Not only the well known and spread horizontal axis machines are present in the wind turbine scenario, but other architectures have found their niche. Among them, the Darrieus solution is known for its relatively compact design and small size, but, even more, for its vertical axis, as well as for the vertical blades distributed on the side of a rotating cylinder, even when twisted with special 3D helical shapes. Contrary to the horizontal axis solution mostly as 3-bladed version, the Darrieus design can not take advantage of the axis orientation control of the blade plane, because it accepts wind from any direction. But in order to maximise the efficiency in harvesting energy from the wind, the Darrieus turbine searches for the best attack angle between each blade and the wind flow at a specific speed, optimised along the complete rotation of the blade around the central axis. Together with a simple self-control towards the wind flow direction, a solution to improve the energy conversion into torque comes from the design of a controlled guidance of the attack angle of the vertical blades towards the flow. In this work the common use of an old mechanism, the four-bar linkage, is analysed to generate the passive control of each of the 3 blades in a simple Darrieus turbine design to improve the efficiency. This activity was made to understand, with relatively simple models, the advantages and drawbacks of such mechanism architecture for the optimal guidance of each blade, as a preliminary and feasibility methodological study for a potential research path in wind energy harvesting alternative solutions. The work therefore deals with the selection of a common wing profile and a 3-bladed machine scheme, together with the adoption of four-bar linkage for each passively controlled blade. The aerodynamic force distribution and torque simulation follow, as functions of the angular position, at two different wind speeds in a complete turbine rotation. The assumptions, the formulation and results for the simple Darrieus machine with an attack angle guidance mechanism are discussed in detail.

AN OLD MECHANISM TO IMPROVE WIND ENERGY HARVESTING

A. Zanarini
2019

Abstract

Not only the well known and spread horizontal axis machines are present in the wind turbine scenario, but other architectures have found their niche. Among them, the Darrieus solution is known for its relatively compact design and small size, but, even more, for its vertical axis, as well as for the vertical blades distributed on the side of a rotating cylinder, even when twisted with special 3D helical shapes. Contrary to the horizontal axis solution mostly as 3-bladed version, the Darrieus design can not take advantage of the axis orientation control of the blade plane, because it accepts wind from any direction. But in order to maximise the efficiency in harvesting energy from the wind, the Darrieus turbine searches for the best attack angle between each blade and the wind flow at a specific speed, optimised along the complete rotation of the blade around the central axis. Together with a simple self-control towards the wind flow direction, a solution to improve the energy conversion into torque comes from the design of a controlled guidance of the attack angle of the vertical blades towards the flow. In this work the common use of an old mechanism, the four-bar linkage, is analysed to generate the passive control of each of the 3 blades in a simple Darrieus turbine design to improve the efficiency. This activity was made to understand, with relatively simple models, the advantages and drawbacks of such mechanism architecture for the optimal guidance of each blade, as a preliminary and feasibility methodological study for a potential research path in wind energy harvesting alternative solutions. The work therefore deals with the selection of a common wing profile and a 3-bladed machine scheme, together with the adoption of four-bar linkage for each passively controlled blade. The aerodynamic force distribution and torque simulation follow, as functions of the angular position, at two different wind speeds in a complete turbine rotation. The assumptions, the formulation and results for the simple Darrieus machine with an attack angle guidance mechanism are discussed in detail.
2019
Dodicesima giornata di studio Ettore Funaioli – 20 luglio 2018
15
36
A. Zanarini
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/705416
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