GB2180411A

GB2180411A - An electric generator and a bearing arrangement for use therewith

Info

Publication number: GB2180411A
Application number: GB08618567A
Authority: GB
Inventors: Roger Hall
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-07-30
Filing date: 1986-07-30
Publication date: 1987-03-25
Also published as: GB8618567D0; GB8519171D0; GB2180411B

Abstract

An electric generator is described which uses the principle of Crooke's radiometer. A rotor (1) carrying vanes (2,3) and permanent magnets (5) of opposite polarity is mounted on a shaft (4) within a partially evacuated radiation transparent vessel (6). The shaft (4) is mounted in substantially frictionless magnetic bearings (10)(11) and a coil of wire (8) is wound longitudinally around the vessel (6). The vanes are black on one side and white on the other side and incident radiation on the black side causes the rotor (1) to rotate and movement of the magnets (5) past the coil (8) causes a current to be induced to flow in the coil (8) which can be taken off at a load. The generator has applications in space and also in energy recovery systems. <IMAGE>

Description

SPECIFICATION An electric generator and a bearing arrangement for use therewith The present invention relates to an electric generator and to a bearing arrangement for use therewith.

Over the last couple of decades the need to pioduce cheap, clean energy has become increasingly important. Fossil fuels, which at the present time produce most of our electrical energy are a finite resource and as such their cost rises as sources for them are exhausted.

In addition, when fossil fuels are burnt they produce products of combustion which are considered by many to be responsible for the pollution of the environment.

Nuclear energy is used as an alternative to fossil fuels, but it has numerous opponents who oppose nuclear energy on the grounds of cost and safety. Another source of energy which has been considered for exploitation is solar energy which is clean and virtually free to all. At the present time solar energy is converted into electrical energy using banks of solar cells which convert incident radient energy into electricity.

As is well known the efficiency of an electrical generator can never be one hundred percent because of the losses which occur within the generator. Where the generator includes a rotor a significant amount of energy is lost as a result of friction at the bearings of the rotor.

It is an object of the present invention to provide an electric generator which is clean to run, in that it can make use of solar energy and other sources of radiant energy.

It is a further object of the present invention to provide a very low friction bearing arrangement.

According to a first aspect of the present invention there is provided an electric generator comprising means for generating a magnetic field, at least one coil of wire and drive means for moving said at least one coil of wire relative to said magnetic field so as to induce an electric current therein, wherein said drive means comprises a plurality of vanes mounted about a central, substantially freely rotatable shaft located within a partially evacuated radiant energy transparent vessel, each vane being energy absorbent on one side and energy reflecting on the other side.

In one embodiment of the present invention the magnetic field is generated by permanent magnets carried by the vanes and a coil of wire is wrapped around the said tube. Wire is wound lengthwise along the outside of the partially evacuated vessel then radially to the bearing housing, round this housing so that when a current passes through this wire a magnetic field is generated such that it repels the polarity of the adjacent rotor end. It is then taken radially and then along the length of the vessel to the other end, and round the bearing housing again such that the magnetic field generated repels the polarity of the rotor shaft at that end. The circuit is completed either,at its most basic, by simply joining the wires together to form a closed loop or by completing the circuit through a load.

In an alternative embodiment of the present invention a plurality of coils are carried by the said vanes, which lie within a magnetic field.

In this embodiment of the present invention the output of each coil is connected to a commutator. Furthermore, in this embodiment of the present invention the magnetic field may be generated by a pair of permanent magnets or a pair of electro-magnets.

The reflector, parabolic or otherwise,is arranged such that it does not focus solar radiation onto the apparatus in such a way as to raise the magnetic material to a termperature where its magnetism is depleted or eliminated or that any of the material of the generator is deformed by focussed heat. To achieve this the vessel is coated so that the radiation permitted by the coating to enter the vessel permits it to work or that a shield be placed in front of the reflector such that the radiation entering the vessel again permits it to work.

A combination of the two above arrangements may be used.

Preferably, a parabolic reflector is provided to focus incident radiant energy into the path of the radiant energy absorbing vanes. Conveniently, the vanes are flat planes. Alternatively the vanes are provided in planes formed by twisting the vanes about the longitudinal axis.

Where the drive means comprises only two vanes these are preferably twisted about their logitudinal axis through approximately ninety degrees so as to effectively provide a surface upon which radiant energy may be focused by the said parabolic reflector at all times.

Preferably, each vane is black on one side and white on the other.

Preferably, the said partially evacuated radiant energy transparent vessel is comprised of glass.

The ends of the freely rotatable shaft may be mounted in needle bearings, or alternatively may use a bearing arrangement according to the second aspect of the present invention.

According to a second aspect of the present invention there is provided a bearing ar rangement for a magnetic rotor comprising means for generating a magnetic field of sub stantially uniform strength about the end of the rotor such that the end of the rotor is maintained within the centre of the uniform magnetic field.

Preferably, a magnetic bearing is provided at each end of the rotor, in which case means for generating a magnetic field at each end of the longitudinal axis of the rotor is provided to prevent longitudinal movement of the rotor.

Preferably, the magnetic field generated by the magnetic bearing opposes the magnetic field of the magnetic rotor, thereby causing the end of the rotor to be repelled to the centre of the magnetic field generated by the magnetic bearing.

The means for generating the uniform magnetic field may comprise one or more permanent magnets, or one or more electro-magnets. Where the bearing arrangement makes use of electro-magnets and is used in an electric generator the output of the generator can be tapped to drive the electro-magnets.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a perspective view of an electric generator according to the first aspect of the present invention, supported by a pair of bearings according to the second aspect of the present invention; Fig. 2 shows an end view of the electric generator of Fig. 1, and Fig. 3 is a front elevation of the generator of Fig. 1 without the heat shield and windings.

The generator of the present invention is based upon the principle of a radiometer, that is a device first proposed by William Crookes in 1876 in which a plurality of vanes or "flies" are connected to a shaft which is mounted on a needle bearing and positioned inside a partially evacuated glass tube. The flies are black on one side and white an the other and, as a consequence,when the device is placed in the path of a source of radiant energy energy is absorbed by the black side of each fly, whilst being reflected by the white side thereof. This creates a temperature differential across each fly which results in the gases on the black side of each fly having more kinetic energy than those on the white side thereof, which causes the black side of each fly to be driven away from the incident radiant energy.The needle bearing provides a very low friction bearing and as a result the shaft is able to rotate under the drive provided by the flies.

Referring now to the accompanying drawings there is shown a diagrammatic view of an electric generator comprising a rotor 1 having two rectangular vanes 2,3 mounted on opposite sides of a shaft 4. In the interest of clarity parts of a framework for attaching parts together have been omitted. The outer edges of the vanes 2,3 are black on one side and white on the other so as to make use of the principle behind Crooke's radiometer. Between outer edge of each vane 2,3 and the shaft 4 is disposed a permanent magnet 5 such that one vane 2 is South seeking and the edge of the other vane 3 is North seeking, i.e. magnets on opposite vanes are of different polarity.The rotor 1 is mounted in a partially evacuated glass tube 6 and each end of the shaft 4 is freely rotatable in a respective bearing housing arrangement generally indicated by reference numeral 7, which will be discussed in further detail hereinbelow. A coil of wire 8 (shown in broken outline) is wrapped around the glass tube 6 so as to extend along and around the longitudinal axis of the rotor 1 and is then wound radially around bearing housing 7 shown by broken line 8a. A parabolic reflector 9 is provided to one side of the glass tube 6 which focuses incident radiant energy, for example, solar radiation into the path of the black side of each vane 2,3 one vane at a time as the rotor 1 is rotated. This reflector 9, as best seen in Fig.

2 is a half of a parabola and is disposed in relationship to the generator such that the axis of symmetry is on a line between the upper surface of the vessel and incident solar radiation. Thus the vessel is in shadow from heat shield 14 (Fig. 2) and solar radiation to power the apparatus comes from reflections from the reflector 9.

As has already been explained hereinabove when radiant energy is incident upon a fly which absorbs energy on one side and reflects energy from the other the energy absorbent side of the fly is driven forward. In the electric generator according to the present invention radiant energy incident on the vanes 2,3 drives the rotor 1 around and this results in the North and South seeking magnets 5 carried by the vanes 2,3 to move relative to the coil of wire 8 surrounding the glass tube 6. When a wire is moved through a magnetic field an electric current is induced into the wire and hence an electric current is generated in the coil 8. The coil is coupled to a suitable load (not shown in the interest of clarity) and for receiving current generated in the coil.The parabolic reflector 9 focuses radiant energy into the path of the black side of each vane 2,3 which ensures that the temperature differential between the black and the white side of each vane 2,3 is maintained as high as possible. This ensures that the electric generator runs as efficiently as possible.

The magnetic bearing housing arrangement 7 in which each end of the shaft 4 is rotatably mounted comprises a hollow cylindrical permanent magnet 10 arranged so as to fit over the end of the shaft 4. Each end of the shaft 4 is magnetically polarised and is of the opposite polarity to the magnet 10. Wire is wound lengthwise along the outside of the partially evacuated vessel 6 then radially to the bearing housing 7 and round this housing so that when a current passes through this wire 8 a magnetic field is generated such that it repels the polarity of the rotor end adjacent.

The wire is then taken radially and then along the length of the vessel 6 to the other end and round the bearing housing 7 again such that the magnetic field generated repels the polarity of the rotor shaft at that end. The circuit is completed either at its most basic by simply joining the wires together to form a closed loop or by completing the circuit through a load. As a consequence the end of the shaft 4 is always repelled towards the centre of the cylindrical aperture 11 (see Fig.

2).

As there is no physical contact between the end of the shaft 4 and the bearing arrangement 7 the shaft 4 only has to overcome the friction exerted on it by the residual gases in the glass tube.

In the electric generator described hereinabove a plurality of magnets have been rotated relative to a fixed coil of wire to induce an electric current in the coil. However, it will be appreciated that as an alternative the magnets may be fixed in position outside the glass tube and that the vanes may carry one or more coils of wire which move relative to the fixed magnets. In this arrangement the output from each of the coils is preferably connected to a commutator.

It will further be appreciated that whilst the electric generator according to the present invention has been described comprising two vanes in practice more than two vanes may be provided. This allows the rotor to carry more magnets or coils. Permanent magnets may be mounted on the edges of the vanes or below the long edge of the vanes 2,3 and parallel to them. The vane and magnetic material may be either of the same or different materials.

A gap or plurality of gaps may or may not be provided between the vane inner edge and the material interposed between this edge and the rotor shaft. A further gap or plurality of gaps may also be placed between the rotor shaft and any material/s interposed between it and the outer edge of the rotor.

The electric generator according to the present invention may be used as a stand-by electric generator which can be used when incident radiant energy levels are high enough to permit a switch from a main electrical supply. It is expected that the generator would usually rely on solar energy to operate it, however, it could also be run by hot gases or liquids, which means it could be fitted in the outlet of a power plant or industrial installation to recover energy otherwise going to waste.

Of course the generator can be used in many terrestrial situations requiring electricity, but it can also be used in space to replace conventional solar cells.

Whilst the magnets used for the bearing arrangement have been referred to as permanent magnets it will be appreciated that electro-magnets can be used instead. In the case of the bearing housings 7 electro-magnets can be used which are provided by power from the output of the coil 8.

Magnetic bearings may be bar magnetic, one end of which is to be bored out to a distance less than half its overall length and to such a shape as will fit over the bearing housing which itself projects from each end of the vessel. The bearing housing interiors are continuous or integral with the interior of the vessel and may be thought of as the handles of a hollow partially evacuated "rolling pin". The apparatus may be used to apply a torque to the shaft attached to and remote from the rotor or to turn the magnets if attached to the rotor.

Claims

1. An electric generator comprising means for generating a magnetic field, at least one coil of wire and drive means for moving said at least one coil of wire relative to said magnetic field so as to induce an electric current therein, wherein said drive means comprises a plurality of vanes mounted about a central, substantially freely rotatable shaft located within a partially evacuated radiant energy transparent vessel, each vane being energy absorbent on one side and energy reflecting on the other side.

2. An electric generator as claimed in claim 1 wherein the magnetic field is generated by permanent magnets carried by the vanes and a coil of wire is wrapped around the said tube.

3. An electric generator as claimed in claim 1 wherein a plurality of coils are carried by the said vanes, which lie within a magnetic field.

4. An electric generator as claimed in claim 3 wherein the output of each coil is connected to a commutator.

5. An electric generator as claimed in anyone of claims 1,3 or 4 wherein the magnetic field may be generated by a pair of permanent magnets or a pair of electro-magnets.

6. An electric generator as claimed in any preceding claim wherein a parabolic reflector is provided to focus incident radiant energy into the path of the radiant energy absorbing vanes.

7. An electric generator as claimed in any preceding claim wherein the vanes are flat planes.

8. An electric generator as claimed in any preceding claim wherein the drive means comprises only two vanes these are preferably twisted about their longitudinal axis through approximately ninety degrees so as to effectively provide a surface upon which radiant energy may be focused by the said parabolic reflector at all times.

9. An electric generator as claimed in any preceding claim wherein each vane is black on one side and white on the other.

10. An electric generator as claimed in any preceding claim wherein said partially evacuated radiant energy transparent vessel is com prised of glass.

11. An electric generator as claimed in any preceding claim wherein said shaft is mounted in substantially frictionless magentic bearings.

12. An electric generator as claimed in any preceding claim wherein a bearing arrangement for a magnetic rotor comprises means for generating a magnetic field of substantially uniform strength about the end of the rotor such that the end of the rotor is maintained within the centre of the uniform magnetic field.

13. A bearing arrangement as claimed in claim 12 wherein a magnetic bearing is provided at each end of the rotor, in which case means for generating a magnetic field at each end of the longitudinal axis of the rotor is provided to prevent longitudinal movement of the rotor.

14. A bearing arrangement as claimed in claim 12 or claim 13 wherein the magnetic field generated by the magnetic bearing opposes the magnetic field of the magnetic rotor, thereby causing the end of the rotor to be repelled to the centre of the magnetic field generated by the magnetic bearing.

15. A bearing arrangement as claimed in any one of claims 12 to 14 wherein the means for generating the uniform magnetic field may comprise one or more permanent magnets, or one or more electro-magnets.

16. A bearing arrangement as claimed in claim 15 wherein the bearing arrangement makes use of electro-magnets and is used in an electric generator the output of the generator can be tapped to drive the electro-magnets.

17. An electric generator substantially as hereinbefore described with reference to the accompanying drawings.

18. A bearing arrangement substantially as hereinbefore described with reference to the accompanying drawings.