U.S. patent application number 15/665745 was filed with the patent office on 2018-02-08 for gas filling system.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Toshiyuki KONDO.
Application Number | 20180038550 15/665745 |
Document ID | / |
Family ID | 61071376 |
Filed Date | 2018-02-08 |
United States Patent
Application |
20180038550 |
Kind Code |
A1 |
KONDO; Toshiyuki |
February 8, 2018 |
GAS FILLING SYSTEM
Abstract
Provided is a gas filling system capable of further improving
SOC of a gas tank. A gas filling system includes a gas tank and a
gas station. The gas station includes a gas feed line, a gas return
line, a gas circulation pump configured to circulate the gas
between the gas tank and the gas station through the gas feed line
and the gas return line, and a precooler configured to cool the gas
fed from the gas station to the gas tank through the gas feed line.
The gas is supplied from the gas station to the gas tank while the
gas cooled by the gas precooler to a temperature lower than a heat
resistant temperature of the gas tank is being circulated between
the gas tank and the gas station.
Inventors: |
KONDO; Toshiyuki;
(Chiryu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
61071376 |
Appl. No.: |
15/665745 |
Filed: |
August 1, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F17C 2225/036 20130101;
F17C 2250/032 20130101; F17C 2227/0157 20130101; F17C 2250/0439
20130101; Y02E 60/32 20130101; F17C 5/06 20130101; F17C 2260/023
20130101; F17C 2260/026 20130101; F17D 1/08 20130101; F17C
2270/0178 20130101; F17C 2205/0376 20130101; F17C 2227/0341
20130101; Y02E 60/34 20130101; F17C 1/00 20130101; F17C 2221/012
20130101; F17C 2250/0694 20130101; F17C 2270/0184 20130101; F17C
2250/043 20130101; F17C 2223/0123 20130101; F17C 2250/0443
20130101; F17C 2265/065 20130101; F17C 2225/0123 20130101; F17C
13/026 20130101 |
International
Class: |
F17C 13/02 20060101
F17C013/02; F17D 1/08 20060101 F17D001/08; F17C 5/06 20060101
F17C005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2016 |
JP |
2016-155012 |
Claims
1. A gas filling system comprising: a gas tank; and a gas station
configured to supply a gas to the gas tank, wherein the gas station
comprises: a gas feed line configured to feed the gas from the gas
station to the gas tank; a gas return line configured to return the
gas in the gas tank to the gas station; a gas circulation pump
configured to circulate the gas between the gas tank and the gas
station through the gas feed line and the gas return line; and a
gas cooling unit configured to cool the gas fed from the gas
station to the gas tank through the gas feed line, and the gas is
supplied from the gas station to the gas tank while the gas cooled
by the gas cooling unit to a temperature lower than a heat
resistant temperature of the gas tank is being circulated between
the gas tank and the gas station.
2. The gas filling system according to claim 1, wherein after a
temperature of the gas in the gas tank has risen to a predetermined
temperature, the gas is being supplied from the gas station to the
gas tank while the gas is being circulated by the gas cooling unit
between the gas tank and the gas station.
3. The gas filling system according to claim 1, wherein the gas
tank is mounted on a vehicle, and the vehicle comprises a gas
feeding connection port for connecting the gas tank to the gas feed
line and a gas returning connection port for connecting the gas
tank to the gas return line, and shapes of connection parts of the
gas feeding connection ports and the gas returning connection port
differ from each other.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese patent application No. 2016-155012, filed on
Aug. 5, 2016, the disclosure of which is incorporated herein in its
entirety by reference.
BACKGROUND
[0002] The present invention relates to a gas filling system.
[0003] A gas filling system in which a high pressure gas is
supplied from a gas station to a gas tank mounted on a vehicle or
the like to fill the gas tank with the gas is well known. Japanese
Unexamined Patent Application Publication No. 2011-033068 discloses
a gas filling system that cools a hydrogen gas that is at about
room temperature supplied from an accumulator for storing a
pressurized hydrogen gas to a predetermined temperature by heat
exchange in a precooler, and then fills a gas tank with the cooled
gas. The amount of the gas to be supplied to the gas tank is
increased by cooling the gas before supplying it to the gas
tank.
SUMMARY
[0004] Supplying of a hydrogen gas to a fuel cell vehicle is
commonly carried out by a method complying with the filling
protocol standard (SAE J2601). While gas is being supplied to a gas
tank, a gas temperature in the gas tank gradually rises due to heat
generated by adiabatic compression of the gas in the gas tank.
According to the above filling protocol, the upper limit of the gas
temperature in the gas tank is defined as 85.degree. C. The upper
limit value (85.degree. C.) of the gas temperature in the gas tank
defined by the filling protocol is specified as the heat resistant
temperature in the gas tank (heat resistant temperature of the gas
tank in the standard). While the gas is being supplied, the
temperature of the gas in the gas tank rises by adiabatic
compression of the gas. For this reason, it is necessary to prevent
the temperature of the gas in the gas tank from exceeding the heat
resistant temperature of the gas tank while the gas is being
supplied to the gas tank.
[0005] An amount of a hydrogen gas that can be supplied to the gas
tank, i.e., hydrogen gas density .rho. in the gas tank, is
calculated by the formula .rho.=M/V=MP/(nRT) based on the equation
of state for gas (PV=nRT), where P[Pa] represents the pressure of
the hydrogen gas, T[K] represents the temperature of the hydrogen
gas, and M[kg] represents mass of the hydrogen gas. Further, R is a
gas constant, and n is the number of moles of the hydrogen gas. The
hydrogen gas density .rho. in the gas tank is proportional to the
pressure P in the gas tank and inversely proportional to the
temperature T in the gas tank. That is, in order to increase the
hydrogen gas density .rho. in the gas tank, it is necessary to
increase the pressure of the hydrogen gas to be supplied or to
lower the temperature of the hydrogen gas to be supplied.
[0006] As described above, the gas filling system described in
Japanese Unexamined Patent Application Publication No. 2011-033068
increases the hydrogen gas density .rho. in the gas tank by
exchanging heat using the precooler to thereby lower the
temperature of the hydrogen gas to be supplied. However, in the gas
filling system described in Japanese Unexamined Patent Application
Publication No. 2011-033068, in order to further lower the
temperature of the hydrogen gas to be supplied for further
increasing the hydrogen gas density .rho. in the gas tank, it is
necessary to further improve the cooling capacity of the precooler.
That is, it is necessary to replace the precooler by one with a
higher refrigerating ability which will cost more than the replaced
one. In addition, if the cooling capacity of the precooler is
improved, it is necessary to replace the members of the gas
station, such as a seal member, by those that can withstand a lower
temperature, which will cost more, in each element of the gas
station accordingly. Consequently, the installation cost of the gas
station will be greatly increased.
[0007] On the other hand, the pressure of the hydrogen gas to be
supplied could be increased while maintaining the cooling capacity
of the precooler. However, in this way, the temperature of the gas
in the gas tank will exceed the heat resistant temperature of the
gas tank while the gas is being supplied to the gas tank.
Hereinafter, a mechanism in which an increase in the pressure of
the hydrogen gas to be supplied while maintaining the cooling
capacity of the precooler causes the temperature of the gas in the
gas tank to exceed the heat resistant temperature of the gas tank
will be described with reference to FIG. 8.
[0008] FIG. 8 is a graph showing a relationship between the
pressure in the hydrogen gas and the temperature in the gas tank
when the gas is being supplied to the gas tank by a gas filling
system developed by the inventors. The hydrogen gas cooled to
-40.degree. C. by the precooler is supplied to the gas tank from
the gas station. In the graph, a horizontal axis represents the
temperature (unit: .degree. C.) of the hydrogen gas in the gas
tank, and a vertical axis represents the pressure of the hydrogen
gas in the gas tank (unit: MPa). A solid line Ed1 represents an
isopycnic line with SOC of 100%, and a solid line Ed4 represents an
isopycnic line with the SOC of 130%. The SOC (State Of Charge) is
the filling rate of the gas tank, the hydrogen gas density when the
temperature is 15.degree. C. and the pressure is at a Normal
Working Pressure (NWP) of the gas tank is 100%.
[0009] As shown in FIG. 8, when the gas is being supplied to the
gas tank from the empty state (state A3) to the SOC of 100%, the
pressure of the hydrogen gas and the temperature of the hydrogen
gas in the gas tank transition from the state A3 to the state B3 as
indicated by the broken line L21. In the state at the completion of
filling (state B3), the pressure of the hydrogen gas in the gas
tank is 87.5 MPa. At this time, the temperature of the hydrogen gas
in the gas tank is 85.degree. C., which is the heat resistant
temperature of the gas tank.
[0010] On the other hand, when the gas is being supplied to the gas
tank from the empty state (state A3) to the SOC of 130%, the
pressure of the hydrogen gas and the temperature of the hydrogen
gas in the gas tank transition from the state A3 to the state C3 as
indicated by the broken line L22. In the state at the completion of
filling (state C3), the pressure of the hydrogen gas in the gas
tank exceeds 130 MPa which is higher than 87.5 MPa of the state B3.
Therefore, in the state C3, the gas in the gas tank is more
adiabatically compressed than in the state B3. Accordingly, in the
state C3, the temperature of the hydrogen gas in the gas tank
exceeds 100.degree. C., which is higher than the heat resistant
temperature (85.degree. C.) of the gas tank. That is, when the gas
is being supplied to the gas tank up to the SOC of 130%, if the
cooling capacity of the precooler is the same as that when the gas
tank is filled up to the SOC of 100%, the temperature of the
hydrogen gas in the gas tank at the completion of filling exceeds
85.degree. C., which is the heat resistant temperature of the gas
tank.
[0011] The present invention has been made in view of the above
circumstances, and an object of the present invention is to provide
a gas filling system capable of further improving SOC of a gas tank
while preventing a temperature of a gas in the gas tank from
exceeding a heat resistant temperature of the gas tank without a
significant increase in cost.
[0012] In an aspect of the present invention, a gas filling system
includes a gas tank and a gas station configured to supply a gas to
the gas tank. The gas station includes: a gas feed line configured
to feed the gas from the gas station to the gas tank; a gas return
line configured to return the gas in the gas tank to the gas
station; a gas circulation pump configured to circulate the gas
between the gas tank and the gas station through the gas feed line
and the gas return line; and a gas cooling unit configured to cool
the gas fed from the gas station to the gas tank through the gas
feed line. The gas is supplied from the gas station to the gas tank
while the gas cooled by the gas cooling unit to a temperature lower
than a heat resistant temperature of the gas tank is being
circulated between the gas tank and the gas station. When the gas
tank is filled with the gas, the gas is supplied from the gas
station to the gas tank while the gas cooled by the gas cooling
unit to the temperature lower than the heat resistant temperature
of the gas tank is being circulated between the gas tank and the
gas station by the gas circulation pump. In this way, the gas in
the gas tank is cooled to the temperature lower than the heat
resistant temperature of the gas tank. Thus, the temperature of the
gas in the gas tank 3 will not exceed the heat resistant
temperature of the gas tank while the gas is being supplied to the
gas tank. Further, when the gas is being supplied while being
circulated, the gas returned from the gas tank to the gas station
is cooled by the gas cooling unit, whereby the pressure is reduced.
Thus the gas can be replenished from the gas station to the gas
tank by an amount of the reduction in the pressure of the gas by
the cooling. Accordingly, it is possible to further increase SOC of
the gas tank compared with the case where the gas is not circulated
while the gas is being supplied to the gas tank.
[0013] Further, in the gas filling system, after a temperature of
the gas in the gas tank has risen to a predetermined temperature,
the gas is supplied from the gas station to the gas tank while the
gas is being circulated by the gas cooling unit between the gas
tank and the gas station. If the gas is circulated between the gas
tank and the gas station from the beginning when the gas is being
supplied to the gas tank, it takes more time to fill the gas tank
with the gas as compared with the case where there is no gas
circulation. Therefore, the time required to fill the gas tank with
the gas can be shortened by filling the gas tank with the gas
without the gas circulation until the temperature of the gas in the
gas tank reaches a predetermined temperature (e.g., withstand
temperature of the gas tank). Accordingly, it is possible to
further increase SOC of the gas tank without preventing the time
required to fill the gas tank with the gas from being increased by
supplying the gas from the gas station to the gas tank while the
gas is being circulated by the gas cooling unit between the gas
tank and the gas station after the gas temperature in the gas tank
has reached the predetermined temperature.
[0014] Furthermore, in the gas filling system, the gas tank is
mounted on a vehicle, and the vehicle includes a gas feeding
connection port for connecting the gas tank to the gas feed line
and a gas returning connection port for connecting the gas tank to
the gas return line, and shapes of connection parts of the gas
feeding connection ports and the gas returning connection port
differ from each other. Thus, it is possible to prevent the gas
feed line from being incorrectly connected to the gas returning
connection port and to prevent the gas return line from being
incorrectly connected to the gas feeding connection port.
[0015] According to the present invention, it is possible to
further increase SOC of a gas tank while preventing a temperature
of a gas in a gas tank from exceeding a heat resistant temperature
of the gas tank without a significant increase in cost.
[0016] The above and other objects, features and advantages of the
present invention will become more fully understood from the
detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not to be considered as limiting the present invention.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a drawing showing a schematic configuration of a
gas filling system according to embodiments;
[0018] FIG. 2 is a drawing showing a specific configuration of the
gas filling system according to the embodiments;
[0019] FIG. 3 is a drawing for describing a gas filling method of
the gas filling system according to the embodiments;
[0020] FIG. 4 is a drawing for describing a transition of a
pressure in a gas tank and a temperature in the gas tank when a
hydrogen gas is being circulated between the gas tank and a gas
station from SOC of 100%;
[0021] FIG. 5 is a table summarizing the pressures and the
temperatures in the gas tank when the gas tank is filled and used
for respective SOCs;
[0022] FIG. 6 is a drawing for describing a gas filling method by a
gas filling system according to a second embodiment;
[0023] FIG. 7 is a table summarizing comparisons between the
pressures and temperatures in the gas tank when the gas tank is
filled so that the SOC becomes 100% by the gas filling method
performed by the gas filling system according to the second
embodiment and when the gas tank is filled so that the SOC becomes
100% by a gas filling method where there is no gas circulation;
and
[0024] FIG. 8 is a graph showing a relationship between the
pressure and the temperature of the hydrogen gas in the gas tank
when the gas is being supplied to the gas tank by a gas filling
system developed by the inventors.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0025] Hereinafter, a first embodiment of the present invention
will be described with reference to the drawings. As an example of
a gas filling system, an example of supplying a hydrogen gas to a
fuel cell vehicle equipped with a fuel cell system from a gas
station will be described. As is well known, the fuel cell system
includes a fuel cell or the like that generates power by an
electrochemical reaction of a fuel gas (e.g., hydrogen gas) and an
oxidization gas (e.g., air).
[0026] First, a schematic configuration of the gas filling system 1
according to this embodiment will be described with reference to
FIG. 1. FIG. 1 is a drawing showing a schematic configuration of a
gas filling system 1 according to this embodiment. As shown in FIG.
1, the gas filling system 1 according to the this embodiment
includes a gas tank 3 and a gas station 2 that supplies a gas to
the gas tank 3. The gas station 2 includes a gas feed line 11, a
gas return line 12, a gas circulation pump 14 for circulating a gas
between the gas tank 3 and the gas station 2 through the gas feed
line 11 and the gas return line 12, and a precooler 18 as a gas
cooling unit for cooling the gas fed from the gas station 2 to the
gas tank 3 through the gas feed line 11. In the gas filling system
1, the gas is supplied from the gas station 2 to the gas tank 3
while the gas cooled by the precooler 18 to a temperature lower
than the heat resistant temperature of the gas tank 3 is being
circulated between the gas tank 3 and the gas station 2.
[0027] When the gas tank 3 is filled with the gas, the gas is
supplied from the gas station 2 to the gas tank 3 while the gas
cooled by the precooler 18 to a temperature lower than the heat
resistant temperature of the gas tank 3 is being circulated between
the gas tank 3 and the gas station 2 by the gas circulation pump
14. By doing so, the gas in the gas tank 3 is cooled to the
temperature lower than the heat resistant temperature of the gas
tank 3. In this way, the temperature of the gas in the gas tank 3
will not exceed the heat resistant temperature of the gas tank 3
while the gas is being supplied to the gas tank 3. Further, when
the gas is being supplied to the gas tank 3 while being circulated,
the gas returned from the gas tank 3 to the gas station 2 is cooled
by the precooler 18, whereby the pressure is reduced. Thus the gas
can be replenished from the gas station 2 to the gas tank 3 by an
amount of the reduction in the pressure of the gas by the cooling.
Accordingly, it is possible to further increase the SOC of the gas
tank 3 compared with the case where the gas is not circulated while
the gas is being supplied to the gas tank 3.
[0028] Next, a more specific configuration of the gas filling
system 1 according to this embodiment will be described with
reference to FIG. 2. FIG. 2 is a drawing showing a specific
configuration of the gas filling system 1.
[0029] As shown in FIG. 2, the gas filling system 1 includes the
gas tank 3 and the gas station 2.
[0030] The gas tank 3 is mounted on a vehicle 50. The gas tank 3 is
a fuel gas supply source for a fuel cell and is a high pressure
tank capable of storing a hydrogen gas. The hydrogen gas in the gas
tank 3 is supplied to the fuel cell through a supply pipeline (not
shown). In the gas tank 3, a pressure sensor 51 for detecting the
pressure in the gas tank 3 and a temperature sensor 52 for
detecting the temperature inside the gas tank 3 are provided.
[0031] The gas station 2 includes the gas feed line 11, the gas
return line 12, the gas circulation pump 14, accumulators 15, and
the precooler (gas cooling unit) 18. The gas feed line 11 is a gas
flow path for feeding a gas from the gas station 2 to the gas tank
3 and is indicated by the dashed line in FIG. 2. The gas return
line 12 is a gas flow path for returning the gas in the gas tank 3
to the gas station 2 and is indicated by the broken line in FIG.
2.
[0032] The gas circulation pump 14 circulates the gas between the
gas tank 3 and the gas station 2 through the gas feed line 11 and
the gas return line 12. As the gas circulation pump 14, for
example, a blower fan can be used. The accumulators 15 are for
storing a hydrogen gas which has been pressurized to a
predetermined pressure (e.g., 95 MPa), and is provided in the gas
feed line 11. A flow rate control valve 48 for adjusting the flow
rate of the hydrogen gas supplied to the gas feed line 11 is
provided in the accumulators 15. Note that the accumulators 15 may
include a plurality of accumulator tanks each having different
pressures to be accumulated.
[0033] The precooler 18 cools the gas fed from the gas station 2 to
the gas tank 3 through the gas feed line 11 to a temperature lower
than the heat resistant temperature of the gas tank 3 by heat
exchange. Any one of a partition wall type, an intermediate medium
type, and a storage type can be used as a form of the heat exchange
by the precooler 18, and a known structure can be employed as a
structure of the precooler 18. In the example shown in FIG. 2, the
form of the heat exchange by the precooler 18 is the intermediate
medium type where a refrigerant is circulated between a precooling
heat exchanger 32 and a refrigerator 31, and heat is exchanged
between the hydrogen gas and the refrigerant in the precooling heat
exchanger 32.
[0034] The gas station 2 further includes a dispenser (filler) 40
for the user to perform the filling operation when filling the gas
tank 3 with gas. The gas station 2 further includes a control unit
20 for controlling the filling of the gas tank 3 with the gas from
the gas station 2.
[0035] The dispenser 40 has a flow rate control valve 44 for
adjusting the flow rate of the hydrogen gas supplied from the gas
station 2 to the gas tank 3 and a flow meter 43 for measuring a
flow rate of the hydrogen gas supplied from the gas station 2 to
the gas tank 3. In the gas station 2, parts other than the
dispenser 40 are defined as a gas station main body 30. The flow
rate control valve 44 is an electrically driven valve and includes,
for example, a step motor as a drive source. The flow rate control
valve 44 adjusts the flow rate of the hydrogen gas by changing the
degree of valve opening by the step motor in accordance with a
command from the control unit 20. Then the flow rate of the
hydrogen gas supplied to the gas tank 3 is controlled. The
controlled flow rate of the hydrogen gas to be supplied is measured
by the flow meter 43, and the control unit 20 performs feedback
control on the flow rate control valve 44, so that in response to a
result of the measurement, a desirable flow rate will be
achieved.
[0036] The control unit 20 is configured as a microcomputer
including a CPU, a ROM, and a RAM. The CPU executes a desired
calculation according to a control program and performs various
processes and control. The ROM stores the control program and
control data to be processed by the CPU, and the RAM is mainly used
as various work areas for control processing. Although the control
unit 20 is provided in the dispenser 40 in FIG. 2, it is not
limited to this, and instead the control unit 20 may be provided in
the gas station main body 30. Alternatively, the control unit 20
may be provided in the vehicle 50 instead of the gas station 2.
[0037] The above-described precooling heat exchanger 32 of the
precooler 18 is preferably installed in the dispenser 40 in order
for the hydrogen gas to be cooled at a position just before it is
supplied to the gas tank 3. A main stop valve 47 for switching
supplying and stopping of the hydrogen gas from the gas station 2
to the gas tank 3 is provided in the gas feed line 11 at a position
downstream of the precooler 18 in the gas flow direction. A
pressure sensor 41 for detecting the pressure of the hydrogen gas
supplied to the gas tank 3 and a temperature sensor 42 for
detecting the temperature of the hydrogen gas supplied to the gas
tank 3 are provided in the gas feed line 11 at positions downstream
of the precooler 18 in the gas flow direction
[0038] A part of the gas feed line 11 is extended from the
dispenser 40 as a gas feed hose. A part of the gas return line 12
is extended from the dispenser 40 as a gas return hose. A gas
feeding nozzle 45 is provided at a leading end of the gas feed hose
and a gas returning nozzle 46 is provided at a leading end of the
gas return hose.
[0039] In the vehicle 50, a gas feeding receptacle (gas feeding
connection port) 53 and a gas returning receptacle (gas returning
connection port) 54 for connecting the gas tank 3 to the gas feed
line 11 are provided. That is, the gas feeding receptacle 53 is
coupled to the gas feeding nozzle 45, and the gas returning
receptacle 54 is coupled to the gas returning nozzle 46. In order
to simplify the connecting operation, the gas feeding receptacle 53
and the gas returning receptacle 54 are preferably provided in the
same fuel lid in the vehicle 50. In order to prevent the gas
feeding nozzle 45 from being incorrectly coupled to the gas
returning receptacle 54 and to prevent the gas returning nozzle 46
from being incorrectly coupled to the gas feeding receptacle 53,
the shapes of the connection parts of the gas feeding receptacle 53
and the gas returning receptacle 54 are preferably different from
each other.
[0040] A check valve 56 for preventing backflow of the hydrogen gas
is provided in a filling pipeline 55 that connects the gas feeding
receptacle 53 to the gas tank 3. A main stop valve 58 and a
pressure reducing valve 59 for stopping the gas from being
discharged are provided in a recirculation pipeline 57 that
connects the gas tank 3 to the gas returning receptacle 54. When
the pressure of the gas to be discharged from the gas tank 3 to the
gas return line 12 is higher than a predetermined pressure (e.g.,
87.5 MPa), the pressure reducing valve 59 reduces the pressure of
the gas to the predetermined pressure.
[0041] Next, a gas filling method of the gas filling system 1
according to this embodiment will be described with reference to
FIG. 3. In the following description, reference will also be made
to FIG. 2 as appropriate. FIG. 3 is a drawing for describing the
gas filling method of the gas filling system 1. In FIG. 3, a
horizontal axis of the graph represents the temperature (unit:
.degree. C.) of the hydrogen gas in the gas tank 3, and a vertical
axis of the graph represents the pressure (unit: MPa) of the
hydrogen gas in the gas tank 3. A solid line Ed1 is an isopycnic
line with the SOC of 100%, a solid line Ed2 is an isopycnic line
with the SOC of 120%, a solid line Ed3 is an isopycnic line with
the SOC of 125%, and a solid line Ed4 is an isopycnic line with the
SOC of 130%.
[0042] As shown in FIG. 3, firstly, from the empty state of the gas
tank 3 (state A1) to the state with the SOC of 100% (state B1), the
hydrogen gas is supplied to the gas tank 3 without circulating the
hydrogen gas between the gas tank 3 and the gas station 2. That is,
the main stop valve 47 of the gas feed line 11 is opened, and the
high pressure hydrogen gas cooled by the precooler 18 to a
temperature of -40.degree. C. is supplied from the gas station 2 to
the gas tank 3. At this time, the main stop valve 58 of the
recirculation pipeline 57 is kept closed so that the hydrogen gas
in the gas tank 3 will not be returned to the gas station 2. Thus,
the pressure of the hydrogen gas and the temperature of the
hydrogen gas in the gas tank 3 transition as indicated by the
broken line L1. That is, the gas temperature in the gas tank 3
rises from an external temperature (15.degree. C. in this example)
to 85.degree. C., which is the heat resistant temperature of the
gas tank 3, by the above-described adiabatic compression of the
gas, and the gas pressure in the gas tank rises from 0 MPa to a
predetermined pressure (87.5 MPa in this example).
[0043] Next, the hydrogen gas is supplied from the gas station 2 to
the gas tank 3 while the hydrogen gas cooled by the precooler 18 is
being circulated between the gas tank 3 and the gas station 2. That
is, after the temperature of the hydrogen gas in the gas tank 3
detected by the temperature sensor 52 has risen to the heat
resistant temperature of the gas tank 3, the control unit 20 opens
the main stop valve 58 of the recirculation pipeline 57, and the
hydrogen gas is circulated by the gas circulation pump 14 between
the gas tank 3 and the gas station 2. The hydrogen gas circulating
between the gas tank 3 and the gas station 2 is cooled by the
precooler 18. The hydrogen gas returned from the gas tank 3 to the
gas station 2 is cooled by the precooler 18 to a temperature less
than 85.degree. C., which is the heat resistant temperature of the
gas tank 3, whereby the pressure is reduced. Therefore, the control
unit 20 controls the flow rate control valve 48 to replenish the
hydrogen gas from the accumulators 15 so that the pressure of the
hydrogen gas in the gas tank 3 detected by the pressure sensor 51
is maintained at a predetermined pressure (87.5 MPa in this
example). That is, in the gas tank 3, the amount of the hydrogen
gas is increased by the amount of the hydrogen gas replenished by
the accumulators 15.
[0044] In order to increase the SOC of the gas tank 3 from 100% to
120%, it is necessary to continue the circulation of the hydrogen
gas from the state B1 to the state C1 where the broken line L2
crosses the isopycnic line Ed2 with the SOC of 120%, that is, until
the temperature of the hydrogen gas in the gas tank 3 is reduced
from 85.degree. C. to about 0.degree. C. In this case, the hydrogen
gas supplied from the gas station 2 to the gas tank 3 needs to be
cooled to a temperature of 0.degree. C. by the precooler 18.
[0045] In order to increase the SOC of the gas tank 3 from 100% to
125%, it is necessary to continue the circulation of the hydrogen
gas from the state B1 to the state D1 where a solid line L2 crosses
the isopycnic line Ed3 with the SOC of 125%, that is, until the
temperature of the hydrogen gas in the gas tank 3 is reduced from
85.degree. C. to -20.degree. C. In this case, the hydrogen gas
supplied from the gas station 2 to the gas tank 3 needs to be
cooled by the precooler 18 to the temperature of -20.degree. C.
[0046] In order to increase the SOC of the gas tank 3 from 100% to
130%, it is necessary to continue the circulation of the hydrogen
gas from the state B1 to the state E1 where the solid line L2
crosses the isopycnic line Ed4 with the SOC of 130%, that is, until
the temperature of the hydrogen gas in the gas tank 3 is reduced
from 85.degree. C. to -35.degree. C. In this case, the hydrogen gas
supplied from the gas station 2 to the gas tank 3 needs to be
cooled by the precooler 18 to a temperature of -35.degree. C.
[0047] FIG. 4 is a drawing for describing a transition of the
pressure in the gas tank and the temperature in the gas tank when
the hydrogen gas is circulated between the gas tank 3 and the gas
station 2 from the state where the SOC is 100%. In FIG. 4, a
horizontal axis of the graph represents time (unit: seconds).
Further, a broken line represents the SOC of the gas tank 3 (unit
of the vertical axis is %), a dashed-dotted line represents the
pressure of the hydrogen gas in the gas tank 3 (unit of the
vertical axis is MPa), a solid line represents a circulation flow
rate of the hydrogen gas (unit of the vertical axis is g/sec), and
an alternate long and two short dashes line represents the
temperature of the hydrogen gas in the gas tank 3 (unit of the
vertical axis is .degree. C.).
[0048] As shown in FIG. 4, the flow rate of the hydrogen gas
circulating between the gas tank 3 and the gas station 2 is
maintained at a constant value (60 g/sec). As described above, by
replenishing the hydrogen gas from the accumulators 15, the
pressure of the hydrogen gas in the gas tank 3 is maintained at the
predetermined pressure of 87.5 MPa. A temperature Ttank of the
hydrogen gas in the gas tank 3 is gradually reduced from 85.degree.
C., which is the heat resistant temperature of the gas tank 3. As
described with reference to FIG. 3, when the temperature Ttank of
the hydrogen gas in the gas tank 3 reaches about 0.degree. C., the
SOC of the gas tank 3 becomes 120%, when the temperature Ttank of
the hydrogen gas in the gas tank 3 reaches about -20.degree. C.,
the SOC of the gas tank 3 becomes 125%, and when the temperature
Ttank of the hydrogen gas in the gas tank 3 reaches about
-35.degree. C., the SOC of the gas tank 3 becomes 130%.
[0049] Accordingly, as shown in FIG. 4, the time taken for the
circulation of the gas while cooling the gas is about 100 seconds
for the SOC of 120%, about 150 seconds for the SOC of 125% and
about 270 seconds for the SOC of 130%. Since the time required to
fill the gas tank 3 with the hydrogen gas up to the SOC of 100%
without the gas circulation is about 180 seconds, the time required
to achieve up to the SOC of 120% is about 280 seconds (100
seconds+180 seconds), the time required to achieve up to the SOC of
125% is about 330 seconds (150 seconds+180 seconds), and the time
required to achieve up to the SOC of 130% is 450 seconds (270
seconds+180 seconds).
[0050] FIG. 5 is a table summarizing the pressures and the
temperatures in the gas tank when the gas is being supplied to the
gas and the fuel cell system is in-operation for respective SOCs.
As shown in FIG. 5, with different SOCs for the gas tank, the
maximum pressure of the gas in the gas tank 3 varies as a matter of
course when the fuel cell system is in-operation (assumed the fuel
cell system is in-operation at an external temperature of
50.degree. C.). However, in the gas filling system 1 according to
this embodiment, the maximum pressure of the gas in the gas tank 3
while the gas is being supplied to the gas tank 3 is 87.5 MPa,
which is the predetermined pressure, for any of the SOCs 100%,
120%, 125%, and 130%. Moreover, the maximum temperature of the gas
in the gas tank 3 while the gas is being supplied to the gas tank 3
is 85.degree. C., which is the heat resistant temperature of the
gas tank 3, for any of SOCs 100%, 120%, 125%, and 130%.
[0051] The cooling temperature of the hydrogen gas supplied from
the gas station 2 to the gas tank 3 when the gas tank 3 is filled
from the empty state to the state with the SOC of 100% is
-40.degree. C. for any of the SOCs 100%, 120%, 125%, and 130%. At
this time, the cooling capacity of the precooler 18 is -40.degree.
C. On the other hand, when the hydrogen gas is circulated between
the gas tank 3 and the gas station 2, it is necessary to set the
cooling temperature of the hydrogen gas supplied from the gas
station 2 to the gas tank 3 to -35.degree. C. for the SOC of 130%,
-20.degree. C. for the SOC of 125%, and 0.degree. C. for the SOC of
120%. In any case, it is higher than -40.degree. C., which is the
cooling capacity of the precooler 18. Therefore, the SOC of the gas
tank 3 can be increased from 100% to 120%, to 125%, and to 130%
without changing the cooling capacity of the precooler 18. In
addition, the time required to fill the gas tank is within 10
minutes for any of the SOCs 100%, 120%, 125%, and 130%. Thus, the
gas filling system of this embodiment has a sufficient competitive
advantage compared with rapid charging of electric vehicles which
take about 20 to 30 minutes.
[0052] As described above, when the gas tank 3 is filled with the
gas, the gas is supplied from the gas station 2 to the gas tank 3
while the gas cooled by the precooler 18 to the temperature lower
than the heat resistant temperature of the gas tank 3 is being
circulated between the gas tank 3 and the gas station 2 by the gas
circulation pump 14. By doing so, the gas in the gas tank 3 is
cooled to the temperature lower than the heat resistant temperature
of the gas tank 3. In this way, the temperature of the gas in the
gas tank 3 will not exceed the heat resistant temperature of the
gas tank 3 while the gas is being supplied to the gas tank 3.
Further, when the gas is being supplied while being circulated, the
gas returned from the gas tank 3 to the gas station 2 is cooled by
the precooler 18, whereby the pressure is reduced. Thus the gas can
be replenished from the gas station 2 to the gas tank 3 by an
amount of the reduction in the pressure of the gas by the cooling.
Accordingly, it is possible to further increase the SOC of the gas
tank 3 compared with the case where the gas is not circulated while
the gas is being supplied to the gas tank 3.
Second Embodiment
[0053] Hereinafter, a second embodiment of the present invention
will be described with reference to the drawings. A configuration
of a gas filling system according to this embodiment is the same as
that described with reference to FIG. 2 in the first embodiment.
This embodiment differs from the first embodiment in the pressure
of the hydrogen gas in the gas tank 3 just before circulating the
gas between the gas tank 3 and the gas station 2.
[0054] A gas filling method of the gas filling system according to
this embodiment will be described. In the following description,
reference will also be made to FIG. 2 as appropriate. FIG. 6 is a
drawing for describing the gas filling method of the gas filling
system according to this embodiment. In this example, a horizontal
axis of the graph represents the temperature of the gas (unit:
.degree. C.), and a vertical axis of the graph represents the
pressure of the gas (unit: MPa). A solid line Ed1 is an isopycnic
line with the SOC of 100%. When the gas is supplied as indicated by
a dashed line L1 in FIG. 3, the cooling temperature of the hydrogen
gas supplied from the gas station 2 to the gas tank 3 is
-40.degree. C. On the other hand, when the gas is supplied as
indicated by a broken line L11 in FIG. 6, the cooling temperature
of the hydrogen gas supplied from the gas station 2 to the gas tank
3 is -25.degree. C.
[0055] As shown in FIG. 6, firstly, the hydrogen gas is only
supplied from the gas station 2 to the gas tank 3 through the gas
feed line 11, and the gas is not returned from the gas tank 3 to
the gas station 2 from the empty state of the gas tank 3 (state A2)
until the state where the pressure in the gas tank 3 is 60 MPa
(state B2). That is, the main stop valve 47 of the gas feed line 11
is opened to supply the hydrogen gas from the gas station 2 to the
gas tank 3. However, the main stop valve 58 of the recirculation
pipeline 57 is kept closed to stop the hydrogen gas in the gas tank
3 from returning to the gas station 2. Thus, the pressure of the
hydrogen gas and the temperature of the hydrogen gas in the gas
tank 3 transition as indicated by the broken line L11. That is, the
gas pressure in the gas tank 3 rises from 0 MPa to 60 MPa, and the
gas temperature in the gas tank 3 rises from an external
temperature (15.degree. C. in this example) to 85.degree. C., which
is the heat resistant temperature of the gas tank 3, by the
above-described adiabatic compression of the gas. The pressure (60
MPa) in the gas tank 3 in the state B2 is lower than the pressure
(87.5 MPa) in the state B1 when the gas tank 3 is filled up to the
SOC of 100%, which is indicated by the broken line L1 in FIG. 3,
where there is no gas circulation.
[0056] Next, the hydrogen gas is supplied from the gas station 2 to
the gas tank 3 while the hydrogen gas cooled by the precooler 18 is
being circulated between the gas tank 3 and the gas station 2. That
is, after the temperature of the hydrogen gas in the gas tank 3
detected by the temperature sensor 52 has risen to the heat
resistant temperature of the gas tank 3, the control unit 20 opens
the main stop valve 58 of the recirculation pipeline 57, and the
gas circulation pump 14 circulates the hydrogen gas between the gas
tank 3 and the gas station 2. The hydrogen gas circulating between
the gas tank 3 and the gas station 2 is cooled by the precooler 18.
The hydrogen gas returned from the gas tank 3 to the gas station 2
is cooled by the precooler 18 to a temperature of 85.degree. C. or
lower, which is the heat resistant temperature of the gas tank 3,
whereby the pressure is reduced. Therefore, the control unit 20
controls the flow rate control valve 48 to replenish the hydrogen
gas from the accumulators 15 so that the pressure of the hydrogen
gas in the gas tank 3 detected by the pressure sensor 51 is
maintained at a predetermined pressure (60 MPa in this example).
That is, in the gas tank 3, the amount of the hydrogen gas is
increased by the amount of the hydrogen gas replenished by the
accumulators 15. If the circulation of the hydrogen gas is
continued until the solid line L12 crosses the isopycnic line Ed1
of the SOC of 100%, that is, until the hydrogen gas temperature in
the gas tank 3 reaches -25.degree. C., the SOC of the gas tank 3
will become 100%. Therefore, while the hydrogen gas is being
circulated between the gas tank 3 and the gas station 2, it is
necessary to set the cooling temperature of the hydrogen gas
supplied from the gas station 2 to the gas tank 3 to -25.degree.
C.
[0057] FIG. 7 is a table summarizing comparisons between the
pressures and temperatures in the gas tank when the gas tank is
filled so that the SOC becomes 100% by the gas filling method
performed by the gas filling system according to this embodiment
and when the gas tank is filled so that the SOC becomes 100% by a
gas filling method according to a comparative example. The gas
filling method according to the comparative example is a gas
filling method where there is no gas circulation. When the gas tank
is filled so that the SOC becomes 100% by the gas filling method
according to the comparative example, the temperature and the
pressure in the gas tank while the gas is being supplied to the gas
tank 3 transition as indicated by the broken line L1 in FIG. 3.
[0058] As shown in FIG. 7, the maximum temperature of the gas in
the gas tank 3 while the gas is being supplied to the gas tank 3 is
85.degree. C. in either of the gas filling system according to this
embodiment and the gas filling method according to the comparative
example. On the other hand, the maximum pressure of the gas in the
gas tank 3 while the gas is being supplied to the gas tank 3 is
87.5 MPa in the gas filling method according to the comparative
example, while in the gas filling system according to this
embodiment, it is 60 MPa, which is lower than 87.5 MPa.
Accordingly, when the gas tank 3 is filled until the SOC becomes
100% by the gas filling system according to this embodiment,
elements in the gas station 2 can be replaced by ones with lower
withstand voltages as compared with the case when the gas tank 3 is
filled until the SOC becomes 100% by the gas filling system
according to the comparative example. Accordingly, the installation
cost of the gas station can be further reduced.
[0059] When the gas tank is filled until the SOC becomes 100% by
the gas filling method according to the comparative example, the
cooling temperature of the hydrogen gas supplied from the gas
station 2 to the gas tank 3 is -40.degree. C. At this time, the
cooling capacity of the precooler 18 is -40.degree. C. On the other
hand, when the gas tank is filled until the SOC becomes 100% by the
gas filling system according to this embodiment, the cooling
temperature of the hydrogen gas supplied from the gas station 2 to
the gas tank 3 is -25.degree. C. At this time, the cooling capacity
of the precooler 18 is -25.degree. C. That is, when the gas tank is
filled until the SOC becomes 100% by the gas filling system
according to this embodiment, the precooler 18 can be replaced by
one with a lower cooling capacity as compared with the case when
the gas tank 3 is filled until the SOC becomes 100% by the gas
filling system according to the comparative example. Accordingly,
the installation cost of the gas station can be further
reduced.
[0060] Note that the present invention is not limited to the above
embodiments, and changes can be made thereto as appropriate without
departing from the scope of the invention. Although a compressor is
used to pressurize the gas (having a pressure of, for example, 20
to 45 MPa) in a tank of a gas transport vehicle to a predetermined
pressure (for example, 82 to 95 MPa) and supply the gas to
accumulators of a gas station, this compressor may be used also as
a gas circulation pump in a gas filling system. In the above
embodiments, the heat resistant temperature of the gas tank is set
to the upper limit value (85.degree. C.) of the gas temperature in
the gas tank specified by the filling protocol. However, the heat
resistant temperature of the gas tank may be set to a temperature
at which the function or physical property of the gas tank can be
maintained without deterioration such as deformation alteration in
a state where no force is applied.
[0061] The gas may be circulated between the gas tank and the gas
station from the beginning when the gas tank is filled with the
gas. However, if the gas is circulated between the gas tank and the
gas station from the beginning when the gas tank is filled with the
gas, it takes more time to fill the gas tank with the gas as
compared with the case where there is no gas circulation. This is
because, assuming that the gas flow rate is the same in the case
where the gas is circulated and the case where the gas is not
circulated, when the gas tank is filled with the gas in the case
where the gas is circulated, since the gas supplied once in the gas
tank flows out, it takes more time to fill the gas tank with the
gas as compared with when the gas tank is filled in the case where
there is no gas circulation. Therefore, as in the above
embodiments, the time required to fill the gas tank with the gas
can be shortened by filling the gas tank with the gas without
circulating the gas until the temperature of the gas in the gas
tank reaches a predetermined temperature (withstand temperature of
the gas tank). For example, suppose that the temperature of the gas
in the gas tank reaches the predetermined temperature (withstand
temperature of the gas tank) at the SOC of 100% when the gas is
supplied without being circulated. Supposing that a target number
of the SOC is 130%, in order to increase the target SOC to 130%
from the state where the SOC reaches 100% by circulating the gas, a
difference between the current SOC and the target SOC, which should
be reached by the gas circulation, is 30% (130%-100%). On the other
hand, when the gas is circulated from the state where the SOC has
not reached 100% to the target SOC of 130%, a difference between
the current SOC and the target SOC, which should be reached by the
gas circulation, is greater than 30%. That is, the difference
between the current SOC and the target SOC is smaller when the SOC
is increased from the state where the SOC reaches 100% to the
target SOC 130% by circulating the gas than when the SOC is
increased from the state where the SOC has not reached 100% to the
target SOC 130%. Thus the time required to fill the gas tank with
the gas can be shorter in the former case. Therefore, it is more
preferable to supply the gas from the gas station to the gas tank
while circulating the gas by the gas cooling unit between the gas
tank and the gas station after the temperature of the gas in the
gas tank rises to a predetermined temperature
[0062] The program can be stored and provided to a computer using
any type of non-transitory computer readable media. Non-transitory
computer readable media include any type of tangible storage media.
Examples of non-transitory computer readable media include magnetic
storage media (such as floppy disks, magnetic tapes, hard disk
drives, etc.), optical magnetic storage media (e.g. magneto-optical
disks), CD-ROM (compact disc read only memory), CD-R (compact disc
recordable), CD-R/W (compact disc rewritable), and semiconductor
memories (such as mask ROM, PROM (programmable ROM), EPROM
(erasable PROM), flash ROM, RAM (random access memory), etc.). The
program may be provided to a computer using any type of transitory
computer readable media. Examples of transitory computer readable
media include electric signals, optical signals, and
electromagnetic waves. Transitory computer readable media can
provide the program to a computer via a wired communication line
(e.g. electric wires, and optical fibers) or a wireless
communication line.
[0063] From the invention thus described, it will be obvious that
the embodiments of the invention may be varied in many ways. Such
variations are not to be regarded as a departure from the spirit
and scope of the invention, and all such modifications as would be
obvious to one skilled in the art are intended for inclusion within
the scope of the following claims.
* * * * *