JP2005076934A - Heat-recovery-combined heat pump water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the use efficiency of exhaust heat from a fuel cell and the like. <P>SOLUTION: A heat pump water heater comprises a fuel cell unit 3 comprising a heat exchanger 5, a heat pump unit 9 for heating feedwater, a water storage tank 25 whose bottom communicates with a feedwater source, a heat recovery system line having a pump 14 for circulating hot water stored in the bottom of the water storage tank 25 to the top of the water storage tank 25 via the heat exchanger 5, a heat pump system line having a pump 35 for circulating hot water stored in the bottom of the water storage tank 25 to the top of the water storage tank 25 via the heat pump unit 9, a hot water supply line interconnecting the top of the water storage tank 25 and a hot water supply port, and a control system for controlling the water storage in the water storage tank 25. The control system comprises heat recovery system controlling means 47 for controlling an outlet water temperature of the heat exchanger 5 at a set value, and heat pump system controlling means 49 for holding the water storage of a set temperature or higher in the water storage tank 25 in a set range. The use efficiency of exhaust heat from the fuel cell and the like can be thereby increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a heat recovery combined use heat pump water heater that recovers and uses exhaust heat from a fuel cell or the like.

  A fuel cell has high power generation efficiency and can be easily miniaturized, and is therefore used as a power generation device for home use. In general, a fuel cell is configured to generate an electromotive force by supplying hydrogen obtained by reforming city gas or the like and oxygen in the air to both electrodes arranged with an electrolyte interposed therebetween. However, such fuel cells generate exhaust heat simultaneously with power generation. The exhaust heat source is mainly a battery main body, but there are, for example, a reforming section for reforming to hydrogen, exhaust gas discharged from the battery main body, and the like. For this reason, in order to prevent the battery body from being affected by these heats, for example, a method of recovering heat by providing a cooling water circulation path and effectively utilizing the recovered heat has been studied.

  For example, as a technique for using exhaust heat of a fuel cell as a heat source of a hot water heater, a method of recovering exhaust heat through a heat exchanger and storing supply water heated thereby in a hot water storage tank has been proposed ( (See Patent Document 1).

JP 2002-134143 A

  However, in the case of a household fuel cell, the power generation output and the amount of exhaust heat during power generation are small and unstable. In particular, in winter when the hot water supply load is large, it is not possible to sufficiently cover the hot water supply load only with the exhaust heat of the fuel cell, and it is practically necessary to use other hot water supply devices together to cope with the hot water supply load.

  In view of the characteristics of a fuel cell with high energy efficiency and low environmental load, a method of using a heat pump water heater as another hot water supply apparatus and sharing a hot water storage tank between the two apparatuses can be considered.

  In such a hot water supply apparatus, it is preferable to improve the utilization efficiency of the fuel cell without operating the heat pump as much as possible in terms of improving the energy efficiency of the entire apparatus, but this point has been studied at all. Absent.

  An object of the present invention is to improve exhaust heat utilization efficiency of a fuel cell or the like.

  In order to solve the above problems, a heat pump combined use heat pump water heater of the present invention is provided with a fuel cell unit including a heat exchanger for recovering exhaust heat from a fuel cell, a heat pump unit for heating feed water, and a bottom portion. A hot water tank connected to the water source, a heat recovery system line having a pump for circulating hot water stored at the bottom of the hot water tank to the top of the hot water tank via a heat exchanger, and a heat pump unit for storing the hot water stored at the bottom of the hot water tank A heat pump system line having a pump that circulates to the top of the hot water tank, a hot water supply line that communicates the top of the hot water tank and the hot water outlet, and a control device that controls the amount of hot water stored in the hot water tank, Heat recovery system control means for controlling the circulation rate of the heat recovery system line so that the outlet hot water temperature of the heat exchanger is kept at the set value, and the hot water storage amount above the set temperature in the hot water tank is held in the set range Heat pump So as to include a heat pump system control means for controlling the operation of Tsu bets and the heat pump system line.

  According to such a configuration, since hot water having a temperature lower than the set temperature is always stored at the bottom of the hot water tank, heat can be effectively recovered by heating the hot water with the exhaust heat of the fuel cell system. . Even if the amount of hot water stored falls below the set range due to hot water supply, the heat pump is activated to store hot water, so that the shortage of the heat capacity of the fuel cell system is supplemented and hot water shortage can be prevented.

  In this case, it is preferable that the heat pump system control means variably sets the hot water storage amount setting range according to the outside air temperature. According to this, for example, when the outside air temperature decreases, the heat capacity of the heat pump decreases while the hot water supply load increases. Therefore, stable hot water supply can be performed by increasing the amount of stored hot water according to the decrease in the outside air temperature.

  Further, the heat pump system control means does not start the operation of the heat pump unit and the heat pump system line even when the amount of hot water stored in the hot water storage tank falls below the lower limit of the set range when the fuel cell unit is in operation. You can also That is, even if the amount of hot water stored falls below the lower limit of the setting range, the exhaust heat utilization efficiency of the fuel cell can be improved by storing hot water up to the setting range using the power generation of the fuel cell without operating the heat pump. Can do. However, when the amount of hot water stored in the hot water storage tank falls below the lower limit of the setting range while the fuel cell is in operation, the heat pump unit detects the amount of hot water supplied from the water supply port and the hot water supply amount exceeds the set amount. It is preferable to start operation of the heat pump system line. That is, when hot water is supplied, generally, the amount of hot water supplied per hour is larger than the amount of hot water stored per hour of the fuel cell, so the amount of hot water stored above the set temperature decreases. Therefore, when the amount of hot water supply is greater than or equal to the set amount, hot water is supplied with a heat pump having a large heat capacity.

  Also, the heat pump system control means starts the operation of the heat pump unit and the heat pump system line when the amount of hot water stored in the hot water storage tank falls below the upper limit of the setting range from the state where the hot water storage capacity exceeds the upper limit of the setting range. Continue operation until hot water usage is completed. That is, when the amount of hot water stored above the set temperature exceeds the set range, when hot water is supplied, hot water is first supplied from the hot water tank to consume hot water in the hot water tank. After that, when hot water supply is continued and the amount of stored hot water decreases below the upper limit of the set range, it is determined that the amount of remaining hot water has decreased, and hot water is supplied by a heat pump without waiting for the lower limit. According to this, since the decrease in hot water storage is suppressed, the operation of the fuel cell can be continued. Further, when the amount of hot water supply is large, the heat pump operation is started while there is a certain amount of remaining hot water, that is, the amount of hot water stored at the upper limit of the set amount, so that hot water shortage can be prevented.

  Further, when the heat pump system control means starts the hot water storage operation of the heat pump unit and the heat pump system line, it is preferable to reduce the heating capacity of the heat pump unit to a set value during a set time zone. That is, in a time zone such as midnight when the amount of hot water used is relatively small, for example, the set number of hot water is slowly stored by lowering the rotational speed of the compressor. Thereby, the operating efficiency of the heat pump is improved, and the power generated by the fuel cell can be used for the heat pump operation. Moreover, the heating capacity of the heat pump can be kept small by setting the heating capacity variably based on the detected value of the outside air temperature.

  In addition, a three-way switching valve is provided in a portion where the heat pump system line and the hot water supply line communicate with the top of the hot water storage tank, and the three-way switching valve is provided with a flow path for communicating only the hot water supply line with the heat pump system line and the hot water supply line. It is possible to simplify the hot water and hot water storage control by the heat pump and hot water tank by switching between the flow path communicating with the heat pump system line and the hot water tank and the flow path connecting the heat pump system line only with the hot water tank. it can.

  ADVANTAGE OF THE INVENTION According to this invention, exhaust heat utilization efficiency, such as a fuel cell, can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a heat recovery combined use heat pump water heater to which the present invention is applied. As shown in the figure, the heat recovery combined use heat pump water heater of the present invention includes a fuel cell unit 1, a heat pump unit 9, and a hot water tank unit 23. The fuel cell unit 1 includes a power generation stack 3 and an exhaust heat recovery heat exchanger 5 that recovers exhaust heat from the power generation stack 3, and circulates cooling water by a pump 7 to cool the power generation stack 3 and the like. The heat recovery heat exchanger 5 recovers exhaust heat. The heat pump unit 9 is configured by a closed circuit refrigeration cycle in which a compressor 11, a condenser 13, a decompressor 16, and an evaporator 17 are connected by piping. The condenser 13 exchanges heat with water by a water-refrigerant heat exchanger 19. In the evaporator 17, air is blown by the fan 21.

  The hot water storage tank unit 23 includes a hot water storage tank 25, a pump 14 for supplying water to the exhaust heat recovery heat exchanger 5, a pump 15 for supplying water to the water refrigerant heat exchanger 19, a three-way switching valve 27, a check valve 29, 31 is comprised. The hot water storage tank 25 is composed of a vertically long cylindrical container, and a plurality of temperature detectors (thermistors) are arranged in the order of T1 to T5 from the top at predetermined intervals in the height direction inside the side wall. At the bottom of the hot water tank 25, the pump 14, the exhaust heat recovery heat exchanger 5, and the check valve 31 are connected to the top of the hot water tank 25 through pipes 33, 34, 54 in order. The pipe 33 is branched into the pipe 35 before the pump 14, and the pump 15, the water / refrigerant heat exchanger 19, the check valve 29, and the three-way switching valve 27 are sequentially passed through the pipes 35, 36, and 28. It is connected to the top of the hot water tank 25. That is, two inlets 55 and 57 are formed at the top of the hot water tank 25, and hot water stored from the fuel cell unit 1 is introduced into the hot water tank 25 through the pipe 54 and the inlet 55. Hot water stored from the heat pump unit 9 is introduced into the hot water storage tank 25 through the pipe 28 and the inlet 57.

  The hot water storage flow rate due to the exhaust heat of the fuel cell unit 1 is about an order of magnitude smaller than the hot water storage flow rate by the heat pump unit 9 or the hot water supply flow rate supplied from a faucet or the like. Even if hot water is stored by the heat pump unit 9 or hot water is supplied from the faucet or the like during hot water storage by the exhaust heat of the fuel cell unit 1, the hot water storage flow by the exhaust heat of the fuel cell unit 1 is the hot water storage flow by the heat pump unit 9 or faucet or the like. Therefore, the hot water storage control can be simplified and the hot water storage can be stabilized without interfering with the hot water flow rate supplied from the hot water.

  The hot water supply system includes a water supply flow meter 60, a water supply proportional valve 39, a check valve 41, a temperature detector 40, and a hot water supply valve 37. Although only one hot water supply valve 37 is shown in the figure, there are actually a plurality of such as kitchen hot water, bath hot water, and washroom hot water. The reheating system of the bathtub 43 includes a pump 45 that circulates water through the water-refrigerant heat exchanger 19.

  The control system includes a fuel cell control device 47 and a heat pump control device 49, and these control devices are electrically connected via a communication device 51 so that signals can communicate with each other. The hot water storage operation and the hot water supply operation are controlled based on information such as the temperature detected by each detector.

  Next, the operation of the fuel cell will be described. When hydrogen and oxygen are supplied to the power generation stack 3, power generation is started by an electrochemical reaction, and at the same time, the power generation stack 3 generates heat and the temperature rises. When the power generation stack 3 reaches a predetermined temperature, the pump 7 is activated and the cooling water circulates, whereby the power generation stack 3 is maintained at the predetermined temperature. By cooling the power generation stack 3, the cooling water whose temperature has been raised (for example, 70 ° C.) raises the temperature of the exhaust heat recovery heat exchanger 5. When the exhaust heat recovery heat exchanger 5 rises to a predetermined temperature or higher and the temperature detector 53 detects it, the pump 14 is activated. As a result, the hot water extracted from the bottom of the hot water tank 25 (hereinafter referred to as “water” as appropriate) is led to the exhaust heat recovery heat exchanger 3 as the circulating water and heated. Supplied. The pump 14 controls the flow rate so that the water temperature on the outlet side of the exhaust heat recovery heat exchanger 5 detected by the temperature detector 53 becomes a predetermined temperature (for example, 60 ° C.).

  In the hot water storage tank 25, hot water is stored in the upper layer, while normal temperature water is stored in the lower layer. That is, hot water and water are stored in the hot water storage tank 25 in a state of being separated into two layers without being mixed with each other due to the density difference. Therefore, unless hot water is stored up to the bottom of the hot water storage tank 25, water is supplied from the bottom of the hot water storage tank 25 to the exhaust heat recovery heat exchanger 5 to perform exhaust heat recovery.

  Next, the operation of the heat pump unit 9 will be described. When the heat pump unit 9 starts operation, the following three are conceivable. That is, (1) When hot water is stored in a state where the hot water storage amount is less than a preset amount, (2) When the heat pump is operated and hot water is supplied in a state where the hot water storage amount is less than the preset amount, (3) The hot water storage amount is a set amount As described above, since the amount of hot water supply is large, hot water is supplied from both the hot water storage tank 25 and the heat pump unit 9. In any case, as is well known, in the heat pump unit 9, when the compressor 11 is operated, the high-temperature and high-pressure refrigerant flows into the condenser 13 of the water refrigerant heat exchanger 19 and dissipates heat to the water of the water refrigerant heat exchanger 19. To do.

  When the high-temperature and high-pressure refrigerant dissipates heat to water in the condenser 13, the temperature detector 59 detects an increase in the outlet temperature of the water-refrigerant heat exchanger 19, and when the detected temperature reaches a predetermined temperature (for example, 60 ° C.), A pump 15 for circulating water through the refrigerant heat exchanger 19 is started. The flow rate of the pump 15 is controlled so that the water temperature detected by the temperature detector 59 becomes a predetermined temperature (for example, 60 ° C.). In the case of (1), hot water at 60 ° C. is supplied to the three-way switching valve 27 and the pipe 28. Then, it flows into the hot water tank 25 from the inlet 57.

  On the other hand, in the case of the above (2), hot water at 60 ° C. is mixed with water at the water supply proportional valve 39 to reach a predetermined temperature, and hot water is supplied through the hot water supply valve 37. In the case of the above (3), hot water of 60 ° C. coming out of the hot water storage tank 25 and the heat pump unit 9 is mixed with water by the water supply proportional valve 39 to reach a predetermined temperature, and hot water is supplied via the hot water supply valve 37. Is done.

  Here, the three-way switching valve 27 that adjusts the flow path of hot water flowing out from the heat pump unit 9 will be described. The three-way switching valve 27 includes a flow path that allows the heat pump unit 9 to communicate only with the hot water storage tank 25, a flow path that allows the hot water supply line including the pipe 60 and the hot water supply valve 37 to communicate only with the heat pump unit 9, and the hot water supply line. In addition, the flow path communicating with both the hot water storage tank 25 is switched. As shown in FIG. 2, this flow path switching is made up of three types of modes A, B, and C, where (1) is mode C, (2) is mode A, and (3) is mode B. .

  Next, control of the amount of hot water stored in the hot water storage tank 25 will be described. First, when the fuel cell unit 1 and the heat pump unit 9 are used together and the hot water storage tank 25 is shared, the water in the hot water storage tank 25 does not boil up the entire amount, and the hot water of the minimum required amount is stored in the upper part. In addition, it is necessary to send the water to the fuel cell during fuel cell operation (power generation) so that the exhaust heat can be recovered. The set amount of hot water storage is determined from the following two viewpoints.

  (1) Generally, a heat pump water heater requires several minutes after starting to stably supply hot water at a predetermined temperature, for example, 60 ° C. Therefore, when a small amount of hot water is supplied in a short time, the hot water supplied by the heat pump unit 9 is not in time, so the hot water stored in the hot water tank 25 is used. Therefore, it is necessary to store a certain amount of hot water in the hot water storage tank 25 as a backup. For example, when hot water is supplied for 2 minutes at a hot water supply amount of 5 L / min, a hot water storage amount of 10 L is required, and it is necessary to assume that such hot water supply is repeated several times.

  (2) When the outside air temperature decreases (for example, −10 ° C.), the water supply temperature also decreases. Therefore, a large amount of hot water is required to heat water from the water supply temperature to a predetermined temperature (for example, 60 ° C.). The amount of heat obtained from the fuel cell is reduced. For this reason, even if power is generated by a fuel cell in accordance with household electric power demand, it cannot cope with a large hot water supply load. Therefore, for example, when a large number of people take a bath after supplying hot water and each uses a shower, it is necessary to use the heat pump unit 9 and the hot water storage tank 25 together to supply hot water. Moreover, since the heat pump water heater is a device that absorbs heat from the outside air and supplies hot water, it has a characteristic that the hot water supply capacity decreases when the outside air temperature is low. As an example, FIG. 3 shows a change in hot water supply capacity with respect to the outside air temperature in a heat pump water heater having three types (A, B, C) of capacity. As shown in the figure, the hot water supply capacity, that is, the heating capacity decreases as the outside air temperature decreases in any hot water supply device, and conversely, the necessary hot water supply capacity tends to increase. For this reason, if the outside air temperature is low, the supply capacity is insufficient, but if the heat pump capacity is set in accordance with the minimum outside air temperature, the capacity is excessive when the outside air temperature is high, resulting in excessive facilities. Therefore, a predetermined amount of hot water is stored in the hot water storage tank 25 in advance, and when the outside air temperature is low, the hot water storage tank 25 and the heat pump unit 9 are used together to supply hot water, thereby optimizing the heat pump capacity. Can do.

  Here, for example, in the case where a large amount of hot water is used in about an hour, such as when 200 L of hot water is supplied to a bath and five people take a bath and each uses a shower, an example of the necessary backup hot water storage capacity is shown in FIG. Show. The example shown in the figure is an example using the water heater B of FIG. 3, and when the outside air temperature is 0 ° C. or higher, the heat pump water heater can cope with the above-mentioned large-capacity hot water supply, but the outside air temperature is lower than that. When the hot water stored in the hot water storage tank and the hot water heated by the heat pump water heater are combined, it shows that it corresponds to the large capacity hot water supply. As described above, the above (1) and (2) need to be considered independently, and the hot water storage amount that is the sum of both is stored as the set amount.

  Next, a control method for storing a set amount of hot water will be described based on the flowchart of FIG. Here, a temperature detected by a temperature detector T1 (for example, a position 50 L from the top of the hot water tank) disposed on the side wall of the hot water tank 25 is a first hot water temperature, and the position is a first hot water position. Similarly, the temperature detected by the temperature detector T2 (for example, a position 100 L from the top of the hot water tank) is set as the second hot water temperature, and the position is set as the second hot water amount position. Further, as an initial state, the heat pump is operated to store hot water until the second hot water temperature reaches, for example, 60 ° C. Note that the set temperatures shown in the following flowcharts are all 60 ° C.

  First, when control of the amount of stored hot water is started in step 1, the first hot water temperature is detected in step 2, and it is determined whether or not the temperature is lower than a set temperature. Here, if the 1st hot water temperature is less than preset temperature, it will progress to step S3 and a heat pump hot water storage operation will be started. When the amount of stored hot water gradually increases, in step S4, the second hot water temperature is detected, and it is determined whether or not the water temperature at the second hot water amount position is equal to or higher than the set temperature. Here, if it is more than preset temperature, it will progress to step S5, it will be judged that the hot water storage to the 2nd hot water amount position was carried out, and a heat pump hot water storage operation will be complete | finished. That is, the set amount of the hot water storage is controlled so as to be maintained in the range of the first hot water position to the second hot water position, and if the hot water storage operation is less than the first hot water position of the lower limit value, the heat pump hot water storage operation is started and the upper limit value is reached. When the hot water is stored up to the second hot water amount position, the operation is stopped.

  Next, the case where the set amount is variably set according to the outside air temperature will be described based on the flowchart of FIG. First, when control is started in step S11, an outside air temperature is detected by an outside air temperature detector (not shown) in step S12. Here, if the outside temperature is equal to or higher than the set outside temperature, the process proceeds to step S13, and if it is less than the set outside temperature, the process proceeds to step S17. In steps S13 to S16, the first hot water temperature and the second hot water temperature are sequentially detected as in S2 to S5 in FIG. 5, and the hot water storage amount is maintained in the range from the first hot water amount position to the second hot water amount position. Be controlled. On the other hand, in steps S17 to S20, since the hot water supply capability of the heat pump may be reduced due to the low outside air temperature, the set amount is increased in advance from the second hot water amount position to the third hot water amount position. . That is, in steps S17 to S20, the second hot water temperature and the third hot water temperature are sequentially detected as in S2 to S5 in FIG. 5, and the hot water storage amount is changed from the second hot water amount position to the third hot water amount position (for example, the top of the hot water tank). To a position of 150 L). Thereby, the hot water supply load of the heat pump is reduced, and the exhaust heat utilization efficiency and the power generation operation operating rate of the fuel cell can be improved. In the flowchart of FIG. 6, an example is shown in which the two-step control is performed with an arbitrary set outside air temperature as a boundary. It may be.

  The above is the basic hot water storage control method. In order to further improve the utilization efficiency of the fuel cell, it is effective to perform the following control. FIG. 7 shows a flowchart of a control method in consideration of the power generation state of the fuel cell. As shown in the figure, first, when control is started in step S21, in step 22, the first hot water temperature is detected, and it is determined whether or not the temperature is lower than the set temperature. Here, when the first hot water temperature becomes lower than the set temperature and the condition for starting the heat pump hot water storage operation is satisfied, the routine proceeds to step 23 where it is determined whether or not the fuel cell is performing the power generation operation. Here, if the fuel cell is performing a power generation operation, the heat pump unit 9 does not start the hot water storage operation, but commands to wait for hot water to be stored up to the second hot water amount position by recovering exhaust heat from the fuel cell. A hot water storage start prohibition signal is issued, and exhaust heat recovery by the fuel cell is performed. In particular, since the amount of hot water used is small and tends to be excessive in the summer, this control suppresses hot water storage operation by heat pump operation as much as possible and allows fuel cell power generation operation to be performed. In addition, when the power generation of the fuel cell is not performed, the process proceeds to step S26 as in other controls, and the heat pump hot water supply operation is performed.

  Next, assuming that power is generated by the fuel cell and hot water is supplied while the hot water storage start prohibition signal is issued, the amount of hot water is generally larger than the amount of hot water stored by the recovery of exhaust heat from the fuel cell ( The amount of hot water supply is from several L / min to about 10 L / min, while the amount of hot water stored by exhaust heat recovery is 1 L / min or less), and hot water cannot be stored up to the second hot water amount position. It tends to approach the position. Therefore, in step S24, whether or not hot water supply (water supply amount = hot water supply amount) is detected by the water supply flow meter 60, and if it is determined that hot water is supplied, in step S25, hot water supply is started. Is calculated. As a result, when the integrated hot water supply amount is equal to or higher than the preset integrated hot water supply amount, the process proceeds to step S26, the hot water storage operation start prohibition signal of the heat pump operation is canceled, and the heat pump hot water storage operation is started. And in step S27, 2nd hot water temperature is detected, and when it is more than preset temperature, it progresses to step S28 and a heat pump hot water storage operation is stopped.

  Next, a case where the hot water storage operation is performed by both the hot water storage tank 25 and the heat pump will be described based on the flowchart of FIG. When the control is started in step S31, the third to fifth hot water temperatures are detected by the temperature detectors T3 to T5 in step S32 (the temperatures detected by the temperature detectors T3 to T5 are respectively changed to the first temperatures). 3 bath temperature to 5th bath temperature). And, when any of the third hot water temperature to the fifth hot water temperature is equal to or higher than the set temperature, in other words, when the amount of hot water is sufficiently close to the bottom of the hot water tank, when hot water supply is started, hot water supply is started only from the hot water tank 25 first. Is done. Subsequently, when the second hot water temperature is detected in step S33 and becomes lower than the set temperature, it is determined that the remaining hot water amount is small, and the hot water supply operation by the heat pump is started. Thereby, the hot water supplied from both the hot water storage tank 25 and the heat pump is mixed and supplied. Then, when the output of the feed water flow meter 60 is detected in step S35 and it is determined that the hot water supply is completed, the process proceeds to step S36. If the second hot water temperature is lower than the set temperature, the hot water storage operation is performed according to the flowchart of FIG. Done. According to this, for example, when hot water is sufficiently stored up to the vicinity of the bottom of the hot water tank 25, when hot water is supplied, by first supplying hot water only in the hot water tank, a large amount of hot water is replaced with water. It is effective in that it continues to operate. When the hot water supply amount is large and the hot water storage amount is reduced from the second hot water amount position, the heat pump hot water supply operation is started early without waiting for the first hot water amount position, thereby preventing hot water shortage.

  Next, in the time zone when the amount of hot water used is small, the hot water stored up to the second hot water amount position is reduced by dividing the first hot water amount position by the hot water supply, and the hot water storage operation control when the condition of the heat pump hot water storage operation is satisfied is shown in FIG. This will be described based on the flowchart of FIG. First, when the control is started in step S40, the first hot water temperature is detected in step S41. If the temperature is lower than the set temperature, the process proceeds to step S42, and whether the current time is a set time zone (for example, midnight time zone). It is determined whether or not. Here, if it is the set time zone, the heating capacity of the heat pump unit 9 is reduced to the set value in step 43. Specifically, the upper limit value of the maximum rotational speed of the compressor 11 is lowered to the set rotational speed. In step S44, when the hot water storage operation is started, hot water is slowly stored over time. Subsequently, in step S45, the second hot water temperature is detected, and in the case of the set temperature, the process proceeds to step S46, and the heat pump operation is stopped.

  According to such control, since the state of the refrigeration cycle corresponds to the fact that the heat exchanger capacity is relatively large with respect to the compressor capacity, the efficiency of hot water storage operation is improved and the midnight time zone is increased. Noise can be reduced. In addition, when the power generated by the fuel cell is used for heat pump operation (system power is also used for the shortage), the exhaust heat utilization efficiency of the fuel cell can be increased by slowly performing heat pump hot water storage operation over time. .

  In addition, since the time period when the amount of hot water used is small varies depending on the lifestyle pattern of each household, providing the system with a save operation time period setting function that allows the user to specify a time period during which the heating capacity of the heat pump is reduced is further enhanced. It can be demonstrated. In this case, it is preferable that the set time zone is not limited to nighttime but can be set by the user according to the lifestyle pattern of each home.

  Also, since the heating capacity of the heat pump varies depending on the outside air temperature, when the maximum rotation speed of the compressor is lowered, when the outside air temperature is high, it can be heated to the set temperature even at a low speed rotation speed, but when the outside air temperature is low If the compressor rotation speed is too low, heating to the set temperature may not be possible. Therefore, as a method of effectively performing the save operation according to the detected outside air temperature, the optimum save operation control can be performed by calculating the function of the outside air temperature and setting the maximum compressor rotation speed.

It is a block diagram of the heat recovery combined use heat pump water heater to which the present invention is applied. It is a figure which shows the switching mode of a three-way switching valve. It is a diagram which shows the mode of the change of the hot_water | molten_metal supply capability with respect to external temperature in the heat pump water heater whose capacity | capacitance is 3 types (A, B, C). FIG. 4 is a diagram showing how the required backup hot water storage capacity changes with respect to the outside air temperature in the water heater B of FIG. 3. It is a flowchart explaining the control in the case of storing a set amount of hot water. It is a flowchart explaining the control which adjusts a setting amount according to outside temperature. It is a flowchart explaining the control which considered the electric power generation state of the fuel cell. It is a flowchart explaining the control in the case of performing hot water supply operation by both a hot water storage tank and a heat pump. It is a flowchart explaining the hot water storage control in the case of supplying hot water in the time slot | zone with little usage-amount of hot water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell unit 3 Fuel cell stack 5 Waste heat recovery heat exchanger 7, 14, 15 Pump 9 Heat pump unit 19 Water refrigerant heat exchanger 25 Hot water storage tank 47 Fuel cell control device 49 Heat pump control device

Claims (8)

A fuel cell unit provided with a heat exchanger for recovering exhaust heat such as a fuel cell, a heat pump unit for heating feed water, a hot water tank whose bottom communicates with a water supply source, and hot water stored at the bottom of the hot water tank A heat recovery system line having a pump that circulates to the top of the hot water tank via a heat exchanger, and a heat pump having a pump that circulates hot water at the bottom of the hot water tank to the top of the hot water tank via the heat pump unit A system line, a hot water supply line that communicates the top of the hot water tank and the hot water outlet, and a control device that controls the amount of hot water stored in the hot water tank,
The control device includes heat recovery system control means for controlling the circulation rate of the heat recovery system line so as to maintain the outlet hot water temperature of the heat exchanger at a set value; A heat recovery combined use heat pump water heater comprising a heat pump system control means for controlling the operation of the heat pump system line and the heat pump system line so as to keep the temperature within a set range. The heat pump combined use heat pump water heater according to claim 1, wherein the heat pump system control means variably sets a set range of the hot water storage amount according to an outside air temperature. When the fuel cell unit is in operation, the heat pump system control means operates the heat pump unit and the heat pump system line even if the amount of hot water stored in the hot water storage tank falls below the lower limit of the set range. It does not start, The heat recovery combined use heat pump water heater according to claim 1 or 2. The heat pump system control means detects the amount of hot water supplied from the hot water outlet when the amount of hot water stored in the hot water storage tank falls below the lower limit of the set range while the fuel cell unit is in operation, and the amount of hot water supplied is The heat recovery combined use heat pump water heater according to claim 1 or 2, wherein operation of the heat pump unit and the heat pump system line is started when the amount is larger than a set amount. The heat pump system control means starts operation of the heat pump unit and the heat pump system line when the amount of hot water stored in the hot water storage tank falls below the upper limit of the setting range from a state where the hot water storage amount exceeds the upper limit of the setting range, 2. The heat recovery combined use heat pump water heater according to claim 1, wherein the operation is continued until use of the hot water supply from the hot water supply port is completed. The heat pump system control means reduces the heating capacity of the heat pump unit to a set value during a set time zone when starting operation of the heat pump unit and the heat pump system line. The heat recovery combined use heat pump water heater according to 1. The heat recovery combined heat pump water heater according to claim 6, wherein the heating capacity of the heat pump unit is variably set based on a detected value of an outside air temperature. A three-way switching valve is provided in a portion that connects the heat pump system line and the hot water supply line to the top of the hot water storage tank, and the three-way switching valve has a flow path that allows the hot water supply line to communicate only with the heat pump system line; 8. A valve that switches between a flow path that connects the hot water supply line to the heat pump system line and the hot water storage tank and a flow path that connects the heat pump system line only to the hot water storage tank. The heat recovery combined use heat pump water heater according to any one of the above.

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