September 24, 2021

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WESEP: Wind Energy Science, Engineering, and Policy

Wind Resource Characterization and Aerodynamics of Wind Farms

Thrust Goal and Connection to Project Objectives

The goal of this thrust is to advance the national aim of increasing the production of renewable energy by enhancing the cost effectiveness of installed wind farms through improved characterization of wind resources, addressing RO2, and by expanding the penetration of wind power in the U.S. via better understanding multiple land uses in high-producing agricultural areas, addressing RO3.

Background and Need for Research

The national goal of achieving 20% of the U.S. energy supply from wind by 2030 puts a high demand on wind energy production in the Central U.S. Achieving this goal requires more efficient use of current production (i.e., better forecasting of future generation), better siting and turbine characteristics (height, wind turbine layout) of future wind farms, and public acceptance of expanded wind farm deployment into areas of high value existing land use (e.g., by understanding the interactions with agricultural crops).

Our attention is focused on key issues identified in a U.S. DOE workshop on resource characterization turbine dynamics, micrositing and array effects, mesoscale processes, and climate effects. In addition, high wind penetration in the Central U.S. requires public acceptance of wind farms in regions already having a land use commitment of high national importance—the production of food, feed, and biofuels. We will address these issues by using a combination of three research methods: (1) mesoscale meteorology and large eddy simulation models built on first principles, (2) physical simulations in wind tunnels of the atmospheric boundary layer (ABL) on various terrains to study its interaction with wind farms to optimize power output, and (3) field measurements of ABL wind profiles and surface layer mean and turbulence fields and vertical fluxes of heat, moisture, momentum, and carbon dioxide. The complex issues we address call for interdisciplinary approaches involving engineers, meteorologists, agronomists, sociologists, and economists, and a close working relationship with our European colleagues who have been studying some of these issues for the last ten years.

Dissertation Project Examples

Improving wind speed forecasting with lead times of 0-54 hr: Alternative forecasting techniques employing multiple mesoscale models combined with advanced statistical analyses will be used to improve forecasts in the time window of highest economic value for power sales.

Cost effectiveness of taller towers for extracting energy from the low-level jet: Wind resources at elevations of ~140 m are substantially higher than those at current turbine hub height (~80 m) due both to a general increase in speeds with height and an enhanced increase on occasion due to the presence of the Low-Level Jet. Because the costs for construction and maintenance also will be higher, a combined meteorological/economic analysis is needed to evaluate this potential.

Wind farm siting and wind turbine interaction within a wind farm: The Aerodynamic/Atmospheric Boundary Layer (AABL) Wind and Gust Tunnel at Iowa State University will be used to generate an AABL in flat and complex terrains to study the wind flow characteristics (e.g., vertical wind speed profiles, turbulence, wake) with and without wind turbines as well as turbine interactions. Flow measurements with a multi-hole Omni probe and Particle Image Velocimetry (PIV) will reveal the influence of upstream terrain, turbine blades and surrounding turbines for use in wind farm siting, optimization of wind power generation and calculation of wind loads on turbine components. Large eddy simulations, validated with wind tunnel data, and complemented with field measurements in local operating wind farms in our neighborhood using Lidar will help provide a comprehensive strategy for wind farm siting and turbine interactions.

Interactions of turbine-generated turbulence with agricultural crops: Turbulence from turbines can change the temperature, humidity, and fluxes of heat, moisture, momentum and CO2 concentrations over crop canopies.  The impact of this on the productivity of crops is unknown. Field measurements are needed to refine surface-layer models for evaluating season-accumulated impacts.

Key Faculty