WO2010064918A1

WO2010064918A1 - Energy conversion system

Info

Publication number: WO2010064918A1
Application number: PCT/NO2008/000430
Authority: WO
Inventors: Asbjørn STRAND
Original assignee: Prototech As
Priority date: 2008-12-03
Filing date: 2008-12-03
Publication date: 2010-06-10

Abstract

An energy conversion system (100) comprises a foundation (110), a generator unit (120) and a structure (130) operable to be airborne. The foundation (110) is coupled to the generator unit (120). Moreover, the generator unit (120) is coupled to the structure (130). Movement of the structure (130) when airborne in operation is operable to cause fluid flow through the generator unit (120) for generating electrical power.

Description

Energy Conversion System

Field of the invention

The present invention relates to energy conversion systems, for example in relation to generating electrical energy from airborne structures although not limited thereto. Moreover, the present invention also concerns methods of generating electricity in relation to airborne structures although not limited thereto.

Background of the invention

Since the beginning of the industrial revolution around year 1850, mankind has experienced a substantially exponential growth in population with a corresponding substantially exponential growth in use of energy based primarily on combusting fossil fuels and biomass.

Economic growth is also known to be closely correlated with energy use by mankind.

Realization of "peak oil" and also mankind-forced climate change has now raised awareness of an acute need to find alternative sources of energy to complement and ultimately replace fossil fuels for energy production.

Renewable energy systems have been known for many decades. Hydroelectric power generating systems have been used in many countries for many years. Moreover, windmills have been employed in the Netherlands for pumping water for centuries, and in the United Kingdom for grinding wheat to flour.

Recently, light-weight high-strength polymeric materials have become available which potentially expands a range of renewable energy systems which are feasible to practically implement. For example, advanced high-strength materials have enabled a system to be realized as described in a published international PCT patent application WO 2007/139412A1 (PCT/PT2007/000022) attributed to Omnidea LDA, Portugal. In this PCT application, there is described a system designed to harness wind power. The system is operable to convert force required to maintain an airborne structure substantially in position into torque and rotation at a ground station for generating electricity. In operation, the system functions in two phases, namely a first phase concerned with work production by unwinding a cable linking the ground station to the airborne structure to allow the structure to move from a first lower height to a second greater height, and a second phase concerned i with recovering the cable in conjunction with the structure being returned from its second greater height to its first lower height. A net energy gain is available when executing the two phases corresponding to a loss of momentum of wind acting upon the airborne structure.

The airborne structure is beneficially implemented to have an area comparable to a conventional jet aircraft, for example a Boeing 747. However, the structure is fabricated from durable light-weight materials and beneficially furnished with adjustable aerofoils and floatation devices filled with hydrogen or helium gas. The airborne structure is therefore operable as a form of giant kite which is lighter than air and susceptible to being acted upon by wind flows at higher altitudes, for example greater than 400 metres above the Earth's surface, where wind flows are more constant and of greater speed in comparison to a region close to the Earth's surface whereat conventional wind turbines are required to operate. The system is capable of being designed to provide an electrical output of several MegaWatts (MW) for each airborne structure and therefore capable of generating appreciable amount of electrical power.

The airborne structure is intended to be permanent in flight, and is tethered by a light-weight tethering line to a ground station comprising a winch coupled to an electrical generator; there is also provided a control unit arrangement for controlling the airborne structure and the winch during the aforementioned first and second phases which are cyclically repeated.

Summary of the invention

The present invention seeks to a provide a system for generating electrical power from airborne structures whilst addressing problems with managing tethering cables in respect of electrical energy generation.

Moreover, the present invention seeks to provide an energy conversion system which is operable to provide a more uniform output supply of energy.

According to a first aspect of the present invention, there is provided an energy conversion system as defined in appended claim 1 : there is provided an energy conversion system comprising a foundation, a generator unit and a structure operable to be airborne, the foundation being coupled to the generator unit, the generator unit being coupled to the structure, wherein movement of the structure when airborne in operation is operable to cause fluid flow through the generator unit for generating electrical power. The invention is of advantage in that use of fluid flow to generate electrical power circumvents problems associated with cable management associated with known contemporary arrangements.

Optionally, in the energy conversion system, the generator unit is adapted to operate in an aqueous region, and the foundation is adapted to be located on a bottom of the aqueous region.

More optionally, in the energy conversion system, the generator unit includes at least one rotor operable to be driven by flow of water therethrough in response to movement of the generator unit through the aqueous region by forces generated by movement of the structure when airborne.

More optionally, in the energy conversion system, the at least one rotor is magnetically suspended in magnetic bearings.

More optionally, in the energy conversion system, the generator unit includes a plurality of rotors disposed to mutually counter-rotate so that the generator unit experiences substantially negligible turning torque when pulled by the structure through the aqueous region.

More optionally, in the energy conversion system, the at least one rotor is provided with electromagnetic inductive power pickoff acting upon a periphery thereof.

Optionally, the system is operable to generate electrical power from the generator unit when the structure is airborne, both for the structure ascending and descending.

Optionally, in the energy conversion system, the structure includes at least one buoyancy tank, at least one aerofoil coupled to at least one associated actuator, and at least one control unit for controlling the at least one actuator, wherein the control unit is operable to energize the actuator for adjusting the at least one aerofoil for causing the structure to cyclically ascend and descend between upper and lower spatial positions respectively. More optionally, in the energy conversion system, the structure is provided with an energy supply which is local to the structure for providing power to the at least one control unit and the at least one actuator.

More optionally, in the energy conversion system, the structure is operable to electrolyse water for generating hydrogen for replenishing hydrogen lost from the at least one buoyancy tank.

According to a second aspect of the invention, there is provided a generator unit adapted for use in a system pursuant to the first aspect of the invention.

According to a third aspect of the invention, there is provided a matrix configuration comprising a plurality of systems pursuant to the first aspect of the invention.

More optionally, the matrix configuration includes a control arrangement for causing the plurality of systems when in operation to be at mutually different portions of their cycles of descent and ascent, for providing a more uniform supply of electrical power from the matrix configuration.

According to a fourth aspect of the invention, there is provided a method of converting energy in an energy conversion system comprising a foundation, a generator unit and a structure operable to be airborne, the foundation being coupled to the generator unit, the generator unit being coupled to the structure, the method including:

arranging for the structure when airborne in operation to vary in altitude to cause fluid flow through the generator unit for generating electrical power.

Optionally^ the method includes:

(a) arranging for a plurality of the energy conversion systems to combine their electrical outputs to provide a combined electrical output; and

(b) operating the plurality of energy conversion systems to be at mutually different portions of their cycle of ascent and descent for providing a more uniform energy output at the combined electrical output.

It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention. Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

Figure 1 (FIG. 1) is a schematic illustration of an energy conversion system pursuant to the present invention;

Figure 2a (FIG. 2a) is a cross-sectional schematic diagram of a generating unit employed in the energy conversion system of Figure 1 ;

Figure 2b (FIG. 2b) is a schematic plan view of the generating unit of Figure 2a;

Figure 3 (FIG. 3) is a multi-rotor implementation of a generating unit for use with the system of Figure 1 ;

Figure 4 (FIG. 4) is an illustration in plan view of a matrix configuration of a plurality of systems illustrated in Figure 1; and

Figure 5 (FIG. 5) is an illustration of an alternative, or additional, energy generation arrangement for use with the system of Figure 1.

In the accompanying diagrams, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non- underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

Description of embodiments of the invention

Referring to Figure 1 , there is shown an offshore environment indicated generally by 10. The environment 10 includes an ocean region 20 above a seabed region 30, and an atmospheric region 40 above the ocean region 20. The atmospheric region 40 includes a low altitude region 50 and a high altitude region 60. A threshold 70 between the low altitude region 50 and the high altitude region 60 occurs at a height in an order of 500 metre to 1 km above an upper surface 80 of the ocean region 20.

There is also shown in Figure 1 an energy conversion system pursuant to the present invention. The system is indicated by 100 and comprises a foundation 110 disposed on the seabed region 30, a generator unit 120, and an airborne structure 130. The generator 120 is tethered by a first cable 140 to the foundation 110. Moreover, the airborne structure 130 is tethered via a second cable 150 to the generator unit 120. The generator unit 120 and the airborne structure 130 are shown in their first position by 120A, 130A and in their second position by 120B, 130B.

The airborne structure 130 is operable to move from its first and second positions by adjustment of aerofoils 200 included in the structure 130. The structure 130 beneficially also includes buoyancy tanks 210 filled with helium and/or hydrogen so that the structure 130 is naturally buoyant in the atmospheric region 40. The airborne structure 130 also beneficially includes a control unit 220 provided with power from solar cells and/or small wind turbines mounted upon the airborne structure; optionally, rechargeable batteries are used to ensure that the control unit is provided with a reliable supply of local electrical power. The control unit 220 is operable to control periodic activation of actuators for adjusting the aerofoils 200 so that the airborne structure 130 moves in a cyclical manner between the first and second positions. As the structure 130 moves between the aforesaid first and second positions, the generator unit 120 moves upon and down within the ocean region 20 with a result that sea water streams through the generator unit 120. The generator unit 120 is furnished with at least one water turbine for converting the streams of sea water flowing therethrough into electrical power.

It will be appreciated from Figure 1 that the system is devoid of any cable winches and requires greatly simpler cable management. Moreover, on account of the cables 140, 150 not suffering wear by being reeled into and out of winches, maintenance required to keep the system operational is much less than earlier known systems, for example as described in the aforementioned PCT patent application. Moreover, the system in Figure 1 has other operational benefits, namely: (a) in an event that the airborne structure 130 needs maintenance, a wireless signal is sent to a wireless receiver of the control unit 220 to cause the control unit 220 to open valves to vent hydrogen and/or helium from the tanks 210 so that the structure can gently fall to the upper surface 80 of the ocean region 20. The tanks 210 enable the structure to float on the upper surface 80 so that it can be collected by ship and then serviced. Subsequently, the tanks 210 can be recharged with hydrogen and/or helium and the structure 130 then allowed to float up to its aforesaid first and second positions; (b) in an event that the generator unit 120 needs servicing, it can be hoisted up onto a ship, especially when a depth D of the ocean region 20 is less than a length of the first cable 140. Such servicing can be implemented without requiring the airborne 130 to be removed from its position within the high altitude region 60.

Beneficially, the airborne structure 130 is fabricated from light-weight high-performance materials such as Kevlar, Mylar, metal foil, carbon fibre, carbon nanofibres and high-strength light-weight metal such as aluminium and titanium. Optionally, the airborne structure 130 includes apparatus for collecting water, for example rain or mists, and then electrolysing the water to generate hydrogen to compensate for losses of hydrogen from the tanks 210, for example by way of gas diffusion through walls of the tanks 210. Such replacement of lost hydrogen enables the structure to be airborne for months or even years without attention. Energy for performing electrolysis at the airborne structure 130 is beneficially supplied from solar cell panels or small wind turbines mounted upon the structure 130.

The cables 140, 150 are beneficially fabricated from light-weight robust fibres, for example from high-strength Kevlar or polyethylene fibre. A high-performance polyethylene fibre suitable for implementing the cables 140, 150 of the system in Figure 1 is manufactured by a company Dyneema B.V. (head office: Mauritslaan 49, Urmond, P.O. Box 1163, 6160 BD Geleen, the Netherlands). Dyneema® is a superstrong polyethylene fibre that offers maximum strength combined with minimum weight. It is up to fifteen times stronger than quality steel and up to 40% stronger than aramid fibres, both on weight for weight basis. Dyneema® floats on water and is extremely durable and resistant to moisture, UV light and chemicals.

Dyneema® is an important component in ropes, cables and nets in the fishing, shipping and offshore industries. Moreover, Dyneema® is also used in safety gloves for the metalworking industry and in fine yarns for applications in sporting goods and the medical sector. In addition, Furthermore, Dyneema® is also used in bullet resistant armour and clothing for police and military personnel.

The foundation 110 is beneficially implemented as one or more of:

(a) a massive assembly, for example a concrete anchor, a steel anchor or similar; (b) a component secured into a hole bored into the sea bed region 30; and

(c) a section-cup arrangement or similar for attachment to the seabed region by way of suction forces.

Beneficially, a flexible electrical cable 300 is connected from the generator unit 120 to a land region 310 via the foundations 110. Beneficially, the electrically cable 300 is optionally mechanically coupled to the first cable 140 and operable to move with the first cable 140 as the generator unit 120 moves up and down in the ocean region 20 during operation when the generator unit 120 is generating electrical power for supply to the land region 310.

Including the control unit 220 on the airborne structure controlled by wireless signals avoids a need for any power cables, optical fibres for control communication to be included in the second cable 150, thereby reducing its weight and avoiding any problems with power cable and/or optical fibre fracture by work hardening caused by repeated motion of the second cable 150. Optionally, metal conductive fibres are included in the second cable for provided a discharge route in an event that the airborne structure is hit by one or more lightening strikes in storm conditions.

By arranging for the generator unit 120 to function with the ocean region at a distance from the upper surface of the ocean region 20, the generator unit 120 is well protected from damage by waves on the upper surface. Energy of waves on the upper surface 80 is contained in an energy field which decays exponential with depth into the ocean region, depending upon wavelengths of the waves. When the generator unit 120 is submerged at a depth of at least one ocean wave wavelength on the upper surface 80, the generator unit 120 is substantially unaffected by storm conditions. Moreover, when the airborne unit 130 is allowed to occupy high altitudes in a range of 1 to 5 km above the upper surface 80 of the ocean region 20, the airborne structure 130 is also relatively unaffected by storm condition raging in the low altitude region 50. This provides the system of Figure 1 with considerable benefits in comparison to ocean wave energy systems, for example a contemporary Pelamis wave energy system (as developed by Pelamis Wave Power, 104 Commercial Street, Edinburgh EH6 6NF, Scotland), and off-shore wind turbine systems which are adversely affected by storm conditions.

The airborne structure 130 beneficially also performs synergistically other functions, for example weather monitoring, surveillance, wireless repeater services for wireless signals, air quality monitoring to mention a few examples. Data gathered by the airborne structure is beneficially communicated to the land region 310 by wireless. Similarly, the generator unit 120 is beneficially also operable to perform water quality measurements for monitoring pollution within the ocean region 20 and data conveyed via the electrical cable 300 to the land region 310.

The present invention is potentially of huge benefit to mankind. Nearly 80% of the Earth's surface is covered by water, namely the ocean region 20 is four times more expansive than the land region 310. Moreover, when the airborne structures 130 are operable to fly at a height less than that employed for aviation, the second cable 150 and the structure 130 itself do not pose a collision hazard.

Optionally, a configuration comprising a plurality of the systems 100 illustrated in Figure 1 is employed off-shore. Moreover, the electrical cables 130 are optionally coupled to a floating island whereat energy intensive industries are located and services by sea vessels travelling between the land region 310 and the floating island. Such an arrangement enables the system to be employed in deep-water area remotely from land coast-lines, thereby avoiding problems with planning permission and alleged degradation of near-coastline regions as caused by off-shore wind turbines secure to the seabed region 30.

The generator unit 120 will now be further described with reference to Figures 2a and 2b. The generator unit 120 is suspended by at least one support cable 410 substantially coupled to a junction region 400 whereat the cables 140, 150 are mutually joined; beneficially, three such support cables 410 are employed in a 120° angular distribution as illustrated in Figure 2b, although other numbers of support cables 410 are optionally employed. The generator unit 120 comprises a substantially cylindrical housing 420 whose outer surface is provided with at least one foil 430 projecting therefrom. Beneficially, the housing 420 is fabricated from non-magnetic materials, for example from fibre-reinforced epoxy material, from plastics material, from aquatic-grade concrete and similar. The at least one foil 430 is beneficially radially projecting from the outer surface of the housing 420; beneficially the at least one foil 430 is spiral form. Moreover, end edges 425 of the housing 420 are beneficially tapered for stream-lining the housing 420 as illustrated. Moreover, the foils 430 are beneficially disposed in a symmetrical manner around the housing 420 as illustrated. In a central region 440 of the housing 420, there is included a rotor shaft 440 provided with at least one spirally- disposed blade 450 whose outer edges most remote from a centre of the rotor shaft 440 are furnished with at least one rare-earth permanent magnet 460 disposed in an alternating spatial manner in respect of magnetic pole polarity. Beneficially, the at least one spirally- disposed blade 450 is symmetrically disposed around the rotor shaft 440. The at least one foil 430 is included to provide a counter-torque to a torque generated in the rotor shaft 440 as a result of water streaming through the housing 420 as it moves between its first and second positions as illustrated in Figure 1.

Ends 470 of the rotor shaft 440 are provided with non-contact magnetic support bearings 480 implemented using repulsive rare-earth permanent magnets 490 incorporated into the support bearings 480 and also into the ends 470 of the rotor shaft 440. The support bearings

480 are included in a bearing housing which, in cooperation with the rotor shaft 440, provide a streamline tapered form as illustrated. A gap 500, for example in an order of 1 cm width, is beneficially provided between the ends 470 of the rotor shaft 440 and the bearings 480 to avoid contact therebetween for avoid wear occurring thereat, even in an event of deposits forming thereupon in operation in the ocean region 20.

The housing 420 includes a coil configuration 510 disposed in a vicinity of the at least one rare-earth permanent magnets 460 as illustrated; the coil configuration 510 optionally includes a plurality of coils. In operation, rotation of the rotor shaft 440 and its at least one spirally-disposed blade 450 relative to the housing 420 and its associated coif configuration 510 causes an induced electrical potential to be generated in the coil configuration 510. A lower region of the housing 420 remote from the support cables 410 is provided with at least one weight 520 for ensuring that the housing 420 naturally assumes an upright position as illustrated when submerged in the ocean region 20. Moreover, at an upper region of the housing 420, there are included power electronic components 530 coupled to the coil configuration 510 and also to the aforementioned electrical cable 300 shown in Figure 1. The power electronic components 530 are operable to condition, for example to rectify and then shift potential, the induced electrical potential in the coil configuration 510 to a suitable form for feeding via the cable 300 to the land region 310. Beneficially, the foils 430 are fabricated from aluminium and used as heat-sinks to cool the power electronic components 530.

Beneficially the rotor shaft 440 and its at least one spirally-disposed blade 450 have a diameter S in a range of 1 to 20 metres, more preferable in a range of 3 to 7 metres.

Optionally, several generator units 120 are disposed together in a multi-rotor configuration

600 as illustrated in Figure 3; beneficially, the are provided an even number of generator units 120, for example four generator units 120 as illustrated. The multi-rotor configuration

600 is coupled to the airborne stricture 130 and to the foundations 110 as described in the foregoing. Such a multi-rotor configuration 600 as illustrated in Figure 3 is of benefit in that power can be generated by the multi-rotor configuration 600 in an event of one of its rotor shaft 440 being jammed by deposits of material, for example due to growth of crustacean, forming in one or more of its gaps 500. Thus, the multi-rotor configuration 600 is capable of providing more reliable operation in service on account of simultaneous jamming of all the rotor shafts 440 in the multi-rotor configuration 600 being most unlikely. A further benefit of the multi-rotor configuration 600 is that its rotor shafts 440 and their associated spirally- disposed blades 450 can have alternative rotation senses so that a housing 610 of the configuration 600 experiences a net zero overall torque as the configuration 600 is drawn through water between the aforesaid first and second positions in response to altitude changes of the airborne structure 130. Beneficially, the configuration includes foils 430 fabricated from aluminium which beneficially function as cooling heat-sinks for cooling the power electronic components 530 as illustrated.

The generator unit 120, likewise the configuration 600, beneficially has all its aforesaid component parts encapsulated and therefore not directly exposed to corrosive seawater present in the ocean region 20. The component parts which are beneficially encapsulated include the permanent magnets 460, the coil configuration 510, the support bearings 480, permanent magnets at the ends 470 of the rotor shaft 440 and the power electronic components 530.

Beneficially, the rotor 440 and its associated at least one spirally-disposed blade 450 are fabricated from a strong light-weight material which is inert to seawater; for example, the rotor 440 and its blade 450 is beneficially fabricated from one or more of: carbon fibres embedded in epoxy resin, moulded polypropylene polymer, high-strength polyethylene polymer, nylon, a strong inert plastics material, an adhesive resin.

Several aforesaid airborne structures 130 are beneficially arranged in a matrix indicated by 700 at an offshore site as illustrated in Figure 4. Such a matrix 700 is of benefit in that the cables 700 of the generator units 120 can be coupled to a junction unit 710, and an overall cable 720 coupled from the matrix 700 to the land region 310. This matrix 700 represents a cost saving because high-power underwater cables are expensive items and duplication of cables to the land region 310 is thereby avoided. In order to avoid the cables 150 of the airborne structures 130 of the matrix 700 becoming ensnarled in operation, the airborne structures 130 together with their associated generator units 120 and foundations are disposed at distances L in a range of 300 metres to 5 km, and more beneficially in a range of 500 metres to 1.5 km. When the matrix 700 comprises 10 x 10 airborne structures 130 of size comparable to a Boeing 747 aircraft, the configuration 700 is capable of potentially generating several hundred MegaWatts (MW) of power. Moreover, when operating the matrix 700, its airborne structures 130 are beneficially in mutual wireless communication so that the airborne structures 130 are controlled to be in mutually different phases of their movement between their first and second positions in operation so that a more constant supply of electrical energy is provided via the overall cable 720 to the land region 310. The system 100, likewise the matrix 700 including a plurality of systems 100, is of benefit in that their one or more generator units 120 are operable to generate electricity when they are being pulled into more shallow water in the ocean region 20 as well as when they are subsequently sinking down into the ocean region 20 to deeper water therein. Such more constant generation of electrical power in the system 100 and also the matrix 700 is a clear benefit in comparison to a system disclosed in the aforementioned published international PCT patent application 2007/139412A1 (PCT/PT2007/000022) attributed to Omnidea LDA, Portugal.

The system 100, either implemented using the generator unit 120 or the configuration 600, functions according to a method including a first phase whereat the airborne structure 130 is rising in height, and a second phase whereat the airborne structure 130 is falling in height. During the first and second phases, the generator unit 120 or configuration 600 changes height within the ocean region 20 causing its one or more rotor shafts 440 and blades 450 to rotate to generate electrical power. Beneficially, the electrical power is conveyed to the land area 20. When a matrix 700 of a plurality of the systems 100 are provided, the method involves ensuring that the plurality of systems 100 are in mutually different stages in their cycles including the first and second phases so as to provide the matrix with a temporally more uniform electrical output.

It will be appreciated that alternative approaches to electrical power generation from movement of the airborne structure 130 is feasible. For example, as illustrated in Figure 5 by an arrangement indicated generally by 750, at least a portion 800 of the second cable 150 is implemented as hollow sleeve and a first flexible tube 810 is included therein. An upper end of the tube 810 is sealed. The first flexible tube 810 includes a liquid, for example a light silicone oil or water. The first tube 810 is connected via a turbine 820 at the generator unit 120 to a reservoir implemented as a second flexible tube 830 beneficially loosely coupled along the first cable 140. The second tube 830 is also filled with the liquid. The second flexible tube 830 is closed at its lower end remote from the generator unit 120. Beneficially, the first and second tubes 810, 820 are fabricated from polypropylene which is capable of undergoing numerous cycles of flexure, for example squeezing, without suffering work- hardening effects. Moreover, the second cable 150 is beneficially implemented as a hollow woven sleeve of high-strength polyethylene as previously described. When the airborne structure 130 increases in height, for example by adjustment of its aerofoils 200, the second cable 150 becomes tensioned causing the first tube 810 to be squeezed, thereby forcing the fluid therein via the turbine 820 to the second tube 830 which is dragged into shallower water of the ocean region 20 and therefore subject to less pressure from the ocean region 20 and thus able to expand in volume. When the airborne structure 130 falls in height, the second cable 150 become slack causing the first tube 810 to widen simultaneously as the second tube 830 sinks further into the ocean region 20 causing more water pressure on the second tube 830, thereby forcing the liquid from the second tube 830 via the turbine 820 to the first tube 810. Liquid flow through the turbine 820 causes the turbine 820 to rotate and to drive an electrical generator coupled thereto for generating electrical power. The arrangement 750 as illustrated in Figure 5 is of benefit in that the turbine 820 and its associated electrical generator are capable of generating electrical power when the airborne structure 130 is falling as well as when it is rising. The arrangement 750 is of benefit in that it is extremely simple and robust, thereby potentially requiring very little maintenance as well as being able to cope with a harsh environment of the ocean region 20.

The arrangement 750 is optionally susceptible to being used simultaneously in combination with embodiments of the invention as illustrated in Figure 1 to 4 to provide a dual method of electrical power generation.

Although the present invention is described for use in association with the ocean region 20, it will be appreciated that the present invention is useable in-land, for example in association with in-land lakes.

Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims.

Expressions such as "including", "comprising", "incorporating", "consisting of, "have", "is" used to describe and claim the present invention are intended to be construed in a non- exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

Claims

1. An energy conversion system (100) comprising a foundation (110), a generator unit (120) and a structure (130) operable to be airborne, the foundation (110) being coupled to the generator unit (120), the generator unit (120) being coupled to the structure (130), wherein movement of the structure (130) when airborne in operation is operable to cause fluid flow through the generator unit (120) for generating electrical power.

2. An energy conversion system (100) as claimed in claim 1 , wherein said generator unit (120) is adapted to operate in an aqueous region (20), and said foundation (110) is adapted to be located on a bottom of the aqueous region (20).

3. An energy conversion system (100) as claimed in claim 2, wherein said generator unit (120) includes at least one rotor (440, 450) operable to be driven by flow of water therethrough in response to movement of said generator unit (120) through said aqueous region (20) by forces generated by movement of said structure (130) when airborne.

4. An energy conversion system (100) as claimed in claim 3, wherein said at least one rotor (440, 450) is magnetically suspended in magnetic bearings (480, 490).

5. An energy conversion system (100) as claimed in claim 3, wherein said generator unit (600) includes a plurality of rotors (440, 450) disposed to mutually counter-rotate so that said generator unit (120) experiences substantially negligible turning torque when pulled by said structure (130) through said aqueous region (20).

6. An energy conversion system (100) as claimed in claim 3, 4 or 5, wherein said at least one rotor (440, 450) is provided with electromagnetic inductive power pickoff acting upon a periphery (460) thereof.

7. An energy conversion system (100) as claimed in any one of the preceding claims, wherein said system (100) is operable to generate electrical power from the generator unit (120) when the structure (130) is airborne, both for the structure (130) ascending and descending.

8. An energy conversion system (100) as claimed in any one of the preceding claims, wherein said structure (130) includes at least one buoyancy tank (210), at least one aerofoil (200) coupled to at least one associated actuator, and at least one control unit (220) for controlling the at least one actuator, wherein said control unit (220) is operable to energize said actuator for adjusting said at least one aerofoil (200) for causing said structure (130) to cyclically ascend and descend between upper and lower spatial positions respectively.

9. An energy conversion system (100) as claimed in claim 8, wherein said structure (130) is provided with an energy supply which is local to the structure (130) for providing power to the at least one control unit (220) and said at least one actuator.

10. An energy conversion system (100) as claimed in claim 9, wherein said structure (130) is operable to electrolyse water for generating hydrogen for replenishing hydrogen lost from said at least one buoyancy tank (210).

11. A generator unit (120) adapted for use in a system as claimed in any one of the preceding claims.

12. A matrix configuration (600) comprising a plurality of systems (100) as claimed in any one of claims 1 to 10.

13. A matrix configuration (600) as claimed in claim 12, including a control arrangement for causing said plurality of systems (100) when in operation to be at mutually different portions of their cycles of descent and ascent, for providing a more uniform supply of electrical power from said matrix configuration.

14. A method of converting energy in an energy conversion system (100) comprising a foundation (110), a generator unit (120) and a structure (130) operable to be airborne, the foundation (110) being coupled to the generator unit (120), the generator unit (120) being coupled to the structure (130), said method including:

arranging for said structure (130) when airborne in operation to vary in altitude to cause fluid flow through the generator unit (120) for generating electrical power.

15. A method as claimed in claim 14, including:

(a) arranging for a plurality of said energy conversion systems (100) to combine their electrical outputs to provide a combined electrical output (720); and (b) operating said plurality of energy conversion systems (100) to be at mutually different portions of their cycle of ascent and descent for providing a more uniform energy output at said combined electrical output (720).