NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

Long-Term Wind Power 

Variability 

Y.H. Wan

Technical Report

NREL/TP-5500-53637

January 2012
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

National Renewable Energy Laboratory

1617 Cole Boulevard

Golden, Colorado 80401

303-275-3000 • www.nrel.gov

Contract No. DE-AC36-08GO28308

Long-Term Wind Power 

Variability 

Y.H. Wan

Prepared under Task No. WE11.0910

Technical Report

NREL/TP-5500-53637

January 2012
NOTICE

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iii

Table of Contents

Table of Contents.......................................................................................................................................iii

List of Figures ............................................................................................................................................iv

List of Tables ............................................................................................................................................... v

1 Introduction ......................................................................................................................................... 1

2 Data Sources ....................................................................................................................................... 1

3 Inter-Annual Variability of Wind Power............................................................................................. 2

4 Monthly Variability of Wind Energy................................................................................................... 4

5 Shorter-Term Variations..................................................................................................................... 9

6 Summary and Conclusions..............................................................................................................12

7 References.........................................................................................................................................13

Appendix A: Average Hourly Wind Power Profile of Lake Benton ......................................................14

Appendix B: Hourly Average Wind Power Profile of Storm Lake ........................................................19

Appendix C: Hourly Average Wind Power Profile of Blue Canyon......................................................23

Appendix D: Hourly Average Wind Power Profile of Trent Mesa.........................................................26

Appendix E: Monthly COV of hourly wind power level changes .........................................................30
iv

List of Figures

Figure 1. Inter-annual variation of wind energy from Lake Benton ........................................... 3

Figure 2. Normalized annual outputs from four WPPs .............................................................. 4

Figure 3. Monthly wind energy production from Lake Benton .................................................. 5

Figure 4. Storm Lake monthly production .................................................................................. 5

Figure 5. Blue Canyon monthly production ............................................................................... 6

Figure 6. Trent Mesa monthly production .................................................................................. 6

Figure 7. 2004 average hourly wind power profiles by month from Lake Benton .................... 7

Figure 8. 2004 average hourly wind power profiles by month from Storm Lake ...................... 8

Figure 9. 2004 average hourly wind power profiles by month from Blue Canyon .................... 8

Figure 10. 2004 average hourly wind power profiles by month from Trent Mesa ....................... 9

Figure 11. Monthly COV of wind power at Lake Benton .......................................................... 11

Figure A-1. 2001 average hourly wind power profiles by month from Lake Benton .................. 14

Figure A-2. 2002 average hourly wind power profiles by month from Lake Benton .................. 14

Figure A-3. 2003 average hourly wind power profiles by month from Lake Benton .................. 15

Figure A-4. 2005 average hourly wind power profiles by month from Lake Benton .................. 15

Figure A-5. 2006 average hourly wind power profiles by month from Lake Benton .................. 16

Figure A-6. 2007 average hourly wind power profiles by month from Lake Benton .................. 16

Figure A-7. 2008 average hourly wind power profiles by month from Lake Benton .................. 17

Figure A-8. 2009 average hourly wind power profiles by month from Lake Benton .................. 17

Figure A-9. 2010 average hourly wind power profiles by month from Lake Benton .................. 18

Figure B-1. 2002 average hourly wind power profiles by month from Storm Lake .................... 19

Figure B-2. 2003 average hourly wind power profiles by month from Storm Lake .................... 19

Figure B-3. 2005 average hourly wind power profiles by month from Storm Lake .................... 20

Figure B-4. 2006 average hourly wind power profiles by month from Storm Lake .................... 20

Figure B-5. 2007 average hourly wind power profiles by month from Storm Lake .................... 21

Figure B-6. 2008 average hourly wind power profiles by month from Storm Lake .................... 21

Figure B-7. 2009 average hourly wind power profiles by month from Storm Lake .................... 22

Figure B-8. 2010 average hourly wind power profiles by month from Storm Lake .................... 22

Figure C-1. 2005 average hourly wind power profiles by month from Blue Canyon .................. 23

Figure C-2. 2006 average hourly wind power profiles by month from Blue Canyon .................. 23

Figure C-3. 2007 average hourly wind power profiles by month from Blue Canyon .................. 24

Figure C-4. 2008 average hourly wind power profiles by month from Blue Canyon .................. 24

Figure C-5. 2009 average hourly wind power profiles by month from Blue Canyon .................. 25

Figure C-6. 2010 average hourly wind power profiles by month from Blue Canyon .................. 25

Figure D-1. 2003 average hourly wind power profiles by month from Trent Mesa .................... 26

Figure D-2. 2005 average hourly wind power profiles by month from Trent Mesa .................... 26

Figure D-3. 2006 average hourly wind power profiles by month from Trent Mesa .................... 27

Figure D-4. 2007 average hourly wind power profiles by month from Trent Mesa .................... 27

Figure D-5. 2008 average hourly wind power profiles by month from Trent Mesa .................... 28

Figure D-6. 2009 average hourly wind power profiles by month from Trent Mesa .................... 28

Figure D-7. 2010 average hourly wind power profiles by month from Trent Mesa .................... 29
v 

List of Tables

Table 1. Locations, Capacities and Available Data of WPPs ......................................................... 1

Table 2. Yearly COV Values Based on Daily Wind Energy Productionsa

 ................................... 10

Table 3. Yearly COV Values of Hourly Wind Power .................................................................. 10

Table 4. Hourly Wind Power Variability by Month at Lake Benton............................................ 11

Table 5. Standard Deviation of Hourly Power Level Changes (Normalized to Plant Nameplate 

Capacity) ....................................................................................................................................... 12

Table E-1. Hourly Wind Power Variability by Month at Storm Lake.......................................... 30

Table E-2. Hourly Wind Power Variability by Month at Blue Canyon ....................................... 31

Table E-3. Hourly Wind Power Variability by Month at Trent Mesa .......................................... 32
vi 
1 

1 Introduction

The National Renewable Energy Laboratory started collecting wind power data from large 

commercial wind power plants (WPPs) in southwest Minnesota with dedicated dataloggers and 

communication links in the spring of 2000. Over the years, additional WPPs in other areas were

added to and removed from the data collection effort. The longest data stream of actual wind 

plant output is more than 10 years. 

The resulting data have been used to analyze wind power fluctuations, frequency distribution of 

changes, the effects of spatial diversity, and wind power ancillary services [1–6]. This report 

uses the multi-year wind power data to examine long-term and shorter-term wind power 

variability, and provide an overview of the results. 

2 Data Sources

Output data from four WPPs are used in this report because the data quality is better for longer 

periods at these locations. Data from other sites have larger gaps (more missing data) or are 

available only for shorter time periods. Table 1 lists the name, location, plant capacity and data 

available period for each of the four WPPs. 

Table 1. Locations, Capacities and Available Data of WPPs

WPP Name Location Plant Capacity Data Available

Lake Benton (LB) Minnesota 104 MW 2000-2010

Storm Lake (SL) Iowa 113 MW 2001-2010

Blue Canyon (BC) Oklahoma 75 MW 2003-2010

Trent Mesa (TM) Texas 150 MW 2004-2010

All data except for Blue Canyon are in 1-second time series. Blue Canyon data are in 1-minute 

time series [7]. The hourly data are derived from the raw 1-second and 1-minute data streams by 

averaging them over 3600 seconds or 60 minutes. All four original data streams contain gaps 

ranging in length from a few minutes to several days because of equipment failures and 

interruptions in communication links. In addition, the data show that sometimes the outputs from 

the WPPs would change abruptly (in one or two seconds) or within a very short period (within 

one minute). These changes were large in magnitude—greater than 15% of the WPP’s nameplate 

capacity. Such a sudden change could be the result of forced outages within or without the WPP

(equipment failures or the transmission line outages) and curtailment operations. Because we do 

not have corresponding wind speed information or operations records of the WPP, it is not 

possible to identify the causes of these sudden changes in plant output and separate them from 

changes caused by naturally occurring wind speed changes. No modifications were attempted to 

the data when the sudden changes occurred. However, when calculating the statistics of wind 

power step changes (the differences from one hour to the next), only continuous data points (i.e., 

consecutive data points with continuous time stamps) were included, so that all changes in power 

level due to data gaps were excluded from the calculation.
2 

3 Inter-Annual Variability of Wind Power

Wind speed fluctuates continuously, and as a result, the power from a wind turbine or plant 

varies. Short-term fluctuations in wind power are stochastic in nature, but distinctive patterns 

exist for longer-term fluctuations. For this report, short-term wind power variations mean 

fluctuations of average wind power from one hour to the next. Longer-term variations of wind 

power mean changes in daily, seasonally, and yearly WPP productions. Short-term wind speed 

changes with duration from several seconds to several minutes, such as turbulence and gusts, will 

manifest as the ramping of turbine or plant output power in varying degrees. Longer-term 

changes in the underlying wind conditions will result in inter-annual, seasonal, monthly, and 

diurnal variations of output power levels. For example, the meteorological inter-annual 

oscillations such as El Niño/La Niña Southern Oscillations could contribute to the wind power 

inter-annual variations observed in the available data during the 2000-2010 period. This report 

only focused on the available wind power data itself. Future efforts will link the wind power data 

to other meteorological and weather data sets and analyze in more detail the correlation between 

WPP production and meteorological inter-annual oscillations or other quasiperiodic climate 

patterns.

Figure 1 shows yearly production at Lake Benton from 2000 to 2010. The actual outputs are 

normalized to the average value of this period.1 The annual production at this plant ranges from a 

low of 82% of the average to a high of 113% of the average. The inter-annual variation is 

relatively large; the highest production year produced 38% more energy than the lowest 

production year during this period. Outputs from this WPP do not seem to show a periodic 

pattern. This could be because there were not enough data to establish a definitive pattern or 

long-term trend.

 

1 The actual production values of these WPPs are not used to protect the business-sensitive information of the plant 

owners.
3 

Figure 1. Inter-annual variation of wind energy from Lake Benton

Figure 2 plots normalized annual production of the four WPPs. Because of the plant size 

differences, the annual production values are normalized to the respective sites’ nameplate 

capacities for easier comparison. 

Traces in Figure 2 again suggest that inter-annual variations of wind energy production can be 

significant. Despite the fact that wind energy production can be relatively high at one plant but 

relatively low at others in the same year, some features can still be identified. For example, 

geographic locations can be detected from these annual output traces. The traces of Blue Canyon 

and Trent Mesa bear some resemblance to each other because these two WPPs are relatively 

close to one another. Traces of Lake Benton and Storm Lake have similar shapes for the same 

reason. 

Although there are no common features or patterns in the annual wind energy production plots 

over the period when data were available, there are slight differences in the individual plant 

behaviors. Trent Mesa, with a standard deviation value of 13% of its 8-year average (2003–

2008), had the most inter-annual variation among the four WPPs. During this period, the highestproduction year produced 47% more energy than the lowest-production year. Blue Canyon, with 

a standard deviation value of 8% of its 7-year average, had the least inter-annual variation. The 

highest production year produced 29% more energy than the lowest production year at Blue 

Canyon. However, by and large, these four WPPs experienced similar inter-annual variations in 

annual energy production. 
4 

Figure 2. Normalized annual outputs from four WPPs

4 Monthly Variability of Wind Energy

The monthly production at these four plants shows readily discernible patterns during the 11-

year period. Figure 3 shows monthly wind energy production at Lake Benton from 2000 to 2010 

and significant monthly variations in wind power. The production from the highest month was 

more than three times more than the production from the lowest month. Even in the same year, 

the production of the highest month could be almost three times more than the production of the 

lowest month. For the same month, the changes from one year to the next could also be 

significant. For example, production during February 2002 was more than twice the production 

during February 2010. 

However, the most distinctive feature of Figure 3 is the consistent low production (dip in the 

traces) during the summer months of June, July, and August at this location. Average wind 

production during spring and winter months was fairly constant through the years. During 

summer months, the production was only about 64% of that of the winter months, on average. 

Although production during summer months was much lower than during the spring and winter 

months, production variations (differences between the highest and the lowest) for summer 

months are generally smaller (i.e., they are more constant). In fact, low production during 

summer months generally held true for other WPPs in the middle part of the continental United 

States. Figures 4, 5, and 6 show the monthly wind energy productions from Storm Lake, Blue 

Canyon, and Trent Mesa. It is obvious they are all subject to similar weather patterns. February 

and May are the two months with the most variability in wind energy production. 
5 

Figure 3. Monthly wind energy production from Lake Benton

Figure 4. Storm Lake monthly production
6 

Figure 5. Blue Canyon monthly production

Figure 6. Trent Mesa monthly production
7 

Figures 7, 8, 9, and 10 show hourly average wind power by month from Lake Benton, Storm 

Lake, Blue Canyon, and Trent Mesa during 2004. Similar plots for other years are in appendices 

A, B, C, and D. The purpose of these plots is to see if there is a common diurnal pattern 

throughout the year. Figures 7 through 10 and similar plots of other years reveal that, on a 24-

hour cycle, average wind power will dip during early evening hours (6:00 to 7:00 p.m.), 

especially during summer months. This low will be more prominent the further south the wind 

plant is located. At Lake Benton, the average hourly wind power over the entire year (the thick 

red trace in Figure 7) shows a relative high point in early morning (5:00 a.m.) and a relative low 

point in early evening (6:00 p.m.). However, this pattern does not exist in every month. 

Individual monthly traces of hourly average wind power at Storm Lake also do not have a 

consistent pattern throughout the year. On average, Storm Lake wind power is slightly higher 

during early morning hours. During the early summer months of May and June, the pattern even 

reverses itself (higher wind power around midday). 

The diurnal pattern becomes much clearer at WPPs located farther south. Wind power from Blue 

Canyon and Trent Mesa—two WPPs more than 1,100 km and 1,300 km to the south—exhibit 

distinctive diurnal patterns for every month of the year. The additional profiles of other years in 

appendices A, B, C, and D show that the diurnal patterns of individual WPPs are very consistent 

throughout the years.

Figure 7. 2004 average hourly wind power profiles by month from Lake Benton
8 

Figure 8. 2004 average hourly wind power profiles by month from Storm Lake

Figure 9. 2004 average hourly wind power profiles by month from Blue Canyon
9 

Figure 10. 2004 average hourly wind power profiles by month from Trent Mesa

5 Shorter-Term Variations

Wind production at these four WPPs has shown significant inter-annual variation and 

distinguished seasonal and diurnal patterns, but the shorter-term behavior of wind power was 

fairly consistent. One way to gauge short-term wind variability is to compare the coefficients of 

variation (COV) of wind power. COV is defined as the ratio of standard deviation value to the 

mean (average) value. If wind speeds were used, the resulting COV is referred to as turbulence 

intensity, and it is a measure of wind turbulence. Turbulence intensities are directly related to the 

surface roughness of the ground (i.e. grassland, forest, urban, etc.) and the atmospheric stability 

[8]. Turbulence intensity generally increases with increased surface roughness, as the wind 

advects horizontally along the surface. Furthermore, turbulence can be generated through vertical 

advection (i.e. convection) in a stable or unstable atmosphere. Additionally, turbulence intensity 

generally decreases with height within the atmospheric boundary layer, due to the reduced 

influence of surface roughness. 

Table 2 lists yearly COV calculated with daily wind production over the entire year of these four 

WPPs.
10 

Table 2. Yearly COV Values Based on Daily Wind Energy Productionsa

LB SL BC TM

2000 0.7

2001 0.7 0.7

2002 0.6 0.7

2003 0.7 0.7 0.6

2004 0.6 0.7 0.7 0.6

2005 0.7 0.7 0.7 0.6

2006 0.7 0.7 0.6 0.6

2007 0.7 0.7 0.8 0.7

2008 0.7 0.7 0.6 0.6

2009 0.8 0.8 0.6 0.7

2010 0.8 0.8 0.7 0.7

a Blanks in the table indicate missing data.

Table 3 lists yearly COV calculated with hourly average wind power over the entire year of these 

four WPPs.

Table 3. Yearly COV Values of Hourly Wind Power

LB SL BC TM

2000 0.9

2001 0.8 0.9

2002 0.8 0.9

2003 0.8 0.9 0.8

2004 0.9 0.9 0.8 0.8

2005 0.9 0.9 0.9 0.8

2006 0.9 0.9 0.8 0.8

2007 0.9 0.9 1.0 1.0

2008 0.9 0.9 0.8 0.9

2009 0.9 1.0 0.8 1.0

2010 1.0 1.0 0.9 0.9

The COV values in the tables are higher than the typical turbulence intensity values of wind 

speed [9]. Wind power data were used in the calculation and the available wind power is 

proportional to wind speed cubed [10]. Values in Table 3 are higher than values in Table 1 

because hourly wind power will show more variability than daily energy (8,760 data points 

compared with 365 data points). The shorter-term variability of the outputs from these four 

WPPs is consistent throughout the years, as indicated by the near-constant yearly COV values. 

The higher values of a particular year are generally correlated to low energy production of that 

year (Figure 2). Lower production implies lower mean wind speed for the year and thus 

relatively higher variability.
11 

Table 4 lists monthly COV values calculated with the average hourly wind power of Lake 

Benton. Figure 11 is a plot of the values in Table 4. Similar tables of COV values for other 

WPPs are in appendix E. At finer resolution, the seasonal variability of wind power begins to 

appear. Again, higher COV values are associated with lower wind energy production months. 

The traces in Figure 11 are almost the reverse of Figure 3, which shows monthly productions at 

Lake Benton. However, Figure 11 shows that the yearly patterns are still fairly consistent. 

Table 4. Hourly Wind Power Variability by Month at Lake Benton

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Jan 0.8 0.8 0.8 0.8 1.0 0.8 0.7 0.8 0.7 0.9

Feb 0.7 0.7 0.6 0.7 0.7 0.9 0.7 0.8 0.9 0.7 1.1

Mar 1.0 0.8 0.8 0.7 0.8 0.8 0.8 0.7 0.9 0.9 0.9

Apr 0.8 0.7 0.7 0.8 1.0 0.7 0.8 0.7 0.7 0.7 0.9

May 0.9 0.8 0.8 1.0 0.8 0.7 0.7 0.7 0.8 0.9 0.9

Jun 0.8 0.9 0.8 1.1 0.9 0.9 1.1 0.9 1.1 1.0 1.0

Jul 1.2 1.1 0.9 0.9 1.1 0.9 1.0 1.0 1.2 1.2 1.3

Aug 0.9 0.9 0.9 1.1 0.9 1.0 1.1 1.2 1.1 1.0 1.1

Sep 0.8 1.0 0.8 0.7 0.9 0.8 1.0 0.7 0.9 1.2 0.9

Oct 0.9 0.7 1.0 0.8 0.8 0.9 0.8 0.8 0.9 1.0 1.0

Nov 0.8 0.7 0.8 0.6 0.7 0.7 0.8 0.9 0.8 0.9 0.8

Dec 0.8 0.7 0.7 0.6 0.7 0.9 0.8 1.0 0.6 0.8 0.9

Figure 11. Monthly COV of wind power at Lake Benton

Short-term fluctuations of wind power can also be examined with the statistics of step changes 

(the differences of wind power levels from successive measurements). The hourly average power 

outputs of these four WPPs were used to calculate the step changes and their standard deviations 

for each month and for the entire year. Table 5 shows the yearly standard deviations of the 

hourly step changes. The actual values were normalized to the nameplate capacity of the 

respective WPPs to eliminate the size bias and enable easy comparison.
12 

Table 5. Standard Deviation of Hourly Power Level Changes

(Normalized to Plant Nameplate Capacity) 

LB SL BC TM

2000 0.08

2001 0.07 0.06

2002 0.07 0.07

2003 0.07 0.07 0.08

2004 0.07 0.07 0.08 0.08

2005 0.07 0.07 0.08 0.08

2006 0.07 0.07 0.08 0.08

2007 0.07 0.06 0.07 0.08

2008 0.07 0.06 0.08 0.09

2009 0.07 0.06 0.08 0.08

2010 0.07 0.06 0.07 0.08

The values in Table 5 indicate that the characteristics of short-term wind power fluctuations do 

not change much. The climate pattern may change from one year to the next, which will result in 

mean wind speeds being high or low and thus change wind energy production, but the nature of 

wind as seen from the point of short-term variations (fluctuations) remains the same.

6 Summary and Conclusions

The wind power data from WPPs in different parts of the country suggest that one can expect 

relatively large inter-annual changes. The climate and regional weather pattern are the driving 

forces behind wind and wind plant outputs. Changes in climate and weather patterns will be 

reflected in the longer-term performance of WPPs. In this respect, wind power is similar to 

hydropower, especially run-of-the-river type, in that there are high energy production (wet) years 

and low energy production (dry) years. The available data show that during the highest 

production year, total wind energy from the same WPP can be almost 40% higher than the 

annual production of the lowest production year. The available data do not appear to be enough 

to establish a long-term pattern or trend.

However, shorter-term variations of wind power appear to be less than longer-term variations. 

The data show that distinctive seasonal and diurnal patterns are persistent over the years

independent of the overall annual wind energy production. 

For even shorter-term variations, such as power level from one hour to the next, changes of wind 

power levels become a stochastic process with a very narrow range of standard deviation values 

around its respective mean. The magnitudes of these mean and standard deviation values are 

functions of the size of the WPP. Larger WPPs obviously have bigger changes, but the 

relationship with size is not linear [3] because the spatial diversity of wind speeds within a large 

WPP will reduce the variability of the plant output relative to a single wind turbine or a small 

WPP with fewer wind turbines. However, when those mean and standard deviation values are 

expressed in terms of the installed capacity of the WPPs, they are almost constant on an annual 

basis (as shown in Table 4). It can be concluded that short-term wind power fluctuations do not 

exhibit year-to-year variability. 
13 

7 References 

1. Wan, Y. H. Analysis of Wind Power Ramping Behavior in ERCOT. NREL/TP-5500-49218. 

Golden, CO: National Renewable Energy Laboratory, 2011. 

2. Wan, Y.; Liao, J. R. Analyses of Wind Energy Impact on WFEC System Operations: Preprint. 

NREL/CP-500-39477. Golden, CO: National Renewable Energy Laboratory, 2006 

3. Wan, Y. “Fluctuation and Ramping Characteristics of Large Wind Power Plants.” Windpower 

2005 (Windpower 05) Conference and Exhibition (CD-ROM), 15-18 May, 2005, Denver, 

Colorado. Washington, D.C.: American Wind Energy Association; Content Management Corp., 

2005; 13 pp. NREL/CP-500-38057. 

4. Wan, Y.; Milligan, M.; Parsons, B. “Output Power Correlation Between Adjacent Wind Power 

Plants.” Journal of Solar Energy Engineering; Transactions of the ASME; Vol. 125(4), 

November 2003; pp. 551–555. NREL/JA-500-33519. doi:10.1115/1.1626127. 

5. Wan, Y. H.; Bucaneg, D. Jr. “Short-Term Power Fluctuations of Large Wind Power Plants.” 

Journal of Solar Energy Engineering: Transactions of the ASME; Vol. 124, November 2002; pp. 

427–431. NREL/JA-500-33842. doi:10.1115/1.1507762. 

6. Cadogan, J.; Milligan, M.; Wan, Y.; Kirby, B. Short-Term Output Variations in Wind Farms--

Implications for Ancillary Services in the United States: Preprint. NREL/CP-500-29155. 

Golden, CO: National Renewable Energy Laboratory, 2000. 

7. Wan, Y. H. Summary Report of Wind Farm Data: September 2008. NREL/TP-500-44348. 

Golden, CO: National Renewable Energy Laboratory, 2009. 

8. Roland B. Stull, An Introduction to Boundary Layer Meteorology, Springer, 1988. 

9. Manwell, J.F., et al. Wind Energy Explained Theory, Design and Application. New York: John 

Wiley & Sons, 2002. 

10. Wan, Y. Primer on Wind Power for Utility Applications. NREL/TP-500-36230. Golden, 

CO: National Renewable Energy Laboratory, 2005. 
14 

Appendix A: Average Hourly Wind Power Profile of Lake Benton

Figure A-1. 2001 average hourly wind power profiles by month from Lake Benton

Figure A-2. 2002 average hourly wind power profiles by month from Lake Benton
15 

Figure A-3. 2003 average hourly wind power profiles by month from Lake Benton 

Figure A-4. 2005 average hourly wind power profiles by month from Lake Benton
16 

Figure A-5. 2006 average hourly wind power profiles by month from Lake Benton

Figure A-6. 2007 average hourly wind power profiles by month from Lake Benton
17 

Figure A-7. 2008 average hourly wind power profiles by month from Lake Benton

Figure A-8. 2009 average hourly wind power profiles by month from Lake Benton
18 

Figure A-9. 2010 average hourly wind power profiles by month from Lake Benton
19 

Appendix B: Hourly Average Wind Power Profile of Storm Lake

Figure B-1. 2002 average hourly wind power profiles by month from Storm Lake

Figure B-2. 2003 average hourly wind power profiles by month from Storm Lake
20 

Figure B-3. 2005 average hourly wind power profiles by month from Storm Lake

Figure B-4. 2006 average hourly wind power profiles by month from Storm Lake
21 

Figure B-5. 2007 average hourly wind power profiles by month from Storm Lake

Figure B-6. 2008 average hourly wind power profiles by month from Storm Lake
22 

Figure B-7. 2009 average hourly wind power profiles by month from Storm Lake

Figure B-8. 2010 average hourly wind power profiles by month from Storm Lake
23 

Appendix C: Hourly Average Wind Power Profile of Blue Canyon

Figure C-1. 2005 average hourly wind power profiles by month from Blue Canyon

Figure C-2. 2006 average hourly wind power profiles by month from Blue Canyon
24 

Figure C-3. 2007 average hourly wind power profiles by month from Blue Canyon

Figure C-4. 2008 average hourly wind power profiles by month from Blue Canyon
25 

Figure C-5. 2009 average hourly wind power profiles by month from Blue Canyon

Figure C-6. 2010 average hourly wind power profiles by month from Blue Canyon
26 

Appendix D: Hourly Average Wind Power Profile of Trent Mesa

Figure D-1. 2003 average hourly wind power profiles by month from Trent Mesa

Figure D-2. 2005 average hourly wind power profiles by month from Trent Mesa
27 

Figure D-3. 2006 average hourly wind power profiles by month from Trent Mesa

Figure D-4. 2007 average hourly wind power profiles by month from Trent Mesa
28 

Figure D-5. 2008 average hourly wind power profiles by month from Trent Mesa

Figure D-6. 2009 average hourly wind power profiles by month from Trent Mesa
29 

Figure D-7. 2010 average hourly wind power profiles by month from Trent Mesa
30 

Appendix E: Monthly COV of hourly wind power level changes

Table E-1. Hourly Wind Power Variability by Month at Storm Lake

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Jan 0.8 0.8 0.9 0.9 1.1 0.8 0.7 0.7 0.8 1.2

Feb 0.8 0.6 0.8 0.8 0.9 0.8 1.0 1.0 0.9 1.1

Mar 0.9 0.9 0.8 0.8 0.9 0.8 0.7 0.9 0.8 1.0

Apr 0.8 0.7 0.8 0.8 0.7 0.8 0.8 0.7 0.8

May 0.8 1.1 0.8 0.6 0.7 0.7 0.8 0.9

Jun 1.0 0.7 1.1 1.2 0.9 1.1 0.9 1.2 1.1

Jul 1. 1.0 1.1 1.3 1.0 1.0 1.0 1.2 1.3 1.3

Aug 1.0 1.0 1.3 1.1 1.1 1.0 1.1 1.3 1.1 1.1

Sep 1.1 0.8 0.8 0.7 0.8 1.0 0.8 0.9 1.4 0.9

Oct 0.8 1.0 0.8 0.9 0.9 0.8 0.9 0.8 1.0 0.9

Nov 0.8 0.9 0.7 0.8 0.7 0.9 0.7 0.8 0.8 0.8

Dec 0.9 0.8 0.7 0.8 1.0 0.8 1.2 0.7 0.9 0.9
31 

Table E-2. Hourly Wind Power Variability by Month at Blue Canyon

2004 2005 2006 2007 2008 2009 2010

Jan 0.8 1.0 0.7 1.1 0.7 0.8 1.1

Feb 0.9 0.9 0.8 0.8 0.8 0.6 1.5

Mar 0.8 0.8 0.7 0.8 0.6 0.6 0.6

Apr 0.8 0.6 0.6 0.8 0.6 0.6 0.6

May 0.5 0.9 0.7 1.1 0.6 1.0 0.9

Jun 0.9 0.7 0.9 1.2 0.8 0.8 0.7

Jul 0.8 1.0 0.8 1.2 0.8 1.0 0.8

Aug 1.0 1.0 1.0 0.9 1.1 0.8 0.9

Sep 0.9 0.9 1.0 0.9 1.1 0.9 0.8

Oct 0.9 0.8 0.8 0.8 1.0 0.9 0.8

Nov 0.9 0.7 0.7 0.9 0.8 0.8 0.6

Dec 0.7 0.8 0.7 1.0 0.7 0.8 1.0
32 

Table E-3. Hourly Wind Power Variability by Month at Trent Mesa

2003 2004 2005 2006 2007 2008 2009 2010

Jan 0.9 0.8 0.9 0.7 1.2 0.8 0.8 1.1

Feb 0.8 0.9 1.0 0.9 0.8 0.8 0.9 1.1

Mar 0.8 0.8 0.7 0.7 0.9 0.7 0.7 0.8

Apr 0.6 0.8 0.7 0.6 0.8 0.7 0.7 0.8

May 0.9 0.5 0.9 0.7 1.1 0.7 1.0 1.1

Jun 1.0 0.8 0.6 1.0 1.0 0.7 0.8 0.7

Jul 0.9 0.8 0.9 0.8 1.2 0.8 1.0 1.0

Aug 1.1 1.0 1.0 1.0 0.9 1.3 0.9 0.9

Sep 0.9 0.9 0.9 1.0 1.0 1.1 1.0 1.1

Oct 0.9 0.9 0.9 0.7 0.8 0.9 1.1 1.0

Nov 0.7 1.0 0.8 0.7 0.9 0.9 1.0 0.7

Dec 0.7 0.7 0.8 0.8 0.9 0.8 1.1 0.8