Articles | Volume 17, issue 23
Research article
01 Dec 2017
Research article |  | 01 Dec 2017

Spatiotemporal distribution of nitrogen dioxide within and around a large-scale wind farm – a numerical case study

Jingyue Mo, Tao Huang, Xiaodong Zhang, Yuan Zhao, Xiao Liu, Jixiang Li, Hong Gao, and Jianmin Ma

Abstract. As a renewable and clean energy source, wind power has become the most rapidly growing energy resource worldwide in the past decades. Wind power has been thought not to exert any negative impacts on the environment. However, since a wind farm can alter the local meteorological conditions and increase the surface roughness lengths, it may affect air pollutants passing through and over the wind farm after released from their sources and delivered to the wind farm. In the present study, we simulated the nitrogen dioxide (NO2) air concentration within and around the world's largest wind farm (Jiuquan wind farm in Gansu Province, China) using a coupled meteorology and atmospheric chemistry model WRF-Chem. The results revealed an edge effect, which featured higher NO2 levels at the immediate upwind and border region of the wind farm and lower NO2 concentration within the wind farm and the immediate downwind transition area of the wind farm. A surface roughness length scheme and a wind turbine drag force scheme were employed to parameterize the wind farm in this model investigation. Modeling results show that both parameterization schemes yield higher concentration in the immediate upstream of the wind farm and lower concentration within the wind farm compared to the case without the wind farm. We infer this edge effect and the spatial distribution of air pollutants to be the result of the internal boundary layer induced by the changes in wind speed and turbulence intensity driven by the rotation of the wind turbine rotor blades and the enhancement of surface roughness length over the wind farm. The step change in the roughness length from the smooth to rough surfaces (overshooting) in the upstream of the wind farm decelerates the atmospheric transport of air pollutants, leading to their accumulation. The rough to the smooth surface (undershooting) in the downstream of the wind farm accelerates the atmospheric transport of air pollutants, resulting in lower concentration level.

Short summary
Wind power is known as one of the cleanest energies. However, wind farms can alter surface characters and meteorological conditions and can affect pollutant distribution around there. We reported an "edge effect" of air pollutants within and around a wind farm, higher concentrations of air pollutants in the adjacent upwind and border regions of a wind farm, and lower concentrations within and in the immediate downwind region. This will provide useful information for air quality forecasting.
Final-revised paper