Impacts of wind farms on surface air temperatures

Abstract

Utility-scale large wind farms are rapidly growing in size and numbers all over the world. Data from a meteorological field campaign show that such wind farms can significantly affect near-surface air temperatures. These effects result from enhanced vertical mixing due to turbulence generated by wind turbine rotors. The impacts of wind farms on local weather can be minimized by changing rotor design or by siting wind farms in regions with high natural turbulence. Using a 25-y-long climate dataset, we identified such regions in the world. Many of these regions, such as the Midwest and Great Plains in the United States, are also rich in wind resources, making them ideal candidates for low-impact wind farms.impact assessment | regional climate model | sustainable energy | wind energy | wind power potential W ind power is one of the fastest growing energy sources in the world. Most of this growth is in the industrial sector based on large utility-scale wind farms (1). Recent studies have investigated the possible impacts of such wind farms on global and local weather and climate. Although debates exist regarding the global-scale effects of wind farms (2-5), modeling studies agree that wind farms can significantly affect local-scale meteorology (6, 7). However, these studies are based only on model simulations and are not validated against observational evidence. In this paper, we used field data and numerical experiments with a regional climate model to answer the following critical questions arising from the prior studies:i. Does observational evidence show that wind farms affect nearsurface air temperatures? ii. Can atmospheric models replicate the observed patterns of near-surface air temperatures within wind farms? iii. How can these impacts be minimized to ensure long-term sustainability of wind power? Observed Impacts of Wind FarmsAlthough observed data on wind speed and turbulence in and around operational wind farms are readily available, information on other meteorological variables do not exist in the public domain. The only available information is temperature data from a wind farm at San Gorgonio, California, collected during June 18-August 9, 1989 (Fig. 1). To the best of our knowledge, this is the only meteorological field campaign conducted in an operational wind farm. The wind farm consisted of 23-m-tall turbines with 8.5-m-long rotor blades arranged in 41 rows that were spaced 120 m apart. Data from the field campaign show that near-surface air temperatures downwind of the wind farm are higher than upwind regions during night and early morning hours, whereas the reverse holds true for the rest of the day (Fig. 2A). Thus, this wind farm has a warming effect during the night and a cooling effect during the day. The observed temperature signal is statistically significant for most of the day according to the results of a Mann-Whitney Rank Sum Test (Table 1).A possible explanation for this phenomenon can be drawn from the hypothesis proposed by Baidya Roy et al. that turbulence generated in the wake of ...

A Case Study of Land-Surface-Temperature Impact from Large-Scale Deployment of Wind Farms in China from Guazhou

“…The warming effect from wind farms at night was firstly revealed and was attributed to the turbulence generated by the rotors enhancing the vertical mixing [13]. In the stable atmosphere when a warm layer overlies a cool layer, enhanced vertical mixing mixes warm air down and cold air up, leading to a warming near the surface [12,13].…”

“…Regarding the possible impacts of wind farms on surface temperature, to date only a few studies have used the observed data from operational wind farms, such as the measurements in California [13] and in the Midwestern US [17]. The warming effect from wind farms at night was firstly revealed and was attributed to the turbulence generated by the rotors enhancing the vertical mixing [13].…”

“…A few studies show that the large-scale deployment of wind farms alters the local temperature by up to a few degrees [10,13,[15][16][17], reduces precipitation by up to 20% [18], and even mitigates extreme weather [19]. These studies are basically based on limited observation analysis [13,16,20] or model simulations [12,[21][22][23]. However, due to the lack of observations, the effects of wind farms are usually parameterized into numerical models by explicitly increasing either surface roughness length or turbulence kinetic energy [24] and the simulating results from these models do not always agree owing to the model or region adopted [25,26], especially the parameterization model of the wind farm effects.…”

“…Wind turbines could modify the surface-atmosphere exchanges by increasing surface roughness [8][9][10], changing the stability of atmospheric boundary layer (ABL) [11], enhancing turbulence in the rotor wakes [12,13], and interrupting the low-level-jet in stable ABL [14]. A few studies show that the large-scale deployment of wind farms alters the local temperature by up to a few degrees [10,13,[15][16][17], reduces precipitation by up to 20% [18], and even mitigates extreme weather [19]. These studies are basically based on limited observation analysis [13,16,20] or model simulations [12,[21][22][23].…”

The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF

“…In large wind farms, the interaction of the flow and the wind turbines is further complicated by the interaction of the wake of one wind turbine with neighbouring turbines. Besides the changed velocity field around the turbines, there is also evidence that wind turbines affect planetary boundary layer (PBL) processes due to the changed turbulence (Baidya Roy et al, 2004;Calaf et al, 2010;Baidya Roy and Traiteur, 2010;Barrie and KirkDavidoff, 2010;Wang and Prinn, 2010;Lu and Porté-Agel, 2011;Hasager et al, 2013;Fitch et al, 2013a).…”