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Wind blade monitor with an ear for trouble

Did you hear that? It’s the sound of another Australian technology business carving itself out a spot in the clean energy market. This time it’s an South Australian company which has developed a “stethoscope” for wind turbines, to pick up early signs of damage to blades that could only be getting worse.

With the help grant funding from the state government and $1.3 million in a seed funding round including venture capital fund Artesian, Ping Services’ “intelligent listening sensor” is now ready for commercial-level production.

It’s been a fast couple of years for acousticians and Ping founders Matthew Stead and Jon Cooper, who have been developing the product since February 2018. The first-generation device was portable and needed to be manually downloaded, whereas the latest iteration is “self-powering, self-communication and self-analysing”, Stead tells EcoGeneration.

The new device has been trialled at locations around Australia and a site in West Virginia in the United States, and Stead says project owners have been impressed by the correlation between known blade damage and what the Ping monitors have been picking up.

It’s not easy monitoring massive machinery that towers into the heavens. Drone inspections have become the “gold standard” for detecting blade damage, he says, although they require turbines to be stopped and can be as infrequent as an annual event. Visual inspections from the ground using binoculars and cameras are otherwise standard practice. The Ping, however, is listening for anomalies day and night – as the propellers keep turning around and around and around.

Matthew Stead has heard good things from owners of wind farms where his technology has been trialled. Photo Rosina Possingham.

That sounds funny

The technology sounds simple. Positioned using magnets on a wind tower about two metres above ground level, a Ping will listen to each blade as it passes and compare it to its two work buddies. “If there is any strange whistle sound or anomalies in one blade, we can compare it to the other two and extract that out,” Stead says. “In some ways our system is self-calibrating. It’s listening for the exceptions; for the unusual things.”

Most of the analysis is carried out within the device, with a summary transmitted to Ping’s cloud service every eight hours, where more analysis is applied. “That’s where we get real meaning from the sound we’re recording,” he says.

Most sound comes from the blade tip and becomes louder as the wind blows harder. The trick is to isolate that sound from ambient noise, such as wind through trees and ground cover. Mechanical noise from the turbine and gearbox is less of a concern as it’s much farther up in the air.

A Ping can also act like a police officer if a wind farm is required to operate within noise limits. At such sites, turbines will have to be slowed or output curtailed if volume levels are pushing close to pre-determined constraints. “We’re able to optimise making enough power and enough sound but not too much,” Stead says.

Find it and fix it

Wind turbines are impressively priced, and owners must look after their investment to satisfy forecasts for expected earnings. Leading-edge erosion on blades is a fairly common complaint, where rain, hail and airborne particles cause pitting near the blade tips. More violent damage – splits and holes – can be caused by direct lightning strikes. General wear and tear on these vast rotating wings can also see them develop cracks on the leading or trailing edges, but Stead says bird strikes have never emerged as a problem.

The company has estimated its device could see $500 million a year in savings to the global wind sector based on current O&M costs. Stead admits this is a “simplistic” measure going on average maintenance cost per tower per year of about $5,000. “The rule of thumb suggests there could be 25% savings on costs with proactive maintenance,” he says.

The company is working on another version that will live inside blades, to detect interior cracking, and a method for picking up when ice is forming on a blade. The units will be assembled in Australia using components sourced locally and from overseas. The technology also has applications in industry, he says, such as listening out for dodgy bearings on conveyor belts.

Australian conditions for mighty wind generation is about on par with Texas, another market Ping is watching, and Stead is confident the little listener will have global appeal. “If we get it to work here it will work around the world.”

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