Liquid desiccant air conditioning system and control method

Abstract

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

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

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

[0002] The present disclosure generally relates to air dehumidification systems utilizing liquid desiccant and methods of controlling the same. Summary of the Invention

[0003] This disclosure describes a highly efficient liquid desiccant air conditioning system that utilizes two moisture removal devices in the cooling air stream: a heat sink that simultaneously cools the air and condenses water from it, and an absorber unit that dehumidifies the air using a liquid desiccant. A control system regulates the amount of heat removed from the air stream in response to sensor data from either the inlet air stream entering the liquid desiccant system or the supply air stream exiting the system. Dynamic adjustment of the control system allows for relatively independent control of the delivered air temperature and humidity, minimizing the overall energy consumption of the liquid desiccant system.

[0004] The present disclosure also describes a method of controlling a liquid desiccant air conditioning system, comprising: circulating a liquid desiccant between an absorber unit and a desorber unit at a liquid desiccant flow rate, cooling an inlet air stream flowing through the liquid desiccant air conditioning system to form a pre-cooled inlet air stream having a pre-cooling temperature value and a pre-cooling humidity value, a regeneration air temperature and flow rate, vapor compression, etc., as described in further detail below. Depending on the temperature and humidity of the inlet air and the pre-cooled inlet air, moisture can be removed from the air stream by condensation, thereby generating a first moisture removal rate. The cooled inlet air is then passed through the absorber unit. The liquid desiccant contacts the pre-cooled inlet air stream and removes water from the pre-cooled inlet air stream to form a supply air stream having a supply air absolute humidity value less than the pre-cooled absolute humidity value, thereby generating a second moisture removal rate and forming a loaded liquid desiccant. The method also includes heating a regeneration air stream flowing through the liquid desiccant air conditioning system, and flowing the loaded liquid desiccant through a desorber unit, wherein the liquid desiccant contacts the heated regeneration air stream, and the heated regeneration air stream removes water from the loaded liquid desiccant to form a regenerated liquid desiccant and a humidified exhaust gas stream. An embodiment of the method includes supplying heat pump energy to cool the cooled inlet air stream to a cooled temperature value and to heat the heated inlet air stream to a heated temperature value. The embodiment includes adjusting the heat pump heat flow rate value by manipulating a pre-cooled air temperature value, a first moisture removal rate, and a second moisture removal rate to achieve a predetermined supply air humidity value and temperature, wherein the first moisture removal rate is primarily controlled by the pre-cooled inlet air temperature set point and the second moisture removal rate is primarily controlled by the liquid desiccant concentration, which is itself determined by the heated temperature value and the heated humidity value.

[0005] The present disclosure also describes a liquid desiccant air conditioning system, comprising a liquid desiccant circuit having an absorber unit in fluid communication with a desorber unit and a liquid desiccant flowing between the absorber unit and the desorber unit. The system includes a supply airflow path that passes through the absorber unit and forms an absorber liquid / air and / or liquid / gas interface within the absorber unit, and a regulated supply airflow exiting the absorber unit. A sensor is configured to measure the regulated supply airflow temperature and humidity value. A regeneration airflow path passes through the desorber unit and forms a desorber liquid / air interface within the desorber unit, as well as an exhaust airflow exiting the desorber unit. In some embodiments, a heat pump is thermally coupled to the supply airflow path and removes heat and moisture via condensation from the supply airflow upstream of the absorber unit. The heat pump is thermally coupled to the regeneration airflow path, thereby adding heat to the regeneration airflow upstream of the desorber unit. The heat pump has a power unit that provides power to the heat pump to cool the supply airflow and heat the regeneration airflow. A controller is operably connected to the sensor and the power unit. In some embodiments, the controller is configured to regulate operation of the power unit to achieve a desired supply air temperature and humidity based on system parameters, including evaporator leaving air temperature, condenser leaving air temperature, refrigerant temperature after condensation, refrigerant temperature at the evaporator, and / or the configuration of various valves. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The following discussion refers to the following drawings, in which like reference numerals may be used to identify similar / identical components throughout the several drawings. The drawings are not necessarily to scale.

[0007] Figure 1 is a schematic diagram of an illustrative liquid desiccant system according to an embodiment.

[0008] Figure 2A is a psychrometric diagram of an illustrative liquid desiccant system process, according to an embodiment.

[0009] Figure 2B and 2C is a psychrometric diagram illustrating a mode of operation of a liquid desiccant system prioritizing supply air dew point relative to supply air dry-bulb temperature, according to an embodiment.

[0010] Figure 3A and 3B is a psychrometric diagram illustrating a mode of operation of a liquid desiccant system prioritizing supply dry-bulb temperature relative to supply air dew point, according to an embodiment.

[0011] Figure 4 The performance of a liquid desiccant system according to an embodiment is shown.

[0012] Figure 5A method of regulating supply air flow using a liquid desiccant system that prioritizes supply air dew point relative to supply air dry-bulb temperature is shown according to an embodiment.

[0013] Figure 6 A method of regulating supply air flow using a liquid desiccant system that prioritizes supply air dew point relative to supply air dry-bulb temperature is shown according to an embodiment.

[0014] Figure 7 A method of regulating supply air flow using a liquid desiccant system that prioritizes supply dry-bulb temperature over supply air dew point is shown according to an embodiment. DETAILED DESCRIPTION

[0015] The present disclosure generally relates to heating, ventilation, and air conditioning (HVAC) systems and methods for controlling the same. In one exemplary embodiment, a gas-to-liquid vapor exchanger includes an absorber unit for extracting moisture from the air into a liquid desiccant and a desorber unit for regenerating the liquid desiccant passed through the two units. These units can be used to absorb water vapor into and desorb water vapor from the liquid desiccant to dehumidify or humidify the air. This humidification and dehumidification can be used in HVAC heating and cooling applications. Control of the unit operations of the liquid desiccant system minimizes energy consumption.

[0016] Air conditioning systems can perform two functions simultaneously: the first is to dehumidify, and the second is to cool a forced air stream. Commonly used air conditioning systems use vapor compression, which can both cool the incoming air and dehumidify it by cooling it below the dew point temperature of the air, thereby condensing water. However, given a humid air stream, vapor compression may rely on cooling the air stream to 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 greatly increases the energy requirements of air conditioning, especially in humid climates. An alternative dehumidification method known as liquid desiccant dehumidification can significantly reduce the energy intensity of air conditioning and is the subject of the present disclosure.

[0017] Using a liquid desiccant to remove moisture from the air is an energy-efficient alternative to vapor compression because it minimizes or eliminates the need for overcooling and reheating the air stream, and improves the coefficient of performance of the integrated heat pump by increasing the low temperature required for the heat pump, which reduces the energy consumption of the heat pump. In a liquid desiccant dehumidification system, wet air exchanges water vapor with a liquid desiccant. A gas-to-liquid vapor exchanger (absorber unit) can be used to contact the wet air and the liquid desiccant and transfer the water vapor in the wet air to the liquid desiccant to form a loaded liquid desiccant. By heating the loaded liquid desiccant to evaporate and / or drive off the water vapor and returning the regenerated liquid desiccant to the absorber unit, this loaded liquid desiccant can be regenerated in a gas-to-liquid vapor exchanger (desorber unit). Alternatively, the loaded liquid desiccant can be regenerated by an electrochemical process (such as electrodialysis) or other process that separates the desiccant into a more dilute and more concentrated desiccant portion. The regeneration rate of the desiccant in the desorber (particularly relative to the collection rate of moisture in the absorber) will change the concentration of the desiccant. The moisture absorption potential of a liquid desiccant is controlled by its concentration, with the potential increasing with higher concentrations. Operating at higher concentrations enables higher rates of moisture removal from air streams; however, higher concentrations require higher temperatures for regeneration. Increasing the temperature required to regenerate a heat pump desiccant reduces the heat pump's coefficient of performance, resulting in higher heat pump energy consumption.

[0018] Advanced liquid desiccant systems pre-cool (remove heat from) the inlet air entering the absorber unit and pre-heat (add heat to) the inlet air entering the desorber unit. A heat pump can be used to move heat from one unit to another to reduce the energy consumption of the entire liquid desiccant system. The liquid desiccant system and control method described herein can maximize the energy efficiency of the entire liquid desiccant system under a selected set of system air flow inlet parameters and desired outlet parameters. More specifically, for example, evaporator temperature, condenser temperature, and desiccant concentration can be considered and selectively manipulated to minimize or optimize energy usage for various combinations of air inlet and outlet conditions.

[0019] The liquid desiccant air conditioning system and method described herein utilize two moisture removal devices in the supply air stream. The first moisture removal device is a radiator (also referred to herein as a cooling unit) that cools the air and can remove moisture from the air by cooling the air below its saturation point and condensing water. The control system can regulate the temperature of the cooling unit and thereby regulate the temperature and dew point of the pre-cooled air, as well as the rate at which moisture and / or condensation (if any) is removed by the unit. The second moisture removal device is a liquid desiccant absorber that uses a liquid desiccant to transfer water vapor from the cooled air to the desiccant. The control system can regulate the amount and / or quality of heat transferred to the desiccant in the regenerator, thereby changing the regeneration rate and desiccant concentration. Changing the desiccant concentration will change the temperature and / or humidity of the supply air.

[0020] In one embodiment, the control system can adjust the heat flow in response to inlet and / or outlet temperature and / or humidity sensor data of the inlet air flow entering the liquid desiccant system and / or the supply air flow leaving the liquid desiccant system. These adjustments affect the moisture removal rate of the cooling section (by adjusting the temperature of the cooling unit and thereby adjusting 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 in the system. If changes in these temperatures result in changes in energy consumption, such as in a heat pump, these dynamic adjustments of the control system can be used to minimize the overall energy consumption of the liquid desiccant air conditioning system.

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

[0022] Figure 1 Schematic diagram of air, water, and heat flows in a liquid desiccant system 100 according to an embodiment. The liquid desiccant system 100 includes a cooling unit 101, an absorber 102, a heat regenerator 103, and a controller 104. The heat regenerator 103 includes a desorber 103B configured to remove moisture from a loaded desiccant and a heating unit 103A for providing heat to the desorber 103B for moisture removal. The cooling unit 101 is operatively coupled to the absorber 102 and the regenerator 103, and the absorber 102 is operatively coupled to the regenerator 103, as shown in FIG. Figure 1In 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 for assisting in the operation and control of the system 100. In such embodiments, the sensors S may be placed at any suitable location within the system 100. For example, Figure 1 As shown in , one or more sensors may be positioned to measure the temperature of air 111 exiting the cooling unit 101; one or more sensors may be positioned to measure the temperature and humidity of the supply air 112 exiting the absorber 102; and one or more sensors may be positioned to measure the air 115 exiting the regenerator 103 (and more specifically, the desorber 103B), as described in further detail below. In some embodiments, one or more sensors may be positioned to measure one or more parameters of the heating unit and / or the cooling unit, such as the temperature of these units. Where these units are operably interconnected 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 evaporation temperature), and / or evaporation temperature.

[0023] The liquid desiccant can be any suitable liquid desiccant. In some implementations, 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 (CuCl2), silver chloride (AgCl), calcium chloride (CaCl2), chlorine fluoride (ClF), methyl bromide (CH3Br), iodoform (CH13), 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 CaCl2. In some embodiments, the halide salt solution is LiCl. In some implementations, the solution can be water and is described as an aqueous solution. The halide salt can be present in the liquid desiccant in a range of about 2 wt% to about 50 wt%, or about 10 wt% to about 40 wt%, or about 20 wt% to about 40 wt%.

[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 an input / output (I / O) device (not shown).

[0025] The cooling unit 101 may be any suitable heat sink configured to remove heat from the 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 Figure 1 As shown in FIG, the cooling unit 101 is configured to receive inlet air 110 and cool the inlet air 110 to a cooling temperature (also referred to as a pre-cooling temperature set point) to produce cooled air 111. In some embodiments, the cooling temperature may be equal to and / or below 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 condensate at a condensate moisture removal rate 131. That is, in some embodiments, the cooling unit 101 may cool and / or pre-cool the inlet air 110, effectively performing a first stage and / or step dehumidification of the inlet air 110, wherein moisture and / or water are removed from the inlet air 110 to produce the cooled air 111 and condensate at a condensate moisture removal rate 131. The cooled air 111 may then be further dehumidified in a second stage and / or step dehumidification in the absorber 102, as further described herein. In some implementations, the cooling unit 101 includes a cooling coil that is an evaporator of a heat pump. In some embodiments, the liquid desiccant system 100 may include a sensor disposed between the cooling unit 101 and the absorber 102, such as Figure 1 . In some implementations, this sensor can be configured to measure the humidity of the cooling air 111, the cooling temperature, or both. The sensor can then send a signal to the controller 104, causing the controller 104 to adjust at least one of the cooling temperature, the absorber moisture removal rate 132, or the desorber moisture discharge rate 103 in response to receiving the signal, as further described herein.

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

[0027] To this 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, produce a regenerated and / or concentrated liquid desiccant 121, and then transport the regenerated and / or concentrated liquid desiccant 121 back to the absorber 102. The desorber 103B defines a liquid / air and / or liquid / gas interface, which can be formed by any vapor / liquid mass transfer unit operation, including, for example, a packed bed, a plate tower, a spray tower, a bubble tower, a membrane, and the like. The desorber 103B can 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 removal rate 133. In this embodiment, the regenerator 103 includes a heating unit 103A configured to deliver heat to the desorber 103B via a preheated air stream 114 to separate moisture and / or water from the loaded liquid desiccant 120 in the desorber 103B. In some embodiments, for example, without a heating unit in the regenerator, heat and / or heated air can be delivered to the desorber 103B in other ways, as described in further detail herein. In some embodiments, the liquid desiccant system 100 can include a sensor disposed between the heating unit 103A and the desorber 103B, such as Figure 1In some implementations, this sensor can be configured to measure the temperature of the preheated air stream 114 and send a signal to the controller 104, causing the controller 104 to adjust at least one of the cooling temperature, the absorber moisture removal rate 132, or the desorber moisture discharge rate 103 in response to receiving the signal, as further described herein.

[0028] Heating unit 103A may provide heat from one or more of any suitable sources, including, for example, excess heat 118 from cooling unit 101, such as Figure 1 Other examples include electric heat, gas heat, hot water, steam, solar heat, geothermal heat, etc. In some implementations, the heating unit 103A may include a fan and a heating coil, which may be used to transfer heat to the regeneration air 113 to produce the preheated air flow 114. The controller 104 may be operably coupled to the heating unit 103B to change and / or modify the volume of air passed through the heating coil, thereby controlling the temperature of the preheated air flow 114. For example, in some implementations, the volume of air passed through the heating coil may be controlled by changing the speed of the fan in the heating unit 103A and / or the pressure drop of the air passed through the heating coil. In some implementations, the heating unit 103A includes a condenser of a heat pump to transfer heat to the regeneration air 113. In some implementations, the heat pump may cool the evaporator and heat the condenser. In use, in some implementations, the heat pump may be capable of operating with a variable flow rate (e.g., adjusting the flow rate of the refrigerant and / or working fluid circulating within the heat pump) to vary the amount of heat transferred between the evaporator and the condenser, thereby providing controllability of the system 100. For example, in some embodiments, the heat pump may be capable of adjusting the speed of the refrigerant compressor to alter, change, and / or modify the mass flow rate of the refrigerant circulating within the heat pump.

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

[0030] Although not shown, in some embodiments, system 100 may include an auxiliary condensing coil configured to receive an external air flow in addition to the regeneration air flow (113-114) to 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 flow and pass the external air flow through heating unit 103A to remove unwanted heat generated in cooling unit 101. In such embodiments, in some implementations, 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 assistance of controller 104) the amount of heat sent to heating unit 103A relative to the external air flow. In some implementations, the amount of heat sent to heating unit 103A can be adjusted by varying the speed of a fan that draws the external air flow into the auxiliary condensing coil. Alternatively, in some implementations, the amount of heat sent to heating unit 103A can be adjusted by varying the pressure drop of the external air flow.

[0031] In use, inlet air 110 enters the cooling unit 101 and is cooled within the cooling unit 101 to a predetermined and / or preferred cooling temperature (also referred to as a pre-cooling temperature set point). If the dew point of the inlet air 110 is above the pre-cooling temperature set point, moisture and / or water condenses from the inlet air 110, thereby forming (a) condensate at a condensate moisture removal rate 131, and (b) cooled air 111 (also referred to as pre-cooled air 111). In other words, in some embodiments, the cooling unit 101 may receive the inlet air 110, cool the inlet air 110 (e.g., reduce the enthalpy of the inlet air 110) to a predetermined and / or preferred cooling temperature (e.g., a temperature below the dew point of the inlet air 110), which results in a first stage and / or stepwise dehumidification of the inlet air 110 and produces cooled air 111 (at a cooling air humidity) that may be further dehumidified in the absorber 102, as further described herein. The cooling air 111 may exit the cooling unit 101 and then be directed and / or flowed from the cooling unit 101 to the absorber 102, wherein the cooling air 111 is introduced to a concentrated liquid desiccant 121 flowing within the absorber 102. Exposure of the cooling air 111 to the concentrated liquid desiccant 121 results in absorption of water vapor from the air stream 111. The absorption of water vapor from the cooling air 111 to the concentrated liquid desiccant 121 dehumidifies the cooling air 111 and produces supply air 112 at a target supply air temperature and humidity, as well as a loaded liquid desiccant 120, as shown. Figure 1. In some embodiments, the absorption of water vapor from the cooling air 111 in the absorber 102 can constitute a second stage and / or step-wise 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 supply air stream 112 exits the absorber 102 at the supply air humidity and temperature set point. The loaded liquid desiccant 120 (i.e., the liquid desiccant after having absorbed water vapor from the cooling air 111 within the absorber 102) is transferred from the absorber 102 to the regenerator 103 (in this case, the desorber 103B of the regenerator). In some embodiments, the desorber 103B can expose the loaded liquid desiccant 120 to a preheated air stream, such as Figure 1 In some embodiments, the preheated air 114 may be generated by passing the regeneration air 113 through the heating unit 103A. In some embodiments, the heating unit 103A may be configured to heat the regeneration air 113 by transferring heat, for example, from heat absorbed in the cooling unit 101 using a heat pump (not shown). The preheated air stream 114 may 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 regenerated and / or concentrated liquid desiccant 121, which may then be used in the absorber 102. The regenerated and / or concentrated liquid desiccant 121 is then returned from the desorber 103B to the absorber 102. In some embodiments, the liquid desiccant system 100 may optionally include an auxiliary condensing coil configured to receive an external air flow (in addition to the regeneration flow 113 or 114) to remove unwanted heat from the heating unit 103A. In some embodiments, a user and / or subject may want to use the liquid desiccant system 100 to produce a supply air 112 having a predetermined and / or preferred supply air humidity and temperature. The controller 104 may be operably coupled to the cooling unit 101, the absorber 102, and the regenerator 103 to regulate and / or control one or more parameters of the liquid desiccant system 100, such as, for example, the flow rate of the inlet air flow 110, the cooling temperature in the cooling unit 101, the amount of heat transferred and / or directed to the desorber 103b, and / or the concentration of the liquid desiccant directed to the absorber 102, to produce a flow rate of the supply air 112 at a predetermined (e.g., target) supply humidity and temperature, as further described herein. In some implementations, the liquid desiccant system 100 may include a sensor disposed downstream of the absorber 102, such as Figure 1As shown in , this sensor can be configured to measure air supply temperature and / or air supply humidity and then send a signal indicative of and / or associated with the measured air supply temperature and / or air supply humidity to controller 104. Controller 104 can receive the signal from the sensor and determine the temperature difference between the measured air supply temperature and a target air supply temperature stored in the controller 104's memory. Similarly, controller 104 can be configured to determine the humidity difference between the measured air supply humidity and a target air supply humidity stored in the controller 104's memory. In some implementations, controller 104 can be further configured to determine other characteristics and / or properties of the air supply based on the measured air supply temperature and air supply humidity, such as, for example, the air supply dry-bulb temperature and / or the air supply dew point. The controller can store additional target parameters and / or characteristics of the supply air flow defined by the user. For example, controller 104 can be configured to store a target supply air dew point and / or a target supply air dry-bulb temperature. In such an implementation, the controller can determine, for example, the difference between the received air supply humidity and the target air supply dew point, or the difference between the supply air dry bulb temperature and the target supply air dry bulb temperature. In some implementations, the controller 104 can be configured to adjust one or more operating conditions of the liquid desiccant system 100 to maintain the air supply humidity within 0.10 degrees, within 0.20 degrees, within 0.25 degrees, within 0.50 degrees, within 1.0 degrees, within 2.0 degrees, within 3.0 degrees, or within 5.0 degrees of the target air supply dew point. In some implementations, the controller 104 can be configured to adjust one or more operating conditions of the liquid desiccant system 100 to maintain the air supply dry bulb temperature within 0.10 degrees, within 0.20 degrees, within 0.25 degrees, within 0.50 degrees, within 1.0 degrees, within 2.0 degrees, within 3.0 degrees, or within 5.0 degrees of the target air supply dry bulb temperature.

[0032] Condensate moisture removal rate 131 (as for Figure 2A , discussed in further detail with reference to 231) is essentially determined by the flow rate and absolute humidity of the inlet air 110 and the temperature of the cooling coil (not shown) within the cooling unit 101. The absorber moisture removal rate 132 (as discussed with reference to Figure 2A , discussed in further detail with reference to 232) is essentially determined by the flow rate of the cooling air 111 and the concentration of the desiccant stream 121. The absorber moisture removal rate 132 (as discussed with reference to Figure 2A , discussed in further detail with reference to 232 ), can be determined from moisture data measured by sensors at 111 and at 112 (ie, upstream and downstream of the absorber 102 ). The desorber moisture removal rate 133 (as discussed with reference to Figure 2A, discussed in further detail at reference 233 , is essentially determined by the flow rate and absolute humidity of the regeneration air 113, the concentration of the desiccant stream 120, and the temperature of the delivery preheated air stream 114. Thus, stable operation of the unit occurs when the moisture absorption rate in the absorber 102 is equal to the desorber moisture removal rate 133 in the regenerator 103. This state can be achieved by controlling the temperature of the cooling unit 101 and the temperature of the heating unit 103A. Furthermore, the rate at which the system becomes stable is set by the liquid desiccant concentration, which in turn has been set by the moisture accumulation rate in the absorber (e.g., the absorber moisture removal rate 132) and the regeneration rate in the desorber (e.g., the desorber moisture removal rate).

[0033] In some implementations, it is desirable to control both the temperature and humidity of the supply air stream 112. This can be achieved by delivering an air stream 111 of a specific temperature and a liquid desiccant stream 121 of a specific concentration to the absorber 102. The concentration of the desiccant stream 121 can be controlled by controlling the desorber moisture removal rate 133 of the regenerator 103, which in turn can 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 (e.g., from the heating unit 103A) to the desorber 103B, the amount of regeneration air 113 delivered to the regenerator 103, and / or the flow rate of the liquid desiccant 120 and 121 flowing between the absorber 103 and the desorber 103B. In some embodiments, for example, in implementations where the regenerator is an electrochemical regenerator, the regeneration rate of the regenerator can be controlled by the amount of current delivered.

[0034] In some implementations, the volume of desiccant in the system is relatively large, such that the desiccant concentration 121 changes more slowly than the cooling unit 101 can change temperature to impart the desired change to the supply air 112. In the event that the desired moisture removal rate of the liquid desiccant system 100 changes rapidly (e.g., a change is required within a time period that is not achievable by simply changing the desiccant concentration), the control system 104 can increase the condensate moisture removal rate 131 by reducing the cooling temperature and / or pre-cooling temperature setpoint of the cooling air 111 until the liquid desiccant concentration in the concentrated liquid desiccant 121 can be sufficiently increased to increase the absorber moisture removal rate 132, as described with respect to FIG. Figure 2A -C is described in more detail.

[0035] In some implementations, a heat pump (not shown) can be used to move the heat flow 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 desirable to control the state of the supply air 112 to a target temperature, humidity, or both. Therefore, to accommodate such situations, 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 meeting the target set point (target temperature and / or humidity) for the state of the supply air 112.

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

[0037] Any of the liquid desiccant systems described herein can employ various control protocols. In some cases, for example, the control system can regulate the rate at which the regenerator removes water from the desiccant in the regenerator (e.g., the desorber moisture removal rate), such as by increasing the quality or amount of heat entering the desorber to match the collection rate of water in the absorber (e.g., the absorber moisture removal rate). In some cases, the control system can further regulate the regeneration rate to change the concentration of the desiccant, thereby achieving the desired temperature and / or humidity of the air in the supply air outlet. In some cases, the control system can regulate the temperature of the cooling coil in the cooling unit and regulate the desiccant concentration to independently control the temperature and humidity of the supply air. In some cases, the temperature of the cooling coil in the cooling unit can be regulated without collecting and / or regenerating moisture to cool the supply air. In some cases, the temperature of the cooling coil and the concentration of the desiccant can be changed to optimize (e.g., minimize energy use) the supply air provided at the supply air outlet at a desired humidity (e.g., humidity ratio or absolute humidity).

[0038] The regeneration rate (e.g., the desorber moisture removal rate) can be varied in one or more ways, including, for example, for a thermal regeneration system, adjusting the temperature of the heating coil; adjusting the amount of heat supplied 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 refrigerant flow to each coil and thereby varying the amount of unwanted heat in the external air flow available for removal from the system by the second condensing coil; and / or by varying the airflow through the external coil and thereby varying the amount of heat available for regeneration of the heating coil); adjusting the airflow rate through the heating unit and / or the desorber, and adjusting the desiccant flow rate (e.g., modulating and / or turning on / off as needed). The regeneration rate can be varied in one or more ways, including, for example, for an electrochemical regeneration system, by varying the voltage across the device, the flow path within the device, and / or the desiccant flow rate to the device.

[0039] For example, the evaporator temperature may be varied by changing the flow rate of the refrigerant (eg, by changing the speed of the compressor, by operating one or more compressors in series), and / or by modulating the amount of refrigerant sent through the hot gas bypass.

[0040] In some embodiments, the control system can 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 lower dew point than the desired supply outlet dew point and dry bulb; and / or transitioning between states when the supply inlet air changes, such that appropriate delays and dead bands are applied.

[0041] In some embodiments, any of the liquid desiccant systems described herein may include two proportional-integral-derivative controllers and control loops, the control loops comprising: a loop that monitors the supply air dew point, and when the supply air dew point is too high compared to a desired target, the system may reduce the cooling temperature in the cooling unit, and when the supply air dew point is too low compared to the desired target, the system may raise and / or increase the cooling temperature in the cooling unit; and a loop that monitors the actual supply air temperature (e.g., the air supply temperature measured by sensor S) and the supply air target temperature, and determines an appropriate desiccant concentration accordingly, which controls the desiccant concentration by determining how much water to regenerate in the desorber, for example, by how much heat to deliver to the desorber - if the actual supply temperature is lower than the supply target temperature, the system may decide the amount of heat to add to the regenerator to increase the desiccant concentration, and thereby increase the actual supply temperature, while the first loop maintains the desired supply air dew point.

[0042] Figures 2A-2C The psychrometric diagram is used to illustrate how a liquid desiccant air conditioning control system 2000 (including any of the control systems described herein) can condition air to meet target humidity and temperature set points. The liquid desiccant system 2000 can be structurally and / or functionally similar to the system described above with reference to FIG. Figure 1 For example, the liquid desiccant system 200 may include one or more components that are structurally and / or functionally similar to the components of the liquid desiccant system 100. Therefore, further details regarding the components of the liquid desiccant system 200 are not provided herein.

[0043] like Figure 2A In this example, the inlet air 210 has a certain temperature and humidity as shown in the figure (approximately 85 degrees Fahrenheit dry bulb and approximately 70 degrees Fahrenheit dew point), and the target temperature and target dew point of the supply air 212 are set to approximately 75 degrees Fahrenheit dry bulb and approximately 50 degrees Fahrenheit dew point. For example, by similar means to those in the above reference Figure 1 The cooling unit 101 described above, the inlet air can be cooled and dehumidified (along Figure 2A 211 ). When the dew point of the inlet air 210 is above the dew point of the pre-cooling temperature 211, water condenses out of the air, resulting in a condensate moisture removal rate 231. This is illustrated by line 201, which first crosses horizontally to its left as it is cooled, and until it reaches its dew point or saturation temperature, at which point additional cooling results in condensation (and dehumidification), as illustrated by line 201, which crosses downward and left along the saturation curve to 211. The cooling unit 201 produces cooled air 211, which is cooled in a manner similar to that described above with reference to FIG. Figure 1 The liquid desiccant absorber of absorber 102 is further dehumidified by the liquid desiccant at a concentration having an equilibrium vapor pressure 230. The liquid desiccant absorbs water vapor from the cooling air 211, as determined by Figure 2A , resulting in an absorber moisture removal rate 232. The result of these two processes is supply air 212 at a target temperature and state 212, which is at a target dew point 220. Therefore, in other words, with a target temperature and dew point for the supply air 212, the inlet air 210 can 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 set point for the supply air 212.

[0044] Likewise Figure 2A As illustrated in , the heat required for regeneration (in some embodiments, the heat is moved (e.g., through the cooling unit) from the inlet air 210 to the regeneration air stream 213) preheats the air stream entering the desorber (as illustrated by the horizontal line connecting 213 and 214). In some implementations, this air stream 213 to be preheated is at the same inlet conditions as the inlet air 210 to the cooling unit 201 (or at least substantially similar, e.g., if from the same or similar environment). The preheated air 214 is used to heat and thereby regenerate the loaded liquid desiccant (as illustrated by the line connecting 214 and 215, which crosses upward and to the left thereof and toward the constant relative humidity line 230 and exits the desorber at 215). In some implementations, the temperature and / or amount of the preheated air 214 entering the desorber can be measured with a sensor and used to control the desorber moisture removal rate 233, i.e., the regeneration rate of the desorber.

[0045] like Figure 2B As described in the Figure 2A The system may be configured to change the target dew point (212) of approximately 75 degrees Fahrenheit dry bulb and approximately 50 degrees Fahrenheit to approximately 73 degrees Fahrenheit dry bulb and approximately 40 degrees Fahrenheit dew point (212"), for example, by an operator desiring less humid air or by a controller having a temperature set point schedule. In one operating mode (e.g., a mode prioritizing supply air dew point), the system prioritizes achieving the target dew point of 40 degrees Fahrenheit (220') by relatively quickly lowering the temperature of the air exiting the cooling unit from 211 to 211'. As a result, the supply air 212' exiting the absorber is at the target dew point (220'), but the target temperature of the supply air has dropped to approximately 67 degrees Fahrenheit dry bulb.

[0046] Next, if Figure 2CAs illustrated in , the desiccant concentration can be increased relatively slowly (e.g., in a thermal regeneration system, by increasing the mass and / or amount of heat entering the desorber via the preheated air 214, e.g., by increasing the heat of the condenser, as illustrated by the line connecting 213 and 214' and extending further to the right (i.e., from 214 to 214')). The desiccant will continue 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 will continue to increase until the system returns to equilibrium; setting the desorber moisture removal rate 233, and thereby the temperature of the air 214' used for regeneration, to meet the desired supply air conditions 212". As the desiccant concentrates, the additional cooling that was just applied can be scaled back, e.g., from 211' to 211", to meet the target dew point and temperature in an energy efficient manner.

[0047] Figure 3A and 3B Another mode of operation of the liquid desiccant system 300 is shown, for example, a mode of operation that prioritizes the supply dry bulb temperature over the supply air dew point. The liquid desiccant system 300 can be structurally and / or functionally similar to the liquid desiccant systems 100 and / or 200 described above. For example, the liquid desiccant system 300 can include one or more components that are structurally and / or functionally similar to the components of such systems. Therefore, further details regarding the components of the liquid desiccant system 300 are not provided herein. Figure 3A In the case of air supply conditions, Figure 2A The system may change the target dry bulb temperature of approximately 75 degrees Fahrenheit and a dew point of approximately 50 degrees Fahrenheit (212) to a dry bulb temperature of approximately 73 degrees Fahrenheit and a dew point of approximately 40 degrees Fahrenheit (312"), for example, by an operator who desires less humid air or by a controller having a temperature set point schedule. The system prioritizes achieving the target dry bulb temperature of 73 degrees Fahrenheit (312') by relatively quickly reducing the temperature of the air exiting the cooling unit from 311 to 311'. As a result, the supply air 312' exiting the absorber is at the target dry bulb temperature (312'), but the dew point of the supply air 312' has only been reduced to approximately 45 degrees and has not yet reached the target dew point 312".

[0048] Next, if Figure 3BAs illustrated in , the desiccant concentration can be increased relatively slowly (e.g., in a thermal regeneration system, by increasing the mass and / or amount of heat entering the desorber via the preheated air stream 114, e.g., by increasing the heat of the condenser, as illustrated by the line connecting 313 and 314' and extending further to the right (i.e., from 314 to 314')). As long as the desorber moisture removal rate 333 exceeds the absorber moisture removal rate 332, the desiccant will continue to concentrate. Thus, the absorber moisture removal rate 332 will continue to increase until the system returns to equilibrium; setting the desorber moisture removal rate 333, and thereby the temperature of the air 314' used for regeneration, to meet the desired supply air conditions 312". As the desiccant concentrates, the additional cooling that was just applied can be reduced, e.g., from 311' to 311", to meet the target dew point and temperature in an energy efficient manner.

[0049] Figure 4 , the performance of the liquid desiccant system 400 is shown. The liquid desiccant system 400 can be structurally and / or functionally similar to other liquid desiccant systems, including, for example, the liquid desiccant systems 100, 200, and / or 300 described herein. For example, the liquid desiccant system 400 can include one or more components that are structurally and / or functionally similar to the components of such systems. Therefore, further details regarding the components of the liquid desiccant system 400 are not provided herein. In some embodiments, the liquid desiccant system 400 can be capable of maintaining the supply air temperature and dew point within 1 degree Fahrenheit of the desired (and / or target) supply air dry-bulb temperature and 1 degree Fahrenheit of the desired (and / or target) dew point over a relatively long period of time (e.g., multiple days). Figure 4 The performance of the liquid desiccant system 400 operating on an inlet air flow (eg, similar to the inlet air 110 ), operating continuously for an extended period of time, is shown. Figure 4 The inlet (i.e., outdoor) air temperature and the inlet (i.e., outdoor) air dew point of the inlet air stream are shown. Despite variations in both the temperature and dew point of the inlet air stream exceeding 10 degrees Fahrenheit, the liquid desiccant system 400 produces a supply air stream (e.g., similar to the supply air 112) characterized by a dry bulb temperature and a dew point that remain within 1 degree Fahrenheit of desired (e.g., target) conditions. Figure 4 The operating mode of the liquid desiccant system 400 in FIG. 4 represents the regulation process described in FIG. 2 , in which dew point is prioritized and the control system quickly changes the evaporator temperature to maintain the dew point while more slowly changing the desiccant concentration. Thus, a relatively more stable dew point of the supply air stream is exhibited.

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

[0051] At step 502, method 500 includes removing heat from an inlet air stream via a cooling coil of a cooling unit to produce 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) so ​​that the control unit can adjust the amount and / or quality of heat removed from the inlet air stream. In this manner, the liquid desiccant system 500 can produce a supply 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 who desires less humid and / or more humid air, or by a controller having a temperature set point schedule. In some cases, the control unit can vary the amount and / or quality of heat removed from the inlet air flow to adjust the target supply temperature and humidity of the supply air flow 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 dew point, including all values ​​and ranges therebetween (for temperatures measured in degrees Fahrenheit). Additionally and / or alternatively, in some cases, the control unit can vary the amount and / or quality of heat removed from the inlet air flow to adjust the target supply temperature and humidity of the supply air flow 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, including all values ​​and ranges therebetween (for temperatures measured in degrees Fahrenheit), of the desired dry bulb temperature of the supply air flow.

[0052] In some embodiments, method 500 may optionally include step 502a ( Figure 4 (not shown in FIG. 5 ). In optional step 502a, method 500 includes changing the cooling temperature of the cooling air flow in the cooling unit using a control unit operatively coupled to the cooling unit, the absorber, and the regenerator to adjust the enthalpy change of the supply air flow. In some embodiments, the cooling temperature of the cooling air flow can be changed, for example, by changing (e.g., increasing and / or decreasing) the mass flow rate of the refrigerant circulating within 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 cooling air flow. Additionally, in some embodiments, the mass flow rate of the refrigerant can be changed by changing the speed of the refrigerant compressor.

[0053] At step 503, method 500 includes directing the cooling air flow to an absorber (e.g., similar to absorber 102) fluidly coupled to the cooling unit. The absorber can 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 plate tower, a spray tower, a bubble tower, a membrane, and / or the like. At step 504, method 500 also includes exposing the cooling air flow to a liquid desiccant at the liquid / air interface of the absorber, such that the liquid desiccant removes moisture from the cooling air flow at the absorber moisture removal rate and produces a supply flow at a target supply temperature and humidity.

[0054] At step 505, method 500 includes directing the liquid desiccant to a regenerator, which includes a desorber, after the liquid desiccant is exposed to the cooling air flow in the absorber (at step 504). In some embodiments, the liquid desiccant is directed to the regenerator after the liquid desiccant is exposed to the cooling air flow in the absorber, wherein the purpose is to remove moisture from the liquid desiccant.

[0055] At step 506, method 500 includes removing moisture from the liquid desiccant at a desorber at a desorber moisture removal rate. In some embodiments, removing moisture from the liquid desiccant at the desorber includes passing the regeneration stream through a heating unit (e.g., similar to heating unit 103A) to produce a preheated air stream. The preheated air stream can then be directed to the desorber. At the desorber, after the liquid desiccant flows into the absorber (and therefore contains moisture removed at the absorber moisture removal rate), the preheated air stream can be exposed to the liquid desiccant to remove water from the liquid desiccant and thus regenerate the liquid desiccant. In some embodiments, the heating unit can be coupled to the desorber and the cooling unit of the liquid desiccant system 500. The heating unit can include a fan and a heating coil. The heating coil can be a condenser of a heat pump, which is configured to transfer heat from the cooling unit (e.g., heat removed to the inlet air stream) to the regeneration stream, thereby heating the regeneration stream and producing a preheated stream at the preheated air stream temperature. In some embodiments, the heating unit can be operably coupled to the control unit to adjust and / or vary the amount and quality of heat transferred to the regeneration flow. For example, in some embodiments, the control unit can adjust and / or vary the amount of heat transferred to the regeneration flow by changing the target temperature of the preheated air flow.

[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, causing the auxiliary condensing coil to flow the outside air stream through the heating unit to remove a portion of the heat transferred from the cooling unit. In some cases, a portion of the heat removed from the cooling unit may be unwanted and / or undesirable heat for the desiccant liquid system 500. In some embodiments, the portion of the heat removed by the outside air stream can be adjusted by varying the speed of a fan (e.g., a fan coupled to the auxiliary condensing coil) that draws the outside air stream through the auxiliary condensing coil. Alternatively and / or optionally, in some embodiments, the portion of the heat removed by the outside air stream can be adjusted by (a) varying the pressure drop of the outside air stream, and / or (b) varying the amount of refrigerant flowing through the auxiliary condensing coil. Finally, at step 507, method 500 includes directing the liquid desiccant back to the absorber after removing moisture at the desorber. Directing the liquid desiccant back to the desorber after removing its moisture facilitates continued moisture removal via exposure of the liquid desiccant to a cooling air stream.

[0057] Figure 6A method 600 of operating a liquid desiccant system to produce an air supply flow is shown, for example, as shown in and described with respect to FIG. 2 . The liquid desiccant system 600 may be structurally and / or functionally similar to other liquid desiccant systems, including, for example, the liquid desiccant systems 100, 200, 300, 400, and / or 500 described herein. For example, the liquid desiccant 600 may include one or more components that are structurally and / or functionally similar to the components of such systems. Accordingly, further details regarding the components of the liquid desiccant system 600 are not provided herein. At step 601, the method includes receiving, at a control unit operably coupled to a cooling unit, an absorber, and a desorber of the liquid desiccant system, a signal from a sensor disposed downstream of the absorber, the signal indicating an air supply temperature and an air supply humidity measured by the sensor. In some implementations, the 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 (where the absorber and desorber are similar to those described above with reference to FIG. Figure 1 The absorber 102 and desorber 103B described above are similar and / or identical). The control unit may be the same as that described above with reference to Figure 1 The control unit may be similar and / or identical to the controller 104 described above. 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 implementations, the control unit may also be operably coupled to an external heating unit. In such an embodiment, the external heating unit may be coupled to the liquid desiccant system and configured to remove a certain amount of excess heat from the system. In some implementations, the control unit may also be operably coupled to one or more sensors (e.g., sensors related to Figure 1The control unit can be configured to send signals to and / or receive signals from the cooling unit, absorber, regenerator, and sensor S to monitor and control their operation (e.g., set points). The sensor can be any suitable sensor or group of sensors capable of measuring various system conditions, including, for example, temperature, humidity, pressure, and / or any other suitable parameter for assisting in the operation and control of the liquid desiccant system. In some implementations, the sensor (or at least one sensor from a group of sensors) can be disposed downstream of the absorber. In such an implementation, the sensor disposed downstream of the absorber can be configured to measure one or more characteristics of a supply stream (e.g., similar to supply stream 110) generated by the liquid desiccant system. For example, the sensor can be configured to measure air supply temperature and / or air supply humidity. The sensor can be coupled to the control unit such that the control unit can receive a signal (e.g., one or more signals) indicating the measured air supply temperature and / or air supply humidity (e.g., reporting the measured temperature and humidity to the control unit). In some embodiments, the sensor may measure the air supply temperature and send a signal to the control unit that is indicative of and / or correlates to the temperature measured in degrees Celsius and / or in degrees Fahrenheit.

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

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

[0060] At step 604, the method includes adjusting the enthalpy change of the supply air in the cooling coil relatively quickly via the control unit based on the humidity difference. For example, this corresponds to Figure 2B The change in humidity is indicated by the arrow from point 211 to 211' and causes the supply air to quickly reach a target outlet humidity provided, such as shown as point 212', in this example a target dew point of 40°F.

[0061] At step 605, the method includes relatively slowly regulating, via the control unit and based on the dry bulb temperature difference, at least one of the amount of heat or the quality of heat entering the desorber. For example, this corresponds to Figure 2C The change in temperature is indicated by the arrow from point 214 to 214' and causes the supply air to relatively slowly reach a provided target outlet temperature such as shown as point 212", which in this example is approximately 73°F.

[0062] At step 606, the method includes further adjusting the enthalpy change of the supply air in the cooling unit relatively slowly via the control unit and based on the humidity difference. For example, this corresponds to Figure 2C 1 , and as the system relatively slowly approaches a provided target outlet dew point and temperature (i.e., in this example, a target dew point of approximately 40°F and a target dry bulb temperature of approximately 73°F) such as shown as point 212″, the supply air humidity is maintained at the target dew point of approximately 40°F, as shown by points 212′ and 212″ and all points in between.

[0063] Figure 7A method 700 of operating a liquid desiccant system to generate an air supply flow is shown, for example, as shown in and described with respect to FIG 3. Steps 701, 702, and 703 in method 700 are the same as steps 601, 602, and 603 in method 600.

[0064] At step 704, the method includes adjusting the enthalpy change of the supply air in the cooling coil relatively quickly based on the dry bulb temperature difference via the control unit. For example, this corresponds to Figure 3B The change shown in FIG, indicated by the arrow from point 311 to 311 ', causes the supply air to quickly reach a provided target outlet dry bulb temperature such as shown as point 312', which in this example is approximately 73°F.

[0065] At step 705, the method includes relatively slowly adjusting at least one of the amount of heat or the quality of heat entering the desorber via the control unit based on the humidity difference. For example, this corresponds to Figure 3B , indicated by the arrow from point 314 to 314', and causes the supply air to relatively slowly reach a provided target outlet dew point such as shown as point 312", in this example a target dew point of 40°F.

[0066] At step 706, the method includes further adjusting the enthalpy change of the supply air in the cooling unit relatively slowly via the control unit and based on the humidity difference. For example, this corresponds to Figure 3B , indicated by the arrow from point 311′ to 311″, and results in the supply air dry bulb maintaining the target dew point of approximately 40°F as shown by points 312′ and 312″ and all points in between as the system relatively slowly reaches a provided target outlet temperature and dew point such as shown as point 312″ (in this example, a dry bulb temperature of approximately 73°F and a target dew point of 40°F).

[0067] Although various embodiments have been described above, it will be understood that they have been presented by way of example and not limitation. Although 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 indicate certain components arranged in a certain direction or position, the arrangement of the components may be modified. Although various embodiments have been described as having a combination of specific features and / or components, other embodiments having any feature and / or combination of components from any of the embodiments discussed above are also possible.

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

[0069] As used herein, the phrase "and / or" should be understood to mean "either or both" of the elements so connected, i.e., elements that are connected in some cases and separated in other cases. Multiple elements listed with "and / or" should be interpreted in the same way, i.e., "one or more" of the elements so connected. In addition to the elements specifically identified by the "and / or" phrase, other elements may optionally be present, whether related or unrelated to those specifically identified. Thus, as a non-limiting example, when used in conjunction with open language such as "comprises" or "comprising", a reference to "A and / or B" may, in one embodiment, refer only to A (optionally including elements other than B); in another embodiment, to B (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); and so on.

[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 the items in a list, "or" or "and / or" should be interpreted as inclusive, i.e., including at least one, but also including more than one in a plurality of or a series of elements, and optionally, additional unlisted items. Only terms that clearly indicate the opposite (such as "only one of ... or "just one of ... or "consisting of ... when used in a claim) will refer to including just one element in a plurality of or a series of elements. Usually, the term "or" as used herein should only be interpreted as indicating an exclusive alternative (i.e., "one or the other, but not both") when preceded by an exclusive term (such as "any one," "one in ...," "only one of ... or "just one of ..."). When used in a claim, "consisting essentially of ... should have the ordinary meaning used in the field of patent law.

[0071] As used herein, the phrase "at least one" with respect 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 each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows that elements may optionally be present in addition to the elements 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") may, in one implementation, refer to at least one (optionally including more than one) A, where B is not present (and optionally including elements other than B); in another implementation, refer to at least one (optionally including more than one) B, where A is not present (and optionally including elements other than A); in yet another implementation, refer to at least one (optionally including more than one) A, and at least one (optionally including more than one) B (and optionally including other elements); and so on.

[0072] As used herein, the terms "approximately," "approximately," and / or "substantially," when used in conjunction with stated value(s) and / or geometric configuration(s) or relationship(s), are intended to convey that the value or property so defined is nominally the stated value or described property. In some cases, the terms "approximately," "approximately," and / or "substantially" may generally mean and / or generally be expected to be within a desired tolerance of the stated value or property (e.g., plus or minus 10% of the stated value or property). For example, a value of approximately 0.01 may include 0.009 and 0.011, a value of approximately 0.5 may include 0.45 and 0.55, a value of approximately 10 may include 9 to 11, and a value of approximately 1000 may include 900 to 1100. Similarly, a first surface may be described as being substantially parallel to a second surface when the surfaces are nominally parallel. While the stated values, configurations, and / or relationships may be desirable, it should be understood that some variation may occur due to, for example, manufacturing tolerances or other practical considerations (such as, for example, pressure or force applied by a portion of a device, catheter, lumen, etc.). Thus, the terms "about," "approximately," and / or "substantially" may be used herein to account for such tolerances and / or considerations.

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

Claims

1. A system comprising: a cooling unit configured to receive the inlet air flow and remove heat from the inlet air flow to produce a cooling air flow at a cooling temperature; an absorber fluidly coupled to the cooling unit, the absorber defining a liquid / air interface configured to expose the cooling air stream to a liquid desiccant such that the liquid desiccant removes moisture from the cooling air stream at an absorber moisture removal rate and produces 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 exposure to the cooling air stream, remove moisture from the liquid desiccant at a desorber moisture removal rate, and then direct the liquid desiccant back to the absorber; as well as a control unit operatively 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 discharge rate to produce the supply air flow at a target temperature and a target humidity.

2. The system of claim 1, wherein: The regenerator further comprises a heating unit disposed upstream of the desorber, wherein the heating unit is configured to: transferring heat to a regeneration stream to produce a preheated stream; as well as At the desorber, the preheated stream is exposed to the liquid desiccant to remove the moisture from the liquid desiccant at the desorber moisture removal rate.

3. The system of claim 2, wherein: The system further comprises a heat pump, and the heating unit comprises: fan; a heating coil, the heating coil being the condenser of the heat pump; and a sensor configured to measure the temperature of the preheated stream, and The control unit is further configured to: receiving a signal from the sensor indicative of a measured temperature of the preheated stream; and At least one of the cooling temperature, the absorber moisture removal rate, or the desorber moisture discharge rate is adjusted based on the signal.

4. The system of claim 3, wherein: The sensor is a first sensor, the signal is a first signal, and the cooling unit comprises: fan; a cooling coil, the cooling coil being the evaporator of the heat pump; and a second sensor configured to measure at least one of the cooling temperature or humidity of the cooling air flow; The control unit is further configured to: receiving a second signal from the second sensor, the second signal indicative of at least one of the measured cooling temperature or humidity of the cooling air flow; and At least one of the cooling temperature, the absorber moisture removal rate, or the desorber moisture discharge rate is adjusted based on the second signal.

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 condenser.

7. The system of claim 5, further comprising an auxiliary condensing coil configured to receive an external air flow 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 the amount of heat delivered to the heating unit.

9. The system of claim 1, wherein: The regenerator includes an electrochemical regenerator.

10. 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 the 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 mode prioritizing the dew point of the supply air.

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 prioritizing supply dry bulb temperature.

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

14. A method comprising: receiving an inlet air flow at a cooling unit; reducing the enthalpy of the inlet air flow via the cooling coils of the cooling unit to produce a cooling air flow at a cooling temperature and humidity, directing the cooling air flow to an absorber fluidly coupled to the cooling unit; exposing the cooling air stream to a liquid desiccant at a liquid / air interface of the absorber such that the liquid desiccant removes moisture from the cooling air stream at an absorber moisture removal rate and produces a supply air stream at a target supply temperature and humidity; After the liquid desiccant is exposed to the cooling air stream in the absorber, directing the liquid desiccant to a regenerator, the regenerator comprising a desorber; removing moisture from the liquid desiccant at the desorber at a desorber moisture removal rate; After removing the moisture at the desorber, directing the liquid desiccant back to the absorber; as well as At least one of the change in enthalpy of the inlet air stream, the absorber moisture removal rate, or the desorber moisture discharge rate is adjusted through the cooling coil using a control unit operatively coupled to the cooling unit, the absorber, and the regenerator to produce the supply air stream at the target supply temperature and / or humidity.

15. The method of claim 14, wherein: receiving, at the control unit, signals from sensors, the signals indicating an air supply temperature and an air supply humidity measured by the sensors; determining, with the control unit, a temperature difference between a measured air supply temperature and a target air supply temperature; determining, with the control unit, a humidity difference between a measured air supply humidity and a target air supply humidity; as well as Adjusting, via the control unit and based on at least one of the temperature difference or the humidity difference, at least one of (1) the amount of heat entering the desorber or the quality of the heat to change the desorber moisture removal rate, or (2) the enthalpy change performed by the cooling unit to produce the supply air flow at the target air supply temperature and the target air supply humidity.

16. The method of claim 15, wherein: In order to prioritize or respond to changes in the target supply air humidity in order to maintain the target supply air humidity: relatively quickly adjusting, via the control unit and based on the humidity difference, a change in enthalpy of the supply air in the cooling unit to produce the air supply at the target supply humidity; as well as At least one of the amount of heat entering the desorber or the quality of the heat is relatively slowly adjusted via the control unit and based on the temperature difference.

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

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

19. The method of claim 17, wherein: The supply air dry bulb temperature is maintained within 1 degree of a target supply air dry bulb temperature.

20. The method of claim 18, wherein: The supply air dry bulb temperature is maintained within 1 degree of a target supply air dry bulb temperature.

21. The method of claim 15, wherein: To prioritize maintaining the target supply air temperature or in response to changes in the target supply air temperature: relatively rapidly adjusting, via the control unit and based on the temperature difference, a change in enthalpy of the supply air in the cooling unit to produce the air supply at the target supply air humidity; as well as At least one of the amount of heat entering the desorber or the quality of the heat is relatively slowly adjusted via the control unit and based on the humidity difference.

22. The method of claim 21, wherein: The supply air dry bulb temperature is maintained within 1.0 degrees of a target supply air dry bulb temperature.

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

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

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

26. The method of claim 15, wherein: The enthalpy change performed by the cooling unit results in the cooling air flow being below a dew point temperature of the inlet air flow, and the cooling unit removes moisture at a condensate moisture removal rate.

27. The method of claim 15, wherein: The enthalpy change performed by the cooling unit is varied by varying the mass flow rate of the refrigerant through the cooling coils of the cooling unit.

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

29. The method of claim 15, wherein: Removing moisture from the liquid desiccant at the desorber comprises: passing a regeneration stream through a heating unit included in the regenerator, the heating unit being coupled to the desorber, the heating unit comprising a fan and a heating coil to generate a preheated air stream; and The preheated air stream is exposed to the liquid desiccant at a liquid / air interface of the desorber to remove the moisture from the liquid desiccant at the desorber moisture removal rate.

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

31. The method of claim 30, wherein: The heating unit is operatively coupled to the cooling coil via a heat pump and transfers heat from the cooling coil to the heating coil.

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

33. The method of claim 32, wherein: The portion of the heat removed by the outside air flow is adjusted by varying the speed of a fan that draws the outside air flow through the auxiliary condensing coil.

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

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

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

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

39. The method of claim 38, wherein The volume of air delivered through the heating coil is controlled by varying the speed of the heating unit's fan.

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

41. The method of claim 15, wherein: The regulating includes regulating, via the control unit and based on at least one of the temperature difference or the humidity difference, (1) at least one of the amount of heat entering the desorber or the mass of the heat to change the desorber moisture removal rate, and (2) the enthalpy change performed by the cooling unit to produce the supply air flow at the target air supply temperature and the target air supply humidity.

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

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