Wind energy, together with other renewable energy sources, are expected to grow substantially in the coming decades and play a key role in mitigating climate change and achieving energy sustainability. One of the main challenges in optimizing the design, operation, control, and grid integration of wind farms is the prediction of their performance, owing to the complex multiscale two-way interactions between wind farms and the turbulent atmospheric boundary layer (ABL). From a fluid mechanical perspective, these interactions are complicated by the high Reynolds number of the ABL flow, its inherent unsteadiness due to the diurnal cycle and synoptic-forcing variability, the ubiquitous nature of thermal effects, and the heterogeneity of the terrain. Particularly important is the effect of ABL turbulence on wind-turbine wake flows and their superposition, as they are responsible for considerable turbine power losses and fatigue loads in wind farms. These flow interactions affect, in turn, the structure of the ABL and the turbulent fluxes of momentum and scalars. This review summarizes recent experimental, computational, and theoretical research efforts that have contributed to improving our understanding and ability to predict the interactions of ABL flow with wind turbines and wind farms.

https://link.springer.com/content/pdf/10.1007/s10546-019-00473-0.pdf

Wind-Turbine and Wind-Farm Flows: A Review

A framework for preliminary large-scale urban wind energy potential assessment: Roof-mounted wind turbines

Winglet design for vertical axis wind turbines based on a design of experiment and CFD approach

Large eddy simulation (LES) is coupled with a turbine model to study the structure of the wake behind a vertical-axis wind turbine (VAWT). In the simulations, a tuning-free anisotropic minimum diss...

Self-similarity and flow characteristics of vertical-axis wind turbine wakes: an LES study

Atmospheric boundary-layer dynamics over heterogeneous surfaces is significant to a wide array of geophysical and engineering applications. Yet, despite over five decades of intense efforts by the research community, numerous open research questions remain. This underlines the complexity of the physical processes that are excited by heterogeneity, the multitude of patterns and manifestations that it can display, and the importance of the implications to research in the atmospheric sciences and beyond. Here, existing knowledge is reviewed and a path forward for research is proposed, starting with the smaller scales near a surface transition and proceeding to the influence on large-scale dynamics and their forecasting.

The Persistent Challenge of Surface Heterogeneity in Boundary-Layer Meteorology: A Review

Vertical-axis wind turbines (VAWTs) are being reconsidered as a complementary technology to the more widely used horizontal-axis wind turbines (HAWTs) due to their unique suitability for offshore deployments. In addition, field experiments have confirmed that vertical-axis wind turbines can interact synergistically to enhance the total power production when placed in close proximity. Here, we use an actuator line model in a large-eddy simulation to test novel VAWT farm configurations that exploit these synergistic interactions. We first design clusters with three turbines each that preserve the omni-directionality of vertical-axis wind turbines, and optimize the distance between the clustered turbines. We then configure farms based on clusters, rather than individual turbines. The simulations confirm that vertical-axis wind turbines have a positive influence on each other when packed in well-designed clusters: such configurations increase the power generation of a single turbine by about 10 percent. In addition, the cluster designs allow for closer turbine spacing resulting in about three times the number of turbines for a given land area compared to conventional configurations. Therefore, both the turbine and wind-farm efficiencies are improved, leading to a significant increase in the density of power production per unit land area.

/pdf/increasing-the-power-production-of-vertical-axis-wind-npr2la603f.pdf

Increasing the Power Production of Vertical-Axis Wind-Turbine Farms Using Synergistic Clustering

Because of several design advantages and operational characteristics, particularly in offshore farms, vertical axis wind turbines (VAWTs) are being reconsidered as a complementary technology to horizontal axial turbines. However, considerable gaps remain in our understanding of VAWT performance since cross-flow rotor configurations have been significantly less studied than axial turbines. This study examines the wakes of VAWTs and how their evolution is influenced by turbine design parameters. An actuator line model is implemented in an atmospheric boundary layer large eddy simulation code, with offline coupling to a high-resolution blade-scale unsteady Reynolds-averaged Navier–Stokes model. The large eddy simulation captures the turbine-to-farm scale dynamics, while the unsteady Reynolds-averaged Navier–Stokes captures the blade-to-turbine scale flow. The simulation results are found to be in good agreement with three existing experimental datasets. Subsequently, a parametric study of the flow over an isolated VAWT, carried out by varying solidities, height-to-diameter aspect ratios and tip speed ratios, is conducted. The analyses of the wake area and velocity and power deficits yield an improved understanding of the downstream evolution of VAWT wakes, which in turn enables a more informed selection of turbine designs for wind farms. Copyright © 2016 John Wiley & Sons, Ltd.

Simulation and wake analysis of a single vertical axis wind turbine

We analyze kinetic energy (KE) transport allowing wind speed recovery behind a row of wind turbines, showing that KE replenishment is significant after about the 6th row. Before that there is net negative transport out of the turbine layer, and initial advection of KE is the main energy source.

Mean kinetic energy replenishment mechanisms in vertical-axis wind turbine farms

.............................................................................................................................. ii Acknowledgements ............................................................................................................ iv List of Figures ..................................................................................................................... x List of Tables ................................................................................................................... xiv Chapter One ........................................................................................................................ 1

Large Eddy Simulation of Vertical Axis Wind Turbines

http://absimage.aps.org/image/DFD13/MWS_DFD13-2013-000392.pdf

Seyed Hossein Hezaveh

Papers

Increasing the Power Production of Vertical-Axis Wind-Turbine Farms Using Synergistic Clustering

Simulation and wake analysis of a single vertical axis wind turbine

Mean kinetic energy replenishment mechanisms in vertical-axis wind turbine farms

Large Eddy Simulation of Vertical Axis Wind Turbines

Large eddy simulations of vertical axis wind turbines to optimize farm design