Liquid desiccant air conditioning system and control method

Abstract

Described herein are liquid desiccant air conditioning systems and methods for operating them to achieve desired supply air dry-bulb temperature and humidity conditions. In some embodiments, the liquid desiccant air conditioning system may include a cooling unit, an absorber, a regenerator, and a control unit. The control unit may be operatively coupled to the cooling unit, absorber, and regenerator such that the control unit can operate the liquid desiccant system to generate an supply air stream at a relatively independent target temperature and humidity. In some embodiments, the control unit can adjust one or more parameters and / or variables of the components of the liquid desiccant system to generate the supply air stream with high energy efficiency.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 387,017, entitled "Liquid Desiccant Air Conditioning System and Control Methods," filed December 12, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Technical Field

[0002] The present disclosure relates generally to air dehumidification systems that utilize liquid desiccants and methods for controlling the same. Summary of the Invention [Means for solving the problem]

[0003] overview This disclosure describes a highly efficient liquid desiccant air conditioning system that utilizes two moisture removal devices in a cooled air stream: a first device is a heat sink that cools the air and simultaneously condenses water from the air, and a second device is an absorption unit that dehumidifies the air using liquid desiccant. A control system adjusts the heat removed from the air stream in response to sensor-sensed data of the inlet air stream entering the liquid desiccant system or the supply air stream exiting the liquid desiccant system. Dynamic adjustments by the control system allow relatively independent control of the temperature and humidity of the output air, minimizing the overall energy consumption of the liquid desiccant system.

[0004]

[0004] The present disclosure also describes a method for controlling a liquid desiccant air conditioning system, the method including circulating liquid desiccant between an absorption unit and a desorption unit at a liquid desiccant flow rate, and cooling an inlet air stream flowing through the liquid desiccant air conditioning system to form a pre-cooled inlet air stream having pre-cooling temperature and humidity values, regeneration air temperature and flow rate, vapor compression, and other parameters, as described in further detail below. Depending on the temperature and humidity of the inlet air and the pre-cooled inlet air, moisture may be removed from the air stream by condensation, while generating a first moisture removal rate. The cooled inlet air then passes through an absorption unit. The liquid desiccant contacts the pre-cooled inlet air stream and removes water from the pre-cooled inlet air stream to form an inlet air stream having a lower inlet absolute humidity value than the pre-cooled absolute humidity value, while generating a second moisture removal rate and forming a packed liquid desiccant. The method also includes heating a regeneration air stream flowing through the liquid desiccant air conditioning system and flowing a charged liquid desiccant through a desorption unit, where the liquid desiccant contacts the heated regeneration air stream, and the heated regeneration air stream removes water from the charged liquid desiccant to form a regenerated liquid desiccant and a humidified exhaust air stream. One embodiment of the method includes energizing a heat pump to cool the cooled inlet air stream to a cooled temperature value and heat the heated inlet air stream to a heated temperature value. This embodiment includes adjusting the heat pump heat flow value to achieve a predetermined supply air humidity value and temperature by manipulating a pre-cooling air temperature value, a first moisture removal rate, and a second moisture removal rate, where the first moisture removal rate is primarily controlled by the pre-cooling inlet air temperature setpoint, the second moisture removal rate is primarily controlled by the liquid desiccant concentration, and the liquid desiccant concentration is itself determined by the heating temperature value and the heating humidity value.

[0005] The present disclosure also describes a liquid desiccant air conditioning system including a liquid desiccant loop having an absorption unit in fluid communication with a desorption unit and liquid desiccant flowing between the absorption unit and the desorption unit. The system includes an intake air flow path passing through the absorption unit and forming an absorber liquid / air and / or liquid / gas interface within the absorption unit, and a conditioned intake air flow exiting the absorption unit. Sensors are configured to measure the conditioned intake air flow temperature and humidity values. A regeneration air flow path passes through the desorption unit and forms a desorber liquid / air interface within the desorption unit, forming an exhaust air flow exiting the desorption unit. In some embodiments, a heat pump is thermally coupled to the intake air flow path and removes heat and moisture from the intake air flow upstream of the absorption unit by condensation. The heat pump is thermally coupled to the regeneration air flow path and adds heat to the regeneration air flow upstream of the desorption unit. The heat pump has a power supply unit that provides power to the heat pump to cool the intake air flow and heat the regeneration air flow. A controller is operatively connected to the sensors and the power supply unit, and in some embodiments, the controller is configured to adjust operation of the power supply unit based on system parameters including air temperature from the evaporator, air temperature from the condenser, refrigerant temperature after condensation, refrigerant temperature at the evaporator, and / or various valve configurations to achieve a desired supply air temperature and humidity.

[0006] BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The following discussion refers to the following figures, in which the same reference numerals may be used to identify similar / identical components in multiple figures. The figures are not necessarily to scale. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of an exemplary liquid desiccant system according to one embodiment. [Figure 2A]

[0008] FIG. 1 illustrates a psychrometric diagram of an exemplary liquid desiccant system process according to one embodiment. [Figure 2B]

[0009] FIG. 10 is a psychrometric diagram illustrating an operating mode of a liquid desiccant system that prioritizes supply air dew point over supply air dry bulb temperature, according to one embodiment. [Figure 2C] FIG. 9 is a psychrometric diagram illustrating an operating mode of a liquid desiccant system that prioritizes supply air dew point over supply air dry bulb temperature, according to one embodiment. [Figure 3A]

[0010] FIG. 10 is a psychrometric diagram illustrating an operating mode of a liquid desiccant system that prioritizes supply dry bulb temperature over supply air dew point, according to one embodiment. [Figure 3B] FIG. 1 is a psychrometric diagram illustrating an operating mode of a liquid desiccant system that prioritizes supply dry-bulb temperature over supply air dew point, according to one embodiment. [Figure 4]

[0011] 1 illustrates the performance of a liquid desiccant system according to one embodiment. [Figure 5]

[0012] 1 illustrates a method for conditioning an intake air stream using a liquid desiccant system that prioritizes intake dew point over intake dry bulb temperature, according to one embodiment. [Figure 6]

[0013] 1 illustrates a method for conditioning an intake air stream using a liquid desiccant system that prioritizes intake dew point over intake dry bulb temperature, according to one embodiment. [Figure 7]

[0014] 1 illustrates a method for conditioning an intake air stream using a liquid desiccant system that prioritizes supply dry bulb temperature over supply dew point, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Detailed Description

[0015] The present disclosure generally relates to heating, ventilation, and air conditioning (HVAC) systems and control methods thereof. In one exemplary embodiment, a gas-liquid vapor exchanger includes an absorption unit that extracts moisture from air and loads it onto a liquid desiccant, and a desorption unit that regenerates the liquid desiccant that passes through both units. These units can be used to absorb and desorb water vapor into and from the liquid desiccant to dehumidify or humidify the air. This humidification and dehumidification can be used in HVAC heating and cooling applications. Energy consumption is minimized through unit operation control of the liquid desiccant system.

[0009]

[0016] Air conditioning systems can simultaneously perform two functions: the first is dehumidification, and the second is cooling a forced air stream. Commonly used air conditioning systems use vapor compression, which cools incoming air below its dew point temperature, thus dehumidifying it by condensing water. However, given a humid air stream, vapor compression may rely on cooling the air stream below its desired delivery temperature to condense the moisture and achieve a low absolute humidity, and then reheating the air to its desired delivery temperature. This moisture condensation process dramatically increases the energy requirements of air conditioners, especially in humid climates. An alternative dehumidification method, known as liquid desiccant dehumidification, can substantially reduce the energy intensity of air conditioning and is the subject of this disclosure.

[0010]

[0017] Using liquid desiccant to remove moisture from air is an energy-efficient alternative to vapor compression because it minimizes or eliminates the need for excessive cooling and reheating of the air stream, improving the coefficient of performance of the integrated heat pump by increasing the low temperature required from the integrated heat pump, thereby reducing the heat pump's energy consumption. In a liquid desiccant dehumidification system, humid air exchanges water vapor with a liquid desiccant. A gas-liquid vapor exchanger (absorption unit) can be used to contact the humid air with the liquid desiccant and transfer the water vapor in the humid air to the liquid desiccant to form a packed liquid desiccant. This packed liquid desiccant can be regenerated in the gas-liquid vapor exchanger (desorption unit) by heating the packed liquid desiccant to evaporate and / or drive off the water vapor and returning the regenerated liquid desiccant to the absorption unit. Alternatively, the packed liquid desiccant can be regenerated by an electrochemical process (such as electrodialysis) or other process that separates the desiccant into a more dilute and a more concentrated fraction. The rate of desiccant regeneration in the desorber, particularly compared to the rate of moisture collection in the absorber, will change the concentration of the desiccant. The moisture absorption capacity of liquid desiccant is governed by its concentration, with absorption capacity increasing as concentration increases. Operating at higher concentrations allows for higher moisture removal rates from the air stream, but higher concentrations require higher temperatures to regenerate. Increasing the temperature required by the heat pump to regenerate the desiccant reduces the heat pump's coefficient of performance, resulting in higher heat pump energy consumption.

[0011]

[0018] Advanced liquid desiccant systems pre-cool (remove heat from) the inlet air entering the absorption unit and pre-heat (add heat to) the inlet air entering the desorption unit. To reduce the energy consumption of the overall liquid desiccant system, a heat pump may be used to transfer heat from one unit to the other. The liquid desiccant systems and control methods described herein may maximize the energy efficiency of the overall liquid desiccant system for a selected set of system airflow inlet parameters and desired outlet parameters. More specifically, for example, the evaporator temperature, condenser temperature, and desiccant concentration can be considered and selectively manipulated to minimize or optimize energy use for various combinations of air inlet and outlet conditions.

[0012]

[0019] The liquid desiccant air conditioning systems and methods described herein utilize two moisture removal devices in the supply air stream. The first moisture removal device is a heat sink (also referred to herein as a cooling unit) that cools the air below its saturation point and may remove moisture from the air by condensing water. A control system can adjust the temperature of the cooling unit, and thus the temperature and dew point of the pre-cooled air, and the rate of moisture removal and / or condensation (if any) by the unit. The second moisture removal device is a liquid desiccant absorber, which uses a liquid desiccant to transfer water vapor from the cooled air to the desiccant. The control system can adjust the amount and / or quality of heat transferred to the desiccant in the regenerator, thus varying the regeneration rate and desiccant concentration. Varying the desiccant concentration changes the temperature and / or humidity of the supply air.

[0013]

[0020] In one embodiment, the control system can adjust heat flow in response to inlet and / or outlet temperature and / or humidity sensor data for the inlet air stream entering the liquid desiccant system and / or the supply air stream exiting the liquid desiccant system. These adjustments affect the moisture removal rate of the cooling section (by adjusting the temperature of the cooling unit and therefore the amount of water condensed from the air) and the moisture removal rate of the liquid desiccant absorber (by controlling the desiccant concentration via the amount and / or quality of heat transferred to the desiccant in the desorber). These adjustments affect the low and high temperatures required for the system. If these temperature changes result in changes in energy consumption, such as for a heat pump, these dynamic adjustments by the control system can be used to minimize the overall energy consumption of the liquid desiccant air conditioning system.

[0014]

[0021] In some embodiments, a liquid desiccant air conditioning system can be configured to select a maximum operating temperature of the cooling unit (e.g., also referred to as a cooling temperature) that results in a moisture removal rate and desiccant concentration in the absorber that can be desorbed at its lowest condenser temperature, resulting in the lowest compressor lift and highest coefficient of performance (COP) of the refrigeration system.

[0015]

[0022] FIG. 1 is a schematic diagram of air, water, and heat flow within a liquid desiccant system 100 according to one embodiment. The liquid desiccant system 100 includes a cooling unit 101, an absorber 102, a heat regenerator 103 including a desorber 103B configured to remove moisture from a loaded desiccant, and a heating unit 103A that provides heat to the desorber 103B for moisture removal, and a controller 104. The cooling unit 101 is operably coupled to the absorber 102 and the regenerator 103, as shown in FIG. 1, and the absorber 102 is operably coupled to the regenerator 103. In some embodiments, the system 100 may also optionally include one or more sensors S configured to measure various system conditions, including, for example, temperature, humidity, pressure, and / or any other suitable parameters, to assist in the operation and control of the system 100. In such embodiments, the sensors S may be located in any suitable location within the system 100. For example, as shown in FIG. 1 , one or more sensors may be positioned to measure the temperature of air 111 exiting cooling unit 101, one or more sensors may be positioned to measure the temperature and humidity of supply air 112 exiting absorber 102, and one or more sensors may be positioned to measure air 115 exiting regenerator 103 (more specifically desorber 103B), as described in more detail below. In some embodiments, one or more sensors may be positioned to measure one or more parameters of the heating and / or cooling units, such as the temperatures of these units. When these units are operably connected to one another via a heat pump, one or more sensors may be positioned to measure operating parameters of the heat pump, such as discharge pressure (which may also be used to determine the condensing temperature), condensing temperature, suction pressure (which may also be used to determine the evaporating temperature), and / or evaporating temperature.

[0016]

[0023] The liquid desiccant can be any suitable liquid desiccant. In some embodiments, the liquid desiccant can be a halide salt solution, including, for example, sodium chloride (NaCl), potassium chloride (KCl), potassium iodide (KI), lithium chloride (LiCl), copper(II) chloride (CuCl), silver chloride (AgCl), calcium chloride (CaCl), chlorine fluoride (ClF), bromomethane (CHBr), iodoform (ChI), hydrogen chloride (HCl), lithium bromide (LiBr), and / or hydrogen bromide (HBr). In some embodiments, the halide salt solution is selected from LiCl, NaCl, LiBr, and / or CaCl. In some embodiments, the halide salt solution is LiCl. In some embodiments, the solution can be water and can be described as an aqueous solution. The halide salt may be present in the liquid desiccant in a range of about 2% to about 50% by weight, or in a range of about 10% to about 40% by weight, or in a range of about 20% to about 40% by weight.

[0017]

[0024] The controller 104 is operably coupled (e.g., physically and / or wirelessly / remotely) to the cooling unit 101, the absorber 102, the regenerator 103, and the sensor S. The controller 104 may be any suitable controller configured to send signals to and / or receive signals from the cooling unit 101, the absorber 102, the regenerator 103, and the sensor S to monitor and control their operation (e.g., set points). The controller 104 may include a memory (not shown), a processor (not shown), and input / output (I / O) devices (not shown).

[0018]

[0025] The cooling unit 101 may be any suitable heat sink configured to remove heat from air, such as, for example, a refrigerant-to-air coil, a chilled water coil, an indirect evaporative cooler, and / or the like. As described in more detail herein and shown in FIG. 1 , the cooling unit 101 is configured to receive and cool inlet air 110 to a cooling temperature (also referred to as a pre-cooling temperature setpoint) to produce cooled air 111. In some embodiments, the cooling temperature may be equal to and / or lower than the saturation temperature of the inlet air 110 (e.g., the inlet air 110 is cooled to or above the dew point of the inlet air in the absorber 102), thereby condensing moisture and / or water from the inlet air 110 and producing a condensate at a condensate moisture removal rate 131. That is, in some embodiments, the cooling unit 101 can cool and / or pre-cool the inlet air 110, effectively performing a first stage and / or step of dehumidification of the inlet air 110, in which moisture and / or water is removed from the inlet air 110 to produce cooled air 111 and condensate at a condensate moisture removal rate 131. The cooled air 111 can then be further dehumidified in a second stage and / or step of dehumidification in the absorber 102, as described further herein. In some embodiments, the cooling unit 101 includes a cooling coil that is the evaporator of a heat pump. In some embodiments, the liquid desiccant system 100 can include a sensor disposed between the cooling unit 101 and the absorber 102, as shown in FIG. 1 . In some embodiments, the sensor can be configured to measure the refrigeration temperature, the humidity of the cooled air 111, or both. The sensor can then send a signal to the controller 104, which, in response to receiving the signal, adjusts at least one of the cooling temperature, absorber moisture removal rate 132, or desorber moisture rejection rate 103, as further described herein.

[0019]

[0026] The absorber 102 is configured to receive cooled air 111, which may be cooled and partially dehumidified by the cooling unit 101. The absorber 102 may be configured to further dehumidify the cooled air 111 by interfacing (e.g., exposing) the cooled air 111 to a condensed liquid desiccant 121, causing absorption of water vapor from the cooled air 111 into the condensed liquid desiccant 121 and formation of feed air 112, as described in further detail herein. The condensed liquid desiccant 121 may absorb water vapor from the cooled air 111 at an absorber moisture removal rate 132. The absorber 102 defines a liquid / air and / or liquid / gas interface, which may be formed by any vapor / liquid mass transfer unit operation, including, for example, a packed bed, a tray column, a spray column, a bubble column, a membrane, and / or the like. As the condensed liquid desiccant 121 absorbs water vapor from the cooled air 111, the concentration of the liquid desiccant decreases. The liquid desiccant produced in absorber 102 after exposure to cooled air 111 may be referred to as packed liquid desiccant 120. Packed liquid desiccant 120 can be regenerated (by removing moisture and / or water from packed liquid desiccant 120) so that it can be used again in absorber 102 to remove additional water vapor (e.g., moisture) from cooled air 111.

[0020]

[0027] To that end, the regenerator 103 is configured to regenerate the loaded liquid desiccant 120. More specifically, the desorber 103B of the regenerator 103 is configured to receive the loaded liquid desiccant 120 from the absorber 102, remove moisture and / or water from the loaded liquid desiccant 120, generate a regenerated and / or concentrated liquid desiccant 121, and then return the regenerated and / or concentrated liquid desiccant 121 to the absorber 102. The desorber 103B defines a liquid / air and / or liquid / gas interface that may be formed by any vapor / liquid mass transfer unit operation, including, for example, a packed bed, a tray column, a spray column, a bubble column, a membrane, and the like. The desorber 103B may be coupled to the absorber 102 to receive the loaded liquid desiccant 120 and then remove moisture and / or water from the loaded liquid desiccant 120 at a desorber moisture rejection rate 133. In this embodiment, the regenerator 103 includes a heating unit 103A configured to transfer heat to the desorber 103B via the preheated air stream 114 to separate moisture and / or water from the liquid desiccant 120 loaded in the desorber 103B. In some embodiments, the heat and / or heated air may be transferred to the desorber 103B in other ways, e.g., without a heating unit in the regenerator, as described in further detail herein. In some embodiments, the liquid desiccant system 100 may include a sensor disposed between the heating unit 103A and the desorber 103B, as shown in FIG. 1 . In some embodiments, the sensor may measure the temperature of the preheated air stream 114 and send a signal to the controller 104, such that the controller 104 may be configured to adjust at least one of the cooling temperature, the absorber moisture removal rate 132, or the desorber moisture rejection rate 103 in response to receiving the signal, as described further herein.

[0021]

[0028] The heating unit 103A can provide heat from one or more of any suitable sources, including, for example, superheat 118 from the cooling unit 101, as shown in FIG. 1 . Other examples include electric heat, gas-fired heat, hot water, steam, solar heat, geothermal heat, and / or the like. In some embodiments, the heating unit 103A can include a blower and a heating coil. The heating coil can be used to transfer heat to the regeneration air 113 to generate the preheated air stream 114. The controller 104 can be operatively coupled to the heating unit 103B to change and / or modify the amount of air passing through the heating coil to control the temperature of the preheated air stream 114. For example, in some embodiments, the amount of air passing through the heating coil can be controlled by changing the speed of the blower in the heating unit 103A and / or the pressure drop of the air passing through the heating coil. In some embodiments, the heating unit 103A includes a heat pump condenser to transfer heat to the regeneration air 113. In some embodiments, the heat pump can cool the evaporator and heat the condenser. In use, in some embodiments, the heat pump can be capable of operating at a variable flow rate (e.g., adjusting the flow rate of the refrigerant and / or working fluid circulating through the heat pump) to change the amount of heat transferred between the evaporator and the condenser, thereby making the system 100 controllable. For example, in some embodiments, the heat pump can be capable of adjusting the speed of the refrigerant compressor to vary, change, and / or modify the mass flow rate of the refrigerant circulating through the heat pump.

[0022]

[0029] Although not shown, in some embodiments, the regenerator 103 may be an electrochemical regenerator (and thus may not include a heating unit) and may use an electric current to regenerate the loaded liquid desiccant 120 and produce a regenerated and / or concentrated liquid desiccant 121.

[0023]

[0030] Although not shown, in some embodiments, system 100 may include an auxiliary condensing coil configured to receive an external air stream other than the regeneration air stream (113-114) and remove unwanted heat from system 100. For example, in some embodiments, system 100 may include an auxiliary condensing coil configured to receive an external air stream and channel the external air stream through heating unit 103A to remove unwanted heat generated by cooling unit 101. In such embodiments, one or more valves (e.g., one or more valves disposed between the auxiliary condensing coil and the condenser of heating unit 103A) may be included to provide the ability to vary (e.g., with the aid of controller 104) the amount of heat delivered to heating unit 103A relative to the external air stream. In some embodiments, the amount of heat delivered to heating unit 103A can be adjusted by varying the speed of a blower that draws the external air stream through the auxiliary condensing coil. Alternatively, in some embodiments, the amount of heat delivered to heating unit 103 can be adjusted by varying the pressure drop of the external air stream.

[0024]

[0031] During use, inlet air 110 enters cooling unit 101 and is cooled within cooling unit 101 to a predetermined and / or preferred cooling temperature (also referred to as a pre-cooling temperature setpoint). If the dew point of inlet air 110 is higher than the pre-cooling temperature setpoint, moisture and / or water is condensed from inlet air 110 to form (a) a condensate at a condensate moisture removal rate 131 and (b) cooled air 111 (also referred to as pre-cooling air 111). In other words, in some embodiments, cooling unit 101 can receive inlet air 110 and cool (e.g., reduce the enthalpy of inlet air 110) the inlet air 110 to a predetermined and / or preferred cooling temperature (e.g., a temperature below the dew point of inlet air 110), thereby providing a first stage and / or step of dehumidification of inlet air 110 to produce cooled air 111 (with the humidity of the cooled air) that can be further dehumidified within absorber 102, as described further herein. The cooled air 111 can exit the cooling unit 101 and then be directed and / or flowed from the cooling unit 101 to the absorber 102, where the cooled air 111 is introduced into a condensed liquid desiccant 121 flowing within the absorber 102. Exposure of the cooled air 111 to the condensed liquid desiccant 121 causes absorption of water vapor from the air stream 111. As shown in FIG. 1 , absorption of water vapor from the cooled air 111 into the condensed liquid desiccant 121 dehumidifies the cooled air 111, producing supply air 112 at a target supply air temperature and humidity, and a loaded liquid desiccant 120. In some embodiments, absorption of water vapor from the cooled air 111 in the absorber 102 can constitute a second stage and / or step of dehumidification of the inlet air 110 (e.g., after the inlet air 110 flows through the cooling unit 101 and is cooled to a predetermined temperature below the dew point of the inlet air 110). The feed air stream 112 exits the absorber 102 at the feed air humidity and temperature set point. The loaded liquid desiccant 120 (i.e., the liquid desiccant after absorbing water vapor from the cooled air 111 in the absorber 102) is transferred from the absorber 102 to the regenerator 103 (in this case, the regenerator desorber 103B).In some embodiments, the desorber 103b can expose the loaded liquid desiccant 120 to a preheated air stream, such as the preheated air 114 in FIG. 1 . In some embodiments, the preheated air 114 can be generated by flowing the regeneration air 113 through the heating unit 103A. In some embodiments, the heating unit 103A can be configured to heat the regeneration air 113 by transferring heat from heat absorbed in the cooling unit 101, for example, using a heat pump (not shown). The preheated air stream 114 can enter the desorber 103B and contact the loaded liquid desiccant 120 flowing and / or circulating within the desorber 103B, thereby absorbing water from the loaded liquid desiccant 120 and regenerating the loaded liquid desiccant 120 to produce a regenerated and / or concentrated liquid desiccant 121, which can then be used in the absorber 102. The regenerated and / or concentrated liquid desiccant 121 can then be returned from the desorber 103B to the absorber 102. In some embodiments, liquid desiccant system 100 may optionally include an auxiliary condensing coil configured to receive an external air stream (other than regeneration stream 113 or 114) to remove unwanted heat from heating unit 103A. In some embodiments, a user and / or entity may desire to use liquid desiccant system 100 to generate supply air 112 having a predetermined and / or preferred supply air humidity and temperature. Controller 104 may be operatively coupled to cooling unit 101, absorber 102, and regenerator 103 to adjust and / or control one or more parameters of liquid desiccant system 100, such as the flow rate of inlet air flow 110, the cooling temperature within cooling unit 101, the amount of heat transferred and / or directed to desorber 103b, and / or the concentration of liquid desiccant directed to absorber 102, to generate a flow rate of supply air 112 at a predetermined (e.g., target) supply humidity and temperature, as described further herein. In some embodiments, the liquid desiccant system 100 can include a sensor located downstream of the absorber 102, as shown in FIG.The sensor may be configured to measure the supply air temperature and / or supply air humidity and then transmit a signal indicative of and / or associated with the measured supply air temperature and / or supply air humidity to the controller 104. The controller 104 may receive the signal from the sensor and determine a temperature difference between the measured supply air temperature and a target supply air temperature stored in the memory of the controller 104. Similarly, the controller 104 may be configured to determine a humidity difference between the measured supply air humidity and a target supply air humidity stored in the memory of the controller 104. In some embodiments, the controller 104 may be further configured to determine other features and / or characteristics of the supply air, such as, for example, a supply air dry-bulb temperature and / or a supply air dew point, based on the measured supply air temperature and supply air humidity. The controller may store additional target parameters and / or characteristics of the supply air stream target defined by the user. For example, the controller 104 may be configured to store a target supply air dew point and / or a target supply air dry-bulb temperature. In such embodiments, the controller may determine, for example, the difference between the received supply air humidity and the target supply air dew point, or the difference between the supply air dry-bulb temperature and the target supply air dry-bulb temperature. In some embodiments, the controller 104 may be configured to adjust one or more operating conditions of the liquid desiccant system 100 to keep the supply air humidity within 0.10 degrees, 0.20 degrees, 0.25 degrees, 0.50 degrees, 1.0 degrees, 2.0 degrees, 3.0 degrees, or 5.0 degrees of the target supply air dew point. In some embodiments, the controller 104 may be configured to adjust one or more operating conditions of the liquid desiccant system 100 to keep the supply air dry-bulb temperature within 0.10 degrees, 0.20 degrees, 0.25 degrees, 0.50 degrees, 1.0 degrees, 2.0 degrees, 3.0 degrees, or 5.0 degrees of the target supply air dry-bulb temperature.

[0025]

[0032] The condensate moisture rejection rate 131 (discussed in more detail with reference to 231 and with reference to FIG. 2A ) is substantially determined by the flow rate and absolute humidity of the inlet air 110 and the temperature of the cooling coil (not shown) in the cooling unit 101. The absorber moisture rejection rate 132 (discussed in more detail with reference to 232 and with reference to FIG. 2A ) is substantially determined by the flow rate of the cooled air 111 and the concentration of the desiccant stream 121. The absorber moisture rejection rate 132 (discussed in more detail with reference to 232 and with reference to FIG. 2A ) can be determined by moisture data measured by sensors in 111 and 112 (i.e., upstream and downstream of the absorber 102). The desorber moisture rejection rate 133 (discussed in more detail with reference to 233 and with reference to FIG. 2A ) is substantially determined by the flow rate and absolute humidity of the regeneration air 113, the concentration of the desiccant stream 120, and the temperature at which the preheated air stream 114 is delivered. Thus, stable operation of the unit occurs when the moisture absorber rate in absorber 102 equals the desorber moisture rejection rate 133 in regenerator 103. This condition can be achieved by controlling the temperature of cooling unit 101 and the temperature of heating unit 103A. Furthermore, the rate at which the system stabilizes is set by the liquid desiccant concentration, which is set by the moisture accumulation rate in the absorber (e.g., absorber moisture removal rate 132) and the regeneration rate in the desorber (e.g., desorber moisture rejection rate).

[0026]

[0033] In some embodiments, it is desirable to control both the temperature and humidity of the feed air stream 112. This can be achieved by delivering a particular temperature of the air stream 111 and concentration of the liquid desiccant stream 121 to the absorber 102. The concentration of the desiccant stream 121 can be controlled by controlling the desorber moisture rejection rate 133 of the regenerator 103, which can in turn be controlled by controlling one or more of the following parameters: the temperature of the preheated air stream 114, the amount and / or quality of heat input to the desorber 103B (e.g., from the heating unit 103A), the amount of regeneration air 113 delivered to the regenerator 103, and / or the flow rate of the liquid desiccants 120 and 121 flowing between the absorber 102 and the desorber 103B. In some embodiments, for example, in embodiments where the regenerator is an electrochemical regenerator, the regeneration rate of the regenerator can be controlled by the amount of electrical current delivered thereto.

[0027]

[0034] In some embodiments, the volume of desiccant in the system is relatively large, causing the desiccant concentration 121 to change more slowly than the cooling unit 101 can change temperature to impart the desired change to the supply air 112. If the required moisture removal rate of the liquid desiccant system 100 changes abruptly (e.g., if a change is required over a period of time that cannot be achieved by changing the desiccant concentration alone), the control system 104 can increase the condensate moisture removal rate 131 by lowering the cooling temperature and / or pre-cooling temperature setpoint of the cooled air 111 until the liquid desiccant concentration in the condensed liquid desiccant 121 can be increased sufficiently to increase the absorber moisture removal rate 132, as described in more detail with respect to Figures 2A-C.

[0028]

[0035] In some embodiments, a heat pump (not shown) can be used to move the heat stream 118 from the cooling unit 101 to the heating unit 103A. The coefficient of performance of the heat pump, and therefore its energy consumption, increases as the temperature difference between the cooling unit 101 and the heating unit 103A decreases. However, in some cases, it is the condition of the supply air 112 that is desired to be controlled to a target temperature, humidity, or both. Therefore, to accommodate such cases, the energy consumption of the heat pump can potentially be minimized by maximizing the temperature of the cooling unit 101 and minimizing the temperature of the heating unit 103A while simultaneously meeting the target setpoints (target temperature and / or humidity) of the condition of the supply air 112.

[0029]

[0036] 2A-2C show illustrative liquid desiccant system process hygroscopic diagrams according to one embodiment, illustrating how the system can manipulate the condensation moisture removal rate and absorber moisture removal rate to achieve a desired system moisture removal rate. The system can be similar or identical, for example, in function and / or form, to any of the liquid desiccant systems described herein, such as system 100.

[0030]

[0037] Various control protocols may be employed by any of the liquid desiccant control systems described herein. In some cases, for example, the control system may adjust the rate at which the regenerator removes water from the desiccant in the regenerator (e.g., desorber moisture rejection rate), for example, by increasing the quality or quantity of heat entering the desorber to match the water collection rate in the absorber (e.g., absorber moisture removal rate). In some cases, the control system may further adjust the regeneration rate to change the desiccant concentration to achieve a desired temperature and / or humidity of the air in the supply air outlet. In some cases, the control system may adjust the temperature of a cooling coil in a cooling unit and adjust the desiccant concentration to independently control the temperature and humidity of the supply air. In some cases, the control system may adjust the temperature of a cooling coil in a cooling unit without collecting and / or regenerating moisture to cool the supply air. In some cases, the cooling coil temperature and desiccant concentration may be varied to optimize (e.g., minimize energy usage) the supply air to provide a desired humidity (e.g., humidity ratio or absolute humidity) at the supply air outlet.

[0031]

[0038] The regeneration rate (e.g., desorber moisture rejection rate) can be varied in one or more ways, including, for example, for a thermal regeneration system, by adjusting the temperature of the heating coil; adjusting the heat provided to the heating coil; adjusting the amount of heat (e.g., unwanted heat) transferred to the air in the regeneration path relative to the external coil (e.g., by varying the coolant flow to each coil and therefore the amount of unwanted heat available to be removed from the system by a second condensing coil in the external air stream; and / or by varying the air flow across the external coil and therefore the heat available for regeneration by the heating coil); adjusting the air flow rate across the heating unit and / or desorber, adjusting the desiccant flow rate (e.g., adjusting and / or turning on / off as needed). The regeneration rate can be varied in one or more ways, including, for example, in the case of an electrochemical regeneration system, by varying the voltage across the device, the flow paths within the device, and / or the desiccant flow rate to the device.

[0032]

[0039] The evaporator temperature can be varied, for example, by varying the refrigerant flow rate (e.g., by changing the compressor speed, by operating one or more compressors in series), and / or by adjusting the amount of refrigerant sent through the hot gas bypass.

[0033]

[0040] In some embodiments, the control system may be configured to operate in several modes and automatically switch between modes (e.g., based on sensed data and / or user input of set points), including, for example, entering a dehumidification mode when the supply inlet dew point is at a higher dew point than the desired supply outlet; entering a cooling mode when the supply inlet is at a higher dry bulb than the desired supply outlet dry bulb; entering a ventilation mode when the supply air inlet is at a lower dry bulb and dew point than the desired supply air outlet dew point and dry bulb; and / or transitioning between states as the supply inlet air changes so that appropriate delays and deadbands are applied.

[0034]

[0041] In some embodiments, any of the liquid desiccant systems described herein may include two proportional-integral-derivative controllers and control loops, including a loop that monitors the supply air dew point; if it is too high compared to a desired target, the system can reduce the cooling temperature in the cooling unit, and if it is too low compared to the desired target, the system can increase and / or raise the cooling temperature in the cooling unit; and a loop that monitors the actual supply air temperature (e.g., the supply air temperature measured by sensor S) and the supply air target temperature, and therefore determines the appropriate desiccant concentration it controls by determining the amount of water to regenerate in the desorber, e.g., the amount of heat transferred to the desorber; if the actual supply temperature is below the supply target temperature, the system can determine to increase the amount of heat to the regenerator to increase the desiccant concentration, thus increasing the actual supply temperature while the first loop maintains the desired supply air dew point.

[0035]

[0042] 2A-2C illustrate, using a psychrometric chart, how a liquid desiccant air conditioner control system 2000 (including any of the control systems described herein) can condition air to meet target humidity and temperature setpoints. Liquid desiccant system 200 may be structurally and / or functionally similar to liquid desiccant system 100 described above with reference to FIG. 1. For example, liquid desiccant system 200 may include one or more components that are structurally and / or functionally similar to the components of liquid desiccant system 100. Accordingly, further details regarding the components of liquid desiccant system 200 are not provided herein.

[0036]

[0043] As shown in FIG. 2A , in this example, inlet air 210 has a particular temperature and humidity (approximately 85°F dry bulb and approximately 70°F dew point) as shown in the diagram, and the target temperature and dew point 212 for the supply air is set at approximately 75°F dry bulb and approximately 50°F dew point. The inlet air can be cooled and dehumidified (shown in FIG. 2A along line 201) to a cooling and / or pre-cooling temperature 211 by, for example, a cooling unit similar to cooling unit 101 described above with reference to FIG. 1 . Because the dew point of inlet air 210 is above that of pre-cooling temperature 211, water condenses from the air, resulting in a condensate moisture removal rate 231. This is initially indicated by line 201 traversing horizontally to the left as it cools and until the dew point or saturation temperature is reached, at which point additional cooling results in condensation (and dehumidification), as indicated by line 201 traversing downward and left along the saturation curve to 211. Cooling unit 201 produces cooled air 211, which is further dehumidified by liquid desiccant at a concentration with equilibrium vapor pressure 230 in a liquid desiccant absorber similar to absorber 102 described above with reference to FIG. 1. The liquid desiccant absorbs water vapor from cooled air 211, as shown by line 202 in FIG. 2A, resulting in absorber moisture removal rate 232. The result of these two processes is supply air 212 at a target temperature and condition 212 at target dew point 220. Thus, stated another way, the target temperature and dew point of supply air 212 allows inlet air 210 to be selectively cooled and dehumidified to a target enthalpy, and then further dehumidified (and heated) at or near constant enthalpy to reach the target temperature and humidity setpoints for supply air 212.

[0037]

[0044] 2A , in some embodiments, the heat required for regeneration, which is transferred (e.g., by a cooling unit) from inlet air 210 to regeneration air stream 213, preheats the air stream entering the desorber (as shown by the horizontal line connecting 213 and 214). In some embodiments, this preheated air stream 213 is at the same inlet conditions (or at least substantially similar, e.g., coming from the same or similar environment) as inlet air 210 to cooling unit 201. Preheated air 214 is used to heat and thereby regenerate the charged liquid desiccant (as shown by the line connecting 214 and 215 traversing upward and to the left, exiting the desorber at 215 toward constant relative humidity line 230). In some embodiments, the temperature and / or amount of preheated air 214 entering the desorber can be measured with a sensor and used to control the desorber moisture rejection rate 233, i.e., the desorber regeneration rate.

[0038]

[0045] As shown in FIG. 2B, the supply air conditions are changed from FIG. 2A from about 75°F dry bulb and about 50°F dew point (212) to about 73°F dry bulb and about 40°F dew point (212''), for example, by an operator requiring lower humidity air, or by a controller with a temperature setpoint schedule. In one mode of operation, for example, a supply air dew point priority mode, the system prioritizes reaching the target dew point of 40°F (220') by relatively rapidly lowering the temperature of the air leaving the cooling unit from 211 to 211'. As a result, the supply air 212' leaving the absorber is at the target dew point (220'), but the target temperature of the supply air has been lowered to about 67°F dry bulb.

[0039]

[0046] Next, as shown in FIG. 2C , the desiccant concentration can be increased relatively slowly (e.g., in a thermal regeneration system, by increasing the quality and / or quantity of heat entering the desorber via preheated air 214; e.g., by increasing the condenser heat as shown by the line connecting 213 and 214′ and extending further to the right, i.e., from 214 to 214′). The desiccant continues to concentrate as long as the desorber moisture removal rate 233 exceeds the absorber moisture removal rate 232. Thus, the absorber moisture removal rate 232 continues to increase until the system is restored to equilibrium, setting the desorber moisture removal rate 233, and thereby the temperature of the air used for regeneration 214′, to meet the desired supply air condition 212″. As the desiccant concentrates, the additional cooling previously applied can be scaled back, e.g., from 211′ to 211″, to meet the target dew point and temperature in an energy-efficient manner.

[0040]

[0047] 3A and 3B illustrate another operating mode of liquid desiccant system 300, e.g., a mode that prioritizes supply dry-bulb temperature over supply dew point. Liquid desiccant system 300 may be structurally and / or functionally similar to liquid desiccant systems 100 and / or 200 described above. For example, liquid desiccant system 300 may include one or more components that are structurally and / or functionally similar to components of such systems. Accordingly, further details regarding the components of liquid desiccant system 300 are not provided herein. In FIG. 3A, the supply air conditions are changed from about 75°F dry-bulb and about 50°F dew point (212) from FIG. 2A to about 73°F dry-bulb and about 40°F dew point (312″), e.g., by an operator desiring lower humidity air or by a controller with a temperature setpoint schedule. The system prioritizes reaching the target dry bulb temperature of 73°F (312′) by relatively quickly reducing the temperature of the air leaving the cooling unit from 311 to 311′. As a result, the supply air 312′ leaving the absorber is at the target dry bulb temperature point (312′), but the supply air 312′ dew point of the supply air has only decreased to about 45°F, not yet reaching the target dew point 312″.

[0041]

[0048] Next, as shown in FIG. 3B, the desiccant concentration can be increased relatively slowly (e.g., in a thermal regeneration system, by increasing the quality and / or quantity of heat entering the desorber via preheated air stream 114; e.g., by increasing the condenser heat, as shown by the line connecting 313 and 314′ and extending further to the right, i.e., from 314 to 314′). The desiccant continues to concentrate as long as the desorber moisture rejection rate 333 exceeds the absorber moisture rejection rate 332. Thus, the absorber moisture rejection rate 332 continues to increase until the system is restored to equilibrium, setting the desorber moisture rejection rate 333, and thereby the temperature of the air used for regeneration 314′, to meet the desired supply air condition 312″. As the desiccant concentrates, the additional cooling previously applied can be reduced, e.g., from 311′ to 311″, to meet the target dew point and temperature in an energy-efficient manner.

[0042]

[0049] FIG. 4 illustrates the performance of liquid desiccant system 400. Liquid desiccant system 400 may be structurally and / or functionally similar to other liquid desiccant systems, including, for example, liquid desiccant systems 100, 200, and / or 300 described herein. For example, liquid desiccant system 400 may include one or more components that are structurally and / or functionally similar to components of such systems. Accordingly, further details regarding the components of liquid desiccant system 400 are not provided herein. In some embodiments over relatively long periods of time (e.g., multiple days), liquid desiccant system 400 may be able to maintain the supply air temperature and dew point within 1°F of a desired (and / or target) supply air dry-bulb temperature and within 1°F of a desired (and / or target) dew point. FIG. 4 illustrates the performance of liquid desiccant system 400 operating on a continuously operating inlet air stream (e.g., similar to inlet air 110) over an extended period of time. FIG. 4 shows the inlet (i.e., outdoor) air temperature and inlet (i.e., outdoor) air dew point of the inlet air stream. Despite over 10°F fluctuations in both the inlet air stream temperature and dew point, the liquid desiccant system 400 produces an inlet air stream (e.g., similar to the inlet air 112) characterized by a dry-bulb temperature and dew point that remain within 1°F of the desired (e.g., target) conditions. The operating mode of the liquid desiccant system 400 in FIG. 4 represents the conditioning procedure described in FIG. 2, where dew point is prioritized and the control system rapidly changes the evaporator temperature to maintain the dew point while changing the desiccant concentration more slowly. Thus, a relatively more stable dew point of the inlet air stream is demonstrated.

[0043]

[0050] FIG. 5 illustrates a method 500 for conditioning an inlet air stream using a liquid desiccant system 500. The liquid desiccant system 500 may be structurally and / or functionally similar to other liquid desiccant systems, including, for example, liquid desiccant systems 100, 200, 300, and / or 400 described herein. For example, the liquid desiccant system 500 may include one or more components that are structurally and / or functionally similar to components of such systems. Accordingly, further details regarding the components of the liquid desiccant system 500 are not provided herein. In step 501, the method 500 includes receiving an inlet air stream at a cooling unit (e.g., a cooling unit similar and / or identical to the cooling unit 101). In some embodiments, the inlet air stream received at the cooling unit 501 can be characterized by particular temperature and / or humidity conditions. For example, in some embodiments, the inlet air stream 510 can be characterized by a dry-bulb temperature of approximately 85°F and a dew point of approximately 70°F.

[0044]

[0051] In step 502, method 500 includes removing heat from the inlet air stream via a cooling coil of a cooling unit to generate a cooled air stream at a cooling temperature. In some embodiments, the cooling unit can be operably coupled to a control unit (e.g., controller 104) such that the control unit can adjust the amount and / or quality of heat removed from the inlet air stream. In that manner, liquid desiccant system 500 can generate an input air stream (e.g., supply stream 112) at a target supply temperature and humidity. For example, in some cases, the desired temperature and humidity (e.g., desired dew point and / or desired dry-bulb temperature) can be selected by an operator desiring lower and / or higher humidity air, or by a controller with a schedule of temperature setpoints. In some examples, the control unit can vary the amount and / or quality of heat removed from the inlet air stream to adjust the target supply temperature and humidity of the supply air stream, thereby maintaining the target supply temperature within 0.1 degrees, within 0.15 degrees, within 0.2 degrees, within 0.25 degrees, within 0.3 degrees, within 0.5 degrees, within 1.0 degrees, within 1.5 degrees, within 2.0 degrees, or within 5.0 degrees of the desired dew point, including all values ​​and ranges therebetween (temperatures are measured in degrees Fahrenheit). Additionally and / or alternatively, in some examples, the control unit may vary the amount and / or quality of heat removed from the inlet air stream to adjust the target supply temperature and humidity of the supply air stream so that the target supply temperature is maintained within 0.1 degrees, within 0.15 degrees, within 0.2 degrees, within 0.25 degrees, within 0.3 degrees, within 0.5 degrees, within 1.0 degrees, within 1.5 degrees, within 2.0 degrees, or within 5.0 degrees of the desired dry-bulb temperature of the supply air stream, measured in degrees Fahrenheit, including all values ​​and ranges therebetween.

[0045]

[0052] In some embodiments, method 500 may optionally include step 502a (not shown in FIG. 4 ). In optional step 502a, method 500 includes, by a control unit operably coupled to the cooling unit, the absorber, and the regenerator, varying the cooling temperature of the cooled air stream in the cooling unit to adjust the enthalpy change of the supply air stream. In some embodiments, the cooling temperature of the cooled air stream can be varied, for example, by varying (e.g., increasing and / or decreasing) the mass flow rate of the refrigerant circulating through the cooling coil of the cooling unit. Changing the mass flow rate of the refrigerant in the cooling coil of the cooling unit can change the cooling temperature of the cooled air stream. Furthermore, in some embodiments, the mass flow rate of the refrigerant can be varied by changing the speed of a refrigerant compressor.

[0046]

[0053] In step 503, method 500 includes directing the cooled air stream to an absorber (e.g., similar to absorber 102) fluidly coupled to the cooling unit. The absorber may define a liquid / air and / or liquid / gas interface formed by any vapor / liquid mass transfer unit operation, including, for example, a packed bed, a tray column, a spray column, a bubble column, a membrane, and / or the like. In step 504, method 500 further includes exposing the cooled air stream to a liquid desiccant at the liquid / air interface of the absorber, such that the liquid desiccant removes moisture from the cooled air stream at an absorber moisture removal rate to produce a feed stream at a target feed temperature and humidity.

[0047]

[0054] In step 505, method 500 includes directing the liquid desiccant to a regenerator after the liquid desiccant has been exposed to the cooled air stream in the absorber (in step 504), the regenerator including a desorber. In some embodiments, the liquid desiccant is directed to a regenerator after the liquid desiccant has been exposed to the cooled air stream in the absorber for the purpose of removing moisture from the liquid desiccant.

[0048]

[0055] In step 506, method 500 includes removing moisture from the liquid desiccant in a desorber at a desorber moisture rejection rate. In some embodiments, removing moisture from the liquid desiccant in the desorber includes flowing the regeneration stream through a heating unit (e.g., similar to heating unit 103A) to generate a preheated air stream. The preheated air stream can then be directed to the desorber. In the desorber, after the liquid desiccant has been flowed into the absorber (and thus includes moisture removed at the absorber moisture rejection rate), the preheated air stream can be exposed to the liquid desiccant to remove water from the liquid desiccant, thus regenerating the liquid desiccant. In some embodiments, a heating unit can be coupled to the desorber and the cooling unit of liquid desiccant system 500. The heating unit can include a blower and a heating coil. The heating coil can be a condenser of a heat pump configured to transfer heat from the cooling unit (e.g., heat removed into the inlet air stream) to the regeneration stream, thus heating the regeneration stream and generating a preheated stream at the preheated air stream temperature. In some embodiments, the heating unit may be operably coupled to a control unit to adjust and / or vary the amount and quality of heat transferred to the regeneration stream. For example, in some embodiments, the control unit may adjust and / or vary the amount of heat transferred to the regeneration stream by changing the target temperature of the preheated air stream.

[0049]

[0056] In some embodiments, the temperature of the preheated air stream can be adjusted and / or varied with the aid of an optional auxiliary condensing coil operably coupled to the liquid desiccant system 500. In such embodiments, a control unit can be operably coupled to the cooling unit, the absorber, the regenerator, and the auxiliary condensing coil. The control unit can send a signal to the auxiliary condensing coil to cause the auxiliary condensing coil to flow the external air stream through the heating unit to remove a portion of the heat transferred from the cooling unit. In some cases, the portion of the heat removed from the cooling unit can be unwanted and / or unnecessary heat by the desiccant liquid system 500. In some embodiments, the portion of the heat removed by the external air stream can be adjusted by varying the speed of a blower (e.g., a blower coupled to the auxiliary condensing coil) that draws the external air stream through the auxiliary condensing coil. Alternatively and / or optionally, in some embodiments, the portion of the heat removed by the external air stream can be adjusted by (a) varying the pressure drop of the external air stream and / or (b) varying the amount of refrigerant flowing through the auxiliary condensing coil. Finally, in step 507, method 500 includes directing the liquid desiccant back to the absorber after removing moisture in the desorber. By directing the liquid desiccant back to the desorber after removing moisture, exposing the liquid desiccant to a cooled air stream promotes continued removal of moisture.

[0050]

[0057] 6 illustrates a method 600 of operating a liquid desiccant system to generate an intake air stream, such as that shown in and described with respect to FIG. 2. Liquid desiccant system 600 may be structurally and / or functionally similar to other liquid desiccant systems, including, for example, liquid desiccant systems 100, 200, 300, 400, and / or 500 described herein. For example, liquid desiccant system 600 may include one or more components structurally and / or functionally similar to components of such systems. Accordingly, further details regarding the components of liquid desiccant system 600 are not provided herein. In step 601, the method includes receiving, at a control unit operably coupled to the cooling unit, absorber, and desorber of the liquid desiccant system, signals from sensors positioned downstream of the absorber, the signals indicative of the intake air temperature and intake air humidity measured by the sensors. In some embodiments, method 600 enables balancing the amount of moisture absorbed by the liquid desiccant in the absorber and removed from the liquid desiccant in the desorber (the absorber and desorber being similar and / or identical to absorber 102 and desorber 103B described above with reference to FIG. 1). The control unit may be similar and / or identical to controller 104 described above with reference to FIG. 1. For example, the control unit may be operably coupled (e.g., physically and / or wirelessly / remotely) to a cooling unit (e.g., a cooling unit similar to cooling unit 101), an absorber (e.g., an absorber similar to absorber 102), a desorber (e.g., a desorber similar to desorber 103B), and / or a heating unit (e.g., similar to heating unit 103A) of the liquid desiccant system. Optionally, in some embodiments, the control unit may also be operably coupled to an external heating unit. In such embodiments, the external heating unit may be coupled to the liquid desiccant system and configured to remove an amount of excess heat from the system. In some embodiments, the control unit may also be operatively coupled to one or more sensors (eg, similar and / or identical to sensor S with respect to FIG. 1).The control unit may be configured to send and / or receive signals between the cooling unit, absorber, regenerator, and sensors S to monitor and control their operation (e.g., set points). The sensors may be any suitable sensor or set of sensors capable of measuring various system conditions, including, for example, temperature, humidity, pressure, and / or any other suitable parameters, to assist in the operation and control of the liquid desiccant system. In some embodiments, the sensor (or at least one sensor from the set of sensors) may be located downstream of the absorber. In such embodiments, the sensor located downstream of the absorber may be configured to measure one or more characteristics of a feed stream (e.g., similar to feed stream 110) generated by the liquid desiccant system. For example, the sensor may be configured to measure supply air temperature and / or supply air humidity. The sensor may be coupled to the control unit such that the control unit can receive a signal (e.g., one or more signals) indicative of the measured supply air temperature and / or supply air humidity (e.g., can report the measured temperature and humidity to the control unit). In some embodiments, the sensor may measure the supply air temperature and may transmit a signal to the control unit indicating and / or associated with the temperature measured in degrees Celsius and / or degrees Fahrenheit.

[0051]

[0058] In step 602, the method includes determining, with a control unit, a humidity difference between the measured supply humidity and a target supply humidity. In some embodiments, the control unit can receive the measured supply humidity and compare it to a target supply humidity (e.g., desired humidity) selected, for example, by a user of the liquid desiccant system. The target supply humidity can be stored in a memory of the control unit. The control unit can determine a difference (e.g., humidity difference) between the measured supply humidity and the target supply humidity. In some embodiments, the humidity difference determined by the control unit can be used to adjust the operation of one or more components of the liquid desiccant system, as described further herein.

[0052]

[0059] In step 603, the method includes determining, with a control unit, a temperature difference between the measured supply air temperature and a target supply air temperature. In some embodiments, the control unit can receive the measured supply air temperature and compare it to a target supply air temperature (e.g., desired temperature) selected, for example, by a user of the liquid desiccant system. The target supply air temperature can be stored in a memory of the control unit. In some implementations, the target supply air temperature can be a desired supply air dew point (e.g., target dew point). In some embodiments, the target supply air temperature can be a desired dry-bulb temperature (e.g., target dry-bulb temperature). The control unit can determine a difference (e.g., temperature difference) between the measured supply air temperature and the target supply air temperature. In some embodiments, the temperature difference determined by the control unit can be used to adjust the operation of one or more components of the liquid desiccant system, as described further herein.

[0053]

[0060] In step 604, the method involves relatively quickly adjusting the enthalpy change of the supply air in the cooling coil via the control unit and based on the humidity difference, for example, corresponding to the change shown in Figure 2B indicated by the arrow from point 211 to 211', and this corresponds to the change in the supply air until it reaches the target outlet humidity provided, such as that shown as point 212', i.e., 40 in this example. o This results in the target dew point of F being reached more rapidly.

[0054]

[0061] In step 605, the method includes relatively slowly adjusting, via the control unit and based on the dry-bulb temperature difference, at least one of the quantity and quality of heat entering the desorber. This corresponds, for example, to the change shown in FIG. 2C indicated by the arrow from point 214 to point 214', and this corresponds to the change in temperature until the supply air reaches a provided target outlet temperature, such as that indicated as point 212'', i.e., about 73°C in this example. o This results in F being reached relatively slowly.

[0055]

[0062] In step 606, the method further includes adjusting, via the control unit and based on the humidity difference, the enthalpy change of the supply air in the cooling unit relatively slowly, for example, corresponding to the change shown in FIG. 2C indicated by the arrow from point 211′ to 211″, which also corresponds to the change when the system adjusts to a provided target outlet dew point and temperature, such as that shown as point 212″, i.e., about 40°C in this example. o Target dew point of about 73°F o When the target dry bulb temperature of 100°F is reached relatively slowly, the supply air humidity increases to approximately 40°F as shown by points 212' and 212'' and all points in between. o This results in maintaining a target dew point of F.

[0056]

[0063] Figure 7 shows a method 700 of operating a liquid desiccant system to generate an intake air stream, for example, as shown in and described with respect to Figure 3. Steps 701, 702, and 703 of method 700 are identical to steps 601, 602, and 603 of method 600.

[0057]

[0064] In step 704, the method includes relatively quickly adjusting the enthalpy change of the supply air in the cooling coil via the control unit and based on the dry-bulb temperature difference, for example, corresponding to the change shown in FIG. 3B indicated by the arrow from point 311 to 311′, and which occurs when the supply air reaches a provided target outlet dry-bulb temperature, such as that shown as point 312′, i.e., about 73°C in this example. o This results in a rapid attainment of F.

[0058]

[0065] In step 705, the method includes relatively slowly adjusting at least one of the quantity or quality of heat entering the desorber via the control unit and based on the humidity differential, for example, corresponding to the change shown in FIG. 3B indicated by the arrow from point 314 to 314′, and which occurs when the supply air reaches a provided target outlet dew point, such as that shown as point 312″, i.e., 40°C in this example. oThis results in the target dew point of F being reached relatively slowly.

[0059]

[0066] In step 706, the method further includes adjusting, via the control unit and based on the humidity difference, the enthalpy change of the supply air in the cooling unit relatively slowly. This corresponds to the change shown in FIG. 3B, for example, indicated by the arrow from point 311′ to 311″, and this corresponds to the change when the system adjusts to a provided target outlet temperature and dew point, such as that shown as point 312″, i.e., about 73°C in this example. o Dry bulb temperature and 40°F o When the target dew point of 100°F is reached relatively slowly, the inlet air dry bulb rises to approximately 40°C as shown by points 312' and 312'' and all points in between. o This results in maintaining a target dew point of F.

[0060]

[0067] While various embodiments have been described above, it should be understood that they are presented by way of example only, and not limitation. While embodiments have been particularly shown and described, it will be understood that various changes in form and detail may be made. Where the schematic diagrams and / or embodiments described above show particular components disposed in particular orientations or positions, the arrangement of the components may be modified. While various embodiments have been described as having particular features and / or combinations of components, other embodiments are possible having any feature and / or combination of components from any of the above-described embodiments.

[0061]

[0068] As used in this specification and / or any claims contained herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, the term "a member" is intended to mean a single member or a combination of members, "a material" is intended to mean one or more materials, etc.

[0062]

[0069] As used herein, the term "and / or" should be understood to mean "either or both" of the elements so coordinated, i.e., elements present conjunctively in some cases and non-conjunctively in other cases. Multiple elements listed with "and / or" should be construed in the same manner, i.e., "one or more" of the elements so coordinated. Other elements other than the elements specifically identified by the term "and / or" may optionally be present, whether related or unrelated to those specifically identified elements. Thus, as a non-limiting example, a reference to "A and / or B," when used in conjunction with open-ended language such as "comprising" or "including," may refer in one embodiment to A only (optionally including elements other than B), in another embodiment to B only (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), etc.

[0063]

[0070] As used herein, the term "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be construed as inclusive, i.e., the inclusion of at least one of several elements or a list of elements, but also two or more, optionally including additional items not in the list. Only terms clearly indicated to the contrary, such as "only one of" or "exactly one of," or, when used in the claims, "consisting of," shall refer to the inclusion of exactly one element of a list of elements or elements. Generally, as used herein, the term "or" shall only be construed as indicating exclusive alternatives (i.e., "one or the other, but not both") when preceded by terms of exclusivity, such as "either," "one of," "only one of," or "exactly one of." "Consisting essentially of," when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0064]

[0071] As used herein, the phrase "at least one" in reference to a list of one or more elements should be understood to mean at least one element selected from any one or more elements in the list of elements, but not necessarily including at least one of every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition allows for the optional presence of elements other than those specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to those specifically identified elements. Thus, as a non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B," or equivalently, "at least one of A and / or B") refers, in one embodiment, to at least one A, optionally including more than one, with no B present (and optionally including elements other than B); in another embodiment, to at least one B, optionally including more than one, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one A, optionally including more than one, and at least one B (and optionally including other elements), optionally including more than one; and so forth.

[0065]

[0072] As used herein, the terms "about," "approximately," and / or "substantially," when used in connection with a stated value and / or geometric structure or relationship, are intended to convey that the value or characteristic so defined is nominally the stated value or characteristic. In some cases, the terms "about," "approximately," and / or "substantially" may generally mean and / or generally contemplate the stated value or characteristic within a desired tolerance (e.g., plus or minus 10% of the stated value or characteristic). For example, a value of about 0.01 can include 0.009-0.011, a value of about 0.5 can include 0.45-0.55, a value of about 10 can include 9-11, and a value of about 1000 can include 900-1100. Similarly, if a first and second surface are nominally parallel, the first surface can be described as substantially parallel to the second surface. It is understood that while the stated values, structures, and / or relationships may be desirable, some variations may occur, for example, as a result of manufacturing tolerances or other practical considerations (e.g., pressure or force exerted through a portion of a device, conduit, lumen, etc.). Accordingly, the terms "about," "approximately," and / or "substantially" may be used herein to account for such tolerances and / or considerations.

[0066]

[0073] As used herein, the term "humidity," when used to describe the condition of air or an airstream, can refer to any conventional description of the water content of that air, including but not limited to relative humidity, humidity ratio expressed as a ratio, humidity ratio expressed as grains per pound, or dew point.

Claims

1. 1. A system comprising: a cooling unit configured to receive an inlet air stream and remove heat from the inlet air stream to generate a cooled air stream at a cooling temperature; an absorber fluidly coupled to the cooling unit, the absorber defining a liquid / air interface configured to expose the cooled air stream to the liquid desiccant such that the liquid desiccant removes moisture from the cooled air stream at an absorber moisture removal rate to produce a supply air stream at a supply temperature and a supply humidity; a regenerator coupled to the absorber and the cooling unit, the regenerator including a desorber configured to receive the liquid desiccant after it has been exposed to the cooled air stream, remove moisture from the liquid desiccant at a desorber moisture rejection rate, and then return the liquid desiccant to the absorber; a control unit operably coupled to the cooling unit, the absorber, and the regenerator, the control unit configured to adjust at least one of the cooling temperature, the absorber moisture removal rate, or the desorber moisture rejection rate to produce the feed air stream at a target temperature and a target humidity; A system comprising:

2. The regenerator further includes a heating unit disposed upstream of the desorber, the heating unit comprising: transferring heat to the regeneration stream to produce a preheated stream; exposing the preheated stream to the liquid desiccant in the desorber to remove moisture from the liquid desiccant at the desorber moisture rejection rate; The system of claim 1 configured to:

3. The system further comprises a heat pump, the heating unit comprising: A blower and a heating coil, the heating being a condenser of the heat pump; a sensor configured to measure a temperature of the preheated stream; The control unit receiving a signal from the sensor indicative of the measured temperature of the preheated stream; adjusting at least one of the cooling temperature, the absorber moisture removal rate, or the desorber moisture rejection rate based on the signal; The system of claim 2 further configured to:

4. the sensor is a first sensor, the signal is a first signal, and the cooling unit A blower and a cooling coil, the cooling being an evaporator of the heat pump; a second sensor configured to measure at least one of the cooling temperature or humidity of the cooled air stream; The control unit receiving a second signal from the second sensor indicative of the measured at least one of the cooling temperature or humidity of the cooled air stream; adjusting at least one of the cooling temperature, the absorber moisture removal rate, or the desorber moisture rejection rate based on the second signal. The system of claim 3 further configured to:

5. The system of claim 4 , wherein the heat pump is configured to transfer heat from the evaporator to the condenser, thereby cooling the evaporator and heating the condenser.

6. The system of claim 5 , wherein the heat pump is configured to operate at a variable flow rate to vary the amount of heat transferred between the evaporator and the condenser.

7. The system of claim 5 , further comprising an auxiliary condensing coil configured to receive an external air stream to remove unwanted heat from the heating unit.

8. The system of claim 7 , further comprising at least one valve operably coupled to the control unit, the at least one valve configured to vary an amount of heat delivered to the heating unit.

9. The system of claim 1 , wherein the regenerator comprises an electrochemical regenerator.

10. 2. The system of claim 1, wherein the control unit is configured to adjust one or more parameters of the cooling unit, the absorber, and the desorber to relatively independently control both the supply air dry bulb temperature and dew point.

11. The system of claim 10 , wherein the control unit is configured to adjust one or more parameters of the cooling unit, the absorber, and the desorber to operate in a supply air dew point preferred mode.

12. The system of claim 10 , wherein the control unit is configured to adjust one or more parameters of the cooling unit, the absorber, and the desorber to operate in a mode that prioritizes the supply dry-bulb temperature.

13. The system of claim 1 , wherein the cooling unit is configured to remove moisture from the inlet air stream at a moisture removal rate.

14. 1. A method comprising: receiving an inlet air stream at a cooling unit; reducing the enthalpy of the inlet air stream via a cooling coil of the refrigeration unit to produce a cooled air stream at a cooled temperature and humidity; directing the cooled air stream to an absorber fluidly coupled to the cooling unit; exposing the cooled air stream to a liquid desiccant at a liquid / air interface of the absorber such that the liquid desiccant removes moisture from the cooled air stream at an absorber moisture removal rate to produce an inlet air stream at a target supply temperature and humidity; directing the liquid desiccant to a regenerator after the liquid desiccant has been exposed to the cooled air stream in the absorber, the regenerator including a desorber; removing moisture from the liquid desiccant in the desorber at a desorber moisture rejection rate; directing the liquid desiccant back to the absorber after removing moisture in the desorber; adjusting, by a control unit operably coupled to the cooling unit, the absorber, and the regenerator, at least one of the enthalpy change of the inlet air stream by the cooling coil, the absorber moisture removal rate, or the desorber moisture rejection rate to produce the feed air stream at the target supply temperature and / or humidity; A method comprising:

15. receiving, at the control unit, signals from the sensors, the signals indicative of supply air temperature and supply air humidity measured by the sensors; determining, with the control unit, a temperature difference between the measured charge air temperature and a target charge air temperature; determining, using the control unit, a humidity difference between the measured supply air humidity and a target supply air humidity; via the control unit and based on at least one of the temperature differential or the humidity differential, (1) adjust at least one of the quantity or quality of heat entering the desorber to change the desorber moisture removal rate, or (2) adjust the enthalpy change performed by the cooling unit to generate the supply air stream at the target supply air temperature and the target supply air humidity.

15. The method of claim 14.

16. to prioritize maintenance of the target supply air humidity or in response to a change in the target supply air humidity, adjusting, via the control unit and based on the humidity difference, a relatively rapid enthalpy change of the supply air within the cooling unit to produce the supply air at the target supply humidity; and relatively slowly adjusting at least one of the quantity or quality of heat entering the desorber via the control unit and based on the temperature difference.

16. The method of claim 15.

17. 17. The method of claim 16, wherein the supply air humidity is maintained within 1.0 degree of a target supply air dew point.

18. 17. The method of claim 16, wherein the supply air humidity is maintained within 0.25 degrees of a target supply air dew point.

19. 18. The method of claim 17, wherein the inlet dryer bulb temperature is maintained within 1 degree of a target inlet dryer bulb temperature.

20. 20. The method of claim 18, wherein the inlet dryer bulb temperature is maintained within 1 degree of a target inlet dryer bulb temperature.

21. In order to prioritize maintenance of the target supply air temperature or in response to a change in the target supply air temperature, adjusting, via the control unit and based on the temperature difference, a relatively rapid enthalpy change of the supply air within the cooling unit to generate the supply air at the target supply air humidity; 16. The method of claim 15, further comprising relatively slowly adjusting at least one of the amount or quality of heat entering the desorber via the control unit and based on the humidity difference.

22. 22. The method of claim 21, wherein the supply dry bulb temperature is maintained within 1.0 degree of a target supply dry bulb temperature.

23. 22. The method of claim 21, wherein the supply dry bulb temperature is maintained within 0.25 degrees of a target supply dry bulb temperature.

24. 23. The method of claim 22, wherein the supply air humidity is maintained within 1.0 degree of a target supply air dew point.

25. 23. The method of claim 22, wherein the supply air humidity is maintained within 1.0 degree of a target supply air dew point.

26. 16. The method of claim 15, wherein the enthalpy change provided by the refrigeration unit results in the cooled air stream being below a dew point temperature of the inlet air stream, and the refrigeration unit removes moisture at a condensate moisture removal rate.

27. 16. The method of claim 15, wherein the enthalpy change produced by the refrigeration unit is varied by varying the mass flow rate of refrigerant in a cooling coil of the refrigeration unit.

28. 28. The method of claim 27, wherein the refrigerant mass flow rate is varied by varying the speed of a refrigerant compressor of the cooling unit.

29. removing moisture from the liquid desiccant in the desorber; flowing the regenerated stream through a heating unit included in the regenerator, the heating unit being coupled to the desorber, the heating unit including a blower and a heating coil to generate a preheated air stream; exposing the preheated air stream to the liquid desiccant at the liquid / air interface of the desorber to remove moisture from the liquid desiccant at the desorber moisture rejection rate; 16. The method of claim 15, comprising:

30. 30. The method of claim 29, wherein the heat transferred to the regeneration stream in the heating unit, and therefore the moisture removal rate of the desorber, is adjusted by changing the target temperature of the preheated air stream.

31. 31. The method of claim 30, wherein the heating unit is operably coupled to the cooling coil by a heat pump to transfer heat from the cooling coil to the heating coil.

32. 32. The method of claim 31, wherein the temperature of the preheated air is adjusted via an auxiliary condensing coil configured to pass an external air stream through the heating unit to remove a portion of the heat transferred from the cooling unit.

33. 33. The method of claim 32, wherein the portion of the heat removed by the external air stream is adjusted by varying the speed of a blower that draws the external air stream through the auxiliary condensing coil.

34. 33. The method of claim 32, wherein the portion of the heat removed by the external air stream is adjusted by varying the pressure drop of the external air stream.

35. 33. The method of claim 32, wherein the portion of the heat removed by the external air stream is adjusted by varying the amount of heat transferred to the auxiliary condensing coil.

36. 36. The method of claim 35, wherein the amount of heat transferred to the auxiliary condensing coil is adjusted by varying the amount of refrigerant flowing through the auxiliary condensing coil.

37. 37. The method of claim 36, wherein the adjustment of heat flow to the external coil is performed by changing the position of a valve.

38. 32. The method of claim 31 , wherein the temperature of the preheated air stream is controlled by varying the volume of air passing through the heating coil.

39. 39. The method of claim 38, wherein the volume of air passing through the heating coil is controlled by varying the speed of a blower of the heating unit.

40. 39. The method of claim 38, wherein the volume of air passing through the heating coil is controlled by varying the pressure drop of the air passing through the heating coil.

41. 16. The method of claim 15, wherein the adjusting includes: (1) adjusting at least one of the quantity or quality of heat entering the desorber to change the desorber moisture removal rate, and (2) adjusting the enthalpy change made by the cooling unit, via the control unit and based on at least one of the temperature difference or the humidity difference, to generate a supply air stream at a target supply air temperature and a target supply air humidity.

42. 42. The method of claim 41, wherein the adjusting includes (1) adjusting the amount and quality of heat entering the desorber to change the desorber moisture removal rate, and (2) adjusting the enthalpy change made by the cooling unit, via the control unit and based on the temperature difference and the humidity difference, to generate the supply air stream at the target supply air temperature and the target supply air humidity.

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