Reaping the wind with the biggest turbines ever made

BBC

When engineer Lukasz Cejrowski finally saw the world’s largest wind turbine blades installed on a prototype tower in 2016, he stood in front of it and took a selfie. Obviously.

“It was amazing,” he says, recalling the moment with a laugh. “The feeling of happiness – ‘Yes, it works, it’s mounted.'”

Those blades, made by Danish firm LM Wind Power, were a record-breaking 88.4m (290ft) long – bigger than the wingspan of an Airbus A380, or nearly the length of two Olympic-sized swimming pools. The swept area of such a mammoth rotor blade would cover Rome’s Colosseum.

But things move quickly in the wind turbine industry.

In just a few years, those blades could be surpassed by the company’s next project – 107m-long blades.

LM Wind Power is owned by global engineering firm General Electric (GE), which announced in March that it hopes to develop a giant 12MW (megawatt) wind turbine by the year 2020.

A single turbine this size, standing 260m tall, could produce enough electricity to power 16,000 households.

The world’s current largest wind turbine is a third less powerful than that, generating 8MW. Various companies, including Siemens, are working on turbines around the 10MW mark.

When it comes to wind turbines, it seems, size matters.

This is because bigger turbines capture more wind energy and do so at greater altitudes, where wind production is more consistent.

But designing and manufacturing blades of this size is a significant feat of engineering.

Mr Cejrowski says that the firm could in theory use metal, but the blades would be extremely expensive and heavy. Instead, they use a mix of carbon and glass fibre.

First, they make a glass-fibre and polyester shell for each blade – in two halves. Then the spar cap is added. That’s a length of reinforcing material that runs down the inside of each of these halves.

For this, Mr Cejrowski’s team uses a glass-carbon composite fabric, infused with a special resin that hardens in place.

These ultra-large blades are extensively tested. Prototypes are bent, stretched, buffeted in wind tunnels and, during “fatigue tests”, flexed back and forth quickly millions of times to simulate a lifetime of use. They’re also tested against lightning strike.

The world’s biggest wind turbines are generally installed offshore rather than on land. That way, they avoid being gigantic eyesores in our midst and are able to harness the powerful winds out at sea.

 

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