Patent Application
20240301855
This invention belongs to the technical field of renewable energy producing apparatuses, systems and facilities. In particular, it refers to facilities or apparatus for harnessing energy from the ocean waves motion. More particularly, some of the apparatus and/or facilities of the invention for harvesting energy from waves are of the type known as point absorbers, which is a type of Wave Energy Converter. In addition, in some embodiments, the apparatuses may also have the capability of storing energy in the form of potential energy.
It is generally recognised that climate change is mainly due to the result of human activities, conspicuously among them is the fossil-fuel derived energy generation and transportation, which produce colossal amounts of greenhouse gases, such as CO2.
In order to minimise the effects of climate change in the long term, there is an on-going global effort to switch to a more sustainable energy mix in which renewable energy production has increased share in the overall global energy production.
However, the main sources of renewable energy (solar, wind, tidal, waves) are intermittent, which means that there are periods of intense energy availability interspersed with periods of negligible energy availability.
This disadvantage causes that the electric grid is periodically overloaded, such that it is mandatory to temporarily cease renewable energy production from some facilities or apparatus, at a cost for energy consumers, when there is a great amount of energy available, in order to maintain an adequate level of energy in the electrical grid. This contrasts with other periods of time when there is not enough renewable energy available to supply the actual consumption and it is necessary to make use of fossil fuel derived energy.
In other words, renewable energy availability is not always balanced or in phase with the actual energy demand variability.
On another hand, it is currently estimated that seas and oceans can provide tremendous amounts of renewable energy. Marine renewable energy takes the form of kinetic energy (winds and currents), potential energy (tidal amplitude), mechanical energy (waves), thermal potential (vertical temperature gradients) or even osmotic pressure (horizontal gradients of salinity).
In countries and territories with extensive maritime areas, such as Scotland, it is recognised that renewable marine energy can play an important role in a low-carbon electricity production in a sustainable energy mix.
According to a first aspect of the present invention there is provided a wave energy production apparatus for producing energy from the heave motion of the surface of a body of water, said apparatus comprising:
Using a conceptual analogy, in an internal combustion engine, the pistons reciprocate within the cylinders, whereas in this apparatus, the cylinders reciprocate together with a buoyant body called reciprocating assembly, thanks to the action of the ocean, whilst the piston(s) remain fixed to the seabed thanks to a connecting board that acts as an interface.
This apparatus may produce a larger amount of energy from the waves in a body of water compared to other point energy absorbers, because the downward movement of the reciprocating assembly benefits from the surplus potential energy of the water retained in the dynamic compensation tank(s), whereas in the upward movement of the reciprocating assembly, the water in the dynamic compensation tank does not lose its energy because the dynamic compensation tank is in fluid communication with the body of water. Therefore, the energy contained in the water within the Dynamic Compensation Tank is not used to push the Reciprocating Assembly upwards. This advantage has been confirmed by a hydrodynamic study that compares the energy released by a point absorber without and with a dynamic compensation tank, i.e. a reciprocating buoyant assembly without or with openings that allow seawater to partially flood the tank before it initiates the downward movement and the openings are closed to trap the seawater inside the tank, thus exercising an additional downward force dur to the potential energy of the water.
Preferably, the one or more compression modules are supported on a base, henceforth also called a connecting board, by means of one or more piston rods.
Preferably the connecting board is reversibly attachable to an underwater structure fixedly connected to the bottom of the body of water or seabed.
Preferably the apparatus may incorporate a watering system to allow flooding/drying the ballast tank(s).
Preferably, the reciprocating assembly comprises one or more static compensation tank.
This embodiment allows the apparatus to also perform the function of storing energy, because the reciprocating assembly can be jacked up by applying fluid pressure to the cylinders, in a chamber above the piston (the double effect of the Compression Modules will make the chamber below the piston to show lower pressure creating a sucking effect that will contribute to the jacking up process), and the dynamic and static compensation tank may be simultaneously or subsequently completely or partially filled with water with the watering system mentioned above. All this potential energy, (that of the water and assembly pushed several meters high) can be stored indefinitely and be released when it is more convenient in a continuously fluctuating energy price market.
Therefore, the static compensation tank may be completely or partially filled with water in energy storage operational mode.
The dual function of the apparatus is a very important advantage over other wave energy producing apparatuses, in the sense that, by operating a plurality of apparatuses, all, some or none can be in an energy generation mode whereas all, some or none can also be simultaneously in different operating modes. This flexibility allows an energy operator to have a combination of apparatuses in energy generation, energy storage and/or locked mode at any given time, conveniently adapted to the weather and energy market conditions. In this scenario, when the weather is such that a surplus energy is created, some apparatuses might be producing energy and releasing it to the grid, but some might be absorbing it in order to store it and release it at a later moment in time when there is no longer wave energy surplus, thus achieving a premium price for that energy which was previously absorbed in a period of surplus energy production.
By being removably attachable to an underwater structure fixedly connected to the bottom of the body of water, for example, the seabed, it is possible to decouple the apparatus from the underwater structure, at least temporarily, and take the apparatus to another location for repair, for shelter in periods of potentially damaging weather, or to another area where the waves are more suitable.
In the apparatus deployment stage, the connecting board comprises auxiliary elements such as automated thrusters, retractable orientation pins (to undertake horizontal alignment) and position and orientation sensing devices, all of which may be removed from the connecting board once the apparatus has been successfully coupled to an underwater structure.
The compression module may be divided by the piston in an upper chamber and a lower chamber. In the generation functional mode, due to the reciprocating movement of the reciprocating assembly and cylinder caused by the waves, the fluid pressure and volume in the upper chamber are continuously oscillating between a maximum and a minimum value, and vice versa, in the lower chamber, respectively, in each compression module. This causes an oscillating fluid pressure differential between the upper and lower chamber.
Preferably, the one or more compression module are connected to a first fluid circuit configured to transform the oscillating fluid pressure differential between the upper and the lower chamber of the compression module into a pressure differential that is delivered to permanent high- and a low-pressure points of a second fluid circuit.
The first fluid circuit may comprise a regulation valve before the fluid abandons the first fluid circuit, that may be used to synchronise (phase in) the motion of the waves in the ocean with the reciprocating motion of the reciprocating assembly so that crests and troughs are vertically aligned.
Preferably, the permanent high- and low-pressure points are fluidly connected by the second fluid circuit so as to drive one or more turbines configured to transform the pressure differential into electric energy.
Preferably, the permanent high- and low-pressure points are fluidly connected to one or more buffer tank(s) for accommodating variations in fluid quantity and/or pressure within the second fluid circuit.
Preferably, the apparatus comprises a plurality of compression modules. When there is a plurality of compression modules, they can be dynamically interconnected in many ways to optimise fluid flow and pressure in order to reduce the piping system weight.
When the apparatus comprises a plurality of compression modules, the apparatus may comprise several manifolds with automated valves (on/off and three-way) to allow flexible fluid interconnections among the compression modules' upper and lower chambers, respectively, and between these and the first fluid circuit such that the pressures and fluid flows in the first circuit are optimised.
For example, when the compression modules are producing a larger fluid flow at lower pressure, (when the reciprocating assembly is at an intermediate position) all the compression modules are connected in series to the first fluid circuit, such that the resulting pressure in it is the addition of the pressure in each of the compression modules and the flow is the same in all compression modules and when the compression modules are producing a smaller fluid flow at higher pressure (when the reciprocating assembly is at its highest or lowest position) all the compression modules are connected in parallel to the first fluid circuit, such that the pressure in it is the same as in all the compression modules and the flow in the first fluid circuit is the addition of all the flows produced by each compression module.
This configuration may be beneficial because it optimises the pressure and fluid flows in the first circuit and offsets the large fluid volumes produced by each of the compression modules with a lower volume and more pressurised flow and the small volume with high pressure at the end of a stroke with a fluid flow with more volume and less pressure in the piping system. Therefore, the fluid flows and pressures in the first circuit are more uniform and do not vary between extremely low and large pressures and volumes, so that the pipe diameters and pipe wall thicknesses do not need to be extremely large and therefore the cost and the weight of the piping system may be reduced and it is safer, by using lower overall pressures and flows, to avoid turbulent flows that can cause vibrations and/or extreme pressures that require oversizing the thickness of the pipes.
Additionally, the several manifolds with automated on/off and three-way valves are also configured such that, when there are two or more compression modules, these may be also connected in compression module groups combined in series and/or in parallel or a combination of both to optimise the pressure and flow in the first circuit also at intermediate locations of the reciprocating assembly between the intermediate and an extreme (low or high) position.
The reciprocating assembly may comprise a second weight changing mechanism (see page 2, first paragraph of “Summary of invention”) comprising one or more second ballast tank(s), henceforth also called static compensation tank(s). This static compensation tank(s), mainly used for energy storage purposes, may also be filled with more or less ballast weight, typically water, in generation mode, in order to adjust the buoyancy of the reciprocating assembly in any given situation according to any properties of the current waves, such as wavelength, height and/or frequency, for example, in order to increase the performance.
To be used in energy storage mode or, for example, to move the reciprocating assembly to a safe height in case of storms, the compression modules need to extend a considerable length above the water surface, for example, at least 10 meters. This may imply to have a very large amount of fluid within the cylinders. When the apparatus is in generation mode, this may prohibitively increase the weight of the apparatus.
In order to reduce the weight of the apparatus in generation mode, the lower chamber of the compression modules may comprise one partition, comprising a fake piston, to divide the lower chamber in an upper subsection filled with fluid and a lower subsection which can be filled with pressurised gas. These two sections are separated by a vertically movable fake piston that might be lockable with the expansion of a diaphragm. This feature is also considered a weight changing mechanism and it is also known as a specific weight adapter.
In order to fill the lower chamber lower subsection with pressurised gas, a gas supply is necessary, typically nitrogen. This supply is done underwater. For this reason, the lower chambers comprise a gas supply valve covered with a cap defining a fluid inlet and a fluid outlet in order to flush the water in the space beneath the cap and above the valves with dry gas. These are known as dry submerged caps.
The valves managing the flow of gas to the media shutter mechanism may be isolated by caps from the seawater in order to preserve them and maximise their service life. If a maintenance operation is required in these valves, the cap may be open, the maintenance routine takes place and the whole mechanism will be covered again with the caps. Once covered with the caps, the space beneath the caps is flushed with nitrogen supplied by an umbilical to remove all seawater under the cap and leave the space between the cap and the valves completely dry and seawater-free.
Preferably the piston rods are hollow, and their interior is accessible to operators for inspection and repair until their base.
Preferably, the piston rods comprise inspection windows to oversee the interior of the cylinders.
Preferably, one or more of the piston rods comprise at their base a diver hatch connected to a dry floodable dock, such that divers can descend through the piston rods and perform inspection or repair operations on the base.
Optionally, the first fluid circuit may be located on the reciprocating assembly. Preferably, the first fluid circuit is located on the connecting board, to reduce the weight of the reciprocating assembly.
Optionally, the second fluid circuit may be located at the connecting board. Preferably, the second fluid circuit is located on an altogether separate location, henceforth named renewable energy hub, to reduce the weight of the apparatus.
Therefore, it is envisaged that the second fluid circuit (with its turbine(s) and buffer tank(s)) may be located elsewhere, in a renewable energy hub, and shared among one or more wave energy production apparatuses according to the invention. In this manner, we would have a wave energy production facility or association, rather than a single wave energy production apparatus, with the corresponding capital savings in common infrastructure. This renewable energy hub welcomes contributions of other fluid driven apparatuses offshore, and may act as an integrator of offshore apparatuses or facilities, such as wind farms.
Optionally the wave energy production apparatus may be configured to delay the downward motion of the reciprocating assembly with respect of the sinking movement of the surface of the body of water.
This feature causes that the downward movement of the reciprocating assembly is not, or at least, is less affected by its buoyancy within the body of water and therefore, the downward movement takes place faster than if it was not delayed, therefore allowing to retrieve more power from the system into electric power (and allow to match the phasing of the reciprocation motion of the WEC (Wave Energy Converter) making the trough of this, coincide with the trough of the wave—the performance of the power harvesting utterly depends on the relative frequency of the interaction WEC (Wave Energy Converter)/Wave).
According to a second aspect there is provided an energy production facility or association comprising one or more wave energy production apparatus according to the first aspect of the invention and at least one renewable energy hub in which the second fluid circuit, turbine(s) and buffer tank(s) are located, among other equipment.
According to a third aspect there is provided a renewable energy hub comprising a fluid circuit to which at least one turbine adapted to produce electricity is connected, said fluid circuit being located in an offshore rig and being configured to be connected to a wave energy production apparatus, as described before.
In particular, a renewable energy hub may bring, at least one of the following advantages:
According to a fourth aspect there is provided a dynamic compensation tank defining at least one aperture on a bottom surface with a movable closure configured to open and establish fluid communication between the dynamic compensation tank(s) and an external body of water in order to allow water to at least partially flood the dynamic compensation tank(s) when the body of water heaves as a result of wave motion and to close fluid communication between the dynamic compensation tank(s) and the external body of water and retain water inside the dynamic compensation tank(s) when the body of water surface sinks as a result of wave motion.
Preferably, the dynamic compensation tank(s) may comprise magnetic means to open and close the movable closure of the at least one aperture.
Additionally or alternatively, the dynamic compensation tank(s) may comprise pneumatic or hydraulic means to open and close the movable closure of the at least one aperture.
The closure may be formed by a ring or plate rotatable around the dynamic compensation tank.
According to a fifth aspect there is provided a compression module comprising a cylinder and a piston assembly, wherein the piston divides the cylinder in an upper and a lower chamber and wherein a fluid routing system is connected to the piston and this piston is already connected to a connecting board. An upper rod may be the pathway to connect the fluid routing system to the piston and to the connecting board so that all the pipes are fully accessible.
In an analogue structure, in an internal combustion engine, the pistons reciprocate within the cylinders. However, in this apparatus, the cylinder reciprocates with the action of the ocean waves, whilst the piston remains fixed with respect to the ocean thanks to a connecting board that acts as an interface and is rigidly fixed to the seabed.
The connection between the piston and the connecting board is made with piston rods inside the cylinder lower chamber. Given the expected large size of the pistons, one single rod may not be enough to ensure the stability of the assembly, so instead three or more parallel rods are preferably used.
These rods occupy an area, which defines a volume along a stroke. Therefore, the upper chamber has a greater usable cross-sectional area than the lower chamber. If a pipe is used to shortcut the lower and upper chamber in these circumstances, the system will be hydraulically locked, so it was decided to provide an upper rod in the upper chamber to partially compensate for this difference, but also to allow access to the piston, and to the Connecting Board through the lower piston rods.
If it was fully compensated, there would not be a need for driving fluid accumulation but fluid accumulation can be conveniently used to keep energy in the weak period of generation, (i.e. when the device goes up), and release this energy during the strong period, (i.e. on the way down).
The apparatus may comprise a space below the connecting board where most of the pipe and valve work of the apparatus is located. This may also provide buoyancy to the connecting board to alleviate the weight resting on the jacket.
The compression modules may also be used as part of heavy lifting systems because with a little pressure input, a large amount of lifting force might be achieved.
According to a sixth aspect, a specific weight adapter is provided.
The specific weight adapter comprises a fake piston, also called media shutter mechanism, within every cylinder lower chamber separating two different fluids, a liquid which is the driving fluid and a gas, typically nitrogen.
The cylinders in the apparatus are very tall, to allow accumulating large amounts of energy when the apparatus is in storage mode, but the device can also be in generation mode.
To work in energy storage mode, the cylinders need to be filled with a fluid called driving fluid. Nevertheless, filling the cylinders with this fluid is of great advantage when working in storage mode, because the larger the weight the higher the storage capacity.
When the apparatus works in generation mode, that huge amount of weight is no longer an advantage. If the cylinders were filled with driving fluid, the weight of the whole apparatus would be so large, that it would sink or will produce very little power because the power of the waves would not be capable of producing significant motion during the short interaction therewith.
The media shutter mechanism is a (fake) piston that divides the lower chamber of every compression module (the space below the piston in the compression module) into two parts.
Located above the media shutter mechanism, the first part is called the lower chamber liquid phase as it contains the driving fluid. Below the media shutter mechanism is the second part and is called lower chamber gas phase which contains a gas, typically nitrogen.
When the device is in generation mode, the media shutter mechanism is positioned as high as practically possible (see
As it can be inferred, the higher the media shutter mechanism, the smaller the specific weight of the reciprocating assembly and the better the performance of the apparatus.
Motion is crucial to produce energy since the mission of the device in generation mode is to produce pressure in the compression modules that extended to the surface of the pistons means a force.
This force along the stroke of the motion means energy that can be extracted in the form of hydraulic or pneumatic power, and represents the basis of the apparatus power take-off.
The media shutter mechanism comprises an inflatable bladder or diaphragm to reversibly adjust the piston at a given height within the lower chambers by filling the bladder with pressurised gas and hence, the bladder pushes against the lower chamber walls, thus creating a seal between the two parts of the lower chamber.
The specific weight adapter comprises a retractable and expandable hose to supply gas to operate the media shutter mechanism from the lower chamber bottom.
According to a seventh aspect a fundamental parameters optimisation method is provided.
The fundamental parameters in the apparatus are those most related to the production of power. These are pressure and flow and, in this section, it is explained how these parameters can be optimised in order to minimise the size and thickness of the pipes required to drive the driving fluid throughout the entire system, for a case scenario where the reciprocating assembly comprises six compression modules.
The situation when designing a piping system is that if the pressure increases significantly, the thickness of the pipes conducting the driving fluid must be increased accordingly. If the flow increases significantly, in order to avoid turbulent flow, the diameter of the pipes needs to be increased.
The pressure in the compression modules naturally increases as the reciprocating assembly approaches the crest and the trough of the wave whereas close to the neutral point the speed is maximum and so is the flow. These situations can be managed as follows:
Within the explanation on how the six compression modules are connected we will assume that the pressure that one single compression module can create is ‘P’ and the flow it displaces is called ‘F’. In generation mode, the wave energy producing apparatus works essentially as a pump and as such it has its own characteristic curve. Therefore, the power of the six compression modules (Power=6·P·F) is affected by such a curve.
This scheme consists in having all the six compression modules connected in parallel by directing the flow with the appropriate valves in the manifold they are connected to.
This scheme will be automatically implemented when the reciprocating assembly is close to the crest or the trough of the wave because in this situation, the pressure differential would be high and it is convenient to lower it.
Since the pressure is ‘P’ and all the compression modules are connected in parallel, the total pressure would be approximately equal to ‘P’.
Nevertheless, the flow is approximately sixfold higher than the flow that one single compression module can deliver, this would be approximately ‘6F’.
The power produced by all the compression modules working collaboratively would therefore approximately be: Power=6·P·F.
This scheme consists in having two series of three compression modules in parallel.
This scheme may be automatically implemented when the reciprocating assembly is abandoning the crest or the trough of the wave because naturally, in this position, the pressure is lowering but is still high and it needs to be reduced a bit. The flow is increasing though but is still low and the intention is to increase it as well.
Since the pressure is ‘P’ and we have two series of three compression modules in parallel, the total pressure would be approximately equal to ‘2P’.
Nevertheless, the flow may be threefold higher than the flow that one single compression module could deliver, this is ‘3F’.
The power produced by all the compression modules working collaboratively would approximately be, again: Power=(2·P)·(3·F)=6·P·F
This scheme consists in having three series of two compression modules in parallel.
This scheme may be automatically implemented when the reciprocating assembly is approaching the neutral part of the wave because, naturally, in this position, the pressure would be low and it needs to be increased a bit and the flow is high and it needs to be decreased a bit too.
Since the pressure is ‘P’ and we have three series of two compression modules in parallel, the total pressure would be approximately equal to ‘3P’.
Nevertheless, the flow will be twofold higher than the flow that one single compression module can deliver, this would approximately be ‘2F’.
The power produced by all the compression modules working collaboratively would still be kept as close to 6·P·F: Power=(3·P)·(2·F)=6·P·F
Finally, this scheme consists in having all the compression modules in series.
This scheme may be automatically implemented when the reciprocating assembly is almost at or at the neutral part of the wave because, naturally, in this position, the pressure is very close to zero and it needs to be increased as much as possible and the flow is the maximum it can be reached and it needs to be decreased as much as possible to avoid turbulence in the pipes.
Since the pressure of one single compression module is ‘P’ and there are six compression modules in series, the total pressure would approximately be ‘6P’.
Nevertheless, the flow that abandons one compression module will reach the following and so on, so that the flow of the combination for the six compression modules may be equal or approximately the same as the flow for one single compression module, this would approximately be ‘F’.
The power produced by all the compression modules working collaboratively would approximately be, therefore 6·P·F: Power=(6·P). (1·F)=6·P·F
Therefore, the fundamental parameters optimisation method is a method of adjusting two parameters of a system with a given power input and output, wherein said two parameters, such as pressure and flow, temperature and flow, voltage and current intensity, force and speed, etc. operate in counteracting way, that is, when one parameter increases, the other parameter decreases and vice versa and the power input and/or output is proportional to the product of both parameters, said method consisting of dynamically adapting the interconnections of several power producing units, which in this case are the compression modules, in series, in parallel or in group combinations of power producing units in series and parallel, such that any given output power is exerted by a convenient combination of both parameters adapted to a current situation.
The step of dynamically adapting the interconnections of several power producing units may be realised, for example, by providing a manifold with the appropriate valves and a control system to dynamically adapt the operation of the valves to a particular situation, such that the producing units may be connected either in series, in parallel or in intermediate combinations by grouping the units in series groups, or in parallel groups.
According to an eighth aspect a dry submerged cap for protecting valves from corrosive fluid media is provided, said dry submerged cap comprising a fluid entry and a fluid exit.
In order to operate the media shutter mechanism, there is a need for a gas supply, typically nitrogen and/or air. This supply is done underwater. There are valves managing the flow of gas into the dry submerged cap but it is desirable to isolate these valves from the seawater in order to preserve them and maximise service-life.
In order to keep the valves dry underwater, there is a cap covering the valves. If a maintenance operation is required in these valves, the cap is open, the maintenance routine takes place and the whole mechanism is then covered again. Then, compressed gas is sent into the cap using a small pipe and another pipe, both as part of an umbilical, returns the water that leaves the cap as a result of the gas flushing the space under the cap. Eventually, the space below the cap is substantially dry and protected from corrosion under a nitrogen atmosphere and so will be the valves.
According to a ninth aspect a quick coupling system is provided.
The apparatus incorporates a quick coupling system that allows the device to quickly latch with an underwater foundation structure by using a connecting board and a series of hydraulic actuators (quick coupling interlocking actuators) that, when triggered, meet orifices in the foundation jacket or underwater structure.
The connecting board, just before being deployed, may comprise auxiliary equipment to connect the connecting board with its underwater foundation structure. This auxiliary equipment may be removed from the connecting board after the connecting operation takes place.
The auxiliary equipment may comprise orientable thrusters and retractable orientation pins and any other means to direct and control the latching operation between the connecting board and the foundation.
First of all, the device is towed using towing eyes installed both, in the connecting board and in the upper deck of the apparatus.
The quick coupling interlocking actuator system may comprise three orientable thrusters to move the connecting board in a horizontal plane with precision.
When the apparatus is close to its target location, the three thrusters position the apparatus precisely in a horizontal plane above the foundation structure and, using the apparatus manoeuvre mode, by pressurising the chambers with driving fluid, the connecting board is positioned until it engages the target foundation structure. This manoeuvre can also be done with gas (potentially air) provided from the renewable energy hub or an auxiliary ship.
To minimise the oscillation during the connecting operation, the static compensation tank may be filled with seawater to increase the inertia and reduce oscillations.
The quick coupling interlocking actuator may comprise two retractable orientation pins to undertake and secure horizontal alignment. Using cameras, triangulation and signs, one of the retractable orientation pins is aligned with an orifice in the resting jacking up support which belongs to the foundation jacket.
When this pin is aligned, a normally hydraulic or pneumatic actuator is triggered. When the connecting board is pivoting around this precise orifice, it is time to align the other retractable orientation pin with a second orifice on the resting support. Again, with the aid of the thrusters and the triangulation procedure, alignment can be achieved and after that, the apparatus only needs to sit on its foundation underwater structure.
The manoeuvre mode, by pressurising the upper chambers of the cylinders, makes this happen using all the available ballasts to reduce vertical oscillation.
The quick coupling interlocking actuator may comprise eight locking cylinders arranged symmetrically in groups of two in four different perpendicular planes each group, so as to latch a connecting board to an underwater foundation structure with a square connecting section.
When the apparatus sits perfectly on its foundation, the quick coupling interlocking actuator is triggered and the cylinders meet the orifices in the foundation structure latching this with the connecting board. This assembly remains latched until it needs to be disconnected.
After this, the auxiliary elements (i.e., thrusters and retractable orientation pins) are no longer needed and may be taken back to shore for a new commissioning operation.
The invention will be described in more detail with reference to the accompanying drawings, in which:
In each
The reciprocating assembly 24A, 24B comprises one dynamic ballast tank 28A, 28B, (shown in
The cylinders 22A, 22B of the compression modules 18A, 18B, in use, contain a driving fluid (not shown) that is energised (i.e. pressurised) by the reciprocating movement of the cylinders 22A, 22B, in generation mode (i.e. in use), and said energised fluid is used to produce electric energy. Please note that there may also be embodiments in which a pneumatic fluid is used, instead of a hydraulic fluid.
The reciprocating assembly 24A, 24B also comprises a static ballast tank 36A, 36B, also known as a static compensation tank, located concentrically with the dynamic ballast tank 28a, 28B. The static compensation tank 36A, 36B may be partially filled with seawater (or another fluid), to adjust the buoyancy of the reciprocating assembly 24A, 24B to have an optimal energy production from the apparatus, depending on the ocean wave characteristics. The static compensation tank 36A, 36B is a hollow flat cylinder located in the lower part of the reciprocating assembly 24A/24B that is most likely to be used in storage mode to increase the potential energy.
In
The connecting board 38A is reversibly connected by a quick latching or connection mechanism 42 to the upper part of an underwater structure 14A, in use, fixedly connected to the seabed 16A.
As in the embodiments shown in
When the water surface beneath the reciprocating assembly 24C is a wave crest, as in FIG. 2C, the water level 26C within the dynamic compensation tank 28C has reached a maximum and the apertures 30C of the dynamic compensation tank 28C may be closed in order to retain that amount of water for the next stage.
Finally, the water surface beneath the reciprocating assembly 24C is becoming a valley again, as seen in
When a buoyant body, such as the reciprocating assembly, rises as a consequence of the heave of a wave, it acquires, among others, potential energy. On its way down, the interaction with the wave is, however, detrimental for recovering the potential energy into the system. Basically, if the wave was not there once the buoyant body reaches its highest position, there will be a freefall with a bigger acceleration.
This acceleration, together with the mass along the stroke, would result in a bigger production of power since the energy can be delivered faster.
One of the aims of the apparatus is to delay the fall slightly, with respect of the sinking movement of the waves.
In each compression module 18A, one of the three lower piston rods 40 is hollow and in it there are internal ladders 46 with guardrails for accessing the connecting board 38 from the top of the compression modules 18A. Besides there are inspection windows 48 that allow a visual inspection of the upper and lower chambers 22U, 22L. At the bottom of the ladders there is a hatch that gives access to the ocean outside of the lower part of the piston rod 40.
The lower chamber 22L and the upper chamber 22U of the compression modules 18A are filled with a fluid (not shown).
So as to reduce the amount of driving fluid (not shown) within the lower chamber 22U, this comprises a media shutter mechanism 54. A media shutter mechanism 54 is basically a hermetic partition in the lower chamber 22L that divides it in a first lower chamber part 22LA filled with driving fluid and second lower chamber part 22LB filled with gas, which may be nitrogen. In embodiments wherein the driving fluid is a gas, the media shutter mechanism may not be required.
The media shutter mechanism 54 is shown in
For clarity,
During the commissioning of the apparatus, the connecting board 38A, 38B further comprises two retractable orientation pins 76, so as to perform an angular position match between the connecting board and the underwater structure. To do this, first, one retractable pin is inserted in a corresponding hole in the underwater structure 14A, 14B and then the thrusters 72 are used to rotate the connecting board 38A, 38B over the inserted pin until the second pin is aligned with a second hole in the underwater structure 14A, 14B, at which moment, the second pin is actuated and inserted in the second hole. This locks the angular position of the connecting board 38A, 38B and the rest of the apparatus with respect to the underwater structure.
This is followed by the submersion of the pistons 22A, 22B, piston rods 40 and the connecting board 38A, 38B by pressuring the fluid in the upper chambers 22U at a depth at which the horizontal interlocking pins 78 are aligned with the corresponding holes in the underwater structure 14A, 14B and at such moment they can be hydraulically inserted therein.
Note that the process of installing the apparatus 10A, 10B on the underwater structure 14A, 14B (fixed assembly) is reversible, and therefore, if extremely devastating weather is foreseen, such as a hurricane, the apparatus 10A, 10B can be decoupled from the underwater structure and taken to a safe harbour. Alternatively, it can be taken to locations where wave energy is more favourable depending on its seasonality or to evacuate the apparatus in cases of natural catastrophes, such as earthquakes, tsunamis, etc. or simply be disconnected to bring it to shore for major repairs.
Note also that, when jacked up, the apparatus can remain at some 15 meters above the sea level. This means that waves of more than 30 meters in height are required to start jeopardising the integrity of the device.
The dynamic compensation tank 28A, 28B comprises magnetic means to open and close the movable closures 206 of the apertures 202.
The movable closures are formed by a ring 212 rotatable around the dynamic compensation tank 28A, 28B. The rotation of the ring 212 is caused by magnetic forces acting on the ring 212, which displace the closures 206 between an open (
In other embodiments, such as that shown in
When the dynamic compensation tank is sectioned (see
Lorentz force law says that when the magnetic flux B in Y axis intercepts a current in Z axis (carried by the cable 218B), a force F will be induced in the X axis direction, thus creating a torque in the rotating plate and making it turn.
Since the rotating plate 212B or the ring 212 are almost constantly rotating within the dynamic compensation tank, in one sense or the opposite sense, it has gratings 220B (
To clean biofouling the easiest approach is to position bristles attached to the rotating plate rotates and brushes the gratings, thus avoiding the formation of colonies around the gratings that will eventually close the path for the water transfer to take place.
Before presenting the different operating modes of the invention, it is necessary to understand the pipework and valve connections that allow the operation thereof. This is what is called the fluid routing system, shown in
The fluid routing system 200 consists of a first fluid circuit 200A and a second fluid circuit 200B, and they are subdivided into a few fluid subsystems, namely:
The grouping chamber subsystem 202 and the routing subsystem form part of a first fluid circuit 200A and the reversible manoeuvre subsystem 206, the storage subsystem 208, and the delivery subsystem 210 form part of a second fluid circuit 200B.
In practice, the first 200A and second circuits 200B may be located in the same apparatus 10B (
This subsystem 202 connects by means of manifolds 209, 220 all the compression modules 18 (including 18A and 18B) upper and lower chambers to a single output, respectively, thus leading to valve 222, called upper chambers valve (VUC) that fluidly connects all the upper chambers 22U and to a valve 212, called lower chambers valve (VLC) that fluidly connects all the lower chambers 22L.
All the fluid flows of the upper and lower chambers 22U, 22L of all the compression modules 18 are joined at a single valve 212, 222, respectively.
The pressure at the lower chambers valve 212 is continuously changing from high to low- and to high-pressure again due to the reciprocating movement of the reciprocating assembly 24 (including 24A and 24B) and the cylinders 22 (including 22a and 22B), and simultaneously, the opposite is happening at the upper chambers valve 222, where the pressure is low, high and low again, respectively.
The routing subsystem (RSS) 204 is configured to deliver high- and low-pressure fluid consistently to the respective same points of a second circuit 310, 320, at the high-pressure valve (VHP) 312 and the low-pressure valve (VLP) 322.
Therefore, the fluid flow goes straight from VLC to VHP if the reciprocating assembly 24 is moving upwards in which case, VUC and VLP will also be connected.
If the reciprocating assembly 24 is moving downwards, the high-pressure flow leaves the VUC and will be diverted to VHP whilst the low-pressure flow will leave the VLP and will be diverted to VLC.
There is a valve 324, named regulation valve to the storage subsystem (RVSS) that constrains the fluid accumulation in the buffer tank 340 in order to synchronise the harmonic movement of the reciprocating assembly 24 with the parameters coming from the waves in the ocean.
Basically, this valve 324 is intended to create a friction that delays the flow in order to synchronise in phase and frequency as much as possible the motions of both, the reciprocating assembly 24 and the waves, to maximise energy production.
The purpose of this system is to provide pressurised fluid by the action of one or more pumps 342 to the compression modules to jack-up the reciprocating assembly 24 during harsh conditions, as a result of an energy storage operation or during operations of connections and disconnections.
In energy generation and manoeuvre modes, the buffer tank(s) 340 (which can also be named pressure vessel) accumulates or releases fluid from/to the fluid circuit in order to compensate for the different volumes that both the upper and lower chambers can simultaneously displace.
At least one of the buffer tank(s) 340 comprises a membrane (not shown) to separate the hydraulic part which is the fluid, from the pneumatic part, which is a bubble of gas, typically nitrogen, that compresses and decompresses allowing storing energy in the form of pneumatic pressure.
This helps the reciprocating assembly 24 to rise on the way up because the buffer tank(s) 340 will recover or release the excess of energy that was stored as the reciprocating assembly 24 was on its way down.
In locked mode, the buffer tank 340 needs to be isolated and locked in order to stop the fluid flow.
Still belonging to the storage subsystem 208, the regulation valve 328 (VOHPT) has been allocated after the pipe that connects the compensation or buffer tank(s) 340 to the DSS in order to provide regular flow and pressure to the turbines 330a, 330b, 330c.
Apart from the accumulation tank(s) 340 and piping in this storage subsystem 208, there is also a so-called overpressure release mechanism (ORM). This is the pipe that connect the high-pressure branch 310 with the low-pressure branch 320 by means of a safety valve 326 (SV) which is tared and only allows the gradient of pressure between the two branches to reach a certain value.
If this value is exceeded, the safety valve 326 (SV) will allow the fluid to flow from high to low pressure branches, alleviating the extreme difference of pressure and hence protecting the whole apparatus. There is a locking command to all the 4 3-way valves in the RSS (Routing Subsystem) 204 remaining in whichever position they were to stop the system from building up more pressure.
The DSS (Delivery Subsystem) 210 consists of three turbo-generators 330a, 330b, 330c. If the sea state is calm, i.e. not particularly energetic, and there is not much power to harness, the compression modules 18 might be delivering power to only one or two turbo-generator(s).
As a result of this, not only the other generator(s) will be idle but the performance of the running generator may increase because the production rate will be closer to the optimum as a result of the contributions of all compression modules 18.
Typically, a wind turbine has a very tight nacelle where one single generator is enclosed and despite the fact that the generator on its own, is not the main cause of faults for wind turbines, it is also clear that repairing a generator in the wind turbine means stopping supply. This may not happen in this embodiment, because there are three generators, and if one is broken or needs maintenance, the others can be in supply mode, or vice versa.
In the grouping chamber subsystem (GCSS) 202, the first fluid circuit 200A comprises all the pipes and valves that interconnect all the upper chambers 22U and all the lower chambers 22L of the six compression modules 18A. The first fluid circuit 200A comprises two lower chambers manifold 209 and two upper chambers manifold 220.
In the routing subsystem (RSS) 204, the lower chambers manifold 220 of the first fluid circuit 200A is connected via a three-way valve 212 directly to the high-pressure branch 310 of the second circuit 200B. On the other side, the upper chambers' branch of the first circuit 200A is connected via a three-way valve directly to the low-pressure branch 320 of the second circuit 200B.
Additionally, in the routing subsystem (RSS) 204, at the interface between the first fluid circuit 200A and the second fluid circuit 300 there are two pipe branches 250a, 250b fitted with three-way valves 252 that interconnect the lower chambers manifold 209 with the low-pressure branch 320 of the second circuit 200B and the upper chambers manifold 220 with the high-pressure branch 310 of the second fluid circuit 200B.
The routing subsystem (RSS) 204 comprises an automatic control system (not shown) that switches the connections between the grouping chambers subsystem and the second circuits 202, 200B in a manner that fluid at high pressure from the first circuit 200A is always delivered to the high-pressure branch 310 of the second circuit, regardless of its origin in the upper chambers manifold 209 or the lower chambers manifold 220. Simultaneously, the low-pressure fluid is always delivered from the low-pressure branch 320 to any of the upper chambers' manifold 220 or the lower chambers manifold 209 that is at low pressure at any given moment.
Therefore, in energy production mode, there is a flow of fluid in the second circuit 200B from the high-pressure branch 310 towards the low-pressure branch 320 which is used to move one, two or three turbo-generators 330a, 330b, 330c connected in parallel and located between the high-pressure branch 310 and the low-pressure branch 320, depending on the available wave energy, which form the delivery subsystem (DSS) 210.
In addition, there is a buffer tank 340, also known as accumulation tank, in the second circuit 200B that serves to store or supply surplus fluid to the first and second fluid circuits 200A, 200B in order to provide a reservoir or a container for unbalance fluid resulting from the fact that the lower and upper chambers have different cross-sectional area, and thus, displace different volumes of fluid per unit of length in their movement.
In addition, there are three atmospheric tanks 345 (see
Conversely, the pressure difference between the upper and lower chambers 22U, 22L, or vice versa, is at a value between its maximum and its minimum in each reciprocating cycle. Therefore, it makes sense, that in order to compensate a situation with intermediate flow and intermediate pressure difference, to connect in parallel the upper chambers 22U and the lower chambers 22L within groups, and the groups should be connected in series among them, as shown, so that the total flow entering the first circuit 200A is the sum of all the flows of every chamber group that are connected in parallel (i.e. an intermediate flow) and the pressure difference in the first circuit 200A is the difference between the pressure in every upper chambers group that are connected in series and the pressure in every lower chambers group, or vice versa, and is therefore intermediate.
In this way, the automatic interconnections shown in
Since there are six compression modules, when they need to be connected in two groups of three or in three groups of two, the best way to interconnect them, in order to have a better structural stability and more homogeneous stress distribution in the apparatus, is to combine them symmetrically, i.e. when there are three compression module groups connected in series, each compression module is connected in parallel with the compression module situated diametrically opposed to it (for example in
Operating Modes of the Apparatus (these are valid for both associative apparatus 10A or stand-alone apparatus 10B and therefore numerals, where appropriate, should be understood an encompassing both A and B embodiments)
In the energy generation mode, the media shutter mechanism needs to be lifted in order to displace the excess of fluid out of the compression modules.
As the reciprocating assembly 24 and therefore the cylinders 22 move downwards, a huge fluid flow abandons the upper chambers 22U, is diverted to the VHP 312 and runs straight to the accumulation tank(s) 340 where part of the volume is accumulated compressing the pneumatic membrane, hence accumulating energy.
The fluid flow that leaves the tank 340 cannot be higher than what the lower chambers 22L of the compression modules 18 can accommodate, hence part of the fluid needs to remain in the tank.
The regulation valve VOHPT 328 moderates the fluid output from the tank 340 providing a regular flow and pressure to the DSS (Delivery Subsystem) 210 which in turn converts the hydraulic energy into electricity.
The flow on its way back is diverted by the RSS (Routing Subsystem) 204 to VLC 212 first and from there to all the compression modules 18.
The difference with what happens on the way up, are that the flow circulates straight in the RSS (Routing Subsystem) 204 and that the lower flow produced when the high pressure is generated by the lower chambers 22L is complemented by the excess of volume and energy that was stored in the accumulation tank 340 during the previous way down.
In the storing mode, the apparatus 10 receives energy, uses its manoeuvre mode to jack up the reciprocating assembly 24 and by doing so it absorbs electric energy and accumulates it as potential energy.
Before entering in storing mode, the specific weight adapter needs to lower the media shutter mechanism to fill the cylinders with fluid, thus enlarging the stroke.
This mode provides flexibility to ramp up or ramp down power (because the weight of the device may vary substantially, in the region of twenty folds, depending on the filling status of the ballast tanks and these can be filled at the beginning of the lifting up process with a big demand of energy, when the Reciprocating Assembly has reached its highest point or even in between thanks to the watering system). The time to absorb/deliver the energy can also be regulated to deal with different scenarios of demand/supply.
Additionally, the tidal range might be used to potentially deliver more energy than what it was initially absorbed from the grid or at least to improve the performance.
In the manoeuvre mode, shown in
If the pressurised chambers are the upper chambers 22U and the connecting board 38 is latched to the underwater structure 14 (including 14A and 14B), the whole reciprocating assembly 24 is raised, entering in storing mode, but if the connecting board 38 is not latched, then the pistons 20 with the connecting board 38 attached descend (As indicated by arrow 400), for example, to meet the underwater structure 14 and be engaged (latched) with it.
During the commissioning process, rather than using the final routing fluid, air may be compressed creating the required motion and once the device is latched, the routing fluid can be pumped into the system removing all the air in it.
It does not make a lot of sense to use the manoeuvre mode to pressurise the lower chambers 22L if the connecting board 38 is latched to the pistons 20 but it does make sense if it is not, because it will allow the connecting board 38 to raise.
In locked mode (
This mode can have a few uses, being the most important to store the potential energy when the reciprocating assembly 24 has been lifted up with or without ballast weight, and maybe waiting to be fully loaded with potential energy if the dynamic and/or static ballast tanks 28, 36 were not completely full of seawater.
If the ballast tanks 28, 36 are full, then the locked mode serves to keep the energy in place until it is worth delivering the energy to the grid. This is based on the large oscillations the prices of energy experience along the day.
Another use could be for maintenance purposes, or just to remain jacked up in harsh conditions away from storm surges.
Besides the main modes of operation described above, there are two additional modes in which the apparatus 10A, 10B might be encountered: the “In-transit” mode takes place when the device, being decoupled from the foundation jacket, is being towed for any purpose (first installation, relocation, severe storm forecast, maintenance, etc.). To do this, the connecting board will be as close as possible to the bottom of the reciprocating assembly to minimise the dragging force from the water; and the idle mode which takes place when the pressure difference in the second circuit between the high-pressure branch and the low pressure branch is above a certain limit and the security valve opens, then the valves in the routing subsystem are blocked, so that the pressure difference in the second circuit cannot be increased any further.
One standalone wave energy producing apparatus (see
The energy production association or facility 500 is another embodiment of the invention wherein the generation of pressurised fluid and the generation of electric energy therefrom happens at two distinct locations, in the wave energy production apparatuses 502 and a renewable energy hub 504, respectively. The pressurised fluid generated in the wave energy production apparatuses 502 is sent through hoses 506 to the renewable energy hub 504, where the pressurised fluid flows through a second circuit and drives one or more turbines to generate electricity. This renewable energy hub can be mobile, sitting on a lorry, for instance or can be onshore to be used in harbours, as an example.
Additionally, the renewable energy hub 504 receives electric energy from a nearby offshore wind farm through a power line 508. Besides, the renewable energy hub sends and receives electric energy to/from shore through another power line 510. Alternatively, the renewable energy hub can send energy to shore in the form of hydrogen, which has been produced in the renewable energy hub using the electricity produced, through a previously existing pipeline 512. This pipeline can also be used to import/export CO2 or other compatible gases. If the renewable energy hub is sitting on an old well, the well can potentially be repurposed to inject CO2 for carbon sequestration.
There can also be seen the nitrogen tanks 549 used to store the nitrogen used in the specific weight adapter.
It is also envisaged that a renewable energy hub 504 could receive power from other devices in the form of any pressurised fluid or electric current.
Likewise, the renewable energy hub may be adapted to transform surplus power into hydrogen and/or other energy vectors and utilise existing infrastructure, such as pipelines, to convey said energy vectors to/from shore. In this embodiment, there is a hydrogen production facility 550 on the platform.
Furthermore, the renewable energy hub, when installed over an abandoned gas/oil well, may be adapted to perform carbon capture and storage (CCS).
In addition, the renewable energy hub may be adapted to serve as a charging point in the middle of the ocean for devices such as ROUVs (remotely operated underwater vehicles), inspection drones, etc., or a hydro station for vessels.
There are also some atmospheric tanks 345 to deal with the change of mode from generation to storage.
At this stage, the Media Shutter Mechanism's diaphragm is released allowing it to move vertically.
Once at its highest position, the watering system will start pumping seawater to the ballast tanks. This has been shown in
If there was high tide at the stage of
Auxiliary pumps 90 situated in the Connecting Board will absorb seawater from the ocean. Pipes 91 are columns that go through the piston rods and connect to these auxiliary pumps 90 to raise the pumped water. When water is at its highest position the retractile hoses 92 will conduct the water to find a 3-way valve 89 that will divert the seawater to the main pumps 93. This will allow to flood the Dynamic Compensation Tank using pipe 98 or the Static Compensation Tank using pipe 96. Main pumps 93 can also extract water from the Static Compensation Tank absorbing this with foot valve 99 and egressing the water with pipe 97.
Water can also be obtained while the Reciprocating Assembly is buoyant. This can be done using motor 95 to turn valve 94 and using pipe 88 take the water to the main pumps. Valve 94 can either allow seawater to ingress the Static Compensation Tank or to connect with pipes 88.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2108002.3 | Jun 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2022/051391 | 6/1/2022 | WO |
