JP7195519B2 - Hydrogen storage rate estimation system and hydrogen storage rate estimation method - Google Patents

Description

The present invention relates to a hydrogen storage rate estimation system and a hydrogen storage rate estimation method for estimating the hydrogen storage rate of a hydrogen storage alloy in a hydrogen storage alloy tank.

Existing hydrogen storage methods using compressed hydrogen gas and liquid hydrogen currently used in hydrogen stations, etc. have the problem of energy density, required energy, safety and handling, making it difficult to apply near buildings. do. One solution to this problem is a hydrogen storage alloy. Hydrogen storage alloys have a relatively high hydrogen storage capacity among alloys that produce metal hydrides through the gas-solid phase reaction shown in the following formula, and hydrogen storage and release are reversible under mild temperatures and hydrogen pressures. It is a generic term for things that proceed to

2M+xH2←→2MHx+Q

Here, M is the hydrogen storage alloy, MHx is the hydride, and Q is the heat of reaction [kJ/mol].

The hydrogen storage alloy is pulverized to a particle size of μm order or less due to expansion and contraction of volume accompanying absorption and release of hydrogen, and takes the form of powder particles. Therefore, for practical use, the hydrogen storage alloy is stored in a tank and used.

The properties of hydrogen storage alloys are indicated by a PCT (Pressure Composition Temperature) diagram. FIG. 11 is an example of a PCT diagram of a hydrogen storage alloy. The PCT diagram shows the relationship between the hydrogen pressure required for hydrogen absorption and desorption and the amount of hydrogen absorbed at a constant temperature, and the Y axis is the hydrogen pressure at a constant temperature (logarithmic equilibrium hydrogen pressure). , the X-axis shows the composition (hydrogen concentration) at constant temperature. As shown in FIG. 11, the PCT diagram of the hydrogen storage alloy shows hysteresis characteristics such that the behavior differs between the process of absorbing hydrogen and the process of releasing hydrogen. In addition, the PCT diagram of the hydrogen storage alloy has a plateau region where the hydrogen pressure is substantially constant. The plateau region is not limited to one step, and some metal species have multiple plateau regions. FIG. 12 is an example of a PCT diagram of a metal species with multiple plateau regions. In this example, there are two plateau regions, the first stage and the second stage.

Hydrogen storage alloys can achieve a very high hydrogen filling density per volume compared to gases, and can be stored for a long period of time due to the gas-solid phase reaction. In addition, although it depends on the type of metal, hydrogenation and dehydrogenation proceed under the conditions of hydrogen pressure of 1 MPa or less and temperature of 100 degrees or less, so it is possible to prevent accidents due to sudden hydrogen leakage, high pressure, insulation, etc. does not require a container that requires special specifications of Therefore, it can be said that the hydrogen storage alloy has the property of being able to store hydrogen safely and easily as compared with the conventional cylinder system and liquid hydrogen system.

A problem in storing hydrogen using a hydrogen storage alloy is that it is difficult to determine the amount of stored hydrogen. In other words, the hydrogen storage alloy has a low hydrogen filling density per weight and is filled by a solid solution phenomenon and a chemical bond.

Prior art documents relating to the estimation of the storage amount and storage rate of hydrogen storage alloys include those described in Patent Document 1, Non-Patent Document 1 and Non-Patent Document 2 below.

Japanese Patent Application Laid-Open No. 2004-241261

Tomoki Maruoka, Junichiro Kadono, Shohei Shiomi, Yasumasa Kikuuchi, "Study on Quantitative Analysis of Hydrogen Using Hydrogen-absorbing Titanium," Research Report, Kyoto City Institute of Industrial Technology, No.5, P7-11, 2015 Takehiko Hirose, ``Research on low-temperature adsorption hydrogen storage tank system for fuel cell vehicles'', [online], 2015.11.18, Kyushu University, [searched March 19, 2018], Internet <URL:https: //catalog.lib.kyushu-u.ac.jp/opac_download_md/1500723/eng2458.pdf>

As described above, the hydrogen storage alloy has a problem that it is difficult to know the amount of hydrogen stored at that point in time. The technology described in Non-Patent Document 1 is glow discharge emission spectrometry. However, the optical emission spectroscopy method is not suitable for estimating the amount of hydrogen stored, because it is necessary to take out the contents of the tank and measure it.

The technology described in Non-Patent Document 2 is quantification and estimation based on pressure and weight. When estimating by weight, it is difficult to measure an accurate value due to acceleration during operation, and the hydrogen concentration in the hydrogen storage alloy is currently at most 3 wt%, which is within the margin of error. considered unsuitable. In addition, actual measurement with a mass flow meter or the like also has a large measurement error, making it difficult to obtain an accurate value.

It is also known that the effective hydrogen storage capacity of hydrogen storage alloys depends on pressure and temperature in addition to metal species. In the method of Patent Document 1 using this, the slope of the PCT diagram is a constant, so it is not suitable for metal species whose slope depends on temperature. Moreover, metal species having multi-step plateau regions in the range of use as shown in FIG. 12 are not assumed.

In view of the above problems, the present invention provides a hydrogen storage rate estimation system and a hydrogen storage rate estimation method that can easily measure the hydrogen storage amount of a hydrogen storage alloy in a hydrogen storage alloy tank with high accuracy regardless of the metal type or metal temperature. intended to provide

In order to solve the above problems, there is provided a hydrogen storage rate estimation system for estimating the hydrogen storage rate of a hydrogen storage alloy in a hydrogen storage alloy tank, comprising a temperature sensor for detecting the metal temperature of the hydrogen storage alloy in the hydrogen storage alloy tank. a pressure sensor for detecting the hydrogen pressure in the hydrogen-absorbing alloy tank; a storage unit for storing an estimation formula for determining the hydrogen concentration using the metal temperature and the hydrogen pressure as parameters; and a metal temperature detection value from the temperature sensor. A calculation unit that calculates the hydrogen concentration by the estimation formula from the hydrogen pressure detection value from the pressure sensor and outputs an estimated value of the hydrogen storage rate from the calculated hydrogen concentration, and an analysis device , The estimation formula is obtained by obtaining observation data by creating a PCT diagram using a specimen having the same composition as the hydrogen storage alloy of the hydrogen storage alloy tank by the analysis device, and obtaining at least two values from the observation data. It is calculated by creating an approximation line for each temperature by multiplication and stored in the storage unit, and when the approximation line is created by the analysis device, the slope of the approximation line obtained until the previous time and the The deviation from the slope of continuous observation data is determined, and if the deviation between the slope of the approximation line obtained so far and the slope of the continuous observation data is greater than or equal to a predetermined threshold value, a new approximation line is created Hydrogen storage rate estimation system.

A hydrogen storage rate estimation method according to an aspect of the present invention is a hydrogen storage rate estimation method for estimating the hydrogen storage rate of a hydrogen storage alloy in a hydrogen storage alloy tank, wherein A step of calculating an estimation formula for determining the hydrogen concentration using a test body of the same composition using the metal temperature and the hydrogen pressure as parameters, a step of storing the estimation formula, and a metal temperature of the hydrogen storage alloy in the hydrogen storage alloy tank. , from the step of detecting the hydrogen pressure of the hydrogen-absorbing alloy tank, the detected value of the metal temperature of the hydrogen-absorbing alloy of the hydrogen-absorbing alloy tank, and the detected value of the hydrogen pressure of the hydrogen-absorbing alloy tank, according to the estimation formula calculating the hydrogen concentration, and outputting an estimated value of the hydrogen storage rate from the calculated hydrogen concentration, wherein the step of calculating the estimation formula is performed by an analysis device external to the hydrogen storage rate estimation system, the hydrogen Observation data is obtained by creating a PCT diagram using a specimen of the same composition as the hydrogen storage alloy of the storage alloy tank, and an approximate line is created for each temperature by the least squares method from the observation data. When the approximation line is created by the analysis device, the deviation between the slope of the approximation line obtained so far and the slope of the continuous observation data is determined, and the slope of the approximation line obtained so far is determined. The method for estimating the hydrogen storage rate includes creating a new approximation line if the deviation between the slope and the slope of continuous observation data is greater than or equal to a predetermined threshold .

According to the present invention, by estimating the hydrogen storage rate of a hydrogen storage alloy using an estimation formula for determining the hydrogen concentration using the metal temperature and the hydrogen pressure as parameters, the hydrogen storage amount can be easily and accurately estimated. In addition, according to the present invention, the hydrogen storage rate can be estimated even for a temperature-dependent metal species, a metal species having a multi-step plateau region, or the like, and the hydrogen storage rate can be estimated regardless of the metal species.

1 is a block diagram showing the configuration of a hydrogen storage rate estimation system according to a first embodiment of the present invention; FIG. It is a block diagram which shows the structure of the advance preparation system for creating an estimation formula. It is a flowchart which shows the preprocessing for creating an estimation formula. FIG. 4 is an explanatory diagram of observation data processing; 7 is a flowchart showing processing for creating an approximate line; FIG. 10 is an explanatory diagram of a process of creating an approximate line; 4 is a flowchart of hydrogen storage rate estimation processing in the hydrogen storage rate estimation system according to the first embodiment of the present invention. It is explanatory drawing of a process in case it becomes several estimation formulas. 4 is a graph showing observation data and an approximation line in the case of hydrogen absorption; 4 is a graph showing observation data and an approximation line for hydrogen release. It is a graph in an example of the PCT diagram of a hydrogen storage alloy. 1 is a graph of an example of a PCT diagram of a metal species with multiple plateau regions;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a hydrogen storage rate estimation system 1 according to the first embodiment of the present invention. As shown in FIG. 1, the hydrogen storage rate estimation system 1 according to the first embodiment of the present invention includes a hydrogen storage alloy tank 11, a hydrogen generation/supply device 12, a hydrogen consumption device 13, and a temperature sensor 14. , a pressure sensor 15 , a calculation unit 16 , a storage unit 17 and a display unit 18 .

A hydrogen storage alloy is stored in the hydrogen storage alloy tank 11 . Hydrogen storage alloys include various types such as alkaline earth alloys, rare earth alloys, titanium alloys, and solid solution alloys. Any hydrogen storage alloy can be used in this embodiment.

The hydrogen generator/supply device 12 supplies hydrogen into the hydrogen storage alloy tank 11 . Hydrogen in the hydrogen generation/supply device 12 may be generated by any method. For example, the hydrogen generation/supply device 12 uses surplus power to electrolyze water to generate hydrogen. Also, for example, the hydrogen generation/supply device 12 reforms methane, methanol, or the like to generate hydrogen.

The hydrogen consuming device 13 consumes hydrogen extracted from the hydrogen absorbing alloy in the hydrogen absorbing alloy tank 11 . The hydrogen taken out from the hydrogen absorbing alloy in the hydrogen absorbing alloy tank 11 may be consumed in any manner by the hydrogen consuming device 13 . For example, the hydrogen consuming device 13 uses a fuel cell to generate electric power from hydrogen extracted from the hydrogen absorbing alloy in the hydrogen absorbing alloy tank 11 .

A temperature sensor 14 detects the metal temperature of the hydrogen-absorbing alloy in the hydrogen-absorbing alloy tank 11 . The metal temperature detected by the temperature sensor 14 is sent to the calculator 16 .

A pressure sensor 15 detects the hydrogen pressure in the hydrogen storage alloy tank 11 . The hydrogen pressure detected by the pressure sensor 15 is sent to the calculator 16 .

The computation unit 16 performs various computations for estimating the hydrogen storage rate of the hydrogen storage alloy in the hydrogen storage alloy tank 11 . A PC (Personal Computer) can be used as the calculation unit 16 . The storage unit 17 stores various data for estimating the hydrogen storage rate of the hydrogen storage alloy in the hydrogen storage alloy tank 11 . The storage unit 17 may be stored in the PC that constitutes the calculation unit 16, or may be provided in an external database. In this embodiment, the storage unit 17 stores in advance an estimation formula for obtaining the hydrogen concentration using the metal temperature and the hydrogen pressure as parameters. The calculation unit 16 calculates the hydrogen concentration by this estimation formula from the metal temperature detection value from the temperature sensor 14 and the hydrogen pressure detection value from the pressure sensor 15, and calculates the hydrogen storage rate from the calculated hydrogen concentration. Perform processing to output estimated values.

The display unit 18 displays the hydrogen storage rate estimated by the calculation unit 16 to notify the user.

Next, a method for estimating the hydrogen storage rate in the hydrogen storage rate estimation system 1 according to the first embodiment of the present invention will be described.

The properties of hydrogen storage alloys are represented by PCT diagrams. In measuring the PCT diagram, observation data are obtained that indicate hydrogen pressure and hydrogen concentration at a constant temperature. From this observation data, an approximation line representing the relationship between hydrogen pressure and hydrogen concentration at each temperature can be created.

If an approximation line representing the relationship between the hydrogen pressure and the hydrogen concentration at each temperature can be created, an estimation formula for determining the hydrogen concentration using the metal temperature and the hydrogen pressure as parameters can be calculated from the approximation formula of the approximation line at each temperature. By creating and storing this estimation formula in advance, the hydrogen concentration can be obtained from the detected value of the metal temperature and the detected value of the hydrogen pressure.

Therefore, in the hydrogen storage rate estimation system 1 according to the first embodiment of the present invention, a test piece having the same composition as the hydrogen storage alloy to be filled in the hydrogen storage alloy tank 11 is used in advance to determine the hydrogen pressure and hydrogen An approximation line showing the relationship with the concentration is created, and an estimation formula for determining the hydrogen concentration is calculated from the approximation formula of the approximation line at each temperature using the metal temperature and the hydrogen pressure as parameters.

That is, FIG. 2 shows the configuration of a preliminary preparation system for creating an estimation formula, and FIG. 3 is a flow chart showing preprocessing for creating an estimation formula. As shown in FIG. 2, a PCT measurement device 51 and an analysis device 52 are prepared as a preparatory system. The PCT measurement device 51 performs PCT measurement of the specimen 53 . The analysis device 52 uses the PCT measurement observation data from the PCT measurement device 51 to calculate an estimation formula for determining the hydrogen concentration using the metal temperature and the hydrogen pressure as parameters. As the analysis device 52, for example, a PC (Personal Computer) can be used. Moreover, the analysis device 52 may be shared with the calculation unit 16 of the hydrogen storage rate estimation system 1 .

(Step S101) The PCT measuring device 51 uses a test piece 53 having the same composition as that of the hydrogen-absorbing alloy to be filled in the hydrogen-absorbing alloy tank 11, and obtains observation data by creating a PCT diagram in the operating area. A method described in (JIS H 7201:2007) is used as a method for creating a PCT diagram. According to this creation method, the PCT measuring device 51 obtains observation data indicating hydrogen pressure and hydrogen concentration at a predetermined constant temperature.

(Step S102) The analysis device 52 plots the obtained observation data on coordinates in which the X axis is the logarithm of the hydrogen pressure and the Y axis is the hydrogen concentration. FIG. 4 is an explanatory diagram of observation data processing. As shown in FIG. 4, the X-axis is the logarithm of the hydrogen pressure and the Y-axis is the hydrogen concentration. This is an inverse function relationship in which the X axis and the Y axis are interchanged with respect to the PCT diagram in which the hydrogen concentration is on the X axis and the hydrogen pressure is on the Y axis. The reason why the X-axis is an inverse function of the hydrogen pressure is to create an estimation formula showing the relationship between the hydrogen pressure and the metal temperature with respect to the hydrogen concentration in the processes shown in steps S103 to S106 described later. In the process of step S102, as shown in FIG. 4A, observation data d1, d2, . . . are plotted on the XY plane.

(Step S103) After plotting the observation data, the analysis device 52 creates an approximate line using the least squares method. That is, as shown in FIG. 4B, the analysis device 52 creates the approximate line N1 so that the sum of squares of the residuals between the observation data d1, d2, . . . and the approximate line is minimized. Here, it may be difficult to approximate the observation data d1, d2, . . . with a single approximation line. In this case, as shown in FIG. 4C, approximation is performed using two approximation lines N1 and N2.

(Step S104) After the approximation line is created for one temperature, it is determined whether or not all temperatures have been measured. If all the temperatures have not been measured (step S104: No), the process proceeds to step S105. If all temperatures have been measured (step S104: Yes), the process proceeds to step S106.

(Step S105) The analysis device 52 sets the next temperature and returns the process to step S101. Then, by performing the processing from step S101 to step S104, an approximate line is created by the least squares method from the observation data at the next temperature.

(Step S106) When the measurement for each temperature is completed and the approximation line of the observation data of the PCT diagram is created for each temperature (Step S104: Yes), the analysis device 52 creates the approximation line for each temperature. The functions F(T) and G(T) are determined from the approximation formula, and an estimation formula for determining the hydrogen concentration is calculated using the metal temperature and the hydrogen pressure as parameters. That is, the estimation formula using the metal temperature and the hydrogen pressure as parameters has the form shown in formula (1).

x=F(T)×logP+G(T) (1)

Here, P is the absolute pressure (atm) indicating the hydrogen pressure, T is the absolute temperature (K) indicating the metal temperature, x is the hydrogen concentration (wt%), F (T) and G (T) are the metal temperature T is any function of In step S106, the analysis device 52 obtains the functions F(T) and G(T) from the obtained approximation formula of the approximation line for each temperature, and calculates an estimation formula as shown in formula (1).

(Step S107) The analysis device 52 sets the hydrogen pressure at the hydrogen storage rate (y=0) to the reference hydrogen concentration x1 from the usage area, and sets the hydrogen concentration at the hydrogen storage rate (y=100) to the reference hydrogen concentration Set as x2 (x1<x2). These reference hydrogen concentrations x1 and x2 are used for conversion from hydrogen concentration x to hydrogen storage rate y (where x1<x<x2). Conversion from hydrogen concentration x to hydrogen storage rate y can be performed by the following equation.

y=((x−x1)/(x2−x1))×100 (2)

(Step S108) The analysis device 52 stores the estimation formula obtained in step S106 and the reference hydrogen concentrations x1 and x2 set in step S107 in the storage unit 17 of the hydrogen storage rate estimation system 1.

It should be noted that the estimation formula for the time of hydrogen absorption or hydrogen release is generated by the processing of steps S101 to S108 described above. Since the PCT curve has a hysteresis characteristic, the processing of steps S101 to S108 described above is performed when hydrogen is absorbed and when hydrogen is released. The formula is stored.

As shown in FIG. 4C, in this embodiment, a plurality of approximation lines are created depending on the dispersion of observation data. Therefore, there may be multiple estimation formulas. This makes it possible to deal with metal species having multiple plateau regions in the range of use. That is, FIG. 5 is a flow chart showing the process of creating an approximate line in step S103, and FIG. 6 is an explanatory diagram thereof.

(Step S201) First, the analysis device 52 initializes to 1 a variable N that identifies an approximate line.

(Step S202) The analysis device 52 acquires observation data of three points from the top observation data. For example, when the observation data are acquired as shown in FIG. 6, the analysis device 52 first acquires the first observation data d1, d2, and d3.

(Step S203) The analysis device 52 estimates the approximate line N1 so that the sum of squares of deviations between the approximate line and the observation data d1, d2, and d3 is minimized.

(Step S204) The analysis device 52 determines whether or not there is a next observation point. If there is no next observation point (step S204: No), the process proceeds to step S205, and if there is a next observation point (step S204: Yes), the process proceeds to step S206.

(Step S205) The analysis device 52 saves the obtained approximate expression representing the approximate line in the storage unit 17, and ends the process.

(Step S206) The analysis device 52 determines whether the deviation between the slope between the current observation point and the next observation point and the slope of the approximation line exceeds a threshold. That is, assuming that the observation data dn in FIG. 6 is the current observation point and the observation data dn+1 is the next observation point, the slope between the current observation point and the next observation point is b. On the other hand, assume that the slope of the approximation line N1 is a. The analysis device 52 determines whether the residual between the slope b between the current observation point and the next observation point and the slope a of the approximation line N1 exceeds a predetermined threshold. If the deviation between the slope of the current observation point and the next observation point and the slope of the approximation formula does not exceed the threshold value (step S206: No), the process proceeds to step S207. If the deviation between the slope of the point and the slope of the approximation formula exceeds the threshold (step S206: Yes), the process proceeds to step S208.

If the PCT diagram is only within the plateau region, the slope of the approximation line will be substantially constant. Therefore, in step S206, it is determined that the deviation between the slope of the data between the current observation point and the next observation point and the slope of the approximation line does not exceed the threshold. If the deviation between the slope of the data between the current observation point and the next observation point and the slope of the approximation line does not exceed the threshold (step S206: No), the process proceeds to step S207.

(Step S207) The analysis device 52 acquires the observation data of the next observation point and returns the process to step S203.

By repeating steps S203, S204, S206, and S207, one approximate line N1 that minimizes the sum of squares of deviations between each observation data and the approximate line is obtained.

If the plateau region of the PCT diagram ends before processing is completed for all observation point data, the slope of the approximation line changes significantly. Therefore, in step S206, it is determined that the deviation between the slope of the data and the slope of the approximation line between the current observation point and the next observation point exceeds the threshold. If the deviation between the slope of the data and the slope of the approximation line between the current observation point and the next observation point exceeds the threshold (step S206: Yes), the process proceeds to step S208.

(Step S208) The analysis device 52 saves the approximation formula of the approximation line N1 obtained so far in the storage unit 17, and advances the process to step S209.

(Step S209) The analysis device 52 advances the process to step S210 with the current observation data as the top observation data.

(Step S210) The analysis device 52 increments the variable N that identifies the approximate line, and returns the process to step S202.

After that, by repeating steps S203, S204, S206, and S207, the approximate line N2 that minimizes the sum of squares of deviations between each observation data and the approximate line is obtained. Thereby, the second approximate line N2 is created. When the processing for all observation point data is completed, it is determined in step S204 that there is no next observation point data. When it is determined in step S204 that there is no next observation point data (step S204: No), the analysis device 52 saves the approximate line N2 in the storage unit 17 and terminates the process.

Thus, in this embodiment, when the characteristics change significantly from the boundary of the plateau region, a new approximation line is created. Furthermore, even when multi-stage plateau regions are included, similar processing is repeated from the boundaries of the regions, and new approximation lines are created. If there are a plurality of approximation lines representing the relationship between the hydrogen pressure and the hydrogen concentration at each temperature, there are also a plurality of estimation formulas calculated from the approximation lines representing the relationship between the hydrogen pressure and the hydrogen concentration at each temperature.

As described above, in the present embodiment, the preliminary processing creates an estimation equation with the metal temperature and the hydrogen pressure as parameters, as shown in equation (1), for hydrogen absorption and hydrogen release. Also, as described above, in this embodiment, there may be a plurality of estimation formulas.

Next, the process of estimating the hydrogen storage rate of the hydrogen storage alloy in the hydrogen storage alloy tank 11 will be described.

FIG. 7 is a flowchart of a hydrogen storage rate estimation process in the hydrogen storage rate estimation system 1 according to the first embodiment of the present invention. As described above, an estimation formula is created using the metal temperature and the hydrogen pressure as parameters in each of hydrogen absorption and hydrogen release by preprocessing, and this estimation formula is stored in the storage unit 17 . Also, the reference hydrogen concentrations x1 and x2 are stored in the storage unit 17 . Also, FIG. 8 is an explanatory diagram of the process when there are a plurality of estimation formulas. In the example of FIG. 8, there are two approximation lines N1 and N2 as approximation lines showing the relationship between hydrogen pressure and hydrogen concentration at a given temperature. In this case, two estimation formulas are calculated from the two approximation lines N1 and N2, and the storage unit 17 stores the two estimation formulas.

(Step S<b>301 ) The calculation unit 16 acquires the metal temperature T and the hydrogen pressure P from the detection value of the temperature sensor 14 and the detection value of the pressure sensor 15 .

(Step S302) The calculation unit 16 calls from the storage unit 17 an estimation formula using the metal temperature and the hydrogen pressure as parameters, and the reference hydrogen concentrations x1 and x2.

(Step S303) The calculation unit 16 determines whether or not there are a plurality of estimation formulas using the metal temperature and the hydrogen pressure as parameters. If there are not a plurality of estimation formulas (step S303: No), the process proceeds to step S304. If there are a plurality of estimation formulas (step S303: Yes), the process proceeds to step S305.

(Step S304) The calculation unit 16 substitutes the metal temperature T and the hydrogen pressure P into an estimation formula having the metal temperature and the hydrogen pressure as parameters, calculates the hydrogen concentration x, and advances the process to step S307.

(Step S305) The calculation unit 16 substitutes the metal temperature T and the hydrogen pressure P into N estimation formulas having the metal temperature and the hydrogen pressure as parameters, calculates the N hydrogen concentrations xn, and proceeds to step S305. Proceed to S306.

(Step S306) The calculation unit 16 determines the minimum hydrogen concentration xmin among the obtained N hydrogen concentrations xn, and sets the minimum hydrogen concentration xmin as the hydrogen concentration x. That is, as shown in FIG. 8, when there are two approximation lines N1 and N2, when the hydrogen pressure is smaller than p1, the hydrogen concentration obtained by the approximation line N1 is higher than the hydrogen concentration obtained by the approximation line N2. become smaller. Therefore, when the hydrogen pressure is lower than p1, if the minimum hydrogen concentration xmin is determined and the hydrogen concentration is selected, the hydrogen concentration obtained by the approximation line N1 is selected. When the hydrogen pressure exceeds p1, the hydrogen concentration obtained by the approximation line N2 becomes smaller than the hydrogen concentration obtained by the approximation line N1. Therefore, when the hydrogen pressure exceeds p1, if the minimum hydrogen concentration xmin is determined and the hydrogen concentration is selected, the hydrogen concentration determined by the approximation line N2 will be selected.

(Step S307) The calculation unit 16 converts the calculated hydrogen concentration x into a hydrogen storage rate y using the reference hydrogen concentrations x1 and x2. Conversion from the hydrogen concentration x to the hydrogen storage rate y can be performed by the above-described formula (2).

(Step S<b>308 ) The calculation unit 16 displays the obtained hydrogen storage rate on the display unit 18 .

As described above, the hydrogen storage rate estimation system 1 according to the first embodiment of the present invention can accurately estimate the hydrogen storage rate of a hydrogen storage alloy from the hydrogen pressure and the metal temperature. In addition, in the present embodiment, an estimation equation for hydrogen absorption and an estimation equation for hydrogen release are created, respectively, so estimation is possible even when the PCT diagram has a hysteresis characteristic. In this embodiment, the hydrogen storage rate can be estimated even for a temperature-dependent metal species, a metal species having a multi-step plateau region, or the like, and estimation is possible regardless of the metal species.

As an example, an example using a Ti-based alloy as the hydrogen storage alloy will be shown. The physical properties of this Ti-based alloy are as follows. The values below the molar heat capacity are estimated from the composition using the Neumann-Kopp rule. This alloy has two plateau regions.

Hydrogen filling rate per weight: 2 wt%
Molar heat capacity: 25.18 J/molK
Specific heat: 0.48J/gK
Thermal conductivity: 42.52W/mK

FIG. 9 shows observation data and approximate lines for hydrogen absorption. The metal temperatures T are 20°C (293°K), 30°C (303°K), and 60°C (333°K). Data are represented by squares, and observation data at 60°C are represented by triangles. The estimation formula is represented by formula (1) as described above. In the case of hydrogen absorption, the following formula (3) was used as an estimation formula.

x= (3.7368 - 0.0035×T) × logP + (12.646 - 0.0428×T) (3)
F(T) = 3.7368 - 0.0035 x T
G(T) = 12.646 - 0.0428 x T

In the case of hydrogen absorption, the observation data at T=20° C., 30° C. and 60° C. are dispersed as shown in FIG.

In the case of T=20° C., the formula representing the approximation line is as follows, and the approximation line is indicated by A1.

x = 2.7108 x logP + 0.0992

In the case of T=30° C., the equation representing the approximation line is as follows, and the approximation line is indicated by A2.

x = 2.6758*logP - 0.3288

In the case of T=60° C., the formula representing the approximation line is as follows, and the approximation line is indicated by A3.

x = 2.5708*logP - 1.6128

FIG. 10 shows observed data and approximate lines for hydrogen release. The metal temperatures are 20°C, 30°C, and 60°C, and the observation data at 20°C is represented by diamonds, the observation data at 30°C is represented by squares, and the observation data at 60°C is represented by triangles. ing. In the case of hydrogen release, the PCT diagram becomes a multistage plateau, and there are two estimation equations for the first stage and the second stage. The first stage uses the following equation (4) as an estimation equation.

x= (6.2058 - 0.0106×T) × logP + (14.526 - 0.0466×T) (4)
F(T) = 6.2058 - 0.0106 x T
G(T) = 14.526 - 0.0466 x T

The second stage uses the following equation (5) as an estimation equation.

x = (2.1673 - 0.0018 x T) x logP + (9.4414 - 0.0291 x T) (5)
F(T) = 2.1673 - 0.0018 x T
G(T) = 9.4414 - 0.0291 x T

For hydrogen desorption, the observed data at T=20° C., 30° C. and 60° C. are spread out as shown in FIG.

In the first stage, when T=20° C., the equation representing the approximation line is as follows, and the approximation line is indicated by B1.

x = 3.0984 × logP + 0.8652

In the case of T=30° C., the equation representing the approximation line is as follows, and the approximation line is indicated by B2.

x = 2.9924 x logP + 0.3992

In the case of T=60° C., the equation representing the approximation line is as follows, and the approximation line is indicated by B3.

x = 2.6744 × logP - 0.9988

In the second row, when T=20° C., the equation representing the approximation line is as follows, and the approximation line is indicated by C1.

x = 1.6395 x logP + 0.9107

In the case of T=30° C., the equation representing the approximation line is as follows, and the approximation line is indicated by C2.

x = 1.6216 × logP + 0.6197

In the case of T=60° C., the equation representing the approximation line is as follows, and the approximation line is indicated by C3.

x=1.5676×logP-0.2533

All or part of the hydrogen storage rate estimation system 1 in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in this recording medium may be read into a computer system and executed. It should be noted that the "computer system" referred to here includes hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible discs, magneto-optical discs, ROMs and CD-ROMs, and storage devices such as hard discs incorporated in computer systems. Furthermore, "computer-readable recording medium" means a medium that dynamically retains a program for a short period of time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It may also include something that holds the program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in that case. Further, the program may be for realizing a part of the functions described above, or may be capable of realizing the functions described above in combination with a program already recorded in the computer system. It may be implemented using a programmable logic device such as FPGA.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design and the like are included within the scope of the gist of the present invention.

11: Hydrogen storage alloy tank, 12: Hydrogen generation/supply device, 13: Hydrogen consumption device, 14: Temperature sensor, 15: Pressure sensor, 16: Calculation unit, 17: Storage unit, 18: Display unit

Claims (4)

A hydrogen storage rate estimation system for estimating the hydrogen storage rate of a hydrogen storage alloy in a hydrogen storage alloy tank,
a temperature sensor for detecting the metal temperature of the hydrogen-absorbing alloy in the hydrogen-absorbing alloy tank;
a pressure sensor that detects the hydrogen pressure of the hydrogen storage alloy tank;
a storage unit that stores an estimation formula for determining the hydrogen concentration using the metal temperature and the hydrogen pressure as parameters;
Hydrogen concentration is calculated by the estimation formula from the metal temperature detection value from the temperature sensor and the hydrogen pressure detection value from the pressure sensor, and an estimated value of the hydrogen storage rate is output from the calculated hydrogen concentration. a computing unit ;
an analysis device;
with
The estimation formula is obtained by obtaining observation data by creating a PCT diagram using a specimen having the same composition as the hydrogen storage alloy of the hydrogen storage alloy tank by the analysis device, and obtaining at least two values from the observation data. It is calculated by creating an approximate line for each temperature by multiplication and stored in the storage unit,
When the approximation line is created by the analysis device, the deviation between the slope of the approximation line obtained up to the previous time and the slope of the continuous observation data is determined, and the slope of the approximation line obtained up to the previous time and the continuity A hydrogen storage rate estimation system in which a new approximation line is created if the deviation from the slope of the observation data obtained by the method is equal to or greater than a predetermined threshold. 2. The hydrogen storage rate estimation system according to claim 1, wherein the storage unit stores an estimation formula for hydrogen absorption and an estimation formula for hydrogen release. 2. The hydrogen storage rate estimation system according to claim 1, wherein when there are a plurality of estimation formulas, the calculation unit selects the hydrogen concentration that minimizes the calculation result to estimate the hydrogen storage rate. A hydrogen storage rate estimation method for estimating the hydrogen storage rate of a hydrogen storage alloy in a hydrogen storage alloy tank, comprising:
a step of calculating in advance an estimation formula for determining the hydrogen concentration using a test piece having the same composition as the hydrogen storage alloy of the hydrogen storage alloy tank and using the metal temperature and the hydrogen pressure as parameters;
a step of storing the estimation formula;
a step of detecting the metal temperature of the hydrogen-absorbing alloy in the hydrogen-absorbing alloy tank and the hydrogen pressure in the hydrogen-absorbing alloy tank;
From the detected value of the metal temperature of the hydrogen-absorbing alloy in the hydrogen-absorbing alloy tank and the detected value of the hydrogen pressure in the hydrogen-absorbing alloy tank, the hydrogen concentration is calculated by the estimation formula, and the calculated hydrogen concentration is used to store hydrogen. and outputting an estimate of the rate;
In the step of calculating the estimation formula, an analysis device external to the hydrogen storage rate estimation system uses a test specimen having the same composition as the hydrogen storage alloy of the hydrogen storage alloy tank, and observation data is obtained by creating a PCT diagram. Obtained and calculated by creating an approximate line for each temperature by the least squares method from the observation data;
When the approximation line is created by the analysis device, the deviation between the slope of the approximation line obtained up to the previous time and the slope of the continuous observation data is determined, and the slope of the approximation line obtained up to the previous time and the continuity A method for estimating the hydrogen storage rate, comprising creating a new approximation line if the deviation from the slope of the observed data that

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