Process for filling hydrogen into a hydrogen storage tank in automobile

[0002] 1. Field of the Invention

[0003] The present invention relates to a process for filling hydrogen into a hydrogen storage tank in an automobile having a hydrogen engine or a fuel cell mounted thereon.

[0004] 2. Description of the Prior Art

[0005] When hydrogen is filled into an automobile hydrogen storage tank having a metal hydride in a hydrogen station. The hydrogen station has a hydrogen supply tank having a metal hydride with hydrogen absorbed therein. The metal hydride is heated with exothermic reaction of hydrogen absorption in the hydrogen storage tank. In a prior art process, cooling water is circulated into the hydrogen storage tank to cool the metal hydride, thereby providing an increase in the amount of hydrogen absorbed (for example, see Japanese Patent Application Laid-open No. 7-108909).

[0006] With the prior art process, however, the heated metal hydride is merely cooled and for this reason, the effective utilization of the generated quantity of heat is not controlled, which is not preferred for energy saving demand.

[0007] It is an object of the present invention to provide a hydrogen filling process of the above-described type of hydrogen tank, wherein the heat generated by the metal hydride in the hydrogen storage tank in the automobile can be effectively utilized in the hydrogen station for the heating of the metal hydride which is required to release hydrogen, thereby meeting the energy saving demand.

[0008] To achieve the above object, according to the present invention, there is provided a process for filling hydrogen into a hydrogen storage tank in an automobile, the hydrogen storage tank having a metal hydride. The hydrogen is supplied from a hydrogen station provided with a hydrogen supply tank having a metal hydride with hydrogen absorbed therein. The process comprises the steps of circulating a heat transfer medium between the hydrogen supply tank and the hydrogen storage tank. In the hydrogen storage tank, the metal hydride which is heated by exothermic reaction of hydrogen absorption, is cooled by the heat transfer medium. The heat transfer medium which has been raised in temperature by such cooling is then discharged into the hydrogen supply tank. In the hydrogen supply tank, the metal hydride is heated by the heat transfer medium to release hydrogen, and the heat transfer medium which is lowered in temperature by an exothermic reaction of the metal hydride, then flows toward the hydrogen storage tank.

[0009] If a technique as described above is employed, a predetermined heating source may be used to heat the metal hydride to release hydrogen only at the start of the filling in the hydrogen station. In the subsequent steady state, the quantity of heat generated by the heating of the metal hydride in the hydrogen storage tank can be utilized effectively to release hydrogen in the hydrogen station. On the other hand, the heat transfer medium which is lowered in temperature by the heat exchange in the hydrogen supply tank, is used for cooling of the metal hydride in the hydrogen storage tank and hence, any special cooling means for the heat transfer medium is not required.

[0010] FIG. 1 is an illustration showing one example of hydrogen being filled in a hydrogen storage tank of an automobile in a hydrogen stand.

[0011] FIG. 2 is a vertical sectional view of hydrogen supply tank or hydrogen storage tank.

[0012] FIG. 3 is a broken perspective view of an essential portion of an alloy unit.

[0013] FIG. 4 is an illustration showing a hydrogen filling system.

[0014] FIG. 5 is an illustration showing another example of hydrogen being filled in a hydrogen storage tank of an automobile in a hydrogen stand.

[0015] FIG. 6 is a sectional view taken along a line 6—6 in FIG. 5.

[0016] FIG. 7 is an illustration for explaining connected states of various portions in FIG. 5.

[0017] Referring to FIG. 1, a hydrogen station 1 includes a hydrogen supply tank 2 which has a metal hydride in which hydrogen has been absorbed. An automobile 3 includes a hydrogen storage tank 4 having a metal hydride, so that hydrogen released from the hydrogen supply tank 2 can be filled into the hydrogen storage tank 4 in the automobile 3 through a supply stand 5 and a main gas supply pipe 6 in the hydrogen station 1. In this embodiment, the hydrogen supply tank 2 in the hydrogen station 1 and the hydrogen storage tank 4 in the automobile 3 have the same structure. However, the volume of the hydrogen station 1 is larger than that of the hydrogen storage tank 4.

[0018] Referring to FIG. 2, the hydrogen supply tank 2 (and the hydrogen storage tank 4) includes an outer shell 7 made of a stainless steel, and an inner shell 8 made of a stainless steel and located within the outer shell 7. A space between the inner peripheral surface of the outer shell 7 and the outer peripheral surface of the inner shell 8 forms a passage 9 for pure water which functions as a heat transfer medium. The outer shell 7 has an inlet pipe 10 projectingly provided in one of end walls thereof, and an outlet pipe 11 projectingly provided in the other end wall. The interiors of pipes 10 and 11 communicate with the passage 9.

[0019] A hydrogen entrance and exit pipe 12 made of a stainless steel is air-tightly mounted in the end walls of the outer and inner shells 7 and 8 on the side of the inlet pipe 10 and extends through the end walls. A porous hydrogen access pipe 13 functioning as a metal filter made of, for example, sintered nickel is fitted at one open end thereof into an inner end of the hydrogen entrance and exit pipe 12, with the other closed end of the porous hydrogen access pipe 13 being located in the vicinity of the other end wall of the inner shell 8.

[0020] A plurality of disk-shaped alloy units 14 are carried on the hydrogen access pipe 13 which extends through their center bores 15, with adjacent alloy units 14 in close contact with each other, so that outer peripheral surfaces of the alloy units 14 are fitted to an inner peripheral surface of the inner shell 8. Each of the alloy units 14 comprises a thin, disk-shaped, closed container 16 made of aluminum with a powder of metal hydride 17 filled therein, as also shown in FIG. 3. (TiZr)(MnV)₂is used as the metal hydride 17.

[0021] A thermocouple 18 is air-tightly mounted in the end walls of the outer and inner shells 7 and 8 on the side of the outlet pipe 11 and extends through the end walls.

[0022] FIG. 4 shows a hydrogen filling system. In the hydrogen station 1, a first port p1 of a first three-way valve 3V₁is connected to the hydrogen entrance and exit pipe 12 of the hydrogen supply tank 2 through a first gas supply pipe 6₁, and a second port p2 of the first three-way valve 3V₁is connected to a water electrolytic device E which is a hydrogen generating source, through a second gas supply pipe 6₂having a first two-way valve 2V₁. A first water conduit 21₁is connected to the inlet pipe 10 of the hydrogen supply tank 2 and has a heater H provided at a location near the inlet pipe 10, a second two-way valve 2V₂provided at the end connected to the automobile 3, and a circulating pump P provided between the second two-way valve 2V₂and the heater H. A first port p1 of a second three-way valve 3V₂is connected to the outlet pipe 11 of the hydrogen supply tank 2 through a second water conduit 21₂, and a second port p2 of the second three-way valve 3V₂is connected to the first water conduit 21₁at a location between the circulating pump P and the second two-way valve 2V₂through a third water conduit 21₃.

[0023] In the automobile 3, a first port p1 of a third three-way valve 3V₃is connected to the hydrogen entrance and exit pipe 12 of the hydrogen storage tank 4 through a third gas supply pipe 6₃, and a second port p2 of the third three-way valve 3V₃is connected to a fuel cell F through a fourth gas supply pipe 6₄.

[0024] In filling hydrogen into the hydrogen storage tank 4 of the automobile 3, the third port p3 of the third three-way valve 3V₃is first connected to the third port p3 of the first three-way valve 3V₁in the hydrogen station 1 through the main gas supply pipe 6. In addition, the inlet pipe 10 of the hydrogen storage tank 4 in the automobile 3 is connected to the third port p3 of the second three-way valve 3V₂in the hydrogen station 1 through a fourth water conduit 21₄, and the outlet pipe 11 is connected to the second two-way valve 2V₂in the hydrogen station 1 through a fifth water conduit 21₅. Then, the first and second two-way valves 2V₁and 2V₂are closed, and the first and third three-way valves 3V₁and 3V₃are switched over, so that their first and third ports p1 and p3 communicate with each other. Further, the second three-way valve 3V₂is switched over, so that its first and second ports p1 and p2 communicate with each other.

[0025] Thereafter, the circulating pump P and the heater H are operated. Then, pure water is circulated through a water passageway comprising the circulating pump P→the heater H→the passage 9 in the hydrogen supply tank 2→the second three-way valve 3V₂→the circulating pump P. The temperature of the pure water is, for example, about 25° C. at the start of the filling, but is raised by the heating of the pure water by the heater H. Therefore, when the temperature of the pure water in the inlet pipe 10 of the hydrogen supply tank 2 has reached about 44.2° C. the output from the heater H and flow rate of the pure water circulated by the circulating pump P are controlled, so that such temperature is maintained.

[0026] In the hydrogen supply tank 2, the metal hydride 17, which has absorbed hydrogen therein within each of the alloy units 14, is heated by the pure water having a raised temperature. When the temperature of the metal hydride 17 reaches about 44.2° C. which is the same temperature as the pure water, the metal hydride 17 releases the hydrogen. The released hydrogen penetrates the container 16 made of aluminum and the porous wall of the hydrogen access pipe 13 to enter the inside of the hydrogen access pipe 13, and is then passed through the pipe 13, the hydrogen entrance and exit pipe 12, the first three-way valve 3V₁, the main gas supply pipe 6, the third three-way valve 3V₃and the like into the hydrogen storage tank 4.

[0027] In the hydrogen storage tank 4, the hydrogen is passed through the hydrogen entrance and exit pipe 12 into the hydrogen access pipe 13; penetrates the porous wall of the latter and the container 16 made of aluminum of each of the alloy units 14, and thus, is absorbed in the metal hydride 17. As a result of such absorption of the hydrogen, the metal hydride 17 is heated.

[0028] In the hydrogen supply tank 2, on the other hand, the heat of the pure water is consumed for heating of the metal hydride 17 and hence, the temperature of the pure water reaching the inside of the outlet pipe 11 has been lowered to about 26.9° C. At this time point, the second three-way valve 3V₂is switched over, so that the first and third ports p1 and p3 communicate with each other; the second two-way valve 2V₂is opened, and the operation of the heater H is stopped. This causes the pure water of about 26.9° C. discharged from the outlet pipe 11, to flow through the passage 9 in the hydrogen storage tank 4, so that the metal hydride 17 is cooled. Thus, the pure water is raised in temperature up to about 44.2° C. by such cooling, and the pure water having the raised temperature is discharged from the outlet pipe 11 toward the hydrogen supply tank 2.

[0029] In the subsequent steady state, when the pure water is circulated between the hydrogen supply tank 2 and the hydrogen storage tank 4, the metal hydride 17 heated with the exothermic reaction of hydrogen absorption is cooled by the pure water in the hydrogen storage tank 4, and the pure water which is raised in temperature up to about 42.2° C. by the cooling of the metal hydride, is discharged toward the hydrogen supply tank 2. In the hydrogen supply tank 2, on the other hand, the metal hydride 17 is heated by the pure water to release the hydrogen, and the pure water which is lowered in temperature down to about 26.9° C. by such heating, is discharged toward the hydrogen storage tank 4.

[0030] When the flow rate of the pure water in the steady state is 10 L/min in a case where the weight of the metal hydride 17 in the hydrogen supply tank 2 is 90 kg and the amount of hydrogen stored is 0.90 kg, and the weight of the metal hydride 17 in the hydrogen storage tank 4 is 44 kg and the amount of hydrogen stored is 0.54 kg, the amount of hydrogen supplied from the hydrogen supply tank 2 to the hydrogen storage tank 4 is 6 Nm³(268 mol), and the filling time is about 10 minutes.

[0031] If the technique as described above is employed, the heater H may be used in the hydrogen station 1 to heat the metal hydride 17 to release the hydrogen, only at the stage of start of the filling. In the subsequent steady state, the quantity of heat provided by the exothermic reaction of metal hydride 17 in the hydrogen storage tank 4 can be utilized effectively to release the hydrogen in the hydrogen station 1. On the other hand, the pure water lowered in temperature by the heat exchange in the hydrogen supply tank 2 is used for the cooling of the metal hydride 17 in the hydrogen storage tank 4 and hence, any special cooling means for the pure water is not required.

[0032] FIG. 5 shows the hydrogen supply tank 2 in the hydrogen station 1 with a supply stand 5 connected to the hydrogen supply tank 2 in the embodiment. The hydrogen storage tank 4 is in the automobile 3, wherein the supply stand 5 and the hydrogen storage tank 4 are connected to each other through a collecting passage member 22. The collecting passage member 22 includes a first passage 23₁through which hydrogen is passed, a second passage 23₂through which the pure water having a lowered temperature is passed, and a third passage 23₃through which the pure water having a raised temperature is passed, as clearly shown in FIG. 6. The collecting passage member 22 has halves 24₁and 25₁of connectors 24 and 25 at opposite ends thereof. The halves are detachably connected to halves 24₂and 25₂of the other connector existing in the supply stand 5 and the hydrogen storage tank 4, respectively.

[0033] Thus, as shown in FIGS. 7 and 4, a through-bore 26₁connected to the third port p3 in the first three-way valve 3V₁, a through-bore 26₂connected to the third port p3 in the second three-way valve 3V₂and a through-bore 26₃connected to the second two-way valve 2V₂, which exist in the other half 24₂in the supply stand 5, are connected to a through-bore 27₁connected to a third port p3 of the third three-way valve 3V₃, a through-bore 27₂connected to the inlet pipe 10 and a through-bore 27₃connected to the outlet pipe 11, which exist in the other half 25₂in the hydrogen storage tank 4, respectively, through the first to third passages 23₁to 23₃.

[0034] If such a collecting passage member 22 is used, it is easy to connect and disconnect the supply stand 5 and the hydrogen storage tank 4 to and from each other, and the connecting line system can be simplified.

[0035] According to the present invention, by employing the means as described above, the quantity of heat generated by the metal hydride in the hydrogen storage tank of the automobile can be utilized effectively in the hydrogen station for heating the metal hydride which is required for releasing of hydrogen, thereby achieving an energy saving.

[0036] Further, according to the present invention, it is possible to easily perform the connection and disconnection of the hydrogen supply tank in the hydrogen station and the hydrogen storage tank in the automobile, and to simplify the connecting line system.

[0037] The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, to be embraced therein.