WO2022208381A1

WO2022208381A1 - Hydroelectric energy storage system

Info

Publication number: WO2022208381A1
Application number: PCT/IB2022/052934
Authority: WO
Inventors: Christiaan Johannes JOUBERT
Original assignee: Joubert Trust
Priority date: 2021-03-30
Filing date: 2022-03-30
Publication date: 2022-10-06

Abstract

A hydroelectric energy storage and or generation system 110 and method. The system 110 comprises a first vessel 112 floating in a waterbody 114 having a level 116. The first vessel 112 has a first compartment 118 defining a first volume 120, and a first opening 122 associated with a turbine 134, through which water is allowed to flow into or from the first volume 120. The system 110 also includes a position adjustment means 130 for adjusting a vertical position of the first compartment 118 relative to the level 116 of the waterbody 114. The system 110 is configured such that upwards displacement of the first compartment 118 causes water to drain therefrom, driving the turbine.

Description

HYDROELECTRIC ENERGY STORAGE SYSTEM

BACKGROUND TO THE INVENTION

This invention relates to the generation and/or storage of energy. More particularly, the present invention relates to a hydroelectric energy storage system and method, incorporating on-board means of generating energy.

Generally, the supply of and demand for electricity within a larger electrical grid are variable and seldomly match. Times of peak demand call for supply of electricity at rates closer to or even above maximum achievable rates, while excess electricity supply during times of off-peak demand often goes to waste. It will be appreciated that, in a larger grid, the rate of electricity supply cannot easily be varied, since generating facilities are ideally run at constant, and highly efficient, rates. Furthermore, in cases where reliance is placed on renewable natural resources, such as wind or solar sources, energy generation rates are determined by external or natural factors.

One (at least partial) solution to the disjoint between supply and demand of electricity during peak and off-peak times, is to make provision for the storage of surplus energy within a grid. In this way, energy supply can be supplemented from the storage during peak times and absorbed by the storage during off-peak times. Such storage can also be utilised in areas which rely heavily on fluctuating renewable sources such as solar or wind energy, to smooth out provision of electricity (for example during the night-time).

A known, and relatively environmentally friendly means of storing surplus energy, is a so-called “pumped-hydro storage plant”. These plants comprise two water bodies located at different elevations, which are interconnected by a conduit provided with a reversible turbine. The systems store energy in the form of potential energy associated with a static head of water in the higher water body. In times of peak demand, water is directed to flow through the conduit from the higher to the lower water body, causing the turbine to generate electricity. During off-peak times, surplus electricity in the grid is used to power the turbine to pump water back up from the lower water body to the higher water body through the conduit. Pumped hydro storage plants have overall cycle efficiencies of up to 80%. Pumped hydro storage plants therefore act as load-balancing mechanisms within an electricity grid. Pumped hydro storage plants generally have a relatively long service life. That said, initial capital expenditure calls for large scale implementation. Furthermore, geological considerations mean that not all areas are suitable for implementation of pumped hydro storage systems.

A need therefore exists for alternative forms of energy storage systems which require lower initial capital expenditure, are not as limited by geological considerations and which are more scalable and easily implementable.

It is accordingly an object of the invention to provide hydroelectric energy storage system and method that will, at least partially, address the above disadvantages.

It is also an object of the invention to provide a hydroelectric energy storage system and method which will be a useful alternative to existing energy storage systems and methods.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention there is provided an energy storage and/or generation system, comprising: a first vessel, operatively arranged in a waterbody having a level, the first vessel comprising a first compartment defining a first volume and a first opening operatively arranged in fluid flow communication with the waterbody, through which water is allowed to flow into or from the first volume, the first compartment having a bottom surface and a sidewall; and a position adjustment means for adjusting a vertical position of the first compartment relative to the level of the waterbody, wherein the system is configured such that upwards displacement of the first compartment causes water to drain therefrom.

Further according to the first aspect of the invention, a first turbine may be arranged in fluid flow communication with the first opening. The first turbine may comprise a reversible turbine, operatively driven by water flowing into or from the first compartment, to generate electricity.

The bottom surface of the first compartment may be concave and/or may taper towards the first opening. An outer bottom surface of the vessel may also be concave and may also taper towards the first opening.

Furthermore, the sidewall may be manufactured from a flexible material such as polymers and rubbers. For example, the sidewall may be manufactured from chlorosulfonated polyethylene, PVC, nylon, oxford woven cloth, or materials containing synthetic fibres such as aramid or para- aramid materials. The sidewall may take the form of a plurality of inflated, stacked, ring-shaped pontoons.

Alternatively, the sidewall may be manufactured from a substantially rigid material, such as substantially rigid plastics or metals, such as steel, stainless steel, or aluminium. The sidewall may take the form of buoyant tanks, pontoons, or containers.

The sidewall may have a height which is based on the specific configuration of the first compartment. In some embodiments, the height of the sidewall may range between 0.5 m and 10 m, and may typically be around 5 m. In other cases, the sidewall may extend more than 10 m, and may be as high as 30 m. The first container may have an upward facing surface area of up to 10 000m². In some cases, the first container may have an upward facing surface area of up to 20 000m² or even more.

The first container may be open-ended at a top end thereof or may be in fluid flow communication with an outside atmosphere. The first container may have a substantially circular or rectangular shape in plan.

Further in accordance with the first aspect of the invention, the position adjustment means may comprise a buoyancy adjustment system.

The system may further comprise a second compartment defining a second volume, which may form part of the buoyancy adjustment system. The second compartment may comprise a second opening, operatively arranged in fluid flow communication with the waterbody, through which water may be allowed to flow into or from the second volume. The second opening may be provided with a second valve. The second compartment may also comprise a purge opening associated with a purge valve.

A wall of the second compartment may form the bottom surface of the first compartment, and the first opening may take the form of a conduit, which extends through the second compartment.

Typically, the second compartment may be manufactured from a material such as steel, stainless steel, natural rubber, synthetic rubber, neoprene, PVC, or polyurethane.

The buoyancy adjusting system may furthermore comprise an air purge system, with which, operatively, a volume of air may be provided to the second compartment. The air purge system may also comprise a source of compressed air which may be connected in fluid flow communication with the second compartment. The source of compressed air may comprise one or more compressed air tanks filled by means of an air compressor and/or an outlet of an air compressor arranged in direct fluid flow communication with the second compartment.

The air compressor may take the form of a low pressure, large volume blower, for example, a reciprocating piston compressor, and orbital compressor, a screw compressor, a tooth compressor, or a vane compressor.

A substantially rigid and substantially horizontally extending support platform may be arranged vertically above or over the first compartment. The support platform may, operatively, be supported above the level of the water. The support platform may support a plurality of photovoltaic panels, directly or by means of a support lattice structure, and/or may be adapted to serve as a base for further structures such as for supporting a wind renewable energy generator in the form of a wind turbine, housing units, storage units and/or other building units.

Further, in accordance with the first aspect of the invention, the system may comprise a second vessel, which may be substantially similar to the first vessel. The first and second vessels may be arranged proximate one another and allowed to be vertically displaced relative to each other.

The first vessel may typically and substantially function as a base for floating amphibious housing and may take the shape of a barge.

In accordance with a second aspect of the invention, there is provided a method of storing and/or generating energy, comprising the steps of: a) providing a first vessel, comprising a first compartment defining a first volume, within a water body having a water level; b) lowering a vertical position of the first compartment relative to the water level; c) allowing water to enter the first volume via a first opening; d) utilising a position adjustment means to adjust a vertical position of the first compartment in upward fashion; e) allowing water to flow from the vessel to the water body via the first opening.

The method may be undertaken by means of a system according to the first aspect of the invention and may include the step of installing the system in the waterbody.

Further according to the second aspect of the invention, step c) may comprise opening a first valve associated with the first opening and allowing water from the waterbody to flow through the first opening into the first volume.

Furthermore, step e) may comprise opening the first valve and allowing water from the first volume to flow through the first opening into the waterbody.

A first turbine may be provided in fluid flow communication with the first opening. Water flowing through the first opening may drive the first turbine, thereby causing electricity to be generated. Steps d) and e) may be carried out simultaneously.

The method may be based on the principle that upward displacement of the first compartment may facilitate draining of water from the first volume through the first opening.

The first vessel comprises a second compartment defining a second volume and a second opening, and wherein step b) comprises allowing water to flow through the second opening into the second volume, thereby displacing air from the second volume and decreasing a buoyancy of the first vessel, and wherein steps b) and c) are carried out simultaneously.

Air may be allowed to escape from the second volume through a purge opening.

Step d) may comprise the further sub-step of increasing the buoyancy of the first vessel by displacing water from the second volume by at least one of the steps of: f) providing a volume of air to the second volume; and/or g) utilising a turbine or pump to displace water from the second volume.

Further in accordance with the second aspect of the invention, supplementary electricity may be generated by means of a supplementary electricity generating system associated with the first vessel. The supplementary electricity generating system may comprise photovoltaic panels and/or wind turbines.

At least a portion of generated electricity may be stored, while at least a portion of generated electricity may be provided to an electrical grid.

A second vessel may be provided. Steps b) to e) may be conducted in respect of the second vessel. The first and second vessels may be operated in complementary fashion, but out of synchronisation, for example, step b) may be conducted in respect of the first vessel while step d) is conducted in respect of the second vessel and so on. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of an example embodiment of a system for storing and/or generating energy in accordance with the invention;

Figure 2 shows a sectioned side view of the system of Figure 1 ;

Figure 3 shows a diagrammatical side view of the system, of Figure 1 , in which a first vessel forming part of the system floats at a first vertical level;

Figure 4 shows the diagrammatical side view of Figure 3, in which the first vessel floats at a lower vertical level, after a ballast tank and the first vessel has, at least partially, been filled with water; and

Figure 5 shows a diagram setting out a method of storing and/or generating energy, by utilising the system of Figure 1.

Figure 6A-D show diagrammatic side views of the system of Figure 1 , during different stages of operation.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted", "connected", "engaged" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings and are thus intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. Further, "connected" and "engaged" are not restricted to physical or mechanical connections or couplings. Additionally, the words "lower", "upper", "upward", "down" and "downward" designate directions in the drawings to which reference is made. The terminology includes the words specifically mentioned above, derivatives thereof, and words or similar import. It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

It will be appreciated that a reference to a “waterbody” refers to any one of a fresh water or a saltwater waterbody, manmade or naturally occurring bodies and the like. Furthermore, references to a “water level” of the waterbody does not imply that the water level is constant or static. For example, the water level of the waterbody may change due to tidal fluctuations, nett inflow, or outflow of water from the waterbody, and the like.

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of a system for storing or generating energy in accordance with the invention is generally indicated by reference numeral 110.

The system 110 comprises a first vessel 112 which, in use, is arranged within a waterbody 114 which has a water level 116. The first vessel 112 comprises a first compartment 118 which defines a first volume 120. The first compartment 118 furthermore defines a first opening 122, which is provided in fluid flow communication with the waterbody 114. That is to say, the first opening 122 is arranged, so as, in use, to allow water to flow therethrough, either from the first volume 120 to the waterbody 114, or from the waterbody 114 to the first volume 120.

The first volume 120 is defined between at least a lower or bottom surface 124 (or floor) of the first compartment 118, and a sidewall 126 of the first compartment 118. In the example shown in the figures, the sidewall 126 extends substantially vertically from the bottom surface 124, while the first compartment 118 is open to the atmosphere 128.

In an alternative embodiment, which is not shown in the figures, the first compartment 118 is not open-ended, and instead comprises an upper surface. The first vessel 112 floats in the waterbody 114, and is, therefore, at any point in time, associated with a vertical position within the waterbody 114 and therefore relative to the water level 116.

The system 110 furthermore comprises a position adjustment means 130 which is provided for adjusting the vertical position of the first compartment 118 relative to the water level 116 (the adjustment of the vertical position of the first compartment 118 occurs in cyclic fashion and in different stages, as will be discussed more fully below).

It will be appreciated from what follows, that the position adjustment means 130 is external to the first compartment 118.

The configuration of the system 110 is such that upwards displacement of the first compartment 118 (by means of the position adjustment means 130) causes water to drain from the first compartment 118 (through the first opening 122, which, naturally, is configured in an open configuration to allow water to drain therethrough). Also, the configuration of the system 110 is such that downwards displacement of the first compartment 118 (by means of the position adjustment means 130) causes water to flow into the first compartment 118 (through the first opening 122).

It follows that the displacement of the first compartment causes the flow of water into and from the first compartment 118. Therefore, water is not pumped from the first compartment 118 to achieve this.

The first opening is associated with a conduit 132 which is provided with a first valve 123 and a reversible turbine 134, which is driven by water flowing through the first opening 122, to generate electricity.

It is believed that the overall efficiency, or at least the amount of energy that can be stored and/or generated by the system 110, is linked to the overall size of the first compartment 118.

It will be appreciated that a height of the sidewall 126 determines the difference in vertical position of the first compartment 118 relative to the water level (between a higher vertical configuration, and a lower configuration), which impacts on the amount of water which can be stored in the first compartment 118. The height of the sidewall may be selected based on operational and practical requirements and may typically vary between 0.5 m and 10 m. In one example, the height of the sidewall is around 5 m.

It also follows naturally that the energy storage potential of the system is determined by the volume of water that can potentially be stored by the first compartment 118. In some examples, the first compartment 118 has an upward-facing surface of up to 10 000m² (1 hectare). It will however be appreciated that the system 110 may be scaled down significantly in cases where practical constraints call for same.

In the examples shown, the position adjustment means 130 comprises a buoyancy adjustment system.

As part of the buoyancy adjustment system, the system 110 furthermore comprises a second compartment 136 (which may take the form of a ballast tank). The second compartment 136 is typically fixed to, or integrally formed with the first compartment 118. In the example shown in the figures, the second compartment 136 forms the bottom surface 124 of the first compartment 118, and therefore extends below the first volume 120. The second compartment 136 lends structural rigidity to the first vessel 112 and/or the first compartment 118 and is typically manufactured from steel or stainless steel. The use of alternative materials, such as metals or polymers, is also viable.

The second compartment 136 defines a second volume 138 with a second opening 140, which is also provided in fluid flow communication with the waterbody 114. The second opening 140 is associated with a second valve 142. The second opening 140 and second valve 142 facilitate water flowing between the waterbody 114 and the second volume 138.

The second compartment 136 is furthermore associated with a purge opening 144, with a valve (not shown).

The conduit 132 associated with the first opening 122 extends through the bottom surface 124, and therefore, through the second compartment 136. The bottom surface 124 is concave and tapers or funnels inwards or downwards towards the first opening 122 to facilitate water within the first vessel 112 flowing towards the first opening 122 in use. An outer (or bottom) surface 146 may likewise taper or funnel towards the conduit 132 or first opening 122 (not shown). It will be appreciated that a reference to a decreased or lowered vertical position of the first compartment 118 relative to the water level 116 is akin to the first compartment 118 “sinking” deeper into the waterbody 114, whereas an increased or higher vertical position of the first compartment 118 relative to the water level 116 is akin to the first compartment 118 floating higher within the waterbody 114 and therefore relative to the water level 116.

It will furthermore be appreciated that the vertical position of the first compartment 118 is typically determined by the overall buoyancy of the system 110. Here, it will be appreciated that the term “overall buoyancy” of the system 110 refers to the buoyancy of the first compartment 118 itself, but notably, also the second compartment 136.

The overall buoyancy may therefore have a component which is determined by the buoyancy of the first compartment 188 itself, and a component which is determined by the buoyancy of the second compartment 136. The relevance of this will become apparent from what follows.

The second compartment 136 forms part of the position (or buoyancy) adjusting means 130, with which the vertical position of the first compartment 118 relative to the water level 116 is adjusted in use.

The position adjustment means 130 furthermore includes an air purge system which comprises a source of pressurised air (not shown), typically in the form of one or more tanks which is fed with compressed air via a compressor, which may be housed onboard the first vessel, may be situated on a support structure of the system 110, or which may even be located on shore. The compressor may comprise one or more conventional compressors, such as reciprocating piston compressors, orbital compressors, screw compressors, tooth compressors or vane compressors.

The tank is provided in fluid flow communication with the second compartment 136, such that a volume of air from the tank can be channelled into the second compartment 136. It will be appreciated that compressed air provided to the second compartment 136 may be used to displace water from the second compartment 136. This is discussed more fully below.

In an alternative embodiment, which is not shown, high-volume, low-pressure blowers, such as vane or screw blowers may be provided in direct fluid flow communication with the second compartment 136, and may directly feed air into the second compartment 136 to displace water from the second compartment. Further alternatively, or in addition, a pump may be provided with which water from the second compartment 136 may be pumped and therefore replaced with air. In such a setup, an air inlet into the second compartment 136 is provided.

The system 110 is used, primarily, as an energy storage system. The energy stored by the system 110 can be converted into electricity to act as an electricity source as the need therefor arises, for example, during times of peak demand, or to provide electricity at night, in cases where the grid otherwise relies, at least in part, on electricity produced from solar energy.

It will be appreciated that the material from which the sidewall 126 is manufactured is not limited. For example, the sidewall 126 may comprise inflatable bladders of a flexible material, or may be substantially rigid, and may be manufactured from a metal. In such a case, the sidewall may comprise a rigid pontoon, a container, and the like. Generally, however, the sidewall is relatively light, and ideally, close to neutrally buoyant.

A platform (not shown) is typically formed towards an upper part of the vessel. The platform may be used as a base for mounting hardware such as those used while operating the system 110, and additional hardware, or structures.

This means that the platform is, in use, supported above the water level 116. For example, the platform may be provided as a base for mounting photovoltaic cells. The photovoltaic cells may be provided for one or more of the following purposes (this list is not exhaustive or limited):

- generating electricity required to power hardware associated with the system 110, such as blowers or compressors;

- providing supplementary electricity to an electricity grid;

- providing auxiliary power for systems and subsystems (including housing facilities) associated with the first vessel 112.

Furthermore, as an alternative to the photovoltaic cells, or in addition thereto, the platform may serve as a base for mounting wind generating systems, such as one or more wind turbines, to the first vessel 112. The wind turbines may be provided for generating electricity, which may be used for purposes similar to those disclosed in respect to the photovoltaic cells.

Furthermore, the platform may serve as a base for further structures, which may include control rooms, machine rooms, maintenance facilities, storage facilities and the like. It is also foreseen that the platform may in future be adapted for intermittent to permanent dwelling. Therefore, the further structures may include housing facilities, and other facilities and amenities associated with human occupation.

It is foreseen that, due to its size, the first vessel 112 may in future be adapted as a “floating town”, which may provide housing solutions in areas among others, which may in future be affected by rising sea levels or population overcrowding, and the like. It will also be appreciated that these objectives may be supported by the self-sustainable, moveable, and modular nature of the first vessel 112.

In another embodiment, which is not shown in the figures, the system 110 may comprise a second vessel. The second vessel may be substantially similar to the first vessel 112, though the first and second vessels need not be identical. The second vessel is typically arranged in close proximity to the first vessel 112 but is free to move independent thereof. The second vessel provides a function similar to that of the first vessel 112 and operates on the same principle. However, the first and second vessels are or may be operated out of synchronisation with each other. For example, when the first compartment of the first vessel is busy being lowered deeper into the waterbody, the first compartment of the second vessel may be caused to float at a higher vertical level within the waterbody. It is also conceivable that the first and second vessels may be operated in synchronisation with each other.

The provision of a second vessel has a number of immediate advantages. Firstly, an additional vessel adds to the cumulative volume of the system 110 and provides additional storage capacity. Secondly, the additional vessel adds redundancy to the system. Thirdly, the additional vessel provides a means of smoother and/or more continuous storage and delivery of energy. Fourthly, since the first and second vessels are operated out of synchronization, hardware, such as the blower or compressor, can be used more efficiently (instead of only operating during one of the phases of the operating cycle of the system, the blower or compressor can be operated for extended periods of time, or even continually, and as close to a most efficient operating condition as possible). It is believed that this could have a positive effect on the overall efficiency of the system. Furthermore, air displaced from the second container of one vessel (for example, through the relevant purge opening 144), may be directed to the second container of the other vessel, and may therefore supplement air, provided from the tanks or by means of the blowers or compressors. It will be appreciated that some of the hardware used as part of the system, such as the blower or compressor, electrical connection to an electrical grid, and the like, may be shared between the first and second vessels.

Furthermore, it will be appreciated that the system may include a third and further vessels as described above, for the same reasons as above.

Each of the vessels may have a substantially similar volume and/or surface area and/or storage capacity.

The method or process of storing energy (potential energy) and generating electricity therefrom (or converting said stored energy into electricity) is outlined schematically in figure 5 and indicated by reference numeral 150.

The first phase of the method or process revolves around the storage of energy. Typically, this phase is undertaken at a time where the supply of electricity to an electrical grid exceeds the demand for electricity from the electrical grid, or when surplus energy is generated by the photovoltaic cells or wind turbines. Surplus electricity can therefore be consumed by the system 110 to store energy for later use.

The first phase is therefore concerned with storing potential energy in the system 110 for later use or conversion to electricity.

The process will be discussed from an initial state, where the first compartment 118 is substantially empty (does not contain a substantial amount water) and the second compartment 136 is substantially filled with air. The first vessel floats at a first vertical level, which is illustrated in figure 3 and 6a.

The second valve 142 and the valve of purge opening 144 are now both opened. This is illustrated at 152. Water is therefore allowed to flow through the second opening 140, thereby displacing air from the second compartment 136 through the purge opening 144 (at 154).

The increasing volume of water within the second compartment 136 reduces the overall buoyancy of the system and the vertical position of the first vessel 112 is therefore lowered. The first valve 123 is also open (at 156 (even though the first valve is typically also opened when the second valve is opened)) and therefore, water flows through the conduit 132 past the turbine 134 and into the first volume 120 (at 158).

It will immediately be appreciated that:

- water flowing through the conduit 132 into the first volume 120 drives the turbine 134, which in turn generates electricity;

- the overall buoyancy of the system decreases;

- steps 56 and 58 can occur simultaneously with steps 52 and 54, or thereafter.

It will also be appreciated that the amount of water allowed to flow into the second compartment 136 (at step 154) is calculated based on the amount of water that will be allowed to flow into the first volume 120 (at step 158), since both volumes of water will have a bearing on the overall buoyancy of the system 110.

Once a predetermined overall buoyancy has been reached, and therefore, a predetermined vertical level of the system 110 has been reached, and a predetermined volume of water (indicated by reference numeral 200) is contained in the first compartment 118, the first valve 123, second valve 142 and purge opening 144 are closed (shown at 160). This is typically shown in figures 4 and 6B.

It will be appreciated that water will be displaced from (or will drain from) the first compartment 118 through the first opening 122 (and past the turbine), if the first opening 122 is open while the first compartment is lifted vertically higher relative to the water level 116. It will also be appreciated that the rate at which the water is displaced through the first opening 122 is proportional to the rate at which the first compartment 118 is so displaced (provided the size of the first opening is sufficient for this purpose). The turbine is therefore driven by the water passing through the or draining from first opening 122, even though the water within the first compartment is not necessarily kept at a substantially higher head than the waterbody 114. Rather, the first compartment, and therefore the turbine, is moved relative to the water within the first compartment, and as the water drains therefrom, the turbine is driven.

The above can be achieved in a number of ways.

In a first iteration, the first valve 123 is kept closed, while the second valve 142 is opened and the purge opening 144 remains closed (shown at 162). Air is now provided from the source of compressed air, into the second compartment 136, such that at least a portion of the water in the second compartment 136 is displaced through the open second valve 142 (shown at 64). With water escaping from the second compartment 136, and being replaced by air, the overall buoyancy of the system 110 increases. Since the first valve 123 is closed, the effect of this on the vertical level of the first compartment 118 relative to the water level 116 will be minimal.

The system 110 can now be considered in a “primed” condition (or put differently, a maximum amount of potential energy is now stored in the system 110). The system 110 may therefore be maintained in this condition until demand for electricity calls for a generation of electricity.

When required, the first valve may be opened (at 166) to allow the first compartment to start moving vertically upwards, to allow water from the first vessel 112 to flow through the conduit 132 (at 168), thereby driving the turbine 134 and causing electricity to be generated.

The above process does not occur instantaneously, and is determined by fluid dynamic considerations, such as the size and configuration of the first opening 122.

Figure 6C shows an intermediate position while the first container is in the process of being displaced upwards (under the influence of the buoyancy of the second container). Reference numeral 202 indicates a volume of water remaining in the tank at this point. Figure 6D shows a further intermediate position while the first container is in the process of being displaced upwards (under the influence of the buoyancy of the second container). Reference numeral 204 indicates a volume of water remaining in the tank at this point. It will be appreciated that the amount of energy generated by the turbine is, amongst others, determined by the volume of water having drained from the first compartment.

In a second variation of the method, steps 166 and 168 occur in parallel and therefore simultaneously with steps 162 and 164, and therefore, the rising vertical level of the first compartment is associated with concomitant electricity generation by the turbine 134. This variation is therefore used in cases where an immediate production of electricity is required.

It will be appreciated that the system 110 provides a means of utilising displacement of the turbine relative to a volume of water contained in the second compartment, to generate electricity. It will be appreciated that the system can take various shapes and relative sizes and that the system can be operated according to various operating schemes without departing from the underlying principle. Generally, the storage capacity of the system 110 is determined by the size of the first volume 120 of the first compartment 118. It will be appreciated that further compartments or ballast tanks may be provided, all of which may contribute to the overall buoyancy of the system 110, which may ultimately, increase the velocity at which the first compartment may be displaced upwards. For example, the sidewall 126 may be filled with water to decrease buoyancy and re-inflated with air to increase buoyancy.

Furthermore, a secondary ballast tank may be provided which is generally arranged above the water level, which will not (significantly) impact of the buoyancy of the system 110 during normal operation, but which may serve as a safety mechanism in cases where level of buoyancy of the system 110 would cause same to sink, but for the secondary ballast tank.

It will be appreciated that the operation of the system may be optimised in terms of availability or shortage of surplus electricity (from the grid or the photovoltaic cells and/or wind turbines). In one such an example, the vessel may typically be filled with water, and may therefore sit at a low vertical position, as shown in figure 4, early in the morning. The photovoltaic cells may now be used to generate electricity, of which a portion may be supplied to the electrical grid. A surplus or remaining portion of electricity not provided to the grid may be used to pump air into the ballast tank or the air storage tanks. This process will typically be slower than as was described above, since only a portion of the available electricity is used for this purpose. A smaller compressor or blower may be provided for this purpose. The overall buoyancy of the vessel will therefore now increase at a relatively low rate and may be managed such that the overall buoyancy of the system 110 and the vertical level of the first vessel 112 relative to the water level 116 increases to a maximum over the course of a number of hours, such as eight hours or so. Therefore, by the time the amount of electricity generated by the photovoltaic cells starts decreasing due to the availability of direct sunlight (in the late afternoon), the system stores a large or even maximum amount of potential energy, which may at that point be converted to electricity, as was discussed before, whenever the need therefor arises. In cases where a wind turbine is provided, the availability of wind to generate electricity may be taken into account when storing or converting potential energy by or from the vessel and supplying same to the grid. In this way, the supply of electricity from the system may be kept fairly constant over a longer period of time, even in cases where the wind dies down, or during the night-time, overcast or low-light conditions.

In each instance where reference is made to an opening, it will be appreciated that such an opening may similarly be replaced by a plurality of openings, to enhance flow through said openings. Similarly, more than one turbine may be provided, to optimise size and flow rates of water through the turbines. The turbines may have variable pitch blades, to provide for variations in flow rates of water through the opening, and to optimise efficiency of the turbine.

Furthermore, it will be appreciated that the system is deployable in almost any waterbody and is not dependent on a second waterbody which is arranged relative to a first waterbody in a specific geological setting. Also, the system can easily and efficiently be scaled according to storage and/or generating needs. Furthermore, the operation of the system 110 does not influence the level 116 of the waterbody 114 and is believed to have a negligible environmental impact.

It is foreseen that other forms of position adjusting arrangements, such as mechanical mechanisms which may be provided for adjusting the vertical position of the first compartment, may be provided.

It will be appreciated that the height of the sidewall will typically be limited by practical considerations, such as the weight and required strength thereof. It is foreseen that the height of the sidewall may in some circumstances exceed 10m. Also, the overall size of the vessel would also be limited by practical considerations. It is foreseen that the vessel may have an upward- facing surface area exceeding 10 000m² (1 hectare), or that the cumulative upward-facing surface areas of the first and second vessels may exceed 10 000m² (1 hectare).

In another example embodiment, which is not shown, the overall upward-facing surface area of the first compartment may be significantly reduced, and the wall height of the first compartment may be increased. In such an example, the first compartment may typically be cylindrical or tubular, and the difference between the lowered and increased vertical positions may be significantly larger than disclosed with reference to the first embodiment.

It will be appreciated that the above description only provides an example embodiment of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention. For example, the second compartment may take various other forms, and may be made up of more than one second compartment or a plurality of compartments. Furthermore, the second compartment need not form a floor of the first compartment and may alternatively simply be fixed to the first vessel. The second compartment may comprise a substantially ring- shaped tank or pontoon, which may be secured towards a bottom portion of the first compartment. In embodiments where the second tank does not contribute to the structural rigidity of the first vessel, the second compartment tank may be manufactured from a flexible material, such as a polymeric material including rubber, PVC, polyurethane, and the like.

It is easily understood from the present application that the particular features of the present invention, as generally described and illustrated in the figures, can be arranged, and designed according to a wide variety of different configurations. In this way, the description of the present invention and the related figures are not provided to limit the scope of the invention but simply represent selected embodiments.

The skilled person will understand that the technical characteristics of a given embodiment can in fact be combined with characteristics of another embodiment, unless otherwise expressed or it is evident that these characteristics are incompatible. Also, the technical characteristics described in a given embodiment can be isolated from the other characteristics of this embodiment unless otherwise expressed.

Claims

1 . An energy storage and/or generation system, comprising: a first vessel, operatively arranged in a waterbody having a level, the first vessel comprising a first compartment defining a first volume and a first opening operatively arranged in fluid flow communication with the waterbody, through which water is selectively allowed to flow into or from the first volume, the first compartment having a bottom surface and a sidewall; and a position adjustment means for adjusting a vertical position of the first compartment relative to the level of the waterbody, wherein the system is configurable such that upwards displacement of the first compartment causes water to drain from the first volume.

2. The system according to claim 1 , wherein a first turbine is arranged in fluid flow communication with the first opening.

3. The system according to claim 2, wherein the first turbine comprises a reversible turbine, operatively driven by water flowing into or from the first compartment, to generate electricity.

4. The system according to any one of the preceding claims, wherein the bottom surface of the first compartment is concave and/or tapers towards the first opening.

5. The system according to any one of the preceding claims, wherein the sidewall is manufactured from a flexible material selected from the group comprising polymers and rubbers, and wherein the sidewall takes the form of a plurality of inflated, stacked, ring- shaped pontoons.

6. The system according to any one of claims 1 to 4, wherein the sidewall is manufactured from a substantially rigid material, selected from the group comprising plastics and metals, including steel and stainless steel.

7. The system according to claim 6, wherein the sidewall takes the form of buoyant tanks, pontoons, or containers.

8. The system according to any one of the preceding claims, wherein the sidewall has a height of between 0.5 m and 30 m.

9. The system according to any one of the preceding claims, wherein the sidewall has a height of about 5 m.

10. The system according to any one of the preceding claims, wherein the first container has an upward facing surface area of up to 10 000m².

11. The system according to any one of the preceding claims, wherein the first container is open-ended at a top end thereof.

12. The system according to any one of the preceding claims, wherein the first container has a substantially circular or rectangular shape in plan.

13. The system according to any one of the preceding claims, wherein the position adjustment means comprises a buoyancy adjustment system.

14. The system according to claim 13, further comprising a second compartment defining a second volume.

15. The system according to claim 14, wherein the second compartment comprises a second opening, operatively arranged in fluid flow communication with the waterbody, through which water is allowed to flow into or from the second volume.

16. The system according to claim 15, wherein the second opening is provided with a second valve.

17. The system according to claim 15 or 16, wherein the second compartment comprises a purge opening associated with a purge valve.

18. The system according to any one of claims 14 to 17, wherein a wall of the second compartment forms the bottom surface of the first compartment.

19. The system according to any one of claims 14 to 18, wherein the first opening takes the form of a conduit, extending through the second compartment.

20. The system according to any one of claims 14 to 19, wherein the second compartment is manufactured from a material selected from the list comprising: i) steel; ii) stainless steel; iii) natural rubber; iv) synthetic rubber; v) neoprene; vi) PVC; vii) polyurethane.

21. The system according to any one of claims 14 to 20, wherein the buoyancy adjusting system furthermore comprises an air purge system, with which, operatively, a volume of air is provided to the second compartment.

22. The system according to claim 21 , wherein the air purge system comprises a source of compressed air, connected in fluid flow communication with the second compartment, the source of compressed air comprising at least one of: i) one or more compressed air tanks filled by means of an air compressor; and ii) an outlet of an air compressor arranged in direct fluid flow communication with the second compartment.

23. The system according to claim 22 wherein the air compressor takes the form of a low pressure, large volume blower, selected from the list comprising: i) reciprocating piston compressors; ii) orbital compressors; iii) screw compressors; iv) tooth compressors; and v) vane compressors.

24. The system according to any one of the preceding claims, further comprising a substantially rigid support platform arranged vertically above the first compartment, which support platform is, operatively, supported above the level of the water.

25. The system according to claim 24, wherein the support platform supports a plurality of photovoltaic panels, directly or by means of a support lattice structure.

26. The system according to any one of claims 24 to 25, wherein the support platform is adapted to serve as a base for further structures.

27. The system according to claim 26, wherein the support platform is adapted to serve as a base for supporting a wind renewable energy generator in the form of a wind turbine.

28. The system according to claim 26 or 27, wherein the support platform is adapted to serve as a base for at least some of housing units, storage units and other building units.

29. The system according to any one of the preceding claims, further comprising a second vessel, substantially similar to the first vessel, wherein the first and second vessels are arranged proximate one another and allowed to be vertically displaced relative to each other.

30. A method of storing and/or generating energy, comprising the steps of: a) providing a first vessel, comprising a first compartment defining a first volume, within a water body having a water level; b) lowering a vertical position of the first compartment relative to the water level; c) allowing water to enter the first volume via a first opening; d) utilising a position adjustment means to adjust a vertical position of the first compartment in upward fashion; e) allowing water to flow from the vessel to the water body via the first opening.

31. The method according to claim 30, wherein step c) comprises opening a first valve associated with the first opening and allowing water from the waterbody to flow through the first opening into the first volume.

32. The method according to claim 31 , wherein step e) comprises opening the first valve and allowing water from the first volume to flow through the first opening into the waterbody.

33. The method according to any one of claims 30 to 32, wherein a first turbine is provided in fluid flow communication with the first opening, and wherein water flowing through the first opening drives the first turbine, thereby causing electricity to be generated.

34. The method according to any one of claims 30 to 33, wherein steps d) and e) are carried out simultaneously, and wherein upward displacement of the first compartment facilitates draining of water from the first volume through the first opening.

35. The method according to any one of claims 30 to 34, wherein the first vessel comprises a second compartment defining a second volume and a second opening, and wherein step b) comprises allowing water to flow through the second opening into the second volume, thereby displacing air from the second volume and decreasing a buoyancy of the first vessel, and wherein steps b) and c) are carried out simultaneously.

36. The method according to claim 35 wherein air is allowed to escape from the second volume through a purge opening.

37. The method according to claim 35 or 36 wherein step d) comprises the further sub-step of: f) increasing the buoyancy of the first vessel.

38. The method according to claim 37 wherein step f) comprises displacing water from the second volume by at least one of the steps of: g) providing a volume of air to the second volume; and/or h) utilising a turbine or pump to displace water from the second volume.

39. The method according to any one of claims 30 to 38, wherein supplementary electricity is generated by means of a supplementary electricity generating system associated with the first vessel.

40. The method according to claim 39, wherein the supplementary electricity generating system comprises photovoltaic panels and/or wind turbines.

41. The method according to any one of claims 30 to 40, wherein at least a portion of generated electricity is stored.

42. The method according to any one of claims 30 to 41 , wherein at least a portion of generated electricity is provided to an electrical grid.

43. The method according to any one of claims 30 to 42, wherein a second vessel is provided and in which steps b) to e) are conducted in respect of the second vessel.

44. The method according to claim 43, wherein the first and second vessels are operated in complementary fashion, but out of synchronisation.

45. The method according to claim 44, wherein step b) is conducted in respect of the first vessel while step d) is conducted in respect of the second vessel.