Large wind farms in certain areas of the United States appear to affect local land surface temperature, according to a paper published April 29 in Nature Climate Change. The study, led by University at Albany Associate Professor of Atmospheric and Environmental SciencesLiming Zhou, provides critical insight about the possible impacts of wind farms and could be important for developing efficient adaptation and management strategies to ensure long-term sustainability of wind power.
Considerable research has linked the carbon dioxide produced by burning fossil fuels with rising global temperatures. Consequently, many nations are moving toward cleaner sources of renewable energy such as wind turbines, as generating wind power creates no emissions, uses no water, and is considered green.
To understand the potential impact of wind farms on local weather and climate, Zhou’s team analyzed NASA satellite-derived land surface temperatures of regions around large wind farms in Texas for the period 2003–2011. The researchers found a nighttime warming effect over wind farms of up to 0.72 °C per decade over the nine years in which data was collected. Since the spatial pattern of warming mirrors the geographic distribution of wind turbines, they attribute the warming primarily to wind farms. In addition, the year-to-year land surface temperature over wind farms shows a persistent upward trend from 2003 to 2011, consistent with the increasing number of operational wind turbines with time.
“This warming effect is most likely caused by the turbulence in turbine wakes acting like fans to pull down warmer near surface air from higher altitudes at night,” stated Professor Somnath Baidya Roy at University of Illinois, Urbana-Champaign, a co-author of the study.
Overall, while the warming effect reported is local and is small compared to the strong background year-to-year land surface temperature variation, the authors suggest that this work draws attention to an important scientific issue that requires further investigation.
“It is also important to note that land surface temperature measures the temperature of the Earth’s surface, which has a stronger day-night variation than the air temperature from daily weather reports, thus the impacts on surface air temperature should be smaller,” noted Dr. Yuhong Tian, a coauthor of this study and a researcher at IMSG at NOAA/NESDIS/STAR.
“The unit of the estimated warming effect (°C per decade) is just one simple way to quantify the wind farm impacts while reducing the year-to-year data noise. The estimated warming trends only apply to the study region and to the study period, and thus should not be interpolated linearly into other regions (e.g., globally) or over longer periods (e.g., for another 20 years),” said Zhou. “For a given wind farm, once there are no new wind turbines added, the warming effect may reach a stable level.”
Several recent studies of the impact of wind farms on weather and climate have utilized numerical models due to the lack of observations over wind farms. As numerical models are computationally intensive and have uncertainties in simulating regional and local weather and climate, the authors believe remote sensing is likely the most efficient and effective way to study wind farm impacts over larger spatial and longer temporal scales.
“The study presents the first observational evidence of wind farm impacts on land surface temperature with spatial detail using satellite data. It represents a first step in exploring the potential of using satellite data to quantify the possible impacts of the development of big wind farms on weather and climate,” said Prof. Chris Thorncroft, a coauthor of this study and chair of the Department of Atmospheric and Environmental Sciences at UAlbany. “We are now expanding this approach to other wind farms and building models to understand the physical processes and mechanisms driving the interactions of wind turbines and the atmosphere boundary layer near the surface.”
“This study indicates that land surface temperatures have warmed in the vicinity of large wind farms in west-central Texas, especially at night,” says Anjuli Bamzai, program director in the National Science Foundation (NSF)’s Division of Atmospheric and Geospace Sciences, which funded the research. “The observations and analyses are for a relatively short period, from 2003 to 2011, but raise important issues that deserve attention as we move toward an era of rapid growth in wind farms in our quest for alternate energy sources.”
“Wind power is going to be a part of the solution to the climate change, air pollution and energy security problems,” said Roy. “Understanding the impacts of wind farms is critical for developing efficient adaptation and management strategies to ensure the long-term sustainability of wind power.”
The other authors for this study include Lance F. Bosart at the University at Albany, and Yuanlong Hu at Terra-Gen Power LLC, San Diego, Calif.