Goldierocks one thing that is not often mentioned is that the output from any one wind turbine is anything but constant. The wind is almost never steady, gusting and dying off, that is why we need base load from gas or coal turbines or from a biiiig battery to balance the fluctuations. I’m guessing that the emi varies with this fluctuation, making it even harder to tune out.
In low winds yes they do build up to max. output & appear they would fluctuate more:
Source: Freely available from a number of internet sources
From above typically wind speeds between 3.5 to 14m/sec sees power output remain in a curve (assume fluctuating with wind drop/increase) until they reach 14m/sec where the rated output maxes out until reaching a cut out speed of ~25m/sec (some turbines have different cut in/out speeds - above is a typical example only).
Note: Cut in speed is the speed the turbines start outputting power i.e. the blades may start up slightly prior to power output cut in but until the turbines reach their set cut in speed (seems to be between 3-4m/sec for the newer turbines) they aren't actually giving any power output.
So to me:
- calm conditions under 3-4m/sec should pose no issue;
- lower winds 3.5-14m/sec could possibly cause fluctuations;
- higher winds 14-25m/sec result in a constant max. rated output;
- Both the lower & higher winds could have the potential to cause issues for nearby detector users for differing reasons IMO.
Remains to be 100% determined how much effect or what might cause the most, if any, issues?
We can look at various studies on EMF/EMI all we like but the only feedback that will matter in these areas is that of detectorists who have experienced differing conditions near to these installations. The studies mean little as none that I've found have even considered metal detectors let alone done any testing -
the reality is it's not a big enough concern.
Interesting wind scale:
Source:
www.EngineeringToolBox.com
How often do we get wind velocity of 14-25m/sec at these locations for the max. rated output?
I'd assume they are running in the 3.5-14m/sec bracket more often than not?
Like with other sources of EMI (radio/mobile towers, wind, static discharge), that we are told are rare to cause issues & more likely to be spherics, my own personal experience is that these issues are rare when looked at over the broader picture but when drilling down to specific areas they may not be so "rare" but rather something that is common for people in that specific area to need to contend with. I'd assume wind farm installations will be no different & as with other areas have good/bad days + other influences contributing to increase any issue (like spherics or other infrastructure combining) & no doubt with some thought + perseverance solutions or practical means to reduce any issues i.e. DD coils, cancel modes, more frequent noise cancel/tuning, using more EMI resistant detectors etc. will be shared.
