Method for estimating remaining amount in hydrogen storage tank

Abstract

To enhance accuracy in estimating a remaining amount of hydrogen in a tank that stores hydrogen by means of a hydrogen storage alloy.MEANS: A method for estimating a remaining amount in a hydrogen storage tank that stores hydrogen by means of a hydrogen storage alloy, comprises the steps of: detecting a hydrogen pressure in the hydrogen storage tank; determining whether an amount of change in the hydrogen pressure is above or below a threshold value; a reading a hydrogen storage amount on the basis of a plateau area in PCT characteristics of the hydrogen storage alloy when the amount of change is above or below the threshold value; and calculating a remaining amount of hydrogen from the read hydrogen storage amount.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a method for estimating the remaining hydrogen amount in a tank that stores hydrogen using a hydrogen storage alloy.

Background Art

[0002] Patent Document 1 discloses a method for detecting the remaining amount of a hydrogen storage tank that calculates the remaining hydrogen amount from the hydrogen consumption amount.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, there are problems such as hydrogen leakage during the use of the hydrogen storage tank, hydrogen diffusion due to hydrogen permeating through the tank, and a decrease in the hydrogen storage capacity due to deterioration of the hydrogen storage alloy. Therefore, errors in the remaining hydrogen amount are likely to occur in the detection based on the hydrogen consumption amount.

[0005] In view of the above problems, an object of the present disclosure is to improve the estimation accuracy of the remaining hydrogen amount in a tank that stores hydrogen using a hydrogen storage alloy.

Means for Solving the Problems

[0006] The present application discloses a method for estimating the remaining amount of a hydrogen storage tank that stores hydrogen using a hydrogen storage alloy, the method comprising: a process of detecting the hydrogen pressure in the hydrogen storage tank; a process of determining whether the change amount of the hydrogen pressure exceeds or falls below a threshold value; a process of reading the hydrogen storage amount based on the plateau region in the PCT characteristics of the hydrogen storage alloy when the change amount exceeds or falls below the threshold value; and a process of calculating the remaining hydrogen amount from the read hydrogen storage amount.

[0007] Here, the "PCT characteristic" refers to the characteristic in which the hydrogen storage amount (C) in the hydrogen storage alloy changes depending on the hydrogen pressure (P) and temperature (T). Also, as the overall hydrogen storage amount increases, the hydrogen pressure increases, but there is a region where the hydrogen pressure does not increase despite the increase in the hydrogen storage amount in a predetermined region, and this is the "plateau region".

[0008] The hydrogen storage alloy may be configured to have three or more plateau regions by combining materials having a plurality of characteristics.

[0009] The determination of whether the change amount exceeds or falls below the threshold value may be made based on a plurality of hydrogen pressure measurement values in a certain period immediately before.

Advantages of the Invention

[0010] According to the present disclosure, by estimating the remaining hydrogen amount using the PCT characteristic of the hydrogen storage alloy, errors can be suppressed and the accuracy of estimating the remaining hydrogen amount can be improved.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0012] 1. Hydrogen Storage Tank FIG. 1 shows a conceptual diagram of a hydrogen storage tank 10 used in a method for estimating the remaining amount of a hydrogen storage tank. As shown in FIG. 1, in the hydrogen storage tank 10, a hydrogen storage alloy 12 is stored in a container 11, and a pipe 13 for supplying hydrogen to the hydrogen storage alloy 12 and extracting hydrogen from the hydrogen storage alloy 12 is provided. The pipe 13 is equipped with an on-off valve 14, and is configured to be able to switch the permission and regulation of the supply of hydrogen into the container 11 and the extraction of hydrogen from the container 11. Further, a pressure gauge 15 and a thermometer 16 are arranged on the pipe 13 so as to be able to measure the hydrogen pressure and temperature in the hydrogen storage alloy 12.

[0013] Here, the specific material of the hydrogen storage alloy 12 is not particularly limited as long as it is a known material. For example, as types of hydrogen storage alloys, rare earth-based alloys, Laves phase alloys, titanium-based alloys, magnesium-based alloys, etc. can be mentioned. Further, the shape of the container 11 is typically cylindrical, but it is not necessarily cylindrical, and the shape can be determined as necessary as long as the pressure requirements such as a housing or a saddle shape are satisfied.

[0014] 2. Method for Estimating the Remaining Amount of a Hydrogen Storage Tank FIG. 2 shows the flow of a method S10 for estimating the remaining amount of a hydrogen storage tank according to one embodiment. As can be seen from FIG. 2, the method S10 for estimating the remaining amount of a hydrogen storage tank includes processes S11 to S16. Each process will be described below. Note that, as will be described later, processes S11 to S16 are repeatedly and continuously performed in a state where the closed state of the on-off valve 14 continues in process S11.

[0015] 2.1. Process S11 for Confirming the Closed State of the Valve In process S11, it is confirmed that the on-off valve 14 is in the closed state. Since the method S10 for estimating the remaining amount of the hydrogen storage tank of this embodiment is performed in a state where there is no entry or exit of hydrogen to the hydrogen storage tank 10, it is confirmed that the on-off valve 14 is in the closed state. If the on-off valve 14 is in the open state, the method S10 for estimating the remaining amount of the hydrogen storage tank is terminated as No. If the on-off valve 14 is in the closed state, proceed to process S12 with Yes.

[0016] 2.2. Process S12 of pressure measurement In process S12, the hydrogen pressure in the container 11 (hydrogen storage alloy 12) is obtained. The measurement of the hydrogen pressure can be obtained by the pressure gauge 15. Also, at this time, the temperature inside the container 11 may be obtained by the thermometer 16.

[0017] 2.3. Process S13 of calculating the hydrogen pressure change amount In process S13, the hydrogen pressure change amount is calculated. The change amount only needs to be able to obtain how much the hydrogen pressure obtained in process S12 has changed compared to just before, and is not particularly limited. However, since it is determined in the next process S14 whether the change amount exceeds or is below the threshold value, in process S13, it is set to a value that can be used in process S14. Specific examples can include the following (1) to (3) for example. Also, in order to improve the estimation accuracy, two or more determination methods may be switched or combined. In addition, in order to capture more geometric features of the hydrogen pressure change, the hydrogen pressure change amount may be reinterpreted as the change amount of the hydrogen pressure change amount. (1) The value of the slope (differentiated by elapsed time) of the change between the hydrogen pressure obtained in process S12 and the hydrogen pressure obtained just before it. (2) The deviation when the hydrogen pressure obtained in the most recent 5 minutes is used as the parameter. However, this "5 minutes" is not a value limited to this, and can be set appropriately to an appropriate time. (3) The ratio of the deviation when the hydrogen pressure obtained in the most recent 5 minutes is used as the parameter to the hydrogen pressure difference between two plateau regions determined by the PCT characteristics of the hydrogen storage alloy obtained in advance. However, this "5 minutes" is not a value limited to this, and can be set appropriately to an appropriate time. Note that, as described above, in process S11, when the on-off valve 14 is opened, the hydrogen storage tank remaining amount estimation method S10 ends once. However, after that, when the on-off valve 14 is closed, the hydrogen storage tank remaining amount estimation method S10 is performed again. For the hydrogen pressure data of the "hydrogen pressure obtained immediately before" in (1) above and the "hydrogen pressure obtained in the most recent 5 minutes" in (2) and (3), the hydrogen pressure data obtained in the previous hydrogen storage tank remaining amount estimation method S10 can be used. Thereby, it is possible to continuously grasp the change in the occluded hydrogen amount and obtain an appropriate hydrogen amount estimation value.

[0018] 2.4. Process S14 for determining whether it exceeds (or falls below) the threshold value In process S14, it is determined whether the hydrogen pressure change amount calculated in process S13 exceeds or falls below the threshold value. The specific form of the threshold value is not particularly limited, but corresponding to the examples (1) to (3) of the change amount shown in process S13, for example, the following threshold values can be set. Corresponding to (1) above, the value at which the slope (differentiated by elapsed time) of the hydrogen pressure change amount obtained in process S13 becomes -1. However, the value of "-1" is an example and an appropriate value can be applied as needed. Corresponding to (2) above, the value at which the obtained deviation becomes a constant multiple of the standard deviation. Corresponding to (3) above, the value at which the obtained ratio becomes 50%. However, the 50% is an example and an appropriate value can be applied as needed.

[0019] If it is below (or above) the threshold value in process S14, it is set to No, and the processes are repeated by returning to process S11. If it exceeds (or falls below) the threshold value in process S14, it is set to Yes and the process proceeds to process S15.

[0020] 2.5. Process S15 for reading the hydrogen occlusion amount In process S15, the hydrogen occlusion amount is read from the hydrogen pressure obtained in process S12. In this embodiment, it is specifically performed as follows. Even if the hydrogen storage alloy is pulverized or there are changes in the hydrogen storage performance, the plateau region due to hydrogen pressure and temperature during hydrogen absorption and desorption is less likely to be affected. Also, by combining materials with multiple characteristics, a hydrogen storage alloy having a plurality of plateau regions with different hydrogen pressures can be obtained. This disclosure uses the characteristics of these multiple plateau regions to stably estimate the remaining hydrogen amount regardless of the number of times the hydrogen storage alloy is used or the degree of pulverization of the hydrogen storage alloy. Here, as an example, the case where a hydrogen storage alloy has three plateau regions with different hydrogen pressures due to a combination of materials with multiple characteristics will be described. However, it is not necessary to have three plateau regions, and it is sufficient to have at least two. From the perspective of estimating the hydrogen storage amount with higher accuracy, it is preferable to have a larger number of plateau regions with different hydrogen pressures due to differences in the hydrogen storage amount.

[0021] FIG. 3 schematically shows PCT characteristics according to one example. In FIG. 3, the horizontal axis represents the hydrogen storage amount, and the vertical axis represents the hydrogen pressure. In the example shown in FIG. 3, due to a combination of materials with multiple characteristics, it has first to third plateau regions, and in each region, the pressures are P1, P2, and P3, respectively. In this exemplified hydrogen storage alloy, as the hydrogen storage amount decreases due to hydrogen desorption, a stable hydrogen pressure of P3 is maintained in the third plateau region. During this period, it can be seen that a hydrogen storage amount of C2 or more where the hydrogen pressure changes is ensured. Similarly, in the second plateau region, a stable hydrogen pressure of P2 is maintained, and a hydrogen storage amount is ensured between C1 and C2. In this way, although it is stepwise, the remaining hydrogen amount (hydrogen storage amount) can be obtained based on the measured value according to the hydrogen pressure in the actual container. In process S15, the hydrogen storage amount is read in this way based on the hydrogen pressure obtained in process S12 from the PCT characteristics.

[0022] 2.6. Process S16 for calculating the estimated remaining hydrogen amount In process S16, an estimated remaining hydrogen amount is calculated from the hydrogen storage amount read in process S15. Here, the hydrogen storage amount read in process S15 can be used as an estimated value of the remaining hydrogen amount. Even if there are temperature changes in the container and the internal hydrogen storage alloy due to the ambient environment or the like, there is no change in the relationship (the shape of the curve) of the PCT characteristics. Therefore, by utilizing this and grasping points C1, C2, etc. that constantly indicate the hydrogen storage amount, even if there are changes in the estimation conditions due to the external environment, diffusion during connection, permeability from the container, etc. during the usage period of the repeatedly usable container, the remaining hydrogen amount can be accurately grasped.

[0023] In addition, complementarily, a method for estimating the remaining hydrogen amount by integrating the conventionally used hydrogen consumption amount may be used in combination with the estimation method of the present disclosure.

[0024] After process S16, the process proceeds to S11, and each process is repeated.

Explanation of Reference Numerals

[0025] 10…Hydrogen storage tank, 11…Container, 12…Hydrogen storage alloy, 13…Pipe, 14…On-off valve, 15…Pressure gauge, 16…Thermometer

Claims

1. A method for estimating the remaining amount of a hydrogen storage tank that stores hydrogen using a hydrogen storage alloy, comprising: a process of detecting the hydrogen pressure in the hydrogen storage tank; a process of determining whether the change amount of the hydrogen pressure exceeds or falls below a threshold value; a process of reading the hydrogen storage amount based on the plateau region in the PCT characteristics of the hydrogen storage alloy when the change amount exceeds or falls below the threshold value; a process of calculating the remaining hydrogen amount from the read hydrogen storage amount, a method for estimating the remaining amount of a hydrogen storage tank.

2. The method for estimating the remaining amount of a hydrogen storage tank according to claim 1, wherein the hydrogen storage alloy comprises three or more of the plateau regions by a combination of materials having a plurality of characteristics.

3. The method for estimating the remaining amount of a hydrogen storage tank according to claim 1 or 2, wherein the determination of whether the change amount exceeds or falls below the threshold value is performed based on a plurality of hydrogen pressure measurement values in a certain period immediately before.

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