Abstract
The collocation of cropland and wind turbines in the US Midwest region introduces complex meteorological interactions that could influence both agriculture and wind-power production. Crop management practices may affect the wind resource through alterations of land-surface properties. We use the weather research and forecasting (WRF) model to estimate the impact of crop height variations on the wind resource in the presence of a large turbine array. A hypothetical wind farm consisting of 121 1.8-MW turbines is represented using the WRF model wind-farm parametrization. We represent the impact of selecting soybeans rather than maize by altering the aerodynamic roughness length in a region approximately 65 times larger than that occupied by the turbine array. Roughness lengths of 0.1 and 0.25 m represent the mature soy crop and a mature maize crop, respectively. In all but the most stable atmospheric conditions, statistically significant hub-height wind-speed increases and rotor-layer wind-shear reductions result from switching from maize to soybeans. Based on simulations for the entire month of August 2013, wind-farm energy output increases by 14 %, which would yield a significant monetary gain. Further investigation is required to determine the optimal size, shape, and crop height of the roughness modification to maximize the economic benefit and minimize the cost of such crop-management practices. These considerations must be balanced by other influences on crop choice such as soil requirements and commodity prices.
Highlights
The abundance of realized and potential wind-power resources in the agriculture-intensive Midwest and Great Plains regions of the USA stimulates discussion on the interactions between wind farms and cropland (Baidya Roy and Traiteur 2010; Rajewski et al 2013)
4-month-long simulations are produced spanning August 2013. (Recall, August was chosen as the month with the most significant differences between the heights and roughness lengths of the crops.) The first two simulations compare the effect of maize versus soybean surface roughness in an atmosphere undisturbed by the presence of a wind farm
The second set of simulations represent this crop effect in the presence of the hypothetical wind farm, which itself modifies winds aloft by extracting momentum from the flow and generating additional turbulence. Data from these four simulations are identified with the following abbreviations: FSM for freestream maize, FSS for freestream soybeans, WFM for wind-farm maize, and WFS for wind-farm soybeans. This suite of simulations allows us to determine whether the wind farm contributes to and/or inhibits the roughness effect in a significant way, and whether or not the effect of the surface is still distinguishable in the presence of a wind farm
Summary
The abundance of realized and potential wind-power resources in the agriculture-intensive Midwest and Great Plains regions of the USA stimulates discussion on the interactions between wind farms and cropland (Baidya Roy and Traiteur 2010; Rajewski et al 2013). As interest in wind power grows, the effects of wind-farm development on regional and global climate have been simulated by modifying the roughness lengths used in atmospheric models (Ivanova and Nadyozhina 2000; Keith et al 2004; Kirk-Davidoff and Keith 2008; Barrie and Kirk-Davidoff 2010; Wang and Prinn 2010, 2011). These studies attempt to quantify the aggregate effect of turbines on the large-scale wind field, boundary-layer temperature and precipitation.
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