S&F Ref: P000680 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address Rinnai Corporation, of 2-26, Fukuzumi-cho, Nakagawa of Applicant: ku, Nagoya-shi, Aichi-ken, 454-0802, Japan Actual Inventor(s): Akira Kumagai Address for Service: Spruson & Ferguson St Martins Tower Level 35 31 Market Street Sydney NSW 2000 (CCN 3710000177) Invention Title: Solar heat-utilizing water heater system The following statement is a full description of this invention, including the best method of performing it known to me/us: 5845c(5271212_1) 1 SOLAR HEAT-UTILIZING WATER HEATER SYSTEM BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a solar heat-utilizing hot water supply system 5 that heats water supplied into a stored hot water tank by utilizing solar heat collected through a solar heat collector, and uses the hot water stored in the stored hot water tank. DESCRIPTION OF THE RELATED ART From a viewpoint of an energy saving, there has been known a conventional solar heat-utilizing hot water supply system comprising: a solar heat collector for heating 1o a heating medium by utilizing solar heat; a stored hot water tank; a heating medium circulation pipe line for circulating the heating medium between the solar heat collector and the stored hot water tank; a circulating pump for circulating the heating medium in the heating medium circulation pipe line; and an auxiliary heat source unit such as a water heater for heating hot water outputted from the stored hot water tank at a predetermined is temperature. In this type of the solar heat-utilizing hot water supply system, the heating medium heated by the solar heat collector is guided to the stored hot water tank through the heating medium circulation pipe line by means of the circulating pump, hot water is stored by performing heat exchange between supplied water and the heated heating medium in the stored hot water tank, the auxiliary heat source unit is operated during a 20 hot water supplying operation if a temperature of the hot water heated by the heating medium in the stored hot water tank is low, and the hot water heated up to the predetermined temperature is supplied to a hot water supplying terminal. However, a heat collecting amount by the solar heat collector depends on the weather. Therefore, if the circulating pump is actuated under cloudy or rainy weather as 25 the solar heat can not be sufficiently obtained, the heat collecting amount becomes smaller than the electric power consumption required for actuating the circulating pump, 2 which causes a problem that use of the solar heat for the energy saving becomes meaningless. From the above point of view, for example, there has been proposed a solar heat-utilizing hot water supply system having a circulating pump, a heating medium s temperature sensor, near the stored hot water tank, for detecting a heating medium temperature, and a water temperature sensor, in the stored hot water tank, for detecting a hot water temperature, wherein the circulating pump is actuated or stopped based on a temperature difference between the heating medium temperature detected by the heating medium temperature sensor and the hot water temperature detected by the water 1o temperature sensor. (Prior Art 1 : Japanese Unexamined Patent Publication No. 2004-44952) However, according to the solar heat-utilizing hot water supply system in Prior Art 1, the circulating pump is kept actuated when the temperature difference between the heating medium temperature near the stored hot water tank and the hot water temperature 15 in the stored hot water tank is equal to or larger than a predetermined reference temperature, while the circulating pump is stopped when the temperature difference is smaller than the predetermined reference temperature. Accordingly, as far as the temperature difference is equal to or larger than the predetermined reference temperature, the heating medium is circulated at a constant flow regardless of degree of the 20 temperature difference. Since the temperature difference between the heating medium temperature and the hot water temperature in the stored hot water tank becomes smaller as a heat-collecting operation continues, the hot water temperature in the stored hot water tank hardly increase. Even in such a condition, the heating medium is circulated at the same heating medium flow rate as the one in the condition where the temperature 25 difference between the heating medium temperature and the hot water temperature is much larger than the predetermined reference temperature, it results in a circulation of the 3 heating medium while heat collection in the stored hot water tank is insufficient, which causes of a problem of an inefficient heat-collecting operation. In addition, according to Prior Art 1, the heating medium temperature is detected by the heating medium temperature sensor provided near the stored hot water tank which 5 is far away from the solar heat collector installed outdoor, and the circulating pump is started to be actuated when the temperature difference between the heating medium temperature and the hot water temperature is equal to or larger than the predetermined reference temperature. Accordingly, when the circulating pump is not actuated, an increase in the heating medium temperature detected by the heating medium temperature 10 sensor near the stored hot water tank only depends on heat transfer through the heating medium in a heating medium circulation pipe line and through the pipe line itself. Consequently, since the heating medium temperature near the stored hot water tank hardly increase during a certain amount of time despite of that the solar heat is started to be collected by the solar heat collector, the heat-collecting operation is not started at an early is stage, which causes a problem that an efficient heat-collecting operation can not be performed. In this case, it is conceived that the circulating pump is always actuated at a low rotation speed or a solar radiation sensor is provided near the solar heat collector. However, in the former case, the circulating pump is actuated even if the heat collecting amount is insufficient, which goes against the energy saving. In the latter case, the 20 heating medium is circulated when the solar luminosity is equal to or higher than a reference value despite of that the heating medium temperature is not sufficiently higher than the hot water temperature in the stored hot water tank. Accordingly, there are problems that not only a heat collecting efficiency decrease but also the hot water temperature in the stored hot water tank is lowered. 25 Further, in the case where the hot water temperature in the stored hot water tank is measured during the heat-collecting operation as described in Prior Art 1, the hot water 4 temperature in the stored hot water tank does not increase if the circulating pump is not actuated continuously for a certain period of time. Accordingly, it is necessary to actuate the circulating pump to allow the measurement of the temperature difference between the heating medium temperature and the hot water temperature even if the solar 5 heat is insufficient and the heat collecting amount is small. In addition, in a facility such as a hospital, since the bathing time for the patients is fixed, a hot water supply system including a large-sized stored hot water tank is used considering a case where a large amount of water is used for a short period of time. In the solar heat-utilizing hot water supply system including such a large-sized stored hot 10 water tank, collection of heat by a solar heat collector is not used for largely increasing the hot water temperature in the stored hot water tank but preliminarily used for preheating. Accordingly, this causes a problem that it is difficult to raise the hot water temperature in the stored hot water tank by the heat-collecting operation, and also it is difficult to accurately calculate the heat collecting amount based on an amount of 15 temperature increase of the hot water in the stored hot water tank. Further, in the above-mentioned facility, a small amount of water is used for hand washing or the like in addition to the use of a large amount of hot water for bathing or the like. Consequently, a difference between a maximum flow rate and a minimum flow rate is large, so that it is difficult to measure the flow rate of the hot water with high precision, and therefore it is 20 difficult to accurately assess the heat collecting amount. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and an object of the present invention is, for an energy saving, to provide a solar heat-utilizing hot water supply system capable of efficiently collecting solar heat. 25 According to the present invention, there is provided a solar heat-utilizing hot water supply system comprising: 5 a solar heat collector for heating a heating medium by utilizing solar heat; a stored hot water tank for storing hot water; a heating medium circulation pipe line including an inlet side-heating medium circulation pipe line for feeding the heating medium from the solar heat collector to the s stored hot water tank, a heat exchanger provided in the stored hot water tank, and an outlet side-heating medium circulation pipe line for returning the heating medium from the stored hot water tank to the solar heat collector; a circulating pump for circulating the heating medium in the heating medium circulation pipe line; 10 a heat collector side-heating medium temperature sensor provided near the solar heat collector in the inlet side-heating medium circulation pipe line or in the outlet side-heating medium circulation pipe line; an inlet side-heating medium temperature sensor provided near the stored hot water tank in the inlet side-heating medium circulation pipe line; 15 an outlet side-heating medium temperature sensor provided near the stored hot water tank in the outlet side-heating medium circulation pipe line; a heating medium flow meter for measuring a heating medium flow rate in the heating medium circulation pipe line; a supply water temperature sensor provided near an inlet port of the stored hot 20 water tank; and a control device for controlling a heat-collecting operation by the solar heat collector, wherein the control device actuates the circulating pump to start the heat-collecting operation when a temperature difference (TmO-TwO) between a heat collector 25 side-heating medium temperature TmO detected by the heat collector side-heating medium temperature sensor and a supply water temperature TwO detected by the supply 6 water temperature sensor is equal to or larger than a predetermined starting temperature TnO, and the control device controls, during the heat-collecting operation, a rotation speed of the circulating pump such that a heat collecting amount [(Tin-Tout) O V O C O d] to 5 be supplied from the heating medium to the stored hot water tank is equal to or larger than a power consumption required to actuate the circulating pump, the heat collecting amount being determined from a product of (Tin-Tout) representing a temperature difference between an inlet side-heating medium temperature Tin detected by the inlet side-heating medium temperature sensor and an outlet side-heating medium temperature Tout detected 10 by the outlet side-heating medium temperature sensor, V representing the heating medium flow rate detected by the heating medium flow meter, C representing a specific heat of the heating medium, and d representing a specific gravity of the heating medium. According to one aspect of the present invention, it is possible to collect solar heat efficiently and to provide the solar heat-utilizing hot water supply system suitable for is the energy saving. Other objects, features and advantages of the present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention. 20 BRIEF DESCRIPTION OF THE DRAWINGS FIG I is a schematic configuration diagram showing a solar heat-utilizing hot water supply system according to an embodiment of the present invention; and FIG 2 is an operation flowchart showing a control operation of a heat-collecting operation in the solar heat-utilizing hot water supply system according to the embodiment 25 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 7 Referring to drawings, the best mode for carrying out the present invention is described below. As illustrated in FIG 1, a solar heat-utilizing hot water supply system according to an embodiment of the present invention includes a solar heat collector 1, a stored hot 5 water tank 2, an auxiliary heat source unit 3 such as a water heater for, as required, heating hot water outputted from the stored hot water tank 2, a remote controller 4 for setting a hot water supply temperature and an operation of an entire system, and displaying an effective heat collecting amount during a heat-collecting operation, a heating medium circulation pipe line 7 for circulating a heating medium between the solar io heat collector I and the stored hot water tank 2, and a control device 10 for controlling the heat-collecting operation and a hot water supplying operation. The auxiliary heat source unit 3 may be used an electric heater instead of the water heater. The solar heat collector I is installed in a balcony of a housing complex or on a roof of a building. The solar heat collector I is provided with a collector panel I a is having a plate-like shape. The collector panel la has an internal flow path therein and the heating medium circulates in the internal flow path. The internal flow path constitutes a part of the heating medium circulation pipe line 7. The stored hot water tank 2 is a tank made of a metal excellent in corrosion resistance (for example, stainless steel) and has a heat insulator on a periphery thereof. 20 Also, the stored hot water tank 2 includes, in a lower portion thereof, an inlet port connected to a water supply pipe 5 for supplying water and, in an upper portion thereof, an outlet port connected to a hot water outlet pipe 6 for outputting hot water. Further, a supply water thermistor (supply water temperature sensor) 20a for detecting a supply water temperature is provided near the inlet port located in the lower portion inside the 25 stored hot water tank 2 and stored hot water tank thermistors 20b and 20c for respectively detecting hot water temperatures in a middle portion and a top portion are provided in the 8 stored hot water tank 2. Detection signals of these thermistors 20a, 20b, and 20c are continuously and individually outputted to the control device 10, and each of the detected temperatures is utilized for controlling the heat-collecting operation and the hot water supplying operation. 5 The water supply pipe 5 is provided, sequentially from an upstream thereof, with a water supply main valve 51, a pressure reducing valve 52, an inlet water temperature thermistor 53 for detecting a supply water temperature for use in mixing, a check valve 54, and a drain valve 55. The pressure reducing valve 52 is a valve for adjusting a water supply pressure to the stored hot water tank 2. When an amount of the hot water in the io stored hot water tank 2 is reduced, a downstream pressure of the pressure reducing valve 52 decreases, and, in response to this, water is supplied into the stored hot water tank 2 to maintain a pressure in the stored hot water tank 2. A detection signal of the inlet water temperature thermistor 53 is outputted to the control device 10. The stored hot water tank 2 and the auxiliary heat source unit 3 are connected to 15 each other by means of the hot water outlet pipe 6. The hot water outlet pipe 6 is provided, sequentially from an upstream thereof between the stored hot water tank 2 and the auxiliary heat source unit 3, with a pressure release valve 61, a solenoid valve 62, a mixing valve 63, a water flow sensor 64, and a mixing thermistor 65. The water flow sensor 64 detects a flow rate of the hot water in the hot water outlet pipe 6 and a detection 20 signal detected by the water flow sensor 64 is outputted to the control device 10. The mixing thermistor 65 detects a hot water temperature in the hot water outlet pipe 6 and a detection signal detected by the mixing thermistor 65 is outputted to the control device 10. A mixing water supply pipe 9 that is branched off from the water supply pipe 5 is 25 branch-connected to the mixing valve 63 provided to the hot water outlet pipe 6. The mixing valve 63 is a valve for mixing the hot water outputted from the stored hot water 9 tank 2 with the water supplied from the water supply pipe 5 through the mixing water supply pipe 9 according to the hot water temperature outputted from the stored hot water tank 2, and an opening degree of the mixing valve 63 is adjusted according to a signal from the control device 10. 5 The heating medium circulation pipe line 7 is includes an inlet side-heating medium circulation pipe line 7a for feeding the heating medium heated by the solar heat collector 1 to the stored hot water tank 2, a heat exchanger 7b for performing heat exchange between the water supplied in the stored hot water tank 2 and the heated heating medium, an outlet side-heating medium circulation pipe line 7c for returning the heating io medium cooled by the heat exchange to the solar heat collector 1, and a bypass line 7d for allowing the inlet side-heating medium circulation pipe line 7a to communicate with the outlet side-heating medium circulation pipe line 7c both of which are located outside the stored hot water tank 2. The heat exchanger 7b is constituted of a pipe that is bent in a lower portion inside the stored hot water tank 2. A conventionally known antifreeze 15 solution including propylene glycol or the like may be used as the heating medium. The inlet side-heating medium circulation pipe line 7a is provided, sequentially from an upstream thereof between the solar heat collector 1 and the stored hot water tank 2, with a heat collector side-heating medium thermistor (heat collector side-heating medium temperature sensor) 71 for detecting a heat collector side-heating medium 20 temperature near the solar heat collector 1, an inlet side-heating medium thermistor (inlet side-heating medium temperature sensor) 72 for detecting an inlet-side heating medium temperature of the heating medium flowing into the stored hot water tank 2, and a first thermal valve (first on-off valve) 73 for communicating or cutting off a flow of the heating medium to the stored hot water tank 2. The heat collector side-heating medium 25 thermistor 71 is provided near the solar heat collector I in the inlet side-heating medium circulation pipe line 7a; the inlet side-heating medium thermistor 72 is provided near the 10 stored hot water tank 2 and on an upstream side of a connecting portion connected the inlet side-heating medium circulation pipe line 7a to the bypass line 7d; and the first thermal valve 73 is provided between a connecting portion connected the inlet side-heating medium circulation pipe line 7a to the bypass line 7d and the stored hot s water tank 2. In the meantime, the heat collector side-heating medium thermistor 71 may be provided near the solar heat collector 1 in the outlet side-heating medium circulation pipe line 7c. The first thermal valve 73 is an on-off valve that is normally open during a period other than an initial stage of the heat-collecting operation which will be described later, and is opened or closed according to a signal from the control device 10 10, whereby a flow of the heating medium to the stored hot water tank 2 is communicated or cut off. In the meantime, the first thermal valve 73 may be provided between the connecting portion connecting the outlet side-heating medium circulation pipe line 7c to the bypass line 7d and the stored hot water tank 2. A detection signal of the heat collector side-heating medium thermistor 71 is continuously outputted to the control 15 device 10, and a detection signal of the inlet side-heating medium thermistor 72 is outputted to the control device 10 during the heat-collecting operation. The outlet side-heating medium circulation pipe line 7c is provided, sequentially from an upstream thereof between the stored hot water tank 2 and the solar heat collector 1, with an outlet side-heating medium thermistor (outlet side-heating medium temperature 20 sensor) 74 for detecting an outlet side-heating medium temperature of the heating medium returning from the stored hot water tank 2 to the solar heat collector 1, an expansion tank 75 for storing the heating medium, a heating medium flow sensor (heating medium flow meter) 76 for measuring a heating medium flow rate, and a circulating pump P. The outlet side-heating medium thermistor 74 is provided near the stored hot 25 water tank 2 in the outlet side-heating medium circulation pipe line 7c and on a downstream side of a connecting portion connected the outlet side-heating medium 11 circulation pipe line 7c to the bypass line 7d. Detection signals of the outlet side-heating medium thermistor 74 and the heating medium flow sensor 76 are outputted to the control device 10 during the heat-collecting operation. The bypass line 7d is provided with a second thermal valve (second on-off valve) 5 77 for communicating or cutting off a flow of the heating medium in the bypass line 7d. The second thermal valve 77 is opened or closed according to a signal from the control device 10, whereby a flow of the heating medium to the bypass line 7d is communicated or cut off. The circulating pump P is actuated by power from the control device 10 which is 10 applied through a control board 33 connected to a power supply (not illustrated) of a commercial power source. The auxiliary heat source unit 3 is provided with a hot water supply heating unit 31 and a control board 33 for controlling an operation of the hot water supply heating unit 31. The hot water supply heating unit 31 includes a hot water heat exchange unit 311 is and a hot water supply gas burner 312. The hot water supply heat exchange unit 311 is connected to the hot water outlet pipe 6. When the hot water supplying operation is performed, as required, the hot water supply gas burner 312 is ignited to heat the hot water supply heat exchange unit 311, hot water flowing into the hot water supply heat exchange unit 311 is subjected to heat 20 exchange, so that hot water having a predetermined hot water set temperature is supplied from a hot-water supply pipe L to a hot water supplying terminal such as a water faucet or a shower head provided in a bathroom. In a case where the hot water supplying operation is performed by the solar heat-utilizing hot water supply system according to this embodiment, water is supplied 25 from the mixing water supply pipe 9 to the hot water outlet pipe 6 through the mixing valve 63 by opening the hot water supplying terminal. When the water flow sensor 64 12 detects a water flow having a predetermined or larger flow rate, the control device 10 opens the solenoid valve 62 provided to the hot water outlet pipe 6. When the solenoid valve 62 is opened, hot water is outputted from the stored hot water tank 2 to the hot water outlet pipe 6. Then, if a hot water temperature detected by the stored hot water 5 tank thermistor 20c in the stored hot water tank 2a is higher than a demanded temperature at the hot water supplying terminal by inputted into the control device 10 by operating a hot water supply temperature setting switch of the remote controller 4, the opening degree of the mixing valve 63 is adjusted by the control device 10, the hot water outputted from the store hot water tank 2 and the water supplied from the mixing water supply pipe 9 are io mixed at a predetermined ratio, and hot water having the predetermined temperature is supplied to the hot water supplying terminal without operating the hot water supply heating unit 31. On the other hand, if the hot water temperature outputted from the stored hot water tank 2 is lower than the demanded temperature at the hot water supplying terminal, the control device 10 adjusts the opening degree of the mixing valve 63 at a is predetermined ratio, operates the hot water supply heating unit 31, and ignites the hot water supply gas burner 312. Then, the hot water outputted from the stored hot water tank 2 is mixed with the water supplied from the mixing valve 63 and, thereafter, heated by the hot water supply heat exchange unit 311, and the hot water having a predetermined temperature is supplied to the hot water supplying terminal. 20 The control device 10 is mainly configured of a microcomputer. A ROM (not illustrated) of the control device 10 stores a heat-collecting operation program for performing a preset heat-collecting operation, a heat-collecting amount calculation program, a specific heat C [J/kg-K] of the heating medium to be used, a specific gravity d [kg/m 3 ] of the heating medium, and a power consumption according to a rotation speed of 25 the circulating pump P. Further, the control device 10 is provided with a hot water operation unit for performing the hot water supplying operation, a heat-collecting 13 operation unit for performing the heat-collecting operation, a timer, and so on. The control device 10 is connected to the control board 33 in the auxiliary heat source unit 3, the circulating pump P, the water flow sensor 64, each of the thermistors 20a, 20b, 20c, 53, 65, 71, 72 and 74 described above, the thermal valves 73 and 77, the heating medium 5 flow sensor 76, the solenoid valve 62, the mixing valve 63, and the like. Furthermore, the control device 10 is connected to the remote controller 4 provided in a bath room or the like via the control board 33 in the auxiliary heat source unit 3. The remote controller 4 is provided with a switch (not illustrated) such as an operation switch or the hot water supply temperature setting switch, and a display for 10 displaying information such as an effective heat collecting amount during heat-collecting operation that is obtained by deducting power consumption consumed by actuating the circulating pump P from the heat collecting amount by solar heat, a hot water setting temperature, and an amount of hot water in the stored hot water tank 2. Next, with reference to a flowchart of FIG. 2, a control operation upon is performing the heat-collecting operation in the solar heat-utilizing hot water supply system according to this embodiment will be specifically described. When the operation switch of the remote controller 4 is pressed on, the control device 10 determines whether a temperature difference (TmO-TwO) between a heat collector side-heating medium temperature TmO [K] outputted from the heat collector 20 side-heating medium thermistor 71 and a supply water temperature TwO [K] outputted from the supply water thermistor 20a indicates a predetermined starting temperature TnO (for example, 10K) or higher for a certain amount of time (for example, 10 seconds) (step STI). If the temperature difference (Tm0-TwO) is equal to or higher than the starting temperature TnO (Yes in step ST1), the control device 10 launches the heat-collecting 25 operation program, actuates the circulating pump P at a maximum rotation speed, and starts the heat-collecting operation (step ST2). With this, it is possible to quickly detect 14 increase in the heating medium temperature by the heat collection of the solar heat collector 1. In addition, since the heat-collecting operation is started when the temperature difference (Tm0-Tw0) between the heat collector-side heating medium temperature TmO detected by the heat collector-side heating medium thermistor 71 5 provided near the solar heat collector 1 and the supply water temperature TwO detected by the supply water thermistor 20a provided near the inlet port of the stored hot water tank 2 is equal to or larger than the predetermined starting temperature TnO, it is possible to avoid a heat-collecting operation that is uneconomical in terms of energy and to prevent decrease in the hot water temperature in the stored hot water tank 2 due to the io heat-collecting operation. When the heat-collecting operation is started, the control device 10 determines whether a heating medium flow rate V outputted from the heating medium flow sensor 76 is equal to or larger than a predetermined flow rate Va which is necessary to perform the heat-collecting operation (step ST3). If the heating medium flow rate V is smaller than 15 the predetermined flow rate Va (No in step ST3), the control device 10 stops the circulating pump P and aborts the heat-collecting operation (step ST16). With this, it is possible to avoid a heat-collecting operation in the case where the heating medium is not normally circulated in the heating medium circulation pipe line 7 due to a problem such as a malfunction of the circulating pump P or clogging of the heating medium circulation 20 pipe line 7. In this case, abnormality of the circulation of the heating medium may be warned by the remote controller 4. On the other hand, if the heating medium flow rate V is equal to or larger than the predetermined flow rate Va (Yes in step ST3), the control device 10 closes the first thermal valve 73 provided to the inlet side-heating medium circulation pipe line 7a and 25 opens the second thermal valve 77 provided to the bypass line 7d, so that the heating medium does not flow into the stored hot water tank 2 but flow in the bypass line 7d (step 15 ST4). With this arrangement, the heating medium circulates through a shorted heating medium circulation path indicated by a broken line thick arrow in FIG. 1. Thus, by switching the heating medium circulation path to the shorted heating medium circulation path, as the heating medium does not flow into the stored hot water tank 2 but flow in the 5 bypass line 7d upon the start of the heat-collecting operation, the heating medium circulates through the heating medium circulation pipe line 7 in a state in which the heating medium is not subjected to the heat exchange with supplied water in the stored hot water tank 2. Accordingly, a change in the heating medium temperature in the heating medium circulation pipe line 7 can be reduced, and it is possible to determine io whether the heating medium has a temperature for performing an efficient the heat-collecting operation at an early stage. After the heating medium circulation path is switched to the shorted heating medium circulation path, the heating medium is circulated for a predetermined period (for example, 30 seconds) (step ST5). Then, in this circulation state, the control device 10 is compares an initial heat collector side-heating medium temperature Tml [K] outputted from the heat collector side-heating medium thermistor 71 with an initial supply water temperature TwI [K] outputted from the supply water thermistor 20a, and determines whether the temperature difference (Tml-Twl) is equal to or larger than a predetermined continuous operating temperature Tnl (for example, 5K) (step ST6). Specifically, 20 although the heat-collecting operation is started when the temperature difference (TmO-TwO) between the heat collector side-heating medium temperature TmO and the supply water temperature TwO is equal to or larger than the predetermined starting temperature TnO, the heating medium temperature in the heating medium circulation pipe line 7 in a position away from the solar heat collector 1 is usually lower than the heat 25 collector side-heating medium temperature TmO, so that in accordance with the circulation of the heating medium at an initial stage upon the start of the heat-collecting 16 operation, the heating medium temperature decreases to a level insufficient for performing the efficient heat-collecting operation. Therefore, according to the process above, it is possible to determine more accurately whether the heat-collecting operation should be continued or not by comparing the initial heat collector-side heating medium 5 temperature Tml with the initial supply water temperature Twl, after elapse of the predetermined period from the start of the heat-collecting operation. If the temperature difference (Tml-Twl) between the initial heat collector-side heating medium temperature Tml and the initial supply water temperature Tw1 is smaller than the predetermined continuous operating temperature Tnl (No in step ST6), it can be 1o determined that there is a possibility that the power consumption of the circulating pump P may become larger than the heat collecting amount. Accordingly, the control device 10 stops the circulating pump P and ends the heat-collecting operation (step ST16). Through this process, it is possible to abort, at an early stage, the heat-collecting operation which is uneconomical in terms of energy. is On the other hand, if the temperature difference (Tml-Twl) between the initial heat collector side-heating medium temperature Tml and the initial supply water temperature Tw1 is equal to or larger than the predetermined continuous operating temperature Tnl (Yes in step ST6), it can be determined that sufficient heat is collected by the solar heat collector I to perform the heat-collecting operation. Accordingly, the 20 control device 10 opens the first thermal valve 73 and closes the second thermal valve 77, so that the heating medium flows into the stored hot water tank (step ST7). With this, the circulating pump P is not stopped, the heat-collecting operation is smoothly continued, and the heating medium circulates through a normal heating medium circulation path indicated by a solid line thick arrow in FIG 1. In this case, the second thermal valve 77 25 may be kept opened, since the heating medium can flow into the stored hot tank 2.
17 If the temperature difference (Tml -Tw1) between the initial heat collector-side heating medium temperature Tml and the initial supply water temperature Tw1 is equal to or larger than the predetermined continuous operating temperature Tn I (Yes in step ST6) and it is possible to continue the heat-collecting operation, the control device 10 measures, 5 for a predetermined period of time (for example, one minute), the heating medium flow rate V outputted from the heating medium flow sensor 76, an inlet side-heating medium temperature Tin outputted from the inlet side-heating medium thermistor 72, and an outlet side-heating medium temperature Tout outputted from the outlet side-heating medium thermistor 74. Then, the measured values are multiplied by the specific heat C and the to specific gravity d of the heating medium based on the heat-collecting amount calculation program to obtain a heat collecting amount Qi (which equals to (Tin - Tout) l V l C E d) (step ST9). Through this process, it is possible to accurately calculate the heat collecting amount supplied into the stored hot water tank 2 by the heating medium without using the temperature of the hot water having a small change in temperature is inside the stored hot water tank 2, or without using a highly accurate flow meter. Next, the control device 10 determines whether or not the calculated heat collecting amount Qi within the predetermined period of time is equal to or larger than a minimum power consumption Rmin consumed by actuating the circulating pump P at the minimum rotation speed (step STIO). Then, if the heat collecting amount Qi is equal to 20 or larger than the minimum power consumption Rmin (Yes in step STI 0), the control device 10 controls the rotation speed of the circulating pump P such that the power consumption Ri required for actuating the circulating pump P becomes smaller than the heat collecting amount Qi based on the relationship between the rotation speed and the power consumption of the circulating pump P that is stored in the ROM (step ST 11). 25 For example, when a temperature difference (Tin-Tout) between the inlet side-heating medium temperature Tin and the outlet side-heating medium temperature Tout upon 18 elapse of a predetermined period of one minute is 5 [K], the specific heat C of the heating medium is 3,600 [J/kg-K], the specific gravity d of the heating medium is 1,050 [kg/m 3 ], and the heating medium flow rate V is 0.0002 [m 3 /sec], the heat collecting amount Qi for one minute is 226,800 [J] (which equals to 5 D 3,600 E 1,050 0 0.0002 E 60). 5 Consequently, the rotation speed of the circulating pump P is controlled according to the capability of the circulating pump P (relationship between the rotation speed and the power consumption) that is stored in the ROM such that the power consumption Ri becomes smaller than the calculated heat collecting amount Qi. With this arrangement, the circulating pump P is actuated by the power consumption Ri which is smaller than the io heat collecting amount Qi supplied to the stored hot water tank 2 from the heating medium heated by the solar heat, and therefore it is possible to perfonn the efficient heat-collecting operation. During the heat-collecting operation, the hot water temperature in the stored hot water tank 2 increases, and the temperature difference (Tin-Tout) between the inlet-side heating medium temperature Tin and the outlet-side is heating medium temperature Tout becomes smaller. Therefore, the heat collecting amount Qi decreases, resultantly the rotation speed of the circulating pump P decreases, and the power consumption Ri decreases. However, as far as the collecting heat amount Qi is equal to or larger than the minimum power consumption Rmin consumed by actuating the circulating pump P at the minimum rotation speed, actuation of the 20 circulating pump P by the minimum power consumption Rmin is maintained. When the rotation speed of the circulating pump P is controlled based on the heat collecting amount Qi, the control device 10 stores the calculated heat collecting amount Qi and the power consumption Ri of the circulating pump P (step ST12), compares heat collecting amount Qi with the power consumption Ri, and outputs a difference 25 therebetween to the remote controller 4 at predetermined intervals as an effective heat 19 collecting amount Ei (step ST13). With this, the user can recognize an actual saved amount of energy achieved by the heat-collecting operation. Next, the control device 10 determines whether the hot water temperature outputted from the stored hot water tank thermistor 20c provided at the uppermost portion s in the stored hot water tank 2 is equal to or higher than a hot water output forbidden temperature Th (for example, 60*C) (step ST14). If the temperature of the water is equal to or higher than the hot water output forbidden temperature Th (Yes in step ST14), the circulating pump P is stopped preventing supply of the hot water in high temperature by the continuity of the heat-collecting operation (step ST16). 10 On the other hand, if the hot water temperature in the stored hot water tank 2 is lower than the hot water output forbidden temperature Th (No in step ST 14), the process returns to step ST8, a heat collecting amount Qi+1 for the next predetermined period is calculated in a manner similar to the foregoing, and the heat-collecting operation is continued. 15 During the heat-collecting operation, if the calculated heat collecting amount Qi is smaller than the minimum power consumption Rmin consumed by actuating the circulating pump P at the minimum rotation speed (No in step ST10), the control device 10 compares an integrated heat collecting amount 1Qi obtained by summing up the latest predetermined number (for example, five times) of heat collecting amounts Qi with an 20 integrated power consumption IRi obtained by summing up the latest predetermined number of power consumptions Ri of the circulating pump P, and determines whether or not the integrated heat collecting amount IQi is equal to or larger than the integrated power consumption IRi (step ST15). If the integrated heat collecting amount XQi is equal to or larger than the integrated power consumption IRi (Yes in step ST15), the 25 process returns to step ST8, and the heat-collecting operation is continued. Specifically, the heating medium temperature of the heating medium heated by the solar heat collector 20 1 may decrease briefly due to a temporary cloudy weather. In such a case, even if the circulating pump P is stopped based on the decrease of the heat collecting amount Qi for a short period of time, it is necessary to actuate the circulating pump P again after the weather changes from cloudy to clear sky and the heat collecting amount increases. s From this point of view, if the continuity of heat-collecting operation is determined based on only a single heat collecting amount Qi, it is necessary to actuate and stop the circulating pump P frequently. In contrast, according to the process above, even if the heat collecting amount Qi is smaller than the minimum power consumption Rmin, it is possible to perform a smooth heat-collecting operation since the circulating pump P is io continuously actuated as far as the integrated heat collecting amount EQi is equal to or larger than the integrated power consumption Ri. If the integrated heat collecting amount EQi is smaller than the integrated power consumption Ri (No in step ST15), the control device 10 stops the circulating pump P and aborts the heat-collecting operation since it can be determined that heat collecting by the solar heat collector 1 is not 15 sufficiently performed for a certain period of time. Other Embodiments i) In the above-described embodiment, the solar heat collector only has the heat collector panel. However, a solar heat collector may have a collector panel and a power generation panel such as a solar cell panel. According to this configuration, it is possible 20 to more save energy. ii) In the above-described embodiment, when the heat collecting amount is smaller than the minimum power consumption consumed by actuating the circulating pump at the minimum rotation speed, the control device further compares the integrated heat collecting amount with the integrated power consumption, and determines whether the 25 heat-collecting operation should be continued. However, the control device may stop 21 the circulating pump without comparing the integrated heat collecting amount with the integrated power consumption. iii) In the above-described embodiment, the heating medium is only heated by the solar heat collector. However, an electric heater or a heat exchanger for heating a 5 heating medium circulation pipe line may be provided near the heating medium circulation pipe line. As describe above in detail, according to one aspect of the present invention, there is provided a solar heat-utilizing hot water supply system comprising: a solar heat collector for heating a heating medium by utilizing solar heat; 10 a stored hot water tank for storing hot water; a heating medium circulation pipe line including an inlet side-heating medium circulation pipe line for feeding the heating medium from the solar heat collector to the stored hot water tank, a heat exchanger provided in the stored hot water tank, and an outlet side-heating medium circulation pipe line for returning the heating medium from is the stored hot water tank to the solar heat collector; a circulating pump for circulating the heating medium in the heating medium circulation pipe line; a heat collector side-heating medium temperature sensor provided near the solar heat collector in the inlet side-heating medium circulation pipe line or in the outlet 20 side-heating medium circulation pipe line; an inlet side-heating medium temperature sensor provided near the stored hot water tank in the inlet side-heating medium circulation pipe line; an outlet side-heating medium temperature sensor provided near the stored hot water tank in the outlet side-heating medium circulation pipe line; 25 a heating medium flow meter for measuring a heating medium flow rate in the heating medium circulation pipe line; 22 a supply water temperature sensor provided near an inlet port of the stored hot water tank; and a control device for controlling a heat-collecting operation by the solar heat collector, wherein 5 the control device actuates the circulating pump to start the heat-collecting operation when a temperature difference (TmO-TwO) between a heat collector side-heating medium temperature TmO detected by the heat collector side-heating medium temperature sensor and a supply water temperature TwO detected by the supply water temperature sensor is equal to or larger than a predetermined starting temperature 10 TnO, and the control device controls, during the heat-collecting operation, a rotation speed of the circulating pump such that a heat collecting amount [(Tin-Tout) O V 0 C E d] to be supplied from the heating medium to the stored hot water tank is equal to or larger than a power consumption required to actuate the circulating pump, the heat collecting amount is being determined from a product of (Tin-Tout) representing a temperature difference between an inlet side-heating medium temperature Tin detected by the inlet side-heating medium temperature sensor and an outlet side-heating medium temperature Tout detected by the outlet side-heating medium temperature sensor, V representing the heating medium flow rate detected by the heating medium flow meter, C representing a specific heat of the 20 heating medium, and d representing a specific gravity of the heating medium. According to the solar heat-utilizing hot water supply system above, since the heat collector side-heating medium temperature sensor is provided near the solar heat collector, it is possible to quickly detect increase in the heating medium temperature by the heat collection of the solar heat collector. Also, since the heat-collecting operation is 25 started when the temperature difference (TmO-TwO) between the heat collector-side heating medium temperature TmO detected by the heat collector-side heating medium 23 sensor provided near the solar heat collector and the supply water temperature TwO detected by the supply water sensor provided near the inlet port of the stored hot water tank is equal to or larger than the predetermined starting temperature TnO, it is possible to avoid a heat-collecting operation that is uneconomical in terms of energy. Further, it is 5 possible to prevent decrease in the hot water temperature in the stored hot water tank due to the heat-collecting operation in winter season, as the heating medium temperature is lower than the supply water temperature. Furthermore, according to the solar heat-utilizing hot water supply system above, since the heat collecting amount is obtained by utilizing the temperature difference io (Tin-Tout) between an inlet side-heating medium temperature Tin detected by the inlet side-heating medium temperature sensor and an outlet side-heating medium temperature Tout detected by the outlet side-heating medium temperature sensor, and the heating medium flow rate V detected by the heating medium flow meter during the heat-collecting operation, it is possible to accurately calculate the heat collecting amount is supplied into the stored hot water tank by the heating medium without using the temperature of the hot water having a small change in temperature inside the stored hot water tank, or without using a highly accurate flow meter. In addition, since the rotation speed of the circulating pump is controlled such that the power consumption becomes smaller than the calculated heat collecting amount, it is possible to perform the efficient 20 heat-collecting operation and to save energy. Preferably, in the solar heat-utilizing hot water supply system above, the control device stops the circulating pump if, after elapse of a predetermined time from the start of the heat-collecting operation, a temperature difference (Tm1-Twl) between an initial heat collector side-heating medium temperature TmI detected by the heat collector-side 25 heating medium temperature sensor and an initial supply water temperature TwI detected 24 by the supply water temperature sensor is smaller than a predetermined continuous operating temperature Tnl. Since the solar heat collector is installed outdoor and the heating medium circulation pipe line connecting the solar heat collector to the stored hot water tank has a 5 certain length, the heating medium temperature in the heating medium circulation pipe line near the stored hot water tank is usually lower than the heat collector side-heating medium temperature. Therefore, even if the temperature difference (Tm0-Tw0) between the heat collector side-heating medium temperature TmO near the solar heat collector and the supply water 10 temperature TwO is equal to or larger than the predetermined starting temperature TnO and the heat-collecting operation is started, the heating medium temperature may decrease to a level insufficient for performing the efficient heat-collecting operation in accordance with the circulation of the heating medium. On the other hand, according to the solar heat-utilizing hot water supply system is above, the control device compares the initial heat collector side-heating medium temperature Tml with the initial supply water temperature TwI after elapse of the predetermined time from the start of the heat-collecting operation, and stops the circulating pump if the temperature difference (Tml-Twl) is smaller than the predetermined continuous operating temperature Tnl. Accordingly, it is possible to 20 abort, at an early stage, the heat-collecting operation which is uneconomical in terms of energy. Preferably, the solar heat-utilizing hot water supply system above further comprising: a bypass line for bypassing the inlet side-heating medium circulation pipe line and the 25 outlet side-heating medium circulation pipe line, 25 a first on-off valve for communicating or cutting off a flow of the heating medium to flow into the stored hot water tank, the first on-off valve being provided to the bypass line closer to a side of the stored hot water tank than a connecting portion connecting the bypass line to the inlet side-heating medium circulation pipe line or the 5 outlet side-heating medium circulation pipe line; and a second on-off valve for communicating or cutting off a flow of the heating medium to flow in the bypass line, the second on-off valve being provided to the bypass line, wherein the control device, upon the start of the heat-collecting operation, switches a io heating medium circulation path by closing the first on-off valve and opening the second on-off valve such that the heating medium does not flow into the stored hot water tank but flows in the bypass line, the control device, after the heating medium circulation path is switched, further switches the heating medium circulation path by opening the first on-off valve such that is the heating medium flows into in the stored hot water tank and continues the heat-collecting operation, if the temperature difference (Tml-Twl) between the initial heat collector side-heating medium temperature Tml and the initial supply water temperature Tw 1 is equal to or larger than the predetermined continuous operating temperature Tn1, and 20 the control device stops the circulating pump if the temperature difference (Tml -TwI) between the initial heat collector side-heating medium temperature Tml and the initial supply water temperature TwI is smaller than the predetermined continuous operating temperature Tnl. According to the solar heat-utilizing hot water supply system above, since the 25 heating medium circulation path is switched upon the start of the heat-collecting operation in such a manner that the heating medium does not flow into the stored hot 26 water tank but flow in the bypass line, the heating medium circulates through the heating medium circulation pipe line in a state in which the heating medium is not subjected to the heat exchange with supplied water in the stored hot water tank. Accordingly, a change in the heating medium temperature in the heating medium circulation pipe line s can be reduced, and it is possible to determine whether the heating medium has a temperature for performing the efficient heat-collecting operation at an early stage. Further, if the temperature difference (Tm I -Tw 1) between the initial heat collector side-heating medium temperature Tml and the initial supply water temperature Tw I is equal to or larger than the predetermined continuous operating temperature Tn 1, in to the state in which the heating medium does not flow into the stored hot water tank but flow in the bypass line, the heating medium circulation path is again switched in such a manner that the heating medium flows into the stored hot water tank, and the heat-collecting operation is continued. Accordingly, the circulating pump is not stopped, so that the heat-collecting operation can be smoothly continued. is On the other hand, if the temperature difference (Tm1 -Twl) between the initial heat collector side-heating medium temperature Tml and the initial supply water temperature TwI is smaller than the predetermined continuous operating temperature Tnl, in the state in which the heating medium does not flow into the stored hot water tank but flow in the bypass line, the circulating pump is stopped, so that it is possible to abort, at 20 an early stage, the heat-collecting operation which is uneconomical in terms of energy. Preferably, in the solar heat-utilizing hot water supply system above, the control device stops the circulating pump if the heat collecting amount is smaller than a minimum power consumption consumed by actuating the circulating pump at a minimum rotation speed. 25 According to the solar heat-utilizing hot water supply system above, since the circulating pump is stopped if the heat collecting amount is smaller than the minimum 27 power consumption of the circulating pump, it is possible to avoid the heat-collecting operation under weather as the solar heat can not be sufficiently obtained. Preferably, in the solar heat-utilizing hot water supply system above, the control device stops the circulating pump if the heat collecting amount is smaller than a minimum 5 power consumption consumed by actuating the circulating pump at a minimum rotation speed and an integrated heat collecting amount obtained by integrating a predetermined number of heat collecting amounts is smaller than an integrated power consumption obtained by integrating the predetermined number of power consumptions. According to the solar heat-utilizing hot water supply system above, if the heat io collecting amount during the heat-collecting operation is smaller than the minimum power consumption consumed by actuating the circulating pump at a minimum rotation speed and the integrated heat collecting amount is smaller than the integrated power consumption, the circulating pump P is stopped. On the other hand, if the heat collecting amount for a short period is smaller than the minimum power consumption due to a 15 temporary cloudy weather but the integrated heat collecting amount is equal to or larger than the integrated power consumption, the circulating pump is not stopped. Accordingly, it is possible to avoid actuate and stop the circulating pump frequently. Although the present invention has been described in detail, the foregoing descriptions are merely exemplary at all aspects, and do not limit the present invention 20 thereto. It should be understood that an enormous number of unillustrated modifications may be assumed without departing from the scope of the present invention.