inspeed anemometer

 

Hi,

I bought the following anemometer as a cheap way to inexpensively get a
rough idea of the wind potential on my land -
http://www.inspeed.com/anemometers/Pole%20Mount2.asp

I don't understand the measurements I am getting - take some recent
data -

Date/time               DT      RT      AS
2005-03-15 18:55    69.81    11:19    7.00
2005-03-16 18:15    182.90    21:47    9.63
2005-03-18 17:43    356.15    45:41    8.05

(DT=Distance Travelled; RT=Run Time; AS=Average Speed)

How is the average calculated?
If I take DT/RT for the 16th 182.90/21:49 = 8.38 -Way different to the
9.63 shown on the display.

Does anyone have any ideas why the average does not match what is
calculated manually? I'd just like to know if the anemometer is
accurate or not. There may be a good reason for the difference. The
"manufacturer" is less than helpful and heading for either a return or
a negative ebay feedback.

Before someone says it, I know that this isn't the right way of
measuring average wind speed and that wind speed is actually DT/Actual
time to allow for times when then wind isn't blowing so for the
measurement taken on the 16th I had 23:20 actual time so 182.9/23:20 =
7.84

And finally, while I am here, has anyone got any experience with this?
-
http://www.alphalink.com.au/~derekw/ane/anemain.htm

Thanks,

Alan.

 



Ummm, thisis from the web site;

IMPORTANT NOTE ABOUT AVERAGE WIND SPEED: 
Since bicyclists do not want their average speed to be diminished when
they come to a stop, the computer will only record and average when the
wind is blowing.  It stops recording below approximately 1 mph.  That
means that  if the wind blows for 2 hours at 20 mph and 2 hours at zero,
the average shown will be 20, not 10!  Please keep this in mind for your
desired use of the Vortex. 
WORKAROUND :  if you want to know the real average wind speed - even
with spells near zero, do the following:  reset the computer, note the
time.  When desired, simply divide the total number of wind "miles" on
the display by the number of hours since reset. 

Note the work around.

The "DT" is for bicycles.

 

Hi George,

Thanks for your reply. I said as much in my original message although I
should have mentioned the information on the web site.
.
At the moment, wind speed is incidental to the problem. I simply want
to know why the average displayed on the meter doesn't match the
average calculated using the distance travelled and time taken
displayed on the meter.

If I were a cyclist, I would expect the average calculated to be the
same as that displayed.

In actual fact, to use this anemometer to work out the power available
from the wind, it is better to use the average displayed (or calculated
- whichever is correct) - for example, say one day the wind blows at
8m/s for 12 hours and at next to zero for the rest of the day This
gives a daily average of 12*8/24 = 4m/s. A Proven WT2500 would produce
6.8 KWh if run for 24 hours at this speed.
But, at 8m/s, this turbine produces 28.1 KWh in 24 hours so in 12
hours, it would produce just over 14 KWh - more than double than if I
used the average. So, it is better to ignore the time the wind doesn't
blow and use the average when the wind is blowing and reduce the number
of hours accordingly.
Of course, if there are significant periods of the day with zero wind
then it is unlikely that site would be suitable for wind power.

I just need to know which average (if any) is correct.

Alan.

 



First you are not travelling any distance, so that info is a moot point.

To get power output you would use the average of time wind was blowing.
This would give you less than reality but is better than a false
positive reading. Still you are only trying to assess the wind potential
so the average wind speed while the wind is blowing would seem to be the
best bet. Then you have to decide wether or not you get enough energy to
make it worth the trouble/cost for wind compared to other means of
energy production.

The average over the day would be useless unless the wind blows all day.

I would rather use a wind speed figure averaged for each hour of wind.
This would give the best indication of energy production.

Hope this helps. Glade to discuss further if you wish.