Hot water circulation system and agricultural facilities

Abstract

To provide a warm water supply circulation system attached to an agricultural greenhouse using a water heater.SOLUTION: A warm water circulation system uses, as a hot water supply source, a water heater group 120 having a plurality of water heaters 121; when returning to the water heater group 120 through a hot water pipe 110 in an agricultural greenhouse 200, adjusts a flow rate of water flowing through the water heater group 120; after discharging heated hot water, mixes it with hot water that has not passed through the water heater group 120; adjusts it to a predetermined circulation temperature; and then circulates it. Although a certain amount of hot water is always circulating through the hot water pipe 110 of a hot water circulation system 100 attached to the agricultural greenhouse 200, by controlling a flow rate of water flowing into the water heater group 120 depending on the temperature of hot water when returning to the water heater group 120, it is possible to adjust the number of operating water heaters 121, and adjust a predetermined circulation temperature with the minimum number of operating water heaters.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hot water circulation system that circulates hot water for heating the inside of an agricultural greenhouse, and an agricultural facility provided with this hot water circulation system.

Background Art

[0002] As shown in Patent Documents 1 and 2, a hot water circulation system is known in which hot water pipes are laid in passages between adjacent cultivation beds in an agricultural greenhouse (greenhouse) or the like, and heating is performed by passing hot water through the pipes. Patent Document 3 discloses a combined waste heat recovery and carbon dioxide supply system that uses a boiler as the heat source for the hot water supplied to the hot water pipes, cools the exhaust gas of the boiler with a heat exchanger, and supplies carbon dioxide into the greenhouse.

[0003] Conventionally, the hot water supply source of such a hot water circulation system uses a large-sized boiler (see Patent Document 2). Due to its large size, one unit is deployed for heating per agricultural greenhouse of a predetermined scale, and a boiler room is provided separately from the agricultural greenhouse. When both heating and carbon dioxide supply operations are performed, a separate boiler for carbon dioxide supply is additionally installed in addition to the heating boiler. Therefore, the conventional hot water circulation system requires securing a site separate from the agricultural greenhouse for installing the boiler room that houses one or more large-sized boilers, resulting in enormous costs such as site securing and boiler room construction expenses.

[0004] On the other hand, Patent Document 4 discloses a heating device in which a plurality of household heat pump water heaters are connected to a sub-tank having a predetermined volume, the water stored in the sub-tank is heated to a predetermined temperature, and hot water is supplied to pipes laid in the greenhouse. According to this technology, the above problems may be solved in that a large-sized boiler is not required.

[0005] Furthermore, Patent Documents 5 and 6 disclose a technology that increases the apparent hot water supply capacity by installing multiple water heaters in the same location, and that allows for labor savings in hotels, commercial facilities, etc., by adjusting the number of operating units according to the water flow rate to change the hot water supply capacity. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2001-346427 [Patent Document 2] Japanese Patent Publication No. 2000-262160 [Patent Document 3] Japanese Patent Publication No. 2004-344154 [Patent Document 4] Japanese Patent Publication No. 2013-215182 [Patent Document 5] Japanese Patent Application Publication No. 2-40446 [Patent Document 6] Japanese Patent Publication No. 2005-98638 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0007] As shown in Patent Documents 1-3, hot water circulation systems used in agricultural greenhouses are configured to circulate a constant amount of hot water between hot water pipes laid inside the greenhouse and a boiler. In the technology of Patent Document 4, even though the number of operating water heaters is adjusted according to the water temperature stored in a sub-tank, it cannot be directly applied to a hot water circulation system configured to circulate a constant amount of hot water as shown in Patent Documents 1-3. A sub-tank must be newly installed and the water heaters connected to this sub-tank. Since such a sub-tank cannot be connected to the hot water pipes in a sealed manner, the configuration with a sub-tank is open to the atmosphere, which can cause rust to form in the sub-tank and hot water pipes, potentially increasing the frequency of failures. Furthermore, although it is a standard function for this type of water heater to change the combustion efficiency according to the water temperature, if the number of operating units is controlled by detecting the water temperature in the sub-tank as in Patent Document 4, it is not possible to quickly and accurately control the temperature of the constantly circulating hot water. Furthermore, in the technology described in Patent Document 4, the number of water heaters that can be installed depends on the size of the sub-tank. If more water heaters are to be installed, the sub-tank must be larger, which in turn requires a considerably large installation area.

[0008] The technology of connecting multiple water heaters as shown in Patent Documents 5 and 6 is superior in that the number of operating units changes rapidly according to the water flow rate, making it easy to accurately guide the water temperature to a target value. Also, since it only requires connecting small water heaters to the hot water supply path, it can be installed at a lower cost compared to installing a large boiler. However, because the number of operating water heaters changes with the water flow rate, if applied as is to a system where the amount of hot water circulating through the hot water pipes is always constant, such as the hot water circulation system in Patent Documents 1 to 3, the number of operating units will always remain constant, making it impossible to control the temperature of the hot water. On the other hand, when supplying carbon dioxide to an agricultural greenhouse, it was necessary to install a dedicated boiler for using exhaust gas, as shown in Patent Document 3, but it would be convenient if small water heaters could be used instead, contributing to a reduction in installation costs, operating costs, etc.

[0009] The present invention has been made in view of the above, and aims to provide a hot water circulation system and an agricultural facility equipped with this hot water circulation system that reduces installation costs, operating costs, etc. by using multiple hot water heaters, can quickly and accurately control the temperature of the constantly circulating hot water, and can also supply carbon dioxide. [Means for solving the problem]

[0010] To solve the above-mentioned problems, the hot water circulation system of the present invention is A hot water circulation system comprising a hot water pipe installed inside an agricultural greenhouse and a hot water supply source that supplies hot water to the hot water pipe, wherein the hot water is circulated between the hot water supply source and the hot water pipe, The hot water supply source is configured to have a group of water heaters equipped with multiple water heaters, the number of operating water heaters being controlled based on the inflow rate of water, The hot water returning via the hot water pipe has an inlet flow rate adjustment valve installed just before it enters the group of water heaters, which adjusts the inlet flow rate to the group of water heaters and also has an inlet condition adjustment mechanism that combines the hot water that does not enter the group of water heaters with the hot water on the outlet side of the group of water heaters. It has, The system is characterized in that the number of operating water heaters is adjusted by adjusting the water inflow rate using the water inflow condition adjustment mechanism, and the circulating temperature of the hot water circulating through the hot water pipes is adjusted.

[0011] The aforementioned water inlet condition adjustment mechanism is: In addition to the aforementioned water inlet flow rate control valve, A bypass pipe connecting the inlet water flow rate control valve and the hot water pipe located on the outlet side of the group of water heaters, A control unit controls the bypass flow rate of the hot water flowing into the bypass pipe and the inflow flow rate of the hot water supplying to the group of water heaters by controlling the inflow flow rate adjustment valve. It has, It is preferable that the unheated hot water that has passed through the bypass pipe and the hot water that has been heated by the group of water heaters merge at the outlet side, are adjusted to a predetermined circulation temperature, and then circulate through the hot water pipe.

[0012] The control unit, It is preferable that the inlet flow rate adjustment valve is controlled based on the measured return temperature of the hot water before it passes through the inlet flow rate adjustment valve, the target inlet temperature to the water heater group, and the target circulation temperature, thereby adjusting the bypass flow rate and the inlet flow rate.

[0013] Furthermore, the present invention relates to a hot water circulation system comprising a hot water pipe installed in an agricultural greenhouse and a hot water supply source that supplies hot water to the hot water pipe, wherein the hot water is circulated between the hot water supply source and the hot water pipe. The hot water supply source is configured to have a group of water heaters equipped with multiple water heaters, the number of operating water heaters being controlled based on the inflow rate of water, The hot water returning via the hot water pipe has an inlet flow rate adjustment valve installed just before it enters the group of water heaters, which adjusts the inlet flow rate to the group of water heaters and also has an inlet condition adjustment mechanism that combines the hot water that does not enter the group of water heaters with the hot water on the outlet side of the group of water heaters, A carbon dioxide supply system that supplies carbon dioxide generated by the operation of each water heater in the aforementioned group of water heaters into the agricultural greenhouse. It has, The present invention provides a hot water circulation system characterized in that the number of operating hot water heaters is adjusted by adjusting the water inflow rate using the water inflow condition adjustment mechanism, and the amount of carbon dioxide supplied from the carbon dioxide supply system is adjusted.

[0014] The aforementioned water inlet condition adjustment mechanism is: In addition to the aforementioned water inlet flow rate control valve, A bypass pipe connecting the inlet water flow rate control valve and the hot water pipe located on the outlet side of the group of water heaters, A control unit controls the bypass flow rate of the hot water flowing into the bypass pipe and the inflow flow rate of the hot water supplying to the group of water heaters by controlling the inflow flow rate adjustment valve. It has, It is preferable that the control unit is configured to control the inlet water flow rate adjustment valve to adjust the bypass flow rate and the inlet water flow rate in accordance with the difference between the target value and the measured value of the carbon dioxide concentration in the agricultural greenhouse.

[0015] Each of the water heaters constituting the water heater group is configured such that the combustion efficiency is controlled by the inlet water temperature, The inlet water condition adjustment mechanism includes an inlet water cooling device that cools the hot water entering the water heater group, It is preferable that when the measured temperature of the hot water returning through the hot water pipe is higher than the target inlet water temperature, the control unit cools the hot water entering the water heater group by the inlet water cooling device.

[0016] Further, the present invention is a hot water circulation system that has a hot water pipe provided in an agricultural greenhouse and a hot water supply source that supplies hot water to the hot water pipe, and circulates the hot water between the hot water supply source and the hot water pipe, the hot water circulation system being The hot water supply source includes a plurality of water heaters, and each of the water heaters is configured such that the combustion efficiency is controlled by the inlet water temperature, An inlet water condition adjustment mechanism that is provided before the hot water returning through the hot water pipe enters the water heater group, and adjusts the temperature of water entering the water heater group, and a carbon dioxide supply system that supplies carbon dioxide contained in exhaust gas generated by the operation of each water heater in the water heater group into the agricultural greenhouse , and The hot water circulation system is characterized in that by adjusting the inlet water temperature by the inlet water condition adjustment mechanism, the combustion efficiency of each of the water heaters is adjusted, and the supply amount of the carbon dioxide is adjusted.

[0017] The inlet water condition adjustment mechanism has a return hot water cooling device that cools at least a part of the hot water returning through the hot water pipe, and a cooling flow rate adjustment valve that adjusts the flow rate of inlet water to the return hot water cooling device, and , and Preferably, the configuration is such that a target water inlet temperature is set for the water entering the hot water heater group according to the difference between the target value and the measured value of carbon dioxide concentration inside the agricultural greenhouse, and the flow rate cooled by the return hot water cooling device is adjusted by the cooling flow rate adjustment valve so that the target water inlet temperature is reached.

[0018] Furthermore, the present invention relates to an agricultural facility comprising an agricultural greenhouse and a hot water circulation system that circulates hot water through hot water pipes installed inside the agricultural greenhouse for heating, The present invention provides an agricultural facility characterized in that at least one of the aforementioned hot water circulation systems is attached as the hot water circulation system. [Effects of the Invention]

[0019] This invention utilizes a group of multiple water heaters as a hot water supply source. When the hot water returns to the group of water heaters via hot water pipes within an agricultural greenhouse, the inflow rate of the water passing through the group is adjusted. The heated hot water is then combined with the hot water that did not pass through the group after discharge, adjusting it to a predetermined circulation temperature before circulation. While a constant amount of hot water circulates through the hot water pipes of a hot water circulation system attached to an agricultural greenhouse, controlling the inflow rate to the group of water heaters based on the temperature of the hot water returning to the group allows for adjustment of the number of operating water heaters, enabling the adjustment to a predetermined circulation temperature with the minimum necessary number of operating units. By employing a group of multiple water heaters, installation costs, operating costs, etc., can be reduced compared to installing a large boiler.

[0020] Furthermore, by configuring the system to allow adjustment of the water inflow rate to the group of water heaters, and by configuring the system to adjust this water inflow rate based on changes in the carbon dioxide concentration inside the greenhouse, the amount of carbon dioxide generated from the group of water heaters can be adjusted, and consequently, the amount of carbon dioxide supplied to the agricultural greenhouse can be controlled.

[0021] Furthermore, by employing a configuration in which the combustion efficiency of each water heater constituting the group of water heaters is controlled by the inlet water temperature, and by providing a mechanism to adjust the inlet water temperature to the group of water heaters, the amount of carbon dioxide generated from the group of water heaters can be adjusted, and consequently, the amount of carbon dioxide supplied to the agricultural greenhouse can be controlled. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 is a diagram showing a schematic configuration of an agricultural facility in which a hot water circulation system according to the first embodiment of the present invention is applied to an agricultural greenhouse. [Figure 2] Figure 2 is a schematic diagram showing the hot water circulation system shown in Figure 1. [Figure 3] Figure 3 is a flowchart illustrating the heating process using the hot water circulation system according to the first embodiment. [Figure 4] Figure 4 is a diagram showing a schematic configuration of an agricultural facility in which a hot water circulation system according to a second embodiment of the present invention is applied to an agricultural greenhouse. [Figure 5] Figure 5 is a schematic diagram showing the hot water circulation system shown in Figure 4. [Figure 6] Figure 6 is a flowchart illustrating the carbon dioxide supply process by the hot water circulation system according to the second embodiment. [Figure 7] Figure 7 shows a schematic configuration of an agricultural facility in which a hot water circulation system according to the third embodiment of the present invention is applied to an agricultural greenhouse. [Figure 8] Figure 8 is a schematic diagram showing the hot water circulation system shown in Figure 7. [Figure 9] Figure 9 is a flowchart illustrating the carbon dioxide supply process by the hot water circulation system according to the third embodiment. [Modes for carrying out the invention]

[0023] The present invention will be described in more detail below based on embodiments. Figures 1 to 3 show a first embodiment of the present invention. In this embodiment, an agricultural facility is provided, which includes a hot water circulation system 100 and an agricultural greenhouse 200, and the hot water circulation system 100 is configured to include hot water pipes 110 and a group of water heaters 120.

[0024] The hot water pipe 110 is laid inside the agricultural greenhouse 200, for example, in a passage between adjacent cultivation beds, and hot water circulates inside it. The circulating hot water is heated by each of the water heaters 121 that make up the group of water heaters 120, which are located in the middle of the hot water pipe 110. Therefore, the hot water discharged from the group of water heaters 120 travels back and forth between the group of water heaters 120 and the agricultural greenhouse 200 via the hot water pipe 110 at a predetermined circulation temperature. For the sake of explanation, depending on the context, the hot water pipe 110 may be referred to as the greenhouse circulation section 111 if it is located in a passageway between cultivation beds within the agricultural greenhouse 200 and heats the inside of the greenhouse 200, the outlet pipe section 112 if it is located from the outlet side of the entire group of water heaters 120 to the greenhouse circulation section 111, the return pipe section 113 if it is located from the greenhouse pipe section 111 back to the group of water heaters 120 and includes the water inlet flow rate adjustment valve (described later), and the water inlet pipe section 114 if it is located from the water inlet flow rate adjustment valve to the entire group of water heaters 120. All of these are directly connected to form a single hot water pipe 110.

[0025] The water heater group 120 is the water supply source for the hot water circulation system 100 of this embodiment, and is composed of multiple water heaters 121. The water heaters 121 referred to here may be gas-powered, electric, or otherwise, but are small, compact water heaters that convert water into hot water and supply it, and are used to produce hot water in ordinary households, as disclosed in the above-mentioned Patent Documents 5 and 6. They are different from large boilers that are often used in factories, as disclosed in Patent Documents 1 to 3. Also, since hot water is constantly circulating in the hot water circulation system 100, instantaneous water heaters are preferred over storage-type water heaters 121. The installation location of the water heater group 120 is preferably outside the agricultural greenhouse 200 because exhaust gas is generated from each water heater 121. Since each water heater 121 is small, even if multiple units (for example, about 20 to 30 units) are installed, they can be installed adjacent to the agricultural greenhouse 200, and there is no need to provide a separate boiler room as in conventional boiler types. Furthermore, because of its compact size, by providing a suitable exhaust path (not shown) for discharging the exhaust gas from each water heater 121 to the outside, it is possible to install it inside the agricultural greenhouse 200, depending on the size of the greenhouse.

[0026] Each water heater 121 is connected in parallel. The water inlet pipe section 114 located on the water inlet side of the entire water heater group 120 and the hot water outlet pipe section 112 located on the hot water outlet side are directly connected as described above. However, the connecting pipes 121a for the water inlet and hot water outlet of each water heater 121 constituting the water heater group 120 are connected to the hot water pipe 110 located between them via solenoid valves 121b. In this water heater group 120, the number of operating water heaters 121 is adjusted according to the water inlet flow rate to the entire water heater group 120. That is, the solenoid valves 121b are opened and closed according to the water inlet flow rate from the water inlet pipe section 114, and water is supplied to and operates only for the water heater 121 whose solenoid valve 121b is open.

[0027] In this embodiment, the hot water circulation system 100 has hot water constantly circulating within the hot water pipe 110, as described above. Therefore, if the individual water heaters 121 of the water heater group 120 are connected as is, the water inflow rate to the water heater group 120 will not change, and it will not be possible to control the number of operating water heaters 121. To address this, a water inflow condition adjustment mechanism 130 is provided in the hot water pipe 110, which is essentially a closed circuit, in order to change the water inflow rate.

[0028] The water inlet condition adjustment mechanism 130 of this embodiment includes a water inlet flow rate adjustment valve 131, a bypass pipe 132, and a control unit 133. The water inlet flow rate adjustment valve 131 is installed in the hot water pipe 110, just before it enters the water heater group 120 via the greenhouse circulation section 111. The bypass pipe 132 is connected to the water inlet flow rate adjustment valve 131 and the portion of the hot water pipe 110 located on the outlet side of the entire water heater group 120 (the range of the outlet side pipe section 112). Due to the water inlet flow rate adjustment valve 131, a portion of the hot water that has passed through the return side pipe section 113 flows into the bypass pipe 132 without flowing into the water inlet side pipe section 114 of the water heater group 120. Therefore, by adjusting the opening degree of the water inlet flow rate adjustment valve 131, it is possible to change the water inlet flow rate that enters the water heater group 120 in a hot water circulation system 100 in which a constant amount of hot water always flows through the hot water pipe 110. As a result, in response to changes in the water inflow rate to the group of water heaters 120, the solenoid valve 121b between the group of water heaters 120 and the hot water pipe 110 that controls the water flow to each water heater 121 is opened and closed as described above, and the number of operating units that are in combustion operation is adjusted.

[0029] The control unit 133 controls the operation of the inlet water flow rate adjustment valve 131. In this embodiment, the control unit outputs a control signal to the inlet water flow rate adjustment valve 131 based on the actual measured temperature of the hot water in the return pipe section 113 before the inlet water flow rate adjustment valve 131 (measured return water temperature Tr), the target value of the inlet water temperature when water is introduced into the water heater group 120 from the inlet pipe section 114 (target inlet water temperature cTr), and the target value when circulating water in the greenhouse circulation section 111 (target circulation temperature cTs). The target circulation temperature cTs is initially set by input, but thereafter, at predetermined intervals, it is automatically set within a predetermined range relative to the initial setting value based on the difference between the measured value and the actual circulation temperature. The target inlet water temperature cTr is always set to be a certain temperature lower than the target circulation temperature cTs. By introducing water at a temperature lower than predetermined, the combustion efficiency of each water heater 121 is set to a certain level or higher. Then, based on the difference between the target inlet water temperature cTr and the measured return water temperature Tr determined in this way, the inlet water flow rate adjustment valve 131 is controlled to determine the inlet water flow rate heated by the water heater group 120 and the bypass flow rate passing through the bypass pipe 132. When the heated water is discharged to the outlet pipe section 112 by the water heater group 120, the unheated hot water that has passed through the bypass pipe 132 is merged and mixed with it, and the mixed hot water flows to the greenhouse circulation section 111 at a circulation temperature close to the target circulation temperature cTs.

[0030] In this embodiment, as shown in Figure 3, when the heating operation is turned ON (S10), each water heater 121 of the water heater group 120 and other pumps, etc. are turned ON (S11). Next, the control unit 133 calculates the difference between the target inlet temperature cTr, which is a certain temperature lower than the target circulation temperature cTs, and the measured return water temperature Tr. Based on this, it multiplies it by a predetermined coefficient Kp and converts it into the adjustment angle (opening degree) of the inlet flow rate control valve 131 (S12). A control signal reflecting the control result is sent to the inlet flow rate control valve 131, and its opening degree is controlled (S13). As a result, hot water at a predetermined inlet flow rate is sent to the water heater group 120, and the number of water heaters 121 corresponding to the inlet flow rate operates. The more the inlet flow rate increases, the more water heaters 121 operate. The high-temperature hot water heated by the water heaters 121 flows out to the outlet pipe section 112. Subsequently, the unheated hot water (which flows from the return pipe section 113 to the bypass pipe 132, so the hot water that passes through the bypass pipe 132 is at approximately the same temperature as the measured return temperature Tr) is mixed with the hot water that has passed through the bypass pipe 132, which is connected to the outlet pipe section 112, and the temperature is adjusted to be close to the target circulation temperature cTs before flowing into the greenhouse circulation section 111. The above process is repeated unless the heating operation is turned OFF (NO in S14), and when the heating operation is turned OFF (YES in S14), the water heater 121 and pumps etc. are also turned OFF (S15), and the inlet water flow rate adjustment valve 131 is closed (S16).

[0031] The measured return water temperature Tr is measured at predetermined intervals. Each time, the inlet water flow rate control valve 131 is adjusted to control the inlet water flow rate, and the number of operating water heaters 121 is adjusted accordingly. The predetermined interval can be set arbitrarily, such as every few seconds, or each time the hot water circulates through the hot water pipe 110, depending on the flow rate of the hot water. By configuring the system to control the number of operating water heaters 121 in this way, the number of operating water heaters 121 required to circulate hot water at a predetermined circulation temperature can always be kept to the minimum necessary, contributing to a reduction in operating costs.

[0032] Next, a second embodiment of the present invention will be described based on Figures 4 to 6. This embodiment is a system that uses a hot water circulation system 100 for the supply of carbon dioxide. In this embodiment, a carbon dioxide supply system 300 is provided that supplies carbon dioxide by guiding the exhaust from each water heater 121 constituting the group of water heaters 120 into the agricultural greenhouse 200. The carbon dioxide supply system 300 is configured to include exhaust guide pipes 301 connected to each supply unit 121. In Figure 4, the exhaust guide pipes 301 are shown to be directly connected to the end wall of the agricultural greenhouse 200, but since the exhaust is at a relatively high temperature, it is preferable to mix the exhaust that has passed through each exhaust guide pipe 301 with outside air and supply it into the agricultural greenhouse 200.

[0033] Furthermore, in this embodiment, an inlet water cooling device 134 is interposed in the inlet side pipe section 114, which is located on the hot water heater group 120 side of the inlet water flow rate adjustment valve 131. The inlet water cooling device 134 operates when the measured return water temperature Tr is higher than the target inlet water temperature cTr, and cools the hot water in the inlet side pipe section 114. The water heater 121 is cooled so that the difference between the measured return water temperature Tr and the target inlet water temperature cTr is within a predetermined range, as the combustion efficiency decreases when the measured return water temperature Tr is higher than the target inlet water temperature cTr. For example, in the case of high temperatures in summer, when the temperature of the hot water hardly decreases even when circulating through the hot water pipe 110, the inlet water cooling device 134 is operated to cool the water and suppress the decrease in the combustion efficiency of the water heater 121. Depending on the time of year the hot water circulation system 100 of this embodiment is used and the climatic conditions of the installation location of the agricultural greenhouse 200, if the measured return water temperature Tr does not exceed the target inlet water temperature cTr, the installation of the inlet water cooling device 134 is not essential. However, a configuration having an inlet water cooling device 134 is preferable because it can address all of these issues.

[0034] Other hardware configurations are the same as in the first embodiment, but the control program set in the control unit 133 that controls the inlet flow rate adjustment valve 131 is different. In this embodiment, the inlet flow rate adjustment valve 131 is controlled according to the difference between the target value (cCO2) and the measured value (CO2) of carbon dioxide concentration inside the agricultural greenhouse 200, thereby changing the bypass flow rate passing through the bypass pipe 132 and the inlet flow rate supplied to the water heater group 120. That is, if the difference between the target value and the measured value of carbon dioxide concentration is large, controlling the inlet flow rate adjustment valve 131 to increase the inlet flow rate to the water heater group 120 increases the number of operating water heaters 121 and increases the exhaust volume, thus increasing the amount of carbon dioxide supplied via the exhaust induction pipe 301. Conversely, if the difference between the target value (cCO2) and the measured value (CO2) of carbon dioxide concentration is small, controlling the inlet flow rate adjustment valve 131 to decrease the inlet flow rate to the water heater group 120 reduces the number of operating water heaters 121. This reduces the amount of carbon dioxide supplied through the exhaust induction pipe 301.

[0035] In this embodiment, as shown in Figure 6, when the hot water circulation system 100 is set to carbon dioxide supply mode (S20), each water heater 121 of the water heater group 120 and other pumps are turned ON (S21). Also, dampers installed near the boundary between each exhaust guide pipe 301 of the carbon dioxide supply system 300 and the agricultural greenhouse 200, which are used to send carbon dioxide into the agricultural greenhouse 200, are opened, and the blower is turned ON (S22). Next, the control unit 133 compares the measured return water temperature Tr and the target inlet water temperature cTr to see if "Tr > cTr" (S23), and if "YES", the inlet water cooling device 134 is turned ON (S24). Depending on the season and the outside temperature, if the rate of decrease in the temperature of the hot water circulating in the hot water pipe 110 is low, the measured return water temperature Tr may be high in this way.

[0036] Furthermore, the control unit 133 compares the latest measured value (CO2) of carbon dioxide concentration inside the agricultural greenhouse 200 with the target value (cCO2), calculates the difference between the two, and determines the opening degree of the inlet flow rate adjustment valve 131 according to that difference (S25). As a result, the bypass flow rate passing through the bypass pipe 132 and the inlet flow rate entering the water heater group 120 are adjusted, and the number of water heaters 121 corresponding to the inlet flow rate of the water heater group 120 are put into operation. Since the total exhaust volume of the water heater group 121 changes depending on the number of water heaters 121 in operation, the exhaust corresponding to this number of operations is sent to the carbon dioxide supply system 300, and carbon dioxide is supplied into the agricultural greenhouse 200 via the exhaust induction pipe 301. As a result, the carbon dioxide concentration inside the agricultural greenhouse 200 approaches the target value (cCO2).

[0037] In S23, if the measured return water temperature Tr is less than or equal to the target inlet water temperature cTr, the inlet water cooling device 134 is switched OFF (S27), and the hot water is supplied to the water heater group 121 without being cooled.

[0038] The above process is repeated until the carbon dioxide supply operation is stopped (if "NO" is answered in S28, steps S21 to S27 are repeated). Once the carbon dioxide supply operation is stopped (if "YES" is answered in S28), the fan is turned off and the damper is closed (S29). Subsequently, the water heater 121 and pumps are also turned off (S30), and the water inlet flow rate control valve 131 is closed (S31). The carbon dioxide supply may be automatically stopped when the carbon dioxide concentration inside the agricultural greenhouse 200 reaches the target carbon dioxide concentration (cCO2), or it may be set to supply carbon dioxide at appropriate operating times throughout the day.

[0039] Here, the second embodiment is the same as the first embodiment except that it has a carbon dioxide supply system 300 and an inlet water cooling device 134, and the control program set in the control unit 133 is different. Therefore, in the configuration of the second embodiment, if the control program of the first embodiment is introduced as the control unit 133, the manner of keeping the circulation temperature of the hot water constant as described in the first embodiment can be implemented. Accordingly, if the configuration of the second embodiment is attached to the agricultural greenhouse 200, the control program executed by the control unit 133 can be used to control the hot water circulation system 100 to a constant circulation temperature for heating, as in the first embodiment, and to supply carbon dioxide, as in the second embodiment. Furthermore, for a hot water pipe 110 attached to a single agricultural greenhouse 200, the group of water heaters 120, etc. of the first embodiment can be arranged, as well as the group of water heaters 120 and carbon dioxide supply system 300, etc. of the second embodiment, and a configuration can be used to switch between controlling the circulation temperature to a constant level and supplying carbon dioxide. In this case, since the configuration for controlling the circulation temperature to a constant level can also be implemented by switching the control program in the configuration of the second embodiment, the water heater group 120 etc. for the second embodiment can be operated together with the water heater group 120 etc. for the first embodiment when controlling the circulation temperature to a constant level.

[0040] Figures 7-9 show a third embodiment. This embodiment controls the supply of carbon dioxide in the same way as the second embodiment. In this embodiment, the number of operating water heaters in the group 120 is not controlled. As described above, the combustion efficiency of the water heater 121 changes depending on the inlet water temperature, and the combustion efficiency increases as the inlet water temperature decreases. Therefore, in this embodiment, the combustion efficiency of the water heater 121 is adjusted by controlling the inlet water temperature using the carbon dioxide concentration, and the amount of carbon dioxide supplied is adjusted.

[0041] The hot water circulation system 100 of this embodiment includes a hot water inlet condition adjustment mechanism 130, which includes a hot water return cooling device 135 disposed in the hot water return pipe section 113 and a cooling flow rate adjustment valve 136 that adjusts the flow rate to the hot water return cooling device 135. The control program set in the control unit 133 controls the cooling flow rate adjustment valve 136 based on the difference between the target inlet temperature cTr to the hot water heater group 120 and the hot water return temperature Tr of the hot water return pipe section 113. However, the target inlet temperature cTr is obtained by subtracting the value obtained by multiplying the difference between the target carbon dioxide concentration cCO2 and the measured carbon dioxide concentration CO2 by a predetermined coefficient Kc and converting it to temperature from the initial target inlet temperature oTr. The larger the difference between the target carbon dioxide concentration cCO2 and the measured carbon dioxide concentration CO2, the lower the target inlet temperature cTr becomes. Assuming the hot water return temperature Tr is the same, the lower the target inlet temperature cTr, the more the cooling flow rate adjustment valve 136 adjusts its opening to increase the amount of hot water flowing into the hot water return cooling device 135 and reduce the amount of hot water that is not cooled.

[0042] The lower the water temperature entering the water heater group 120, the higher the combustion efficiency of each water heater 121 that makes up the water heater group 120. As a result, the amount of exhaust supplied to the carbon dioxide supply system 300 increases, and the amount of carbon dioxide supplied into the agricultural greenhouse 200 via the exhaust induction pipe 301 also increases.

[0043] In this embodiment, as shown in Figure 9, when the hot water circulation system 100 is set to carbon dioxide supply mode (S40), each water heater 121 of the water heater group 120 and other pumps are turned ON (S41), the damper is opened, and the blower is turned ON (S42), similar to the second embodiment. Next, the control unit 133 calculates the difference between the latest measured value (CO2) and the target value (cCO2) of carbon dioxide concentration inside the agricultural greenhouse 200, multiplies this by a predetermined coefficient Kc to convert it into a difference corresponding to temperature, and subtracts this value from the preset initial target inlet water temperature oTr to obtain the target inlet water temperature cTr (S43). Next, the target inlet water temperature cTr is compared with the measured return water temperature Tr (S44). If "Tr>cTr" (if "YES" is given in S44), the return hot water cooling device 135 is turned ON (S45), and the cooling flow rate control valve 136 is opened and closed based on the difference between the target inlet water temperature cTr and the measured return hot water temperature Tr (S46, S47). Then, according to the opening degree of this cooling flow rate control valve 136, a predetermined amount of cooling water flows into the return hot water cooling device 135 and is cooled. Then, before entering the water heater group 120, the hot water that has not passed through the return hot water cooling device 135 and the cooled hot water merge, are adjusted to a predetermined target inlet water temperature cTr, and then enter the water heater group 120.

[0044] In this embodiment, the number of water heaters 121 constituting the water heater group 120 is not controlled, but the water flows into the water heater group 120 at a target inlet temperature cTr determined according to the carbon dioxide concentration. As a result, each water heater 121 burns with combustion efficiency according to that inlet temperature, and the exhaust is sent to the carbon dioxide supply system 300, where carbon dioxide is supplied into the agricultural greenhouse 200 via the exhaust guide pipe 301. This causes the carbon dioxide concentration inside the agricultural greenhouse 200 to approach the target value (cCO2).

[0045] In S44, if the answer is "NO", the measured return water temperature Tr is below the target inlet water temperature cTr, so the return water cooling device 135 is left OFF. In this case, the cooling flow rate control valve 136 is adjusted so that the hot water passing through the return water side pipe section 113 is not cooled and is instead fed into the water heater group 120 (S46, S47).

[0046] The above process is repeated until the carbon dioxide supply operation is stopped (if "NO" is answered in S49, steps S41 to S48 are repeated). Once the carbon dioxide supply operation is stopped (if "YES" is answered in S49), the blower is turned OFF and the damper is closed (S50). Subsequently, the water heater 121 and pumps are also turned OFF (S51), and the cooling flow rate control valve 136 is closed (S52).

[0047] The third embodiment does not adjust the number of operating water heaters 121 by adjusting the amount of water entering the water heater group 120, and therefore cannot be used to adjust the circulation temperature. However, it is possible to construct an agricultural facility in which the hot water circulation system 100 of the first embodiment is installed alongside the agricultural greenhouse 200. In this case, the hot water pipe 110 is a separate system from the hot water pipe 110 of the first embodiment, and the third embodiment is dedicated to carbon dioxide supply. By adjusting the operating times of both systems, heating management and carbon dioxide concentration management can be performed within the agricultural greenhouse 200. The third embodiment can also be used in combination with the second embodiment. In this case, both systems can be used simultaneously for carbon dioxide supply. Furthermore, it is possible to provide an agricultural facility in which the first, second, and third embodiments are all installed alongside the agricultural greenhouse 200. The hot water pipe 110 can be separate for each system corresponding to each embodiment, or it can be shared between the first and second embodiments. In any case, when heating the inside of the agricultural greenhouse 200, or when managing carbon dioxide concentration, it is possible to appropriately determine whether to operate only one of the three systems, a combination of two of these systems, or a combination of all three systems, taking into consideration the size of the agricultural greenhouse 200 and the operating efficiency.

[0048] According to the embodiments described above, by using multiple water heaters, heating control and carbon dioxide concentration control can be performed within the agricultural greenhouse 200. This eliminates the need to install a large boiler as in the past, and also eliminates the need for a boiler room, contributing to a reduction in facility construction costs, operating costs, and maintenance costs. [Explanation of Symbols]

[0049] 100 Hot water circulation system 110 Hot water pipe 111 Circulation section inside the greenhouse 112 Hot water outlet side pipe section 113 Return pipe section 114 Inlet pipe section 120 water heaters 121 Water heater 130 Water entry condition adjustment mechanism 131 Inlet water flow control valve 132 Bypass pipe 133 Control Unit 134 Inlet water cooling system 135 Return hot water cooling system 136 Cooling flow control valve 200 Agricultural Greenhouses 300 Carbon Dioxide Supply System 301 Exhaust Induction Pipe

Claims

1. A hot water circulation system comprising a hot water pipe installed inside an agricultural greenhouse and a hot water supply source that supplies hot water to the hot water pipe, wherein the hot water is circulated between the hot water supply source and the hot water pipe, The hot water supply source is configured to have a group of water heaters equipped with multiple water heaters, the number of operating water heaters being controlled based on the inflow rate of water, The hot water returning via the hot water pipe has an inlet flow rate adjustment valve installed just before it enters the group of water heaters, which adjusts the inlet flow rate to the group of water heaters and also has an inlet condition adjustment mechanism that combines the hot water that does not enter the group of water heaters with the hot water on the outlet side of the group of water heaters, A carbon dioxide supply system that supplies carbon dioxide contained in the exhaust generated by combustion during the operation of each of the aforementioned water heaters into the agricultural greenhouse. It has, The water inlet flow rate is adjusted by the water inlet condition adjustment mechanism, thereby adjusting the number of operating water heaters and the amount of carbon dioxide supplied from the carbon dioxide supply system. The aforementioned water inlet condition adjustment mechanism is: In addition to the aforementioned water inlet flow rate control valve, A bypass pipe connecting the inlet water flow rate control valve and the hot water pipe located on the outlet side of the group of water heaters, A control unit controls the bypass flow rate of the hot water flowing into the bypass pipe and the inflow flow rate of the hot water supplying to the group of water heaters by controlling the inflow flow rate adjustment valve. It has, The control unit controls the inlet water flow rate adjustment valve according to the difference between the target value and the measured value of carbon dioxide concentration inside the agricultural greenhouse, thereby adjusting the bypass flow rate and the inlet water flow rate in the hot water circulation system.

2. The water inlet condition adjustment mechanism includes a water inlet cooling device for cooling the hot water that enters the group of water heaters, The hot water circulation system according to claim 1, wherein the control unit cools the hot water entering the group of water heaters with the water inlet cooling device when the measured temperature of the hot water returning via the hot water pipe is higher than the target water inlet temperature.

3. The control unit is If the carbon dioxide concentration measured inside the aforementioned agricultural greenhouse reaches the target value, the operation of the aforementioned group of water heaters will be stopped. The hot water circulation system according to claim 1.

4. The control unit further comprises: The system has a function to control the inlet flow rate control valve based on the measured return temperature of the hot water before it passes through the inlet flow rate control valve, the target inlet temperature to the water heater group, and the target circulation temperature. It is possible to control the circulation temperature when the unheated hot water that has passed through the bypass pipe and the hot water heated by the water heater group merge and circulate on the outlet side to reach the target circulation temperature. The hot water circulation system according to claim 1.

5. When performing the function of controlling the circulation temperature to reach the target temperature, the group of water heaters that heat the hot water, When performing the function of controlling according to the difference between the target value and the measured value of the carbon dioxide concentration, separately from the group of water heaters that heat the hot water, The hot water pipe is provided The hot water circulation system according to claim 4.

6. A hot water circulation system comprising a hot water pipe installed inside an agricultural greenhouse and a hot water supply source that supplies hot water to the hot water pipe, wherein the hot water is circulated between the hot water supply source and the hot water pipe, The hot water supply source is configured with a group of water heaters, each consisting of multiple water heaters. A water inlet condition adjustment mechanism is provided before the hot water returning via the hot water pipe enters the group of water heaters, and adjusts the water temperature entering the group of water heaters. A carbon dioxide supply system that supplies carbon dioxide contained in the exhaust generated by combustion during the operation of each of the aforementioned water heaters into the agricultural greenhouse. It has, The aforementioned water inlet condition adjustment mechanism is: A return hot water cooling device that cools at least a portion of the hot water returning through the hot water pipe, a cooling flow rate adjustment valve that adjusts the water flow rate into the return hot water cooling device, and a control unit that controls the cooling flow rate adjustment valve. It has, The control unit sets a target water inlet temperature for the water entering the group of hot water heaters according to the difference between the target value and the measured value of carbon dioxide concentration inside the agricultural greenhouse, and controls the cooling flow rate adjustment valve to adjust the flow rate cooled by the return hot water cooling device so that the target water inlet temperature is reached. When the measured value of carbon dioxide concentration inside the agricultural greenhouse reaches the target value, the control unit stops the operation of the group of hot water heaters. Hot water circulation system.

7. An agricultural facility comprising the hot water circulation system described in Claim 6, and also having another hot water circulation system provided separately from the hot water circulation system described in Claim 6, wherein The aforementioned other hot water circulation system is: The hot water supply source that supplies hot water to the hot water pipe is configured to have a group of water heaters comprising multiple water heaters, the number of operating water heaters controlled based on the inflow rate of water, The hot water returning via the hot water pipe has an inlet flow rate adjustment valve installed just before it enters the group of water heaters, which adjusts the inlet flow rate to the group of water heaters and also has an inlet condition adjustment mechanism that combines the hot water that does not enter the group of water heaters with the hot water on the outlet side of the group of water heaters. It has, The water inlet flow rate is adjusted by the water inlet condition adjustment mechanism, thereby adjusting the number of operating water heaters and the circulation temperature of the hot water circulating through the hot water pipes. The aforementioned water inlet condition adjustment mechanism is: In addition to the aforementioned water inlet flow rate control valve, A bypass pipe connecting the inlet water flow rate control valve and the hot water pipe located on the outlet side of the group of water heaters, A control unit controls the bypass flow rate of the hot water flowing into the bypass pipe and the inflow flow rate of the hot water supplying to the group of water heaters by controlling the inflow flow rate adjustment valve. It has, The unheated hot water that has passed through the bypass pipe and the hot water that has been heated by the group of water heaters merge at the outlet side, are adjusted to a predetermined circulation temperature, and then circulate through the hot water pipe. Agricultural facilities.

8. The control unit comprising the other hot water circulation system is: Based on the measured return temperature of the hot water before it passes through the inlet flow rate control valve, the target inlet temperature to the water heater group, and the target circulation temperature, the inlet flow rate control valve is controlled to adjust the bypass flow rate and the inlet flow rate. The agricultural facility according to claim 7.

Images