Economized cycle with thermal energy storage

1. An air conditioning system comprising:

a refrigeration circuit having a refrigerant and an economizer circuit, the refrigeration circuit including a compressor, a condenser, a heat exchanger, and an evaporator; and

a subcooling circuit thermally coupled to the refrigeration circuit, the subcooling circuit including a thermal energy storage (TES) unit and a phase change material (PCM) for thermal exchange with the refrigerant;

a heat exchanger circuit having a heat transfer medium and thermally coupled to the refrigeration circuit and the subcooling circuit, the heat transfer medium cooled by the evaporator;

wherein the heat exchanger circuit is thermally coupled to the TES unit to transfer thermal energy from the heat transfer medium cooled by the evaporator to the subcooling circuit to cool and charge the PCM stored in the TES unit and return the heat transfer medium to the evaporator.

2. The system of claim 1 , wherein the refrigeration circuit further comprises:

a first conduit fluidly coupled between the condenser and the heat exchanger and configured to supply a first portion of the refrigerant from the condenser to the heat exchanger; and

a second conduit fluidly coupled between the first conduit and the compressor and configured to supply a second portion of the refrigerant from the condenser to the heat exchanger, wherein the second conduit is the economizer circuit.

3. The system of claim 1 , wherein the subcooling circuit is thermally coupled to the refrigeration circuit via the heat exchanger.

4. The system of claim 1 , wherein the heat exchanger circuit is thermally coupled to the evaporator to transfer thermal energy between a serviced space and the refrigeration circuit, thus cooling the serviced space.

5. The system of claim 1 , wherein the heat exchanger circuit comprises a bypass line configured to bypass the heat transfer medium around the TES unit.

6. The system of claim 1 , wherein the heat exchanger comprises a first heat exchanger and a second heat exchanger.

7. The system of claim 6 , wherein the refrigeration circuit further comprises:

a first conduit fluidly coupled between the condenser and the first heat exchanger and configured to supply a first portion of the refrigerant from the condenser to the first heat exchanger; and

a second conduit fluidly coupled between the first conduit and the compressor and configured to supply a second portion of refrigerant form the condenser to the second heat exchanger, wherein the second conduit is the economizer circuit.

8. The system of claim 7 , wherein the subcooling circuit is thermally coupled to the first heat exchanger and the second heat exchanger, the subcooling circuit configured to selectively supply cooled PCM stored in the TES unit to the first heat exchanger to provide supplemental cooling to the refrigeration circuit.

9. The system of claim 1 , wherein the PCM has a transition temperature of greater then 32 degrees F.

10. A method of operating an air conditioning system, the method comprising:

operating a refrigeration circuit to cool a first portion of refrigerant, the refrigeration circuit configured to cool a heat transfer medium supplied to a serviced space;

cooling a second portion of the refrigerant in an economizer circuit; and

operating a subcooling circuit thermally coupled to the refrigeration circuit, the subcooling circuit including a thermal energy storage (TES) unit and a phase change material (PCM) for thermal exchange with the first portion of refrigerant;

directing the heat transfer medium to the TES unit to transfer thermal energy from the heat transfer medium cooled by the refrigeration circuit to the subcooling circuit to cool and charge the PCM stored in the TES unit and returning the heat transfer medium to the evaporator.

11. The method of claim 10 , further comprising cooling the first portion of refrigerant in a heat exchanger with the PCM from the TES unit, the refrigeration circuit including a compressor, a condenser, and an evaporator.

12. The method of claim 11 , further comprising cooling the first portion of refrigerant in the heat exchanger with the second portion of refrigerant.

13. The method of claim 10 , further comprising:

cooling the first portion of refrigerant in a first heat exchanger with the PCM from the TES unit; and

cooling the PCM in a second heat exchanger with the second portion of refrigerant, the refrigeration circuit including a compressor, a condenser, and an evaporator.