WO2007055585A1

WO2007055585A1 - Turbine generator

Info

Publication number: WO2007055585A1
Application number: PCT/NO2006/000401
Authority: WO
Inventors: Tørris SKAALUREN; Stein Stendahl
Original assignee: Elinova As
Priority date: 2005-11-08
Filing date: 2006-11-08
Publication date: 2007-05-18
Also published as: EP1952014A1; NO20055236A; EP1952014A4; NO323150B1; NO20055236D0

Abstract

A turbine generator to generate electric power from through-flowing water is described, comprising a pipe-formed stator (12) with built-in, watertight, electric magnet windings (22), a pipe-formed rotor (10) with no hub which is mounted rotary in the stator (12) and end flanges (14a, 14b) for mounting of the rotor (10) in the stator (12), where the rotor (10) forms the turbine pipe and comprises a through-running, inner opening (38), and also vanes (16) that extend in towards the centre of said opening, arranged to be driven by the through-flow of water. The rotor (10) comprises built-in, watertight, permanent magnets (24) arranged to cooperate with the magnet windings (22) in the stator (12) to generate electric power, and that the rotor (10) is mounted with the help of a side bearing (26) at each end and also at least one top bearing (32) between the stator (12) and the rotor (10), arranged to take up both radial and axial forces and to prevent the stator (12) and rotor (10) from coming into contact with each other.

Description

TURB INE GENERATOR

The present invention relates to a turbine generator to generate electric power from through-flowing water, comprising a pipe-formed stator with built-in, watertight, electric magnet windings, a pipe-formed rotor without a hub that is rotary mounted in the stator, and also at least one top bearing and end flanges for mounting the rotor in the stator, where the rotor forms the turbine pipe and comprises a through-going, inner opening, and vanes that extend in toward the centre of said opening, arranged to be driven by the through-flowing water.

The invention is in the main developed for, but not limited to, the use of slowly flowing water streams, such as in rivers and fjords with tidal streams, and also outflow from dams and power stations where the fall height is too low to use conventional turbines.

From prior art, among others US 4,123,666 shall be mentioned, where the document describes a water turbine where the turbine wheel is mounted in a pipe and with vanes secured to a hub in the centre and, at the end, to a ring that rotates together with the rest of the turbine wheel. Furthermore, the rotor part of an electric generator is fastened to the ring. US 2,652,505 concerns a propulsion device for a ship, with vanes that extend out from a ring and in towards the middle of the pipe, and functions as a pump. From JP 9177652, US 6,648,589, US 6,729,840 and US 5,592,816, a water turbine where the rotor has vanes that are fastened in the periphery and which extends in towards the centre of the pipe is also known. The rotors have no hub. Power transmission is mechanical in that the rotor drives a drive wheel, which in turn drives a shaft of a generator. To shape the rotor poles in a turbine generator in the form of permanent magnets is known from EP 0977343 A1 , but the turbine generator in said document is axially mounted.

Of the preferred embodiments, it is US 2,652,505 that appear to be the most pertinent citation. What in particular separates the two systems is that the present turbine generator is comprised of only four main components, namely a stator, a rotor, bearings and flanges, while the solution described in US 2,652,505 is comprised of very many parts, where some of the parts are very vulnerable to water penetration because of the necessary sealing between the rotating part and the stator (brushes/slip rings). In addition, the bearings are oiled and only at the periphery between rotor and stator. The present invention uses a different electric principle, namely a permanent magnet generator. Thus, the need for electric brush transmission between rotor and stator is removed, as the permanent magnets are placed in the rotating part. This ensures that there is no need for watertight or pressure tight encasing between rotor and stator. Regulation of voltage, frequency and load etc., in the present solution is carried out with the help of newly developed power electronics.

Furthermore, in the present invention, a principle of building-in auxiliary windings in the rotor to be able to re-magnetise the permanent magnets if the magnetism for different reasons disappears is developed. Isolated contact points can be opened at the end of the rotor for the magnetisation without dismantling the rotor, which one must do today. This will simplify the operation and maintenance. The mounting of the rotating part is different, as the present solution can use ball bearings at each end, in addition to spacer rollers between rotor and stator. This is necessary to take up the large radial and axial forces. Furthermore, the bearings can be lubricated by water.

The turbine generator according to the invention is, as mentioned, comprised, in the main, of only four main parts: Stator, rotor with vanes and two end flanges. The rotor of the generator is preferably formed as a tube. In the walls of the tube (of the rotor), permanent magnets are placed. The turbine vanes (or wings) are preferably secured to the inner wall of the tube and do not meet in the centre. The windings of the stator can be sealed watertight, as can be the permanent magnets in the rotor. The electric cable connection can also be made to be watertight.

This combination of turbine and permanent magnet generator without a hub in one composite, watertight unit is not previously known, and the advantages are a simple and robust construction of few parts and no mechanical transmissions in the form of gear ratio and shaft that lead to a low mechanical loss. Sizes up to 500 kW or more will be possible with the present technology.

The object of the turbine generator according to the invention is to transform the kinetic energy in slowly flowing water streams, such as rivers and tidal streams to electric energy in a cost efficient way without building dams and pipe trenches. With the present technology, renewable energy sources are used without impinging on nature, and with units that can easily be dismantled and be removed without leaving signs of defacement. The turbine generator according to the invention can have many application areas. The units can either be fitted on frameworks placed on the river bottom or fjord bottom, or be suspended from pontoons that are anchored in the stream. Another alternative can be to fasten the unit to outliers on the riverbank or fastened/integrated in piers that stand in the stream.

For these above-mentioned application areas, a water-collecting funnel can, for example, be fitted to lead as much of the water stream as possible into the turbine.

Another application area for the turbine generator can be to flange the unit on the outlet pipe of a dam, or the outlet channel from existing power stations where the fall height is low. In these cases, the turbine generator can be flanged below a snail shell-formed inlet that sets the water in circulation before it flows in to the turbine. With this method, better through-flow and lower cavitation and thus improved total efficiency are achieved.

The above mentioned objects are reached with a turbine generator as described in the introduction, and as characterised by the characteristic in the independent claim 1 , in that the rotor comprises built-in, watertight, permanent magnets arranged to cooperate with the magnet windings in the stator to generate electric power, and that the rotor is mounted with the help of at least one side bearing at each end and also said top bearing between the stator and the rotor, arranged to take up both radial and axial forces and to prevent that the stator and rotor come into contact with each other.

Alternative preferred embodiments are characterised by the dependent claims 2-9. The side bearing of the rotor, preferably on each side surface, comprises half of a ball bearing path arranged circularly on the side surface and each end flange comprises a corresponding half of a ball bearing path, which together form a ball bearing path and which is arranged to receive a number of bearing balls so that the rotor is fitted a certain distance from the end flanges dependent on the diameter of the ball bearings. The top bearing is arranged internally in the stator and comprises preferably a number of ball bearings, adjoining both sides of the internal boring of the stator, set out to roll against the outer surface of the rotor and to keep the rotor a certain distance from the stator. The water turbine according to the invention can comprise a power-electronic control system for control of voltage, frequency, load, etc. to the net, and where the system comprises at least one of an active rectifier, a reactive effect compensator, a net stabiliser, an active filter and/or fully digital control electronics.

Furthermore, the rotor can comprise built-in auxiliary windings arranged to re- magnetise the permanent magnets if the magnetism disappears. For magnetisation, isolated contact points can be arranged at the end of the rotor where the contact points are adapted to be opened.

It is preferred that an inlet channel in the form of a guiding funnel is arranged to at least one side of the stator, where the guiding funnel can internally be spiral formed. The inlet angle in the guiding funnel can, in one embodiment, preferably be between 5° and 20°, more preferably between 10° and 15°, and most preferably be about 11°.

The invention shall now be described in more detail with reference to the enclosed figures, in which:

Figure 1 shows in perspective a permanent magnet generator according to the invention.

Figure 2 shows an exploded permanent magnet generator shown in figure 1.

Figure 3 shows a general arrangement of a generator system according to the invention viewed from the side.

Figure 4 shows a partial section of the permanent magnet generator according to the invention.

Figure 5 shows a partial section of the permanent magnet generator according to the invention in axial direction. Figures 6 and 7 shows a partial section of auxiliary windings in the rotor of the permanent magnet generator.

Figures 8 and 9 show an example of an inlet funnel for use at a generator according to the invention.

Figures 10 to 18 show different application areas for a generator system according to the invention.

As the figures show, the present invention comprises a permanent magnet generator with a pipe-formed stator 12 incorporating built-in, watertight, electric magnet windings 22, a pipe-formed rotor 10 without a hub which is mounted rotary in the stator 12 and end flanges 14a, 14b for mounting of the rotor 10 in the stator 12, where the rotor 10 forms the turbine pipe and comprises a through-going, inner opening 38, and also vanes 16 that extend in toward the centre of said opening, arranged to be driven by the water flowing through. The rotor 10 is consequently placed rotary in the stator 12 and inside the rotor 10 there are a number of rotor blades 16 or vanes arranged mutually spaced apart. The rotor blades 16 extend into the centre of the rotor's internal bore, preferably without the rotor blades touching each other. Thus, there is an opening in the centre that leads to better through-flow of water and less cavitation. The rotor 10 can thereby, because of the blades 16 being driven to transform the kinetic energy in slow flowing streams of water, such as in rivers and fjords with tidal streams, or outlets from dams and power stations where the height of fall is too low to use conventional turbines, to electric power that can be made available to power companies and/or private individuals. It shall be noted that the invention can also be used in fast flowing streams, but in this case, it must be adapted to the application area.

The stator 12, or more precisely, the stator housing, comprises preferably watertight, electric connection points 20 and is part of a power electronic control system 18 for control of voltage, frequency, load, etc. to the net, where the system comprises at least one of an active rectifier, a reactive effect compensator, a net stabiliser, an active filter and/or fully digital control electronics.

To generate electric power, the stator 12 comprises the built-in said field windings 22, while the rotor 10 comprises built-in permanent magnets 24. When the rotor 10 is rotated because of the effect of the water on the rotor blades 16, the electric power is generated due to the fields that arise between the windings 22 and the magnets 24. Use of permanent magnets are previously known and will therefore not be described in more detail as a person skilled in the arts will know of this technology.

So that the rotor 10 shall be correctly arranged and mounted in the stator 12 all the time, at least one side bearing 26 with a ball bearing path 28 between rotor and end flange(s) is provided. The ball bearing path 28 is divided into two halves 28a, 28b with the same or different radius, where one half 28a is arranged circularly internally on the end flanges 14a and 14b, while the other half 28b is correspondingly arranged on the outside of the side surface of the rotor 10. Preferably, a ball bearing path 28 is provided on each side, but it shall not be disregarded that one or more than what is shown in the figures can be used. In the ball bearing path 28, a number of bearing balls 30 are arranged. Correspondingly, at least one top bearing 32 is provided between the rotor and the stator, where the top bearing 32 is arranged internally in the bore of the stator 12 and comprises a number of roller bearings 34, which are mounted, for example, on a shaft 36. A top bearing 32 is preferably arranged adjoining both sides of the internal bore of the stator, and which is arranged to roll against the outer surface of the rotor 10 and to hold the rotor 10 at a certain distance from the stator 12. Said side bearings and top bearings can be water lubricated.

The figures 6 and 7 show a principle drawing of the rotor 10 with the permanent magnets 24 arranged in the periphery of the rotor and with a number of auxiliary windings 40 arranged between the magnets for the magnetising according to need. These auxiliary windings 40 can be used for re- magnetisation if the permanent field in the generator disappears. Furthermore, contact points 42 are provided, which are preferably sealed, and where there is access from one or both sides of the ends of the rotor for connection of auxiliary voltage. The isolated contact points 42 can be opened at the end of the rotor for magnetising without dismantling the rotor as one must do today. This will consequently simplify operation and maintenance.

To increase the efficiency of the turbine generator, an inlet funnel 50 or a supply pipe can be arranged in the inflow direction of the water. The funnel 50 is shaped with the idea to achieve the best possible through-flow of water with as little cavitation as possible and the funnel is therefore preferably in the form of a spiral, internally. The spiral form can, if desired, be omitted. The inlet angle of the inlet funnel 50 can preferably be between 5° and 20°, more preferably between 10° and 15°, and most preferably be about 11°.

By forming the inlet funnel 50 as a funnel with profiles/guiding rails 52 in the form of a spiral, two things are obtained: To capture as much water as possible and increase the speed of the water stream, and to set the stream of water in rotation before the water hits the turbine blades. Tests have shown up to 25% increase in through-flow of water in certain installations. The shape of the guiding rails must be adjusted for optimisation for each individual case, based on fluid flow calculations. The production of power from integrated turbine/generators based on a permanent magnet generator according to the invention must be harmonised with the net before being phased in. Traditionally, such harmonisation is carried out partially mechanically by altering the flow of water, and partially electrically with the use of power electronics.

AC/DC transformers, synchronised against an AC net, alternatively against, for example, windmill generators are widespread. The challenges that arise when power electronic transformers are connected to the net have to do with the dimensions of the transformer. In particular, it is with "weak" nets that the problems are greatest. The conditions that cause problems are resonance and stability, voltage quality, power governing and behaviour at faults (component limitations).

Over recent years, power electronic transformers have seen much development. A modern power electronic transformer to be used in permanent magnet generators can be composed of: Active rectifiers (pulls active effect. This can be configured to pull sine-formed currents. The effect can also be driven in both directions and be altered instantaneously). Reactive effect compensators. Net stabiliser. Active filter ("repairs the voltage curve shapes" by injecting current overtones, i.e. they can also go as electronic controlled resistive load). Completely digital control electronics.

Power semi-conductors are under continuous development, where the yield grows and they become sturdier, reliable and the switching characteristics increase. Control has become simplified and the production costs are falling. Interaction between the components is steadily improving. The power electronic control system can consequently be made from known solutions, or from solutions that will be developed in the future.

The figures 10 to 18 show implementation of the invention in different environments. Figures 10 and 11 show principle drawings for mini power stations that utilise discharge water from an existing power station. The inlet funnel can in these cases be fitted in the direction of, or across, the inlet of the turbine generator. Figure 12 shows a variant to be joined to a dam, a lock, outlet source for drinking water, etc. Figure 13 shows an example of fitting of the generator in connection with a pier in rivers and tidal streams, where the generator is placed to the side of the pier. However, the generator can also be integrated into the pier. The figures 14 and 15 show examples of placing at a riverbank, suspended or sitting at the bottom, respectively. Figure 16 shows the generator system suspended from a barge. Furthermore, figures 17 and 18 show the generator system suspended in pontoons or buoys, so that boats and ships can sail over the system.

Claims

CLAIMS.

1. Turbine generator to generate electric power from through-flowing water, comprising a pipe-formed stator (12) with built-in, watertight, electric magnet windings (22), a pipe-formed rotor (10) with no hub that is mounted rotary in the stator (12), and also at least one top bearing (32) and end flanges (14a, 14b) for mounting the rotor (10) in the stator (12), where the rotor (10) forms the turbine pipe and comprises a through-running inner opening (38), and vanes (16) that extend in towards the centre of said opening, arranged to be driven by the water flowing through, characterised in that the rotor (10) comprises built-in, watertight, permanent magnets (24) arranged to cooperate with the magnet windings (22) in the stator (12) to generate electric power, and that the rotor (10) is mounted with the help of at least one side bearing (26) at each end and also said top bearing (32) between the stator (12) and the rotor (10), arranged to take up both radial and axial forces and to prevent that the stator (12) and the rotor (10) come in contact with each other.

2. Turbine generator according to claim 1, characterised in that said side bearing (26) comprises a ball bearing path half (28b) arranged circularly on the side surfaces of the rotor (10) and corresponding ball bearing path half (28a) on each end flange (14a, 14b), where the halves (28a,28b) form a ball bearing path (28) which is arranged to receive a number of ball bearings (30), whereby the rotor (10) is rotary mounted at a certain distance from the end flanges (14a, 14b), dependent on the diameter of the ball bearings (30).

3. Turbine generator according to claims 1 and 2, characterised in that the top bearing (32) is arranged inside the bore of the stator (12) and comprises a number of roller bearings (34), adjoining both sides of the internal bore of the stator, arranged to roll against the outer surface of the rotor (10) and to hold the rotor (10) a certain distance from the stator (12).

4. Turbine generator according to claim 3, characterised in that the water turbine comprises a power electronic control system (18) for the control of voltage, frequency, load, etc. to the net, and where the system comprises at least one of an active rectifier, a reactive effect compensator, a net stabiliser, an active filter and/or completely digital control electronics.

5. Turbine generator according to claims 3 or 4, characterised in that the rotor (10) comprises built-in auxiliary windings (40), arranged to re- magnetise the permanent magnets (24) if the magnetism disappears.

6. Turbine generator according to claim 5, characterised in that isolated contact points (42) for the magnetisation are arranged at the end of the rotor (10), where the contact points (42) are arranged to be opened.

7. Turbine generator according to one of the preceding claims, characterised in that an inlet channel in the form of a guiding funnel (50) is arranged to at least one of the sides of the stator (12).

8. Turbine generator according to claim 7, characterised in that the guiding funnel (50) is internally in the form of a spiral.

9. Turbine generator according to claims 7 or 8, characterised in that the inlet angle of the guiding funnel (50) is preferably between 5° and 20°, more preferably between 10° and 15°, and most preferably about 11°.