Liquid desiccant air conditioning system and control methods

A method, comprising:

• receiving, at a cooling unit, an inlet air stream;
• reducing, via a cooling coil of the cooling unit, enthalpy of the inlet air stream to produce a cooled air stream at a target enthalpy;
• directing the cooled air stream to an absorber that is fluidically coupled to the cooling unit;
• exposing, at a liquid/air interface of the absorber, the cooled air stream to a liquid desiccant such that the liquid desiccant removes moisture from the cooled air stream at an absorber moisture removal rate and produces a supply air stream at a target relative humidity;
• directing the liquid desiccant after the liquid desiccant is exposed to the cooled air stream in the absorber to a regenerator, the regenerator including a desorber;
• removing, at the desorber, moisture from the liquid desiccant at a desorber moisture rejection rate;
• and
• directing, after removing the moisture at the desorber, the liquid desiccant back to the absorber.

A method of operating a liquid desiccant system to adjust one or both of a temperature or a humidity of a supply air stream, the liquid desiccant system including a cooling unit, an absorber, a regenerator, and a control unit operably coupled to the cooling unit, the absorber, and the regenerator, the method comprising:

• receiving, at the control unit, a target temperature and a target humidity of the supply air stream;
• measuring, with a sensor disposed downstream of the absorber, a temperature and a humidity of the supply air stream;
• calculating, with the control unit, a temperature difference between the measured temperature and the target temperature of the supply air stream, and a humidity difference between the measured humidity and the target humidity of the supply air stream;
• determining, with the control unit, a mode of operating the liquid desiccant system that reduces the temperature difference and the humidity difference;
• and
• implementing, via the control unit, the mode of operating the liquid desiccant system.

A method of operating a liquid desiccant system to produce a supply air, the liquid desiccant system including a first and a second moisture removal device operably coupled to a control unit, the method comprising:

• receiving, at the control unit, a signal from a sensor disposed downstream of the second moisture removal device, the signal indicative of a supply air temperature and humidity measured by the sensor;
• determining, with the control unit, a temperature difference between the measured supply air temperature and a target supply air temperature;
• determining, with the control unit, a humidity difference between the measured supply air humidity and a target air supply humidity;
• and
• increasing, via the control unit and based on at least one of the temperature difference or the humidity difference, a first moisture removal rate at the first moisture removal device such that a second moisture removal rate at the second moisture removal device is minimized to produce the supply air at the target temperature and humidity.

A method of operating a liquid desiccant system, comprising:

• receiving, at a cooling unit, an inlet air stream;
• reducing, via a cooling coil of the cooling unit, enthalpy of the inlet air stream to produce a cooled air stream at a target enthalpy;
• directing the cooled air stream to an absorber that is fluidically coupled to the cooling unit;
• eliminating the flow of the liquid desiccant in the absorber to reduce an absorber moisture removal rate;
• exposing, at a liquid/air interface of the absorber, the cooled air stream to a liquid desiccant such that residual liquid desiccant removes moisture from the cooled air stream at a residual absorber moisture removal rate and produces a supply air stream;
• and
• intermittently, to remove the moisture gathered by the residual absorber desiccant:
• directing the liquid desiccant after the liquid desiccant is exposed to the cooled air stream in the absorber to a regenerator, the regenerator including a desorber;
• removing, at the desorber, moisture from the liquid desiccant at a desorber moisture rejection rate;
• and
• directing, after removing the moisture at the desorber, the liquid desiccant back to the absorber.