ALP No. 45 - Gobblers Knob West

This site was part of the Utility Wind Resource Assessment Program (UWRAP). Data provided by the Utility Wind Interest Group in cooperation with AWS Truewind, National Renewable Energy Laboratory, Electrotek Concepts, and Xcel Energy - Public Service Company of Colorado. The site was located approximately 29 miles south of the town of Lamar.

The collected data includes the following data fields:

Wind speed, standard deviation of the wind speed, and data quality flag for an anemometer at 10m height and facing E
Wind speed, standard deviation of the wind speed, and data quality flag for an anemometer at 25m height and facing S
Wind speed, standard deviation of the wind speed, and data quality flag for an anemometer at 40m height
Wind direction, standard deviation of the wind direction, and data quality flag for a wind vane at 25m height
Wind direction, standard deviation of the wind direction, and data quality flag for a wind vane at 40m height
Temperature from a sensor mounted at a height of 4m

Wind speed data at 40 meters represent a combination of data from primary and redundant sensors.

Only a text data file is available from this site. You can find this file here.

The file includes suspect data and when that data occurs, the value is generally a negative number. There is also a flag filed that indicates these suspect data values. For a version of this wind data with blanks rather than negative numbers, you can download here.

CSU was chosen as the contractor for the program on September 14, 2007. Using the raw data from all data plugs for this site, an analysis of the wind resource report was developed using Windographer 1.21. No data quality analysis was performed for this data other than what was available from the flag data fields included in the data. The suspect data was first removed from the collected data. Windographer was then used to add in synthetic data to these intervals with suspect data. The Windographer files (with blanks for the suspect data and with the blanks filled with synthetic data) are given below:

Highlights of the wind resource analysis at this site are shown below:

Data Properties
Data Set Starts:	4/23/1996 00:00
Data Set Ends:	5/01/1998 00:00
Data Set Duration:	24 months
Length of Time Step:	60 minutes
Mean air density (kg/m³):	1.053
Wind Power Coefficients
Power Density at 50m:	356 W/m²
Wind Power Class:	3 (Fair)
Wind Shear Coefficients
Power Law Exponent:	0.164
Surface Roughness:	0.0427 m
Roughness Class:	1.33
Roughness Description:	Crops

Variable	WS40	WS25S	WS10E
Height above ground	40 m (131 ft)	25 m (82 ft)	10 m (33 ft)
Mean wind speed (mph)	16.21	14.74	12.87
Median wind speed (mph)	15.9	14.34	12.10
Min wind speed (mph)	0	0	0
Max wind speed (mph)	54.21	50.18	43.90
Mean power density (W/m²)	327	251	171
Mean energy content (kWh/m²/yr)	2,869	2,200	1,496
Energy pattern factor	1.63	1.67	1.71
Weibull k	2.40	2.33	2.31
Weibull c (mph)	18.28	16.61	14.53
1-hr autocorrelation coefficient	0.89	0.89	0.89
Diurnal pattern strength	0.09	0.05	0.05
Hour of peak wind speed	23	22	16
Mean turbulence intensity	0.18	0.21	0.21
Standard deviation (mph)	7.18	6.66	5.88
Coefficient of variation (%)	44.3	45.2	45.7
Frequency of calms (%)	0.02	0.04	0.02
Possible records	17,712	17,712	17,712
Valid records	17,310	17,350	17458
Suspect records	402	362	254
Data completeness (%)	97.7	98	98.6

Windographer was used to match up the wind at this site with the performance curves of some common turbines of various sizes and various heights, allowing for losses of about 13%. The table below shows the results. For the larger turbines, the tower height was increased to account for the larger turbine blades - the wind resource was extrapolated to these higher heights. Keep in mind that the larger and the higher the turbine, the better the wind and the greater the output. But of course, as the tower heights and turbine sizes increase so does the cost.

Turbine	Rotor Diameter meters	Rotor Power kW	Hub Height meters	Hub Height Wind Speed mph	Time At Zero Output percent	Time At Rated Output percent	Average Net Power Output kW	Average Net Energy Output kWh/yr	Average Net Capacity Factor %
Bergey Excel-R	6.7	7.5	40	16.21	10.26	7.35	2.47	21,600	32.9
Bergey Excel-S	6.7	10	40	16.21	3.96	3.35	2.65	23,200	26.5
Bergey XL.1	2.5	1	40	16.21	0.75	10.39	0.37	3,200	36.7
Southwest Skystream 3.7	3.7	1.8	40	16.21	8.73	0	0.65	5,700	36.3
Southwest Whisper 500	4.5	3	40	16.21	10.18	8.79	1.15	10,100	38.4
Northern Power NW 100/20	20	100	40	16.21	15.99	0	22.4	196,500	22.4
Vestas V47 - 660 kW	47	660	65	17.49	9.20	0.73	207	1,814,700	31.4
GE 1.5s	70.5	1,500	80.5	18.16	12.57	6.5	453	3,969,700	30.2
Vestas V80 - 2.0 MW	80	2,000	100	18.88	11.96	3.51	718	6,293,700	35.9
GE 2.5xl	100	2,500	110	19.20	8.75	10.13	1,007	8,825,200	40.3

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Last updated: June 2009
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