The X-Rotor Offshore Wind Turbine Concept

Leithead, W.E.; Camciuc, Arthur; Amiri, Abbas Kazemi; Carroll, J. Douglas

doi:10.1088/1742-6596/1356/1/012031

Cited by 27 publications

(57 citation statements)

References 5 publications

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“…Secondary rotors have not been used on an operational wind turbine although a design is now being developed (Leithead et al, 2019). The main aim in using secondary rotors is to have a drivetrain with much reduced design torque compared to the usual transmission system based on power takeoff from a central shaft.…”

Section: Discussionmentioning

confidence: 99%

“…The preliminary evaluation of the X-rotor VAWT design (Leithead et al, 2019) suggests that use of secondary rotors will lead to more competitive VAWT designs. Another innovative VAWT design, the DeepWind VAWT of Paulsen et al (2015), has major savings through integration of the rotor blade shaft and support structure into a single element.…”

Section: Discussionmentioning

confidence: 99%

“…This is a huge increase in steady operational loading compared to conventional design. Also the steady and turbulent components of the ambient wind speed will introduce cyclic and random disturbances to secondary-rotor inflow, which may increase available power (Leithead et al, 2019) but will inevitably introduce fatigue loading. Now it is vital for the secondary rotors to minimise parasitic drag in the hub region as torque from this will absorb power from the primary rotor that cannot be recovered.…”

Section: Design Characteristics Of Secondary Rotorsmentioning

confidence: 99%

“…Jamieson (2011) highlighted it as a possible solution to the design challenge faced by large vertical-axis wind turbines (VAWTs), where a very low optimum speed leads to high drivetrain torque, weight and cost if the power is extracted in the most usual way from the central shaft. Leithead et al (2019) employed secondary rotors for power take-off in an innovative X-rotor VAWT design.…”

Section: Introductionmentioning

confidence: 99%

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Top-level rotor optimisations based on actuator disc theory

Jamieson

2020

Wind Energ. Sci.

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Abstract. Ahead of the elaborate rotor optimisation modelling that would support detailed design, it is shown that significant insight and new design directions can be indicated with simple, high-level analyses based on actuator disc theory. The basic equations derived from actuator disc theory for rotor power, axial thrust and out-of-plane bending moment in any given wind condition involve essentially only the rotor radius, R, and the axial induction factor, a. Radius, bending moment or thrust may be constrained or fixed, with quite different rotor optimisations resulting in each case. The case of fixed radius or rotor diameter leads to conventional rotor design and the long-established result that power is maximised with an axial induction factor, a=1/3. When the out-of-plane bending moment is constrained to a fixed value with axial induction variable in value (but constant radially) and when rotor radius is also variable, an optimum axial induction of 1∕5 is determined. This leads to a rotor that is expanded in diameter 11.6 %, gaining 7.6 % in power and with thrust reduced by 10 %. This is the low-induction rotor which has been investigated by Chaviaropoulos and Voutsinas (2013). However, with an optimum radially varying distribution of axial induction, the same 7.6 % power gain can be obtained with only 6.7 % expansion in rotor diameter. When without constraint on bending moment, the thrust is constrained to a fixed value, and the power is maximised as a→0, which for finite power extraction would require R→∞. This result is relevant when secondary rotors are used for power extraction from a primary rotor. To avoid too much loss of the source power available from the primary rotor, the secondary rotors must operate at very low induction factors whilst avoiding too high a tip speed or an excessive rotor diameter. Some general design issues of secondary rotors are explored. It is suggested that they may have the most practical potential for large vertical axis turbines avoiding the severe penalties on drivetrain cost and weight implicit in the usual method of power extraction from a central shaft.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Design Characteristics Of Secondary Rotorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Top-level rotor optimisations based on actuator disc theory

Jamieson

2020

Wind Energ. Sci.

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“…Jamieson (2011) mentioned it as a possible solution to the design challenge faced by large VAWTs where a very low optimum speed leads to high drive train torque, weight and cost if the power is extracted in the most usual way from the 10 central shaft. Leithead (2019) employs secondary rotors for power take-off in an innovative X-rotor VAWT design. The design tip speed of a large offshore HAWT may be 2 or 3 times greater than the 40 -45 m/s typical of a VAWT.…”

Section: Introductionmentioning

confidence: 99%

Top Level Rotor Optimisations based on Actuator Disc Theory

Jamieson¹

2019

Preprint

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Abstract. Ahead of the elaborate rotor optimisation modelling that would support detailed design, it is shown that significant insight and new design directions can be indicated with simple, high level analyses based on actuator disc theory. The basic equations derived from actuator disc theory for rotor power, axial thrust and out of plane bending moment in any given wind condition involve essentially only the rotor radius, R, and the axial induction factor, a. Radius, bending moment or thrust may be constrained or fixed with quite different rotor optimisations resulting in each case. The case of fixed radius or rotor diameter leads to conventional rotor design and the long-established result that power is maximised with an axial induction factor, a = 1 / 3. When the out of plane bending moment is constrained to a fixed value with axial induction variable in value (but constant radially) and when rotor radius is also variable, an optimum axial induction of 1 / 5 is determined. This leads to a rotor that is expanded in diameter 11.6 % gaining 7.6 % in power and with thrust reduced by 10 %. This is the “low induction rotor” which has been investigated by Chaviaropoulos (2013). However, with an optimum radially varying distribution of axial induction, the same 7.6 % power gain can be obtained with only 6.7 % expansion in rotor diameter. When without constraint on bending moment, the thrust is constrained to a fixed value, the power is maximised as a → 0 which for finite power extraction would require R → ∞. This result is relevant when secondary rotors are used for power extraction from a primary rotor. To avoid too much loss of the source power available from the primary rotor, the secondary rotors must operate at very low induction factors whilst avoiding too high a tip speed or an excessive rotor diameter. Some general design issues of secondary rotors are explored. It is suggested that they may have most practical potential for large vertical axis turbines avoiding the severe penalties on drive train cost and weight implicit in the usual method of power extraction from a central shaft.

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On the use of secondary rotors for vertical axis wind turbine power take‐off

Morgan,

Leithead,

Carroll

2024

Wind Energy

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This work introduces and explores the use of secondary rotors for vertical axis wind turbine power take‐off. A parametric framework based on optimally designed secondary rotors is developed which calculates the maximum achievable efficiency of power conversion between the primary and secondary rotors. It is shown that practicable rotor designs can convert between 87% and 90% of primary rotor power to the secondary rotors whilst facilitating nacelle mass reductions between 85% and 87% compared to traditional reference turbine drivetrains.

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The X-Rotor Offshore Wind Turbine Concept

Cited by 27 publications

References 5 publications

Top-level rotor optimisations based on actuator disc theory

Top-level rotor optimisations based on actuator disc theory

Top Level Rotor Optimisations based on Actuator Disc Theory

On the use of secondary rotors for vertical axis wind turbine power take‐off

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