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Contra-rotating floating turbines
promise unprecedented scale and power
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Contra-rotating vertical turbines could radically improve yield
and reduce LCoE for floating offshore wind projects, according
to World Wide Wind
Norway's World Wide Wind has a radically
different take on offshore wind power. These floating, vertical-axis
wind turbines (VAWTs) feature two sets of blades, tuned to
contra-rotate – and they promise more than double the output of
today's biggest turbines.
Taking wind farms way offshore can certainly
help make them less obtrusive, and open up a lot more opportunities –
but as the ocean gets deeper, conventional horizontal-axis wind
turbines (HAWTs) begin making less and less sense. HAWTs need to hold
a lot of heavy components – drivetrains, gearboxes, generators and
their colossal blades – right up the top of a long pole, so mounting
them on floating platforms that don't want to tip over is a huge
challenge – not to mention maintaining the business end of a turbine
so far above the ground.
Some engineers and operators believe this could be
a niche where VAWTs could shine instead. Their blades reach
upward, but all their other heavy bits are at the bottom, so their
natural tendency is to sit upright. Also, they can accept wind energy
from any direction, rather than needing to turn to face into the wind,
cutting down on some more heavy gear you'd find up high on a HAWT.
They're typically far less efficient than a regular three-blade HAWT,
sucking less energy out of a given breeze, but on the other hand, you
can place them closer together without a drop in performance, meaning
they could potentially suck more energy out of a given patch of
ocean.
![](images/images_08_31_2022/pic4.jpg)
The top
turbine, mounted to a central blade, spins in one direction, while
the bottom, and the tower's exterior, spins in the other, with the
generator at the bottom
World Wide Wind
And so to the device at hand. World Wide
Wind has proposed an entirely new type of floating VAWT specifically
designed for offshore deployment and massive scalability. Indeed, it's
two VAWTs in one; the lower one is fixed to the outer casing of the
tower, and set to rotate one way, and the upper one is mounted to a
shaft running right up the middle of the tower, and it's set to rotate
the other way.
Under the surface, one turbine is fixed
to the rotor, the other to the "stator," doubling the relative speed
of rotation as compared to a static stator, and generating a whole
bunch of electricity we can burn our toast with. The company calls
this a contra-rotating vertical turbine, or CRVT.
Again, the heaviest parts and the ones
requiring most maintenance are at the bottom, below the buoyant
pontoon, right down near where the tethers and power cable attach. But
the whole thing isn't designed to sit perfectly upright; these
enormous towers will tilt with the wind. World Wide Wind says this,
and the blade designs, which sweep a conical area, helps to reduce the
turbulent wake downstream of each floating tower, allowing operators
to cram even more of these things into a given site. The ability to
tilt will also help these things resist sudden, violent wind gusts and
damaging vibrations.
![](images/images_08_31_2022/pic5.jpg)
The company
says this design leaves much less turbulence behind it, allowing a
much higher density of towers per given site -
World Wide Wind
You need serious scale
to get the best out of wind energy, and these guys aren't holding
anything back on that front. The
world's largest wind turbine as it stands is the mammoth MingYang
Smart Energy 16.0-242. Standing 242 m (794 ft) tall, it has a rated
capacity of 16 MW.
World Wide Wind plans to absolutely dwarf
that piddly windmill. This design, says the company, is far easier to
scale than any HAWT, and could grow up to a ridiculous 400 m (1,312
ft) in height, with a monster 40-megawatt capacity per unit. In an
interview with
Recharge,
company representatives appear to have suggested a projected Levelized
Cost of Energy (LCoE) of less than US$50 per megawatt – less than half
the LCoE the US Energy Information Administration projects for the
average offshore wind project going to market in 2027.
The company tells Recharge it's
working to accelerate development of the CRVT through rapid
prototyping. The targets are to have a 3-MW model up and running by
2026, and the big mama 40-MW machine as soon as 2029.
![](images/images_08_31_2022/pic6.jpg)
WWW claims its
bottom-heavy, tilting, contra-rotating coaxial turbines solve
offshore wind's scale limitations, and will grow to 400 m high, with
a 40 MW capacity
World Wide Wind
Will it work? It's hard to say. The startup
provides no supporting research, or evidence that it's tested
micro-scale prototypes. It's unclear why the company hasn't gone with
Darrieus-style turbine blades, which connect back to the central axis
at the top, and tend to be both structurally stronger and more
efficient. One wonders about longevity, since all VAWT blades are
subjected to strong forces from every angle as they spin – and about
the efficiency losses, lifespan and replacement procedures for the
gigantic bearings you'd need to support and spin a 400-meter-long
shaft inside a counter-rotating 400-meter-long tube, with the mass
tilted off-center most of the time. In seawater, of course, for
decades.
Not to mention, it's apparently getting
hard to find test locations for wind tech in the North Sea, because
there are too many other test projects "almost queueing up" in the
region,
according to Norway's Teknisk Ukeblad.
On the positive side,
there's not a tie to be seen amongst the leadership team, so clearly
they're feeling confident and relaxed about this whole thing. World
Wide Wind claims partnerships with Uppsala University, Sinted, North
Wind, Kjeller Vindteknik, Norwegian Energy Partners, and the Norwegian
Offshore Wind Cluster.
As with all clean energy moonshot
projects, we desperately want to believe. The expansion and
decarbonization of worldwide energy grids cannot possibly happen fast
enough, as climate change enters its terrible toddler phase and the
unthinkable consequences start becoming
impossible to ignore. Giant 40-megawatt coaxial towers way out at
sea, undercutting the LCoE of today's offshore wind, could make a huge
contribution in the existential battle of the coming century. But we
don't need renders, diagrams and promises, we need tangible results –
and we need them yesterday.
We've reached out to World Wide Wind, and
we hope to bring you a closer look at this technology as soon as
possible.
Source:
World Wide Wind via
Recharge
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