How big could a wind turbine possibly be?
The iconic Dutch windmills after all were only about 40 metres high.
But we’ve come a long way since the 12th century and engineers are now
pushing the boundaries as to just how big these structures can get.
Wind turbines are now going up in Europe that are higher
than some of the continent's tallest skyscrapers.
But how are these enormous structures put together?
And is there a limit to how big we can make them?
Welcome to the age of the supertall wind turbine.
Right now there is a race to build the world’s tallest wind turbine.
In the last three years alone the tallest of these prototypes has skyrocketed.
These are far, far taller than the height of a typical wind
turbine which more or less stands at 80 metres.
This is the world’s tallest wind turbine … for the moment.
It was erected at the beginning of 2023 at a test facility in Denmark.
It is 280 metres tall and has an absolutely gigantic rotor diameter
of 236 metres – that’s 100 metres greater than that of the London Eye.
The blades themselves are 115 metres long, each one taller than Big Ben. They were assembled
at the nearby blade factory in Nakskov and carefully transported to the site.
Just one of these enormous wind turbines is capable of
producing 80 gigawatt hours of energy per year.
That’s enough to power around 20,000 European households and save more than
38,000 tonnes of carbon dioxide.
That’s the same as removing
25,000 passenger cars from the road every year. For just a single turbine.
For comparison, just a couple decades ago the UK was lauded for building an offshore
wind farm capable of producing less than three percent of what Denmark’s latest turbine can.
With numbers like that it’s no wonder then that these
giant structures are becoming increasingly common.
Not to be outdone, over in Germany they’re testing the limits of just
how tall a wind turbine can be with this giant 300-metre high testing mast.
SPRIND, the company behind the test mast,
has already said that these high-altitude turbines could produce twice as much
electricity as smaller ones and even hold multiple turbines at different heights.
Something the Norwegian “Wind Catching Systems” is already working on.
They have proposed a 300-metre by 300-metre offshore wind farm. A gigantic square taller
than the Eiffel Tower that would sit out at sea and produce as much
energy as five of the strongest floating turbines in existence.
So how on Earth did we get here? And why is there
now a race to build the world’s tallest supersized wind turbine?
Right now there is urgency across the world to
switch to greener energy sources to reduce carbon emissions and fight climate change.
For a long time wind power was not seen as a viable alternative
to produce power on the scale we need. But that’s changing.
In just the last year alone power generation from wind has increased globally by 17 percent.
And in the last decade wind power has increased fivefold.
This is thanks to these larger turbines that are able to produce more energy for less cost.
But this isn’t enough,
and the race to build the world’s tallest wind turbines is all about maximising.
There are two ways to get more energy out of a wind turbine, and therefore more money.
The first is to have a bigger rotor and blades with a larger diameter, capturing more of the
wind. The second is to have the wind turbine higher up where the wind blows more steadily.
Combining these is the most ideal.
Not only will these mega wind turbines produce an enormous amount of energy,
they will do so for less.
250–metre high off shore wind turbines in the UK are already producing energy below
£50 per megawatt-hour, eliminating the need for government subsidies
and making this type of clean energy competitive with other forms of power.
Despite having turbine blades the size of Big Ben, they could theoretically keep getting bigger.
The bigger the blade is the more energy it
extracts from the wind. But then there are other issues.
In order to avoid erosion the very tips of the blades cannot spin faster than 90
metres per second. This means the bigger the blade is the slower it has to spin.
Slowing the rotor down to accommodate these larger blades increases the forces put upon
the entire turbine. To combat these forces the weight of the turbine has to increase,
but this also increases the cost of the whole structure.
Eventually there reaches a point where the cost of
the larger turbine is more than the profit that would be made from it.
This is the ceiling we will reach with these structures. At least economically.
Engineering-wise, the longer a blade gets the more wobbly it is as well,
making it harder to control in high winds. But experts are optimistic
these kinds of design challenges could eventually be overcome.
Once the engineering is sorted, the next important factor in wind capture is the location.
And right about here just so happens to be the
perfect place for consistent strong winds. The middle of the ocean.
You might look at these structures and wonder how exactly they’re
standing in the open water? How deep do they go under the waves?
Well they don’t.
They float.
In waters deeper than 60 metres these floating
turbines are anchored to the seabed with multiple moorings.
Ironically, these green energy producers modelled their floating turbines off floating oil platforms
that use similar engineering techniques to stay afloat in the middle of the sea.
Sensors and computers then regulate the turbine blades
in relation to the wind gusts to ensure they don’t tip over.
There are different ways to accomplish this. The Spar model is weighted at the
bottom. Buoyancy then comes from the geometry of the cylinder,
while stability is provided by this weight at the lowest point.
Other models have the turbine on floating platforms or barges, like these.
Overcoming the logistics of shipping the gigantic parts of the turbine to
their offshore location will be these megastructures’ next major challenge.
The blades must be shipped in one piece, which requires enormous ports,
vessels and cranes capable of assembling these structures in the middle of the ocean.
The UK is already brushing up against these limitations. The country likely
won’t meet its ambitious 2030 target to triple its number of wind turbines.
That’s not because of the technology or lack of offshore sites but because the
turbines can’t be manufactured and assembled fast enough.
Gigantic wind turbines like these are going
to become increasingly common in the fight against climate change.
Making them as efficient and able to produce as much energy as possible is paramount. As a
result, we will probably be seeing even taller skyscraper-sized wind turbines in the near future.
You can learn more about this and the other topics on our channel over on The
World’s Best Construction Podcast – available right now wherever you get your podcasts.
And as always, if you want to learn more about where construction is headed,
make sure you’re subscribed to Tomorrow’s Build.