CO

1. A CO 2 refrigeration system comprising:

a CO 2 refrigeration subsystem that provides cooling for a refrigeration load using carbon dioxide (CO 2 ) as a refrigerant;

a direct CO 2 heat exchange subsystem that uses the CO 2 refrigerant from the CO 2 refrigeration subsystem to provide heating or cooling for a building zone, the direct CO 2 heat exchange subsystem comprising a heat exchanger that exchanges heat directly between the CO 2 refrigerant and an airflow provided to the building zone;

a gas cooler/condenser that cools the CO 2 refrigerant and discharges the cooled CO 2 refrigerant into a cooled refrigerant line;

wherein the direct CO 2 heat exchange subsystem receives the cooled CO 2 refrigerant from the cooled refrigerant line and delivers the cooled CO 2 refrigerant to the heat exchanger to provide cooling for the building zone;

wherein the direct CO 2 heat exchange subsystem further comprises a cooled refrigerant intake line connecting the cooled refrigerant line to the heat exchanger; and an expansion valve located along the cooled refrigerant intake line upstream of the heat exchanger;

a controller configured to operate the expansion valve to control an amount of the cooled CO 2 refrigerant provided to the heat exchanger;

a high pressure valve that receives the cooled CO 2 refrigerant from the cooled refrigerant line, expands the cooled CO 2 refrigerant, and discharges the expanded CO 2 refrigerant into an expanded refrigerant line;

wherein the controller monitors a position of the high pressure valve and operates the expansion valve based on the position of the high pressure valve.

2. The CO 2 refrigeration system of claim 1 , wherein the controller monitors a temperature of the building zone and operates the expansion valve based on the temperature of the building zone.

3. The CO 2 refrigeration system of claim 1 , wherein the controller determines an amount of superheat of the cooled CO 2 refrigerant and operates the expansion valve based on the determined amount of superheat.

4. The CO 2 refrigeration system of claim 1 , further comprising a high pressure valve that receives the cooled CO 2 refrigerant from the cooled refrigerant line, expands the cooled CO 2 refrigerant, and discharges the expanded CO 2 refrigerant into an expanded refrigerant line;

wherein the direct CO 2 heat exchange subsystem comprises a discharge line that receives the CO 2 refrigerant from the heat exchanger and discharges the CO 2 refrigerant into the expanded refrigerant line.

5. The CO 2 refrigeration system of claim 4 , wherein the expanded refrigerant line connects the high pressure valve to a receiver that separates the expanded CO 2 refrigerant into a liquid CO 2 refrigerant and a gas CO 2 refrigerant.

6. The CO 2 refrigeration system of claim 1 , wherein the CO 2 refrigeration subsystem comprises a compressor that compresses the CO 2 refrigerant to a high temperature high pressure state and discharges the hot compressed refrigerant into a hot compressed refrigerant line;

wherein the direct CO 2 heat exchange subsystem receives the hot compressed CO 2 refrigerant from the hot compressed refrigerant line and delivers the hot compressed CO 2 refrigerant to the heat exchanger to provide heating for the building zone.

7. The CO 2 refrigeration system of claim 6 , wherein the direct CO 2 heat exchange subsystem comprises:

a hot refrigerant intake line that receives the hot compressed CO 2 refrigerant from the hot compressed refrigerant line and provides the hot compressed CO 2 refrigerant to the heat exchanger; and

a hot refrigerant discharge line that receives the CO 2 refrigerant from the heat exchanger and provides the CO 2 refrigerant to the hot compressed refrigerant line.

8. The CO 2 refrigeration system of claim 7 , wherein the direct CO 2 heat exchange subsystem comprises a control valve operable to control an amount of the hot compressed CO 2 refrigerant provided to the heat exchanger.

9. The CO 2 refrigeration system of claim 8 , wherein the control valve is a three-way valve that receives the hot compressed CO 2 refrigerant from the hot refrigerant intake line and directs the hot compressed CO 2 refrigerant to either the heat exchanger or the hot refrigerant discharge line based on a position of the control valve.

10. The CO 2 refrigeration system of claim 8 , further comprising a controller configured to operate the control valve to control an amount of the hot compressed CO 2 refrigerant provided to the heat exchanger.

11. The CO 2 refrigeration system of claim 10 , wherein the controller monitors a temperature of the building zone and operates the control valve based on the temperature of the building zone.

12. The CO 2 refrigeration system of claim 10 , wherein the controller determines a difference between a temperature of the hot compressed CO 2 refrigerant and the temperature of the building zone and operates the control valve based on the difference.

13. A CO 2 cooling system for a building, the CO 2 cooling system comprising:

a CO 2 refrigeration subsystem that provides cooling for a refrigeration load using carbon dioxide (CO 2 ) as a refrigerant;

a gas cooler/condenser that cools the CO 2 refrigerant and discharges the cooled CO 2 refrigerant into a cooled refrigerant line;

a heat exchanger that receives the cooled CO 2 refrigerant from the cooled refrigerant line and exchanges heat directly between the cooled CO 2 refrigerant and an airflow provided to the building zone; and

a high pressure valve that receives the cooled CO 2 refrigerant from the cooled refrigerant line, expands the cooled CO 2 refrigerant, and discharges the expanded CO 2 refrigerant into an expanded refrigerant line;

wherein the heat exchanger discharges the CO 2 refrigerant into the expanded refrigerant line.

14. A CO 2 heating system for a building, the CO 2 heating system comprising:

a CO 2 refrigeration subsystem that provides cooling for a refrigeration load using carbon dioxide (CO 2 ) as a refrigerant;

a compressor that compresses the CO 2 refrigerant to a high temperature high pressure state and discharges the hot compressed refrigerant into a hot compressed refrigerant line;

a heat exchanger that receives the hot compressed CO 2 refrigerant from the hot compressed refrigerant line and exchanges heat directly between the hot compressed CO 2 refrigerant and an airflow provided to the building zone;

a hot refrigerant discharge line that receives the CO 2 refrigerant from the heat exchanger and provides the CO 2 refrigerant to the hot compressed refrigerant line;

a control valve operable to control an amount of the hot compressed CO 2 refrigerant provided to the heat exchanger;

wherein the control valve is a three-way valve that receives the hot compressed CO 2 refrigerant from the hot refrigerant intake line and directs the hot compressed CO 2 refrigerant to either the heat exchanger or the hot refrigerant discharge line based on a position of the control valve.

15. A CO 2 refrigeration system comprising:

a CO 2 refrigeration subsystem that provides cooling for a refrigeration load using carbon dioxide (CO 2 ) as a refrigerant;

a direct CO 2 heat exchange subsystem that uses the CO 2 refrigerant from the CO 2 refrigeration subsystem to provide heating or cooling for a building zone, the direct CO 2 heat exchange subsystem comprising a heat exchanger that exchanges heat directly between the CO 2 refrigerant and an airflow provided to the building zone;

a gas cooler/condenser that cools the CO 2 refrigerant and discharges the cooled CO 2 refrigerant into a cooled refrigerant line;

a high pressure valve that receives the cooled CO 2 refrigerant from the cooled refrigerant line, expands the cooled CO 2 refrigerant, and discharges the expanded CO 2 refrigerant into an expanded refrigerant line;

wherein the direct CO 2 heat exchange subsystem receives the cooled CO 2 refrigerant from the cooled refrigerant line and delivers the cooled CO 2 refrigerant to the heat exchanger to provide cooling for the building zone; and

wherein the direct CO 2 heat exchange subsystem includes a discharge line that receives the CO 2 refrigerant from the heat exchanger and discharges the CO 2 refrigerant into the expanded refrigerant line.

16. The CO 2 refrigeration system of claim 15 , further comprising a controller configured to operate the expansion valve to control an amount of the cooled CO 2 refrigerant provided to the heat exchanger.

17. A CO 2 refrigeration system comprising:

a CO 2 refrigeration subsystem that provides cooling for a refrigeration load using carbon dioxide (CO 2 ) as a refrigerant;

a direct CO 2 heat exchange subsystem that uses the CO 2 refrigerant from the CO 2 refrigeration subsystem to provide heating or cooling for a building zone, the direct CO 2 heat exchange subsystem comprising a heat exchanger that exchanges heat directly between the CO 2 refrigerant and an airflow provided to the building zone;

wherein the CO 2 refrigeration subsystem comprises a compressor that compresses the CO 2 refrigerant to a high temperature high pressure state and discharges the hot compressed refrigerant into a hot compressed refrigerant line;

wherein the direct CO 2 heat exchange subsystem receives the hot compressed CO 2 refrigerant from the hot compressed refrigerant line and delivers the hot compressed CO 2 refrigerant to the heat exchanger to provide heating for the building zone;

wherein the direct CO 2 heat exchange subsystem includes a hot refrigerant intake line that receives the hot compressed CO 2 refrigerant from the hot compressed refrigerant line and provides the hot compressed CO 2 refrigerant to the heat exchanger and a hot refrigerant discharge line that receives the CO 2 refrigerant from the heat exchanger and provides the CO 2 refrigerant to the hot compressed refrigerant line;

wherein the direct CO 2 heat exchange subsystem comprises a three-way control valve that receives the hot compressed CO 2 refrigerant from the hot refrigerant intake line and directs the hot compressed CO 2 refrigerant to either the heat exchanger or the hot refrigerant discharge line based on a position of the control valve to control an amount of the hot compressed CO 2 refrigerant provided to the heat exchanger.

18. The CO 2 refrigeration system of claim 17 , further comprising a controller configured to operate the control valve to control an amount of the hot compressed CO 2 refrigerant provided to the heat exchanger.

19. The CO 2 refrigeration system of claim 18 , wherein the controller monitors a temperature of the building zone and operates the control valve based on the temperature of the building zone.