JP2007305429A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of executing appropriate power generation operation of a fuel cell for stably keeping an internal temperature of the fuel cell, even if disturbances occur in a heater for heating a second heating medium that has passed through a heat exchanger. <P>SOLUTION: This fuel cell system 100 is provided with the fuel cell 11; a heat transmitter 42 for transmitting heat to the second heating medium; a heater 33 for heating the second heating medium; a passage 101 of the second heating medium, extending from an entrance for guiding the second heating medium toward the heat transmitter 42 to an exit for guiding the second heating medium that has passed through the heater 33; a flow regulator 35 for regulating the flow rate of the second heating medium flowing through the passage 101; a first temperature-measuring instrument 55 for sensing the temperature of the second heating medium having passed through the heater 33 as a first reference temperature; a first detector 23 for detecting a first correlation amount correlated to a supply heat quantity to the second heating medium from the heater 33; and a controller 52. The controller 52 controls the flow rate of the second heating medium by the flow regulator 35 so as to set the first reference temperature at a target value defined, in response to the first correlation amount. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a temperature control technique for a second heat medium that recovers heat (exhaust heat) in the fuel cell system.

  An example of a power control system of a conventional fuel cell system includes an inverter that converts DC generated power output from a fuel cell into AC power, a generated power detector that detects AC power output by the inverter, and this AC And a power difference detector that detects reverse power (surplus power) obtained by subtracting power consumed in the power load (hereinafter referred to as “load power consumption”) from the power.

Then, from the viewpoint of effectively using such surplus power, the heat recovery water of the fuel cell system that enables the heat recovery water flowing toward the hot water storage tank to be appropriately cooked by a heater using the surplus power. Temperature control technology has already been developed, and here, as an example of temperature control of the heat recovery water, the circulation capacity of the hot water storage pump is adjusted so that the temperature of the heat recovery water after passing through the heater becomes a certain appropriate temperature. (See Patent Document 1).
Japanese Patent No. 3403667

  A heat recovery water temperature control technique as described in Patent Document 1 (hereinafter referred to as “conventional heat recovery water temperature control technique”) in which the water temperature is made constant after sequentially monitoring the temperature of the heat recovery water after passing through the heater. ) Is ideal for temperature control of an electric heat supply system because it can always supply water that has been optimally heated to a hot water storage tank.

  However, the present inventors consider that there is room for improvement in the conventional heat recovery water temperature control technology when the load power consumption is greatly and instantaneously fluctuating as described below.

  The change in the power generated by the fuel cell is normally limited to about 100 W / min in consideration of the stability of the entire fuel cell system, while the change in the load power consumption reaches 1 KW or more instantaneously. There are many.

  In other words, the surplus power detected by the power difference detector is difficult to quickly change the fuel gas generation based on the raw material gas reforming reaction by the fuel processor of the fuel cell system. Therefore, the power supplied to the heater set by the power setting device fluctuates greatly and instantaneously so as to be interlocked with the change.

  In such a situation, if the conventional heat recovery water temperature control technology is adopted as it is, the temperature of the heat recovery water after passing through the heater will be kept at a certain appropriate temperature, triggered by a large and instantaneous fluctuation in the power supplied to the heater. This can lead to significant changes in the circulation capacity of the hot water storage pump.

  It is estimated that such an excessive change in the circulation capacity of the hot water storage pump adversely affects the heat exchange effect of the heat exchanger for cooling the fuel cell.

  For example, if the temperature of the cooling water passing through the heat exchanger is shifted due to a rapid change in the flow rate of heat recovery water that exchanges heat with this, the internal temperature of the fuel cell becomes unstable. If the internal temperature of the fuel cell becomes unstable, proper power generation operation of the fuel cell is hindered.

  The present invention has been made in view of such circumstances, and some excessive disturbance (for example, power load) is applied to the heater that heats the second heat medium that has passed through the heat exchanger for cooling the fuel cell. It is an object to provide a fuel cell system capable of maintaining the internal temperature of the fuel cell stably even when an excessive fuel based on fluctuations) occurs, and capable of proper power generation operation of the fuel cell. And

  In order to solve the above problems, a fuel cell system according to the present invention includes a fuel cell that generates power using fuel gas and an oxidant gas, and a first heat medium that transports heat generated in the system during the power generation. A heat transfer device that transfers heat to the second heat medium, a heater that heats the second heat medium using surplus energy supplied from the fuel cell, and the heat transfer device toward the heat transfer device. A flow path of the second heat medium that extends from an inlet that leads the second heat medium to an outlet that leads the second heat medium that has passed through the heater to the outside; and a second heat medium that flows through the flow path A flow rate adjuster for adjusting the flow rate, a first temperature measuring device for detecting the temperature of the second heat medium passing through the heater as a first reference temperature, and the heater to the second heat medium. A first detector for detecting a first correlation amount that correlates with the amount of heat supplied; And the controller controls the flow rate of the second heat medium by the flow rate regulator so that the first reference temperature becomes a target temperature determined according to the first correlation amount. It is characterized by controlling.

  With such a configuration, large fluctuations in the energy supplied to the heater that heats the second heat medium that has passed through the heat transfer device for cooling the fuel cell (for example, excessive heating due to fluctuations in power load due to excessive power) Even when excessive power supply occurs), the target temperature of the second heat medium that has passed through the heater is set according to the first correlation amount that correlates with the amount of heat supplied from the heater to the second heat medium. By setting and controlling the flow rate of the second heat medium so as to match the target temperature, the temperature of the second heat medium in the flow path between the heat transfer device and the heater is stabilized, and the fuel It becomes possible to keep the internal temperature of the battery stable.

  In the configuration of the present invention, the target temperature is determined to be proportional to the first correlation amount.

  In the configuration of the present invention, the target temperature is determined such that the temperature of the second heat medium in the flow path between the heat transfer device and the heater is maintained at a predetermined temperature. To do.

  With such a configuration, the temperature of the second heat medium in the flow path between the heat transfer device and the heater is maintained at a predetermined temperature, and the internal temperature of the fuel cell can be kept more stable.

  In the configuration of the present invention, the heater is a heater that heats the second heat medium using the surplus power, and the first detector example is configured to generate a power load from the generated power of the fuel cell. It is a power difference detector which detects the surplus electric power which deducted the electric power by (2) as said 1st correlation amount.

  With such a configuration, even when excessive surplus power is supplied from the fuel cell to the surplus power heater, a target temperature after the heater is set according to the surplus power detected by the power difference detector. By controlling the flow rate of the second heat medium so as to match the target temperature, the temperature of the second heat medium in the flow path between the heat transfer device and the heater and the internal temperature of the fuel cell can be stabilized. It becomes possible to keep.

  In the configuration of the present invention, the heater is a combustion heater capable of combusting the combustible gas, and the first detector example is a flow rate of the combustible gas discharged from the fuel cell. Is a combustible gas flow rate detector that detects the above as the first correlation amount.

  With such a configuration, even when the flammable gas surplus from the power generation of the fuel cell is excessively supplied to the combustion heater, the flammable gas detected by the flammable gas flow detector is detected. By setting the target temperature of the second heat medium after the combustion detector according to the flow rate, and controlling the flow rate of the second heat medium so as to match the target temperature, the heat transfer device, the heater, It becomes possible to keep the temperature of the second heat medium in the flow path between and the internal temperature of the fuel cell stable.

  In the configuration of the present invention, a second detector that detects a second correlation amount that correlates with the temperature of the second heat medium in the flow path between the heat transfer device and the heater. The target temperature is based on the first correlation amount and the second correlation amount, and the temperature of the second heat medium in the flow path between the heat transfer device and the heater is predetermined. It is determined to be maintained at a temperature of

  With such a configuration, when the amount of heat supplied from the heat transfer device fluctuates, the temperature of the second heat medium in the flow path between the heat transfer device and the heater is predetermined in consideration of the change. The temperature is maintained, and the internal temperature of the fuel cell can be kept more stable.

  In the configuration of the present invention, an example of the second correlation amount is an amount of heat supplied to the second heat medium of the heat transfer device converted from the generated power of the fuel cell, and the second An example of the detector is a generated power detector that detects the generated power.

  In the configuration of the present invention, the second detector example is a second heat medium flow detector that detects the flow rate of the second heat medium as the second correlation amount.

  With such a configuration, the second value of the heat transfer device correlated with the temperature of the second heat transfer medium in the flow path between the heat transfer device and the heater from the flow rate value of the second heat transfer medium. The amount of heat to the heat medium is estimated. For this reason, it is not necessary to specially provide a detector that directly detects the amount of heat to the second heat medium of the heat transfer device, which is preferable because it can suppress an increase in cost of the fuel cell system.

  Further, in addition to the configuration of the present invention, a second temperature measuring device that detects the temperature of the second heat medium in the flow path between the heat transfer device and the inlet as a second reference temperature. And the target temperature is determined based on the first correlation amount, the second correlation amount, and the second reference temperature, the second heat in the flow path between the heat transfer device and the heater. The temperature of the medium is determined to be maintained at a predetermined temperature.

  When the reference temperature of the second heat medium sent out from the outlet of the hot water storage tank fluctuates with the passage of time, it is better to consider this temperature as well. Since the temperature of the second heat medium in the path is maintained at a predetermined temperature, it is preferable that the target temperature is more accurate.

  The first heat medium described above is cooling water that cools the inside of the fuel cell.

  In addition to the water, fuel gas and / or oxidant gas (power generation gas) may be used as the first heat medium.

  The target temperature has an upper limit temperature set in advance.

  By providing such an upper limit temperature, it is possible to prevent overheating of the second heat medium by the heater.

  Here, an example of the second heat medium is water, and includes a hot water storage tank that stores hot water heated by the heat exchanger and the heater, and an inlet and an outlet of the flow path are the hot water storage tank. Communicating with

  According to the present invention, large fluctuations in the energy supplied to the heater that heats the second heat medium that has passed through the heat exchanger for cooling the fuel cell (for example, due to excessive power due to fluctuations in the power load) Even when excessive power supply occurs, the temperature of the second heat medium in the flow path between the heat transfer device and the heater is stabilized, and the internal temperature of the fuel cell is kept stable. enable.

  Hereinafter, preferred embodiments 1 and 2 of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration example of a fuel cell system according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the fuel cell system 100 (fuel cell cogeneration system) uses a hydrogen-rich fuel gas (power generation gas) and an oxidant gas (power generation gas) such as air to generate power and generate heat (exhaust heat release). The fuel cell 11 is configured.

  Such a fuel cell system 100 roughly includes a power generation gas system for supplying and exhausting power to the fuel cell 11, a power control system for controlling power output from the fuel cell 11, and a fuel cell 11. A cooling system for circulating the cooling water that functions to keep the temperature at an appropriate temperature, and an exhaust that efficiently recovers the heat generated by the heat generation (exhaust heat) of the fuel cell system 100 through heat exchange with the power generation gas and cooling water of the fuel cell system 100. There are a heat recovery system and an operation control system for appropriately controlling the operation of the fuel cell system 100.

  The power generation gas system of the fuel cell system 100 includes, for example, a fuel processor 12 and a blower 13.

  The fuel processor 12 is attached to the fuel cell 11 and is reformed by adding water to a raw material gas such as city gas or natural gas supplied from the existing infrastructure, so that it is a hydrogen-rich high-temperature (for example, several hundred degrees) fuel. It is configured to generate gas. The fuel processor 12 is based on a known technique, and a detailed description of its configuration is omitted here.

  Further, as shown by the double line with an arrow in FIG. 1, the fuel processor 12 causes heat recovery water (second heat) to be described later in the fuel gas / heat recovery water heat exchanger 41 (heat transfer unit; hereinafter). The fuel gas exchanged with the medium) to supply heat to the heat recovery water is supplied to the anode of the fuel cell 11.

  Further, an oxidant gas such as air is supplied to the cathode of the fuel cell 11 by the blower 13 provided along with the fuel cell 11 as indicated by a double line with an arrow in FIG.

  Here, the remaining fuel gas (off-gas) at an appropriate temperature (for example, 70 ° C.) that has not been consumed at the anode of the fuel cell 11 is transferred to the heat recovery water in the first condenser 43 (heat transfer unit; described later). Thus, heat is exchanged so as to transfer heat to the heat recovery water, and it is discharged by the pumping force of the fuel processor 12 toward the heating burner 10 of the fuel processor 12 and burned as fuel of the burner 10.

  Further, the remaining oxidant gas at an appropriate temperature (for example, 70 ° C.) that has not been consumed at the cathode of the fuel cell 11 is exchanged with the heat recovery water in the second condenser 44 (heat transfer unit; described later). Heat is exchanged so as to transfer heat to the recovered water, and the air is discharged into the atmosphere by the pumping force of the blower 13.

  As shown in FIG. 1, the power control system of the fuel cell system 100 includes an inverter 21 that converts DC generated power of the fuel cell 11 into AC power, and a generated power detector 22 that detects AC power output from the inverter 21. And a power difference detector 23 for detecting surplus power obtained by subtracting the load power consumed in the power load from the AC power.

  Here, the output side of the inverter 21 that has passed through the generated power detector 22 is connected to both a power load (for example, a household power load) that supplies AC power of the inverter 21 and a power system of an existing infrastructure. .

  For this reason, when the output power of the inverter 21 is less than the load power consumption, it is possible to supply power required for the power load from both the inverter 21 and the power system.

  Conversely, when the output power of the inverter 21 exceeds the load power consumption, the surplus power detected by the power difference detector 23 (the portion of the output power of the inverter 21 that exceeds the load power consumption) The setting device 34 sets power supply power to a heater 33 (heater) for heat recovery water heating described later and is consumed by the heater 33, whereby the heat recovery water is heated and heated by the heater 33.

  Further, in the cooling system of the fuel cell system 100, the cooling water flow path indicated by the thick one-dot chain line arrow in FIG. Heat medium). The cooling water plays a role of transporting heat generated by the heat generation (reaction heat) of the fuel cell 11 to the outside of the fuel cell 11.

  The cooling system further includes a cooling water pump 31 that circulates the fuel cell 11 while adjusting the flow rate of the cooling water in the cooling water flow path so as to keep the inside of the fuel cell 11 at an appropriate temperature (for example, 70 ° C.). A cooling water / heat recovery water heat exchanger 42 (heat transfer unit; described later) configured to transmit heat to the heat recovery water by heat exchange between the heat recovery water and the heat recovery water is provided in the middle of the cooling water flow path. ing.

  Further, the exhaust heat recovery system of the fuel cell system 100 is provided with a hot water storage tank 32 (heat storage unit) for storing hot water (hot water stored in the city water of the existing infrastructure). Then, the heat recovery water taken out from the heat recovery water outlet 32A at the lower part of the hot water storage tank 32 is supplied to the fuel through a combined heat exchange system (details will be described later) by a hot water storage pump 35 which is a flow rate regulator of the present invention. The heat (exhaust heat) in the battery system 100 and the heat from the heater 33 are received, whereby the heat recovery water is heated to an appropriate temperature and then returned to the heat recovery water inlet 32B in the upper part of the hot water storage tank 32.

  Here, the heat recovery water outlet 32A guides the water in the vicinity of the city water (tap water) inlet of the hot water storage tank 32 to the heat recovery water passage 101 toward the combined heat exchange system. It corresponds to the entrance. The heat recovery water inlet 32 </ b> B corresponds to an outlet of the heat recovery water passage 101 that guides the heat recovery water that has passed through the heater 33 to the hot water storage tank 32. That is, the heat recovery water passage 101 is connected to the heat recovery water outlet 32A (the inlet of the heat recovery water passage 101) of the hot water storage tank 32 and the heat recovery water inlet 32B (the outlet of the heat recovery water passage 101) of the hot water storage tank 32. The hot water storage tank 32 is communicated with and extends from the inlet to the outlet. Moreover, although the hot water storage pump was illustrated as a flow regulator of this invention, the valve (needle valve; not shown) which can adjust flow volume may be sufficient.

  Further, here, the heater 33 of the exhaust heat recovery system is disposed in the middle of the heat recovery water passage 101 located between the cooling water / heat recovery water heat exchanger 42 and the heat recovery water inlet 32B of the hot water storage tank 32. Yes.

  As an example of the combined heat exchange system of the exhaust heat recovery system, in the present embodiment, moisture discharged from the cathode in order along the flow direction of the heat recovery water flow path 101 indicated by the thick solid arrow in FIG. A second condenser 44 serving both as a heat exchange function between the oxidant gas containing oxygen and the heat recovery water and a function of removing moisture in the oxidant gas, and the off gas containing water discharged from the anode and the heat recovery water Between the first condenser 43 serving both as a heat exchange function between the fuel processor and the moisture removal function in the off-gas, and between the fuel gas and the heat recovery water that are being sent from the fuel processor 12 to the fuel cell 11 The fuel gas / heat recovery water heat exchanger 41 having a heat exchange function and a cooling water / heat recovery water heat exchanger having a heat exchange function between the cooling water circulated by the cooling water pump 31 and the heat recovery water 42 are provided.

  In short, the heat recovery water flowing out from the heat recovery water outlet 32A of the hot water storage tank 32 is pumped by the hot water storage pump 35, and the second condenser 44, the first condenser 43, and the fuel gas in the middle of the heat recovery water flow path 101. / Heat recovery water heat exchanger 41 and cooling water / heat recovery water heat exchanger 42 in this order, enter the heater 33, and then the heat recovery water exiting the heater 33 is the heat recovery water flow of the hot water storage tank 32 It is returned again to the entrance 32B. In this way, heat recovery water is circulated.

  The operation control system of the fuel cell system 100 includes a plurality of control devices including, for example, microprocessors. An example of the control device group here is the one after passing through the heater 33 (more precisely, the heater 33 and the hot water storage tank 32). The flow rate / temperature for determining the target temperature Ra of the heat recovery water temperature (hereinafter referred to as “water temperature after heating the heater”) of the heat recovery water flow path 101) located between the heat recovery water inlet 32 </ b> B and the heat recovery water inlet 32 </ b> B. An arithmetic unit 51, a hot water storage pump regulator 52 capable of adjusting the discharge flow rate of the heat recovery water by the hot water storage pump 35, a cooling water pump regulator 53 capable of adjusting the discharge amount of the cooling water by the cooling water pump 31, and a fuel cell. And a controller 102 that controls the overall operation of the system 100.

  In the fuel cell system of the present embodiment, the controller of the present invention includes the hot water storage pump regulator 52 and the flow rate / temperature calculator 51. Further, these devices are distributedly arranged, and are not limited to a configuration in which the operation of the fuel cell system is controlled in cooperation with each other, and means a single control device in which these devices are integrated. That is, the flow rate / temperature computing unit 51 and the hot water storage pump regulator 52 may be integrated and configured as a single controller.

  The detector that detects input data when the flow rate / temperature calculator 51 determines the target temperature Ra of the water temperature after heating the heater is between the second condenser 44 and the heat recovery water outlet 32A of the hot water storage tank 32. A second temperature detector 54 that detects the temperature of the heat recovery water flowing through the heat recovery water flow channel 101 before being heated by heat exchange (hereinafter referred to as “heat recovery water temperature before heat exchange”) (for example, A thermistor or a thermocouple), a power difference detector 23 that detects the power supplied to the heater 33, and a generated power detector 22 that detects the amount of power generated by the fuel cell 11.

  Then, as will be described in detail later, the flow rate / temperature calculator 51, based on the data detected by these detectors 54, 23, and 22, some sort of excessive disturbance (for example, power load fluctuation) Heat supply that can maintain the temperature of the heat recovery water after passing through the cooling water / heat recovery water heat exchanger 42 at a constant value (for example, about 62 ° C. described later) The flow rate of water is estimated and calculated as a target flow rate, and the target temperature Ra is calculated and set from the estimated value of the flow rate of the heat recovery water, and the target temperature Ra is output to the hot water storage pump regulator 52. Has been.

  On the other hand, the hot water storage pump regulator 52 compares the target temperature Ra received from the flow rate / temperature calculator 51 with the heat recovery water temperature detected by the first temperature detector 55 (for example, a thermistor or a thermocouple). And it is comprised so that the discharge flow volume (heat recovery water circulation capability) by the hot water storage pump 35 may be adjusted so that both may correspond.

  The first temperature detector 55 measures the water temperature after heating the heater.

  Further, the cooling water pump adjuster 53 monitors the temperature of the cooling water circulating through the cooling water flow path by a third temperature detector 56 (for example, a thermistor or a thermocouple), and this temperature is maintained at a certain appropriate temperature (for example, The cooling water discharge flow rate (cooling water circulation capability) by the cooling water pump 31 is adjusted so as to be controlled to 70 ° C.).

  Next, the operation of the fuel cell system 100 according to the present embodiment will be described.

  Even when the power supplied to the heater 33 for heating the heat recovery water, which is located downstream of the cooling water / heat recovery water heat exchanger 42 in the heat recovery water flow direction, fluctuates greatly and instantaneously, the stability of the fuel cell system 100 is improved. In order to maintain the correct power generation, it is important to keep the internal temperature of the fuel cell 11 as constant as possible (for example, around 70 ° C.).

  Accordingly, it is essential to eliminate a significant instantaneous fluctuation in the heat exchange capacity of the cooling water / heat recovery water heat exchanger 42 that cannot be controlled by the cooling water circulation capacity adjustment by the cooling water pump regulator 53. , After passing through the cooling water / heat recovery water heat exchanger 42 (more precisely, heat recovery in the vicinity of the cooling water / heat recovery water heat exchanger 42 between the cooling water / heat recovery water heat exchanger 42 and the heater 33) The inventors of the present invention estimate that stabilization of the temperature of the heat recovery water in the water channel 101) is most effective.

  Based on such a design concept, the target temperature Ra with respect to the water temperature after heating the heater is set so as to maintain the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42 at a constant temperature.

  Since the hot water in the hot water storage tank 32 is used for hot water supply, it is desirable to adjust the temperature of the heat recovery water returned to the hot water storage tank 32 to 60 ° C. or higher. In view of the non-energized state of the heater 33, the temperature of the heat recovery water after passing through the cooling water / heat recovery water heat exchanger 42 in anticipation of the amount of heat released when flowing toward the hot water storage tank 32 is It can be said that it is preferable to set the temperature to about 62 ° C. slightly higher than 60 ° C.

  First, various heat calculation formulas necessary for setting the target temperature Ra by the flow rate / temperature calculator 51 will be described.

<First thermal calculation formula>
The combined heat exchange system (here, the first and second condensers 43 and 44, the fuel gas / heat recovery water heat exchanger 41 and the cooling water / heat recovery water heat exchanger 42) allows the fuel cell system 100 to operate. The total supply heat amount Qa (watt hour; Wh) to be supplied to the heat recovery water from the power generation power amount Qf (Wh) detected by the generated power detector 22 as shown in the following equation (1) It is approximated as a numerical value obtained by multiplying a predetermined constant (about 1.4 here) obtained by experiment.

  Thus, by estimating the total supplied heat amount Qa from the generated power amount Qf, there is no need to provide a detector for directly detecting the total supplied heat amount Qa of the combined heat exchange system, and the cost of the fuel cell system 100 is reduced. This is preferable because it can suppress the increase.

Qa = 1.4 × Qf (1)
However, this constant (1.4) is a numerical value peculiar to the fuel cell system 100 according to the present embodiment. Of course, if the system configuration of the fuel cell system changes, this constant also needs to be corrected.

<Second thermal calculation formula>
The heat recovery water temperature Ti before heat exchange detected by the second temperature detector 54 and the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42 (here, 62 ° C. is substituted) are used. The flow rate Gwa (liter / min; L / min) per unit time of the heat recovery water flowing through the heat recovery water channel 101 is expressed by the equation shown in the following (2) from the relationship with the total supply heat amount Qa. .

  Thus, by substituting a predetermined constant (62 ° C.) as the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42, the flow rate Gwa (the target temperature Ra setting calculation) can be calculated. In addition to simplification, it is not necessary to provide a detector for directly detecting the temperature of the heat recovery water after passing through the cooling water / heat recovery water heat exchanger 42, which is preferable because the cost increase of the fuel cell system 100 can be suppressed. is there.

Qa = 1 (kcal / kg · ° C) x 1 (kg / L) x 1.16 (Wh / kcal) x Gwa (L / min) x 60 (min)
× (62-Ti) (° C.) = 1.16 × 60 × Gwa × (62-Ti) (2)
<Third thermal calculation formula>
Here, the power supply amount Qh (Wh) (hereinafter referred to as “heater supply power amount Qh”) to the heater 33 corresponding to the surplus power detected by the power difference detector 23 is supplied to the heat recovery water by the heater 33. It is a physical quantity (correlation quantity) that has a correlation with the amount of heat generated, and can be considered to be equivalent to the heat quantity of heat recovery water heating by the heater 33.

  Therefore, the target temperature Ra by the flow rate / temperature calculator 51 is expressed by the equation shown in the following (3) using the heater power supply amount Qh and the flow rate Gwa.

  In addition, this target temperature Ra is a temperature (corresponding to the water temperature after heating the heater) detected by the first temperature detector 55 (for example, a thermistor or a thermocouple) as understood from the following equation (3). Target temperature).

Qh = 1.16 × 60 × Gwa × (Ra-62) (3)
Next, FIG. 2 shows a calculation method of Gwa as the target flow rate and target temperature Ra as the set temperature by the flow rate / temperature calculator 51 based on the above formulas (1), (2), and (3). The description will be given with reference.

  FIG. 2 is a flowchart showing an example of the operation of the flow rate / temperature calculator according to this embodiment.

  The flow rate / temperature computing unit 51 may generate any excessive disturbance to the heater 33 that heats the second heat medium that has passed through, for example, the cooling water / heat recovery water heat exchanger 42 (for example, surplus due to power load fluctuations). In preparation for excessive power supply to the heater due to excessive power), the process shown in FIG. 2 is repeatedly executed at regular intervals.

  That is, since the total supply heat amount Qa and the heater supply power amount Qh are highly likely to change from moment to moment, the flow rate / temperature computing unit 51 monitors these fluctuations sequentially, and this flow rate / temperature computation. The determination of the target temperature of the water temperature after heating by the heater 51 and the adjustment of the heat recovery water flow rate by the hot water storage pump regulator 52 are appropriately performed in accordance with the fluctuations in the total supply heat amount Qa and the heater supply power amount Qh. Executed according to

  Here, the above equations (1), (2), and (3) are all stored in advance in a storage device (not shown) such as a ROM, and the control device (flow rate / temperature calculator 51) These equations are appropriately read out to perform necessary calculations.

  First, the flow rate / temperature computing unit 51 reads the power amount Qf, the heat recovery water temperature Ti before heat exchange, and the heater power supply amount Qh from each detector 22, 23, 54 (step S201).

  Then, the flow rate / temperature computing unit 51 substitutes the cooling water / heat recovery water heat exchanger 42 by substituting the electric energy Qf and the heat recovery water temperature Ti before heat exchange into the above formulas (1) and (2). The flow rate Gwa (target) capable of maintaining the heat recovery water temperature after passing through at about 62 ° C. is calculated and acquired as a target flow rate (step S202).

  Subsequently, the flow rate / temperature calculator 51 calculates and obtains the target temperature Ra by substituting the calculated flow rate Gwa (target) and the heater power supply amount Qh into the above equation (3) (step S203). .

  Here, the flow rate / temperature calculator 51 compares the target temperature Ra with an upper limit temperature (described later) of a predetermined allowable range, and determines whether or not the target temperature Ra is equal to or lower than the upper limit temperature of the allowable range ( Step S204).

  If the calculated target temperature Ra is equal to or lower than the upper limit temperature (“Yes” in step S204), the flow rate / temperature calculator 51 sets the target temperature Ra as the target temperature, and sets this value as the hot water storage pump adjuster 52. (Step S205).

  On the other hand, if the calculated target temperature Ra exceeds the upper limit temperature (“No” in step S204), this upper limit temperature is set as the target temperature and this value is output to the hot water storage pump regulator 52 ( Step S206).

  The hot water storage pump regulator 52 receives the target temperature Ra (or upper limit temperature) from the flow rate / temperature calculator 51, and the target temperature Ra (or upper limit temperature) and the water temperature after heater heating by the first temperature detector 55. The discharge flow rate of the hot water storage pump 35 for heat recovery water pumping is changed so that the two coincide with each other.

  As described above, according to the fuel cell system 100 of the present embodiment, the heater supplied power amount Qh for heating the heat recovery water located downstream of the cooling water / heat recovery water heat exchanger 42 in the heat recovery water flow direction is greatly increased. And even if it fluctuates instantaneously, since the heat recovery water flow rate is appropriately adjusted so as to keep the heat recovery water temperature stable after passing through the cooling water / heat recovery water heat exchanger 42, the cooling water / The heat exchange capacity of the heat recovery water heat exchanger 42 can be stabilized, whereby the temperature of the fuel cell 11 is maintained at an appropriate temperature (for example, around 70 ° C.), and the fuel cell system 100 can maintain stable power generation. .

  In this case, if the heater supply power amount Qh for heating the heat recovery water is extremely increased due to some factor, the target temperature Ra by the flow rate / temperature calculator 51 is the boiling point (100 ° C.) of the heat recovery water. It is assumed that the situation will exceed. For this reason, it can be said that it is desirable to provide an upper limit temperature as an allowable range of the target temperature Ra from the viewpoint of preventing boiling of the heat recovery water due to excessive heating of the heat recovery water of the heater 33.

  Here, the upper limit temperature of the target temperature Ra does not exceed at least the boiling point (100 ° C.) of the heat recovery water, and the first temperature when adjusting the heat recovery water discharge flow rate of the hot water storage pump 35 by the hot water storage pump adjuster 52 is set. In consideration of a transient delay in obtaining the data of the water temperature after heating the heater detected by the temperature detector 55, the temperature is set to about 85 ° C., which is lower than the boiling point.

  In the above-described embodiment, when the target temperature Ra is set, the target temperature Ra is calculated in real time based on the first to third heat calculation formulas by the flow rate / temperature calculator 51. The power amount Qf detected by the detector 22, the heater supply power amount Qh detected by the power difference detector 23, and the pre-heat exchange heat recovery water temperature Ti detected by the second temperature detector 54 are independent of each other. It is also possible to use a target temperature Ra obtained by the above heat calculation formula as a dependent variable and make a database of the relationship between the two in advance. If it does so, it will be equipped with the memory | storage device (not shown) which memorize | stored each Ra value matched with each Qf, each Qh value, and each Ti, Furthermore, it replaces with the flow volume / temperature calculator 51, and an appropriate processing apparatus ( (Not shown), and this processing apparatus detects the power amount Qf detected by the generated power detector 22, the heater power supply amount Qh detected by the power difference detector 12, and the second temperature detector 54. The target temperature Ra corresponding to the combination of the heat recovery water temperature Ti before heat exchange to be performed can be read out from the storage device, and the hot water storage pump adjuster 52 controls the hot water storage pump 35 so that the target temperature Ra matches the water temperature after heating the heater. It can be controlled properly.

(Embodiment 2)
FIG. 3 is a block diagram showing a configuration example of the fuel cell system according to Embodiment 2 of the present invention.

  Of the constituent members of the fuel cell system 110 of the present embodiment, the same members as those of the fuel cell system 100 of the first embodiment are denoted by the same reference numerals and are common to both. The description of the constituent members will be omitted or kept briefly.

  In short, the fuel cell system 110 is configured so that the power control system of the fuel cell system 110 can output the maximum power in a range that does not reverse flow while monitoring the load power consumption in conjunction with the power system of the existing infrastructure. While controlling the power generation operation of the fuel cell 11, the fuel gas supplied from the hydrogen supply device 61 and not consumed by the fuel cell 11 (residual hydrogen gas) is used to heat the heat recovery water for the hot water storage tank for heating. It is a system that is configured to be used effectively.

  Therefore, in the fuel cell system 110 of the present embodiment, the consumption per unit time of the hydrogen gas by the fuel cell 11 varies according to the change in load power consumption with time, and as a result, heat recovery from the fuel cell 11 The remaining hydrogen gas supplied to the water heating combustion heater 62 (heater) varies over time.

  For this reason, if the fuel cell system of the present embodiment is controlled in accordance with the conventional heat recovery water temperature control technology, the heat recovery water temperature detector after passing through the combustion heater 62 as in the first embodiment. The circulating capacity of the hot water storage pump 35 may be significantly changed so as to keep the temperature at an appropriate temperature.

  The power generation gas system of the fuel cell system 110 is replaced with the fuel processor 12 and the burner 10 of the fuel processor 12 described in the first embodiment (FIG. 1), as shown in FIG. A hydrogen supply device 61 for supplying hydrogen gas (power generation gas) at a constant flow rate per hour is provided.

  The hydrogen gas directed to the anode of the fuel cell 11 is adjusted in humidification conditions by an appropriate humidifier (not shown).

  Further, the remaining hydrogen gas at an appropriate temperature (for example, 70 ° C.) that has not been consumed in the anode of the fuel cell 11 is removed by a suitable condenser (not shown), and then in Embodiment 1 (FIG. 1). It is discharged by the pumping force of the hydrogen supply device 61 toward the combustion heater 62 that performs the same function as the heater 33 described above (heating of the heat recovery water through the cooling water / heat recovery water heat exchanger 42). Thus, the remaining hydrogen gas is used as a combustion fuel gas for the combustion heater 62, and the heat recovery water is heated and heated by the combustion heater 62.

  Here, the combustion heater 62 of the exhaust heat recovery system is arranged in the middle of the heat recovery water flow path 101 located between the cooling water / heat recovery water heat exchanger 42 and the heat recovery water inlet 32B of the hot water storage tank 32. Has been.

  Further, the power control system of the fuel cell system 110 is output by the fuel cell 11 as shown in FIG. 3 without the detector corresponding to the power difference detector 23 described in the first embodiment (FIG. 1). The inverter 21 is configured to convert DC generated power into AC power, and the generated power detector 22 detects AC power output from the inverter 21.

  As an example of the heat exchange system, in the present embodiment, the first and second condensers 43 and 44 and the fuel gas / heat recovery water heat exchanger 41 shown in the first embodiment (FIG. 1) are used. Instead, only the cooling water / heat recovery water heat exchanger 42 having a heat exchange function between the cooling water circulated by the cooling water pump 31 and the heat recovery water is provided.

  In short, the heat recovery water flowing out from the heat recovery water outlet 32 A of the hot water storage tank 32 is pumped by the hot water storage pump 35, passes through the cooling water / heat recovery water heat exchanger 42 in the middle of the heat recovery water flow path 101, and then the combustion heater Thereafter, the heat recovery water that has exited the combustion heater 62 is returned to the heat recovery water inlet 2B of the hot water storage tank 32 again. In this way, heat recovery water is circulated.

  Here, the flow rate / temperature calculator 51 detects data when determining the target temperature Rb of the temperature of the heat recovery water after passing through the combustion heater 62 (hereinafter referred to as “water temperature after combustion heating”). The heat exchanger flows through the heat recovery water flow path 101 (upstream heat recovery water flow path 101) between the cooling water / heat recovery water heat exchanger 42 and the heat recovery water outlet 32A of the hot water storage tank 32, and rises by heat exchange. A second temperature detector 54 for detecting the temperature of the heat recovery water before being heated (hereinafter referred to as “heat recovery water temperature before heat exchange”), and the remaining hydrogen gas flow rate sent from the anode of the fuel cell 11 There are a hydrogen gas flow rate detector 63 for detecting the generated power and a generated power detector 22 for detecting the generated power of the fuel cell 11.

  Then, as will be described in detail later, the flow rate / temperature computing unit 51 performs any excessive disturbance (for example, power load) to the combustion heater 62 based on the data detected by these detectors 54, 63, 22. In the case of extreme fuel excess due to fluctuations), the flow rate of the heat recovery water that can maintain the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42 at a constant value (for example, about 62 ° C. described later) is the target flow rate. The target temperature Rb is calculated and set from the estimated value of the flow rate of the heat recovery water, and the target temperature Rb is output to the hot water storage pump regulator 52.

  On the other hand, the hot water storage pump regulator 52 is detected by the target temperature Rb received from the flow rate / temperature calculator 51 and the first temperature detector 55 (for example, a thermistor or a thermocouple) as in the first embodiment. The heat recovery water temperature is compared, and the discharge flow rate (heat recovery water circulation capability) of the heat recovery water by the hot water storage pump 35 is adjusted so that both coincide with each other.

  The first temperature detector 55 measures the water temperature after combustion heating.

  Furthermore, the cooling water pump regulator 53 monitors the temperature of the cooling water circulating in the cooling water flow path by the third temperature detector 56 (for example, a thermistor or a thermocouple), as in the first embodiment. In order to control this temperature to a constant appropriate temperature (for example, 70 ° C.), the cooling water discharge flow rate (cooling water circulation capability) by the cooling water pump 31 is adjusted.

  Next, the operation of the fuel cell system 110 according to the present embodiment will be described.

  The fuel cell when the amount of residual hydrogen gas to the combustion heater 62 for heating the heat recovery water located downstream of the cooling water / heat recovery water heat exchanger 42 in the heat recovery water flow direction fluctuates greatly and instantaneously. In order to maintain stable power generation in the system 110, it is important to keep the internal temperature of the fuel cell 11 as constant as possible (for example, around 70 ° C.).

  Therefore, it is essential to eliminate a significant instantaneous fluctuation in the heat exchange capacity of the cooling water / heat recovery water heat exchanger 42 that cannot be controlled by the cooling water circulation capacity adjustment by the cooling water pump regulator 53. , After passing through the cooling water / heat recovery water heat exchanger 42 (more precisely, between the cooling water / heat recovery water heat exchanger 42 and the combustion heater 62, in the vicinity of the cooling water / heat recovery water heat exchanger 42 The inventors estimate that stabilization of the temperature of the heat recovery water in the heat recovery water flow channel 101) is most effective.

  Based on such a design concept, the target temperature Rb corresponding to the water temperature after combustion heating is set so as to maintain the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42 at a constant temperature. The

  Since the hot water in the hot water storage tank 32 is used for hot water supply, it is desirable to adjust the temperature of the heat recovery water returned to the hot water storage tank 32 to 60 ° C. or higher. Therefore, in consideration of the non-combustion state of the combustion heater 62, the temperature of the heat recovery water after passing through the cooling water / heat recovery water heat exchanger 42 is estimated in consideration of the amount of heat released when flowing toward the hot water storage tank 32. It can be said that it is preferable to set the temperature to about 62 ° C., slightly higher than 60 ° C.

  First, various heat calculation formulas necessary for setting the target temperature Rb by the flow rate / temperature calculator 51 will be described.

<First thermal calculation formula>
The total amount of heat Qb (watt hour; Wh) provided to the heat recovery water from the fuel cell system 110 by the heat exchange system (here, the cooling water / heat recovery water heat exchanger 42) is expressed by the following equation (1). As described above, the power generation amount Qf (Wh) detected by the generated power detector 22 is approximated as a numerical value obtained by multiplying a predetermined constant (about 1.2 in this case) obtained in advance by experiments.

  Thus, by estimating the total supplied heat quantity Qb from the generated power quantity Qf, it is not necessary to provide a detector for directly detecting the total supplied heat quantity Qb of the heat exchange system, and the cost increase of the fuel cell system 110 is suppressed. This is preferable.

Qb = 1.2 × Qf (1)
However, this constant (1.2) is a numerical value peculiar to the fuel cell system 110 according to the present embodiment. Of course, if the system configuration of the fuel cell system changes, this constant also needs to be corrected.

<Second thermal calculation formula>
The heat recovery water temperature Ti before heat exchange detected by the second temperature detector 54 and the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42 (here, 62 ° C. is substituted) are used. The flow rate Gwb (liter / min; L / min) per unit time of the heat recovery water flowing through the heat recovery water channel 101 is expressed by the equation shown in the following (2) from the relationship with the total supply heat amount Qb. .

  Thus, by substituting a predetermined constant (62 ° C.) as the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42, the flow rate Gwb is calculated (target temperature Rb setting calculation). In addition to simplification, it is not necessary to provide a detector for directly detecting the temperature of the heat recovery water after passing through the cooling water / heat recovery water heat exchanger 42, which is preferable because the cost increase of the fuel cell system 110 can be suppressed. is there.

Qb = 1.16 × 60 × Gwb × (62-Ti) (2)
<Third thermal calculation formula>
Here, the remaining hydrogen gas flow rate discharged from the cathode of the fuel cell 11 detected by the hydrogen gas flow rate detector 63 is a physical quantity (correlation) correlated with the amount of heat supplied to the heat recovery water by the combustion heater 62. The combustion heat quantity Qv (Wh) of the combustion heater 62 (hereinafter referred to as “combustion heater combustion heat quantity Qv”) can be easily converted from this hydrogen gas flow rate.

  Therefore, the target temperature Rb by the flow rate / temperature calculator 51 is expressed by the following equation (3) using the combustion heater combustion heat quantity Qv and the flow rate Gwb converted from the hydrogen gas flow rate.

  The target temperature Rb is a temperature (target temperature) detected by the first temperature detector 55 (for example, a thermistor or a thermocouple) corresponding to the water temperature after combustion heating, as understood from the following equation (3). ).

  Of course, instead of detecting the remaining hydrogen gas flow rate by the hydrogen gas flow rate detector 63, the combustion heater 62 is combusted by the combustion heater 62 by detecting the temperature of the combustion heater 62 by an appropriate temperature detector (not shown). The amount of heat Qv may be converted.

Qv = 1.16 × 60 × Gwb × (Rb−62) (3)
Next, a calculation method of Gwb as the target flow rate and the target temperature Rb as the set temperature by the flow rate / temperature calculator 51 based on the above formulas (1), (2) and (3) is shown in FIG. Please refer to.

  FIG. 4 is a flowchart showing an operation example of the flow rate / temperature calculator according to this embodiment.

  Note that the flow rate / temperature calculator 51 generates some excessive disturbance to the combustion heater 62 that heats the second heat medium that has passed through, for example, the cooling water / heat recovery water heat exchanger 42 (for example, based on power load fluctuations). In preparation for extreme fuel surplus), the processing shown in FIG. 4 is repeatedly executed at regular intervals.

  That is, since the total supply heat quantity Qb and the combustion heater combustion heat quantity Qv are likely to change from moment to moment, the flow rate / temperature calculator 51 monitors these fluctuations sequentially, and the flow rate / temperature calculation is performed. The setting of the target temperature of the water temperature after combustion heating by the vessel 51 and the adjustment of the heat recovery water flow rate by the hot water storage pump regulator 52 are appropriately performed in accordance with the fluctuations in the total supply heat amount Qb and the combustion heater combustion heat amount Qv. It is executed according to the processing.

  Here, the above equations (1), (2), and (3) are all stored in advance in a storage device (not shown) such as a ROM, and the control device (flow rate / temperature calculator 51) These equations are read to perform necessary calculations.

  First, the flow rate / temperature computing unit 51 reads the power amount Qf, the pre-heat exchange heat recovery water temperature Ti, and the combustion heater combustion heat amount Qv from the detectors 22, 54, 63 (step S401).

  Then, the flow rate / temperature computing unit 51 substitutes the cooling water / heat recovery water heat exchanger 42 by substituting the electric energy Qf and the heat recovery water temperature Ti before heat exchange into the above formulas (1) and (2). A flow rate Gwb (target) capable of maintaining the heat recovery water temperature after passing through at about 62 ° C. is calculated and acquired as a target flow rate (step S402).

  Subsequently, the flow rate / temperature calculator 51 calculates and acquires the target temperature Rb by substituting the calculated flow rate Gwb (target) and the combustion heater combustion heat quantity Qv into the above equation (3) (step S403). ).

  Here, the flow rate / temperature calculator 51 compares the target temperature Rb with an upper limit temperature (described later) of a predetermined allowable range, and determines whether or not the target temperature Rb is equal to or lower than the upper limit temperature of the allowable range ( Step S404).

  If the calculated target temperature Rb is equal to or lower than the upper limit temperature (“Yes” in step S404), the flow rate / temperature calculator 51 sets the target temperature Rb as the target temperature, and sets this value as the hot water storage pump regulator 52. (Step S405).

  On the other hand, if the calculated target temperature Rb exceeds the upper limit temperature (“No” in step S404), this upper limit temperature is set as the target temperature, and this value is output to the hot water storage pump regulator 52 ( Step S406).

  The hot water storage pump regulator 52 receives the target temperature Rb (or upper limit temperature) from the flow rate / temperature calculator 51, and the target temperature Rb (or upper limit temperature) and the water temperature after combustion heating by the first temperature detector 55. The discharge flow rate of the hot water storage pump 35 for heat recovery water pumping is changed so that the two coincide with each other.

  As described above, according to the fuel cell system 110 of the present embodiment, the combustion heater combustion heat quantity Qv for heating the heat recovery water, which is located downstream of the cooling water / heat recovery water heat exchanger 42 in the heat recovery water flow direction, is obtained. Since the heat recovery water flow rate is properly adjusted so that the temperature of the heat recovery water after passing through the cooling water / heat recovery water heat exchanger 42 is kept stable even if there is a large and instantaneous fluctuation, the cooling water / The heat exchange capacity of the heat recovery water heat exchanger 42 can be stabilized, whereby the temperature of the fuel cell 11 can be maintained at an appropriate temperature (for example, around 70 ° C.), and the fuel cell system 110 can maintain stable power generation. Become.

  In this case, if the combustion heater combustion heat quantity Qv for heating the heat recovery water is extremely increased due to some factor, the target temperature Rb by the flow rate / temperature calculator 51 is equal to the boiling point of the heat recovery water (100 ° C. ) Is also expected. Therefore, it can be said that it is desirable to provide an upper limit temperature as an allowable range of the target temperature Rb from the viewpoint of preventing boiling of the heat recovery water due to unexpected excessive heating of the heat recovery water of the combustion heater 62.

  Here, the upper limit temperature of the target temperature Rb does not exceed at least the boiling point (100 ° C.) of the heat recovery water, and the first temperature when adjusting the heat recovery water discharge flow rate of the hot water storage pump 35 by the hot water storage pump regulator 52. Taking into account the transient delay in the acquisition of post-combustion water temperature data detected by the temperature detector 55, the temperature is set to about 85 ° C., which is lower than the boiling point.

In the above-described embodiment, when the target temperature Rb is set, the target temperature Rb is calculated in real time by the flow rate / temperature calculator 51 based on the first to third heat calculation formulas. The amount of electric power Qf detected by the detector, the amount of combustion heat Qv converted from the detected value of the hydrogen gas flow rate detector 63, and the heat recovery water temperature Ti before heat exchange detected by the second temperature detector 54 Each of these may be an independent variable, and the target temperature Rb obtained by the above thermal calculation formula may be used as a dependent variable, and the relationship between the two may be stored in a database in advance. If it does so, it will be provided with the memory | storage device (not shown) memorize | stored as each Rb value matched with each Qf, each Qv, and each Ti, Furthermore, it replaces with the flow volume / temperature computing unit 51, and appropriate processing apparatus ( (Not shown), and this processing apparatus includes an electric energy Qf detected by the generated electric power detector 22, a combustion heater combustion heat Qv converted from a detected value of the hydrogen gas flow detector 63, and a second temperature. The target temperature Rb corresponding to the combination of the heat recovery water temperature Ti before heat exchange detected by the detector 54 can be read from the storage device, and the hot water storage pump adjuster 52 so that the target temperature Rb matches the water temperature after heating the heater. Can appropriately control the hot water storage pump 35.
[Modification 1]
In the first embodiment and the second embodiment, this value is input to the flow rate / temperature calculator 51 so that the heat recovery water temperature Ti before heat exchange detected by the second temperature detector 54 is taken into consideration. Yes.

  However, the heat recovery water outlet 32A of the stacked boiling hot water storage tank 32 and the supply port of city water supplied from the existing infrastructure are provided close to the lower part of the hot water storage tank 32 due to the structure of the hot water storage tank 32. In this case, there is a high possibility that the temperature of the heat recovery water temperature Ti before heat exchange substantially matches the temperature of city water.

  For this reason, for example, if the temperature change of city water is expected to be within a range of several degrees C. as in an apartment house, the heat recovery water outlet 32A of the hot water storage tank 32 and the tap water supply port are By arranging it close to the lower part of the hot water storage tank 32, the heat recovery water temperature Ti before heat exchange can be regarded as a constant (for example, 20 ° C.).

  According to such a configuration, it is possible to simplify the calculation of the flow rates Gwa and Gwb (target) capable of maintaining the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42 at about 62 ° C., The heat recovery water temperature Ti before heat exchange need not be provided with a detector that directly detects the heat recovery water temperature Ti, which is preferable because the cost increase of the fuel cell system can be suppressed.

Also in this modification, as in the first and second embodiments, the amount of power Qf detected by the generated power detector 22 and the heater supply power amount Qh of the power difference detector 23 or the hydrogen gas flow rate detection With respect to the combustion heater combustion heat quantity Qv converted from the detected value of the condenser 63, the target temperatures Ra and Rb obtained from the above heat calculation formulas are set as Ra values corresponding to the respective Qf and each Qh or each Qv. Alternatively, a storage device stored as an Rb value and an appropriate processing device in place of each flow rate / temperature computing unit 51, the processing device read from the storage device based on the Qf value, the Qh value, or the Qv value. You may comprise so that the hot water storage pump regulator 52 may control the hot water storage pump 35 so that it may correspond with target temperature Ra, Rb.
[Modification 2]
In the above-described modified example 1, the heat recovery water temperature Ti before heat exchange detected by the second temperature detector 54 is illustrated as a constant, but in addition to the Ti, the generated power detection is further performed. Similarly, with respect to Qa and Qb calculated from the electric energy Qf detected by the vessel 22, the operation mode in which the generated power of the fuel cell 11 maintains constant power during the steady operation of the fuel cell system 100 or its When the system is designed with such a specification, it is not necessary to calculate Qa and Qb using Qf detected by the generated power detector 22 as needed, and it can be considered as a constant.

  In the above description, it is assumed that the flow rate / temperature calculator 51 calculates the flow rates Gwa and Gwb (target) based on the second calculation formula, and then calculates the target temperatures Ra and Rb based on these flow rate values. However, the heater supply power amount Qh or the hydrogen gas flow rate detection of the power difference detector 23 is calculated without calculating the flow rate as shown in the following formulas (4) and (5) obtained by adding the first to third heat calculation formulas. The target value can be calculated based only on the combustion heater combustion heat quantity Qv converted from the detection value of the heater 63.

Ra = Qh / Qa × (62−Ti) +62 (4)
Rb = Qv / Qb × (62−Ti) +62 (5)
Also in this modification, as in the first and second embodiments, the combustion of the combustion heater converted from the heater supply power amount Qh of the power difference detector 23 or the detection value of the hydrogen gas flow rate detector 63 A storage device that stores target temperatures Ra and Rb obtained from these heat calculation formulas for each heat quantity Qv as each Qh or Ra value or Rb value associated with each Qv, and each flow rate / temperature calculation An appropriate processing device is provided instead of the vessel 51, and the hot water storage pump regulator 52 adjusts the hot water storage pump 35 so that the processing device matches the target temperatures Ra and Rb read from the storage device based on the Qh value or the Qv value. It may be configured to control.
[Modification 3]
In the first embodiment and the second embodiment, in the above formula (1), the total supply heat amounts Qa and Qb to the heat recovery water by the heat exchanger are estimated from the power generation amount Qf.

  In this modification, an appropriate heat recovery water flow rate detector (not shown) is provided in the middle of the heat recovery water channel 101, and the total amount of heat supplied to the heat recovery water by the heat exchanger Qa, Qb as follows. The rough estimation based on the power generation amount Qf is omitted.

  First, based on the known flow rate and ΔT from the relational expression “heat amount = flow rate × ΔT (heat recovery water temperature detected by the first temperature detector 55−heat recovery water temperature Ti before heat exchange)”, The total total amount of heat supplied to the heat recovery water from both the heat exchanger and the heater (for example, the heater 33 in the first embodiment) is obtained. Here, if the amount of heat supplied to the heat recovery water by the heater is known, the total amount of heat supplied to the heat recovery water by the heat exchanger is subtracted from this total total supply heat amount by the heat recovery water supply heat amount by the heater. Can be estimated. Then, using such an estimated value of the total supply heat amount, a target flow rate capable of maintaining the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42 at about 62 ° C. is calculated. The target temperatures Ra and Rb are calculated using the third heat calculation formula based on the estimated heat supply value from the heat exchanger and the heat supply to the heat recovery water by the heater, and the target temperature Ra is calculated. You may comprise so that the hot water storage pump regulator 52 may control the hot water storage pump 35 so that it may correspond to Ra and Rb.

Thus, as understood from the first and second embodiments and this modification, the flow rate / temperature calculator 51 has a predetermined correlation with the heat recovery water temperature after passing through the cooling water / heat recovery water heat exchanger 42. The target flow rate and the target set temperature can be calculated based on a physical quantity (correlation amount) having a relationship (for example, the heat recovery water flow rate of the heat recovery water channel 101).
[Modification 4]
In the first and second embodiments, heat recovery water (city water) stored in the hot water storage tank 32 is taken as an example as the second heat medium circulating in the heat recovery flow path 101 passing through the heater 33 or the combustion heater 62. Said.

  However, such a second heat medium is not limited to city water, and may be a second heat medium for other uses, for example, an antifreeze liquid for heat storage type floor heating, and electric heat using such an antifreeze liquid. It is possible to divert this technology to the supply system.

However, in this case, the allowable range of the temperature of the antifreeze liquid is appropriately reviewed according to the application.
[Modification 5]
In the second embodiment, as an example of the heat exchange system, only the cooling water / heat recovery water heat exchanger 42 having a heat exchange function between the cooling water circulated by the cooling water pump 31 and the heat recovery water is provided. However, heat exchange is performed with the first condenser 43 that exchanges heat with the fuel gas shown in the first embodiment (FIG. 1), the fuel gas / heat recovery water heat exchanger 41, and the oxidant gas. It is possible to use only one or a plurality of the second condensers 44.

  In the fuel cell system of the present invention, large fluctuations in the energy supplied to the heater that heats the second heat medium that has passed through the heat exchanger for cooling the fuel cell (for example, heating due to excess power due to power load fluctuations). Even if excessive power supply to the battery occurs, it is possible to keep the internal temperature of the fuel cell stable, and the convenience is improved so that proper power generation operation of the fuel cell can be achieved, for example, It is useful as a fuel cell cogeneration system for home use.

It is the block diagram which showed the example of 1 structure of the fuel cell system by Embodiment 1 of this invention. 3 is a flowchart illustrating an operation example of a flow rate / temperature calculator according to the first embodiment. It is the block diagram which showed the example of 1 structure of the fuel cell system by Embodiment 2 of this invention. 6 is a flowchart illustrating an operation example of a flow rate / temperature calculator according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Burner 11 Fuel cell 12 Fuel processor 13 Blower 21 Inverter 22 Generated power detector 23 Power difference detector 31 Cooling water pump 32 Hot water tank 32A Hot water tank outlet 32B Hot water tank inlet 33 Heater 34 Electricity setting device 35 Hot water storage Pump 41 Fuel gas / heat recovery water heat exchanger 42 Cooling water / heat recovery water heat exchanger 43 First condenser 44 Second condenser 51 Flow rate / temperature calculator 52 Hot water storage pump regulator 53 Cooling water pump regulator 54 Second temperature detector 55 First temperature detector 56 Third temperature detector 61 Hydrogen supply device 62 Combustion heater 63 Hydrogen gas flow rate detector 100, 110 Fuel cell system Gwb, Gwa Target flow rate Qa, Qb Total Heat supply amount Qf Electric power amount Qh Heater supply electric energy amount Qv Combustion heater combustion heat amount Ra, Rb Target temperature

Claims (11)

A fuel cell that generates power using fuel gas and oxidant gas;
A heat transfer device that transfers heat to a second heat medium by a first heat medium that transports heat generated in the system during the power generation;
A heater for heating the second heat medium using surplus energy supplied from the fuel cell;
A flow path of the second heat medium extending from an inlet for guiding the second heat medium toward the heat transfer device to an outlet for guiding the second heat medium to the outside through the heater;
A flow controller for adjusting the flow rate of the second heat medium flowing through the flow path;
A first temperature measuring device that detects the temperature of the second heat medium that has passed through the heater as a first reference temperature;
A first detector that detects a first correlation amount that correlates with the amount of heat supplied from the heater to the second heat medium;
A controller, and
The controller controls the flow rate of the second heat medium by the flow rate regulator so that the first reference temperature becomes a target temperature determined according to the first correlation amount. Fuel cell system.   The fuel cell system according to claim 1, wherein the target temperature is determined to be proportional to the first correlation amount.   2. The fuel cell system according to claim 1, wherein the target temperature is determined such that the temperature of the second heat medium in the flow path between the heat transfer device and the heater is maintained at a predetermined temperature.   The heater is a heater that heats the second heat medium using the surplus power, and the first detector is a surplus power obtained by subtracting the power from the power load from the power generated by the fuel cell. The fuel cell system according to claim 1, wherein the fuel cell system is a power difference detector that detects the difference as the first correlation amount.   The heater is a combustion heater capable of burning the combustible gas, and the first detector detects a flow rate of the combustible gas discharged from the fuel cell as the first correlation amount. The fuel cell system according to claim 1, which is a combustible gas flow rate detector. A second detector that detects a second correlation amount that correlates with the temperature of the second heat medium in the flow path between the heat transfer device and the heater;
The target temperature is based on the first correlation amount and the second correlation amount, and the temperature of the second heat medium in the flow path between the heat transfer device and the heater is a predetermined temperature. The fuel cell system of claim 3, wherein the fuel cell system is defined to be maintained.   The second correlation amount is an amount of heat supplied to the second heat medium of the heat transfer device converted from the generated power of the fuel cell, and the second detector detects the generated power. The fuel cell system according to claim 1, wherein the fuel cell system is a generated power detector. A second temperature measuring device for detecting a temperature of the second heat medium in the flow path between the heat transfer device and the inlet as a second reference temperature;
The target temperature is a second heat medium in the flow path between the heat transfer device and the heater based on the first correlation amount, the second correlation amount, and the second reference temperature. The fuel cell system according to any one of claims 1 to 7, wherein the target temperature is determined such that the temperature of the fuel is maintained at a predetermined temperature.   The fuel cell system according to any one of claims 1 to 8, wherein the first heat medium is cooling water for cooling the fuel cell.   The fuel cell system according to any one of claims 1 to 9, wherein an upper limit temperature of the target temperature is preset. The second heat medium is water, and includes a hot water storage tank for storing hot water heated by the heat exchanger and the heater, and an inlet and an outlet of the flow path communicate with the hot water storage tank. Item 11. The fuel cell system according to any one of Items 1 to 10.

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