Michael Howland

Unsteady loading and spatiotemporal characteristics of power output are measured in a wind tunnel experiment of a microscale wind farm model with 100 porous disk models. The model wind farm is placed in a scaled turbulent boundary layer, and six different layouts, varied from aligned to staggered, are considered. The measurements are done by making use of a specially designed small-scale porous disk model, instrumented with strain gages. The frequency response of the measurements goes up to the… Show more

Unsteady loading and spatiotemporal characteristics of power output are measured in a wind tunnel experiment of a microscale wind farm model with 100 porous disk models. The model wind farm is placed in a scaled turbulent boundary layer, and six different layouts, varied from aligned to staggered, are considered. The measurements are done by making use of a specially designed small-scale porous disk model, instrumented with strain gages. The frequency response of the measurements goes up to the natural frequency of the model, which corresponds to a reduced frequency of 0.6 when normalized by the diameter and the mean hub height velocity. The equivalent range of timescales, scaled to field-scale values, is 15 s and longer. The accuracy and limitations of the acquisition technique are documented and verified with hot-wire measurements. The spatiotemporal measurement capabilities of the experimental setup are used to study the cross-correlation in the power output of various porous disk models of wind turbines. A significant correlation is confirmed between streamwise aligned models, while staggered models show an anti-correlation. Show less

Reducing wake losses in wind farms by deflecting the wakes through turbine yawing has been shown to be a feasible wind farm controls approach. Nonetheless, the effectiveness of yawing depends not only on the degree of wake deflection but also on the resulting shape of the wake. In this work, the deflection and morphology of wakes behind a porous disk model of a wind turbine operating in yawed conditions are studied using wind tunnel experiments and uniform inflow. First, by measuring velocity… Show more

Reducing wake losses in wind farms by deflecting the wakes through turbine yawing has been shown to be a feasible wind farm controls approach. Nonetheless, the effectiveness of yawing depends not only on the degree of wake deflection but also on the resulting shape of the wake. In this work, the deflection and morphology of wakes behind a porous disk model of a wind turbine operating in yawed conditions are studied using wind tunnel experiments and uniform inflow. First, by measuring velocity distributions at various downstream positions and comparing with prior studies, we confirm that the non-rotating porous disk wind turbine model in yaw generates realistic wake deflections. Second, we characterize the wake shape and make observations of what is termed as curled wake, displaying significant spanwise asymmetry. The wake curling observed in the experiments is also reproduced qualitatively in Large Eddy Simulations using both actuator disk and actuator line models. Results suggest that when a wind turbine is yawed for the benefit of downstream turbines, the curled shape of the wake and its asymmetry must be taken into account since it affects how much of it intersects the downstream turbines. Show less

In this study porous disc models are used as a wind turbine model for a wind-tunnel wind
farm experiment, allowing the measurement of the power output, thrust force and spatially
averaged incoming velocity for every turbine. The model's capabilities for studying the
unsteady turbine loading, wind farm power output intermittency and spatio temporal
correlations between wind turbines are demonstrated on an aligned wind farm, consisting of
100 wind turbine models.

With the DOE 20% by 2030 scenario for wind capacity, wind penetration is on the rise, and intermittency of this energy resource must be addressed since it hurts grid reliability and increases ancillary service needs. To cope with the rising variability, this study analyzed the effects of wind control, specifically absolute power rate limitation (ramping control). A ramping constraint was modeled to cap the increase in energy output of a wind generation unit for a minute interval, simulated… Show more

With the DOE 20% by 2030 scenario for wind capacity, wind penetration is on the rise, and intermittency of this energy resource must be addressed since it hurts grid reliability and increases ancillary service needs. To cope with the rising variability, this study analyzed the effects of wind control, specifically absolute power rate limitation (ramping control). A ramping constraint was modeled to cap the increase in energy output of a wind generation unit for a minute interval, simulated using the IEEE 24 bus system. Results of this study include a decrease in variability of the wind output, a decrease in the ancillary service regulation requirement, a decrease in the production cost of the system, a decrease in de-commitments of coal-fired power plants, and a decrease in cycling cost of the system. Show less