The SWiFT Benchmarks

The blind comparison exercise has now been completed, and the results submitted for publication. For more data/info, go to the GitHub repository. For past presentations, consult Timeline. If you are planning a benchmark, check out Lessons Learned.


Figure: The DOE SWiFT facility in Lubbock, Texas

What is SWiFT?

The Scaled Wind Farm Technology (SWiFT) facility supports open-source research and technology innovation in the field of wind-turbine and wind-plant aerodynamics. The facility is funded by the United States (U.S.) Department of Energy (DoE), and is operated by Sandia National Laboratories, hosted at Texas Tech University’s National Wind Institute Research Center in Lubbock, Texas. All data collected at SWiFT through the wake-steering experiment are freely available through the DoE Data Archive Portal (DAP).

Atmospheric Conditions at the SWiFT Facility

The SWiFT site is located in the U.S. Great Plains and is therefore exempt from complex, terrain-induced flow patterns. In the absence of weather phenomena (e.g., fronts, storms), the atmospheric conditions at the SWiFT site approximate canonical diurnal cycles. The relative simplicity of atmospheric conditions at the site make it a valuable resource for research in complex turbulent flows such as wind-turbine wakes. In other words, the mean and dynamic characteristics of wakes and their effect on downstream turbines can be considered without the influence of complex terrain and weather. For more detail on the atmospheric conditions at this site, see Kelley and Ennis (2016).

Wind Turbines at the SWiFT Facility

The facility hosts 3 variable-speed, variable-pitch, modified Vestas V27 wind turbine generators (WTGs). These are substantially smaller than utility-scale WTGs (i.e., rotor diameter is 27 m and hub height is 32.1 m), facilitating the deployment of instrumentation and reducing the cost of conducting experiments and testing new technology. One of the ongoing research areas around SWiFT is the impact of rotor scale on the interaction of wake phenomenon with the atmosphere.

Instrumentation at the SWiFT Facility

The largest wind-energy experiment conducted at the SWiFT site to date is the “wake-steering experiment”. In 2016 and 2017, the upstream WTG was intentionally yawed into and out of the wind in order to steer the propagation direction of its wake. This deliberate control of the wake has a direct effect on the power and loads of both WTGs. The data used to define this benchmark were collected during this experiment. A meteorological tower collected freestream atmospheric measurements and a rear-facing, nacelle-mounted scanning lidar mesured the wake. In addition, power and loads measurements were collected at the wake-producing WTG and the wake-bearing WTG.

The Benchmarks

Researchers at the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (SNL) have worked together to define three benchmarks for validation of wind-turbine wake simulations:

If possible, participants are encouraged to engage in all benchmarks in order to investigate the performance of their simulation tool under different stratification scenarios. Participants using steady-state models are limited to the evolution benchmarks: Wake Evolution in a Nearly Neutral Atmosphere and Wake Evolution in a Stable Atmosphere.


Each benchmark has 3 phases:

  1. Code calibration
    First, the atmospheric inflow and turbine response are compared to a subset of the measurements.
  2. Blind comparison
    • Code-to-code comparison: Simulation results from all participants are cross-compared, to identify potential mistakes in model configuration.
    • Code-to-data comparison: Simulation results from all participants are compared to the measurement data.
  3. Iteration
    Participants are encouraged to revise their simulations and perform their own comparison with the measurement data.

Each phase will be carried out concurrently for the three benchmarks, according to this Timeline.

Data Accessibility

The benchmark is open to all participants of the International Energy Agency (IEA) Wind Task 31.


Christopher Lee Kelley and Brandon Lee Ennis, “SWiFT Site Atmospheric Characterization” (Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States), 2016),