JP7494730B2 - Fuel Cell Systems - Google Patents

Description

The present invention relates to a fuel cell system.

A hot water floor heating device has been proposed that includes a floor heating panel installed indoors, a heat source unit that generates hot water, a thermal valve that opens and closes a hot water passage that connects the heat source unit and the floor heating panel, and a control unit that controls the operation of the heat source unit and the thermal valve (see, for example, Patent Document 1). This device includes a remote control that includes an operation button for setting a target temperature in the room and a room temperature sensor that detects the room temperature, and the control unit controls the thermal valve by switching between an operating state in which hot water is supplied to the floor heating panel with the thermal valve open and an operating state in which hot water is supplied while opening and closing the thermal valve so that the room temperature becomes the target temperature.

JP 2013-40737 A

The above-mentioned device uses a dedicated heat source for heating, which is disadvantageous in terms of improving energy efficiency.

The main objective of this invention is to improve energy efficiency while maintaining comfort.

The present invention takes the following measures to achieve the above-mentioned main objective.

The first fuel cell system of the present invention comprises:
A fuel cell system including a fuel cell,
a heat exchanger for recovering exhaust heat from the fuel cell by heat exchange with a heat exchange liquid;
a heating heat exchanger connected to a heating pipe in which a heating liquid circulates in the hot water heating device and configured to heat the heating liquid by heat exchange with the heat exchange liquid;
a circulation pipe connecting the exhaust heat recovery heat exchanger and the heating heat exchanger;
A pump that circulates a heat exchange liquid in the circulation pipe;
a heater provided in the circulation pipe for heating the heat exchange liquid;
a control device that controls at least the pump so that the heating liquid is heated at least using exhaust heat from the fuel cell when the fuel cell is generating power, and controls the heater and the pump so that the heating liquid is heated by heat from the heater when the fuel cell is not generating power;
The gist of the present invention is as follows.

In the first fuel cell system of the present invention, when the fuel cell is generating electricity, the heating liquid is heated using at least the exhaust heat from the fuel cell that is generated during power generation, so energy efficiency can be improved compared to systems that use a dedicated heat source device to heat the heating liquid. Also, when the fuel cell is not generating electricity, the heating liquid is heated using heat from the heater, so heating is possible regardless of the power generation state of the fuel cell. As a result, energy efficiency can be improved while maintaining comfort.

In the first fuel cell system of the present invention, a first temperature sensor is provided to detect the temperature at the outlet of the heating liquid of the heating heat exchanger, and the control device may set a temperature target value that is higher as the heating intensity is stronger when the fuel cell is generating electricity, and control the pump so that the temperature detected by the first temperature sensor matches the temperature target value. In this way, the heating liquid can be heated to an appropriate temperature according to the heating intensity, further improving comfort.

In this case, a second temperature sensor may be provided to detect the temperature at the inlet of the heating liquid of the heating heat exchanger, and the control device may set the temperature target value so that the target value increases as the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor increases. In this way, the operating state of the hot water heating device can be quickly converged to an appropriate state.

Furthermore, in this case, the control device may control the pump so that the temperature detected by the first temperature sensor due to the exhaust heat of the fuel cell coincides with the temperature target value when the temperature difference is less than a predetermined value, and control the heater and the pump so that the temperature detected by the first temperature sensor due to the exhaust heat of the fuel cell and the heat of the heater coincides with the temperature target value when the temperature difference is equal to or greater than the predetermined value. In this way, it is possible to prevent a shortage of the amount of heat required for heating operation.

The first fuel cell system of the present invention further includes a radiator disposed in the circulation piping between the outlet of the heat exchange liquid of the heating heat exchanger and the inlet of the heat exchange liquid of the exhaust heat recovery heat exchanger, a blower for blowing air to the radiator, and a third temperature sensor for detecting the temperature at the inlet of the heat exchange liquid of the exhaust heat recovery heat exchanger, and the control device may control the blower so that the temperature detected by the third temperature sensor does not exceed a predetermined temperature when the fuel cell is generating electricity. In this way, the necessary amount of condensed water can be generated and the hot water from the hot water heating device can be prevented from being excessively heated.

The second fuel cell system of the present invention comprises:
A fuel cell system including a fuel cell,
a heat exchanger for recovering exhaust heat from the fuel cell by heat exchange with a heat exchange liquid;
a heating heat exchanger connected to a heating pipe in which a heating liquid circulates in the hot water heating device and configured to heat the heating liquid by heat exchange with the heat exchange liquid;
a circulation pipe connecting the exhaust heat recovery heat exchanger and the heating heat exchanger;
A pump that circulates a heat exchange liquid in the circulation pipe;
a control device that is installed separately from the fuel cell system and communicatively connected to a heat source device capable of heating the heating liquid, and that controls at least the pump so that the heating liquid is heated at least using exhaust heat from the fuel cell when the fuel cell is generating power, and instructs the heat source device to heat the heating liquid when the fuel cell is not generating power;
The gist of the invention is to provide the following:

In the second fuel cell system of the present invention, when the fuel cell is generating electricity, the heating liquid is heated using at least the exhaust heat from the fuel cell that is generated during power generation, so the heat source device can be stopped and energy efficiency can be further improved. Also, when the fuel cell is not generating electricity, an instruction is given to the heat source device to heat the heating liquid, so heating can be performed regardless of the power generation state of the fuel cell. As a result, energy efficiency can be further improved while maintaining comfort.

1 is a schematic configuration diagram of a floor heating system including a fuel cell system according to a first embodiment. FIG. 1 is a schematic diagram of a fuel cell system. 5 is a flowchart illustrating an example of a radiator fan operation control routine. FIG. 11 is an explanatory diagram showing the relationship between temperature TH1 and fan duty Df. 4 is a flowchart showing an example of a heating control routine. 4 is a flowchart showing an example of heating control processing during power generation. 11 is an explanatory diagram showing the relationship between the heating intensity and the target temperature TH8tag for within the control range, the relationship between the heating intensity and the target temperature TH8tag for within the low temperature range, and the relationship between the heating intensity and the target temperature TH8tag for within the high temperature range. FIG. 4 is a flowchart showing an example of a heating control process during non-power generation. FIG. 11 is a schematic diagram of a floor heating system according to a second embodiment. FIG. 2 is an explanatory diagram showing the connection relationship between a fuel cell system, a water heater, and a floor heating device. 10 is a flowchart showing a heating control routine in a second embodiment.

The embodiment of the present invention will be described with reference to the drawings.

Figure 1 is a schematic diagram of a floor heating system including a fuel cell system of the first embodiment, and Figure 2 is a schematic diagram of the fuel cell system. As shown in Figure 1, the floor heating system of the first embodiment is a hot water floor heating system, and includes a hot water floor heating device 100 in which heating piping 101 is laid under the floor through which hot water circulates, and a fuel cell system 10 of this embodiment including a hot water heating device 60 that heats the hot water circulating in the heating piping 101.

As shown in FIG. 2, the fuel cell system 10 includes a housing 12, a power generation module 20 including a fuel cell stack 21 that generates power by an electrochemical reaction between hydrogen in an anode gas (fuel gas) and oxygen in a cathode gas (oxidizer gas), a raw fuel gas supply device 30 that supplies raw fuel gas (e.g., natural gas or LP gas) that is the raw material for the anode gas to the power generation module 20, a reforming water supply device 40 that supplies reforming water required for reforming (steam reforming) the raw fuel gas to the power generation module 20, an air supply device 50 that supplies air as a cathode gas to the power generation module 20 (fuel cell stack 21), and a hot water heating device 60 that heats hot water from a hot water floor heating device 100 using heat (exhaust heat) from the combustion exhaust gas generated in the power generation module 20. The housing 12 is formed with an intake port 12a and an exhaust port 12b, and a ventilation fan 14 is installed near the intake port 12a to take in outside air and ventilate the inside of the housing 12.

The power generation module 20 includes a fuel cell stack 21, a vaporizer 22, and two reformers 23, which are housed in a thermally insulating module case 29. In this embodiment, the power generation module 20 has two fuel cell stacks 21, which are installed on a manifold 24 arranged in the module case 29 so as to face each other with a gap between them.

Each fuel cell stack 21 has an electrolyte such as zirconium oxide, an anode electrode and a cathode electrode that sandwich the electrolyte, and has multiple solid oxide type single cells arranged in the left-right direction (horizontal direction) in FIG. 2. An anode gas passage (not shown) is formed in the anode electrode of each single cell so as to extend in a direction perpendicular to the arrangement direction of the single cells, i.e., in the vertical direction. In addition, a cathode gas passage (not shown) for circulating cathode gas is formed around the cathode electrode of each single cell so as to extend in a direction perpendicular to the arrangement direction of the single cells, i.e., in the vertical direction. The anode gas passage of each single cell is connected to the manifold 24, and the cathode gas passage of each single cell is connected to the air passage in the module case 29. Furthermore, a temperature sensor 82 is installed between (near) the two fuel cell stacks 21 so that the distance between them is the same. The temperature sensor 84 detects a temperature (stack temperature) T4 that correlates with the temperature of each fuel cell stack 21.

The vaporizer 22 and reformer 23 of the power generation module 20 are disposed above the two fuel cell stacks 21 in the module case 29 at a distance from each other. In this embodiment, the vaporizer 22 and one reformer 23 are disposed above one fuel cell stack 21, and the other reformer 23 is disposed above the other fuel cell stack 21. Furthermore, between the one fuel cell stack 21 and the vaporizer 22 and one reformer 23, and between the other fuel cell stack 21 and the other reformer 23, combustion sections 25 are defined to generate heat required for the operation of the fuel cell stack 21 and the reactions in the vaporizer 22 and reformer 23. An ignition heater 26 is installed in each combustion section 25.

The vaporizer 22 heats the raw fuel gas from the raw fuel gas supply device 30 and the reforming water from the reforming water supply device 40 using heat from the combustion section 25, preheating the raw fuel gas and evaporating the reforming water to generate steam. The raw fuel gas preheated by the vaporizer 22 is mixed with steam, and the mixed gas flows from the vaporizer 22 into the reformer 23. The reformer 23 is also provided with a temperature sensor 81 that detects the temperature (vaporizer temperature) T1 of the mixed gas flowing into the reformer 23.

The reformer 23 has a Ru-based or Ni-based reforming catalyst filled therein, and generates hydrogen gas and carbon monoxide by a reaction (steam reforming reaction) of the mixed gas from the vaporizer 22 with the reforming catalyst in the presence of heat from the combustion section 25. Furthermore, the reformer 23 generates hydrogen gas and carbon dioxide by a reaction (carbon monoxide shift reaction) between the carbon monoxide generated in the steam reforming reaction and steam. As a result, the reformer 23 generates anode gas containing hydrogen, carbon monoxide, carbon dioxide, steam, unreformed raw fuel gas, etc. The anode gas generated by the reformer 23 flows into the anode gas passage of each single cell via the piping and manifold 24 and is supplied to the anode electrode.

Air is supplied as a cathode gas to the cathode electrode of each unit cell of the fuel cell stack 21 through an air passage formed in the module case 29. Oxide ions (O ^2- ) are generated at the cathode electrode of each unit cell, and the oxide ions pass through the electrolyte and react with hydrogen and carbon monoxide at the anode electrode to generate electric energy. The anode gas (hereinafter referred to as "anode off-gas") and cathode gas (hereinafter referred to as "cathode off-gas") that are not used in the electrochemical reaction (power generation) in each unit cell flow out from the anode gas passage and cathode gas passage of each unit cell to the combustion section 25 above.

The anode offgas that flows into the combustion section 25 from each unit cell is a combustible gas containing fuel components such as hydrogen and carbon monoxide, and is mixed with the cathode offgas that contains oxygen that flows into the combustion section 25 from each unit cell. Hereinafter, the mixed gas of the anode offgas and the cathode offgas is referred to as "offgas". When the offgas is ignited by the ignition heater 26 and ignited in the combustion section 25, the combustion of the offgas generates heat required for the operation of the fuel cell stack 21, preheating the raw fuel gas in the vaporizer 22, generating steam, and the steam reforming reaction in the reformer 23. In addition, in the combustion section 25, a combustion exhaust gas containing unburned fuel and steam is generated, and the combustion exhaust gas is supplied to the condensation heat exchanger 62 via the combustion catalyst 27. The combustion catalyst 27 is an oxidation catalyst for reburning the unburned fuel in the combustion exhaust gas.

The raw fuel gas supply device 30 has a raw fuel gas supply pipe 31 that connects the raw fuel supply source 1 that supplies the raw fuel gas to the vaporizer 22, and on-off valves (two valves) 32, 33, an orifice 34, a gas pump 35, and a desulfurizer 36 installed in the raw fuel gas supply pipe 31. By operating the gas pump 35, the raw fuel gas is pressure-fed (supplied) from the raw fuel supply source 1 to the vaporizer 22 via the desulfurizer 36. The desulfurizer 36 is configured as, for example, a room temperature desulfurization type desulfurizer. In addition, between the on-off valve 33 and the orifice 34 of the raw fuel gas supply pipe 31, a pressure sensor 37 that detects the pressure inside the raw fuel gas supply pipe 31 and a flow rate sensor 38 that detects the flow rate per unit time of the raw fuel gas flowing through the raw fuel gas supply pipe 31 (gas flow rate Qg) are installed.

The reforming water supply device 40 has a reforming water tank 42 that stores reforming water, a reforming water supply pipe 41 that connects the reforming water tank 42 and the vaporizer 22, and a reforming water pump 43 installed in the reforming water supply pipe 41. By operating the reforming water pump 43, the reforming water in the reforming water tank 42 is pumped (supplied) by the reforming water pump 43 to the vaporizer 22.

The air supply device 50 has an air supply pipe 51 connected to an air passage formed in the module case 29, an air filter 52 provided at the inlet of the air supply pipe 51, and an air pump 53 installed in the air supply pipe 51. By operating the air pump 53, air as cathode gas is sucked into the air supply pipe 51 through the air filter 52, and is pumped (supplied) to each fuel cell stack 21 (cathode electrode) via the air passage in the module case 29.

The hot water heating device 60 has a condensing heat exchanger 62 that exchanges heat between the combustion exhaust gas generated in the combustion section 25 of the power generation module 20 and a heat exchange liquid (e.g., long-life coolant), a heating heat exchanger 63 that exchanges heat between the heat exchange liquid and hot water from the hot water floor heating device 100, a circulation pipe 61 that is connected to the condensing heat exchanger 62 and the heating heat exchanger 63 and circulates the heat exchange liquid between them, and a circulation pump 65 installed in the circulation pipe 61 that runs from the heating heat exchanger 63 to the condensing heat exchanger 62. The hot water heating device 60 further has a reservoir tank 64 installed in the circulation pipe 61, a radiator 66 installed between the condensing heat exchanger 62 and the circulation pump 65 of the circulation pipe 61, a radiator fan 67 that blows air to the radiator 66, and a heater 68 installed between the radiator 66 and the circulation pump 65 of the circulation pipe 61.

The condensing heat exchanger 62 is configured as a plate-type heat exchanger in which a flow path is formed so that the combustion exhaust gas and the heat exchange liquid flow, for example, across a heat transfer plate. The flow path on the heat exchange liquid side of the condensing heat exchanger 62 is connected to the circulation pipe 61, and the heat exchange liquid in the circulation pipe 61 is introduced into the condensing heat exchanger 62 by operating the circulation pump 65, and is heated by heat exchange with the combustion exhaust gas in the condensing heat exchanger 62, and then sent to the heating heat exchanger 63. The water vapor in the combustion exhaust gas is condensed by heat exchange with the heat exchange liquid in the condensing heat exchanger 62, thereby generating condensed water. The flow path on the combustion exhaust gas side of the condensing heat exchanger 62 is connected to the reforming water tank 42 via the condensed water pipe 44, and the condensed water generated by condensing the water vapor in the combustion exhaust gas is introduced into the reforming water tank 42 via the condensed water pipe 44. A temperature sensor 83 is installed near the inlet of the flow path on the heat exchange liquid side of the condensation heat exchanger 62 to detect the temperature TH1 of the heat exchange liquid immediately before being introduced into the condensation heat exchanger 62, and a temperature sensor 84 is installed near the outlet of the flow path on the heat exchange liquid side to detect the temperature TH3 of the heat exchange liquid immediately after passing through the condensation heat exchanger 62. A water purifier (not shown) is installed in the condensed water pipe 44, and the condensed water generated in the condensation heat exchanger 62 is purified by the water purifier before being introduced into the reforming water tank 42. Furthermore, the flow path on the combustion exhaust gas side of the condensation heat exchanger 62 is connected to the combustion exhaust gas exhaust pipe 45. The exhaust gas discharged from the combustion section 25 of the power generation module 20 and from which moisture has been removed by the condensation heat exchanger 62 is discharged into the atmosphere through the combustion exhaust gas exhaust pipe 45.

The heating heat exchanger 63 is configured as a plate-type heat exchanger in which a flow path is formed so that the heat exchange liquid and the hot water flow through, for example, a heat transfer plate. The hot water side flow path of the heating heat exchanger 63 is connected to the heating pipe 69 connected to the heating pipe 101 of the hot water floor heating device 100 via the water inlet port 16a and the water outlet port 16b, and the hot water introduced from the hot water floor heating device 100 through the water inlet port 16a is heated by heat exchange with the heat exchange liquid introduced from the condensing heat exchanger 62 to the heating heat exchanger 63, and then sent to the water outlet port 16b. This allows heated hot water to be sent to the hot water floor heating device 100. A temperature sensor 86 is provided near the entrance of the flow path on the heat exchange liquid side of the heating heat exchanger 63 to detect the temperature TH6 of the heat exchange liquid immediately before it is introduced into the heating heat exchanger 63, and a temperature sensor 85 is provided near the exit of the flow path on the heat exchange liquid side to detect the temperature TH4 of the heat exchange liquid immediately after it has passed through the heating heat exchanger 63. In addition, a temperature sensor 87 is provided near the entrance of the flow path on the hot water side of the heating heat exchanger 63 to detect the temperature TH7 of the hot water immediately before it is introduced into the heating heat exchanger 63, and a temperature sensor 88 is provided near the exit of the flow path on the hot water side to detect the temperature TH8 of the hot water immediately after it has passed through the heating heat exchanger 63.

An input terminal of a power conditioner 95 is connected to the output terminal of the fuel cell stack 21, and an output terminal of the power conditioner 95 is connected to a power line 3 from the power system 2 to the load 4 via a relay (not shown). The power conditioner 95 has a DC/DC converter that converts the DC voltage output from the fuel cell stack 21 to a predetermined voltage (e.g., DC 250V to 300V), and an inverter that converts the converted DC voltage to an AC voltage (e.g., AC 200V) that can be connected to the power system 2. A current sensor (not shown) that detects the current I output from the fuel cell stack 21 is provided at the output terminal of the fuel cell stack 21, and a voltage sensor (not shown) that detects the terminal-to-terminal voltage of the fuel cell stack 21 is provided between the output terminals of the fuel cell stack 21.

A power supply board 96 is connected to the power line branched off from the power conditioner 95. The power supply board 96 converts the DC voltage from the fuel cell stack 21 and the AC voltage from the power system 2 into a DC voltage suitable for the operation of the auxiliary equipment and supplies it to the auxiliary equipment. In the embodiment, examples of the auxiliary equipment include the ventilation fan 14, the on-off valves 32 and 33, the gas pump 35, the reforming water pump 43, the air pump 53, the circulation pump 65, the radiator fan 67, and the heater 68.

The control device 70 is configured as a microprocessor centered on the CPU 71, and in addition to the CPU 71, it is equipped with a ROM 72 that stores a processing program, a RAM 73 that temporarily stores data, a timer 74 that keeps time, a non-volatile memory (not shown), and an input/output port (not shown). Various detection signals from the pressure sensor 37, the flow sensor 38, the temperature sensors 81 to 88, etc. are input to the control device 70 via the input port. In addition, the control device 70 outputs various control signals to the fan motor of the ventilation fan 14, the solenoids of the on-off valves 32 and 33, the pump motor of the gas pump 35, the pump motor of the reformed water pump 43, the pump motor of the air pump 53, the pump motor of the circulation pump 65, the fan motor of the radiator fan 67, the heater switch of the heater 68, the DC/DC converter and inverter of the power conditioner 95, the power supply board 96, the ignition heater 26, etc. via the output port. The control device 70 is also connected to a remote controller 90 installed indoors via a communication line, and data and control signals are exchanged between them.

The remote control 90 is equipped with a display device that displays the operating status of the system and a power switch. In addition, although not shown in the figure in this embodiment, it also has a heating switch that turns the heating operation of the hot water floor heating device 100 on and off, and a heating intensity setting switch that sets the heating intensity (strong, medium, weak).

The operation of the fuel cell system 10 of the present embodiment thus configured will be described. When the system is started and power generation is requested, the CPU 71 of the control device 70 controls the supply amounts of raw fuel gas, reforming water, and air so that the target current Itag corresponding to the requested power generation output is output from the fuel cell stack 21, thereby generating power. The supply amount of raw fuel gas is controlled by setting the target gas flow rate Qgtag so as to obtain a predetermined fuel utilization rate Uf based on the target current Itag, and controlling the gas pump 35 so that the gas flow rate Qg detected by the flow sensor 38 matches the set target gas flow rate Qgtag. The supply amount of reforming water is controlled by setting the target reforming water flow rate Qwtag based on the target gas flow rate Qgtag so that the steam carbon ratio SC (the molar ratio of carbon contained in the hydrocarbons in the raw fuel gas and the steam added for steam reforming) in the reformer 23 matches the predetermined target ratio SCtag, and controlling the reforming water pump 43 so that reforming water of the set target reforming water flow rate Qwtag is supplied. The amount of air supplied is controlled by setting a target air flow rate Qtag through feedback control so that the temperature T4 detected by the temperature sensor 84 coincides with a predetermined target temperature T4tag, and by controlling the air pump 53 so that air is supplied at the set target air flow rate Qtag.

Next, the operation of the radiator fan 67 during system power generation will be described. Figure 3 is a flowchart showing an example of a radiator fan operation control routine executed by the CPU 71 of the control device 70. This routine is repeatedly executed at predetermined time intervals.

In the radiator fan operation control routine, first, it is determined whether or not the system is generating power (step S100). If it is determined that the system is not generating power, the radiator fan operation control routine is terminated. On the other hand, if it is determined that the system is generating power, the temperature TH1 from the temperature sensor 83 installed near the outlet of the flow path on the heat exchange liquid side of the condensing heat exchanger 62 is input (step S110), and it is determined whether or not the input temperature TH1 is equal to or higher than the set temperature Tset (step S120). Here, the set temperature Tset is set to a value near the upper limit value in the appropriate temperature range of the heat exchange liquid for condensing the water vapor in the combustion exhaust gas. If it is determined that the temperature TH1 is not equal to or higher than the set temperature Tset but is lower than the set temperature Tset, it is determined that cooling of the heat exchange liquid is not necessary, and the operation of the radiator fan 67 is stopped (step S130), and the radiator fan operation control routine is terminated. On the other hand, if it is determined that the temperature TH1 is equal to or higher than the set temperature Tset, the fan duty Df is set based on the temperature TH1 (step S140), the fan motor of the radiator fan 67 is driven and controlled at the set fan duty Df (step S150), and the radiator fan operation control routine is terminated. In this embodiment, the fan duty Df is set by determining the relationship between the temperature TH1 and the fan duty Df in advance and storing it in the ROM 72 as a map, and when the temperature TH1 is given, deriving the corresponding fan duty Df from the map. An example of this map is shown in FIG. 4. As shown in the figure, the fan duty Df is set so that it increases as the temperature TH1 increases within the range from the minimum value Dmin to the maximum value Dmax. The minimum value Dmin is set when the temperature TH1 is the set temperature Tset, and the maximum value Dmax is set so that the noise of the radiator fan 67 does not exceed the allowable value.

Next, the operation of the hot water floor heating device 100 when the system is generating power or when the system is stopped will be described. Figure 5 is a flow chart showing an example of a heating control routine executed by the CPU 71 of the control device 70. This routine is executed repeatedly at predetermined time intervals.

When the heating control routine is executed, the CPU 71 of the control device 70 first determines whether the heating switch is turned on based on the operation signal from the remote control 90 (step S200). If it is determined that the heating switch is not turned on, the heating control routine is terminated. On the other hand, if it is determined that the heating switch is turned on, the heating intensity is input based on the operation signal from the remote control 90 (step S210), and it is determined whether the system is generating electricity (step S220). If it is determined that the system is generating electricity, the heating control process during power generation is executed (step S230) and the heating control routine is terminated, and if it is determined that the system is not generating electricity, the heating control process during non-power generation is executed (step S240) and the heating control routine is terminated. Here, the heating control process during power generation and the heating control process during non-power generation will be explained in order below.

Figure 6 is a flowchart showing an example of the heating control process during power generation. In the heating control process during power generation, first, the temperature TH7 at the inlet of the hot water side of the heating heat exchanger 63 and the temperature TH8 at the outlet are input from the temperature sensors 87, 88 (step S300). Next, the temperature difference ΔTH (= TH8 - TH7) is calculated by subtracting the temperature TH7 from the input temperature TH8 (step S310), and it is determined whether the temperature difference ΔTH is equal to or greater than the low temperature determination value (step S320). If it is determined that the temperature difference ΔTH is not equal to or greater than the low temperature determination value but is less than the low temperature determination value, the heater current control flag F is set to 0 (step S330), and it is determined whether the temperature difference ΔTH is equal to or less than the high temperature determination value (step S340). Here, the low temperature judgment value and the high temperature judgment value are temperature judgment values for judging the operating state of the hot water floor heating device 100, and when the temperature difference ΔTH is smaller than the low temperature judgment value and larger than the high temperature judgment value, it is judged to be within the control range (within the appropriate temperature range); when it is equal to or greater than the low temperature judgment value, it is judged to be within the low temperature range and promotion of hot water heating is necessary; when it is equal to or less than the high temperature judgment value, it is judged to be within the high temperature range and suppression of hot water heating is necessary.

If it is determined in S320 that the temperature difference ΔTH is not equal to or greater than the low temperature judgment value, and if it is determined in S340 that the temperature difference ΔTH is not equal to or less than the high temperature judgment value, a target temperature TH8tag for the control range is set based on the heating intensity (step S350). On the other hand, if it is determined in S320 that the temperature difference ΔTH is not equal to or greater than the low temperature judgment value, and if it is determined in S340 that the temperature difference ΔTH is equal to or less than the high temperature judgment value, a target temperature TH8tag for the high temperature range is set based on the heating intensity (step S360). Here, the target temperature TH8tag is a temperature target value when feedback controlling the temperature TH8, and can be set using the relationship illustrated in FIG. 7. As shown in the figure, the target temperature TH8tag becomes higher as the heating intensity becomes stronger, and when the temperature difference ΔTH is in the low temperature range, it is set to be higher than when it is in the control range in order to promote hot water heating, and when the temperature difference ΔTH is in the high temperature range, it is set to be lower than when it is in the control range in order to suppress hot water heating.

When the target temperature TH8tag is set, a duty (pump duty) is set by feedback control to make the temperature TH8 from the temperature sensor 88 coincide with the target temperature TH8tag (step S370), and the circulation pump 65 (pump motor) is driven and controlled at the set pump duty (step S380), and the heating control process during power generation is terminated. Note that when the heating switch is off and heating is not required, a target temperature TH3tag (e.g., 50°C) is set for the outlet of the heat exchange liquid of the condensing heat exchanger 62 in order to prevent corrosion of the condensing heat exchanger 62 and improve its durability, and the circulation pump 65 is driven and controlled by feedback control to make the temperature TH3 from the temperature sensor 83 coincide with the target temperature TH3tag.

If it is determined in step S320 that the temperature difference ΔTH is equal to or greater than the low temperature judgment value, it is determined whether the heater energization control flag F is equal to 0 (step S390). The heater energization control flag F is a flag indicating whether the heater 68 is on or off, and if it is equal to 1, it indicates that the heater 68 is on, and if it is equal to 0, it indicates that the heater 68 is off. If it is determined that the heater energization control flag F is equal to 1 rather than 0, it proceeds to step S420. On the other hand, if it is determined that the heater energization control flag F is equal to 0, it is determined whether the state in which the temperature difference ΔTH is equal to or greater than the low temperature judgment value continues for a predetermined time (step S400). If it is determined that the state has not continued for the predetermined time, it proceeds to step S340. In this case, since it is determined in step S340 that the temperature difference ΔTH is not equal to or less than the high temperature judgment value, the target temperature TH8tag for the control range is set, and the circulation pump 65 is driven and controlled based on the target temperature TH8tag for the control range. On the other hand, if it is determined that the temperature difference ΔTH has continued for a predetermined time, the heater energization control flag F is set to a value of 1 (step S410), and the circulation pump 65 (pump motor) is driven and controlled at a constant pump duty (step S420). Then, a target temperature TH8tag for the low temperature range is set based on the heating intensity (step S430), a duty (heater duty) is set by feedback control to make the temperature TH8 from the temperature sensor 88 coincide with the target temperature TH8tag (step S440), and the heater 68 is driven and controlled at the set heater duty (step S450), and the heating control process during power generation is terminated. In this way, when the temperature difference ΔTH is within the low temperature range, the heat exchange liquid is heated by the heat from the heater 68 in addition to the exhaust heat of the combustion exhaust gas, and the heated heat exchange liquid is used to heat the hot water in the heating heat exchanger 63, thereby promoting the heating of the hot water. In steps S390 and S400, even if the temperature difference ΔTH is equal to or greater than the low temperature judgment value, the heater 68 is turned on after waiting for that state to continue for a predetermined period of time in order to prevent the heater 68 from being repeatedly turned on and off in a short period of time (to prevent hunting) when the temperature difference ΔTH fluctuates near the low temperature judgment value.

Figure 8 is a flow chart showing an example of heating control processing when no power generation is occurring. In the heating control processing when no power generation is occurring, first, the circulation pump 65 (pump motor) is driven and controlled at a constant pump duty (step S500). Next, temperatures TH7 and TH8 are input from temperature sensors 87 and 88 (step S510), and temperature TH7 is subtracted from temperature TH8 to calculate temperature difference ΔTH (step S520). Then, it is determined whether temperature difference ΔTH is equal to or greater than a low temperature determination value (step S530) and whether it is equal to or less than a high temperature determination value (step S540).

If it is determined in step S530 that the temperature difference ΔTH is not equal to or greater than the low temperature judgment value, and if it is determined in step S540 that the temperature difference ΔTH is not equal to or less than the high temperature judgment value, then a target temperature TH8tag for use within the control range is set based on the heating intensity (step S550). If it is determined in step S530 that the temperature difference ΔTH is not equal to or greater than the low temperature judgment value, and if it is determined in step S540 that the temperature difference ΔTH is equal to or less than the high temperature judgment value, then a target temperature TH8tag for use within the high temperature range is set based on the heating intensity (step S560). If it is determined in step S530 that the temperature difference ΔTH is equal to or greater than the low temperature judgment value, then a target temperature TH8tag for use within the low temperature range is set based on the heating intensity (step S570). The setting of the target temperature TH8tag for use within the control range, the setting of the target temperature TH8tag for use within the high temperature range, and the setting of the target temperature TH8tag for use within the low temperature range have been described above.

After the target temperature TH8tag is set in this manner, a duty (heater duty) is set by feedback control to make the temperature TH8 from the temperature sensor 88 equal to the target temperature TH8tag (step S580), and the heater 68 is driven and controlled at the set heater duty (step S590), ending the non-power generation heating control process. In this manner, in the non-power generation heating control process, since no combustion exhaust gas is produced when the fuel cell system 10 is not generating power, the heater 68 is driven using power from the power grid 2, and the heat from the heater 68 is used to heat the hot water. This allows the hot water floor heating device 100 to continue operating even when the fuel cell system 10 is not generating power.

In the fuel cell system 10 of the present embodiment described above, when generating electricity, the heat exchange liquid is circulated and the heat of the combustion exhaust gas recovered in the condensing heat exchanger 62 is used to heat the hot water of the hot water floor heating device 100 in the heating heat exchanger 63. This can improve energy efficiency compared to a system that uses a dedicated heat source device to heat hot water. In addition, when not generating electricity, the heater 68 installed in the circulation piping 61 is driven and the heat of the heater 68 is used to heat the hot water of the hot water floor heating device 100 in the heating heat exchanger 63. This allows heating operation to be continued regardless of the power generation state of the fuel cell system 10. In addition, since a heat source unit is not required for heating and the fuel cell system 10 can be installed alone, the degree of freedom of installation can be increased. For example, by installing the fuel cell system 10 close to the floor heating device 100, the length of the piping can be shortened, and heat radiation in the piping can be suppressed, making it possible to further improve energy efficiency. Furthermore, the heat of the combustion exhaust gas recovered by the condensation heat exchanger 62 is dissipated by the heating heat exchanger 63, making it possible to reduce the operating time of the radiator fan 67, thereby extending its lifespan, and to make the radiator fan 67 smaller.

In addition, the fuel cell system 10 of this embodiment sets a target temperature TH8tag as a temperature target value at the outlet of the heating heat exchanger 63 so that the higher the heating intensity, the higher the temperature is, and controls the circulation pump 65 by feedback control based on the deviation between the temperature TH8 from the temperature sensor 88 and the target temperature TH8tag. This allows the hot water to be heated to an appropriate temperature according to the heating intensity, further improving comfort.

Furthermore, in the fuel cell system 10 of this embodiment, the target temperature TH8tag is set so that it becomes higher as the temperature difference ΔTH between the temperature (water temperature) TH7 at the inlet of the hot water of the heating heat exchanger 63 and the temperature (water temperature) TH8 at the outlet is larger. This allows the operating state of the hot water floor heating device 100 to quickly converge to an appropriate state. Furthermore, when the temperature difference ΔTH is equal to or greater than the low temperature judgment value, the heat exchange liquid circulating between the condensing heat exchanger 62 and the heating heat exchanger 63 is heated by the heater 68, and the hot water from the hot water floor heating device 100 is heated by the heating heat exchanger 63 using the heat of the combustion exhaust gas and the heat of the heater 68. This makes it possible to prevent a shortage of the amount of heat required for heating operation.

In addition, when the fuel cell system 10 of this embodiment is generating electricity, if the temperature TH3 at the inlet of the heat exchange liquid of the condensation heat exchanger 62 is equal to or higher than the set temperature Tset, the radiator fan 67 is controlled to be lower than the set temperature Tset. This allows the necessary amount of condensed water to be produced and prevents the hot water from the hot water floor heating device 100 from being overheated.

Next, a second embodiment of the floor heating system will be described. Figure 9 is a schematic diagram of the floor heating system of the second embodiment, and Figure 10 is an explanatory diagram showing the connection relationship between the fuel cell system, the water heater, and the floor heating device. As shown in Figure 9, the floor heating system of the second embodiment includes, in addition to the fuel cell system 10 and hot water floor heating device 100 described above, a water heater 200 that is installed between the hot water floor heating device 100 and the fuel cell system 10 as a heat source device for the hot water floor heating device 100. The water heater 200 is configured as a well-known gas water heater equipped with a heat exchanger 211 and a burner device 212, and includes a first connection pipe 201 connecting one end of the heating pipe 101 and the water inlet port 16a of the fuel cell system 10, a second connection pipe 202 connecting the other end of the heating pipe 101 and the water outlet port 16b of the fuel cell system 10, heating pipes 203 branching from the first connection pipe 201 and the second connection pipe 202, connecting the two, and having a heat exchanger 211 installed therein, a first three-way valve 204 installed at the branching point of the first connection pipe 201, a second three-way valve 205 installed at the branching point of the second connection pipe 202, and a control device 220 that controls the entire device. This water heater 200 can heat the hot water passing through the heat exchanger 211 by burning combustion gas with the burner device 212 to heat the heat exchanger 211. Although not shown, the control device 220 is configured as a microprocessor centered on a CPU, and in addition to the CPU, it is equipped with ROM, RAM, input/output ports, and communication ports. From the control device 220, control signals to the burner device 212 and control signals to the first and second three-way valves 204, 205 are output via the output port. The control device 220 also communicates with the control device 70 of the fuel cell system 10 via the communication port, and exchanges control signals and data with each other.

Figure 11 is a flowchart showing the heating control routine in the second embodiment. The same step numbers are used for the processes in the heating control routine of the second embodiment that are the same as those in the heating control routine of the first embodiment, and their explanations are omitted to avoid duplication. In the heating control routine of the second embodiment, if it is determined in step S220 that the system is generating electricity, the heating control process during power generation similar to that in Figure 6 is executed (step S230), and if it is determined that the system is not generating electricity, a heating request is sent to the water heater 200 (step S240). The control device 220 of the water heater 200 that receives the heating request cuts off the connection between the heating pipe 101 and the heating pipe 69 of the fuel cell system 10 and controls the first and second three-way valves 204, 205 to connect the heating pipe 101 and the heating pipe 203 of the water heater 200, and controls the burner device 212 to heat the heat exchanger 211 installed in the heating pipe 69.

In the fuel cell system 10 of the second embodiment, when power is being generated, the heat of the combustion exhaust gas recovered in the condensation heat exchanger 62 is used to heat the hot water of the hot water floor heating device 100 in the heating heat exchanger 63, as in the first embodiment. This allows the water heater 200 to be stopped, further improving energy efficiency. Also, when power is not being generated, a heating request is sent to the water heater 200 to heat the hot water of the hot water floor heating device 100. This allows heating operation to continue regardless of the power generation state of the fuel cell system 10.

The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be described. In the embodiment, the fuel cell stack 21 corresponds to the "fuel cell", the circulation pipe 61 corresponds to the "circulation pipe", the circulation pump 65 corresponds to the "pump", the condensation heat exchanger 62 corresponds to the "exhaust heat recovery heat exchanger", the heating heat exchanger 63 corresponds to the "heating heat exchanger", the heater 68 corresponds to the "heater", and the control device 70 corresponds to the "control device". The temperature sensor 88 corresponds to the "first temperature sensor". The temperature sensor 87 corresponds to the "second temperature sensor". The radiator 66 corresponds to the "radiator", the radiator fan 67 corresponds to the "blower", and the temperature sensor 83 corresponds to the "third temperature sensor".

Note that the correspondence between the main elements of the embodiment and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the embodiment is an example for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the Means for Solving the Problem column.

The above describes the form for carrying out the present invention using an embodiment, but the present invention is not limited to such an embodiment in any way, and it goes without saying that the present invention can be carried out in various forms without departing from the spirit of the present invention.

The present invention can be used in the power generation system manufacturing industry, etc.

1 raw fuel supply source, 2 power system, 3 power line, 4 load, 10 fuel cell system, 12 housing, 12a intake port, 12b exhaust port, 14 ventilation fan, 16a water inlet port, 16b water outlet port, 20 power generation module, 21 fuel cell stack, 22 vaporizer, 23 reformer, 24 manifold, 25 combustion section, 26 ignition heater, 27 combustion catalyst, 29 module case, 30 raw fuel gas supply device, 31 raw fuel gas supply pipe, 32, 33 opening and closing valve, 34 orifice, 35 gas pump, 36 desulfurizer, 37 pressure sensor, 38 flow sensor, 40 reforming water supply device, 41 reforming water supply pipe, 42 reforming water tank, 43 reforming water pump, 44 condensate water pipe, 45 combustion exhaust gas exhaust pipe, 50 air supply device, 51 Air supply pipe, 52 Air filter, 53 Air pump, 60 Hot water heating device, 61 Circulation pipe, 62 Condensation heat exchanger, 63 Heating heat exchanger, 64 Reservoir tank, 65 Circulation pump, 66 Radiator, 67 Radiator fan, 68 Heater, 69 Heating pipe, 70 Control device, 71 CPU, 72 ROM, 73 RAM, 74 Timer, 76 Opening and closing valve, 81-88 Temperature sensor, 90 Remote controller (remote control), 95 Power conditioner, 96 Power supply board, 100 Hot water floor heating device, 101 Heating pipe, 200 Water heater, 201 First connection pipe, 202 Second connection pipe, 203 Heating pipe, 204 First three-way valve, 205 Second three-way valve, 211 Heat exchanger, 212 Burner device, 220 Control device.

Claims (6)

A fuel cell system including a fuel cell,
a heat exchanger for recovering exhaust heat from the fuel cell by heat exchange with a heat exchange liquid;
a heating heat exchanger connected to a heating pipe in which a heating liquid circulates in the hot water heating device and configured to heat the heating liquid by heat exchange with the heat exchange liquid;
a circulation pipe connecting the exhaust heat recovery heat exchanger and the heating heat exchanger;
A pump that circulates a heat exchange liquid in the circulation pipe;
a heater provided in the circulation pipe for heating the heat exchange liquid;
a control device that controls at least the pump so that the heating liquid is heated at least using exhaust heat from the fuel cell when the fuel cell is generating power, and controls the heater and the pump so that the heating liquid is heated by heat from the heater when the fuel cell is not generating power;
A fuel cell system comprising: 2. The fuel cell system according to claim 1,
a first temperature sensor for detecting a temperature at an outlet of the heating liquid of the heating heat exchanger;
the control device sets a temperature target value so that the higher the heating intensity is, when the fuel cell is generating power, and controls the pump so that the temperature detected by the first temperature sensor coincides with the temperature target value.
Fuel cell system. 3. The fuel cell system according to claim 2,
a second temperature sensor for detecting a temperature at an inlet of the heating liquid of the heating heat exchanger;
the control device sets the target temperature value so as to be higher as a temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor increases.
Fuel cell system. 4. The fuel cell system according to claim 3,
When the temperature difference is less than a predetermined value, the control device controls the pump so that the temperature detected by the first temperature sensor due to the exhaust heat of the fuel cell coincides with the temperature target value, and when the temperature difference is equal to or greater than the predetermined value, the control device controls the heater and the pump so that the temperature detected by the first temperature sensor due to the exhaust heat of the fuel cell and the heat of the heater coincides with the temperature target value.
Fuel cell system. 5. The fuel cell system according to claim 1,
a radiator disposed in the circulation piping between an outlet of the heat exchanger for heating and an inlet of the heat exchanger for exhaust heat recovery;
A blower that blows air to the radiator;
a third temperature sensor for detecting a temperature at an inlet of the heat exchange liquid of the exhaust heat recovery heat exchanger;
Equipped with
the control device controls the blower so that the temperature detected by the third temperature sensor does not exceed a predetermined temperature when the fuel cell is generating power.
Fuel cell system. A fuel cell system including a fuel cell,
a heat exchanger for recovering exhaust heat from the fuel cell by heat exchange with a heat exchange liquid;
a heating heat exchanger connected to a heating pipe in which a heating liquid circulates in the hot water heating device and configured to heat the heating liquid by heat exchange with the heat exchange liquid;
a circulation pipe connecting the exhaust heat recovery heat exchanger and the heating heat exchanger;
A pump that circulates a heat exchange liquid in the circulation pipe;
a control device that is installed separately from the fuel cell system and communicatively connected to a heat source device capable of heating the heating liquid, and that controls at least the pump so that the heating liquid is heated at least using exhaust heat from the fuel cell when the fuel cell is generating power, and instructs the heat source device to heat the heating liquid when the fuel cell is not generating power;
A fuel cell system comprising:

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