JP2002013823A - Heat storage control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat storage control device capable of shortening a heat insulation time available after the temperature of a heat storage material reaches a target heat storage temperature. SOLUTION: The heat storage control device 11 comprises a heater 24 to heat a heat storage material 22; a temperature detecting sensor 25 to detect the temperature of the heat storage material 22; and a control part 15 to control energization to the heater 24 based on temperature detected by the temperature detecting sensor 25. The control part 15, when a midnight power time zone comes to a stating time, computes and decides a heat storage stating time ts from the current temperature of the heat storage material 22 detected by the temperature detecting sensor 25, a heat storage upper limit temperature, and a terminal time of a midnight power time zone. The heater 24 is energized and generates heat from the heat storage starting time ts. Thereby, the temperature of the heat storage material 22 reaches a heat storage upper limit temperature near the terminal time of the midnight power time zone, a heat insulation time starting from a time after the temperature of the heat storage material 22 reaches a heat storage upper limit temperature and ending to the terminal time of the midnight power time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat storage control device that stores heat in a substance having a large specific heat and uses the sensible heat later.

[0002]

2. Description of the Related Art Heretofore, there has been known a heat storage control device in which pure water is supplied during the day to a heat storage tank heated to about 500 ° C. by electric power at midnight, and the generated steam is used for a dryer and a water heater. . As shown in FIG. 8, usually, the heat storage is started at the start time of the midnight power time zone (for example, 22:00). Then, when the heat storage temperature reaches the target heat storage temperature, that is, the heat storage upper limit temperature 500 ° C., the heat storage temperature 500 ° C. is maintained by controlling the heater ON / OFF until the end time of the midnight power time zone (for example, 8:00). .

[0003]

However, in the conventional heat storage control device, the operation time in the daytime is short, and the heat storage residual temperature of the heat storage tank is, for example, about 400 ° C. at the start time of the midnight power time zone. In this case, the temperature reaches the heat storage upper limit temperature of 500 ° C. in a short time after the start of the heat storage using the midnight power. For this reason, there is a problem in that late-night electric power is used only for keeping warm, and electric energy is wasted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a heat storage control device capable of shortening a heat retention time after a temperature of a heat storage material reaches a target heat storage temperature. To provide.

[0005]

According to a first aspect of the present invention, there is provided a heating means for heating a heat storage material, a temperature detection means for detecting a temperature of the heat storage material, and a temperature detecting means for detecting a temperature of the heat storage material. A heat storage control device including a control unit that controls energization of the heating unit, wherein the control unit detects when the temperature detection unit detects a start time of a preset heat storage time zone. The gist is that the heat storage start time is calculated and determined from the temperature of the heat storage material, the target heat storage temperature, and the target heat storage completion time, and the heating means is energized and heated from the heat storage start time.

According to a second aspect of the present invention, in the first aspect of the present invention, the storage unit of the control means stores heat storage characteristic data indicating a relationship between a heat storage time and a heat storage temperature at a predetermined ambient temperature. In the same manner, heat radiation characteristic data indicating the relationship between the heat radiation time and the heat storage temperature under a predetermined ambient temperature are stored in advance, and the control unit, when the start time of the heat storage time zone set in advance, From the temperature of the heat storage material at that time detected by the temperature detecting means and the two characteristic data, the equations for the heat storage characteristic curve and the heat radiation characteristic curve are obtained, and the solution of both equations is calculated. The gist is that the later is set as the heat storage start time.

According to a third aspect of the present invention, in the first or second aspect, the heat storage possible time is a start time of a midnight power time zone, and a heat load is applied in the midnight power time zone. When the heat load is detected by the heat load detecting means, the heating means is energized and heated, and when the heat load is removed, the elapsed time from the start time of the midnight power time zone, the current temperature of the heat storage material and Accordingly, the gist is that the equations of the heat storage characteristic curve and the heat radiation characteristic curve after that point are obtained, and the intersection of the two equations is calculated to determine the heat storage start time. (Operation) In the invention according to claim 1, when the preset time of the heat storage time zone is reached, the temperature of the heat storage material at that time detected by the temperature detecting means, the target heat storage temperature, A heat storage start time is calculated and determined from the target heat storage completion time, and the heating unit is energized and generates heat from the heat storage start time. Then, the temperature of the heat storage material reaches the target heat storage temperature near the target heat storage completion time. Therefore, the heat retention time from the time when the temperature of the heat storage material reaches the target heat storage temperature to the time when the target heat storage is completed is reduced.

According to the second aspect of the present invention, in addition to the operation of the first aspect of the present invention, when a preset heat storage possible time comes, the heat storage at that time detected by the temperature detecting means. Equations of a heat storage characteristic curve and a heat release characteristic curve are obtained from the temperature of the material and the heat storage and heat release characteristic data. Then, the solution of both equations is calculated, and the time after the calculated time is set as the heat storage start time. That is, when the heat storage possible time comes, the ON time of the heating means is set. Therefore, it is not necessary to constantly monitor the heat storage temperature.

According to the third aspect of the present invention, in addition to the operation of the first or second aspect of the present invention, when a heat load is applied in the midnight power time zone, the heating means is energized and generates heat. At the time when the heat load has disappeared, the equations of the heat storage characteristic curve and the heat radiation characteristic curve after that time are obtained from the elapsed time from the start time of the midnight power time zone and the current temperature of the heat storage material. Then, by calculating the intersection of the two equations, the heat storage start time is determined.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is embodied in a heat storage control device will be described below with reference to FIGS.

As shown in FIG. 1, the heat storage control device 11 includes a heat storage tank 12, a heat exchanger 13, a hot water tank 14, and a control unit 15. (Heat Storage Tank) The case 21 of the heat storage tank 12 is filled with a heat storage material 22 mainly composed of magnesia and nitrate. Inside the heat storage material 22, a heat transfer tube 23 through which the primary-side circulating water flows and a heater 24 as a heating means for heating the heat storage material 22 are provided, and are respectively led out of the case 21. The heat storage material 22 has the same heat storage material 2
A temperature detection sensor 25 is provided as temperature detection means for detecting the temperature of 2 (heat storage temperature). Both ends of the heat transfer tube 23 are connected to a primary-side inlet and a primary-side outlet of a heat exchange vessel 41 constituting the heat exchanger 13 described later via connection tubes 26a and 26b, respectively. Usually, the primary inlet is provided at the upper part of the heat exchange vessel 41, and the primary outlet is provided at the lower part.

A primary circulation pump 27 is provided on the connection pipe 26b.
And an electromagnetic valve 28 are provided. In the middle of the connecting pipe 26a and the primary side circulation pump 27-solenoid valve 28 of the connecting pipe 26b.
A bypass pipe 29 is connected between the gaps. An electromagnetic valve 30 and a needle valve (not shown) are provided on the bypass pipe 29, and the amount of primary circulating water flowing from the bypass pipe 29 to the connection pipe 26a can be adjusted by the needle valve. The heater 24 is connected to a midnight power supply line 32 via a switch 31.

(Heat Exchanger) The heat exchanger 13 includes a heat exchange vessel 41 in which a predetermined amount of primary circulating water is stored, and a heat transfer tube 42 provided in the heat exchange vessel 41. The heat transfer tube 42 is arranged above the water surface so as not to contact the primary side circulating water. Both ends of the heat transfer tube 42 are led out of the heat exchange container 41, and both ends thereof are connected to the connection tube 43, respectively.
a, 43b are connected to the hot water storage tank 14. Hot water supplied to a bathtub (not shown) or the like is stored in the hot water storage tank 14. A secondary circulation pump 44 is provided on the connection pipe 43a. A supply pipe 45, one end of which is connected to a water source (not shown) such as tap water, is connected to a lower portion of the hot water storage tank 14. When the hot water in the hot water storage tank 14 is used and the water level decreases, the water level is lowered. Water is detected and supplied by a level sensor (not shown). The temperature of the hot water in the hot water storage tank 14 is detected by a secondary-side temperature detection sensor (not shown).

(Control Unit) The control unit 15 includes a ROM 51, a RAM 52, a CPU 53, and a clock IC 5 as storage units.
4 is provided. The ROM 51 stores various control programs executed by the control unit 15, heat storage characteristic data, heat radiation characteristic data, and the like obtained in advance through experiments and the like.
Read as needed. The detailed description of the heat storage and heat radiation characteristic data will be described later. The RAM 52 is a data storage area for developing the control program of the ROM 51 and executing various processes by the control unit 15, that is, a work area. CP
U53 performs various calculations based on data such as a control program, heat storage characteristic data and heat radiation characteristic data stored in the ROM 51, and based on the calculation results, the heat storage control device 1
1 is controlled in its entirety.

An input side of the control unit 15 is connected to a daytime power supply line 55 and a temperature detection sensor 25. On the output side of the control unit 15, both pumps 27 and 44, and both solenoid valves 2
8, 30 and a switch 31 are connected. From the daytime power supply line 55, normal daytime power under a metered light contract is supplied to the solenoid valves 28 and 30, the pumps 27 and 44, the control unit 15, and the like. Late-night power is supplied from the late-night power supply line 32 to the heater 24 in accordance with a time-of-day lamp fee system and a heat storage adjustment contract.

The controller 15 controls energization of the heater 24 based on the temperature of the heat storage material 22 detected by the temperature detection sensor 25. That is, the detected temperature signal from the temperature detection sensor 25 is input to the control unit 15, and the control unit 15 stores the detected temperature input at each time in the RAM 52. Control unit 15
Calculates a heat storage start time and a scheduled heating time based on various data such as the detected temperature, heat storage and heat dissipation characteristic data, and causes the switch 31 to open and close according to a control program stored in the ROM 51. The control unit 15 keeps track of the time by the clock IC 54. The control unit 15 also controls both the solenoid valves 28 and 28 based on the temperature of the hot water stored in the hot water tank 14.
30 is controlled to open and close, and both pumps 27 and 4 are controlled.
4 is driven and controlled.

(Thermal storage characteristic data) The thermal storage characteristic data is a heating pattern showing the relationship between the elapsed time after the heater 24 is energized and heated and the heat storage temperature rise. Are stored in the ROM 51. Specifically, the outside air temperature is 40 ° C, 20 ° C,
The temperature rise patterns at 0 ° C. and −20 ° C. are stored, and are indicated by straight lines U1 to U4 in FIG. In any of the heating patterns, the heat storage temperature rises substantially linearly. That is, the heat storage temperature is shown in FIG.
It has a characteristic that rises along the slope of the straight lines U1 to U4 in FIG. Therefore, it is possible to determine from the heat storage characteristic data how long it takes to raise the heat storage temperature by the predetermined temperature. This heating pattern is created in advance based on data obtained by experiments and the like. FIG. 2B shows experimental data when the ambient temperature is 20 ° C.

(Heat radiation characteristic data) The heat radiation characteristic data is a heat radiation pattern showing a relationship between a time elapsed after the power supply to the heater 24 is stopped and a decrease in the heat storage temperature, and for each ambient temperature (outside air temperature). Multiple heat radiation patterns in ROM 51
Is stored in Specifically, when the outside air temperature is 40 ° C., 20
The heat radiation patterns at 0 ° C., 0 ° C., and −20 ° C. are stored, and are indicated by straight lines D1 to D4 in FIG. In any of the heat radiation patterns, the heat storage temperature falls substantially linearly. That is, the heat storage temperature is shown in FIG.
It has a characteristic of falling along the slope of the straight lines D1 to D4 in FIG. Therefore, it is possible to determine how many times the heat storage temperature is after a predetermined time from the heat radiation characteristic data. This heat radiation pattern is created based on data obtained in advance through experiments and the like. FIG.
(B) is experimental data at an ambient temperature of 20 ° C. (Operation of Embodiment) Next, the operation of the heat storage control device 11 configured as described above during the heat dissipation operation will be described.

(During the heat dissipation operation) When the temperature of the hot water in the hot water storage tank 14 detected by the secondary side temperature detection sensor (not shown) is lower than a preset lower limit temperature (for example, 70 ° C.), the controller 15 Opens the solenoid valves 28 and 30 to drive the primary circulation pump 27. Then, the primary side circulating water in the heat exchange vessel 41 is connected to the connection pipe 26b → the primary side circulation pump 27 → the electromagnetic valve 28 → the heat transfer pipe 23 → the connection pipe 26a → the heat exchange vessel 41.
And the connection pipe 26b → the primary side circulation pump 27 → the bypass pipe 29 → the solenoid valve 30 → the connection pipe 26a.
→ Circulate in the path of the heat exchange container 41.

The amount of primary circulating water flowing into the connection pipe 26a from the bypass pipe 29 is previously adjusted to a fixed amount (slight amount) by the needle valve. The primary circulating water is heat transfer tube 2
3, the heat of the heat storage material 22 is heated by being transmitted through the tube wall of the heat transfer tube 23, and is heated as superheated steam and ejected into the connection tube 26 a. This superheated steam is mixed with the circulating water from the bypass pipe 29 to become saturated steam, and then condensed by heat exchange in the heat exchange container 41 to become water, and stored in the heat exchange container 41. Then, it circulates through both of the above paths again.

On the other hand, when the secondary circulation pump 44 is driven, the hot water (secondary circulation water) in the hot water storage tank 14
a → secondary circulation pump 44 → heat transfer tube 42 → connection tube 43b
→ Circulates along the route of hot water tank 14. Heat exchange is performed between the secondary circulating water in the heat transfer tube 42 and the saturated steam ejected into the heat exchange container 41.

When the hot water in the hot water storage tank 14 is heated and reaches a preset upper limit temperature (for example, 80 ° C.), the controller 1
5 closes the solenoid valve 28. Then, the primary-side circulating water is circulated only by the path of the connecting pipe 26b → the primary-side circulating pump 27 → the bypass pipe 29 → the solenoid valve 30 → the connecting pipe 26a → the heat exchange vessel 41 by driving the primary-side circulating pump 27. Since the primary-side circulating water flows by bypassing the heat storage tank 12, it is not heated and does not jet into the heat exchange container 41 as saturated steam. For this reason, overheating of the secondary side circulating water is prevented. The heated hot water in the hot water storage tank 14 is supplied to a bathtub (not shown) or the like for use.

(Normal Heat Storage) Next, the operation at the time of normal heat storage during which the heat dissipation operation is not performed in the midnight power time zone as the heat storage time zone will be described with reference to the flowchart shown in FIG. 4 and FIG. The flowchart shown in FIG. 4 proceeds based on a control program stored in the ROM 51. The heat storage upper limit temperature as the target heat storage temperature is 500 ° C., and the ambient temperature of the heat storage control device 11 is 20 ° C. The midnight power time zone is 10 hours from 22:00 to 8:00.

The start time of the midnight power time zone, ie, 22: 0
When the temperature becomes 0 (S1), the control unit 15 detects the heat storage temperature T1 at this time by the temperature detection sensor 25 (S1).
2). In the present embodiment, T1 = 400 ° C.

Next, the control section 15 obtains a heat storage curve and a heat radiation curve at an ambient temperature of 20 ° C. from the heat storage and heat radiation characteristic data stored in the ROM 51 (S3). That is, the control unit 15
Calculates the values of a, b, c, and d in the heat storage curve and the heat release curve expressed as (Equation 1) and (Equation 2) below.

Heat storage curve y = ax + b (Equation 1) Heat dissipation curve y = cx + d (Equation 2) where a and c are slopes of heat storage and heat dissipation curves and are constant. b and d are the heat storage temperature (° C) at the start of the midnight power time zone,
x is time (h) and y is heat storage temperature (° C.).

First, consider the heat storage curve (Equation 1).
At an ambient temperature of 20 ° C., if the temperature at the start of heat storage is 100 ° C., the heat storage temperature will be 500 ° C. after 10 hours.
By substituting b = 100, x = 10, y = 500 into the above (Equation 1), a = 40 can be obtained. Therefore, the heat storage curve (Equation 1) is as follows.

Heat storage curve y = 40x + 100 (Equation 3) Next, a heat dissipation curve (Equation 2) will be considered. It is determined from the heat radiation characteristic data shown in FIG. 3 that the heat storage temperature drops by 300 ° C. in 10 hours. Therefore, even if the heat storage temperature is 400 ° C. at the start of the midnight power time zone, the heat storage temperature falls to 100 ° C. if left undisturbed until the end of the midnight power time zone 10 hours later. In the above (Equation 2), d = 400, x
= 10 and y = 100, c = −30
Is required. Therefore, the heat dissipation curve (Equation 2) is as follows.

Heat dissipation curve y = −30x + 400 (Equation 4) Next, the controller 15 obtains an intersection between the heat storage curve (Equation 3) and the heat dissipation curve (Equation 4), and based on the result, the heat storage start time ts is determined (S4). That is, time x and heat storage temperature y
Is as follows.

X = approximately 4.3 (h), y = approximately 272 (° C.) Accordingly, the start time of the midnight power time zone of the day (22:00)
If the heat storage is started about 4.3 hours after the starting time, that is, at about 2:18, the heat storage temperature becomes 500 ° C. immediately before or at the end time (8:00) of the midnight power time zone of the next day as the target heat storage completion time.
Reach

At the heat storage start time ts, that is, at about 2:18 mentioned above (S5), the control unit 15 closes the switch 31 to energize the heater 24 to generate heat (S6). And
When the heat storage temperature detected by the temperature detection sensor 25 reaches a preset heat storage upper limit temperature of 500 ° C. (S7), the control unit 15 opens the switch 31 and cuts off the power supply to the heater 24 (S8). . The time at this time is the end time of the midnight power time zone or immediately before it. This is shown in a graph of time and heat storage temperature as shown in FIG.

(When used during heat storage) Next, one hour after the start of the midnight power time zone (23:00), the heat storage control device 1
The operation in the case where the operation of No. 1 is started and the operation is stopped one hour after that (0 o'clock) will be described based on FIG. It is assumed that the heat storage temperature T1 at the start of the midnight power time zone is 400C. The ambient temperature is 20 ° C., and the slope of the heat radiation curve (Equation 4) is the same as that at the time of the ordinary heat storage. The controller 15 determines the operation and stop of the device 11 by detecting the drive and stop of the primary-side circulation pump 27.

First, the controller 15 controls the primary circulation pump 27
Is detected, the switch 31 is closed, and the heater 24 is energized to generate heat (at 23:00). And the control unit 15
Is the time when the stop of the primary side circulation pump 27 is detected (0 o'clock)
The heat storage temperature is detected by the above, and the above calculation is performed to obtain a heat storage start time (heater ON time) ts.

Assuming that the heat storage temperature at 0 o'clock is T2 = 300 ° C., the radiation curve (Equation 5) at an ambient temperature of 20 ° C. is as follows. y = −30x + 360 (Equation 5) By the calculation of (Equation 5) and (Equation 3), the time x is as follows.

X = 3.7 (h) However, since two hours have already passed from the start time of the midnight power time zone, the new heat storage start time ts ′ is x ′ after the primary circulation pump 27 stops. = 3.7-2 = 1.7 (h).

Therefore, if the heater is turned on one hour and 42 minutes after the operation is stopped halfway (0:00), that is, at 1:42, the heat storage temperature is at the upper limit at the end of the midnight power time zone (8:00). The temperature reaches 500 degrees. Note that even if the use after entering the midnight power time zone is repeated a plurality of times, the ON time of the heater 24 can be obtained from the elapsed time from the start of the midnight power time zone to the final use stop time and the heat storage temperature. .

(Case of Power Failure During Heat Storage) Next, a case of a power failure immediately after entering the midnight power time zone will be described. Considering the case where the ambient temperature is 20 ° C., if the power failure is restored within 4.3 hours from the start time of the midnight power time zone, the ON time of the heater becomes the same as the above-described normal heat storage time. This is because it is similar to the case of simply radiating heat. on the other hand,
If the power failure does not recover within 4.3 hours from the start time of the midnight power time zone, the heat storage temperature will fall below the temperature rise curve (Equation 3) and reach the maximum heat storage temperature of 500 degrees at the end of the midnight power time zone. There is no. (Effects of Embodiment) Therefore, according to the present embodiment, the following effects can be obtained.

(1) When the start time of the midnight power time zone is reached, the control unit 15 detects the temperature of the heat storage material 22 detected by the temperature detection sensor 25, the heat storage upper limit temperature, and the midnight power time zone. The heat storage start time ts is calculated and determined from the end time, and the heater 24 is energized to generate heat from the heat storage start time ts. For this reason, the ON time of the heater 24 can be obtained at the start of the midnight power time zone on the assumption that the device is not operated during the midnight power time zone. The temperature of the heat storage material 22 reaches the heat storage upper limit temperature near the end time of the midnight power time zone. Therefore, the heat retention time from the time when the temperature of the heat storage 22 material reaches the heat storage upper limit temperature to the end time of the midnight power time zone can be reduced.

(2) The heat storage and heat radiation characteristic data are stored in the ROM 51 in advance. Then, when the start time of the midnight power time zone is reached, the equations of the heat storage characteristic curve and the heat radiation characteristic curve are obtained from the heat storage temperature detected by the temperature detection sensor 25 and the heat storage and heat radiation characteristic data, respectively. The solution was calculated, and the time after the calculated time was set as the heat storage start time. Therefore, when the start time of the midnight power time zone is reached, the ON time of the heater 24 is set. Therefore, it is not necessary to constantly monitor the heat storage temperature.

(3) When the heat dissipation operation is performed in the midnight power time zone, the time elapsed from the start time of the midnight power time zone at the time when the operation was stopped and the current temperature of the heat storage material are used. Equations of the heat storage characteristic curve and the heat radiation characteristic curve are obtained, and the intersection of the two equations is calculated to determine the heat storage start time. For this reason,
Even when the heat dissipation operation is performed in the midnight power time zone, the optimum heater ON time can be obtained.

The above embodiment may be modified as follows. The outside air temperature may be detected, and a heat storage and heat radiation characteristic curve corresponding to the detected outside air temperature may be selected from a plurality of curves. In this way, a more accurate heat storage start time can be calculated and determined.

Next, technical ideas other than the claimed invention which can be grasped from the embodiment will be described below together with their effects. In the storage device of the control unit, heat storage and heat radiation characteristic data for each of a plurality of outside air temperatures are stored in advance, and when the start time of the midnight power time zone is reached, the ambient temperature and the heat storage temperature are detected, The heat storage control device according to any one of claims 1 to 4, wherein an optimum heat storage start time is calculated based on both values, and heat storage is started from the calculated heat storage start time.

In the midnight power time zone, the operation time:
2. The heat storage device according to claim 1, wherein equations of the heat storage characteristic curve and the heat release characteristic curve are obtained based on the heat storage temperature at the time of the operation stop, and a heat storage start time is obtained by calculating a solution of both equations. Control device.

[0044]

According to the present invention, since the temperature of the heat storage material reaches the target heat storage temperature near the target heat storage completion time, the heat retention from the time when the temperature of the heat storage material reaches the target heat storage temperature to the target heat storage completion time is achieved. Time can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a heat storage control device.

FIG. 2 is a graph showing a relationship between a heat storage time and a heat storage temperature for each ambient temperature.

FIG. 3 is a graph showing a relationship between a heat release time and a heat storage temperature for each ambient temperature.

FIG. 4 is a flowchart showing a procedure for obtaining a heat storage start time.

FIG. 5 is a graph for calculating an intersection between a heat storage characteristic curve and a heat radiation characteristic curve.

FIG. 6 is a graph showing a relationship between heat storage time and heat storage temperature.

FIG. 7 is a graph showing an intersection between a heat storage characteristic curve and a heat radiation characteristic curve when used halfway.

FIG. 8 is a graph showing a conventional heat storage state.

[Explanation of symbols]

11 heat storage control device, 12 heat storage tank, 15 control unit (control means), 22 heat storage material, 24 heater (heating means),
25: temperature detection sensor (temperature detection means), 15: control unit, 51: ROM (storage unit), 52: RAM, 53: C
PU, 54 ... Clock IC.

Claims (3)

[Claims] 1. A heating means for heating a heat storage material, a temperature detection means for detecting a temperature of the heat storage material, and a control means for controlling energization to the heating means based on the temperature detected by the temperature detection means. In the heat storage control device provided, when the start time of the heat storage time zone set in advance is reached, the temperature of the heat storage material at that time detected by the temperature detection means, a target heat storage temperature, and a target A heat storage control device which calculates and determines a heat storage start time from a heat storage completion time, and causes the heating means to conduct and generate heat from the heat storage start time. 2. The storage section of the control means includes heat storage characteristic data indicating a relationship between a heat storage time and a heat storage temperature under a predetermined ambient temperature, and a heat release time and a heat storage temperature under the predetermined ambient temperature. The heat radiation characteristic data indicating the relationship is stored in advance, the control means, when the start time of the heat storage time zone set in advance, the temperature of the heat storage material at that time detected by the temperature detection means and From the two characteristic data, while obtaining the equation of the heat storage characteristic curve and the heat radiation characteristic curve, respectively,
2. The heat storage control device according to claim 1, wherein solutions of both equations are calculated, and a time after the calculated time is set as a heat storage start time. 3. The heat storage time zone is a midnight power time zone. When a heat load is applied during the midnight power time zone, the heat load is sensed by the heat load detection means, and the heating means is energized to generate heat. At the time when the load disappears, from the elapsed time from the start time of the midnight power time zone and the current temperature of the heat storage material, the equations of the heat storage characteristic curve and the heat radiation characteristic curve after that point are obtained. The heat storage control device according to claim 1 or 2, wherein the heat storage start time is determined by calculating an intersection.