GB2462880A

GB2462880A - Horizontal axis cross flow turbine

Info

Publication number: GB2462880A
Application number: GB0815612A
Authority: GB
Inventors: Allister Mcdonald Galbraith Roderick
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-08-28
Filing date: 2008-08-28
Publication date: 2010-03-03
Also published as: WO2010023437A3; WO2010023437A2; GB0815612D0

Abstract

A transverse axis underwater turbine 10 has its axis 26 perpendicular to the tidal or current flow direction. The rotation axis 26 may be horizontal, vertical or inclined, for example parallel to the sea or river bed. End supports 12, 14 may comprise a tripod structure with three legs 30. The turbine may drive a generator or pump.

Description

IMPROvEMpS IN AND RELATING TO TURBINES

FIELD OF INVENTION

The present invention relates to an improved turbine, and in particular, though not exclusively, to an improved underwater or tidal or current driven turbine. The invention also concerns a related apparatus for electrical power generation and a method of electrical power generation.

BACKGROUND TO INVENTION

Traditional methods of producing electricity, such as burning of fossil fuels and nuclear power have caused growing concerns over their environmental impact.

Therefore, a number of alternative energy production methods have been developed which use renewable energy sources, such as wind, water and geothermal energy. Increasing effort has been made to enhance the economic viability and efficiency of such alternative methods as they are normally substantially more expensive per kwh than that of an average fossil fuel power station, for example.

Throughout the world, in oceans, seas, rivers, and the like the movement of water, like that of the wind, contains significant amounts of energy. Unlike the wind however, the flow of tides and rivers are more predictable in both direction and strength (set and rate). Whilst Hydro and estuary-tidal power are well developed and understood, the modern harnessing of power from the natural flow, that is without any form of barrage, is at an early stage of development. To date, the most popular method mimics the most successful method for wind turbines, that is Horjzonal-j<i Wind-Turbine (HAWT).

Such HAWT turbines have the rotational axis of a rotor thereof parallel to the mean flow as shown in Figure 1.

In reality, however, small amounts of yaw occur and are undesirable. To maintain an axis design condition of zero yaw f or large turbines, the rotor plane has to be rotated, either actively (upwind turbines) or passively (downwind turbines) about the vertical axis as shown in Figure 2.

Equivalent devices for hydrodynamjc flows would require similar capabilities.

The requirement of yaw control can be alleviated by the use of Vertical-Axis Wind-Turbines (VAWT's) . The most successful of which are depicted in Figures 3(a) to 3(c) and which are known as the "Darrieus" the "H"-VAWT and the "V"-VAWT, respectively. Unlike their horizontal counterparts, VAWT'S have a fixed rotational axis and are passively stall-regulated. In other words, they operate for all wind conditions and, when the wind is too strong, limit the power, and hence the forces on the blades, by shedding of aerodynamic force. Their main disadvantages tend to be poorer aerodynamic efficiency and severe load paths; in particular, the stabilisation of the vertical support.

A Vertical Axis Wind Turbine (VAWT) has as, its name suggests, a rotational axis that is always vertical. This restriction is necessary because the horizontal wind direction may be from any direction. For natural hydrodynamjc flows, however, this restriction does not apply since, for example, the tides are very predictable and, locally, they can flow in a well-defined direction (set) and at a well-defined strength (rate) for both the flood and ebb tides.

It is an object of the present invention to obviate, or at least mitigate at least one of the aforementioned

disadvantages of the prior art.

StTh(ARY OF INVENTION According to a first aspect of the present invention there is provided a turbine assembly comprising a turbine means mounted to rotate around an axis substantially perpendicular to a flow direction, the axis of rotation being disposed at angle 0 from the vertical, where 0°<�<90°.

The inventor in the present case has termed the invention the Multiple Axis Hydro-Turbine (MART).

Preferably 0°<0<90°.

Preferably 0 is substantially 90°.

The turbine assembly may comprise at least first substantially rigid means for fixing the turbine relative to a fixed first location, e.g. on a seabed, ocean floor, riverbed or the like.

In a preferred embodiment the turbine assembly comprises first and second substantially rigid means for fixing first and second ends of the turbine assembly relative to fixed first and second locations, respectively.

According to a second aspect of the present invention there is provided a turbine assembly comprising first and second substantially rigid means for fixing first and second ends of the turbine assembly relative to fixed first and second locations respectively.

The fixed first and second locations may be on a fixed surface, e.g. a seabed, ocean floor, or riverbed or the like.

The following apply to both the first and second aspects.

The turbine assembly is most preferably a turbine adapted for use in electrical power generation.

Most preferably, the turbine assembly is adapted for use submerged in a body of water such as a sea, ocean, river or the like, i.e. is driven by hydrodynamjc flow.

Preferably, the turbine assembly is operated by the action of a flow of fluid, e.g. water, e.g. tidal or current flow.

The turbine assembly may comprise a plurality of blades.

The turbine assembly may include means for mounting the plurality of blades for movement around an/the axis of rotation.

The blades may be disposed substantially parallel to the axis of rotation.

The axis of rotation may, in use, be disposed at angle � to a vertical or perpendicular direction from the fixed surface where 00<�<900.

Preferably the angle � is substantially 90°, i.e. the axis of rotation is substantially parallel to the fixed surface.

The fixed surface may be a geostationary surface, e.g. a bed of a body of water, such as a seabed, ocean floor, riverbed, or the like.

Preferably the axis of rotation is substantially horizontal.

In one form the turbine assembly may be provided with two opposing blades. This configuration may provide the turbine with a high efficiency power output.

In an alternative form the turbine assembly may be provided with three equi-spaced blades. This configuration may provide the turbine assembly with an advantage of being self-starting.

Preferably each of the blades is an aerofoil. This enables the turbine assembly to rotate in a predetermined direction irrespective of the direction of flow of water.

Preferably, but not exclusively, the aerofoil has a symmetric NACA profile such as that of the 0015. This means that the thickest part of the aerofoil is equivalent to 15% of the total length of the blades chord/width.

Preferably, but not exclusively, each blade has a uniform cross-section across the length thereof.

The blades may be arranged so as to form a rotor, preferably which the fixing means support. The rotor may include first and second arms respectively extending from first and second ends of each blade to or adjacent to the axis of rotation at a respective hub.

Preferably the turbine assembly includes means for coupling to a generator, a pump or the like.

The first and second rigid fixing means may each comprise at least one and preferably a plurality of legs, first ends of the legs of each fixing means meeting at a respective first or second bearing for the rotor, while second ends of the legs are fixed, in use, to the fixed surface.

Most advantageously the turbine usually has a negative buoyancy, that is to say sinks in a body of water.

According to a third aspect of the present invention there is provided an electrical power generating apparatus including at least one turbine assembly according to either of the first or second aspects of the present invention.

Preferably the or each turbine assembly is fixed or pinned to the fixed location(s) such that the rotational axis is substantially perpendicular to the flow of water, e.g. the tidal or current flow or set.

The or each turbine assembly may be fixed such that the or each rotational axis is substantially horizontal.

Alternatively the or each turbine may be fixed such that the rotational axis of the or each turbine assembly is at an angle 0 to the vertical of 0<0<900.

Preferably the or each turbine assembly is positioned such as to be located in a free flow of the current of flood and ebb tides. That is to say that the or each turbine assembly is located where there the flow characteristics of the tide are even and not where the flow has large recirculations.

According to a fourth aspect of the present invention there is provided a method of generating electrical power comprising: providing an electrical power generating apparatus according to the third aspect; fixing the or each turbine assembly at a respective location within a body of flowing water; operating the or each turbine assembly.

Preferably the method comprises providing, e.g. longitudinally spacing, a plurality of turbine assemblies.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described by way of example only, with reference to the accompanying diagrams which are: Figure 1 a schematic side view of a first Horizontal-Axis Wind-Turbine (HAWT) according to the prior art; Figure 2 a schematic top view of a second HAWT

according to the prior art;

Figures 3(a) to (c) schematic illustrations of first, second and third Vertical Axis Wind-Turbines (VAWT)

according to the prior art;

Figure 4 a schematic illustration of a turbine assembly according to a first embodiment of the present invention; Figure 5 a schematic illustration of the turbine assembly of Figure 4 mounted to a sloping seabed; Figures 6(a) and (b) schematic illustrations showing a preferred location of the turbine assembly of Figure 1 and showing fluid or tidal flow patterns for flood and ebb tides; Figure 7 a schematic illustrations showing an electrical power generating apparatus according to an embodiment of the present invention including a plurality of turbine assemblies according to Figure 1 located across a span of a seabed; Figures 8 (a) and (b) schematic illustrations of a turbine assembly, and power generation assembly, in accordance with a third embodiment of the present invention, located in the "Doris Mhor'; and Figure 9 a schematic diagram illustrating the relationship between flow direction and axis of rotation in HAWTs, VAWTs and in a turbine assembly according to the present invention.

DETAILED DESCRIPTION OF DRAWINGS

Referring initially to Figure 4, there is provided a turbine assembly, generally designated by reference numeral 10, according to a fist embodiment of the present invention.

The turbine assembly 10 comprises substantially rigid first and second means 12, 14 for fixing first and second ends 16, 18 of the turbine assembly 10 relative to a fixed surface 20, such as the sea bed.

The turbine assembly 10, which has been termed a Multjple-Axjs Hydro-Turbine (MAT-IT), is provided with coupling means (not shown) allowing a generator (not shown) to be affixed to the turbine assembly 10, such that rotation of a rotor of the turbine assembly 10 can be used for electrical power generation.

The turbine assembly 10 is submersed in a body of water 11 and is, in use, driven by hydrodynan-ic flow which may be tidal or current flow.

The turbine assembly 10 may be made at least in part of stainless steel, Keviar, fibreglass or the like, in order that the turbine assembly 10 can withstand the harsh working environment of being operated submersed underwater.

The turbine assembly 10 comprises a number of blades 22. In the embodiment shown in Figure 4 there are three blades, which is the minimum amount needed in order that the turbine is self-starting and, therefore, the turbine assembly 10 does not require the need of additional equipment to commence rotation of the blade 22.

The blades 22 are coupled or integrally formed to mounting means 24 forming a rotor 28 which enables the blades 22 to rotate around an axis 26. Furthermore, in this embodiment the blades 22 are mounted to the mounting means 24 such that the blades 22 are substantially parallel to the axis of rotation 26. The rotor 28 further comprises arms 38 that extend between each of the blades 22 and hubs 40, which lie on the axis of rotation 26.

As shown in Figure 4, the axis of rotation 26 may be parallel to the fixed surface, which in this example is close to the horizontal. 1-lowever, as shown in Figure 5, the turbine assembly 10 may be affixed to a seabed 20 such that the turbine assembly 10 is inclined due to the prevailing conditions of the topography of the seabed.

The turbine assembly 10 may be mounted such that the axis of rotation 26 has an angle 0 to the vertical direction which is between �90°; but most preferably not 0°, that is to say that the turbine assembly 10 can be mounted in almost any terrain as long as the axis of rotation 26 is most preferably not vertical.

The blades 22 of the turbine assembly 10 are aerofoil in design, which enables the turbine assembly 10 to rotate in a predetermined direction irrespective of the direction of flow of water. The aerofoil design can be of any suitable form, however, one suitable aerofoil profile is such that the blade has a NACA 0015 profile. This means that the thickest part of the aerofojl is equivalent to 15% of the total width or chord of the blade 22.

The first and second fixing means 12,14 comprise in this embodiment three legs 30, forming a tripod like structure 32. At an apex of each tripod structure 32 there is a bearing 34 in which the rotor 28 is mounted for rotation. There are also provided feet 36 at the bottom of each of the legs 30, which enable the legs 30 of the tripod structure 32 to be anchored by pinning the feet 36 to the seabed 20.

The structure of the turbine assembly 10 is advantageously designed such that the turbine assembly 10 has a negative buoyancy, in order that the assembly 10 sinks in a body of water. This feature aids with the required provisions needed to be taken to ensure that the turbine assembly 10 is securely anchored to the seabed 20.

Referring now to Figures 6 (a) and (b), the turbine assembly 10 is positioned such that it is located in a free flow of the current of flood and ebb tides and, therefore, out of large recirculatory flow of the tides. In addition, the turbine assembly 10 is positioned such that the axis of rotation 26 is substantially perpendicular to the flow of both the flood and ebb tides.

Referring to Figure 7, there is shown how a number of turbine assemblies lOa may be spaced apart from each other to form an electricity generating apparatus lOOa. In this case the turbine assemblies l0a are longitudinally disposed, in order to harness some of the potential tidal energy.

Referring next to Figures 8(a) and (b), there is shown a turbine assembly 10 and electricity generating apparatus 10Db in accordance with the present invention which is proposed to be located in the "Doris Mhor'.

Typically the size of these particular turbine assemblies l0,lOa, lOb is such that the blades are around 2Dm in length, and around l.5m wide. The diameter of the rotor is typically 1Dm and the rotor assembly is located in the free flow of the tidal current having three blades mounted to it.

It is calculated that a turbine of such a design located in the "Doris Mhor" is capable of harnessing 400 kW of power from a total available power of 100 MW. If five such turbines were located across a span of the "Doris Mhor" it would, therefore, be possible to generate 2 Megawatts of power, which is 2% of the total energy available. A further favourable location envisaged at this time is the Sound of Is lay.

Referring finally to Figure 9 there is shown a schematic diagram illustrating the relationship between flow direction and axis of rotation in HAWT's, VAWT's and in a turbine assembly according to the present invention.

As can be seen from Figure 9 the direction of flow is taken to be along the x-axis. The axis of rotation of an HAWT is therefore around the x-axis. The axis of rotation of a VAWT is around the vertical z-axis. In contradiction in a turbine assembly of the present invention the axis of rotation lies in the y-z plane at an angle e from the z-axis, where 0°<�<90°.

U

It will be appreciated that the embodiments of the present invention hereinbefore described are given by way of example only, and are not meant to limit the scope of the invention in any way.

Claims

CLAIMS1. A turbine assembly, particularly an underwater turbine assembly, comprising turbine means mounted to rotate around an axis substantially perpendicular to a flow direction, the axis of rotation being disposed at an angle � from the vertical, where 0°<e<90°.
2. A turbine assembly as claimed in claim 1, wherein 0°<O<90°
3. A turbine assembly as claimed in either claims 1 or 2, wherein 0 is substantially 90°.
4. A turbine assembly as claimed in any of claims 1 to 3, wherein the turbine assembly comprises at least first substantially rigid means for fixing, such as statically fixing, the turbine means relative to a fixed first location, such as on a sea bed, ocean floor, or river bed.
5. A turbine assembly as claimed in any of claims 1 to 4, wherein the turbine assembly comprises first and second substantially rigid means for fixing first and second ends of the turbine assembly relative to fixed first and second locations, respectively.
6. A turbine assembly comprising first and second substantially rigid means for fixing first and second ends of the turbine assembly relative to fixed first and second locations respectively.
7. A turbine assembly as claimed in claim 6, wherein the fixed first and second locations are on a fixed surface, such as a sea bed, ocean floor, or river bed.
8. A turbine assembly as claimed in any of claims 1 to 5 or either of claims 6 or 7, wherein the turbine assembly is adapted for use in electrical power generation.
9. A turbine assembly as claimed in any of claims 1 to 5, either of claims 6 or 7, or claim 8, wherein the turbine assembly is adapted for use submerged in a body of water/flowing water such as a sea, ocean, or river so as to be driven by hydrodynamic flow.
10. A turbine assembly as claimed in any of claims 1 to 5, either of claims 6 or 7, or claims 8 or 9, wherein the turbine assembly is operated by the action of a flow of fluid, such as water, such as tidal or current flow.
11. A turbine assembly as claimed in any of claims 1 to 5, either of claims 6 or 7, or any of claims 8 to 10, wherein the turbine assembly comprises a plurality of blades.
12. A turbine assembly as claimed in any of claims 1 to 5, either of claims 6 or 7, or any of claims 8 to 11, wherein the turbine assembly comprises means for mounting the plurality of blades for movement around an/the axis of rotation.
13. A turbine assembly as claimed in claim 12, wherein the blades are disposed substantially parallel to the axis of rotation.
14. A turbine assembly as claimed in either of claims 12 or 13, wherein the axis of rotation is, in use, disposed at angle 0 to a vertical or perpendicular direction from a/the fixed surface where O°<e<90°.
15. A turbine assembly as claimed in any of claims 12 to 14, wherein the angle 0 is substantially 90° such that the axis of rotation is substantially parallel to a/the fixed surface.
16. A turbine assembly as claimed in any preceding claim, wherein the fixed surface is a geostationary surface, such as a bed of a body of watef, such as a sea bed ocean floor, river bed, or the like.
17. A turbine assembly as claimed in any preceding claim, wherein the/an axis of rotation is substantially horizontal.
18. A turbine assembly as claimed in any preceding claim, wherein the turbine assembly is provided with two opposing blades.
19. A turbine assembly as claimed in any of claims 1 to 17, wherein the turbine assembly is provided With three equi-spaced blades.
20. A turbine assembly as claimed in any preceding claim, wherein each of the blades is an aerofoil.
21. A turbine assembly as claimed in claim 20, wherein the/each aerofoil has a symmetric NACA profile such that of the 0015.
22. A turbine assembly as claimed in either of claims 20 or 21, wherein a thickest part of the/each aerofoil is equivalent to 15% of the total length of the/a respective blade' s chord/width.
23. A turbine assembly as claimed in any preceding claim, wherein each blade has a uniform cross-section across the length thereof.
24. A turbine assembly as claimed in any preceding claim, wherein the blades are arranged so as to form a rotor, optionally which the fixing means support.
25. A turbine assembly as claimed in claim 24, wherein the rotor comprises first and second arms respectively extending from first and second ends of each blade to or adjacent to the axis of rotation at a respective hub.
26. A turbine assembly as claimed in any Preceding claim, wherein the turbine assembly comprises means for coupling to a generator and/or to a pump.
27. A turbine assembly as claimed in any preceding claim, wherein the first and second rigid fixing means each comprise at least one or a plurality of legs, first ends of the legs of each fixing means meeting at a respective first or second bearing for the rotor, while second ends of the legs are fixed, in use, to the fixed surface.
28. A turbine assembly as claimed in any preceding claim, wherein each fixing means comprises a tripod arrangement or three legs or portions, a first forward inclined leg or portion, a second rearward inclined leg or portion, and a third sideward inclined leg or portion.
29. A Lurbine assembly as claimed in any preceding claim, wherein the turbine assembly has a negative buoyancy.
30. An electrical power generating apparatus comprising at least one turbine assembly according to any of claims 1 to 29.
31. An electrical power generating apparatus as claimed in ciaim iU, w1-ere1n fle or each turbine assembly is fixed or pinned to the fixed location(s) such that the rotational axis is substantially perpendicular to the flow of water, such as the tidal or current flow or set.
32. An electrical power generating apparatus as claimed in either of claims 30 or 31, wherein the or each turbine assembly is fixed such that the or each rotational axis is substantially horizontal.
33. An electrical power generating apparatus as claimed in any of claims 30 to 32, wherein the or each turbine assembly is fixed such that the rotational axis of the each turbine assembly is at an angle 0 to the vertical of Q°<�<90°.
34. An electrical power generating apparatus as claimed in any of claims 30 to 33, wherein the or each turbine assembly is positioned such as to be located in a free flow of the current of flood and ebb tides.
35. A method of generating electrical power comprising: providing an electrical power generating apparatus according to any of claims 30 to 34; fixing the or each turbine assembly at a respective location within a body of flowing water; operating the or each turbine assembly.
36. A method of generating electrical power as claimed in claim 35, wherein the method comprises providing a plurality of turbine assemblies.
37. A turbine assembly as hereinbefore described with reference to the accompanying drawings.
38. An electrical power generating apparatus as hereinbefore described with reference to the accompanying drawings.
39. A method of generating electrical power as hereinbefore described with reference to the accompanying drawings.