Research Papers: Alternative Energy Sources

Wind Tower System With a Helical Wind Deflecting Structure, Computational Fluid Dynamics, and Experimental Studies

[+] Author and Article Information
Majid Rashidi

Cleveland State University,
Cleveland, OH 44115
e-mail: m.rashidi@csuohio.edu

Jaikrishnan R. Kadambi

Case Western Reserve University,
Cleveland, OH 44106
e-mail: jrkadambi@case.edu

David Kerze

Gorman-Lavelle Corporation,
Cleveland, OH 44127
e-mail: dkerze@Gorman_Lavelle.com

Contributed by the Advanced Energy Systems Division of ASME for publication in the Journal of Energy Resources Technology. Manuscript received April 22, 2013; final manuscript received July 23, 2013; published online October 17, 2013. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 136(2), 021202 (Oct 17, 2013) (7 pages) Paper No: JERT-13-1135; doi: 10.1115/1.4025409 History: Received April 22, 2013; Revised July 23, 2013

A wind tower system having a three dimensional heliacal wind deflecting structure is studies in this work. The purpose of the helical structure is to increase the natural wind speed and direct the follow of the wind toward two columns of horizontal-axis rooftop-size wind turbines that are installed in the grooves of the helical structure, diametrically opposed to each other. Computational fluid dynamics analyses were conducted to determine the influence of the helical structure on the wind speed reaching the turbines. A wind speed amplification coefficient was determined for a helical structure of 6.7 m outer diameter. The velocity profiles of the wind flow around the helical structure were determined under a postulated wind speed of 4.47 m/s. The flow was modeled as turbulent with a Reynolds Number of 2,052,167. Standard “k–ε” turbulent model with “near wall treatment” and “standard wall function” were adapted in all analysis. A “y+” value of 50 was held constant in all simulation. The grid-size effects on the accuracy of the results were examined. Convergence criterion was satisfied in each case. This study shows that the helical structure having an outer diameter of 6.7 m results in an average wind speed increase factor of 1.52. An experimental wind tower system was fabricated and installed at an elevation of 40 m above the ground. The wind tower system comprised of four identical rooftop size wind turbines, each having 1.6 KW name-plate-rating. A helical wind deflecting structure of 11 m tall, and 7 m in major diameter was used in fabrication of the tower. An active yaw-control mechanism was used to orient the tower into the prevailing wind. The experimental results show that as the result of the use of the wind deflecting structure, an average power amplification factor of 4.69 was obtained for the tower, in comparison with the standard standalone installation of the four wind turbines.

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Fig. 1

An innovative wind tower with a helical shape wind deflecting structure

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Fig. 2

A front view of the tower

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Fig. 3

A longitudinal cross-section of the tower

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Fig. 4

Stationary steel structure for supporting of the yaw-able wind-deflecting shell

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Fig. 5

Construction of the helical structure from multitude of the same panel

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Fig. 6

Domain sizing; (Kulkarni and Moeykens [6])

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Fig. 7

2D cylinder under inviscid flow regime

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Fig. 8

2D cylinder, structured grid, entire domain

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Fig. 9

Close-up of the 2D cylinder, structured grid

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Fig. 10

2D cylinder, scaled residuals (inviscid flow)

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Fig. 11

Structured to unstructured grid transition

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Fig. 12

Close-up of the unstructured grid

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Fig. 13

Elevation details of the unstructured grid

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Fig. 14

Velocity magnitude on a longitudinal plane intersecting the tower (k–ε turbulence model)

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Fig. 15

Velocity magnitude on a transverse plane intersecting the tower (k–ε turbulence model)

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Fig. 16

Velocity distribution across a 2-m diameter window in the wind speed amplified zone

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Fig. 17

A picture of the experimental set up

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Fig. 18

Power Curve of a typical the wind turbine for a standalone installation




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