Hi,
Could you confirm which option (0-4 OutputOpt) in the Windvector function is most appropriate for assessing wind power for turbines?
Should a unit speed variable or the nearest measured wind speed be used with the wind direction measurement with this setting, or does it not matter?
I've read the manual several times, but am still unsure.
Thanks,
A
Hello artyb,
Options 3 and 4 were created specifically for wind power applications. They treat all wind direction readings as if the wind speed were a unit vector. The chosen input for wind speed is ignored. Option 3 gives only the average unit vector wind direction over the interval where option 4 will include the standard deviation over the interval as well. Some wind power evaluation software packages look for instances when the standard deviation of the wind direction is 0, but there is a wind speed, to detect the onset of icing conditions.
Options 0 - 3 do not include wind direction in calculations of average and standard deviation if the associated wind speed is 0.
Hi ZooKeeper,
Thank you. We've been using option 4, sometimes with a variable declared to act as the magnitude of the wind speed unit vector, sometimes with the nearest anemometer reading. I understood from the docs that the speed was ignored with option 4, as you state. Good to have these confirmed.
Could you clarify what options 0-3 output then if the associated wind speed is 0? The associated wind speed would have to be 0 for the whole data table period in order for this amended output to be detectable by analysis software though? If an offset is used and not suppressed in zero wind speed then presumably this variation of the calculaiton wouldn't function? Shame there isn't an option to calculate in this way and obtain the SD using option 4 if it's useful to some analysis software? I've more often noticed icing from anemometers stopping reading than vanes.
Thanks,
A
You are correct in both your statements for options 0 - 3. Every scan with the windvector instruction is tread using vector math. No magnitude, no direction. All scans in a 10 minute averaging interval would have to be 0 wind speed for the 10 minute average wind speed to be zero and thus the wind direction 0 as well.
Please clarify your idea for a better way to do this by emailing directly krhodesatcambellscidotcom. I'm very interested in what you have to say. After making the measurment and prior to doing the vector processing, you can force the wind speed magnitude to zero by assuming any wind speed below the threshold is zero ( if WS<0.5 then WS=0) for options 0 - 3.