Patent Publication Number: US-2023158451-A1

Title: Autothermal direct air capture system

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Pat. Application 62/990,894, filed Mar. 17, 2020, titled “Autothermal CO 2  Direct Air Capture System,” the entirety of the disclosure of which is hereby incorporated by this reference. 
    
    
     TECHNICAL FIELD 
     Aspects of this document relate generally to an autothermal direct air capture system. 
     BACKGROUND 
     The need for technologies to remove carbon dioxide from the atmosphere has been well established. In addition to conservation, reduced-carbon processes, and on-site capture efforts, a significant amount of carbon dioxide will need to be removed from the atmosphere to avoid a looming climate change crisis. Technology that pulls carbon dioxide from the air or other dilute sources and turns it into a marketable and utilizable product can drive widespread adoption, if the capture and purification process is economical. The costs have to be competitive with other carbon sources to persuade the carbon-processing industries to change their carbon source to captured CO 2 . 
     Unfortunately, many conventional air capture processes are expensive to set up and costly to operate, particularly the energy costs. Since the carbon dioxide in the ambient air is very dilute, atmospheric CO 2  collectors can quickly overrun a tight energy budget for drawing in and processing air. 
     SUMMARY 
     According to one aspect, an autothermal direct air capture (ADAC) system includes a chamber having an interior, a water reservoir including water, a vacuum compressor in fluid communication with the interior of the chamber, and a sorbent material configured to release water under an ambient condition. The ambient condition includes an ambient temperature and an ambient moisture level. The sorbent material is further configured to bind water under a first moisture level that is higher than the ambient moisture level, bind carbon dioxide under the ambient condition, and release carbon dioxide under a release condition including at least one of a first temperature that is higher than the ambient temperature and the first moisture level. The ADAC system also includes a water resupply line in fluid communication with the water reservoir, a heat exchanger in thermal contact with the water resupply line and a product stream passing from the interior of the chamber and through the vacuum compressor, and a circulation compressor having an input and an output. The input and output are in fluid communication with the interior of the chamber. The ADAC further includes a sprayer in fluid communication with the water reservoir and the output of the circulation compressor. The ADAC system is movable between a capture configuration and a regeneration configuration. The capture configuration includes the sorbent material being positioned outside the chamber and exposed to a first gas volume including carbon dioxide under the ambient condition. The capture configuration also includes the sorbent material binding with carbon dioxide within the first gas volume while desorbing water into the first gas volume, the sorbent material selected so heat generated due to the adsorption of carbon dioxide is less than heat consumed in desorbing water, under the ambient condition, such that the sorbent material extracts heat while the ADAC system is in the capture configuration, resulting in the thermal charging of the sorbent material. The regeneration configuration includes the sorbent material being enclosed within the chamber, the water reservoir being put into fluid communication with the interior of the chamber such that the sorbent material is in contact with water, the sorbent material releasing the adsorbed carbon dioxide into the chamber while binding water inside the chamber and causing the sorbent material to deposit heat into the interior of the chamber, the vacuum compressor removing a carbon dioxide rich product stream from the interior of the chamber. Heat is transferred by the heat exchanger from the product stream removed from the chamber to the water as it passes through the water resupply line while the ADAC system is in the regeneration configuration. At least one of the sorbent material and the chamber moves while the ADAC system transitions to the regeneration configuration such that the sorbent material is enclosed within the interior of the chamber. The circulation compressor is configured to remove a portion of the gas within the interior of the chamber through the input and deliver the portion of the gas back to the interior of the chamber through the output, while the ADAC system is in the regeneration configuration. The sprayer is configured to spray water droplets into the interior of the chamber when the ADAC system is in the regeneration configuration, the droplets propelled by the gas delivered to the interior of the chamber by the circulation compressor. 
     Particular embodiments may comprise one or more of the following features. The sorbent material may include a moisture-swing material. The sorbent material may include a thermal-swing material. The transition from the capture configuration to the regeneration configuration may include at least the partial evacuation of the chamber. The chamber may be evacuated by the vacuum compressor while the ADAC system is in the regeneration configuration such that a partial pressure of water vapor within the chamber may be at least a majority of a total pressure within the chamber, while the ADAC system is in the regeneration configuration. The sorbent material may be a composite material including a first material configured to release water under the ambient condition and bind water under the first moisture level, and a second material configured to bind carbon dioxide under the ambient condition, and release carbon dioxide under the release condition. The water reservoir may be inside the chamber. The water within the water reservoir may be maintained at a supply temperature that is at most equal to the ambient temperature. 
     According to another aspect of the disclosure, an autothermal direct air capture (ADAC) system includes a chamber having an interior, a water reservoir having water, and a sorbent material configured to release water under an ambient condition including an ambient temperature and an ambient moisture level, bind water under a first moisture level that is higher than the ambient moisture level, bind carbon dioxide under the ambient condition, and release carbon dioxide under a release condition including at least one of a first temperature that is higher than the ambient temperature and the first moisture level. The ADAC system is movable between a capture configuration and a regeneration configuration. The capture configuration includes the sorbent material being exposed to a first gas volume having carbon dioxide under the ambient condition, the sorbent material binding with carbon dioxide within the first gas volume while desorbing water into the first gas volume, the sorbent material selected so heat generated due to the adsorption of carbon dioxide is less than heat consumed in desorbing water, under the ambient condition, such that the sorbent material extracts heat while the ADAC system is in the capture configuration, resulting in the thermal charging of the sorbent material. The regeneration configuration includes the sorbent material being enclosed within the chamber, the water reservoir being put into fluid communication with the interior of the chamber such that the sorbent material is in contact with water, the sorbent material releasing the adsorbed carbon dioxide into the chamber while binding water inside the chamber and causing the sorbent material to deposit heat into the interior of the chamber. 
     Particular embodiments may comprise one or more of the following features. The ADAC system may further include a water resupply line in fluid communication with the water reservoir, and/or a heat exchanger in thermal contact with the water resupply line and the product stream removed from the chamber. Heat may be transferred from the product stream removed from the chamber to the water as it passes through the water resupply line while the ADAC system is in the regeneration configuration. The capture configuration may further include the sorbent material positioned outside the chamber. At least one of the sorbent material and the chamber may move while the ADAC system transitions to the regeneration configuration such that the sorbent material is enclosed within the interior of the chamber. The sorbent material may be positioned within the interior of the chamber in both the capture configuration and the regeneration configuration. The first gas volume may pass through the interior of the chamber while the ADAC system is in the capture configuration. The sorbent material may be in direct contact with liquid water from the water reservoir while the ADAC system is in the regeneration configuration. The ADAC system may further include a sprayer in fluid communication with the water reservoir, the sprayer configured to spray water droplets into the interior of the chamber when the ADAC system is in the regeneration configuration. The ADAC system may further include a vacuum compressor in fluid communication with the interior of the chamber. The chamber may be evacuated by the vacuum compressor while the ADAC system is in the regeneration configuration such that a partial pressure of water vapor within the chamber is at least a majority of a total pressure within the chamber, while the ADAC system is in the regeneration configuration. The ADAC system may further include a circulation compressor having an input and an output, the input and output in fluid communication with the interior of the chamber, the circulation compressor configured to remove a portion of a gas within the interior of the chamber through the input and deliver the portion of the gas back to the interior of the chamber through the output, while the ADAC system is in the regeneration configuration. The gas delivered to the interior of the chamber by the circulation compressor may bubble through liquid water from the water reservoir after exiting the output of the circulation compressor, while the ADAC system is in the regeneration configuration. The ADAC system may further include a sprayer in fluid communication with the water reservoir, the sprayer configured to spray water droplets into the interior of the chamber when the ADAC system is in the regeneration configuration. The gas delivered to the interior of the chamber by the circulation compressor may propel the water droplets out of the sprayer and into the interior of the chamber. The first gas volume may be sized to maintain a temperature of the sorbent material close to the ambient temperature while providing the heat to desorb water while the ADAC system is in the capture configuration. The first gas volume may be one of ambient outdoor air, indoor air, flue gas, and gas from a fermenter. The ADAC system may further include a vacuum compressor in fluid communication with the interior of the chamber. The regeneration configuration may further include the vacuum compressor removing a carbon dioxide rich product stream from the interior of the chamber. 
     Aspects and applications of the disclosure presented here are described below in the drawings and detailed description. Unless specifically noted, it is intended that the words and phrases in the specification and the claims be given their plain, ordinary, and accustomed meaning to those of ordinary skill in the applicable arts. The inventors are fully aware that they can be their own lexicographers if desired. The inventors expressly elect, as their own lexicographers, to use only the plain and ordinary meaning of terms in the specification and claims unless they clearly state otherwise and then further, expressly set forth the “special” definition of that term and explain how it differs from the plain and ordinary meaning. Absent such clear statements of intent to apply a “special” definition, it is the inventors’ intent and desire that the simple, plain and ordinary meaning to the terms be applied to the interpretation of the specification and claims. 
     The inventors are also aware of the normal precepts of English grammar. Thus, if a noun, term, or phrase is intended to be further characterized, specified, or narrowed in some way, then such noun, term, or phrase will expressly include additional adjectives, descriptive terms, or other modifiers in accordance with the normal precepts of English grammar. Absent the use of such adjectives, descriptive terms, or modifiers, it is the intent that such nouns, terms, or phrases be given their plain, and ordinary English meaning to those skilled in the applicable arts as set forth above. 
     Further, the inventors are fully informed of the standards and application of the special provisions of 35 U.S.C. § 112(f). Thus, the use of the words “function,” “means” or “step” in the Detailed Description or Description of the Drawings or claims is not intended to somehow indicate a desire to invoke the special provisions of 35 U.S.C. § 112(f), to define the invention. To the contrary, if the provisions of 35 U.S.C. § 112(f) are sought to be invoked to define the inventions, the claims will specifically and expressly state the exact phrases “means for” or “step for”, and will also recite the word “function” (i.e., will state “means for performing the function of [insert function]”), without also reciting in such phrases any structure, material or act in support of the function. Thus, even when the claims recite a “means for performing the function of ... ” or “step for performing the function of... ,” if the claims also recite any structure, material or acts in support of that means or step, or that perform the recited function, then it is the clear intention of the inventors not to invoke the provisions of 35 U.S.C. § 112(f). Moreover, even if the provisions of 35 U.S.C. § 112(f) are invoked to define the claimed aspects, it is intended that these aspects not be limited only to the specific structure, material or acts that are described in the preferred embodiments, but in addition, include any and all structures, materials or acts that perform the claimed function as described in alternative embodiments or forms of the disclosure, or that are well known present or later-developed, equivalent structures, material or acts for performing the claimed function. 
     The foregoing and other aspects, features, and advantages will be apparent to those artisans of ordinary skill in the art from the DESCRIPTION and DRAWINGS, and from the CLAIMS. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will hereinafter be described in conjunction with the appended drawings, where like designations denote like elements, and: 
         FIG.  1 A  is a schematic view of an autothermal direct air capture (ADAC) system in the capture configuration; 
         FIG.  1 B  is a schematic view of another embodiment of an ADAC system in the capture configuration; 
         FIG.  2 A  is a schematic view of the ADAC system of  FIG.  1 A  in the regeneration configuration; 
         FIG.  2 B  is a schematic view of the ADAC system of  FIG.  1 B  in the regeneration configuration; and 
         FIG.  3    is a top view of a composite sorbent material. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure, its aspects and implementations, are not limited to the specific material types, components, methods, or other examples disclosed herein. Many additional material types, components, methods, and procedures known in the art are contemplated for use with particular implementations from this disclosure. Accordingly, for example, although particular implementations are disclosed, such implementations and implementing components may comprise any components, models, types, materials, versions, quantities, and/or the like as is known in the art for such systems and implementing components, consistent with the intended operation. 
     The word “exemplary,” “example,” or various forms thereof are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” or as an “example” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Furthermore, examples are provided solely for purposes of clarity and understanding and are not meant to limit or restrict the disclosed subject matter or relevant portions of this disclosure in any manner. It is to be appreciated that a myriad of additional or alternate examples of varying scope could have been presented, but have been omitted for purposes of brevity. 
     While this disclosure includes a number of embodiments in many different forms, there is shown in the drawings and will herein be described in detail particular embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the disclosed methods and systems, and is not intended to limit the broad aspect of the disclosed concepts to the embodiments illustrated. 
     The need for technologies to remove carbon dioxide from the atmosphere has been well established. In addition to conservation, reduced-carbon processes, and on-site capture efforts, a significant amount of carbon dioxide will need to be removed from the atmosphere to avoid a looming climate change crisis. Technology that pulls carbon dioxide from the air or other dilute sources and turns it into a marketable and utilizable product can drive widespread adoption, if the capture and purification process is economical. The costs have to be competitive with other carbon sources to persuade the carbon-processing industries to change their carbon source to captured CO 2 . 
     Unfortunately, many conventional air capture processes are expensive to set up and costly to operate, particularly the energy costs. Since the carbon dioxide in the ambient air is very dilute, atmospheric CO 2  collectors can quickly overrun a tight energy budget for drawing in and processing air. 
     Contemplated herein is a system for autothermal direct air capture for carbon dioxide. The autothermal direct air capture systems (hereinafter ADAC system or ADAC) contemplated herein are able to operate with much lower energy requirements than conventional capture systems, by transferring thermal energy from the ambient air from which the CO 2  is being extracted into the system at a higher temperature. The thermal energy can be used to perform a thermal swing CO 2  desorption process, and/or to generate water vapor for the hydration of a CO 2  sorbent to trigger the release of CO 2  via a moisture-driven desorption. 
     In some embodiments, the capture and purification process of an ADAC system may only require a supply of water, a gas having CO 2 , and sufficient electrical energy to operate devices such as pumps, motors, control devices, and the like. As will be discussed in greater detail below, the ADAC system comprises a sorbent material that can absorb water during a regeneration stage and desorb water when it is exposed to ambient air during a capture stage. The sorbent material also performs CO 2  absorption when contacting ambient air during the capture stage. The heat released from the sorbent material during water adsorption in the regeneration stage is again used for steam generation, which further hydrates the sorbent material until it is fully loaded with water. This results in a kind of self-amplifying sorption heat pump cycle. During the regeneration stage, carbon dioxide is desorbed because of the presence of water, elevated temperatures due to water adsorption, reduced total pressure due to water adsorption, or a combination of these factors. Hence, the operating costs of the ADAC system can be much lower than that of comparable capture systems that must use more valuable energy sources for the heat supply. This approach may also allow ADAC systems to be deployed in environments that would be less suitable for conventional capture systems. 
     It should be noted that while the following discussion of ADAC systems will be done in the context of capturing dilute CO 2  from ambient, atmospheric air, the systems contemplated herein may be adapted for use in capturing CO 2  from a variety of sources, including but not limited to indoor air, flue gas, and gaseous product streams from other production methods or processes such as fermenters and the like. Furthermore, the ADAC systems contemplated herein may also be adapted for use in the capture of other gases, using appropriate sorbent materials that have an affinity for said gases and also conform to the operating constraints to be discussed below. 
       FIGS.  1 A and  1 B  are schematic views of non-limiting examples of different embodiments of an ADAC system  100  in a capture configuration  130 . As shown, the ADAC  100  comprises a chamber  102  having a hollow interior  106 , a sorbent material  104 , a water reservoir  108  containing water  110 , and a vacuum compressor  112  in fluid communication with the interior  106  of the chamber  102 . Some embodiments comprise additional elements, which will be discussed in greater detail, below. 
     As shown, the ADAC  100  comprises a sorbent material  104 . In the context of the present description and the claims that follow, a sorbent material  104  is a material that (1) can bind water under wet conditions and release water under an ambient condition  124  and (2) can bind CO 2  under the ambient condition  124  and release that CO 2  at elevated temperature and/or high moisture levels. This condition having an elevated temperature and/or high moisture levels (e.g. the previously mentioned wet conditions, a “first moisture level” etc.) will be referred to as a release condition, and will be discussed with respect to  FIGS.  2 A and  2 B , below. These two different functionalities are central to the ADAC systems  100  ability to extract both CO 2   133  and heat  138  from the ambient air. 
     According to various embodiments, the sorbent material  104  is chosen or configured such that it releases bound water under an ambient condition  124  comprising an ambient temperature  126  and an ambient moisture level  128 . In the context of the present description and the claims that follow, a “condition” such as the ambient condition  124  is one or more characteristics describing the environment (e.g. atmosphere) localized around the ADAC  100 , and in some cases localized around the sorbent material  104  itself. Ambient condition  124  refers to the temperature and moisture level of a first gas volume  132  comprising carbon dioxide that is in fluid and thermal contact with the ADAC  100 . It should be noted that while many of the following examples are given in the context of an ADAC  100  operating outdoors, ambient condition  124  should not be construed to require an outdoor environment, and may also refer to any other first gas volume  132  comprising carbon dioxide that is in fluid and thermal contact with the ADAC  100  including, but not limited to, indoor atmosphere, output or by-product of another process, and the like. According to various embodiments, the ADAC  100  interacts with this first gas volume  132  in meaningful ways while in a capture configuration  130 , as will be discussed below. In some embodiments, the first gas volume  132  may have additional beneficial interactions with the ADAC  100  independent of the configuration. 
     On the one hand, the sorbent material  104  binds CO 2   133  with sufficient strength to remove CO 2   133  from ambient air, (e.g. at a partial pressure of CO 2  of about 40 Pa, etc.) and temperatures  126  and relative humidity levels (e.g. ambient moisture levels  128 ) that are typical for ambient conditions  124  at a particular location. However, heating the sorbent material  104  and/or exposing it to moisture (depending on the nature of the sorbent material  104 ) will cause the release of the CO 2   133 . On the other hand, the sorbent material  104  is chosen for having a significant affinity to water vapor, with a binding energy for water vapor that exceeds the heat of condensation of water under similar temperature and pressure conditions, according to various embodiments. However, the affinity to water is sufficiently low for the sorbent material  104  to shed a significant amount of water  110  when it is moved from a condition of water saturation, or near saturation, to drier air conditions that reflect ambient conditions  124  in certain locations. 
     Furthermore, under ambient conditions  124  and according to various embodiments, the ratio of CO 2  uptake and water release is such that the sorbent material  104  cools as it absorbs CO 2   133 . In other words, the evaporative cooling for appropriately designed sorbent materials  104  overwhelms the heat  134  delivered by the adsorption of CO 2 . The reverse is true while the ADAC  100  is in a regeneration configuration, where the water  110  adsorbed onto the sorbent material  104  will heat the sorbent material  104 , and such heat is likely to exceed the cooling associated with the release of the bound CO 2   133 . The regeneration configuration will be discussed further with respect to  FIGS.  2 A and  2 B , below. 
     According to various embodiments, the sorbent material  104  may take on a variety of forms, depending on the nature of the capture mechanism and the environment in which it is being used. Examples include, but are not limited to, filter or cloth-like structures that increase exposed surface area and may allow air to flow through them, fiber structures, tubular structures, one or more surfaces coated with one or more sorbents, meshes, disks, tiles, grids, arrays of plates, and the like. In some embodiments, the sorbent material  104  may be contained in a single unit, while in other embodiments, the sorbent material  104  may be in multiple segments spread apart to allow greater interaction with the atmosphere. In some embodiments, the sorbent material  104  may comprise a moisture-swing material, while in other embodiments it may comprise a thermal-swing material. 
     The ADAC  100  further comprises a water reservoir  108  containing liquid water  110  that will be introduced to the sorbent material  104  while the ADAC  100  is in a regeneration configuration. While  FIGS.  1 A and  1 B  depict the water reservoir  108  as being located outside of the chamber  102 , it should be noted that these are schematic views showing how the various elements of the ADAC  100  interact. According to various embodiments, some or all of these elements may be housed within a shared thermally insulating housing, to enhance heat integration. In some embodiments, the water reservoir  108  may be outside of the chamber  102 , while in other embodiments, it may be inside the chamber  102 . 
     As shown, in some embodiments, a water resupply line  116  is in fluid communication with the water reservoir  108 . This facilitates the replacement of water  110  lost during the operation of the ADAC  100  (e.g. cycling between configurations). Additionally, in some embodiments, the water resupply line  116  presents an additional opportunity to make use of heat that tends to be wasted by conventional capture systems, as will be discussed with respect to  FIGS.  2 A and  2 B , below. 
     The liquid water  110  stored within the water reservoir  108  will be used to release the carbon dioxide  133  bound to the sorbent material while in a regeneration configuration. In some embodiments, this is facilitated by maintaining the water  110  within the reservoir  108  at a supply temperature  114  by some form of heat input. In some embodiments, the supply temperature  114  may be maintained at or below ambient temperature  126 , allowing the heat to simply be ambient heat, which advantageously does not require any energy for delivery and does not increase the operational cost. In some embodiments, the water  110  within the reservoir  108  is in thermal contact with the ambient surroundings for at least a portion of the capture/regeneration cycle. 
     As shown, the ADAC  100  comprises a vacuum compressor  112  that is in fluid communication with the interior  106  of the chamber  102 . The vacuum compressor  112  may be used to evacuate the chamber and/or extract a CO 2 -enriched product stream. The vacuum compressor  112  will be discussed further in the context of the regeneration configuration, below. Additionally, some embodiments may further comprise a heat exchanger  118 , a circulation compressor  122 , and/or a sprayer  120 . These embodiments will also be discussed with respect to  FIGS.  2 A and  2 B , below. 
     According to various embodiments, an ADAC system  100  operates with a capture configuration  130  or stage, where CO 2   133  is pulled from the atmosphere by the sorbent material  104  that is also releasing water vapor, and a regeneration configuration or stage, where the sorbent material  104  releases the captured CO 2   133  while adsorbing water  110 . The ADAC  100  is movable between these two configurations. 
       FIGS.  1 A and  1 B  are schematic views of non-limiting examples of two embodiments of a ADAC  100  in the capture configuration  130 . In the context of the present description and the claims that follow, the capture configuration  130  of an ADAC  100  is the state in which the sorbent material  104  is pulling carbon dioxide  133  out of a body of gas, such as the atmosphere or some other source. Specifically, the capture configuration  130  comprises the sorbent material  104  being exposed to a first gas volume  132  comprising carbon dioxide  133  under ambient condition  124 . While in the capture configuration  130  the sorbent material  104  binds with carbon dioxide  133  within the first gas volume  132  while desorbing water  110  into the first gas volume  132 . As discussed earlier, the sorbent material  104  is selected and designed so that heat generated  134  due to the adsorption of carbon dioxide  133  is less than heat consumed  136  in desorbing water  110 , under the ambient condition  124 , the net result being that the sorbent material  104  extracts heat  138  from the first gas volume  132  while the ADAC system  100  is in the capture configuration  130 . This results in the thermal charging of the sorbent material  104 , which will be used advantageously while the ADAC  100  is in the regeneration configuration, which will be discussed with respect to  FIGS.  2 A and  2 B , below. In other words, the sorbent material  104  extracts heat from the first gas volume  132  without raising the temperature of the sorbent material  104 , while it is drying out and adsorbing CO 2 . 
     In some embodiments, this process is a (semi-)batch process, one step in the process being the capture of CO 2   133  from the CO 2  source (e.g. the first gas volume  132 ), which for example is air, combined with the thermal charging of the sorbent material  104  through the evaporation of water  110 . In other embodiments, this process may be implemented as a continuous process, with the ADAC  100  comprising elements that can be in either configuration, with both configurations active at the same time, and able to transition those elements from one configuration to the other in a continuous manner. For example, in some embodiments, the sorbent material  104  may form a continuous loop, so that as one part gradually moves from the capture configuration to the regeneration configuration, another part of the sorbent material  104  is moving from the regeneration configuration to the capture configuration. As an option, in one embodiment, the sorbent material  104  may be a liquid sorbent that is placed in contact with the first gas volume  132  in a suitable way (e.g. distributed over a surface, dispersed as droplets, etc.) in order to absorb CO 2  from that gas and then into the chamber  102 , in a continuous liquid stream. 
     While this discussion is being done in the context of the first gas volume being ambient air, this disclosure is not limited to the capture of CO 2  from natural air currents and wind. In some embodiments, the first gas volume  132  may be a contained gas volume  132 , rather than ambient outdoor air (e.g. indoor air, flue gas, gas from a fermenter, a product stream, etc.). Rather than limiting the system  100  contemplated herein to only unbounded atmospheric applications, it may be said that, in some embodiments, the first gas volume  132  is sized to be sufficiently large as to maintain a temperature  140  of the sorbent material close (e.g. within a few degrees, etc.) to the ambient temperature  126  (e.g. the temperature of the first gas volume  132 ) while providing the heat  136  to desorb water while the ADAC system  100  is in the capture configuration  130 . 
     According to some embodiments, the sorbent material  104  is exposed to the first gas volume  132  at a relatively low humidity during capture. As the sorbent material  104  collects CO 2   133 , it also releases water vapor into the first gas volume  132  resulting in a net cooling of the sorbent material  104  and the gas that passes over it. For a large airmass flowing over/through the sorbent material  104 , the process occurs near ambient temperatures  126 . 
     The ADAC  100  may transition between the capture and regeneration configurations through a variety of mechanisms. In some embodiments, including the non-limiting example shown in  FIG.  1 A , the sorbent material  104  may be physically moved with respect to the chamber  102 . While the ADAC  100  is in the capture configuration  130 , the sorbent material  104  is not contained within the chamber  102 , but is instead directly exposed to the first gas volume  132  (e.g. the atmosphere).  FIG.  2 A  is a schematic view of this the non-limiting example shown in  FIG.  1 A , in the regeneration configuration  200 . As shown, transitioning from the capture configuration  130  to the regeneration configuration  200  comprises moving the sorbent material  104  into the interior  106  of the chamber  102 , which is sealed to enclose the sorbent material  104 . It should be noted that in some embodiments the sorbent material  104  may be moved into a stationary chamber  102 , and in other embodiments the chamber  102  may be moved to enclose and contain a stationary sorbent material  104 . 
     As a specific example, in some embodiments, the ADAC  100  may comprise a sorbent material  104  in the form of a plurality of disks suspended below a lid that is lifted for the capture configuration  130 , and then lowered to seal the disks inside the chamber  102  for the regeneration phase. 
     In other embodiments, the sorbent material  104  may be stationary with respect to the chamber  102 . Instead, the chamber  102  may be configured to open as part of the capture configuration  130  and seal for the regeneration configuration  200 . See, for example, the non-limiting example shown in  FIGS.  1 B and  2 B . In still other embodiments, the sorbent material  104  may remain sealed inside a chamber  102  configured to execute both parts of the cycle (i.e. capture and regeneration) by bringing the needed materials (e.g. the first gas volume  132 , water vapor/steam, etc.) inside the chamber  102 . As a specific example, in some embodiments the sorbent material  104  may be a liquid sorbent. In both variations, the first gas volume  132  passes through the chamber  102  while the ADAC  100  is in the capture configuration  130 . 
       FIGS.  2 A and  2 B  are schematic views of non-limiting examples of an ADAC  100  in a regeneration configuration  200 . Specifically,  FIG.  2 A  is a schematic view of the ADAC system  100  of  FIG.  1 A  in the regeneration configuration  200 , and  FIG.  2 B  is a schematic view of the ADAC system  100  of  FIG.  1 B  in the regeneration configuration  200 . In the context of the present description and the claims that follow, a regeneration configuration  200  comprises the sorbent material  104  being enclosed within the chamber  102  and the water reservoir  108  being put into fluid communication with the interior  106  of the chamber  102  such that the sorbent material  104  is in contact with water  110 , whether it be in liquid or vapor form. While in this configuration  200 , the sorbent material  104  releases the adsorbed carbon dioxide  133  into the chamber  102  while binding water  110  inside the chamber  102  and causing the sorbent material  102  to deposit heat  138  into the interior  106  of the chamber  102 . Put differently, the heat collected by the sorbent material  104  while in the capture configuration  130  is transferred into the chamber  102  while in the regeneration configuration  200 , against a temperature differential. Ultimately, the regeneration configuration  200  also comprises the vacuum compressor  112  removing a carbon dioxide rich product stream  212  from the interior  106  of the chamber  102 . 
     According to various embodiments, the sorbent material  104  is selected and/or configured to bind water  110  when under a release condition  206  (as opposed to ambient condition  124 , discussed previously). The release condition  206  comprises at least one of a first moisture level  210  that is higher than the ambient moisture level  128 , and a first temperature  208  that is higher than the ambient temperature  126 . The sorbent material  104  is selected and/or configured to release bound carbon dioxide when under the release condition  206 . 
     According to various embodiments, the regeneration configuration of an ADAC system  100  comprises the CO 2 -laden sorbent material  104  being enclosed in the chamber  102 , which is then at least partially evacuated by the vacuum compressor  112 . In some embodiments, it is substantially evacuated. After evacuation, the chamber  102  then is exposed to the liquid water reservoir  108  that is maintained at a supply temperature  114  by some form of heat input. In some embodiments, the supply temperature  114  is at or below ambient temperature  126 , allowing the heat to simply be ambient heat, which does not require any energy for delivery and does not increase the operational cost. It should be noted that in other embodiments, which may not comprise a vacuum compressor  112 , the chamber  102  may be exposed to water  110 , in some form, by simply using a carrier gas (not shown), e.g. such as carbon dioxide. 
     In some embodiments, the chamber  102  is evacuated by the vacuum compressor  112  while the ADAC  100  is in the regeneration configuration  200  such that a partial pressure  202  of water vapor within the chamber  102  is at least a majority of a total pressure  204  within the chamber  102 . The water vapor over the liquid water  110  of the reservoir  108  will aim to maintain a water vapor pressure in the chamber  102  that matches the equilibrium pressure over the water  110 . At the same time, the adsorption of water at the sorbent material  104  surfaces will drive the pressure lower, forcing further evaporation of water  110 . The process will stop when the temperature of the sorbent  140  is so high that it is in equilibrium with the same partial pressure  202  of water. For most sorbent materials  104  that have a heat of adsorption for water vapor in excess of the heat of condensation, this temperature will be higher than the supply temperature  114 . 
     In some embodiments, the water reservoir  108  may be small. For example, the reservoir  108  might be comprised by a small liquid volume inside the chamber  102  in the form of water  110  that is in contact with interior  106  surfaces, or small droplets embedded into the gas volume within the chamber  102 . With these smaller reservoirs  108 , it is possible to heat up the water reservoir  108  against the warmer sorbent material  104  and thus drive temperatures even higher. For example, one embodiment comprises a direct gas/liquid heat exchange, accomplished by spraying the water as fine droplets  220  into the chamber  102  using a sprayer  120 . These droplets  220  will tend to evaporate and pick up heat from the surrounding water vapor to maintain the same temperature. The water vapor in turn will adsorb onto the sorbent material  104 , where it heats the sorbent material  104  to temperatures higher than that of the surrounding steam. 
     In other embodiments, where the density of the sorbent material  104  is too high to support the transport of droplets  220 , liquid water  110  may be brought into direct contact with the heated sorbent surfaces  104 . This in turn raises the temperature of the steam, and the cycle continues at a higher temperature. Ultimately, this process may be limited by the water storage capacity of the sorbent material  104 . 
     One advantage that is obtained by these embodiments, where the majority of the total pressure  204  within the chamber  102  is delivered by the water vapor, is that water vapor can be applied evenly throughout the volume of the chamber  102 . While liquid water  110  may accumulate in one section or another of the chamber  102 , water vapor at low pressures will readily distribute itself by fluid dynamic pressure changes and thus reach every section of the chamber  102 . 
     In other embodiments, parts of the gas  222  inside the chamber  102  may not be evacuated, and instead is circulated through the chamber  102  to provide a means of heat transfer from the sorbent material  104  to the water reservoir  108 . In this way, it is possible to increase water condensation inside the chamber  102 . By controlling the temperature difference between the sorbent material  104  and the water reservoir  108 , a water vapor pressure differential can be maintained between the interior and the exterior (i.e. chamber  102  and the reservoir  108 ). It should be noted that the terms exterior and interior are here used to express different locations for steam generation and sorbent material  104  gathering or packing. However, this does not exclude embodiments where the location of both water vapor generation and sorbent material  104  gathering are housed within one thermally insulated apparatus, to optimize heat integration. Such a configuration may be advantageous in embodiments that rely on a moisture swing to remove CO 2  from the sorbent material  104 . 
     In some embodiments, the circulation of the gas  222  remnants in the partially evacuated chamber may be accomplished with a circulation compressor  122 . The circulation compressor  122  comprises an input  214  and an output  216 , both in fluid communication with the interior  106  of the chamber  102 . The circulation compressor  122  is configured to remove a portion of the gas  222  within the interior  106  of the chamber  102  through the input  214  and deliver the portion of the gas back to the interior  106  of the chamber  102  through the output  216  such that it interacts with the water  110  provided by or stored within, the water reservoir  108 , while the ADAC  100  is in the regeneration configuration  200 . 
     According to various embodiments, the chamber  102  has room for the introduction of gas while the ADAC  100  is in the regeneration configuration  200 . This may be accomplished in a way that further achieves thermal transfer between the circulated gas and the water supply  108 . See, for example,  FIG.  2 A , which is a schematic view of a non-limiting example of an ADAC  100  in the regeneration configuration  200 . As shown, the gas delivered to the interior of the chamber by the circulation compressor bubbles through liquid water  110  from the water reservoir  108  after exiting the output  216  of the circulation compressor  122 . These bubbles  218  facilitate the thermal transfer between the gas and the water. In some embodiments, this may be accomplished using a bubble column, or similar apparatus. 
       FIG.  2 B  is a schematic view of a non-limiting example of the ADAC  100  of  FIG.  1 B  in the regeneration configuration  200 . As shown, the ADAC  100  may comprise a sprayer  120  in fluid communication with the water reservoir  108  and configured to spray water droplets  220  into the interior  106  of the chamber  102 . The gas delivered to the interior  106  of the chamber  102  by the circulation compressor  122  propels these water droplets  220  out of the sprayer  120  and into the chamber  102 , according to various embodiments, facilitating the heat transfer between gas and liquid, as discussed above. Of course, in other embodiments, the sprayer  120  may be utilized to create water droplets  220  within the chamber  102  without a circulation compressor  122  being present. 
     Some embodiments may implement this concept of maximizing water deposition on the sorbent material  104  through the use of heat exchangers  118 . As shown, in some embodiments, the ADAC  100  may comprise a heat exchanger  118  in thermal contact with the water resupply line  116  and the product stream  212 , which comprises moist, hot carbon dioxide enriched gas. Heat is transferred from the product stream  212  removed from the chamber  102  to the water  110  as it passes through the water resupply line  116 , while the ADAC system  100  is in the regeneration configuration  200 . 
     According to some embodiments, the heat exchanger  118  surfaces inside the chamber  102  are maintained at a temperature that is intermediate to the ambient temperature of the water source and the temperature at which the water vapor pressure of the sorbent material  104  would equal that of the ambient water source. Heat is transferred from the sorbent  104 , to the gas circulating in the chamber  102 . The gas transfers heat to the heat exchanger  118  without condensation. Since the temperature of the sorbent  104  is lowered by the transfer of heat to the circulating gas in the chamber  102 , it can proceed to bind more water. 
     Such a configuration may be advantageous because the sorbent material  104  has a strong tendency to even out its loading and heating. Any part of the sorbent  104  that is cooler than the average system  100  will tend to condense water out and thus heat up, any place that is hotter, will rapidly release water and thus cool down. 
       FIG.  3    is a top view of a non-limiting example of a composite sorbent material  300 . In some embodiments, the sorbent material  104  may be homogeneous, combining the two properties concerning the binding and release of carbon dioxide and water into a single material. In other embodiments, the sorbent material  104  may comprise a composite material  300  where these two properties arise from two or more different compounds present and in close proximity to each other. According to various embodiments, the heterogeneity of the material  300  is on scales sufficiently small for heat transfer to result in an average temperature driven by the combination of water adsorption and CO 2  sorption or desorption. 
     More specifically, in some embodiments, the sorbent material  104  is a composite material  300  comprising a first material  302  configured to release water under ambient conditions  124  and bind water under the first moisture level  210  (e.g. a drying agent with isotherms that rise steeply at ambient water vapor pressures, etc.), and a second material  304  configured to bind carbon dioxide  133  under ambient conditions  124 , and release carbon dioxide  133  under the release condition  206 . 
     These two (or more) materials may be combined in a number of different ways, depending on the nature of the sorbent materials being used. For example,  FIG.  3    shows a non-limiting example of a composite material  300  made of two fabric-type sorbents, a first material  302  and a second material  304 , which have been woven together in strips small enough that heat transfer results in an average temperature driven by the combination of water adsorption and CO 2  sorption or desorption. 
     According to various embodiments, the sorbent material(s)  104  may include, but are not limited to, strong base anionic exchange resins (e.g. marathon A, polystyrene-based resins with quaternary ammonium ions, other quaternary ammonium ion exchange resins, etc.), secondary and tertiary amines, metal-organic frameworks, zeolith, and the like. In some embodiments, the sorbent material  104  may be solid, while in other embodiments, the sorbent material  104  may be, or may include a liquid sorbent (e.g. hygroscopic and strong alkaline liquids/solutions, etc.). 
     Because the sorbent material  104  must load up with water at high relative humidity and dry out a low relative humidity conditions that can be achieved outside, various embodiments of the ADAC system  100  operate within a set of constraints. In effect, these constraints can limit the binding energy of water to the sorbent. 
     As a specific, though simplified, example the sorbent material  104  may be characterized by the enthalpy change and entropy change in the sorption reaction. If the nominal values are given as, ΔH, and ΔS, respectively, then 
     
       
         
           
             Δ 
             G 
             = 
             Δ 
             H 
             − 
             T 
             
               
                 Δ 
                 S 
                 + 
                 R 
                   
                 ln 
                   
                 p 
               
             
           
         
       
     
     For many materials, ΔH and ΔS are approximately constant over a wide range of temperature and pressure conditions. Here, T is the temperature, R the universal gas constant, and p the pressure in units of the normal pressure (e.g., 1 atm), p = P/P 0 . 
     Given a capture temperature T 1  and a regeneration temperature T 2 , the pressure amplification in the thermal swing may be estimated: 
     
       
         
           
             
               
                 
                   P 
                   2 
                 
               
               
                 
                   P 
                   1 
                 
               
             
             = 
             
               e 
               
                 − 
                 
                   
                     
                       
                         
                           T 
                           2 
                         
                         − 
                         
                           T 
                           1 
                         
                       
                       
                         
                           T 
                           2 
                         
                       
                     
                   
                 
                 
                   
                     
                       
                         Δ 
                         S 
                         + 
                         R 
                           
                           
                         ln 
                         
                           P 
                           1 
                         
                         / 
                         
                           P 
                           0 
                         
                       
                       R 
                     
                   
                 
               
             
           
         
       
     
     For systems of interest, the entropy change under sorption is negative, as a result the amplification factor is larger than one, for heating. The amplification factor does not depend on ΔH. The bigger the entropy change is in absolute terms, the larger the multiplier can be. This suggests that sorbents that undergo entropic changes as they bind the sorbate can increase the pressure amplification. 
     For CO 2  capture, this means that the lowest regeneration temperature can be achieved by maximizing the entropy change. Even then, it may be difficult to go from ambient partial pressures to one atmosphere in a single step if the upper temperature is limited to less than 100° C. As has been pointed out by Tao Wang et al [Wang, T.; Lackner, K. S.; Wright, A. B. Moisture-Swing Sorption for Carbon Dioxide Capture from Ambient Air: A Thermodynamic Analysis. Phys. Chem. Chem. Phys. 2013, 15, (2), 504-514.], likely values for ΔS range from -130 to -218 J/mol/K. 
     At equilibrium, a solution for p = P/P 0  may be found: 
     
       
         
           
             ln 
               
             p 
             = 
             − 
             
               
                 Δ 
                 S 
               
               R 
             
             + 
             
               
                 Δ 
                 H 
               
               
                 R 
                 T 
               
             
           
         
       
     
     In other words, the log of the pressure is a linear function of the inverse temperature. This equation can be applied not just to sorbents, but also to the condensation of water from water vapor. In this case, p is the saturation pressure of the water vapor at saturation, and ΔS, and ΔH the thermodynamic parameters of the condensation reaction. For the range of outside conditions, these two numbers are roughly constant. 
     For a sorbent material  104 , similar parameters may be introduced, although here it is likely that the two terms depend on the loading condition of the sorbent. Going forward, it is assumed that these two terms may be compared to the terms in the condensation of water. In other words, multipliers are introduced that relate the various parameters 
     
       
         
           
             Δ 
             
               S 
               
                 s 
                 o 
                 r 
                 b 
                 a 
                 n 
                 t 
               
             
             = 
             
               α 
               s 
             
             Δ 
             
               S 
               
                 
                   H 
                   2 
                 
                 O 
               
             
           
         
       
     
     
       
         
           
             Δ 
             
               Η 
               
                 s 
                 o 
                 r 
                 b 
                 a 
                 n 
                 t 
               
             
             = 
             
               α 
               H 
             
             Δ 
             
               H 
               
                 
                   H 
                   2 
                 
                 O 
               
             
           
         
       
     
     Typically, the two log P lines for the sorbent and the condensation will intersect somewhere. The intersection point may be as 
     
       
         
           
             
               1 
               
                 
                   T 
                   0 
                 
               
             
             = 
             
               
                 Δ 
                 
                   S 
                   
                     
                       H 
                       2 
                     
                     O 
                   
                 
               
               
                 Δ 
                 
                   H 
                   
                     
                       H 
                       2 
                     
                     O 
                   
                 
               
             
             
               
                 
                   α 
                   s 
                 
                 − 
                 1 
               
               
                 
                   α 
                   H 
                 
                 − 
                 1 
               
             
           
         
       
     
     Of interest are cases where α H  &gt; 1 and α s  ~1. Since both, ΔS H2O  and ΔH H2 O are negative, their ratio is positive. It is therefore the sign of the term α s  ― 1 that determines the sign of the expression. 
     If the expression is negative, the two lines do not intersect for positive values of the temperature. At any temperature, the water vapor pressure over the sorbent in equilibrium is smaller than that over liquid water. Otherwise, there is a maximum temperature above which the sorbent will dry out, even in a water saturated environment. 
     A sorbent that binds water strongly enough to remove it from water saturated air, but not so strongly that it could not at least partially dry, when exposed to dry air, will warm up in a closed container, if it is exposed to moisture. 
     Contemplated herein is a method of estimating the temperature such a system can reach without introducing external heat sources. For purposes of this discussion it shall be assumed that the sorbent has been dried out in the open air. It is now contained in a closed, evacuated container that holds the sorbent and some structural materials. The heat capacity of the entire assembly per unit capacity of the sorbent is given by c v . The heat capacity encompasses the structural material including the parts of the container that get heated in the process, the sorbent material and any water vapor or other gases in the gas space surrounding the sorbent. By injecting an amount of heat Q into the system the temperature of the system rises by 
     
       
         
           
             Δ 
             T 
             = 
             
               Q 
               
                 
                   C 
                   V 
                 
               
             
           
         
       
     
     It can be assumed that the ADAC system  100  goes through a cycle, where at some point it is exposed to ambient temperature conditions, and at others the temperature is elevated. It is also assumed that at least some of the heat that was incorporated in the last hot stage of the cycle has been taken and used to preheat the sorbent chamber prior to its next warming cycle. If the ambient temperature is T o  and the peak regeneration temperature is T R , then the starting temperature of the next cycle is going to be somewhere between these two temperatures. 
     
       
         
           
             
               T 
               0 
             
             ≤ 
             
               T 
               S 
             
             ≤ 
             
               T 
               R 
             
           
         
       
     
     The more efficient the heat recovery system is, the closer it can get to the regeneration temperature, according to various embodiments. 
     It may be estimated how much additional heat is available to warm up the system by taking advantage of the heat of sorption for water that can be released in the process. The heat of adsorption of water vapor onto a sorbent material is given by 
     
       
         
           
             
               Q 
               V 
             
             = 
             − 
             Δ 
             
               H 
               S 
             
           
         
       
     
     Here AHs is the enthalpy of the gas-solid adsorption reaction between water vapor and the sorbent material. 
     The heat of binding liquid water to the sorbent material is given by 
     
       
         
           
             
               Q 
               L 
             
             = 
             − 
             Δ 
             
               H 
               S 
             
             + 
             Δ 
             
               H 
               W 
             
           
         
       
     
     Where ΔH w , is the enthalpy change during the condensation of water. In some embodiments, this number could be negative. 
     Heating up a chamber  102  which contains the sorbent  104 , structural material (e.g. structure to hold the sorbent in an advantageous configuration, etc.) and some water vapor requires heat input which comes from contact with either water vapor at ambient temperature T 0 , or from contact with liquid water at the same temperature. Water vapor in equilibrium with this temperature is always available, as a heat exchanger can extract heat from the environment to evaporate the water. The regeneration chamber can then heat up as long as the water vapor pressure over the sorbent remains lower than the saturation pressure under ambient conditions. At T 0 , the equilibrium partial pressure of water vapor over the sorbent is lower than the saturation pressure at T 0 , consequently the heat of adsorption can raise the temperature of the sorbent, until either the sorbent is saturated with water or the equilibrium pressure over the sorbent has risen to match the water vapor saturation pressure at T 0 . The temperature at which the two pressures match is referred to as T 1  ≥ T 0 . Assuming that the ADAC  100  has sufficient sorption capacity to reach this temperature, the material can be further heated if Q L  &gt; 0, by presenting it with liquid water which is brought in at a temperature T 0 , heats itself up to the temperature of the sorbent and then gets bound to the sorbent in the process releasing more heat. It is possible that Q L  is negative. If that were the case, then adding more water would be detrimental, as it would cool rather than heat the chamber. If Q L  &gt; 0, the temperature in the chamber will rise further until either the sorbent is fully saturated, or the water vapor pressure in the chamber exceeds the saturated water vapor pressure at the same temperature. The temperature at which this happens is referred to as T2 ≥ T 1 . In that case, water would condense elsewhere in the chamber rather than being absorbed onto the sorbent. Not all sorbents would have such a critical temperature. Even if they have such a temperature, it could be much higher than the temperature that can be reached by saturating the sorbent with water. 
     In short, the heat deposited into the chamber, per mole of sorbent water capacity is given as 
     
       
         
           
             Q 
             = 
             α 
             
               Q 
               V 
             
             + 
             β 
             
               Q 
               L 
             
           
         
       
     
     Where α + β ≤ 1, and β= 0 if Q L  &lt; 0. 
     The temperature reached is a more or less linear function of Q. It will depend on the starting temperature and the heat capacity embedded into the system. If 
     
       
         
           
             T 
             
               
                 
                   Q 
                   V 
                 
               
             
             ≤ 
             
               T 
               1 
             
               
             then  
             α 
             = 
             1 
             , 
             β 
             = 
             0. 
           
         
       
     
     Otherwise, a &lt; 1 is chosen, such that T(αQ v ) = T 1 . If Q L  &gt; 0 and T(αQ v  + (1 - α)Q L ) &lt; T 2  then β = 1 - α 
     Otherwise, β &lt; (1 - α) is chosen such that T(αQ v  + (βQ L ) = T 2 . 
     To simplify the discussion, it is assumed the sorbent material is a simple sorbent whose water sorption is characterized by ΔS S  and ΔH S . Such a sorbent has a step function isotherm. Realistic sorbents will have an additional entropy term that is of the form ln(ϑ) -In (1 - ϑ). 
     The thermodynamics of this reaction can be anticipated with the condensation of water, which is characterized by ΔS w,  and ΔH W . 
     The free energy of condensation or absorption can be written as 
     
       
         
           
             Δ 
             G 
             = 
             Δ 
             H 
             − 
             T 
             
               
                 Δ 
                 S 
                 + 
                 R 
                   
                 ln 
                   
                 P 
               
             
           
         
       
     
     Therefore, at equilibrium 
     
       
         
           
             ln 
               
             P 
             = 
             − 
             
               
                 Δ 
                 S 
               
               R 
             
             + 
             
               
                 Δ 
                 H 
               
               
                 R 
                 T 
               
             
           
         
       
     
     In other words, the logarithm of the equilibrium pressure is a linear function of the inverse of T, with an intercept of  
     
       
         
           
             − 
             
               
                 Δ 
                 S 
               
               R 
             
           
         
       
     
      (which is positive) and slope of  
     
       
         
           
             
               
                 Δ 
                 H 
               
               R 
             
           
         
       
     
     (which is negative). 
     Where the above examples, embodiments and implementations reference examples, it should be understood by those of ordinary skill in the art that other direct capture systems could be intermixed or substituted with those provided. In places where the description above refers to particular embodiments of autothermal direct air capture systems, it should be readily apparent that a number of modifications may be made without departing from the spirit thereof and that these embodiments and implementations may be applied to other capture technologies as well. Accordingly, the disclosed subject matter is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the disclosure and the knowledge of one of ordinary skill in the art.