Study: Global wind speed dropping, wind farms victim of “atmospheric stilling”

Widespread decrease in wind energy resources found over the Northern Hemisphere

 

Widespread decrease in surface winds is found over the Northern Hemisphere. Wind energy resources are in rapid decline in many places. Study finds atmospheric stilling is a widespread and potentially global phenomenon.

 

From the INSTITUTE OF ATMOSPHERIC PHYSICS, CHINESE ACADEMY OF SCIENCES

Asia’s biggest wind farm, the Dabancheng wind farm in China’s Xinjiang province. CREDIT Gang Huang

As climate change is becoming more and more a matter of concern, efforts on mitigation are being undertaken by the world community. Developing clean and renewable energy is a major component of those efforts for its significant contribution to reducing carbon emission to the atmosphere compared with fossil fuel. In 2016, renewable energy contributes more than 19% to the global final energy consumption. Of all the renewable energy sources, the wind is one of the key players in terms of installed electricity generating capacity, only exceeded by hydropower.

Wind energy is a natural resource characterized by instability. Previous studies mainly focus on the assessment of wind energy reserves, but it’s not clear how the wind energy evolves over time.

A new study focusing on the change in wind energy resources and models’ simulation ability over the Northern Hemisphere by the collaboration of IAP researchers–Ph.D. candidate Qun Tian, Professor Gang Huang, Associate Professor Kaiming Hu, and Purdue University researcher–Professor Dev Niyogi was recently published. It reveals a widespread decline in wind energy resources over the Northern Hemisphere. Using station observation data, the study finds that approximately 30%, 50% and 80% of the stations lost over 30% of the wind power potential since 1979 in North America, Europe, and Asia, respectively. The study also reveals that global climate models (GCM) cannot replicate the long-term changes on wind energy, indicating wind energy projections based on GCM simulations should be used with careful consideration to the model performance.

“Our study is one of the first comprehensive assessments of the GCM-based winds against surface observations over multiple continents. We found that the decline of wind energy is a widespread and potential global phenomenon. In addition, the finding that the climate models have a notable deficiency in simulating wind energy is an important conclusion that needs further attention.”, said Tian, the lead author of the paper.

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The paper: https://www.sciencedirect.com/science/article/abs/pii/S036054421832231X?via%3Dihub

Preprint here: http://www.escience.cn/system/file?fileId=102783

Observed and global climate model based changes in wind power potential over the Northern Hemisphere during 1979–2016

Abstract

Using an observed dataset, we study the changes of surface wind speeds from 1979 to 2016 over the Northern Hemisphere and their impacts on wind power potential. The results show that surface wind speeds were decreasing in the past four decades over most regions in the Northern Hemisphere, including North America, Europe and Asia. In conjunction with decreasing surface wind speeds, the wind power potential at the typical height of a commercial wind turbine was also declining over the past decades for most regions in the Northern Hemisphere. Approximately 30%, 50% and 80% of the stations lost over 30% of the wind power potential since 1979 in North America, Europe and Asia, respectively. In addition, the evaluation of climate models shows their relatively poor ability to simulate long-term temporal trends of surface winds, indicating the need for enhancing the process that can improve the reliability of climate models for wind energy assessments.

Excerpts from the paper:

Figure 2. Percentile wind speed trend. Evolution, as a function of year,
of annual percentile for observed surface wind speeds. 5th, 10th – 90th in 10
percentile increment and 95th percentile are shown. The domain considered
for a)North America, b)Europe, c)Asia, while
d)Global considers all the sites available in the dataset.

 

The results show that a reduction in wind power potential occurs in most of the areas (Figure 3), as deduced from analysis of section 3.1. There are 59 out of 214 (27.6%) stations in North America that have lost over 30 percent of their wind power potential since 1979 (Figure 4). Stations located in Wisconsin, Kentucky, Tennessee, Louisiana, Virginia and Maine in the United States are among those which appear experienced notable impact.

Remarkable alterations occur in Asia, where 65.0% of the stations show more than a 30 percent decrease with 50.5% with more than a 50 percent decrease (Figure 4).

Figure 4: Frequency distribution of cumulative changes in wind
power potential. Cumulative changes in the wind power potential from
1979 to 2016.

The results from analysis of observational surface wind speeds reemphasize that atmospheric stilling is a widespread and potentially global phenomenon. Among three continents included in this study, the decline in Asia is much sharper compared to North America and Europe. In terms of wind speed percentiles, strong winds decline faster than weak winds in Asia and Europe, while in North America, weak winds exceed strong winds in decline ratio.

Consistent with the decrease of surface wind speeds, the wind power potential was also decreasing in most regions of the Northern Hemisphere in the past decades. Around one third of the stations in North America, have experienced a huge decrease (over 30 percent) in wind power potential while over half of the stations in Europe and around four-fifths in Asia have the same magnitude of decrease.

For China, the country with the largest installed wind energy capacity, regions which have a considerable decrease are mainly regions with abundant wind energy resources and where a number of gigantic commercial wind farms were built. Changes in all four seasons are of the similar magnitude despite of the large differences in their mean states. For Asia and North America, the sharpest decrease appears along with the largest mean wind power potential. However, this is not the case for Europe, where the sharpest decrease in wind power potential appears in the autumn, while the largest mean value occurs in the winter.

The pattern of climatological wind speeds in CMIP5 simulations is also not consistent with the observations compared to the surface temperature simulation [62]. Thus the CMIP5 simulations of the changes in surface wind speeds should be used with considerable caution and likely not reliable.

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December 5, 2018 at 01:02PM

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