Method and system for generating electricity using a piezoelectric generator.

Abstract

The invention relates to an electricity generation system comprising a hydraulic circuit (1), a fluidic cavity (3) housing a piezoelectric generator (4, 4') connected to an electronic charge extraction circuit (5), and a fluid circulation control means (6', 6'') allowing the fluid to enter the fluidic cavity (3) to create mechanical pressure and to evacuate said fluid from said cavity (3), said fluid circulation control means (6', 6'') being controlled by a control unit. Figure to be published with the abbreviation: Fig. 5

Description

Title of the invention: Method and system for generating electricity using a piezoelectric generator. Technical field.

[0001] The present invention relates to a method and a system for generating electricity using a piezoelectric generator to produce electrical energy.

[0002] It relates in particular, but not exclusively, to the technical field of renewable energy recovery systems such as wind systems, wave energy systems, small hydroelectric systems or even marine current turbines. The present invention also finds application to on-board systems having a hydraulic power circuit in order to recover unused hydraulic energy or make the hydraulic power system reversible. State of the art.

[0003] In the following, the invention is illustrated mainly in connection with a wind turbine but of course the invention is not limited to this application.

[0004] Wind power systems are known which are intended to use renewable and free energy, in this case wind, to generate electrical power which can be used in a general power supply network.

[0005] Examples of such wind systems are described in documents US2021207577, US2021197675 or KR20210065074.

[0006] Like these wind systems, wave energy systems, small hydroelectric systems or marine current turbines are well known today as systems capable of generating electrical power from renewable energy.

[0007] However, all these systems using renewable energy generate slow and intermittent movements, typically less than 1 meter per second and / or 10 revolutions per minute.

[0008] These systems conventionally use electricity generation solutions consisting of permanent magnet or induction generators which are not suitable for such movements since these generators are made to rotate at high speeds (greater than 100 revolutions per minute and / or 10 meters per second) and lose efficiency at low rotation speeds.

[0009] Hydraulic transmission systems are promising because low-speed hydraulic pumps or cylinders can be used to generate hydraulic power with high efficiency and excellent power density.

[0010] However, converting hydraulic energy into electricity is currently not very profitable because it requires combining a hydraulic motor and a traditional generator.

[0011] The invention aims to remedy this state of affairs.

[0012] In particular, the present invention intends to propose a method and a system for directly converting hydraulic power - more generally power coming from a liquid - into electricity with high efficiency and high controllability.

[0013] An essential objective of the invention is to propose such a system which is particularly simple in its design so as to be suitable for all types of installations producing electrical energy from renewable energy. The system according to the invention can be integrated into such an installation to be built or into an installation already built, given its simplicity of implementation.

[0014] An additional objective is to propose a system that is as inexpensive as possible, both in terms of assembly / installation and / or manufacturing and in terms of the various elements making up such a system.

[0015] Finally, a complementary objective consists of proposing an electricity generation system capable of being considered and integrated into on-board systems having a power hydraulic circuit in order to recover unused hydraulic energy or to make the power hydraulic system reversible. Presentation of the invention.

[0016] It has thus been noted by the applicant, after various experiments and manipulations, that it is particularly interesting to produce a bypass on a pipe for circulating a pressurized liquid making it possible to supply a fluidic cavity housing a piezoelectric material for generating electricity, the management of this bypass being adapted to offer the best possible production of electrical energy.

[0017] According to one interpretation of the invention, the present invention combines one or more valves for connecting a high pressure hydraulic circuit, a hydraulic chamber, a piezoelectric transducer or generator and an electrical charge extraction circuit.

[0018] The solution proposed by the invention is an electricity generation system.

[0019] The system is remarkable in that it includes: • a hydraulic circuit in which a pressurized liquid called hydraulic liquid circulates, a fluidic cavity arranged on at least a portion of the circuit, which cavity houses a piezoelectric generator connected to an electronic charge extraction circuit capable of recovering the electrical energy coming from the piezoelectric generator when it is subjected to pressure mechanical, which cavity has an inlet port and an outlet port, and • a means for managing the circulation of the liquid allowing the liquid circulating in the circuit portion to enter the fluid cavity through the inlet port to form the above-mentioned mechanical pressure and to evacuate said liquid through the outlet port of said cavity, said means for managing the circulation of the liquid being controlled by a control unit.

[0020] The expression "piezoelectric generator" means any materials or elements or even combination of said materials / elements capable of electrically polarizing under the action of a mechanical stress and reciprocally of deforming when an electric field is applied to them. In this case, in the context of the present invention, the piezoelectric material is firstly used to produce electrical energy when it is subjected to a mechanical stress.

[0021] In this case, in the context of the present invention, the mechanical pressure consists of the pressure of the liquid circulating in the hydraulic circuit. This mechanical pressure acts on the piezoelectric generator not only when a certain liquid flow rate enters the fluid cavity but also when this liquid leaves or is evacuated from this hydraulic cavity. In other words, in the context of the present invention, the mechanical pressure results from a variation in pressure on the piezoelectric material between two instants / moments.

[0022] Thus, thanks to the system according to the invention, electrical energy is recovered on the one hand when the liquid penetrates into the fluid cavity and on the other hand when the liquid is evacuated from this cavity.

[0023] As a non-limiting example of a piezoelectric material or element used in a piezoelectric generator according to the invention, we can cite:

[0024] - a ferroelectric material of perovskite structure such as lead titanate PbTiO3, barium titanate BaTiO3, potassium niobate KNbO3, bismuth ferrite BiFeO3;

[0025] - a tungsten-bronze structure such as PbNb2O6;

[0026] - an ilmenite structure such as lithium niobate LiNbO3 and tantalate of lithium LiTaO3 .

[0027] - a quartz or a non-ferroelectric oxide such as GeO2 or phosphates and ar- seniates;

[0028] - a polymer such as polyvinylidine difluoride (PVDF) and its derivatives;

[0029] - a piezoelectric salt such as Rochelle salt (NaKC4H4O6.4H2O), phosphate of monopotassium (KH2PO4) or triglycine sulfate [(NH2CH2COOH)3H2SO4].

[0030] The expression "hydraulic fluid", also referred to as hydraulic oil, means a liquid used as a means of transmitting power in a hydraulic system. This is, for example, a mineral oil in compressible capable of quickly transmitting energy from the pump or cylinders to the receivers, here the piezoelectric generator.

[0031] The term “power electronics” means all devices capable of recovering electrical energy – the released electrons – coming from the piezoelectric generator.

[0032] Thanks to the invention, there is now available an electricity generating system which is robust, of simple design and reliable. Given this simple structure, the elements of the system according to the invention are easily modifiable or replaceable so that the maintenance of this system is particularly easy. According to one interpretation, the electricity generating system comprises several independent modules which are easily replaceable or modifiable, with:

[0033] - the module of the fluidic cavity housing the piezoelectric generator,

[0034] - the management module,

[0035] - the power electronics module,

[0036] - possibly the current converter module (direct to alternating).

[0037] Other advantageous characteristics of the apparatus which is the subject of the invention are listed below. Each of these characteristics can be considered alone or in combination with the remarkable characteristics defined above. Each of these characteristics contributes, where appropriate, to the resolution of specific technical problems defined further in the description and in which the remarkable characteristics defined above do not necessarily participate. The latter may be the subject, where appropriate, of one or more divisional patent applications:

[0038] According to a particular feature of an advantageous embodiment of the system according to the invention, the means for managing the circulation of the liquid consists of a mechanical or electromechanical element positioned at (or between) the inlet port and the outlet port of the fluidic cavity.

[0039] According to an advantageous embodiment of the invention, the above-mentioned management means consists of a three-way valve.

[0040] The term "valve" is used herein with the same meaning as the term "valve". Thus, the term "three-way valve" is identical to a "three-way valve".

[0041] According to another advantageous embodiment of the invention, the above-mentioned management means consists of an intake valve arranged at the inlet port and a discharge valve arranged at the outlet port, said valves being alternately in the open and closed position to allow the penetration and evacuation of the liquid from the fluid cavity.

[0042] Advantageously, the piezoelectric generator consists of a stacking structure of piezoelectric elements (also referred to hereinafter as a “piezoelectric pillar”) or of a piezoelectric membrane.

[0043] In the case of the piezoelectric membrane, it is advantageously a component of the polyvinylidine difluoride (PVDF) family, more particularly a PVDF derivative such as a PVDF / PDMS (PDMS: polydimethylsiloxane).

[0044] According to a particularly interesting aspect of the invention, the control unit controls the penetration and evacuation of the liquid in the fluidic cavity to obtain a liquid penetration-evacuation frequency ranging from a quasi-static frequency up to the resonance frequency of the piezoelectric generator, preferably to the resonance frequency of the piezoelectric generator.

[0045] According to an advantageous embodiment, the electricity generation system comprises a plurality of circuit portions for the circulation of the liquid arranged in parallel, each circuit portion comprising a fluidic cavity housing a piezoelectric generator connected to an electronic charge extraction circuit capable of recovering the electrical energy coming from the piezoelectric generator when it undergoes pressure or decompression as well as a means for managing the circulation of the liquid allowing the liquid to penetrate into the fluidic cavity to form the mechanical pressure and to evacuate said cavity, said means for managing the circulation of the liquid being controlled by a control unit, advantageously the above-mentioned control unit.

[0046] Preferably, the liquid is pressurized by a pump or cylinders powered by a renewable energy source, advantageously a wind source, a hydro turbine source, a wave energy source, a hydroelectric source or a source using marine currents.

[0047] Advantageously, the portion(s) of circuit for the circulation of liquid comprise(s) a pressure sensor measuring the liquid pressure in said portion(s) of circuit, advantageously said sensor being connected to the above-mentioned control unit.

[0048] According to a particularly interesting aspect of the invention, the fluidic cavity has a variable volume due to the contraction of the piezoelectric generator when the liquid enters the fluidic cavity and to the expansion of said piezoelectric generator when said liquid is evacuated from said cavity, the variation of the volume of said fluidic cavity being adjustable.

[0049] According to one embodiment, the above adjustment of the variation of the volume of the fluidic cavity is carried out by adjusting the stiffness of the piezoelectric generator.

[0050] The term "stiffness" refers to the compression of the piezoelectric generator for a given mechanical pressure. The stiffness of the piezoelectric generator can be modified using the aforementioned power electronics.

[0051] According to another embodiment, the above-mentioned adjustment of the variation of the volume of the fluidic cavity is carried out by adjusting the frequency of penetration and evacuation of the liquid in said cavity, moving away from or approaching the resonant frequency of the piezoelectric generator.

[0052] Of course, it is possible to associate or combine the two modes of adjustment of the variation of the volume of the fluidic cavity, either via the frequency of penetration and evacuation of the liquid in the cavity, or via the stiffness of the piezoelectric generator.

[0053] Advantageously, the power electronics are connected to a direct current to alternating current converter.

[0054] The present invention also relates to an installation for the production of electricity from renewable energy, such as wind, swell, tides or a hydraulic current, in which said installation comprises an electricity generation system as described briefly above.

[0055] The invention finally relates to a method for generating electricity characterized in that it comprises the following steps: • arrange a fluid cavity on at least a portion of a hydraulic circuit in which a pressurized liquid called hydraulic fluid circulates, which cavity has an inlet port and an outlet port, • install a piezoelectric generator in the fluid cavity, which piezoelectric generator is connected to an electronic charge extraction circuit capable of recovering the electrical energy coming from the piezoelectric generator when it is subjected to mechanical pressure, • manage the circulation of the liquid to allow said liquid circulating in the circuit portion to enter the fluid cavity through the inlet port to form the above-mentioned mechanical pressure and to evacuate said liquid through the outlet port of said cavity.

[0056] Preferably, the penetration and evacuation of the liquid in the fluidic cavity are controlled to obtain a liquid penetration-evacuation frequency ranging from a quasi-static frequency up to the resonance frequency of the piezoelectric generator, preferably to the resonance frequency of the piezoelectric generator.

[0057] According to one aspect of the invention, the fluidic cavity has a variable volume due to the contraction of the piezoelectric generator when the liquid enters the fluidic cavity and to the expansion of said piezoelectric generator when said liquid is evacuated from said cavity, said method comprising a step of adjusting the variation of the volume of the fluidic cavity by adjusting the stiffness of the piezoelectric generator.

[0058] According to one aspect of the invention, the fluidic cavity has a variable volume due to the contraction of the piezoelectric generator when the liquid enters the fluidic cavity and to the expansion of said piezoelectric generator when said liquid is evacuated from said cavity, said method comprising a step of adjusting the variation of the volume of the fluid cavity by adjusting the frequency of penetration and evacuation of the liquid in said cavity.

[0059] It should be noted here that the characteristics presented, previously and in the following, in connection with the electricity generation system are transposable to the electricity generation method, and vice versa. Brief description of the figures.

[0060] Other advantages and characteristics of the invention will appear more clearly on reading the description of a preferred embodiment which follows, with reference to the appended drawings, produced as indicative and non-limiting examples and in which:

[0061] [Fig-1] is a schematic representation illustrating the principle of the system according to the invention with a stack or pillar of piezoelectric elements.

[0062] [Fig.2] is a schematic representation illustrating the principle of the invention with a piezoelectric membrane.

[0063] [Fig.3] is a schematic representation identical to [Fig.l] in which the two valves, intake and discharge, were replaced by a three-way valve.

[0064] [Fig.4] is a schematic representation identical to [Fig.2] in which the two valves, intake and discharge, were replaced by a three-way valve.

[0065] [Fig.5] is a schematic representation of the system according to the invention presented on [Fig.l] applied to a wind turbine.

[0066] [Fig.6] is a schematic representation of the system shown in [Fig.5] in which the circulation channel is subdivided into five circulation portions each comprising a fluid cavity.

[0067] [Fig.7] is a schematic representation of the fluidic cavity in a first state of electric voltage of the piezoelectric generator.

[0068] [Fig.8] is a schematic representation of the fluidic cavity in a second electrical voltage state of the piezoelectric generator. Description of the embodiments.

[0069] [Fig.l] illustrates an embodiment incorporating the essential elements of the electricity generation system according to the invention, namely the hydraulic circuit 1, more precisely a portion of the hydraulic circuit 2 on which or at the level of which a fluid cavity 3 is arranged housing a piezoelectric stack or pillar 4' forming the piezoelectric generator 4, this pillar 4' being connected to an electronic charge extraction circuit 5, as well as a means for managing the circulation of the liquid 6', 6”.

[0070] This means of managing the circulation of the liquid 6 is here constituted by a valve inlet 6' and by a discharge or evacuation valve 6” of the liquid once it has penetrated the fluidic cavity 3 so as to generate mechanical pressure on the piezoelectric pillar 4'.

[0071] The expression “mechanical pressure” in relation to the piezoelectric generator 4 is understood to mean that the latter 4 receives or undergoes a force impacting a receiving surface of said generator 4, this impact force being created solely by the pressurized liquid circulating in the hydraulic circuit 1, 2, to the exclusion of all other forces of any nature (electric, magnetic or other) whatsoever.

[0072] The hydraulic circuit 1, 2 of [Fig. 1], like that of figures 2 to 6, is connected to a chamber or the like containing the liquid advantageously at a low pressure, close to 1 bar. Thus the portion or portions of hydraulic circuit 2 presented in the appended figures are connected to this chamber, via a supply section coming from said chamber upstream of said portion of circuit 2 and a return section leading to said chamber downstream of said portion of circuit. This chamber containing the hydraulic liquid as well as these supply and return sections are not shown in the appended figures.

[0073] Surrounding the piezoelectric pillar 4' there is a support structure 10 for the pillar 4'.

[0074] In operation, in the modes specific to the invention, in a first sequence, the intake valve 6' is open while the discharge valve 6" is closed. As a result, the pressurized liquid exerts pressure or a mechanical force on the piezoelectric generator 4', causing a deformation of said pillar 4' so that the pillar 4' generates electrical charges, also referred to as electrical energy, which are recovered by the electronic charge extraction circuit 5. The compression of said piezoelectric generator 4' allows the admission of the pressurized liquid into the fluid cavity 3.

[0075] Following this first sequence, a second sequence comprises the closing of the inlet valve 6' and the opening of the discharge valve 6” so that the pillar 4' deforms to return to its initial state at rest (without pressure exerted by the liquid), which again allows the generation of electrical charges, still recovered by the electronic charge recovery circuit 5. The expansion of said piezoelectric generator 4' allows the discharge of the liquid at low pressure out of the fluidic cavity 3.

[0076] Thus, if we compare the first sequence and the second sequence, the inlet valve 6' and the discharge valve 6” respectively have inverse or opposite opening / closing positions. Otherwise, when one - for example the inlet valve 6' - is open, the other 6” is closed and the two sequences are advantageously closely linked to each other within the framework of the present invention.

[0077] The invention is characterized, in such a specific system, by the alternation of the first sequence and the second sequence mentioned above. Furthermore, the frequency of occurrence of the first sequence, or of the second sequence, is modifiable or adaptable according to different parameters, including in particular the resonance frequency of the piezoelectric generator 4, the latter itself being modifiable by modifying the stiffness of the piezoelectric generator 4.

[0078] Thus, the opening / closing of the inlet 6' and discharge 6” valves, i.e. the frequency of the first or second sequence, can be controlled by the control unit so that this opening / closing frequency, or of the first or second sequence, corresponds to the resonant frequency of the piezoelectric generator 4 so as to recover a maximum of electrical energy. Such optimum operation in which the recovery of charges or electrical energy is maximum is obviously possible with all the embodiments illustrated in the attached figures 1 to 6.

[0079] Below are presented details explaining the operation of the piezoelectric pillar 4' and its interaction with the electronic charge extraction circuit 5, it being understood that when the piezoelectric generator 4 consists of a 4” piezoelectric membrane, the structure of the generator 4 is different but its operation and its interaction with the electronic charge extraction circuit 5 is identical, similar or almost identical / almost similar. A piezoelectric stack / pillar 4' as well as a 4” piezoelectric membrane are known to those skilled in the art.

[0080] Each piezoelectric generator is preferably in the form of a pillar of piezoelectric elements or materials 4' respectively each formed by the alternation of piezoelectric ceramics and axially stacked electrodes.

[0081] A piezoelectric pillar or stack consists of a stack of piezoelectric ceramics alternating with electrodes made of a conductive material, such as copper or bronze. The electrodes are wired in parallel or in series. The number of ceramics and electrodes varies from 2 to 100, or even 1000. These ceramics and electrodes have the same shape and preferably have a circular section. They are drilled axially. For example, their external diameter is between 0.5 cm and 20 cm, and their thickness is between 0.2 mm and 100 mm. The diameter of the axial drilling is, for example, between 0.5 cm and 10 cm. The axial drillings ensure axial alignment of the ceramics and electrodes.

[0082] When the ceramics and the electrodes are stacked, the axial holes delimit a central bore coaxial with the axis of the pillar 4'. This central bore allows the passage of a rod which ensures centering, alignment and participates in maintaining the ceramics and the electrodes. Fixing means are arranged at the ends of the rod. These fixing means are for example in the form of rigid parts fixed to the ends of the rod so as to grip the stack of ceramics and electrodes. The part is, for example, in the form of a nut screwed onto the threaded end of the rod. The part can also be a nut, or a threaded part, fixed to a frame, and into which the other threaded end of the rod is screwed.

[0083] For safety reasons, the stack of ceramics and electrodes is advantageously electrically insulated. To do this, the rod can be placed in a sheath or sheath made of an electrically insulating material such as plastic. It is also possible to provide for housing the stack in a sheath or in an outer sheath also made of an electrically insulating material.

[0084] The pillar 4' is connected to an electronic charge extraction circuit 5. This circuit 5 recovers the electrical energy produced by the piezoelectric pillar 4'. It comprises: - a high-voltage switch with control, advantageously with thyristors, - a voltage rectifier bridge, - an inductance whose connection with the pillar 4' constitutes a resonant circuit of the LC type, the capacitive element being constituted by the pillar itself, - a parallel filtering capacitor or capacitor, - a storage system can be used to store this energy electrical system before its packaging for use on the network. This storage system consists, for example, of a battery or a bank of supercapacitors. The circuit can be common to each pair of pillars respectively, being connected simultaneously to each of the pillars of said pair. A DC bus can then be responsible for collecting the pulses from each of the storage systems. - A DC-AC converter can also be used to connect directly to the electrical network.

[0085] The configuration of the circuit 5 is adapted to maximize the electrical energy produced by the pillar 4'. This configuration in fact makes it possible to double the electrical energy generated by the pillar 4' by recovering it a first time when said pillar 4' is crushed (first sequence described above), and a second time when it is released (second sequence described above).

[0086] When the pillar 4' is subjected to an alternating excitation (according to the principle described further in the description), and during the increasing phase of the constraint, the switch is kept open. The pillar 4' is in open circuit and the electrical charges accumulate at the terminals of said pillar 4', the latter functioning as a capacitor.

[0087] When the mechanical stress applied to pillar 4' is maximum, the switch is briefly closed for a duration corresponding to half a period of the resonance of the LC circuit. Thus, all the electric charges accumulated at the terminals of pillar 4' are extracted from said pillar 4'.

[0088] During the decreasing phase of the stress, the pillar 4' recharges. When the mechanical stress is minimal, the switch is again briefly closed for a duration corresponding to half a period of the resonance of the LC circuit, so as to extract the electrical charges. Then the cycle resumes with the alternation of the first and second sequences.

[0089] In the examples chosen to illustrate the invention, the pillar 4' is connected to an electronic circuit called a charge extraction circuit 5. Although only one pillar 4' is shown, in practice, it is possible for a circuit to be connected simultaneously to several pillars 4', as can be seen in [Fig.6].

[0090] In [Fig.2] is presented a diagram identical to that of [Fig. 1] except that the piezoelectric pillar 4' is replaced by a piezoelectric membrane 4”. The operation with the two valves 6', 6” is identical to that described in connection with [Fig.l].

[0091] In the case of a 4” piezoelectric membrane, the latter 4” may consist of piezoelectric nanocomposite films based on PVDF copolymer or advantageously vinylidene fluoride and trifluoroethylene P(VDF-TrFE), possibly comprising various nanoparticles of metal oxides.

[0092] It is understood that the attached figures do not show any dimensioning or dimensioning ratio of the different elements between them which is consistent with the reality of the electricity generation system according to the invention.

[0093] [Fig. 3] shows an embodiment identical to that of [Fig. 1] in which the 6' inlet and 6” discharge valves have been replaced by a 6'” three-way valve, the latter 6”’ still being advantageously controlled or commanded by the control unit. In this embodiment, the 6'” three-way valve alone manages the different sequences described previously:

[0094] - so-called rest sequence in which the piezoelectric pillar 4' does not undergo any mechanical pressure: the 6'” three-way valve is open downstream to the fluid cavity 3, leaving the piezoelectric generator 4 subjected to low pressure.

[0095] - the first sequence in which the liquid circulating in the portion of the circuit hy hydraulic circuit 2 enters the fluid cavity 3 and, incidentally, the piezoelectric generator 4 undergoes mechanical pressure: the three-way valve 6'” closes the downstream to the fluid cavity 3 of the portion of the hydraulic circuit 2, communication is established between the upstream to the fluid cavity 3 and the latter 3. Then

[0096] - the second sequence, following the first sequence, in which the liquid present in the fluid cavity 3 is evacuated or discharged: the 6” three-way valve closes upstream to the fluid cavity 3 of the portion of the hydraulic circuit 2, communication is established between the downstream to the fluid cavity 3 and the latter 3.

[0097] Again, it is clearly understood here that the first and second sequences are those specific to the system and method for generating electricity according to the invention, in other words they are the sequences during which or in the course of which the primary object of the invention occurs, namely the generation of electricity.

[0098] We will see in the following that the invention is not limited to the achievement of this first objective of generating electricity and that the invention also makes it possible - in a second objective - to influence the hydraulic circuit 1, 2 by creating a more or less significant resistance, by variation of the (internal) volume of the fluidic cavity 3, which makes it possible to increase or decrease the torque of the energy source 21 to which the pump 20 is connected. As a reminder, this energy source 21 is very advantageously a renewable energy source which by nature presents a fairly significant fluctuation or variation in their energy supply, whether it is wind energy, waves, or tides. This is why this second objective of the present invention is particularly interesting for renewable energy recovery systems.

[0099] [Fig.4] illustrates an embodiment identical to that of [Fig.2] in which the 6' inlet and 6” discharge valves have been replaced by a 6'” three-way valve, but the operation of the system according to this embodiment remains identical with the three sequences called “at rest”, “first sequence” and “second sequence” presented previously.

[0100] [Fig.5] adds to [Fig.l] the fact that: - the electronic charge extraction circuit 5 is connected to at least one current converter 22, of a direct current recovered from the piezoelectric generator 4' into an alternating current capable of supplying the general electrical network; - the hydraulic circuit 1 may comprise one or more accumulator(s) 24 making it possible to store a liquid reserve to supply or re-supply the hydraulic circuit 1, or even to remove part of the fluid circulating in said circuit 1. Such an accumulator 24 thus makes it possible to manage - in addition to the presence of the chamber containing the liquid - the pressure and the flow rate in the hydraulic circuit 1 by adjusting or regulating the quantity of liquid in circulation. - the hydraulic circuit 1 comprises at least one pressure measuring device in the circuit 26 (pressure sensor) intended to measure the pressure in the PID loop or to control or regulate the torque of the hydraulic pump 20, and therefore that of the energy source 21 supplying the pump 20 of hydraulic circuit 1. - the pump 20 is connected or linked to at least one blade 21 representing a renewable energy source, here of the wind turbine type, intended to supply energy in particular to the pump of the hydraulic circuit.

[0101] Of course, this current converter 22, this accumulator 24, this device for measuring the pressure in the circuit 26 as well as the blade 21, although advantageous in the context of the present invention, are not essential elements of the system or of the energy generation method according to the invention.

[0102] [Fig.6] is identical to [Fig.5] but the single portion of hydraulic circuit 2 of [Fig.5] is replaced by a plurality of portions of hydraulic circuit 2 - in this case five portions of hydraulic circuit 2 - each comprising an assembly comprising a hydraulic cavity 3 housing a piezoelectric pillar 4' with an inlet valve 6' and a discharge valve 6”. These five portions of hydraulic circuit 2 extend in parallel with each other from a common upstream section and join in a single downstream section, these common upstream and downstream sections forming part of hydraulic circuit 1.

[0103] From the common upstream section, we consider for example a flow rate of one hundred (100) liters per minute (l.min1). In this case, we can consider that each of the five parallel portions 2 has a flow rate of 20 liters per minute or that some of these portions 2 have a greater flow rate than other portions 2. The piezoelectric pillars 4' of each of these portions 2 are connected or linked to the same electronic charge extraction circuit 5.

[0104] In such a hydraulic circuit 1 with a plurality of portions 2 in parallel, the electrical charges of each pillar 4' can be accumulated and the recovery of electrical charges can again be optimized by adjusting the frequency of the penetration-discharge sequences (or 1st / 2nd sequences) of each of the portions 2 to correspond to the resonance frequency of the piezoelectric pillar 4' associated with it. This adjustment to the resonance frequency is done by controlling / controlling the openings / closings of the inlet 6' / discharge 6” valves and / or by adjusting the stiffness of the piezoelectric pillar 4' or of the membrane 4' and / or by adjusting the flow rate of liquid circulating in the portion of the hydraulic circuit 2 considered.

[0105] According to one aspect of the system and the method according to the invention, the following characteristics are possible or conceivable for those skilled in the art: - the frequency of the so-called “first” or “second” sequences as well as the frequency of the piezoelectric generator is established between 10 Hertz (Hz) and 1000 Hz; - the flow rate in the hydraulic circuit 1 and in a portion of said circuit 2 is between 1 l.min 1 (liters per minute) and 10,000 l.min 1; - the pressure of the liquid in the hydraulic circuit 1 and in a portion of said circuit 2 is between 5 and 500 bars, advantageously between 200 and 500 bars; - the Hydraulic Power is between 1 W (Watt) and 100 MW (Mega Watt), advantageously between 10 kW (Kilo Watt) and 10 MW. We recall here that the Power is equal to the Flow rate in the hydraulic circuit times the Pressure of the liquid in said circuit (assuming atmospheric pressure downstream of the fluid cavity 3).

[0106] Figures 7 and 8 illustrate a second object of the present invention, briefly stated previously.

[0107] Thus, the invention makes it possible, thanks to the piezoelectric generator 4, to increase or reduce the volume of the fluidic cavity 3. To do this, it is sufficient to apply two different voltages - defining the two states of the piezoelectric generator - to the piezoelectric generator 4 so that the latter 4 has a first state of contraction - for example that shown in [Fig.7] - and a second state of contraction - that shown in [Fig.8]. These two states of contraction reflect a different stiffness or stiffness coefficient for the piezoelectric generator 4.

[0108] It is then noted that, considering the fact that these two states of contraction generate a different height or length of the piezoelectric pillar, there are two different volumes in the fluidic cavity 3. In this case in the first state of contraction ([Fig.7]), the volume of the fluidic cavity is defined by the volume Vo corresponding to a first distance from the end of the piezoelectric pillar 4' of the inlet section of said fluidic cavity 3 while in the second state of contraction ([Fig.8]), the volume of the fluidic cavity 3 is defined by the volume Vo + V i so that in this second state, the volume of the fluidic cavity is greater.

[0109] This difference in volume of the fluid cavity 3 has a direct effect on the flow rate of the liquid circulating in the hydraulic circuit 1, 2, and therefore on the power of this hydraulic circuit, and therefore on the torque of the pump 20, and by extension on the resistance or torque of the renewable energy source 21, in this case on the resistivity or resistive torque of the blade of a wind turbine.

[0110] Such a second objective of the invention allows the system according to the invention, and its method, to adjust the torque of the energy source 21 to which the system is connected or linked. As mentioned previously, this is particularly desirable for installations using renewable energy, which by nature varies over time either periodically (tides) or aperiodically (wind, sea currents, swell).

[0111] Thus, the present invention can be envisaged not for recovering energy electrical but to adjust the power and / or torque of the pump(s) 20 used in the hydraulic circuit 1, 2 and by extension of the energy source 21 supplying this pump 20. Of course, it is also possible to recover electrical energy while carrying out this adjustment of the torque / power of the pump(s) 20, and of the external energy source 21 supplying this pump(s) 20.

[0112] Although the invention has been described in connection with several particular embodiments, it is quite obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0113] The arrangement of the various elements and / or means and / or steps of the invention, in the embodiments described above, should not be understood as requiring such an arrangement in all implementations. In any event, it will be understood that various modifications may be made to these elements and / or means and / or steps, without departing from the spirit and scope of the invention. In particular: - the number of pillars 4' or piezoelectric membranes 4” used may vary and one or more membranes 4” and one or more piezoelectric pillars 4' may be used in the same electricity generation system, arranged in parallel, as can be seen in [Fig. 6], or in series; - the characteristics of the piezoelectric generators 4 - for example the type of material used for the electrodes, number of ceramics or even the holding elements - may be different from those described, for one, several or even all of said generators 4; - the circuit making up the charge extraction system 5 may be different from one device to another; - the electricity generation system or the installation using such a system may or may not contain a temporary energy storage system; - the liquid of the hydraulic circuit 1, 2 may possibly consist of any type of liquid, or even fluid, suitable for allowing pressure to be applied to the piezoelectric generator 4.

[0114] The use of the verb “comprise”, “comprise” or “include” and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

[0115] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

[0116]

Claims

Claims

1. An electricity generation system comprising: • a hydraulic circuit (1) in which a pressurized liquid called hydraulic liquid circulates, a fluidic cavity (3) arranged on at least a portion of the circuit (2), which cavity (3) houses a piezoelectric generator (4, 4'), which generator is a piezoelectric pillar consisting of a stacking structure of piezoelectric elements (4'), which pillar is connected to an electronic charge extraction circuit (5) capable of recovering the electrical energy coming from said pillar when it is subjected to mechanical pressure or depression, which cavity (3) has an inlet port and an outlet port, and • a means of managing the circulation of the liquid (6, 6', 6”, 6”') allowing the liquid to circulate in the circuit portion (2): • to penetrate into the fluid cavity (3) through the inlet port to form the above-mentioned mechanical pressure, which mechanical pressure causes compression of the piezoelectric pillar (4, 4') so that said pillar generates electrical charges recovered by the electronic charge extraction circuit (5), which compression causes an increase in the volume of the fluid cavity (3), • and to evacuate said liquid through the outlet port of said cavity (3), so that without mechanical pressure exerted by the liquid, the piezoelectric pillar (4, 4') expands to return to an initial state at rest allowing the generation of electrical charges again, always recovered by the electronic charge recovery circuit (5), which expansion leads to a reduction in the volume of the fluidic cavity (3), • a control unit for controlling said liquid circulation management means (6, 6', 6”, 6”').

2. An electricity generation system according to claim 1, wherein the liquid circulation management means (6, 6', 6”, 6”') consists of a mechanical or electromechanical element positioned at the inlet port and the outlet port of the fluidic cavity (3).

3. An electricity generation system according to claim 1 or 2, wherein said management means (6, 6', 6”, 6'”) consists of a three-way valve (6”').

4. An electricity generation system according to claim 1 or 2, wherein said management means (6, 6', 6”, 6'”) consists of an inlet valve (6') arranged at the inlet port and a discharge valve (6”) arranged at the outlet port, said valves (6', 6”) being alternately in the open and closed position to allow the liquid to enter and exit the fluid cavity (3).

5. An electricity generation system according to any preceding claim, wherein the control unit controls the penetration and discharge of the liquid into the fluid cavity (3) to obtain a liquid penetration-discharge frequency ranging from a quasi-static frequency up to the resonance frequency of the piezoelectric pillar (4, 4'), preferably the resonance frequency of the piezoelectric pillar (4, 4').

6. An electricity generation system according to any one of the preceding claims, comprising a plurality of circuit portions (2) for the circulation of the liquid arranged in parallel, each circuit portion (2) comprising a fluidic cavity (3) housing a piezoelectric pillar (4, 4') connected to an electronic charge extraction circuit (5) capable of recovering the electrical energy coming from said pillar when it is subjected to pressure as well as a means for managing the circulation of the liquid (6, 6', 6”, 6”') allowing the liquid to enter the fluidic cavity (3) to form the mechanical pressure and to evacuate said cavity (3), said means for managing the circulation of the liquid (6, 6', 6”, 6'”) being controlled by a control unit, advantageously the above-mentioned control unit.

7. An electricity generation system according to any one of the preceding claims, wherein the liquid is pressurized by a pump (20) or cylinders powered by a renewable energy source (21), advantageously a wind source, a hydro-source, a wave source, a hydroelectric source or a source using ocean currents.

8. An electricity generation system according to any one of the preceding claims, wherein the circuit portion(s) (2) for the circulation of liquid comprises a pressure sensor (26) measuring the liquid pressure in said circuit portion(s) (2), advantageously said sensor being connected to the above-mentioned control unit.

9. An electricity generation system according to any one of the preceding claims, wherein the fluid cavity (3) has a variable volume due to the contraction of the piezoelectric pillar (4, 4') when liquid enters the fluid cavity (3) and to the expansion of said piezoelectric pillar (4, 4') when said liquid is evacuated from said cavity (3), the variation of the volume of said fluid cavity (3) being adjustable.

10. System according to claim 9, wherein the adjustment of the variation of the volume of the fluidic cavity (3) is carried out by adjusting the stiffness of the piezoelectric pillar (4, 4').

11. System according to claim 9, wherein the adjustment of the variation of the volume of the fluidic cavity (3) is carried out by adjusting the frequency of penetration and evacuation of the liquid in said cavity (3).

12. Installation for the production of electricity from renewable energy, such as wind, waves, tides or a hydraulic current, in which said installation comprises an electricity generation system according to any one of the preceding claims.

13. Method for generating electricity, characterized in that it comprises the following steps: • arranging a fluidic cavity (3) on at least a portion of a hydraulic circuit (2) in which a pressurized liquid called hydraulic fluid circulates, which cavity (3) has an inlet port and an outlet port, • installing a piezoelectric generator (4, 4') in the fluidic cavity (3), which generator is a piezoelectric pillar consisting of a stacking structure of piezoelectric elements (4'), which pillar is connected to an electronic charge extraction circuit (5) capable of recovering the electrical energy coming from said pillar when it is subjected to pressure or a mechanical depression, • manage the circulation of the liquid to allow said liquid circulating in the circuit portion (2): • to enter the fluidic cavity (3) through the inlet port to form the above-mentioned mechanical pressure, which mechanical pressure causes a compression of the piezoelectric pillar (4, 4') so that said pillar generates electrical charges recovered by the electronic charge extraction circuit (5), which compression causes an increase in the volume of the fluidic cavity (3), • and to evacuate said liquid through the outlet port of said cavity (3) so that without mechanical pressure exerted by the liquid, the piezoelectric pillar (4, 4') expands to return to an initial state at rest allowing again the generation of electrical charges, still recovered by the electronic charge recovery circuit (5), which expansion causes a decrease in the volume of the fluidic cavity (3).

14. Method according to claim 13, in which the penetration and evacuation of the liquid in the fluidic cavity (3) are controlled to obtain a liquid penetration-evacuation frequency ranging from a quasi-static frequency up to the resonance frequency of the piezoelectric pillar (4, 4'), preferably to the resonance frequency of said pillar.

15. Method according to one of claims 13 or 14, wherein the fluidic cavity (3) has a variable volume due to the contraction of the piezoelectric pillar (4, 4') when the liquid enters the fluidic cavity (3) and to the expansion of said pillar when said liquid is evacuated from said cavity (3), said method comprising a step of adjusting the variation of the volume of the fluidic cavity (3) by adjusting the stiffness of said piezoelectric pillar (4, 4').

16. Method according to one of claims 13 or 14, in which the fluidic cavity (3) has a variable volume due to the contraction of the piezoelectric pillar (4, 4') when the liquid enters the fluidic cavity (3) and to the relaxation of said pillar when said liquid is evacuated from said cavity (3), said method comprising a step of adjusting the variation of the volume of the fluidic cavity (3) by adjusting the frequency of penetration and evacuation of the liquid in said cavity (3).

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