WO2010001141A2

WO2010001141A2 - Vertical axis wind turbine

Info

Publication number: WO2010001141A2
Application number: PCT/GB2009/001697
Authority: WO
Inventors: Stephen Peace; Paul Marsh
Original assignee: Vertical Wind Engergy Limited
Priority date: 2008-07-04
Filing date: 2009-07-08
Publication date: 2010-01-07
Also published as: GB0812234D0; WO2010001141A3; WO2010001141A8

Abstract

A vertical axis wind turbine comprising at least three blades each attached to a central hub via support struts angled at between 55° to 85° to each other.

Description

VERTICAL AXIS WIND TURBINE

The present invention relates to a vertical axis wind turbine.

There is an increasing need within the wind turbine industry to provide improved wind turbines to harness wind energy in a more efficient, affordable and reliable manner. It is the Applicant's perception that the next generation of wind turbines are likely to be constructed with vertical blade configurations as opposed to horizontal blade configurations.

The present invention seeks to provide an improved vertical axis wind turbine capable of generating in the region of 3kW of power.

A vertical wind turbine blade of modular construction is described in European patent application No. EP1769156. This invention described therein has common inventors with the present application and the construction disclosed is applicable to the present invention and is incorporated herein by reference.

In one aspect, there is provided a vertical axis wind turbine comprising at least three blades each attached to a central hub via support struts angled at between 55° to 85° to each other.

Preferably the struts are angled at between 60° and 80° degrees to each other.

Preferably still the struts are angled at around 70° to each other.

One embodiment of the invention will now be described by way of example only with reference to the accompanying figures in which : Figure 1 is a perspective view of a vertical axis wind turbine constructed in accordance the invention;

Figure 2 illustrates a blade profile of the turbine of Figure 1;

Figure 3 is a cross-sectional view of the blade of Figure 2;

Figure 4 illustrates a support strut profile of the turbine of Figure 1;

Figure 5 is a cross-sectional view of the support strut of Figure 4;

Figure 6 illustrates the turbine hub of the turbine of Figure 1;

Figure 7 illustrates a protective cap for the hub of Figure 6;

Figure 8 illustrates the profile of a top strut bracket of the turbine of Figure 1;

Figure 9 is a cross-sectional view of the top strut bracket of figure 8;

Figure 10 illustrates the profile of a bottom strut bracket of the turbine of Figure 1;

Figure 11 is a cross-sectional view of the bottom strut bracket of figure 10; and

Figure 12 illustrates a profile of a blade saddle clamp of the turbine of Figure 1. The turbine hereinafter described has been developed and tested extensively using simulated computational methods to assess its structural characteristics. Computational Fluid Dynamics and Finite Element methods were employed to simulate the turbine at various operating conditions.

The turbine has been found to provide power generation of approximately 3 kW. The turbine is designed to have a nominal operational speed of approximately 250 rpm with a Tip Speed Ratio (TSR) ranging from 2.5 to 3.0. The desired lifespan of the turbine is approximately 20 years.

Figure 1 illustrates the full structure of the vertical axis wind turbine. Generally, the turbine consists of three vertical blades 10 attached to a central hub 12 via support struts 14.

The struts 14 are angled at approximately 70° to each other. The preferred ranges of angle have been found to be between 55° to 85°, and further between 60° and 80°.

Tests have shown that the strut angle is a key factor in the optimum performance and can have the effect of reducing the bending movement on the struts themselves due to the more radial arrangement, whilst also supporting the blade further inboard from the ends, also reducing bending movement.

The blades 10, as seen in figures 2 and 3 are constructed from extruded aluminium. The blades 10 have a modular construction, such as that disclosed in the aforementioned European patent application. The blade walls have a thickness of between 2mm to 4mm and preferably, approximately 2.5mm.

The support struts 14 are shown in figures 4 and 5. The struts 14 are also constructed from extruded aluminium. They may also have a modular construction. This blade profile chosen was found to be the optimum in terms of bending thickness and modal response. Each blade 10 has two struts 14 forming a generally triangular configuration.

The turbine hub 12 is shown in figure 6. The hub 12 is generally hexagonal in shape and has a central aperture to allow the hub 12 to fit over and rotate around the main turbine column 16.

In a further embodiment the sides of the hub 12 are not of equal length but the hub 12 is symmetrical to provide the correct weight/balance ratio. In such a case the cord of the hub 12 is slightly offset.

The hub 12 has three strut mounting blocks 18 to receive the ends of the struts 14 of each blade 10 (as can be seen in Figure 1). The mounting blocks 18 are constructed from aluminium. Each strut 14 is connected to a respective mounting block 18 at four connection points and four large dowels. Bolts are used to absorb the sheer forces (the centrifugal forces) of the machine during use.

A protective cap 20 is mounted over the hub 12, as can be seen in Figure 7. The cap 20 is constructed from aluminium.

The struts 14 are connected to the blades 10 via top and bottom brackets 22, 24 which can be seen in figures 8 to 11. The brackets have apertures 26 formed therein to receive the end of strut 14. Each bracket 22, 24 is constructed from aluminium. Each bracket 22, 24 has an end surface 28 angled at approximately 35°. The brackets are riveted to the blades.

The brackets 22, 24 are connected to the blades 10 via saddle clamps 28. The saddle clamp profile can be seen in figure 12. The saddle clamps 28 form an aperture through which to receive each blade 10. The clamps 28 are constructed from aluminium. They are constructed in two parts from identical extrusions as mirror items. Drain holes (not shown) are provided through each clamp 28 to prevent water build up which would otherwise effect the centrifugal forces during use

Numerous and stringent tests on the aforementioned structure have predicted the turbine to survive in excess of 380 million 0-3-0 rpm cycles and the maximum stress under the 400 rpm case was found to be 113 MPa which is comfortably less than the material yield and hence is not expected to cause any problems. The maximum displacement under 300 rpm load was found to be 7.99 mm.

The above described embodiment has been given by way of example only, and the skilled reader will naturally appreciate that many variations could be made thereto without departing from the scope of the present invention.

Claims

1. A vertical axis wind turbine comprising at least three blades each attached to a central hub via support struts angled at between 55° to 85° to each other.

2. A vertical axis wind turbine according to claim 1 wherein the central hub is generally hexagonal in shape.

3. A vertical wind turbine according to claim 1 or claim 2, wherein the struts are angled at between 60° and 80° degrees to each other.

4. A vertical wind turbine according to claim 3, wherein the struts are angled at around 70° to each other.

5. A vertical wind turbine as substantially hereinbefore described and referred to in the accompanying figures.