Aerodynamic interaction of diffuser augmented wind turbines in multi-rotor systems

Göltenbott, Uli; Ohya, Yuji; Yoshida, Shigeo; Jamieson, Peter

doi:10.1016/j.renene.2017.05.014

Cited by 52 publications

(32 citation statements)

References 13 publications

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“…The center WLT #2 in SBS arrangement was influenced most strongly due to wake interference of three WLTs. It is noted that unstable behavior of gap flow between wind turbines has an effect on the performance of wind turbines similar to the studies of G€ oltenbott et al [12].…”

Section: Methodssupporting

confidence: 75%

“…That is to say, with the number of wind turbines in the system as "n," the output of the overall system is a multiple n of the output of each single wind turbine. It should be noted that improvement of such conventional multirotor systems has limitations in power output increase and provide only a small increase in efficiency on the order of at most 1-3% [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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Multirotor Systems Using Three Shrouded Wind Turbines for Power Output Increase

Watanabe

Ohya

2019

Journal of Energy Resources Technology

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Brimmed-diffuser augmented wind turbines (B-DAWTs) can significantly increase the performance of the rotor. Multirotor systems (MRSs) have a lot of merits such as significant saving mass and overall cost of the wind turbine system. In the present research, B-DAWTs are studied in a MRS. In wind tunnel experiments, the power output and aerodynamics of three B-DAWTs placed in close vicinity have been investigated. The results show a significant increase of up to 12% in total power output of the MRS with B-DAWTs compared to the sum of the stand-alone (SA) same turbines. The accelerated gap flows between B-DAWTs in a MRS cause lowered pressure regions due to vortex interaction behind the brimmed diffusers and draw more wind into turbines.

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Section: Methodssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Multirotor Systems Using Three Shrouded Wind Turbines for Power Output Increase

Watanabe

Ohya

2019

Journal of Energy Resources Technology

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“…In this preliminary study, a uniform approach-flow with turbulence intensity less than 0.5% was used in the wind-tunnel test. Wind tunnel top walls were removed in Sections 3-5 ( Figure 2) so as to minimize wind tunnel blockage effects [38,39].…”

Section: Test Facilitymentioning

confidence: 99%

Wind Turbine Wake Modeling in Accelerating Wind Field: A Preliminary Study on a Two-Dimensional Hill

Ibrahim

Yoshida

Hamasaki

et al. 2019

Fluids

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Complex terrain can influence wind turbine wakes and wind speed profiles in a wind farm. Consequently, predicting the performance of wind turbines and energy production over complex terrain is more difficult than it is over flat terrain. In this preliminary study, an engineering wake model, that considers acceleration on a two-dimensional hill, was developed based on the momentum theory. The model consists of the wake width and wake wind speed. The equation to calculate the rotor thrust, which is calculated by the wake wind speed profiles, was also formulated. Then, a wind-tunnel test was performed in simple flow conditions in order to investigate wake development over a two-dimensional hill. After this the wake model was compared with the wind-tunnel test, and the results obtained by using the new wake model were close to the wind-tunnel test results. Using the new wake model, it was possible to estimate the wake shrinkage in an accelerating two-dimensional wind field.

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“…A much more efficient solution to improve the power extraction of tidal, river or small wind generators is the diffuser, namely a device capable of increasing the local flow velocity at the turbine location. The effectiveness of diffuser augmented turbines has been investigated by several reputed authors [7][8][9][10][11][12], but its technical and economic feasibility is still debatable [13]. So far most of the studies in the literature concern horizontal axis turbines.…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations

2019

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With the aim of finding efficient solutions for cross flow turbine (CFT) bi-directional diffusers able to harvest non perfectly rectilinear tidal currents, a 2D CFD analysis of ducted CFTs was carried out with focus on the effects of diffuser shape and yaw angle. The HARVEST hydrofoil shaped diffuser, equipped with a pair of counter-rotating turbines, and a bi-directional symmetrical diffuser were compared in terms of coefficient of power (CP), torque ripple, overall thrust on diffuser and wake characteristics. Slightly better CP were predicted for the symmetrical diffuser, due to the convergent walls that address the flow towards the blade with a greater attack angle during early and late upwind and to the viscous interactions between the turbine wakes and strong vortices shed by the diffuser. A CP’s extraordinary improving resulted when yaw increased up to 22.5° for the hydrofoil shaped and up to 30° for the symmetrical diffuser. Similar behaviour in yawed flows also occurred in case of a ducted single rotor, demonstrating that it is a characteristic of CFTs. The insertion of a straight throat in the diffuser design proved to be an effective way to mitigate torque ripple, but a CP loss is expected.

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Aerodynamic interaction of diffuser augmented wind turbines in multi-rotor systems

Cited by 52 publications

References 13 publications

Multirotor Systems Using Three Shrouded Wind Turbines for Power Output Increase

Multirotor Systems Using Three Shrouded Wind Turbines for Power Output Increase

Wind Turbine Wake Modeling in Accelerating Wind Field: A Preliminary Study on a Two-Dimensional Hill

Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations

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