Total system - accuracy
of wind monitoring systems
Accuracy
data of the windlogger EKO21B
Thanks to many years research
of the MAX40+ anemometer in wind tunnels the exact calibration
curve of the anemometer is programmed in the instrument.The resolution
of the stored average values is only 0.01 m/s.
The total system-accuracy is typ. 0.2 m/s by using the MAX40+
anemometer.
This has been achieved by an excellent anemometer calibration,
the right way of signal conditioning & sampling.
An optional individual calibration certificate
with 0.1 m/s calibration accuracy (including calibration report)
can be supplied, according to the latest European MEASNET procedure.
This certificate is a guarantee for the high accuracy, but is
not required in all cases, as the standard accuracy is typ 0.2
m/s.
The EKO 21B meets all the accuracy recommendations of IEA, IEC,
WMO and AWEA.
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Accuracy
data of some other suppliers
By simplifying the calibration
curve to a "straight
line" (without offset),
deviations up to appr. 0.5 m/s are possible. Moreover the resolution
of the samples of the MAX40 anemometer for puls counting inputs
is 1 pulse, or 0.7 m/s with sample period of 1 second! This will
affect the accuracy of the recorded values! Most other suppliers,
who use the MAX40 anemometer, probably meet (or not) the accuracy
standard of the WMO/AWEA: 0.5 m/s.
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Accuracy
of the energy prediction
As the energy production of
a wind turbine is proportional to the cube of the long-term average
wind speed (v3), a small deviation in wind speed will highly
affect the calculation of the energy production.
The relative deviation of the expected energy production is equal
to:
3 * total system accuracy /
average wind speed
For example: when the average wind speed is 6 m/s, measured with
a system accuracy of 0.5 m/s, the error in the prediction of
the energy production is approx. 25%.
As a valuable feasibility studie should give the energy prediction
within appr. 5-10 %, the required system- accuracy should be
in the range of 0.1 to 0.2 m/s when the long term average wind
speed is < 10 m/s.
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Conclusions
For wind energy feasibility
studies accurate measurements with total system accuracy of 0.1
to 0.2 m/s is required. Especially in areas with low or moderate
average wind speed it is important to measure the wind accurately
as the economic feasibility of windpower may be critical in that
case. The EKO 21B may be some more expensive than less accurate
instruments, but it can save a lot of money as it can prevent
wrong decisions for investments in wind energy projects! The
EKO 21B is an appropriate sytem for feasibility studies, the
evaluation of wind energy projects and even as a low-cost system
for scientific wind-research projects and meteorological studies.
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If you are interested in Ekopower's products please contact
us.