By Bob Moser, US correspondent

There aren't many products out there that provide a historical data-trending solution that can monitor turbines in real time. However, new forms of data collection are now available that enable operators to maximise gearbox longevity and optimise wind farm output. 

The established monitoring systems today are vibration/acoustic controlled for the turbine, and optical strain gauged for the blades. The noise frequencies of pristine components are recorded, so that if the noise frequency changes, an alert is signaled.

While this provides indication that a downstream component has degraded, it doesn't give an operator advance notice to prevent the deterioration from occurring. That is where the new technologies differ.

After two years of rigorous tests, analysts at engineering firm M4 Wind Services identified a way to preempt gearbox problems.

“We found a turbine's clearest and earliest health indications came from the bending and azimuth measuring devices attached to its main rotor shaft. All other measurements indicated that a problem already occurred, meaning the news came too late,” explains Robert Schmidt, sales director of M4 Wind Services, in a recent article for Wind Systems magazine.

Measuring the bending moments and torsion loads of the shaft allowed for operational adjustments, and general maintenance that would relieve this type of stress on a turbine. The result? Equipment problems avoided, unscheduled downtime minimized and power generation increased.

M4 describes its new Rotor Redline monitoring technology as a ‘vertically integrated data acquisition, transmission, reception, conversion, collection and analysis system that evaluates main shaft loads to predict equipment wear and failure, while advising on inefficient wind-to-rotor alignment’.

“It's about the cost avoidance. You don't want the cost and incident, you don't want that surprise of a major gearbox failure that will shut down your turbine,” Schmidt told WindEnergyUpdate.

General Electric also recently released ADAPT.wind 1.1, a similar software and hardware package that is targeted at GE 1.5 MW generators, as well as other wind turbine types, and is an application designed specifically for turbine monitoring. ADAPT.wind software makes gearbox longevity a primary objective.

Planetary/helical gearbox failure is a top concern for operators, and as much as 25% to 30% of wind farm operating and maintenance costs are tied to gearboxes alone, GE says. The ADAPT.wind system allows operators to coordinate efficient maintenance outages, consolidating multiple turbine visits for one scheduled crane, saving hundreds of thousands of dollars for the owner.

Monitoring drives efficiency

The less often mentioned - but equally important benefit, in Schmidt's view - is the operational improvement tied to performance monitoring. If owner/operators know that in peak periods they're generating more power than the grid can manage, they're likely still shutting down turbines based on guesswork alone.

“If you knew that this turbine had higher loads in a certain weather condition than that turbine, you will know which one to shut down,” Schmidt said. “Why damage that turbine if I don't have to?”

Operators put a lot of effort into orienting a tower on site to optimize power production. But winds are inconsistent, and calculations based on averages, hence directional control based solely on anemometer readings have a built in inefficiency of 3-10%. A turbine thought to be operating at 90-98% efficiency may actually be misaligned, and losing revenue. New systems like Rotor Redline, however, fine-tune a turbine to avoid this.

For example, data analysis may find the shaft is often bending in one direction, and the root cause is yaw misalignment. The operator is alerted to adjust the turbine X degrees in the Y/Z direction to reduce loads and optimize power production. A side benefit is that the turbine is relieved of negative stress from the bending.

Performance gains can pay off quickly. Every percentage of uptime increase on a turbine can generate new power that covers the monitoring system's cost for a year. Using the Rotor Redline solutions as a basis, that is US$10,000 - US$15,000 savings per turbine, per percentage gained. And every 1% boost to power output from every corrected degree of misalignment can result in more than US$30,000 per turbine in added annual revenue.

Removing the guesswork

Along with clear benefits of fine-tuning rotor-to-wind alignment and catching maintenance needs well in advance, another major benefit of Rotor Redline is real-time life expectancy that can be determined for a turbine's major components.

M4 engineers examine the condition of all major components when Rotor Redline is installed, and establish a baseline for the remaining operating life of each part. Operators can know well in advance when major components will fail, and can plan for it. In this way, operators can avoid days of idle turbines while a replacement part is on backorder, or blowing money on replacement stock that won't be needed for a long time.

M4 Wind Services began installing Rotor Redline in February this year, at a cost of US$10,000 per turbine. “There's a lot of debate on what's the value of that cost avoidance, and different people quantify it differently. Most people have the assumption that you'll replace a gearbox after 15 years,” Schmidt said.  

While companies like M4 aren't guaranteeing how much longer gearboxes will last under their watch, the benefits of stress detection and load maintenance would point towards increased longevity for gearboxes that have been built to last 20 years, but which in fact, struggle to go 10 years under today's stresses.  

To comment on this article, please write to:

Bob Moser: bobmoser333@gmail.com 

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Rikki Stancich: rstancich@gmail.com