WO2004020283A2

WO2004020283A2 - Electric generator

Info

Publication number: WO2004020283A2
Application number: PCT/IS2003/000026
Authority: WO
Inventors: Bjorgvin Bjornsson
Original assignee: Djupraf Ehf.
Priority date: 2002-09-02
Filing date: 2003-09-02
Publication date: 2004-03-11
Also published as: AU2003256065A8; AU2003256065A1; WO2004020283A3

Abstract

The present invention relates to an electric generator that is capable of producing electricity independent of whether it is filled with a fluid such as water, or a gas. Furthermore, the generator is free of traditional bearing systems and is capable of functioning in water or sea-water at large depths.

Description

ELECTRIC GENERATOR

Field of the invention

The present invention relates to an electric generator that is capable of producing electricity independent of whether it is filled with a fluid such as water, or a gas. Furthermore, the generator is free of traditional bearing systems and is capable of functioning in water or sea- water at large depths.

Background The fishing industry has in the last years increasingly utilised modern technology. During fishing it is of crucial importance to be able to monitor incoming fish, actual depth of the pelagic trawl, as well as other parameters such as the temperature of the water. In nearly all modern trawlers the fishing trawl is provided with different kinds of sensors for such surveillance, and for this purpose the ships use as an example a deep-see-transmitter, a manometer and a thermometer. Without such instruments, present-day fishing is virtually impossible.

Today, over 150 deep-see-transmitters are used in trawling in Iceland. These instruments, as well as many other instruments, typically operate using 12 Voltage (8*1,5V batteries) disposable batteries. The lifetime of such batteries depends on conditions, i.e. the depth and the temperature of the water, as well as the conditions of the instruments. It is common that the batteries need to be replaced twice every 24 hours. This means that the fishing trawl, to which the instruments are attached, must be heaved up for replacing the batteries. This can be very time consuming and expensive, and there are also examples of occasions where no extra batteries where available, due to human mistakes, so that fishing had to be stopped until exhausted batteries were replaced with new ones. In such cases one or even a few days are lost, which means an enormous loss in profit. Furthermore, in some cases, the shoal of fish can be lost in this time gap. Additionally, the risk of damaging the equipment increases when batteries must be replaced this frequently.

Electric generators for driving instruments and small appliances in open water are well known. For example, NO 176226 and US 4,102,291 disclose methods for using a propeller immersed in water or sea-water to produce electricity by a connection to a generator located on board a vessel, such as a boat or a ship.

However, if appliances used at large depths such as those experienced by trawls or other fishing appliances are to be driven by electricity generated in situ, a method and device for generating electricity at such depths is needed. Therefore the is a need for reliable power sources and/or a generator that can deliver sufficient power for underwater instruments used with modern fishing trawls, or to deliver power to other appliances used at large depths.

Description of the invention

It is an object of the present invention to provide a generator that can run in an aqueous environment, where it is surrounded with fresh water or sea water, or where it is surrounded with any kind of gas. Furthermore, it is an object of the present invention to provide a generator that can run in a high pressure environment, such as that experienced at a water depth of up to 2000 m, or even more.

In a first aspect, the present invention provides an electric generator comprising

• a housing,

• a shaft mounted in said housing, said shaft being rotatable along a rotation axis,

• a propeller comprising at least one propeller blade attached to said shaft and positioned at a first end of said shaft, said end defining a proximal end,

• supporting means for supporting a second end of said shaft, said end defining a distal end,

• a rotor system attached to said shaft, said rotor system comprising a magnetic field generator positioned normally to and attached to said shaft,

• a stator system arranged on said housing and normally to said rotation axis, said stator system being encapsulated by an electrically insulating material and positioned adjacent to said magnetic field generator.

As the magnetic field generator attached to said shaft rotates, a electromagnetic field is generated which leads to the formation of electric current in the stator system.

The magnetic field generator may optionally be insulated by an electrically non-conducting material. Thus, in one preferred embodiment, the magnetic field generator is encapsulated by an electrically non-conducting material.

Encapsulation of said stator system and optionally said magnetic field generator typically comprises moulding said stator system and optionally said magnetic field generator in an electrically non-conducting material. The purpose of the encapsulation is to provide insulation of the stator and optionally the magnetic field generator from the surrounding sea water. By providing this insulation, the present invention provides a generator which can be essentially filled with a fluid such as sea water while producing electricity.

The electrically non-conducting material can be any electrical insulator suitable for use in encapsulating or moulding the stator system and optionally the magnetic field generator. Furthermore, the insulator needs to be resilient, and ideally should be able to resist pressure corresponding to a water depth of up to 2000m or more. The insulator should furthermore be resistant to water, such that it does not allow water to permeate the material even at high water presssure. Possible materials can for example be selected from the group consisting of plastic insulators, epoxy-type plastic insulators, glass insulators, ceramic insulators, silicon elastomers, or any mixture thereof. Other materials fulfilling the physical requirements of the electric insulator are also possible. In a preferred embodiment, epoxy-type plastic material are used, since such materials are easily moulded and are resistant to water, even at high pressures. The magnetic field generator can be any permanent magnet. Examples of magnets that can be used are ferrite magnets, rare earth magnets such as neodymium iron boron (NdFeB) magnets, samarium cobalt (SmCo) magnets, aluminum-nickel-cobalt (AINiCo) magnets, or any other permanent magnet capable of utiliziation in the context of electric generators.

In a preferred embodiment, the electric generator futher comprises an electronic control. The generated electric current is transferred from the stator to the electronic control. The electronic control can serve to regulate the voltage generated by the generator, it can generate DC from AC current, and may optionally include other electronic controls appropriate for any given embodiment of the invention.

For optimal transfer of induced electromagnetic current from the magnetic field generator to the stator, the stator is ideally positioned in close proximity to the magnetic field generator. Thus, a spacing separating the stator and the magnetic field generator with dimensions on the order of about 0.2-5 mm is typically employed, such as about 0.5-3 mm, including 1-2 mm.

The electronic control may be positioned within said housing. In such an embodiment, the electronic control is positioned such that it is isolated from the surrounding liquid such as water, and is surrounded by the housing and a separation wall positioned between the electronic control and the stator system (which is surrounded by a liquid sucha as water). The separation wall may be of any dimension and material suitable for realising the invention. The wall needs to form a seal with the housing, such that no water can penetrate into the electronic control unit. The wall is comprised of a resilient material, such as stainless steel, or any other suitable non-corrosive, resilient material.

In an alternative embodiment, the electronic control is moulded into an electrically nonconducting material which is water-impermeable. The material can for example be a plastic material, such as an epoxy plastic. By moulding the electronic unit, alternative embodiments in which the electronic unit is not isolated from the surrounding sea-water are possible. Water-resistant wires will in such embodiments transfer electrical energy from the stator to the electrical control unit, the wires being moulded into the moulding material surrounding the electronic control unit and the stator unit in a water-tight fashion.

The supporting means may in one embodiment be comprised of a a casing, against which the the distal end of said shaft is propped, and which provides support for the shaft while simultaneously allowing free rotation of the shaft. The casing may be comprised of any suitable low-resistant material, such as a nylon material. In an alternative embodiment, a bearing system can replace the housing.

In one embodiment, the generator of the invention further comprises a chargeable power source connected to said electric field generator. Said connection is typically realized by an electrically insulated wire, or by other means well known to those skilled in the art. The chargeable power source may for example be a rechargable battery. By having the electricity generated by the generator provided through a rechargable battery, added security of the system is provided. Thus, if the electric generator fails, the instruments that are being powered by the generator can be powered by the rechargable battery until the generator can be either fixed or replaced.

The generator is in a typical embodiment submerged in water, usually sea-water, at a considerably depth that will depend on the purpose of the instrumentation that the generator is powering. The power needed to generate electricity is provided by the movement of the generator with respect to the surrounding sea-water, in a direction substantially parallel to the rotational axis of the generator. The movement is typically performed by pulling the generator by a suitable external force agent in a direction, such that the proximal-distal ends of the rotation axis of the generator are in a relative orientation which is substantially parallel to the direction of movement of the external force agent.

The external force agent is in one embodiment provided by a ship or a boat, or other equivalent means to which the generator is connected, typically via a trawl or other means for fishing. As the generator is dragged through the water, the propeller and the magnetic field generator attached to it, are rotated. The rate of the rotation will vary depending on configuration of the propeller and the speed of the ship. In a typical embodiment, however, the rotation is on the order of 200-400 revolutions/minute, but may in alternative embodiments go up thousands of revolutions per minute.

As the generator is pulled through the water, sea-water penetrates the generator and fills all cavities that are reachable. Thus, the magnetic field generator and the insulated stator will be surrounded by water. However, since the stator, and optionally the magnetic field generator, is encapsulated by an insulating material or moulded into such material, electricity is generated in the stator unit by the magnetic field generated by the revolving magnetic field generator.

The sea-water penetrating the generator furthermore serves the role of providing cooling to the system; as sea-water is typically at a temperature of no more than a few degrees C, the circulation of cold sea-water through the unit prevents the system from over-heating, which is an added benefit of the present invention.

In one embodiment of the invention, a net or equivalent means may mounted on the housing, may be placed in front of the propeller. The purpose of such a net is to prevent undesired articles or organisms from colliding with the generator and thus possibly damaging it.

A wide range of appliances or instruments can be powered by the electric generator of the invention. Thus, in one embodiment the generator produces electricity of up to 70-80 V, which means that all common instruments requiring either 12 V or 24 V can, by adjusting the voltage output, be powered by the generator. Such instruments can for example be an inspection camera, a deep-sea transmitter, a trawley sensor, a transponder sensor, a hydrophone, a thermometer or a manometer. However, it is envisaged that other instruments or appliances requiring higher voltage of up to at least 120 V can be powered by generators according to the present invention. Furthermore, while the generator produces AC current, it can be run either in an AC mode or a DC mode, by additional electronic controls well known to those skilled in the art. Therefore, common instruments requiring DC current can be powered using the generator of the present invention.

In one preferred embodiment, the magnetic field generator is comprised of a first annular magnetic field generator with a center of mass along said rotation axis, and a second annular magnetic field generator with a center of mass along said rotation axis and positioned radially to said first magnetic field generator. The stator system may in the preferred embodiment be comprised of an annular stator system positioned in between said first and said second magnetic field generators.

A distinct advantage of the present invention is that no sealings for preventing water from reaching or penetrating moisture-sensitive electrical components of the generator are required. The water-sensitive stator part of the generator is isolated from the surrounding water by an electrically non-conducting material, and the whole system, with the exception of electronic controls, operate while submerged in water. However, in alternative embodiments, even the electronic controls may be encapsulated by an electronically insulated material, in which case also those components may be submerged in water. Water-tight connection provided by electrically insulated wires will in such embodiments provide means for transferring generated electricity to the electronic controls.

In a second aspect, the present invention provides a method of generating electricity in an aqueous environment comprising movement of an electric generator of the invention in the proximal-orientation through water in the direction of said rotation axis, whereby water is forced through said generator, the flow of water resulting in rotation of said propeller and resulting in electricity being induced within said generator. In a preferred embodiment, the movement is accomplished by a ship.

The ship can be any vessel that either requires or would benefit from additional electricity itself, or carrying or dragging an instrument or appliance in need of electricity. Such instruments can in one embodiment be instruments used in the context of fishing using trawls, which require electricity to run at a water depth of up to 2000m.

Detailed description

In the following, the present invention, and in particular preferred embodiments thereof, will be described in greater details in connection with the accompanying drawings in which

Figure 1 shows a cross section of an electric generator according to the present invention,

Figure 2 shows an overview of a trawl with underwater instruments and an electric generator, and Figure 3 shows a schematic overview of a generator according to the present invention,

Figure 4 shos induced current as a function of the speed of a ship pulling an electric generator according to the invention,

Figure 5 shows power generated as a function of rotation speed,

Figure 6 shows induced current as a function of induced current by an electric generator according to the invention.

In Figure 1 is shown a cross-section of a generator, comprising a housing 1, a propeller shield 6b, and a supporting means for the propeller shield 6a, which may be made of steel or other appropriate material, a propeller 13, a shaft 17 on which the propeller is mounted 16, and propeller blades 7a, 7b fastened radially to said propeller. The number of propeller blades is not essential. Thus, in alternative embodiments, fewer (i.e. one) or additional blades are also compatible with the invention.

In this embodiment the rotor system comprises two permanent magnetic field generators 11, 12. Each magnetic field generator comprises a plurality of permanent magnets moulded together in a material, preferably a plastic material, in a way such that the symmetry of the moulded material comprising said plurality of magnets is circular, with a center of mass along the rotational axis along which the shaft 17 is positioned. Furthermore, the two magnetic field generators 11, 12 have a mutual center of mass along the rotational axis and are arranged within each other as Fig. 1 shows. The outer magnetic field generator 11 has a radius (Ri), which is larger than that of the inner magnet systeml2 (R₂). These two magnetic field generators 11, 12 are furthermore moulded together to form a single rotor system which is furthermore moulded to the shaft 17.

The stator unit comprises in this embodiment a plurality of coils (not shown) arranged in a circular manner in a mould such that the center of mass axis is along the rotational axis, and further such that the radius R₃ defining the distance from the radial edge of the stator unit to the rotational axis is such that R_!<R₃<R₂. The gap between the stator unit 10 and the magnetic field generators 11,12 is typically approximately 1 mm.

By varying the number of permanent magnets in the rotor unit as well as the number of coils and/or the number of turns in each coil, the induced current may be in the generator may be adjusted. Furthermore, the speed at which the generator is moving (defined by the cruising speed of the ship or vessel pulling the generator) will influence the electric field generation in the generator.

The shaft 17 is supported by the casing 3, which is made of any kind of low resistance material such as nylon. The casing as well as other supports for the rotation axis replace therefore traditional bearing systems. However, in an alternative embodiment, the casing may be replaced by a traditional bearing system, which is preferrably water-resistant or isolated from the surrounding water.

Additional support may be provided by an internal housing 18, which may be of a conical shape and molded to the shaft 17. The internal housing provides supplementary support to the structure, as well as providing a stream-lined dimension to the rotor system-internal housing structure.

To prevent the shaft 17 from sliding backwards and/or forwards along the rotational axis, a disk or similar means is arranged radially outwards on the rotation axis 20 between the interior housing 18 and the rotor system. Furthermore, a cap 21 may optionally be arranged on the propeller as a shield for the rotor.

In this embodiment the necessary electronic control unit is arranged in the interior 2 behind the stator unit 9,10. A separation wall 4 is arranged in-between the stator unit and the interior, forming a seal with the housing and thus preventing water from entering the interior. The induced current 19a, 19b is transferred from the stator to the electronic control via electrical wires.

As the stator unit is isolated from the environment by moulding the stator in a non-insulating material, and by arranging the electronic controls such that water cannot penetrate the interior, the generator can be operated in any environment in which water, sea-water and/or air is used to drive the propeller. The presence of water does not prevent the magnetic field generator connected to the rotor from rotating and generating electric current in the stator system.

Additionally, in normal underwater operation, sea-water will penetrate the interior 15 of the generator and the spaces between the rotor, the stator system and the housing, so as to provide cooling via heat transfer from the generator to the water.

As the stator unit and magnetic field generators are moulded into a water-resistand, resilient material, they are virtually waterproof, even at high water pressures. Furthermore, the control station is well isolated from the surrounding water. In an alternative embodiment, however, the electronic control is also moulded into an appropriate material, such as a plastic material.

Figure 2 illustrates a fish trawl 1 being provided with a plurality of underwater instruments 5,6 which can for example be one or more deep-see-transmitters, trawleye sensors, transponder sensors, hydrophones, thermometers, or manometers. As an example, the deep-see- transmitter is used for monitoring the incoming of fish into the trawl as well as monitoring the distance from the fish trawl to the ocean floor. In this embodiment an underwater generator 3 is mounted to the fish trawl with a rechargable power source 4 such as a battery, which supplies the instruments 5 and 6 with electricity. The generator loads the power source 4 with electric energy when an external force 2, which can for example be supplied by a cruising ship, is provided. As the fish trawl is pulled through water by the external force, the propeller of the generator rotates as a result of water being forced through the generator, leading to electricity being generated, and which can load the the power supply 4. Accordingly, the generator must be oriented in such a way on the trawl that the water is forced through it in a proximal-distal direction as the trawl is pulled through water. The instruments being powered typically require a 12 Volt DC current, so the generator is in one embodiment adapted for producing 12 V DC current. The housing for covering and protecting the generator and the power supply can be made of stainless steel or other resilient and water-resistant material so that it can tolerate a pressure up to 2000 meters or more.

Figure 3 shows a schematic overview of one embodiement of the invention, in which propellers 7 can be seen in a proximal view of the housing 9 of the generator. In this embodiment, a wire net is implemented in front of the propeller to prevent any kind of undesirable objects to enter the generator, and thus possibly damaging the propellers or other components of the generator. The housing 9 with the propellers must be oriented so that the water 10 flows in a proximal-distal direction through the generator, powering the propeller, forcing it to rotate and providing the necessary electromagnetic field for generating electricity. The induced current can either be used directly to power underwater instruments or to load a power source such as a chargeable battery.

In the following non-limiting examples, specific embodiments of the present invention will be illustrated.

Shown are experimental results where:

1) the generator was mounted to a ship at approximately 700 m depth, and the cruising speed of the ship was used to run the generator, and

2) a rotation unit was used to run the generator according to the present invention.

Example 1.

The generator of the present invention was mounted to a ship at approximately 700 m depth, and the cruising speed of the ship was used to run the generator. The results are indicated in Table I and Figure 4. Table I.

It is apparent that increased cruising speed results in increased induced current at a constant voltage. Increased cruising speed leads to increased induced current at a constant voltage, as expected. The current generated is significant, and suffices to power typical instrumentation used for monitoring trawls or other means for fishing.

Example 2

In the following example a rotation unit was used to run the generator at varying rotation speed in a laboratory setting in the absence of water. Results are indicated in Table II and Figures 5 and 6.

Table II.

The induced current and generated power are approximately linear with respect to rotation speed at a constant voltage of 13 Volt, showing that the speed of the rotor (and thus the speed of the vessel) can be adjusted so as to generate increasing/decreasing electrical power.

Claims

1. An electric generator comprising

• a housing,

• a stator system arranged on said housing and normally to said rotation axis, said stator system being encapsulated by an electrically insulating material.

2. The electric generator according to claim 1, wherein said magnetic field generator is encapsulated by an electrically insulating material.

3. The electric generator according to claims 1 or claims 2, wherein said stator system and/or said magnetic field generator being encapsulated comprises moulding said stator system and/or said magnetic field generator in an electrically insulating material.

4. The electric generator according to any of the claims 1-3, wherein said electrically insulating material is selected from the group consisting of plastic insulators, epoxy-type plastic insulators, glass insulators, ceramic insulators, or a mixture thereof.

5. The electric generator according to any of the preceding claims, further comprising an electronic control.

6. The electric generator according to claim 5, whereein said electronic control is positioned within said housing.

7. The electric generator according to claim 6, wherein said electronic control is positioned distally to said stator system.

8. The electronic generator according to claim 7, wherein said electronic control is arranged on said housing and separated from said stator system by a separation wall such that the wall and the housing form an isolated chamber.

9. The electric generator according to any of the preceding claims, wherein said magnetic field generator is comprised of a first annular magnetic field generator with a center of mass along said rotation axis, and a second annular magnetic field generator with a center of mass along said rotation axis and positioned radially to said first magnetic field generator.

10. The electric generator according to claim 9, wherein said stator system is comprised of an annular stator system positioned in between said first and said second magnetic field generators. 11. The electric generator according to any of the preceding claims, wherein said supporting means is comprised of a a casing, against which the the distal end of said shaft is propped.

12. The electric generator according to any of the preceding claims, further comprising a chargeable power source connected to said electric field generator.

14. The electric generator according to any of the preceding claims, wherein said generator is a submerged in water and driven by an external force agent in the direction of said rotation axis.

15. The electric generator according to claim 14, wherein said external force agent is a ship.

16. The electric generator according to claim 14, wherein the electric field generator is mounted on a trawling means or other means used for fishing, and wherein by movement of said ship, water is forced in the direction of said rotation axis and through said underwater generator.

17. The electric generator according to any of the preceding claims, wherein said electric generator is adapted to power at least one instrument selected from the group consisting of an inspection camera, a deep-sea transmitter, a trawley sensor, a transponder sensor, a hydrophone, a thermometer and a manometer.

18. The electric generator according to any of the preceding claims, wherein said generator is adapted to run in a DC mode.

19. The electric generator according to any of the preceding claims, wherein said generator is adapted to run in an AC mode.

20. A method of generating electricity in an aqueous environment comprising movement of an electric generator as disclosed in claim 1 in a proximal-distal orientation through water in the direction of said rotation axis, whereby water is forced through said generator, the flow of water resulting in rotation of said propeller and resulting in electricity being induced within said generator.

21. A method according to claim 20, wherein the movement is accomplished by a ship.