Method and system for controlling a direct air capture system for use with a heating, ventilation and / or air conditioning system

Abstract

A method (400) for controlling a direct air capture (DAC) system (220) including measuring (402) a first parameter indicative of a concentration of substance in a flow of ambient air into the DAC system (220); measuring (404) a second parameter indicative of the concentration of the substance in a flow of exhaust air from the DAC system (220); determining (406) a first threshold factor and a second threshold factor based on one or more properties of the ambient air; comparing (408) the first parameter with the first threshold factor; initiating (410) a regeneration process for at least one region of one or more adsorbent units (122) of the DAC system (220) in a positive determination that the first parameter is greater than or equal to the first threshold factor; comparing (412) the second parameter with the second threshold factor; and terminating (414) the regeneration process when the second parameter is lower than the second threshold factor.

Description

METHOD AND SYSTEM FOR CONTROLLING A DIRECT AIR CAPTURE SYSTEM FOR USE WITH A HEATING, VENTILATION AND / OR AIR CONDITIONING SYSTEMTechnical field

[0001] Various aspects of this disclosure relate to a method and a system for controlling a direct air capture (DAC) system.Background

[0002] Conventional direct air capture (DAC) technology focuses primarily on capturing carbon dioxide (CO2) directly from the atmosphere efficiently and economically. The captured CO2 are then stored underground or utilized in various applications, such as carbon-neutral fuel production or carbon-negative processes. While the DAC technology has shown promising potential in reducing greenhouse gas emissions, enhance carbon sequestration efforts, and contributing to a more sustainable and climate-resilient future, little has been done to advance the application of DAC technology other than storage and / or utilization of captured CO2.

[0003] Further, conventional DAC systems are designed as standalone units or are otherwise not optimised to work synergistically with other air management systems, in particular, heating, ventilation and / or air conditioning (HVAC) systems. Implementation of a conventional DAC system into an existing HVAC system requires complex retrofitting of the existing HVAC system to accommodate the DAC system.

[0004] Thus, there exists a need for a method and a system for controlling a DAC system that allows synergistic integration of the DAC system with a HVAC system.Summary

[0005] Various embodiments concern a method for controlling a direct air capture (DAC) system by a controller that includes a sensing arrangement and a processor. The method may include measuring, by the sensing arrangement, a first parameter indicative of a concentration of a substance in a flow of ambient air into the DAC system and a second parameter indicative of the concentration of the substance in a flow of exhaust air from the DAC system. The method may further include determining, by the processor, a first threshold factor and a second threshold factor based on one or more properties of the ambient air. The method may further include comparing, by the processor, the first parameter with the first threshold factor. The method may further include initiating, by the processor, a regeneration process for at least oneregion of one or more adsorbent units of the DAC system in a positive determination that the first parameter is greater than or equal to the first threshold factor. The method may further include comparing, by the processor, the second parameter with the second threshold factor. The method may further include terminating, by the processor, the regeneration process when the second parameter is lower than the second threshold factor.Brief description of the drawings

[0006] The disclosure will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:- FIG. 1 shows a schematic diagram of a heating, ventilation and / or air conditioning (HVAC) system according to various embodiments;- FIG. 2 shows a schematic diagram of an air management system according to various embodiments;- FIG. 3 shows a breakthrough characteristic curve illustrating a relationship between a concentration of a substance in air and a time of operation of a direct air capture (DAC) system according to various embodiments;- FIG. 4 shows a flow chart of a method for controlling the DAC system according to various embodiments;- FIG. 5A shows a control strategy of the DAC system according to various embodiments;- FIG. 5B shows a breakthrough characteristic curve illustrating a relationship between a humidity level and the time of operation of the DAC system according to various embodiments;- FIG. 6A shows a control strategy of the DAC system according to various embodiments; and- FIG. 6B shows a breakthrough characteristic curve illustrating a relationship between a carbon dioxide (CO2) concentration and the time of operation of the DAC system according to various embodiments.Detailed description

[0007] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure. Other embodiments may be utilized and structural, and logical changes may be made without departing from the scope of the disclosure. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0008] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0009] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0010] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0011] As used herein, the terms “first”, “second”, “third”, “fourth”, and so on, are used for purposes of clarity and do not imply order or precedence.

[0012] As used herein, the term “data” may be understood to include information in any suitable analog or digital form, for example, provided as a file, a portion of a file, a set of files, a signal or stream, a portion of a signal or stream, a set of signals or streams, and the like. The term data, however, is not limited to the aforementioned examples and may take various forms and represent any information as understood in the art.

[0013] As used herein, the term “processor” refers to a circuit, including analog circuits, digital circuits, or hybrid circuits, or their constituent components. Any other kind of implementation of the respective functions which will be described in more detail below may also be understood as a “circuit” in accordance with an alternative embodiment. A digital circuit may be understood as any kind of a logic implementing entity, which may be special purpose circuitry or a processor executing software stored in a memory, or a firmware.

[0014] Various embodiments generally relate to a direct air capture (DAC) system. In particular, various embodiments generally relate to a DAC system employing the use of DACtechnology to harness the advantage thereof so as to indirectly reduce carbon footprint of an air management system. The indirect carbon footprint reduction may be achieved through energy savings, with a focus on saving latent cooling load of inlet air with the application of DAC.

[0015] According to various embodiments, the DAC system may synergistically combine with a heating, ventilation and / or air conditioning (HVAC) system to form the air management system. Accordingly, various embodiments may provide that the operation of DAC, e.g. the adsorption and the regeneration processes, occur continuously and synchronously in the air management system so as to ensure uninterrupted operation of the HVAC system for providing a comfortable indoor environment for occupants. According to various embodiments, the DAC system may capture moisture (H2O) and carbon dioxide (CO2), via adsorption, from ambient air being drawn into (or supplied to) the HVAC system. The adsorption of the moisture may reduce the latent cooling load of the HVAC system. Further, the adsorption of the CO2 may reduce an indoor CO2 level, which may in turn increase the utilization of return air by the HVAC system resulting in higher return air ratio. The higher return air ratio may reduce the amount of fresh ambient air being drawn and cooled by the HVAC. The reduction in latent cooling load and the reduction in the amount of fresh ambient air to be cooled may lead to energy savings which may contribute to indirect carbon footprint reduction. According to various embodiments, the DAC system may also be configured to regenerate and release the captured CO2 back into the atmosphere in order to provide a continuous operation of DAC without expensing energy for CO2 storage or utilization. Therefore, the various embodiments are capable of achieving indirect carbon footprint reduction through energy savings and provide a sustainable and resource-efficient approach to air treatment by adsorption of moisture and CO2 and by regeneration thereof.

[0016] FIG. 1 shows a schematic diagram of a HVAC system 100 including a supply air conduit 112 and an exhaust air conduit 114 according to various embodiments. The supply air conduit 112 and the exhaust air conduit 114 may be located in an air passageway of the HVAC system 100.

[0017] As shown, according to various embodiments, the supply air conduit 112 and the exhaust air conduit 114 may be co-located alongside each other within a cylindrical duct 190. Accordingly, the cylindrical duct 190 may be partitioned longitudinally such that half of thecylindrical duct 190 may be the support air conduit 112 and another half of the cylindrical duct may be the exhaust air conduit 114.

[0018] A DAC system 120 may be located within the supply air conduit 112 and the exhaust air conduit 114. The DAC system 120 may include one or more adsorbent units 122. The one or more adsorbent units 122 may be configured to capture moisture and / or CO2 via adsorption. For example, the one or more adsorbent units 122 may include adsorbent materials capable of co-adsorption of moisture and CO2.

[0019] According to various embodiments, each adsorbent unit 122 may be actuable to dispose at least one region of the adsorbent unit 122 in the supply air conduit 112 of the HVAC system 100. When the at least one region of the adsorbent unit 122 is in the supply air conduit 112 of the HVAC system 100, the at least one region of the adsorbent unit 122 may be exposed to a flow of the ambient air along the supply air conduit 112 as the HVAC system 100 draws in fresh supply of ambient air. With a flow of ambient air passing through the at least one region of the adsorbent unit 122, adsorption of moisture and / or CO2 may occur. Accordingly, an air supply for the HVAC system 100 that has passed through the adsorbent unit 122 of the DAC system 120 may have reduced moisture and / or reduced CO2.

[0020] Further, according to various embodiments, each adsorbent unit 122 of the DAC system 120 may include a wheel structure. The wheel structure may be filled with adsorbent materials for adsorption of moisture and CO2. As shown, the adsorbent unit 122 in the form of the wheel structure may be disposed with a center of the wheel structure aligned to a longitudinal axis 192 of the cylindrical duct 190. According to various embodiments, the wheel structure of the adsorbent unit 122 may be rotatable to move the at least one region of the adsorbent unit 122 between an adsorption zone within the supply air conduit 112 for exposure to the flow of the ambient air and a regeneration zone within the exhaust air conduit 114 for exposure to a flow of exhaust air. In other words, the adsorbent unit 122 in the form of the wheel structure may be rotatable about the longitudinal axis 192 of the cylindrical duct 190 such that the at least one region of the adsorbent unit 122 may rotate through the supply air conduit 112 and the exhaust air conduit 114. The adsorption zone may be a space in the supply air conduit 112 which the adsorbent unit 122 in the form of the wheel structure may occupy and rotate therethrough. Similarly, the regeneration zone may be a space in the exhaust air conduit 114 which the adsorbent unit 122 in the form of the wheel structure may occupy and rotate therethrough. Accordingly, each the adsorbent unit 122 may be actuated or moved viarotating the adsorbent unit 122. Hence, the actuator of the adsorbent unit 122 may impart a rotation motion to the adsorbent unit 112 for the at least one region of the adsorbent unit 122 to rotate through the supply air conduit 112 and the exhaust air conduit 114.

[0021] FIG. 2 shows a schematic diagram of an air management system 200 according to various embodiments. The air management system 200 may include a HVAC system 210. The HVAC system 210 of FIG. 2 may include all the features of the HVAC system 100 of FIG. 1. Accordingly, all features, changes, modifications, and variations that are applicable to the HVAC system 100 of FIG. 1 may also be applicable to the HVAC system 220 of FIG. 2 and vice versa. The HVAC system 210 may be configured to regulate and move heated / cooled air in an enclosed indoor environment for residential or commercial buildings so as to provide regulated indoor air. The HVAC system 210 may include the supply air conduit 112 for taking in ambient air. The ambient air may be air outside of the HVAC system 210 and the enclosed environment regulated by the HVAC system 210. The drawing in of ambient air by the supply air conduit 112 may provide a fresh supply of air for the HVAC system 210 to regulate the indoor air quality.

[0022] According to various embodiments, the HVAC system 210 may include the exhaust air conduit 114 for expelling exhaust air into an ambient environment (i.e., external environment). The exhaust air being expelled via the exhaust air conduit 114 may be low quality air or air that has deteriorated. The exhaust air may be drawn out from the indoor environment via the exhaust air conduit 114 and expelled to the ambient environment. According to various embodiments, each adsorbent unit 122 of the DAC system 220 may be actuable to dispose the at least one region of the adsorbent unit 122 in the exhaust air conduit 114 of the HVAC system 210. When the at least one region of the adsorbent unit 122 is in the exhaust air conduit 114 of the HVAC system 210, the at least one region of the adsorbent unit 122 may be exposed to a flow of the exhaust air along the exhaust air conduit 114 as the HVAC system 210 pushes out the exhaust air. With the flow of exhaust air passing through the at least one region of the adsorbent unit 122, regeneration of the at least one region of the adsorbent unit 122 may occur. Accordingly, an expelled air that has passed through the adsorbent unit 122 of the DAC system 220 may carry moisture and / or CO2 from the adsorbent unit 122. According to various embodiments, the DAC system 220 may include a heater 229 disposed in the exhaust air conduit 114 to support regeneration of the adsorbent unit 122. The heater 229 may provide heat to the adsorbent units 122 such that moisture and / or CO2 may be releasedfrom the adsorbent units 122 for regeneration. According to various embodiments, the DAC system 220 may sustain continuous adsorption and regeneration by actuating the one or more adsorbent units 122 to shuttle the at least one region of the adsorbent unit 122 (or the adsorbent unit 122) between the supply air conduit 112 for adsorption and the exhaust air conduit 114 for regeneration.

[0023] According to various embodiments, the air management system 200 may include a DAC system 220. The DAC system 220 of FIG. 2 may include all the features of the DAC system 120 of FIG. 1. Accordingly, all features, changes, modifications, and variations that are applicable to the DAC system 120 of FIG. 1 may also be applicable to the DAC system 200 of FIG. 2 and vice versa. Further, elements which are the same as those described earlier are assigned the same reference numerals, and repetition of their corresponding descriptions is omitted for brevity. The following descriptions focusing on the various possible additional features and details.

[0024] According to various embodiments, the DAC system 220 may be selectively switchable between an active state and an inactive state (or selectively set in the active state or the inactive state). In the active state, the DAC system 220 may support continuous adsorption in the supply air conduit 112 of the HVAC system 210. Accordingly, the DAC system 220 may actively control, move and / or synchronize the one or more adsorbent units 122 into and out of the supply air conduit 112 of the HVAC system 210 to ensure adsorption continuously take place in the supply air conduit 112 as the HVAC system 210 continuously drawn in ambient air, while regeneration of the one or more adsorbent units 122 continuously takes place outside of the supply air conduit 112. In the inactive state, the DAC system 220 may be inactivated or become dormant or be idling such that adsorption may be omitted or ignored or bypassed or dismissed from the supply air conduit 112 whereby the flow of ambient air may flow through the supply air conduit 112 without adsorption occurring. Hence, the DAC system 220 in the inactive state may not cause adsorption to take place in the supply air conduit 112 and the ambient air may be directly supplied “as is” to the HVAC system 210 without undergoing adsorption. According to various embodiments, when the DAC system 220 is in the inactive state, the one or more adsorbent units 122 may be moved out of the supply air conduit 112 and / or be left in the supply air conduit 112 to become saturated such that adsorption may no longer take place.

[0025] According to various embodiments, the DAC system 220 may be selectively switchable between the active state and the inactive state based on one or more properties of the ambient air entering the supply air conduit 112. Climatic conditions and / or seasonality may result in changes to the one or more properties of the ambient air. The one or more properties of ambient air may include, but not limited to, temperature, dry-bulb temperature, wet-bulb temperature, vapor pressure, relative humidity, specific humidity, dew point temperature, enthalpy and / or mixing ratio. Depending on the climate and / or season, there will be variation in the one or more properties of ambient air throughout the year. In particular, fluctuation in a temperature and / or a humidity level of the ambient air may affect the performance of the DAC system 220 in the air management system 200. Accordingly, the DAC system 220 may be selectively switched between an active state and an inactive state based on one or more properties of the ambient air entering the supply air conduit 112 to adapt to the climatic and seasonal changes for adjusting the operation of the air management system 200 to maximize energy efficiency and maintain indoor comfort. Hence, when the ambient air is of a condition (based on the one or more properties of the ambient air) whereby the synergy between the DAC system 220 and the HVAC system 210 (in operation together), may result in energy savings contributing to both cost-efficiency and environmental sustainability, the DAC system 220 may be set in or switched to the active state. On the other hand, when it is more efficient and energy saving to run the HVAC system 210 without the DAC system 220, the DAC system 220 may be set in or switched to the inactive state.

[0026] According to various embodiments, the DAC system 220 may include a controller 224. The controller 224 may receive the one or more properties of the ambient air as inputs for determining whether the DAC system 220 should be in the active state or the inactive state. Accordingly, the controller 224 of the DAC system 220 may determine and control the DAC system 220 to be in the active state or the one or more operating parameters and one or more environmental parameters of the HVAC system 210. According to some embodiments, the controller 224 may include a sensing arrangement 226 disposed along the supply air conduit 112 and / or along the exhaust air conduit 114 of the one or more adsorbent units 122 of the DAC module 220. The sensing arrangement 226 may measure the one or more properties of the ambient air and provide the measured data to the controller 224 of the DAC system 220 for determining and controlling whether the DAC system 220 should be in the active state or the inactive state.

[0027] According to various embodiments, the sensing arrangement 226 may include at least one first sensor, for example, sensor 226B or 226D, placed along the flow of the ambient air. According to various embodiments, the at least one first sensor may be positioned before and / or after the flow of the ambient air reaches the one or more adsorbent units 122.

[0028] According to various embodiments, the sensing arrangement 226 may include at least one second sensor, for example, sensor 226F or 226H, placed along the flow of the exhaust air. According to various embodiments, the at least one second sensor may be positioned before and / or after the flow of the exhaust air passes through the one or more adsorbent units 122.

[0029] According to various embodiments, the sensing arrangement 226 may include a first plurality of sensors 226 A to 226D disposed within the supply air conduit 112 of the DAC system 210. Referring back to FIG. 2, the first plurality of sensors 226A to 226D is placed along the flow of the ambient air. According to various embodiments, at least one of the first plurality of sensors (e.g. 226A and 226C) may be positioned before the flow of the ambient air reaches the one or more adsorbent units 122. According to various embodiments, at least one of the first plurality of sensors (e.g. 226B and 226D) may be positioned after the flow of the ambient air passes through the one or more adsorbent units 122.

[0030] According to various embodiments, the sensing arrangement 226 may include a second plurality of sensors 226E to 226H disposed within the exhaust air conduit 114 of the DAC system 210. Referring back to FIG. 2, the second plurality of sensors 226E to 226H is placed along the flow of the exhaust air. According to various embodiments, at least one of the second plurality of sensors (e.g. 226E and 226G) may be positioned before the flow of the exhaust air reaches the one or more adsorbent units 122. According to various embodiments, at least one of the second plurality of sensors (e.g. 226F and 226H) may be positioned after the flow of the exhaust air passes through the one or more adsorbent units 122.

[0031] According to various embodiments, the DAC system 220 may include one or more actuators 228. The one or more actuators 228 may be coupled to the one or more adsorbent units 122 of the DAC system 220 for actuating and / or moving the at least one region of the adsorbent unit 122 (or the adsorbent unit 122) into the supply air conduit 112 of the HVAC system 210 for adsorption and out of the supply air conduit 112 of the HVAC system 210 for regeneration. According to various embodiments, when the DAC system 220 is in the active state, the controller 224 of the DAC system 220 may control the one or more actuators 228 of the DAC system 220 so as to coordinate and synchronize the movement of the one or moreadsorbent units 122 to ensure continuous adsorption takes place in the supply air conduit 112. For example, the one or more actuators 228 may be configured to coordinate a rotation of a first adsorbent unit to a rotation of a second adsorbent unit. According to various embodiments, when the DAC system 220 is in the inactive state, the controller 224 of the DAC system 220 may cease control of the one or more actuators 228 of the DAC system 220 so as to leave the one or more actuators 228 of the DAC system 220 in the supply air conduit 112 or out of the supply air conduit 112, or the controller 224 of the DAC system 220 may control of the one or more actuators 228 of the DAC system 220 to move out of the supply air conduit 112 without returning.

[0032] According to various embodiments, the controller 224 may comprise a processor 260, the processor 260 configured to determine an energy-saving parameter of the DAC system 220 based on one or more operating parameters and one or more environmental parameters of the HVAC system 210.

[0033] As shown in FIG. 2, in the air management system 200, the supply air conduit 112 and the exhaust air conduit 114 of the HVAC system 210 may be alongside each other according to various embodiments. Further, according to various embodiments, each adsorbent unit 122 of the DAC system 220 may be disposed such that a first half of the adsorbent unit 122 may be in the supply air conduit 112 and a second half of the adsorbent unit 122 may be in the exhaust air conduit 114.

[0034] According to various embodiments, the HVAC system 210 may include a heat exchanger 282 and a heating / cooling coil 284. As shown in FIG. 2, the ambient air drawn into the supply air conduit 112 may pass through the adsorbent units 122 followed by the heat exchanger 282 and the heating / cooling coil 284 before being supplied to the indoor environment. According to various embodiments, the DAC system 220 may include at least two adsorbent units 122 upstream of the heat exchanger 282 and / or the heating / cooling coil 284 of the HVAC system 210.

[0035] According to various embodiments, the HVAC system 210 may draw indoor air from the indoor environment and channel some indoor air as return air to the heat exchanger 282 and / or the heating / cooling coil 284 of the HVAC system 210 (see arrow 286). The remaining indoor air may be directed into the exhaust air conduit 114 for flowing out into the ambient environment.

[0036] According to various embodiments, an actuation of the one or more adsorbent units 122 may be initiated based on a breakthrough behaviour of the one or more adsorbent units 122. The breakthrough behaviour defines or describes the behaviour of an adsorbent material via identification of a critical point which signifies the end of an adsorption process.

[0037] Under normal operating conditions, the adsorption capacity of the adsorbent material of the one or more adsorbent units 122 may become saturated over time due to moisture and CO2 adsorption from continuous exposure to the ambient air drawn into the HVAC system 210. As the adsorbent material captures and holds moisture and CO2, the one or more adsorbent units 122 may reach a point when the adsorption sites become fully occupied (i.e., the one or more adsorbent units 122 may be saturated), leading to the breakthrough behaviour.

[0038] FIG. 3 shows a breakthrough characteristic curve 300 illustrating a relationship between a concentration of a substance in air and a time of operation 304 of the DAC system 220 of FIG. 2, according to various embodiments. The substance may include moisture and / or CO2.

[0039] A breakthrough behaviour may refer to a process where an adsorption capacity of the adsorbent material becomes saturated overtime due to continuous exposure to an air stream. The breakthrough behaviour may be represented by a ratio 302 of the concentration (y) of the substance in the air stream after adsorption to an influent or initial concentration (yo) of the substance in the air stream. The ratio 302 may be a y / yo value. For example, as air passes through the adsorption unit 122, the concentration of moisture and / or CO2 in the air changes due to interaction between moisture and / or CO2 and the adsorbent material. As shown by FIG. 3, initially, in an adsorption phase 306, the y / yo value is low, indicating efficient removal of moisture and / or CO2 from the air stream by the adsorbent material. However, as time progresses, the y / yo value gradually increases, reaching a point 308 where a breakthrough occurs. The breakthrough may signify that the adsorbent material has reached a breakthrough phase 310. As time further progresses, the adsorbent material may become increasingly saturated such that the adsorbent material reaches a saturation phase 312. In the saturation phase 312, the ratio 302 is close to 1, indicating that the concentration y of the substance in the air stream after adsorption is close to the initial concentration yo. At this stage, the adsorbent material may become highly saturated such that the captured substance may be released back into the air stream.

[0040] The breakthrough characteristic curve 300 helps to determine the adsorption capacity of the adsorbent material, indicating how much moisture or CO2 the adsorbent material can effectively capture before reaching the breakthrough. In addition, a slope of the breakthrough curve 300 may provide indications on a rate of breakthrough, an adsorption kinetics and / or a material performance. By analyzing the breakthrough characteristic curve 300, operational parameters, such as flow rate, adsorbent bed depth, and regeneration timing, may be optimized to ensure efficient adsorption process before the breakthrough occurs. By understanding the breakthrough behavior, a method for controlling the DAC system 220 can be fine-tuned to ensure prolonged efficient operation and improved indoor air quality.

[0041] FIG. 4 shows a flow diagram of a method 400 for controlling the DAC system 220 by the controller 224. The controller 224 may include the sensing arrangement 226 and the processor 260. The method 400 may be implemented as executable software instructions capable of being executed by the processor 260 or a module thereof.

[0042] In step 402, the sensing arrangement 226 may be configured to measure a first parameter indicative of the concentration of the substance in the flow of ambient air into the DAC system 220. The DAC system 220 may include the one or more adsorbent units 122 in a wheel structure for capturing the substance from the flow of the ambient air. The concentration of the substance may include a humidity level and / or a CO2 concentration. According to various embodiments, the first plurality of sensors 226A to 226D may be configured to measure the first parameter indicative of the concentration of the substance in the flow of ambient air into the DAC system 220.

[0043] In step 404, the sensing arrangement 226 may be configured to measure a second parameter indicative of the concentration of the substance in the flow of exhaust air from the DAC system 220. According to various embodiments, the second plurality of sensors 226E to 226H may be configured to measure the second parameter indicative of the concentration of the substance in the flow of exhaust air from the DAC system 220.

[0044] In step 406, the processor 260 may be configured to determine a first threshold factor and a second threshold factor based on the one or more properties of the ambient air. According to various embodiments, the one or more properties of the ambient air may include, in addition to the examples as mentioned earlier, room temperature, room humidity, room pressure and / or energy consumption.

[0045] In step 408, the processor 260 may be configured to compare the first parameter with the first threshold factor.

[0046] In step 410, the processor 260 may be configured to initiate the regeneration process for the at least one region of one or more adsorbent units 122 of the DAC system 220 in a positive determination that the first parameter is greater than or equal to the first threshold factor. According to various embodiments, the one or more adsorbent units 122 may be rotated to move the at least one region of the one or more adsorbent units 122 between the adsorption zone within the supply air conduit 112 for exposure to the flow of the ambient air and the regeneration zone within the exhaust air conduit 114 for exposure to the flow of exhaust air. According to various embodiments, the initiating the regeneration process may include initiating a heating process, by the heater 229, for the at least one region of the one or more adsorbent units 122 to release the substance from the at least one region of the one or more adsorbent units 122. According to various embodiments, the at least one region of the one or more adsorbent units 122 may be heated to 60 degrees Celsius (°C).

[0047] In step 412, the processor 260 may be configured to compare the second parameter with the second threshold factor.

[0048] In step 414, the processor 260 may be configured to terminate the regeneration process when the second parameter is lower than the second threshold factor. According to various embodiments, the terminating the regeneration process may include terminating the heating process by switching off the heater 229.

[0049] FIG. 5A shows a control strategy 500 of the DAC system 220 according to various embodiments. In particular, the control strategy 500 controls the actuation of the one or more adsorbent units 122 to shuttle the at least one region of the adsorbent unit 122 (or the adsorbent unit 122) between the supply air conduit 112 for adsorption and the exhaust air conduit 114 for regeneration based on the humidity level of the flow of ambient air into the DAC system 220 and the humidity level of the flow of exhaust air from the DAC system 220. According to various embodiments, the control strategy 500 may be implemented by the controller 224 of the DAC system 220 for selectively switching the DAC system 220 between the active state and the inactive state (or setting the DAC system 220 in the active state or the inactive state) based on the one or more properties of the ambient air entering the supply air conduit 112 as may be obtained in step 502. As shown in FIG. 5A, the one or more properties of the ambient air may include, in addition to the examples as mentioned earlier, a temperature, , which maybe a temperature of the ambient air or a desired temperature set by a user, a humidity level, RH, which may be a humidity level of the ambient air or a desired humidity level set by the user, and / or a humidity level, co, as measured by the sensing arrangement 226.

[0050] As shown, in step 504, a dimensionless factor & may be computed by the processor 260 based on one or more inputs that may include the one or more properties of the ambient air. The dimensionless factor & may be a threshold factor, such as the first threshold factor of step 406, which indicates that the adsorption capacity of the at least one region of the adsorbent unit 122 in the supply air conduit 112 may be lower than an optimal limit and should therefore be transited to the exhaust air conduit 114 for regeneration.

[0051] FIG. 5B shows a breakthrough characteristic curve 550 illustrating a relationship between a humidity level 552 and a time of operation 554 of the DAC system 220, according to various embodiments. During an adsorption process, the humidity level of air after passing through the one or more adsorbent units 122, coi, may be measured by one or more sensors (e.g. the sensor 226B) which may be positioned at a point in the supply air conduit 112. Initially, coi remains at a lower limit for the time duration of tmoi-i until a moisture breakthrough occurs. After the breakthrough, for next tmoi-2, coi may continue to increase until a predetermined humidity level, cocrit. (Ocrit may be determined by & and the humidity level of air before passing through the one or more adsorbent units 122, coo. coo may be measured by one or more sensors (e.g. the sensor 226A) which may be positioned at a point in the supply air conduit 112. The time tcycie-coi may be a sum of tmoi-1 and tmoi-2, and may be indicative of a time period for a switching cycle so as to shuttle the at least one region of the adsorbent unit 122 (or the adsorbent unit 122) between the supply air conduit 112 for adsorption and the exhaust air conduit 114 for regeneration.

[0052] Referring back to FIG. 5A, in step 506, the humidity levels coo and coi are obtained. In step 508, the value of a humidity ratio coi / coo is obtained. In step 510, when coi is measured to be equal to or more than cocrit, the adsorption capacity of the at least one region of the adsorbent unit 122 in the supply air conduit 112 may be deemed as lower than an optimal limit. The regeneration process may then be initiated in step 512.

[0053] In step 514, during the regeneration process in the exhaust air conduit 114, the air temperature around the at least one region of the adsorbent unit 122 may be maintained at around 60°C by at least one heater.

[0054] Under normal operating conditions, a time period required for adsorption may be longer than a time period required needed for regeneration of the adsorbent unit 122. To reduce energy consumption by the DAC system 220, the regeneration process may be terminated well before a subsequent switching cycle. A termination of the regeneration process may be determined by the humidity levels (coe and co?) measured by one or more sensors (e.g. the sensors 226G and 226H) which may be positioned at a point in the exhaust air conduit 114.

[0055] In step 532, coe may be measured at a point before the exhaust air passes through the one or more adsorbent units 122 and co? may be measured at a point after the exhaust air passes through the one or more adsorbent units 122. During the regeneration process, coe may exceed co?. The regeneration process may be terminated when coe equals co?.

[0056] In step 534, a dimensionless factor 5, such as the second threshold factor of step 414, may be introduced as a buffer to ensure energy efficiency. In step 536, a value of (co? / coe - 8) is obtained. In step 538, if the value of (co? / coe - 6) is lower than 1, the regeneration process would be terminated. In step 540, the heater would be set as inactive until the next switching cycle.

[0057] FIG. 6A shows a control strategy 600 of the DAC system 220 according to various embodiments. In particular, the control strategy 600 controls the actuation of the one or more adsorbent units 122 to shuttle the at least one region of the adsorbent unit 122 (or the adsorbent unit 122) between the supply air conduit 112 for adsorption and the exhaust air conduit 114 for regeneration based on the CO2 concentration of the flow of ambient air into the DAC system 220 and the CO2 concentration of the flow of exhaust air from the DAC system 220. According to various embodiments, the control strategy 600 of FIG. 6A includes all the features of the control strategy 500 of FIG. 5A. Accordingly, all features, changes, modifications, and variations that are applicable to the control strategy 500 of FIG. 5 A may also be applicable to the control strategy 600 of FIG. 6 A. Further, elements which are the same as those described earlier are assigned the same reference numerals, and repetition of their corresponding descriptions is omitted for brevity. The following descriptions focusing on the various possible additional features and details.

[0058] FIG. 6B shows a breakthrough characteristic curve 650 illustrating a relationship between a CO2 concentration 652 and a time of operation 654 of the DAC system 220, according to various embodiments. During an adsorption process, the CO2 concentration of air after passing through the one or more adsorbent units 122, C3, may be measured by a sensor(e.g. the sensor 226D) which may be positioned at a point in the supply air conduit 112. Initially, C3 remains at a lower limit for the time duration of tC02-i until a CO2 breakthrough occurs. As time progresses, this may lead to a higher indoor CO2 concentration, C4. C4 may be measured by one or more sensors (e.g. the sensor 226E) which may be positioned at a point in the exhaust air conduit 114. After the breakthrough, for next tco-2, C4 may continue to increase until a predetermined CO2 concentration, Cmax. The time tcycie-<o2 may be a sum of tco2-i and tco- 2, and may be indicative of the time period for the switching cycle.

[0059] Referring back to FIG. 6A, the one or more properties of the ambient air may include, in addition to the examples as mentioned earlier, the indoor CO2 concentration.

[0060] In step 602, an upper limit of the CO2 concentration, Cmax, is determined. In step 604, the indoor CO2 concentration, C4, is obtained. In step 606, when C4 is measure to be equal or more than Cmax, the adsorption capacity of the at least one region of the adsorbent unit 122 in the supply air conduit 112 may be deemed as lower than an optimal limit. The regeneration process may then be initiated in step 608.

[0061] In step 610, during the regeneration process in the exhaust air conduit 114, the air temperature around the at least one region of the adsorbent unit 122 may be maintained at around 60°C by at least one heater. To reduce energy consumption by the DAC system 220, the regeneration process may be terminated well before the subsequent switching cycle. A termination of the regeneration process may be determined by the CO2 concentrations (C4 and C5) measured by one or more sensors (e.g. the sensors 226E and 226F) which may be positioned at a point in the exhaust air conduit 114.

[0062] In step 632, C4 may be measured at a point before the exhaust air passes through the one or more adsorbent units 122 and C5 may be measured at a point after the exhaust air passes through the one or more adsorbent units 122. In step 634, the dimensionless factor 5 may be introduced as a buffer to ensure energy efficiency. In step 636, a value of (C5 / C4 - 5) is obtained. In step 638, if the value of (C5 / C4 - 5) is lower than 1, the regeneration process would be terminated. In step 640, the heater would be set as inactive until the next switching cycle.

[0063] According to yet another aspect of the disclosure, there is a computer program, the computer program comprising instructions to execute the computer-assisted method 400. In some embodiments, there may comprise a non-transitory computer readable medium configured to store executable software instructions thereon, such that when executed, performs the method 400.

[0064] While the disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1. A method (400) for controlling a direct air capture (DAC) system (220) by a controller (224), the controller (224) comprising a sensing arrangement (226) and a processor (260), the method (400) comprising: measuring (402, 404), by the sensing arrangement (226), a first parameter indicative of a concentration of a substance in a flow of ambient air into the DAC system (220) and a second parameter indicative of the concentration of the substance in a flow of exhaust air from the DAC system (220); determining (406), by the processor (260), a first threshold factor and a second threshold factor based on one or more properties of the ambient air; comparing (408), by the processor (260), the first parameter with the first threshold factor; initiating (410), by the processor, a regeneration process for at least one region of one or more adsorbent units (122) in a positive determination that the first parameter is greater than or equal to the first threshold factor; comparing (412), by the processor (260), the second parameter with the second threshold factor; and terminating (414), by the processor (260), the regeneration process when the second parameter is lower than the second threshold factor.

2. The method (400) as claimed in claim 1, wherein each of the one or more adsorbent units (122) comprises a wheel structure.

3. The method (400) as claimed in claim 2, wherein the initiating (410) the regeneration process comprises rotating the wheel structure about a pivot to move the at least one region of the one or more adsorbent units (122) between an adsorption zone within a supply air conduit (112) for exposure to the flow of the ambient air and a regeneration zone within an exhaust air conduit (114) for exposure to the flow of exhaust air.

4. The method (400) as claimed in any one of the preceding claims, wherein the initiating (410) the regeneration process comprises initiating a heating process, by a heater (229), for theat least one region of the one or more adsorbent units (122) to release the substance from the at least one region of the one or more adsorbent units (122).

5. The method (400) as claimed in claim 4, wherein the terminating (414) the regeneration process comprises terminating the heating process by switching off the heater (229).

6. The method (400) as claimed in claim 4, wherein the at least one region of the one or more adsorbent units (122) is heated to 60 degrees Celsius.

7. The method (400) as claimed in claim 3, wherein the rotating the one or more adsorbent units (122) is performed by one or more actuators (228) of the DAC system (220) to coordinate a rotation of a first adsorbent unit to a rotation of a second adsorbent unit. .

8. The method (400) as claimed in any one of the preceding claims, wherein each of the one or more adsorbent units (122) is configured to capture the substance from the ambient air during adsorption, and wherein the substance comprises moisture and / or carbon dioxide.

9. The method (400) as claimed in any one of the preceding claims, wherein the sensing arrangement (226) comprises at least one first sensor (226B, 226D) placed along the flow of the ambient air, and wherein the at least one first sensor (226B, 226D) is positioned after the flow of the ambient air passes through the one or more adsorbent units (122).

10. The method (400) as claimed in any one of the preceding claims, wherein the sensing arrangement (226) comprises at least one second sensor (226F, 226H) placed along the flow of the exhaust air, and wherein the at least one second sensor (226F, 226H) is positioned after the flow of the exhaust air passes through the one or more adsorbent units (122).

11. The method (400) as claimed in any one of the preceding claims, wherein the one or more properties of the ambient air comprises room temperature, room humidity, room pressure and / or energy consumption.

12. A controller (224) for a direct air capture (DAC) system (220) comprising: a sensing arrangement (226), wherein the sensing arrangement (226) is configured to measure a first parameter indicative of a concentration of a substance in a flow of ambient air into the DAC system (220) and a second parameter indicative of the concentration of the substance in a flow of exhaust air from the DAC system (220); and a processor (260), wherein the processor (260) is configured to: determine a first threshold factor and a second threshold factor based on one or more properties of the ambient air, compare the first parameter with the first threshold factor, initiate a regeneration process for at least one region of one or more adsorbent units (122) in a positive determination that the first parameter is greater than or equal to the first threshold factor, compare the second parameter with the second threshold factor, and terminate the regeneration process when the second parameter is lower than the second threshold factor.

13. An air management system (200) comprising the controller (224) as claimed in claim

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