The wind turbine market is dominated by General Electric (GE), Goldwind, Vestas and Envision, which accounts for more than half of all the wind machines sold around the world. As a result, these companies are always one-upping each other with new technology and innovation. And with that, developing the world’s largest wind turbines.

Over the past two decades, wind turbines keep getting bigger and bigger. For wind turbines, bigger is definitely better.

The bigger the radius of the rotor blades (or diameter of the “rotor disc”), the more wind the blades can use to turn into torque that drives the electrical generators in the hub. More torque means more power. Increasing the diameter means that not only more power can be extracted, but it can be done so more efficiently.

Larger and longer turbine blades mean greater aerodynamic efficiency. Creating more power in one turbine means less energy is lost as it is moved into the transmission system, and from there into the electrical generator. The economies of scale provide an overwhelming push for wind energy companies to develop larger rotor blades.

Wind turbines are also growing taller because of the way wind travels around the world. Because air is viscous (like very thin honey) and “sticks” to the ground, the wind velocity at higher altitudes can be many times higher than at ground level.

Hence it is advantageous to put the turbine high in the sky where there is more energy to extract. Hilly terrain (like a mountain ridge) may also distort the wind, requiring engineers to design the wind turbines to be even taller to catch the wind. Wind turbines used offshore are generally larger and taller because of the higher levels of wind energy available at sea.

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Typically, onshore turbines (most common in Australia) have blades between 40m and 90m long. Tower heights are usually in the range of 150m. Offshore turbines (those situated at sea and common in Europe) are much larger.

Currently, the world’s biggest wind turbine is General Electric’s all-new Haliade-X. Rising some 260 metres above sea level, each turbine is capable of generating at least 12MW of energy with an impressive, industry-leading 63% capacity factor above industry standard.

When fully operational, the Haliade-X will be capable of producing 67 GW Hours per year. That’s 45% more than the most powerful and efficient windmills operating in the market right now. The capacity factor is a metric that compares how much energy is generated within a certain timeframe compared to the maximum that could potentially have been generated during that same period. It’s estimated that a single Haliade-X turbine in an offshore setting can generate enough power to supply 16 000 European households.

Another benefit of wind power is emission reduction as they don’t burn fossil fuels. The clean energy generated is the equivalent of taking 9 000 cars a year off the road or 42 000MT of carbon emissions from the atmosphere – and that’s just for one turbine.

These turbines are big. As tall as an 85 story building and each of the Haliade’s windmill blades is 107m long. To put that into perspective, the wingspan of an Airbus A380 is only 80m. This makes sense from an engineering point of view. For one thing, it is no small undertaking to install these enormous turbines in the seabed. So the fewer you need to put there, the better and cheaper it is for everyone. The blades of the Haliade-X’s tips whirr along at about 80m/s cover a so-called ‘swept area’ of 28 000m2. The swept area is the area of the circle created by the blades as they sweep through the air. Because of the way the area of a circle is worked out, π x r2, doubling the length of the blades can multiply this all-important swept zone by a factor of 4.

Presently standing proud at Maasvlakte at the Dutch port of Rotterdam, the prototype proof of concept Haliade-X is an inspiring glimpse into the future. Perhaps its most striking early application will be on the vast new $10 billion Dogger Bank Wind Farm being developed to serve the UK market. A 160km off the Yorkshire coast out in the North Sea, Dogger Bank will roll out in three stages, A, B, and C. Phases A and B will collectively generate 2400 MWS from a remarkable 190 Haliade X 13MW offshore turbines, scheduled to deliver their first power to the grid as early as 2023. Once fully operational in around 2026, Dogger Bank will supply about 6 million UK homes – the equivalent of 5% of the entire country’s energy consumption.

In a strange twist of fate, the final confirmation order of the 190 Haliade-X turbines landed on GE’s desk the same day GE announced it would no longer be supplying power equipment to new coal-fired power plants. Renewable green energy is the way of the future. Offshore wind projects around the world are now lining up to order GE’s groundbreaking behemoth. Energy giant Orsted ordered several for its projects off of the East Coast of the United States. Swedish utility firm Vattenfall also announced it will deploy the 12MW Haliade-X turbine for use on its Baltic and North Sea farms. In China – where wind energy has an even bigger market than in the UK – a dedicated GE factory is being built purely to serve that key Asia Pacific turbine market.

Getting these turbines through development was no easy task for GE, which sunk a reported $400 million investment into the scheme. The essential safety certification which proves they’re worthy of real-world deployment was only issued in November 2020 following rigorous testing of the 12MW Rotterdam prototype with separate blades transported to the UK’s Offshore Renewable Energy in Blyth, Northumberland and the Massachusetts Wind Technology Testing Centre in Boston.

As you’d expect with such record-setting blades, building and transporting them is a formidable operation in itself. With specially built facilities custom erected to do the job in Cherbourg, France. It’s the first wind turbine ever to surpass 100m in length, 4m around at the root made largely of fibreglass and cleverly engineered with a deliberate bend to prevent the blade from flexing and striking the tower on especially windy days.

The pandemic presented its own challenges to the process. The chief architects of the project were forbidden to go to Blyth for the final static tests. “I was able to guide the test team and monitor the tests via a live stream,” says Cornelis van Beverin, lead engineer. “Streaming it across three monitors made my office desk feel like a kind of space launch environment. We weren’t launching a rocket, but observing the blade pass extreme loads was just as exciting.”

In conjunction with these massive blades, other innovations are also being tried for the first time on Haliade-X. Many of the onboard ITS diagnostic systems now work remotely. This is to avoid costly and dangerous seaborne maintenance missions, which can be especially treacherous on the North Sea.

The engineering team also developed a brand new compact type of switchgear for the project. A switchgear is similar to the fusebox in your house, just on a much grander scale. The switchgear helps energy flow seamlessly from the turbine to the power grid, but also holds that flow should any calamity occur –  like a lightning strike. At conventional offshore wind projects, these crucial switchgears occupy separate buildings connected to the turbines via cables. However, at sea, that’s not really an option. So engineers at GE set themselves the challenge of developing a switchgear powerful enough to function, but small enough to fit into the tower. The result is the so-called F35, which at 2,4m high and 3,7m long, is an impressive 30% smaller than the previous 66KV switchgears. One solution mooted to use a lower voltage switchgear, something in the 33KV range, but that would mitigate the benefits of such a large turbine and mean that less power would make it over to the mainline grid.

To be sure, GE isn’t the only company marketing colossal wind turbines right now. Danish manufacturer Vestas has a giant 15MW beast ready for manufacturing and trials. The company claims that on a 900MV wind farm, their model would boost productivity by 5% and require 34 fewer turbines. So far, alas, none have been constructed. Siemens also has a 14MW, the Gamesa, which they claim can produce up to 15MW and even further. A prototype will be constructed in the spring of 2021, but orders may flow in even before that.

As one analyst memorably put it, “Clean energy investors are quite happy to invest in so-called ‘green bananas’ – projects that aren’t quite ready yet – if it means they can get an edge on the competition.”

The largest wind turbines in South Africa is a turbine Enel Green Power, an energy management and development company, has awarded to one of the world largest turbine installation and manufacturer companies, Vestas Turbines, an order of V136-4.2 MW turbines for two separate projects in the Cape. The Karusa and Soetwater wind farms – the two wind farms that will make use of these turbines – is still under construction, and is expected to go live at the end of 2021. These turbines have a 150m rotor diameter and a 123m hub height. Not even close to the size of a Haliade-X, but nonetheless capable of generating 585GWh annually per 145MW farm from 40 turbines.

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