Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
2000-07-07
2002-12-24
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S006000, C429S006000
Reexamination Certificate
active
06497972
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell system and a method for controlling operating pressure of a fuel cell system, and more particularly to a fuel cell system in which water can be preferably reclaimed and accumulated from exhaust gas emitted from a fuel cell and a method for controlling the operating pressure thereof.
According to an investigation by the inventor of the present invention, a configuration mounted in a fuel cell vehicle
101
shown in
FIG. 9
is one configuration of fuel cell system.
In the fuel cell system SS of the fuel cell vehicle
101
, methanol
17
, which is used as a fuel, is steam reformed by a reformer
13
using water
21
, thereby generating a reformed gas
23
that includes hydrogen, this being fed to the anode side of the fuel cell
29
.
Air
27
from a compressor
25
is sent to the cathode side of the fuel cell
29
.
In the fuel cell
29
, the hydrogen contained in the reformed gas
23
and the oxygen contained in the air
27
are used to generate electric power.
The hydrogen contained in the reformed gas
23
and the oxygen contained in the air
27
are not completely consumed within the fuel cell
29
, a part that is not consumed being sent to a combustor
37
, via a condenser
35
, as exhaust reformed gas
31
and exhaust air
33
.
In the combustor
37
, the exhaust reformed gas
31
and the exhaust air
33
are combusted, together with the air
39
from the compressor
25
and the methanol from a methanol tank
15
, the heat of the combustion reaction thereof being re-used as a source of heat for vaporizing methanol
17
and water
21
in the reformer
13
.
In a system controller
57
, based on the pressures of the air and reformed gas detected by pressure sensors
59
and
61
provided upstream from the fuel cell
29
, the opening of the pressure adjustment valves
63
and
65
provided downstream of the condenser
35
is adjusted, thereby controlling the operating pressure of the fuel cell SS, this being the operating pressure of the fuel cell
29
. When the operating load on the fuel cell system SS is large, control is performed so that this operating pressure is increased so as to achieve the maximum electric power from the fuel cell system SS. When the operating load is small, however, control is performed so that the operating pressure is reduced, so as to increase the efficiency of the fuel cell system.
At the condenser
35
, cooling water W is used to cool exhaust reformed gas
31
and exhaust air
33
exhausted from the fuel cell
29
, the steam included in the exhaust reformed gas
31
and exhaust air
33
being condensed and reclaimed, the reclaimed water
43
being then returned to a water tank.
In
FIG. 9
, the bold solid line EL indicates the electric power line, and the EXT indicates the exhaust gas from the combustor
37
.
In some cases, air A from the compressor
25
is sent to the reformer
13
.
SUMMARY OF THE INVENTION
In the above-noted fuel cell system SS, however, the system controller
57
, based on the pressures of the air and the reformed gas detected by the pressure sensors
59
and
61
. provided upstream of the fuel cell
29
, adjusts the openings of the pressure adjustment valves
63
and
65
provided downstream of the condenser
35
so as to control the operating pressure of the fuel cell
29
.
For this reason, the reclamation of water by the condenser
35
is dependent upon the operating condition of the system controller
57
.
Thus, depending upon the operating condition of the system controller
57
, it can be envisioned that there occurs a reduction in the amount of water reclaimed into the water tank
19
from the condenser
35
.
Given the above, in order to prevent water in the water tank
19
from running dry, one method that can be envisioned is that of increasing the capacity thereof. However, this is not desirable from the standpoint of layout for installing the fuel cell system SS in a vehicle.
With the fuel cell system SS, because it is necessary to replenish the water tank
19
with water before it runs dry of water, which can happen while the vehicle is being operated, for example, this being undesirable.
Accordingly, the present invention was made in consideration of the above-noted investigation, and has as an object to provide a fuel cell system and a method for controlling operating pressure thereof which substantially do not require replenishment of water used in the fuel cell system and which contributes to the improvement of the practicality thereof.
A fuel cell system according to the present invention comprises: a water tank; a reformer obtaining reformed gas by reforming fuel using water from the water tank; a fuel cell generating electric power using reformed gas from the reformer and gas that includes oxygen; a condenser reclaiming water from exhaust gas from the fuel cell, the exhaust gas reclaimed by the condenser being returned to the water tank; an exhaust gas temperature detector detecting temperature of exhaust gas from the condenser; and an operating pressure controller controlling the operating pressure of the fuel cell system. Here, the operating pressure controller, in response to the temperature of the exhaust gas from the condenser detected by the exhaust gas temperature detector, calculates equilibrium operating pressure of the fuel cell system at which inflow and outflow of the water within the fuel cell system is balanced, in response to operating load on the fuel cell system, calculates maximum efficiency operating pressure at which operating efficiency of the fuel cell system is maximum, and performs control of the operating pressure of the fuel cell system so as to achieve higher pressure of the equilibrium operating pressure and the maximum efficiency operating pressure.
In other words, a fuel cell system according to the present invention comprises: a water tank; a reformer obtaining reformed gas by reforming fuel using water from the water tank; a fuel cell generating electric power using reformed gas from the reformer and gas that includes oxygen; a condenser reclaiming water from exhaust gas from the fuel cell, the exhaust gas reclaimed by the condenser being returned to the water tank; an exhaust gas temperature detecting means for detecting temperature of exhaust gas from the condenser; and an operating pressure control means for controlling the operating pressure of the fuel cell system. Here, the operating pressure control means, in response to the temperature of the exhaust gas from the condenser detected by the exhaust gas temperature detecting means, calculates equilibrium operating pressure of the fuel cell system at which inflow and outflow of the water within the fuel cell system is balanced, in response to operating load on the fuel cell system, calculates maximum efficiency operating pressure at which operating efficiency of the fuel cell system is maximum, and performs control of the operating pressure of the fuel cell system so as to achieve higher pressure of the equilibrium operating pressure and the maximum efficiency operating pressure.
On the other hand, a method for controlling operating pressure of a fuel cell system according to the present invention is applied to a fuel cell system having a water tank, a reformer obtaining reformed gas by reforming a fuel using water from the water tank, a fuel cell generating electric power using reformed gas from the reformer and a gas that contains oxygen, and a condenser reclaming water from exhaust gas from the fuel cell and returning the water to the water tank. Here, the method detects temperature of exhaust gas from the condenser; calculates, in response to the temperature of the exhaust gas from the condenser, equillibrium operating pressure of the fuel cell at which inflow and outflow of the water within the fuel cell system is balanced; calculates operating load on the fuel cell system; calculates maximum efficiency operating pressure at which operating efficiency of the fuel cell system is maximum; and control the operating pressure of the fuel cell system s
Kalafut Stephen
Nissan Motor Co,. Ltd.
Wills M.
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