I am a DIY. I would like monitor the wind speed in my area where I live (to decide if to build or not the wind turbine). I do not wish to invest to much money in to this monitoring. I have decided to buy only anemometer cups (€20) and dataloger (€10), and it will be controlled by microprocessor (programed by me).
My question is:
If I buy only the cups, how can I calculate the wind speed without buying the expensive wind speed meter for calibration?
Can I calculate the wind speed from the cup rpm?
I have seen a few calculation on internet, that wind speed = speed of the cups. I think it is not true.
This calculation can work if we blow only on one side of the cups circumference and ignore the spin resistivity.
But the wind blows as well on the opposite side of the cups circumference, where slows down the cups. So the wind speed is always > as cups speed.
Am I right or not? Thanks for reply in advance.
* Last updated by: romiadam on 11/9/2014 @ 6:39 AM *
The relationship of an anemometer rotational speed vs wind speed depends on the cup design and the friction of the bearings. High quality anemometers have moving parts that were machined with tight tolerances to keep them perfectly balanced in shape and weight. The bearings are high quality to provide low friction and long life. The anemometer manufacture will provide a coefficient of pulses per km/hr.
Any new anemometer cup design has to be calibrated in a wind tunnel. As you guessed, blowing air just on one side will spin an anemometer faster than wind blowing on the entire sensor.
I would strongly urge the usage of high quality measurement equipment if making decisions on wind turbine installation. Margins can be very small for wind generation. Measurement equipment over reporting by 5% could lead to installing a wind turbine which loses money. Good investment decisions require good data.
Measurements matter.