day is

[00:38:13] Jens Kristensen: uh, August 19th,

[00:38:15] Wojciech Wegrzynski: August

[00:38:15] Jens Kristensen: one o'clock, uh, days slash Polish time.

[00:38:19] Wojciech Wegrzynski: August 19 one. O'clock the real time. And for anyone living, not in Denver or Poland, you have to figure out

[00:38:25] Jens Kristensen: Yeah,

[00:38:26] Wojciech Wegrzynski: what's the

[00:38:27] Jens Kristensen: good luck summertime and whatever we have

[00:38:29] Wojciech Wegrzynski: that's fun. That's fantastic. , I'll make sure that this episode airs, than that, and, people who are listening, to the podcast,

[00:38:36] Wojciech Wegrzynski: you'll get a better experience, with pictures and, and the technicalities of the fire, problem that we have just discussed.

[00:38:45] Wojciech Wegrzynski: And if you are listening to this episode long after that, and the answer is now a professor

[00:38:50] Jens Kristensen: I will not, I will leave university

[00:38:53] Wojciech Wegrzynski: Well, then if he's just a Playboy billionaire living of, of testing, affordable tags, I'm [00:39:00] sure there will be plenty of resources available online to catch up

[00:39:04] Jens Kristensen: Yes, yes. Yes.

[00:39:05] Wojciech Wegrzynski: am sure he has, this topic will not be outdated in five or 10 years from this recording. Uh

[00:39:11] Jens Kristensen: hopefully the. hopefully the.

[00:39:13] Jens Kristensen: topic is maybe, maybe someone found a smart way to do it. And I'll, I'll appreciate that. yeah, but I'll continue with, with DBI here in Denmark, working with, with their team, and, and see what comes in the door. It looks like there was already some stuff, uh, and they have some, some very great labs, and great bunch of people.

[00:39:31] Jens Kristensen: so, so that's gonna be really good. Fun.

[00:39:34] Jens Kristensen: Yeah.

[00:39:35] Wojciech Wegrzynski: The future looks bright. And, once again, congratulations on your, uh, PhD. You rarely see examiners being excited about the PhD thesis they just

[00:39:45] Jens Kristensen: Yeah. Yeah.

[00:39:46] Wojciech Wegrzynski: were so, so that's a good sign that it's, it's a great piece of work. And I, I have been reviewing parts of that as your ongoing Griffs to publish. And I also also enjoyed it,

[00:39:57] Jens Kristensen: I think, I I've been, uh, very [00:40:00] privileged to have a hot topic, so to say, uh, a topic which, uh, with is just my own topic. and, and it's very, Extremely relevant. I think everyone with that topic would be able to write a good thesis. Cause it's, it's just a, a funny or interesting topic, which is highly relevant.

[00:40:18] Jens Kristensen: And when you know that your topic is applied or, people are interested, then you try to, to do your best. So, so I guess that's it.

[00:40:25] Wojciech Wegrzynski: That's it. Okay. Jens thank you very much for coming to Fire Science Show and all the best in your future journeys with fire photoable tags and beyond.

[00:40:34] Jens Kristensen: Thank you very much. And thanks for the once again.

[00:40:37] Wojciech Wegrzynski: And thats it, I hope you really enjoyed the episode. I must tell you them. But cause doesn't tell a full story of Jens and his research obviously . Something private to him, but I admire his, Insistence on doing this passion for fire science. And seeing how amazing research because the research has done [00:41:00] is just really good. Is, is good on itself. Seeing how it has been done. In the circumstances he was going through the forced change of location, health issues and stuff like that. Ah, It's amazing what this guy has pulled up. So Jens I'm really, really happy with you're a full doctor now. And your research is really good.

[00:41:22] Wojciech Wegrzynski: The variables that you've identified as the most, Important in the process. I am sure they will lead to forming solutions. So your work is not only good, but also is going to get applied. And, Most of all, I'm in a way, disappointed with the systems that we far shown in these episodes. Maybe you remember the episode with Anja Boelinghaus, where we discuss the differences between.

[00:41:45] Wojciech Wegrzynski: The bus and train industry in terms of how they treat the reaction to fire off. upholstered furniture in the vehicles. I have flashbacks to that episode in this episode, because come on, if we consider the roof and PV [00:42:00] panel separately, they're great together. They. Somehow dangerous or bad in a way.

[00:42:05] Wojciech Wegrzynski: We need to consider systems as systems, not as a bunch of parts, because then we often miss what's important in making them safe. And this is the important message of the episode. I mean, We have this in many ans of fires and fire engineering, and we really need to learn how to think systems, not products, not items, not elements systems. So yeah, with this thought, I'm going to leave you.

[00:42:34] Wojciech Wegrzynski: The whole next Wednesday where we're gang to have another great episode. The same, I'm really going to deliver the glass up. I know I promised it this week with, It's in the pipeline then. I'm sure you are getting thoroughly enjoyed that one as well. So if you gave me here for the glass, you've received three panels.

[00:42:54] Wojciech Wegrzynski: I guess that's, that's also good. And uh the glass coming next week see the ansi next [00:43:00] wednesday thank you bye