GB2451478A

GB2451478A - Wind turbine and generator with ovoid frame.

Info

Publication number: GB2451478A
Application number: GB0714904A
Authority: GB
Inventors: John Queenan
Original assignee: SUBSEA ENERGY
Current assignee: SUBSEA ENERGY
Priority date: 2007-07-30
Filing date: 2007-07-30
Publication date: 2009-02-04
Also published as: WO2009016372A3; GB0714904D0; WO2009016372A2

Abstract

A wind turbine comprises an axial flow rotor 14 which is mounted on a shaft 22, along with an electric generator 24, said components being housed within an ovoid frame 20. The turbine rotor 14 may comprise one or more helical, or quasi-helical, blades 18. The generator 24 may be tubular and located internally of the turbine rotor 14. The generator 24 may be a radial flux generator with permanent magnets attached to the rotor and copper windings mounted on an internal stator. It may be possible to incline the shaft 22 with respect to the horizontal axis. Magnetic bearings may be provided for any rotating parts of the turbine. A ring shaped flywheel may be provided about the axis of rotation of the turbine rotor 14.

Description

2 PATENT SPECIFICATION

4 WIND ENERGY GENERATION APPARATUS 6 Subsea Energy (Scotland) Ltd 7 July 2007

DESCRIPTION

12 Background

14 The demand for small-scale decentralised power generating units has * 15 increased in recent years and the trend is set to continue as public attitude changes and 16 as fossil fuel supplies run out. If the generated power is derived from renewable 17 resources then it does not produce harmful greenhouse gases or incur any significant 18 running costs. Decentralised (stand-alone) power units are of prime importance in 19 isolated areas without a grid connection as well as in mobile transport units such as caravans and yachts. Additionally stand-alone generation has the advantage of 21 removing transmission losses inherent in long power lines and gives consumers 22 independence and control over their choice of generation.

24 Wind power is intermittent but is an abundant source of extractable energy worldwide, notably so in many rural areas in the United Kingdom. Domestic-scale, or 26 "micro-wind", turbines are available on the market and can be used to charge batteries 27 or plug into the electricity grid to offset a user's supply. The most common types of 28 micro-wind generating systems available currently are horizontal axis machines with 29 a number of discrete propeller blades. There are also a variety of designs that operate as vertical axis machines.

* 32 Disadvantages of existing systems include: low performance in turbulent air 33 streams; high start-up torque reducing the output at low wind speeds; difficulties of 34 installation and maintenance partly due to large blade diameters and complex heavy generators; and noise pollution caused by the relatively high angular velocity of 36 propeller blade tips. There are also arguments over aesthetic appeal.

39 Summary

41 An invention is therefore presented that is a self-contained wind generator 42 comprising an axially extended turbine rotor, internal to which is a tubular generator, 43 both of which rotate on a shaft that may be on a horizontal axis or adjustable to an 44 angle relative to the horizontal axis, all of these components being contained within a fish-shaped frame mounted on a pole with a swivel mechanism and down which 46 output wires are fed for eventual distribution to an electrical conversion device such 47 as a battery charger. * I

I Detailed Description

3 Many existing small-scale wind turbines experience difficulty in starting up in 4 low wind speeds and do not have a frontal blade area sufficient for extracting optimum energy from the wind according to the theoretical Betz limit. Therefore a 6 rotor design is presented that extends along the longitudinal axis to a length greater 7 than its diameter, to allow greater extraction of energy from the wind in comparison to 8 existing rotors that are effectively planar. Start-up torque is also overcome, due to the 9 solid frontal area presented. Existing wind turbines do not perform well in turbulent wind conditions or on rooftops where the incoming wind is at an angle to the 11 rotational axis. However the rotor in the present invention takes advantage of such 12 conditions due to its multi-directional geometry, resulting in improved rotation.

14 Preferably the said rotor will be of helical construction, consisting of a * 15 plurality of blades each forming a helix around a cylinder, the longitudinal axis of 16 which forms the axis of rotation, which may be either horizontal or at an inclination to 17 the horizontal. The shape of each blade may be described by a regular helix with a 18 constant pitch and width; alternatively the pitch and the width of the helix may follow 19 a variable profile along the longitudinal axis.

21 Different turbine designs and blade shapes may be employed depending on the 22 characteristics of the device deployment such as wind profile, generator location, size 23 limitations and power demand, as well as with due consideration to the cost and ease 24 of manufacture.

26 Other non-helical designs may be used for the turbine rotor, provided that they 27 conform to the requirement for an internal generator and rotate along a horizontal 28 axis. A person skilled in the art of turbine design will be able to consider the design 29 of such a rotor.

31 Preferably the turbine blade material will be constructed from a reinforced 32 plastic or a composite material. *33

34 The generator is designed to be small and simple so as to apply a minimal load to the support frame and increase the ease of installation and maintenance. Preferably 36 the generator is contained within a cylindrical section internal to the rotor, such that it 37 is concealed from view.

39 Alternatively a generator that is shorter in the axial direction may be mounted on the shaft between the rotor and the frame, or two similar generators may be 41 mounted on the shaft on either side of the rotor, between the rotor and the frame.

43 Preferably this tubular generator will use permanent magnets to generate flux 44 thai is directed through copper coils as the rotor spins, thus generating an electric current. In a preferable embodiment of the invention, a plurality of permanent 46 magnets are mounted on a cylinder that is internal to and coupled with the turbine 47 rotor, producing a rotating radial magnetic flux that passes through a plurality of coils 48 that are mounted on a stationary cylinder that is internal to and co-axial with the * * I rotating cylinders. These coils are connected to form a three-phase output, and may 2 be partitioned along the length of the cylindrical axis.

4 A generator thus described constitutes one example of a radial configuration; however other possible radial and axial configurations exist and may be known to 6 those skilled in the art.

8 The generator configuration, number of permanent magnets, number of coils 9 and wiring configuration may be selected to produce the desired electrical output characteristics. The three-phase output wires from the generator are preferably fed 11 internally through the shaft to the frame, then fed internally through the frame to the 12 support pole, then fed internally down the support pole and finally output from the 13 device. The output wires may be passed through a three-phase rectifier or a 14 transformer or may require power conditioning to be applied to the electrical output.

16 The rotor and generator are mounted with standard bearings onto a shaft, 17 whereupon there can optionally be nose-cones mounted on either side of the rotor 18 assembly to act as aerodynamic shapers to the flow of air. The shaft may be hollow 19 with the output wires from the generator passed therein to be concealed and fed to the frame.

22 The shaft will typically rotate on a horizontal axis; however in alternative 23 embodiments of the design the shaft may be adjusted to be inclined at an angle to the 24 horizontal via a tilting mechanism within the support assembly.

26 Magnetic bearings may be used to increase the mechanical efficiency and 27 reduce maintenance requirements.

29 A flywheel may be added to the assembly to increase the inertia and thus smooth out some of the irregularity in the rotational speed that may be caused by an 31 unsteady flow of air.

33 The frame which houses the working part of the wind turbine is ovoid (fish- 34 shaped) along the longitudinal axis and is designed to provide the necessary structural stiffness to support the turbine as well as render an aesthetic representation of a fish.

36 The width of the frame horizontally perpendicular to the rotational axis, at the central 37 nose section especially, should be thin enough to cause minimal disruption to the 38 prevailing flow of air. On the downstream edge of the frame a furling tail is present 39 to catch the wind and thus cause the structure to self-orient towards the prevailing wind by means of a swivel joint. The output wires from the generator are concealed 41 within the frame to protect them from exposure and to minimise visual obstruction.

43 The ovoid frame is connected to a vertical pole for mounting the turbine at a 44 suitable height, either on top of a structure or as a free-standing unit. A swivel joint is used to connect said frame and pole, to allow orientation of the longitudinal axis into 46 the wind.

48 The frame consists preferably of a toughened plastic such as glass-reinforced 49 plastic or a metal that is non-corrosive or protected against corrosion such as * I aluminium or galvanised steel. The pole consists preferably of a metal that is non- 2 corrosive or protected against corrosion such as aluminium or galvanised steel. For 3 ease of construction the frame preferably consists of two segments that are joined 4 together during the assembly of the device. The assembled frame should provide a waterproof housing for the output wires.

7 Description of Drawings

9 These and other aspects of the present invention will now be described by way of example only and with reference to the accompanying Figures, in which: 11 Figure I shows a front elevation of an apparatus for generating energy in 12 accordance with an embodiment of the present invention; 13 Figure 2 shows a plan view of the apparatus of Figure 1; 14 Figure 3 shows a perspective view of the apparatus of Figure 1.

16 A turbine rotor 14 is mounted on a shaft 22 that may be horizontal or may be 17 inclined to the horizontal; in the example in the attached drawings the shaft is 18 horizontal. Bearings used to mount the rotor 14 are not shown. Optionally, nose- 19 cones 24 may be placed on the shaft at either end of the rotor. The rotor 14 may have a plurality of helical blades 18. Figure 1 shows a typical embodiment with three such 21 helical blades.

23 The shaft 22 is secured to an ovoid frame 20 that provides structural support to 24 the shaft assembly. The said frame is intended to represent the shape of a fish for aesthetic purposes. As can be seen from the plan view in Figure 2, the width of the 26 frame in the direction horizontally perpendicular to the rotational axis should be thin 27 enough to cause minimal disruption to the prevailing flow of air while still providing 28 the necessary lateral and torsional stiffness.

The generator is mounted on the shaft 22 internally to the rotor 14. The output 31 wires are fed into a hollow core internal to the shaft, feeding to the frame 20 that 32 likewise channels the wires through an internal space to the mounting pole 26. The 33 wires are then fed down the pole for eventual output from the device.

The furling tail 32 consists of a vertically planar surface, shown in Figure 1 as 36 a triangle, which will catch the wind and cause the device to rotate by means of a 37 swivel joint 38 between the frame and the pole, such that the rotational axis of the 38 turbine becomes aligned with the prevailing wind direction. * *

Claims

2 CLAIMS 4 1. An apparatus for generating energy from flowing air, the apparatus comprising a turbine rotor that extends along the axis of rotation such that energy is extracted 6 from the air continually along said axis; the axis of rotation having its horizontal 7 length aligned with the prevailing horizontal direction of air flow; said turbine rotor 8 being mounted on a shaft along with an electrical generator; said components being 9 housed within an ovoid frame that is mounted on a pole.

11 2. An apparatus according to claim 1, wherein the turbine rotor comprises one or 12 more helical blades whereby any point on the outer diameter of any blade forms a 13 regular helix along the axis of rotation, with the blades equally spaced 14 circumferentially.

16 3. An apparatus according to claim 1, wherein the turbine rotor comprises one or 17 more quasi-helical blades, whereby the helical shape outlined in claim 2 has variable 18 pitch and diameter and the blades may or may not be equally spaced 19 circumferentially.

21 4. An apparatus according to any preceding claims, wherein there exists a tubular 22 generator internal to the turbine rotor.

24 5. An apparatus according to claim 4, wherein the generator is a radial flux permanent magnet machine with permanent magnets attached to an outer cylinder that 26 is coupled to the turbine rotor generating a flux which passes through copper windings 27 mounted on an internal stator.

29 6. An apparatus according to any preceding claims, wherein the shaft can be inclined at an adjustable angle to the horizontal axis.

* 32 7. An apparatus according to any preceding claims, wherein any rotating part is 33 mounted on the shaft with magnetic bearings.

8. A flywheel comprising a ring of any dimension and any material, rotating 36 around the axis of rotation at any location within the assembly of the apparatus that is 37 according to any preceding claim.

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