Hot water supply system

Abstract

To provide a hot water supply system capable of taking an appropriate action regardless of a temperature of hot water in a hot water storage tank.SOLUTION: A hot water supply system comprises: a hot water storage tank that stores hot water; a water heater configured to deliver hot water supplied from the hot water storage tank toward a demand destination, and capable of performing a heating operation to heat the hot water; and a temperature control valve capable of performing a mixing operation to mix the hot water delivered from the water heater with supply water to lower a temperature.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a hot water supply system having a water heater.

Background Art

[0002] Conventionally, a power supply system that can perform self-generation using a fuel cell or the like and supply the self-generated power to consumers has been used. By using such a power supply system, a part of the commercial power (for example, thermal power generated from coal or LNG as a primary energy source) purchased by consumers from a power company can be switched to self-generated power, and as a result, it is also possible to reduce the amount of carbon dioxide emissions.

[0003] Furthermore, as a power supply system for performing the above-described self-generation, a system that enables self-operation when a power outage occurs in a commercial power supply system has also been proposed. By realizing such a system that can maintain power supply independently when a power outage occurs due to a natural disaster or the like, it is possible to reduce the adverse effects on social life and economic activities.

[0004] In addition, as described above, the power supply system can also be configured as a cogeneration specification in which hot water is heated using the heat generated during the power generation operation, as described in Patent Document 1. In this case, it is common to construct a hot water supply system in which the hot water in the hot water storage tank is circulated and heated by the heat generated during the power generation operation, and the hot water supplied from the hot water storage tank where hot water has run out is heated to a predetermined temperature (for example, 50 to 60°C) by a gas water heater and sent to the demand destination.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a general water heater, an upper limit temperature (e.g., 55°C) is set for the incoming water temperature to prevent boiling, and combustion stops when the upper limit temperature is exceeded. Therefore, a temperature control valve (e.g., the mixing valve 7 in Patent Document 1) is installed on the front stage side of the water heater, and by mixing water with a lower temperature as needed, the hot water entering the water heater is adjusted to be below the upper limit temperature.

[0007] In the water supply system configured in this way, when the hot water in the hot water storage tank is in a high temperature state exceeding the above upper limit temperature, this hot water is temperature-adjusted to be below the upper limit temperature and then introduced into the water heater, and this hot water is heated to the required temperature (the temperature required by the demand side) in the water heater and supplied to the demand side. However, doing so will first lower the temperature of the hot water in the high temperature state and then heat this hot water in the water heater, which has problems in terms of energy utilization efficiency and the like.

[0008] On the other hand, if the restriction on the incoming water temperature in the water heater is removed and when high-temperature hot water enters the water heater, the hot water is allowed to flow toward the demand side without being heated, there is a risk that hot water exceeding the required temperature will be supplied to the demand side. From the perspective of preventing burns and the like at the demand side, it is necessary to prevent such a situation.

[0009] In view of the above problems, an object of the present invention is to provide a water supply system capable of taking appropriate measures regardless of the temperature of the hot water in the hot water storage tank.

Means for Solving the Problems

[0010] The water supply system according to the present invention includes a hot water storage tank for storing hot water, and a water heater that sends out the hot water supplied from the hot water storage tank toward the demand side and is capable of performing a heating operation to heat the hot water, and a temperature control valve capable of performing a mixing operation of mixing water supply with the hot water sent out from the water heater to lower the temperature. According to this configuration, appropriate measures can be taken regardless of the temperature of the hot water in the hot water storage tank.

[0011] More specifically, in the above configuration, when the temperature of the hot water supplied from the hot water storage tank is lower than a predetermined lower limit temperature, the heating operation is executed. When the temperature of the hot water sent out from the water heater exceeds a predetermined upper limit temperature, the temperature control valve may be configured to execute the mixing operation. Further more specifically, in the above configuration, the temperature control valve may be a self-operated valve mechanism that adjusts the mixing ratio of the hot water and the feed water so that the hot water outlet temperature to the demand destination reaches the upper limit temperature.

[0012] More specifically, in the above configuration, a water supply line for supplying the feed water to the hot water storage tank and the temperature control valve may be provided. The hot water storage tank stores the hot water generated by heating the feed water, and the temperature control valve uses the feed water for the mixing operation. The hot water storage tank may be configured to be provided with a heater that heats the hot water using the heat generated by the power generation operation of the fuel cell unit.

Advantages of the Invention

[0013] According to the hot water supply system of the present invention, appropriate responses can be made regardless of the temperature of the hot water in the hot water storage tank.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the respective drawings.

[0016] <Configuration Outline of Fuel Cell System> First, the configuration outline of the fuel cell system 100 according to the present embodiment will be described. FIG. 1 is an explanatory diagram showing the configuration of the fuel cell system 100. As shown in FIG. 1, the fuel cell system 100 includes a plurality of cell stacks (fuel cell stacks) 1, a reformer 2, a burner 3, an evaporator 4, an air preheater 5, an anode off-gas cooler 6, an anode off-gas condenser 7, a CO oxidizer (carbon monoxide oxidizer) 8, a condensed water recovery tank 9, a first raw fuel blower 10, a first air blower 11, a water pump 12, a second raw fuel blower 13, a second air blower 14, a power conditioner 15, a unit controller 16, a third air blower 17, a heat recovery device 18, a heater 81, and a radiator fan 82. Further, the fuel cell system 100 also includes a heater 19, a radiator 20, and a circulation pump 21 as elements related to the heat recovery unit HR described later (see FIG. 4).

[0017] In the example of the present embodiment, a total of eight cell stacks 1 are provided, including those not shown in FIG. 1. In the following description, the fuel cell system 100 may be simply referred to as the "power generation unit" or the "fuel cell unit".

[0018] The fuel cell system 100 also includes lines (pipelines) such as a raw fuel line La, a mixed gas line Lb, an anode fuel line Lc, an anode off-gas line Ld, a cathode air line Le, a cathode off-gas line Lf, a combustion gas line Lg, a burner cooling air line Lh, a reformed water line Li, a startup air line Lj, a cooling air line Lk, a condensed water recovery line Lw, and a cooling water line Lm.

[0019] The anode fuel line Lc includes a first distribution manifold Ma that serves as the main pipe for introducing anode fuel, and the cathode air line Le includes a second distribution manifold Mb that serves as the main pipe for introducing cathode air. These distribution manifolds Ma and Mb have an inlet and a plurality of outlets corresponding to each cell stack 1, and cause the fluid flowing into the inlet to flow out from each of the outlets.

[0020] The anode off-gas line Ld includes a first collection manifold Mc that serves as the main pipe for discharging anode off-gas, and the cathode off-gas line Lf includes a second collection manifold Md that serves as the main pipe for discharging cathode off-gas. These collection manifolds Mc and Md have a plurality of inlets and outlets corresponding to each cell stack 1, and cause the fluid flowing into each of the inlets to flow out from the outlets.

[0021] The combustion gas line Lg includes a heat radiation cylinder Za and a combustion gas pipe Zb. The cooling air line Lk includes a cooling pipe Zc and a collection pipe Lk1.

[0022] The raw fuel line La is a pipeline connecting the fuel inlet E1 and the burner 3, and a second raw fuel blower 13 is arranged in this pipeline. The second raw fuel blower 13 is a device that boosts the raw fuel gas Gf (for example, methane-containing gas such as city gas 13A) taken in from the fuel inlet E1 and sends it to the downstream side of the raw fuel line La, and is typically driven during the startup operation of the power generation unit.

[0023] The mixed gas line Lb is a pipeline connecting the fuel inlet E2 and the reformer 2, and in this pipeline, a first raw fuel blower 10, an evaporator 4, and a first bellows type expansion joint B1 are arranged in order from the upstream side. The first raw fuel blower 10 is a device that boosts the raw fuel gas Ga taken in from the fuel inlet E2 and sends it to the downstream side of the mixed gas line Lb, and is typically driven during the power generation operation of the power generation unit.

[0024] The anode fuel line Lc is a pipeline connecting the reformer 2 and the anode of each cell stack 1. More specifically, the anode fuel line Lc includes, in order from the upstream side, a pipeline connecting the reformer 2 and the inlet of the first distribution manifold Ma, the first distribution manifold Ma, and eight pipelines (branches of the first distribution manifold Ma) connecting each outlet of the first distribution manifold Ma and the anode of each cell stack 1.

[0025] The anode off-gas line Ld is a pipeline connecting the anode of each cell stack 1 and the burner 3. More specifically, the anode off-gas line Ld includes, in order from the upstream side, eight pipelines (branches of the first collection manifold Mc) connecting the anode of each cell stack 1 and each inlet of the first collection manifold Mc, the first collection manifold Mc, and a pipeline connecting the outlet of the first collection manifold Mc and the burner 3 (hereinafter referred to as "pipeline Ld1"). In the middle of the pipeline Ld1, a second bellows expansion joint B2, an anode off-gas cooler 6, an anode off-gas condenser 7, and a gas-liquid separation section Sa are arranged in order from the upstream side.

[0026] The cathode air line Le is a pipeline connecting the air inlet E3 and the cathode of each cell stack 1. More specifically, the cathode air line Le includes, in order from the upstream side, a pipeline (hereinafter referred to as "pipeline Le1") connecting the air inlet E3 and the inlet of the second distribution manifold Mb, the second distribution manifold Mb, and eight pipelines (branches of the second distribution manifold Mb) connecting each outlet of the second distribution manifold Mb and the cathode of each cell stack 1.

[0027] In the middle of pipeline Le1, in order from the upstream side, a first air blower 11, an anode off-gas cooler 6, an air preheater 5, and a third bellows type expansion joint B3 are arranged. The first air blower 11 is a device that pressurizes the air Aa taken in from the air inlet E3 and sends it to the downstream side of the cathode air line Le, and is typically driven during the power generation operation of the power generation unit. Further, in the pipeline Le1, a bypass path Le2 that bypasses the anode off-gas cooler 6 and the air preheater 5 is provided so as to connect the midpoint between the air inlet E3 and the anode off-gas cooler 6 and the midpoint between the air preheater 5 and the third bellows type expansion joint B3.

[0028] The cathode off-gas line Lf is a pipeline that connects the cathode of each cell stack 1 and the burner 3. More specifically, the cathode off-gas line Lf includes, in order from the upstream side, eight pipelines (the branch pipes of the second collection manifold Md) that connect the cathode of each cell stack 1 and the inlets of the second collection manifold Md, the second collection manifold Md, and a pipeline that connects the outlet of the second collection manifold Md and the burner 3 (hereinafter referred to as "pipeline Lf1").

[0029] The combustion gas line Lg is a pipeline that connects the burner 3 and the gas discharge port D1. More specifically, the combustion gas line Lg includes, in order from the upstream side, a heat radiation cylinder Za, a pipeline that connects the heat radiation cylinder Za and the combustion gas pipe Zb, the combustion gas pipe Zb, and a pipeline that connects the combustion gas pipe Zb and the gas discharge port D1 (hereinafter referred to as "pipeline Lg1"). In the middle of the pipeline Lg1, in order from the upstream side, a fourth bellows type expansion joint B4, an air preheater 5, a CO oxidizer 8, and an evaporator 4 are arranged.

[0030] The burner cooling air line Lh is a pipeline connecting the pipeline Le1 and the starting air line Lj, and a flow rate adjusting means (such as an orifice) (not shown) is provided in this pipeline. More specifically, the burner cooling air line Lh branches at an intermediate point of the pipeline Le1 connecting the first air blower 11 and the anode off-gas cooler 6, and merges into the starting air line Lj on the downstream side of the second air blower 14. It is configured such that a minute flow rate of air Ab flows toward the burner 3 when the first air blower 11 is driven. Note that the burner cooling air line Lh can be omitted depending on the combustion temperature of the burner 3.

[0031] The cooling air line Lk is a pipeline connecting the air intake E5 and a predetermined location of the pipeline Lg1 (a location between the evaporator 4 and the gas discharge port D1), and in this pipeline, a third air blower 17 and a cooling pipe Zc are arranged in order from the upstream side. The third air blower 17 is a device that boosts the cooling air Ad taken in from the air intake E5 and sends it to the downstream side of the cooling air line Lk.

[0032] The reformed water line Li is a pipeline connecting the condensed water recovery tank 9 and the evaporator 4, and a water pump 12 is arranged in this pipeline. The water pump 12 is a device that sends the condensed water Wb stored in the condensed water recovery tank 9 as reformed water Wa to the downstream side of the reformed water line Li.

[0033] The starting air line Lj is a pipeline connecting the air intake E4 and the pipeline Lf1, and a second air blower 14 is arranged in this pipeline. The second air blower 14 is a device that boosts the air Ac taken in from the air intake E4 and sends it to the downstream side of the starting air line Lj, and is typically driven during the startup operation of the power generation unit.

[0034] The condensate recovery line Lw is a pipeline that connects the gas-liquid separation section Sa disposed in the middle of the pipeline Ld1 and the condensate recovery tank 9. The gas-liquid separation section Sa is a member that separates the condensate Wb generated in the anode off-gas condenser 7 from the anode off-gas Gd, and the separated condensate Wb flows down in the condensate recovery line Lw. The tip of the condensate recovery line Lw is opened to the gas phase portion without being immersed in the aqueous phase portion of the condensate recovery tank 9 so that the condensation amount does not increase or decrease under the influence of the water temperature of the stored condensate Wb. Note that the tip of the condensate recovery line Lw is not immersed in the aqueous phase portion in order not to change the flow rate of the anode off-gas Gd sent to the burner 3. In particular, this configuration is effective when the anode off-gas Gd after separating the condensate Wb is recycled to the primary side of the cell stack or used for power generation in the subsequent cell stack. For the gas-liquid separation section Sa, for example, a T-shaped pipe in which a straight pipe section is arranged horizontally and a branch pipe section is arranged downward is used. Also, a small-capacity cylindrical container erected vertically can be used as the gas-liquid separation section Sa.

[0035] The cell stack 1 is a power generator composed of a solid oxide fuel cell (SOFC). The solid oxide fuel cell is a high-temperature operating fuel cell in which the solid electrolyte, anode, and cathode constituting the power generation cell are all ceramics, and a power generation unit in which a predetermined number of power generation cells are integrated via a metal interconnect material (also referred to as a separator material) is called a cell stack. The battery output of the cell stack 1 is supplied after being adjusted by the power conditioner 15.

[0036] The reformer 2 reforms the raw fuel gas Ga using steam to generate a reformed gas Gc and sends it to the subsequent stage side. The reformer 2 has a catalyst for steam reforming, reacts methane contained in the raw fuel gas Ga with steam, and generates a reformed gas Gc containing carbon monoxide and hydrogen. Although steam reforming is an endothermic reaction, the reformer 2 can stably generate the reformed gas Gc by heat supply from the burner 3.

[0037] The burner 3 burns the incoming gas to generate heat and discharges the combustion gas Gg generated by the combustion into the combustion gas line Lg. The evaporator 4 is a device that indirectly heat-exchanges the reformed water Wa and the combustion gas Gg (heat source fluid). By heat-exchanging with the combustion gas Gg, it evaporates the reformed water Wa and at the same time plays a role in heating the raw fuel gas Ga. The heat recovery device 18 plays a role in recovering the heat of the combustion gas Gg by heat-exchanging with the cooling water Wc flowing through the cooling water line Lm.

[0038] Both the air preheater 5 and the anode off-gas cooler 6 are heat exchangers that indirectly heat-exchange low-temperature fluid and high-temperature fluid. The air preheater 5 plays a role in preheating the air Aa in the cathode air line Le by heat-exchanging with the combustion gas Gg, and the anode off-gas cooler 6 plays a role in cooling the anode off-gas Gd by heat-exchanging with the air Aa in the cathode air line Le.

[0039] The anode off-gas condenser 7 plays a role in cooling the anode off-gas Gd and condensing the water vapor contained in the anode off-gas Gd. The anode off-gas condenser 7 of this embodiment employs a water-cooled heat exchanger and cools the anode off-gas Gd by heat-exchanging with the cooling water Wc flowing through the cooling water line Lm.

[0040] The CO oxidizer 8 is a device that brings the harmful carbon monoxide contained in the combustion gas Gg into contact with a catalyst and converts it into harmless carbon dioxide. The CO oxidizer 8 does not operate when the oxidation reaction in the burner 3 is complete, and operates only when the oxidation reaction in the burner 3 is incomplete.

[0041] The condensate recovery tank 9 recovers the condensate Wb discharged from the gas-liquid separation section Sa and serves to make it reusable as reformed water Wa. In the condensate recovery tank 9, a water level detector Sb and a drain valve Sc are provided to adjust the water level of the stored reformed water Wa within a predetermined range. When the water level detector Sb detects the upper limit water level, the drain valve Sc is opened, while when the water level detector Sb detects the lower limit water level, the drain valve Sc is closed. In this way, a required amount of reformed water Wa is ensured in the condensate recovery tank 9. In order to prevent the anode off-gas Gd from leaking to the outside during the drainage operation of the reformed water Wa, the drainage position by the drain valve Sc is set near the bottom of the condensate recovery tank 9.

[0042] Also, as shown by the dashed line frame in FIG. 1, each cell stack 1, reformer 2, burner 3, each manifold Ma to Md, heat radiation cylinder Za, combustion gas pipe Zb, and cooling pipe Zc are arranged in the first region R1. The first region R1 is maintained at a temperature exceeding 600°C during the power generation operation of the power generation unit and independently maintains the heat balance of heat absorption and heat generation. On the other hand, the evaporator 4, air preheater 5, anode off-gas cooler 6, and CO oxidizer 8 are arranged in the second region R2. The second region R2 is maintained at a temperature lower than that of the first region R1 and higher than room temperature during the power generation operation of the power generation unit. The first region R1 and the second region R2 are each surrounded by a heat insulation box, and the power generation module is formed by integrating the two heat insulation boxes. The anode off-gas condenser 7, condenser fan 7a, condensate recovery tank 9, each blower 10, 11, 13, 14, 17, water pump 12, power conditioner 15, unit controller 16, heater 81, and heat radiation fan 82 are arranged outside the power generation module (room temperature region). In addition, the above-mentioned bellows type expansion pipe joints B1 to B4 are used to absorb the expansion and contraction of the pipes caused by the temperature change between the cold state and the operation state.

[0043] The power conditioner 15 is a device for converting the electric power generated by the cell stack 1 into a state that can be used in business activities and social life. FIG. 2 schematically illustrates the internal configuration of the power conditioner 15 and the connection state to peripheral devices.

[0044] As shown in Fig. 2, the power conditioner 15 includes a first DC / DC converter 91, a second DC / DC converter 92, a first control circuit 93, a second control circuit 94, a grid-connected inverter 95, a grid-connected switch 96, and a household outlet switch 97. Connected to the power conditioner 15 are auxiliaries AU for operating the power generation module and a load module LD including a heater 81 and a radiator fan 82. The auxiliaries AU include, in addition to the aforementioned first primary fuel blower 10, first air blower 11, water pump 12, second primary fuel blower 13, second air blower 14, third air blower 17, and spark plug of the burner 3, a fan and a circulation pump 21 of the radiator 20 described later. In the self-sustained operation mode of the power generation unit, the load module LD causes the heater 81 to generate heat to consume the surplus generated power of the cell stack 1, and the radiator fan 82 dissipates the heat generated from the heater 81. Further, as shown in Fig. 2, a household outlet 200 and a switchboard 300 are connected to the power conditioner 15.

[0045] The first DC / DC converter 91 (boost circuit) boosts the DC voltage output from the cell stack 1. The second DC / DC converter 92 adjusts the DC voltage boosted by the DC / DC converter 91 to a DC voltage suitable for driving the auxiliaries AU. The first control circuit 93 supplies the DC voltage adjusted by the second DC / DC converter 92 to the auxiliaries AU to appropriately drive the auxiliaries AU. The second control circuit 94 supplies the DC voltage boosted by the DC / DC converter 91 to the load module LD to appropriately drive the load module LD. The grid-connected inverter 95 (voltage conversion circuit) converts the DC voltage boosted by the DC / DC converter 91 into an AC voltage synchronized with the commercial power grid.

[0046] The system connection inverter 95 is electrically connected to, for example, the switchboard 300 of the commercial power supply system 400 installed in a building. The system connection inverter 95 and the switchboard 300 can be switched between parallel connection and disconnection via the system connection switch 96. The commercial power supply system 400 and the demand equipment 500 are electrically connected to the switchboard 300. The demand equipment 500 includes a plurality of distribution boards, and load devices such as lighting fixtures, power devices, or outlets used in the building, for example, are electrically connected to each distribution board.

[0047] Note that the auxiliary equipment AU is driven using commercial power during the startup operation and shutdown operation of the power generation unit, and is driven using the generated power during the power generation operation of the power generation unit. Further, the power supply device 100 also supports independent operation during a power outage, and the system connection inverter 95 is also electrically connected to the independent outlet 200 via the independent outlet switch 97. The independent outlet 200 can be connected to various power-using devices (such as electrical products used by consumers), and can supply independent operation power (output power generated by the power supply device 100 through independent operation) to the connected power-using devices. The independent operation power is preset within a range not exceeding the rated output power and not less than the minimum output power in the connection operation mode based on the equipment information of the load module LD. Note that the minimum output power is set based on the minimum fuel supply amount that can maintain the thermal self-sufficiency of the power generation module and the minimum fuel utilization rate that can maintain the water self-sufficiency of the power generation module.

[0048] The unit controller 16 is a device that controls the operations of the auxiliary equipment AU, the power conditioner 15, etc. (that is, the power generation unit operation) according to a control program created and stored in advance. The unit controller 16 is provided with a communication unit that communicates with the outside of the power generation unit. Remote monitoring of the power generation unit may be enabled using the communication unit.

[0049] <Outline of the operation of the fuel cell system> Next, the general operation of the fuel cell system 100 will be described with reference to FIG. 1. The raw fuel gas Ga supplied into the mixed gas line Lb from the fuel inlet E2 is sent to the downstream side by the action of the first raw fuel blower 10. In parallel with the supply of the raw fuel gas Ga, the reformed water Wa supplied into the reformed water line Li from the condensed water recovery tank 9 has its water volume adjusted by the water pump 12 and flows into the mixed gas line Lb.

[0050] The reformed water Wa flows into the evaporator 4 together with the raw fuel gas Ga in the mixed gas line Lb, and is heated by heat exchange in the evaporator 4 to become water vapor (superheated steam). The water vapor is mixed with the heated raw fuel gas Ga and flows into the reformer 2 as the mixed gas Gb.

[0051] The reformer 2 reforms the raw fuel gas Ga using the water vapor in the mixed gas Gb, generates the reformed gas Gc, and sends it to the downstream side. The reformed gas Gc sent out from the reformer 2 is distributed to the anodes of the respective cell stacks 1 through the anode fuel line Lc.

[0052] On the other hand, in parallel with the supply of the above-described raw fuel gas Ga, air Aa is supplied from the air inlet E3 into the cathode air line Le. The air Aa in the cathode air line Le is sent to the downstream side by the action of the first air blower 11. This air Aa is heated by heat exchange in the anode off-gas cooler 6, and further heated by heat exchange in the air preheater 5, and then distributed to the cathodes of the respective cell stacks 1. Note that, for temperature adjustment of the air Aa, etc., a part of the air Aa, namely air Aa1, can also be made to flow into the cathodes of the respective cell stacks 1 through the bypass path Le2.

[0053] Furthermore, in synchronization with the supply of the air Aa to the cathode, air Ab is supplied into the burner cooling air line Lh. The air Ab in the burner cooling air line Lh is sent to the burner 3 by the action of the first air blower 11. This air Ab acts as a coolant for reducing the combustion temperature of the burner 3.

[0054] Each cell stack 1 generates electricity using the reformed gas Gc flowing into the anode and the air Aa flowing into the cathode, and discharges the anode off-gas Gd from the anode to the anode off-gas line Ld and the cathode off-gas Ge from the cathode to the cathode off-gas line Lf. The anode off-gas Gd contains fuel components that were unreacted at the anode, and the cathode off-gas Ge contains oxygen that was unreacted at the cathode.

[0055] The anode off-gas Gd discharged from each cell stack 1 to the anode off-gas line Ld is collected in the first collection manifold Mc, then cooled by heat exchange in the anode off-gas cooler 6, and flows into the anode off-gas condenser 7. In the anode off-gas condenser 7, the anode off-gas Gd is cooled to below the dew point temperature, and the water vapor contained in the anode off-gas Gd condenses.

[0056] The anode off-gas Gd that has passed through the anode off-gas condenser 7 is sent to the gas-liquid separation section Sa for gas-liquid separation, and the condensed water Wb is recovered in the condensed water recovery tank 9. The condensed water Wb recovered in the condensed water recovery tank 9 is reused as the reformed water Wa as described above. Note that the non-condensed portion of the anode off-gas Gd (the anode off-gas Gd after gas-liquid separation) is sent to the burner 3.

[0057] The cathode off-gas Ge discharged from each cell stack 1 to the cathode off-gas line Lf is collected in the second collection manifold Md, then mixed with the air Ab flowing in through the burner cooling air line Lh in the pipeline Lf1, and sent to the burner 3. In addition, to the burner 3, according to the operating state of the system, the raw fuel gas Gf supplied from the fuel inlet E1 is sent through the raw fuel line La, and the air Ac supplied from the air inlet E4 is sent through the starting air line Lj.

[0058] The burner 3 allows the gas Gx for the first burner, which is the raw fuel gas Gf and / or the anode off-gas Gd, and the gas Gy for the second burner, which is the air Ac and / or the cathode off-gas Ge, to flow in, and burns them to generate heat. That is, the gas Gx for the first burner is a mixture of the raw fuel gas Gf and the anode off-gas Gd, or is in the state of either the raw fuel gas Gf or the anode off-gas Gd, and which state it is in can vary depending on the operating state of the power generation unit, etc. Also, the gas Gy for the second burner is a mixture of the air Ac and the cathode off-gas Ge, or is in the state of either the air Ac or the cathode off-gas Ge, and which state it is in can vary depending on the operating state of the system, etc. That is, according to the startup operation, power generation operation (full load operation or partial load operation), shutdown operation, etc. of the power generation unit, the supply gas to the burner 3 changes its state as appropriate.

[0059] Note that the raw fuel gas Gf is a type of hydrocarbon-containing gas. On the other hand, the air Ac is a type of oxidant-containing gas. During the combustion operation of the burner 3, air Ab is continuously supplied from the burner cooling air line Lh to adjust the combustion temperature.

[0060] The combustion gas Gg generated by the combustion in the burner 3 is sent to the combustion gas line Lg, passes through the heat radiation cylinder Za, the combustion gas pipe Zb, the air preheater 5, the CO oxidizer 8, the evaporator 4, and the heat recovery unit 18 in sequence, and is discharged to the outside of the power generation module. The heat radiation cylinder Za and the combustion gas pipe Zb are arranged so as to be able to effectively heat the reformer 2 using the combustion gas Gg. Also, the combustion gas Gg in the combustion gas line Lg is utilized for heat exchange when passing through the air preheater 5 and the evaporator 4, and when carbon monoxide is contained, the carbon monoxide is converted to carbon dioxide when passing through the CO oxidizer 8.

[0061] In addition, the cooling air Ad supplied from the air intake E5 to the cooling air line Lk serves to cool the interior of the power generation module when passing through the cooling pipe Zc. The cooling pipe Zc is installed near the cell stack 1, and it is possible to effectively cool the cell stack 1 with the cooling air Ad. Then, the cooling air Ad finally passes through the collection pipe Lk1 and is discharged to the outside of the power generation module together with the combustion gas Gg.

[0062] Also, in the fuel cell system 100, the amount of heat (temperature) inside the power generation module is controlled by adjusting the flow rate of the cooling air Ad introduced into the cooling pipe Zc. As an example, when the temperature inside the power generation module (for example, the maximum value of the surface temperature of the end plate of each cell stack 1) exceeds the upper limit temperature, the fuel cell system 100 drives the third air blower 17 and controls the rotation speed of the third air blower 17 so that the temperature inside the power generation module becomes the target temperature (a temperature lower than the upper limit temperature by a predetermined temperature). Further, when the rotation speed below the lower limit value continues for a predetermined time, the fuel cell system 100 stops the third air blower 17. Note that the greater the rotation speed of the third air blower 17, the greater the flow rate of the cooling air Ad introduced into the cooling pipe Zc. Such control operations may be performed by the unit controller 16.

[0063] Note that the cooling pipe Zc installed near the cell stack 1 can also be used to heat up the cell stack 1 during the startup operation of the power generation unit. Specifically, in the startup operation of the power generation unit, first, the second fuel blower 13 and the second air blower 14 are driven to burn the burner 3. The combustion gas Gg generated by this combustion flows through the heat radiation cylinder Za and the combustion gas pipe Zb, and heats up the cold reformer 2 from the outside by radiative heat transfer while flowing through them. Further, the combustion gas Gg becomes the heat source of the evaporator 4 and generates water vapor from the reforming water Wa. This water vapor flows through the cold reformer 2 and the cell stack 1 in sequence, and heats up these devices from the inside by heat conduction. When there is residual heat in the combustion gas Gg discharged from the evaporator 4, the combustion gas Gg is allowed to flow from the pipeline Lg1 to the collecting pipe Lk1. As a result, the combustion gas Gg flows through the cooling pipe Zc, so that the cold cell stack 1 can be heated from the outside by radiative heat transfer and its temperature can be raised.

[0064] In addition, the unit controller 16 constantly monitors the presence or absence of a power outage in the commercial power supply system. When a power outage is detected, it turns off the system connection switch 96 and turns on the self - contained outlet switch 97. As a result, the fuel cell system 100 shifts from the grid - connected operation mode to the self - contained operation mode. When an electrical equipment is connected to the self - contained outlet 200, the output power of the power conditioner 15 can be supplied to the electrical equipment as the self - contained operation power. When the commercial power supply system resumes power supply from a power outage, the unit controller 16 shifts the power supply device 100 from the self - contained operation mode to the grid - connected operation mode.

[0065] When the supply amount of the self - contained operation power exceeds the consumption amount in the self - contained operation mode, the fuel cell system 100 causes the load module LD to consume the surplus of the self - contained operation power. The adjustment of the power consumption amount of the load module LD can be realized by adjusting the calorific value of the heater 81 (for example, adjusting the number of heaters to be energized, or adjusting the on / off duty ratio of the energization).

[0066] Figure 3 is a perspective view of the fuel cell system 100 (power generation unit). The fuel cell system 100 is configured such that each element such as the power generation unit is housed in a housing 100a. A load module LD is disposed above the housing 100a.

[0067] Figure 4 schematically shows the configuration of the hot water supply system 600 and the heat recovery unit HR according to the present embodiment. As shown in FIG. 4, some devices of the fuel cell system 100 form the heat recovery unit HR together with the hot water storage tank 22 that constitutes the hot water supply system 600. The heat recovery unit HR is a unit that recovers heat from at least one of the anode off-gas Gd and the combustion gas Gg and makes the recovered heat available for heating the hot water stored in the hot water storage tank 22. Thus, the fuel cell system 100 of the present embodiment is configured as a cogeneration system.

[0068] The heat recovery unit HR is mainly formed by an anode off-gas condenser 7, a heat recovery device 18, a heater 19, a radiator 20, a circulation pump 21, a hot water storage tank 22, and a cooling water line Lm. The cooling water line Lm is configured as a path for circulating the cooling water Wc so as to pass through the heat recovery device 18, the anode off-gas condenser 7, the heater 19, the circulation pump 21, the radiator 20 in this order and return to the heat recovery device 18. The hot water storage tank 22 of the present embodiment is a closed hot water storage tank used in a heat pump type water heater or the like

[0069] The heater 19 is a heat exchange coil disposed in the hot water storage tank 22, and heats the hot water in the hot water storage tank 22 with the heat of the cooling water Wc. The circulation pump 21 is a pump that circulates the cooling water Wc in the cooling water line Lm, and its rotation speed is variable. By changing the rotation speed of the circulation pump 21, it is possible to adjust the circulation flow rate of the cooling water Wc. The radiator 20 is configured to efficiently dissipate the heat of the cooling water Wc using a fan.

[0070] The operation of the heat recovery unit HR is controlled by the unit controller 16. Specifically, the rotation speed of the circulation pump 21 is controlled so that the return temperature of the cooling water Wc (the temperature near the outlet of the anode off-gas condenser 7) becomes a predetermined target temperature Ts. If the return temperature exceeds the target temperature Ts even when the rotation speed of the circulation pump 21 is adjusted to the upper limit, the fan of the radiator 20 is driven to ensure the cooling amount of the anode off-gas Gd in the anode off-gas condenser 7, and heat dissipation from the cooling water Wc is promoted. The fan of the radiator 20 is driven when there is no consumption of hot and cold water at the demand destination and the heat storage amount (heat recovery amount) of the hot water storage tank 22 is maximized.

[0071] In this embodiment, as an example, the target temperature Ts is set so that the hot and cold water in the hot water storage tank 22 is approximately 75°C. However, the actual temperature of the hot and cold water in the hot water storage tank 22 may vary depending on the demand amount of the hot and cold water at that time. For example, immediately after the feed water Wd is supplied to the hot water storage tank 22 that has run out of hot water, the temperature of the hot and cold water in the hot water storage tank 22 may be significantly lower than 75°C. Also, when the condensed water Wb in the condensed water recovery tank 9 falls below the lower water level while the rotation speed of the circulation pump 21 is below the upper limit, the fan of the radiator 20 is driven to recover the water storage amount.

[0072] The specific configuration of the heat recovery unit HR is not limited to that shown in FIG. 4 and can be changed according to various circumstances. For example, in the example of FIG. 4, the anode off-gas condenser 7 is arranged on the downstream side of the heat recovery device 18, but the heat recovery device 18 may be arranged on the downstream side of the anode off-gas condenser 7. Also, when the temperature of the combustion gas Gg after heat is utilized in the evaporator 4 etc. is low, the installation of the heat recovery device 18 may be omitted. Also, the installation of the heater 19 may be omitted, and instead of the cooling water line Lm, a path for circulating the hot and cold water in the hot water storage tank 22 (a path for circulating the hot and cold water so that it passes through the hot water storage tank 22, the circulation pump 21, the radiator 20, the heat recovery device 18, and the anode off-gas condenser 7 in sequence and returns to the hot water storage tank 22) may be provided. In this case, it is preferable that the hot and cold water returning to the hot water storage tank 22 returns to the top of the hot water storage tank 22.

[0073] The hot water supply system 600 includes, in addition to the hot water storage tank 22, a water heater 23, a temperature control valve 24, and a water supply line 25, and serves to supply hot water at a required temperature (the temperature or temperature range of the hot water required by the demand destination) to the demand destination. In this embodiment, as an example, this required temperature is in the range of 50 to 60°C.

[0074] The water heater 23 is arranged on the downstream side of the hot water storage tank 22, and is configured to send out the hot water supplied from the hot water storage tank 22 toward the demand destination, and is capable of performing a heating operation to heat the hot water. In this embodiment, as the water heater 23, a gas water heater that burns city gas, propane gas, or the like to perform the heating operation is adopted.

[0075] The temperature control valve 24 is arranged on the downstream side of the water heater 23, and is capable of performing a mixing operation of mixing the supplied water Wd into the hot water sent out from the water heater 23 to lower the temperature. The water supply line 25 is a line that supplies the supplied water Wd to the hot water storage tank 22 and the temperature control valve 24. The hot water storage tank 22 is supplied with the amount of supplied water Wd corresponding to the hot water consumed at the demand destination, and the temperature control valve 24 is supplied with the supplied water Wd for use in the mixing operation. As the supplied water Wd, tap water, well water, softened water treated by a water softening device, or the like can be adopted.

[0076] The operation regarding the temperature control of the hot water performed in the hot water supply system 600 will be described with reference to the flowchart shown in FIG. 5.

[0077] When the temperature of the hot water supplied from the hot water storage tank 22 to the water heater 23 is lower than a predetermined lower limit temperature Ta (Yes in step S1), the water heater 23 executes a heating operation to heat the hot water (step S2), and then sends out the hot water toward the demand destination. On the other hand, if the temperature of the hot water is equal to or higher than the lower limit temperature Ta (No in step S1), the water heater 23 does not perform the heating operation and directly sends out the hot water toward the demand destination. The lower limit temperature Ta is set to a temperature at which hot water at the required temperature can be supplied to the demand destination without performing the heating operation. In this embodiment, as an example, it is set to 55°C.

[0078] When the temperature of the hot water sent from the water heater 23 is higher than a predetermined upper limit temperature Tb (Yes in step S3), the temperature control valve 24 performs a mixing operation of mixing the hot water with makeup water Wd to lower the temperature (step S4), and then allows the hot water to flow toward the demand destination. On the other hand, if the temperature of the hot water is equal to or lower than the upper limit temperature Tb (No in step S3), the temperature control valve 24 does not perform the mixing operation and allows the hot water to flow directly toward the demand destination. In this embodiment, as an example, the upper limit temperature Tb is set to 60°C, which corresponds to the upper limit of the aforementioned required temperature.

[0079] Note that the temperature control valve 24 of this embodiment employs a self-operated valve mechanism (self-operated temperature control valve) that performs a mixing operation so that the temperature of the hot water sent toward the demand destination becomes the upper limit temperature Tb when the temperature of the hot water sent from the water heater 23 is higher than the upper limit temperature Tb. Thereby, in the mixing operation, the mixing ratio of the hot water and the makeup water Wd is adjusted so that the hot water temperature at the outlet to the demand destination becomes the upper limit temperature Tb. The main types of self-operated temperature control valves that can be adopted include bellows type temperature control valves, wax type temperature control valves, or bimetal type temperature control valves.

[0080] A bellows type temperature control valve transmits the evaporation pressure of the enclosed liquid in the temperature sensing cylinder into the bellows at the valve top, and operates the valve mechanism by the expansion and contraction of the bellows. A wax type temperature control valve operates the valve mechanism by a wax element filled with wax that expands at a melting temperature or higher and contracts at a temperature lower than the melting temperature. A bimetal type temperature control valve operates the valve mechanism by the expansion and contraction of a bimetal thermostat, and is known to be widely used in combination faucets.

[0081] In the hot water supply system 600, the above-described series of operations (steps S1 to S4) are continuously repeated, enabling appropriate responses regardless of the temperature of the hot water in the hot water storage tank 22.

[0082] More specifically, when the temperature of the hot water in the hot water storage tank 22 is relatively low and the temperature of the hot water supplied to the water heater 23 is lower than the lower limit temperature Ta, the hot water can be heated by the heating operation in the water heater 23, and the hot water at the required temperature can be supplied to the demand side. Even when the temperature of the hot water exceeds the upper limit temperature Tb due to the heating operation in the water heater 23, the temperature control valve 24 performs a mixing operation to prevent the situation where the overheated hot water is supplied to the demand side.

[0083] On the other hand, when the temperature of the hot water in the hot water storage tank 22 is relatively high and the temperature of the hot water supplied to the water heater 23 is equal to or higher than the lower limit temperature Ta, the hot water at the required temperature can be supplied to the demand side without performing the heating operation in the water heater 23. Therefore, in this case, since the execution of the heating operation is unnecessary, it is omitted, and the consumption of the fuel gas required for the heating operation can be suppressed. Even when the temperature of the hot water in the hot water storage tank 22 is too high and the temperature of the hot water reaching the temperature control valve 24 exceeds the upper limit temperature Tb, the temperature control valve 24 performs a mixing operation to prevent the situation where the overheated hot water is supplied to the demand side.

[0084] As described above, the hot water supply system 600 includes a hot water storage tank 22 for storing hot water, and a water heater 23 that can perform a heating operation to heat the hot water sent from the hot water storage tank 22 toward the demand side, and a temperature control valve 24 that can perform a mixing operation to mix the water supply Wd with the hot water sent from the water heater 23 to lower the temperature. Therefore, appropriate responses can be made regardless of the temperature of the hot water in the hot water storage tank 22, and safety is ensured for the users of the hot water.

[0085] Also, in the hot water supply system 600, the water heater 23 is configured to execute a heating operation when the temperature of the hot water supplied from the hot water storage tank 22 is lower than a predetermined lower limit temperature Ta, and not to execute the heating operation otherwise. Further, the temperature control valve 24 is configured to execute a mixing operation when the temperature of the hot water sent from the water heater 23 exceeds a predetermined upper limit temperature Tb, and not to execute the mixing operation otherwise.

[0086] In addition, the hot water storage tank 22 is provided with a heater 19 that heats the hot water in the hot water storage tank 22 by using the heat generated by the power generation operation of the fuel cell unit (fuel cell system 100). Thus, the hot water supply system 600 constitutes a highly energy-efficient cogeneration system together with the fuel cell unit. Note that the heat generated by the above power generation operation includes the heat of the anode off-gas Gd recovered by the anode off-gas condenser 7 (the power generation reaction heat due to the power generation reaction in the fuel cell stack 1) and the heat of the combustion gas Gg recovered by the heat recovery unit 18 (the combustion reaction heat due to the combustion reaction of the off-gas).

[0087] In addition, the hot water supply system 600 is not limited to the type that heats the hot water in the hot water storage tank by using the heat generated by the power generation operation of the fuel cell unit, and may have other heat sources. For example, the heat generated by the power generation operation of a gas engine generator, the heat generated by the cycle operation of a heat pump, or the heat generated by the heat storage operation of a solar water heater may be used to heat the hot water in the hot water storage tank.

[0088] As described above, the embodiments of the present invention have been described. However, the configuration of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. That is, the above embodiments should be considered as illustrative in all respects and not restrictive. The technical scope of the present invention is shown not by the description of the above embodiments but by the claims, and it should be understood that all modifications belonging to the meaning and scope equivalent to the claims are included.

[0089] <Contribution to the Sustainable Development Goals (SDGs) Led by the United Nations> The fuel cell system and the hot water supply system according to the present disclosure can contribute to the achievement of Goal 13, "Take urgent action to combat climate change and its impacts," and Goal 11, "Make cities and human settlements inclusive, safe, resilient and sustainable," of the SDGs (Sustainable Development Goals).

Industrial Applicability

[0090] The present invention can be used in a hot water supply system having a water heater.

Explanation of Signs

[0091] 1 Cell stack 2 Reformer 2a Reaction vessel 3 Burner 4 Evaporator 5 Air preheater 6 Anode off-gas cooler 7 Anode off-gas condenser 8 CO oxidizer 9 Condensate recovery tank 10 First fuel blower 11 First air blower 12 Water pump 13 Second fuel blower 14 Second air blower 15 Power conditioner 16 Unit controller 17 Third air blower 18 Heat recovery device 19 Heater 20 Radiator 21 Circulation pump 22 Hot water storage tank 23 Water heater 24 Temperature control valve 25 Water supply line 81 Heater 82 Heat dissipation fan 91 First DC / DC converter 92 Second DC / DC converter 93 First control circuit 94 Second control circuit 95 System connection inverter 96 System connection switch 97 Stand-alone outlet switch 100 Fuel cell system 100a Housing 200 Stand-alone outlet 300 Switchboard 400 Commercial power supply system 500 Load equipment 600 Hot water supply system Aa~Ac Air Ad Cooling air AU Auxiliary equipment B1 First bellows type expansion pipe joint B2 Second bellows type expansion pipe joint B3 Third bellows type expansion pipe joint B4 Fourth bellows type expansion pipe joint E1, E2 Fuel inlets E3, E4, E5 Air inlets Ga Raw fuel gas Gb Mixed gas Gc Reformed gas Gd Anode off-gas Ge Cathode off-gas Gf Raw fuel gas Gg Combustion gas HR Heat recovery unit La Raw fuel line Lb Mixed gas line Lc Anode fuel line Ld Anode off-gas line Le Cathode air line Lf Cathode off-gas line Lg Combustion gas line Lh Burner cooling air line Li Stack cooling air line Lj Reformed water line Lk Cooling air line Lka First cooling air line Lkb Second cooling air line Lm Cooling water line LD Load module Ma First distribution manifold Mb Second distribution manifold Mc First collection manifold Md Second collection manifold Wa Reformed water Wb Condensate Wc Cooling water Za Heat radiation cylinder Zb Combustion gas pipe Zc cooling pipe

Claims

1. A hot water storage tank for storing hot water, A water heater that sends out the hot water supplied from the hot water storage tank toward the demand destination and is capable of performing a heating operation for heating the hot water, A hot water supply system comprising a temperature control valve capable of performing a mixing operation for mixing water supply with the hot water sent out from the water heater to lower the temperature.

2. When the temperature of the hot water supplied from the hot water storage tank is lower than a predetermined lower limit temperature, the water heater executes the heating operation, The hot water supply system according to Claim 1, wherein when the temperature of the hot water sent out from the water heater exceeds a predetermined upper limit temperature, the temperature control valve executes the mixing operation.

3. The hot water supply system according to Claim 2, wherein the temperature control valve is a self-operated valve mechanism that adjusts the mixing ratio of the hot water and the water supply so that the hot water discharge temperature to the demand destination becomes the upper limit temperature.

4. Comprising a water supply line for supplying the water supply to the hot water storage tank and the temperature control valve, The hot water storage tank stores the hot water generated by heating the water supply, The hot water supply system according to any one of Claims 1 to 3, wherein the temperature control valve uses the water supply for the mixing operation.

5. The hot water supply system according to any one of Claims 1 to 3, wherein the hot water storage tank is provided with a heater for heating the hot water by using the heat generated by the power generation operation of the fuel cell unit.

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