WINDExchange Offshore Wind Webinar: Technology Above the Water

WINDExchange Offshore Wind Webinar: Technology Above the Water

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>>Liz: Hi, everyone. Thank you for joining  us today. My name is Liz Gill and I   am a researcher here at NREL and the lead for   the Offshore Wind Technology webinar series  that this webinar is a part of. I just want   to thank you all first for being here. We're  really excited about this webinar and series. I want to take a moment to thank our sponsors,  the DOE, Department of Energy's Wind Energy   Technology Office, in particular Maggie Yancey  and Greg Ball for being such great support on   this project. I just want to make sure that  we thank them for all their support here. Before we get started with kind  of the meat of this presentation   I want to go over a few logistics.

If we could go to the next slide. So this webinar will be recorded and posted on  the NREL YouTube channel and also on the Wind   Exchange website. So we will let the group  that joins today know when those are posted.   There will be a Q&A following the presentation,  so please put any questions that you have   during the presentation and after in the  Q&A function at the bottom of Zoom. And   we're really looking forward to  introducing Walt, our speaker today. So we can go to the next slide.

So Walt is a principal engineer here at NREL and  he leads the offshore wind research platform.   He's worked at NREL for 33 years now, and  in 2003 he actually initiated the offshore   wind energy research program here at  NREL. He studied at UMass Amherst,   where he got his bachelors and Masters Degree  and specialized in energy conversion with a focus   in wind energy engineering. Walt has over 120  publications and two patents. We're so lucky to   have him as a colleague and really appreciate his  willingness to help us with this webinar series. So with that I'm going to pass it off to Walt for  the meat of the presentation here. Thanks, Walt.

>>Walt: Let me go the other way. Thank you,  Liz. So I'd like to thank – first start off,   thank Liz Gill and Mary Hallisey for helping me  put this presentation together and working on it   with me, and also our sponsors at DOE, again,  for setting this whole thing up and sponsoring   the time it took to get this put together. This is really designed to be an introductory  webinar on the technology of offshore wind   and what we see when we look at it above the  water. There's a lot of the structure, a lot of  

the cost is below the water, but this  is focused on what's above the water.   So I'll start with that introduction and  why we're doing offshore wind energy,   why it makes sense for the United States and for  the parts of the world. And then I'll talk about   probably in more detail what goes into  characterizing the fuel that powers   these wind turbines, which is the wind,  and understanding those characteristics,   both in terms of the wind resource itself  and then the technology implications. And then the second part we'll drift into  describing the technology of the wind turbine   itself and go through the different parts  of that. So that's what this is all about.   This will be an introduction, again. Some of my buttons aren't working,   so I'm just getting used to which ones do  work to flip the slides. But here we are.

The first slide here is you can  recognize a map of the continuous 48   lower United States. And this is a wind resource  map. We see different color schemes relate to the   different wind speed based on annual averages. So  offshore the darker blues represent higher wind   speeds and then you can see the yellow colors are  the lower wind speeds. And the proximity of these   offshore winds to the population centers is  apparent where 80-percent of the population   lives in one of the states that's bordering  an ocean or one of the Great Lakes. So we have – that's where the energy gets used, so  we want to generate close to where the energy gets   used. And you can see by comparison the other  places where it's dark blue are the Midwest,   where we have lots of room for wind turbine  power plants and we can power those areas   and through transmission can generate power for  other regions. But it's convenient sometimes to  

not have to build such long transmission lines,  and in some cases that may not be possible,   especially in some of the more populated areas. So  offshore wind creates a great option for looking   at that. The winds are stronger offshore,  and in populated areas where it's difficult   to build large wind farms or solar arrays, which  take up a lot of space, we can use the space in   the ocean to build larger scale projects.  And these create unique economic benefits   for communities and revitalize it – we're  seeing this already, revitalization of the ports   along the East Coast and the introduction  of new domestic manufacturing options and   technologies offshore, which are less constrained  by transportation and construction than land-based   systems, which need to transport components  under bridges and erect systems with land-based   cranes. We can do that with bit ships  offshore, and I'll talk more about that. This next slide is really, it's kind of a  snapshot or a summary of where the industry is   today. And I just said today, but we really took  all this data at the end of last year, so we'll  

be compiling this data as we – again, as we hit  the end of the year. But as of the end of last   year there were over 200 projects worldwide, with  a capacity that we tallied over 33,000 megawatts.   That number is going to grow close to 40,000 when  we add up the projects that were put in this year.   The average project size is growing;  it's getting up to about 1,000 megawatts,   and that's because these developers are taking  advantage of the economies of scale of larger   and larger projects and turbines and amortizing  a lot of the equipment over larger projects. Ninety-nine-percent of these  projects are fixed to the bottom,   which means they have rigid foundations  that are attached to the seedbed,   but growingly a percentage of those are going  to become floating, which means that there's   going to be buoyant foundations. And we  have several demonstration projects and   pilot projects that are underway right now, and  that's the number of – that percentage between   floating and fixed is going to change over time.  But floating is a much more nascent technology.

Another big trend is that we're seeing the average  rating of turbines growing. This past year if you   took all the projects, about 7.5 megawatts was  the average turbine size, but really people are   putting in 10 megawatt machines; like that's  what's commercially available right now. And  

the developers will be using 12 to 15 megawatt  turbines by the middle of this decade,   and that number is going to probably continue  to grow somewhat. And there's a tradeoff   between the turbine size and industrializing  that supply chain at a particular level. But   generally the larger the turbine the more  economical the project, and that's why   we're seeing that turbine growth. And that  translates to larger rotors. Rotors are the  

component that attaches all the blades to  the machine and generates 100-percent of   the energy. Those rotors are about 170 meters  in diameter are ready and are growing to 220 or   to 240 meters over this decade, which  is the length of two football fields. So   that's a fairly impressive size.  I'll talk more about that as well.

Correspondingly, the tower heights have  to grow along with the blade length,   so you can – as a rule of thumb, it's  not exact, but you can take the length   of a blade and add 30 meters to it and that's  how high the hub is off the water. And so for   blades like the GE blade, which is 107  meters, adding 30 meters, you've got 140-150   meter tower. So these are getting very tall, which  means we needed tall cranes and heavy lift cranes. The drive trains are one of the areas that  we're seeing changes in as we get further out.   The direct drive generator is taking over with  permanent magnets as the mainstay for that.   But certainly there's geared systems still.  

Even geared systems, though, are using median  speed generator with permanent magnets as well.   So that's a trend towards those  machines which have lower moving parts. And overall the costs are coming down, and that's  what's driving a lot of the policy decisions.   But we're going to continue to see higher  costs for offshore wind than land-based,   but when it comes to deciding what's the best  option, proximity to the load is very much a big   consideration. And offshore wind is leveraging  – and we couldn't do this without some of these   industries that already exist, like the oil and  gas industry and the subsea cable industries that   are helping us and we're tapping into those  industries to develop these new projects.

One of the things that we should  note this year is that through   the past four or five years there's been a  substantial commitment to develop offshore   wind through the states. And in March 2021  the Biden Administration, federal government   announced support for offshore wind and set a  national target to reach 30 gigawatts by 2030.   And that's commensurate with the level of policy  that's already been committed by the states on   the East Coast. There are eight states that have  adopted over 30 gigawatts of policy commitments. In addition to the target, the US  projects are being supported through   jobs programs that will develop well-paying  unionized jobs, and the investments in   the American infrastructure to strengthen those  domestic supply chains and enable these projects   to be deployed and developed out of significant  port upgrades that are happening up and down the   East Coast. And in addition to that there's also  support for critical research and development   that is necessary to bring these technologies into  other regions such as floating wind turbines or   turbines that can survive  in hurricane-prone regions.

Now I'm going to talk about the resource and  how we calculate it and why it's important.   So I'm going to talk about the resource  assessment and how we get the data   and what some of the important characteristics  are for the data. And your average wind speed,   for example, probability distributions, wind  direction distributions, and then the diurnal   and seasonal variations which are important for  planning the utility and how that generation's   going to get used. And then I'll point you to  some of where those resource data can be obtained. So first of all, offshore is a little bit  different than land because we don't have   as many observations to rely on, so we have to  rely more heavily on computer models to give us   the information, although computer models are  certainly what's used primarily now on land   because they're just getting so much better. These  high-fidelity weather research and forecasting  

model, this is what we call WRF, was developed  by the National Center for Atmospheric Research,   is used to estimate the wind speed over wide  geographic areas at a very high resolution.   And it takes a super-computer to run these models,  and we can generate data for every five minutes of   the day, and right now we're using ensembles  that are up to 20 years in length, and right   NREL is redoing the data for the entire country  using what we call the Wind Toolkit Long-Term   Ensemble Data Set, LED, which is characterizing  the wind speed at all regions at a much tighter   time scale and looking at these ensembles to get  more accurate data over a much longer record. But even with that data we need to calibrate  it. We do that we're – they're validated. And  

we validate it through measurements, which are  very sparse. NOAA operates a whole buoy system   offshore, but those measurements are taken at  the surface or near the surface, about five   meters above the surface. And we need measurements  that are at hub height, because the wind isn't the   same at surface as it is at hub height. And  those measurements are very hard to come by. The picture on the right shows two different ways  to get that. The MET towers that can be installed   in the water are very expensive and difficult to  measure, even – 'cause the turbines keep getting   taller. On the left of that picture there's  a floating LIDAR system, and this is becoming   the mainstay for measuring wind speeds aloft,  but they're still expensive and very sparse,   so we don't have that many measurements offshore,  and that's one of the biggest challenges.

So if we're looking at the data and we calculate  – we want to look at a specific site, every site   can be characterized on an annual average basis  by these probability distributions. And so the   lower-right is a distribution of wind speed and  the probability of how strong it would blow over   the year. Statisticians will recognize this as  a Weibull distribution, or can be approximated   by a Weibull distribution. And it's showing on the  dotted lines when the turbine starts or cuts in,   when it reaches its rated power, that's where it  hits maximum power and then it flattens out and it   runs at that level till it hits cutout. And this  is a distribution that's actually developed for   the Humboldt call area, which is now a wind energy  area in Northern California. And the top figure  

is a wind rose, and you can see that's based on  the north south east west coordinates and shows   the direction that the wind comes from, and this  shows a very strong northerly component with very   little wind coming from other directions, which  is usually pretty good for citing a wind turbine. So these annual averages are very  important and probably the most important   for characterizing the performance of a project,  but there are other variables including turbulence   intensity, atmospheric stability, and wind  shear, which we have to pay attention to as well. So the diurnal variations and the  seasonal variations are very important   for characterizing when the generation is  going to happen and understanding how that   information or how that electricity, rather,  is distributed and input integrated into the   grid and meshed with the other sources that  are being generated. And we have to consider   that because seasonally the load varies; you've  got air conditioning in the summer, you've got   electric heating in the winter, and various other  loads that happen from the time people wake up in   the morning to the time they go to sleep. So you  see these variations seem to be fairly consistent. These examples showing you on the left are  from Oregon and they are representative of   five sites that we looked at up and down  the coast of Oregon, starting from north   on site one, or the lower curve, to the south. So  the stronger winds in Oregon are in the south. And  

then seasonally on the lower curve these diurnal  variations with just a snapshot taking in July,   so I drew the dotted line on July, where you see  that's a very strong – that's the windiest month   and the biggest variation, by the way, from site  to site. But you see that it's very important to   know that the month of July will generate more  electricity in some of the regions and that   needs to be taken into account when setting  up the distribution through the grid. So now I'm just going to mention wind shear.  And I did mention this already, but it's very   important to know what the wind speed is at hub  height. So if we're measuring wind speeds using   surface buoys we're not going to have the right  answer to what the hub height wind speed is, so   we won't be able to predict the energy generation.  So we're estimating that through models, but we   also have LIDAR systems now that can project  their sensors up to hub height and above and   measure the wind speeds aloft. And that's our main  objective, and we need that kind of validation.

The models that we're using, the weather  forecasting models also give us that data,   but we need to validate that. So the wind shear  is very important; it varies from site to site,   it varies depending on the atmospheric  conditions. So we're always tuned into that. And then when we go to try to assess where  the good sites are we're looking at these   heat maps of where the wind speed conditions  are strongest, and this is showing   an offshore wind map of the state of California;  the darker red areas are the areas where the wind   speeds are the strongest. You can see there's  a cluster in the central coast off of San Luis   Obispo, where there's a wind energy area, Morro  Bay, that's being considered right now, and also   on the north where the Humboldt Bay wind energy  area is being considered. And both of those are   excellent wind sites, but you  can see on the map how they vary.

So these heat maps will describe the wind  and we can find that data on these resources   below, the Github and Wind Prospector. These  are live links and this presentation will   provide those to anybody who  wants to follow up with that.   This map is showing 100-meter wind speeds, but  we can draw a map for any elevation we need to. So another important parameter of wind resource  is understanding the extremes and whether extremes   can affect the reliability of the wind turbines,  but also their energy production. So we have to  

understand how the wind extremes vary. Some  of the things that we need to consider are   the possibility of hurricanes, and especially  hurricane-prone regions, let's say south of   Virginia and all through the Gulf of Mexico,  where we're starting to consider projects.   Extreme winds and wave events, and what this is  saying is really that the worst case scenario   for a wind turbine may not be just the highest  wind speed, but it may be a combination of a high   wind event with a high wave event that comes  from an odd direction. So we need to consider   multiple load cases in order to design  these machines so that they don't fail. And then icy conditions; sometimes the ice  can build up, sometimes if we're looking at   Great Lakes wind there's ice on the surface, and  that has to be considered. Extra-tropical storms,  

that means – if you're from the East, that's  a Nor'easter, and those can be very damaging,   but they have a much different  characteristic than a hurricane,   and they have to be considered in their  own light. And then extreme heat and cold,   as we've observed this past year in Texas,  there were events where the turbines in Texas   were not outfitted with cold packages that  were necessary to keep them online, and the   machines were offline until the grid could come  back. So those extremes need to be considered. And then finally the last bullet really  is something – it's a new field that's   necessary for us to understand.  It hasn't really been studied   very much, but climate change may affect the  frequency and the severity of these weather   events and it may also affect the average  wind speeds as well. So we need to start  

looking at that and anticipating what  that's going to do for future machines. So now I'm going to talk about the above  the water projects, above the water   wind turbine characteristics. And what we're  seeing here is a wind turbine on the right with   the major parts labeled. And I think  most people would recognize these parts,  

but I'll just go through them quickly. We have  the blade, which is the part that makes all the   energy and converts the wind to electricity, or  at least it converts it to mechanical energy.   There's the hub that connects the blades together,  and that blades and hub together form the rotor.   The nacelle is the big box, it's like – under  modern turbines it's the size of a railroad car.   And then there's the tower that holds the  whole assembly up, and then you have a deck   where the crew can access and stage some  of their operations, and a transition piece   that connects the tower tot eh foundation,  in this case it's a monopile. And this is  

just showing a Siemens 2.3 megawatt offshore wind  turbine, which is now small by current standards. So turbines offshore are  bigger than they are on land.   The average capacity of land-based  turbines was just 2.75 megawatts last year,   and if I take the average offshore  turbine it was 7.5 megawatts and growing   rapidly. The offshore machines have more complex  support structures. They have to because they're  

in the water and they have to withstand not just  the aerodynamic loads, but the hydrodynamic loads   that come from the waves, especially under  extreme conditions. And they have to be   designed to withstand the marine environment,  and I have more on that in just a minute. So first let's start with just the basics of what  an offshore wind farm looks like. It's very much   like other wind farms on land. Multiple machines  are connected together and the power is sent to  

a substation. But on a single machine we've got  this machine and the schematic in the foreground,   the wind direction is coming from  the left side towards the hub,   goes through the rotor, and that's an  upwind machine, so that means the rotor is   upwind of the tower. And that wind passes through  the rotor. And let's just – giving some examples,   for a GE machine that's now rated at about  12 to 13 megawatts, the rotor diameter is   200 meters in diameter, so there's about 10 acres  that's swept by that rotor as it's spinning.   That means that there's about – the weight of  the wind passing through that rotor is equal to   the weight of the machine every two seconds.

So it's a very large span; it's one  of the largest rotating machines   ever built by humans. And as that rotor spins it  converts the mechanical or the kinetic energy of   the wind to mechanical energy and transmits that  energy through a big shaft that sends it to the   drive train. And then the drive train is generally  a direct-drive generator or a geared system that   sends it to a medium-speed generator  and then converts it to power. So the   offshore wind plants can be 1,000 megawatts  or more in size, and the peak energy output   is comparable to a conventional large power plant  such as a coal or natural gas or nuclear plant. One of these machines, if it's a GE 12 megawatt  offshore machine, can power 4,500 US residences.   And another little fun fact that I've heard  GE say is that one revolution of one of these   machines can power your house for  two days. And they keep rotating.

So here's the – sorry. Here's the   slide. I just want to talk a little bit about how  we adapt these machines. All of these machines   started out as land-based machines and then they  evolved, and the evolution means larger machines,   but it also means that all these foundations are  treated very heavily with corrosion-resistant   coatings that were developed over many, many  decades by the oil and gas industry to prevent   rust and corrosion and compromising their  strength. The nacelles up top are pressurized so   that the salt air doesn't get into the components  that are up there and compromise them over time. And they're designed – and you can see this  on the figure – on the picture in the left,   they're designed for safety, accessibility, and  crew transfer. So there's a lot of components   that go into just those features so that  the crews can aboard these things safely.

They all have a drive train that deviates a little  bit from a lot of the land-based conventions,   which means they have direct drive generators.  They send the shaft power at very slow speed to   a generator and convert it immediately  to electricity, or through a doored   gearbox that goes through a medium-speed generator  that's running at hundreds of RPM, not thousands.   And then there's a specialized workforce training  to operate and maintain those technologies.

So these turbines are getting larger,  and I said the larger the turbines   the better from a developer's standpoint.  But the turbines have to be matured as they   get developed. But generally speaking, the  larger turbine requires fewer installations   and reduces the number of turbines that have to be  maintained, and it provides more energy, because   these turbines are taller, the hub heights are  higher, and therefore there's more wind up top.  

And there's no real physical barrier that  would prevent us from going even larger.   The big tradeoff is whether or not it makes  sense to go larger and larger or to industrialize   the systems that are already developed and  use the ports and infrastructure that were   developed around those sizes. And  that's decisions that the industry is   working on right now. But by 2024 all of  the major wind turbine manufacturers will   have a commercialized version  of a 12 to 15 megawatt   turbine that the developers will  bet aping into those supply chains. So I'm going to talk about the components one  by one. You'll see that the tower is one of the   most prominent components and it's a static  structure that rises up from the sea bed and   holds the nacelle assembly up. It's a tube tower  and it's tapered, but it has to be structurally  

very strong to hold all of the thrust loads and  all of the other loads that the turbine rotors are   generating. It protects the workers because you  can climb through the middle and it's protected   with ladders. It protects against avian species  that might want to perch because there's no perch   places. And they're easier to maintain. And we  can see that these cross sections are very large.   And they can be manufactured – they  need to be manufactured near an ocean. If somebody could – I'm getting  a little feedback; if you can   mute I would be appreciative. Thank you.

The yaw bearing is at the top of the  tower, and I'm going to talk a little   bit about that in just a minute. So inside  the nacelle – the nacelle is pretty much the   components that are inside that big box  that we see up top, everything but the   rotor itself. And it contains the drive train,  which is the mechanical pathway that converts   the rotor torque to electricity. And it can  have a gearbox, but typically it doesn't. In the  

figure that's shown it does not; this is  showing just a direct drive generator that's   mounted in front of the tower and it converts the  electricity right there and then sends it back to   the power electronics that are in the top of the  nacelle there, and those power electronics convert   the variable wild AC power that comes off the  generator and then they rectify it to a quality   AC signal that can be sent to the grid and used at  grid voltages and frequencies. So that's what the   power electronics do, and that's all inside  the cutaway that you see of that nacelle. The yaw system is mounted at the top of the tower,   and it's a big turntable bearing that allows  that entire assembly, the rotor and the nacelle,   to rotate. And there's a sensor on the nacelle  that determines where the wind is coming from and  

it orients the whole machine towards the wind  direction and that keeps the power at maximum   levels. And you can see that yaw bearing has to  work pretty hard as the machine rotates around.   It's carrying the bending and thrust loads  of the whole system as it's also rotating. The exterior of the nacelle, if  we get rid of the cutaway here,   you see there's a few features on the outside that  are relevant. There's a helideck that is used for   helicopter landings. This isn't  always used, but it's there and it's  

available so that crew transfer can take  place by helicopter. There are sensors that   determine the wind speed and the temperature and  the wind direction, and there's other sensors   that can determine displacement. And then you see  there's aviation warning lights that are required   to warn aircraft, and those can be activated  by radar or they can be on all the time,   but they need to be there. And then there's just  the composite nacelle enclosure that houses all   the equipment and allows the equipment to  be protected from the marine environment. So now we'll talk about just the rotor; that's the  part that I described earlier. It has three blades   connected to the central hub that is connected  to the main shaft, and that's all rotating. One  

of the key features of the rotor assembly is that  the three blades are all connected to this hub by   these circular turntable bearings that are mounted  to the root of the blade and those turntable   bearings allow the blade to rotate at least  90-degrees. In one direction on one extreme the   blade is parked and the rotor cannot turn; in  the other extreme the blade is hitched to power   and it can turn and generate a lot of power. And  then on a finer tuning the blade can modify its   angle to adjust power so that the power never  exceeds the maximum power of the machine. Each of the blades, though, has this independent  pitch control. Normally they're pitching at  

the same rate at the same time and you wouldn't  know that they were not connected to each other.   But in the event of an emergency any one of  the blades can shut the machine down by itself   by just simply pitching to a non-power position.   And that makes the machines very, very  reliable, because we have triple redundancy. This is what a blade looks like, and this is kind  of a historic view as well. I have at the bottom   what the seven-meter blades used to look like in  the 1980s. Basically all the European machines had   this style blade. These worked well, but they were  not optimized. And these come from our colleague,  

Ken Thomason, who first published this picture,  but I've used it a lot. In the evolution of   wind turbine blades, they've become a lot more  slender. And the above blade, which is now   representative – not precisely, but  representative of the larger machines,   you can see how much slenderer they are  and they have much more sculpted, tapered   shapes to adapt them for the loads that are  coming and to maximize energy production. If we just scaled up that 7 meter blade to  107 meters like the GE blade, the weight of   that blade would be so large that it would fall  off the hub itself, just on its own weight. So  

a lot of technology has gone into the development  of these larger blades, which are made of   mostly fiberglass, but now we're introducing  carbon fibers to stiffen the blades some. Usually   the blades are a combination of carbon  and fiberglass and balsa cores that are   used to stiffen the panels. You can see  a cutaway on the right side of kind of an   earlier version of one of the blades. And most of  it is hollow inside, but you can see that it does   have these sheer webs that prevent the panels  from buckling. That's a typical section. So now I'm just going to talk about the  substations. This is where all the power   is aggregated. The turbines are all  connected to one of these substations,  

and at this substation it collects power at about  66,000 volts from the turbines, which have their   own transformers, to bring it to that level.  And then from that level it's stepped up even   further, to about 220 kilovolts, and then it's  aggregated together and sent to an export cable   that is buried in the sea and brought to shore,  where it can be connected to the land-based grid. The substations are using the same substructures  as some of the machines themselves, and attached   to the seabed. It's all technology that was  developed from the oil and gas industry in  

being able to attach these heavy substructures to  the seabed. Floating substations are on their way,   but they're nascent and will have to be developed  and they will be a slightly different animal. Some of these substations also have   temporary sleeping quarters so if  crew have to stay out there they can. And then finally I have this comparison. So as  we wrap up the what's above the water, these are   three machines. One of them is a fixed-bottom  machine, the one on the right. And the two on  

the left are floating machines and they look  very much the same; they use the same turbines,   but they have different substructures.  And depending on the substructures,   they can look identical and you might  not even be able to tell them apart. So the one in the middle is a spar that was  installed by Equinor, and it is a floating spar.

So now I'm just going to wrap up. From a   big picture standpoint we now have a national goal  in the United States for 30 gigawatts by 2030.   This was set in March and it's really commensurate  with the policy commitments that have been made   by each of the states. The wind resource, which  is a very important parameter for us to understand   and to measure, is determined by many  factors, but wind speed is probably the most   important one. Wind direction is important,  and we need to know the time of day and the   seasonality of these wind measurements. And  I've talked a little bit about all of that. Offshore wind turbines are derived from land-based  turbines and are adapted – and they are adapted   to the marine environment, so therefore they are  bigger and they are protected from the salty air.  

Offshore wind turbines are getting increasingly  larger because larger turbines are more   economical, but we're right now reaching a new  plateau of 12 to 15 megawatt turbines that will   be deployed over the next decade, and the industry  is building infrastructure to accommodate that   size machine, both in the supply chain and  the manufacture of these 12 to 15 megawatt   components, as well as the ports and harbors and  vessels that go into installing those machines.   And when you look at these  machines from above the water   they're very similar between the fixed-bottom  systems and the floating systems, and   we'll be likely putting in both  kinds in the next 10 to 15 years. And that's the end of my talk. I'll be  happy to take questions at this time. >>Liz: Great. Thanks, Walt. We really appreciate  all that information. We've been collecting   some questions in the Q&A, so I'm  going to go through some of those now. To start, folks are wondering what  are some of the ways to reduce   maintenance costs for offshore wind generally? >>Walt: Yeah, that's a good question. So we're  just getting started in this country, but we do  

have a lot of insights from our European partners  who have encountered some of this. We know   a lot about how to maintain wind turbines  from land-based wind, but a big part of the   cost is to access the turbines in the offshore  environment. So it's very important that we know   more about the nature of the failure and the  maintenance that we're going to perform before   we go out there because it costs a lot to  send somebody out to say look at a machine. So remote sensing and remote data collection  and diagnostics is going to be very important   so that a lot of the troubleshooting can be done  before anyone even approaches a wind turbine.   And then once we get out to  sea the use of robotics and   machinery, drones that can look at the  systems without a human having to climb   up will be very important as well. And these are  all nascent technologies that are being developed,  

but show very high promise for  lowering maintenance costs. >>Liz: Great. And actually to build on that,   we just had a question come in asking about  how the buffer and safety radius is determined   for a wind turbine. So for like a 12 or 15  megawatt turbine how is that determined? >>Walt: I think this could be answered a couple  different ways. Are we talking about the spacing   between the turbines or are we talking about how  close can one get to a turbine? 'Cause there is   no – necessarily no setback from the turbine  itself; they have to go up to the turbine to   maintain them, and a ship or say a fishing vessel  could at least theoretically go right next to   those turbines and go up under them, 'cause a  blade passing is 30 meters above the waterline.   But that would have to be taken into account. I  don't know if any setbacks have been established  

by the Bureau of Ocean Energy Management  that regulates offshore wind projects. If the question is more about spacing  the turbines apart from each other, that   is also being negotiated. But it's a tradeoff  between the length of the cable that's necessary   to connect all the turbines together and the wakes  that are being generated by the turbines. So if   the turbines are close together they're going to  generate higher wakes and have more interference,   especially for the downstream turbines. So  that has to be all taken into consideration.

In the Massachusetts Wind Energy Area   the spacing of wind turbines has been established  at one nautical mile, which corresponds to   a little over eight rotor diameters if  you're putting in GE machines. So that's   pretty conservative spacing for wind turbines, so  it should help in the power generation as well. >>Liz: Great. There were a  couple of questions about   offshore wind development in the Great Lakes and  the recent approval of the ice breaker project.   And I'm hoping you can talk a little bit about  just generally offshore wind development in the   Great Lakes, but then also what technology  you see being used in that setting.

>>Walt: Yeah, so the Great Lakes are  unique because they have freshwater ice,   also in order to access the lakes you have to  bring ships in through the locks of the St.   Lawrence, which are limited in the beam width  mostly. So the large turbine installation   vessels that we're familiar with in European  wind farms and we'll soon be familiar with in   the Atlantic installations, those ships  can't fit into the Great Lakes. So   the Great Lakes will have to have its own  infrastructure that lives on the lakes, and   it may be lake dependent. So Lake Erie  is a shallow lake and it freezes harder   than the other lakes; it will have its own  requirements. And that's where Icebreaker is,  

it's off the coast of Cleveland. In Lake  Ontario it's mostly a New York-owned   lake, that will have lighter ice, but it's deeper,  so the technologies in Ontario will have to be   floating, whereas in Lake Erie they'll have to  be fixed-bottom. And each of these situations   requires a different take on the infrastructure  that will need to be built in terms of the ports. There's a lot of new technologies that  we're seeing that are promising for   the Great Lakes or other areas where some of  the other foundation types might not work,   such as float-out systems that don't require  heavy-lift vessels. And it's yet to be seen what   the optimum technology would be for the lakes, but  there's several options on the drawing board, but   very few that have been demonstrated  and practiced yet because of the ice.

>>Liz: We actually had a  question come in about vessels   and the Jones Act and if you see the Jones Act  potentially influencing what types of technology   will be used here in the US or if you see it  as a big barrier for offshore wind generally? >>Walt: I would say it's a challenge, but we're  already seeing ships being built in the US   that are compliant with the Jones Act.  And there's no reason why the US couldn't   build its own ships and have a fleet of ships  that are available for not just installation,   but maintaining a fleet that's going  to be built. So that's one option. But there's no reason why the US has to do  this the same as Europe. And even Europe has   the same challenge, because most of the  ships that they built for the first say   33 gigawatts of offshore wind, most  of those ships won't work for the 15   megawatt machines. So they're going  to have to build new ships as well.

So the industry is at kind  of a crossroads where we're   moving towards just building larger ships and  it scaling up the technology, but there's also   the option to start looking at technologies  that don't require such heavy-lift vessels   so that we can maybe more efficiently install  some of these machines and maintain them. >>Liz: Great. Thank you. We had some  questions come in about the difference   between wind speeds and seasonal variations  between land and offshore and if they were   different. You know, usually wind  speeds on land are lower in the  

summer and higher in the winter, and if  it's opposite in offshore situations. >>Walt: I don't think we – first of all, that's a  very regionally specific question and it may vary,   so I wouldn't say there's one answer  for all. There's definitely differences   between the offshore characteristics and the  land-based characteristics at a particular site.   In California we see capacity credit   is about twice as high for the offshore wind  resources than we see for the land-based resource,   because the winds blow more steady and more  consistently offshore. And we may see some of that   same trend in other areas, but we haven't really  looked at it extensively in the other areas, but   I think the short answer is that they  do vary and in some cases we've seen   better load matching or better matching  of the peak wind speeds with the peak   loads in places where they're building  or they want to build offshore winds.

>>Liz: Gotcha. Great. Thank you. So we've  had a couple questions come in about   ocean life and birds. And I know, Walt, that  isn't your expertise necessarily. But do you   have anything to say there? I'll just say that  we actually have a webinar series happening with   our wildlife group through the _____ program,  and we can provide that information to folks   when we send out the Q&A answers. So just  to preface that before you _____ _____. >>Walt: Yeah. So I will probably  be brief there, but we haven't seen  

a catastrophic threat to either birds or ocean  life. There's strong evidence that the fish   can thrive in some cases in the wind farms, so  it doesn’t – you know, we're not worried about   that. But there is more of an impact to the  fishing industry than there is to the fish.   When it comes to marine mammals we've seen  impacts, especially during construction,   where the noise could affect the marine mammals.  And so we take very strong precautions against   producing noise that could injure their hearing  or even threaten their lives. So that's all   taken into account during the construction  and it has to be very carefully monitored.

And birds, the same way, we'd be very  careful about where we sited the machines   and how they would impact fly-ways and things  like that. I'll leave those questions for others,   but generally on land wind turbines aren't  the major threat to birds. Glass buildings and   housecats and cell towers and automobiles all  have higher threats, but that doesn’t mean that we   discount the possibility that we could affect the  avian communities as well, and we take precautions   in that light as well. And I'll leave the rest  of that to the other webinars that you mentioned. >>Liz: Yeah. And another great resource  is the International Energy Agency  

has 34 REN website. There's a lot of great state  of the science briefing sheets if anyone is   interested, that we can  send out that link as well. We had a question about control strategies  and if you can talk about any control   strategies that are commonly used at the farm  mobile. So just when farm controls, if not – >>Walt: Anything specific on  controls? I mean it's a big field.   I will say unless there's a specific part  to that, I will say that controls and   the advancements that we've seen in controls  over the last decade have allowed a lot of the   innovation that we're seeing today on the large  wind turbines, and they've allowed us to reduce   the weight of the machines by sensing loads  before they happen in some cases, and allowing   stabilization of floating platforms,  for example. So that's a huge thing. On a farm level we're seeing control  systems implemented that allow us to   actually operate the wind farm as one  unit rather than individual turbines.  

So we're maximizing the power output of the  entire system by having say the front turbines   that see the wind first, steer the wakes away  from the turbines that see the wind first steer   the wakes away from the turbines that are behind  them so that they experience better energy flow   and things like that that we're seeing that are  still in the experimental stage in some cases, but   think of the wind turbines acting  like a flock of birds rather than   just a bunch of random turbines all  independently out for themselves. >>Liz: Great. Thank you for helping us  answer that very broad question. I think   we've gone through a lot of questions, you've  answered a lot of questions for us today,   Walt. We really appreciate your time. I think  we're going to go ahead and wrap up the webinar. I just want to say thank you to everyone who   joined us today. And there was many  questions about if this presentation  

and recording will be available. Yes, it  will, but we will be posting it to YouTube,   NREL's Wind Exchange website, and sending it  to the group that signed up for this webinar.   That will take about 7 to 14 days, but we will  try and get it out to you as soon as possible.

Just want to thank you again from the  National Renewable Energy Laboratory   for joining us today. I think  we will wrap up with that. >>Walt: Thank you, Liz. >>Liz: Thanks, Walt. Really appreciate your time.

2021-12-04 21:23

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