16 August 2021
The average lightning bolt is three miles long and no thicker than your thumb. It’s five thousand times hotter than the sun and can release as much as a gigajoule of energy in one go. When lightning strikes an exposed beach it fuses the grains of sand into a rather beautiful tube known as a fulgurite. But when it strikes a poorly maintained wind turbine, it can burn the whole thing to the ground and incur damages that run into many millions. And yet the maintenance contracts for many wind farms do not include adequate maintenance of lightning protection systems – leaving them exposed to a critical but often overlooked risk.
The wind power risk engineer
Due to their exposed and weather-beaten locations, wind farms face a unique and complex set of risks, says Murray Banks, a Risk Engineering Consultant at RSA who specialises in renewable energy. He joined RSA as a graduate, and specialised early on. “I got an email from my manager one day, asking me how I felt about working at heights,” says Banks. Intrigued, he agreed to do all the training needed to work at heights of up to 80 metres in all weathers – and now relishes every site survey he goes on, preferably in the wilder corners of Scotland.
Murray now helps businesses prevent the damages and loss at wind farms, and other renewables sites. Prevention is absolutely crucial for wind farms, he says, because once something goes wrong it’s extremely difficult to put it right. “If a turbine catches fire, then there’s very little the emergency services can do to put it out,” says Murray. “So they let it burn, and you get a total loss on that turbine.”
Where lightning does actually strike twice
Wind turbines are hot targets for lightning strikes, and not just because they’re often the tallest objects in the landscape. Evidence suggests that the combination of moving parts and their exposed location makes them particularly vulnerable.
All turbines come with in-built lightning protection. Each blade is fitted with a conducting material – a copper cable, for instance – that runs the length of the blade to the central nacelle, where it stays connected to an earth wire through a set of components that’s a bit like a rotating brush. Those components wear out over time, and if you’re not regularly checking them as part of a maintenance regime, then it only takes one hit of lightning to fry the electrics, damage the blades or spark a fire.
"If a turbine catches fire, there is very little the fire services can do to put it out"Murray Banks - Risk Engineering Consultant
Significant risks for wind farms: old age and breakdowns
Lightning is not the only risk to wind farms. Turbines have a 20-year lifespan – after which their parts begin to fail, and as the technology develops it’s often hard to find spares for older turbines. The gearbox can wear out, just like a car, except it costs a few hundred thousand pounds to replace. The electrical equipment can easily get damaged in all the wind and rain of the Scottish Highlands. And even in their remote settings, wind turbines are at risk of theft and vandalism – especially of those lightning-conducting copper cables.
The cost of a breakdown in a wind turbine can quickly mount up. “It’s not just about the cost of repairs,” says Murray, “but the whole business interruption. Their remote locations makes everything harder. It can be a while before a service technician can make it out to the site. If large components need to be replaced, such as gearboxes, then you need a crane. There can be long lead times on booking the type of crane you need to work at that height – and all of these details add up to significant loss of energy production.”
Risk prevention for wind farms: early detection is key
So what can businesses do to prevent losses, breakdowns and downtime? “Most of the risks can be mitigated with regular inspection and maintenance,” says Murray.
The best risk prevention strategy for any turbine is to spot the signs early. “All turbines should have a Condition Monitoring System fitted to the drive train to monitor for increased vibration,” he says. “It’s good at detecting faults very early so they can be repaired before significant damage occurs. If these systems are not fitted, then the fault could go unnoticed for an extended period and lead to a greater loss.”
Wind farm site surveys: the 360-degree view
On a site survey, Murray will work with the site manager to advise on the best practices and help spot any gaps. “I’ll check the site’s maintenance routines and equipment installation, and make sure there are adequate systems in place to shut down the turbine in event of a fault or failure. Then we look for signs of wear inside the nacelle of the turbine.” That involves climbing countless ladders to the top of the turbine, though the newer ones thankfully have a lift. And once he’s done all that, there’s one final part of the survey: “it’s always nice to lift the hatch and have a look at the view.”