WO2023152516A1

WO2023152516A1 - Improvements in and relating to energy conversion and harvesting

Info

Publication number: WO2023152516A1
Application number: PCT/GB2023/050322
Authority: WO
Inventors: Daniel James WALFORD
Original assignee: Walford Construction Limited
Priority date: 2022-02-14
Filing date: 2023-02-13
Publication date: 2023-08-17
Also published as: GB2615589A; GB202201913D0

Abstract

An energy converter unit for an energy-harvesting system comprising a first turbine arrangement and a generator connected to the first turbine arrangement to generate electrical energy, the energy converter unit comprising: a container for containing fluidic contents, the container having a variable internal volume, wherein the container is configured such that under the influence of a force from a body of water the internal volume of the container is reduced thereby to cause the fluidic contents of the container to be expelled from the container via a set of openings.

Description

IMPROVEMENTS IN AND RELATING TO ENERGY CONVERSION AND HARVESTING

Field

The present disclosure relates to an energy converter unit for an energy-harvesting system, an energy-harvesting system, and a method of harvesting energy.

Background to the invention

Tidal energy is a predictable and reliable source of renewable energy. Despite this, tidal energy is somewhat underexploited at present, particularly when compared with other sources of renewable energy.

In a known tidal energy-harvesting system, a body of water exhibiting tidal variation is used to turn a turbine. The turbine is connected to a generator and energy storage apparatus, enabling electrical energy to be generated and stored for subsequent use.

There are a number of problems with known tidal energy-harvesting systems. One problem is the high initial installation costs. Moreover, there are a limited number of suitable locations for installation and effective operation of known tidal energy-harvesting systems.

These problems are exacerbated by the requirement to maintain the system to ensure longterm effective operation. Partially or completely submerged turbines and other components are difficult to access for inspection and maintenance. Thus, inspection and maintenance is timeconsuming and expensive.

Similar problems exist with hydroelectric power generation.

More generally, a problem with renewable energy generation is the visual impact of the necessary infrastructure.

Summary of the invention

It is one aim of the present invention, amongst others, to provide a improved system and/or method thereof and/or address one or more of the problems discussed above, or discussed elsewhere, or to at least provide an alternative system and/or method. A first aspect provides an energy converter unit for an energy-harvesting system comprising a first turbine arrangement and a generator connected to the first turbine arrangement to generate electrical energy, the energy converter unit comprising: a container for containing fluidic contents, the container having a variable internal volume, wherein the container is configured such that under the influence of a force from a body of water the internal volume of the container is reduced thereby to cause the fluidic contents of the container to be expelled from the container via a set of openings.

In one example, the container is a deformable container.

In one example, the container is a bag.

In one example, the container is provided at the surface of the body of water or is provided such that the force of the body of water acts, or is allowed to act, on a lower portion or lower surface of the container.

In one example, the unit is configured such that by a reduction or removal of the force of the body of water the internal volume of the container remains constant or is increased by fluidic contents being taken into the container via the set of openings.

In one example, a second turbine arrangement is arranged to be driven by the fluidic contents taken into the container and/or wherein a second turbine arrangement is arranged to drive fluidic contents thereby to cause fluidic contents to be taken into the container.

In one example, the internal volume of the container is increased by allowing fluidic contents into the container via the set of openings.

In one example, the energy converter unit comprises a first duct extending from a first opening of the set of openings.

In one example, the first turbine arrangement is located in the first duct.

In one example, the energy converter unit comprises a second duct extending from a second opening of the set of openings.

In one example, the second turbine arrangement is located in the second duct.

In one example, the fluidic contents is gaseous, for example air. In one example, the container is mounted in a support frame.

In one example, the unit is provided in a coastal cliff-face or coastal cave or area of tidal variation.

In one example, the energy converter unit further comprises an energy storage apparatus.

In one example, the container is a first container and the energy converter unit further comprises a second container for containing fluidic contents, the second container being in fluid connection with the first container, wherein the second container is configured to receive and contain fluidic contents that are expelled from the first container, optionally wherein the second container is configured to provide fluidic contents to be taken into the first container.

In one example, the container is housed in a chamber.

In one example, the energy converter unit comprises an inlet gate selectively operable to provide a fluidic connection between an upstream body of water and the chamber, and openable to allow water into the chamber, optionally wherein the inlet gate is openable to allow water into the chamber, thereby to cause the internal volume of the container to decrease.

In one example, the energy converter unit comprises an outlet gate selectively operable to provide a fluidic connection between the chamber and a downstream body of water, and openable to allow water to exit the chamber, optionally wherein the outlet gate is openable to allow water to exit the chamber, thereby to allow the internal volume of the container to increase.

In one example, the energy converter unit comprises a bypass gate selectively operable to provide a fluidic connection between the upstream body of water and the downstream body of water thereby to bypass the chamber.

In one example, the energy converter unit comprises auxiliary turbines.

In one example, the body of water is sea, river or reservoir.

In one example, the energy converter unit is a tidal energy converter unit.

In one example, the energy converter unit is a gravitational potential energy converter unit. A second aspect provides a coastal structure comprising an energy converter unit of the first aspect.

A third aspect provides a dam structure comprising an energy converter unit of the first aspect.

A fourth aspect provides an energy-harvesting system comprising: an energy converter unit, coastal structure or dam structure of the first, second and/or third aspects; a first turbine arrangement arranged to be driven by the fluidic contents as they are expelled from the container via the set of openings; and a generator connected to the first turbine arrangement to generate electrical energy.

A fifth aspect provides a method of converting or harvesting energy comprising using an energy converter unit, coastal structure, dam structure and/or energy-harvesting system of any previous aspect.

In one example, the method comprises providing an energy-harvesting system comprising a first turbine arrangement and a generator connected to the first turbine arrangement to generate electrical energy.

In one example, the method comprises installing an energy converter unit in the energy harvesting system.

In one example, the method comprises containing fluidic contents in a container of the energy converter unit, the container having a variable internal volume.

In one example, the method comprises configuring the container such that under the influence of a force from a body of water the internal volume of the container is reduced thereby to cause the fluidic contents of the container to be expelled from the container via a set of openings.

In one example, the method comprises locating the container in a location where the container may be influenced, or acted on, by a force from a body of water.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of any aspect of the invention may incorporate any of the features described with reference to the apparatus of any aspect of the invention and vice versa. Other preferred and advantageous features of the invention will be apparent from the following description.

Brief description of the figures

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which:

Fig. 1 shows a schematic of an energy converter unit in an energy harvesting system;

Fig. 2 shows a front view of a coastal structure;

Fig. 3 shows a cross section view through the coastal structure of Fig. 2;

Fig. 4 shows a cross section view through a coastal structure;

Fig. 5 shows a cross section view through a dam structure;

Fig. 6 shows a plan view of the dam structure of Fig. 5; and

Fig. 7 shows general methodology principles.

Detailed description of the invention

According to the present invention there is provided a system and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

The description which follows describes a number of embodiments. The embodiments are only embodiments of the invention where the system and method is as defined in the claims that follow. The reader will appreciate that features of the embodiments which do not fall within the scope of the invention may nevertheless be incorporated in embodiments of the invention which do fall within the scope of the invention. For this reason, the description of the embodiments which are absent these features are retained in order to provide useful background information to the reader.

Referring to Figure 1 , an energy converter unit 100 is shown. The energy converter unit 100 is for an energy-harvesting system 200. The energy-harvesting system 200 comprises a first turbine arrangement 210 and a generator 230 connected to the first turbine arrangement 210. The generator 230 is connected to the first turbine arrangement 210 thereby to generate electrical energy. As will be well understood by those skilled in the art, the generator 230 converts rotational kinetic energy of the first turbine arrangement 210 to electrical energy.

The energy converter unit 100 comprises a container 110. The container 110 is for containing fluidic contents. The container 110 has a variable internal volume. The container 110 is configured such that under the influence of a force from a body of water the internal volume of the container 110 is reduced thereby to cause the fluidic contents of the container 110 to be expelled from the container via a set of openings 112.

Advantageously, in this way, the fluidic contents of the container 110 can be expelled from the container 110 via the openings 112 by the action of force on the container 110. This enables the kinetic energy of the fluidic contents to be captured by, for example, the first turbine arrangement 210. That is, the energy of the body of water (for example, tidal, gravitational potential or kinetic) can be converted into kinetic energy of the fluidic contents for subsequent harvesting. By this construction, direct contact of the first turbine arrangement 210, or indeed any turbine or component other than the container 110, with the body of water is avoided. Improvements in longevity are thereby realised. Furthermore, problems associated with maintenance and inspection of submerged turbines are avoided, as the first turbine arrangement 210 can be accessibly located.

By providing a container 110 having a variable internal volume, installation costs may be reduced and the number of suitable locations in which to install the energy converter unit 100 may be increased. In particular, that is in contrast to units or structures which make use of a fixed volume container or chamber, thus requiring a suitable cave space or the formation of a suitable volume in, for example, a land feature.

Maintenance, inspection, and even replacement of the container 110 is simple as this can be performed at times when the body of water does not act on the container 110, or enables the container 110 to be readily removed from contact with the body of water. Furthermore, in many implementations, the body of water acts primarily on a lower portion or lower surface of the container 110, allowing the remaining portion or surfaces of the container to be maintained and inspected. That is, the present construction is particularly suited to use on the surface of a body of water. This may be preferential to a sub-surface/submerged unit or system, as the present construction solves problems related to maintenance and inspection of the unit or system. These advantages will be apparent from the description herein of exemplary embodiments of the energy converter unit 100 and energy-harvesting system 200. The container 110 being for containing fluidic contents may mean that the container is adapted to provide a barrier between the internal volume of the container and the external environment. That is, the container 110 may provide an impermeable or impenetrable barrier, or membrane, to liquids or gases. The container 110 having a variable internal volume may mean that the container comprises one or more sides or surfaces which are flexible or deformable. In this way, the fluidic contents of the container 110 can be caused to be expelled by the deformation, or change of shape, of the one or more sides or surfaces of the container 110. Providing a container 110 having a plurality of flexible sides, surfaces or membranes is advantageous as a greater change of internal volume can be caused by deformation of said plurality of sides, surfaces, or membranes, leading to a greater displacement and expulsion of the fluidic contents via the openings 112. Additionally, providing a container 110 having a plurality of flexible sides, surfaces or membranes leads to a container 110 that is adapted for resting, or floating, on the surface of the body of water and being acted upon by said body of water as the water level rises.

Referring to Figure 2, a front view of a coastal structure 300 is shown. The coastal structure 300 comprises a cliff face 310. It will of course be understood that the coastal structure 300 may be any other suitable area of coastline or land feature. The coastal structure 300 comprises a cave, indicated generally at 320 in Figure 3. The cave 320 may be man-made or naturally formed. Inlets 330 are provided extending through the cliff-face 310 from an outer surface 340 of the cliff-face 310 to the cave 320. The inlets 330 provide fluid communication between the outer surface 340 and the cave 320. The inlets 330 are provided below sea level 350. In this instance, the aforementioned body of water is the sea, and the sea level is indicated at 360. The inlets 330 may be below sea level 360 throughout the entire tidal variation cycle, or may be below sea level 360 during only a part of the tidal variation cycle. The inlets 330 allow seawater to enter the cave 320.

Whilst in this exemplary embodiment the container 110 is provided in a cave 320 in a cliff face 310, it is also envisioned that a support frame may be provided to support the container 110. By doing so, the energy converter unit 100 can be installed away from the coast, and without the need for a cave 320. That is, the energy converter unit 100 can be installed out at sea, or in a “free-standing” arrangement, by virtue of being held and supported in the support frame. The support frame may support and locate the container 110 relative to the body of water such that the energy converter unit 100 may operate as described herein. Advantageously, such a construction of a “free-standing” arrangement may have a low profile, which reduces the visual impact on the environment, particularly when compared with other renewable energy infrastructure such as wind turbines. For example, the energy converter unit 100 may be installed on or retrofitted to an (in-use or disused) oil rig. The oil rig may provide the support frame to support the container 110. A station 350 is further provided. The station 350 houses turbine arrangements, including the first turbine arrangement 210 and a second turbine arrangement 220. The station 350 houses generator 230 and energy storage apparatus 240. The first turbine arrangement 210 is arranged to be driven by the fluidic contents expelled from the container. The second turbine arrangement 220 is arranged to be driven by the fluidic contents taken into the container 110 and/or is arranged to drive fluidic contents thereby to cause fluidic contents to be taken into the container 110.

Referring to Figure 3, a cross section view through the coastal structure 300 is shown. The cross section view shows a cross section through the cave 320. The container 110 of the energy converter unit 100 is provided in the cave 320. In the exemplary embodiment shown and described herein, the container 110 is a deformable container. In particular, the deformable container is a bag 110. A bag 110 is advantageous as all, or a major portion of, its outer surface is deformable. Thus, the bag 110 enables a greater displacement and expulsion of the fluidic contents. Furthermore, the bag 110 is suited to tidal energy conversion by virtue of floating on the surface of the body of water. Advantageously, such a coastal structure 300 has a reduced visual impact on the environment, as it may be hidden in land features, such as a coastal cave 320.

The container 110 comprises a set of openings 112. The set of openings 112 are provided in an upper surface of the container 112. In the exemplary embodiment shown, the container 110 comprises two openings 112a, 112b. Nevertheless, the skilled person will appreciate that in some embodiments the container 110 may comprise a single (e.g., a set comprising one) opening 112. A first duct 114a connects to, and extends from, the first opening 112a. A second duct 114b connects to, and extends from, the second opening 112b. The first turbine arrangement 210 is provided, or located, in the first duct 114a. The second turbine arrangement 220 is provided, or located, in the second duct 114b. Advantageously, the ducts 114a, 114b provide a suitable means for directing the fluidic contents away from the container, and channelling said fluidic contents to increase their velocity. The ducts 114a, 114b advantageously provide a suitable location for the turbine arrangements.

As shown in Figure 3, the container 110 is provided at the surface of the body of water, which in the figure is sea level 360. That is, the container 110 floats on the surface of the body of water. As the sea level 360 rises, for example with the tide, the force from the body of water on the container 110 causes the internal volume of the container to be reduced. It will be appreciated that the container 110 may be acted on by other surfaces of surrounding structures, such as cave walls, walls of a chamber in which the container 110 is housed or parts of a support frame, and the rising sea level will then compress the container 110 to force the fluidic contents to be expelled therefrom. As the container 110 is acted upon by the body of water, the fluidic contents of the container 110 is expelled from the set of openings 112. The kinetic energy of the fluidic contents as they are expelled is to be converted into rotational energy as described herein.

In one exemplary embodiment of the energy converter unit 100, the first duct 114a and second duct 114b extend to the environment. That is, the first duct 114a and second duct 114b allow air to be expelled from the container 110 to the environment, and allow air to be taken into the container from the environment.

In an exemplary embodiment, the first duct 114a is an “expulsion duct” and the second duct 114b is an “intake duct”. That is, the first duct 114a may be in use during an “expulsion stroke”, and the second duct 114b may be in use during an “intake stroke”. One duct may be closed whilst the other is open. This may be achieved by use of shutters, valves or the like.

In operation, the container 110 may repeatedly expel and take in fluidic contents, as the sea level rises and falls. Advantageously, the fluidic contents may be gaseous, which can be moved at high velocity through turbines, whilst minimising degradation of the turbines and thus increasing operational lifetime. In a highly advantageous embodiment, the fluidic contents is air, allowing the container to be repeatedly refilled and expelled into the environment with no environmental impact or financial cost.

In an expulsion stroke of the energy converter unit 100 operation, seawater enters the cave 320 via the inlets 330 and contacts the lower surface of the container 110. As the sea level 360 rises and applies a force to the container, the container 110 is compressed and its internal volume is reduced. The fluidic contents of the container 110 (in this instance, air) are expelled from the container 110 via the first opening 112a. The fluidic contents are directed through the first duct 114a and the first turbine arrangement 210 is thereby driven. The generator 230 generates electrical energy from the rotation of the first turbine arrangement 210.

In an intake stroke of the energy converter unit 100 operation, seawater exits the cave 320 via the inlets 330. As the sea level 360 falls, the internal volume of the container 110 is allowed to increase. Air is taken into the container via the second opening 112b due to pressure differential with the external environment and/or by operation of the second turbine arrangement 220. Air passes through the second duct 114b to the container 110. Where air is taken into the container due to pressure differential with the external environment, the air drives the second turbine arrangement 220. The generator 230 generates electricity from the rotation of the second turbine arrangement 220. The second turbine arrangement 220 may also be driven to force air back into the container 110. The internal volume of the container 110 is thereby increased.

By the operation described above, the energy converter unit 100 can convert the kinetic energy of the expelled fluidic contents to rotational energy of the turbines continuously during the expulsion stroke. Similarly, the energy converter unit 100 can convert the kinetic energy of the fluidic contents taken into the container into rotational energy of the turbines continuously during the intake stroke. Each intake stroke and expulsion stroke takes around six hours, facilitating continuous energy generation, or a six-hour period of energy generation if energy is only converted and harvested during the expulsion stroke. It will be understood that the energy conversion, and level of power generated, will be fairly constant during the operational period. This is highly advantageous in managing storage and delivery of electrical power.

The electricity generated by the generator 230 can then be stored in the energy storage apparatus 240, used immediately by on-site electrical systems, or provided directly to the grid.

Referring to Figure 4, in another exemplary embodiment of the energy converter unit 100, the first duct 114a and second duct 114b provide a fluidic connection between the container 110 (as a “first container 110”) and a second container 410. That is, the first container 110 and second container 410 are in fluid connection. The second container 410 is configured to receive and contain fluidic contents that are expelled from the first container 110. In a similar manner to that described above, this occurs where the container is under the influence of force from the body of water to cause the internal volume of the container 110 to reduce, and cause the fluidic contents to be expelled from the first container 110. Rather than being expelled to the environment, the fluidic contents are expelled to the second container 410. In this way, fluidic contents with a greater density than air (for example, higher density gases) may be used in the energy converter unit 100, which can lead to greater energy conversion and ultimately higher levels of energy harvesting. In this case, the energy converter unit 100 may be described as a “closed system”.

In an advantageous operation, during a period of the expulsion stroke, the first opening 112a and second opening 112b and/or first duct 114a and second duct 114b may be closed to cause the pressure to build in the container 110 as the container 110 is acted upon by the force of the body of water. Subsequently, the relevant openings 112a, 112b and ducts 114a, 114b (which may be only the first opening 112a or first duct 114a, as described above) are opened to allow the fluidic contents to be expelled and thereby turn the turbine. Due to the increase in pressure in the container 110, the velocity of the expelled fluidic contents is greater, leading to a higher level of energy harvesting. This is advantageous where a surge in power requirement is expected. The expulsion stroke may involve one or more alternating periods of open and closed openings 112a, 112b and ducts 114a, 114b.

Referring to Figures 5 and 6, a cross section view and a plan view of a dam structure 500 are shown respectively. Operation of the energy converter unit 600 and energy harvesting system 700 in the dam structure 500 is substantially identical to that of the energy converter unit 100 and energy harvesting system 200 as described above. The dam structure 500 is a hydroelectric energy harvesting implementation, and the necessary features will be described herein.

The figures show an upstream body of water 510 and a downstream body of water 520. In this exemplary embodiment the body of water is a river, having upstream section 510 at a height H1 and downstream section 520 at height H2, where H1 > H2. The dam structure 500, and incorporated energy converter unit 600, separates the upstream section 510 and downstream section 520.

The energy converter unit 600 comprises a container 610. The container 610 is for containing fluidic contents. The container 610 has a variable internal volume. The container 610 is configured such that under the influence of a force from a body of water the internal volume of the container 610 is reduced thereby to cause the fluidic contents of the container 610 to be expelled from the container via a set of openings 620. In this exemplary embodiment, the container 610 is housed in a chamber 630.

Similar to the coastal structure 300 described above, the dam structure 500 comprises a station 550. The station 550 houses turbine arrangements, including a first turbine arrangement 710 and a second turbine arrangement 720. The station 550 houses generator 730 and energy storage apparatus 740. The first turbine arrangement 710 is arranged to be driven by the fluidic contents expelled from the container 610. The second turbine arrangement 720 is arranged to be driven by the fluidic contents taken into the container 610 and/or is arranged to drive fluidic contents thereby to cause fluidic contents to be taken into the container 610.

The energy converter unit 600 comprises one or more inlet gates 640, one or more outlet gates 650, and one or more bypass/ diversion gates 660 (as shown in Figure 6). In this exemplary embodiment, the energy converter unit 600 comprises a plurality of inlet gates 640, one outlet gate 650 and a pair of bypass gates 660 either side of the chamber 630.

The inlet gates 640 are selectively operable to provide a fluidic connection between the chamber 630 and the upstream section 510 of the body of water. That is, by opening the inlet gates 640, water is allowed into the chamber 630 from the upstream section 510 of the body of water. Closing the inlet gates 640 prevents water from entering the chamber 630 from the upstream section 510 of the body of water. The inlet gates 640 are openable to allow water into the chamber 630. By doing so, the chamber 630 may be filled with water. The water in the chamber 630 acts on the container 630 to compress it, thereby causing the internal volume of the container to decrease. The fluidic contents of the container 610 are thereby expelled therefrom. This corresponds with the “expulsion stroke” as described above. Water is allowed into the chamber for a desired time period, which may be minutes or hours. The inlet gates 640 are closed once the volume of the container 610 is sufficiently reduced and/or once the desired amount of energy has been harvested.

The outlet gate 650 is selectively operable to provide a fluidic connection between the chamber 630 and the downstream section 520 of the body of water. That is, by opening the outlet gate 650, water is allowed to exit the chamber. In this way, the chamber 630 can be drained of water, and the container 610 allowed to expand or decompress to increase the internal volume of the container 610. The fluidic contents of the container 610 are thereby taken into the container 610 - it is refilled with fluidic contents. This corresponds with the “intake stroke” as described above. Water is allowed to exit the chamber for a desired time period, which may be minutes or hours. The outlet gate 650 is closed once the volume of the container 610 is sufficiently increased and/or once the desired amount of energy has been harvested. The outlet gate 650 is closed to prevent water from exiting the chamber 630 or once the chamber 630 is emptied of water.

The bypass gates 660 are selectively operable to provide a fluidic connection between the upstream section 510 of the body of water and the downstream section 520 of the body of water. In this way, the chamber 630 is bypassed. By this construction, the chamber 630 may be accessed for inspection and maintenance, without disrupting the flow of water from the upstream section 510 of the body of water and the downstream section 520 of the body of water.

Applicable to all above-described exemplary embodiments, the first turbine arrangement 210 and second turbine arrangement 220 further comprise auxiliary turbines (not shown). The auxiliary turbines are arranged to capture kinetic energy of the fluidic contents that is not captured by the main turbines of said first and second turbine arrangements 210, 220. The auxiliary turbines may be smaller than the main turbines, and located downstream in the respective ducts 114a, 114b.

As described above, the body of water may be a sea, river or reservoir. The energy converter unit 100 may be described as a “tidal energy converter unit”, in implementations which convert tidal energy of a body of water. The energy converter unit 100 may be described as a “gravitational potential energy converter unit”, in implementations which convert gravitational potential energy of a body of water falling from height.

Whilst an energy-harvesting system 200 has been introduced above, it will be apparent to the skilled person that an energy-harvesting system 200 may comprise an energy converter unit 100, coastal structure comprising an energy converter unit 100 or dam structure comprising an energy converter unit 100, as described above, in addition to at least a first turbine arrangement 210 and a generator 230. The first turbine arrangement 210 is arranged to be driven by the fluidic contents as they are expelled from the container 110 via the set of openings 112. The generator is connected to the first turbine arrangement 210 to generate electrical energy.

It will be appreciated that the energy converter unit 100 may be retrospectively incorporated in an existing energy-harvesting system. For example, the energy converter unit 100 may be retrofit in a system comprising a turbine arrangement and a generator. Such systems may be improved by incorporation of an energy-converter unit 100 according to the present disclosure. In particular, a system which comprises a container or chamber of fixed volume may be improved by retrofitting the present unit 100 having a variable volume container 110.

Referring to Figure 7, a method of converting energy is schematically shown. Step 7010 comprises using an energy converter unit 100, 600 coastal structure 300, dam structure 500 and/or energy-harvesting system 200, 700, for example to convert energy from one form to another (e.g. to convert tidal motion into electrical energy).

The method may comprise providing an energy-harvesting system comprising a first turbine arrangement and a generator connected to the first turbine arrangement to generate electrical energy. The method may comprise installing an energy converter unit in the energy harvesting system. The method may comprise containing fluidic contents in a container of the energy converter unit, the comprising: the container having a variable internal volume. The method may comprise configuring the container such that under the influence of a force from a body of water the internal volume of the container is reduced thereby to cause the fluidic contents of the container to be expelled from the container via a set of openings. The method may comprise locating the container in a location where the container may be influenced, or acted on, by a force from a body of water.

Definitions Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.

Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of others.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. An energy converter unit for an energy-harvesting system comprising a first turbine arrangement and a generator connected to the first turbine arrangement to generate electrical energy, the energy converter unit comprising: a container for containing fluidic contents, the container having a variable internal volume, wherein the container is configured such that under the influence of a force from a body of water the internal volume of the container is reduced thereby to cause the fluidic contents of the container to be expelled from the container via a set of openings.

2. An energy converter unit according to claim 1 wherein the container is a deformable container.

3. An energy converter unit according to either of claim 1 or claim 2 wherein the container is a bag.

4. An energy converter unit according to any previous claim wherein the container is provided at the surface of the body of water or is provided such that the force of the body of water acts, or is allowed to act, on a lower portion or lower surface of the container.

5. An energy converter unit according to any previous claim, wherein the unit is configured such that by a reduction or removal of the force of the body of water the internal volume of the container remains constant or is increased by fluidic contents being taken into the container via the set of openings.

6. An energy converter unit according to claim 5 wherein a second turbine arrangement is arranged to be driven by the fluidic contents taken into the container and/or wherein a second turbine arrangement is arranged to drive fluidic contents thereby to cause fluidic contents to be taken into the container.

7. An energy converter unit according to either claim 5 or claim 6 wherein the internal volume of the container is increased by allowing fluidic contents into the container via the set of openings.

8. An energy converter unit according to any previous claim comprising a first duct extending from a first opening of the set of openings.

9. An energy converter unit according to claim 8 wherein the first turbine arrangement is located in the first duct.

10. An energy converter unit according to any previous claim comprising a second duct extending from a second opening of the set of openings.

11. An energy converter unit according to claim 10 wherein a or the second turbine arrangement is located in the second duct.

12. An energy converter unit according to any previous claim wherein the fluidic contents is gaseous, for example air.

13. An energy converter unit according to any previous claim wherein the container is mounted in a support frame.

14. An energy converter unit according to any previous claim wherein the unit is provided in a coastal cliff-face or coastal cave or area of tidal variation.

15. An energy converter unit according to any previous claim further comprising an energy storage apparatus.

16. An energy converter unit according to any previous claim wherein the container is a first container and the energy converter unit further comprises a second container for containing fluidic contents, the second container being in fluid connection with the first container, wherein the second container is configured to receive and contain fluidic contents that are expelled from the first container, optionally wherein the second container is configured to provide fluidic contents to be taken into the first container.

17. An energy converter unit according to any previous claim wherein the container is housed in a chamber.

18. An energy converter unit according to any previous claim comprising an inlet gate selectively operable to provide a fluidic connection between an upstream body of water and the chamber, and openable to allow water into the chamber, optionally wherein the inlet gate is openable to allow water into the chamber, thereby to cause the internal volume of the container to decrease.

19. An energy converter unit according to claim 18 comprising an outlet gate selectively operable to provide a fluidic connection between the chamber and a downstream body of water, and openable to allow water to exit the chamber, optionally wherein the outlet gate is openable to allow water to exit the chamber, thereby to allow the internal volume of the container to increase.

20. An energy converter unit according to claim 19 comprising a bypass gate selectively operable to provide a fluidic connection between the upstream body of water and the downstream body of water thereby to bypass the chamber.

21 . An energy converter unit according to any previous claim comprising auxiliary turbines.

22. An energy converter unit according to any previous claim wherein the body of water is sea, river or reservoir, optionally wherein the energy converter unit is a tidal energy converter unit or gravitational potential energy converter unit.

23. A coastal structure or dam structure comprising an energy converter unit according to any previous claim.

24. An energy-harvesting system comprising: an energy converter unit, coastal structure or dam structure according to any previous claim; a first turbine arrangement arranged to be driven by the fluidic contents as they are expelled from the container via the set of openings; and a generator connected to the first turbine arrangement to generate electrical energy.

25. A method of converting or harvesting energy comprising using an energy converter unit, coastal structure, dam structure and/or energy-harvesting system according to any previous claim.