GB2468853A

GB2468853A - Helical axial flow water turbine

Info

Publication number: GB2468853A
Application number: GB0904926A
Authority: GB
Inventors: Daniel Manners
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-24
Filing date: 2009-03-24
Publication date: 2010-09-29
Also published as: WO2010109233A3; WO2010109233A2; GB0904926D0

Abstract

A hydro power generation apparatus 10 comprises counter-rotating horizontal axis turbines 12, 14. The turbines include an inner housing (20, Fig 2), a generator (22, Fig 2) and two gearboxes (24,26, Fig 2) mounted within the inner housing (20). A plurality of substantially helical blades 25 are mounted on a rotary casing 32 which extend around and rotate about the inner housing (20) for driving the gearboxes (24,26) and generator (22). The turbines are supported by front and rear buoyancy tanks 38, 40, and the apparatus 10 controls its own buoyancy to place it at optimum depth in a tidal flow. The apparatus also includes fins 52 and control surfaces 54 for positioning.

Description

Title: Horizontal Axis Turbine Assembly and Hydro-power Generation Apparatus The present invention relates to a horizontal axis turbine assembly and a hydro-power generation apparatus for use in a flowing body of water.

Background to the Invention

In a UK tidal stream energy resource assessment commissioned by the Carbon Trust (RTM), it has been found that many of the potential sites for placement of hydro-electric power generation equipment are small with low water flow rate velocities.

Furthermore, a number of larger sites have been identified, but which also have low flow rate velocities. There are only several areas identified around the UK' s shores, in which the flow rate velocities exceed 2.SmIs and the depth of water is within 30 to 40m, allowing seabed standing devices to be erected. Approximately 50% of the UK resource is within deep sites, with depths of over 40m, which require more sophisticated and expensive equipment to harness the power in the water movement.

It is generally recognised that the number of available sites for power generation and the amount of power cable of being extracted from tidal movements would be much greater if power generation devices could operate efficiently not only at lower velocities, for example, below 2,SmJs but also in greater depths. Existing hydro-power generation systems employ either propeller, turbine or Archimedes screw type blades resulting in limited or low energy transfer surface area.

It is an object of the invention to provide a horizontal axis turbine assembly and hydro-power generation apparatus which reduces or substantially obviates the above mentioned problems

Statement of Invention

According to a first aspect of the present invention there is provided horizontal axis turbine assembly for placement in a flow of water comprising an inner housing, a generator and a gearbox mounted within the inner housing.

and a plurality of substantially helical blades extending around and adapted to rotate about the inner housing for driving the gearbox and generator.

The hydro power generation apparatus is advantageous because the surface area of the helical blades available for energy transfer is much greater than in known apparatus, enabling the gearbox to substantially gear up the rotational velocity to the generator for efficient electricity generation at relatively low water flow rates.

Preferably the helical blades are mounted on a rotary casing, which is adapted to rotate with the helical blades about the inner housing.

Preferably each helical blade is made from a single continuous member.

Alternatively, each blade may be made from at least two blade members, which may be sealed together to act as a single continuous surface. In a further alternative arrangement, each blade may be made from at least two spaced blade members.

Preferably each helical blade includes a substantially smooth continuous surface.

Preferably each helical blade gently curves in a first arc to a tip extending along the outer edge of the blade, the tip curving sharply in a second arc away from the first arc.

The sharp curving of the blade tip away from the majority of the lightly curved body of the blade has the effect of reducing cavitation, by streamlining the flow of water from the high pressure surfaces to the low pressure surfaces.

Preferably each blade is mounted to the rotary casing in a plurality of fixing positions extending along the length of the blade. The blade is advantageously made from a flexible composite material.

Preferably bearings are mounted at either end of the inner housing, about which the helical blades rotate. The hearings are preferably sealed bearings.

Preferably a drive gear is mounted in driving communication with the gearbox, the drive gear being driven by rotation of the turbine blades.

Preferably the rotary casing is in driving engagement with the drive gear.

A second gearbox is preferably mounted in the inner housing and a second drive gear may be mounted in driving communication with the second gearbox, the second drive gear being driven by rotation of the turbine blades. The rotary casing may be in driving engagement with the second drive gear.

Preferably the first and second gearboxes and respective first and second drive gears are disposed at opposite ends of the generator.

Preferably a respective buoyancy structure is disposed at each end of the horizontal axis turbine assembly.

Preferably the buoyancy structures are mounted externally of the inner housing to the bearings.

According to a second aspect of the present invention there is provided hydro-power generation apparatus for placement in a flow of water comprising first and second horizontal axis turbine assemblies in accordance with the first aspect of the invention, in which the rotational axes of the first and second horizontal axis turbine assemblies are parallel with one-another and the helical blades of each assembly are adapted to rotate in a different direction, when both are disposed in a water flow.

By virtue of the turbine blades of the respective assemblies helically twisting in opposite directions, the apparatus is substantially stable in use in a water flow.

Preferably the first and second horizontal axis turbine assemblies are mounted in a supporting structure including a first buoyancy tank and a second buoyancy tank.

Preferably the first buoyancy tank is connected to and extends between the front ends of the first and second horizontal axis turbine assemblies and the second buoyancy tank is connected to and extends between the rear ends of the first and second horizontal axis turbine assemblies.

Preferably powered control surfaces are disposed on the buoyancy tanks for controlling the position of the apparatus in a water flow.

Preferably a supporting strut extends between the first and second buoyancy tanks.

The strut may be disposed between the first and second horizontal axis turbine assemblies.

Preferably at least one fin is mounted on the supporting strut for stabilising the apparatus in a water flow. A fin may be mounted to both the upper and lower sides of the supporting strut. The fins stabilise the apparatus in the horizontal plane.

Preferably compressed air tanks are disposed on the supporting strut.

Preferably a programmable controller, battery, pressure sensor and flow meter are mounted to the apparatus for controlling the depth of the apparatus in use, in a body of water.

Preferably the controller is adapted to maintain the position of the apparatus at a depth where the water flow rate relative to a substantially fixed lateral position of the apparatus is a maximum.

The controller may control the buoyancy of the apparatus by flooding the buoyancy tanks with water or by expelling water from the tanks with air from the compressed air tanks. The controller may maintain the apparatus with neutral buoyancy in order position the apparatus at a substantially fixed depth in a water flow.

The apparatus may be moored by a mooring line. Advantageously the apparatus can be moored in any depth of water, for example, in excess of 40m and the apparatus can generate power in both slow moving water flows, eg less than 2.5m/s and fast moving water flows of around 4.5m/s.

Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a schematic plan view from above of a hydro-power generation apparatus; Figure 2 shows a schematic side view, partly in cut-away, of a horizontal axis turbine assembly of the hydro-power generation apparatus of Figure 1; Figure 3A shows a schematic side view of a horizontal axis turbine assembly of the hydro-power generation apparatus of Figure 1, with fluid flow lines shown passing over the turbine blades; Figure 38 shows a schematic side view of a continuous unitary turbine blade; Figure 3C shows a schematic end view of the continuous turbine blade of Figure 3B; Figure 4 shows a schematic cross-sectional view through a mooring cable for use with the hydro-power generation apparatus of Figure 1; and Figure 5 shows a schematic side view of the hydro-power generation apparatus of Figure 1, in use, in a body of flowing water.

Description of Preferred Embodiments

Referring firstly to Figure 1, a hydro-power generation apparatus is indicated generally at 10. The hydro-power generation apparatus 10 includes first and second counter-rotating horizontal axis turbine assemblies 12,14 mounted side by side with parallel axes 16,18 of rotation. Referring also to Figure 2, each assembly 12,14 includes an inner housing 20 containing a generator 22 and first and second gearhoxes 24,26. The gearboxes 24 and 26 are mounted in-line with the generator 22 and their output shafts drive the generator from either end. Drive gears 28,30 are mounted to the input shafts of the gearboxes 24,26 and are also mounted in-line. Rotation of the drive gears 28,30 causes rotation of the gearbox input shafts and geared drive at increased rotational velocity of the generator 22.

A rotary casing 32, constructed in two sections to aid assembly and maintenance, is disposed around the inner housing 20 and is arranged to rotate about first and second sealed bearings 34,36 mounted at respective ends of the inner housing 20. As shown in Figure 2, individual floats or buoyancy tanks 38,40 are mounted at the distil ends of the assembly, and are mounted to the sealed bearings. Helical blades 25 are mounted to the rotary casing 32 and are connected to the casing, for example, with bolts at a plurality of spaced fixing positions. Referring also to Figures 3A to 3C, each helical blade is continuous and has a smooth surface. When mounted to the rotary casing 32, each helical blade 25 includes a major surface region 46 which is slightly curved in a first arc and a tip region 48 extending from the region 46, the tip region being sharply curved in a second arc. The distil end of the tip region 46 lies almost perpendicular to the major surface region 46, and in use, helps to keep turbulence due to cavitation to a minimum.

Referring back to Figure 1, the first buoyancy tank 38 extends across the front of the horizontal axis turbine assemblies 12,14 perpendicular to the axes of rotation 16,18 and the sealed bearings 34 are mounted to the side of the tank 38. Similarly the second buoyancy tank 40 extends across the rear of the horizontal axis turbine assemblies 12,14 perpendicular to the axes of rotation 16,18 and the sealed bearings 36 are mounted to the side of the tank 40.

A structural strut 48 extends between the buoyancy tanks 38,40 and is positioned parallel and mid-way between the horizontal axis turbine assemblies 12,14. A plurality of compressed air tanks 50 are mounted on the strut 48 together with upper and lower stahilising fins 52. These fins 52 stabilise the assembly in the horizontal plane. Control surfaces 54, powered by servos, are mounted to the ends of the buoyancy tanks 38,40.

Also mounted to the hydro-power generation apparatus 10 are an Industrial Programmable Logic Controller (PLC), an operating battery, and a plurality of sensors for sensing external pressure readings forward and aft, water flow-rate, water temperature, water salinity, power output, statuses of the gearbox & generator, compressed air levels & orientation (not shown). The PLC can also control automatic lubrication of the generator 22 and gearboxes 24,26.

Referring to Figure 4, a mooring cable for use with the assembly 10 is indicated generally at 56. The mooring cable has two load hearing cores 58 made, for example, from steel, buoyancy fibres 60 running on either side of the load bearing cores 58, at least one ruggedized optic fibre 62 for relaying control information to and from the assembly 10 (two are shown) and two armoured electrical power cables 64 for transmitting the generated electrical power. The inner cables are all retained in a reinforced outer sheath 66.

In use, as shown in Figure 3A, the horizontal axis turbine assemblies 12,14 of the assembly 10 provide blades 25 with a much larger surface area than in known hydo-power generation devices, which more effectively utilise increases in flow rate as water passes over the surface of the housing, in order to maximise the pressure exerted on the blades. The blades 25 and overall design are such that cavitation of the water flow is reduced to a minimum.

Another advantage over existing designs is that due to the increased surface area of the blades, the required flowrate for operation can be much lower. Additionally, the blades can be customised to suit the environmental conditions expected at a specific installation. With a low external rotational velocity the adverse effects on marine animals is reduced to a minimum.

Under normal operating conditions the assembly 10 is automatically locally controlled by the PLC. The mooring method can be adapted to suit the sea or river bed conditions and the fiowrate of the water. If installed in a tidal stream, the generation unit will maintain the same depth but slowly change direction in relation to the mooring during a tide change. The mooring cable 56 requires only enough buoyancy in order that a majority of its own weight is self-supported.

Referring to Figure 5, the assembly 10 is shown at different depths in a water flow, indicated at 68. The sea floor is shown at 70 and the surface of the water is indicated at 72. The assembly 10 can easily be located within a band of water flowing at optimum flow rate, as shown for example, between the dotted lines 74.76. Once neutral buoyancy has been achieved, i.e. no depth change with the control surfaces at zero degrees pitch, depth can be regulated by the control surfaces. This control will only be active if the flowrate is above a pre-determined flowrate. The control surfaces are independently controlled, allowing control over both orientation and depth of the apparatus. Controlling depth with the control surfaces during nominal flow conditions greatly reduces the amount of compressed air being consumed.

The design has the additional advantage of being able to utilise short durational peaks in flow velocity; because any sudden increases in velocity will temporarily force the assembly 10 slightly closer to the seafriver bed.

If maintenance is required, the PLC controls air pressurisation of the buoyancy tanks 3 8,40 causing the apparatus 10 to return to the surface. Compressed air is stored locally on the assembly, however if multiple units are installed as part of a "farm", compressed air can be stored centrally.

Under normal operating conditions the assembly is automatically and locally controlled via the PLC using the readings obtained from the sensors. It will control orientation and depth positioning. The PLC can be pre-programmed to seek out the highest available flow rate at varying depths within a given operating depth band.

The on-board batteries, which are charged by the generation of power locally, supply the control systems with power. Each system is connected to the PLC and the PLC can be connected to a remote control device, for example, by fibre optics, in the event of malfunction, replacement, or checking. If the PLC detects a malfunction, the apparatus 10 can be programmed to automatically float to the surface or flood the tanks and lay on the sealriver bed.

Advantages of the invention include: * Simplistic Design * High Energy Conversion ratio due to the increased flow velocity produced across the large surface area of the blades * Operation in Low Flow Environments, ie less than 2.Smls * Can be Installed and Operated at far greater depths than traditional inonopile designs * Extremely Low Environmental Impact * Comparatively low Installation & Maintenance Costs * Easily Deployed in a Range of Environments * Flexible and Scalable * Autonomous Control * Not Flow Direction Dependant The apparatus 10 utilises a pair of horizontal axis turbine assemblies 12,14, which are arranged to counter-rotate in order to balance the apparatus in a flow of water.

However, where there is a large movement of water and space permits, further pairs of horizontal axis turbine assemblies can be assembled in a single apparatus, as required. For example, it is envisaged that an apparatus (not shown) could include 4, 6, 8 or more horizontal axis turbine assemblies. The pairs of assemblies could be arranged in a line, or arranged in a stack or otherwise arranged to suit a particular flow channel.

The apparatus 10 provides an alternative method of electrical energy generation and is suitable for many offshore locations, unsuited to other types of known device. The ability of the apparatus 10 to maintain neutral buoyancy and to locate itself in an optimum flow channel of water ensures that it harnesses the maximum power available in a given flow of water.

Claims

CLAIMS1. A horizontal axis turbine assembly for placement in a flow of water comprising an inner housing, a generator and a gearbox mounted within the inner housing, and a plurality of substantially helical blades extending around and adapted to rotate about the inner housing for driving the gearbox and generator.
2. A horizontal axis turbine assembly as claimed in claim 1, in which the helical blades are mounted on a rotary casing, which is adapted to rotate with the helical blades about the inner housing.
3. A horizontal axis turbine assembly as claimed in claim 1 or claim 2, in which each helical blade is continuous.
4. A horizontal axis turbine assembly as claimed in claim 1 or claim 2, in which each helical blade is made from at least two blade members.
5. A horizontal axis turbine assembly as claimed in any preceding claim, in which each helical blade includes a substantially smooth continuous surface.
6. A horizontal axis turbine assembly as claimed in claim 5, in which each helical blade gently curves in a first arc to a tip extending along the outer edge of the blade, the tip curving shaiply in a second arc away from the first arc.
7. A horizontal axis turbine assembly as claimed in any one of claims 2 to 6, in which each blade is mounted to the rotary casing in a plurality of fixing positions extending along the length of the blade.
8. A horizontal axis turbine assembly as claimed in any preceding claim, in which hearings are mounted at either end of the inner housing, about which the helical blades rotate.
9. A horizontal axis turbine assembly as claimed in any preceding claim, in which a drive gear is mounted in driving communication with the gearbox, the drive gear being driven by rotation of the turbine blades.
10. A horizontal axis turbine assembly as claimed in claim 9, in which the rotary casing is in driving engagement with the drive gear.
11. A horizontal axis turbine assembly as claimed in any preceding claim, in which a second gearbox is mounted in the inner housing.
12. A horizontal axis turbine assembly as claimed in claim 11, in which a second drive gear is mounted in driving communication with the second gearbox, the second drive gear being driven by rotation of the turbine blades.
13. A horizontal axis turbine assembly as claimed in claim 12, in which the rotary casing is in driving engagement with the second drive gear.
14. A horizontal axis turbine assembly as claimed in claim 13, in which the first and second gearboxes and respective first and second drive gears are disposed at opposite ends of the generator.
15. A horizontal axis turbine assembly as claimed in claim 9, in which a respective buoyancy structure is disposed at each end of the horizontal axis turbine assembly.
16. A horizontal axis turbine assembly as claimed in any preceding claim, when dependent on claim 8, in which the buoyancy structures are mounted externally of the inner housing to the bearings.
17. A hydro-power generation apparatus for placement in a flow of water comprising first and second horizontal axis turbine assemblies as claimed in any preceding claim, in which the rotational axes of the first and second horizontal axis turbine assemblies are parallel with one-another and the helical blades of each assembly are adapted to rotate in a different direction, when both are disposed in a water flow.
18. A hydro-power generation apparatus as claimed in claim 17, in which the first and second horizontal axis turbine assemblies are mounted in a supporting structure including a first buoyancy tank and a second buoyancy tank.
19. A hydro-power generation apparatus as claimed in claim 18, in which the first buoyancy tank is connected to and extends between the front ends of the first and second horizontal axis turbine assemblies and the second buoyancy tank is connected to and extends between the rear ends of the first and second horizontal axis turbine assemblies.
20. A hydro-power generation apparatus as claimed in any one of claims 17 to 19, in which powered control surfaces are disposed on the buoyancy tanks for controlling the position of the apparatus in a water flow,
21. A hydro-power generation apparatus as claimed in any one of claims 17 to 20, in which a supporting strut extends between the first and second buoyancy tanks and also between the first and second horizontal axis turbine assemblies.
22. A hydro-power generation apparatus as claimed in claim 21, in which at least one fin is mounted on the supporting strut for stabilising the apparatus in a water flow.in which compressed air tanks are disposed on the supporting strut.
23. A hydro-power generation apparatus as claimed in claim 20 or claim 21, in which compressed air tanks are disposed on the supporting strut.
24. A hydro-power generation apparatus as claimed in any one of claims 17 to 22, in which a programmable controller, battery, pressure sensor and flow meter is mounted to the apparatus for controlling the depth of the apparatus in use, in a body of water.24. A hydro-power generation apparatus as claimed in claim 24, in which the controller is adapted to maintain the position of the apparatus at a depth where the water flow rate relative to a substantially fixed lateral position of the apparatus is a maximum.
25. A hydro-power generation apparatus as claimed in any one of claims 17 to 24, in which the apparatus is moored by a mooring line.
26. A horizontal axis turbine assembly substantially as described herein with reference to and as illustrated in Figures 1 to 5 of the accompanying drawings.
27. A hydro-power generation apparatus substantially as described herein with reference to and as illustrated in Figures 1 to 5 of the accompanying drawings.