1 DESCRIPTION TITLE OF THE INVENTION: COOLING SYSTEM TECHNICAL FIELD [0001] 5 The present invention concerns a cooling system for cooling a heating medium utilizing solar heat, and particularly relates to a cooling system permitting optimal control that energy saving and operating cost reduction are taken into account. D BACKGROUND ART [0002] There exist techniques disclosed in Patent Document 1 and Patent Document 2 as thermal collecting systems utilizing solar heat. In the technique of Patent Document 1, there are provided 5 a solar thermal collector for collecting solar heat energy and giving the collected solar energy to a heating medium, a first heat exchanger for performing heat exchange between the heating medium which has been made high in temperature with heat collected by the solar thermal collector and supply water transferred from a water supply tank, and a second heat exchanger for performing heat exchange between the supply water which has been made high in temperature by the heat exchange in this heat exchanger and a high-temperature working medium, and heating the supply water with the working medium concerned to generate vapor for process use.
2 [0003] In the technique of Patent Document 2, there is presented an absorption cooling and heating device which has a solar thermal collecting tube for directly introducing and heating a diluted absorbent and a flushing regenerator for concentrating the absorbent heated by the solar thermal collecting tube by flushing it in order to promote more stable air conditioning effect and miniaturization by utilizing solar heat directly to heat and concentrate the absorbent to make it possible to operate with no need of a heat source for heating a regenerator such as a burner or the like, and sensing a state of the absorbent heated with solar heat which changes in accordance with weather conditions or the like to automatically operate an auxiliary regenerator. PATENT DOCUMENT [0004] Patent Document 1: Japanese Patent Application Laid-Open No. S63-183346 Patent Document 2: Japanese Patent Application Laid-Open No. 2001-82823 [0005] 3 However, in Patent Document 1, although it is of the type that solar heat in the daytime is utilized for generating vapor for process use and of the type that the fuel (gas) cost of a hot water boiler is saved by making hot water by the hot water 5 boiler in bad weather and in the nighttime, it does not concern optimal control for saving the operating cost of the entire system that the fuel cost and the cost of electricity of a pump and the like are summed up. [0006] ) In addition, in Patent Document 2, since the absorbent such as lithium bromide or the like is heated by making it flow within piping as a heating medium, a large quantity of absorbent is required, handling and management thereof are troublesome and the cost rises. In addition, if boiling occurs on the 5 absorbent when heated, it will be feared that the pressure be abnormally increased to induce a backward flow and temperature management will become difficult. Then, in a case where the temperature of the absorbent heated in the solar thermal collecting tube is low, it is heated by the heat source such as the burner or the like as in Patent Document 1. However, it does not concern optimal control for saving the operating cost of the entire system that the fuel cost of the burner or the like and the cost of electricity of the pump or the like are summed up. [0007] 4 OBJECT OF THE INVENTION It is the object of the present invention to substantially overcome or at least ameliorate one or more of the foregoing disadvantages. SUMMARY OF THE INVENTION [0008] The present invention provides A cooling system for cooling a heating medium load, comprising: a solar thermal collector for collecting heat energy of the sun; an absorption refrigerator for using heat collected by the solar thermal collector as driving energy; an outside air condition detecting means for detecting an outside air condition of a specific enthalpy of outside air or a wet-bulb temperature of outside air; a direct solar irradiance amount detecting means for detecting a direct solar irradiance amount of the sun; a load detecting means for detecting a cooling load of a heating medium; a thermal collector pressure detecting means for detecting the pressure of the solar thermal collector; a thermal collector pressure adjustment means for adjusting the pressure inside the solar thermal collector; and a controller for controlling the solar thermal collector, the absorption refrigerator, the outside air condition detecting means, the direct irradiance amount detecting means, the load detecting means, the thermal collector pressure detecting means and the thermal collector pressure adjustment means,wherein the controller has a database which stores the pressure inside the solar thermal collector as a set value obtained by repetitively performing calculation by changing a control target value using 5 simulation under which the running cost of the entire system is minimized in advance, wherein the above database is a control table that when the outside air condition, the direct solar irradiance amount of the sun and the cooling load are determined, the set value of the pressure at least inside the solar thermal collector is obtained, and the controller changes the pressure inside the solar thermal collector in accordance with the outside air condition, the direct solar irradiance amount of the sun and the cooling load detected. [0009] [INTENTIONALLY LEFT BLANK] [0010] [INTENTIONALLY LEFT BLANK] [0011] [INTENTIONALLY LEFT BLANK] [0012] Preferably, the above controller extracts the set value of the pressure inside the above solar thermal collector from the above control table in accordance with the outside air condition, the direct solar irradiance amount of the sun and the cooling load detected by the above and controls the pressure inside the solar thermal collector to this set value. [0013] Preferably, calculation is repetitively performed by changing control target values of the outside air condition, the direct solar irradiance amount of the sun and the cooling load using simulation, and the number of the refrigerators in operation and the pressure inside the solar thermal collector with which the running cost of the entire system is minimized are stored as set values in the above database.
6 [0014] Preferably, the cooling system further includes a cooling tower for cooling water into the above absorption refrigerator; and a cooling water pump which is driven by an inverter or a fan for the cooling tower which is driven by an inverter, wherein further the number of the above absorption refrigerators in operation and the frequencies of the above respective inverters with which the running cost of the entire system is minimized are stored as set values in the above database. [0015] According to an embodiment of the present invention, it becomes possible to reduce the consumed energy cost when running the cooling system for cooling the heating medium using solar heat as the energy source. BRIEF DESCRIPTION OF THE DRAWINGS [0016] [Fig. 1] Fig. 1 is a configuration diagram of a system according to an embodiment of the present invention. [Fig. 2] Fig. 2 is an imaginative diagram for obtaining an optimal set value similarly. [Fig. 3] Fig. 3 is a concrete configuration diagram of a database similarly. [Fig. 4] Fig. 4 is a flowchart of a database preparing method.
7 [Fig. 5] Fig. 5 is a flowchart of simulation calculation of Fig. 4. [Fig. 6] Fig. 6 is an operational flowchart showing an optimizing control operation.
8 [Fig. 7] Fig. 7 is a relationship diagram between vapor pressure and maximum refrigerating capacity of an absorption refrigerator. 5 [Fig. 8] Fig. 8 is a relationship diagram between vapor pressure and thermal collecting efficiency of a solar thermal collector. BEST MODE FOR CARRYING OUT THE INVENTION [0017] ) In the following, an embodiment of the present invention will be described in detail using the drawings. Fig. 1 is a system configuration diagram of a cooling system which is the embodiment. 1 is a solar thermal collector within which water flows as a heating medium, water which has been led into it 5 through a lower inlet is heated with solar heat and is led out through an upper outlet as a fluid mixture of a liquid (hot water) with a gas (vapor). The fluid mixture of the liquid with the gas flows into a gas-liquid separator 2 and is separated into the liquid and the gas. 80 is a controller for executing control which will be described hereinafter with respect to the entire system. [0018] A temperature sensor 212 is a sensor for measuring the temperature at the outlet of the solar thermal collector 1, and a pressure sensor 232 is a sensor for measuring the pressure 9 at the outlet of the solar thermal collector 1. A pressure regulating valve 272 is a pressure regulating valve for controlling such that the pressure at the outlet of the solar thermal collector 1 reaches a command value from the controller 5 80. The pressure regulating valve 272 is regulated by a PID controller 252 in accordance with a measured value of the pressure sensor 232 and a command from the controller 80. Thereby, the vapor pressure inside the solar thermal collector 1 is controlled. 3 [0019] 201 is a temperature sensor for the separated gas, 231 is a pressure sensor for the separated gas, and 202 is a temperature sensor for a return liquid to an absorption refrigerator (described later). In the controller 80, the 5 collected heat amount of solar heat collected by the above-mentioned solar thermal collector 1 is calculated on the basis of measured values of the temperature sensors 201 and 202, and the pressure sensor 231. [0020] 250 is a pyrheliometer (a direct solar irradiance amount detecting means) for measuring the direct solar irradiance amount of the sun (the solar irradiance amount only from the range of the sun's photosphere, obtained by measuring direct sunlight). Incidentally, the direct solar irradiance amount may be estimated from the global solar irradiance amount 10 measured by a pyranometer. [0021] 3 is a pump for sending water (the heating medium) of the liquid separated by the gas-liquid separator 2 to the 5 above-mentioned solar thermal collector 1 and driven by an inverter 103. The flow rate of the heating medium flowing into the solar thermal collector 1 is controlled by changing the frequency of the inverter 103. The heating medium flowing into the solar thermal collector 1 is controlled to efficiently take 0 in the heat amount such that the flow rate is increased when the collected heat amount is large and the flow rate is reduced when the collected heat amount is small. [0022] 31, 32 and 33 are absorption refrigerators and the vapor 5 separated by the above-mentioned gas-liquid separator 2 is utilized as their driving energy. 4 is a boiler 4 in which the vapor is produced with the fuel (the gas) and which operates when the amount of vapor produced with solar heat is smaller than the amount of vapor required in the absorption refrigerators 31 to 33 to produce a shortage of the vapor. [0023] 10 is a cooling tower arranged side by side in plural and for cooling cooling water of the above-mentioned absorption refrigerators 31 to 33. 10a is a fan of each cooling tower and the air flow is changed by changing its rotational frequency 11 by an inverter 110, and thereby the temperature of cold water is controlled. [0024] 21 to 23 are cooling water pumps for respectively sending 5 cooling water to the above-mentioned absorption refrigerators 31 to 33 and driven by inverters 121 to 123 for changing the flow rates of respective streams of the cooling water. [0025] 41, 42 and 43 are cold water pumps for sending cold water D from a cold water tank 50 (described later) respectively to the above-mentioned absorption refrigerators 31 to 33, and the respective pumps are controlled in cold water flow rate respectively by inverters 141 to 143. [0026] 5 50 is the cold water tank in which the cold water cooled by the above-mentioned absorption refrigerators 31 to 33 is stored. The cold water in this cold water tank 50 is sent to a load which is the heating medium by a cold water secondary pump 60 and returns to the cold water tank 50 in a state of being heated by consumption of cold heat in the load 70. 203 and 204 are respectively temperature sensors of an inlet and an outlet of the load 70, and 221 is a flow rate sensor. The cooling load of the load 70 is calculated on the basis of measured values of the above-mentioned temperature sensors 203 and 204 and the flow rate sensor 221. An inverter 160 for 12 changing the flow rate of the cold water to be sent to the load 70 is connected to the cold water secondary pump 60. [0027] Drive of the cold water secondary pump 60 is controlled 5 such that a difference in temperature between the temperature sensor 203 and the temperature sensor 204 is fixed with the frequency of the inverter 160. In addition, the inverters 141 to 143 are controlled such that the total flow rate of the cold water sent to the absorption refrigerators 31 to 33 becomes the D same as the flow rate of the cold water sent to the load 70 by the cold water secondary pump 60. Incidentally, since the frequencies of the inverters 141 to 143 and the flow rates of the cold water sent to the absorption refrigerators 31 to 33 have a f ixed relationship (an almost proportional relationship) , 5 that relationship is obtained in the controller 80 in trial operation and the frequencies are controlled with that relationship. In addition, at that time, a relationship between the frequencies of the inverters 141 to 143 and the power consumptions of the cold water pumps 41 to 43 is also obtained in the controller 80. [0028] 205 is a temperature sensor for measuring the temperature of outside air, and 211 is a humidity sensor for measuring the humidity of outside air. The wet-bulb temperature (an outside air condition) of outside air is calculated on the basis of 13 measured values of the temperature sensor 205 and the humidity sensor 211. Incidentally, although description is made in terms of the wet-bulb temperature here, since the wet-bulb temperature and the specific enthalpy have a fixed relationship, 5 the specific enthalpy may be used as the outside air condition in place of the wet-bulb temperature. [0029] In the present embodiment, the collected heat amount of the solar thermal collector 1 is detected from the measured values of the temperature sensor 201, the temperature sensor 202, the pressure sensor 231 and the flow rate sensor 222, the cooling load is detected from the measured values of the temperature sensor 203, the temperature sensor 204 and the flow rate sensor 221, and the wet-bulb temperature of outside air 5 is detected from the measured values of the temperature sensor 205 and the humidity sensor 211. Then, the pressure of the solar thermal collector 1, the number of the absorption refrigerators 31, 32 and 33 in operation, the frequency of the inverter 110 of the fans of the cooling towers 10, and the frequencies of the inverters 121 to 123 of the cooling water pumps 21 to 23 are obtained from a database (a control table or an approximate curve or the like) 80a which is stored in advance in the controller 80, in accordance with the direct solar irradiance amount, the outside air wet-bulb temperature (the outside air condition) and the cooling load which have been detected, and 14 values thereof are sent to the respective devices to control them. [0030] A relationship between vapor pressure and maximum refrigerating capacity of the absorption refrigerators 31 to 33 is shown in Fig. 7. The absorption refrigerators 31 to 33 have such characteristics that the higher the vapor pressure is, the more the maximum refrigerating capacity is increased. This is because since the higher the vapor pressure is, the higher the vapor temperature is, a large amount of heat can be heat-exchanged by heat exchangers of regenerators of the absorption refrigerators 31 to 33. [0031] In addition, a relationship between vapor pressure and 5 thermal collecting efficiency of the solar thermal collector 1 is shown in Fig. 8. In the solar thermal collector 1, since the higher the vapor pressure is, the higher the vapor temperature is, the surface temperature of the solar thermal collector 1 rises, the amount of heat radiated to the outside is increased, the loss is increased and the thermal collecting efficiency is lowered. Therefore, since the lesser the vapor pressure is, the higher the thermal collecting efficiency of the solar thermal collector 1 is, the collected heat amount of solar heat is increased. [0032] 15 However, as described above, since the lesser the vapor pressure is, the lesser the maximum refrigerating capacity of the absorption refrigerators 31 to 33 becomes, the amount of heat of vapor which can be utilized in the absorption 5 refrigerators 31 to 33 is lessened. Thus, in a case where the amount of heat of the vapor generated by the solar thermal collector 1 is larger than the maximum amount of the amount of heat of the vapor which can be utilized in the absorption refrigerators 31 to 33, it is necessary to discard the vapor. 0 [0033] In the present embodiment, an optimal vapor pressure is calculated by simulation so as to set a vapor pressure with no waste in consideration of such matters and the cooling system is controlled with a set value thereof. A method of calculating 5 the optimal vapor pressure using simulation will be described later. [0034] Fig. 2 is a diagram showing an image of extracting the set value. After the outside air wet-bulb temperature (the Y-axis), the cooling load (the X axis) and the direct solar irradiance amount (the Z axis) of the sun have been determined, the set value of a black circle part of an intersection point of broken lines is determined and the cooling system is controlled with that value. [0035] 16 Fig. 3 is a diagram showing a concrete configuration of a control table 80a. The control table 80a is a table of the type that when the outside air wet-bulb temperature, the cooling load and the direct solar irradiance amount are determined, the 5 set value is determined. The outside air wet-bulb temperature (the specific enthalpy of the outside air) and the cooling load are plotted on the horizontal axis, the direct solar irradiance amount of the sun is plotted on the vertical axis and three kinds of set values are provided on their intersection point. 0 [0036] The three kinds of set values 80b are the number of the absorption refrigerators 31 to 33 in operation, the frequency of the inverter 110 of the fans of the cooling towers 10, the frequencies of the inverters 121 to 123 of the cooling water 5 pumps 21 to 23, and the vapor pressure of the solar thermal collector 1. The above-mentioned set values 80b are not intermediate set values for controlling the system, but final set values with which the system can be directly controlled. Therefore, since the inverters and the pressure regulating D valve can be directly controlled without converting the extracted set values, a response of control is good. [0037] As for the above-mentioned set values 80b, the power consumption and the gas consumption of the entire system when 5 the collected heat amount of the sun, the outside air wet-bulb 17 temperature (the outside air condition) and the cooling load are changed are calculated in advance by later described simulation calculation, and then values with which the operation energy costs (the running cost) is minimized are 5 obtained from the consumptions and unit prices. [0038] Fig. 4 is a flowchart showing a method of generating the control table 80a. The flowchart in Fig. 4 is a flowchart for determining the set values at one black circle point shown in D Fig. 2, or one point (one intersecting section) shown in Fig. 3. Set values at all points (sections) are determined by repetitively calculating this flowchart. Although in the present embodiment, the operation energy cost is described as an evaluation function, other evaluation functions may be used. 5 [0039] In step 401 in Fig. 3, the direct solar irradiance amount, the outside air wet-bulb temperature and the cooling load corresponding to one point which is to be determined in the control table 80a are input. Then, through step 402 to step 405, respective combinations of the vapor pressure of the solar thermal collector 1, the operable number of the absorption refrigerators 31 to 33 in operation, the frequency of the inverter 110 of the cooling tower 10, and the frequencies of the inverters 121 to 123 of the cooling water pumps 21 to 23 i are sequentially set, and when calculation of all the 18 combinations is terminated, the process shifts from step 405 to step 407. Incidentally, it is supposed that the frequencies of the inverters 110, and 121 to 123 are values set at certain fixed intervals. 5 [0040] In step 403, the direct solar irradiance amount, the outside air wet-bulb temperature, the cooling load, the number of the refrigerators in operation, the frequency of the inverter 110 of the cooling tower 10, and the frequencies of the inverters 3 121 to 123 of the cooling pumps 21 to 23 are input to calculate the power consumption and the gas consumption of the entire system by simulation calculation. A simulation calculation method in step 403 will be described in detail later. [0041] 5 In step 404, calculation and comparison of the evaluation function are performed. First, the running cost which is the evaluation function is calculated using an electricity unit price and a gas unit price. Next, comparison of the evaluation function is performed. In a case where a value of the evaluation function is not stored (a first calculation) , the combination of the number of the refrigerators in operation and the frequencies of the inverters 110, and 121 to 123 and the value of the evaluation function at that time are stored. In a case where the value of the evaluation function is stored (second and succeeding), when a value of the evaluation function which 19 has been calculated this time is smaller in comparison with the stored evaluation function, the combination of the number of the refrigerators in operation and the frequencies of the inverters 110, and 121 to 123 and the value of the evaluation 5 function at that time are update stored, while when it is larger, it is left as it is (not update stored). [0042] At the completion of calculation of all settings, in step 407, the combination of the number of the refrigerators in operation and the frequencies of the inverters 110, and 121 to 123, and the vapor pressure of the solar thermal collector 1 when the evaluation function which has been compared in step 404 is minimized (the running cost is minimized) are stored in the control table 80a in Fig. 3. 5 [0043] Fig. 5 is a flowchart of simulation that the inside of step 403 in Fig. 4 is described in detail. The power consumption and the gas consumption are obtained by simulation in Fig. 5 and the running cost is calculated using the electricity and gas unit prices. [0044] In Fig. 5, instep 500, the direct solar irradiance amount, the outside air wet-bulb temperature, the cooling load, the number of the refrigerators in operation, the frequency of the inverter 110 of the cooling tower 10, the frequencies of the 20 inverters 121 to 123 of the cooling water pumps 21 to 23, and the vapor pressure inside the solar thermal collector 1 are input. [0045] In step 501, the collected heat amount of solar heat is calculated from the direct solar irradiance amount of the sun and the vapor pressure of the solar thermal collector 1. Although the vapor pressure and the thermal collecting efficiency of the solar thermal collector are shown in Fig. 7, such a relationship (the higher the vapor pressure is, the lesser the thermal collecting efficiency becomes in the solar thermal collector 1) is also used in calculation in step 501. [0046] In step 502, the power consumptions of the cold water pumps are calculated. The flow rates of the cold water pumps 41 to 43 are obtained from the cooling load and the number of the refrigerators 31 to 33 in operation, and the frequencies of the inverters 141 to 143 are obtained from these flow rates, and the power consumptions of the cold water pumps 41 to 43 are obtained from these frequencies. [0047] In step 503, the power consumptions and the cooling water flow rates of the cooling water pumps are calculated. The flow rates of cold water flowing through the refrigerators 31 to 33 and the power consumptions of the cooling water pumps 21 to 23 21 are calculated from the number of the refrigerators 31 to 33 in operation and the frequencies of the inverters 121 to 123. Incidentally, since a fixed relationship is present among the inverter frequencies, the flow rates and the power consumptions, they are obtained in trial operation. Alternatively, they may be obtained using a law that the characteristic curve of a pump and a resistance characteristic of a passage, and the flow rate, the lifting height and the electric power of that pump are respectively proportional to the first power, the second power and the third power of the frequency of its inverter. In the following, since in calculation of the inverter frequency, the flow rate, the power consumption and others of the pump, they are calculated by the same method, description thereof will be omitted. [0048] In step 504, the supply temperature of cooling water is set. Here, it is supposed that the supply temperature of cooling water is a temperature which is lower in temperature of the cooling water and a higher temperature is called the return temperature of the cooling water. [0049] In step 505, the vapor consumptions and the power consumptions of the absorption refrigerators 31 to 33 and the return temperature of the cooling water are obtained. The vapor consumptions of the absorption refrigerators 31 to 33 are 22 determined each by the cooling water supply temperature, the cooling water flow rate, the cooling load, the cold water supply temperature, and the cold water flow rate. A relational expression thereof is obtained by cycle simulation and calculation is performed utilizing this relational expression. Alternatively, in a case where a manufacturer of the absorption refrigerators opens the relational expression to the public, that relational expression is used. Alternatively, the relational expression may be previously obtained by actual measurement. Since as for the power consumption, it is almost fixed, it is measured in trial operation and that value is used. Then, the return temperature of the cooling water is obtained from heat balance. [0050] In step 506, calculation of the power consumption and the cooling water supply temperature of the cooling tower 10 is performed. First, the air flow and the power consumption of the cooling tower fan are calculated from the frequency of the inverter 110. Since there exists a fixed relationship among them, they are obtained in advance in trial operation. Alternatively, they may be calculated from a law that the air flow, the power consumption and the flow rate, and the electric power at a rated inverter frequency are respectively almost proportional to the first power and the third power of the 5 inverter frequency.
23 [0051] Next, the supply temperature of the cooling water is calculated from the return temperature of the cooling water calculated in step 505, the flow rate of the cooling water, the wet-bulb temperature of outside air and the air flow of the cooling tower fan calculated in step 504. Here, description thereof is omitted because it is stated in a literature such as Manual or the like as a calculation method utilizing the enthalpy-based overall volume heat transfer coefficient. [0052] When calculations in steps 505 and 506 are repeated several times, the supply temperature and the return temperature of the cooling water show no change and converge. Therefore, converge test is performed in step 507, and when they converge, the process shifts to step 508. [0053] In step 508, the gas consumption of the boiler is calculated. The amount of vapor to be generated in the boiler is calculated by taking a difference between the amount of vapor ) required in the absorption refrigerators which has been calculated in step 505 and the amount of vapor which can be generated from the collected heat amount of solar heat. Then, the gas consumption required for generation of that amount of vapor is calculated. [0054] 24 In step 509, the power consumptions of the pumps 3 and 5, and the cold water secondary pump 60 are calculated. Since the flow rate of water to be sent by the pump 5 can be calculated from the vapor amount, the inverter frequencies and the power consumptions at that time are calculated. In addition, since the flow rate of water to be sent to the solar thermal collector 1 is obtained from the collected heat amount of solar heat, the flow rate, the inverter frequency, and the electric power of the pump 3 at that time are calculated. In addition, since the flow rate of the cold water secondary pump 60 is obtained from the cooling load, the inverter frequency and the power consumption at that time are calculated. [0055] In step 510, the power consumptions and the gas consumptions calculated in steps 502 to 509 are respectively summed up. From the above, the operation energy consisting of the power consumption and the gas consumption of the entire system can be calculated. [0056] According to the present embodiment, it becomes possible to set the vapor pressure, the number of units in operations and the inverter frequencies with which the running cost (the operation energy cost) of the entire system is minimized in accordance with the states of the outside air, the sun and the load.
25 [0057] In addition, although the case where there exists the pyrheliometer has been described in the present embodiment, in absence of the pyrheliometer, the collected heat amount of the solar thermal collector 1 may be obtained by the flow rate sensor 222, the temperature sensors 201 and 202, and the pressure sensor 231, the vapor pressure at the outlet of the solar thermal collector 1 may be measured from the pressure sensor 232, and the direct solar irradiance amount may be calculated on the basis of these values and the characteristics of the thermal collecting efficiency of the solar thermal collector in Fig. 7. In this case, the above-mentioned respective parts configure a direct solar irradiance amount detecting means for detecting the direct solar irradiance amount. [0058] The controller 80 controls the operation of the cooling system on the basis of the control table 80a generated by the flowcharts in Fig. 4 and Fig. 5. Fig. 6 is an operational flowchart showing optimizing control of the entire system on the basis of the set values 80b in the above-mentioned control table 80a. [0059] First, as for the system which is in operation, measured values of the pyrheliometer 250, the temperature sensors 201, 202, 203, 204, 205 and 212, the flow rate sensors 221 and 222, 26 the humidity sensor 211 and the pressure sensor 231 are acquired in the controller 80 (step 730). [0060] Next, the direct solar irradiance amount is held by the 5 controller 80, the cooling load is calculated from the measured values of the temperature sensor 203, the temperature sensor 204 and the flow rate sensor 221, and the wet-bulb temperature of outside air is calculated from the measured values of the temperature sensor 205 and the humidity sensor 211 (step 731). 0 [0061] Next, the respective set values 80b corresponding to the wet-bulb temperature of outside air, the cooling load and the direct solar irradiance amount of the sun obtained in the aforementioned step 731 are extracted with reference to the 5 control table 80a in Fig. 3. As the set values, the number of the absorption refrigerators 31 to 33 in operation, the frequency of the inverter 110 of the fan 1Oa of the cooling tower 10, the frequencies of the inverters 121 to 123 of the cooling water pumps 21 to 23 and the vapor pressure of the solar thermal collector are extracted (step 732). Then, the respective extracted set values 80b are sent to the respective devices to control the operation of the system (step 733). [0062] As for the entire system, operation by which the running cost is minimized is executed by this control.
27 [0063] Incidentally, with respect to the collected heat amount of solar heat, the wet-bulb temperature of outside air and the cooling load, predicted values may be prepared from time-series 5 data obtained so far and may be used. DESCRIPTION OF REFERENCE NUMERALS [0064] 1... solar thermal collector, 2... gas-liquid separator, 4... boiler, 10... cooling tower, 10a... fan of the cooling tower, 21 3 to 23... cooling water pump, 31 to 33... absorption refrigerator, 70... cooling load, 80... controller, 80a... control table, 80b... set value, 110... inverter of the fan, 121 to 123... inverter of the cooling water pump, 201... temperature sensor for separated gas, 202... temperature sensor for liquid returned from the absorption 5 refrigerator, 231... pressure sensor for separated gas, 201, 202, 222, 231... collected heat amount detecting means, 205, 211... outside air condition detecting means, 212... thermal collector temperature sensor, 203, 204, 221... load detecting means, 232... thermal collector pressure detecting means, 250... pyrheliometer (direct solar irradiance amount detecting means), 272... thermal collector pressure adjusting means.