Small inexpensive microphones are embedded into the wind turbine tower, blade spar, gearbox, generator, and various other places. Engineers and technicians can download short audio samples (30 seconds?) via the SCADA system in order to listen for abnormalities. The turbine controller occasionally takes samples of the various audio signals, and performs a spectral analysis on the data. The resulting spectra may be compared against several baseline spectra. Possibilities for baseline spectra include:
- An average of many spectra taken from healthy turbines,
- An average of many spectra taken from turbines having approximately the same total lifetime number of operating hours as this turbine,
- the spectra recorded and stored during this turbine’s first day of operation,
- the spectra recorded and stored after this turbine has been “broken in” (after 30 days of operation?),
- the spectra of this turbine that was recorded and stored yesterday.
If the controller determines that the current spectrum is significantly different from the baseline spectra, it sends an email to the service department warning of a possible problem.
Microphones may also record aerodynamic noise of the blades. Small, inexpensive cameras (like “web cams”) provide visual feedback on the condition of the surface of turbine blades. These cameras are mounted at the blade root, and look longitudinally down the blade. In addition to damage, accumulation of smashed bugs and other foreign matter may be observed.
I got these ideas from troubleshooting turbines in the field. It always amazed me at how much you could learn about a wind turbine simply by listening to it. Usually I’d just walk around the wind park listening, but sometimes I’d put my head against the tower in order to hear the highly amplified intimate details of the turbine’s inner life. I don’t know why I was surprised by how revealing this audio information was… after all, doctor’s diagnose many illnesses with a stethoscope, so why not turbines? As a matter of fact, this idea might be applied to a wide variety of machinery, from bulldozers to airplanes.
For some strange reason, engineering has long suffered under a trend of making everything “idiot-proof”. You don’t troubleshoot an electronic control system anymore, you read an error code off of a display that tells you which circuit board isn’t working right. Then you replace the bad board with a good one, and send the bad one back to headquarters. This is simply a waste of resources. Sure, if you can speed up troubleshooting in the field, that’s a good thing. But most technicians who do this kind of work have skills that are not being leveraged (and certainly not being developed) by the “idiot-proof” ideology. Some of the technicians I’ve worked with in the wind industry were quite talented. Why waste a resource like that? A better approach is to find the right balance, where on the one hand you wouldn’t be soldering transistors onto a circuit board at the wind park, but you also wouldn’t pay good money for an over-engineered solution when field technicians are perfectly capable of performing a certain amount of on-the-spot troubleshooting. The irony of the idiot-proof ideology is that people who have all of the challenge siphoned out of their jobs eventually lose even the skills they started with.
The problem with idiot-proof technology is that it creates idiots.
A person can acquire an amazing amount of knowledge through troubleshooting, and thus becomes more valuable to the company every day simply by showing up for work. And the feedback and input of an experienced technician like this can greatly improve the design of the next generation wind machine (assuming it is in some way derived from the current generation machine).
Think for a moment of how much you know about your own body on the basis of sound and feeling. For example, when I go to the gym and get on the stairmaster, I know that my right knee will always “tick” when it passes through a certain angle. It always does this, and it’s always at the same angle. Is this normal? No way! It certainly indicates some kind of a problem, even if it’s only an insignificant one. But this example illustrates the need to record audio that is outside of the audibal spectrum, especially the sub-audio. Sub-audio is important because it includes what you might call “vibration”. You can’t hear vibration, but it is obviously very important. I would classify the tick in my right knee as vibration – it is something I feel, not something I can hear.