Patent Description:
The need for technologies to remove carbon dioxide from ambient air 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. Nevertheless, the technologies are still new and the early air capture processes require large amounts of energy to operate. Since the carbon dioxide in the ambient air is very dilute, atmospheric CO<NUM> collectors can quickly overrun a tight energy budget for drawing in and processing air in bulk. Additionally, conventional carbon dioxide collection systems often exhibit the unfortunate combination of being costly and fragile. Conventional capture devices also often have a large initial capital cost along with a high operating cost.

A system and method for passive collection of atmospheric carbon dioxide is disclosed in <CIT>.

According to one aspect not claimed, a system for passive collection of atmospheric carbon dioxide includes a harvest chamber having a first opening and a sorbent regeneration system including a release medium, a release medium emitter, and a liquid extractor. The system also includes a capture body coupled to and movable by a support structure. The support structure has at least a first portion inside of the harvest chamber and a second portion outside of and above the harvest chamber at a height. The capture body includes a sorbent material and is movable by the support structure to be in a collection configuration wherein at least a portion of the capture body able to capture carbon dioxide is in contact with a natural airflow outside the harvest chamber such that atmospheric carbon dioxide is captured by the sorbent material, and a release configuration wherein at least a portion of the capture body holding captured carbon dioxide is in contact with the release medium inside the harvest chamber such that captured carbon dioxide is released into the harvest chamber to form an enriched gas. The system also includes a product outlet in fluid communication with the inside of the harvest chamber and configured to receive a product stream of enriched gas displaced by a sweep gas inside the harvest chamber. The sweep gas is introduced to the harvest chamber. Finally, the system for passive collection of atmospheric carbon dioxide includes a control system communicatively coupled to the support structure, and configured to cycle the capture body through the collection configuration and the release configuration.

Particular embodiments may comprise one or more of the following features. The release medium may be steam and the sorbent material may be one of a moisture swing sorbent material and a heat swing sorbent material. The capture body may be a closed-loop belt having a flexible substrate upon which the sorbent material is disposed. The first and second portions of the support structure may each comprise a plurality of rollers. At least one of the rollers of the support structure may be coupled to a motor communicatively coupled to the control system. The capture body may be able to be in the collection configuration and the release configuration simultaneously. The first opening of the harvest chamber may be a liquid trap having an external aperture exposed to the atmosphere and/or an internal aperture below the external aperture and submerged under water such that the water separates the inside of the harvest chamber from the external aperture. The internal and external apertures may be connected by a conduit. The first opening may be an open channel having at least one flow generator communicatively coupled to the control system. The control system may be communicatively coupled to a sensor that may be one of a pressure sensor, a flow speed sensor, and a mass flow sensor. The control system may be configured to operate the at least one flow generator in response to sensor readings such that an average flow rate across the channel may be maintained at a desired flow rate to create a dynamic air lock. The harvest chamber may further include a second opening. The closed-loop belt may enter the harvest chamber through the first opening and may exit the harvest chamber through the second opening. The product outlet may be opposite the second opening and proximate the first opening. The first and second portions of the support structure may each include an upper rack of rollers and/or a lower rack of roller. For each of the first and second portions of the support structure, the closed-loop belt may be woven back and forth between the upper rack of rollers and the lower rack of rollers. The support structure includes a lid movable between an open position above and separated from the harvest chamber, and a closed position wherein the lid covers the first opening of the harvest chamber. The support structure further includes a collapsible tether coupled to an interior of the harvest chamber and the lid. The capture body includes a plurality of plates coupled to and spaced out along the collapsible tether such that the plurality of plates hangs from the lid by the tether when the capture body is in the collection configuration and the plurality of plates are enclosed within the harvest chamber when the capture body is in the release configuration. Each plate may include the sorbent material. Lastly, the sweep gas may be atmospheric air.

A system as claimed for passive collection of atmospheric carbon dioxide includes a harvest chamber having a first opening and a sorbent regeneration system. The system further includes a capture body coupled to and movable by a support structure. The support structure has at least a first portion inside of the harvest chamber and a second portion outside of the harvest chamber. The capture body includes a sorbent material and is movable by the support structure to be in a collection configuration wherein at least a portion of the capture body able to capture carbon dioxide is in contact with an airflow outside the harvest chamber such that atmospheric carbon dioxide is captured by the sorbent material, and a release configuration wherein at least a portion of the capture body holding captured carbon dioxide is operated upon by the sorbent regeneration system inside the harvest chamber such that captured carbon dioxide is released into the harvest chamber to form an enriched gas. The system also includes a product outlet in fluid communication with the inside of the harvest chamber and configured to receive a product stream of enriched gas displaced by a sweep gas inside the harvest chamber. The sweep gas is introduced to the harvest chamber. Lastly, the system for passive collection of atmospheric carbon dioxide includes a control system communicatively coupled to the support structure, and configured to cycle the capture body between the collection configuration and the release configuration.

The sorbent material may be a moisture swing sorbent material. The sorbent regeneration system may include a release medium, a release medium emitter, and/or a liquid extractor. The release medium may be one of liquid water and steam. The sorbent material may be a heat swing sorbent material and the sorbent regeneration system may include a heat source. The second portion of the support structure may be positioned above the harvest chamber at a height. The height may be adjustable. The support structure includes a lid movable between an open position above and separated from the harvest chamber, and a closed position covering the first opening of the harvest chamber. The capture body is coupled to the lid and an interior of the harvest chamber such that the capture body hangs from the lid when the capture body is in the collection configuration and the capture body is enclosed within the harvest chamber when the capture body is in the release configuration. The support structure further includes a collapsible tether coupled to the interior of the harvest chamber and the lid. The capture body is coupled to the lid through the collapsible tether. The capture body includes a plurality of plates coupled to and spaced out along the collapsible tether. Each plate includes the sorbent material. The system may also include an external sensor outside the harvest chamber communicatively coupled to the control system. The control system may be configured to automatically modify at least one of a ratio of closed-loop belt inside the harvest chamber to closed-loop belt outside the harvest chamber and/or a belt speed in response to an ambient condition detected by the external sensor.

According to yet another aspect of the disclosure, a method as claimed for passively collecting atmospheric carbon dioxide includes exposing at least a portion of a capture body able to capture carbon dioxide to a natural airflow. The capture body includes a sorbent material that captures atmospheric carbon dioxide upon contact. The method also includes moving the at least a portion of the capture body holding captured carbon dioxide into a harvest chamber using a support structure coupled to the capture body and driven by a control system communicatively coupled to the support structure. The portion of the capture body holding captured carbon dioxide enters the harvest chamber through a first opening of the harvest chamber. The method further includes regenerating the sorbent material and releasing the captured carbon dioxide into the harvest chamber to form an enriched gas by exposing the sorbent material to a release medium introduced to the harvest chamber by a release medium emitter, the release medium being one of liquid water and steam. The method also includes extracting the release medium in liquid form from the harvest chamber using a liquid extractor, removing a product stream of enriched gas from the harvest chamber through a product outlet by displacing the enriched gas with a sweep gas, and removing the at least a portion of the capture body now having regenerated sorbent material from the harvest chamber by driving the support structure with the control system.

Particular embodiments may comprise one or more of the following features. The method may also include maintaining an average flow rate across the first opening at a desired flow rate to create a dynamic air lock by operating at least one flow generator proximate the first opening using the control system and in response to a sensor reading from a sensor communicatively coupled to the control system. The first opening may be an open channel. The sensor may be one of a pressure sensor, a flow speed sensor, and a mass flow sensor. The desired flow rate maintained at the first opening may account for the sweep gas introduced to the harvest chamber. The desired flow rate maintained at the first opening may be substantially zero. The at least one flow generator may include a drag belt moving along a wall of the open channel to generate flow in a direction the drag belt is moving. The at least one flow generator may be a blower.

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.

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.

The disclosure will hereinafter be described in conjunction with the appended drawings, where like designations denote like elements, and:.

This disclosure, its aspects and implementations, are not limited to the specific material types, components, methods, or other examples disclosed herein. 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.

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.

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. Captured atmospheric carbon dioxide may be sequestered to off-set other carbon emissions, or processed as part of material, agricultural, or food applications. Sequestration methods include but are not limited to the following examples: geological sequestration (e.g. the injection of compressed CO<NUM> into underground formations, etc.), mineral sequestration (e.g. methods of carbon storage that transform CO<NUM> into mineral carbonates, etc.), disposal as biochar or other forms of solid carbon, and injection into the ocean. Examples of material applications include but are not limited to: fuel production, and feed stocks for plastics or higher value organic materials. Agricultural and food applications include, but are not limited to, the use of CO<NUM> for photosynthetic processes (e.g. in greenhouses, algae ponds, etc.), the use of CO<NUM> as preservative, use as a fire suppressant (e.g. in a grain silo, etc.), use for refrigeration in food processing, and the like.

Because CO<NUM> in the air is very dilute (<NUM> parts per million by volume), CO<NUM> collectors must not invest a significant amount of energy to draw in bulk air. Heating or cooling the air, drying the air, or significantly changing the air pressure would exceed any reasonable energy budget. Furthermore, conventional collection systems tend to exhibit the unfortunate combination of being costly and fragile. Conventional capture systems often have a large initial capital cost along with a high operating cost.

Contemplated herein are systems and methods for passive collection of atmospheric carbon dioxide that avoid the use of fans and blowers to capture from the ambient air in bulk. Instead, the systems and methods contemplated herein rely on wind and other natural air flows. In addition to having low energy requirements, these systems are also durable and easily adapted to a variety of harvesting conditions.

As will be discussed in detail below, some embodiments of the passive collection system operate continuously, while other embodiments operate in batches. Systems operated in a continuous manner are advantageous over other systems in terms of energy cost and adaptability. However, such systems may be difficult to optimize for harvesting airflows from multiple directions (e.g. efficiency may be poor for certain vectors), something for which batch systems are well suited.

<FIG> and <FIG> are perspective views of a non-limiting example of a system <NUM> for passive collection of atmospheric carbon dioxide (hereinafter "passive collection system", "collection system", or just "system"). Specifically, <FIG> is a perspective view, and <FIG> is the same view, with the side of the harvest chamber <NUM> removed to provide an internal view. According to various embodiments, the system <NUM> comprises a harvest chamber <NUM>, a capture body <NUM> comprising a sorbent material <NUM>, a support structure <NUM>, a sorbent regeneration system <NUM>, a control system <NUM>, and at least a first opening <NUM>.

In the context of the present description and the claims that follow, a harvest chamber <NUM> is an enclosure having an exterior <NUM> and an interior <NUM> within which captured carbon dioxide is released for subsequent sequestration or application. The harvest chamber <NUM> has at least one opening, first opening <NUM>, through which it receives captured carbon dioxide and the material in which it is captured (e.g. the capture body <NUM> and its sorbent material <NUM>, etc.). In some embodiments, the harvest chamber <NUM> may also have a second opening <NUM>, and still other embodiments, the harvest chamber <NUM> may have even more openings. In some embodiments, the first opening <NUM> and/or the second opening <NUM> may simply be an aperture in a wall of the harvest chamber <NUM>, while in other embodiments the first opening <NUM> and/or the second opening <NUM> may comprise a channel or conduit connecting the exterior <NUM> with the interior <NUM>. In some embodiments, the channel may have a depth that is longer than at least one of its length and width, creating an environment not possible with an aperture in a thin wall.

In some embodiments, the first opening <NUM> may remain open during operation of the system <NUM> (e.g. continuous operation), while in other embodiments the first opening <NUM> may be periodically covered, or even sealed, during the operation of the system <NUM> (e.g. batch operation). Both modes of operation will be discussed further, below.

The harvest chamber <NUM> may be constructed of a durable material appropriate for both the external environment in which the system <NUM> is being employed, as well as the internal environment (e.g. the nature of the sorbent regeneration system <NUM>, etc.). In some embodiments, the harvest chamber <NUM> may be a repurposed shipping container.

In the context of the present description and the claims that follow, a capture body <NUM> is the structure or collection of structures upon which, or in which, the CO<NUM> is captured. The capture body <NUM> comprises a sorbent material <NUM> responsible for the capture of carbon dioxide. In some embodiments, the sorbent material <NUM> may be disposed on one or more surfaces of the capture body <NUM>, while in other embodiments, the capture body <NUM> itself may be made of sorbent material <NUM>. As will be discussed below, the sorbent material <NUM> releases captured CO<NUM> when it is regenerated (e.g. upon application of a sorbent regeneration system <NUM> inside the harvest chamber <NUM>, etc.).

According to various embodiments, the capture body <NUM> is coupled to, and movable by, a support structure <NUM>. In the context of the present description and the claims that follow, a support structure <NUM> is a structure configured to hold the capture body <NUM> in an arrangement suitable for collecting atmospheric carbon dioxide (e.g. a collection configuration <NUM>), and further configured to move the capture body <NUM> such that captured CO<NUM> may be released into the harvest chamber <NUM> as the sorbent material <NUM> is regenerated (e.g. a release configuration <NUM>). According to various embodiments, the support structure <NUM> may have a first portion <NUM> that is inside of the harvest chamber <NUM>, and a second portion <NUM> that is outside of the harvest chamber <NUM>. In some embodiments, the second portion <NUM> may also be positioned above the harvest chamber <NUM> at a height <NUM>.

In some embodiments, the support structure <NUM> may be attached to, or even integral with, the harvest chamber <NUM>. In other embodiments, the support structure <NUM> may be separate from the harvest chamber <NUM>. The support structure <NUM> may move the capture body <NUM> using various methods and devices, including but not limited to, motors, rollers, linear actuators, pistons, screw drives, lifts, and other devices known in the art.

The control system <NUM> is responsible for the cyclical operation of the system <NUM>. In the context of the present description and the claims that follow, the control system <NUM> is a device capable of executing a series of predefined instructions to cause the system <NUM> to operate in a cyclical manner, capturing CO<NUM> from the atmosphere and releasing it within the harvest chamber <NUM>. Examples include, but are not limited to, embedded systems, conventional computer systems, mobile devices, and the like. The control system <NUM> is communicatively coupled with the various components that either provide information (e.g. sensors, etc.) or perform actions (e.g. the support structure <NUM>, the sorbent regeneration system <NUM>, etc.). In some embodiments, the control system <NUM> may be responsible for additional functions. As will be discussed further in the context of <FIG> and <FIG>, in some embodiments the control system <NUM> may provide automation for the system <NUM> that allows it to run unattended.

In operation, the system <NUM> exposes the capture body <NUM>, or at least a portion of the capture body <NUM>, to a natural air flow <NUM> (e.g. wind, etc.) outside of the harvest chamber <NUM>. Atmospheric carbon dioxide <NUM> is captured by the sorbent material <NUM> of the capture body <NUM> on contact. The portion of the capture body <NUM> (or the entire body, in some embodiments) holding captured CO<NUM> is then moved into the harvest chamber <NUM> through the first opening <NUM> by the support structure <NUM> which is driven by the control system <NUM>. Next, the sorbent material <NUM> is regenerated by the sorbent regeneration system <NUM> inside of the harvest chamber <NUM>, releasing the captured CO<NUM> to mix with the gas inside the harvest chamber <NUM> to form an enriched gas <NUM> (i.e. a gas enriched with CO<NUM>). The enriched gas <NUM> is removed from the harvest chamber <NUM> to become a product stream, and the regenerated capture body <NUM> is moved back outside the chamber <NUM> to capture more atmospheric carbon dioxide and begin the cycle again.

The system <NUM> can be used with a wide range of different sorbents <NUM> that can be regenerated by various means, including solid sorbents and liquid sorbents. The sorbents <NUM> can be made from inorganic materials or from organic materials, and may also be composites. Sorbents <NUM> could be materials that bind CO<NUM> chemically or physically, i.e., they could be absorbers. They could also be adsorbents that bind CO<NUM> on internal surfaces, (e.g. inside porous structures, on fiber surfaces, etc.). Examples of regeneration methods for a sorbent material <NUM> include, but are not limited to, a moisture swing, a thermal swing, a vacuum swing, or in a combination of these approaches. The above discussion of different sorbents <NUM> is meant to exemplify the options, rather than provide an exhaustive description. Other sorbent-based technologies that can be provided by those skilled in the art, may be adapted for use in the collection system <NUM>.

The sorbent material <NUM> can be selective for a single sorbate or interact with multiple sorbates that cooperate or compete with each other. Sorbents <NUM> could be autocatalyzing their own absorption. As a specific example, some embodiments may employ sorbents <NUM> for which the sorbent's affinity to CO<NUM> can be controlled by moisture. In some cases, the presence of moisture will increase the binding of CO<NUM> to the sorbent <NUM>, while in other cases it will reduce it. One particular class of sorbents, which are known as moisture swing sorbents, bind CO<NUM> under dry conditions and release it again when made wet. Some moisture swing sorbents, as for example, polystyrenes with quaternary ammonium ions, respond strongly to relative humidity. This means that the impact of raising the temperature of the surrounding air increases the loading of the sorbent with CO<NUM> as the associated reduction in relative humidity decreases the Gibbs free energy of sorption more than it is raised by the increase in temperature. However, if warming occurs at a constant relative humidity, for example <NUM>% relative humidity, or wet conditions, then heating the sorbent will drive CO<NUM> off the sorbent. Therefore, moisture swing sorbents can be used with moisture alone, or with a combination of moisture (water, fog or other droplet forms, or vapor), temperature, and pressure. In some embodiments, the use of such a versatile sorbent may be optimized by the control system <NUM> using algorithms that choose the regeneration pathway based on efficiency in light of ambient conditions.

Apart from a few specific examples directed to specific modes of operation, the preceding discussion of the elements and operation of a collection system <NUM> may be applicable to systems <NUM> that are either continuous or batch. The following will focus more on specific operation modes. For example, <FIG> and <FIG> are perspective views of a non-limiting example of a system <NUM> configured for continuous operation.

According to various embodiments, the capture body <NUM> may be a closed-loop belt <NUM> that enters the harvest chamber <NUM> through the first opening <NUM>. In some embodiments, the belt <NUM> exits the harvest chamber <NUM> through a second opening <NUM>, while in other embodiments the belt <NUM> may exit the harvest chamber <NUM> through the same opening by which it entered (i.e. the first opening <NUM>).

The belt <NUM> moves in a closed loop across a series of rollers <NUM>, at least one of which is driven by the control system <NUM> (e.g. coupled to a motor <NUM>, etc.). The belt <NUM> may be composed of a fabric or similarly flexible material or substrate <NUM>. According to various embodiments, the belt <NUM> may comprise a sorbent material <NUM>. Natural air flow or wind is used to expose the belt <NUM> to ambient CO<NUM> <NUM>. According to various embodiments, continuous operation allows for reduced energy cost. Furthermore, these systems <NUM> are flexible and may be adapted to function optimally in varying weather and climate conditions.

The dominant component of the enriched gas <NUM> in the harvest chamber <NUM> is air, but the CO<NUM> concentration is raised from the ambient levels of about <NUM>% to several percent. Another way to look at this is that the process removes roughly <NUM>% of the air from the gas mixture that contains the CO<NUM>.

In some embodiments, the belt material may be a simple fabric, which could be from active sorbent material <NUM> or have active sorbent material <NUM> embedded into it. In some embodiments, the fabric material may be a woven fabric, while in others it may be a felt-like material. In some embodiments, the belt <NUM> may be made from a plastic-type material. The belt <NUM> may be made of a mesh, having channels that pass through it. In some embodiments, the belt <NUM> may be a composite, analogous to a rug having fibers sticking out on both sides that can absorb CO<NUM>. The belt <NUM> may be made from parallel slats of material that are attached to each other. In some embodiments, the belt <NUM> may contain stiffening ribs.

According to various embodiments, the rollers <NUM> only touch parts of the belt <NUM> designed for contact. The belt <NUM> may consist of a "tough layer" designed to come in contact with the rollers <NUM>. These contact areas may include the two outside edges of the belt <NUM>, but in some embodiments might include one or more strips in the middle of the belt <NUM>. The forces holding the belt <NUM> onto the rollers <NUM> may be adjusted to be large enough to allow the belt <NUM> to move forward without slipping providing enough tension to prevent the belt <NUM> from sagging into undesired areas. Some sorbents are sensitive to UV light. In some embodiments, only one side of the belt <NUM> (i.e. the side facing downward) may comprise the sorbent material <NUM>, reducing the cost of the system. In other embodiments, the support structure <NUM> may comprise some form of shade to shield the exposed sorbent material <NUM> from direct sunlight.

In some embodiments, the belt may fold like fan-fold paper into a stack, which may be arranged vertically, where an incoming section is added to the "top of the stack" and an outgoing section is removed from the "bottom of the stack. " In such a design, the whole stack is slowly sliding through the harvest chamber <NUM> for regeneration and air slowly flows through the stack as it moves through the atmosphere.

In some embodiments, one or both portions of the support structure <NUM> may comprise two sets or racks of rollers, an upper rack <NUM> and a lower rack <NUM> between which the belt <NUM> is woven back and forth in a zigzag path. The belt path may be designed in a fashion that the fraction of length of the belt <NUM> in the chamber <NUM> can vary from a very small portion of the length of the belt <NUM> to nearly the entire length of the belt <NUM>. According to some embodiments, the portion of the belt <NUM> outside the chamber <NUM> may move from the second opening <NUM> of the harvest chamber <NUM> in zigzag path, alternatingly over a top roller and under a bottom roller, and eventually back into the first opening <NUM> of the harvest chamber <NUM>. In some embodiments, the height <NUM> of the top rollers outside the chamber <NUM> may be adjusted, either collectively or individually, until they come down to the level of the bottom rollers. Lowering all or some of the top rollers makes it possible to shorten the length of the belt-section exposed to the atmosphere.

In another embodiment, the bottom rollers may be idlers and maintain tension in the belt <NUM> through their weight, while a speed differential between individually-driven top rollers controls the length of the belt <NUM> between two top rollers. In such embodiments, the top rollers may all be at the same height <NUM>. Said height <NUM> may be fixed in some embodiments, while in others the top rollers may move up or down to minimize the exposure of the belt <NUM>, when so desired. For example, during high winds the belt <NUM> may need to be protected inside the harvest chamber <NUM>. Even if the height <NUM> of the top rollers is fixed the total length of the exposed belt section can be adjusted if the height of the bottom rollers changes.

The belt <NUM> in the harvest chamber <NUM> may move over a large number of top and bottom rollers that also can adjust their relative distance to adjust the amount of belt <NUM> that is inside the harvest chamber <NUM>, according to various embodiments. Some embodiments may have two racks of rollers, an upper rack <NUM> and a lower rack <NUM>, and the belt <NUM> may move in a zigzag fashion alternating between going over a top roller and going below a bottom roller. The total length of belt <NUM> in the chamber may be varied by having one or both racks move. When the two racks reach their maximum distance nearly all the belt is inside the harvest chamber <NUM>.

According to various embodiments, some or all of the rollers <NUM> in the system may be driven (e.g. coupled to a motor <NUM>, etc.). Driven rollers <NUM> can maintain a speed differential, to accommodate an increase or decrease in the distance between rollers <NUM>. In other embodiments, all of the rollers <NUM> may be passive.

In some embodiments, the control system <NUM> may be used to ensure that the total belt <NUM> is under tension, while also allowing the ratio of the belt <NUM> inside and outside the harvest chamber <NUM> to be changed. For example, if ambient conditions <NUM> (as determined by an external sensor <NUM> communicatively coupled to the control system <NUM>) allow for fast uptake, a larger fraction of the belt may be kept in the harvest chamber <NUM>, and the belt speed <NUM> may be increased. If ambient conditions <NUM> are less favorable, the control system <NUM> may slow down the belt <NUM> and a smaller fraction of the belt <NUM> is inside the harvest chamber <NUM>. Conversely, if conditions in the harvest chamber <NUM> improve (e.g. temperatures increase, etc.) the control system <NUM> may speed up the belt <NUM> and maintain a larger fraction inside the harvest chamber <NUM>. If wind conditions threaten to exceed the maximum allowable wind force on the belt <NUM>, the belt <NUM> left outside may first be reduced, to reduce wind drag, and if necessary the exposure to the weather may be nearly completely eliminated by completely lowering the belt <NUM>, according to various embodiments. If other weather conditions require protection of the belt <NUM> (e.g. a sandstorm, etc.) the belt <NUM> can also be retracted into the harvest chamber <NUM>, according to some embodiments. The control system <NUM> will be discussed further with respect to <FIG> and <FIG>, below.

Controls for moving the belt <NUM> and allocating it between inside and outside act on the individual motorized rollers <NUM> in the system <NUM>. In some embodiments, rollers <NUM> may consist of a central shaft and two or more sections that come in direct contact with parts of the belt <NUM>. The contact with the belt <NUM> may be simple friction, or may involve teeth that match holes in the edge or rib of the belt <NUM>.

<FIG> is a side view of a non-limiting example of a passive capture system <NUM> configured for continuous operation. It should be noted that in the context of the present description and the claims that follow, continuous operation does not mean that the system <NUM> must always be in operation, but rather that it is capable of capturing CO<NUM> from the atmosphere on one part of the capture body <NUM> while simultaneously releasing captured CO<NUM> from another part of the capture body <NUM> inside of the harvest chamber <NUM>. While such a capability may allow the system to be in constant motion, it should not be interpreted as requiring it to do so. In contrast, a system <NUM> operating in a batch mode alternates between capturing and releasing, but is not able to do both at the same time. It should also be noted that, in <FIG>, <FIG>, and <FIG>, a portion of the harvest chamber <NUM> has been removed to reveal the interior. Additionally, some elements are portrayed using a schematic or iconic representation, for the sake of clarity.

When the capture body <NUM>, or a portion of the capture body <NUM>, is laden with CO<NUM> and has been moved into the harvest chamber <NUM>, the sorbent material <NUM> is regenerated to release the captured CO<NUM> into the harvest chamber <NUM>. As previously discussed, this regeneration and release is accomplished by the sorbent regeneration system <NUM>. According to various embodiments, including the non-limiting example shown in <FIG>, the sorbent material <NUM> of the capture body <NUM> may be a moisture swing sorbent material <NUM>. In embodiments where the active sorbent material <NUM> in the belt <NUM> is a moisture swing sorbent <NUM>, stimulation of CO<NUM> release in the chamber <NUM> can occur by wetting the material <NUM> with liquid water <NUM> or exposure to high levels of moisture or steam. In embodiments making use of a moisture swing sorbent material <NUM>, the sorbent regeneration system <NUM> comprises a release medium <NUM>, at least one release medium emitter <NUM>, and at least one liquid extractor <NUM>.

In the context of the present description, the release medium <NUM> is a material or substance that stimulates the release of CO<NUM> from the sorbent material <NUM>. In the case of a moisture swing sorbent material <NUM>, the release medium <NUM> may be liquid water <NUM> or steam <NUM>. In other embodiments, the release medium may be any other solution or substance that is compatible with that particular sorbent material <NUM>. Furthermore, in the context of the present description and the claims that follow, a release medium emitter <NUM> is a device configured to promote the interaction of the release medium <NUM> and the CO<NUM>-laden sorbent material <NUM>. Exemplary release medium emitters <NUM> include, but are not limited to, misters, nozzles, foggers, liquid jets, a reservoir of release medium through which the sorbent passes, steam nozzles, and the like.

In embodiments where the release medium <NUM> takes a liquid form, either when being applied through an emitter <NUM> or after application (e.g. steam <NUM> condensing into liquid water <NUM> upon cooling, etc.), the sorbent regeneration system <NUM> may further include one or more liquid extractors <NUM>, which are devices and/or structures configured to collect the liquid release medium <NUM> and remove it from the chamber <NUM> after it has stimulated the CO<NUM> release, either for disposal, immediate reuse, or conditioning in preparation for reuse (e.g. removing impurities, etc.). For example, as shown in <FIG>, liquid water <NUM> may be sprayed on to the belt <NUM> with a release medium emitter <NUM>, after which it drips down to the bottom of the harvest chamber <NUM>. The liquid extractor <NUM> comprises a drain <NUM> at the bottom of the chamber <NUM> that is coupled to a release medium reservoir <NUM> through a pump <NUM>. Collected liquid water <NUM> is returned to the reservoir <NUM> by the pump <NUM> for repeated use, reducing the overall water requirements for operating the system <NUM> and making it usable in environments with reduced water availability.

After the CO<NUM> has been released from the sorbent material <NUM> of the capture body <NUM> inside the chamber <NUM>, it mixes to form an enriched gas <NUM>. According to various embodiments, the enriched gas <NUM> is subsequently removed from the chamber <NUM> through a product outlet <NUM> as a product stream <NUM>. In some embodiments, the product outlet <NUM> may be a valve, while in others it may comprise a pump. The product outlet <NUM> is in fluid communication with the inside of the harvest chamber <NUM>.

In some embodiments, the product stream <NUM> is formed by displacing the enriched gas <NUM> with a sweep gas <NUM> introduced to the inside of the harvest chamber <NUM>. In some embodiments, the sweep gas <NUM> is atmospheric air <NUM>, while in others the sweep gas <NUM> is another readily available gas. In some embodiments, the sweep gas <NUM> is introduced to the chamber <NUM> by passing through an opening (e.g. first opening <NUM>, second opening <NUM>, etc.). In other embodiments, the sweep gas <NUM> may be introduced to the chamber <NUM> through an intake <NUM>.

According to various embodiments, the belt <NUM> enters and leaves the harvest chamber <NUM> through a channel or channels that are designed to minimize airflow in and out of the chamber <NUM>. Precautions are taken to minimize airflow between the inside and the outside to prevent or minimize the loss of CO<NUM> from the harvest chamber <NUM>, but rather allowing the CO<NUM> to build-up the harvest chamber <NUM>. In some embodiments, the flow through one or more of these channels may be manipulated or otherwise controlled such that the sweep gas <NUM> is introduced to the chamber <NUM> at a desired rate.

In some embodiments, the air flow through a channel (e.g. first opening <NUM>, etc.) may be eliminated or held very close to zero. One example, a liquid trap <NUM>, will be discussed below. In embodiments having a first opening <NUM> where the belt <NUM> enters and a second opening <NUM> where the belt exits, and where the air flow is eliminated at the first opening <NUM>, the sweep gas <NUM> will enter through the second opening <NUM>.

The atmospheric air <NUM> enters the chamber <NUM> through the second opening <NUM> and flows over the belt <NUM>, initially encountering portions of the belt <NUM> that have mostly discharged their CO<NUM> and eventually arriving at the end of the chamber <NUM> where the belt <NUM> is still fully loaded with CO<NUM>. Advantageously, the product outlet may be placed near the first opening <NUM>, where the sweep gas <NUM> is driving the enriched gas <NUM>, and opposite the second opening <NUM>. The CO<NUM> laden air (i.e. enriched gas <NUM>) is then removed from the chamber <NUM> for use or further processing.

On the side where the belt <NUM> enters, airflow through the channel may be minimized or eliminated, while on the side where the belt <NUM> leaves airflow may enter through the second opening <NUM> and add to the sweep gas stream <NUM> for collecting the CO<NUM>. If the airflow through the second opening <NUM> is throttled below the required flow rate, a separate air intake <NUM> near the exit of the belt (i.e. second opening <NUM>) may be used for maintaining the appropriate amount of sweep gas <NUM>, thereby increasing the control over the flow rate of the product stream <NUM>.

In some embodiments, the belt <NUM> may be fed into the chamber <NUM> through a liquid trap <NUM>. A liquid trap <NUM> is a channel that is partially filled with water <NUM> or some other liquid. It comprises an external aperture <NUM> exposed to the atmosphere and an internal aperture <NUM> that is below the external aperture <NUM> and submerged under water <NUM> such that the water <NUM> separates the inside of the harvest chamber <NUM> from the external aperture <NUM>. The internal and external apertures are connected by a conduit <NUM> that is at least partially filled with water <NUM>. In some embodiments, the conduit <NUM> is U-shaped. In this manner, CO<NUM> is prevented from flowing in and out of the chamber <NUM>. In the case of a moisture swing sorbent <NUM>, the liquid trap <NUM> may also provides a means of wetting the sorbent <NUM>. Another method of controlling flow into or out of the chamber <NUM> is making use of dynamic air locks <NUM>, and will be discussed in greater detail with respect to <FIG>.

In a particular embodiment, the harvest chamber <NUM> may contain a fixed set of rollers <NUM> attached at the top of the harvest chamber <NUM>, and a lower rack of rollers <NUM> able to move up and down. The chamber <NUM> may be rectangular in shape and may have dimensions that make it match the size of a standard shipping container. The front end of the shipping container-sized harvest chamber <NUM> may contain the liquid trap <NUM> for letting the belt <NUM> in without losing CO<NUM>. The belt <NUM> may comprise a moisture swing sorbent <NUM> that is wetted as it goes through the water filled liquid trap <NUM>. The belt <NUM> moves out of the chamber <NUM> through a second opening <NUM> at the back end, which also lets air in at a proscribed rate that matches the rate of the product stream <NUM>. For maintenance, the roof may be comprised of panels that can be removed and give access to the motorized rollers <NUM> at the top. Some or all of the top rollers <NUM> are motorized. The speed of the motorized rollers can be independently controlled by the control system <NUM>. As an option, the side panels may be opened to give access to the sides for maintenance and repair.

The release of CO<NUM> in the harvest chamber <NUM> is often slow. For most air capture sorbents <NUM>, the evolution of CO<NUM> is relatively slow and the high partial pressure evolves over a significant amount of time, which can range from a few minutes to a few hours. A major challenge is to move the sorbent material <NUM> into and out of the chamber <NUM> without losing significant amounts of the collected CO<NUM> to the outside ambient air. The higher partial pressure evolves over a long time and thus it is important that the harvest chamber <NUM> does not readily exchange gas with the outside during the regeneration of the sorbent material <NUM>.

This can be accomplished in a batch mode by opening and closing the harvest chamber <NUM> (see <FIG> and <FIG>), but in a continuous process it may need an air lock design that makes it possible to insert CO<NUM>-laden sorbent material <NUM> into the chamber <NUM> in a continuous manner and remove it at the same time, while minimizing the exchange of gas with the outside.

One approach, mentioned above, is to create a liquid trap <NUM>. The liquid level in the trap <NUM> may be high enough that it can adjust to the expected pressure fluctuations between the inside and the outside of the chamber <NUM>, and the movement of the belt <NUM> may be slow enough that most of the water <NUM> or other liquid will flow back to the bottom of the trap <NUM> as the belt <NUM> moves in or out of the chamber <NUM>. Similar designs could be considered for other forms of sorbent material.

The use of a liquid trap <NUM> to inhibit air flow through a channel is advantageous for a number of reasons. It is more responsive to pressure changes (e.g. gusts of wind, etc.) than deliberate mechanisms such as the dynamic air lock, which relay on sensors and programmatic responses. Additionally, the liquid trap <NUM> does not require any energy to operate, and the only resource expended is liquid lost to evaporation or carried off by the belt <NUM>. In some embodiments, the liquid trap <NUM> may also serve as the sorbent regeneration system <NUM>.

However, the use of a liquid trap <NUM> has some pitfalls as well. The amount of wetting applied by the liquid trap <NUM> might be counterproductive for some designs. For example, the wetting can add weight to the sorbent <NUM>, and as the belt <NUM> leaves the chamber <NUM>, the water <NUM> that has been soaked up by the belt <NUM> will have to evaporate into the outside air. This will create a water loss for the system <NUM>, and may also temporarily stop the belt <NUM> from being active. For example, in some embodiments, the belt <NUM> may be made from a moisture swing sorbent <NUM>. The excess water <NUM> associated with belt <NUM> when it leaves the chamber <NUM> will prevent the belt <NUM> from binding additional CO<NUM> until the belt <NUM> has dried.

As discussed above, it is advantageous to control the flow of air through any openings in the harvest chamber <NUM> (e.g. first opening <NUM>, second opening <NUM>, etc.), to prevent loss of CO<NUM> that has been released from the sorbent material <NUM>. According to various embodiments, the flow of air may be controlled, or substantially eliminated, through the use of a dynamic air lock <NUM> that makes use of flows or counter flows generated by one or more flow generators <NUM>. In the context of the present description and the claims that follow, a dynamic air lock <NUM> is an air lock that may be configured and reconfigured to modify how much flow is permitted to pass through an open channel <NUM> of a chamber <NUM>, if any at all, and in what direction.

In the context of the present description and the claims that follow, a flow generator <NUM> is a device that can create an air flow, and that can fit inside an open channel <NUM> (e.g. a conduit or opening bridging the interior of the harvest chamber <NUM> with the ambient air). Examples include, but are not limited to, fans, blowers <NUM>, nozzles supplied with compressed gas (e.g. compressed atmospheric air if injected close to an external aperture of the channel, compressed enriched gas <NUM> if close to the interior of the chamber <NUM>, etc.), and the like.

<FIG> is a side view of a non-limiting example of a passive collection system <NUM> making use of two dynamic air locks <NUM>, in conjunction with a moisture swing sorbent <NUM> and a steam release medium <NUM>. As shown, the vertical channels to the right and left are open to the outside. Unless the chamber <NUM> is sealed, or otherwise prevented from having air exchange between the inside and the outside, pressure fluctuations either on the inside or the outside will cause air to be mixing between the two reservoirs (the enriched gas <NUM> in the chamber <NUM>, and the ambient air <NUM> in the atmosphere).

It should be noted that the following discussion is done in the context of a chamber <NUM> wherein the open channel <NUM> in one dimension may reflect the full width of the interior of the chamber <NUM> whereas the other dimension may be far smaller. The embodiments described below could also apply to a square or circular horizontal cross-section of the channel <NUM>.

The gas flow in and out of the chamber <NUM> is desired to be zero, or to be held constant at a prescribed value that optimizes the CO<NUM> delivery based on a user objective. As shown, both the first opening <NUM> and the second opening <NUM> comprise dynamic air locks <NUM>. In some embodiments, the harvest chamber <NUM> may have more than these two openings/channels. Furthermore, in some embodiments, it is also possible to use a liquid trap to control one of these two channels, as discussed above with respect to <FIG>.

According to various embodiments, the flow between the inside and the outside may be minimized, or to set to a desired level, through the use of devices, in both channels, that can cause air to move forward or backward in the channel. In one embodiment, these flow generators <NUM> (also referred to as pressure drop generators) may be a set of small fans through which the air would have to flow. In some embodiments, the fans may not cover the entire cross section of the open channel <NUM>, but are installed in a sub cross-section which creates an overall airflow. This would make it possible to feed objects, like a belt <NUM>, through the opening <NUM>. In yet another embodiment, air may be pushed out along the edge of the wall in a thin layer that moves along the wall creating a boundary condition that drags air inside the channel <NUM> along in the desired direction. In yet another embodiment, small nozzles may be employed to push air out into the channel <NUM>, either upward or downward. In all of these embodiments, the goal is to adjust these flows such that the net flow through the channel <NUM> is as close to zero, or to the desired level (e.g. desired rate of sweep gas, rate sufficient to maintain a constant CO<NUM> level in the chamber <NUM>, etc.), as can be accomplished. Unless explicitly stated otherwise, in the following discussion no assumptions are made about the particular type of flow generator <NUM>.

According to various embodiments, for such a system <NUM> to become approximately sealed, the channel <NUM> needs to be long enough and narrow enough that the air mixing creates a uniform flow throughout the width of the channel <NUM>. The velocity profile need not be flat. Unless the flow is extremely turbulent there will be a velocity profile across the channel even if the flow is allowed to stabilize.

In one embodiment, a simple control loop implemented by the control system <NUM> for zero flow considers the length of the channel <NUM> either upstream or downstream from the flow generator <NUM> and adjusts the power of the flow generator <NUM> so as to zero out the pressure drop in the section of the channel that entirely resides on one side of the flow generator <NUM>. A zero pressure drop over a long section of the channel <NUM> is accomplished when the net flow through that section is zero. If there is a desire to maintain a fixed flow rate, then the relationship between pressure drop and flow rate may be calibrated to determine the pressure drop. Alternatively, one embodiment replaces measurements of pressure differentials with measurements of flow speeds to develop control algorithms. In other embodiments, mass flows may be determined directly and used to regulate the flow generators <NUM>.

In embodiments where the flow generators <NUM> installed in the first <NUM> and second <NUM> openings are close to the bottom of the channel, the pressure drop in the subsequent vertical part may be controlled. If the flow generator <NUM> is near the top, a similar section in the stream may be used, but this time it is part of the inside stream. If the flow generator <NUM> is close to the middle of the section, either side, or both sides may be considered in the control algorithm.

In other embodiments, the flow generator <NUM> may be used to cause a pressure drop between its two sides near the generator <NUM> that is equal to the overall pressure drop between the inside and outside of the chamber <NUM>. In that case, there would be zero pressure drop in the inside part of the channel <NUM> and zero pressure drop in the outside part of the channel <NUM>, which would suggest that the net flow through the channel <NUM> approaches zero. In a particular embodiment, there may be multiple measurements that provide redundancy and higher accuracy, including but not limited to pressure differentials between the inside and the outside of the chamber <NUM>, a pressure differential across the flow generator <NUM> near the generator, and two pressure differentials of a pair of points, each pair completely on one side of the flow generator <NUM>. In addition, there may be at least one absolute pressure measurement. A control algorithm used by the control system <NUM> may take all data into account, or a subset of the data.

According to various embodiments, the operation of one or more flow generators <NUM> communicatively coupled to the control system <NUM> may depend upon a sensor reading <NUM> obtained by the control system <NUM> from a sensor <NUM> located in or near the open channel <NUM>. Exemplary sensors <NUM> include, but are not limited to, pressure sensors, flow speed sensors, mass flow sensors, thermal anemometers, and ultrasound anemometers.

In embodiments where a closed-loop belt <NUM> is wending its way into and out of the harvest chamber <NUM>, gas entrained in the belt structure may be carried with the belt <NUM> and thus create a mass transfer. This may be compensated for by having an equivalent stream go the opposite direction, employing active blowers <NUM> exchanging air between the open channel <NUM> and the belt <NUM> to minimize carry through. Furthermore, a belt <NUM> effectively splits the channel <NUM> into two separate channels. According to various embodiments, a zero pressure drop may be maintained independently on both sides of the belt <NUM> within the channel <NUM>.

The pressure differential between the inside and the outside may vary substantially on longer time scales. For example, temperature changes inside a closed chamber <NUM> on the order of <NUM>, could result in pressure changes on the order of <NUM>% of an atmosphere (or <NUM> kPa). Power requirements on the flow generators <NUM> may become excessive, if they would have to maintain a pressure difference on that order for substantial amounts of time. On the other hand, in embodiments that allow for a slow gas flow through the chamber <NUM>, it would be possible to gradually adjust the pressure differential without getting outside of the design specifications for the gas flow, simply by configuring for different inflow and outflow rates.

As a specific example, it the sun were to heat up the chamber <NUM>, the system <NUM> could gradually adjust its pressure over a time period that is comparable to the time it takes the belt <NUM> to move through the chamber <NUM>. The blowers would still have to handle short time pressure fluctuations driven, for example by wind gusts. There may be a maximum pressure drop the system <NUM> can generate, and when wind speeds exceed this limit, the performance of the system <NUM> will be degraded. On the other hand, typical wind gusts will lead to much lower pressure fluctuations than diurnal temperature changes. Wind fluctuations are typically in the tens of Pa, but they can reach values on the order of one kPa.

As a specific example, a system <NUM> comprises a harvest chamber <NUM> that is <NUM><NUM> in volume, with dimensions of <NUM> x <NUM> x <NUM>. On the end section are two slits, each <NUM> x <NUM>, that connect the inside to the outside. The wind outside is blowing at some speed, and fluctuations in the wind can cause a change in the pressure differential between the inside and the outside of the chamber <NUM>. There are two types of flows; one is caused by a constant pressure differential between the two openings on the opposite sides of the harvest chamber <NUM>. The other is due to variations in the total pressure on the outside of the chamber <NUM> caused by the Bernoulli effect. The flow speed through the entrance could be as high as <NUM>% of the wind speed, but since the width of the slit is only <NUM> part in <NUM> of the height of the chamber <NUM>, the actual flow speed of air across the inside of the chamber <NUM> could be as much as <NUM>% of the flow speed on the outside. If the wind speed is <NUM>/s, the time to cross the length of the chamber <NUM> on the outside is about <NUM> seconds, while on the inside it would be about <NUM> minute. If the path through the chamber <NUM> is long and narrow, this time can get substantially longer, in part because the distance to travel gets longer, and in part because the flow inside the chamber <NUM> will contribute its own pressure drop, which will take away from the pressure drops at the ends. This might extend a minute to a good fraction of an hour.

Huffing and puffing during wind gusts works differently. A wind gust lowers the pressure on the outside, on both ends, simultaneously. Assuming wind gusts up to <NUM>/s, then the pressure drops on the outside because of Bernoulli's law by about <NUM> Pa on one of the two openings. The same effect might be happening on the other side as well. A single opening would induce a flow rate of up to ten meters second, which could result in an exchange between inside and outside air at a rate of <NUM> cubic meter per second. If the wind moves back and forth every few seconds that could lead again to an air exchange in the chamber that could turn over the air once a minute. Some embodiments address this using a long serpentine path.

To obtain an exchange time on the order of an hour or more, the control system <NUM> needs to effectively lower the uncontrolled flow rates through the openings by one to two orders of magnitude, according to various embodiments. Assuming that the flow through the harvest chamber <NUM> is quadratic in the pressure drop, this means that the control system <NUM> needs to reduce the effective pressure drop in the channel <NUM> by an order of magnitude.

In a specific embodiment, the system <NUM> feeding a belt <NUM> through the gap comprises a set of flow generators <NUM> close to the wall of the channel <NUM>, which can push out gas in small bursts or steady flows that are controlled by a valve that can adjust total flows. Air from the inside of the chamber <NUM> can be used to maintain a fixed pressure drop at the end. On the second opening <NUM> for the belt <NUM>, the airflow is calibrated into the chamber <NUM>. Alternatively, zero flow through the belt exit <NUM> could be attained. It is advantageous to control the flow through the belt channel to zero on this end, since the air extracted from the chamber <NUM> is the product stream <NUM>, making it difficult to collect from the channel <NUM> after the exit.

According to various embodiments, the product flow <NUM> may be removed near the first opening <NUM>. For example, in one embodiment, the product flow <NUM> could be pulled out with a small scroll pump. In one embodiment, the entry and the exit of the belt are on the same side of the chamber <NUM>. This minimizes the pressure differential between the entry and the exit. It furthermore makes it possible to have a small inward leak on both belts <NUM> and have the air exit for the chamber on the opposite side of the flow. The belt <NUM> coming into the chamber <NUM> could therefore still be dry.

<FIG> is a side view of a non-limiting example of a passive collection system <NUM> making use of a heat swing sorbent material <NUM>. In embodiments where the sorbent material <NUM> is a thermal or heat swing sorbent <NUM>, stimulation of the CO<NUM> in the chamber <NUM> can occur by heating the sorbent material <NUM> inside the chamber <NUM>. In other words, the sorbent regeneration system <NUM> for a heat swing sorbent <NUM> comprises one or more heat sources. In some embodiments, heating of the sorbent material <NUM> in the chamber <NUM> may be achieved using mild steam <NUM> that condenses on the sorbent material <NUM>. Heating of the sorbent material in the chamber may be achieved using mild steam that condenses on the sorbent material. This method of regeneration can work with thermal swing materials and moisture swing materials. It provides the advantage of amplifying the moisture swing with a thermal boost, and it eliminates the release of water vapor from the sorbent material into the harvest chamber, which otherwise would consume significant amounts of energy.

Other examples of means of heating the heat swing sorbent <NUM> include, but are not limited to, direct heating of the surrounding air in the harvest chamber <NUM>, radiative heating of the belt <NUM> (e.g. with visible light, infrared light, microwaves, etc.), and guiding the belt <NUM> over heated rollers <NUM>. Adding UV lights to the sorbent regeneration system <NUM> could also be advantageously used to discourage microbial growth on the belt <NUM>.

Additional heat sources <NUM> may include, but are not limited to, geothermal heat, waste geothermal heat left over after geothermal heat of higher temperature has been applied in some other application, residual heat from power plants and other energy consumers, solar heat, and heat collected from cooling solar panels. In some embodiments, the waste heat generated by a CO<NUM> compression system used on the product stream <NUM> may be repurposed for heating the harvest chamber <NUM>.

As shown, in some embodiments, a flow generator <NUM> may comprise one or more drag belts <NUM>, which are flat belts that move along the flat surfaces of a channel wall <NUM> and create a boundary condition where air on the surface moves with the speed of the drag belt <NUM>. Thus, in some embodiments, a dynamic air lock <NUM> may be formed using drag belts <NUM> to create a flow <NUM> in the channel in the direction that the drag belt <NUM> is moving that results in a desirable average flow <NUM> across the channel <NUM>.

In some embodiments, lightweight flexible materials may be attached to the interior of the harvest chamber <NUM> and the racks that minimize gas exchange between the active belt-filled part of the harvest chamber <NUM> and the idle part of the chamber <NUM> that is above the top rollers or below the bottom rollers. In one embodiment, the vertical connections or curtains <NUM> may be a rolled up "jalousie" like material that extends from the top rack down to right above a bottom roller, and conversely a similar design for material extending from the bottom rack right below the opposing top roller. These curtains <NUM>, which may loosely touch the walls of the harvest chamber <NUM>, may extend and shrink as the distance between the racks changes and create a serpentine pathway for air to flow along the belt <NUM>.

<FIG> and <FIG> show side views of the non-limiting example of a system <NUM> shown in <FIG>. Specifically, <FIG> shows the capture body <NUM> of the system <NUM> in a collection configuration <NUM>, and <FIG> shows the capture body <NUM> in a release configuration <NUM>. It should be noted that the closed-loop belt <NUM> is shown with roughly half of the belt <NUM> shaded. This is done to make the two configurations distinct, since in a system <NUM> configured for continuous operation, the capture body <NUM> may be in both configurations simultaneously. The shading allows the capture/release cycle to be easier to observe across <FIG> and <FIG>, and should not be interpreted as limiting or indicating a property of the belt.

In the context of the present description and the claims that follow, a collection configuration <NUM> is an arrangement of the capture body <NUM> wherein at least a portion <NUM> of the capture bod <NUM> able to capture carbon dioxide is in contact with an airflow outside the harvest chamber <NUM>, such that atmospheric carbon dioxide is captured by the sorbent material <NUM>. Furthermore, in the context of the present description and the claims that follow, a release configuration <NUM> is an arrangement of the capture body <NUM> wherein at least a portion <NUM> of the capture body <NUM> holding captured carbon dioxide <NUM> is in contact with the sorbent regeneration system <NUM> inside the harvest chamber <NUM> such that captured carbon dioxide <NUM> is released into the harvest chamber <NUM> to form an enriched gas <NUM>.

According to various embodiments, a method for passively collecting atmospheric carbon dioxide includes exposing at least a portion <NUM> of the capture body <NUM> able to capture carbon dioxide to a natural airflow, and then moving the at least a portion <NUM> of the capture body <NUM> holding captured carbon dioxide <NUM> into the harvest chamber <NUM> using the support structure <NUM> coupled to the capture body <NUM> and driven by a control system <NUM> communicatively coupled to the support structure <NUM>. The portion <NUM> of the capture body <NUM> holding captured carbon dioxide <NUM> enters the harvest chamber <NUM> through a first opening <NUM>. The method then includes regenerating the sorbent material <NUM> of the capture body <NUM> and releasing the captured carbon dioxide <NUM> into the harvest chamber <NUM> to form an enriched gas <NUM> by exposing the sorbent material <NUM> to a release medium <NUM> introduced to the harvest chamber <NUM> by a release medium emitter <NUM>. Additionally, the method includes extracting the release medium <NUM> in liquid form from the harvest chamber <NUM> using a liquid extractor <NUM>. Afterward, or simultaneously, the product stream <NUM> of enriched gas <NUM> is removed from the harvest chamber <NUM> through a product outlet <NUM> by displacing the enriched gas <NUM> with a sweep gas <NUM>. Finally, the at least a portion of the capture body <NUM>, now having regenerated sorbent material <NUM>, is removed from the harvest chamber <NUM> by driving the support structure <NUM> with the control system <NUM>.

According to various embodiments, the control system <NUM> may comprise communication equipment for remote monitoring and operation. In some embodiments, the control system <NUM> may be configured for autonomous operation, adapting to ambient conditions as needed. Power may be supplied directly, via battery, or from a renewable source such as, for example, solar, wind, or thermoelectric.

In some embodiments, the control system <NUM> may be communicatively coupled to one or more sensors (e.g. CO<NUM> sensors, humidity sensors, temperature sensors, air flow sensors, light sensors, etc.) and may be configured with algorithms for efficient operation of the system <NUM>.

In some embodiments, the control system <NUM> may employ algorithms developed to produce the best response from the sorbent <NUM>. These algorithms may be designed to combine heating and moisture applications in a most efficient manner. In some embodiments, the algorithms optimize the balance between performance and operational cost, so that water and heat are deployed to optimize CO<NUM> delivery at optimal rate and optimal partial pressure. Optimization may also account for ambient temperatures, the loading state of the sorbent <NUM>, weather conditions, the cost of heat, water, and electricity, and other relevant parameters.

The control system <NUM> may make use of software configured to control one or more operations or properties, including but not limited to the rate of addition of water in the form of liquid/fog/steam, internal temperature, flow rate of sweep gas, pumping rate to pull product gas out, timing of exposure to air, time within harvest chamber <NUM>, and the like. The software may be configured to optimize various properties, such as yield, water consumption, and/or energy consumption.

Automated system may include, but are not limited to, wind/weather measurement and response, CO<NUM> collection monitoring, automatically timed movement of the capture body <NUM> and/or support structure <NUM>, water and air control systems, temperature measurement & control, internal flow measurement, timing controls to match the function of other system, and the like.

The systems <NUM> configured for continuous operation discussed above are advantageous in terms of energy cost and adaptability over batch processing methods. However, such systems may be difficult to optimize for harvesting airflows from multiple directions (e.g. efficiency may be poor for certain vectors). <FIG>, <FIG>, and <FIG> show a side view of a non-limiting example of a passive collection system <NUM> configured for batch operation. Specifically, <FIG> is a side view, <FIG> is a side view of the system <NUM> of <FIG> with part of the harvest chamber <NUM> removed for clarity and with the lid <NUM> in an open position <NUM>, placing the capture body <NUM> in a collection configuration <NUM>. <FIG> is the same as <FIG>, except the lid <NUM> is in a closed position <NUM>, placing the capture body <NUM> in a release configuration <NUM>.

As shown, the system <NUM> makes use of a capture body <NUM> that is made up of a set of plates <NUM> that are exposed to air while the plates <NUM> hang from a lid <NUM> by a collapsible tether <NUM>, while the lid <NUM> is in an open position <NUM>. The plates <NUM> hang essentially horizontal and parallel to each other in an essentially vertical stack. The circular shape allows for harvesting wind from any direction. According to various embodiments, a plate <NUM> stack could range from a few (<NUM> to <NUM>) plates <NUM>, to a large number (><NUM>).

The plates <NUM> are exposed to the open air that flows through the gaps between the plates <NUM> to absorb CO<NUM>, while the capture body <NUM> is in a collection configuration <NUM> and the lid <NUM> is in an open position <NUM>. The lid <NUM> is in an open position <NUM> when it is above and separated from the harvest chamber <NUM>, according to various embodiments.

Once the sorbent material <NUM> is laden with captured atmospheric CO<NUM>, the support structure <NUM> lowers the capture body <NUM> into the harvest chamber <NUM> over which it hangs. Once the lid <NUM> is a closed position <NUM>, the sorbent regeneration system <NUM> is employed to release the capture CO<NUM>, as described for various embodiments above. The lid <NUM> is in a closed position <NUM> when it is covering the first opening <NUM> of the harvest chamber <NUM>, completely enclosing the capture body <NUM> inside the harvest chamber <NUM>. The system <NUM> then cycles between collection and release, raising and lowering the capture body <NUM> through the first opening <NUM> of the harvest chamber <NUM>.

During the time in the open air, the plates <NUM> are supported by one or more collapsible tethers <NUM>, which may be chains or other flexible supports that are mounted to the lid <NUM> or other part of the support structure <NUM> designed to raise and lower the plates <NUM> from the harvest chamber <NUM>. The tether <NUM> and the plates <NUM> may be raised and lowered automatically or on demand. The sorbent material <NUM> on the plates <NUM> loads up in the open air, and releases CO<NUM> inside the harvest chamber <NUM>.

In some embodiments, within the harvest chamber <NUM> a mechanically driven air stream flows through the chamber <NUM>. The chamber <NUM> may be sealed by the lid <NUM> and/or other structures, except for channels associated with the sorbent regeneration system <NUM> (i.e. release medium emitter <NUM>, liquid extractor <NUM>, etc.), an intake <NUM> for sweep gas <NUM> to enter, and/or a product outlet <NUM> for CO<NUM> laden enriched gas <NUM> to leave the chamber <NUM>.

While the term plates <NUM> is derived from one possible design where plates <NUM> are flat circular shapes, it is important to note that in the context of the present disclosure, the term plate <NUM> is intended to accommodate a much broader range of geometries.

In some embodiments, the plates <NUM> may have a circular cross-section (along the central axis of the stack). In other embodiments, other shapes may be employed, including but not limited to, circular approximations (e.g. higher order polygons), triangles, rectangles, squares, hexagons, stars, rings, and the like. While the circular cross-section may be appropriate for use in environments with unpredictable wind direction, in other embodiments, a more oblong disk may be employed in conditions where the wind has a prevailing direction.

In other embodiments, the plates <NUM> may be non-planar, such as bowl or helmet shaped. In some embodiments, the plates <NUM> may be highly structured to facilitate gas contact with their surface. The plates <NUM> may comprise channels or passageways that create gas flow paths from the top to the bottom of a plates <NUM> to facilitate gas flow that comes in close contact with the sorbent material <NUM> of the plates <NUM>.

In some embodiments, the plates <NUM> may hang vertically, may comprise a plurality of channels that allow natural airflow to pass through, and may be coupled to each other by hinges. When in the release configuration <NUM>, this hinged capture body <NUM> is folded like fan-fold paper into a stack.

It may be advantageous to limit the motion of the plates <NUM> when hanging (e.g. prevent damage, optimize sorbent exposure, etc.). One way of limiting the motion is to contain the hanging plates <NUM> between guides as they are lifted up. One example would be a set of vertical poles, which may also give structural support to the lifting structure (e.g. the support structure <NUM>). Three such poles would already be sufficient to constrain the sideways motion of the plates <NUM>. Another embodiment may have the plates <NUM> connected through guides along a center hole, that prevents relative motions of the plates <NUM>. If the plates <NUM> and the lid <NUM> are ring shaped, then guides could also run on the inside of the plates <NUM>. Another option for limiting movement of the plates <NUM> is to tether the bottom plate to the bottom of the harvest chamber <NUM>.

Claim 1:
A system (<NUM>) for passive collection of atmospheric carbon dioxide, comprising:
a harvest chamber (<NUM>) comprising a first opening and a sorbent regeneration system (<NUM>);
a capture body (<NUM>) coupled to and movable by a support structure (<NUM>), the support structure (<NUM>) having at least a first portion inside of the harvest chamber (<NUM>) and a second portion outside of the harvest chamber (<NUM>), the capture body (<NUM>) comprising a sorbent material and movable by the support structure to be in a collection configuration (<NUM>) wherein at least a portion of the capture body (<NUM>) able to capture carbon dioxide is in contact with a natural airflow outside the harvest chamber (<NUM>) such that atmospheric carbon dioxide is captured by the sorbent material, and a release configuration (<NUM>) wherein at least a portion of the capture body (<NUM>) holding captured carbon dioxide is operated upon by the sorbent regeneration system inside the harvest chamber (<NUM>) such that captured carbon dioxide is released into the harvest chamber (<NUM>) to form an enriched gas;
a product outlet (<NUM>) in fluid communication with the inside of the harvest chamber (<NUM>) and configured to receive a product stream of enriched gas displaced by a sweep gas inside the harvest chamber (<NUM>), the sweep gas introduced to the harvest chamber (<NUM>); and
a control system communicatively coupled to the support structure (<NUM>), and configured to cycle the capture body (<NUM>) between the collection configuration and the release configuration (<NUM>),
wherein the support structure comprises a lid (<NUM>) movable between an open position (<NUM>) above and separated from the harvest chamber (<NUM>), and a closed position (<NUM>) wherein the lid (<NUM>) covers the first opening of the harvest chamber (<NUM>), the support structure (<NUM>) further comprises a collapsible tether (<NUM>) coupled to an interior of the harvest chamber (<NUM>) and the lid (<NUM>), and
wherein the capture body (<NUM>) comprises a plurality of plates (<NUM>) coupled to and spaced out along the collapsible tether (<NUM>) such that the plurality of plates (<NUM>) hangs from the lid (<NUM>) by the tether (<NUM>) when the capture body (<NUM>) is in the collection configuration and the plurality of plates (<NUM>) are enclosed within the harvest chamber (<NUM>) when the capture body (<NUM>) is in the release configuration (<NUM>), each plate (<NUM>) comprising the sorbent material.