Why inverters hold the key to a more resilient energy future with Daniel Duckwitz (SMA)

Hello and welcome to another episode of Transmission. Today, I'm joined by Daniel Duckwitz from SMA, and we are going to be talking about everything to do with grid forming and grid following inverters.

So, what is the difference between these? How does that vary by market? What does a grid forming inverter actually do that is different to a grid following inverter?

We'll then have a bit of a technical discussion around inside these inverters, how different actually are they and what are the things that they are providing technically to a grid that gives us a much more resilient and stable future system. Let's jump in.

Hello, Daniel, and welcome to Transmission.

Hi, Ed. Thanks for having me here.

I'm delighted to have you here. And let's, as ever, kick off with a little bit about you. So who are you, who do you work for, and kinda what's your experience in the space?

Yep. So I work for SMA, solar technology, a a power conversion company based in Germany. And, yeah. Well, my my role is to, care for the, grid stability portfolio. So that means all the utility scale plants that, we equip with our, inverters and control systems, they need the right features for stability. And I care for that on a more long term outlook, but also in the, let's say, day to day evolution of of new requirements in different markets.

Okay. And when you say power conversion, really, what do you what do you mean by that?

It's inverters and, control systems. So the inverters like plant controls, but the main product of SMA is, of course, the the inverters.

But now when we we see different grid services growing around it, the, plant controls and engineering become a bigger part of that. So it's not really about a hardware Only it is about the engineering process, the project development process Yeah. And so on.

Yeah. And just to help people, so, people who may never have heard of SMA, is it, like, what's what's the scale of the company?

It's one and a half billion, revenues per year approximately. So, well, medium size, maybe. And, this translate to translates to about twenty gigawatts of inverter rated power per year that we ship.

That's just huge.

Like, two thirds of that is, utility scale inverters. And in that range, we have, battery equipment for battery plants, for PV plants, and for hydrogen plants that will need a a rectifier instead of an inverter, actually, but it's based on the very same technology.

We're gonna have to talk about a rectifier very quickly. So so so all of this, podcast is is really gonna be about inverters. Yeah. But now that we've brought rectifier into the conversation, let's just have a what what is a rectifier?

Well, a a rectifier will take power from the grid and put it out at a DC terminal and then feed it to the electrolyzer that will generate hydrogen.

Mhmm.

And this is exactly the opposite direction compared to a solar inverter, which will take the power from the DC side and put it out on the AC side. So it's only the direction change, and luckily, the battery inverter will do both directions. So it is really very, very similar technology.

Okay. Really interesting. And and that inverter described for solar, that would typically be something called a grid following inverter. Yeah. We have two types of inverters in a really simple sense, a grid following inverter and a grid forming inverter. What's the difference between those two?

So, traditionally, when, PV plants were first introduced, their job was to to feed in the power as much as power, the maximum power from the PV array.

And, they would just get a set point and feed that to the grid no matter what happens in the grid. And then when we talk about grid forming, these inverters will still do the same job. They will feed power or take power from the grid to charge a battery, but they are also able to to instantly change their output according to the needs of the power system. If there is some some incident in the power system like a loss of generation or a sudden loss of a large load, there will be a power imbalance, and that can be instantly supplied by the grid forming inverter.

Just going back to the grid following inverter, you mentioned that an inverter would have a set point within it. What what's a set point?

So the set point is basically the command from either the maximum power tracker of the PV or from the trading interface of a battery to feed a desired amount of power, for example, for a quarter hour or for full hour depending on the market conditions.

And the set point needs to be executed to, yeah, to execute technically execute the trading of the energy that happened before. Yeah.

Okay. So all inverters on the grid following side essentially have this kind of this set point that's, like, one megawatt, and so they would generate to, say, one megawatt. But the grid forming inverter, instead of having, say, one set point, which is, say, a one megawatt, it also has other things that it can do. So so what are those other things that that grid forming system can do?

So the the grid forming inverter will provide a a steady output and reference of frequency and of voltage amplitude in the power system. And all of the grid forming devices together, they will form the overall grid voltage and grid frequency. And this is something that is required to, balance the system in case there is anything deviating from the from the set points, like any event, like a generation outage or similar.

And so if you need a healthy system, it needs to both balance from a power perspective, but it also needs things like voltage to be balanced in certain parts. It also needs the right frequency to be adhered to. So a grid following inverter will do one of those in the in the power side, but a grid forming inverter can help with keep a few more metrics healthy effectively for a for a power system. Okay. And and just to help people understand, so in terms of the inverters that are out there today, what's the split between grid following and grid forming?

Let's say the installed base is Yes. Ninety five percent grid following or even more, is more than ninety five percent grid following. When we look at what we are installing today, I would say it's one third, grid forming and two thirds grid following.

That might be biased because SMA is trying to be quick with the introduction of new technology to be at the forefront of the evolution here. But I would say every third battery inverter is a grid forming inverter today.

Okay. And if you go forward five or ten years, do you think that will kind of completely flip and so it'll be kind of grid forming inverters that are majority, or or do you kind of not see that happening?

I certainly hope there will be mostly grid forming inverters for batteries, but this is actually another topic we should touch on, what is what about PV and what about wind generation. But then for batteries, I think it will be almost exclusively grid forming inverters in the future because we need them for the system to to be stable when conventional power plants are being phased out. Mhmm. Mhmm.

Okay. And let's let's take a note on the PV and wind and the inverters that go alongside PV and wind because we will definitely come back to that. So maybe to ask a question around, if you have a system that's running on lots of grid following inverters, does that create a problem in terms of the system the system's operability?

It doesn't because, I mean, we see the system is working with grid following inverters today, and a large share of them.

But there is a point where the system stability needs some inertia, some more inertia than the remaining conventional generators provide. So at the moment, there is always some conventional generators online, and these provide, their inertia, and that means a millisecond response time in case of outages.

But if these are getting less and less, there will be basically a tipping point. And now there is a need to to plan in in the system planning from the transmission system operator perspective. They need to account for the need for inertia and need for system strength in their system planning and then find a way to introduce the right amount of inertia system strength through grid forming inverters and the right flavor of grid forming inverters.

I really I really like that.

So, flavors of grid forming inverters. What what do you mean?

Well, there is different things. I mean, the the very basic thing is a grid forming inverter. It it can make the grid. So you can start a grid from a grid forming inverter, and they did this is what they all share.

But then for for inertia to be highly highly available and reliable, there needs to be a power reserve. So, basically, what the the grid forming inverter has to do on top of its normal follow the set point stuff is to have a reserve for a few seconds to provide more active power.

Okay. So does that almost like you have a a large battery, a grid forming inverter, and then you have another source of energy within the grid forming inverter?

No. Actually, it should be the battery. So Okay. We we don't want to to overbuild or to to oversize the systems, but then we need to to enable the inverter to provide, for example, thirty or forty percent more power beyond the rated power for five seconds. So that that would be a typical setup for for the UK inertia market.

Okay.

And it might also be a typical setup for the German inertia market, which means you always have a power reserve, that is available on top of the power the battery is already providing.

And you said that was, like, thirty to forty seconds worth of additional power. Is that right?

I no. No. It's, thirty or forty percent of the rated power available on top.

Yes. And for how for how long?

For for, five seconds.

For five seconds. So, I mean, this is a real fraction of Yeah. So if we think about batteries today, they're an hour. They're two hours. So providing a little bit extra for five seconds is is like a is is a rounding error.

It it it does matter from energy perspective for a battery. And this is why stacking the inertia on top of the base case, like energy trading, is really is really a sweet spot where we can get the inertia at at relatively low effort. But then, of course, the inverter has to be able to to do this five second extra power Mhmm. And to do it reliably, and only then it qualifies for an inertia service market. And and this is, I think, the difference between, let's say, a standard grid forming inverter that can start a grid and have operated, but it wouldn't have the capability to exceed the rated power for a short term. So So you would have to derate the continuous power to have this reserve, and this is where it would constrain the business case of the of the battery. Yeah.

But it's such a it's such a fractional amount that it feels like it wouldn't have too much of a of an impact. You you mentioned that there's stability markets in the UK, and there are also upcoming stability markets in Germany that I think has been a a few bits announced this week on that. So this so today is the twenty first of May, just for just for reference. So we've we've I think we've seen some stuff coming out in Germany around stability markets very recently.

Are those stability markets different by country?

Yeah. They they are different. But luckily, I would say the the German market will be quite similar to the what UK has seen in the stability pathfinder market. So it will be long term contracts over up to ten years, and, performance wise, it's quite similar. It would also need a short term power reserve. It will be different because it's it will only be two and a half seconds instead of five seconds, but the very the other parameters are quite similar.

Okay. And if that's kind of comparing grid to grid, if you then go, like, one step beyond and say so within the German system, are there specific requirements for specific locations? So, for example, is there a need for more inertia in the north or a need for more inertia in the south?

Yeah. Basically, the the regional requirements have been defined in the, in the system planning. So there are studies to make sure that for each region, there is an identified need, how much inertia is required in that area.

And, the tenders will give an incentive to provide inertia in the right area by having different regional prices.

Yes. Yeah. And, I think maybe just to be really clear, so I I there will be an engineer listening to this going, oh, you're talking about inertia. Yeah. You're talking about inertia from a grid forming inverter.

Yes.

We So this you're not talking about real inertia.

This is this we're talking about synthetic inertia. Yeah. So do do you see the difference between those two things?

Of course, the inverter doesn't have a flywheel inside, but it has the equations of a flywheel, inside to replicate the behavior.

And it has also some advantages like improved damping, so a synchronous condenser or synchronous machine, they can oscillate against the grid and cause these inter area or local area oscillations.

And this can be avoided right from the start with the inertia emulation inside the grid forming inverter. So, yeah, it's similar. The behavior is very similar, but in a way, it's also a bit better.

Okay. And there's so two really interesting parts to that. The oscillations we will definitely come to, the the difference between real inertia and synthetic inertia, we're talking milliseconds here. What's like, how quickly can a grid forming inverter respond to that very first signal that comes in?

Right instantaneous. So, I mean, we're talking about one millisecond maybe.

Okay.

But that is the time that it would need the the the current to rise because of the impedance of the grid.

And this is the same for a real inertia and for the Yeah.

Grid forming inertia. Yeah.

Yeah. I mean, this this this totally blows my mind because I I think that if you look at kind of historic grids, you you had either spinning stuff that was already operating, and therefore, you had very much inertia, or you had early versions of, like, response type markets. And those things would be, oh, well, maybe we can get something to ramp up within, say, ten seconds. Yeah. And yet here we are now talking about the technology of the future where effectively we've got inverter led technologies that can react in under one millisecond.

Yeah. That's that's just it gives me huge amounts of hope in terms of, like, where we can get the system to. Let's talk about oscillations because we obviously have seen some bits come out around Iberia and, the the blackout that hits part of the Iberian system.

And some of the analytics of that has talked about oscillations being on the network in the run up to it. Now they haven't directly said that the oscillations are linked to the blackout, so I think this is kind of to be very clear. We are still waiting for more information on this.

But power systems can have oscillations, and you were talking about a sort of a dampening effect from those inverters. How how does that work?

If we come back to the flywheel, you could think of the flywheel being coupled to the grid through a through a spring, so it will effectively it can oscillate against the other flywheels in the system. And this is a natural effect that comes from the physics of the synchronous machine and the grid. But then the the synchronous machines, they have a a damper winding and a power system stabilizer. So these are two. One is a hardware and one is a software control thing for a synchronous machine to to dampen these oscillations.

But they can only be so effective, and they cannot really make it extremely well damped. And there is a difference in the grid forming inverters because we can put arbitrary damping constants in there to make it the damping quite high. And not too high, but then quite high. Mhmm.

And this, means these oscillations will be damped in the first place. And, this it will also help to install grid forming inverters in systems where the, let's say, inter area oscillations are happening. They can also improve the situation.

Yeah.

And and there is more to that, but that's not Yeah.

Maybe maybe, last question just on the dampening side. So do you think that would be a stand alone market? So so, a system operator would pay for that service, or do you think it will become just a requirement? So if you are connecting to the grid, you will have to be able to provide that, and that's just one of the conditions of getting a connection.

I I think it will come together with the inertia. Okay. So the inertia has the inherent damping, and this will come anyways. The question then is, how does the system operator make sure they will get sufficient inertia and also this highly available inertia that has the power reserve? Because just asking for grid forming inverters means you maybe you get inertia, but only sometimes and not when the base is already operating at rated power.

Okay.

And to give an incentive to install this additional power capability, the market would help, like, an inertia market, like we're talking about UK and and Germany and partly Australia. And the question is, how are these markets launched in the future in in other parts of the world and other parts of Europe?

I I think there's lots of people who are looking at GB, Germany, Australia, and saying, okay. How are these markets working? And what works there? We're just gonna copy that.

Yeah. And it's yeah. I I I hope it it's weird. So if you go if you look at sort of pan market history, like, everyone seems to have done their own version.

So, like, the French system works in a very different way to the German system, and the GGB system is very different to those. I hope that in the field of kind of frequency response and inertia, we can kind of get some more towards a common standard, but I'm sure there are good reasons why that might fall over. You mentioned one thing that's really interesting. So you said that a little a little bit of how the inverter responds is dependent on what the battery is doing.

So in order to provide inertia, does the battery have to be, say, fully charged or operating, or can the inertia provision come from the inverter when the battery is idle?

It it would come when the battery is idle, and it would also come when the battery is charging or discharging it at the rated, c rate.

Okay. So it's unrelated?

It is not fully unrelated. The one thing that needs to made needs to be made sure is that the the BMS allows, this short term peak power also from the battery side.

Okay.

And this can easily be done. It's technically the battery will be able to provide it. The BMS must not trip if it does. Yeah.

So this is something where we have a a interface to the DC block manufacturers or DC block suppliers, and this needs to be well arranged, to make sure that this peak power can be provided. It also needs to be contractually agreed. How often does it happen? Does it have an impact on lifetime?

It Interesting. Most likely doesn't have this impact on lifetime. Yeah. But then it needs to be agreed with the battery supplier, of course.

Okay. And you snuck two terms in there that I think not everyone will know. So, would you mind explaining what a BMS is? And would you also mind explaining what a DC block is?

So, in the in the large scale bus, there is usually, DC blocks, which is a container full of battery racks, which is then interfaced to a an inverter station. And we're talking about, for example, five megawatt hour per, standard container, so twenty foot container size. And two of these containers might be connected to a, another twenty foot container that has the inverter and the transformer and the medium voltage interface on it. So that is the the LEGO blocks or the the building blocks of of a bus.

The DC block is basically the battery container.

And, the BMS is the battery management system. So that's the monitoring of all the batteries in that container. And this BMS has a communication interface to the plant controller, but also to the inverter to make sure that the inverter respects the limits of the battery. For example, if the battery is empty, the BMS will tell the inverter it's empty. Don't try to discharge anymore.

Okay. So all of these components essentially interface with each other. Yeah. And for for SMA, for example, so do do SMA make the DC blocks for the batteries?

We don't. No. What what we do is, focus on on the power conversion. So basically from the DC interface to the medium voltage interface.

So this is our focus, also the plant controls and also the interface to the BMS. Okay.

And so you spend a lot of time making sure that the thing that you're putting in between the DC block and the grid is compatible with kind of both sides of it. So that that that's really where that that answer comes from. Okay. A grid forming inverter versus a grid following inverter. If I was to look into a grid forming inverter and a grid following inverter, would they be similar or, like, how are they different inside the inverter?

If you look at the hardware, they look almost identical. You you wouldn't notice a big difference. What we have done is to allow this short term peak power capability, we have changed the semiconductors to have a this additional short term capability.

So we have optimized the product to, avoid any need of oversizing the plant, of having to install more more of more inverters or having a bigger footprint of the plant by changing the type of semiconductors.

For those interested, it is, silicon carbide semiconductors instead of silicon, semiconductors, which means we have this headroom for the inertia provision, for short term peak power. Yeah. So that would be the hardware side.

And and potentially getting a little bit in the in the deep end, the the silicon carbide, I they have slightly better round trip efficiency. Is that right?

Yeah. You you would get about one percent better round trip efficiency along with changing to them. Yeah.

Okay. Super interesting. I think we could go down a very technical rabbit hole. Yeah. And I think we would have a good time.

But I'm I I think listeners might might might find, they're sort of worried, that we have gone slightly, slightly too deep into the topic. So let's let's move from the technical discussion into a commercial discussion. So why are people coming to you and buying a grid forming inverter?

So there are two main reasons for using grid forming inverters in grid connected applications.

One is you have to use it because the system is very weak in that area. That would be a case for Australia, where there is a system strength framework that requires you to make sure that you're basically not weakening the system anymore in remote grid connections.

If you use a grid forming inverter, you strengthen the system and you're fine. If you don't use a grid forming inverter, then you would have to pay a fee that the transmission operator would use to reinforce the grid. So you save the fee. And apart from that, if you wanted to build a battery anyways, it's a no brainer because you would mainly change the software. So the the second reason for, using, grid forming inverters in in batteries nowadays is the the service markets for inertia service or, system strength services like, like in UK and Germany. So the the first is improving system strength to be able to do a project in that place, and the second one is you get additional revenues due to the service markets.

Okay. So picking up on the Australian example, this concept that effectively you would pay a fee if you're weakening the system, but don't have to pay the fee if you're not weakening system, so you're you're a grid forming inverter.

The cost or the process of going for a grid forming inverter, we covered kind of the operational piece, which effectively you have to save a small portion of your energy, and that doesn't feel to me like a very big cost. So is is the cost of going for a grid forming inverter that it is relatively more expensive to a grid following inverter?

It is it is almost the same. Because it's new technology at the moment, there is a fee for having the new software adapted to each market. So we are actually asking for a small premium to justify the relatively small market, to be covered with new requirements that require a lot of certification testing, lot of technology validation. But this will this will not change the business case of the battery. So, yeah, in general, there is not a big impact.

But I need to add for or I maybe should add for these Australian projects where there is a system strength reason to build it, there is no need to have this extra power capability.

So you don't even have to have that. It's just having the control of the inverter operating grid forming mode and then pass some grid studies that validate that the system is not weakened. And there is no initial specification, for these projects.

So if you're a transmission network operator or a distribution network operator listening to this, I think you would be really excited around, like, where the market might go to in the sense that actually a lot of the inverters connecting to the system today could go to being sort of things that reinforce system strength rather than being things that effectively follow. So I think that's really exciting. And in in terms of the cost of doing it is not that different to, essentially, grid grid following. The grid forming inverters are doing more. I think they have to work slightly harder.

And in in sort of my simple logic, that feels like they might wear out more quickly.

Is that fair or is that, do do they have sort of the exact same conditions around, expected lifetime?

They're designed to have the the very same lifetime. But like I mentioned, we have changed the semiconductors to allow the short term overload for the five seconds. And but this is related to the inertia performance, and this is a different, let's say, a different approach.

The inverter that that is not able to have this, short term peak power, that one won't change the wear and tear on the components in a significant way way. So there is no effect on lifetime unless the system is is really extremely weak and collapses every day or something like this. Yeah. But let's let's not talk about this. The system is usually quite steady, and the events that we are talking about, they only happen maybe the smaller events, maybe once once a month and the Mhmm. Really huge events probably every five years. So it's not that it has a big effect on on wear or lifetime of the components.

And that's talking about large transmission networks, which are generally extremely secure. I suppose the other place in which grid forming inverters are used is when people talk about microgrids.

Do SMA also work with microgrids?

Yeah. Sure. This is actually where we come from with the grid forming inverters or the grid forming technology for microgrids.

There is usually in the past, there were diesel generators, and then these diesel based microgrids would have at some point, someone came up with the idea, hey. Let's save diesel. Let's use PV in this microgrid. They do that, and they notice, okay.

But during nighttime, I don't save anything. And, also, during the day, I have to run the diesel as the grid forming device, basically. Now adding the battery helps in two ways. One is you can shut down the diesel whenever there is sufficient generation from PV, And, of course, you get the benefit of shifting the energy to the night and potentially run twenty four seven without diesel generator.

So this is a a common setup that that we are still providing or we're we're still taking part in these projects, but the transmission connected batteries are, of course, taking a much bigger share of of the overall market nowadays.

That's super interesting. And and so let's talk about bringing a project to market. So if I decide that today I want to build a battery project, I come to you and I say, right. Can I have an inverter as soon as possible?

How how long would it actually take me to get that inverter on the ground and operating? Are we talking six months, or are we talking three years?

We are talking six months to get the inverter from order to to shipment depending on the location, of course, and don't take it for granted, but are not necessarily arrival on-site. But then the question is, what do you need to do in the engineering process? And, when we look at Australia, we usually have an engineering phase where the grid connection permit needs to be obtained, and this takes way longer than and, also, you wouldn't order the inverters before you have the the grid connection approval. So this takes actually, a long time.

And in Australia, the grid studies are quite extensive. So you study a lot of scenarios. Also, the, TNSP, the transmission operator, will do their own studies with the model of your future plant before they give you the approval for connection. And this needs a well supported modeling and a a consultant that will do most of the the modeling work, but also the support from SMA in having the consultant tune the the model so that they meet the requirements in the end.

Okay.

So let's say someone wants to build a battery site in Australia.

That study will be done. They'll come to you with that study that was that will say, these are the specifics of the inverter that we want to have for this particular site. You'll then fine tune that inverter depending on where your locations are. I think you you do most of your work in Kassel in Germany. Is that right? Okay. So you'll fine tune that work in Kassel, and then you'll put that on a on a shipment and send it out to Australia?

No. It it wouldn't work. In that way, we would we would ship the inverter, and then during commissioning, upload the exact parameters from the grid study. Our team would have a parameter file that is synchronized to the GRID study, upload it, and then, fill out some approval form to confirm to the network operator that exactly these parameters are being used on the site.

Okay. Really interesting. I suppose since we're talking about Australia, one of the other things that is really different in Australia to, regions like, GB or US is that we see more DC coupled structures. And we've talked a lot about grid forming and grid following, but we haven't really talked about AC and DC. And I think it would be remiss of us, to not talk about DC. So how how are you seeing the trend for DC coupled inverters?

Actually, there is there is a stall for DC coupled, inverters because of the need for grid forming, because the grid forming should use an AC coupled battery and an AC coupled, PV feed. There are some plants, attempting to do DC coupling and grid forming in the same setup. Mhmm. And they there is one or two that have done it successfully, but it is quite customized.

And to do it at scale at the moment, our recommendation would be to use AC coupled battery and AC coupled PV and have a common point of interconnection.

But this is a really, really complex topic. Yeah.

Yeah. So sort of final question on this, and we promised that we'd come back to it, and we've kind of gone there with the colocation question is, what can a PV plant do or a wind plant do for system strength and system stability?

The the PV plants, they can do a lot to to help stabilize the system. That is power oscillation damping. We discussed a inter area oscillations.

And a PV plant. It can also have a power oscillation damping controller that will make sure it helps to reduce these, oscillations. And this is something that is very helpful in systems with inter area oscillations, like Europe, that PV plants can provide. And there is one more thing that, PV plants can do, and that is, a fast voltage control, which means the the PV will also behave a bit like a voltage source, but it wouldn't have the inertia and the active power reserves, but it would still stabilize voltage freely, really quickly. And this is something we're also already, applying also in Australia to deal with this system strength short force. And, this is also being introduced in new requirements over in in Europe.

Okay. And what's really interesting about this, right, is that to be sort of a grid forming inverter with a battery, your energy source is like a five second or two and a half second burst effectively from the battery. If you're gonna be providing these services from the PV side, where does the energy come from? Because it could be nighttime and the PV might not be generating.

There isn't any any energy, and also the PV would be shut down during nighttime. So that is the big difference. If you have an inertia service market from a battery, it would supply twenty four seven and with a defined performance. The PV wouldn't operate at nighttime anyways. It would, during the daytime, not be able to increase the power. It has maybe a one millisecond energy buffer in the in the capacitor, but that doesn't really have to stabilize the system because it will empty be empty after one millisecond, which is the reaction time that we're talking about. So I think the the PV should do what it can do, and that is instantaneous support for the voltage, but not for the active power balance and the frequency.

Okay. Makes sense. That moves us on to our final two questions, and they are the first one is, is there anything that you'd like to plug?

Yeah. I think I think we need in in the power systems with higher high inverter penetration or with high amounts of renewable generation, we need initiatives to to fast track the evolution of how we deal with stability, and introducing grid forming inverters and inertia service markets is part of that. But, what what I see is in some markets, this is happening, but in some markets, I think this this should be a bit more fast tracked to make sure that we have stable systems, which are the basis of everything we do.

I think that's a a hugely, important plug, and it's something that we need to be ahead of. Right? So you definitely don't want to be in a situation where you're behind system stability, and events are happening. You want to be ahead of this to make sure that everything is contained. So I think people would wholeheartedly agree with that. And then, onto the final question, is there a contrarian view you hold? So is it something that you believe that the majority of the market don't?

Well, I I think that the the long term service contracts for inertia service or for other stability related services are the key because these long term contracts would help to to justify the investment in the first place and to have a long term revenue stream even if the revenue is maybe a bit bit lower than for a short term contract. But you will get, certainty that you have one disability and the the owner has the the revenue stream over relatively long time. So that would be, in my opinion, the best incentive to to introduce the new technology and provide twenty four seven stability.

Okay. I think we've seen a few markets. So for example, frequency response was originally looking at longer term contracts and then eventually moved down to sort of day ahead contracts. So I I will be quite interesting to see whether those inertia contracts actually do move into, say, like, a a day ahead or month ahead type procurement or whether they stay in, like, a longer term, a a longer term contract. Daniel, thank you very much for coming on Transmission. You've been a fantastic guest, and I think people will be fascinated to hear about how inverters work and how they set up grid stability for the future.

Thanks a lot.