Apparatus for use in generating electricity

Abstract

An apparatus 101, intended to generate electricity, comprises a drive belt 102 rotatable, in an upright orientation, in a drive direction D. Part of the drive belt 102 passes through a first volume of

Description

Field of the Invention The present invention relates to the generation of electricity, and to the storage of energy. 5 Background of the Invention Devices utilising natural resources in the generation of electricity are known, for example wind turbines, water wheels and solar panels; however, the viability of such devices often depends on being able to site the device where there is enough exposure to wind, water 10 flow or sunshine for efficient performance. It is desirable to provide a device that is not subject to the same limitations, and that can be used anywhere. It is known that forces such as gravity and buoyancy are present everywhere around the planet, and it is desirable to use such free and available resources, to increase installation options and decrease operation costs. 15 Summary of the Invention According to a first aspect there is provided an energy storage arrangement as claimed in claim I. 20 According to a second aspect there is provided an energy network comprising an energy storage arrangement according to the first aspect, as claimed in claim 7. There is disclosed herein an energy storage arrangement comprising: a vessel for retaining a volume of a liquid and an object that is floatable by the liquid, and further comprising a 25 fluid control arrangement for selectively: supplying fluid to the vessel, during which the object moves from a lower position to a higher position, and allowing fluid to drain from the vessel, during which the object moves from a higher position to a lower position; in which the range of motion through which the object can rise and fall is constrained. 30 There is disclosed herein apparatus, comprising: a drive belt supported, in a generally upright configuration, within a housing, the drive belt rotatable, in a drive direction, along a path of travel passing sequentially through a plurality of sections of the housing, and through a sealing arrangement of the housing, in which: a first section of the plurality of sections comprises a first volume of a fluid having a first density, whereby to allow the drive belt, when in motion, to move therethrough with gravity, a second section of the plurality of sections comprises a second volume of a fluid having a second density, the second density greater than the first density, whereby to allow the drive belt, when in motion, to move 5 therethrough with buoyancy, and a third section of the plurality of sections comprises a third volume of a fluid; and the drive belt and the sealing arrangement co-operable for surmounting resistance to continuing motion of the drive belt along the path of travel. The achievement of the apparatus surmounting resistance to continuing motion of the drive 10 belt is an important feature of the present disclosure. In a disclosed example, the second volume of a fluid is interfaced directly with the first volume of a fluid, the third volume of a fluid is interfaced directly with the second volume of a fluid, and the third volume of a fluid is interfaced with the first volume of a fluid via a 15 seal of the sealing arrangement. ’’T CM In a disclosed example, a mechanical seal is located separately from the interface between the first and second volumes of a fluid. T"— 20 In a disclosed example, the fluid of each of the first volume of a fluid and the third volume of a fluid is a gas, and the fluid of the second volume of a fluid is a liquid. The gas may comprise air and the liquid may comprise water. In a disclosed example, the first volume of a fluid is at a first pressure, above atmospheric 25 pressure, the third first volume of a fluid is at a second pressure, lower than the first pressure, the first volume of a fluid and the second volume of a liquid are interfaced at the second pressure, the second volume of a fluid and the third volume of a fluid are interfaced at the first pressure, and the sealing arrangement comprises a seal, in which a drive belt entry side of the seal is interfaced with the third volume of a fluid at the first pressure, and 30 a drive belt exit side of the seal is interfaced with the first volume of a fluid at the second pressure. The first pressure may be atmospheric pressure. In a disclosed example, the second volume of a fluid is a column of a liquid, in which the pressure at the bottom of the column is that of the pressure of the gas of the second volume of a fluid and the pressure at the top of the column is that of the pressure of the 5 gas of the third volume of a fluid. In a disclosed example, the apparatus comprises pressure adjusting means for adjusting the pressure of the gas of the first volume of a fluid within the first section. This enables the relative extents of the gas of the first volume of a fluid within the first section and the liquid 10 of the second volume of a fluid within the second section to be adjusted, and the height of a column of a liquid of the second volume of a fluid within the second section to be adjusted. This provides a control feature of the apparatus, allowing the speed / power output of the rotating drive belt. In a disclosed example, the apparatus comprises pressure adjusting means for adjusting a pressure of a gas of the third volume of a fluid within the third section. CM In a disclosed example, the apparatus comprises temperature adjusting means for adjusting a temperature of a liquid of the second volume of a fluid within the second section. This is 20 beneficial for maintaining desired operational conditions. In a disclosed example, the apparatus comprises activation means for initiating rotation of the drive belt and for maintaining subsequent rotation of the drive belt. The activation means may comprise different activation arrangements for initiating rotation of the drive 25 belt and for maintaining subsequent rotation of the drive belt or may comprise an activation arrangement that is designed to provide both functions. In a disclosed example, the upright orientation is canted from vertical. This may beneficially enhance the buoyancy effect on the drive belt as it passes through a liquid of the second 30 volume of a fluid. In a disclosed example, the drive belt is articulated. In a specific example, the drive belt is formed from a series of linked modules, each module having a central axis and comprising a buoyancy chamber disposed between leading and trailing ends of the module, the series of linked modules approximating a continuous tube, but with interruptions between adjacent modules. This is an important feature of the present disclosure. 5 Ina disclosed example, each module has a circular cross-sectional shape, in a plane to which the central axis is normal, the leading end of each module comprises a forward-facing surface profiled as a convex dome, the trailing end of each module comprises a rearward-facing surface profiled as a concave dome, the trailing end of each module arranged to overlap the leading end of the following module, the series of linked modules presenting an 10 external wall that is interrupted at each region of overlap between adjacent modules, whereby adjacent modules, when the central axes thereof are coincident, present a section of the external wall of the drive belt that is straight and interrupted circumferentially at the respective region of overlap. In a disclosed example, each module rotatable about its central axis, preferably rotatable about its central axis though 360 degrees. Optionally, each module may carry ballast positioned to encourage rotation about its central axis. In a disclosed example, adjacent modules are relatively tiltable between a zero angle of tilt, T"— 20 in which the central axes thereof are coincident, to a maximum tilt angle in which the central axes thereof form an internal angle. In a disclosed example, the modules of the series of linked modules being detachable from one another. 25 In a disclosed example, the seal comprises an annular sealing element, the annular sealing element comprising a drive belt cloaking portion dimensioned to span adjacent modules as said adjacent modules travel therethrough. This is an important aspect of the present disclosure. 30 There is disclosed herein apparatus, comprising: a drive belt rotatable, in a drive direction, the drive belt comprising at least one pair of cylinders, each cylinder comprising a rack for engagement with a pinion, the cylinders radially balanced about the pinion; one cylinder of the or each pair of cylinders containing a first volume of a fluid having a first density, through which a mass of the cylinder is movable in either direction along a longitudinal axis of the cylinder, from a radially inward position to a radially outward position, and the other cylinder of the or each pair of cylinders containing a second volume of a fluid having a 5 second, different density through which a mass of the cylinder is movable in either direction along a longitudinal axis of the cylinder, from a radially inward position to a radially outward position. In a disclosed example, the apparatus comprising activation means for initiating rotation of 10 the drive belt and for maintaining subsequent rotation of the drive belt. The activation means may comprise different activation arrangements for initiating rotation of the drive belt and for maintaining subsequent rotation of the drive belt or may comprise an activation arrangement that is designed to provide both functions. 15 There is disclosed herein use of the apparatus for generating electricity. ’’T CM The apparatus may be used in an above ground installation, an underground installation, a deep underground installation, an offshore installation, or a transport installation. 20 An apparatus according of the first aspect or the second aspect and an energy storage arrangement for storing energy extractable from the apparatus provides a fourth aspect. The apparatus may be used to operate the energy storage arrangement of the first aspect. 25 The present disclosure provides a device in which the forces of gravity and buoyancy are used, in combination, to maintain a continuous motion of a drive belt. The device harnesses forces found in the natural world, in a similar manner to the harnessing of the wind or the sun to generate power. The apparatus is activated by an initial input of energy and is a resource-consuming device. Any perception of the device involving “perpetual motion” is 30 therefore misguided. A drive belt formed from close-coupled modules enables the effects of gravity and buoyant force to be used in combination to support rotation of the drive belt. A close-coupling design of the modules renders the drive belt an approximation of a continuous tube but with interruptions along its length; the design striking a balance between removing any “end effects” detrimental to maintaining continuing rotation of the drive belt, as it travels with and against gravity during different phases of its cycle, yet providing sufficient “end effects” 5 beneficial to maintaining continuing rotation of the drive belt, as it travels through fluids of different densities, and fluids at different pressures, during different phases of its cycle. The present disclosure provides a device with a design which achieves linking gravitational effects with buoyancy effects to overcome, with minimal loss of energy and in accordance 10 with accepted laws of physics, a pressure barrier through which a body passes when entering the base of a column of liquid. The device may be used to produce any suitable form of energy. In an application, the device is usable for generating electricity. The generated electricity may be used for any 15 suitable purpose or purposes. Energy may be derived from moving relatively small masses rapidly over relatively large distances or moving relatively large masses slowly over relatively small distances. Operation of the device may involve a rotary motion, a reciprocating motion, or a combination of these. 20 Further particular and preferred aspects of the invention are set out in the accompanying dependent claims. Brief Description of the Drawings The present invention will now be more particularly described, with reference to the 25 accompanying drawings, in which: Figure I is a schematic of apparatus, according to a first example; Figure 2 is a diagram showing a drive belt rotatable through a plurality of sections of a housing; 30 Figure 3 illustrates an example construction of a drive belt; Figure 4 illustrates a feature of an example construction of a drive belt; Figure 5 illustrates an example construction of a seal arrangement; Figures 6 to 9 show example layouts of the apparatus of Figure I ; Figure 10 is a schematic of an example application of apparatus as shown in Figure I ; Figure I I is a schematic of another apparatus, according to a second example; Figure I 2 shows phases in operation of an apparatus; Figure I 3 is a schematic of an energy storage arrangement; 5 Figure 14 shows an example installation of the apparatus of Figure I and the energy storage arrangement of Figure 13; Figure I 5 shows an example installation of an apparatus; and Figure 16 shows another example installation of an apparatus. 10 Description Illustrative embodiments and examples are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the apparatus described herein. It is to be understood that embodiments and examples can be provided in many alternate forms and the invention should not be construed as limited to the embodiments and 15 examples set forth herein but by the scope of the appended claims. Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. In addition, features referred to herein in f the singular can number one or more, unless the context clearly indicates otherwise. 20 Similarly, the terms “comprises”, “comprising”, “includes”, “including”, “has” and / or “having” when used herein, specify the presence of the stated feature or features and do not preclude the presence or addition of one or more other features, unless the context clearly indicates otherwise. 25 In the following description, all orientational terms, such as upper, lower, radially, and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention, unless the context clearly indicates otherwise. The drawings are not necessarily drawn to scale, and in some instances the drawings may 30 have been exaggerated or simplified for illustrative purposes only. Disclosed herein is an apparatus, for generating electricity, that uses the natural resources of gravity and buoyancy in an innovative and environmentally beneficial manner. The apparatus can be designed to be installed in a variety of different environments, including on land, underground, in a body of water, or within the sea bed, and provides significant cost benefits when compared to any other known energy generating means. 5 A disclosed device comprises a drive belt, which during one cycle of rotation, passes through different volumes of fluid and, in doing so, passes through different densities and pressures of fluid. In an example, the drive belt travels from one volume of a fluid at one pressure into another volume of the same density fluid that is at another, higher pressure, and passes from a volume of a fluid having one density at one pressure into another volume 10 of a fluid having another, higher density fluid but the interface between the two fluids of different density being at the same pressure. The disclosed device further comprises a seal arrangement, with which the drive belt is co-operable, for surmounting resistance to continuing motion of the drive belt. Also disclosed herein is an apparatus, for storing energy, which may be used in conjunction with the afore-mentioned apparatus, for generating electricity. CM Apparatus disclosed herein may be used as a standalone system and / or within a networked system, and electricity generated using the apparatus may be used to satisfy a present and / or 20 future demand, at a local or district level. A schematic of apparatus 101 is shown in Figure I. The apparatus is usable to generate electricity, which may be used for any of a variety of different purposes, for example, to provide space heating, water heating, power for appliances, or which may be stored for 25 future use. The apparatus 101 comprises a drive belt 102, which will be described in further detail below. The drive belt 102 is supported, in a generally upright configuration, within a housing 103. When in the afore-mentioned “generally upright orientation” the drive belt 102 may extend vertically or may be canted at an angle from vertical. The drive belt 102 is rotatable, in a drive direction D, along a path of travel that passes sequentially through a plurality of sections S of the housing 103, and through a seal arrangement, indicated generally at SS, of the housing 103. 5 In this example, the drive belt 102 is supported by a drive belt support arrangement, indicated at 104. The drive belt support arrangement 104 may comprise any suitable number and arrangement of support elements, such as rollers, for example roller 105. The drive belt support arrangement may comprise different types of support element. The drive belt support arrangement may comprise at least one powered conveyor. 10 As will be described in further detail, and referring also now to Figure 2, the housing 103 comprises a first section SI, a second section S2, and a third section D3. When in motion, travelling in the drive direction D, each point along the drive belt 102, such as reference point R, passes from the first section SI into the second section S2, from the second section S2 into the third section S3, and from the third section S3 into the first section SI. Each section SI, S2, S3 comprises a volume of fluid. As will be described in further detail, between the volumes of the fluid of the sections SI, S2, S3 there are variances in density and pressure. 20 In this specific example, the first section SI of the housing 103 comprises a first volume of a fluid Fl having a first density, whereby to allow the drive belt, when in motion, to move therethrough with gravity. The second section S2 of the housing 103 comprises a second volume of a fluid F2 having a second density, the second density greater than the first density, whereby to allow the drive belt, when in motion, to move therethrough with 25 buoyancy (against gravity). The third section S3 of the housing 103 comprises a third volume of a fluid, which in this specific example is the same fluid Fl as that in the first section SI, and which further in this specific example is at a lower pressure than the fluid Fl in the first section SI. In this specific example, the sealing arrangement SS comprises a seal 201 through which the drive belt 102 extends and through which each point along the 30 drive belt 102, such as reference point R, passes from the third section S3 into the first section SI. It is to be appreciated that as the drive belt 102, when in motion, is moving through the first section SI of the housing 103 with gravity, it is at the same time moving through the second section S2 of the housing 103 with buoyancy. 5 As will be described in further detail, the drive belt 102 is articulated, and is formed from a series of linked modules, with modules 202, 203, 204 in series indicated. Considering the drive direction D, module 202 is leading module 203, which in turn is leading module 204. In an example, the fluid FI in the first and third sections SI, S3 of the housing 103 is a gas, 10 and the fluid F2 in the second section S2 of the housing 103 is a liquid. In a specific example, the fluid Fl comprises air and the fluid F2 comprises water. It is to be understood that any suitable fluid may be used in each section, depending on the specific application. For example, mercury may be used in the second section S2, which 15 would provide a greater buoyant force to that provided by water. Clearly, it is preferably for any fluid used in the housing sections to be a low-viscosity fluid. CM As will be described further, the gas Fl in the first section SI is ata first pressure P2, above f atmospheric pressure, and the gas Fl in the third section S3 is at a second pressure, lower 20 than the first pressure P2; the gas Fl in the first section SI and the liquid F2 in the second section S2 are interfaced, at W, at the first pressure P2, the liquid F2 in the second section S2 and the gas Fl in the third section S3 are interfaced, at X, at the second pressure PI, and a drive belt entry side of the seal 201 is interfaced, at Y, with the gas Fl in the third section S3 at the first pressure P2, and a drive belt exit side of the seal 201 is interfaced, at 25 Z, with the gas Fl in the first section SI at the second pressure P2. It is to be appreciated that liquid F2 in the second section S2 is held as a column, the pressure in which is greatest at the bottom of the column and least at the top of the column. Referring again to Figure I, as indicated, the first section SI defines at least one opening for 30 allowing the inflow / outflow of a gas, for example opening 106. In this example, the apparatus 101 comprises pressure adjusting means, indicated at 107, for adjusting the pressure of the gas Fl within the first section SI. The pressure adjusting means 107 may be provided by any suitable pressure adjusting arrangement comprising at least one compressor 108 and a pressure sensor arrangement comprising at least one sensor 109 for sensing the pressure of the gas Fl within the first section SI. The pressure adjusting means 107 is operable to provide / maintain the pressure P2 above atmospheric pressure. 10 20 15 As mentioned above, the gas FI in the first section SI and the liquid F2 in the second section S2 are interfaced, at W, at the pressure P2 above atmospheric pressure. The magnitude of the pressure P2 of the gas Fl in the first section SI affects where the interface, W, with the liquid F2 in the second section S2 is present It also affects the rotation of the drive belt 102; more specifically, adjusting the pressure P2 above atmospheric pressure in the first section SI influences the speed of rotation of the drive belt 102 by altering the relative extents of the gas Fl in the first section SI and the depth of liquid F2 in the second section S2 through which the drive belt 102 travels during its cycle. Thus, the pressure P2 can be increased to effectively increase the distance through which the drive belt 102 travels through the first section SI (increasing the extent that the drive belt experiences the effect of gravity as it passes through this section) and increase the distance through which the drive belt 102 travels through the second section S2 (increasing the extent that the drive belt experiences the effect of buoyancy as it passes through this section). Hence, it is to be appreciated that the volumes of the first and second sections SI, S2, and the volumes of a respective fluid Fl, F2 contained therein can be altered, to adjust the speed of travel of the drive belt 102, to in turn, allow a power output of the apparatus to be adjusted. This allows operation of the apparatus 101 to be varied in accordance with changes in demand, for example to increase output to satisfy spikes in electricity demand throughout the day or on a particular occasion (such as is managed by the GB national grid). Thus, the pressure adjusting means 107 provide a control feature, an important one, for the apparatus 101. 25 As indicated, the second section S2 defines at least one opening for allowing the inflow / outflow of air and / or the inflow of a top-up liquid, for example opening 110. As shown, an air vent I I I, which may be an automatic air vent, may be operably connected to the opening I 10. The apparatus 101 may comprise a top-up liquid supply connection 30 arrangement, indicated at 112, for connecting the housing 103 to a top-up liquid supply, indicated at 113. The apparatus 101 may at least one liquid level indicator, such as liquid level indicators 114, I 15 indicated in sections S2, SI respectively. In an example, the apparatus 101 comprises pressure adjusting means (which may be 5 associated with or independent from the pressure adjusting means 107) for providing, and subsequently maintaining, vacuum pressure in the third section S3. This will influence the height of the column of water F2 in the second section S2, the pressure in the third section S3 drawing the liquid F2 upwards. 10 As also indicated, the apparatus 101 comprises temperature adjusting means, indicated at I 16, for adjusting the temperature of a liquid within the second section S2. The temperature adjusting means I 16 may be provided by any suitable temperature adjusting arrangement comprising at least one heating and / or cooling device I 17 and a temperature sensor arrangement comprising at least one sensor I 18 for sensing the temperature of a 15 liquid within the second section S2. The temperature adjusting means I 16 is provided for maintaining a desired operational temperature condition within the housing 103. For example, temperature control is desirable for preventing a temperature to drop so low that unwanted freezing of a liquid within any section of the housing occurs or for a f temperature to rise so high that unwanted evaporation of a liquid within any section of the T"— 20 housing occurs. Further, temperature control is desirable for preventing unwanted expansion / contraction of the drive belt Thus, the temperature adjusting I 16 is functional to support desired operational conditions. As further indicated, the apparatus 101 comprises activation means, indicated at 119, for 25 initiating rotation of the drive belt 102 and, optionally, maintaining subsequent rotation of the drive belt 102. The activation means I 19 may be provided by any suitable activation arrangement. In this specific example, the activation arrangement comprises a roller 120 of the drive belt support arrangement 104, the roller 120 engageable with the drive belt 102, whereby the roller 120 when in motion is operable to effect rotation of the drive belt 30 102, and a roller operating arrangement, indicated at 121, for effecting rotation of the roller 120. The roller operating arrangement 121 may comprise a motor, or a crank handle, which is preferably a removable crank handle. It is to be appreciated that an activation means of the apparatus 101 may comprise different activation arrangements for initiating rotation of the drive belt and for maintaining subsequent rotation of the drive belt or may comprise an activation arrangement that is designed to provide both functions. 5 In an example, and in this example, the apparatus 101 comprises a seal lubrication management arrangement, indicated at 122, operatively connected to at least the seal 201, which may comprise a liquid level sensor 123, for sensing a level of a seal lubricant, indicated at 124, and a pump 125 connectable to a supply of seal lubricant for topping-up the seal 10 lubricant 124 as required. The apparatus 101 comprises, or is operatively connected to, a control system, indicated at 126, by means of which one or more functions of the apparatus 101 can be controlled. The control system 126 may comprise any suitable data processor and memory resource, 15 and may comprise any suitable controls. ’’T CM In this specific example, the drive belt 102 is operatively engageable with a shaft 100, such that the drive belt 102 when in motion is operable to effect rotation of the shaft 100. The shaft 100 may be a shaft of an energy generation or energy storage device. The shaft 100 20 may be disposed at any suitable position along the path of travel of the drive belt, and in this illustrated example is located within an upper end of a loop formed by the drive belt 102, towards an upper end of the housing 103. The drive belt may be operatively engageable with any suitable connection arrangement for utilising the motion of the drive belt to work another device. For example, such a connection arrangement may comprise 25 at least one gear, at least one chain, at least one pneumatic or hydraulic piston, at least one rack and pinion. In an alternative specific example, the drive belt 102 is configured as a rotor of an electric motor. In such an example, a series of magnets can be provided, supported within the 30 drive belt, and a coil arrangement can be provided, extending around the drive belt, such that rotating the drive belt moves the magnets through the coils. It is to be appreciated that a fluid provided in the second section S2 may therefore be an electrically non conducting liquid. A fluid provided in the second section S2 may however be or comprise any suitable liquid, for example an oil, such as a non-conductive transformer oil. The housing 103 may comprise any suitable material or materials. The housing may 5 incorporate material for providing thermal insulation and / or sound insulation. The drive belt 102, and the drive belt 102 and the sealing arrangement SS co-operable for surmounting resistance to continuing motion of the drive belt along the path of travel, will now be described. 10 It is acknowledged that the drive belt would be expected to experience resistance to motion in the drive direction D, as it moves along the path of travel, in particular from pressure and drag at the solid-fluid interface between each module and the fluid in each section of the housing, and buoyant force at the interface between the gas FI in the first , 15 section SI and the liquid F2 in the second section S2. ^r CM The apparatus disclosed herein incorporates resistance-management features for maintaining the drive belt, when in motion, in a desired “force-balanced” condition that serves to support the motion of the drive belt along the path of travel continuing. 1— 20 It is be remembered that, when the drive belt is in motion, modules thereof are present within, and moving through, each section of the housing: thus, at the same time, some modules are moving downwards through the first section SI and other modules are moving upwards through the second section S2. As will be explained more fully, the drive belt 102 25 when in motion, is encouraged to continue rotating in the drive direction D by the action of gravity on modules thereof travelling through the first section SI and is encouraged to continue rotating in the drive direction D by the action of buoyancy on modules thereof travelling through the second section S2. 30 The drive belt 102 is advantageously designed to approximate a continuous tube, but with interruptions between adjacent modules, to beneficially utilise aspects of both a continuous and a non-continuous form in the rotation of the drive belt 102. As mentioned above, the drive belt 102 comprises a series of linked modules, such as modules 202, 203, 204. The drive belt 102 may be any suitable length and may comprise any suitable number of modules. 5 If the module length remains the same, then the length of the drive belt increases with an increase in the number of modules that are coupled together to form the drive belt. The maximum available output and operating efficiency of the apparatus is influenced by the overall distance through which the modules of the drive belt travel through the fluids of the housing section, between the lowest and highest points of a loop formed by the drive 10 belt. An example construction of the drive belt 102 will now be described with reference to Figure 3. 15 In this Figure, module 203 is shown in full and adjacent (leading and trailing) modules 202, 204 each being shown in part. Each module 202 has a central axis, indicated at 301, and comprises a buoyancy chamber 302 disposed between a leading end 303 and a trailing end 303 of the module 203. As indicated, the leading end 303 presents a forward-facing surface 305 and the trailing end 304 presents a rearward-facing surface 306. 20 According to this illustrated example, each module has a circular cross-sectional shape, in a plane to which the central axis 301 is normal. In this example, the forward-facing surface and rearward-facing surfaces 305, 306 are complementarily profiled as male and female elements. In this specific example, the forward-facing surface 305 is profiled as a convex 25 dome and the rearward-facing surface 306 is profiled as a concave dome. The buoyancy chamber 302 may contain a gas and / or a suitable filler material, such as air and / or polystyrene foam, at any suitable pressure. The buoyancy of the module 203 may be adjustable, which may be achieved by enabling the content of the buoyancy chamber 302 30 to be altered. The modules 202, 203, 204 are linked such that the leading end of a trailing module and the trailing end of a leading module are separated by a relatively small extent; this being sufficient to allow an “end effect” to be utilised during at least one phase of the cycle of the drive belt 102 and to be cloaked during at least one phase of the cycle of the drive belt 102, such as when passing through the seal 201. 5 As illustrated, the trailing end 304 of each module 203 is arranged to overlap the leading end 303 of the following module 204, the series of linked modules 202, 203, 204 presenting an external wall, indicated at 307, that is interrupted at each region of overlap between adjacent modules, such as region of overlap 308 between modules 203 and 204, in which an interruption, indicated at 309, is present. It can be seen in this Figure that the convex 10 dome of the forward-facing surface 305 of module 204 extends into the concave dome of the rearward-facing surface 306 of module 203. Preferably, the two surfaces 305, 306 are prevented from making contact, to inhibit wear. In a specific example, a gap G between adjacent modules 203, 204 is in the order of millimetres, for example in the range approximately 2 mm to approximately 4 mm. 15 As also shown, the modules 203, 204, when the central axes 301 thereof are coincident, present a section of the external wall 307, such as the section indicated at 310, that is straight and interrupted circumferentially at the respective region of overlap 308. 20 In an example, and in this example, each module 203 is rotatable about its central axis 301, preferably though 360 degrees. Each module may optionally carry ballast, indicated at 31 I, positioned to encourage rotation about the central axis 301. The ballast may comprise any suitable material or combination of materials, which may be in particulate or solid form. In an example, the ballast comprises sand. In an example, and in this example, adjacent modules 203, 204 are relatively tiltable between a zero angle of tilt, in which the central axes 301 thereof are coincident, to a maximum tilt angle, in which the central axes 301 form an internal angle TA, which may be approximately 20 degrees or any other suitable angle. In an example, and in this example, the modules 202, 203, 204 of the series of linked modules are detachable from one another. This serves to ease maintenance and repair. Any suitable linking arrangement may be used to connect the modules 202, 203, 204 into the series. According to the specific illustrated example, the modules 202, 203, 204 are linked by a 5 linking arrangement that will now be described in detail. As can be seen in this Figure, the leading end 303 of each module 302 presents a generally conical recess, indicated at 312, open to the forward-facing surface 304 and narrowing in diameter towards the trailing end 305. A connecting rod 3 13 connectedly extends from a ball joint 3 14 secured within the leading end 303 of the trailing module 203, through the generally conical recess 312 of that 10 leading end 303, and through an aperture 315 in the rearward-facing surface 305 of the leading module 202 to a lock nut 316 secured in the trailing end 304 of that leading module. 202. The generally conical recess 312, connecting rod 313 and ball joint 313 allows the modules 203, 203 to tilt relative to each other. The connecting rod 3 13 is coincident with the central axis 301, and the module 203 is rotatable around the connecting rod 313, this 15 allowing the module 203 to rotate around its central axis. ’’T CM A “self-priming” lubrication feature of a specific example of the linking arrangement is illustrated in Figure 4, in which the ball joint 3 13 is housed within a lubrication cavity, f indicated at 401, that contains a supply of lubricant and that is dimensioned to allow the 20 ball joint 313 to move longitudinally, along the central axis 301, and pump lubricant as a degree of slack between adjacent modules is introduced and removed during rotation of the drive belt. The “self-priming” lubrication feature is achievable using a gap between adjacent modules in the range previously mentioned of between approximately 2 mm and approximately 4 mm. 25 In this specific example, the generally conical recess 312, through which connecting rod 313 extends, is filled with a resiliently compressible material 402 within the module 203 and profiled to match the convex dome shape of the forward-facing surface 305 of the leading end 303 of the module 203. The resiliently compressible material 402 allows the connecting 30 rod 313 to move within the generally conical recess 312 and at the same time minimises the ingress of fluid into the generally conical recess 3 12. The modules 203 of the drive belt 102 may comprise any suitable material or combination of materials. The modules 203 may comprise steel, which may have a smooth surface finish. The modules 203 may be provided with a coating for minimising drag. 5 An example construction of seal 201 is shown in Figure 5. In the scenario shown in this Figure, modules of the drive belt 102 are passing from air at atmospheric pressure PI, to air at pressure P2 above atmospheric pressure. The seal 201 is located at a different position in the cycle of the drive belt 102 to the air-10 water interface between the fluids Fl, F2 of the first and second sections SI, S2. According to this example, the seal 201 has an entry, indicated at 501, and an exit, indicated at 502. The seal 201 comprises an annular sealing element 503, the annular sealing element 4503 comprising a drive belt contacting portion, indicated at 504, dimensioned to span 15 adjacent modules as those adjacent modules travel therethrough. Thus, as shown, the drive belt cloaking portion 504 is dimensioned to span adjacent modules 202, 203, covering the interruption 309 between them in the external wall 207 of the series of linked modules 203, 204, 204. Thus, the annular sealing element 503 acts to cloak the interruption 309 as it passes through the third section S3 of the housing 103 to the first section SI of the 20 housing SI, this cloaking contributing to the drive belt approximating a continuous tube, which is beneficially for managing pressure differences experienced by the drive belt 102 when in motion. More specifically, the annular sealing element 503 functions to overcome resistance from 25 an “end effect” of modules 203 of the drive belt 102 as the modules 203 pass from one fluid environment to another. It is to be appreciated that the drive belt 102 and the seal 201 co-operate to provide a sealing system, whereby the external walls of the modules 203, which are closely coupled, 30 experience the same forces applied thereto, but in opposite directions, this serving to surmount any longitudinal forces on the end faces of the modules 203 that act to impede motion of the drive belt 102 through the seal 201 as the modules 203 pass from one fluid pressure to another. The close coupling between the modules 203, and more specifically the neighbouring trailing and leading ends of adjacent modules is a key feature of the present disclosure; the gap between the modules 203 is sufficiently small to be readily spanned by the drive belt 5 cloaking portion 504, and to allow substantially the same pressure (whether high or low) to be experienced by the trailing and leading end faces of adjacent modules 203 at the same time. As the modules 203 pass through the seal 201, the leading and trailing ends 303, 304 are 10 experiencing substantially the same pressure as each other; the annular sealing element 503 of the seal 201 does not “open” and “close” as the modules 203 of the drive belt 102 travel therethrough, and thus the trailing end 304 of the leading module 202 and the leading end 303 of the trailing module 202 effectively pass through the seal 201 as a continuous tube would pass through an O-ring, only experiencing pressure in the radial direction. 15 xt According to the illustrated arrangement, the close coupling between the modules 203 is maintained throughout the drive belt 102, and throughout the cycle thereof; thus, the modules 203 remain coupled closely together as they pass through each of the sections of the housing 103; the first section SI (“atmospheric region”), the second section S2 (“high T"— 20 gas pressure region”) and the third section S3 (“high-to-low water pressure region”). The closeness of the coupling between the modules 203 of the drive belt 102 prevents the excessive turbulence and hydraulic drag that would be experienced if the modules were spaced further apart. 25 In this illustrated example, a volume of a seal lubricant, indicated at 505, is provided on the upstream side of the entry 501 of the seal 201. The seal lubricant 505 may be any suitable incompressible liquid. 30 The seal lubricant 505 can flow into the interruption 309 between adjacent modules 202, 203 as they pass therethrough; this compliments the function of the annular sealing element 503 to cloak the interruption 309. It is be understood that the faster the drive belt 102 is rotating, the lesser influence the “end effect” has on the drive belt 102 as is travels through the seal 201. As shown, the seal 201 may comprise a “top hat” seal assembly 506, in which the seal lubricant 505 is also present, and suitable mounting arrangement 507. The annular sealing element 503 is slightly pressurised by the action of the drive belt 102 5 pushing seal lubricant 505 between the external wall of the module 203 and the drive belt cloaking portion 504, this creating a lubricant barrier. In addition, in the present example, the drive belt cloaking portion 504 is provided by a membrane that comprises, on the side facing the drive belt 201, a dimpled surface profile 10 providing recessed regions in which the seal lubricant 505 is receivable. The membrane may comprise any suitable material, for example neoprene. As the membrane of the drive belt cloaking portion 504 is deflected (whether being moved and / or compressed), the incompressible liquid of the seal lubricant 505 leaches out, this providing additional lubrication. 15 xt It is to be appreciated that the apparatus 101 may comprise componentry provided for the purpose of managing the release of fluids from between the modules 203 as during the cycle of the drive belt, for example a drainage arrangement to encourage liquid to be expelled f from between the modules 203 as the modules 203 leave that volume of liquid and for the 20 expelled liquid to be returned to that volume of liquid. Such componentry may comprise a brush / sweep and / or pipework. After initial start-up, continued rotation of the drive belt 102 is assisted by various aspects of the design of the apparatus 101. 25 The convex dome shape of the leading end 303 of each module 203 provides the forwardfacing surface 305 with a streamlined profile, advantageous in both fluid and liquid environments. The rearward facing surface 306 of the trailing end 304 of each module 203 is also profiled for facilitating travel through both “wet” and “dry” sections of the housing 30 103, enabling the gas FI in the first section SI to flow over the module 203 when travelling downwards in the first section SI, to encourage travel in the drive direction D (during a “dropping” phase, under the action of gravity) and enabling the liquid F2 in the second section S2 to flow under the module 203 when travelling upwards in the second section S2, to encourage travel in the drive direction D (in a “rising” phase, under the action of buoyancy). It is to be understood that as the modules 203 pass through the seal 201, the leading and 5 trailing ends 303, 304 are experiencing substantially the same pressure as each other; however, the diameter of the base of the convex dome shape of the leading end 303 of each module 203 is slightly less than that of the concave dome shape of the trailing end 305 of each module 203, which serves to provide a force difference between the leading and trailing ends 303, 304 that is small, but that contributes to travel of the modules 203 of the 10 drive belt 102 in the drive direction D when passing through the seal 201. Thus, the drive belt 102 is thus innovatively designed to approximate a continuous tube, but with interruptions between adjacent modules, to beneficially utilise aspects of both a continuous and a non-continuous form in maintaining rotation of the drive belt 102. 15 xt With the design of the present disclosure, the modules 203 of the drive belt 102 are able to pass from a lower pressure in one section (fluid Fl in section S3, such as air) into a higher pressure in another section (fluid Fl in section SI, such as air), and thus navigate a pressure barrier between those sections, and pass from a fluid having a lower density in 20 one section (fluid Fl in section SI, such as air) into a fluid having a higher density in another section (fluid F2 in section S2, such as water), and thus navigate a gas / liquid barrier that is separate from the pressure barrier, without experiencing significant opposition from pressure differences or density differences. As described, in the illustrated example, a mechanical seal 201 is located separately from the interface between the fluids Fl and F2 25 in the sections SI and S2. The drive belt 102 being canted, rather than completely vertical, may enhance the buoyancy effect on the drive belt 102 as it passes through the liquid F2 of the second section S2 of the housing 103. As already mentioned, the drive belt 102, when in motion, is moving through the second section S2 of the housing 103 with buoyancy at the same time as moving through the first section SI of the housing 103 with gravity. It is to be appreciated that the to the extent that modules 203 moving through one of these sections SI, S2 can be perceived as pulling a trailing module it should similarly be perceived as pushing a leading module due to the close coupling of the modules 203 of the drive belt 102. 5 The drive belt may present soft or hard external surfaces, or a combination of these, and that the drive belt (as appropriate, modules thereof) may be designed to maintain cross-sectional rigidity or to allow resilient changeability thereof. For example, the modules may comprise resiliently deflectable and / or compressible ribs. 10 The apparatus preferably uses fluid substances that are readily available, affordable, nontoxic, non-combustible, long-lasting. One or more additives may be used within the system, at any one or more points, for example a lubricant, an anti-corrosive, an anti-freeze, a coolant, a biological growth inhibitor. The apparatus is advantageously usable in almost any geographical location, as gravity and buoyancy are always present. CM Figures 6 to 9 illustrate a selection of example possible layouts of apparatus as already described. It is to be appreciated that a layout may be selected depending on the general T"— 20 environment (for example, land or sea, low or high elevation altitude), and available area in which to site the apparatus (for example, with more vertical layouts having a lesser footprint, and more horizontal layouts having a lesser overall height). The layouts 601, 701 shown in Figures 6 &7 respectively are suitable for use on land, the 25 layout 801 shown in Figure 8 is suitable for use in water, and the layout 901 shown in Figure 9 is suitable for use on land or in water. An example application 1001 of the apparatus 101, for generating electricity, is illustrated in Figure 10. In the shown example application 1001, the drive belt 102 is operatively connected to a gearing arrangement, indicated at 1002, which is operatively connected to a drive shaft 1003, which in turn is operatively connected to an electrical generator / start up motor, indicated at 1004, to which a power in / out cabling arrangement, indicated at 1005, is connected. Electricity generated using the apparatus 101 may be supplied to an electrical circuit / appliance, or may be directed to an energy storage device. 5 Also indicated in this Figure are an access panel 1006 of the housing 103, allowing access in the housing 103, to facilitate maintenance / repair, and a sealing arrangement 1007 for inhibiting undesirable escape of fluid from the housing 103 when the access panel 1006 is opened or removed (depending on its specific design). Further indicated in this Figure is the top-up liquid supply connection arrangement I 13. 10 A schematic of an apparatus 1101 according to a second example is shown in Figure 11. The drive belt I 102 of the apparatus 1101 differs from the drive belt 102 of apparatus 101 and the drive belt 102 of the apparatus 101, in that it comprises a platform supporting drive 15 member devices. The platform may take any suitable form, for example a frame or a xl substantially planar to which drive member devices are mounted. CM The drive belt 1101 comprises a rotor wheel I 102 supporting at least one pair of drive cylinders, 1103, 1104. As shown, each of the cylinders I 103, 104 comprises a rack portion 20 1105 for engagement with a pinion 1106 that is rotatable around an axis I 100. As shown, the cylinders 1103, 1104 are radially balanced about the pinion I 106, with the rack portions I 105 of the pair of cylinders 1103, 1104 diametrically opposite each other. In this example, the pinion 1106 is not fixed in rotation with the rotor wheel I 102, but 25 serves to synchronise the cylinders 1103, I 104. The rotor wheel 1102 is rotatable, in an upright orientation, in a drive direction D, with one of the cylinders I 103 effecting a first action, to generate a first motion-contributing force, and the other of the cylinders I 104 effecting a second, different action, to generate 30 a second motion-contributing force. The rotor wheel I 102 when in motion, travelling in the drive direction D, is encouraged to continue rotating by the concurrent influences of the first action of the one of the cylinders I 103 and the second, different action by the other of the cylinders I 104. In this specific illustrated example, the first motion contributing force is generated from conversion of potential energy to kinetic energy and the second motion-contributing force is generated from conversion of kinetic energy to potential energy. 5 An activation means I 107, in this illustrated provided by a drive motor 1108, is operable to initiate and then support as appropriate, subsequent rotation of the rotor wheel 1102 in a drive direction D. It is to be appreciated that an activation means of the apparatus 1101 may alternatively comprise different activation arrangements for initiating rotation of the drive belt and for maintaining subsequent rotation of the drive belt. 10 One of the pair of cylinders I 103 is designed as a “gravity weight” cylinder, and the other of the pair of cylinders I 103, is designed as a “buoyancy weight” cylinder. Together, the pair of cylinders 1103, 1104 function to encourage continued rotation of the rotor wheel I 102 when in motion. 15 xt Using gravity and buoyancy effects at different phases of the drive belt cycle, kinetic energy is converted to potential energy and potential energy is converted to kinetic energy. As these phases occur concurrently, on opposite sides of the axis of rotation, they act to f continue the rotation of the drive belt 1— 20 In an example, and in this illustrated example, the “gravity weight” cylinder I 103 and the “buoyancy weight” cylinder I 104 each contain a mass that is movable, in a radial direction R, between a radially inward position A and an radially outward position B, the mass in the “gravity weight” cylinder I 103 being within a fluid having a first density and the mass within 25 the “buoyancy weight” cylinder I 104 being in within a fluid having a second density that is less than the first density. In an example, the fluid of the “gravity weight” cylinder 1103 is water and the fluid of the “buoyancy weight” cylinder I 104 is air. In an example, at least one of the cylinders 1103, I 104 is a double-acting cylinder. 30 In an example, the rotor wheel 1102 is usable to drive an electric motor. In a specific example, and in this illustrated example, the “gravity weight” cylinder 1103 is a doubleacting cylinder that is configured to pump hydraulic fluid to a hydraulic motor, indicated at I 109, for driving an electric generator, indicated at I I 10. In this specific example, the gravity weight” cylinder 1103 is arranged to expel received hydraulic fluid when its mass moves from position Ato position B. In an alternative specific example, the apparatus 1101 is configured for direct drive of the electric generator 1110. The drive belt may comprise multiple cylinder pairs; in an example three pairs of cylinders, in a balanced distribution around the rotor wheel, are utilised. Using a plurality of pairs of cylinders can increase the amount of energy available for extraction when the apparatus is in operation. Thus, it is to be appreciated from foregoing description that, when the drive belt is in motion, at least one part of the drive belt travels through a first volume of a fluid having a first density, to generate a first motion-contributing force for encouraging continued rotation of the drive belt in the drive direction D, and at least one other part of the drive 15 belt concurrently travels through a second volume of a fluid having a second density, to xl generate a second motion-contributing force for encouraging continued rotation of the drive belt in the drive direction D, and each part may be a module of a drive chain (such as, but not limited to, the example disclosed with reference to Figure I) or a drive member f device supported by a platform (such as, but not limited to, the example disclosed with 20 reference to Figure I I). Main phases of operation of an apparatus 101, 1201 as described herein will now be described with reference to Figure 12. 25 During a start-up phase 1201, energy is supplied to the apparatus to initiate rotation of the drive belt from a “standing condition”, in which the drive belt is stationary. From the startup phase 1201, a work phase 1202 is entered, during which the drive belt is rotating, and energy can be extracted from the apparatus. Following the work phase 1202, a shut-down phase 1203 is entered, during which the driving belt is returned to the “standing condition. 30 It is to be understood that the apparatus may have any other additional or alternative phases of operation, and that each phase of operation of the apparatus may comprise more than step. The start-up phase 1201 may involve establishing an operative connection between the drive belt and for example, an electricity generation or energy storage arrangement, and the shut-down phase 1203 may then involve disconnecting that operative connection. 5 The work phase 1202 involves maintaining the drive belt in a “steady state” condition; however, adjustments may be made to the operating conditions, for example to adjust the speed of rotation of the drive belt and, in turn, adjust the amount of energy available for extraction. Thus, operating conditions may be adjusted to cause the drive belt to rotate at 10 a first RPM during a first period of the work phase 1202 and at a second, different RPM during a second, subsequent period of the work phase 1202. Operating conditions may be adjusted dependent on various factors, which may involve reacting to changes in energy demand or avoiding excessive operating speed, temperature, load etc. 15 20 Thus, as indicated, during the work phase 1202 may involve execution of an operating condition management routine 12020, during which at step 12021 a question is asked as to whether an operating condition is to be adjusted; if the question is answered in the negative, step 12021 is entered again, however, if the question is answered in the affirmative, step 12022 is entered, during which an adjustment of the operating condition is effected, and then step 12021 is entered again. Any suitable adjustment or adjustments may be made. By way of example, with the apparatus 101, an adjustment may be made to the pressure P2 of the fluid Fl (air) in the first section SI, to cause a change in the column of the fluid F2 (water) in the section S2, 25 to, in turn, alter the speed or power output of the rotating drive belt 102. By way of further example, with the apparatus 1101, an adjustment may be made to the speed of the drive motor 1108, to change the speed that the rotor wheel 1102 is rotating, to, in turn, alter the ratio of energy output to energy input. 30 It is to be appreciated that the operating condition management routine may comprise other steps, either relating to the same purpose of enquiring as to whether an adjustment is required and, if so, for initiating an appropriate change, or relating to another purpose, for example for recording data, detecting a fault, generating an alert (such as a warning, or a reminder). It is to be understood that when the apparatus is used in an electricity generation 5 application, instances may arise in which more the energy output is higher than the energy demand; in this situation it is desirable for the apparatus to be operatively connected to an energy storage arrangement, for storing the generated electricity for future use. The energy storage arrangement may comprise a battery. The energy storage arrangement may alternatively, or additionally, comprise an energy storage arrangement that is operable by 10 the apparatus. An example of an energy storage arrangement 1301, operable by an apparatus as already described, for example apparatus 101, is shown in Figure 13. 15 The energy storage arrangement 1301 comprises a vessel 1302 for retaining a volume of a liquid 1303 and an object 1304 that is floatable by that liquid 1304. The energy storage arrangement 1301 further comprises a fluid control arrangement, indicated at 1305, comprising a liquid reservoir 1306 and pipework 1307, a pump 1308, and a control system, indicated at 1309, by means of which one or more functions of the fluid control arrangement 1305 can be controlled. The control system 1309 may comprise any suitable data processor and memory resource, and may comprise any suitable controls. According to this specific illustrated example, the fluid control arrangement 1305 is operatively connected to a turbine 1310 and, in turn, an electric generator 1311 with a 25 power-out cable 1312. The fluid control arrangement 1305 allows, selectively, liquid to be supplied to the vessel 1302, in turn causing the object 1304 to be raised, and liquid to be drained from the vessel 1302, in turn causing the object 1304 to be lowered. 30 The pump 1308 is connectable to an apparatus as already described, for example apparatus 101, allowing energy extractable from the apparatus to be used to pump liquid 1303 into the vessel 1302 to raise the object 1304, increasing potential energy associated therewith. When the object 1304 is in a raised condition, liquid can subsequently be allowed to flow from the vessel 1302, the flow being directed to drive the turbine 1310 and, in turn, the electric generator 13 I I. The draining of liquid from the vessel 104 causes the object 1304 5 to move into a lowered condition. The potential energy associated with the object 1304 when in the raised condition is thus converted to kinetic energy as it moves into the lowered condition. The lowered object 1304 can be raised again by refilling the vessel 1302 with liquid. In this way, surplus electricity generated by the apparatus can be stored by operation of the energy storage arrangement. 10 In an example, the energy storage arrangement 1301 is arranged within a flow path of a river, or other geographical source of running water, allowing energy to be extracted from the natural environment. Thus, energy storage arrangement 1301 may be used to generate energy, not just store it. 15 xt Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid is equal to the weight of the fluid that the body displaces; with the volume of the fluid that the body displaces being equal to the volume of the body that is f immersed in the fluid. If the weight of the body is greater than the upward buoyant force, T"— 20 the body will sink into the fluid, but if the weight of the body is equal to the upward buoyant force, the body will float in the fluid. In this specific example, the range of motion through which the object 1304 can rise and fall is constrained. The energy storage arrangement 1301 utilises the object 1304 to 25 maintain a constant liquid head pressure that is independent of the depth of the liquid within the vessel. The energy storage arrangement 1301 also provides for the object 1304 to be floated using a volume of liquid that is less than the volume of liquid that the object 1304 would displace if fully submerged in the liquid. 30 The position of the object 1304 relative to liquid 1303 within the vessel 1302 is managed using a sealing arrangement, indicated at 1313, a channel arrangement, indicated at 1314, and a valve arrangement, indicated at 1315, further comprised by the fluid control arrangement 1305. The object 1304 is disposed within the vessel 102 in a manner that allows liquid 1303 to flow along a longitudinally extending, peripheral surface 1316 of the object 1304. xt CM CM 5 Preferably, the vessel 1302 is provided with a plurality of fluid ports, such as fluid ports 1317, 1318, 1319, at different heights; and each fluid port may be provided with a valve, such as float valve 1320 of fluid port 1317, allowing only the inflow of liquid 1303 into the vessel 1302. 10 In this example, liquid 1303 can flowthrough the pipework 1307 in the direction indicated by arrow 1321. Fluid port 1317, the highest of those illustrated, is an inlet port through which liquid can flow into the vessel 1302, during which the object 1304 moves from a lower to a higher position, and fluid port 1319, the lowest of those illustrated, is an outlet port through which liquid can flow from the vessel 1302, during which the object 1304 15 moves from a higher to a lower position. The following considerations are to be noted at this point It has been found that a body can be made to float in a volume of fluid substantially less than its displacement, if the body is in a container where a volume of liquid is restricted to ensure the liquid level or “head” 20 of liquid is identical (relative to the body) to what it would be if the liquid were not so constrained. Pouring liquid into the container containing the floating body increases the potential energy of that body by raising it in a direction opposite to that which gravity acts. If the weight of the floating body is identical to or greater than the weight of liquid in which it is immersed, a significant gain in energy can be achieved on discharge of that liquid at its 25 lowest level. Using float assisted discharge means that the discharge head pressure cannot be lower than that created by the body, giving consistency of output. In an application, the energy storage arrangement 1301 is primarily intended for storage purposes and for occasion use; this lends to it being allowed to recharge slowly but be 30 discharged rapidly (for high, short-term output). A plurality of energy storage arrangements as described can be used to provide longer output and / or a continuous availability of output. It is to be understood that an apparatus as already described, for example the apparatus 101, may be used in various applications, whether onshore or offshore, and whether as a standalone apparatus or within a network of apparatus. For example, the apparatus may be used to supply electricity to one or more buildings, which may, for example, be 5 residential or industrial. The apparatus may be used to supply electricity to one or more devices, which may be associated with a portable or permanent construction or site. The apparatus may be used to supply power to a vehicle, for example an automobile or a train. Thus, the apparatus may be used in a transport installation. 10 In Figure 14, a rural village 1401 is illustrated, in which a number of the apparatus 101 have been installed for use in supplying electricity. For example, apparatus 101 A, 101B, 101C and 101D have been installed alongside houses 1402, 1403, 1404 and 1405 respectively, and apparatus 101E has been installed alongside church 1406. Each apparatus 101 A-101 E can be associated with an electricity storage arrangement, such as electricity storage arrangement 1301A shown for apparatus 101A sited at house 1402, electricity storage arrangement 130IB shown for apparatus 101C sited at house 1404, and electricity storage arrangement 130IC shown for apparatus 101 D sited at house 1405. Each apparatus may be arranged to supply electricity to a respective individual building only, 20 and an apparatus may be arranged for excess electricity extractable therefrom to be stored using a respective electricity storage arrangement. Alternatively, two or more of the apparatus, and any associated one or more electricity storage arrangement, can be networked. Thus, for example, the apparatus 101A-I0IE can 25 each be part of a network controlled by an energy management control system, indicated at 1400, allowing any one of the associated buildings 1402-1406 to be supplied with electricity from any of the apparatus 101 A-101E and / or any of the associated electricity storage arrangements 1301 A-1301C. 30 Thus, a network comprising the apparatus 101 A-101 E can allow building 1402 to receive electricity from associated apparatus 101A and / or any of the other apparatus 101B-101 E, for example in the instance that the energy demand of the building 1402 is greater than can be met by apparatus 101A alone, or for example in the instance that apparatus 101A is undergoing maintenance and therefore not able to contribute to meeting the energy demand of the building 1402. Similarly, a network comprising the electricity storage arrangements 1301 A-130 IC can not only allow any building associated with the network to receive power from any of the electricity storage arrangements 1301 A-1301C but can 5 allow excess electricity available from any of the associated apparatus 101 A-101E to be stored in any of the electricity storage arrangements 1301 A-1301C having available capacity at that time. Thus, the network can be used to ensure that all electricity available for extraction from a group of the apparatus can be used or stored for future use, with the aim of ensuring that power can be supplied to any associated building any time there is a 10 demand for power to be supplied to that building. The energy management control system 1400 can have any number of functions relating to monitoring energy demand and supply within the network. The energy management control system 1400 can control the distribution of electricity from the apparatus 101A-15 101E to one or more buildings 1402-1406 and / or one or more electricity storage xl arrangements 1301 A-130 IC connected to the network and the distribution of electricity from one or more electricity storage arrangements 1301 A-1301C to one or more buildings 1402-1406. Interesting energy plans can be made available for consumers, including consumers of a network being collectively responsible for covering installation and / or 20 maintenance costs but individual consumers not incurring usage-dependent charges for consuming electricity supplied by the network. It is important to note at this point that the use of the freely available resources of gravity and buoyancy as such does not involve a cost, and this can be reflected directly in an energy plan. 25 The energy management control system 1400 may incorporate fault detection and alert functionality. The energy management control system 1400 may incorporate machine learning. For example, the energy management control system 1400 may use artificial intelligence for anticipating energy demand at different times and managing available network supply configurations to meet that demand most efficiently. 30 It should be noted that any suitable energy storage device arrangement may be used with an apparatus or within a network of the apparatus. It should also be understood that while in Figure 14 each apparatus is shown above ground and each energy storage device arrangement is shown underground, either other these may be located above or below ground level, onshore or offshore. An example application 1501 of an apparatus 1502 according to an example of the present 5 disclosure that is designed for use offshore is shown in Figure 15. The seabed is indicated at 1503 and the sea water level is indicated at 1504. The apparatus 1502 is supported in position by a support structure 1505, and cabling 1506 suitable for providing electrical power to, and taking electrical power from, the apparatus 1502 is 10 provided. It should be noted at this point that the offshore apparatus 1502 is usable at great depths since the density of air when at a sufficiently high enough pressure for maintaining a “dry” section SI is still low enough to have no significant effect on the apparatus 1502. Further, the offshore apparatus 1502 provides a unique opportunity for a deep ocean installation (in an example, at a depth of at least 1000 feet / 300m) that can produce multi megawatts of electrical energy on a ground footprint that is smaller than any other known energy generating means. 20 Other features indicated in this Figure, which are particularly applicable to the illustrated scenario, include a docking bay 1507, helipad 1508 and crane 1509. 25 Another example application 1601 of an apparatus 1602 according to an example of the present disclosure is shown in Figure 16. The apparatus 1602 is provided at the location of building 1603, in this illustrated example a house, with the apparatus 1602 installed below ground level 1604. Also shown in this Figure is a wind turbine 1605, installed to extend upwardly from ground level 1604. Both the apparatus 1602 and the wind turbine 1605 can both be one megawatt (I MW) power plants; however the following advantages are, or can be provided by, apparatus 1602 when compared to the wind turbine 1605: less intrusive; the apparatus being underground does not interfere with the environment above ground, either aesthetically or physically; lower maintenance requirements; the apparatus being underground is not affected by the elements in the same way as if it was above ground; higher capacity; higher power output per unit area. 10 15 It is to be appreciated that many variants of apparatus as disclose herein may be achievable currently or in the future after further development. For example, designs of the apparatus for use in air or in water are envisaged. Such designs may include features or aspects not already specifically disclosed, for example an aeration arrangement for aerating a liquid contained within a section of the housing of apparatus having a design similar to that shown of apparatus 101. Apparatus with a relatively small size may be designed, for example for use in providing a vehicle with an on-board power generation for supplying power to circuity comprised by the vehicle. Apparatus with a relatively large size may be designed, for providing a local power supply for a remote settlement The apparatus, which innovatively uses the forces of gravity and buoyancy, and be used to generate power for supply at the time / point of demand or for centralisation for satisfying larger demand levels. Thus, the apparatus may be used for providing electricity at a local or a district level. Clearly, there are many possibilities to be explored. 20 Apparatus, for use in generating electricity, is thus disclosed that comprises a drive belt rotatable, in an upright orientation, in a drive direction. When the drive belt is in motion, at least a first part thereof moves through a first volume of a fluid having a first density and, at the same time, at least a second part thereof moves through a second volume of a fluid having a second density; the forces of gravity and buoyancy being utilised to generate first 25 and second motion-contributing forces that encourage continuing rotation of the drive belt in the drive direction. An energy storage arrangement is also thus disclosed that comprises a vessel for retaining a volume of a liquid and an object that is floatable by the liquid, and constrained, and that further comprises a fluid control arrangement for controlling rising and falling of the object. 30 Although illustrative embodiments and examples of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment and examples shown and / or described and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims. 16 1224

Claims

1015I. An energy storage arrangement, comprising:a vessel for retaining a volume of a liquid and comprising an object that is floatable by the liquid, andthe energy storage arrangement further comprising a fluid control arrangement for controlling rising and falling of the object, the fluid control arrangement comprising a control system for selectively:allowing liquid to be supplied to the vessel, to cause the object to be raised from a lower position to a higher position, andallowing liquid to be drained from the vessel, to cause the object to fall from a higher position to a lower position;in which the range of motion through which the object can rise and fall is constrained, andthe position of the object relative to liquid in the vessel is managed using a sealing arrangement, a channel arrangement and a valve arrangement further comprised by the fluid control arrangement.

2. The energy storage arrangement of claim I, wherein the fluid control arrangement comprises a liquid reservoir and pipework, and a pump.

3. The energy storage arrangement of claim 2, wherein the vessel is provided with a plurality of fluid ports at different heights for allowing the inflow of liquid into the vessel.25 4. The energy storage arrangement of any one of claims I to 3, wherein the object isdisposed within the vessel in a manner that allows liquid to flow along a longitudinally extending, peripheral surface of the object5. The energy storage arrangement of claim 4 when dependent on claim 2 or claim 3, 30 wherein the allowing liquid to be supplied to the vessel, to cause the object to be raised from a lower position to a higher position, comprises allowing liquid to be supplied to the vessel above the object, to flow along the longitudinally extending, peripheral surface of the object.

6. The energy storage arrangement of any one of claims I to 5, wherein the fluid control arrangement is operatively connected to a turbine and, in turn, an electric generator with a power-out cable.5102015257. An energy network, comprising:an energy storage arrangement according to any one of claims 2 to 6, andan apparatus comprising: a drive belt supported, in a generally upright configuration, within a housing, the drive belt rotatable, in a drive direction, along a path of travel passing sequentially through a plurality of sections of the housing, and through a sealing arrangement of the housing, in which:a first section of the plurality of sections comprises a first volume of a fluid having a first density, whereby to allow the drive belt, when in motion, to move therethrough with gravity,a second section of the plurality of sections comprises a second volume of a fluid having a second density, the second density greater than the first density, whereby to allow the drive belt, when in motion, to move therethrough with buoyancy, anda third section of the plurality of sections comprises a third volume of a fluid; andthe drive belt and the sealing arrangement co-operable for surmounting resistance to continuing motion of the drive belt along the path of travel; andthe apparatus further comprising activation means for initiating rotation of the drive belt, optionally for maintaining subsequent rotation of the drive belt;and wherein the pump of the fluid control arrangement of the energy storage arrangement is operatively connected to the drive belt of the apparatus for allowing energy extractable from the apparatus to be used to pump liquid into the vessel to raise the object.

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