Not everyone is convinced that condition monitoring systems (CMS) are a panacea for the US wind industry. At somewhere around $20,000 per unit, a good vibration system can pick out exactly which bearing is failing and depict it, in real time, on a computer screen thousands of miles away. Considerably less expensive real-time oil-particulate systems can reveal increasing metal fragments that suggest potential problems.
But the key information - time until the turbine breaks down - is something CMS cannot predict, says Harm Toren (pictured), head of US operations services for Spanish-based Iberdrola, the world's largest wind farm operator. The company's US arm, building at a 1GW annual rate, has implemented a pilot CMS programme on around 100 of its 2,500-turbine North American fleet, but it has no plans to add more as it studies the technology.
"The unfortunate nature of it is that the industry is currently in a research and development mode," Toren says of CMS. "I can predict trending. I can see that things are happening. But I'm not quite certain whether they will occur today, tomorrow, ten days from now or a year from now. Or even at all."
Timing is paramount because scheduling repairs during calmer wind periods and coordinating crane call-outs around multiple jobs can save big money. But, since virtually every turbine sees at least one gearbox replacement during a 20-year life, Toren says that Iberdrola would rather replace the entire gearbox when trouble is brewing, committing to spend upwards of $500,000 instead of making an up-tower bearing replacement at $30,000.
"It would be similar to your car," Toren says. "If you didn't change oil, then you had several bearing problems and, rather than replace the engine, you just took the top off and replaced some of the bearings. But you didn't do the pistons, you didn't do the gears, you didn't do the transmission."
Toren says the philosophy is rooted in Iberdrola's penchant for long-term ownership and operation of the projects it builds - not maintenance to provide suitable balance-sheet value for eventual sale. And as almost any problem will lead to replacement, an up-tower oil sample sent to a lab for results, costing $30, will give enough information.
But Toren also believes there is potential value in CMS and that vibration and oil-particulate systems work especially well in concert. "It's important that we have the capabilities to monitor particles and vibration levels," Toren says. "Unfortunately, the cost to do that isn't currently commercially viable. You can imagine if I spent $20,000 times 2,500 units, how much I would spend."
One solution, Toren says, is for turbine makers to add factory-installed CMS. Manufacturers could differentiate themselves by integrating reliable and easy-to-use CMS directly into the Supervisory Control And Data Acquisition (Scada) systems that come standard with all modern turbines.
"Red light, yellow light, green light," Toren says. "If it's red, stop the turbine and fix it. If it's yellow, give me a counter to say when this component is going to break. If it's green, we're good to go."