Wind farm blockage effects: comparison of different engineering models

Branlard, Emmanuel; Quon, Eliot; Forsting, Alexander Meyer; King, Jennifer; Moriarty, Patrick

doi:10.1088/1742-6596/1618/6/062036

Cited by 29 publications

(29 citation statements)

References 11 publications

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“…Traditionally, wind farm models employed in the wind energy industry assumed that the wind speed upstream of an entire wind farm was unaffected by the presence of the wind farm itself. Now this assumption is known to be incorrect, and several correction methods to account for the wind farm blockage have been proposed in the last few years [4,5]. However, none of the existing correction methods are universal or robust enough to predict the wind farm blockage effect accurately under different conditions.…”

Section: Introductionmentioning

confidence: 99%

Time-Dependent Upper Limits to the Performance of Large Wind Farms Due to Mesoscale Atmospheric Response

2021

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A prototype of a new physics-based wind resource assessment method is presented, which allows the prediction of upper limits to the performance of large wind farms (including the power loss due to wind farm blockage) in a site-specific and time-dependent manner. The new method combines the two-scale momentum theory with a numerical weather prediction (NWP) model to assess the “extractability” of wind, i.e., how high the wind speed at a given site can be maintained as we increase the number of turbines installed. The new method is applied to an offshore wind farm site in the North Sea to demonstrate that: (1) Only a pair of NWP simulations (one without wind farm and the other with wind farm with an arbitrary level of flow resistance) are required to predict the extractability. (2) The extractability varies significantly from time to time, which may cause more than 30% of change in the upper limit of the performance of medium-to-high-density offshore wind farms. These results suggest the importance of considering not only the natural wind speed but also its extractability in the prediction of (both long- and short-term) power production of large wind farms.

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Section: Introductionmentioning

confidence: 99%

Time-Dependent Upper Limits to the Performance of Large Wind Farms Due to Mesoscale Atmospheric Response

2021

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“…The importance of blockage, most often defined as the slowdown of streamwise velocity in the region upstream from a turbine or farm, has received increased attention for reasons ranging from the impact on wildlife (Quon et al, 2021) to the discrepancy between predicted and observed power in newly-constructed plants (Bleeg et al, 2018). Previous work has examined engineering models to capture the effects of blockage (Branlard et al, 2020). Formalizing a method to measure this blockage effect in a manner that facilitates layout optimization enables turbine array designs that balance total power output while also mitigating the impact on upstream conditions.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the effect of blockage for wind farm layout optimization

Young

Allen

Jasa

et al. 2022

Preprint

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Abstract. Wind plant blockage is a phenomenon where the presence of a large wind farm creates a disturbance to air flow external to the farm itself that is not accounted for by wake effects. This is typically manifested as a slowdown in wind velocity upstream from a plant, which can be shown to decrease power production. Knowing a priori how a wind farm's layout will generate blockage could help to improve the accuracy of AEP calculations and suggest more blockage-optimal turbine layouts. In this study, we consider the effect of wind plant blockage and perform multiple types of layout optimization to reduce blockage while solving the flow physics using computational fluid dynamics. We present a variety of methods to quantify this blockage effect, ranging from localized measurements taken in the proximity of each turbine to farm-wide integral measurements designed to capture the velocity decrease in a more global way. We then investigate each blockage metric using simple case studies designed to isolate effects due to layout changes. While all metrics show sensitivity during this testing, the integral metrics better avoid spurious effects due to waking and are better suited to evaluating blockage which we find to be a cumulative effect. We then perform multiple farm layout optimizations using these blockage metrics as objectives and find that in the absence of a power production constraint the optimized layouts tend to minimize disturbance to the surrounding flow by creating streamwise rows of turbines. Finally, we present a power-constrained layout optimization which explicitly illustrates the trade-off between designing for blockage and power. This work presents a variety of different blockage definitions and offers a set of recommendations regarding their deployment, expected behavior, and viability for consideration as part of layout planning.

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“…Presently, there are attempts to incorporate the blockage effect in the engineering models. The four models reviewed by Branlard et al [5] consider the blockage effect through modeling the speed from the induction zone. Segalini [6] creates a new model that includes the blockage effect, which is based on the linearized RANS equation.…”

Section: Introductionmentioning

confidence: 99%

A Study of Blockage Effects at the Wind Turbine and Wind Farm Scales

Popescu

Flåtten

2021

Energies

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The paper provides novel insights into the physics behind the wind turbine and wind farm blockages as well as their effects on the energy yield based on the momentum and energy balance. The current work presents blockage effects at two scales: the local scale and the wind farm scale. We clarify the combined effect of local blockages when more than one turbine is present. The work demonstrates why two turbines, which are positioned one behind the other, induce a mutual decrease in energy yield. When the turbines are placed in a row, there is an increase of energy from the end to the middle of the row because of the restriction of the expansion flow. As in the case of two turbines placed behind each other, back rows induce a power decrease for the rows in front of them and the effect increases from the edge to the center. The work also elucidates for the first time how the power output of an isolated row has a maximum in the center, whereas, in a wind farm, wind turbines on the edge of the first row could have maximum power. The findings are supported by CFD.

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Wind farm blockage effects: comparison of different engineering models

Cited by 29 publications

References 11 publications

Time-Dependent Upper Limits to the Performance of Large Wind Farms Due to Mesoscale Atmospheric Response

Time-Dependent Upper Limits to the Performance of Large Wind Farms Due to Mesoscale Atmospheric Response

Quantifying the effect of blockage for wind farm layout optimization

A Study of Blockage Effects at the Wind Turbine and Wind Farm Scales

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