WMOD00387

• Title: Wind Site Prospecting Studies
• Prepared By: W. F. Harrison, S. J. Hightower
• Date: 10/1/1982
• Weather Modification - Doc Type: Report

4. Calculate the density using the equation:

, P
Density - -
- RT

F. The power density is calculated using:

PO = V2 PSL (OM) V3

where OM = density multiplier, V = windspeed at
height of concern. (An annual available power at
50 meters, exceeding 400 W/m2, is sometimes
used as a "rule-of-thumb" for a good potential
wind turbine site.)

G. All times indicated are local standard time.

DISCUSSION

The heights of 10, 50, 61, and 80 meters were
chosen to correlate the sites relative to each
other. Ten meters is a World Meterological Organi-
zation standard reporting height. Fifty meters is
used as a common "rule-of-thumb" height to
report available power in W 1m2. Sixty one meters
is the hub height of the MOD-2 and 80 meters is
the hub height of the WTS-4.

Because of the difference in installation times,
nine different comparisons are in this report.
Dates of the comparisons and the corresponding
table numbers follow.

..

1. October 1, 1980 to September 30, 1982
- 6 stations
2. October 1, 1980 to September 30, 1981
- 6 stations
3. October 1, 1981 to September 30, 1982
- 13 stations
4. October 1, 1980 to April 30, 1981
- 9 stations
5. December 1, 1980 to October 31, 1981
- 14 stations
6. December 1, 1980 to April 30, 1981
- 1 5 stations
7. April 1 , 1981 to March 31, 1982
- 9 stations
8. August 1, 1981 to July 31, 1982
- 13 stations
9. December 1, 1981 to September 30, 1982
- 14 stations

The comparisons present the data for the included
stations for the following parameters:

A. Available hours of wind recorded, as a per-
centage of total hours available.

B. Average extrapolated windspeed (ml s) at the
10- and 50-meter heights.

C. Average extrapolated available power (W 1m2)
at 10 and 50 meters.

D. Cumulative energy (kWh) calculated for the
WTS-4 and MOD-2 wind turbine generators.

E. Duration of time (hours) when the windspeed
exceeded 4 m/s at 10- and 50-meter heights.

The last comparison may be used as an evaluation
tool for establishing the maximum number of
hours any wind turbine could be expected to be
operating since most wind turbines have cut-in
speeds above this value.

The stations are listed in each of the comparisons
in descending order based on the calculated
cumulative energy (kWh) predicted for the WTS-4
wind turbine.

A study. was made of the data to determine if the
cause of missing data was a function of extremely
high windspeeds, an electronic malfunction, wind
sensor bearing seizure, Of other predictable
failure. This determination indicated that it was
not extreme windspeed that caused the missing
data; therefore, each station has had its values of
WTS-4and MOD-2 normalized to 100 percent;
i.e., if the wind turbine was predicted to generate
90 percent of the month, it was assumed it would
have predicted 1.0 million kWh if the station had
reported the entire month.

1. October " 1980toSeptember30, 1982, table
1. - The PTH site was predicted to have had
28.269 million kWh of energy that would have
been generated by a WTS-4 wind turbine over
this 2-year period, an average of 1.178 million
kWh/mo and WKR had 18.344 million kWh, Le.,
a monthly average of 0.764 million kWh.

Only ELL, of the other four sites, showed over 12
million kWh or an average of greater than 0.5
million kWh/mo. It should be emphasized that
this assumes the windspeeds at hub height are
proportional to the 117 power law at all sites. [4]
In actuality, where the anemometer is located on
a hill or ridge (as at PTH and WKR), the windspeeds
at hub height are not expected to be as high as
this equation predicts; therefore, it would be

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