JP2005078976A - Fuel cell co-generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell co-generation system in which, shortage of hot water and lowering of the temperature of supplied water are improved to a substantially manageable level in case that the demand of power supply and hot water supply are unbalanced. <P>SOLUTION: An auxiliary heating electric heater (12H) is provided at a hot-water storage tank (12). When a detected temperature (T3) of a temperature sensor at an lower part of the hot-water storage tank is higher than a hot-water supply temperature (Tref); and the detected temperature (T3) of the temperature sensor at the lower part is less than the hot-water supply temperature and a detected temperature (T2) of a temperature sensor at a middle part is higher than the hot-water supply temperature; and generated power (Pac) at a fuel cell power generating part is higher than a given hot-water generating power Pwmin; power supply to the electric heater is stopped. When the detected temperature of the temperature sensor at the lower part is less than the hot-water supply temperature; and the detected temperature of the temperature sensor at the middle part is higher than the hot-water supply temperature; and generated power at the fuel cell power generating part is less than the hot-water generating power Pwmin; a single-phase 100V power source is supplied to the electric heater. When the detected temperature of the temperature sensor at the lower part and that at the middle part are both less than hot-water supply temperature, a single-phase 200V power source is supplied to the electric heater. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell cogeneration system that generates electric power and heat, and more particularly to a technique for stably performing hot water supply using heat.

In recent years, it has been possible to generate electricity using a fuel cell and to supply hot water using heat generated during the power generation process or heat generated during the process of generating the hydrogen-rich reformed gas necessary for the fuel cell from the fuel gas. The development of such a fuel cell cogeneration system is underway.
In the power generation by this fuel cell, a hydrocarbon gas such as natural gas, LPG, or butane supplied from the outside is used as a fuel gas, and this is heated in a steam atmosphere in a reformer to produce a hydrogen-rich reformed gas first. To generate. Next, the generated reformed gas is supplied to a fuel cell together with an oxidizing gas such as air, and DC power is generated by an electrochemical reaction. The generated DC power is usually converted into AC power having a commercial frequency by an inverter, and then connected to the commercial power system and supplied to an external power load.

  The fuel cell cogeneration system not only generates power in the fuel cell, but also aims to effectively use the exhaust heat generated in the process of generating reformed gas and the exhaust heat generated in the process of direct current power generation in the fuel cell. System. Specifically, using a heat exchanger, hot water is generated from the exhaust heat and stored in a hot water tank, and supplied to an external heat load for hot water supply or heating for the kitchen. The fuel cell cogeneration system is an effective system with very high energy utilization efficiency in order to recover the exhaust heat, which is a power generation loss in the power generation process, as hot water for effective use. However, while there is a certain correlation between the amount of heat recovered as hot water and the generated power, there is a correlation between the amount of used hot water (the amount of recovered heat) and the amount of generated power used. There is no correlation. For example, when considering a normal life in a general household, there are electrical appliances that use only electric power, such as televisions and electric refrigerators, and sometimes only hot water is used during washing. In addition, some electric pots use electric power and hot water at the same time. These uses are basically random because they depend on the life of each individual.

  For this reason, when the demand for hot water is too large relative to the power demand, the hot water in the hot water storage tank is insufficient, causing hot water to run out (hot water running out), or the temperature of hot water to be supplied to be too low. . On the other hand, when the electric power demand greatly exceeds the hot water demand, the hot water storage tank becomes full of hot water and the exhaust heat cannot be recovered. If such a situation occurs, the merit of the cogeneration system, which is the effective use of energy, will be diminished.

As a method for coping with such a problem, a second heat exchanger for adding a gas instantaneous boiling device in series as an auxiliary heat source on the outlet side of hot water in a hot water tank or collecting and recovering heat from sunlight is used. A method of adding (for example, refer to Patent Document 1) has been proposed.
JP 2002-289212 A JP 2002-134143 A JP-A-11-223385 Japanese Patent Laid-Open No. 11-097045

  The present invention was made in order to solve the problems of the fuel cell cogeneration system as described above. Problems such as running out of hot water and a decrease in hot water temperature that occur when power demand and hot water demand are imbalanced. Improve to a level that does not cause any practical problems. In addition, fuel cells that can always generate hot water and make additional cooking, including when the fuel cell cogeneration system is stopped, and can supply hot water at a temperature higher than the temperature that can be generated by the heat exchanger of the fuel cell cogeneration system The issue is to provide a cogeneration system.

In order to achieve the above object, the invention according to claim 1 generates electric power and hot water, and generates the generated electric power to the cogeneration power load (3) through the single-phase three-wire commercial power system (2). A fuel cell cogeneration system (1) for supplying the warm water to the hot water use equipment (4),
The fuel cell cogeneration system includes a fuel cell power generation unit (11) and a hot water storage tank (12), and the hot water storage tank uses heat taken from its lower cold water port (122) as heat recovery circulating water as a heat recovery water circulation pump. (13) is sent to the heat exchanger (114) in the fuel cell power generation unit, heat is exchanged with the exhaust heat in the heat exchanger to make hot water and return to the hot water return port (121) at the top of the hot water tank, Hot water is supplied to the hot water using equipment from the upper water outlet (123), and city water is replenished from the lower water inlet (124).
The amount of the heat recovery circulating water is determined by detecting the temperature of the heat recovery circulating water just before returning to the hot water storage tank with a temperature detector (12T0) and setting the detected temperature (T0) to the specified hot water supply temperature (Tref). The discharge water amount of the heat recovery water circulation pump is configured to be proportional and integral controlled by the circulation pump control circuit (15) so as to be equal,
In the hot water tank, a lower temperature detector (1T3) is attached to the lower portion, an intermediate temperature detector (1T2) is attached to the intermediate portion, and an electric heater (12H) for auxiliary heating is further attached to the electric heater. Is configured such that single-phase 200 V power or single-phase 100 V power is supplied from the single-phase three-wire commercial power system by switching operation of the heater power switching relay (16) controlled by the heater power switching control circuit (17). Has been
The heater power supply switching control circuit includes the intermediate portion when the detected temperature (T3) of the lower temperature detector is equal to or higher than a specified hot water supply temperature (Tref) and when the detected temperature of the lower temperature detector is lower than the hot water supply temperature. The detected temperature (T2) of the temperature detector is equal to or higher than the hot water supply temperature, and the generated power (Pac) of the fuel cell power generation unit is equal to or higher than the hot water generation power (Pwmin) necessary for generating a predetermined amount of hot water per unit time. If it is, stop the power supply to the electric heater,
The detection temperature of the lower temperature detector is lower than the hot water supply temperature, the detection temperature of the intermediate temperature detector is higher than the hot water supply temperature, and the generated power (Pac) of the fuel cell power generation unit is lower than the hot water generation power (Pwmin). If so, supply the single-phase 100V power to the electric heater,
A fuel cell cogeneration system that supplies the electric heater with the single-phase 200V power when both the temperature detected by the lower temperature detector and the temperature detected by the intermediate temperature detector are lower than the hot water supply temperature. System.

  According to such a configuration, when there is an imbalance between the generated power of the fuel cell power generation unit and the demand for hot water and the amount of hot water stored is reduced, the amount of hot water generated can be increased by auxiliary heating by the electric heater. It is possible to eliminate almost all problems such as running out of hot water in the hot water tank and lowering of the water supply temperature.

Further, the invention according to claim 2 is the fuel cell cogeneration system according to claim 1, wherein instead of the lower temperature detector and the intermediate temperature detector, the hot water tank has a top to bottom in the hot water tank. In order, first, second, third, and fourth temperature detectors (2T1, 2T2, 2T3, 2T4) are attached at approximately equal intervals,
The heater power supply switching control circuit uses the first, second, third, and fourth detected temperatures (T1, T2, T3, T4) detected by the first, second, third, and fourth temperature detectors. Individually compared with a predetermined first reference temperature (T1ref) and a lower second reference temperature (T2ref), and when the detected temperature is equal to or higher than the first reference temperature, the weight is set to 2, and the detected temperature Is less than the first reference temperature and greater than or equal to the second reference temperature, the weight is set to 1, and when the detected temperature is less than the second reference temperature, the weight is set to 0 and the weight is set. Obtain a total value, obtain a percentage of the weighted total value when the first to fourth detection temperatures of the total value are all equal to or higher than the first reference temperature, and obtain a warm water estimated ratio (A),
When the estimated hot water ratio is greater than or equal to a predetermined first warm water ratio reference value (A1ref), and when the estimated warm water ratio is less than the first warm water ratio reference value and greater than or equal to the second warm water ratio reference value (A2ref) And when the generated power of the fuel cell power generation unit is equal to or higher than the hot water generation power (Pwmin), the power supply to the electric heater is stopped,
When the estimated hot water ratio is less than the first warm water ratio reference value and greater than or equal to the second warm water ratio reference value, and the power generated by the fuel cell power generation unit is less than the warm water generation power, the electric heater Supplying the single-phase 100V power supply;
In the fuel cell cogeneration system, the single-phase 200V power is supplied to the electric heater when the estimated hot water ratio is less than the second hot water ratio reference value.

  According to such a configuration, the estimation accuracy of the remaining amount of hot water in the hot water tank is further improved, so that the same effect as that of the first aspect of the invention can be achieved more reliably.

Further, the invention according to claim 3 is the fuel cell cogeneration system according to claim 2, wherein the hot water in the hot water storage tank is replaced with the first, second, third and fourth temperature detectors. Is divided into n layers of approximately equal thickness d1 to dn in order from the top, and a temperature detector (3T1 to 3Tn) is attached to the intermediate height of each layer, and the detected temperature of the temperature detector is set to T1 in order from the top. Tn, the temperature of the city water is Tc, the hot water supply temperature is Tref, and the hot water estimated ratio (R) is calculated by the following equation:
R = 100 × (Σ ((Ti−Tc) · di)) / Σ ((Tref−Tc) · di)
Where i = 1 to n
A fuel cell cogeneration system, wherein the calculated value is used in place of the hot water estimated ratio (A) according to claim 2.

  According to such a configuration, the estimation accuracy of the remaining amount of hot water in the hot water tank is further improved, so that the same effect as that of the first aspect of the invention can be achieved more reliably.

  According to a fourth aspect of the present invention, in the fuel cell cogeneration system according to the second or third aspect of the present invention, the amount of decrease in the hot water estimated ratio within the most recent predetermined time (Δt) exceeds a predetermined value (K1). When the estimated hot water ratio is less than the first hot water ratio reference value (A1ref) and is equal to or greater than the second hot water ratio reference value (A2ref), the single-phase 200V power supply is supplied to the electric heater. This is a fuel cell cogeneration system that is modified to supply the fuel cell.

  According to such a configuration, when the amount of hot water in the hot water tank rapidly decreases, the amount of hot water is rapidly recovered by auxiliary heating in which a single-phase 200 V power source is supplied to the electric heater. There is an effect that it is possible to avoid problems such as running out and a decrease in hot water supply temperature.

  Further, according to a fifth aspect of the present invention, in the fuel cell cogeneration system according to any of the second to fourth aspects, the value of the hot water estimated ratio is a predetermined value greater than the first hot water ratio reference value (A1ref). Is equal to or higher than the reference value (A1ref ′), the generated power (Pac) of the fuel cell power generation unit is reduced to the lowest generated power (Pacmin) that the fuel cell power generation unit can continue to generate power. In the fuel cell cogeneration system, the power generation of the fuel cell power generation unit is stopped when the estimated ratio of hot water is still equal to or greater than the reference value (A1ref ′) even after the predetermined time (Δt1) is continued. is there.

  According to such a configuration, when the hot water tank is filled with hot water, the generated power of the fuel cell power generation unit is set to the minimum value or zero, so that the amount of exhaust heat generation is reduced, and the hot water tank Dangerous situations such as overheating of the hot water inside and temperature rise of the fuel cell power generation unit are avoided.

The invention according to claim 6 is the fuel cell cogeneration system according to any one of claims 2 to 5, wherein the single-phase three-wire commercial power system is changed from the single-phase three-wire commercial power system to the fuel cell cogeneration system and the cogeneration power load. The generated power (Pac) of the fuel cell power generation unit is proportionally integrated and controlled so that the received power (Pr) supplied toward the target power value (Prmin) coincides with the predetermined received power target value (Prmin), and the received power (Pr) When it is less than the predetermined first reference power (Pr1), the power generation of the fuel cell power generation unit is stopped,
In a state where the received power is greater than or equal to the first reference power (Pr1) and less than the predetermined second reference power (Pr2), the value of the warm water estimated ratio is greater than or equal to the second warm water ratio reference value (A2ref). In some cases, the fuel cell cogeneration system is modified so as to cause the electric heater to perform at least auxiliary heating by the single-phase 100V power source.

  According to such a configuration, when the received power decreases, the generated power of the fuel cell power generation unit is reduced and the power consumption of the electric heater may be increased. Reverse power flow conditions are avoided.

The invention according to claim 7 is the fuel cell cogeneration system according to claim 1, wherein the fuel cell cogeneration system is supplied from the single-phase three-wire commercial power system toward the fuel cell cogeneration system and the cogeneration power load. Proportional integral control of the generated power (Pac) of the fuel cell power generation unit is performed so that the received power (Pr) matches a predetermined received power target value (Prmin), and the received power (Pr) is a predetermined first value. If it is less than the reference power (Pr1), the power generation of the fuel cell power generation unit is stopped,
In a state where the received power is equal to or higher than the first reference power (Pr1) and lower than the predetermined second reference power (Pr2), the detected temperature (T3) of the lower temperature detector is lower than the hot water supply temperature (Tref). In addition, when the temperature detected by the intermediate temperature detector (T2) is less than or equal to or higher than the hot water supply temperature, the electric heater is changed so as to perform at least auxiliary heating by the single-phase 100V power source. This is a fuel cell cogeneration system.

  According to such a configuration, when the received power decreases, the generated power of the fuel cell power generation unit is reduced and the power consumption of the electric heater may be increased. Reverse power flow conditions are avoided.

  The invention according to claim 8 is the fuel cell cogeneration system according to any one of claims 1 to 7, wherein the heater power supply switching control circuit supplies the single-phase 200V power to the electric heater. In the determined state, if it has been specified to prioritize the reduction of the received power charge over the amount of hot water storage, it is determined whether the current time zone is higher than the normal unit price of the received power charge. In the fuel cell cogeneration system, a change is made so that a single-phase 100V power supply is supplied instead of a single-phase 200V power supply in the time zone.

  According to such a configuration, the amount of received power can be reduced in a time zone in which the received power rate unit price is high, so that the received power rate can be reduced.

  In the fuel cell cogeneration system according to claim 8, when a hot water supply request is made by designating a hot water temperature (Thref) higher than normal as the hot water supply temperature in the fuel cell cogeneration system according to claim 8. The heater power supply switching control circuit determines whether or not the detected temperature of the uppermost temperature detector in the hot water storage tank is lower than a specified high-temperature water temperature (Thref). 10 is regarded as a state in which it is determined that the single-phase 200V power supply is supplied, and one of the single-phase 100V power supply and the single-phase 200V power supply is supplied to the electric heater according to the determination method according to claim 9. Thus, the fuel cell cogeneration system is characterized by having been modified as described above.

  According to such a configuration, it becomes possible to quickly generate and supply hot water at a temperature higher than usual.

  In the fuel cell cogeneration system according to claim 9, when a hot water supply request is made by designating a hot water temperature (Thref) higher than normal as the hot water supply temperature in the fuel cell cogeneration system according to claim 9. The circulating pump control circuit is configured to control the amount of water discharged from the heat recovery water circulation pump by proportional integral control so that the detected temperature (T0) immediately before returning to the hot water tank is equal to the high temperature water temperature. It is a fuel cell cogeneration system characterized by controlling.

  According to such a configuration, it is possible to generate hot water at a higher temperature than usual and supply hot water more quickly.

  An eleventh aspect of the invention is the fuel cell cogeneration system according to any of the ninth to tenth aspects, wherein a second hot water return port is provided at a position below the hot water return port on the upper part of the hot water tank. And a switching valve (125) for switching the return port of the heat recovery circulating water returning from the heat exchanger to either the warm water return port or the second warm water return port. The fuel cell cogeneration system is characterized in that the switching valve is switched so that the heat recovery circulating water returns to the second hot water return port.

  According to such a structure, the production | generation of high temperature warm water higher than the temperature which can be produced | generated with a heat exchanger can be performed rapidly and efficiently.

The invention according to claim 12 is the fuel cell cogeneration system according to any one of claims 1 to 11,
The method of attaching each temperature detector for detecting the temperature of hot water in the hot water tank is changed to the method of attaching to detect the temperature of the outer surface from the outside of the hot water tank container, and each detected temperature detected in the attached state is changed. On the other hand, the fuel cell cogeneration system is characterized in that the correction previously obtained through experiments is performed and the corrected value is used as each detected temperature of hot water in the hot water tank.

  According to such a configuration, it is possible to significantly reduce the man-hours for attaching the temperature detection to the hot water tank.

  In the fuel cell cogeneration system of the present invention, an electric heater capable of receiving power from the generated power and the commercial power system is provided in the hot water storage tank, and auxiliary heating is appropriately performed. Therefore, the electric power demand and the hot water demand are unbalanced. Problems such as running out of hot water and a decrease in hot water supply temperature can be improved to a level that does not cause a problem in practice. In addition, hot water can be generated and cooked, including when the fuel cell cogeneration system is stopped, and hot water having a temperature higher than the temperature that can be generated by the heat exchanger can be supplied.

(First embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 1. FIG. 1 shows a block diagram of the overall configuration of the fuel cell cogeneration system 1 of the present embodiment, and a connection relationship between a commercial power system 2, a cogeneration power load 3, and a hot water using device 4 connected thereto.

The fuel cell cogeneration system 1 includes a fuel cell power generation unit 11, a hot water storage tank 12, a heat recovery water circulation pump 13, a circulation pump control circuit 15, a heater power supply switching relay 16, and a heater power supply switching control circuit 17.
The fuel cell power generation unit 11 includes a reformer 111, a fuel cell 112, an inverter 113, a heat exchanger 114, and a power generation amount control circuit 115. The reformer 111 is supplied with a hydrocarbon gas such as natural gas, LPG, butane, methanol, or kerosene as a fuel gas, and is heated in a steam atmosphere to generate a hydrogen-rich reformed gas. The generated reformed gas is supplied to the fuel cell 112. For example, air is also supplied to the fuel cell 112 as an oxygen source.

  In the fuel cell 112, hydrogen and oxygen in the reformed gas cause an electrochemical reaction with the aid of the catalyst, and DC power Pdc is generated. The generated DC power Pdc is converted by the inverter 113 into AC generated power Pac having a voltage and frequency equal to those of the commercial power system 2 and supplied to the commercial power system 2 in a grid connection. The value of the generated power Pac of the fuel cell power generation unit 11 is controlled by the power generation amount control circuit 115.

  The power generation amount control circuit 115 controls the fuel cell power generation unit 11 so that the value of the generated power Pac matches the target value. The generated power Pac is controlled by adjusting the amount of fuel gas supplied to the reformer 111, adjusting the output current of the inverter 113, and the like. The target value of the generated power Pac is determined at any time in consideration of various conditions as described later in addition to the fuel gas supply amount, the power generation capacity of the fuel cell 112, the power demand of the cogeneration power load 3, and the like.

This fuel cell cogeneration system 1 assumes a single-phase three-wire commercial power system 2 capable of obtaining two types of power sources of AC 100V and 200V as a commercial power system for supplying generated power. The inverter 113 supplies power to the commercial power system 2 with a voltage of AC 100V.
A cogeneration power load 3 is connected to the commercial power system 2. However, the cogeneration power load 3 is a load that operates mainly using the power generated by the fuel cell cogeneration system 1, for example, a home appliance used in one house where the fuel cell cogeneration system 1 is installed. It means power load. Since the commercial power system 2 is a power system that supplies power over a wide area, in addition to the cogeneration power load 3 shown in the figure, many general power loads (not shown) are connected.

When the power consumed by the cogeneration power load 3 exceeds the generated power Pac generated by the fuel cell power generation unit 11, the shortage is supplied from the commercial power system 2. On the other hand, when the power consumed by the cogeneration power load 3 is lower than the generated power Pac, surplus generated power is supplied to the commercial power system 2.
The reaction in the reformer 111 in the fuel cell power generation unit 11 is an endothermic reaction, and heating with a burner is performed because the temperature of the catalyst for promoting the reaction needs to be maintained at around 700 ° C. Accordingly, exhaust heat is generated at that time. Also in the fuel cell 112, heat is also generated when hydrogen gas and oxygen gas cause an electrochemical reaction.

  The exhaust heat is guided to the heat exchanger 114, exchanges heat with the low-temperature heat recovery circulating water sent from the hot water storage tank 12 by the heat recovery water circulation pump 13, and changes this into hot water. The heat recovery circulating water that has become hot water is returned to the hot water storage tank 12. In this way, the heat energy of the exhaust heat is recovered.

  The circulation amount of the heat recovery circulating water is performed by controlling the discharge water amount of the heat recovery water circulation pump 13 by the circulation pump control circuit 15. The circulation pump control circuit 15 performs proportional-integral control so that the hot water temperature T0 detected by the temperature detector 12T0 inserted in the pipe close to the hot water return port 121 to the hot water tank 12 is equal to a predetermined hot water set temperature T0ref. The amount of water discharged from the heat recovery water circulation pump 13 is controlled by the above. Accordingly, the hot water temperature returning to the hot water tank 12 is sufficiently set to the hot water set temperature T0ref as long as the exhaust heat is sufficiently generated and the heat recovery water circulation pump 13 operates within the range of the minimum and maximum discharge water amount. Will be equal. The amount is substantially proportional to the amount of exhaust heat generated inside the fuel cell power generation section 11 when the hot water set temperature T0ref is constant. Note that the value of the hot water set temperature T0ref is a value equal to a hot water supply temperature set on an operation panel (not shown) in a normal operation state.

  The hot water generated in the heat exchanger 114 is temporarily stored in the hot water tank 12. Hot water is injected from a hot water return port 121 provided in the upper part of the hot water tank 12. The heat recovery circulating water supplied to the heat exchanger 114 is taken out from a cold water port 122 provided at the bottom of the hot water tank 12 or near the bottom. Accordingly, the hot water begins to accumulate from the upper part in the hot water tank 12 due to the specific gravity, and the thickness of the hot water layer increases as the amount increases. The hot water exits from a water outlet 123 provided in the upper part of the hot water storage tank 12 and is supplied to the hot water using device 4. The amount of water reduced due to the hot water supply is replenished by supplying city water from a water inlet 124 provided at the bottom of the hot water tank 12 or a lower part near the bottom, and the hot water tank 12 is always full of water. It is kept in.

  With such a configuration and operation, the generated power Pac generated by the fuel cell power generation unit 11 is supplied to the cogeneration power load 3 and the exhaust heat is supplied to the hot water using device 4 as hot water. However, if the amount of hot water used by the hot water use device 4 temporarily increases as it is, there is a problem that the hot water in the hot water storage tank 12 is insufficient and the hot water runs out (hot water is out) or the hot water supply temperature is lowered. Can occur. Conversely, when the amount of hot water used is reduced and the hot water storage tank 12 is filled with hot water, the hot water in the hot water storage tank 12 is overheated and sufficient heat recovery is not performed in the heat exchanger 114. As a result, the temperature of each part in the fuel cell power generation unit 11 rises and power generation cannot be continued.

  Next, a control method according to this embodiment for improving the situation such as running out of hot water (out of hot water) and lowering of the hot water supply temperature to a level where there is no practical problem will be described. Inside the hot water storage tank 12 of the present embodiment, three temperature detectors are attached: a temperature detector 1T1 at the top, a temperature detector 1T2 at the middle, and a temperature detector 1T3 at the bottom. The upper temperature detector 1T1 is mounted at substantially the same height as the water outlet 123, and detects the upper hot water temperature T1. The lower temperature detector 1T3 is attached to a position slightly higher than the water inlet 124, and detects the hot water temperature T3 in the lower portion of the hot water tank 12. The intermediate temperature detector 1T2 is mounted at a substantially intermediate height of the hot water storage tank 12, and detects the hot water temperature T2 in the intermediate portion.

  Furthermore, an electric heater 12 </ b> H for auxiliary heating of hot water is provided inside the hot water tank 12. The electric heater 12 </ b> H is attached at a position that is approximately equal to or higher than the intermediate height in the hot water storage tank 12 and below the hot water return port 121 and the water outlet 123. The electric heater 12H is supplied with power from the commercial power system 2. A heater power supply switching relay 16 including two relays 16a and 16b is provided between the electric heater 12H and the single-phase three-wire commercial power system 2, and when the relay 16a is turned on, a single phase is provided. When the relay 16b is turned on at 100V, a single-phase 200V is supplied to the electric heater 12H.

  ON / OFF of the heater power supply switching relay 16 is controlled by a heater power supply switching control circuit 17. The heater power switching control circuit 17 receives the hot water temperatures T1, T2, and T3 detected by the three temperature detectors 1T1, 1T2, and 1T3 described above. Further, the value of the generated power Pac of the fuel cell power generation unit 11 is measured and inputted by a power meter (not shown).

  Next, the control logic of the heater power supply switching control circuit 17 will be described. FIG. 2 is a flowchart for explaining the control logic of the heater power supply switching control circuit 17. First, in step S1, it is determined whether or not the hot water temperature T3 detected by the temperature detector 1T3 attached to the lower part of the hot water storage tank 12 is higher than the hot water supply temperature Tref of hot water to be supplied. The hot water supply temperature Tref is set from an operation panel (not shown) of the fuel cell cogeneration system 1.

  The temperature of the hot water heated by the heat exchanger 114 and returned to the hot water tank 12 is controlled to the hot water set temperature T0ref by the circulation pump control circuit 15 as described above. Accordingly, if the value of the hot water supply temperature Tref is set as the value of the hot water set temperature T0ref, the hot water having the hot water supply temperature Tref is stored in the hot water storage tank 12. However, in actuality, a temperature drop due to heat radiation can be considered while hot water is stored in the hot water storage tank 12, and therefore it is desirable to set a temperature slightly higher than the hot water supply temperature Tref as the hot water set temperature T0ref.

  If the detected lower hot water temperature T3 is equal to or higher than the hot water supply temperature Tref, the process proceeds to step S2. The fact that the lower hot water temperature T3 is equal to or higher than the hot water supply temperature Tref means that the hot water storage tank 12 is full of hot water equal to or higher than the hot water supply temperature Tref and the hot water storage amount is sufficient. Therefore, in this case, since it is not necessary to auxiliaryly heat the hot water, all the heater power supply switching relays 16 are turned off to turn off the electric heater 12H.

If the lower hot water temperature T3 is lower than the hot water supply temperature Tref in step S1, it means that the lower portion of the hot water tank 12 is in a cold water state. In this case, the process proceeds to step S3. In step S3, it is determined whether or not the hot water temperature T2 detected by the temperature detector 1T2 attached to the intermediate portion in the hot water storage tank 12 is higher than the hot water supply temperature Tref.
When it is higher than the hot water supply temperature Tref, the process proceeds to step S4. In this case, the upper part from the middle of the hot water tank 12 is hot water, and the lower part is in the state of cold water. In this state, it is necessary to increase the amount of hot water so that the entire hot water storage tank 12 is filled with hot water.

There are two ways to increase the amount of hot water. One is a method of waiting for the amount of stored hot water to increase due to the warm water that has been heated by the heat exchanger 114 and returned. The second is a method of increasing the amount of hot water by auxiliary heating the water in the hot water tank 12 with the electric heater 12H. In step S4, it is determined whether or not auxiliary heating by the electric heater 12H is necessary.
Whether or not auxiliary heating is necessary is determined based on whether or not the current generated power Pac of the fuel cell power generation unit 11 is equal to or higher than the hot water generation power Pwmin necessary for generating a predetermined amount of hot water per unit time. Do. The hot water generation power Pwmin is generated power of the fuel cell power generation unit 11 necessary to generate, for example, 2 liters of hot water of 50 ° C. per minute by the exhaust heat.

  If the current generated power Pac is equal to or higher than the hot water generation power Pwmin, a predetermined amount of hot water equal to the hot water supply temperature Tref should be generated without unit heating. This is a case where YES is determined in step S4. Therefore, in this case, it is determined that auxiliary heating is unnecessary for the time being, and the process proceeds to step S5 where all the heater power supply switching relays 16 are turned off, and the electric heater 12H is turned off.

  If it is determined in step S4 that the current generated power Pac is less than the hot water generated power Pwmin, the process proceeds to step S6. In this case, since the amount of exhaust heat is insufficient with the current generated power Pac, the hot water at the hot water supply temperature Tref cannot be generated by a predetermined amount per unit time. Therefore, if it is left as it is, the amount of hot water decreases, leading to a situation where the hot water runs out or the hot water supply temperature decreases. Therefore, in step S6, auxiliary heating by the electric heater 12H is performed. In this case, about half of the hot water tank 12 is still filled with hot water, and it is not an emergency that the hot water must be increased rapidly. Therefore, the relay 16a of the heater power supply switching relay 16 is turned on to supply single-phase 100V power to the electric heater 12H, and auxiliary heating is performed with a low heat generation amount.

In step S3, when the hot water temperature T2 of the intermediate part in the hot water storage tank 12 is lower than the hot water supply temperature Tref, the process proceeds to step S7. In step S7, it is determined whether or not the hot water temperature T1 detected by the temperature detector 1T1 attached to the upper part of the hot water storage tank 12 is higher than the hot water supply temperature Tref. If it is higher, the process proceeds to step S8.
Step S <b> 8 is a state in which a little hot water remains in the upper part of the hot water tank 12. In this case, since it is necessary to increase hot water urgently, a single-phase 200V power source is supplied to the electric heater 12H to perform auxiliary heating with a high calorific value regardless of the current value of the generated power Pac. Therefore, the relay 16b of the heater power supply switching relay 16 is turned on. When a single-phase 200V power source is supplied, the amount of heat generated by the electric heater 12H is four times that of a single-phase 100V power source, so a large amount of hot water is generated in a short time.

  When it is determined in step S7 that the hot water temperature T1 in the hot water tank 12 is lower than the hot water supply temperature Tref, the process proceeds to step S9. Step S9 means that the upper part of the hot water storage tank 12 is also cold water, that is, the hot water runs out (hot water running out state). Therefore, in this case as well, it is necessary to quickly recover the amount of hot water, so that the relay 16b is turned on and single phase 200V is supplied to the electric heater 12H as in step S8, and auxiliary heating is performed with a high calorific value.

  In the present embodiment, since the amount of hot water generated is increased by controlling the heat generation amount of the auxiliary heating of the electric heater 12H according to such control logic, an imbalance is generated between the generated power Pac of the fuel cell power generation unit 11 and the hot water demand. Even if there is, there is an effect that almost no troubles such as running out of hot water in the hot water storage tank 12 and lowering of the water supply temperature occur.

(Second Embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 2. FIG. 3 shows a block diagram of the overall configuration of the fuel cell cogeneration system 1 of the present embodiment, and the connection relationship of the commercial power system 2, the cogeneration power load 3, and the hot water using device 4 connected thereto. In addition, the same code | symbol is attached | subjected to FIG. 1 of 1st Embodiment, or an equivalent part, and the description is not repeated.

  The difference between the present embodiment and the first embodiment is how to install the temperature detector in the hot water tank 12 and the control logic of the heater power supply switching control circuit 17. In the hot water storage tank 12 of the present embodiment, four temperatures of a first temperature detector 2T1, a second temperature detector 2T2, a third temperature detector 2T3, and a fourth temperature detector 2T4 are sequentially arranged from the top. Detectors are mounted at approximately equal intervals. The temperatures T1, T2, T3, and T4 detected by each temperature detector are input to the heater power supply switching control circuit 17.

  In the first embodiment, the amount of hot water in the hot water tank 12 is estimated by determining whether or not the temperature detected by the three temperature detectors is higher than the hot water supply temperature Tref. In this embodiment, the amount of warm water is estimated with a little more accuracy. Therefore, in the first embodiment, the reference temperature for determination is one type of the hot water supply temperature Tref, whereas in the present embodiment, the first reference temperature T1ref and the second reference temperature are used to estimate the amount of hot water. The reference temperature T2ref is provided.

The value of the first reference temperature T1ref is set to a temperature equal to or slightly lower than the hot water supply temperature Tref (for example, 60 ° C.). The second reference temperature T2ref is set to a temperature (for example, 50 ° C.) slightly lower than the first reference temperature T1ref and higher than the temperature Tc of city water supplied from the lower part of the hot water tank 12.
Then, the four detected temperatures T1 to T4 are compared with the first and second reference temperatures T1ref and T2ref to weight the detected temperatures. For example, when the detected temperature Ti (i = 1 to 4) is higher than the first reference temperature T1ref (60 ° C.), the value of the weight a (Ti) is set to “2”, and the first reference temperature T1ref (60 ° C.) is set. When it is intermediate between the temperature T1ref (60 ° C.) and the second reference temperature T2ref (50 ° C.), the weight a (Ti) is set to “1”, which is lower than the second reference temperature T2ref (50 ° C.). In this case, the value of the weight a (Ti) is set to “0”.

Such weighting is performed for each of the detected temperatures T1 to T4, and the sum Σa (Ti) of the weights is calculated.
Σa (Ti) = a (T1) + a (T2) + a (T3) + a (T4) (1) Equation (1) In this value, for example, the detection temperatures T1 to T4 are all higher than the first reference temperature T1ref (60 ° C.) ( For example, 62 ° C)
Σa (Tn) = 2 + 2 + 2 + 2 = 8 (2). This corresponds to the case where the inside of the hot water tank 12 is filled to the bottom with warm water having a temperature equal to or higher than the first reference temperature T1ref (60 ° C.).

On the other hand, when the detection temperatures T1 to T4 are all lower than the second reference temperature T2ref (50 ° C.) (for example, 20 ° C.),
Σa (Ti) = 0 + 0 + 0 + 0 = 0 (3) This is because the hot water tank 12 is filled with cold water having a temperature equal to or lower than the second reference temperature T2ref (50 ° C.), which corresponds to a state where the hot water runs out.

For example, when the detected temperatures T1, T2, T3, and T4 are 62 ° C., 60 ° C., 54 ° C., and 25 ° C.,
Σa (Ti) = 2 + 2 + 1 + 0 = 5 (4) This corresponds to a case where about 2/3 of the hot water tank 12 is hot water and the remaining about 1/3 is cold water.

  As described above, when the detected temperatures T <b> 1 to T <b> 4 are weighted as described above to obtain a total, the total value Σa (Ti) is a value that is substantially proportional to the amount of hot water in the hot water storage tank 12. In order to obtain an evaluation value for estimating the ratio of the hot water in the hot water tank 12 from the total value Σa (Ti), the total value Σa (Ti) is used as the first reference temperature T1ref (60 ° C.) in the hot water tank 12. The percentage (%) (hereinafter referred to as hot water estimated ratio A) is obtained by dividing by the total value when the hot water is full.

Hot water estimated ratio A = 100 × (Σa (Ti) / (Σa (Ti) when hot water is full))
However, if i = 1 to 4 (5) and the above-described example is applied to the calculation, the hot water tank 12 in which the total value is calculated by the equation (2) is hot and full. The value of the estimated ratio A of hot water is 100%. In the state of running out of hot water where the total value is calculated by the equation (3), the value of the hot water estimated ratio A is 0%. When the hot water whose total value is calculated by the equation (4) is about 2/3, the value of the hot water estimated ratio A is 63%. Thus, it can be seen that the numerical value of the hot water estimated ratio A calculated by the equation (5) represents the ratio of the hot water existing in the hot water tank 12 with considerably good accuracy.

  In the present embodiment, the above-described weighting is performed on the detected temperatures T1 to T4 as described above, and the evaluation numerical value as the warm water estimated ratio A is calculated by the equation (5). Then, based on the value, the amount of heat generated by the electric heater 12H in the hot water tank 12 is controlled by the heater power supply switching control circuit 17.

  Next, the control logic of the heater power supply switching control circuit 17 will be described with reference to the control flow of FIG. In the first step S10, the above-described weighting is performed on each value of the detected temperatures T1 to T4, and the value of the estimated hot water ratio A, which is an evaluation value, is calculated by the equation (5).

  In subsequent step S11, it is determined whether or not the obtained hot water estimated ratio A is equal to or greater than a predetermined first hot water ratio reference value A1ref. The first warm water ratio reference value A1ref is, for example, 95%. When the value of the warm water estimated ratio A is equal to or greater than the first warm water ratio reference value A1ref (95%), it is estimated that the amount of warm water in the hot water tank 12 is sufficient, and the process proceeds to step S12. In this case, since the amount of hot water is sufficient and does not require auxiliary heating, all the heater power supply switching relays 16 are turned off in step S12 to turn off the electric heater 12H.

When the value of the warm water estimated ratio A is smaller than the first warm water ratio reference value A1ref in step S11, the process proceeds to step S13. In step S13, it is determined whether or not the value of the hot water estimated ratio A is greater than a predetermined second hot water ratio reference value A2ref. The second warm water ratio reference value A2ref is a value smaller than the first warm water ratio reference value A1ref and is, for example, 40%.
When the value of the warm water estimated ratio A is equal to or greater than the second warm water ratio reference value A2ref, the process proceeds to step S14. In this case, the amount of hot water in the hot water tank 12 is estimated to be between the first hot water ratio reference value A1ref and the second hot water ratio reference value A2ref (40 to 95%). That is, the hot water storage amount is estimated to be in an intermediate state. In this state, it is necessary to increase the amount of hot water so that the entire hot water storage tank 12 is filled with hot water.

As with the first embodiment, there are two means for increasing the amount of hot water. One is a method of waiting for the amount of stored hot water to increase due to the warm water that has been heated by the heat exchanger 114 and returned. The second is a method of increasing the amount of hot water by auxiliary heating the water in the hot water tank 12 with the electric heater 12H.
Therefore, in step S14, it is determined whether or not auxiliary heating by the electric heater 12H is necessary. The determination as to whether or not auxiliary heating is necessary is necessary for the current generated power Pac in the fuel cell power generation unit 11 to generate a predetermined amount of hot water per unit time, as in the case of the first embodiment. This is performed depending on whether or not the warm water generation power Pwmin is exceeded. The hot water generation power Pwmin is generated power of the fuel cell power generation unit 11 necessary to generate, for example, 2 liters of hot water of 50 ° C. per minute by the exhaust heat.

  If the current generated power Pac is equal to or higher than the hot water generation power Pwmin, a predetermined amount of hot water equal to the hot water supply temperature Tref should be generated without unit heating. This is a case where YES is determined in step S14. Therefore, in this case, it is determined that auxiliary heating is unnecessary for the time being, and the process proceeds to step S15 where all the heater power supply switching relays 16 are turned off to turn off the electric heater 12H.

  If it is determined in step S14 that the current generated power Pac is less than the hot water generated power Pwmin, the process proceeds to step S16. In this case, since the amount of exhaust heat is insufficient with the current generated power Pac, the hot water at the hot water supply temperature Tref cannot be generated by a predetermined amount per unit time. Therefore, if it is left as it is, the amount of hot water decreases, leading to a situation where the hot water runs out or the hot water supply temperature decreases.

  Therefore, in step S16, auxiliary heating is performed by the electric heater 12H. In this case, a considerable amount of hot water still remains in the hot water storage tank 12, and this is not an emergency situation in which the hot water must be increased rapidly. Therefore, by turning on the relay 16a of the heater power supply switching relay 16, a single-phase 100V power supply is supplied to the electric heater 12H, and auxiliary heating is performed with a low calorific value.

  When it is determined in step S13 that the value of the hot water estimated ratio A is smaller than the predetermined second hot water ratio reference value A2ref, the process proceeds to step S17. In step S17, it is determined whether the value of the estimated hot water ratio A is equal to or greater than a predetermined third warm water ratio reference value A3ref. The predetermined third hot water ratio reference value A3ref is a value smaller than the previous second hot water ratio reference value A2ref, for example, 15%. If it is greater than or equal to the third hot water ratio reference value A3ref, the process proceeds to step S18.

  In step S18, the amount of hot water in the hot water tank 12 is estimated to be not less than the third warm water ratio reference value A3ref and not more than the second warm water ratio reference value A2ref (between 15 and 40%). That is, it is determined that the remaining amount of hot water is small. In this case, since it is necessary to increase hot water urgently, regardless of the current value of the generated power Pac, single-phase 200V is supplied to the electric heater 12H, and auxiliary heating is performed with a high calorific value. For this purpose, the relay 16b of the heater power supply switching relay 16 is turned on, and a single-phase 200V power supply is supplied to rapidly recover the amount of hot water. When a single-phase 200V power supply is supplied, the amount of heat generated by the electric heater 12H is four times that of a single-phase 100V power supply, so the amount of hot water generated per unit time is greatly increased.

  If it is determined in step S17 that the value of the hot water estimated ratio A is smaller than the predetermined third hot water ratio reference value A3ref, the process proceeds to step S19. In step S19, it is determined that the remaining amount of hot water is equal to or less than the third hot water ratio reference value A3ref (15%) and that the hot water is in a running out state. Therefore, in this case as well, since it is necessary to quickly recover the amount of hot water, the relay 16b of the heater power supply switching relay 16 is turned on to supply a single-phase 200V to the electric heater 12H in the same manner as in step S18, and a high calorific value is generated. Auxiliary heating is performed.

In accordance with such control logic, the heater power supply switching control circuit 17 controls the heater power supply switching relay 16 to perform auxiliary heating, so that the hot water storage tank 12 runs out of hot water and the temperature of the feed water is not practically problematic. It becomes possible to improve even to.
In the present embodiment, four temperature detectors are attached in the hot water storage tank 12, but the number of temperature detectors may be further increased. In general, the accuracy of hot water ratio estimation is improved by increasing the number of temperature detectors. When the number of temperature detectors is n, the hot water estimated ratio A is calculated by the following equation.

Hot water estimated ratio A = 100 × (Σa (Ti) / (Σa (Ti) when hot water is full))
However, i = 1-n (6) Moreover, about the 1st warm water ratio reference value A1ref with respect to the warm water estimated ratio A, the 2nd warm water ratio reference value A2ref, and the 3rd warm water ratio reference value A3ref, it makes it variable. It is good to make it variable. By doing so, by setting and changing these values as appropriate according to the hot water usage status, seasonal factors, or time factors in the hot water using device 4, optimal hot water generation control suitable for the actual situation at that time can be achieved. It becomes possible to do.

  For example, when the demand for hot water is relatively low, such as in summer, the first hot water ratio reference value A1ref, the second hot water ratio reference value A2ref, and the third hot water ratio reference value A3ref are set to small values. Thus, it is possible to reduce the auxiliary heating by the electric heater 12H (increase the non-energized state).

(Third embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 3. The present embodiment is an embodiment in which the amount of hot water in the hot water tank 12 is estimated more precisely than in the first and second embodiments.

  The configuration of the fuel cell cogeneration system of the present embodiment is the same as that of the first and second embodiments shown in FIGS. 1 and 3 except for the configuration of the temperature detector in the hot water tank 12. Is the same. The configuration of the external device of the fuel cell cogeneration system 1 is also the same. Therefore, those same parts will be referred to FIG. 1 and the description will not be repeated.

FIG. 5 shows a configuration of the hot water tank 12 in the present embodiment. In this embodiment, the ratio of the hot water in the hot water tank 12 is estimated by calculating the total amount of heat that the hot water has. The estimation calculation method performed by the heater power supply switching control circuit 17 will be described.
It is considered that the hot water in the hot water tank 12 is cut in a horizontal plane and divided into n pieces, and the hot water is composed of n layers. This n division is preferably equal division. The thickness of each layer is d1, d2,-, and dn in order from the top. Three temperature detectors 3T1, 3T2, --- 3Tn are attached in order from the top to the intermediate height position of each layer. The temperatures T1, T2,-, and Tn detected by these temperature detectors are input to the heater power supply switching control circuit 17 shown in FIG.

  Let Tc be the temperature of city water (cold water) supplied from the water inlet 124 at the bottom of the hot water tank 12. The city water temperature Tc is preferably measured with a temperature detector attached, but may be treated as a constant when the temperature is constant. The value is input to the heater power supply switching control circuit 17. The city water supplied to the hot water storage tank 12 absorbs heat energy by heat exchange in the heat exchanger 114 and auxiliary heating by the electric heater 12H, becomes hot water, is stored in the hot water storage tank 12, and is discharged from the outlet 123. To the external hot water use device 4.

Of the amount of heat absorbed by the city water by such heat recovery in the heat exchanger 114 and auxiliary heating by the electric heater 12H, the amount of heat remaining in the hot water tank 12 in the form of hot water (hereinafter referred to as incremental heat amount QT). Can be approximated by the following equation.
QT = Σ ((Ti−Tc) · S · di), i = 1 to n (7) where S is a cross-sectional area inside the hot water tank 12 and its value is assumed to be constant.

Assuming that QT ′ is an incremental heat quantity QT in the case where the hot water tank 12 is full of hot water at the hot water supply temperature Tref, the value is calculated by the following equation.
QT ′ = Σ ((Tref−Tc) · S · di), i = 1 to n (8) Also, when there is no hot water in the hot water tank 12, that is, when the hot water runs out, the detected temperature Ti Are all equal to the cold water temperature Tc, the incremental heat quantity QT is zero.

From these facts, the ratio R of the incremental heat quantity QT calculated by the equation (7) with respect to the incremental heat quantity QT ′ when the water is full with hot water having a temperature equal to the hot water supply temperature Tref represents the ratio of the hot water in the hot water storage tank 12 to be occupied. Can be considered. That is, it is presumed that R calculated by the following formula represents the ratio of hot water.
R = 100 × QT / QT ′
= 100 × (Σ ((Ti−Tc) · di)) / Σ ((Tref−Tc) · di)
However, i = 1 to n (9) For example, the value of the estimated hot water ratio R according to the expression (9) is 100% when the hot water tank 12 is full of hot water at the hot water supply temperature Tref, and when the hot water runs out. Becomes 0%.

Incidentally, when all the n layers have the same thickness, the value of the estimated hot water ratio R in equation (9) is calculated as follows.
R = 100 × (Σ (Ti−Tc)) / n / (Tref−Tc) (10) Equation (Σ (Ti−Tc)) / n is the average temperature rise, and (Tref−Tc) is the city water temperature Tc. To a hot water supply temperature Tref. Therefore, it can be said that the estimated hot water ratio R represents the current average temperature rise ratio with respect to the temperature rise up to the hot water supply temperature Tref.

  The heater power supply switching control circuit 17 switches the heater power supply switching relay 16 based on the value of the estimated hot water ratio R calculated by the equation (9) to control the amount of heat generated by auxiliary heating by the electric heater 12H. The control logic is shown in FIG. The control logic only replaces the hot water estimated ratio A in the control logic of FIG. 4 in the case of the second embodiment with the hot water estimated ratio R calculated by the equation (9), and the description thereof will be omitted.

  Since the estimation logic of the amount of hot water in the hot water storage tank 12 in this embodiment is more precise than the estimation methods in the first and second cases, it is more effective for situations such as running out of hot water in the hot water storage tank 12 and lowering the feed water temperature. In addition, it can be improved to a level where there is no practical problem.

(Fourth embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 4. In this embodiment, in the second and third embodiments, a measure is added when the amount of hot water in the hot water storage tank 12 suddenly decreases due to a large amount of hot water supply while the heater power supply switching control circuit 17 controls the electric heater 12H. Embodiment.

  A new control flow added to the heater power supply switching control circuit 17 is shown in FIG. In the first step S20, a hot water rapid decrease flag Fd for notifying whether or not a rapid decrease in hot water has occurred is provided, and the flag is initially turned off. In the following step S21, the current hot water estimated ratio is calculated. When the present embodiment is added to the second embodiment, the calculation of the current hot water estimated ratio is estimated by equation (5), and when added to the third embodiment, equation (9) is used. Estimated by The estimated value is stored as A (t) when applied to the second embodiment, and is stored as R (t) in the case of the third embodiment. In FIG. 7, for the sake of convenience, A (t) is described assuming the case of the second embodiment.

In the subsequent step S22, the process waits for a predetermined time Δt. After the lapse of Δt time, the process proceeds to step S23, the hot water estimated ratio A is calculated again, and the value is stored as A (t + Δt) (R (t + Δt) in the case of the third embodiment).
In the subsequent step S24, a value of A (t) −A (t + Δt) is calculated, and it is determined whether or not the value is larger than a predetermined value K1. When A (t) −A (t + Δt) is larger than K1, it is determined that the state is rapidly decreasing. The predetermined value K1 is a reference numerical value for determining whether or not the hot water is rapidly decreased, and is determined in consideration of the hot water generation capability of the fuel cell cogeneration system 1, the capacity of the hot water tank 12, and the like.

If it is determined that the hot water is suddenly decreased, the process proceeds to step S25, and the hot water rapid decrease flag Fd is turned ON. If it is not the hot water rapid decrease, the process proceeds to step S26 and the hot water rapid decrease flag Fd is turned OFF.
In the subsequent step S27, the value of the warm water estimated ratio A (t + Δt) is transferred to the warm water estimated ratio A (t). Then, the process returns to step S22, and the determination as to whether or not the sudden decrease in hot water has occurred is repeated.

  Next, the control logic of the heater power supply switching control circuit 17 taking into account such a rapid decrease in hot water will be described. FIG. 8 is the control flow of FIG. 4 which is the second embodiment, with a correction taking into account the rapid decrease in hot water. The control flow in FIG. 8 is the same as the control flow in FIG. 4 except that steps S13a and S13b are newly added. The control flow in FIG. 7 and the control flow in FIG. 8 are processed in parallel.

In step S13, when the value of the warm water estimated ratio A is equal to or greater than the second warm water ratio reference value A2ref, the process proceeds to step S13a, and it is determined whether or not the warm water rapid decrease flag Fd is ON. If it is not ON, the processing after step S14 is executed in the same manner as in FIG.
If the hot water rapid decrease flag Fd is ON, the process proceeds to step S13b. In step S13b, single-phase 200V is supplied to the electric heater 12H in order to cope with the hot water suddenly decreasing state and increase the hot water rapidly. If single-phase 200V power feeding is performed, the amount of hot water generated per unit time increases due to a large amount of heat generation, and a sudden decrease in hot water can be dealt with.

FIG. 9 is the control logic of FIG. 6 which is the third embodiment, with a modification taking into account the rapid decrease in hot water. The control flow in FIG. 9 differs from the control flow in FIG. 6 only in that steps S13a and S13b are added to the control flow in FIG.
As described above, in the present embodiment, it is detected whether or not a rapid decrease in hot water has occurred. If a rapid decrease has occurred, it is not necessary to wait for the amount of hot water stored in the hot water tank 12 to decrease, but immediately. Auxiliary heating is performed using a phase 200V power supply. Therefore, it is possible to prevent a malfunction such as running out of hot water in which the hot water in the hot water storage tank 12 disappears or a decrease in hot water supply temperature.

(Fifth embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 5. In the second to fourth embodiments, this embodiment is an embodiment in which additional control is performed when it is determined that the hot water storage tank 12 is full of hot water. FIG. 10 is a control flow executed in addition to the second to fourth embodiments. This control flow is a control flow executed by the power generation amount control circuit 115 in FIG. 1 or FIG.

  In the first step A1, the target value of the generated power Pac of the fuel cell power generation unit 11 is set to a normal value. This normal value is a target value when the fuel cell power generation unit 11 is in a normal operation state, and is a target value when the hot water storage tank 12 is not full of hot water. This normal value is determined in consideration of the power demand of the cogeneration power load 3 in addition to the facility capacity of the fuel cell power generation unit 11. The power generation amount control circuit 115 controls the amount of fuel gas supplied to the reformer 111, the output current of the inverter 113, and the like so that the value of the generated power Pac of the fuel cell power generation unit 11 matches this target value.

In continuing step A2, it is determined whether the hot water tank 12 is full with warm water. In the case of the second embodiment, this determination is made with a predetermined reference value in which the value of the hot water estimated ratio A calculated by the equation (5) is larger than the predetermined first hot water ratio reference value A1ref in the control flow of FIG. This is performed depending on whether or not it is greater than or equal to A1ref ′.
In the case of the third embodiment, the value of the estimated hot water ratio R calculated by the equation (9) is greater than or equal to a predetermined reference value A1ref ′ greater than the predetermined first hot water ratio reference value A1ref in the control flow of FIG. Depending on whether or not.

The fourth embodiment is a modified embodiment of the second and third embodiments, and the criteria for determining whether or not the hot water is full is the same as in the second and third embodiments.
The temperature 12T0 of the hot water that exchanges heat with the heat exchanger 114 and returns to the hot water tank 12 is controlled by the integral integration control of the amount of water discharged from the heat recovery water circulation pump 13 by the circulation pump control circuit 15, so that the hot water set temperature T0ref (circulation pump The temperature is controlled to an input set temperature to the control circuit 15). This hot water set temperature T0ref is set to a value equal to or slightly higher than the specified hot water supply temperature Tref in the normal operation state as described above.

  When the temperature of the heat recovery circulating water supplied to the heat exchanger 114 from the cold water port 122 at the bottom of the hot water tank 12 approaches the hot water set temperature T0ref, the amount of heat that must be absorbed by the heat exchanger 114 is small. Therefore, the time for the heat recovery circulating water to pass through the heat exchanger 114 may be short. Therefore, in that case, the amount of water discharged from the heat recovery water circulation pump 13 increases, and the amount of hot water returning to the hot water tank 12 increases.

  In the state where the hot water storage tank 12 is determined to be full of hot water in step A2, the temperature of the heat recovery circulating water supplied from the cold water port 122 to the heat exchanger 114 is almost equal to the hot water set temperature T0ref. The amount of water discharged from the water circulation pump 13 is maximized. Even in this state, if the exhaust heat generated in the fuel cell power generation unit 11 continues to be supplied to the heat exchanger 114, the temperature of the hot water returning to the hot water storage tank 12 becomes the hot water set temperature T0ref or higher, that is, the hot water supply temperature Tref or higher. It becomes overheated. Here, it is absolutely necessary to avoid that hot water having a temperature higher than the hot water supply temperature Tref is supplied to the hot water using device 4 in order to cause an accident.

Further, when the temperature of the heat recovery circulating water supplied to the heat exchanger 114 rises, the exhaust heat generated in the fuel cell power generation unit 11 becomes difficult to be removed, so the temperature of each part of the fuel cell power generation unit 11 increases. There is a risk that normal operation cannot be continued.
In order to avoid such a dangerous situation, when it is determined that the hot water storage tank 12 is full of hot water, the target value of the generated power Pac is changed to the lowest generated power Pacmin of the facility in the next step A3. The minimum generated power Pacmin of this facility is the minimum generated power that the fuel cell power generation unit 11 can continue to operate. As a result, the amount of heat per unit time given to the heat recovery circulating water in the heat exchanger 114 is reduced to the minimum value, so that the temperature of the hot water returning to the hot water tank 12 is less likely to become the hot water set temperature T0ref or higher. At the same time, the temperature rise of each part of the fuel cell power generation unit 11 is also reduced.

In addition, when it is determined in step A2 that the hot water storage tank 12 is filled with hot water, the electric heater 12H is in a non-energized state because it may be determined that the hot water storage amount is sufficient in the control flow of FIGS. It has become.
In step A4, the system waits for a predetermined time Δt1 while maintaining the minimum generated power Pacmin. After the lapse of Δt1 time, in step A5, it is determined again whether or not the hot water tank 12 is full of hot water in the same manner as in step A2.

And as a result of determination, when it is still full with warm water, it moves to step A6 and makes the target value of generated electric power Pac zero, and stops the electric power generation of the fuel cell power generation unit 11. As a result, the amount of heat supplied to the heat exchanger 114 is quickly reduced to zero, so that the hot water in the hot water storage tank 12 is prevented from being overheated.
If it is determined in step A2 and step A5 that the water is not full with warm water, the process returns to step A1 and the normal operation state is continued.

  As described above, in the present embodiment, when it is determined that the hot water storage tank 12 is filled with warm water, the generated power Pac of the fuel cell power generation unit 11 is lowered to the lowest level at which the operation can be continued and the state is observed for a while. Even if such a state is maintained for a while, if the state of full water continues with hot water, the power generation of the fuel cell power generation unit 11 is stopped. In this way, since the amount of exhaust heat supplied to the heat exchanger 114 is reduced, the hot water in the hot water tank 12 is prevented from being overheated. Further, it is possible to avoid an abnormal rise in the temperature of each part in the fuel cell power generation unit 11.

(Sixth embodiment)
This embodiment is an embodiment corresponding to the inventions described in claims 6 and 7. The present embodiment is an embodiment in which control for preventing a reverse power flow state is added to the first to fifth embodiments. That is, the generated power Pac of the fuel cell power generation unit 11 does not exceed the total power consumed in the cogeneration power load 3 and the electric heater 12H, and excess power difference is not supplied to the commercial power system 2. This is an embodiment in which control to be added is added.

  In order to perform the control of the reverse power flow prevention, in the configuration diagrams of FIGS. 1 and 3, the electric power (hereinafter referred to as power reception) supplied from the commercial power system 2 to the fuel cell cogeneration system 1 and the cogeneration power load 3. The power Pr is measured with a wattmeter (not shown). In order to prevent the reverse power flow, the value of the received power Pr is controlled to a value close to a predetermined small target value Prmin so that the received power Pr does not become negative, and conversely, the purchased power amount does not increase. To do.

  In order to maintain the value of the received power Pr at a constant value close to a predetermined small target value Prmin, the fluctuation of the power consumption Pl of the cogeneration power load 3 is adjusted to the value of the generated power Pac of the fuel cell power generation unit 11. Need to be absorbed. In order to realize such control, in this embodiment, the value of the target value Pacref of the generated power Pac controlled by the power generation amount control circuit 115 is adjusted by a circuit as shown in FIG.

  In the control circuit of FIG. 11, a deviation between the received power target value Prmin and the received power Pr is calculated by the subtracting circuit 50, and the deviation is proportional-integral calculated by the proportional-integral calculating circuit 51. Then, the calculation result Pac ′ is passed through the next limiter circuit 52 to limit the upper limit and the lower limit, and the value is set as the generated power target value Pacref. The power generation amount control circuit 115 controls the fuel cell power generation unit 11 so that the generated power Pac becomes equal to the generated power target value Pacref.

Here, the upper limit value Pacmax of the limiter circuit 52 is the maximum rated generated power of the fuel cell power generation unit 11, and the lower limit value Pacmin is the minimum rated generated power, that is, the lowest generated power that allows the fuel cell power generation unit 11 to continue operation. It is.
The proportional constant of the proportional-integral calculation of the proportional-integral calculation circuit 51 has a minus sign, and the calculation result Pac ′ increases when the received power Pr is larger than the received power target value Prmin. When the calculation result Pac ′ increases, the generated power target value Pacref increases and the generated power Pac increases. If the power consumption Pl of the cogeneration power load 3 is constant during that time, the received power Pr decreases and approaches the received power target value Prmin.

Conversely, when the received power Pr is smaller than the received power target value Prmin, the generated power target value Pacref decreases and the generated power Pac also decreases. If the power consumption Pl of the cogeneration power load 3 is constant during that time, the received power Pr increases and approaches the received power target value Prmin. Due to such adjustment action, the received power Pr is always controlled in a direction approaching the received power target value Prmin.
However, the problem here is when the power consumption Pl of the cogeneration power load 3 becomes very small. There is the following relationship among the received power Pr, the generated power Pac, the power consumption Pl of the cogeneration power load 3, and the power consumption Ph of the electric heater 12H.

Pr + Pac = Pl + Ph (11) Here, let us consider a case where the power consumption Pl suddenly decreases when the power consumption Ph of the electric heater 12H is zero. In this case, the supply power (Pr + Pac) on the left side must decrease rapidly.
By the way, the generated power Pac of the fuel cell power generation unit 11 cannot be decreased rapidly. This is because there is no meaning in reducing the generated power Pac unless the DC generated power Pdc in the fuel cell 112 is decreased. In order to reduce the DC generated power Pdc, it is necessary to reduce the amount of fuel gas supplied to the reformer 111 to reduce the amount of reformed gas supplied to the fuel cell 112 and weaken the electrochemical reaction in the fuel cell 112. However, this change in the operating state cannot be performed abruptly.

  For this reason, when the power consumption Pl decreases rapidly, the received power Pr decreases more rapidly. When the received power Pr decreases, the generated power target value Pacref decreases due to the control of FIG. 11 described above, and the generated power Pac also decreases, but the rate of decrease is slow as described above. Furthermore, the value of the generated power target value Pacref does not fall below the lower limit value Pacmin of the limiter circuit 52. Therefore, when the power consumption Pl falls below the lowest power generation power Pacmin of the fuel cell power generation unit 11 or when the power consumption Pl decreases rapidly even if it does not fall below, the power reception power Pr may become negative. That is, a reverse power flow state can occur.

  As described above, when the power consumption Pl of the cogeneration power load 3 is greatly reduced or suddenly decreased, the power consumption Ph of the electric heater 12H is increased to increase the power reception Pr as a means for preventing the reverse power flow state. Alternatively, it is conceivable to stop the power generation of the fuel cell power generation unit 11 and cover all of the power consumption Pl with the received power Pr. In the present embodiment, in addition to adjusting the generated power target value Pacref by the control method of FIG. 11 described above, means for increasing the power consumption Ph of the electric heater 12H and stopping the power generation of the fuel cell power generation unit 11 Take.

Next, a control method for increasing the power consumption Ph of the electric heater 12H and a control method for stopping the power generation of the fuel cell power generation unit 11 will be described. FIG. 12 is a control flow performed by the power generation amount control circuit 115 in addition to the control logic so far in order to implement this embodiment.
In the first step B1, a 100V power supply flag F1 is provided and turned off. In the subsequent step B2, the magnitude relation between the received power Pr of the commercial power system 2 and the predetermined first reference power Pr1 is determined. Here, the first reference power Pr1 is a power level at a danger level that the received power Pr becomes negative if the power consumption Pl of the cogeneration power load 3 is further reduced, that is, a reverse power flow state occurs. .

  When it is determined that the power is equal to or lower than the first reference power Pr1, the process proceeds to step B3 and the power generation of the fuel cell power generation unit 11 is stopped. If the power generation of the fuel cell power generation unit 11 is stopped, the power consumption Pl of the cogeneration power load 3 is all covered by the received power Pr of the commercial power system 2, so that the received power Pr does not become negative and the power is in a reverse power flow state. Is prevented from occurring. After power generation is stopped, the process returns to step B1, the 100V power supply flag F1 is turned OFF, and the level check of the received power Pr is repeated.

If it is determined in step B2 that the received power Pr is greater than or equal to the predetermined first reference power Pr1, the process proceeds to step B4. In step B4, power generation is resumed if the fuel cell power generation unit 11 is stopped, and power generation is continued if power generation is in progress.
In subsequent step B5, the magnitude relation between the received power Pr and the predetermined second reference power Pr2 is determined. Here, the second reference power Pr2 is not so imminent that the power generation of the fuel cell power generation unit 11 must be stopped immediately, but it can be determined that the received power Pr has dropped to a considerably dangerous level. It is a power value.

  If it is less than the second reference power Pr2, the process proceeds to step B6, where the 100V power supply flag F1 is turned on and the process returns to step B2. Then, the level check of the received power Pr is repeated. If it is equal to or higher than the second reference power Pr2, the risk of a reverse power flow state is low, so the process returns to step B1 and the 100V power supply flag F1 is turned OFF, and the level check of the received power Pr is repeated.

  Next, the effect of the 100V power supply flag F1 turned on in step B6 will be described. The ON / OFF state of the 100V power supply flag F1 is checked in the flow in which the heater power supply switching control circuit 17 controls the auxiliary heating power of the electric heater 12H, thereby switching the control flow. Therefore, the ON / OFF state of the 100V power supply flag F1 is notified to the heater power supply switching control circuit 17 (not shown in FIGS. 1 and 3).

  FIG. 13 is obtained by adding the control of this embodiment to the control flow diagram (FIG. 8) of the heater power supply switching control circuit 17 in the fourth embodiment. The control flow of FIG. 8 is obtained by adding the control of the fourth embodiment to the control flow of FIG. 4 that is the second embodiment, and this embodiment is added only to the second embodiment. For this, steps S13a and S13b in the control flow of FIG. 13 may be omitted.

  The flowchart of FIG. 13 is different from the control flowchart of FIG. 8 in that steps S11a, S11b, S13c, and S13d are added. If it is determined in step S11 that the value of the warm water estimated ratio A is equal to or greater than the first warm water ratio reference value A1ref, it is first determined in step S11a whether the 100V power supply flag F1 is ON. If it is OFF, the process proceeds to step S12 as in FIG. 8, and the electric heater 12H is turned off.

  On the other hand, if the 100V power supply flag F1 is ON, the process proceeds to step S11b to supply power to the electric heater 12H with a single-phase 100V power source. The 100V power supply flag F1 is turned ON in the control flow of FIG. 12 when the value of the received power Pr is equal to or higher than the first reference power Pr1 and smaller than the second reference power Pr2. That is, although the power generation of the fuel cell power generation unit 11 must not be stopped immediately, the received power Pr has been lowered to a considerably dangerous level where a reverse power flow state may occur. Therefore, in such a case, if the electric heater 12H is fed with a single-phase 100V power source in step S11b, the risk that the received power Pr increases and a reverse power flow state occurs is reduced.

  The reason for adding steps S13c and S13d is the same. If NO is determined in step S13a, the process does not immediately shift to step S14, but before that, the 100V power supply flag F1 is turned on in step S13c. It is determined whether or not. And when it is ON, it transfers to step 13d and supplies single phase 100V to the electric heater 12H. In this way, similarly to the case of step S11b, it is possible to reduce the risk that the value of the received power Pr increases and a reverse power flow state occurs.

  FIG. 14 is a control flow diagram in which the control of the present embodiment is added to another control flow diagram (FIG. 9) of the heater power supply switching control circuit 17 of the fourth embodiment. The control flow of FIG. 9 is obtained by adding the control of the fourth embodiment to the control flow of FIG. 6 which is the third embodiment. The control flow diagram of FIG. 14 differs only in that the estimated hot water ratio A calculated by the equation (5) in the control flow of FIG. 13 is replaced with the estimated hot water rate R calculated by the equation (9). Description is omitted.

  FIG. 15 is a control flow diagram in which the control of the present embodiment is added to the control flow diagram (FIG. 2) of the heater power supply switching control circuit 17 of the first embodiment. The difference from the control flow of FIG. 2 is that steps S3a and S3b are added. If YES is determined in step S3, the process does not immediately shift to step S4, but before that, it is determined in step S3a whether or not the 100V power supply flag F1 is ON. And when it is ON, it transfers to step 3b and supplies single phase 100V to the electric heater 12H. In this way, the value of the received power Pr increases and the risk of a reverse power flow state is reduced.

  As described above, in the present embodiment, the generated power target value Pacref of the fuel cell power generation unit 11 is determined by the control logic of FIG. 11 so that the reverse power flow state does not occur and the received power Pr is reduced. The power Pac is controlled. Then, the value of the received power Pr is further monitored, and when the value is larger than the first reference power Pr1 and smaller than the second reference power Pr2, the electric heater 12H is fed with at least 100V to receive power. Increase the power Pr and reduce the risk of a reverse power flow condition. Even in such a case, when the received power Pr is reduced and a reverse power flow state is about to occur, the power generation of the fuel cell power generation unit 11 is stopped so that all the power is covered by the received power Pr. As described above, since the generated power Pac of the fuel cell power generation unit 11 and the power consumption of the electric heater 12H are adjusted, there is almost no risk that the received power Pr becomes negative, and the occurrence of a reverse power flow state is effectively prevented. The

(Seventh embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 8. In this embodiment, in the first to sixth embodiments, when 200 V is supplied to the electric heater 12H to perform auxiliary heating, an embodiment is added in which the received power unit price for each season and each time zone is taken into consideration. It is.
In general, the unit price of received power varies depending on the time and season of using power. The received power Pr for compensating for the shortage of generated power in the fuel cell cogeneration system 1 is desirably kept to a minimum in the time zone and the season zone where the power unit price is high. On the other hand, if the received power Pr is too small, the auxiliary heating by the electric heater 12H becomes insufficient, causing problems such as running out of hot water and a decrease in hot water supply temperature, and may cause a reverse power flow state.

  Therefore, in the present embodiment, whether to give priority to auxiliary heating, that is, to give priority to avoiding hot water shortage and a decrease in hot water supply temperature, or to give priority to an operation that reduces the electricity bill is selected from the outside. When the priority is given to the auxiliary heating, the same control as in the previous embodiments is performed. However, if the priority is given to the electricity charge, the control flow in the past is performed. When the single-phase 200V power supply is supplied to the electric heater 12H, the received power Pr is reduced by changing the single-phase 200V power supply to the single-phase 100V power supply, and the operation for suppressing the electricity charge is performed.

  FIG. 16 shows a flow in which such an idea is added to the control flow of FIG. 13 which is the sixth embodiment obtained by developing the second embodiment. The difference from FIG. 13 is that steps S13b, S17, S18, and S19 are eliminated, and steps S17a, S17b, S18a, and S18b are provided instead. As described above, in the present embodiment, when the electricity charge priority is selected, the conventional single-phase 200 power supply is changed to the single-phase 100V power supply. Therefore, Steps S13b, S18, and S19, which were supplied with single-phase 200V power in the control flow of FIG.

  In the control flow of FIG. 16, after the determination of YES in step S <b> 13 a that has conventionally reached single-phase 200 V power supply and the determination of NO in step S <b> 13, the determination of newly provided step S <b> 17 a is performed. In step S17a, it is determined which of hot water storage priority (hot water running out and hot water temperature drop prevention priority) or electricity charge priority is selected. This selection is performed from an operation panel (not shown).

  If hot water priority is selected, the process proceeds to step S18a, and the single heater 200H is fed to the electric heater 12H as in the conventional case to perform auxiliary heating. If the electricity rate priority is selected, the process proceeds to step S17b. In step S17b, it is determined whether or not the current time is a time zone in which the unit price of the electricity charge is higher than normal. If the time zone is not high, the process proceeds to step S18a and single-phase 200V power supply is performed. If it is a time zone with a high charge, the process proceeds to step S18b, where the single-phase 200V power supply is changed to the single-phase 100V power supply, and auxiliary heating is performed.

In this way, the usage amount of the received power Pr in the time zone where the electricity bill unit price is high is reduced, so that the electricity bill can be reduced. On the other hand, however, it cannot be denied that problems such as running out of hot water and a decrease in hot water supply temperature are slightly more likely to occur than in the past.
Note that the idea of the present embodiment can also be applied to the third embodiment and an embodiment obtained by developing the third embodiment, for example, the control flow of FIG. 14 of the sixth embodiment. Since the flow when applied to the control flow of FIG. 14 is merely a replacement of the hot water estimated ratio A in the control flow of FIG. 16 with the hot water estimated ratio R of equation (9), the figure is omitted.

  Similarly, the idea of the present embodiment can be applied to the control flow of the first embodiment and the seventh embodiment which is an extension of the first embodiment. In either case, it can be realized by replacing the step portion that has been conventionally supplied with single-phase 200V with steps S17a, S17b, S18a, and S18b in the control flow of FIG.

(Eighth embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 9. In the first to seventh embodiments, the present embodiment is an embodiment in which control corresponding to a case where hot water (high hot water supply temperature) higher than usual is temporarily required is added. In the present embodiment, in order to generate this high-temperature water, control is additionally performed to raise the temperature by temporarily heating the hot water in the hot water storage tank 12 with the electric heater 12H.

FIG. 17 shows a flow in which a control flow for obtaining high-temperature water is added to the control flow of FIG. 16 of the seventh embodiment. The control flow of FIG. 17 differs from the control flow of FIG. 16 in that steps S10p and S10q are newly added.
In step S10p, it is determined whether there is a request for high-temperature water. The designation of whether or not there is a request for the high-temperature water is performed from an operation panel (not shown). If there is no request for high-temperature water, the process immediately proceeds to step S10 and the conventional control is performed.

  If there is a request for high-temperature water, the process proceeds to step S10q. In step S10q, the detected temperature of the uppermost temperature detector in the hot water tank 12 is compared with the specified temperature Thref of the high temperature water. The designated temperature Thref of the high temperature water is also designated from an operation panel (not shown). If the detected temperature of the uppermost temperature detector is equal to or higher than the specified temperature Thref, the process proceeds to step S10 and conventional control is performed.

  When the temperature detected by the uppermost temperature detector in the hot water tank 12 is lower than the designated temperature Thref, auxiliary heating is performed by the electric heater 12H to increase the temperature of the hot water. In the case of the control flow in FIG. 17, since control whether or not to give priority to the electricity charge is also incorporated, if the temperature is lower than the specified temperature Thref specified in step S10q, the process proceeds to step S17a. Then, auxiliary heating is performed by determining whether single-phase 100V power supply or single-phase 200V power supply should be performed according to the selection.

  In the case of the embodiment that does not incorporate the selection of whether or not to prioritize the electricity charge, single-phase 200V power supply is performed to generate high-temperature water.

  Thus, in this embodiment, when there is a temporary high-temperature water request, the electric heater 12H is set so that the detected temperature of the uppermost temperature detector in the hot water tank 12 is equal to or higher than the specified temperature Thref. Auxiliary heating is performed. Therefore, it is possible to meet the demand for hot water supply of high temperature hot water that cannot be achieved only by heat exchange in the heat exchanger 114.

In the above control, control is performed using the detection temperature of the uppermost temperature detector in the hot water tank 12 as temperature detection for obtaining high-temperature water, but instead of the uppermost position, a position below that is not the uppermost position. You may control using the detection temperature of the temperature detector attached to. By doing so, there is an advantage that the amount of hot water stored in the hot water storage tank 12 can be increased.
Moreover, such a high temperature water request | requirement may be automatically requested | required only for a short time regularly. By doing so, it is possible to expect the effect of preventing the propagation of germs and the like in the hot water tank 12.

(Ninth embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 10. The present embodiment is also an embodiment corresponding to a case where hot water (high hot water supply temperature) higher than usual is temporarily required, and is an embodiment added in addition to the eighth embodiment.
In the eighth embodiment, the hot water in the hot water storage tank 12 is supplementarily heated by the electric heater 12H to generate high temperature water. On the other hand, in the present embodiment, in addition to this, the temperature of the hot water that exchanges heat with the heat exchanger 114 and returns to the hot water tank 12 is increased more than usual, thereby accelerating the generation of high-temperature water. Control to do.

  The temperature of the hot water returning to the hot water tank 12 is controlled by controlling the circulation amount of the heat recovery circulating water by the circulation pump control circuit 15 in FIGS. That is, as described in the description of the first embodiment, the circulation pump control circuit 15 measures the temperature of the hot water generated by the temperature detector 12T0 inserted in the piping of the heat recovery circulating water, and the temperature T0 is The discharge water amount of the heat recovery water circulation pump 13 is controlled by proportional integral calculation so as to be equal to a predetermined hot water set temperature T0ref. Therefore, the temperature of the hot water returning to the hot water tank 12 can be changed by changing the value of the hot water set temperature T0ref.

  This hot water set temperature T0ref is normally set to a temperature equal to or slightly higher than the hot water supply temperature set from an operation panel (not shown). Accordingly, when a request for hot water supply is issued and the temperature is specified from the operation panel, the value of the hot water set temperature T0ref is changed to the specified high temperature water temperature only while the request is issued. By doing, the temperature of the hot water which returns to the hot water storage tank 12 can be raised. In this way, combined with the auxiliary heating by the electric heater 12H described in the eighth embodiment, it is possible to more easily achieve the generation of high-temperature hot water at a specified temperature.

(Tenth embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 11. This embodiment is also an embodiment corresponding to a case in which hot water having a temperature higher than usual (high hot water supply temperature) is temporarily required, and is an embodiment additionally implemented in the eighth and ninth embodiments. is there. In the present embodiment, the number of hot water return ports to the hot water tank 12 is increased to two, and when hot water having a temperature higher than normal is required, the two hot water return ports are switched.

FIG. 18 shows how the hot water return port is attached to the hot water tank 12. The hot water storage tank 12 is additionally provided with a second hot water return port 121 a slightly below the conventional hot water return port 121. The hot water returned from the heat exchanger 114 enters the newly provided switching valve 125, and returns to the hot water tank 12 through either the hot water return port 121 or the hot water return port 121a by the switching operation.
The switching valve 125 selectively switches between the two hot water return ports in response to a signal for selecting whether or not there is a request for hot water from an operation panel (not shown). The switching is performed so that the hot water from the heat exchanger 114 returns to the hot water tank 12 through the lower second hot water return port 121a when there is a request for high-temperature water. In FIG. 18, the temperature detector in the hot water tank 12 is omitted.

This embodiment is control performed in addition to the eighth and ninth embodiments. In the case of the ninth embodiment, high-temperature hot water is generated by two means for increasing the hot water temperature returned from the heat exchanger 114 by raising the hot water set temperature T0ref of the circulation pump control circuit 15 by auxiliary heating by the electric heater 12H. It was done.
By the way, the method of raising the warm water set temperature T0ref of the circulation pump control circuit 15 and raising the warm water temperature returning from the heat exchanger 114 has a limit (upper limit) in the produced warm water temperature. When high-temperature water exceeding the limit is required, the temperature rise of the shortage needs to be raised by auxiliary heating by the electric heater 12H. That is, in such a case, the temperature of the hot water returning from the heat exchanger 114 is lower than the required temperature of the high-temperature water.

  Here, in the embodiments so far, the hot water return port 121 and the water discharge port 123 are provided at substantially the same height. In such a state, when hot water having a temperature lower than the required temperature is returned from the conventional hot water return port 121, the high temperature of the uppermost layer that is at the required high temperature by the auxiliary heating by the electric heater 12H. When mixed with water, the temperature is lowered.

In the present embodiment, in order to improve such problems, hot water returning from the heat exchanger 114 is provided below the conventional water outlet 123 by switching the switching valve 125 while a request for high-temperature water is issued. The hot water is returned to the hot water tank 12 through the second hot water return port 121a.
In this way, the problem that hot water lower than the required temperature returning from the heat exchanger 114 is mixed with the high-temperature water stored in the uppermost portion of the hot water tank 12 is reduced. Hot water heated by the electric heater 12H is accumulated in the uppermost layer portion of the hot water tank 12, and hot water is supplied from the outlet 123 without lowering the temperature, so that hot water can be efficiently supplied. It becomes like this.

(Eleventh embodiment)
This embodiment is an embodiment corresponding to the invention described in claim 12. This embodiment relates to a method for measuring the hot water temperature in the hot water tank 12 in the first to tenth embodiments. In the embodiments so far, a hole has been made in the side wall of the hot water tank 12, and a temperature detector has been inserted and fixed therein for detection.

However, since the hot water tank 12 is generally made of metal, a large number of processing steps are required to open a large number of holes and attach the temperature detector. In this embodiment, in order to reduce such processing man-hours, a temperature detector is attached to the outer surface of the hot water tank 12 to detect the temperature.
The container material of the hot water tank 12 is often a metal having good thermal conductivity such as copper or stainless steel, and the outside of the container is covered with a heat insulating material to prevent heat dissipation. Therefore, if a temperature detector is attached in contact with the outer surface of the container, a temperature close to the hot water temperature inside the container can be detected.

In order to increase the accuracy of the temperature thus detected, the temperature difference between the temperature measured in advance on the outer surface of the container by experiment and the hot water temperature inside the container is obtained. And the temperature of warm water is estimated by performing temperature correction using the experimental result at the time of temperature detection.
If the temperature detector is attached to the outer surface of the container of the hot water tank 12 to estimate the internal hot water temperature in this way, it is not necessary to make a hole in the container, so that the installation man-hour for temperature detection is greatly reduced. Can do.

It is a block diagram which shows the structure of the fuel cell cogeneration system which concerns on 1st Embodiment, and its connection relation with the peripheral device. It is a control flowchart of the heater power supply switching control circuit according to the first embodiment. It is a block diagram which shows the connection relationship with the structure of the fuel cell cogeneration system which concerns on 2nd Embodiment, and its peripheral device. It is a control flowchart of the heater power supply switching control circuit according to the second embodiment. It is a figure which shows arrangement | positioning of the temperature detector in the hot water tank which concerns on 3rd Embodiment. It is a control flowchart of the heater power supply switching control circuit according to the third embodiment. It is a control flow figure which detects warm water sudden decrease concerning a 4th embodiment. It is a control flowchart of the heater power supply switching control circuit which concerns on 4th Embodiment. It is another control flowchart of the heater power supply switching control circuit which concerns on 4th Embodiment. It is an additional control flowchart of the electric power generation amount control circuit which concerns on 5th Embodiment. It is explanatory drawing of the generated electric power target value adjustment logic which concerns on 6th Embodiment. It is an additional control flowchart of the electric power generation amount control circuit which determines the magnitude | size of the received electric power which concerns on 6th Embodiment. It is a control flowchart of the heater power supply switching control circuit which concerns on 6th Embodiment. It is another control flowchart of the heater power supply switching control circuit which concerns on 6th Embodiment. It is another control flowchart of the heater power supply switching control circuit which concerns on 6th Embodiment. It is a control flowchart of the heater power supply switching control circuit which concerns on 7th Embodiment. It is a control flowchart of the heater power supply switching control circuit which concerns on 8th Embodiment. It is a figure which shows the structure of the hot water return port of the hot water tank which concerns on 10th Embodiment.

Explanation of symbols

In the figure, 1 is a fuel cell cogeneration system, 2 is a single-phase three-wire commercial power system, 3 is a cogeneration power load, 4 is a device using hot water, 11 is a fuel cell power generation unit, 12 is a hot water tank, and 13 is a heat recovery unit. Water circulation pump, 15 is a circulation pump control circuit, 16 is a heater power supply switching relay, 17 is a heater power supply switching control circuit, 114 is a heat exchanger, 121 is a hot water return port, 121a is a second hot water return port, and 122 is lower cold water , 123 is an upper outlet, 124 is a lower inlet, 125 is a switching valve, 1T1 to 1T3 are temperature detectors, 2T1 is a first temperature detector, 2T2 is a second temperature detector, 2T3 is a third outlet Temperature detector, 2T4 is a fourth temperature detector, 12T0 is a temperature detector, 12H is an electric heater, A1ref is a first hot water ratio reference value, A2ref is a second hot water ratio reference value, and Pac is a fuel cell power generation unit Generated power, Pwm in is the generated hot water power, Pacmin is the lowest generated power of the fuel cell power generation unit, Pr is the received power, Prmin is the received power target value, Pr1 is the first reference power, Pr2 is the second reference power, and T0 is the temperature detection 12T0 detection temperature, T1 is the first detection temperature, T2 is the second detection temperature, T3 is the third detection temperature, T4 is the fourth detection temperature, T1ref is the first reference temperature, and T2ref is the second , Tc is the city water temperature, Tref is the hot water supply temperature, and Thref is the hot water temperature.

Claims (12)

Fuel cell cogeneration that generates electric power and hot water, and supplies the generated electric power to the cogeneration power load (3) via the single-phase three-wire commercial power system (2) and the generated hot water to the hot water use equipment (4) System (1),
The fuel cell cogeneration system includes a fuel cell power generation unit (11) and a hot water storage tank (12), and the hot water storage tank uses heat taken from its lower cold water port (122) as heat recovery circulating water as a heat recovery water circulation pump. (13) is sent to the heat exchanger (114) in the fuel cell power generation unit, heat is exchanged with the exhaust heat in the heat exchanger to make hot water and return to the hot water return port (121) at the top of the hot water tank, Hot water is supplied to the hot water using equipment from the upper water outlet (123), and city water is replenished from the lower water inlet (124).
The amount of the heat recovery circulating water is determined by detecting the temperature of the heat recovery circulating water just before returning to the hot water storage tank with a temperature detector (12T0) and setting the detected temperature (T0) to the specified hot water supply temperature (Tref). The discharge water amount of the heat recovery water circulation pump is configured to be proportional and integral controlled by the circulation pump control circuit (15) so as to be equal,
In the hot water tank, a lower temperature detector (1T3) is attached to the lower portion, an intermediate temperature detector (1T2) is attached to the intermediate portion, and an electric heater (12H) for auxiliary heating is further attached to the electric heater. Is configured such that single-phase 200 V power or single-phase 100 V power is supplied from the single-phase three-wire commercial power system by switching operation of the heater power switching relay (16) controlled by the heater power switching control circuit (17). Has been
The heater power supply switching control circuit includes the intermediate portion when the detected temperature (T3) of the lower temperature detector is equal to or higher than a specified hot water supply temperature (Tref) and when the detected temperature of the lower temperature detector is lower than the hot water supply temperature. The detected temperature (T2) of the temperature detector is equal to or higher than the hot water supply temperature, and the generated power (Pac) of the fuel cell power generation unit is equal to or higher than the hot water generation power (Pwmin) necessary for generating a predetermined amount of hot water per unit time. If it is, stop the power supply to the electric heater,
The detection temperature of the lower temperature detector is lower than the hot water supply temperature, the detection temperature of the intermediate temperature detector is higher than the hot water supply temperature, and the generated power (Pac) of the fuel cell power generation unit is lower than the hot water generation power (Pwmin). If so, supply the single-phase 100V power to the electric heater,
A fuel cell cogeneration system that supplies the electric heater with the single-phase 200V power when both the temperature detected by the lower temperature detector and the temperature detected by the intermediate temperature detector are lower than the hot water supply temperature. system. The fuel cell cogeneration system according to claim 1,
In place of the lower temperature detector and the intermediate temperature detector, first, second, third, and fourth temperature detectors (2T1, 2T2, 2T3, 2T4) in the hot water tank from the top to the bottom in order. ) Are mounted at approximately equal intervals,
The heater power supply switching control circuit uses the first, second, third, and fourth detected temperatures (T1, T2, T3, T4) detected by the first, second, third, and fourth temperature detectors. Individually compared with a predetermined first reference temperature (T1ref) and a lower second reference temperature (T2ref), and when the detected temperature is equal to or higher than the first reference temperature, the weight is set to 2, and the detected temperature Is less than the first reference temperature and greater than or equal to the second reference temperature, the weight is set to 1, and when the detected temperature is less than the second reference temperature, the weight is set to 0 and the weight is set. Obtain a total value, obtain a percentage of the weighted total value when the first to fourth detection temperatures of the total value are all equal to or higher than the first reference temperature, and obtain a warm water estimated ratio (A),
When the estimated hot water ratio is greater than or equal to a predetermined first warm water ratio reference value (A1ref), and when the estimated warm water ratio is less than the first warm water ratio reference value and greater than or equal to the second warm water ratio reference value (A2ref) And when the generated power of the fuel cell power generation unit is equal to or higher than the hot water generation power (Pwmin), the power supply to the electric heater is stopped,
When the estimated hot water ratio is less than the first warm water ratio reference value and greater than or equal to the second warm water ratio reference value, and the power generated by the fuel cell power generation unit is less than the warm water generation power, the electric heater Supplying the single-phase 100V power supply;
The fuel cell cogeneration system, wherein the single-phase 200V power is supplied to the electric heater when the estimated hot water ratio is less than the second hot water ratio reference value. The fuel cell cogeneration system according to claim 2,
Instead of the first, second, third, and fourth temperature detectors, the hot water in the hot water tank is divided into n layers of approximately equal thicknesses d1 to dn in order from the top, and the intermediate height of each layer is divided. Furthermore, a temperature detector (3T1 to Tn) is attached, the temperature detected by the temperature detector is T1 to Tn from the top, the temperature of the city water is Tc, the hot water supply temperature is Tref, and the estimated hot water ratio (R )
R = 100 × (Σ ((Ti−Tc) · di)) / Σ ((Tref−Tc) · di)
Where i = 1 to n
A fuel cell cogeneration system, wherein the calculated value is used instead of the estimated hot water ratio (A) according to claim 2. In the fuel cell cogeneration system according to claim 2 or 3,
In a state where the amount of decrease in the hot water estimated ratio within the latest predetermined time (Δt) exceeds a predetermined value (K1), the hot water estimated ratio is less than the first hot water ratio reference value (A1ref) and the second The fuel cell cogeneration system is modified to supply the single-phase 200V power to the electric heater when the hot water ratio reference value (A2ref) is exceeded. The fuel cell cogeneration system according to any one of claims 2 to 4,
When the value of the estimated hot water ratio is equal to or greater than a predetermined reference value (A1ref ′) greater than the first warm water ratio reference value (A1ref), the generated power (Pac) of the fuel cell power generation unit is used as the fuel. When the battery power generation unit reduces the generated power (Pacmin) to the lowest possible power generation and continues the state for a predetermined time (Δt1), the hot water estimated ratio is still above the reference value (A1ref ′) A fuel cell cogeneration system characterized by stopping the power generation of the fuel cell power generation unit. The fuel cell cogeneration system according to any one of claims 2 to 5,
The fuel cell power generation so that the received power (Pr) supplied from the single-phase three-wire commercial power system to the fuel cell cogeneration system and the cogeneration power load matches a predetermined received power target value (Prmin). Proportionally integral control of the generated power (Pac) of the fuel cell and when the received power (Pr) is less than the predetermined first reference power (Pr1), the power generation of the fuel cell power generator is stopped.
In a state where the received power is greater than or equal to the first reference power (Pr1) and less than the predetermined second reference power (Pr2), the value of the warm water estimated ratio is greater than or equal to the second warm water ratio reference value (A2ref). In some cases, the fuel cell cogeneration system is modified so as to cause the electric heater to perform at least auxiliary heating by the single-phase 100V power source. The fuel cell cogeneration system according to claim 1,
The fuel cell power generation so that the received power (Pr) supplied from the single-phase three-wire commercial power system to the fuel cell cogeneration system and the cogeneration power load matches a predetermined received power target value (Prmin). Proportionally integral control of the generated power (Pac) of the fuel cell and when the received power (Pr) is less than the predetermined first reference power (Pr1), the power generation of the fuel cell power generator is stopped.
In a state where the received power is equal to or higher than the first reference power (Pr1) and lower than the predetermined second reference power (Pr2), the detected temperature (T3) of the lower temperature detector is lower than the hot water supply temperature (Tref). In addition, when the temperature detected by the intermediate temperature detector (T2) is less than or equal to or higher than the hot water supply temperature, the electric heater is changed so as to perform at least auxiliary heating by the single-phase 100V power source. Fuel cell cogeneration system. The fuel cell cogeneration system according to any one of claims 1 to 7,
In a state where the heater power supply switching control circuit is determined to supply the single-phase 200V power to the electric heater, if it is specified that priority is given to reducing the amount of received power over securing the amount of stored hot water, It was determined whether or not the received power unit price is higher than usual during the time period, and if it was a high time period, it was changed to supply single-phase 100V power instead of single-phase 200V power A fuel cell cogeneration system characterized by The fuel cell cogeneration system according to claim 8,
When a hot water supply request is made by specifying a hot water temperature (Thref) higher than normal as the hot water supply temperature, the heater power supply switching control circuit detects the temperature detector at the top in the hot water storage tank. It is determined whether or not the temperature is lower than a specified high-temperature water temperature (Thref), and if it is lower, the state is determined to be the case where the single-phase 200V power supply is supplied. A fuel cell cogeneration system, wherein a change is made so that any one of a single-phase 100V power source and a single-phase 200V power source is supplied to the electric heater in accordance with the determination method described. The fuel cell cogeneration system according to claim 9,
When a hot water supply request is made by specifying a hot water temperature (Thref) higher than normal as the hot water supply temperature, the circulation pump control circuit detects the heat recovery circulating water immediately before returning to the hot water storage tank. A fuel cell cogeneration system, wherein the amount of water discharged from the heat recovery water circulation pump is controlled by proportional integral control so that the temperature (T0) is equal to the high temperature water temperature. The fuel cell cogeneration system according to any one of claims 9 to 10,
A second hot water return port is provided below the hot water return port in the upper part of the hot water tank, and a return port of the heat recovery circulating water returning from the heat exchanger is provided between the hot water return port and the second hot water return port. A switching valve (125) for switching to either one is provided, and when the high-temperature water supply request is made, the switching valve is switched so that the heat recovery circulating water returns to the second hot water return port. Battery cogeneration system. The fuel cell cogeneration system according to any one of claims 1 to 11,
The method of attaching each temperature detector for detecting the temperature of hot water in the hot water tank is changed to the method of attaching to detect the temperature of the outer surface from the outside of the hot water tank container, and each detected temperature detected in the attached state is changed. The fuel cell cogeneration system is characterized in that the correction previously obtained through experiments is performed and the corrected value is used as each detected temperature of hot water in the hot water tank.

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