Power generation method and power generation system

Abstract

This electricity generation method is for generating electric power from an electric power generating element (2). The electric power generating element (2) has an electric polarization state which changes in accordance with a phase transition. First, without changing the temperature of the electric power generating element (2), an electric field is applied to the electric power generating element (2) by means of an electric field applying device (4) for applying an electric field to the electric power generating element (2), in such a way that a phase transition temperature of the electric power generating element (2) changes. Then, electric power is generated from the electric power generating element (2) by changing the electric polarization state of the electric power generating element (2) by means of the application and control of the electric field.

Description

Technical Field

[0001] The present invention relates to a power generation method and a power generation system.

Background Art

[0002] Conventionally, various methods for reusing waste heat energy have been studied. For example, a power generation system has been proposed that includes a heat source whose temperature fluctuates over time, a first device (dielectric) that is electrically polarized according to the temperature change of the heat source, and a second device (electrode) that is disposed opposite to sandwich the first device in order to extract electric power from the first device. Further, in the above power generation system, it has also been proposed to apply a voltage (electric field) to the first device according to the temperature change of the first device (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, in power generation by the above power generation system, it is necessary to change the temperature of the first device (dielectric). However, it is not easy to find an environment for changing the temperature of the first device (dielectric). Further, even in an environment where there is a temperature change, depending on the mass and thermal conductivity of the first device itself, the temperature of the first device may not follow the temperature change of the environment.

[0005] The present invention is a power generation method and a power generation system that can generate power without preparing an environment for changing the temperature.

Means for Solving the Problems

[0006] The present invention [1] is a method for generating electricity from a power generation element whose electric polarization state changes by a phase transition, comprising: an electric field application step of applying an electric field to the power generation element by electric field application means for applying an electric field to the power generation element without changing the temperature of the power generation element, such that the phase transition temperature of the power generation element changes; and a power generation step of changing the electric polarization state of the power generation element by applying and controlling the electric field, thereby generating electricity from the power generation element.

[0007] The present invention [2] includes the power generation method described in [1] above, wherein in the electric field application step, the phase transition temperature of the power generation element is changed to repeatedly alternate between a first state in which the phase transition temperature exceeds the ambient temperature and a second state in which the phase transition temperature is below the ambient temperature.

[0008] The present invention [3] includes the power generation method described in [1] or [2] above, wherein the temperature difference between the phase transition temperature of the power generation element when no electric field is applied and the ambient temperature of the power generation element is 50°C or less.

[0009] The present invention [4] includes a power generation method according to any one of the above [1] to [3], wherein the power generation element contains at least one selected from the group consisting of barium titanate [BaTiO3], barium zirconate titanate [Ba(Zr,Ti)O3] and calcium barium zirconate titanate [(Ba,Ca)(Zr,Ti)O3].

[0010] The present invention [5] further comprises the power generation method described in [4] above, wherein the power generation element further contains a doped rare earth element.

[0011] The present invention [6] includes the power generation method described in [5] above, wherein the doped rare earth element contains at least one selected from the group consisting of Ce, Y, and La.

[0012] The present invention [7] includes the power generation method described in [5] or [6] above, wherein the doped rare earth element contains Ce, and the content of Ce is 0.00005 mol% or more and 50 mol% or less with respect to the total amount of metal elements in the power generation element.

[0013] The present invention [8] includes a power generation method according to any one of the above [4] to [7], wherein the power generation element is annealed in an oxidizing atmosphere.

[0014] The present invention [9] includes a power generation element whose electric polarization state changes by a phase transition, and a power generation means for generating electricity from the power generation element, wherein the power generation means includes an electric field application means for applying an electric field to the power generation element to change the phase transition temperature of the power generation element without providing a temperature change means for changing the ambient temperature of the power generation element, an extraction means for extracting the electricity generated by the change in the electric polarization state of the power generation element, and a control means for controlling the electric field applied by the electric field application means, wherein the control means applies an electric field to the power generation element so that the phase transition temperature of the power generation element changes.

[0015] The present invention

[10] includes the power generation system described in [9] above, wherein the control means applies an electric field to the power generation element such that the phase transition temperature of the power generation element is changed to repeatedly alternate between a first state in which the phase transition temperature exceeds the ambient temperature and a second state in which the phase transition temperature is below the ambient temperature.

[0016] The present invention

[11] includes the power generation system described in [9] or

[10] above, wherein the power generation element contains at least one selected from the group consisting of barium titanate [BaTiO3], barium zirconate titanate [Ba(Zr,Ti)O3] and calcium barium zirconate titanate [(Ba,Ca)(Zr,Ti)O3].

[0017] The present invention

[12] includes the power generation system described in

[11] above, wherein the power generation element further contains a doped rare earth element.

[0018] The present invention

[13] includes the power generation system described in

[12] above, in which the doped rare earth element contains at least one selected from the group consisting of Ce, Y, and La.

[0019] The present invention

[14] includes the power generation system described in

[12] or

[13] above, in which the doped rare earth element contains Ce, and the content ratio of Ce is 0.00005 mol% or more and 50 mol% or less based on the total amount of the metal elements of the power generation element.

[0020] The present invention

[15] includes the power generation system according to any one of

[11] to

[14] above, in which the power generation element is annealed in an oxidizing atmosphere.

Advantages of the Invention

[0021] In the power generation method and power generation system of the present invention, power is generated from a power generation element by applying an electric field to the power generation element so that the phase transition temperature of the power generation element changes without changing the temperature of the power generation element. Therefore, power can be generated without searching for an environment in which the temperature of the power generation element changes. In addition, the method of controlling the electric polarization by changing the electric field applied to the power generation element has fewer restrictions on the mass and thermal conductivity of the power generation element than the method of changing the temperature of the power generation element, and is excellent in applicability.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 is a schematic configuration diagram showing an embodiment of the power generation system of the present invention. [Figure 2] FIG. [Figure 3] FIG. 3 is a graph showing the relationship between the net power generation obtained in Comparative Example 1 and the temperature conditions. <000 [Figure 4] FIG. 4 is a graph showing the relationship between the net power generation obtained in Example 2 and the temperature conditions. [Figure 5]Figure 5 is a graph showing the relationship between the net power generated in Example 3 and the temperature conditions. [Figure 6] Figure 6 is a graph showing the relationship between the net power generated in Example 4 and the temperature conditions. [Figure 7] Figure 7 is a graph showing the relationship between the net power generated in Example 5 and the temperature conditions. [Figure 8] Figure 8 is a graph showing the relationship between the net power generated in Example 6 and the temperature conditions. [Figure 9] Figure 9 is a graph showing the relationship between the net power generated in Example 7 and the temperature conditions. [Figure 10] Figure 10 is a graph showing the relationship between the net power generated in Example 8 and the temperature conditions. [Figure 11] Figure 11 is a graph showing the relationship between the net power generated in Example 9 and the temperature conditions. [Figure 12] Figure 12 is a graph showing the relationship between the net power generated in Example 10 and the temperature conditions. [Figure 13] Figure 13 is a graph showing the relationship between the net power generated in Example 11 and the temperature conditions. [Figure 14] Figure 14 is an operation diagram showing the operation of the power supply, application switch, and recovery switch in Examples 12-14 and Comparative Example 2. [Figure 15] Figure 15 is a graph showing the relationship between the net power generated in Examples 12-14 and Comparative Example 2, the strength of the applied electric field, and the frequency of the applied electric field. [Modes for carrying out the invention]

[0023] Figure 1 is a schematic diagram showing one embodiment of the power generation system of the present invention. In Figure 1, the power generation system 1 comprises a power generation element 2 and a power generation device 3 as a power generation means (power generation unit).

[0024] The power generation element 2 is a device in which the electric polarization state changes due to a phase transition. Electric polarization is a phenomenon in which dielectric polarization occurs and a potential difference is generated due to the displacement of positive and negative ions accompanying the distortion of the crystal (change in three-dimensional symmetry).

[0025] Examples of power generation element 2 include materials that exhibit pyroelectric and / or piezoelectric effects. Examples of such materials include dielectrics. Examples of dielectrics include lead-containing inorganic materials. Dielectrics , lead-free inorganic Dielectrics and polymeric organic Dielectrics These are some examples.

[0026] lead-containing inorganic Dielectrics Examples include lead-containing dielectrics and metal-doped materials obtained by doping such dielectrics with doped metals (excluding rare earth elements, as described later). Dielectrics More specifically, examples include lead titanate [PbTiO3], lead zirconate [PBZrO3], lead zirconate titanate [Pb(Zr,Ti)O3], lead niobate manganate [Pb(Mg,Nb))O3], lead niobate zincate [Pb(Zn,Nb)O3], lead tantalate magnesiumate [Pb(Mg,Ta)O3], and lead niobate indinate [Pb(In,Nb)O3]. Furthermore, lead-containing inorganic materials... Dielectrics As an example, rare earth element doped materials obtained by doping the above-mentioned dielectric and / or metal-doped materials thereof with the doped rare earth elements described later can also be mentioned. These can be used individually or in combination of two or more types.

[0027] Examples of lead-free inorganic dielectrics include lead-free dielectrics and metal-doped materials obtained by doping such dielectrics with doped metals (excluding rare earth elements as described later). DielectricsMore specifically, for example, barium titanate [BaTiO3], barium zirconate titanate [Ba(Zr,Ti)O3], calcium barium titanate [(Ba,Ca)TiO3], calcium barium zirconate titanate [(Ba,Ca)(Zr,Ti)O3], calcium titanate [CaTiO3], quartz [SiO2], zinc oxide [ZnO], sodium potassium tartrate [KNaC4H4O6], lithium niobate [LiNbO3], lithium tantalate [LiTaO] 3], lithium tetraborate [Li2B4O7], aluminum nitride [AlN], tourmaline, polyvinylidene fluoride [PVDF], calcium vanadate [Ca3(VO4)2], lithium tantalate niobate [Li(Nb,Ta)O3], calcium tantalate niobate [Ca3{(Nb,Ta)O4}2], potassium niobate [KNbO3], magnesium niobate [MgNbO3], calcium niobate [CaNbO3], potassium sodium niobate [(K, Na )NbO3], bismuth potassium sodium niobate [Bi(K,Na)NbO3], strontium potassium sodium niobate [Sr(K,Na)NbO3], barium potassium sodium niobate [Ba,(K,Na)NbO3], lithium potassium sodium niobate [Li,(K,Na)NbO3], strontium sodium niobate [Sr2NaNb5O 15 ], Strontium calcium sodium niobate [(Sr,Ca)NaNb5O 15 ], barium sodium niobate [Ba2NaNbO 15 Examples include lead-free inorganic nitrate [Ba2Nb2O6]. Dielectrics As an example, rare earth element doped materials obtained by doping the above-mentioned dielectric and / or metal-doped materials thereof with the doped rare earth elements described later can also be mentioned. These can be used individually or in combination of two or more types.

[0028] polymer organic DielectricsExamples include homopolymers and copolymers of vinylidene fluoride. An example of a homopolymer is polyvinylidene fluoride (PVD). An example of a copolymer is a copolymer of vinylidene fluoride (VDF) and trifluoroethylene (TrFE). These can be used individually or in combination of two or more.

[0029] These dielectrics can be used individually or in combination of two or more types. From an environmental standpoint, lead-free inorganic dielectrics and polymeric organic dielectrics are preferred. Lead-free inorganic dielectrics and polymeric organic dielectrics satisfy the requirement of being lead-free and are environmentally friendly. From the viewpoint of power generation efficiency, lead-free inorganic dielectrics are more preferred.

[0030] Preferably, lead-free inorganic dielectrics include dielectrics having a perovskite crystal structure, and more preferably, barium titanate [BaTiO3], barium zirconate titanate [Ba(Zr,Ti)O3], and calcium barium zirconate titanate [(Ba,Ca)(Zr,Ti)O3]. That is, from the viewpoint of power generation efficiency, preferably, the power generation element 2 contains at least one selected from the group consisting of barium titanate [BaTiO3], barium zirconate titanate [Ba(Zr,Ti)O3], and calcium barium zirconate titanate [(Ba,Ca)(Zr,Ti)O3].

[0031] From the viewpoint of power generation efficiency, more preferably, the power generation element 2 contains barium zirconate titanate [Ba(Zr,Ti)O3] and / or calcium barium zirconate titanate [(Ba,Ca)(Zr,Ti)O3].

[0032] From the viewpoint of power generation efficiency, it is even more preferable that the power generation element 2 contains barium zirconate titanate [Ba(Zr,Ti)O3]. From the viewpoint of power generation efficiency, it is particularly preferable that the power generation element 2 is made of barium zirconate titanate [Ba(Zr,Ti)O3].

[0033] Furthermore, from the viewpoint of power generation efficiency, the power generation element 2 preferably contains doped rare earth elements. In other words, as the power generation element 2, a dielectric containing doped rare earth elements (hereinafter referred to as a rare earth element-doped dielectric) is preferred.

[0034] Examples of rare earth element-doped dielectrics include the lead-containing inorganic dielectric described above and the lead-free inorganic dielectric described above, with the lead-free inorganic dielectric described above being preferred.

[0035] Examples of rare earth elements used to dope dielectrics (hereinafter referred to as doped rare earth elements) include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). These can be used individually or in combination of two or more. Preferably, doped rare earth elements include Ce, Y, and La. In other words, the doped rare earth elements preferably contain at least one selected from the group consisting of Ce, Y, and La.

[0036] From the viewpoint of power generation efficiency, Ce is particularly preferred as the doped rare earth element. More specifically, the doped rare earth element particularly preferably includes at least Ce. In this case, the doped rare earth element may also include Y and / or La in addition to Ce. In other words, preferred doped rare earth elements include the sole use of Ce, and the combination of Ce and Y and / or La.

[0037] As rare earth element doped dielectrics, preferred examples include rare earth element doped [Ba(Zr,Ti)O3], and more preferably, Ce doped [Ba(Zr,Ti)O3], Y doped [Ba(Zr,Ti)O3], La doped [Ba(Zr,Ti)O3], Ce,Y doped [Ba(Zr,Ti)O3], and Ce,La doped [Ba(Zr,Ti)O3].

[0038] In [Ba(Zr,Ti)O3], Ce is preferably substituted for part of Zr and / or part of Ti. That is, the Ce-doped compound of [Ba(Zr,Ti)O3] is preferably represented as [Ba(Zr,Ti,Ce)O3].

[0039] Furthermore, in [Ba(Zr,Ti)O3], Y is preferably substituted for part of Zr and / or part of Ti. That is, the Y-doped form of [Ba(Zr,Ti)O3] is preferably represented as [Ba(Zr,Ti,Y)O3]. Also, the Ce,Y-doped form of [Ba(Zr,Ti)O3] is preferably represented as [Ba(Zr,Ti,Ce,Y)O3].

[0040] Furthermore, in [Ba(Zr,Ti)O3], La is preferably substituted for a portion of Ba. That is, the La-doped form of [Ba(Zr,Ti)O3] is preferably represented as [(Ba,La)(Zr,Ti)O3]. Also, the Ce,La-doped form of [Ba(Zr,Ti)O3] is preferably represented as [(Ba,La)(Zr,Ti,Ce)O3].

[0041] In a rare-earth element doped dielectric material, the content ratio of the doped rare-earth elements (or their total amount if used in combination) is, from the viewpoint of power generation efficiency, for example, 0.00005 mol% or more, preferably 0.0001 mol% or more, more preferably 0.001 mol% or more, and even more preferably 0.005 mol% or more, relative to the total amount (total number of moles) of metal elements in the power generation element (rare-earth element doped dielectric material).

[0042] Furthermore, in the rare earth element-doped dielectric material, the content ratio of the doped rare earth elements (or their total amount if used in combination) is, from the viewpoint of power generation efficiency, for example, 50 mol% or less, preferably 10 mol% or less, more preferably 1 mol% or less, even more preferably 0.1 mol% or less, and particularly preferably 0.01 mol% or less, relative to the total amount (total number of moles) of metal elements in the power generation element (rare earth element-doped dielectric material).

[0043] Furthermore, when the doped rare earth element contains Ce, the Ce content is, from the viewpoint of power generation efficiency, for example, 0.00005 mol% or more, preferably 0.0001 mol% or more, more preferably 0.001 mol% or more, and even more preferably 0.005 mol% or more, relative to the total amount (total number of moles) of metal elements in the power generation element (dielectric rare earth element doped body).

[0044] Furthermore, when the doped rare earth element contains Ce, the Ce content is, from the viewpoint of power generation efficiency, for example, 50 mol% or less, preferably 10 mol% or less, more preferably 1 mol% or less, even more preferably 0.1 mol% or less, and particularly preferably 0.01 mol% or less, relative to the total amount (total number of moles) of metal elements in the power generation element (dielectric rare earth element doped body).

[0045] Furthermore, when the doped rare earth element contains Y, the content of Y is, from the viewpoint of power generation efficiency, for example, 0.00005 mol% or more, preferably 0.0001 mol% or more, more preferably 0.0005 mol% or more, and even more preferably 0.001 mol% or more, relative to the total amount (total number of moles) of metal elements in the power generation element (dielectric rare earth element doped body).

[0046] Furthermore, when the doped rare earth element contains Y, the content of Y is, from the viewpoint of power generation efficiency, for example, 10 mol% or less, preferably 1 mol% or less, more preferably 0.1 mol% or less, even more preferably 0.05 mol% or less, and particularly preferably 0.01 mol% or less, relative to the total amount (total number of moles) of metal elements in the power generation element (dielectric rare earth element doped body).

[0047] Furthermore, when the doped rare earth element contains La, the La content is, from the viewpoint of power generation efficiency, for example, 0.00005 mol% or more, preferably 0.0001 mol% or more, more preferably 0.0005 mol% or more, and even more preferably 0.001 mol% or more, relative to the total amount (total number of moles) of metal elements in the power generation element (dielectric rare earth element doped body).

[0048] Furthermore, when the doped rare earth element contains La, the La content is, from the viewpoint of power generation efficiency, for example, 10 mol% or less, preferably 5 mol% or less, more preferably 1 mol% or less, even more preferably 0.5 mol% or less, and particularly preferably 0.05 mol% or less, relative to the total amount (total number of moles) of metal elements in the power generation element (rare earth element doped dielectric).

[0049] The method for producing dielectrics, the method for producing metal-doped dielectrics, and the method for producing these rare-earth element-doped dielectrics are not particularly limited. For example, first, a main raw material containing a dielectric metal element is mixed in an appropriate proportion. If necessary, the main raw material containing a dielectric metal element is mixed with a doped metal raw material containing a doped metal (excluding rare-earth elements) and / or a doped rare-earth raw material containing a doped rare-earth element in the above proportions. Examples of the main raw material, doped metal raw material, and doped rare-earth raw material include known compounds and complexes, more specifically, oxides, carbonates, oxychlorides, and alkoxide complexes. The mixing method is not particularly limited, and known methods can be used. This yields a raw material mixture.

[0050] Next, the raw material mixture is calcined (primary calcination) in the presence of oxygen. The calcination temperature is, for example, 600°C or higher, preferably 800°C or higher. Alternatively, the calcination temperature is, for example, 1300°C or lower, preferably 1100°C or lower. The calcination time is, for example, 30 minutes or more, preferably 2 hours or more. Alternatively, the calcination time is, for example, 12 hours or less, preferably 6 hours or less. This yields calcined powder (primary calcined powder).

[0051] Next, the calcined powder is crushed as necessary, and then pressure-molded to obtain a compacted powder. The compacted powder is then calcined (main calcination, secondary calcination) to sinter it. The calcination temperature is higher than the calcination temperature, for example, 800°C or higher, preferably 1000°C or higher. The calcination temperature is, for example, 1800°C or lower, preferably 1600°C or lower. The calcination time is, for example, 1 hour or more, preferably 2 hours or more. The calcination time is, for example, 24 hours or less, preferably 12 hours or less. This yields a dense sintered body (main calcined body, secondary calcined body).

[0052] This makes it possible to obtain a sintered body of a dielectric material (including doped rare earth elements as needed) as the power generation element 2.

[0053] Furthermore, a sintered dielectric body (containing doped rare earth elements as necessary) for the power generation element 2 can also be obtained by firing (main firing) a commercially available dielectric under the above conditions and then sintering it.

[0054] The power generation element 2 is annealed in an oxidizing atmosphere as necessary. For example, if the power generation element 2 has a perovskite crystal structure, it is preferably annealed. That is, the power generation element 2 is preferably an annealed dielectric material having a perovskite crystal structure. The annealing process can repair oxygen lattice defects in the perovskite crystal structure, resulting in a sintered body with a more favorable lattice structure. As a result, better power generation performance can be obtained.

[0055] In the annealing process, the oxidizing atmosphere is, for example, air, preferably under air circulation, and more preferably in an atmosphere where the oxygen concentration is adjusted to be higher than that of air by an atmospheric firing furnace. In such cases, the oxygen concentration (by volume) is the atmosphere firing furnaceThe amount of gas filling the container is, for example, 30% or more, preferably 50% or more. The annealing temperature is, for example, 600°C or more, preferably 800°C or more. The annealing temperature is, for example, 1400°C or less, preferably 1200°C or less. The annealing time is, for example, 5 minutes or more, preferably 10 minutes or more. The annealing time is, for example, 24 hours or less, preferably 12 hours or less, more preferably 3 hours or less.

[0056] Furthermore, the power generation element 2 is subjected to polarization treatment as necessary. Preferably, the power generation element 2 is subjected to polarization treatment. Polarization treatment provides superior power generation performance.

[0057] The strength of the electric field applied during the polarization process is, for example, 500 V / mm or more, preferably 1 kV / mm or more, and more preferably 10 kV / mm or more. Alternatively, the electric field strength may be, for example, 200 kV / mm or less, preferably 100 kV / mm or less. The polarization process time may be, for example, 1 minute or more, preferably 5 minutes or more. Alternatively, the polarization process time may be, for example, 5 hours or less, preferably 1 hour or less.

[0058] The power generation element 2 has a phase transition temperature. The phase transition temperature is the temperature at which the power generation element 2 undergoes a phase transition, causing a change in the electric polarization state within the power generation element 2. In other words, the power generation element 2 undergoes a phase transition depending on the relationship between the ambient temperature and the phase transition temperature. The electric polarization state of the power generation element 2 changes due to the phase transition. That is, the electric polarization state of the power generation element 2 changes significantly before and after the phase transition temperature. The phase transition temperature of the power generation element 2 is set appropriately depending on the material of the power generation element 2. The phase transition temperature of the power generation element 2 may be single or multiple. Phase transitions are generally thought to be governed by temperature and pressure.

[0059] As will be explained in more detail later, the phase transition temperature of the power generation element 2 changes when an electric field is applied to it. The above-mentioned phase transition temperature is the phase transition temperature of the power generation element 2 when no electric field is applied.

[0060] The shape and size of the power generation element 2 are not particularly limited and are set appropriately according to the purpose and application. Examples of shapes for the power generation element 2 include rectangular parallelepiped, cubic, sheet, disc, thin film, spherical, and lump, with sheet, disc, and thin film shapes being preferred. When the power generation element 2 is sheet or disc-shaped, the thickness of the power generation element 2 is preferably thinner, for example, 2.0 mm or less, preferably 0.5 mm or less. When the power generation element 2 is thin film-shaped, the thickness of the power generation element 2 is, for example, 0.1 mm or less.

[0061] The power generation device 3 comprises an electric field application device 4 as an electric field application means (electric field application unit), an extraction device 5 as an extraction means (extraction unit), and a control device 6 as a control means (control unit).

[0062] The power generation device 3 does not have a temperature changing means (temperature changing unit) to change the ambient temperature of the power generation element 2. More specifically, the power generation device 3 does not have a heater to heat the power generation element 2, nor a cooler to cool the power generation element 2. Therefore, in the power generation system 1, the power generation element 2 is neither actively heated nor actively cooled. As a result, the temperature of the power generation element 2 does not change, or follows the ambient temperature of the environment in which the power generation element 2 is located.

[0063] The ambient temperature is set appropriately according to the material of the power generation element 2. The ambient temperature is usually between 0°C and 350°C.

[0064] The electric field application device 4 is a device that applies an electric field to the power generation element 2 to change the phase transition temperature of the power generation element 2. The electric field application device 4 is electrically connected to the power generation element 2 in order to apply a voltage to the power generation element 2. More specifically, the electric field application device 4 comprises a pair of electrodes 41 arranged opposite each other with the power generation element 2 in between, a power supply 42 for applying an electric field to the power generation element 2, and a conductor 43 connecting the electrodes 41 and the power supply 42. In this way, the power supply 42 and the power generation element 2 are electrically connected.

[0065] The power supply 42 is electrically connected to the control device 6 (described later). The control device 6 (described later) controls the output of the power supply 42. As a result, the strength of the electric field applied to the power generation element 2 is controlled by the control device 6 (described later) (see dashed line in Figure 1).

[0066] An application switch 44 is interposed in the conductor 43. The application switch 44 is electrically connected to a control device 6 (described later). The control device 6 (described later) controls the opening and closing of the application switch 44. As a result, the timing of the application of the electric field to the power generation element 2 is controlled by the control device 6 (described later) (see dashed line in Figure 1).

[0067] The extraction device 5 is a device for extracting the electricity generated by the change in the electric polarization state of the power generation element 2. The extraction device 5 is electrically connected to the power generation element 2 in order to extract the electricity generated in the power generation element 2.

[0068] The extraction device 5, for example, directly utilizes and / or stores the power generated by the power generation element 2. When the extraction device 5 directly utilizes the power, it includes an electric motor that consumes power to operate. When the extraction device 5 stores power, it includes a power storage device. The electric motor and the power storage device may be used together as needed. For example, in Figure 1, the extraction device 5 includes a power storage device. More specifically, the extraction device 5 includes a pair of electrodes 51 positioned opposite each other with the power generation element 2 in between, a power storage device 52 for storing the extracted power, and a conductor 53 connecting the electrodes 51 and the power storage device 52. This electrically connects the power storage device 52 and the power generation element 2.

[0069] The energy storage device 52 is not particularly limited as long as it is a device that can store the power extracted from the power generation element 2. Examples include capacitors and batteries, with capacitors being preferred.

[0070] A recovery switch 54 is interposed in the conductor 53. The recovery switch 54 is electrically connected to the control device 6 (described later). The control device 6 (described later) controls the opening and closing of the recovery switch 54. As a result, the timing of power recovery from the power generation element 2 is controlled by the control device 6 (described later) (see dashed line in Figure 1).

[0071] Note that electrode 51 may be the same electrode as electrode 41. That is, the pair of electrodes 41 that sandwich the power generation element 2 may be shared as electrode 51. Furthermore, a portion of the conductor 43 connected to electrode 41 may be shared as conductor 53.

[0072] The control device 6 is a unit that performs electrical control in the power generation system 1. The control device 6 is provided to control the electric field applied by the electric field application device 4. The control device 6 is also provided to control the timing of power recovery by the extraction device 5. The control device 6 consists of a microcomputer equipped with a CPU, ROM, RAM, etc.

[0073] The control device 6 is electrically connected to the electric field application device 4. More specifically, the control device 6 is electrically connected to the power supply 42. The control device 6 controls the output of the power supply 42, thereby controlling the strength of the electric field applied to the power generation element 2.

[0074] Furthermore, the control device 6 is electrically connected to the application switch 44. Thus, the control device 6 controls the opening and closing of the application switch 44. Additionally, the control device 6 is electrically connected to the recovery switch 54. Thus, the control device 6 controls the opening and closing of the recovery switch 54.

[0075] The control device 6 has a control program. The control program includes an intensity control program for controlling the output of the power supply 42, thereby arbitrarily controlling the strength of the electric field applied to the power generation element 2. The control program also includes an application control program for arbitrarily controlling the opening and closing timing of the application switch 44. The control program also includes a recovery control program for arbitrarily controlling the opening and closing timing of the recovery switch 54. Such control programs are created by known methods and stored in the control device 6.

[0076] As shown by the dashed line (two-dot dashed line) in Figure 1, the power generation system 1 may be equipped with any auxiliary components 9 as needed. Examples of auxiliary components 9 include diodes, capacitors, low-pass filters, voltmeters, resistors, coils, relays, and grounds. The auxiliary components are appropriately interposed at any position according to their type. For example, a diode 91 as an auxiliary component 9 can be interposed in the conductor 43 between the power supply 42 and the power generation element 2. Also, for example, a capacitor 92 as an auxiliary component 9 can be interposed in the conductor 43 between the power supply 42 and the power generation element 2. Also, for example, a low-pass filter 93 as an auxiliary component 9 can be interposed between the control device 6 and the power supply 42.

[0077] In such a power generation system 1, the control device 6 controls the electric field application device 4 and applies an electric field to the power generation element 2 so that the phase transition temperature of the power generation element 2 changes. This causes the power generation element 2 to be electrically polarized and generate electricity in the power generation element 2 without actively heating or cooling it.

[0078] The following describes in detail a method of generating electricity from a power generation element 2 whose electric polarization state changes due to a phase transition.

[0079] In this method, first, a power generation element 2 having a phase transition temperature corresponding to the ambient temperature (ambient temperature) of the power generation element 2 is selected. The temperature difference between the phase transition temperature of the power generation element 2 when no electric field is applied and the ambient temperature of the power generation element 2 is set appropriately according to the purpose and application. The temperature difference between the phase transition temperature of the power generation element 2 when no electric field is applied and the ambient temperature of the power generation element 2 is, for example, 1°C or more, preferably 5°C or more. Also, the temperature difference between the phase transition temperature of the power generation element 2 when no electric field is applied and the ambient temperature of the power generation element 2 is, for example, 50°C or less, preferably 30°C or less. If the temperature difference is within the above range, power can be generated with excellent efficiency. The power generation element 2 is placed between the electrodes 41 (electrode 51) in the power generation device 3 shown in Figure 1.

[0080] In this method, an electric field is applied to the power generation element 2. More specifically, without changing the temperature of the power generation element 2, an electric field is applied to the power generation element 2 by the electric field application device 4 so that the phase transition temperature of the power generation element 2 changes (electric field application step).

[0081] In other words, in this process, the control device 6 keeps the application switch 44 in the closed state. The control device 6 also keeps the recovery switch 54 in the open state. The control device 6 then controls the output of the power supply 42 and the strength of the electric field to apply an electric field to the power generation element 2. The output of the power supply 42 and the strength of the electric field are set appropriately according to the type of power generation element 2 and the ambient temperature of the power generation element 2.

[0082] Subsequently, in this power generation method, the electric polarization state of the power generation element 2 is changed by applying and controlling an electric field to the power generation element 2. This generates electricity from the power generation element (power generation process).

[0083] In other words, the phase transition temperature of the power generation element 2 is different when an electric field is applied to the power generation element 2 and when no electric field is applied to the power generation element 2.

[0084] More specifically, the phase transition temperature of the power generation element 2 when an electric field is applied (electric field ON) is higher than the phase transition temperature of the power generation element 2 when no electric field is applied (electric field OFF).

[0085] Therefore, by controlling the application and cessation of the electric field to the power generation element 2 (electric field ON / electric field OFF), the phase transition temperature of the power generation element 2 can be changed without changing the temperature of the power generation element 2.

[0086] Furthermore, the phase transition temperature of the power generation element 2 when a relatively strong electric field is applied (strong electric field) is higher than that of the power generation element 2 when a relatively weak electric field is applied (weak electric field).

[0087] Therefore, by controlling the intensity of the electric field applied to the power generation element 2 (weak electric field / strong electric field), the phase transition temperature of the power generation element 2 can be changed without changing the temperature of the power generation element 2.

[0088] In this method, either a method of controlling the application and stopping of an electric field to the power generation element 2 (electric field ON / electric field OFF) or a method of controlling the strength of the electric field applied to the power generation element 2 (weak electric field / strong electric field) may be adopted.

[0089] In this method, the power generation element 2 is either subjected to an electric field (electric field ON) or a relatively strong electric field (strong electric field), resulting in a relatively high phase transition temperature, and the power generation element 2 is either not subjected to an electric field (electric field OFF) or a relatively weak electric field (weak electric field), resulting in a relatively low phase transition temperature, and this cycle repeats at an arbitrary period.

[0090] In the following, the state in which the phase transition temperature of the power generation element 2 is relatively high will be referred to as the first state. The state in which the phase transition temperature of the power generation element 2 is relatively low will be referred to as the second state. Furthermore, the repeated cycle between the first state and the second state will be referred to as the electric field application cycle.

[0091] In the electric field application cycle, even after the application of the electric field begins, the period during which the voltage is not sufficiently increased and the phase transition temperature does not change is the second state in which the phase transition temperature of the power generation element 2 is relatively low. Conversely, even after the application of the electric field is stopped, the period during which the voltage is not sufficiently decreased and the phase transition temperature does not change is the first state in which the phase transition temperature of the power generation element 2 is relatively high.

[0092] In the first state, where the phase transition temperature is relatively high, the phase transition temperature of the power generation element 2 is appropriately set according to the material of the power generation element 2, the ambient temperature, the external pressure, and the electric field conditions.

[0093] In the second state, where the phase transition temperature is relatively low, the phase transition temperature of the power generation element 2 is appropriately set according to the material of the power generation element 2, the ambient temperature, the external pressure, and the electric field conditions.

[0094] For example, both the phase transition temperature of the power generation element 2 in the first state and the phase transition temperature of the power generation element 2 in the second state may be above the ambient temperature. Alternatively, for example, both the phase transition temperature of the power generation element 2 in the first state and the phase transition temperature of the power generation element 2 in the second state may be below the ambient temperature. In other words, the power generation element 2 does not necessarily have to undergo a phase transition between the first state and the second state.

[0095] From the viewpoint of power generation efficiency, preferably, the power generation element 2 undergoes a phase transition between a first state and a second state. More specifically, from the viewpoint of power generation efficiency, preferably, in the first state, the phase transition temperature of the power generation element 2 exceeds the ambient temperature. Also, from the viewpoint of power generation efficiency, preferably, in the second state, the phase transition temperature of the power generation element 2 is below the ambient temperature.

[0096] In other words, the control device 6 applies an electric field to the power generation element 2 so that it changes the phase transition temperature of the power generation element 2 without changing the temperature of the power generation element 2, and so that it alternates between a first state in which the phase transition temperature exceeds the ambient temperature and a second state in which the phase transition temperature is below the ambient temperature. That is, the control device 6 applies an electric field to the power generation element 2 so that the phase transition temperature of the power generation element 2 changes across the ambient temperature.

[0097] In such cases, the phase transition temperature in the first state is, for example, [ambient temperature + 0.1°C] or higher, preferably [ambient temperature + 5°C] or higher, and for example, [ambient temperature + 50°C] or lower, preferably [ambient temperature + 30°C] or lower.

[0098] Furthermore, the phase transition temperature in the second state is, for example, below [ambient temperature -0°C], preferably below [ambient temperature -5°C], and for example, above [ambient temperature -50°C], preferably above [ambient temperature -30°C].

[0099] Furthermore, in the electric field application cycle, the time during which the power generation element 2 is in the first state is not particularly limited, but is, for example, 1 / 200000 seconds or more, preferably 1 / 2000 seconds or more. Also, in the electric field application cycle, the time during which the power generation element 2 is in the first state is not particularly limited, but is, for example, 5 seconds or less, preferably 1 second or less, per cycle.

[0100] Furthermore, during the voltage application cycle, the time that the power generation element 2 is in the second state is, for example, 1 / 200000 seconds or more, preferably 1 / 2000 seconds or more per cycle. Also, during the voltage application cycle, the time that the power generation element 2 is in the second state is, for example, 5 seconds or less, preferably 1 second or less per cycle.

[0101] Furthermore, in one cycle, the time during which the power generation element 2 is in the second state is, for example, 0.5 times or more, preferably 2 times or more (for example, 0.5 seconds or more, preferably 2 seconds or more) compared to the time during which the power generation element 2 is in the first state (for example, 1 second).

[0102] Furthermore, the time required per cycle is, for example, 1 / 100000 of a second or more, preferably 1 / 1000 of a second or more. Also, the time required per cycle is, for example, 10 seconds or less, preferably 2 seconds or less.

[0103] In other words, the frequency of the electric field application cycle is, for example, 0.1 Hz or higher, preferably 0.5 Hz or higher, more preferably 1.0 Hz or higher, even more preferably 1.5 Hz or higher, and for example, 100,000 Hz or lower, preferably 1,000 Hz or lower.

[0104] In the power generation element 2, the temperature difference between the ambient temperature (outside air temperature) and the phase transition temperature of the power generation element 2 fluctuates as it repeatedly cycles between the first and second states. In response to this fluctuation in temperature difference, the power generation element 2 undergoes a phase transition accompanied by a change in its polarization state.

[0105] In other words, the power generation element 2 has a different crystalline state in the first state and a different crystalline state in the second state. Therefore, by repeatedly switching between the first and second states in the power generation element 2, the crystalline state of the power generation element 2 can be repeatedly changed, and the electric polarization state of the power generation element 2 can be repeatedly changed. As a result, electricity is generated in the power generation element 2.

[0106] Furthermore, the crystal state of the power generation element 2 in the first state may be one type or multiple types. That is, the crystal state of the power generation element 2 may change while it is in the first state. In addition, the crystal state of the power generation element 2 in the second state may be one type or multiple types. That is, the crystal state of the power generation element 2 may change while it is in the second state.

[0107] Then, in accordance with the above-mentioned change in the crystalline state, electrical energy is generated from the power generation element 2. Subsequently, in this method, the electrical energy generated in the power generation element 2 is recovered in the energy storage device 52 (recovery step).

[0108] More specifically, the control device 6 controls the recovery switch 54 to a closed state and the application switch 44 to an open state at any desired timing. As a result, the power generated in the power generation element 2 is recovered to the energy storage device 52 via the electrodes 51 and the conductors 53.

[0109] Although not shown in the diagram, the power generated by the power generation element 2 can be boosted by a voltage booster or converted by an AC / DC converter as needed. The recovered power can be used for any electric device as needed. Alternatively, the power generated by the power generation element 2 can be used directly for any electric device without being recovered to the energy storage device 52.

[0110] In this power generation method and power generation system 1, electricity is generated from the power generation element 2 by applying an electric field to the power generation element 2 so that the phase transition temperature of the power generation element 2 changes, without changing the temperature of the power generation element 2. Therefore, power can be generated without having to find an environment that changes the temperature of the power generation element 2. Furthermore, the method of controlling electric polarization by changing the electric field applied to the power generation element 2 has fewer constraints on the mass and thermal conductivity of the power generation element 2 compared to the method of changing the temperature of the power generation element 2, and is highly applicable.

[0111] In particular, in the above-described power generation method and power generation system 1, the power generation element 2 can convert ambient thermal energy into electrical energy, thus enabling efficient recovery of waste heat energy generated in various industrial fields, for example. [Examples]

[0112] 1. BT (Barium titanate, BaTiO3) Example 1 In the power generation system shown in Figure 1, barium titanate [BaTiO3], as shown in Tables 1 and 2, was used as the power generation element. More specifically, the barium titanate sintered body was manufactured by the following method.

[0113] Specifically, commercially available barium titanate [BaTiO3] powder (manufactured by Sakai Chemical Industry, BT-05) was dry-ground for 1 hour in an alumina automatic mortar and pestle. Then, ethanol was added to this powder and wet-ground for 30 minutes. Next, this powder was dried in a drying oven at 100°C for 15 minutes. Finally, this powder was formed into a disc shape by uniaxial compression molding and hydrostatic molding.

[0114] Next, the resulting powder compact was fired in an electric furnace (main firing) to sinter it. During firing, the heating rate was set to 5°C / min, and it was held at 1400°C for 3 hours in air. This resulted in a dense sintered body (main firing body).

[0115] Next, the sintered body was polished and then annealed. In the annealing process, the heating rate was set to 10°C / min, and the body was held at 1000°C for 30 minutes in an oxidizing atmosphere (50% oxygen, 50% nitrogen).

[0116] Next, a silver electrode was deposited onto the sintered body under an argon atmosphere at room temperature. Afterward, the sintered body was polarized in an oil bath. The electric field strength during polarization was 30 kV / mm, and the polarization time was 30 minutes. This yielded barium titanate (BaTiO3) as a power generation element.

[0117] The effective size of the power generation element was 14.0 mm × 14.0 mm × 0.44 mm thick. The effective size refers to the volume of the portion sandwiched between the electrodes.

[0118] Furthermore, the strength of the electric field applied by the electric field application device was set to 1200V / mm, 1400V / mm, or 1600V / mm, and the electric field application cycle was set to 0.5Hz (0.5 seconds of boosting, 0.3 seconds of application, and 1.2 seconds of stopping).

[0119] Then, the ambient temperature of the power generation element was set to a constant level, and the phase transition temperature of the power generation element was changed by applying the electric field described above. This caused the power generation element to be electrically polarized, and electricity was recovered. The temperature conditions were set in 10°C increments between 120 and 170°C. After that, the net power generated was calculated by subtracting the power consumed by the electric field application device from the recovered power. The results are shown in Figure 2.

[0120] Comparative Example 1 As the power generation element, the same barium titanate [BaTiO3] as in Example 1 was prepared. The power generation element was then heated and cooled over time to change its temperature. For heating, a high temperature (T high A heat source capable of blowing air at ) was prepared. In addition, for cooling, a low-temperature (T low A heat source capable of blowing air at a specific temperature (T) was prepared. The temperature of each heat source was set to a constant level. The power generation element was heated and cooled by switching the airflow from each heat source. The temperature change due to heating (ΔT) was set to 40°C. The heating and cooling cycle was set to 0.05Hz (heating 10 seconds / cooling 10 seconds). high The fan temperature on the ) side was set in increments of 10°C between 150°C and 190°C.

[0121] This caused the power generation element to be electrically polarized, and electricity was recovered. The recovered power was measured under two conditions: one with an electric field applied to the power generation element at the start of heating, and another without. When an electric field was applied to the power generation element, the field strength was set to 1200 V / mm or 2400 V / mm. The net generated power was then calculated by subtracting the power consumed during the application of the electric field from the recovered power. The results are shown in Figure 3.

[0122] 2. BZT (Barium zirconate titanate, Ba(Zr,Ti)O3) Example 2 In the power generation system shown in Figure 1, barium zirconate titanate [Ba(Zr,Ti)O3] as shown in Tables 1 and 2 was used as the power generation element. More specifically, the following method was used to generate the titanate Zirconic acid A sintered body of barium [Ba(Zr,Ti)O3] was manufactured.

[0123] Specifically, the main raw materials and doped metal raw materials shown in Table 3 were prepared as raw materials for barium zirconate titanate (Ba(Zr,Ti)O3), with the proportions of each element being as shown in Tables 1 and 2.

[0124] Next, the prepared raw materials and ethanol were placed in an alumina pot mill (400 mL), and ground and mixed in a ball mill to obtain a raw material slurry. YSZ balls with a diameter of 3 mm were used as the grinding balls. The rotation speed was set to 72 rpm. The mixing time was 70 hours.

[0125] Next, the YSZ balls were removed from the raw material slurry. Then, the raw material slurry was processed in an alumina automatic mortar and pestle to remove the ethanol. This yielded the raw material powder.

[0126] Next, the raw material powder was calcined (primary calcination) in an electric furnace. In the calcination process, the heating rate was set to 5°C / min, and the mixture was held at 1050°C for 4 hours in air. This yielded calcined powder.

[0127] Next, the calcined powder was dry-ground in an alumina automatic mortar for 1 hour. Then, ethanol was added to the calcined powder and wet-ground for 30 minutes. Next, the calcined powder was dried in a drying oven at 100°C for 15 minutes. Finally, the calcined powder was formed into a disc shape by uniaxial pressure molding and hydrostatic molding in the same manner as in Example 1.

[0128] Subsequently, the molded product was sintered using the same method as in Example 1 to obtain a sintered body of barium zirconate titanate (Ba(Zr,Ti)O3). The obtained sintered body was then annealed and polarized using the same method as in Example 1.

[0129] This resulted in obtaining barium zirconate titanate (Ba(Zr,Ti)O3) as a power generation element. The effective size of the power generation element was 26.0 mm in diameter and 0.48 mm in thickness.

[0130] Furthermore, the strength of the electric field applied by the electric field application device was set to 1400V / mm or 1600V / mm, and the electric field application cycle was set to 0.5Hz (0.5 seconds of boosting / 0.3 seconds of application / 1.2 seconds of stopping).

[0131] Then, the ambient temperature of the power generation element was set to a constant level, and the phase transition temperature of the power generation element was changed by applying the electric field described above. This caused the power generation element to be electrically polarized, and electricity was recovered. The temperature conditions were set to room temperature of 25°C, and then in 10°C increments between 60°C and 90°C. After that, the net power generated was calculated by subtracting the power consumed by the electric field application device from the recovered power. The results are shown in Figure 4.

[0132] 4. BCZT (Barium Calcium Zirconate Titanate, (Ba,Ca)(Zr,Ti)O3) Example 3 In the power generation system shown in Figure 1, barium calcium zirconate titanate [(Ba,Ca)(Zr,Ti)O3] as shown in Tables 1 and 2 was used as the power generation element.

[0133] More specifically, the main raw materials and doped metal raw materials shown in Table 3 were prepared as raw materials for barium calcium zirconate titanate [(Ba,Ca)(Zr,Ti)O3], so that the proportions of each element were as shown in Tables 1 and 2.

[0134] Otherwise, a sintered body of barium calcium zirconate titanate [(Ba,Ca)(Zr,Ti)O3] was obtained using the same method as in Example 2. The obtained sintered body was then annealed and polarized using the same method as in Example 2.

[0135] This yielded barium calcium zirconate titanate [(Ba,Ca)(Zr,Ti)O3] as a power generation element. The effective size of the power generation element was 18.5 mm × 18.0 mm × 0.50 mm.

[0136] Furthermore, the strength of the electric field applied by the electric field application device was set to 800V / mm, 1000V / mm, or 1200V / mm, and the electric field application cycle was set to 0.5Hz (0.4 seconds of boosting, 0.3 seconds of application, and 1.3 seconds of stopping).

[0137] Then, the ambient temperature of the power generation element was set to a constant level, and the phase transition temperature of the power generation element was changed by applying the electric field described above. This caused the power generation element to be electrically polarized, and electricity was recovered. The temperature conditions were set in 10°C increments between 50 and 110°C. After that, the net power generated was calculated by subtracting the power consumed by the electric field application device from the recovered power. The results are shown in Figure 5.

[0138] 4. Rare earth element doped form of BZT (barium zirconate titanate, Ba(Zr,Ti)O3) Examples 4-11 In the power generation system shown in Figure 1, rare earth element-doped barium zirconate titanate [Ba(Zr,Ti)O3], as shown in Tables 1 and 2, was used as the power generation element.

[0139] More specifically, as raw materials for rare earth element-doped barium zirconate titanate [Ba(Zr,Ti)O3], the main raw materials, doped metal raw materials, and doped rare earth raw materials shown in Table 3 were prepared so that the proportions of each element were as shown in Tables 1 and 2.

[0140] Otherwise, a sintered body of barium zirconate titanate [Ba(Zr,Ti)O3] doped with rare earth elements was obtained using the same method as in Example 2. The obtained sintered body was then annealed and polarized using the same method as in Example 2.

[0141] This resulted in obtaining a rare-earth element-doped barium zirconate titanate [Ba(Zr,Ti)O3] as a power generation element. The effective size of the power generation element was 19.0 mm in diameter and 0.5 mm in thickness.

[0142] Furthermore, the strength of the electric field applied by the electric field application device was set to 1400V / mm or 1600V / mm, and the electric field application cycle was set to 0.5Hz (0.5 seconds of boosting / 0.3 seconds of application / 1.2 seconds of stopping). Note that in Examples 8 to 11, electric field The strength was set to 1600V / mm.

[0143] Then, the ambient temperature of the power generation element was set to a constant level, and the phase transition temperature of the power generation element was changed by applying the electric field described above. This caused the power generation element to be electrically polarized, and electricity was recovered. Subsequently, the net power generated was calculated by subtracting the power consumed by the electric field application device from the recovered power. The results are shown in Figures 5 to 13.

[0144] [Table 1]

[0145] [Table 2]

[0146] [Table 3]

[0147] Examples 12-15 In the power generation system shown in Figure 1, the strength of the applied electric field and the frequency of the electric field application cycle were varied, and their behavior was observed.

[0148] More specifically, the rare-earth element-doped barium zirconate titanate [Ba(Zr,Ti)O3] from Example 11 was used as the power generation element. The ambient temperature of the power generation element was set to 25°C, and the phase transition temperature of the power generation element was changed by applying an electric field.

[0149] Furthermore, the strength of the electric field applied by the electric field application device and the frequency of the electric field application cycle were varied as described below. This electrically polarized the power generation element and recovered power. Subsequently, the net power generated was calculated by subtracting the power consumed by the electric field application device from the recovered power. These results are shown in Figure 15.

[0150] The strength of the electric field applied to the power generation element by the electric field application device was set as follows: In Example 12, the electric field strength was set to 400 V / mm. In Example 13, the electric field strength was set to 800 V / mm. In Example 14, the electric field strength was set to 1200 V / mm. In Example 15, the electric field strength was set to 1600 V / mm.

[0151] The electric field application cycles were set to 0.25 Hz, 0.5 Hz, 1.0 Hz, and 2.0 Hz. The operations (operation of the power supply, application switch, and recovery switch) in each application cycle are shown in Figure 14 as one cycle (one period). Details of each operation in Figure 14 are shown in Table 4.

[0152] [Table 4]

[0153] Comparative Example 2 Instead of a power generation element, a commercially available capacitor (multilayer ceramic capacitor, Murata Manufacturing Co., Ltd., RDER72J103K2K1H03B, capacitance 0.01μF) was used, and the net power generated was calculated using the same method as in Example 12 (400V / mm). The strength of the electric field applied by the electric field application device was set to 400V / mm. The results are shown in Figure 15.

[0154] The above invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and should not be interpreted restrictively. Modifications of the present invention that are obvious to those skilled in the art are included in the claims described below. [Industrial applicability]

[0155] The power generation method and power generation system of the present invention are suitably used in various industrial fields that require electricity. [Explanation of symbols]

[0156] 1. Power generation system 2 Power generation 3. Power generation equipment 4. Electric field application device 5 Removal device 6. Control device

Claims

1. A method of generating electricity from a power generation element in which the electric polarization state changes due to a phase transition, An electric field application step is performed by applying an electric field to the power generation element using an electric field application means for applying an electric field to the power generation element without changing the temperature of the power generation element, such that the phase transition temperature of the power generation element changes. The system comprises a power generation process that changes the electric polarization state of the power generation element by applying and controlling an electric field, thereby generating electricity from the power generation element. A power generation method wherein the frequency of the electric field application cycle to the power generation element is 1.5 Hz or higher, and the electric field strength is 800 V / mm or higher.

2. In the electric field application step, by changing the phase transition temperature of the power generation element, The first state in which the phase transition temperature exceeds the ambient temperature, The power generation method according to claim 1, wherein the phase transition temperature is lower than the ambient temperature and the process is repeated between this state and a second state.

3. The phase transition temperature of the power generation element when no electric field is applied, The temperature difference between the power generation element and the ambient temperature is 50°C or less. The power generation method according to claim 1.

4. The aforementioned power generation element, Barium titanate [BaTiO] ３ ], barium zirconate titanate [Ba(Zr,Ti)O ３ ] and barium calcium zirconate titanate [(Ba,Ca)(Zr,Ti)O ３ The power generation method according to claim 1, comprising at least one selected from the group consisting of ].

5. The power generation method according to claim 4, wherein the power generation element further contains a doped rare earth element.

6. The power generation method according to claim 5, wherein the doped rare earth element contains at least one selected from the group consisting of Ce, Y, and La.

7. The doped rare earth element contains Ce, The power generation method according to claim 5, wherein the content of Ce is 0.00005 mol% or more and 50 mol% or less with respect to the total amount of metal elements in the power generation element.

8. The power generation method according to claim 4, wherein the power generation element is annealed in an oxidizing atmosphere.

9. The system comprises a power generation element whose electric polarization state changes due to a phase transition, and a power generation means for generating electricity from the power generation element. The aforementioned power generation means is Without providing a temperature change means for changing the ambient temperature of the power generation element, An electric field application means for applying an electric field to the power generation element to change the phase transition temperature of the power generation element, An extraction means for extracting the power generated by a change in the electric polarization state of the aforementioned power generation element, Control means for controlling the electric field applied by the electric field application means, Equipped with, The control means is An electric field is applied to the power generation element such that the phase transition temperature of the power generation element changes. The frequency of the electric field application cycle to the power generation element is 1.5 Hz or higher, and the electric field strength is 800 V / mm or higher. Power generation system.

10. The control means is By changing the phase transition temperature of the power generation element, The first state in which the phase transition temperature exceeds the ambient temperature, The phase transition temperature is lower than the ambient temperature, and the second state is repeated thereafter. An electric field is applied to the aforementioned power generation element. The power generation system according to claim 9.

11. The aforementioned power generation element, Barium titanate [BaTiO] ３ ], barium zirconate titanate [Ba(Zr,Ti)O ３ ] and barium calcium zirconate titanate [(Ba,Ca)(Zr,Ti)O ３ The power generation system according to claim 9, comprising at least one selected from the group consisting of ].

12. The power generation system according to claim 11, wherein the power generation element further contains a doped rare earth element.

13. The power generation system according to claim 12, wherein the doped rare earth element contains at least one selected from the group consisting of Ce, Y, and La.

14. The doped rare earth element contains Ce, The power generation system according to claim 12, wherein the content of Ce is 0.00005 mol% or more and 50 mol% or less with respect to the total amount of metal elements in the power generation element.

15. The power generation system according to claim 11, wherein the power generation element is annealed in an oxidizing atmosphere.

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