JP2005044713A - Cogeneration system and its operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cogeneration system capable of reducing a running cost concerning its operation by enhancing effective efficiency. <P>SOLUTION: This cogeneration system has a power generating device 11 to generate electric power and heat, and a hot water storage tank 17 in which heat generated by the power generating device 11 is stored as hot water, and the start starting time of the power generating device 11 is set so that heat stored in the hot water tank 17 does not exceed the prescribed maximum amount of heat stored in it at the prescribed time when the hot water stored in the hot water tank 17 is supplied to a prescribed large heat load. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cogeneration system that recovers heat generated together with electricity in a power generator and supplies it as hot water and an operation method thereof.

  Among conventional cogeneration systems, in particular, a fuel cell cogeneration system using a fuel cell, as shown in FIG. 5, is an oxidant supply device 4 and a fuel gas supply that generates a fuel gas containing hydrogen using city gas. The apparatus 5, the fuel cell 1 that generates electricity using the oxidant supplied from the oxidant supply device 4 and the fuel gas supplied from the fuel gas supply device, the exhaust heat of the fuel cell is recovered via the heat exchanger 2, and hot water It is comprised from the hot water storage tank 3 stored as.

  In the above fuel cell cogeneration system, when there is little demand for hot water supply and hot water of the upper limit temperature is stored in the hot water storage tank, the power generation continues while dissipating the exhaust heat of the fuel cell, and the exhaust heat recovery efficiency decreases. As a result, there is a drawback that energy saving performance is lowered.

  To solve this problem, the fuel cell output is adjusted to be smaller than the maximum generated power when the predetermined heat storage amount, which is smaller than the maximum heat storage amount in the hot water storage tank, is reached. There has been proposed a method of operating a fuel cell system that suppresses the generation and extends the time until the amount of heat stored in the hot water storage tank becomes full (see, for example, Patent Document 1).

Moreover, in the said patent document 1, the said setting heat storage amount is further provided with two types, the setting low heat storage amount and the setting high heat storage amount, and the time zone when the hot water supply demand is peaked from the change over time of the hot water supply demand is specified. If it is just before, the operation with the maximum generated power is continued until the set high heat storage amount is reached, and the generated power is reduced when the set high heat storage amount is exceeded. There has also been proposed an operation method that extends the time until the amount is full and secures as much heat storage as possible during peak hours.
JP 2002-289239 A

  Here, FIG. 6 shows a temporal change pattern of the generated power of the power generation apparatus and the heat load of the consumer when the consumer such as a household using the cogeneration system is operated so as to follow the power load.

  As shown in this figure, the time period when the power load increases and the time period when the demand for the heat load increases usually overlap, and when the operation is performed to reduce the power output in the time period when the power load is large, the power generation efficiency and The execution efficiency of the exhaust heat recovery efficiency tends to decrease due to an increase in the heat dissipation ratio. This is because the cogeneration system has the highest energy execution efficiency at the maximum output, and the energy efficiency is lower at the low output than at the high output, so the load power demand is high and the power generation output can be set high. In addition, there is a problem that the operation with the power generation output kept low reduces the energy saving effect of the cogeneration system as described above.

  In the above operation method, the time until the heat storage amount in the hot water storage tank is full is extended and the heat dissipation time is reduced to reduce the energy loss. When the amount is full, there is also a problem that heat dissipation is continued while maintaining the minimum output, and energy loss cannot be avoided.

  In addition, the decline in energy efficiency is suppressed by delaying the timing of power generation output so that it is as full as possible at the peak of heat demand specified from the change in demand for heat load over time. When hot water supply is the peak of heat demand, the time of bathing usually differs depending on the day, and the peak of actual heat demand is delayed from this specified peak time zone, and as a result, the large heat load as described above The problem of energy loss due to heat dissipation due to the heat storage being full before demand comes can occur.

  An object of the present invention is to suppress the possibility of the occurrence of the above-described problems, and to provide an energy-efficient cogeneration system and an operation method thereof.

  In order to solve the above problems, a cogeneration system of the present invention is a cogeneration system having a power generation device that generates electric power and heat, and a hot water storage tank in which heat generated by the power generation device is stored as hot water, The start-up time of the power generation device is set so as not to exceed a predetermined maximum heat storage amount of the hot water storage tank at a predetermined hot water supply time for supplying hot water stored in the hot water storage tank to a predetermined large heat load. .

  Further, the present invention is characterized in that the predetermined hot water supply time is a time set in advance so as to supply hot water from a hot water storage tank to a large heat load.

  Further, the present invention is characterized in that the predetermined large heat load is a heat load that requires a large amount of heat among the heat loads at the consumption destination to which electric power and heat are supplied from the cogeneration system.

  Further, the present invention provides a hot water storage system whose start time is before a predetermined hot water supply time predicted from the amount of heat accumulated in the hot water storage tank before the start-up and the time integration value of the power generation amount of the power generation device or the temporal change pattern of the power load. It is set based on the amount of heat recovered into the tank.

  In addition, the present invention provides a recovery to a hot water storage tank with a start time before a predetermined hot water supply time predicted from a temporal change pattern of the amount of heat accumulated in the hot water storage tank before the start and the amount of exhaust heat recovered from the power generator. It is set based on the amount of heat.

  The cogeneration system of the present invention is a cogeneration system having a power generation device that generates electric power and heat, and a hot water storage tank in which heat generated by the power generation device is stored as hot water. The operation mode switching time for switching from the operation mode to the high output operation mode is set so that the predetermined maximum heat storage amount of the hot water storage tank is not exceeded at the predetermined hot water supply time for supplying the hot water stored in the hot water storage tank to the predetermined large heat load. It is characterized by setting.

  Further, the present invention provides a predetermined hot water supply time in which the operation mode switching time is predicted from the amount of heat accumulated in the hot water storage tank before the operation mode is switched and the time integrated value of the power generation amount of the power generation device or the temporal change pattern of the power load. It is set based on the amount of heat recovered in the previous hot water storage tank.

  Further, the present invention predicts the operation mode switching time from the temporal change pattern of the amount of heat accumulated in the hot water storage tank immediately before the operation mode switching in the low output mode and the amount of exhaust heat recovered from the power generator in the high output mode. It is set based on the amount of heat recovered in the hot water storage tank from the operation mode switching to the predetermined hot water supply time.

  According to the present invention, the exhaust heat recovery amount before the hot water supply time is predicted based on the hot water supply time to a predetermined large heat load (bath, floor heating, etc.), and the fuel cell is started or switched to the high output mode operation. The possibility of reaching the maximum heat storage before the peak of heat demand decreases. Therefore, when the maximum heat storage amount is reached before the peak of heat demand, the reduction of the energy saving effect due to the start-up energy loss when the fuel cell is stopped or the heat dissipation loss when the operation is continued is suppressed. Can do.

  Further, the present invention predicts the amount of exhaust heat recovered before the hot water supply time to a predetermined large heat load based on the power generation (exhaust heat) pattern when power is generated according to the load demand. There is no need to reduce the amount of power generation as in the above-described conventional operation method during a time period when power demand is large, and it is possible to suppress a decrease in the efficiency of power generation efficiency and exhaust heat recovery efficiency.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a system configuration diagram of a cogeneration system according to Embodiment 1 of the present invention. In FIG. 1, 11 is a power generation device, 12 is an oxidant supply device that supplies an oxidant containing oxygen to the power generation device 11, 13 is a fuel supply device that supplies fuel to the power generation device 11, and 14 is power generation. A cooling water path through which cooling water for recovering the exhaust heat of the apparatus 11 flows, 15 is a hot water tank water path through which the hot water tank water circulates by connecting the lower and upper parts of the hot water tank 17, and 16 is the heat recovered by the cooling water. A heat exchanger for transferring water to the water in the hot water storage tank by heat exchange, 17 is a hot water storage tank for storing water in the hot water tank water path heated by the heat exchanger 16 and becomes hot water, and 18 is a hot water storage tank Circulating means for circulating water in the path 15, 19 is a temperature detector before entering the heat exchange 16 of water taken from the lower part of the hot water tank 17 to the hot water tank path 15, and 20 is heated by heat exchange Hot water storage after being done A temperature detector 21 that detects the water temperature in the tank path 15, a hot water supply amount control means 22 that controls the supply amount when the hot water in the hot water storage tank 17 is supplied to the heat load of the consumer (for example, home), 22 The output power control means 23 for controlling the amount of power supplied from the power generation device 11 to the power load of the consumer, from the command value of the output power control means 22 and the time variation data of the power load pattern and the output value of the hot water supply amount control means It is a control means for accumulating the temporal change data of the thermal load pattern and starting the power generation device 11 or changing the power generation output mode based on the accumulated data. The power generation device 11 may be any power generation device that generates power using fuel and an oxidant. Examples thereof include a fuel cell and a gas heat pump. The output power control means 22 and the control means 23 may be a computer such as a microcomputer, a memory, or a system LSI, or may be a program for realizing these means.

  Next, a general operation of the cogeneration system having the above-described configuration will be described. First, electricity generated in the power generator 11 using the oxidant containing oxygen supplied from the oxidant supply device 12 and the fuel supplied from the fuel supply device 13 is detected by a load power detection means (not shown). The output is controlled by the output control means 22 in accordance with the load power thus supplied, and then supplied to a power load (not shown) such as a home. The heat generated at this time is transmitted to the water in the hot water tank water path through the heat exchanger 16 by the circulation of the water in the cooling water path 14 and stored as hot water in the hot water tank 17. At this time, the water in which the low temperature water is taken out from the lower part of the hot water storage tank is circulated by the hot water circulation pump 18 and the water in the hot water tank path heated by the heat exchanger is heated and used as hot water. Then, so-called stacked boiling is formed in which hot hot water is stored in layers from the upper part of the hot water storage tank 9. The hot water stored in the hot water storage tank 9 is supplied to the heat load while the supply amount is controlled by the hot water supply amount control means 21 when there is a request for the heat load. When hot water is supplied to the hot load, city water is supplied to the lower part of the hot water storage tank, so that the hot water layer is pushed up, and hot hot water is always present at the upper part of the hot water storage tank 9, so the entire hot water storage tank 9 is boiling. Even without it, a high hot water supply temperature can be secured.

  Next, the operation of the cogeneration system according to the present invention in the present embodiment will be described. As described above, the power generation device 11 performs a power generation operation according to the power load 4, and at this time, the generated heat is stored as hot water in the hot water storage tank 17, but all of the hot water storage tank 17 is boiled to hot water having a predetermined upper limit temperature. If it rises (the amount of heat in the hot water storage tank reaches the maximum heat storage amount), the power generation device 11 cannot discharge heat unless it dissipates heat in either the cooling water path or the hot water storage tank path, and it becomes difficult to continue operation. For this reason, in the case of a cogeneration system that assumes regular start-up and stop without assuming continuous operation, the system operation is normally stopped while avoiding energy loss due to heat dissipation. However, since the cogeneration system requires a considerable amount of activation energy at the time of activation, frequent activation / deactivation leads to energy loss, which is not preferable from the viewpoint of energy saving.

  Therefore, in the present embodiment, during normal operation after startup, the power generation operation according to the load is performed, and a large amount of the heat load at the consumer that consumes the power and heat generated in the system is large. The purpose is to set the starting time so that the hot water storage tank does not reach the maximum heat storage amount before a request from the heat load is received. In addition, examples of the above-mentioned consumption destination include a home, a facility using hot water, and the like. Moreover, as a large heat load, a bath, floor heating, etc. are mentioned at home.

  In order to achieve the above-described object, the present invention provides a heat storage amount that is predicted when a heat storage amount of a hot water storage tank before start-up and an operation according to a load before a predetermined hot water supply time to a predetermined large load are performed. The starting time is set from the quantity. As a result, the possibility of reaching the maximum heat storage amount before hot water supply to a large heat load is greatly reduced, i.e., the frequency at which the hot water storage tank reaches the maximum heat storage amount is reduced, so the number of start / stop operations is reduced and the system is operated. The time can be extended and the energy loss can be greatly reduced. In addition, as a prediction method, there are a method of predicting the exhaust heat recovery amount from the past change pattern of the power generation amount, and a method of predicting the exhaust heat recovery amount directly from the past change pattern of the exhaust heat recovery amount. . Hereinafter, embodiments of the present invention using the respective methods will be described.

[Method of predicting power generation over time pattern]
As shown in FIG. 2, when a predetermined hot water supply time to a large heat load (such as a bath) is set by the user at the consumer, the control means 23 is configured to control the past power generation amount when the cogeneration system is stopped. Data is extracted from the temporal change pattern, and the exhaust heat recovery amount (PQ) is calculated from the cumulative power generation amount that is the integral value of the temporal change pattern of the power generation amount that goes back before the predetermined hot water supply time. The time when the predicted value (PQ) of the recovered amount does not exceed the allowable heat storage amount (CQ), which is the difference between the maximum heat storage amount (MQ) of the hot water storage tank and the remaining heat storage amount (RQ) before startup, is set as the startable time Set. When the start time set in this way is reached, the control means 23 issues an oxidant and fuel supply command to the oxidant supply device 12 and the fuel supply device 13, respectively, and the power generation device 11 starts to start.

  Here, the remaining heat storage amount (RQ) of the hot water storage tank is obtained by the difference represented by the following equation between the exhaust heat recovery amount (EQ) and the heat supply amount (SQ) to the heat load.

RQ = EQ-SQ
The exhaust heat recovery amount (EQ) is the cumulative power generation amount (GW) that is the time integral value of the power generation amount before startup, the system specific power generation efficiency (PE), and the exhaust heat recovery efficiency (QE) to the hot water storage tank. It is calculated by the product represented by the following equation with the ratio.

EQ = GW × QE / PE
The supply amount (SQ) to the heat load is the following expression of the supply amount (L) supplied from the hot water supply amount control means 21 and the predetermined temperature (T) of hot water in the hot water storage tank supplied to the heat load. Calculated by the product shown.

SQ = T × L
Further, the predicted value (PQ) of the exhaust heat recovery amount before the predetermined hot water supply time is also calculated from the accumulated power generation amount (GW ′) before the predetermined hot water supply time in the same manner as described above.

  The optimum start time is set based on the remaining heat storage amount (RQ) calculated as described above and the predicted value (PQ) of the exhaust heat recovery amount.

  In the above description, the accumulated power generation dated before the predetermined hot water supply time is calculated by the time integration of the temporal change pattern of the past power generation. However, as indicated by the dashed line in FIG. By calculating the accumulated power generation based on the power generation pattern corrected in consideration of the increase capability, it is possible to set the startup time with higher accuracy.

  Moreover, in the prediction of the amount of exhaust heat recovery, the prediction was made using the temporal change pattern data of the past power generation amount. However, when the system operation method of the present embodiment is used, in the region where load power actually exists. Since there is a case where there is a basin where power generation is not performed, load power aging data detected by a load detection means (not shown) is stored in the control means 23 without using past generated power data. It is preferable to extract and predict this data because the prediction accuracy is improved. At this time, the estimated generation power is assumed by assuming the power generation pattern corresponding to the extracted data from the operation method adopted in each system without using the extracted time-dependent change data of the load power as it is. Prediction based on the time-dependent change pattern is preferable because the prediction accuracy is further improved. Here, as an operation method adopted in each of the above systems, for example, in a high-output operation mode, for example, a load follow-up method that outputs a detected value of load power as generated power as it is, an average value of load power for a predetermined time A load follow-up system that generates power as a power generation output, or an operation system that performs constant output at rated power.

  Further, the start time set by the control means 23 is as long as possible until the sum of the predicted value of the exhaust heat recovery amount and the remaining heat storage amount approaches the maximum heat storage allowable amount as much as possible, that is, until the predetermined hot water supply time. It is preferable to set the start time so that it can be operated, and this improves the energy saving effect of the operation of the cogeneration system.

  In addition, since the predicted value is calculated based on the temporal change pattern of the power generation amount when the power generation operation is performed according to the load, the load demand time before a predetermined hot water supply time is high as in the conventional operation method. It is not necessary to reduce the power generation output in the belt, which leads to improvement in energy efficiency including power generation efficiency and exhaust heat recovery efficiency.

  Next, the past history data extraction of the power generation amount temporal change pattern described above is important because it greatly affects the predicted value. For example, as a method thereof, a day of the week when a predetermined hot water supply time is set, and It is conceivable to extract data from the viewpoint of the month or season.

  The data extracted by the control means 23 is further integrated using the averaged power generation amount change pattern over time, and the starting time is set.

  In addition, the activation time is set using the extracted data that has the maximum accumulated power generation dated before the predetermined hot water supply time without using the averaged temporal change pattern. That is, it is possible to set the start time assuming that the amount of exhaust heat recovery is the largest, and to ensure that the maximum stored amount of the hot water storage tank is not reached before the predetermined hot water supply time.

  In the above prediction, the hot water supply pattern to the heat load before the predetermined hot water supply time is not taken into consideration. It goes without saying that this is for ensuring the effect of preventing the maximum heat storage amount from being reached before the predetermined hot water supply time, but the hot water supply amount before the predetermined hot water supply time is a considerable amount. If this is the case, the startup time may be set in consideration of the temporal change pattern of the amount of heat supplied to the heat load. It is possible to set longer.

[Method of predicting the amount of exhaust heat recovery from changes over time]
Next, a method of predicting from the temporal change pattern of the exhaust heat recovery amount will be described.

  As shown in FIG. 4, when the co-generation system is stopped, when the user of the consumer sets a predetermined hot water supply time to a large heat load (such as a bath), the control means 23 causes the past discharge to occur. Data is extracted from the temporal change pattern of the heat recovery amount, and the cumulative exhaust heat recovery amount, which is the integrated value of the temporal change pattern of the exhaust heat recovery amount, is calculated retroactively before the predetermined hot water supply time. Is set as a startable time at which the predicted value of does not exceed the allowable heat storage amount that is the difference between the maximum heat storage amount of the hot water storage tank and the remaining heat storage capacity before start-up. When the start time set in this way is reached, the control means 23 issues an oxidant and fuel supply command to the oxidant supply device 12 and the fuel supply device 13, respectively, and the power generation device 11 starts to start. Note that the time-dependent change data of the exhaust heat recovery amount includes the temperature (T1) detected by the temperature detection means 19, the temperature (T2) detected by the temperature detection means 20, and the circulation means 18 as shown in FIG. The value of the output P is output to the control means 23, and the control means 23 calculates an exhaust heat recovery amount (EQ) by the product of these output values as shown in the following equation, and the time-dependent change data of the exhaust heat recovery amount Q. Has accumulated.

EQ = P × (T2-T1)
In the above description, the amount of exhaust heat recovered retroactively from the predetermined hot water supply time is calculated by the time integration of the temporal change pattern of the past power generation, but as shown by the dashed line in FIG. By calculating the accumulated exhaust heat recovery amount based on the temporal change pattern of the exhaust heat recovery amount corrected in consideration of the increasing capability of the power generation output, it is possible to set the startup time with higher accuracy.

  In this method, the temporal change pattern of the exhaust heat recovery amount was used. However, for the same reason as described above, using the predicted value of the exhaust heat recovery amount based on the load power temporal change data improves the prediction accuracy. Connected and considered desirable. At this time, it is preferable to estimate the generated power pattern from the time-dependent change data of the load power and predict the amount of exhaust heat recovery in the same manner as described above.

  Note that, similarly to the method for predicting from the temporal change pattern of the power generation amount described above, the start time may be set so that the sum of the predicted value of the exhaust heat recovery amount and the remaining heat storage amount is as close to the maximum heat storage allowable amount as possible. Preferably, this improves the energy saving effect due to the operation of the cogeneration system.

  In addition, since the predicted value is calculated based on the temporal change pattern of the exhaust heat recovery amount when the power generation operation is performed according to the load, similarly to the method of predicting from the temporal change pattern of the power generation amount described above, It leads to improvement of energy efficiency including power generation efficiency and exhaust heat recovery efficiency.

  As for the history data extraction of the temporal change pattern of the exhaust heat recovery amount, it is preferable to extract data from the viewpoint of the day of the week, month, season, or the like when a predetermined hot water supply time is set as described above.

  Further, when the exhaust heat recovery amount is predicted, the extracted data is averaged and used as described above, or predicted using past data that maximizes the exhaust heat recovery amount. The effects produced thereby are the same as described above.

  In addition, although the hot water supply pattern to the heat load before the predetermined hot water supply time is not taken into account, this also brings about the same effect as described above, and in the winter season when the hot water supply load is large, the temporal change of the hot water supply pattern is considered. Thus, it is preferable to make a prediction, and this makes it possible to set a longer operation time until a predetermined hot water supply time.

(Embodiment 2)
A cogeneration system according to Embodiment 2 of the present invention will be described. Since the system configuration is the same as that of the first embodiment, the description thereof is omitted.

  In the present embodiment, the difference from the first embodiment is that the cogeneration system is based on the premise of continuous operation. The embodiment of the present invention in this case will be described in the same manner as in the first embodiment.

[Method of predicting power generation over time pattern]
First, in the case of continuous operation, normally, the low output operation mode operation is continued at a predetermined low power generation output in the low load power time zone, and the operation is switched to the high output mode that outputs according to the load in the large load power time zone. . As shown in FIG. 5, when a predetermined hot water supply time to a large heat load (such as a bath) is set by the user at the consumer, the control means 23 is configured to store the past power generation amount during the low output mode operation of the cogeneration system. Data as indicated by the broken line is extracted from the time-dependent change pattern. Based on the extracted temporal change pattern of generated power, the amount of exhaust heat recovered in the hot water storage tank when going back to the time CT before the predetermined hot water supply time and switching from the low output mode to the high output mode at the time CT Predict.

  Here, the exhaust heat recovery amount (PQ) from the time T at which the control means 23 makes a determination for setting the switching time to the predetermined hot water supply time is predicted from the accumulated power generation amount that is an integral value of the power generation pattern in the same manner as described above. Then, the predicted time (PQ) does not exceed the allowable heat storage amount (CQ) that is the difference between the maximum heat storage amount (MQ) of the hot water storage tank and the remaining heat storage amount (RQ) at time T. Set as. The accumulated power generation amount is the integrated power generation amount (GW) in the low output mode from time T to time CT and the integrated value of the temporal change pattern of the past power generation amount from time CT to a predetermined hot water supply time ( GW ′). When the switching time set in this way is reached, the control means 23 changes the mode to the high output mode corresponding to the load, and the output control means 22 generates power according to the load power detected by the load detection means (not shown). The power generation means 11 is commanded. In response to this command, the oxidant supply device 12 and the fuel supply device 13 are controlled to supply oxidant and fuel, respectively.

  The remaining heat storage amount (RQ) of the hot water storage tank is obtained in the same manner as described above, except that the calculation point is changed from time before start to time T.

  As described above, the optimal start-up time is set based on the remaining heat storage amount (RQ) calculated by the above method and the predicted value (PQ) of the exhaust heat recovery amount.

  In the above description, the accumulated power generation dated before the predetermined hot water supply time is calculated by the time integration of the temporal change pattern of the past power generation. However, as indicated by the wavy line in FIG. By calculating the accumulated power generation based on the power generation pattern corrected in consideration of the increase capability, it is possible to set the startup time with higher accuracy.

  Moreover, in the prediction of the exhaust heat recovery amount, prediction is made using the temporal change pattern data of the past power generation amount. However, in the same manner as in the first embodiment, when the operation method of the present embodiment is used, the output is actually low. Since there is a basin that operates in the low output operation mode in the region where the load power larger than the predetermined power in the operation mode exists, the load detection means (not shown) is used without using the past generated power data. It is considered that it is preferable to store the detected time-dependent change data of the load power in the control means 23, extract this data, and predict it to improve the prediction accuracy. At this time, the estimated generation power is assumed by assuming the power generation pattern corresponding to the extracted data from the operation method adopted in each system without using the extracted time-dependent change data of the load power as it is. Prediction based on the temporal change pattern is preferable because the prediction accuracy is further improved. Here, as an operation method adopted in each of the above systems, for example, in a high-output operation mode, for example, a load follow-up method that outputs a detected value of load power as generated power as it is, an average value of load power for a predetermined time A load follow-up system that generates power as a power generation output, or an operation system that performs constant output at rated power.

  The switching time set by the control means 23 is preferably that the sum of the predicted value of the exhaust heat recovery amount and the remaining heat storage amount is as close as possible to the maximum heat storage allowable amount, including its effect, as in the first embodiment. It is the same.

  In addition, since the predicted value is calculated based on the temporal change pattern of the power generation amount when the power generation operation is performed according to the load, it leads to improvement in energy efficiency even in a cogeneration system based on continuous operation. Is the same as in the first embodiment.

  Next, it is preferable that the past history data extraction of the power generation amount change pattern with time described above is performed, for example, by extracting data from the viewpoint of the day of the week, month, or season when a predetermined hot water supply time is set.

  When the data extracted by the control means 23 is used for predicting the exhaust heat recovery amount, the same method as in the first embodiment is used, such as averaging past data or using data that maximizes the exhaust heat recovery amount. The same applies to the effects that can be considered.

  In the above prediction, the hot water supply pattern to the heat load before the predetermined hot water supply time is not considered, but if the amount of hot water supply before the predetermined hot water supply time is a considerable amount, the supply to the heat load is not performed. The start-up time may be set in consideration of the temporal change pattern of the amount of heat. As a result, the operation time until the predetermined hot-water supply time can be set longer in winter when there is a high demand for hot-water supply.

[Method of predicting the amount of exhaust heat recovery from changes over time]
Next, a method of predicting from the temporal change pattern of the exhaust heat recovery amount will be described.

  In this method, as shown in FIG. 6, when the user of the consumer sets a predetermined hot water supply time to a large heat load (such as a bath), the control means 23 is operated during the low output mode operation of the cogeneration system. Then, data is extracted from the temporal change pattern of the exhaust heat recovery amount in the past. Exhaust heat recovery to the hot water storage tank when going back to the time CT before the predetermined hot water supply time based on the extracted temporal change pattern of the exhaust heat recovery amount and changing from the low output mode to the high output mode at the time CT Predict the amount.

  Here, the exhaust heat recovery amount (PQ) from the time T at which the control means 23 makes a determination for setting the switching time to the predetermined hot water supply time, as shown in FIG. The predicted value (PQ) exceeds the allowable heat storage amount (CQ) which is the difference between the maximum heat storage amount (MQ) of the hot water storage tank and the remaining heat storage amount (RQ) at time T. The above-described time CT is set as the switching time. When the switching time set in this way is reached, the control means 23 changes the mode to the high output mode corresponding to the load, and the output control means 22 generates power according to the load power detected by the load detection means (not shown). The power generation means 11 is commanded. In response to this command, the oxidant supply device 12 and the fuel supply device 13 are controlled to supply oxidant and fuel, respectively.

  The time-dependent change data of the exhaust heat recovery amount is based on the temperature detected by the temperature detecting means 19 and the temperature detecting means 20 shown in FIG. 3 and the value of the output P of the circulating means 18 described above. 1 is calculated in the same manner.

  Further, the remaining heat storage amount (RQ) of the hot water storage tank is obtained in the same manner as described above except that the calculation point is changed to time T from before activation.

  As described above, the optimal start-up time is set based on the remaining heat storage amount (RQ) calculated by the above method and the predicted value (PQ) of the exhaust heat recovery amount.

  In the above description, the amount of exhaust heat recovered retroactively from the predetermined hot water supply time is calculated by the time integration of the temporal change pattern of the past power generation, but as shown by the dashed line in FIG. By calculating the accumulated exhaust heat recovery amount based on the temporal change pattern of the exhaust heat recovery amount corrected in consideration of the increasing capability of the power generation output, it is possible to set the startup time with higher accuracy.

  Similarly to the method of predicting from the temporal change pattern of the power generation amount described above, the switching time may be set so that the sum of the predicted value of the exhaust heat recovery amount and the remaining heat storage amount is as close as possible to the maximum heat storage allowable amount. Preferably, this improves the energy saving effect due to the operation of the cogeneration system.

  In addition, since the predicted value is calculated based on the temporal change pattern of the exhaust heat recovery amount when the power generation operation is performed according to the load, similarly to the method of predicting from the temporal change pattern of the power generation amount described above, It leads to improvement of energy efficiency including power generation efficiency and exhaust heat recovery efficiency.

  As for the history data extraction of the temporal change pattern of the exhaust heat recovery amount, it is preferable to extract data from the viewpoint of the day of the week, month, season, or the like when a predetermined hot water supply time is set as described above.

  Further, when the exhaust heat recovery amount is predicted, the extracted data is averaged and used as described above, or predicted using past data that maximizes the exhaust heat recovery amount. The effects produced thereby are the same as described above.

  In addition, although the hot water supply pattern to the heat load before the predetermined hot water supply time is not taken into account, this also brings about the same effect as described above, and in the winter season when the hot water supply load is large, the temporal change of the hot water supply pattern is considered. Thus, it is preferable to make a prediction, and this makes it possible to set a longer operation time until a predetermined hot water supply time.

  The cogeneration system of the present invention has an effect that it is possible to suppress a decrease in effective efficiency of power generation efficiency and exhaust heat recovery efficiency, and is useful as a cogeneration system using a fuel cell, a gas heat pump, or the like.

The system block diagram of the cogeneration system in Embodiment 1 and 2 of this invention Operational diagram of cogeneration system in Embodiment 1 of the present invention The system block diagram of the cogeneration system in Embodiment 1 and 2 of this invention Operational diagram of cogeneration system in Embodiment 1 of the present invention Operational operation diagram of cogeneration system in Embodiment 2 of the present invention Operational diagram of cogeneration system in Embodiment 1 of the present invention Configuration diagram of a conventional cogeneration system Schematic showing general power generation pattern and thermal load pattern of cogeneration system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Power generation device 2,16 Heat exchanger 3,17 Hot water storage tank 4,12 Oxidant supply device 5,13 Fuel supply device 14 Cooling water flow path 15 Hot water storage tank water flow path 18 Circulation means 19, 20 Temperature detector 21 Hot water supply amount Control means 22 Output power control means 23 Control means

Claims (15)

A cogeneration system having a power generation device that generates electric power and heat, and a hot water storage tank in which heat generated by the power generation device is stored as hot water, and supplies the hot water stored in the hot water storage tank to a predetermined large heat load A start-up time of the power generator is set so as not to exceed a predetermined maximum heat storage amount of the hot water storage tank during a predetermined hot water supply time. The cogeneration system according to claim 1, wherein the predetermined hot water supply time is a time set in advance to supply hot water from a hot water storage tank to a large heat load. The startup start time is the amount of heat collected in the hot water storage tank before the predetermined hot water supply time predicted from the amount of heat accumulated in the hot water storage tank before startup and the time integral value of the power generation amount of the power generator or the power load over time pattern. The cogeneration system according to claim 2, wherein the cogeneration system is set based on the setting. The cogeneration system according to claim 3, wherein the recovered heat amount is predicted from a time integration value before a predetermined hot water supply time with respect to an average pattern of a power generation amount of the power generation apparatus or a temporal change pattern history of the power load. 4. The cogeneration system according to claim 3, wherein the recovered heat amount is predicted from a maximum value of a time integral value before a predetermined hot water supply time with respect to a power generation amount of the power generation device or a temporal change pattern history of the power load. The startup start time is set based on the amount of heat accumulated in the hot water storage tank before startup and the amount of heat recovered in the hot water storage tank before the predetermined hot water supply time predicted from the temporal change pattern of the amount of exhaust heat recovered from the power generator. The cogeneration system according to claim 2. The cogeneration system according to claim 6, wherein the recovered heat amount is an amount of recovered heat to the hot water storage tank before a predetermined hot water supply time predicted from an average pattern of a temporal change pattern history of the exhaust heat recovery amount from the power generator. The cogeneration system according to claim 6, wherein the recovered heat amount is a maximum value of the recovered heat amount to the hot water storage tank before a predetermined hot water supply time predicted from a temporal change pattern history of the exhaust heat recovered amount from the power generator. The cogeneration system according to any one of claims 1 to 8, wherein the predetermined large heat load is a heat load that requires a large amount of heat among heat loads at a consumer to which electric power and heat are supplied from a cogeneration system. system. A cogeneration system having a power generation device that generates electric power and heat, and a hot water storage tank in which heat generated by the power generation device is stored as hot water, wherein the power generation device is switched from a low output operation mode to a high output operation mode. The mode switching time is set so as not to exceed a predetermined maximum heat storage amount of the hot water storage tank at a predetermined hot water supply time for supplying hot water stored in the hot water storage tank to a predetermined large heat load. . The cogeneration system according to claim 10, wherein the predetermined hot water supply time is a time set in advance to supply hot water from a hot water storage tank to a large heat load. The operation mode switching time indicates the amount of heat accumulated in the hot water storage tank before the operation mode switching and the hot water storage tank before the predetermined hot water supply time predicted from the time integration value of the power generation amount of the power generation device or the temporal change pattern of the power load. The cogeneration system according to claim 11, wherein the cogeneration system is set based on a recovered heat amount. The operation mode switching time is after the operation mode switching predicted from the temporal change pattern of the amount of heat accumulated in the hot water storage tank immediately before the operation mode switching in the low output mode and the exhaust heat recovery amount from the power generator in the high output mode. The cogeneration system according to claim 11, wherein the cogeneration system is set based on an amount of heat recovered in the hot water storage tank from a predetermined hot water supply time to a predetermined hot water supply time. An operation method of a cogeneration system having a power generation device that generates electric power and heat, and a hot water storage tank in which heat generated by the power generation device is stored as hot water, wherein the hot water stored in the hot water storage tank A method for operating a cogeneration system, characterized in that a start-up time of the power generator is set so as not to exceed a predetermined maximum heat storage amount of the hot water storage tank at a predetermined hot water supply time supplied to a load. An operation method of a cogeneration system having a power generation device that generates electric power and heat, and a hot water storage tank in which heat generated by the power generation device is stored as hot water, wherein the power generation device is changed from a low output operation mode to a high output operation mode. The operation mode switching time for switching to is set so as not to exceed a predetermined maximum heat storage amount of the hot water storage tank at a predetermined hot water supply time for supplying hot water stored in the hot water storage tank to a predetermined large heat load. How to operate the cogeneration system.

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