Can a wind turbine handle hurricane speed winds?

Wind farm developers have long been intimidated by the world’s greatest storms, which roil the high seas or flatten buildings on land. But that is changing.

Operators are increasingly deploying turbines designed to withstand tropical cyclones. One recent example is a “typhoon-resistant” floating wind turbine that will soon help power an offshore oil platform in China.

According to manufacturer MingYang Smart Energy, this 7.25 megawatt (MW) turbine can withstand wind speeds of up to 134 miles per hour for 10 minutes. It was installed at a facility 136 km off the coast of the island province of Hainan.

MingYang didn’t respond to a BBC request for comment, but her turbine isn’t the first to withstand such an onslaught. In 2021, the US company GE received Typhoon certification for its mammoth Halide-X turbine. It is fixed, non-floating, and has a capacity of up to 13 MW.

The rapid growth of the wind energy industry is pushing turbines to their limits, and some are wondering if the pace of adoption is reasonable.

Components like turbine blades, while remarkably strong, are not indestructible. And the forces of nature, particularly at sea, are notoriously unpredictable, meaning there’s pressure to prove wind turbines are truly hurricane-capable.

Tropical cyclones — often called typhoons or hurricanes depending on location — are a known threat in certain parts of the world, including the Gulf of Mexico and much of Southeast Asia.

Such storms can produce wind speeds well in excess of 160 km/h. Hurricane Patricia in the eastern Pacific generated the strongest sustained one-minute winds on record in 2015 at 345 km/h.

Despite the meteorological challenges in such regions, the expansion of wind energy is expected there in the coming years and decades.

Today’s turbines can withstand quite a few strong storms. Those positioned off the UK’s north-east coast in the North Sea are generally rated for winds of up to 50mph, notes Durham University’s Simon Hogg. Prof. Hogg holds the Ørsted Chair at the University, which is funded by the energy company Ørsted.

Leon Mishnaevsky from the Technical University of Denmark points out that wind turbine blades are generally quite reliable. Today, they’re made from strong but lightweight carbon fiber composites, and automated manufacturing processes help ensure even fiber placement, which is important for the blades’ robustness, he notes.

Wind turbine manufacturers also carry out a series of stress tests on rotor blades to ensure they meet the requirements.

This may involve attaching large “exciters” to the wings that bounce up and down, simulating the repeated stresses that winds put on the structure. Huge leaves are also sometimes bent to the point of fracture, says Prof. Hogg, which helps confirm the maximum load they can carry.

But the fallibility of turbines, especially the largest ones, is becoming increasingly apparent over time. Insurer GCube notes in a recent report that offshore wind losses have risen from £1m in 2012 to more than £7m in 2021.

Also, machines with capacity greater than 8MW can experience component failures within just two years of installation, the company says, more than twice as fast as 4-8MW units.

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Some of the most dangerous forces that disrupt turbine blades are torsional or twisting loads, says Find Mølholt Jensen, managing director of Bladena, a company that specializes in diagnosing and repairing large turbine blades, around 60m or more in length.

Repeated twisting of the blades can lead to hard-to-recognize fractures, he says: “The damage cannot be seen from the outside.”

The longer the blade, the greater the risk, comments a Bladena spokesman.

Current tests and industry standards are insufficient to prove that the largest turbine blades can withstand these loads, argues Dr. jensen

However, new designs could help. In Japan, Challenergy has been working on a turbine with tall, vertical blades rotating around a central tower.

While currently much smaller and less powerful than the largest traditional three-bladed turbines in operation today, Challenergy’s device is said to be able to cope with very strong winds.

When a powerful typhoon called Hin Nam No hit the Philippines and Japan last August, it rolled over two of the company’s turbines. One of the devices in Ishigaki City in Okinawa recorded wind speeds of around 100 km/h. According to Challenergy, the turbine continued to run without any problems.

In the USA, a research team used nature as a guide when designing an alternative hurricane-resistant turbine.

“We were inspired by palm trees,” explains Lucy Pao of the University of Colorado Boulder. “In strong winds they kind of swim with the current, they bend with the wind.”

She and her colleagues designed a prototype two-bladed wind turbine with flexible blades. Also, the rotor is oriented upwind rather than upwind as is common in traditional configurations, which helps it absorb the effects of strong storms.

During testing at an onshore Colorado site, blade tips were observed to deflect by up to 600mm, more than half a meter. “None of them broke,” says Prof. Pao.

Wind speeds in the area can reach 100 mph in winter, she adds.

However, the wind energy industry has almost universally adopted the downwind three-blade design, making it difficult to sell a new concept, explains Prof. Pao. Her research in this area is currently on hold pending further funding.

She shares the concerns of other observers who wonder if wind turbines are really ready for some of the strongest winds nature can throw at them.

“The new materials are stronger, they’re pretty amazing, but I don’t know if they’ve been tested as thoroughly as they might be,” she says.

Then there’s the tricky economics of placing turbines in locations where winds are particularly variable. James Martin is Chief Executive at Gulf Wind Technology, a company studying turbine deployment in the Gulf of Mexico.

Low wind speeds are common in this area most of the year – with the occasional hurricane blowing through the area.

“If you design this turbine to be strong enough to withstand the peak wind event, then you’re incurring a lot of extra cost for those times when you have light winds,” notes Mr. Martin. He declines to share details of the turbines or technologies his company is considering.

In the coming years, however, it can be expected that more and more turbines will advance into hurricane-affected regions.

“We need [turbines] there as much as we need them in any other area of ​​the world,” argues Prof. Hogg. “I don’t think we should shy away from it.”