Ventilation system and control device

Abstract

To reduce a CO2 discharge amount while suppressing a ventilation amount.SOLUTION: The ventilation device is provided in an outside air introduction path that connects the outside of the target space and the inside of the target space, and sends air from the outside of the target space into the target space. The CO2 removing device is provided in the outside air introduction path and removes CO2 contained in air flowing through the outside air introduction path. The control device controls the ventilation device so that the CO2 concentration in the target space approaches a set CO2 concentration.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ventilation system and a control device. [Background technology]

[0002] Air conditioning is controlled by air conditioners to improve the indoor environment. Patent Document 1 discloses a technology for removing CO2 from a room using a carbon dioxide gas removal device to maintain good indoor air quality. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-275487 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the CO2 concentration in the outside air is high, a large amount of ventilation is required to reduce the CO2 concentration in the target space. As a result, it is not possible to reduce the amount of ventilation, making it difficult to reduce the energy used by the ventilation system and reduce CO2 emissions. An object of the present invention is to provide a ventilation system and a control device that can reduce CO2 emissions while suppressing ventilation volume. [Means for solving the problem]

[0005] (A1) One aspect of the present invention is a ventilation system comprising: a CO2 removal device provided in an outside air introduction path connecting the outside of a target space with the inside of the target space, which removes CO2 contained in air circulating in the outside air introduction path; a ventilation device which blows air so that air flows from outside the target space into the target space through the outside air introduction path; and a control device which determines whether to operate the CO2 removal device based on the amount of reduction in energy required to operate the ventilation device by operating the CO2 removal device and the energy required to operate the CO2 removal device. (A2) Furthermore, in the ventilation system according to one aspect of the present invention, the control device may control the ventilation device so that the CO2 concentration in the target space approaches a set CO2 concentration. (A3) Furthermore, in a ventilation system according to one embodiment of the present invention, the control device may calculate the amount of reduction in energy required to operate the ventilation device by operating the CO2 removal device based on the CO2 concentration outside the target space. (A4) Furthermore, in one embodiment of the ventilation system of the present invention, an air conditioner that adjusts the temperature of air in a target space and blows it into the target space may be provided, and the control device may determine whether to operate the CO2 removal device based on the amount of reduction in energy required to operate the air conditioner by operating the CO2 removal device. (A5) Furthermore, in a ventilation system according to one embodiment of the present invention, the control device may convert the energy into CO2 emissions and determine whether to operate the CO2 removal device based on the amount of CO2 emissions when the CO2 removal device is operated, the amount of CO2 emissions when the CO2 removal device is not operated, and the amount of CO2 removed by operating the CO2 removal device. (A6) One aspect of the present invention is a control device for a ventilation system that includes a CO2 removal device that is provided in an outside air inlet path that connects the outside of a target space with the inside of the target space and that removes CO2 contained in air circulating in the outside air inlet path, and a ventilation device that blows air so that air flows from outside the target space into the target space through the outside air inlet path, and the control device determines whether to operate the CO2 removal device based on the amount of reduction in energy required to operate the ventilation device by operating the CO2 removal device and the energy required to operate the CO2 removal device. (B1) One aspect of the present invention is a ventilation system comprising: a CO2 removal device provided in an outside air introduction path connecting the outside of a target space with the inside of the target space, which removes CO2 contained in air circulating in the outside air introduction path; a ventilation device which blows air so that air flows from outside the target space into the target space via the outside air introduction path; and a control device which controls the ventilation device so that the CO2 concentration in the target space approaches a set CO2 concentration.

[0006] (B2) Furthermore, in a ventilation system according to one embodiment of the present invention, the control device may determine whether to operate the CO2 removal device based on the amount of reduction in energy required to operate the ventilation device due to operation of the CO2 removal device and the energy required to operate the CO2 removal device.

[0007] (B3) Furthermore, a ventilation system according to one embodiment of the present invention may include an air conditioner that adjusts the temperature of air in a target space and blows the air into the target space, and the control device may determine whether to operate the CO2 removal device based on the amount of reduction in energy required to operate the air conditioner by operating the CO2 removal device.

[0008] (B4) Furthermore, in a ventilation system according to one embodiment of the present invention, the control device may convert the energy into CO2 emissions and determine whether to operate the CO2 removal device based on the amount of CO2 emissions when the CO2 removal device is operated, the amount of CO2 emissions when the CO2 removal device is not operated, and the amount of CO2 removed by operating the CO2 removal device.

[0009] (B5) Furthermore, a ventilation system according to one embodiment of the present invention is a control device for a ventilation system that includes a CO2 removal device that is provided in an outside air introduction path that connects the outside of a target space with the inside of the target space and that removes CO2 contained in air circulating in the outside air introduction path, and a ventilation device that blows air so that air flows from outside the target space into the target space via the outside air introduction path, and that acquires a measured value of the CO2 concentration in the target space and controls the ventilation device based on the measured value so that the CO2 concentration in the target space approaches a set CO2 concentration. [Effects of the Invention]

[0010] According to the above aspect, it is possible to reduce the amount of CO2 emissions while suppressing the ventilation volume. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing the configuration of an air conditioning ventilation system according to a first embodiment. [Figure 2] 1 is a diagram showing a configuration example of a CO2 removal device according to a first embodiment. [Figure 3] 4 is a flowchart showing a ventilation control method performed by the control device according to the first embodiment. [Figure 4] 4 is a flowchart showing a method for switching the CO2 removal device by the control device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment Hereinafter, the embodiments will be described in detail with reference to the drawings. 1 is a diagram showing the configuration of an air conditioning and ventilation system 1 according to a first embodiment. The air conditioning and ventilation system 1 performs air conditioning control and ventilation control of a target space R. The air conditioning and ventilation system 1 includes an indoor temperature sensor 11, an indoor humidity sensor 12, an indoor CO2 sensor 13, an outdoor temperature sensor 14, an outdoor humidity sensor 15, an outdoor CO2 sensor 16, an air conditioning indoor unit 17, an exhaust fan 18, an intake fan 19, a CO2 removal device 20, and a control device 21.

[0013] The indoor temperature sensor 11 measures the temperature of the target space R and outputs the measurement value to the control device 21. The indoor humidity sensor 12 measures the absolute humidity in the target space R and outputs the measurement value to the control device 21. The indoor CO2 sensor 13 measures the CO2 concentration in the target space R and outputs the measurement value to the control device 21. The outdoor temperature sensor 14 measures the temperature of the outdoor air and outputs the measured value to the control device 21. The outdoor humidity sensor 15 measures the absolute humidity of the outdoor air and outputs the measurement value to the control device 21. The outdoor CO2 sensor 16 measures the CO2 concentration of the outdoor air and outputs the measurement value to the control device 21.

[0014] The air conditioning indoor unit 17 takes in air from the target space R through an intake port, adjusts the temperature and humidity of the taken-in air, and blows the air out through an outlet into the target space R. As shown in FIG. 1 , the air conditioning indoor unit 17 includes a first flow rate adjustment valve 172, a heat exchange unit 173, a second flow rate adjustment valve 174, a humidification unit 175, and an air conditioning fan 176.

[0015] The first flow rate adjustment valve 172 adjusts the flow rate of refrigerant supplied to the heat exchange unit 173. The heat exchange unit 173 is provided in the flow path between the inlet and the outlet and adjusts the temperature of the taken-in air by heat exchange between the passing air and the refrigerant supplied via the first flow rate adjustment valve 172. The second flow rate adjustment valve 174 adjusts the flow rate of humidified feedwater supplied to the humidifier unit 175. The humidifier unit 175 is provided in the flow path between the inlet and the outlet and humidifies the air with the humidified feedwater supplied from the second flow rate adjustment valve 174. The humidifier unit 175 may spray the humidified feedwater using a spray, vaporize the humidified feedwater using a humidifying filter impregnated with the humidified feedwater, or heat and evaporate the humidified feedwater. The air conditioning fan 176 pressure-feeds the air from the inlet to the outlet. The air conditioning fan 176 may have a rotation speed that can be varied, for example, by inverter control.

[0016] The exhaust fan 18 is provided in an air exhaust path that connects the inside and outside of the target space R, and when driven, exhausts the air in the target space R to the outside. The intake fan 19 is provided in an outside air introduction path that connects the inside and outside of the target space R, and supplies outside air (outside air) to the target space R when driven. The exhaust fan 18 and the intake fan 19 may have variable rotation speeds, for example, by inverter control. The exhaust fan 18 and the intake fan 19 are an example of a ventilation device that blows air so that it flows from outside the target space R into the target space R through an outside air introduction path. Note that the ventilation device according to this embodiment is equipped with the exhaust fan 18 and the intake fan 19 and performs type 1 ventilation. However, in other embodiments, the ventilation device may be equipped with only the intake fan 19 and perform type 2 ventilation, or may be equipped with only the exhaust fan 18 and perform type 3 ventilation. The ventilation device may also be equipped with a total heat exchanger or a sensible heat exchanger.

[0017] The CO2 removal device 20 is provided in the outside air introduction path and removes CO2 contained in the outside air, i.e., reduces the CO2 concentration of the air taken into the target space R. FIG. 2 is a diagram showing an example of the configuration of the CO2 removal device 20 according to the first embodiment. The CO2 removal device 20 includes, for example, a first motor damper 201, a second motor damper 202, a booster fan 203, and a DAC (Direct Air Capture) 164. The CO2 removal device 20 has two paths (a first path and a second path) for circulating air between the outdoor side of the outside air introduction path and the indoor side of the outside air introduction path. The first motor damper 201 is provided in the first path. The second motor damper 202 is provided in the second path. The first motor damper 201 and the second motor damper 202 are controlled so that one is open and the other is closed. Therefore, air flows through either the first path or the second path. The DAC 204 is provided in the second path. DAC204 is a filter made of materials such as amines that have the property of absorbing CO2. When air passes through DAC204, the CO2 in the air is absorbed by DAC204, and it can be removed from the air. DAC204 can remove CO2 from the air at a predetermined removal rate. The CO2 absorbed by DAC204 can be released by heating or reducing the pressure of DAC204. The CO2 released from DAC204 can be processed into products such as dry ice or buried underground to prevent it from being released into the outside air. The booster fan 203 pressurizes and sends air to the DAC 204. Since the intake fan 19 is provided in the outside air introduction path where the CO2 removal device 20 is provided, the air is guided into the target space R by driving the intake fan 19. However, pressure loss occurs when the air passes through the DAC 204. By driving the booster fan 203, it is possible to compensate for the energy equivalent to the pressure loss. Note that in the first embodiment, the booster fan 203 rotates at a constant rotation speed regardless of the ventilation volume.

[0018] The control device 21 controls the air conditioning indoor unit 17, the exhaust fan 18, the intake fan 19, and the CO2 removal device 20. The control device 21 controls the air conditioning indoor unit 17 based on the measurement value of the indoor temperature sensor 11. For example, the control device 21 receives in advance settings of the operation mode (heating or cooling) and the set temperature of the target space R. When the operation mode is heating, the control device 21 compares the measurement value of the indoor temperature sensor 11 with the set temperature, and if the measurement value is lower than the set temperature, opens the first flow rate adjustment valve 172 and supplies refrigerant to the heat exchange unit 173. On the other hand, when the measurement value is equal to or higher than the set temperature, the control device 21 closes the first flow rate adjustment valve 172. When the operation mode is cooling, the control device 21 compares the measurement value of the indoor temperature sensor 11 with the set temperature, and if the measurement value is higher than the set temperature, opens the first flow rate adjustment valve 172 and supplies refrigerant to the heat exchange unit 173. On the other hand, when the measurement value is equal to or lower than the set temperature, the control device 21 closes the first flow rate adjustment valve 172. The control device 21 can switch the air conditioning function on and off. That is, when the air conditioning function is set to OFF, the control device 21 closes the first flow rate adjustment valve 172 and the second flow rate adjustment valve 174 of the air conditioning indoor unit 17, and stops the air conditioning fan 176.

[0019] FIG. 3 is a flowchart showing a ventilation control method by the control device 21 according to the first embodiment. The control device 21 acquires the measurement value of the indoor CO2 sensor 13 (step S11). The control device 21 determines whether the acquired measurement value exceeds a predetermined set CO2 concentration (step S12). If the measured CO2 value exceeds the set CO2 concentration (step S12: YES), the control device 21 increases the ventilation rate by a predetermined amount (step S13). On the other hand, if the measured CO2 value does not exceed the set CO2 concentration (step S12: NO), the control device 21 decreases the ventilation rate by a predetermined amount (step S14). The control device 21 controls the exhaust fan 18 and the intake fan 19, and, if the CO2 removal device 20 is operating, the booster fan 203, according to the set ventilation rate (step S15).

[0020] FIG. 4 is a flowchart showing a method for switching the CO2 removing device 20 by the control device 21 according to the first embodiment. The control device 21 acquires measured values ​​from the indoor temperature sensor 11, the indoor CO2 sensor 13, the outdoor temperature sensor 14, and the outdoor CO2 sensor 16 (step S21). The control device 21 also acquires the current ventilation volume (step S22). The current ventilation volume is set in step S13 or step S14 of the flowchart shown in FIG. 3.

[0021] Based on the measured values ​​of the indoor CO2 sensor 13 and the outdoor CO2 sensor 16 acquired in step S21, the control device 21 calculates the required ventilation volume when the CO2 removal device 20 is stopped and the required ventilation volume when the CO2 removal device 20 is operated (step S23). Specifically, the control device 21 calculates the required ventilation volume according to the following formula (1). Required ventilation volume = (CO2 intake concentration - indoor CO2 concentration) x current ventilation volume / (set CO2 concentration - indoor CO2 concentration) ... (1) The CO2 intake concentration when the CO2 removal device 20 is stopped is equal to the measurement value of the outdoor CO2 sensor 16. On the other hand, the CO2 intake concentration when the CO2 removal device 20 is stopped is calculated from the measurement value of the outdoor CO2 sensor 16 and the CO2 removal rate by the DAC 204. The control device 21 calculates the difference between the ventilation volume when the CO2 removal device 20 is stopped and the required ventilation volume when the CO2 removal device 20 is operating, thereby calculating the amount of change in the required ventilation volume due to whether the CO2 removal device 20 is operating (step S24).

[0022] Next, the control device 21 calculates the amount of change in the energy required to operate the exhaust fan 18 and the intake fan 19 per unit time depending on whether or not the CO2 removal device 20 is operating, based on the amount of change in the required ventilation volume calculated in step S24 (step S25). That is, the control device 21 can calculate the amount of change in the energy required to operate the exhaust fan 18 and the intake fan 19 per unit time depending on whether or not the CO2 removal device 20 is operating, by multiplying the amount of change in the required ventilation volume by the known fan rotational energy per unit ventilation volume.

[0023] Next, the control device 21 calculates the amount of change in energy required to operate the air conditioning indoor unit 17 per unit time depending on whether the CO2 removal device 20 is operating or not, based on the measured values ​​of the indoor temperature sensor 11, indoor humidity sensor 12, outdoor temperature sensor 14, and outdoor humidity sensor 15 acquired in step S21, and the amount of change in the required ventilation volume calculated in step S24 (step S26). Specifically, the control device 21 calculates the amount of change in sensible heat load according to the following formula (2) and the amount of change in latent heat load according to the following formula (3), and calculates the amount of change in energy required to operate the air conditioning indoor unit 17 from the sum of these values.

[0024] Change in sensible heat load = specific heat of air × air density × change in required ventilation rate × |outdoor temperature - indoor temperature| (2) Change in latent heat load = latent heat of vaporization of water × air density × change in required ventilation rate × | outdoor absolute humidity - indoor absolute humidity| (3) The specific heat of air, the latent heat of vaporization of water, and the density of air may be constants. The specific heat of air and the latent heat of vaporization of water may be calculated from measurements by a temperature sensor. The density of air may be calculated from measurements by a temperature sensor and a barometer.

[0025] Next, the control device 21 converts the energy change calculated in steps S25 and S26, the energy required to operate the CO2 removal device 20 per unit time, and the energy required to recover CO2 from the CO2 removal device 20 into CO2 emissions (step S27). The control device 21 converts energy into CO2 emissions using CO2 emission coefficients published by government agencies, laws and regulations, electric power companies, etc. The energy required to recover CO2 from the CO2 removal device 20 is the energy required to heat and depressurize the DAC 204, and is correlated with the amount of CO2 to be recovered. The amount of CO2 to be recovered can be calculated, for example, by multiplying the ventilation volume required when the CO2 removal device 20 is operating, the CO2 concentration in the outside air, and the CO2 removal rate.

[0026] The control device 21 compares the sum of the CO2 emission amount converted from the energy required to operate the CO2 removal device 20 per unit time and the CO2 emission amount converted from the energy required to recover CO2 from the CO2 removal device 20 with the sum of the amount of CO2 absorbed by the CO2 removal device 20 and the amount of CO2 converted from the energy related to ventilation and air conditioning reduced by operation of the CO2 removal device 20. In other words, the control device 21 compares the increase in CO2 due to operation of the CO2 removal device 20 with the decrease in CO2 due to operation of the CO2 removal device 20. The control device 21 determines whether the decrease in CO2 exceeds the increase in CO2 (step S28).

[0027] If the amount of CO2 reduction exceeds the amount of CO2 increase (step S28: YES), the control device 21 decides to operate the CO2 removal device 20 (step S29). That is, if the CO2 removal device 20 is already operating, the operation state is maintained, and if the CO2 removal device 20 is stopped, the operation of the CO2 removal device 20 is started. On the other hand, if the amount of CO2 reduction does not exceed the amount of CO2 increase (step S28: NO), the control device 21 decides to stop the CO2 removal device 20 (step S30). That is, if the CO2 removal device 20 is already stopped, the stopped state is maintained, and if the CO2 removal device 20 is operating, the CO2 removal device 20 is stopped.

[0028] In other words, the control device 21 operates the CO2 removal device 20 when operation of the CO2 removal device 20 contributes to reducing CO2 emissions in the environment, and does not operate the CO2 removal device 20 when the energy consumed by the operation of air conditioning, ventilation, and DAC would actually increase CO2 emissions.

[0029] As described above, the air conditioning ventilation system 1 according to the first embodiment includes a ventilation device (intake fan 19) that sends air from outside the target space into the target space via an outside air introduction path, and a CO2 removal device 20 that removes CO2 contained in the air circulating through the outside air introduction path. By removing CO2 from the outside air taken in by ventilation, it is possible to reduce the ventilation volume required to suppress the CO2 concentration in the target space R. This makes it possible to reduce the amount of CO2 emissions required to calculate the energy required to power the intake fan 19.

[0030] Furthermore, the air conditioning ventilation system 1 according to the first embodiment determines whether operation of the CO2 removal device 20 contributes to reducing CO2 emissions in the environment by converting into CO2 emissions the amount of reduction in energy required to operate the intake fan 19 by operating the CO2 removal device 20, the energy required to operate the CO2 removal device 20, and the energy required to operate the air conditioning indoor unit 17 by operating the CO2 removal device 20. The control device 21 operates the CO2 removal device 20 when operation of the CO2 removal device 20 contributes to reducing CO2 emissions in the environment, and does not operate the CO2 removal device 20 when energy consumption due to operation of the air conditioning, ventilation, and DAC would actually increase CO2 emissions. This allows the control device 21 to reduce CO2 emissions.

[0031] Other Embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some processes may be executed in parallel. The control device 21 according to the above-described embodiment may be configured by a single computer, or the configuration of the control device 21 may be divided into multiple computers that cooperate with each other to function as the control device 21. For example, the control device 21 may include a control device for the air conditioning indoor unit 17 and a control device for the ventilation system in separate devices.

[0032] For example, the control device 21 according to the embodiment described above determines whether to operate the CO2 removal device 20 based on the amount of CO2 emissions, but this is not limited to this. For example, the control device 21 according to other embodiments may determine to operate the CO2 removal device 20 when operating the CO2 removal device 20 requires less energy to operate the air conditioning ventilation system 1 than operating the CO2 removal device 20. That is, the control device 21 may determine whether to operate the CO2 removal device 20 based on the amount of energy change per unit time required to operate the exhaust fan 18 and the intake fan 19, the amount of energy change per unit time required to operate the air conditioning indoor unit 17, and the energy required to operate the CO2 removal device 20 per unit time.

[0033] In addition, the control device 21 in other embodiments may determine whether or not to operate the CO2 removal device 20 based on the sum of the converted CO2 emission amount of the energy change required to operate the exhaust fan 18 and the intake fan 19 per unit time, the converted CO2 emission amount of the energy change required to operate the air conditioning indoor unit 17 per unit time, and the converted CO2 emission amount of the energy required to operate the CO2 removal device 20 per unit time, without taking into account the energy required to release CO2 from the CO2 removal device 20.

[0034] Furthermore, the air conditioning ventilation system 1 according to another embodiment may perform only ventilation without performing air conditioning control. In other words, the air conditioning ventilation system 1 according to another embodiment may be a ventilation system that does not include the air conditioning indoor unit 17. In this case, too, by including the air conditioning ventilation system 1 in the intake fan 19 and the CO2 removal device 20, it is possible to reduce the amount of ventilation while also reducing CO2 emissions.

[0035] In another embodiment, the air conditioning and ventilation system 1 may control the relative humidity of the target space R in addition to the temperature of the target space R. In this case, the air conditioning and ventilation system 1 determines the amount of humidified water to be supplied to the humidification unit 175 based on the measured values ​​of the indoor humidity sensor 12 and the outdoor humidity sensor 15, the required ventilation rate, the set temperature, and the set humidity. In this case, in step S26, the control device 21 may calculate the amount of change in latent heat load taking into account the effect of humidification.

[0036] The control device 21 includes a processor, memory, auxiliary storage device, etc., all connected via a bus, and executes an air conditioning / ventilation control program to realize the above-mentioned functions. Examples of the processor include a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and a microprocessor. The air conditioning and ventilation control program may be recorded on a computer-readable recording medium, such as a magnetic disk, a magneto-optical disk, an optical disk, or a semiconductor memory. The air conditioning and ventilation control program may be transmitted via a telecommunications line. All or part of the functions of the air conditioning and ventilation control may be realized using custom LSIs (Large Scale Integrated Circuits) such as ASICs (Application Specific Integrated Circuits) and PLDs (Programmable Logic Devices). Examples of PLDs include PALs (Programmable Array Logic), GALs (Generic Array Logic), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays). These integrated circuits are also examples of processors. [Explanation of symbols]

[0037] 1...Air conditioning ventilation system 11...Indoor temperature sensor 12...Indoor humidity sensor 13...Indoor CO2 sensor 14...Outdoor temperature sensor 15...Outdoor humidity sensor 16...Outdoor CO2 sensor 17...Air conditioning indoor unit 18...Exhaust fan 19...Intake fan 20...CO2 removal device 204...DAC 21...Control device R...Target space

Claims

1. a CO2 removal device provided in an outside air introduction path connecting the outside of the target space with the inside of the target space, the CO2 removal device removing CO2 contained in air circulating in the outside air introduction path; a ventilation device that blows air so that air flows into the target space from outside the target space through the outside air introduction path; a control device that determines whether to operate the CO2 removal device based on an amount of reduction in energy required to operate the ventilation device due to operation of the CO2 removal device and the energy required to operate the CO2 removal device; A ventilation system comprising:

2. The control device controls the ventilation device so that the CO2 concentration in the target space approaches a set CO2 concentration. The ventilation system of claim 1 .

3. The control device calculates a reduction in the amount of energy required to operate the ventilation device by operating the CO2 removal device based on the CO2 concentration outside the target space. The ventilation system of claim 1 .

4. An air conditioner that adjusts the temperature of air in the target space and blows it into the target space, The control device determines whether to operate the CO2 removal device based on the amount of reduction in energy required to operate the air conditioner by operating the CO2 removal device. The ventilation system of claim 1 .

5. The control device converts the energy into CO2 emissions, and determines whether to operate the CO2 removal device based on the amount of CO2 emissions when the CO2 removal device is operated, the amount of CO2 emissions when the CO2 removal device is not operated, and the amount of CO2 removed by operating the CO2 removal device.

5. The ventilation system of claim 4.

6. a CO2 removal device provided in an outside air introduction path connecting the outside of the target space with the inside of the target space, the CO2 removal device removing CO2 contained in air circulating in the outside air introduction path; a ventilation device that blows air so that air flows into the target space from outside the target space through the outside air introduction path; A control device for a ventilation system comprising: Whether or not to operate the CO2 removal device is determined based on the amount of reduction in energy required to operate the ventilation device due to operation of the CO2 removal device and the energy required to operate the CO2 removal device. Control device.

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