Power curve and wake analyses of the Vestas multi-rotor demonstrator

Laan, P. van der; Andersen, Søren Juhl; Ramos‐García, Néstor; Angelou, Nikolas; Pirrung, Georg Raimund; Ott, Søren; Sjöholm, Mikael; Sørensen, Kim Hylling; Neto, Júlio Xavier Vianna; Kelly, Mark; Mikkelsen, Torben; Larsen, Gitte

doi:10.5194/wes-4-251-2019

Cited by 63 publications

(49 citation statements)

References 33 publications

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“…(3), d should be equal to 40m for the MR4 case. The value of rotor spacing s is selected to be 0.1d, inspired by the multi-rotor turbine concept demonstrator previously installed by Vestas Wind Systems A/S at DTU Risø campus 13 .…”

Section: A Detailed Comparison Of Turbine Wakes: Mr Versus Sr Turbinesmentioning

confidence: 99%

“…Moreover, due to the representation of turbines using the standard actuator-disk model, effects of turbine-induced flow rotation were dismissed. Recently, van der Laan et al 13 have studied the wake flow behind the multi-rotor turbine demonstrator installed by Vestas Wind Systems A/S. In particular, using Reynolds-averaged Navier-Stokes (RANS) simulations, they showed that the multi-rotor wind turbine wake recovers faster compared to the wake of a single-rotor wind turbine with an equivalent rotor diameter.…”

Section: Introductionmentioning

confidence: 99%

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Multirotor wind turbine wakes

Bastankhah

Abkar

2019

Physics of Fluids

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To fulfill the increasing need for large power generation by wind turbines, the concept of multi-rotor wind turbines has recently received attention as a promising alternative to conventional massive single-rotor wind turbines. To shed light on the viability of this concept, large-eddy simulation is employed in this study to compare wake flow properties of a multi-rotor wind turbine with those of a single-rotor turbine. The wake of a multi-rotor turbine is found to recover faster at short downwind distances, where the whole wake is characterized as an array of localized high velocity-deficit regions associated with each rotor. However, as the wake moves downstream, rotor wakes start interacting with each other until they eventually form a single wake. This transition from a wake array to a single wake adversely affects the initial fast recovery of multirotor turbine wakes. A budget analysis of mean kinetic energy is performed to analyze the energy transport into the wake before and after this transition. In addition, the effect of different geometrical configurations on wake characteristics of a multi-rotor turbine was examined. We found that the recovery rate of multi-rotor turbine wakes is enhanced by the increase of rotor spacing, whereas the number and rotation direction of rotors do not play a significant role in the wake recovery. A simple analytical relationship is also developed to predict the streamwise distance at which the transition from a wake array to a single wake occurs for multi-rotor wind turbines.

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Section: A Detailed Comparison Of Turbine Wakes: Mr Versus Sr Turbinesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multirotor wind turbine wakes

Bastankhah

Abkar

2019

Physics of Fluids

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show abstract

“…Studies from the INNWIND project showed the potential of a 20 MW MRS with 45 rotors to reduce the levelized cost of energy (LCoE) compared to a power equivalent single rotor (SR) (Jamieson et al, 2017). Recent results from Vestas' four rotor MRS demonstrator revealed advantages in aerodynamic efficiency and in wake recovery when compared to a SR (van der Laan et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Simplified support structure design for multi rotor wind turbine systems

Störtenbecker¹,

Dalhoff²,

Tamang³

et al. 2020

Preprint

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Abstract. In this study different multi rotor wind turbine systems (MRSs) will be designed in such a way that the space frame, forming the connection between rotor nacelle assemblies (RNAs) and tower, will be modeled as an ideal truss work. To dimension the tube diameters and wall thicknesses, a simplified load case will be used with an adjusted safety factor for loads. This simplified approach allows fast computations of a large variety of different support structure designs. By variation of rotor number, space frame topology, space frame depth and the positioning of yaw bearings, it is possible to gain an understanding of the optimal MRS design. As such, the simplified approach is a preliminary step helping to choose a good design parameter combination for a more detailed and comprehensive analysis.

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“…Thus, a constant and uniform thrust coefficient is applied to all four rotors of the 4-rotor turbine. The controller adopted in van der Laan et al (2019), on the other hand, allowed for small variations of up to 5 % in the thrust coefficients of the lower and upper rotors. Second, the dimensions 60 of the turbines are different in the two studies.…”

mentioning

confidence: 99%

“…Second, the dimensions 60 of the turbines are different in the two studies. Assuming a typical value of 1000 m for the boundary layer height, the rotors of the 4-rotor turbines in the present study have a diameter of 50 m, which is approximately 1.7 times that of the 4R-V29 turbine considered in van der Laan et al (2019). Finally, only isolated 4-rotor turbines are considered in van der Laan et al (2019), while interactions between multiple 4-rotor turbines is studied in this paper.…”

mentioning

confidence: 99%

Effect of tip spacing, thrust coefficient and turbine spacing inmulti-rotor wind turbines and farms

Ghaisas¹,

Ghate²,

Lele³

2019

Preprint

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Large eddy simulations (LES) are performed to study the wakes of a multi-rotor wind turbine configuration comprising of four identical rotors mounted on a single tower. The multi-rotor turbine wakes are compared to the wake of a conventional turbine comprising of a single rotor per tower with the same frontal area, hub height and thrust coefficient. The multi-rotor turbine wakes are found to recover faster, while the turbulence intensity in the wake is smaller, compared to the wake of the conventional turbine. The differences with the wake of a conventional turbine increase as the spacing between the 5 tips of the rotors in the multi-rotor configuration increases. The differences are also sensitive to the thrust coefficients used for all rotors, with more pronounced differences for larger thrust coefficients. The interaction between multiple multi-rotor turbines is contrasted with that between multiple single-rotor turbines by considering wind farms with five turbine units aligned perfectly with each other and with the wind direction. Similar to the isolated turbine results, multi-rotor wind farms show smaller wake losses and smaller turbulence intensity compared to wind farms comprised of conventional single-rotor turbines. The 10 benefits of multi-rotor wind farms over single-rotor wind farms increase with increasing tip spacing, irrespective of the axial spacing and thrust coefficient. The mean velocity profiles and relative powers of turbines obtained from the LES results are predicted reasonably accurately by an analytical model assuming Gaussian radial profiles of the velocity deficits and a hybrid linear-quadratic model for merging of wakes. These results show that a larger planform energy flux can be achieved without significantly increased fatigue loads by using multi-rotor turbines instead of conventional, single-rotor turbines.

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Power curve and wake analyses of the Vestas multi-rotor demonstrator

Cited by 63 publications

References 33 publications

Multirotor wind turbine wakes

Multirotor wind turbine wakes

Simplified support structure design for multi rotor wind turbine systems

Effect of tip spacing, thrust coefficient and turbine spacing inmulti-rotor wind turbines and farms

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