Near-Surface Wind-Speed Stilling in Alaska during 1984-2016 and Its Impact on the Sustainability of Wind Power

Gerhard Kramm,John Cooney,Ralph Dlugi,Nicole Mölders

doi:10.4236/jpee.2019.77006

Gerhard Kramm, John Cooney + Show 2 more

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https://doi.org/10.4236/jpee.2019.77006

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Abstract

Based on wind-speed records of Alaska’s 19 first-order weather stations, we analyzed the near-surface wind-speed stilling for January 1, 1984 to December 31, 2016. With exception of Big Delta that indicates an increase of 0.0157 m·s–1·a–1, on average, all other first-order weather stations show declining trends in the near-surface wind speeds. In most cases, the average trends are less then –0.0300 m·s–1·a–1. The strongest average trend of –0.0500 m·s–1·a–1 occurred at Homer, followed by –0.0492 m·s–1·a–1 at Bettles, and –0.0453 m·s–1·a–1 at Yakutat, while the declining trend at Barrow is marginal. The impact of the near-surface wind-speed stilling on the wind-power potential expressed by the wind-power density was predicted and compared with the wind-power classification of the National Renewable Energy Laboratory and the Alaska Energy Authority. This wind-power potential is, however, of subordinate importance because wind turbines only extract a fraction of the kinetic energy from the wind field characterized by the power efficiency. Since wind turbine technology has notably improved during the past 35 years, we hypothetically used seven currently available wind turbines of different rated power and three different shear exponents to assess the wind-power sustainability under changing wind regimes. The shear exponents 1/10, 1/7, and 1/5 served to examine the range of wind power for various conditions of thermal stratification. Based on our analysis for January 1, 1984 to December 31, 2016, Cold Bay, St. Paul Island, Kotzebue, and Bethel would be very good candidates for wind farms. To quantify the impact of a changing wind regime on wind-power sustainability, we predicted wind power for the periods January 1, 1984 to December 31, 1994 and January 1, 2006 to December 31, 2016 as well. Besides Big Delta that suggests an increase in wind power of up to 12% for 1/7, predicted wind power decreased at all sites with the highest decline at Annette (≈38%), Kodiak (≈30%), King Salmon (≈26%), and Kotzebue (≈24%), where the effect of the shear exponents was marginal. Bethel (up to 20%) and Cold Bay (up to 14%) also show remarkable decreases in predicted wind power.

Highlights

There is observational evidence of declining trends in the near-surface wind speeds over the last five decades in numerous areas of the world [1]
With exception of Big Delta that indicates an increase of 0.0157 m∙s−1∙a−1, on average, all other first-order weather stations show declining trends in the near-surface wind speeds
To estimate the wind-power potential in Alaska, we considered the daily mean wind data provided by the 19 first-order weather stations in Alaska for Periods I, II, and III

Summary

Introduction

There is observational evidence of declining trends in the near-surface wind speeds over the last five decades in numerous areas of the world [1]. McVicar et al [1] analyzed 148 studies reporting terrestrial trends of the wind speed at anemometer height, vR = vR , from across the globe (with uneven and incomplete spatial distribution and differing periods of measurement). They found an average trend of −0.014 m∙s−1∙a−1 for studies with more than 30 sites with observing data for more than 30 years. The exact causes, have not yet been identified [17]

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