Berrybank lightning strike could be the new normal for wind farms, says expert

The working theory is that a massive lightning strike is behind the dramatic collapse of a wind turbine at the Berrybank wind farm in Victoria last week, and that’s an issue that one expert is seeing more and more often.

The collapse is still under investigation by wind farm owner Global Power Generation, turbine supplier Vestas, and WorkSafe Victoria, but a direct lightning strike during the storms on February 3 is being fingered as the likely culprit, and not strong winds.

Lightning is a fact of life for wind farm owners, and one that is increasingly frequent as towers get taller and materials needed to make them change, says turbine blade expert Rosie Barnes. 

“Each wind turbine blade gets struck one to 20 times each year depending on the location, in Australia,” she told Renew Economy this week.

“The vast majority of the time, getting struck by lightning is no big deal for a wind turbine. It happens all the time. But not every lightning strike is the same so every now and then something slips through the cracks and there is damage.

” It’s like that for any engineered thing. You never get to 100% reliability. Sometimes a coal power plant shuts itself down in hot weather even though it’s been designed with hot weather in mind.

“It’s not at a rate that’s worse than any other kind of infrastructure but it does make a good photograph.” 

In 2022, loss adjusting firm Global Risk Solutions analysed its database of onshore wind farm operator claims and found lightning damage accounted for 60 per cent of operational blade losses and nearly 20 per cent of operational losses overall.

Australia’s earliest commercial wind farms clustered around Victoria’s south-east, where according to Bureau of Meteorology (BOM) data there are fewer lightning strikes. 

Fast forward to the heady years of wind development from the 2010s and developers began pushing northwards through New South Wales (NSW) and into Queensland, where BOM data shows a much higher rate of lightning flashes each year. 

“It sounds so obvious that if you have 20 times more strikes, your problem will be 20 times as big, but it doesn’t feel like it for the people working on those sites,” Barnes says

Helping wind farm owners deal with the aftermath of lightning strikes is a big part of her work now, particularly those venturing into heavy lightning areas who didn’t factor in the BOM data.

Lightning strikes highest point

It’s not just that 200-metre-plus high tip heights and blades measuring 80 metres or more long are natural conductors in lightning-prone areas. 

The materials required to build structures that are strong yet light enough for low winds to move are also a part of the reason why wind turbines are becoming more likely to be hit by lightning. 

“Longer blades, taller wind turbines, have definitely been demonstrated to cause lightning strikes because they are the tallest things in the area,” Barnes says. 

Furthermore, carbon fibre – which is a great electrical conductor – is now a common strengthening agent to stiffen very long blades.

They’re so long that the easiest route downwards may not be where engineers have put the lightning attractive cable — or a static charge can “flash over” to another point — heating up part of the blade and causing it to melt and the fibreglass layers to sheer apart, Barnes says.

In effect, the blade explodes in mid air or catches fire, like a Catherine wheel.

“Lightning protection systems have had to change to suit the new types of blades,” she says. 

“Blades are too long to have a single receptor, because lightning can attach further down the blade.”

In the 1990s, particularly in Japan and Texas, wind turbines were installed without lightning protection systems. 

Anecdotally, Barnes says she has heard engineers believed the fibre-glass blades, which aren’t conductive, would protect the structure from lightning strikes and a protective system would just undermine a natural defence.

Discovering that fibre glass wasn’t a cure-all was an “unpleasant surprise”, leading to a system of adding a hunk of metal to the tip of a blade which connected to the tower by a steel, aluminum or copper wire down its length, Barnes says.   

 Still in testing mode

The longer, carbon fibre blades created a need for a new system, one which a decade in still has “teething problems”.

These include a multi-receptor design where there are multiple locations on the blade that will attract lightning, but they’re complicated and less well tested. 

The old adage that lightning doesn’t strike twice shows just how unlikely it is that a single prototype tower will be hit enough times in a year of testing to prove how a system will hold up. 

Barnes says given the nature of lightning it’s only when thousands of turbines have been erected that the maker will really find out whether their protective system works, or is a dud. 

“It can take quite a few years to get the feedback that you need to change the design,” she says. 

Retrofit options today include a strip of tiny copper coins that can be glued onto a blade to keep lightning charge on the surface.