Refrigerant management control and method for a thermal energy storage system

An air conditioning system comprising a plurality of refrigerant circuits, each refrigerant circuit having a compressor, a condensing unit, a temporary refrigerant storage vessel, a storage module containing a thermal energy storage medium, a liquid refrigerant pump associated with the module, expansion means and an evaporator operatively interconnected, each of said refrigerant circuits being operable in (i) a shift cooling mode wherein the module is utilized as a condenser coil and the liquid refrigerant pump circulates refrigerant between the module and the evaporator to provide space cooling, (ii) a direct cooling mode wherein the condensing unit and evaporator are utilized in their normal manner to provide space cooling, and (iii) a storage medium cooling mode wherein the module is utilized as an evaporator for cooling the storage medium, said system further including:

• control means responsive to a predetermined first condition for controlling a first selected one or more of said refrigerant circuits to operate in a first transitory mode wherein the compressor and liquid refrigerant pump of each of said first selected one or more of said refrigerant circuits is off and the storage module of each of said first selected one or more of said refrigerant circuits is utilized as a heat sink to draw refrigerant from the corresponding condensing unit, temporary refrigerant storage vessel and evaporator into the storage module, said control means being further responsive to said first condition and completion of said first transitory mode for controlling said first selected one or more of said refrigerant circuits to operate in the shift cooling mode;
• said control means being responsive to a predetermined second condition for controlling a second selected one or more of said refrigerant circuits to operate in a second transitory mode wherein the compressor of each of said second selected one or more of said refrigerant circuits is operated to draw refrigerant into the corresponding condensing unit and temporary refrigerant storage vessel, said control means being further responsive to said second condition and completion of said second transitory mode for controlling said second selected one or more of said refrigerant circuits to operate in the direct cooling mode;
• said control means being responsive to a predetermined third condition for controlling a third selected one or more of said refrigerant circuits to operate in the storage medium cooling mode.

A method of operating an air conditioning system having a compressor, a condensing unit, a temporary refrigerant storage vessel, a storage module containing a thermal energy storage medium, a liquid refrigerant pump associated with the storage module, expansion means, and an evaporator operatively interconnected, said method comprising the steps of:

• temporarily interconnecting the condensing unit, temporary refrigerant storage vessel, storage module and evaporator and operating the system in a first transitory mode in response to a predetermined first condition, the compressor and the liquid refrigerant pump being off and the storage module being utilized as a heat sink to draw refrigerant from the condenser, temporary refrigerant storage vessel and evaporator into the storage module when the system is operated in said first transitory mode;
• isolating the compressor, condensing unit and temporary refrigerant storage vessel and operating the system in a shift cooling mode in response to said first condition and completion of said first transitory mode, the storage module being utilized as a condenser coil and the liquid refrigerant pump being activated to circulate refrigerant between the storage module and evaporator when the system is operated in the shift cooling mode, the system being operated in the first transitory mode before the system is operable in the shift cooling mode;
• temporarily inhibiting the flow of refrigerant to the storage module and evaporator and operating the system in a second transitory mode in response to a predetermined second condition, the compressor being operated to draw refrigerant into the condensing unit and temporary refrigerant storage vessel when the system is operated in the second transitory mode;
• isolating the storage module and operating the system in a direct cooling mode in response to said second condition and completion of said second transitory mode, the evaporator being utilized for space cooling and excess refrigerant being stored in the temporary refrigerant storage vessel when the system is operated in the direct cooling mode, the system being operated in the second transitory mode before the system is operable in the direct cooling mode;
• and
• isolating the evaporator to allow the system to be operated in a storage medium cooling mode in response to a predetermined third condition, the storage module being utilized as an evaporator for cooling the storage medium and excess refrigerant being stored in the temporary refrigerant storage vessel when the system is operated in the storage medium cooling mode.

A method of operating an air conditioning system having a plurality of refrigerant circuits, each refrigerant circuit including a compressor, a condensing unit, a temporary refrigerant storage vessel, a storage module containing a thermal energy storage medium, a liquid refrigerant pump associated with the module, expansion means and an evaporator operatively interconnected, each of said refrigeration circuits being operable in (i) a shift cooling mode wherein the module is utilized as a condenser coil and the liquid refrigerant pump circulates refrigerant between the module and the evaporator to provide space cooling, (ii) a direct cooling mode wherein the condensing unit and evaporator are utilized in their normal manner to provide space cooling, and (iii) a storage medium cooling mode wherein the module is utilized as an evaporator for cooling the storage medium, said method comprising the steps of:

• operating a first selected one or more of said refrigerant circuits in a first transitory mode in response to a predetermined first condition, the compressor and liquid refrigerant pump of each of said first selected one or more of said refrigerant circuits being off and the storage module of each of said first selected one or more of said refrigerant circuits being utilized as a heat sink to draw refrigerant from the corresponding condensing unit, temporary refrigerant storage vessel and evaporator into the corresponding storage module when said first selected one or more of said refrigerant circuits is operated in said first transitory mode;
• operating said first selected one or more of said refrigerant circuits in said shift cooling mode in response to said first condition and completion of said first transitory mode;
• operating a second selected one or more of said refrigerant circuits in a second transitory mode in response to a predetermined second condition, the compressor of each of said second selected one or more of said refrigerant circuits being operated to draw refrigerant into the corresponding condensing unit and temporary refrigerant storage vessel when said second selected one or more of said refrigerant circuits is operated in said second transitory mode;
• operating said second selected one or more of said refrigerant circuits in the direct cooling mode in response to said second condition and completion of said second transitory mode;
• and
• operating a third selected one or more of said refrigerant circuits to operate in the storage medium cooling mode in response to a predetermined third condition.