Control systems for liquid desiccant air conditioning systems

A method of operating a liquid desiccant air-conditioning system to maintain target temperature and humidity level in a space, the liquid desiccant air conditioning system comprising:

• a conditioner for treating a first air stream flowing therethrough and provided to the space as a supplied air stream, said conditioner using a heat transfer fluid and a liquid desiccant to treat the first air stream;
• a device for measuring temperature and a device for measuring humidity in the supplied air stream;
• a regenerator connected to the conditioner such that the liquid desiccant can be circulated between the regenerator and the conditioner, the regenerator causing the liquid desiccant to desorb water vapor to a second air stream or to absorb water vapor from the second air stream depending on a selected mode of operation of the system;
• a refrigerant system;
• a first refrigerant-to-heat transfer fluid heat exchanger connected to the conditioner and the refrigerant system for exchanging heat between the refrigerant heated or cooled by the refrigerant system and the heat transfer fluid used in the conditioner;
• a second refrigerant-to-heat transfer fluid heat exchanger connected to the regenerator and the refrigerant system for exchanging heat between the refrigerant heated or cooled by the refrigerant system and the heat transfer fluid used in the regenerator;
• and
• a system controller for controlling operation of the system;
• wherein the method comprising the steps of:
• (a) measuring the temperature and humidity level in the supplied air stream;
• (b) comparing the temperature measured in (a) to a target temperature to determining a temperature error, and comparing the humidity level measured in (a) to a target humidity level to determine a humidity error;
• (c) comparing the humidity error and the temperature error on a common scale to determine the greater error;
• (d) using the greater error to drive the system controller to control operation of the system to reduce the greater error;
• (e) repeat (a) through (d) a plurality of times.