>>Alex: Good morning everyone wherever you
are. It could be afternoon or evening. But I wanted to welcome you to today’s webinar
Floating Offshore Wind Systems of Tomorrow. My name is Alex Lemke and I’m really excited to
be part of NREL’s ongoing wind energy science leadership series that includes presentations
and discussions on wind energy related topics featuring speakers from the National Renewable
Laboratory, in some cases academia and our industry partners. These webinars will discus
the challenges facing wind energy and the pathways forward for making wind one of the
most prevalent energy sources of the future. Today we begin with a panel of some
NREL’s senior research engineers to discuss the research needed to design and
optimize innovative floating wind systems that will enable the deep cost reductions necessary
for the commercialization of offshore wind. But before we begin, I have a few housekeeping
items to cover. First, today’s webinar will be recorded and available on demand and will
be posted on NREL’s website shortly after the webinar today. Please mute your lines and make
sure your cameras are off unless you’re speaking. Next, we encourage you to use the
chat feature to ask questions. And we’ll be answering those questions at
the end of the session. If we do not get to your questions during today’s webinar, we
will be sure to follow up with you afterward. And finally, I would like to introduce Nate
McKenzie from the United States’ Department of Energy Wind Energy Technologies office
to say a few words before we begin. Nate? >>Nate: Thank you Alex. I’m the technology manager for offshore wind R&D here at the Wind
Energy Technologies Office or WETO. I joined WETO earlier this year on the first day
of quarantine. I’m a naval architect coming over from the contractor side at the Office of Naval
Research where I worked on a variety of seabasing and energy projects. And prior to that I spent a
good bit of time at a shipyard working on naval ship design. At WETO research into floating
wind is a top priority. Floating wind offers a tremendous opportunity to cost effectively
harness a reliable energy source. The floating space is nascent with several demonstration
projects and a wide variety of concepts. As such we see a wide need, a strong need
for significant research across a variety of technical areas. These include platform
and turbine design and assessment tools, development of controls which can include platform
motions and full wake effects for the whole farm and understanding of wind behavior
across the marine boundary layer. The team at NREL is critical to making progress
against these priorities and I’m delighted to be able to work with an extremely capable group
of engineers and scientists. And the four that we’ll be presenting to you today are some of
the best, Amy Robertson, Jason Jonkman, Garrett Barter and Senu Sirnivas from NREL are leading key
research in floating platform tool development, system engineering, aerodynamics and platform
design. And with that I’ll turn it over to Amy. >>Amy: Thank Nate. Good morning everyone. My name is Amy
Robertson and I work at the National Renewable Energy Laboratory and I will be moderating this
webinar on the floating wind systems of tomorrow. In addition to myself you’ll be hearing from three
other speakers today including Jason Jonkman, Garrett Barter and Senu Sirnivas who are
all senior researchers here at NREL. Now the purpose of this panel is to introduce you
to the floating wind research that is being done at NREL that will help pave the path to its
commercialization. I’ll first give a bit of an overview of why we are studying floating wind
and what our overarching research focus is. And then the three speakers will provide details
on some of the more prominent research areas. So why are we pursuing offshore wind? Well, this
map of the US shows what the wind speeds are on land and offshore and indicates that
in general the winds offshore are stronger but they are also less turbulent and more
consistent. Building wind turbines in the water means that you’ll be less encumbered by
transportation and construction constraints which will enable the turbine size
to grow and can help to reduce cost. It will also be closest to the largest
population centers in the US and you’ll provide economic benefits to those coastal
states revitalizing ports and adding new jobs. Most offshore wind turbines in the world
today are what we call fixed bottom design where the support structure for the
wind turbine is built to the sea floor. Here you can see a couple of the examples of
these types of systems including the monopile and four legged jacket which are the
most prominent designs being built today. But in the US and other places in the world a
lot of the offshore wind regions are in water depths where it starts to become too costly to
built a system all the way to the sea floor. And that threshold is considered to be commonly
around about 60 meters. For the US 58 percent of the offshore wind development areas are in these
deeper water depths as you can see here with the delineation between the darker for the deeper
water and the light blue for the shallower water. For these deep-water regions wind turbines are
needed that float on the surface of the water and are tethered to the sea floor using mooring
lines and anchors. Here we see the three general architects of floating wind designs which are
categorized by the way that they stabilize the system to keep it from tipping over during
wind and wave excitation. These structures closely resemble those used in the oil and gas
industry but these design approaches at present are too costly for the competitive wind energy
market. New floating wind system designs are needed that push beyond these traditional designs
to find ways to lower the costs of the system. At present floating wind is at a precommercial
stage of development and here you can see the evolution its taken over the years.
Starting in about 2009 to 206 a number of one off demonstration projects were developed
which was able to show the feasibility of floating wind as a technology. We’re now in what we call
a precommercial stage where small multi-unit farms are being built including the Equinor
Hywind Scotland farm with five turbines and the Wind Float Atlantic with three turbines.
But the next big step is to get to full commercialization where we have large wind farms
of about 400 megawatts and plus. To get there we need to overcome the hurdles of getting the
cost on par with land based systems, developing the industrialized infrastructure and also
addressing the social and environmental issues. So NREL is working to address these issues
to achieve floating wind commercialization in three fundamental areas. The first focus area
is developing a suite of tools and methods for floating wind design which can be used to search
for optimal solutions that will lower cost. These tools incorporate the ability to characterize
the meteorological and oceanographic conditions offshore which we shorten here to Metocean, their
loads and the structures and their power output and their associated cost. We’re also developing
tools to help to optimize these design solutions. Today Jason and Garrett are going to be presenting
on these tools and the topic areas they’ll be discussing are highlighted here in these lighter
blue colors. Another critical area of research is the verification and validation of these
tools which is needed to ensure their accuracy to enable optimization and the development of
experimental methods and measurements to acquire the data needed. The foundational support of this
research comes from the Department of Energy’s Wind Energy Technology Office and their mission is
to advance to scientific knowledge to enable clean low cost wind energy options nationwide. The
folded list on this slide and the next two show some of the DOE funded projects NREL
is working on in some of these areas. The second research focus area is technology
innovation where we use the developed tool sets to explore innovative pathways
that most effectively lower cost. Today Senu is going to be talking about some
work on the area of floating substructure design again colored here in light blue. But our
work also looks at large turbine design and floating wind control methods
both at the turbine and farm level. Sensitivity analyses are used to assess the
impact of tradeoffs in different design approaches and regional conditions to help us understand the
impact on the entire system. This allows us to identify what components most affect cost and how
to combine them to achieve a pathway that provides optimal system cost reduction. We’re also starting
to do work in the operation and maintenance space where we’re looking to develop methods that are
specifically applicable to floating wind designs. The final area we focus on is the
adoption of floating wind technology. The work at NREL in this area includes
resource assessment which assesses the amount of wind energy available in our offshore
wind regions as shown here in this map. Then the grid where we work to coordinate
and develop and vet a strategy for the integration of floating wind into the US
infrastructure. Environmental social acceptance which includes the SEER project mentioned here,
workforce development where we examine offshore wind workforce needs and skills and develop
curricula for K to 12 education. And finally the development of standards for the installation
of floating wind technology in US waters. In addition to the funding we get from WETO,
NREL performs floating wind research through other funding mechanisms as well. One is through
the Department of Energy’s National Offshore Wind Research and Development Consortium which
hosts a number of competitive solicitations for offshore wind research. The NOWRDC is focused
on building connections between the research and industrial communities to produce innovations
that directly address near term challenges to the advancement of offshore wind in the US.
This is a bit different than the WETO work we are showing on the previous slides which is
focused on more long term research goals. This slide shows some of the funding areas in the
first round of awards where 7 of the 20 projects awarded were focused on floating wind including
topics like wind farm control optimization, advancing mooring design and the development
of the National Offshore Wind Resource Dataset. Another research program coming out of the RPE
arm of the Department of Energy is the Atlantis program which is focused on using controlled
codesign to achieve more optimized floating wind designs. The controller on wind turbine
will tell the blades to pitch, the turbine yaw or changes to the rotational speed to try to
maximize power while not overtaxing the system. But when on a floating platform these actions
can excite dynamics into the system which can lead to instability issues. But this ability to
impose dynamic excitation can also be used to improve the stability of the system which could
allow for smaller and more lightweight designs. A controller codesign approach means
that you’re integrating the controllers, the fundamental component in the wind turbine
design process rather than developing it after the design is already fixed. Atlantis
includes a series of projects that are looking at developing the computer tools to enable
controls codesign, experiments to validate these tools and the exploration of radically new
floating designs based on these capabilities. At NREL we’re leading a project in each of
these areas including USFLOWT in area one, WEIS in area two and the
FOCAL project in area three. A lot of the research that NREL performs in
coordination with the larger international research community through the International
Energy Agency which is focused on advancing wind energy deployment by bringing together a global
network of researchers and policy experts. There are a total of 17 active research projects right
now in IEA Wind and four of these at least have some focus on floating wind. Those include Task
26 which is focused on the cost of wind energy, task 28 focused on social acceptance for offshore
wind, task 30 which performs the verification and validation of offshore wind modeling tools,
task 37 focused on system engineering which has also created just recently a 50 megawatt
floating wind reference model and then a future task that’s being developed presently
that will focus on floating array challenges. NREL also supports the adoption of offshore
wind in the US through support of the Bureau of Ocean Energy Management. BOAM is the one
that oversees the leasing of offshore wind development sites off the US coastlines. To
support BOAM, NREL has updated floating wind cost predictions in California as well
as working on lease area delineation and outreach and education in California and other
analysis work in Oregon and Hawaii as well. NREL has also been leading the development
of the US design standards for offshore wind including a working group
specifically focused on floating wind. Finally in addition to the government based
funding NREL works directly with industry partners to help bridge the gap from basic science to
commercial application. This direct engagement allows NREL to help accelerate innovation and
the commercialization of floating wind in the US. Here you can see some of the partners
that we work with in offshore wind. So hopefully that presentation has provided
you some insight into the vast research NREL is doing in floating wind to help push
it towards commercialization. Our next three speakers will provide some more
detail on some of these research areas. And so now I’ll hand it over to Jason Jonkman. >>Jason: Thank you Amy. So I’m going to
continue on the discussion with the focus on wind turbine modeling. First of
all I should introduce myself. I’m the senior engineer at NREL. I’ve
been here for about 20 years now. I actually got my PhD study in the dynamics of
floating wind turbines back in 2007 and lead our numerical modeling work for engineering
applications to floating wind. I also support the development of international departments
through the IAC design standard for floating wind. Get that out of the way here. First of all when we talk about modeling the
main goal of course is to develop advanced wind energy technology. And the pathway to doing that
through modeling is to basically develop models that are based on first of all international
design requirements like IAC design standards or as well as the local jurisdiction requirements.
Of course you have to base the design of technology on the physics, the fundamental physics
of the motion and unloading of the turbine. Any sort of unique technology
innovations that have come to play, say here a partial span play pitch
or some novel floating system you need to capture the right physics of those
systems in these tools to enable their design. Because typically we need to run
thousands of load case simulations when we do technology development, we can’t run
full up high-performance computing solutions and we can’t solve the problem fully
with test data. However, both of those really feed into the development of
these tools for advanced technology. I want to have tools that can really be
applied for a range of technology solutions including novel rotor concepts, novel sensors
and actuations. There’s a whole transition within NREL to focus on not just individual
turbine technology but also design at the full plant level including this active control. And
then of course things like novel drive trains, towers and all these floating support
structures that we’ve been talking about today. When talking about floating wind one thing
that’s very critical is the coupled nature of the problem. So these are large structures,
basically as large as civil engineering structures like skyscrapers. However they’re
active machines that have basically a brain inside a control system that interacts with
the environment. So of course we have the wind loading and dynamic loading of the structure
and that responds structurally to that. Because it’s now installed on a floating platform we
also have the dynamics of the floating system and station keeping system as well as of course
the hydrodynamic loads for impact. That’s the coupled nature of this problem that makes
floating wind challenging but also quite exciting. In some ways some of the modeling challenges we
face when we talk about floating wind. First of all, large effects is a major concern particular
as we go from the precommercial stage now to full we expect turbines to get much larger than they
are now. So nowadays it’s sub ten megawatt. Turbine designs on the drawing board are around
14 megawatts. And then in the research community we’re looking at the 15 megawatt turbine with
IEA task 37 as well as larger turbines up to 20 megawatts. And these turbines are not the
same as we had before. The spatial variability of the inflow can be very dramatic. And to
make sure they’re cost effective we need to make them night and that makes them flexible.
And so the interaction there is very important. Floating wind also presents some quite unique
hydrodynamic challenges. Floating structures tend to look like structures that have been designed
for oil and gas platforms like the semi ATLP inspar that Amy showed. However we have to keep in
mind that they’re not really oil and gas platform. First of all they’re quite a bite smaller and that
makes the hydrodynamic theory that’s being used to develop them only semi applicable. So we have
potential flow as well as viscus effects that are important. Also, these systems can be much more
compliant than an oil and gas platform could. Dynamic stability is a core consideration as
normally you design structures of course it has to be floating stable. But because of the
dynamic nature of the floating wind problem treating the stability in the
dynamic sense is also important. The area is simply the coupled nature of the
turbine with its environment. So of course the rotor has an impact on the floater response. The
floater response also has an impact on the rotor effect. And that can impact say how the rotor
interacts with it’s wake and say how the wakes are generated in a wind farm. Another concern that we
have, particularly off the US Gulf of Mexico and east coast locations as tropic cyclones. And this
presents certain unique challenges in terms of extreme wind conditions as well as extreme wave
conditions and what happens when those things come through. We want to make sure that the systems
in the end are cost effective but also reliable. Finally another major challenge is simply that
the huge probabilistic design space that we have, normally we have to consider of course a range of
wind conditions. You have your operational cases as well as parked cases. You also have to
consider the range of wave conditions and the directionality between them. And you
can kind of consider the full combination of these things. You could have a million
plus timed simulations that you need to run. And so finding trackable ways of
narrowing down that probabilistic design space so you can capture the overall ultimate
particulars reliably is quite a challenge. So the Department of Energy and Wind
Energy Program heavily involved with NREL is really developing a suite of tools to
support the design of floating wind systems. These kind of tools you think of in terms
of whether they apply to the turbines themselves in isolation or full wind plants.
And then also from a range of model fidelity. So at the lowest fidelity we have tools that
basically run practically instantaneously. Things that you can run millions of combinations
in very little time. This is a good way to explore the design space of the system. What’s my
general configuration of my turbine or my plants? At the highest fidelity level what we’re really
trying to do is resolve as much physics as we can to really understand the problem. So really
trying to understand the physical interactions of the turbine and the sea environment, both
of them being at the turbine plant level. That’s with our SOFA out annexes and platforms
and actually Mike Spreg led a webinar a couple months ago on these topics. So then the middle
is engineering tools, really meant for detailed design applications to open fast for the turbine
itself and then tools like fast farm and Wind SE for analysis of turbines at the farm level.
So these tools can effectively run real time such that you can still run hundreds of
thousands of timed domain simulations to capture the main physics necessary to do the
actual structural design calculations with. Talk a little bit about OpenFAST ‘cause that’s
really our workhorse simulation tool here. So, we want to try to capture the coupled
aerodynamic structure and control capability of these floating wind turbines. The main purpose
is to run nonlinear time domain simulations. So, we try to capture the aero in hydrodynamic
input, put it to the model and then the reaction in terms of structural response,
the control system as well as the mooring or station keeping system behaves. So this is
doing that for kind of detailed time domain loads analysis calculations basically following
what’s required in the national design standards. Another major important feature of OpenFAST is
developing delinearized models and underlying equations that themselves are nonlinear. But
if you can linearize them then you can really understand what this, what the physics really
means. And so the linearization feature is really important to calculate things like eigen solution.
That means calculating the natural frequencies, the load shapes and damping and various
modes of operation. Linear models are great for controlled design applications as
well as analyzing things like instabilities. Because engineering models themselves
don’t fully resolve all physics we had to make some simplified assumptions to make them
efficient enough to run the full load suite. Verification and validation of
these tools is highly important. And so as I mentioned earlier what we really do
is a combination of verification and validation. Verification, by that we really mean comparing
the model with some underlying mathematical model. And we often do this by basically
comparing one model against the other among similar levels of fidelity. That tells us
that the software has been implemented properly as we expect. But validation of course is also very
critical. That’s really saying test our model, fully represent the reality of interest that we’re
considering. We do that through a combination of analysis against of course real world test data
whether that’s some model scale experiment, in let’s say a wave-basin, and if they are a full
scale operational turbine. We also use the high fidelity models like the SOFA and Exelon tools to
do validation of our real world models and try to form development of these tools. And of course to
use those tools in their technology development. This slide summarizes some of the major
accomplishments that we’ve had over the years, particularly in the area of engineering
modeling. And so first of all OpenFAST is used worldwide to design systems not only in
the research and academic communities but also in the ministry. In fact 80 percent of the first
precommercial and prototypes in floating wind were actually designed with support from OpenFAST.
These are some of the examples shown here. Another major accomplishment is
NREL has led this international codes comparison collaboration or
what’s known as OC 3, 4, 5, and now 6 really leading the international community
in the verification and validation of these tools. And that’s happened since 2005.
Finally most recently NREL has now developed basically new capability which for the first time
ever will enable us to do full loads calculations of turbines and wind farms. This is showing
actually not a floating case. This is a flowing complex terrain but showing basically the streak
lines of flow through the wind farm. So these are simulations now we can do practically real time
to do loads calculations of turbines and farms. Final couple slides will just summarize
some of the key developments that are ongoing now and sort of recent accomplishments.
So first of all – and actually this was presented at the last webinar. We’ve introduced a
new free wake vortex model to capture, better capture the ergonomic interaction of the
rotor with its near wake. This is quite important for floating wind because of the floater platform
induced motion of the rotor. Another area that we’ve been working on is in the area of improving
Fast Farm at high thrust conditions. The current model in Fast Farm is quite robust for low thrust
cases where basic momentum theory applies. But in high thrust cases effectively momentum theory
breaks down and the wake expands quite quickly. And so we’ve been developing a model based on
this, high fidelity Exelon wind simulations to allow us to understand what happens there in the
high thrust conditions that are in wind models. Another example is from our high-fidelity
modeling group where they’ve been using or upgrading Exelon wind recently to study
the turbulence induced wave fields. And this may impact of course how we do
FIDEEP analysis of floating offshore turbines. Another major area that we focus on is really
improving the models to better support specific technology enhancements. One area we’ve done in
partnership with Stiesdal Offshore Technology with their tetraspar design making sure our tools
dually capture the highly compliant nature of these systems. We have quite slender structures
here as well as things like pretension cables and hanging ballast systems that we want to make
sure we can capture of course the structural loads in those components. Historically we
also modeled the floater as a rigid body. That really doesn’t apply to these next
generation technologies that they’re much more compliant. So that has been a great partnership in
highly advanced capability of the OpenFAST tool. Another example is a partnership we had with
Makani. This one, this is a project fully actually funded by Makani. It’s basically
to support the development of a _ that we actually called KiteFAST for airborne floating
wind systems. And so this tool is now publicly available to the community to support airborne
technology development. Final example I’ll show. This is from Matt Hall at NREL who is leading an
effort to do basically development of floating technologies that have shared mooring systems.
So here the turbines interact not just because of wakes that may come by and controls that may
be talking to each other but also directly through the mooring connections. And so we’ve been now
making improvements say to FAST Farm to be able to model this and develop design techniques to
analyze these types of unique floating concepts. Final slide here is on verification and
validation. This is just showing a couple of examples recently that we’ve been addressing.
One was a partnership we had with Siemens when they used a highly instrumented 2.3 megawatt
turbine with aero elastically tethered blades and nice inflow measurement as well. And we used
that to validate our next capability in FAST called Bindine to do aero elastic calculations for
these highly flexible blades. This is showing sort of the mean plus or minus one standard deviation
across a thousand time series cases and showing we’ve matched quite well to the experimental data.
Finally Amy leads a project actually was an OC6 in IEA task 30 that’s really focused on improving
our understanding and ability to model the moving of the towers for floating wind systems.
Historically in OC5 we found actually quite consistent under prediction across a range of
modeling tools for a range of load cases as well, basically a 20 percent under prediction of
ultimate and peak loads. We found out this was basically caused by a resonance excitation from
hydrodynamic loading that we weren’t properly capturing in our model. And now within OC6 we’re
actively working to resolve that so our models can predict this better in the future. So with
that I’ll pass the control now to Garrett. >>Garrett: Thank you Jason. We rehearsed this and now it’s not working. >Female: Garrett I can go ahead and share the screen. >>Garrett: this is Garrett Barter. >>We can see it now. >>Garrett: Yeah. Hi. My name is Garrett
Barter. I’ve been at NREL about three and a half years having previously spent time at
Sandia National Labs in aerospace industry. I lead the systems engineering for wind research
portfolio. And I like to continue on the theme of the talk of moving towards cost competitive
commercial floating wind energy. And I’m going to talk about getting there through
systems engineering and optimization. So I’d like to take a step back first
and look at the current design paradigm for offshore wind plants. I would call it the
iterative design paradigm. Really reflects the current market reality where each company
that’s involved uses its specialized expertise. And multiple companies have to come
together to make a plan to reality. You have your OEM which designed turbine. Another company
will design the substructure. The two have to come together and iterate on a controller that
minimizes the loads and maximizes the power. Once that product is refined they hand it over to a
developer who owns the array layout and logistics of your balance of plant, assembly installations,
operations and maintenance, that sort of thing. Now again this reflects the current market reality
which you can’t really knock too much. Offshore wind has been successful over the past 20 years or
so. It’s grown tremendously. However we think that this approach when applied to floating will give
you solutions that work, just not necessarily that are cost competitive. May need to show this
integrated paradigm at work. I’ll take a look at recent or kind of the only somewhat commercial
wind, offshore wind project here in the US, the Block Island wind farm installed off
of Rhode Island. It was installed by then Deep Water Wind now part of Orstead. And
there were many suppliers. Their turbine was supplied by GE. They have their own network of
subcontractors. There’s a little diagram there on the drive train components. You can’t read
it but lots of other contractors are listed. The blades were from LM. The jacket was made by
Gulf Island Fabrication. The cables were supplied by somebody else and other companies owned the
vessels. Deep Water Wind was responsible for getting all of these players together to make
one cohesive project. But they didn’t possess the final design authority over everything. If you
compare that to the aerospace industry where wind is also considered a younger cousin of sorts
one recent big introduction in aerospace was the Boeing 787 although maybe not so recent
anymore. Certainly also a complex system, maybe subcontractors responsible for executing on
different components. Boeing however is the prime systems contractor. They retain ultimate design
authority and as the prime systems integrator over everything. Since they own the whole design they
can trade off and make changes to one component that might go to the system. That’s something
we’re not yet able to do for a full wind plant. So why won’t iterative design
paradigm cut it for floating? Well, Jason already explained to you how complex the
floating environment is in terms of the physics. I would say that as engineers we typically want to
understand that environment thoroughly and design a product meant to operate in that environment.
But even if you’re wildly successful at that your turbine costs, your turbo capital costs are
really only a small fraction of the lifetime cost, the lifetime levelized cost of energy LCOE. A
lot of other cost is buried in the additional complexity of your logistics, balance a
plant, operation maintenance, financing. Now all of these are tied in certainly to your
engineering choices but you really need a systems approach in order to reflect that coupling
and tackle the whole balance sheet at once. So we would propose then an integrated
approach through multidisciplinary analysis and optimization, MDAO. We think this is the most
promising pathway to getting to cost competitive floating wind. And the concept, you take a
given innovation which could be for a specific component, a logistic, really anything and you
would insert that into a big framework that has all your engineering and all your cost represented
together. And that are moreover coupled with one another which is in some ways the hardest thing
to do. From there you apply analyses that can vary from simply parametric sweeps or sensitivity
studies to a little bit more wonky mathematical approaches that do optimization in the presence
of uncertainty. In the end you’ve derived the cost benefit tradeoffs or the levelized cost of energy
impact for a given innovation on the whole system. And this way you can start to evaluate which
pathways or innovations make the most sense. So our thoughts and our approach is to use this
type of tool and technique to move from these say more archetype floating platform geometries
which Amy described that were borrowed mostly from oil and gas into something else a little bit
more innovative, a little bit more systems aware. Some attempts at that are shown on the
right and there are many ideas out there. Not all of these will be successful. We
don’t know which ones are going to win out. It’s going to be a combination of
engineering and market reasons. But we’d like to build the tools to ease
that transition as much as possible. Now it’s also easy to think that all you have
to do is build the Uber or the ultimate systems framework here and click optimize and you’re
done. But that’s actually not how it works. Actually a lot of [Break in Audio] the
entire space of possible designs. And there’s things that make sense and things that
don’t make sense. You can think of maybe the area of cost competitive floating wind systems
as a corner of this trade space which is shown here on the bottom. So we want to narrow from
the yellow circle to the dark blue circle. And there’s a few ways we go through
that. First there are standards and regulations that get applied. We also
have lessons learned from experience. And this could be a floating prototype, could be
oil and gas. And then after that is when you start to apply your optimization to squeeze out the last
iota of performance and cost from your system. So when it comes to standards I’m not going to
talk about them. Amy mentioned them briefly. There are no formal standards yet for floating
wind. We’re moving in that direction but it takes a long time. Currently what we have is
the force of guidelines or recommendations. For the lessons learned I will
talk about those just briefly. And these are a list of some of the
concepts or ideas that we have in mind that are borrowed from prior projects and that we
know will lead to our cost competitive solution. So I’ll talk about some of these, not all of
them. Don’t quite have the time budget today. But all of these could have an entire presentation
of their own. Now the ideally we like to ingest these or insert these
into our design framework. And that’s easier for some of them more than
others. So really what that means is the engineer and the model have to work closely together. It is
a cooperation and collaboration between the two. That’s another key point I want to make is just
because you want to make is just because you can do fancy optimization that doesn’t remove
the value of the engineer from the process. Ok. So, with that soapbox message
aside let’s dive into some of these. So let’s first think about assembly. Well,
for instance what would make sense for a floating turbine to make it easy to assemble and
cheap to assemble? Shallow draft so this is the depth of the substructure as it extends into
the water column. If it's more shallow it can be easily assembled at ports or at keyside and also
go into a lot of different ports around the world which was another listing on our key learnings.
it also means that if you can do assembly at the port, you could use land-based crawler cranes
instead of specialized offshore cranes which are bigger and can lift heavier items. But they're
much more expensive and it requires labor at sea. To further alleviate your crane requirements
you can see some designs here on the right have off center turbines. And one of the reasons
for this is now it requires a shorter boom length and smaller counterweight on your
land-based crane to assemble. Going onto from assembly to installation
if you are able to assemble at the port your full turbine in floater you'd be able to
tow it out directly to site. We think that would certainly be the cheapest option as opposed to
again labor at sea and specialized vessels at sea. if turbines could be transported horizontally
as that diagram shows or that image shows, it would certainly open up new possibilities
and excite the spar enthusiast. But that is a new load case on the drive train and
the bearings that really hasn't been examined or considered yet by the OEMS. So we're not quite
ready for that. But who knows. Maybe it could come. Once you've towed it all you have to install
and get the turbines set upon station. That can also take some specialized vessels especially
around moorings and anchors. One idea from DMVGL is to includes wenches on the platform
or at least allow them to be easily attached. That could might eliminate some of the time for
again specialized vessels. Gravity anchors shown there on the top right are also gaining popularity
especially for some of the tauter mooring ideas or semi taught mooring ideas. again there's very
little sea bed prep and anchor deployment that would require there. Finally I should mention
the Stiesdal TetraSpar which Jason talked about in depth. Just know that it's a transformer of
sorts and that I mean it has a - it looks like a semi-submersible with a very shallow draft during
tow out. And once it gets on station it drops a ballast to gain some stability but it's also
very easy installation step. And it looks more like a spar when in operation. So we think there
are a lot of good merits there in that concept. Ok. So now I finally made it to the
final narrowing of the trade space to applying optimization so
we'll talk about that now. Now it's probably very easy to think about
optimization as a way to do cost reduction. Most folks jump to the area of weight reduction
as that pathway. And pretty much any component you can consider on the turbine has a pathway
to weight reduction. Oftentimes you could just substitute in a new material like carbon fiber or
move to something like super conducting generators which has a lot of nice scaling capabilities.
Two bladed downwind rotors, much more lightweight or something more radical like generative
designs with additive manufacturing or a complete concept change is kind of shown
there on the top left. Now each of these would essentially require fewer kilograms but might be
more expensive per kilogram as you introduce a new innovation. It's very difficult for a human
brain to wrap around what makes sense, how to do all those system tradeoffs. This goes back
to the need for an integrated design paradigm, So I would say that this isn't something that I'm
saying is completely novel. Folks are doing this. You will dive into literature and finally many
examples in wind, even floating offshore wind where folks are trying systems optimization.
We just haven't yet hit the bar of doing full floating turbine and platform as a systems
optimization. Here are some examples where optimization has been applied, the 15 megahertz
wind turbine. Many components were designed with optimization but not the floating substructure
together with the turbine. Our own Matt Hall has some nice papers in his publication history of
doing something similar. But again it was mostly focused on the platform. And our own John Yasa was
recently involved in a paper had some really nice takes and thoughts on how to do spar optimization.
and you can some very nonstandard designs coming out of the optimization process, things that the
engineer might not have thought of by themselves. So how are we going to get there? Well, I'll just
wrap up with this message. We've, both Jason and Amy have also talked about Atlantis, this idea,
this project from RPE to do controls codesign where you design the geometry, the architecture
at the same time as the controller as opposed to leaving the controller for the end. So we think
that is a great pathway and in order to enable that, we're going to do a multi fidelity approach.
Since the floating environment is so complex and the numeric are going to be so complex, we kind
of have to chip away through a multi fidelity approach. So we're going to bring together
wisdom and Open FAST, two common NREL tools, the idea being Wisdom is a good design tool but
not a - but too low fidelity to handle floating. OpenFAST is a great analysis tool but it was never
meant to be a systems optimization design tool. So we're going to combine those together
and use the best of both worlds. That's it for me. So I'd like to turn it over now
to Senu Sirnivas to discuss how we go from this conceptual design approach to the practicality
of real world design. Thank you very much. >>Senu: Hello everyone. I hope everyone is doing well. I'm going to talk about design
and let me share my screen here. All right. So Amy talked about - >>Amy: Sorry Senu. We're still seeing Garrett's screen right
now. Not seeing anything shared from you yet. Disappeared but not seeing anything from you. >>Senu: Thought I was sharing my screen. All right. Is that coming through? >>Amy: Yeah. Thanks. >>Senu: All right. Thanks for keeping me straight
Amy. Amy talked about general resources and why we should do floating wind. Jason came in and
talked about the physics and all the complexity that has to be modeled and then we had Garrett
talking about optimization and tools in general. I'm going to talk about design. So we have the
resource. We have the physics. We have the tools. Now design is a little different in the sense
that we have to use these tools and to put these platforms that we can install in the water. So
one of the things that Amy talked about and so did Jason and Garrett, that we've brought a lot of
technology from oil and gas. Here you see that there is an oil and gas drilling and production
platform which is huge. Usually the oil and gas fields are designed and developed as one
offs. They don't really mass produce them. So there's really no automation
in the process. And in a sense then this becomes very expensive if we use
technologies coming from oil and gas. And on top of that it's also bulky. So we need
to come up with new ways of doing things. So one of the things that I started with
in the beginning - and I'm going to talk about one design here although the tools and
things that Jason and Garrett talked about is agnostic and can be used for any floating
structures. There are mainly three floating structures that you could think of them at spars,
as semis and as TLPs and then variations of that. Right? And people are always coming up with more
imaginary ideas and wacky designs that we have to - that the tools have to adapt to. Right? And
in this specific instance that I'm talking about the SpiderFLOAT, we're only going to consider the
floating structure, substructure design and not the turbine itself. Right? Because
that's constrained by the manufacturer. So in 2017 we started this LDRD and to look at
innovative floating structures and we wanted to go in with an open idea in the sense that we
can come up with something new, think outside the box. But one of the things that we knew in 2017
that the cost of the LCOE needed to be about 15 cents a kilowatt hour as you can see on this
slide here. This is for a semi and the cost of the substructure was going to be about $10.72
million. So we kind of had this constraint and wanted to either meet this or beat this at least
in 2018. And we started this project in 2017. So we wanted to come up with a
floating substructure design and have a functional requirement that we came up with that
we wanted to address. There were a total of 16 of them but we mainly wanted to concentrate on
the first few here which is highlighted in red. I talked about the 15 cents a kilowatt hour for
the LCOE. And also if you look at the ports in where we can actually build and assemble these
things, we wanted to keep the draft to a very shallow draft about 14 meters so that we can
actually do all the pre-commissioning and everything on the key site before taking it off
at site. And we also wanted to use off the shelf components. We didn't want any special components
because that will just increase the cost. So the water depth we considered was about 60 meters
and beyond. Anything below that you could use a fixed bottom structure so we wanted
to concentrate on 60 meters and above. The rest of the functional requirements we
have here, a design life of 25 years. And I talked a little bit about pitch here, six
degrees. But really it could go more than that. But we kind of want to limit the pitch
in extreme conditions to about six degrees. We also wanted to have station keeping
redundancy. What that means is we wanted to have additional mooring lines. If one mooring
line does fail the system is still there. And the other big thing
is also simple decommissioning, Right? We didn't want to have very complex heavy
vessels, heavy lift vessels out there to do the commissioning or also the installing. So all
of this plays into trying to lower the LCOE. And the other big thing that we wanted to
do that should be highlighted in red here is minimize the wave loads. And if we
minimize the wave loads then we can minimize the amount of steel or material that we
need on the floating structure itself. So having these functional requirements, we
start looking at different concepts. What can we do to come up with innovative idea. What
kind of materials we can use. Right? So there are all kinds of materials you can
use. There's concrete. There's steel. There's fiberglass, composite that can go into building a
floating system. So we start looking, exploring at the materials and also different designs
and how to capture maybe added mass and different things. And also to reduce the
loads being transmitted to the central structure. And these are some of the ideas that we came up
with. We have a barge here. This is all made of concrete. And I wanted to grab some water in the
space here so we can have some added mass that we have to move about and reduce the heat. And
then this idea here is about having a bunch of connections here. They are moment free connections
and also a retractable ballast. And this is just a variation of that. It's some buoyancy cans on
the side here and another variation of that. So we looked at all of these and we finally
concluded that what we really wanted to do was incorporate some of the ideas that
we were considering in the concept and we came up with this innovative
concept called SpiderFLOAT. Now I'm going to go through this in a little bit
of detail. Sorry. All right. I've got to go back. There we go. So we wanted to have moment free
connections so that we can reduce the load being transmitted to the central. And if you look at
these schematic that we have here, we said ok. We're going to make joints here, universal joints
that connects the buoyancy cans which is going to provide the buoyancy that's needed. We have a
central column here and a couple - there's arms, three arms here that you can see. There's one
on the back here. So we have the arms here and these are moment free connections here and
here. So the scans in fact they can flex as the waves come in and go. So we also wanted to use
different kinds of materials. We wanted to keep the heavy materials at the bottom and we wanted to
keep the light materials at the top. So I called this material for purpose. And so what we ended up
doing was we said we're going to make these cans out of fiberglass and then we're going to make
the central column here and these legs here using concrete because we want the heavy stuff to be in
the bottom and the light stuff to be at the top. So this design finally we called it SpiderFLOAT
because it kind of looks like a spider in some ways. And as I said earlier we are constrained
by what we were going to do at the top so we were only concentrating on the platform here
and we also considered retractable ballast. The design that we're considering now
does not have a retractable ballast but this is an option that we can add to it to get
better stability. So here is a simulation that we did in ANSYS. Part, I'll get to why we're using
different tool sets to Open FAST in a bit here. But what we wanted to do is to have a lightweight
design and we wanted structural compliance. So we wanted the cans to move and we wanted to
have all this moment free connections. And what this is is really if you look at this picture
here, if you have a hurricane coming through and you see these palm trees they're
flexing. The more flex you have, they can, you can actually come up with lighter
design and that's what we wanted to do. So now we have the design sort of figured out
and we really know what we wanted from the functional requirements we had.
And we have the simulations done. one of the other things that needs to be done in
any design is you have to go into a model base. And you've got to actually test this in a model
scale to see how you actually perform in the actual model scale and compare that back to
your simulation and adapt your simulation tools to match your model test. So Matt Hall here has
done this hybrid testing that's come on board and he's going to help us move this along
to do a model test probably at a 150 scale at one of the model basins here. And so here
we have a hybrid simulation system where we have the platform here. Of course these are
individual cans. Now they're all as one big can in the model test. And we have this optional
thing for adjusted, adjustable ballast here so that we can try different things if we want
to go that route. This is being in the process of being done. We haven't really got there
yet. But we will be doing this model test soon. So here's the detail of the LDRE itself,
the SpiderFLOAT. And we applied for an RPE project and we got awarded. Amy talked about
this earlier. It's called US Float and US Float is really a combination of SpiderFLOAT
plus the D2 10 megawatt machine. And I talked about this a little bit earlier about
the buoyancy cans being made of fiberglass and we wanted to make them at factory or on
site so that we can easily produce them and have it be cost effective. And here
are the connections that I talked about earlier where we wanted to have moment free
connections so these cans can really move. And we also wanted to have And connecting it to
the arms and we have actuators here that we can control the tensions of these cables. And these
arms now they can be built on site or they can be done at the factory as well and brought in and
assembled. And talked about he cables. That's how we're going to control the tension on these
arms. And the central column is also going to be of column and that can be done on site. So a lot
the cost savings here is really going to come from either building a lot of these components in
factory and assembling them at port or actually pouring them out since we're using concrete, using
the port itself and making the pieces on site. Here's an animation of the system, complete
system. I'm going to move this forward a little bit because it takes a little while to run. And we
modeled this in OrcaFLEX and part of the reason we did this is because Open FAST as it stands right
now does not have the capability to do multibody modeling with the flexible cans we have
and the flexible arms we have. We don't have the capability to do the cables with active
tensioning and also joint damping which is not available in OrcaFLEX as well. And our tapered
buoyancy cans which can be done in OrcaFLEX. And linearization. Right? So part of the reason
we are using OrcaFLEX at this time is because these capabilities are available in OrcaFLEX but
OrcaFLEX is not able to do linearization which is needed for control codesign as what we need in
RPE Atlantis program. And I wanted to say that a lot of the work although we're doing it
in OrcaFLEX as Jason talked about and as Garrett talked about, a lot of these capabilities
are being added to Open FAST and we would be - we will be moving to Open FAST in the future here
to do the US Float CCD design using Open FAST. So I just wanted to leave one
thing with the audience here. And Amy talked about market resource and what's
available and how this can - we need designs to place in this market. So we have designs.
And people are coming up with wacky designs. The US Float is kind of wacky design in some
ways. And wacky designs need new physics and so new physics need to be added to Open FAST. And
then what happens is we need to have the physics being added to the simulation tool and the
simulation tool to be applied to the design. This is an iterative process. It's not a process
where like Garrett was saying you press a button and you get an optimized solution. It is really
iterative design. It has new wacky designs come into place and physics need to be solved. And the
physics need to be added to the simulation tool and the simulation tool can be used in the design.
And so this is iterative process and I want to leave everyone with that. And that's all I had
really. Thank you. I hope that was 15 minutes. >>Amy: Thank you Senu. And thanks Garrett and
thanks Jason for your presentations. That was all really great. I'll just remind people that there
is a chat function associated with this webinar that you can posting your questions in. A
few people have done that but just encourage more people to do that if you like. So there
should be like a little bubble looking thing at the top to be able to - that you can click
on to enter some questions. So for the next 15 minutes approximately we're going to go through
some question and answers first trying to address any that are being posted in the chat area. And
then if we have some extra time we can look at some additional ones as well. So based on the
ones in the chat I think maybe we'll go to this one first that I think Jason I'd like you to see
if you'd like to answer. And the question is what is the level of error in these models. Or given
the amount of variables do you expect a certain percent of installed turbines to not produce or
break? Does this factor into commercialization? >>Jason: Yeah. That's really a great question.
I would say it's kind of fundamental to the work we do. So we don't just do the
tool development. We also do a lot of work on verification and validation. I would say
the answer is not completely straightforward. I can't just say it's 20 percent or whatever
'cause it certainly depends on many things. Just a couple comments. I'll say certainly that
because we know there is uncertainty that can never fully be eliminated - obviously
we will make improvements over time. But because we'll never fully make perfect models
there is some built in safety into the design. The standards require that basically a load
safety factor. The typical value is 1.35. We typically assume about half of that comes
from uncertainty in numerical modeling and about another half comes from uncertainty in your
environment in which you operate your turbine in. So that's probably a general
rule of thumb that we use. But then if you kind of talk
about specifics, certainly things we do quite well, structural dynamics
tends to be quite well captured within the model. I think the physics are well known and as long
as you have the material properties known that's quite good. Hydrodynamics we have quite good I
would say for say like direct wave excitation, first order wave excitation at the model.
Things like nonlinear wave excitation and some of the difference we can see we tend to have
a hard time with. And then I think the biggest source of uncertainty in any of these models is
really on the aerodynamics side. Highly nonlinear, highly challenging when you talk about large
rotors in the atmospheric boundary layer and so the aerodynamic uncertainty is probably the
biggest source and often the one we focus on. >>Amy: Great. Thanks Jason. And if any of
the speakers ever want to chime in addition please just go ahead. Senu we're still seeing your
slides. I don't know if you were trying to share still but just so you know. Ok. The
next question actually I was going to direct at Senu. The question is how is the
design process impacted when designing larger systems with 15 to 20 megawatt wind turbines if
it is or is it just a straightforward upscale? >>Senu: Yeah. [Break in audio] 15 is not really that big of a
deal, right? Just need to make it a little bigger. So in the US Float system that we're designing
it's actually sort of modular in some sense that you could scale anything from 6 megawatt
up to 20 megawatt. And the incremental cost factor is not that big. So let's say for
example if you're going from a 10 to 15 the platform cost would be a lot smaller
than let's say the turbine cost for example. >>Jason: I might want to add to that. Garrett
can step in too. I might want to add to that. If you simply take a smaller turbine and
scale it up generally the rule of thumb if you say the mass would go as the cube and that's basically
the cost. And then tower would go with the square of the say the rotor diameter or link scale.
And so you can't really solve that by scaling directly. Eventually you're going to hit a
limit where basically building bigger is more expensive. And so there's definitely lots of
technology innovation that goes with building bigger systems. And then as I mentioned
in my presentation as well, large rotors introduce quite a number of unique challenges
at large spatial temporal variability of the wind across the rotor as well as because you're
trying to eliminate that square cube law and make it lighter, more flexible
aero elastic challenges as well. >>Garrett: The only thing I would add is your
computer and your design found [Break in Audio] just can't be manufactured today. So now you have
to either invent some new manufacturing method or put in an additional constraint which then has
other system impacts. So maybe for small steps, yeah, scaling works. But for big
steps changes are you're going to run into some sort of constraint like that. >>Senu: So those are really constraints
on the turbine and the blades and whatnot. >>Amy: Yeah. I think there's also a constraint
that I've heard about on the moorings. Again as the system, the turbine size grows again
your support structure will grow in size too. There's constraints on whether facilities
are able to produce those larger turbines. And for moorings from my understanding can get
to be such a long lengthy heavy mooring line at these larger scales that that can actually max out
the capabilities we have right now in terms of the installation vessels to lay down those moorings.
So I think there's yeah, there's multiple areas that we might have that effect. I have the next question I'm not sure if we - the
next three questions we have and then we have a fourth. The next three I'm not sure if the panel
is the best for answering. But I think I'll just pose this one just in case. The question is do
you envision some acoustic constraints offshore as on shore and will any changes or relaxation of
acoustic constraints allow you to increase energy production and reduce LCOE. So Jason I thought
maybe you might be able to take that. If you like. >>Jason: Yeah. Well, certainty the
acoustics is the noise emission. When you talk about something far offshore
you can certainly say that's likely less of an issue which means you can tend to push
up your speed ratio and your blade tip speeds which means you can go to a lower solidity
rotor in general. That's about all I can say. >>Garrett: I'll just add that yeah, so relaxing your acoustic constraints may
get you to - you think you might be able to get to a higher tip speed. But offshore there's
also a leading edge erosion issue that can come into play. And that can sometimes drive
your max tip speed. So just because you don't have the acoustics issue doesn't mean you
have free reign to go as fast as possible. >>Amy: Yeah. Thank. And I don’t think the
question is directed in this way but there is acoustic constraints also on the installation
process offshore and that’s another thing we’re looking at for innovative designs to think this
is more problematic on the fixed bottom rather than floating. But actually installing the
system itself, pile driving in the sea bed, things like that, doing work in the ocean has an
affect acoustically on the oceanographic animals. And the other two questions were related to the
electrical system which yeah, the speakers here on this panel I don’t think are really the
appropriate ones unfortunately to answer that question. One was related to whether we’re
looking at transmission challenges associated with floating offshore wind. And another is if
the offshore electrical collection system for floating wind is straightforward or a solved
issue. I will just from myself mention and I can let others interject if they do have
anything to say on this. I know this is an area that we’re working on in terms of
the offshore wind integration into the US grid. As far as kind of the focus areas that we
have in terms of the modeling and dynamics, there is an issue with the – for floating wind the way
the power is transported is through a power cable. For a fixed bottom offshore wind system that
will be very static cable. But for a floating wind system it also needs to hang, kind of similar
to the mooring line, hang off the floating wind system. So there are challenges in modeling or
designing, sorry, that cable system that will take the energy from the floating platform
into the grid infrastructure. So that is an ongoing challenge of trying to understand what
the dynamics of these floating wind systems are and ensuring that we can create a cable design
that can withstand the motion characteristics. >>Garrett: Amy, the only thing I’ll add is like Amy said the dynamic cables can be
both a modeling and a maintenance challenge. But also floating projects tend to be a little
bit further from shore than fixed bottom. So in that sense you may – other folks at NREL
are considering medium voltage or high voltage DC export cables and collection systems. Like Amy
said, the folks here on the panel, that’s not really our area of expertise but it’s definitely
something to consider. I think once you get the energy on shore the electronics look the same
as fixed bottom wind. So integrating into the grid isn’t necessarily the challenge. It’s just
getting it on shore that is the bigger challenge. >>Amy: Great. Thanks. Ok. Another question is are
there any issues with aero elastic instabilities such as wave flutter with larger rotor systems.
Jason do you want to maybe start that one off? >>Jason: Yeah. So certainly because you’re trying
to beat this square ______ you try to make your systems generally lighter, more flexible. And
with that the flexibility means that you’re likely approaching flutter limits. So you want to
make sure that say your torsional, first torsional frequency is above the operational speed of the
rotor. Or if it’s not to make sure that you don’t rest on that frequency well. So this is a big
reason why we focus on our modeling work, not just on time demand simulations which of course
is important to analyze these systems but also focusing on linearization so we can properly
predict natural frequencies in a range of conditions but ultimately focusing on aero elastic
tailored waves so being able to model the torsion and of course offset say mass and stiffness from the fixed axis including composite tailoring.
So yeah. Definitely it’s an issue. It’s becoming more important as you get to larger systems mostly
‘cause you’re pushing them to be more flexible. >>Amy: Ok. Great. Thanks.
We have another question. How is Open FAST multibody
dynamic solver being changed to model systems like the SpiderFLOAT and
will a third party multibody solver be used. So maybe Senu if you want to start with that
and Jason or Garrett if you want to add in. >>Senu: Sure. So one of the biggest challenges
we had when we were coming up with the idea for SpiderFLOAT is tools. And the tools were not there
for us to really investigate. The flexibility of what we had in SpiderFLOAT. So in the very
beginning the way we addressed it was we said ok. We’re just going to look at it like a fixed system
for now because that’s what we could do in FAST. And then just get the turbine loads that we can
from FAST and then impose that in ANSYS model where you can do multibody. Right? So there’s
always these tools that are always lagging what I call wacky designs. And so somehow you
have to come up with a way to engineer it. And you could use tools like FAST that is not
there yet. But you can use other tools that have some of the features you need and then try
to use them together until a tool is ready. And Jason is working on this and the Wise team is. And
they’re adding a lot of features of flexibility, multibody, cables with tensions and whatnot which
we’ll eventually be able to use with SpiderFLOAT. And OrcaFLEX on the other hand
also has the turbine in there, right? So you could do – you could do multibody
with the cables and the turbine. But it has its own lack of features. You can’t
do linearization that you need for a CCD approach that we need to do in RPE.
So you just need to find [Break in Audio] and try to bridge the gap. And that’s kind of
what we did and now we have let the Wise team know these are the features we need and they’re adding
to Open FAST. So this is a cyclic process. Right? >>Jason: Maybe I’ll just add that I mentioned the
Stiesdal project where we vetted the ability to model the substructure as basically a series
of bean elements and various joint types. So we can represent the arms so you have the
SpiderFLOAT as beams. And then we also have – we’ve introduced things like ball joints
and universal joints within those beams as well as pretension cable elements. That gets most of
the way there for the SpiderFLOAT. But the thing that was still missing is the buoyancy cans which
are heavily bound linear as Senu showed in his animation that they move a lot. And so we can’t
assume things that we’ve assumed in other models. And so we’re actually introducing that now
with our nonlinear solver called Bordine. Matt Hall is taking the lead on that and so
soon I think we’ll actually be able to model the SpiderFLOAT quite well. We chose not to
use a third party multibody solver for this. A big part, big reasons for that is
because a lot of our focus is on full, not just single turbines but also full floating
wind farms. And so having a multi body solver would make that sort of coupled problem quite
challenging. And so but if we can control the coupling scheme and how it solves then
it’s easier if we do that ourselves. >>Amy: Ok. Great. Thanks
everyone. I think we are actually out of time and we’re out of questions on the
panel. I had some staged but I think since we’ve run out of time maybe we should just close it
there. And I’d just like to take the time to thank Alex and Nate for the introduction and
organization of this webinar. And to Jason, Garrett and Senu for their great presentations
and their great discussions in the panel as well. >>Jason: Thank you Amy. >>Amy: Yeah. And I think Alex posted. I think
this will be – Alex is this being shared, the recording of this that
people can download as well? >>Alex: Yes. It’s on the Wind Energy Science
Leadership series page and I will go ahead and put the link in the chat box so everyone can
look forward to the next topic in December. >>Amy: Great. Thank you. Thanks everyone.
