KR101739045B1 - On-board cold thermal energy storage system for hydrogen fueling process - Google Patents

Abstract

According to an embodiment of the present invention, there is provided a high-voltage energy recovery apparatus for a fuel cell hydrogen supply system, comprising: a hydrogen tank for storing hydrogen; An inflator for generating a power by discharging the hydrogen discharged from the hydrogen tank by a single thermal expansion, and discharging hydrogen that is thermally expanded; A fuel cell to which hydrogen discharged from the inflator is supplied; And a heat exchanger disposed in a second path between the inflator and the fuel cell for cooling hydrogen on the first path and for heating hydrogen on the second path, A high-pressure energy recovery device for a fuel cell hydrogen supply system comprising:

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-energy energy recovery system for a hydrogen fuel cell system,

The present invention relates to a hydrogen fuel cell system, and more particularly, to a high-pressure energy recovery system for hydrogen in a hydrogen fuel cell system capable of improving energy efficiency by recovering high-pressure energy of high-pressure hydrogen stored in a hydrogen tank .

Hydrogen fuel cell vehicles are being actively studied as one of the future eco-friendly automobiles. A hydrogen fuel cell vehicle uses a principle in which a fuel cell, which uses a chemical reaction between hydrogen and oxygen, drives an electric motor to move an automobile and generates electricity when hydrogen and oxygen (air) are supplied to the fuel cell.

In this regard, FIG. 1 is a block diagram of a hydrogen supply system of a conventional fuel cell, and shows a process of supplying hydrogen to the fuel cell. The hydrogen tank 1 is charged with hydrogen at a high pressure (for example, 35 MPa) at a place such as a hydrogen charging station, and the hydrogen tank 1 supplies the charged hydrogen to the regulator 3 constantly. The regulator 3 reduces the pressure of hydrogen to a low pressure (for example, 1 MPa) and supplies it to the fuel cell 5.

In the recent hydrogen fuel cell system, in order to increase the charging amount of the hydrogen tank 1, the pressure is increased to a higher pressure than the conventional one, for example, up to 70 MPa. However, since the pressure of the hydrogen tank 1 is rapidly increased when the hydrogen is rapidly charged, the temperature rises and sometimes the temperature of the hydrogen tank 1 becomes higher than the temperature defined by the ISO safety code (for example, 85 degrees Celsius) have. In order to solve this problem, a chiller for preventing the temperature rise of the tank has been conventionally used. That is, the hydrogen to be charged is cooled in advance by the chiller (for example, to -20 degrees Celsius) and then charged to the hydrogen tank 1, which causes power consumption due to the use of the chiller.

In addition, since the high-pressure hydrogen discharged from the hydrogen tank 1 filled with the high pressure is conventionally reduced by using the regulator 3, the high-pressure energy is not appropriately utilized and wasted.

Patent Document 1: Korean Patent No. 10-1281011 (issued on July 8, 2013)

According to an embodiment of the present invention, there is provided a high-pressure energy recovery system for hydrogen in a hydrogen fuel cell system capable of improving energy efficiency by recovering high-pressure energy of hydrogen stored in a hydrogen tank of a fuel cell system.

According to an embodiment of the present invention, there is no need to use a chiller to charge hydrogen in a fuel cell system. Therefore, in a hydrogen fuel cell system capable of reducing power consumption and further improving energy efficiency as a result of using a chiller, Energy recovery system.

According to an embodiment of the present invention, there is provided a high-voltage energy recovery apparatus for a fuel cell hydrogen supply system, comprising: a hydrogen tank for storing hydrogen; An inflator for generating a power by discharging the hydrogen discharged from the hydrogen tank by a single thermal expansion, and discharging hydrogen that is thermally expanded; A fuel cell to which hydrogen discharged from the inflator is supplied; And a heat exchanger disposed in a second path between the inflator and the fuel cell for cooling hydrogen on the first path and for heating hydrogen on the second path, And a high voltage energy recovery device for a fuel cell hydrogen supply system.

According to an embodiment of the present invention, there is provided a method of recovering high-pressure energy of a fuel cell hydrogen supply system, comprising: charging hydrogen into a hydrogen tank; Expanding the hydrogen discharged from the hydrogen tank to generate power; And supplying the adiabatically expanded hydrogen to the fuel cell, wherein heat exchange is performed between a first path through which the hydrogen to be charged is supplied to the hydrogen tank and a second path through which the adiabatically and expanded hydrogen is supplied to the fuel cell A high pressure energy recovery method of a fuel cell hydrogen supply system is provided, wherein the heat exchanger cools the hydrogen on the first path and heats the hydrogen on the second path.

According to an embodiment of the present invention, energy efficiency can be improved by recovering the high-pressure energy of hydrogen stored in the hydrogen tank of the fuel cell system. As an example, high pressure energy of hydrogen can be recovered by using an inflator instead of a conventional regulator for hydrogen depressurization, thereby providing a fuel efficiency improvement of about 2 to 4% on the basis of the calorific value of hydrogen.

According to an embodiment of the present invention, since the hydrogen to be charged is cooled using a heat exchanger, there is no need to use a chiller when charging hydrogen, thereby reducing power consumption of about 1 to 2% It is effective.

1 is a block diagram of a hydrogen supply system of a fuel cell according to the prior art;
2 is a view for explaining a high-pressure energy recovery device of a fuel cell hydrogen supply system according to an embodiment of the present invention,
3 is a view for explaining an exemplary configuration of a heat exchanger according to an embodiment,
4 is a view for explaining a temperature change of hydrogen and a phase change material during hydrogen charging,
5 is a view for explaining the temperature change of the hydrogen and the phase-change material at the time of supplying hydrogen to the fuel cell,
FIG. 6 is a graph for explaining the hydrogen temperature change according to the pressure of the hydrogen tank and the inflator efficiency in one embodiment,
Figure 7 is a graph illustrating the expansion power and cooling capacity of hydrogen according to the inflator efficiency in one embodiment,
8 is a view for explaining the characteristics of the phase change material used in one embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, and advantages of the present invention will become more readily apparent from the following description of preferred embodiments with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In this specification, when an element is referred to as being "above" (or "below", "right", or "left") another element, ) Or it may mean that a third component may be interposed therebetween. Also, in the figures, numerical values such as length, width, thickness, etc. of the components are exaggerated for an effective explanation of the technical content.

Also, in this specification, expressions such as 'upper', 'lower (lower)', 'left', 'right', 'front', 'rear' And it is a relative expression used for convenience of explanation based on the drawings when describing the present invention with reference to the respective drawings.

Where the terms first, second, etc. are used herein to describe components, these components should not be limited by such terms. These terms have only been used to distinguish one component from another. The embodiments described and exemplified herein also include their complementary embodiments.

In the present specification, the singular form includes plural forms unless otherwise specified in the specification. The terms "comprise" and / or "comprising" used in the specification do not exclude the presence or addition of one or more other elements.

Hereinafter, the present invention will be described in detail with reference to the drawings. Various specific details are set forth in the following description of specific embodiments in order to provide a more detailed description of the invention and to aid in understanding the invention. However, it will be appreciated by those skilled in the art that the present invention may be understood by those skilled in the art without departing from such specific details. In some cases, it is noted that parts of the invention that are not commonly known in the art and are not largely related to the invention are not described in order to avoid confusion in describing the invention.

2 is a view for explaining a high-pressure energy recovery device of a fuel cell hydrogen supply system according to an embodiment of the present invention. The high-pressure energy recovery device of the fuel cell hydrogen supply system according to the illustrated embodiment is assumed to be mounted on, for example, a fuel cell vehicle. However, the high-voltage energy recovery device according to the present invention is not limited to the automobile field, and may be applied to various fields where a fuel cell hydrogen supply system is installed.

2, the high pressure energy recovery device of the illustrated fuel cell hydrogen supply system may include a heat exchanger 10, a hydrogen tank 20, an inflator 30, and a fuel cell 40.

The hydrogen tank 20 is a container for storing hydrogen to be charged via the heat exchanger 10 from outside. In a preferred embodiment, the hydrogen tank stores high pressure hydrogen. For example, in the case of a fuel cell vehicle, hydrogen can be stored at a pressure of about 35 to 70 MPa.

The hydrogen stored in the hydrogen tank 20 is supplied to the inflator 30. The high-pressure hydrogen discharged from the hydrogen tank 20 is thermally expanded in the inflator 30 to generate power. The structure of the inflator that generates power from high pressure hydrogen may vary depending on the embodiment. For example, in one embodiment, the high pressure hydrogen introduced into the inflator 30 may expand to generate power by driving the turbine or piston. At this time, since the high-pressure hydrogen expands in a single thermal expansion in the inflator 30, the hydrogen expands and the pressure drops and the temperature also falls. The hydrogen whose pressure and temperature have been lowered through the expander 30 is supplied to the fuel cell 40 via the heat exchanger 10.

The heat exchanger 10 is disposed in a first path through which hydrogen is externally supplied to the hydrogen tank 20 and a second path between the inflator 30 and the fuel cell 40 to cool the hydrogen on the first path, The hydrogen on the second path can be heated. That is, when hydrogen is charged in the fuel cell vehicle, hydrogen supplied from the outside flows into the hydrogen tank 20 through the heat exchanger 10. At this time, while passing through the heat exchanger 10, And is supplied to the tank 20. Also, when hydrogen is supplied to the fuel cell 40 to drive the fuel cell vehicle, the hydrogen discharged from the expander 30 passes through the heat exchanger 10 and is supplied to the fuel cell 40 after the temperature rises.

In one embodiment, the heat exchanger 10 may include a thermal energy storage (TES) that stores thermal energy of hydrogen. For example, the heat exchanger 10 may comprise a PCM reservoir containing a phase change material (PCM), and the hydrogen passing through the heat exchanger 10 may exchange thermal energy in contact with the PCM. For example, the low-temperature hydrogen discharged from the inflator 30 receives heat energy from the PCM while passing through the heat exchanger 10, so that the hydrogen temperature rises and hydrogen injected from the outside for passing the hydrogen passes through the heat exchanger 10 While the PCM absorbs thermal energy from the hydrogen, the hydrogen temperature is lowered and then supplied to the hydrogen tank 20.

Taking a specific temperature as an example, the hydrogen temperature (T1) flowing from the outside at the time of charging the hydrogen may be approximately equal to the outside air temperature, for example, 20 degrees Celsius. The hydrogen to be charged is charged to the hydrogen tank 20 while the temperature is lowered to -20 degrees Celsius (T2 = -20 degrees), for example, through the heat exchanger 10. The heat exchanger 10 includes a liquid phase-to-solid phase change material (PCM) at, for example, -25 degrees centigrade, and the temperature of the heat exchanger 10 during the descent of hydrogen from 20 degrees Celsius to- The PCM absorbs energy from hydrogen and transforms from solid to liquid.

The hydrogen tank 20 can charge hydrogen at a high pressure of about 70 MPa. Since the hydrogen temperature naturally rises in such a high-pressure charging process, for example, the temperature T3 of the charged hydrogen is about 50 to 60 degrees, P3) can be assumed to be approximately 70 MPa. High pressure hydrogen of the hydrogen tank 20 is then supplied to the inflator 30 to generate power. The temperature and the pressure decrease while the hydrogen expands in the inflator 30 and the temperature T4 of the hydrogen discharged from the inflator 30 is -70 degrees Celsius and the pressure P4 is 1 MPa, for example. Thereafter, the discharged hydrogen passes through the heat exchanger 10, and the temperature T5 can be increased to about -30 degrees and supplied to the fuel cell 40. At this time, the PCM of the heat exchanger 10 may be phase-changed from liquid to solid while transferring thermal energy to hydrogen.

The temperature and pressure values described above are exemplary values for facilitating understanding, and it goes without saying that the temperature and pressure of hydrogen, the temperature (Ts) of the phase change material and the like may be changed according to a specific embodiment. For example, the temperature and pressure of the hydrogen as shown in the above examples depend on the temperature of the outside air during the hydrogen charging, the charging time and pressure of the hydrogen tank 20, the type of the phase change material (PCM) and the phase change temperature, the efficiency of the inflator 30, And the like can be changed.

3 is a view for explaining an exemplary configuration of a heat exchanger according to an embodiment. The heat exchanger 10 according to the illustrated embodiment may include a heat exchanger case 11 and a PCM storage unit 13.

The PCM storage unit 13 is a storage unit filled with a phase change material (PCM). A phase change material (PCM) is a latent heat material, a heat accumulating material, or a material capable of controlling heat, capable of absorbing or releasing heat while changing from a solid to a liquid, a liquid to a gas, And has a temperature control function for storing and releasing the surrounding heat. The PCM includes, for example, a mixture of an organic compound of a hydrocarbon, a higher fatty acid series, an inorganic hydrate salt, and a mixture of two or more organic compounds and / or an inorganic compound.

In the present invention, the PCM used in the heat exchanger 10 is not limited to any particular component or kind. In one embodiment, considering the temperature of the hydrogen charged in the hydrogen tank 20 and the temperature of the hydrogen supplied to the fuel cell 40, the phase change material PCM may be between -30 and -20 degrees Celsius It is preferable to have a melting point.

The heat exchanger case 11 surrounds the PCM storage part 13 and has an internal space through which hydrogen can pass so that hydrogen can exchange heat with the PCM storage part 13.

In the illustrated embodiment, the case 11 includes an inlet pipe 15 forming a path for supplying hydrogen from the outside into the case 11 for charging, a path for discharging hydrogen from the case 11 to the hydrogen tank 20, An inflow pipe 17 forming a path for introducing hydrogen into the case 11 from the inflator 30 and an inflow pipe 17 for forming a path for discharging hydrogen to the fuel cell 40, (18). In addition, the inlet pipes 15 and 17 may include open / close valves 55 and 57 in an arbitrary path, respectively, and the outlet pipes 16 and 18 may also include open / close valves 56 and 58 .

In this configuration, for example, when hydrogen is charged in the hydrogen tank 20, the valves 55 and 56 are opened and the valves 57 and 58 are closed, so that hydrogen supplied from the outside is discharged from the heat exchanger 10 And can be charged into the hydrogen tank 20 after the temperature is lowered. When hydrogen is supplied to the fuel cell 40, the hydrogen discharged from the inflator 30 by the valves 55 and 56 is closed and the valves 57 and 58 are opened by the heat exchanger 10 Fuel cell 40, as shown in FIG.

Fig. 4 is a diagram for explaining the temperature change of the hydrogen and the phase change material at the time of filling with hydrogen, and schematically shows the temperature change of the hydrogen and the phase change material (PCM) when the hydrogen tank 20 is charged with hydrogen.

In the figure, the temperature is T1 when hydrogen flows into the heat exchanger 10 through the inlet pipe 15, T2 is the temperature of hydrogen discharged from the outlet pipe 16 after passing through the heat exchanger 10, (PCM) is assumed to be Ts. Hydrogen enters the heat exchanger 10, contacts the PCM, and undergoes heat exchange, causing the temperature to drop from T1 to T2. In this case, the PCM absorbs thermal energy from the hydrogen and changes phase from solid to liquid, and can keep the temperature (Ts) constant during this phase change.

In an exemplary embodiment, a material having a phase change temperature between about -30 degrees Celsius and about -20 degrees Celsius may be used as the PCM. In this case, for example, the temperature T1 of the hydrogen flowing into the heat exchanger 10 is 20 degrees, and the temperature of the hydrogen is lowered to -20 degrees by the heat exchange in the heat exchanger 10, have. However, it should be understood that the hydrogen temperature and the PCM temperature are exemplary and may vary depending on the embodiment.

5 is a diagram for explaining a temperature change of hydrogen and a phase change material at the time of supplying hydrogen to the fuel cell, and schematically shows a temperature change of hydrogen and PCM when supplying hydrogen to the fuel cell 40. Fig.

The temperature is T4 when the hydrogen flows into the heat exchanger 10 through the inlet pipe 17 and the temperature of the hydrogen discharged to the outlet pipe 18 after passing through the heat exchanger 10 is T5 and the temperature of the PCM Is assumed to be Ts. Hydrogen enters the heat exchanger 10 and contacts the PCM and undergoes heat exchange to raise the temperature from T4 to T5. In this case, the PCM emits thermal energy to hydrogen so that the PCM phase changes from liquid to solid and the temperature (Ts) during this phase change can be kept constant.

In an exemplary embodiment, when a material with a phase change temperature between about -30 and -20 degrees Celsius is used as the PCM, the temperature T4 of hydrogen entering the heat exchanger 10 from the inflator 30 is -70 degrees and can be supplied to the hydrogen tank 20 after the temperature of the hydrogen is increased to -30 degrees by heat exchange in the heat exchanger 10. The hydrogen temperature and the PCM temperature are also illustrative and may vary depending on the embodiment.

On the other hand, when the high-pressure hydrogen expands in the inflator 30 to generate power, the temperature of the hydrogen decreases as the hydrogen adiabatically expands. At this time, the lowering temperature becomes lower than the efficiency of the inflator 30 and the pressure of the hydrogen tank 20 ≪ / RTI > In this regard, Figure 6 illustrates the hydrogen temperature change according to the inflator efficiency and the pressure of the hydrogen tank, according to one embodiment.

6, the horizontal axis represents the pressure of hydrogen discharged from the hydrogen tank 20 as the pressure of the hydrogen tank 20 and supplied to the inflator 30, and the vertical axis represents the temperature of the hydrogen expanded by the thermal expansion in the inflator 30 . In FIG. 6, the efficiency of the inflator 30 is plotted with different colors. For example, if the inflator efficiency is 1.0 and the first minority temperature is 20 degrees Celsius, the descent of the hydrogen temperature relative to the pressure of the hydrogen follows the black graph at the bottom, for example when the hydrogen pressure is in the range of 70 MPa to 1 MPa A temperature drop of approximately 201.6 degrees occurs. As can be seen from the figure, the smaller the efficiency of the inflator, the smaller the degree of decrease in the hydrogen temperature due to the thermal expansion. Also, at any given expander efficiency, the smaller the initial hydrogen pressure (i.e., the pressure of the hydrogen tank), the smaller the extent to which the hydrogen temperature falls.

7 is a graph for explaining expansion force and cooling capacity of hydrogen according to inflator efficiency in one embodiment. In FIG. 7, the horizontal axis represents the inflator efficiency and the vertical axis represents the expansion work and cooling capacity.

It is useful to calculate the average value of the expanded hydrogen because the expansion force and the cooling capacity of the expanding hydrogen decrease as the hydrogen pressure in the hydrogen tank drops from 70 MPa to 1 MPa. Conventionally, a chiller has been used to pre-cool hydrogen when filling the hydrogen tank 20 with hydrogen at a hydrogen filling station. In an embodiment of the present invention, by using the heat exchanger 10 and the inflator 30 The need for chillers can be eliminated. For example, the minimum cooling requirement for cooling from 20 to -20 degrees Celsius at 70 MPa is approximately 600.7 KJ / Kg, neglecting the loss of the thermal energy storage system of the heat exchanger 10. Referring to FIG. 7, if the inflator efficiency is greater than 0.53, this minimum cooling requirement can be met and if the inflator efficiency is 0.53, the inflation power is 1671.3 KJ / Kg.

Of course, in an embodiment of the present invention, even if the inflator efficiency is less than 0.53, it may contribute to reducing energy consumption by reducing the amount of chiller used. That is, by monitoring the change in the hydrogen temperature in the heat exchanger 10 and selectively using the chiller as needed, there is an advantage in that the energy consumption is reduced as compared with the conventional use of the chiller continuously.

8 is a view for explaining the characteristics of the phase change material used in one embodiment.

In one embodiment of the present invention, SavENRGTM PCM-HS26N product from RGEES can be used as a phase change material (PCM). This material is composed of a mixture of inorganic flame and has the characteristics shown in Fig. 8 (see "PCM properties" in Fig. 8).

In the case of using this PCM-HS26N, as shown in the item "Hydrogen storage" in FIG. 8, in order to satisfy the cooling requirement for 100 liters of hydrogen of 70 MPa, the volume of approximately 9.7 liters and 11.6 kg Weight PCM-HS26N should be stored.

As described above, although the present invention has been described with reference to the limited embodiments and drawings, the present invention is not limited to the above embodiments. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention as defined by the appended claims. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

10: Heat exchanger
20: Hydrogen tank
30: inflator
40: Fuel cell

Claims (12)

A high pressure energy recovery device for a fuel cell hydrogen supply system,
A hydrogen tank for storing hydrogen;
An inflator for generating a power by discharging the hydrogen discharged from the hydrogen tank by a single thermal expansion, and discharging hydrogen that is thermally expanded;
A fuel cell to which hydrogen discharged from the inflator is supplied; And
A heat exchanger,
A first path for supplying hydrogen from the outside to the hydrogen tank and a second path between the inflator and the fuel cell are both passed through the heat exchanger so that the hydrogen on the first path is cooled by the heat exchanger, Wherein the heat exchange between the first path and the second path is made in the heat exchanger by heating the hydrogen on the second path. The method according to claim 1,
Characterized in that the heat exchanger comprises a thermal energy storage (TES) for storing thermal energy of hydrogen. The heat exchanger according to claim 1,
A PCM storage comprising a phase change material (PCM); And
And a case in which hydrogen on the first path or the second path provides a space for heat exchange with the PCM storage unit. The heat exchanger according to claim 3,
A first valve (55) for opening and closing a path through which hydrogen is supplied from outside to the case in the first path;
A second valve (56) for opening and closing a path through which hydrogen is discharged to the hydrogen tank in the first path;
A third valve (57) for opening and closing a path through which hydrogen is supplied from the inflator to the case in the second path; And
And a fourth valve (58) for opening and closing a path through which hydrogen is discharged to the fuel cell in the second path. The method of claim 3,
Wherein the phase change material (PCM) is a material having a melting point between -30 and -20 degrees Celsius. The method of claim 3,
Characterized in that the phase change material (PCM) is a mixture of inorganic flames. A method of recovering high-pressure energy in a fuel cell hydrogen supply system,
Filling the hydrogen tank with hydrogen;
Thermally expanding hydrogen discharged from the hydrogen tank to generate power; And
And supplying the thermally expanded hydrogen to the fuel cell,
A heat exchanger is disposed between a first path through which hydrogen to be charged is supplied to the hydrogen tank and a second path through which the hydrogen is supplied to the fuel cell,
Wherein during the step of charging the hydrogen, the hydrogen on the first path is cooled by the heat exchanger, and the step of supplying the thermally expanded hydrogen to the fuel cell is performed by the heat exchanger, Wherein heat exchange between the first path and the second path is made in the heat exchanger by heating the first path and the second path. 8. The method of claim 7,
Wherein the heat exchanger comprises a thermal energy storage (TES) for storing thermal energy of hydrogen. 8. The heat exchanger according to claim 7,
A PCM storage comprising a phase change material (PCM); And
And a case for providing a space where hydrogen on the first path or the second path is heat-exchanged with the PCM storage part. 10. The heat exchanger according to claim 9,
When the hydrogen is charged into the hydrogen tank, opening the first path and closing the second path,
And when the thermally expanded hydrogen is supplied to the fuel cell, closing the first path and opening the second path. 10. The method of claim 9,
Wherein the phase change material (PCM) is a material having a melting point between -30 and -20 degrees centigrade. 10. The method of claim 9,
Wherein the phase change material (PCM) is a mixture of inorganic flames.

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