Patent Description:
While necessary for comfort, and in parts of the world survival, air conditioning has a significant negative impact on the environment. Currently, air conditioning systems produce heat that measurably increases urban temperatures, and they have the potential to discharge unsafe chemicals, such as greenhouse gases, to the atmosphere. To do this, they also consume vast amounts of energy, primarily electricity. With the climate's ever- increasing temperatures, the demand for air conditioning systems will continue to increase such that energy demand from air conditioning systems is expected to triple in the next thirty years.

Using liquid desiccant regenerators in an air conditioning system can reduce energy consumption as compared with vapor compression-based air conditioning systems. Some types of air conditioning systems utilize at least two air contactors (e.g., air-liquid contactors); however, these systems do not electrochemically regenerate the liquid desiccant. Instead they utilize one of the air contactors to regenerate the liquid desiccant by rejecting moisture to a second air stream. These types of systems necessarily perform all of their liquid desiccant regeneration via the second air contactor. The first air contactor is then dedicated to dehumidifying a first air stream. Described herein are air conditioning systems and processes that reduce both energy consumption and overall system costs while increasing system operating ranges by electrochemically regenerating a liquid desiccant in combination with two or more air contactors.

<CIT> concerns air flows across an air-liquid interface such that liquid desiccant flowing through the interface absorbs water from the air and is thereby diluted to form an output stream. The output stream is circulated through an electrodialytic stack having a central ionic exchange membrane and first and second outer ionic exchange membranes. A redox shuttle loop circulates around the first and second outer ionic exchange membranes. A voltage is applied across the electrodialytic stack, which regenerates the liquid desiccant.

The present invention is directed to a system according to claim <NUM>.

In another embodiment, a system is provided according to claim <NUM>.

A further embodiment is directed to a method according to claim <NUM>.

The above summary is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The figures and the detailed description below more particularly exemplify illustrative embodiments.

The discussion below refers to the following figures, wherein the same reference number may be used to identify the similar/same component in multiple figures. However, the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

The present invention relates to electrochemically regenerated liquid desiccant dehumidification systems. A liquid desiccant system may be used in, among other things, heating, ventilation, and air-conditioning (HVAC). As set forth above, air conditioning is an energy intensive process and is responsible for nearly <NUM>% of U. electricity consumption, with dehumidification accounting for more than half of the energy load in humid regions. The systems described herein provide an efficient, thermodynamic approach to dehumidification for air conditioning including a redox-assisted electrodialysis liquid desiccant regenerator in combination with two or more air contactors.

The systems each utilize two, or more air contactors in conjunction with an electrochemical regenerator in order to perform dehumidification and/or cooling using liquid desiccants. This combination leverages an electrochemical system which does not require contact with air, or heat input, to regenerate liquid desiccants. The electrochemical regeneration system feeds a first air contactor that dehumidifies a first air stream and at least partially feeds at least a second air contactor that also regenerates liquid desiccants. This allows for control over the amount of regeneration taking place in the second air contactor in a range from fully regenerating liquid desiccants to performing no regeneration in the second air contactor, which means that the size and/or cost of the second air contactor can be reduced. The dual modes of regeneration (i.e., electrochemical regenerator and at least one air contactor) make the systems more robust to a variety of operating conditions (e.g., ranges of environmental humidity and temperatures).

Each of the disclosed systems include an electrochemical regeneration system that utilizes a redox-assisted electrodialysis process that enables a membrane-based liquid desiccant air conditioning system. In this redox-assisted electrodialysis (ED) process, an aqueous solution of a redox-active species is circulated between the anode and cathode of an electrochemical stack to concentrate ionic solutions, eliminating thermodynamic phase changes driven by the heat or pressure necessary for vapor compression (VC) or desiccant based air conditioning. Liquid desiccants (e.g., aqueous solutions of salts such as lithium chloride) will absorb moisture from air across a membrane interface. Diluted liquid desiccants will be efficiently re-concentrated, avoiding the latent heat input required to evaporate water. It is estimated that the enhanced efficiency of this cycle leads to <NUM> quads of energy savings yearly by <NUM>.

In <FIG>, a diagram illustrates a dehumidification system <NUM> utilizing an electrochemical regeneration system <NUM> in conjunction with a single air contactor <NUM>. The regeneration system outputs a concentrated solution of liquid desiccant (e.g., an aqueous salt solution) to an air contactor <NUM> (e.g., a liquid to air mass and energy exchanger, which may, or may not, include a membrane). Air is flowed over the concentrated solution of liquid desiccant either directly or via a membrane where water from the air stream is absorbed by the liquid desiccant stream. The air stream may be outside air, return air or exhaust air from an enclosed space (e.g., building) that the system <NUM> is used to supply, or a combination of two or more of outside, exhaust, and return air. After absorbing the water from the air, the liquid desiccant stream is diluted and output from the air contactor <NUM>. The diluted liquid desiccant stream is then cycled back to the electrochemical regeneration system <NUM> for regeneration (i.e., increased concentration of liquid desiccant).

In addition, a dehumidified air stream <NUM> (e.g., having a lower relative humidity than air stream <NUM>) is output from the air contactor <NUM>. A heat transfer system <NUM> can be used to remove sensible heat from the air to supply a conditioned air stream <NUM> to the enclosed space (i.e., building).

In systems with a single air contactor, there is a single solution stream between the electrochemical regeneration system and the air contactor. The concentrated liquid desiccant solution enters the air contactor at the highest needed concentration and leaves at some lower concentration of liquid desiccant. In these systems, a high flow rate of solution has a low concentration change across the air contactor and requires more energy to concentrate the solution. However, there may be less need for integration with heat rejection. Alternatively, low flow rates of the solution provide an increased, or maximum, concentration change across the air contactor and use less energy to concentrate the solution. However, additional temperature control for the air contactor may be needed. These operating conditions are better understood with a more detailed description of the electrochemical regeneration system.

<FIG> illustrates a diagram of an electrodialytic liquid desiccant air conditioning (ELDAC) system <NUM> as described above in accordance with certain embodiments. The system <NUM> includes a desiccant section <NUM> and a cooling section <NUM>. In the desiccant section <NUM>, outdoor air <NUM> (and/or recirculated air) is forced across an air contactor <NUM> such as an air-liquid interface or liquid-carrying membrane dryer. In certain embodiments, the air <NUM> may be outside air of high temperature and high relative humidity (RH). Water <NUM> from the air <NUM> is absorbed at the air contactor <NUM> into a concentrated liquid desiccant <NUM>, e.g., an aqueous salt solution, is then passed through a redox-assisted electrochemical regenerator <NUM> to separate dilute stream <NUM> (e.g., discharge water) and re-concentrate the desiccant stream <NUM>. Example salts that may be used for the desiccant include, for example, LiCl, NaCl, LiBr, and CaCl<NUM>.

The humidity is reduced in the air <NUM> leaving the desiccant section <NUM>, wherein it is cooled by the cooling section <NUM>. This cooling section <NUM> may include an evaporator <NUM> and other components not shown (e.g., condenser, compressor). Because the air <NUM> entering the cooling section <NUM> has lower relative humidity compared to the outside/recirculated air <NUM>, the evaporator <NUM> is more efficient and can reduce the temperature of the cooled air <NUM> by a greater amount than if the evaporator <NUM> had to also condense moisture from the incoming air <NUM>. Experimental results measuring the energy used by redox-assisted electrodialysis to concentrate ionic aqueous solutions show that ELDAC system <NUM> can have a regeneration specific heat input (RSHI) less than <NUM> kBTU/lb, which is up to <NUM> times lower than currently used thermal regeneration methods.

As seen in the detail view <NUM> of <FIG>, redox-assisted regenerator <NUM> has two outer ion exchange membranes <NUM> that separate the outer redox channels <NUM> from the inner concentrate <NUM> and dilute <NUM> streams. In this example the outer ion exchange membranes <NUM> are configured as anion exchange membranes (AEM). The concentrate <NUM> and dilute <NUM> streams are separated by a central ion exchange membrane <NUM>, which in this example is a cation exchange membrane (CEM). In other configurations, the central ion exchange membrane <NUM> may be an AEM and the outer membranes <NUM> may be CEMs. An efficient membrane pair of one CEM and one AEM in the redox-assisted regenerator <NUM> has a Coulombic efficiency above <NUM>%.

The four (or more) chambered desalination cell may use either one redox-active species that is circulated around the anode and cathode, where it undergoes faradaic reactions at both electrodes, or two redox-active species that are each confined to the anode or cathode respectively. An external voltage <NUM> induces oxidation or reduction in redox-active shuttle molecules, driving ion movement across the membranes <NUM>, <NUM> without splitting water or producing other gaseous byproducts (e.g. chlorine) and creating two streams: re-concentrated desiccant <NUM> and discharge water <NUM>. The percentages of salt concentrations shown in <FIG> are examples only - both inlets do not need to have the same concentration and the output concentrations may have a range of differences in concentrations. This goal can be achieved over multiple stages. One proposed redox shuttle is a positively charged ferrocene derivative such as (bis(trimethylammoniopropyl)ferrocene/bis(trimethylammoniopropyl) ferrocenium, [BTMAP-Fc]<NUM>+/[BTMAP-Fc]<NUM>+) <NUM>, which is non-toxic, highly stable, has very rapid electrochemical kinetics and negligible membrane permeability. Other redox shuttle solutions may include ferrocyanide/ferricyanide ([Fe(CN)<NUM>]<NUM>-/[Fe(CN)<NUM>]<NUM>-) or a negatively charged ferrocene derivative. The moving parts of the system may include low pressure pumps for liquid circulation and fans for air circulation. Additional details of this type of four-channel, electrodialytic, stack with redox shuttle assist can be found in commonly-owned <CIT>, which is hereby incorporated by reference in its entirety.

Embodiments described herein utilize an electrochemical regenerator, as described above, in connection with two, or more, air contactors. Unlike the systems described above, which utilize a single air contactor and require a drain for discharge water, the systems with two, or more, air contactors do not require a drain. In the systems described further below, an electrochemical regenerator reconcentrates one or more liquid desiccants, which are supplied to at least one air contactor that dehumidifies air and to at least one air contactor that humidifies air. The at least one humidifying air contactor is at least partially fed from the desalinate stream of the electrochemical regenerator.

The systems described herein provide efficiencies over both thermally regenerated liquid desiccant dehumidifying systems as well as electrochemically regenerated liquid desiccant dehumidifying systems utilizing a single air contactor. For example, embodiments described herein reduce energy consumption. In thermally regenerated systems, regeneration is carried out solely through evaporation of water, a process that requires more energy than utilizing a two-step, combination electrochemical-evaporative regeneration method. In electrochemical systems with a single air contactor, the desalinate stream must be reduced to desiccant concentrations that are considered safe to discharge. However, the amount of energy required for desalination is proportional to the level of desalination such that further desalination requires increasing amounts of energy. In contrast, the multiple air contactor systems described herein need only electrochemically regenerate the diluted desiccant solution to a level that can be further regenerated by available air streams. For many climates and conditions, this desiccant concentration level is higher than that required of discharge streams, reducing energy consumption by the system.

The systems described herein further reduce system costs and complication. In single air contactor electrochemical systems, the desalination concentration level is proportional to the size of the electrochemical membrane; however, electrochemical membranes are significantly more expensive than air contactor materials. Since the described systems do not need to reduce the desalination concentration level as much as in single air contactor electrochemical systems, smaller electrochemical membranes may be utilized, thereby reducing material costs. There are also operating costs related to discharging the desiccant/water of a single air contactor electrochemical system since those systems cannot fully remove desiccant and require that at least some portion be discharged from the system. The systems described herein utilize at least a second air contactor to further regenerate the diluted desiccant solution, which eliminates the need to discharge water/desiccant. By removing the need to discharge water with trace desiccants, the systems described herein eliminate the need for a drain. This makes the system installation more flexible and efficient. Various systems utilizing an electrochemical regeneration system in combination with two or more air contactors are further described below.

<FIG> illustrates a dehumidification system <NUM> utilizing an electrochemical regeneration system <NUM> in conjunction with two air contactors <NUM>, <NUM>. The regeneration system <NUM> operates as described above in connection with <FIG> and <FIG>, unless otherwise described. The electrochemical regeneration system <NUM> outputs a concentrated solution of liquid desiccant (e.g., an aqueous salt solution) <NUM> to a first air contactor <NUM> (e.g., a liquid to air mass and energy exchanger, including a membrane energy exchanger), which in certain embodiments is a dehumidifying air contactor. The concentrated solution of liquid desiccant may have a range of concentrations, depending upon the system design, from about <NUM>-<NUM> %. Air <NUM> is flowed over the concentrated solution of liquid desiccant either directly or via a membrane where water from the air stream is absorbed by the liquid desiccant stream. The air stream <NUM> may be outside (e.g., ambient) air, return air from an enclosed space (e.g., building) that the system <NUM> is used to supply, exhaust air from the building, or a combination of these, and the air stream <NUM> has a first water concentration. The water concentration of an air stream, as used to herein, refers to the absolute humidity of the air. After absorbing the water from the air <NUM>, the liquid desiccant stream is diluted and the diluted solution stream <NUM> is output from the first air contactor <NUM>. The diluted liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for regeneration (i.e., increased concentration of liquid desiccant).

The first air contactor <NUM> also outputs a dehumidified air stream <NUM> (e.g., having a lower relative humidity/lower water concentration than air stream <NUM>). A heat transfer system <NUM> removes sensible heat from the air to supply a conditioned air stream <NUM> to an enclosed space (i.e., building). In other embodiments, sensible heat is removed earlier in the system for improved thermodynamic efficiencies. Sensible heat refers to the amount of energy needed to increase, or in this case decrease, the temperature of the air stream <NUM> independent of phase changes. The heat transfer system <NUM> may include any type of known heat exchange system such as vapor compression, indirect evaporative cooling, chilled water or glycol, and/or heat pipes.

To keep the system supplied with the concentrated stream of liquid desiccant solution <NUM>, the electrochemical regeneration system <NUM> regenerates the diluted liquid desiccant stream <NUM> received from the first air contactor <NUM>. As described above, the regeneration system <NUM> outputs the concentrated stream <NUM> as well as a second, less concentrated stream <NUM>. Output stream <NUM> has a concentration of liquid desiccant lower than that of stream <NUM>, and in certain embodiments, output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %. This second, less concentrated output stream <NUM> is fed, directly or indirectly, to a second air contactor <NUM>, which in certain embodiments is a humidifying air contactor. Similar to air contactor <NUM>, air contactor <NUM> may be a liquid to air mass and energy exchanger, including a membrane energy exchanger.

Air <NUM> is flowed over the concentrated output stream <NUM> from the regeneration system <NUM>, either directly or via a membrane, where water from the output stream <NUM> is absorbed by the air stream <NUM>. The air stream <NUM> is outside air from the environment, or exhaust air as discussed further below, and received from outside of the dehumidification system <NUM> components. The resulting humidified air is output from the second air contactor <NUM> as an output, humidified air stream <NUM> that is returned to the environment external to the components of the dehumidification system <NUM>. The resulting concentrated liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for further regeneration. The second air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of stream <NUM>, and in certain embodiments, second air contactor output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %.

<FIG> is a block diagram to illustrate the flows of liquid desiccant solutions and multiple air streams through the dehumidification system <NUM>. While each of these flows may occur simultaneously, the timing of various portions the system may also be individually controlled. For example, the air contactors <NUM>, <NUM> and/or electrochemical regeneration system <NUM> may be operated simultaneously, or in various combinations. The system may include storage containers, with or without bypass valves, at various positions throughout the system to store/contain diluted and/or regenerated solutions of liquid desiccant to take advantage of energy savings (e. g,, to operate energy intensive portions of the system during off-peak or less expensive times).

Embodiments consistent with <FIG> utilize external air to regenerate the liquid desiccant in the second air contactor <NUM>. Therefore, the second air contactor may be limited to operating in environments where the outside air can accept humidity (e.g., drier climates). It may also be difficult to control the driving pressure in these embodiments. Additional systems utilizing an electrochemical regeneration system in combination with two or more air contactors are described below.

<FIG> illustrates a dehumidification system <NUM> utilizing an electrochemical regeneration system <NUM> in conjunction with two air contactors <NUM>, <NUM>. The regeneration system <NUM> operates as described above in connection with <FIG> and <FIG>, unless otherwise described. The electrochemical regeneration system <NUM> outputs a concentrated solution of liquid desiccant (e.g., an aqueous salt solution) <NUM> to a first air contactor <NUM> (e.g., a liquid to air mass and energy exchanger, including a membrane energy exchanger), which in certain embodiments is a dehumidifying air contactor. The concentrated solution of liquid desiccant may have a range of concentrations, depending upon the system design, from about <NUM>-<NUM> %. Air <NUM> is flowed over the concentrated solution of liquid desiccant either directly or via a membrane where water from the air stream is absorbed by the liquid desiccant stream. The air stream <NUM> may be outside air, return air from an enclosed space (e.g., building) that the system <NUM> is used to supply, exhaust air from the building, or a combination of these. After absorbing the water from the air <NUM>, the liquid desiccant stream is diluted and the diluted solution stream <NUM> is output from the first air contactor <NUM>. The diluted liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for regeneration (i.e., increased concentration of liquid desiccant).

Air <NUM> is flowed over the concentrated output stream <NUM> from the regeneration system <NUM>, either directly or via a membrane, where water from the output stream <NUM> is absorbed by the air stream <NUM>. The air stream <NUM> is outside air from the environment, or exhaust air from the building as discussed further below and received from outside of the dehumidification system <NUM> components. The resulting humidified air is heated, as discussed further below, and output from the second air contactor <NUM> as an output, heated, humidified air stream <NUM> that is returned to the environment external to the components of the dehumidification system <NUM>. The resulting concentrated liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for further regeneration. The second air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of stream <NUM>, and in certain embodiments, second air contactor output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %.

The first air contactor <NUM> also outputs a dehumidified air stream <NUM> (e.g., having a lower relative humidity than air stream <NUM>). A heat transfer system <NUM> removes sensible heat from the air to supply a conditioned air stream <NUM> to an enclosed space (i.e., building). The heat transfer system <NUM> may be a vapor evaporator to remove sensible heat from the dehumidified air stream <NUM>. The heat transfer system <NUM> is coupled to the second air contactor <NUM> by a condenser or a hot gas loop <NUM>. Therefore, the sensible heat removed from the dehumidified air stream <NUM> is transferred to the second air contactor <NUM> to heat the humidified air stream <NUM>. The sensible heat transfer may be performed inside the mass and energy exchanger/second air contactor <NUM> so that the heat transfer and mass exchange occur approximately simultaneously, using a heat exchanger to pre-heat concentrated desiccant output stream <NUM>, using a heat exchanger to pre-heat air stream <NUM>, or a combination of any two or more of these techniques.

<FIG> is a block diagram to illustrate the flows of liquid desiccant solutions, multiple air streams, and heat through the dehumidification system <NUM>. While each of these flows may occur simultaneously, the timing of various portions the system may also be individually controlled. For example, the air contactors <NUM>, <NUM> and/or electrochemical regeneration system <NUM> may be operated simultaneously, or in various combinations. The system may include storage containers, with or without bypass valves, at various positions throughout the system to store/contain diluted and/or regenerated solutions of liquid desiccant to take advantage of energy savings (e. g,, to operate energy intensive portions of the system during off-peak or less expensive times).

Embodiments consistent with <FIG> utilize external air to regenerate the liquid desiccant in the second air contactor <NUM> along with a condenser. By raising the temperature of the outside air in the second air contactor <NUM>, the humidity capacity of the outside air is also increased. The increased capacity allows for humidity rejection at a wider range of relative humidity levels. The increased heat also leads to evaporation, which helps cool the condenser (i.e., reject heat) without incurring additional operating costs. Additional systems utilizing an electrochemical regeneration system in combination with two or more air contactors are described below.

Air <NUM> is flowed over the concentrated output stream <NUM> from the regeneration system <NUM>, either directly or via a membrane, where water from the output stream <NUM> is absorbed by the air stream <NUM>. The air stream <NUM> is outside air from the environment and received from outside of the dehumidification system <NUM> components. The resulting humidified air is heated, as discussed further below, and output from the second air contactor <NUM> as an output, heated, humidified air stream <NUM> that is returned to the environment external to the components of the dehumidification system <NUM>. The resulting concentrated liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for further regeneration. The second air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of stream <NUM>, and in certain embodiments, second air contactor output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %.

The first air contactor <NUM> also outputs a dehumidified air stream <NUM> (e.g., having a lower relative humidity than air stream <NUM>) that is also cooled. A heat transfer system <NUM> is fully coupled to both the first air contactor <NUM> and the second air contactor <NUM>. The heat transfer system <NUM> may be a vapor condenser coupled to the first air contactor <NUM> to remove sensible heat from the first air contactor <NUM> through an evaporation loop <NUM>. The heat transfer system <NUM> is also coupled to the second air contactor <NUM> by a condenser or a hot gas loop <NUM>. Therefore, the sensible heat removed from the first air contactor <NUM> is transferred to the second air contactor <NUM> to heat the humidified air stream <NUM>. By removing the sensible and latent heat in the first air contactor <NUM>, a conditioned, and cooled, air stream <NUM> is supplied to an enclosed space (i.e., building). The heat transfer may be performed using any one, or combination, of the techniques described above in connection with <FIG>.

Similar to embodiments consistent with <FIG>, embodiments consistent with <FIG> utilize external air to regenerate the liquid desiccant in the second air contactor <NUM> along with a vapor condenser. By raising the temperature of the outside air in the second air contactor <NUM>, the humidity capacity of the outside air is also increased. The increased capacity allows for humidity rejection at a wider range of relative humidity levels. Coupling the heat transfer system <NUM> to both air contactors <NUM>, <NUM> eliminates the need for other condensers and/or evaporators. The coupling also addresses the temperature of the final concentration stage to increase, or maximize, the efficiency of both the heat transfer system <NUM> and the electrochemical regeneration system <NUM>. Additional systems utilizing an electrochemical regeneration system in combination with two or more air contactors are described below.

<FIG> illustrates a dehumidification system <NUM> utilizing an electrochemical regeneration system <NUM> in conjunction with two air contactors <NUM>, <NUM>. The regeneration system <NUM> operates as described above in connection with <FIG> and <FIG>, unless otherwise described. The electrochemical regeneration system <NUM> outputs a concentrated solution of liquid desiccant (e.g., an aqueous salt solution) <NUM> to a first air contactor <NUM> (e.g., a liquid to air mass and energy exchanger, including a membrane energy exchanger), which in certain embodiments is a dehumidifying air contactor. The concentrated solution of liquid desiccant may have a range of concentrations, depending upon the system design, from about <NUM>-<NUM> %. Air <NUM> is flowed over the concentrated solution of liquid desiccant either directly or via a membrane where water from the air stream is absorbed by the liquid desiccant stream. The air stream <NUM> may be outside air, return air from an enclosed space (e.g., building) that the system <NUM> is used to supply, or a combination of outside and return air. After absorbing the water from the air <NUM>, the liquid desiccant stream is diluted and the diluted solution stream <NUM> is output from the first air contactor <NUM>. The diluted liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for regeneration (i.e., increased concentration of liquid desiccant).

To keep the system supplied with the concentrated stream of liquid desiccant solution <NUM>, the electrochemical regeneration system <NUM> regenerates the diluted liquid desiccant stream <NUM> received from the first air contactor <NUM>. As described above, the regeneration system <NUM> outputs the concentrated stream <NUM> as well as a second, less concentrated stream <NUM>. Output stream <NUM> has a concentration of liquid desiccant lower than that of stream <NUM>, and in certain embodiment, output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %. This second, less concentrated output stream <NUM> is fed, directly or indirectly, to a second air contactor <NUM>, which in certain embodiments is a humidifying air contactor. Similar to air contactor <NUM>, air contactor <NUM> may be a liquid to air mass and energy exchanger, including a membrane energy exchanger.

Air <NUM> is flowed over the concentrated output stream <NUM> from the regeneration system <NUM>, either directly or via a membrane, where water from the output stream <NUM> is absorbed by the air stream <NUM>. The air stream <NUM> is exhaust air, which is air exhausted from the building. Because the exhaust air has been previously treated by the dehumidification system <NUM> to be at comfortable conditions, the exhaust air <NUM> likely has a lower humidity than outdoor air so it has a greater capacity to absorb water from the liquid desiccant. The resulting humidified air has increased latent heat and is output from the second air contactor <NUM> as an output, heated, humidified air stream <NUM> that is returned to the environment external to the components of the dehumidification system <NUM>. The resulting concentrated liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for further regeneration. The second air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of stream <NUM>, and in certain embodiments, second air contactor output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %.

The first air contactor <NUM> also outputs a dehumidified air stream <NUM> (e.g., having a lower relative humidity than air stream <NUM>). While not shown, a heat transfer system removes sensible heat from the air to supply a conditioned (e.g., dehumidified and cooled) air stream <NUM> to an enclosed space (i.e., building). The heat transfer system may be a vapor evaporator utilizing outside air in stages to remove sensible heat from the dehumidified air stream <NUM>. In various embodiments, the heat transfer system may involve the condenser only (e.g., as shown in <FIG>), the condenser coupled with the second air contactor <NUM> (e.g., as shown in <FIG>), or the condenser coupled with both the first and second air contactors <NUM>, <NUM> (as shown in <FIG>). The heat transfer may also be performed using any one, or combination, of the techniques described above in connection with <FIG>.

Embodiments consistent with <FIG> utilize exhaust air to regenerate the liquid desiccant in the second air contactor <NUM>. In various embodiments, the contactor <NUM>, or an additional contactor, may be placed remotely from the system <NUM>, e.g., any location in the building where exhaust air is available and desiccant streams <NUM> and <NUM> can be piped from the remote collection location back to the main system <NUM>. This could involve a smaller footprint as compared with the ductwork necessary to deliver exhaust air back to where the majority of the component of system <NUM> are located, and such architecture could be retrofitted with existing buildings. In further embodiments, air contactor <NUM> may be a plurality of air contactors placed at locations throughout a building (and remote from the above-discussed components of system <NUM>) to collect exhaust air energy, all of which may be piped back to the remaining components of system <NUM>.

Further, embodiments consistent with <FIG> utilize exhaust air to regenerate the liquid desiccant in the second air contactor <NUM>. However, exhaust air may be incorporated in any fashion where input air is utilized in any of the embodiments discussed above in connection with <FIG> as well. In addition, exhaust air energy exchange can be introduced to other parts of the system loop or staged with outside air. For example, an energy recovery ventilator (ERV) may be placed in air stream <NUM>, which transfers heat and humidity from incoming outdoor air into the exhaust air in order to pre-treat the incoming air at no energy cost and lower the amount of work required by the system <NUM>. In certain embodiments, sensible and latent heat exchange can be separated for the exhaust air. Additional systems utilizing an electrochemical regeneration system in combination with two or more air contactors are described below.

<FIG> illustrates a dehumidification system <NUM>, similar to that illustrated in <FIG> but that utilizes exhaust air as described in connection with <FIG>. The system <NUM> utilizes an electrochemical regeneration system <NUM> in conjunction with two air contactors <NUM>, <NUM>. The regeneration system <NUM> operates as described above in connection with <FIG> and <FIG>, unless otherwise described. The electrochemical regeneration system <NUM> outputs a concentrated solution of liquid desiccant (e.g., an aqueous salt solution) <NUM> to a first air contactor <NUM> (e.g., a liquid to air mass and energy exchanger, including a membrane energy exchanger), which in certain embodiments is a dehumidifying air contactor. The concentrated solution of liquid desiccant may have a range of concentrations, depending upon the system design, from about <NUM>-<NUM> %. Air <NUM> is flowed over the concentrated solution of liquid desiccant either directly or via a membrane where water from the air stream is absorbed by the liquid desiccant stream. The air stream <NUM> may be outside air, return air from an enclosed space (e.g., building) that the system <NUM> is used to supply, exhaust air from the building, or a combination of these sources. After absorbing the water from the air <NUM>, the liquid desiccant stream is diluted and the diluted solution stream <NUM> is output from the first air contactor <NUM>. The diluted liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for regeneration (i.e., increased concentration of liquid desiccant).

Air <NUM> is flowed over the concentrated output stream <NUM> from the regeneration system <NUM>, either directly or via a membrane, where water from the output stream <NUM> is absorbed by the air stream <NUM>. The air stream <NUM> is exhaust air, which is air exhausted from the dehumidification system <NUM>. Because the exhaust air has been dehumidified and heated by the system, it has an increased capacity to accept humidity from the liquid desiccant. The resulting humidified air has increased latent heat and is output from the second air contactor <NUM> as an output, heated, humidified air stream <NUM> that is returned to the environment external to the components of the dehumidification system <NUM>. The resulting concentrated liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for further regeneration. The second air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of stream <NUM>, and in certain embodiments, second air contactor output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %.

Embodiments consistent with <FIG> utilize exhaust air to regenerate the liquid desiccant in the second air contactor <NUM>. However, exhaust air may be incorporated in any fashion where input air is utilized in any of the embodiments discussed above in connection with <FIG>. In addition, exhaust air energy exchange can be introduced to other parts of the system loop or staged with outside air. For example, an energy recovery ventilator (ERV) may be placed in air stream <NUM>, which transfers heat and humidity from incoming outdoor air into the exhaust air in order to pre-treat the incoming air at no energy cost and lower the amount of work required by the system <NUM>. In certain embodiments, sensible and latent heat exchange can be separated for the exhaust air. Additional systems utilizing an electrochemical regeneration system in combination with two or more air contactors are described below.

<FIG> illustrates a dehumidification system <NUM> utilizing an electrochemical regeneration system <NUM> in conjunction with two air contactors <NUM>, <NUM>. The system <NUM> may be suited for hot, humid operating conditions, such as tropical climates. The regeneration system <NUM> operates as described above in connection with <FIG> and <FIG>, unless otherwise described. The electrochemical regeneration system <NUM> outputs a concentrated solution of liquid desiccant (e.g., an aqueous salt solution) <NUM> to a first air contactor <NUM> (e.g., a liquid to air mass and energy exchanger, including a membrane energy exchanger), which in certain embodiments is a dehumidifying air contactor. The concentrated solution of liquid desiccant may have a range of concentrations, depending upon the system design, from about <NUM>-<NUM> %. Hot, humid air <NUM> is flowed over the concentrated solution of liquid desiccant either directly or via a membrane where water from the air stream is absorbed by the liquid desiccant stream in an amount to over dehumidify the air (e.g., lower the water concentration in the air to a level less than a level used for supplying an enclosure). The air stream <NUM> may be outside air or a combination of outside air with return and/or exhaust air. After absorbing the water from the air <NUM>, the liquid desiccant stream is diluted and the diluted solution stream <NUM> is output from the first air contactor <NUM>. The diluted liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for regeneration (i.e., increased concentration of liquid desiccant).

To keep the system <NUM> supplied with the concentrated stream of liquid desiccant solution <NUM>, the electrochemical regeneration system <NUM> regenerates the diluted liquid desiccant stream <NUM> received from the first air contactor <NUM>. As described above, the regeneration system <NUM> outputs the concentrated stream <NUM> as well as a second, less concentrated stream <NUM>. The electrochemical regeneration system <NUM> includes a water connection for receiving a water input <NUM>. The water stream <NUM> further dilutes the less concentrated stream <NUM> to form a weak liquid desiccant solution. The weak solution <NUM> has a concentration of liquid desiccant lower than that of stream <NUM>, and in certain embodiments, output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %. This second, less concentrated output stream <NUM> is fed, directly or indirectly, to a second air contactor <NUM>, which in certain embodiments is an evaporative and cooling air contactor. Similar to air contactor <NUM>, air contactor <NUM> may be a liquid to air mass and energy exchanger, including a membrane energy exchanger.

The first air contactor <NUM> also outputs an over-dehumidified air stream <NUM> (e.g., having a lower relative humidity than air stream <NUM>). A heat transfer system <NUM> removes sensible heat from the first air contactor <NUM>, from the over dehumidified air stream <NUM>, or both to reject heat to outside air. The over dehumidified air stream <NUM> is flowed over the weak output stream <NUM> from the regeneration system <NUM>, either directly or via a membrane, where water from the output stream <NUM> is absorbed by the air stream <NUM> to evaporatively cool the air stream <NUM>. The cooled, slightly re-humidified, conditioned air stream <NUM> is output to supply an enclosed space (i.e., building).

The second air contactor <NUM> also outputs the resulting concentrated liquid desiccant stream <NUM> and cycles stream <NUM> back to the electrochemical regeneration system <NUM> for further regeneration with output stream <NUM> and the water input <NUM>. The second air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of stream <NUM>, and in certain embodiments, second air contactor output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %.

<FIG> is a block diagram to illustrate the flows of liquid desiccant solutions and an air stream through the dehumidification system <NUM>. While each of these flows may occur simultaneously, the timing of various portions the system may also be individually controlled. For example, the air contactors <NUM>, <NUM> and/or electrochemical regeneration system <NUM> may be operated simultaneously, or in various combinations. The system may include storage containers, with or without bypass valves, at various positions throughout the system to store/contain diluted and/or regenerated solutions of liquid desiccant to take advantage of energy savings (e. g,, to operate energy intensive portions of the system during off-peak or less expensive times).

Embodiments consistent with <FIG> utilize evaporative cooling to produce a conditioned air stream. In certain embodiments, instead of rejecting heat to outside or exhaust air, at least a portion can be used to cool air through further evaporation. Also, any of the integrations discussed above in connection with <FIG> may be incorporated into the embodiments of <FIG>, such as one or more heat transfer systems.

While each of the above-discussed systems involve combinations of an electrochemical regeneration system with two air contactors, it should be understood that each of the systems can be adapted to include three, or more, air contactors. An example of such a system is provided in <FIG>.

<FIG> illustrates a dehumidification system <NUM> utilizing an electrochemical regeneration system <NUM> in conjunction with three air contactors <NUM>, <NUM>, and <NUM>. The regeneration system <NUM> operates as described above in connection with <FIG> and <FIG>, unless otherwise described. The electrochemical regeneration system <NUM> outputs a concentrated solution of liquid desiccant (e.g., an aqueous salt solution) <NUM> to a first air contactor <NUM> (e.g., a liquid to air mass and energy exchanger, including a membrane energy exchanger), which in certain embodiments is a dehumidifying air contactor. The concentrated solution of liquid desiccant may have a range of concentrations, depending upon the system design, from about <NUM>-<NUM> %. Air <NUM> is flowed over the concentrated solution of liquid desiccant either directly or via a membrane where water from the air stream is absorbed by the liquid desiccant stream. The air stream <NUM> may be outside air, return air from an enclosed space (e.g., building) that the system <NUM> is used to supply, exhaust air, or a combination of these. After absorbing the water from the air <NUM>, the liquid desiccant stream is diluted and the diluted solution stream <NUM> is output from the first air contactor <NUM>. The diluted liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for regeneration (i.e., increased concentration of liquid desiccant).

Air <NUM> is flowed over the concentrated output stream <NUM> from the regeneration system <NUM>, either directly or via a membrane, where water from the output stream <NUM> is absorbed by the air stream <NUM>. The air stream <NUM> may be outside air, exhaust air, or a combination thereof. The resulting humidified air has increased latent heat and is output from the second air contactor <NUM> as an output, heated, humidified air stream <NUM> that is returned to the environment external to the components of the dehumidification system <NUM>. The resulting concentrated liquid desiccant stream <NUM> is then cycled back to the electrochemical regeneration system <NUM> for further regeneration. The second air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of stream <NUM>, and in certain embodiments, second air contactor output stream <NUM> has a concentration in a range of about <NUM>-<NUM> %.

The first air contactor <NUM> also outputs a dehumidified air stream <NUM> (e.g., having a lower relative humidity than air stream <NUM>). The dehumidified air stream is input to a third air contactor <NUM>, where the air stream <NUM> is flowed, directly or indirectly via a membrane, over a portion of liquid desiccant stream <NUM> mixed with water <NUM>. Similar to air contactors <NUM>, <NUM> air contactor <NUM> may be a liquid to air mass and energy exchanger, including a membrane energy exchanger. Water from the diluted liquid desiccant stream <NUM> is evaporated and absorbed by the air stream <NUM> thereby consuming heat to evaporatively cool the air stream <NUM>. In other embodiments, sensible heat is removed through indirect evaporative cooling. The resulting cooled, conditioned air stream <NUM> is output to supply an enclosed space (i.e., building). Air contactor <NUM> then outputs a concentrated liquid desiccant stream <NUM> to combine with output stream <NUM>, where the combined stream is cycled back to the electrochemical regeneration system <NUM> for further regeneration. The third air contactor liquid desiccant output stream <NUM> has a concentration of liquid desiccant higher than that of the combined input stream of water and stream <NUM>.

<FIG> is a block diagram to illustrate the flows of liquid desiccant solutions, multiple air streams, and heat through the dehumidification system <NUM>. While each of these flows may occur simultaneously, the timing of various portions the system may also be individually controlled. For example, the air contactors <NUM>, <NUM>, <NUM> and/or electrochemical regeneration system <NUM> may be operated simultaneously, or in various combinations. The system may include storage containers, with or without bypass valves, at various positions throughout the system to store/contain diluted and/or regenerated solutions of liquid desiccant to take advantage of energy savings (e. g,, to operate energy intensive portions of the system during off-peak or less expensive times).

As mentioned, features of the embodiments of <FIG> may be incorporated in the triple air contactor configuration of <FIG> and vice versa. Further embodiments are not limited to three air contactors and may involve any number of air contactors, any number of staging desiccant flows, and/or any number of air flows.

<FIG> each refer to a system comprising various components including at least one electrochemical regeneration system and two or more air contactors. These components may be included in a single housing or in multiple housings. In certain embodiments the components are co-located at one location in or near the enclosed space (e.g., building) that the system serves. However, in other embodiments one or more components may be located remote from the rest of the system components. For example, one or more air contactors may be positioned at one or more locations throughout a building proximate a location where exhaust air is generated, or released, and the output(s) of the remote air contactor(s) is transferred (e.g., via piping) back to where the remaining system components are co-located.

Turning to <FIG>, a method for dehumidifying air using one, or more, of the systems described above is illustrated. A concentrated liquid desiccant stream is circulated through a first air contactor to dehumidify a first air stream and produce a diluted output stream of liquid desiccant <NUM>. The diluted output stream of liquid desiccant is circulated to an electrochemical regeneration system where a concentrated stream of liquid desiccant is produced to be output to the first air contactor, and a regenerator diluted liquid desiccant stream is produced <NUM>. The regenerator diluted liquid desiccant stream is circulated through a second air contactor to humidify a second air stream and produce an air contactor concentrated liquid desiccant stream that is output to the electrochemical regenerator <NUM>. Sensible and/or latent heat is transferred from at least the dehumidified air stream <NUM>. The heat may be transferred outside the system, or it may be recycled to the second air contactor to facilitate regeneration of the liquid desiccant through evaporation.

<FIG> illustrates another method, according to various embodiments, for dehumidifying air using one, or more of the systems described above. A concentrated liquid desiccant stream is circulated through a first air contactor to over-dehumidify a first air stream and produce a diluted output stream of liquid desiccant <NUM>. Sensible and/or latent heat is transferred to outside air from the first air contactor, from the dehumidified air stream, or both <NUM>. The diluted output stream is circulated to an electrochemical regenerator to produce a concentrated liquid desiccant stream that is output to the first air contactor and an output solvent stream having a lower concentration of liquid desiccant combined with water <NUM>. The output solvent stream is circulated through a second air contactor to humidify and evaporatively cool the over-dehumidified air stream <NUM>. The second air contactor produces a conditioned air stream to supply to an enclosed space (e.g., building) and produces a second diluted output stream that has a higher liquid desiccant concentration than the output solvent stream that is output to the electrochemical regenerator <NUM>. As discussed above, various portions of these methods may be performed simultaneously or in series with any combination of overlap among the various steps.

The systems described herein with respect to various embodiments involve an electrochemical regeneration system utilizing a redox-assisted electrodialytic cell in combination with two or more air contactors. These systems reduce energy consumption in electrochemically regenerated dehumidification and air conditioning systems, reduce system costs, increase the options for system operating ranges, and eliminate the loss of desiccant materials in the system. They provide increased efficiency and environmentally responsible options for meeting the expected, increased need for dehumidification and air conditioning systems.

Claim 1:
A dehumidification system (<NUM>), comprising:
an electrochemical liquid desiccant regeneration system (<NUM>) comprising a first output desiccant stream (<NUM>), wherein the first output desiccant stream (<NUM>) has a first concentration of liquid desiccant; and
a first air contactor (<NUM>) coupled to the first output desiccant stream (<NUM>) disposing a first input air stream (<NUM>) having a first water concentration in fluid communication with the first output desiccant stream (<NUM>) to form a first output air stream (<NUM>) having a second water concentration lower than the first water concentration and a diluted desiccant output stream (<NUM>), wherein the diluted desiccant output stream (<NUM>) is circulated back into the electrochemical liquid desiccant regeneration system (<NUM>); the dehumidification system (<NUM>) being characterized by:
the electrochemical liquid desiccant regeneration system (<NUM>) further comprising a second output desiccant stream (<NUM>), wherein the second output desiccant stream (<NUM>) has a second concentration of liquid desiccant smaller than the first concentration; and by comprising,
a second air contactor (<NUM>) coupled to the second output desiccant stream (<NUM>) and disposing a second input air stream (<NUM>) having a third water concentration in fluid communication with the second output desiccant stream (<NUM>) to form a second output air stream (<NUM>) having a fourth water concentration higher than the third water concentration and a concentrated desiccant output stream (<NUM>), wherein the concentrated desiccant output stream (<NUM>) is circulated back into the electrochemical liquid desiccant regeneration system (<NUM>).