Use of external air for closed cycle inventory control

1. A method comprising:

(a) in a closed cycle system operating in a power generation mode, circulating a working fluid through a closed cycle fluid path including, in sequence, a compressor, a hot side heat exchanger, a turbine, and a cold side heat exchanger, wherein the closed cycle fluid path comprises a high pressure leg and a low pressure leg, and wherein the closed cycle system is configured to thermally contact the working fluid circulating through the cold side heat exchanger with a cold side thermal storage (“CTS”) medium;

(b) compressing a quantity of environmental air;

(c) thermally contacting the quantity of environmental air with at least a portion of the CTS medium; and

(d) subsequently to steps (b) and (c), injecting the quantity of environmental air into the low pressure leg.

2. The method of claim 1 , wherein the working fluid circulates through the closed cycle system in the same direction in both a charge mode and a discharge mode.

3. The method of claim 1 , further comprising:

extracting working fluid from the high pressure leg of the closed cycle fluid path;

storing the extracted working fluid in a working fluid storage tank; and

injecting the extracted working fluid from the working fluid storage tank into the low pressure leg.

4. The method of claim 1 , wherein step (b) occurs before step (c).

5. The method of claim 1 , wherein step (b) occurs after step (c).

6. The method of claim 1 , wherein thermally contacting the quantity of environmental air with at least the portion of CTS medium causes water to condense out of the quantity of environmental air.

7. The method of claim 1 , wherein injecting the quantity of environmental air into the low pressure leg is performed in response to a demand for increased power generation.

8. The method of claim 1 , wherein the working fluid is air.

9. A method comprising:

in a closed cycle system in a power generation mode, circulating a working fluid through a closed cycle fluid path including, in sequence, a compressor, a hot side heat exchanger, a turbine, and a cold side heat exchanger, wherein the closed cycle fluid path comprises a high pressure leg and a low pressure leg, and wherein the closed cycle system is configured to thermally contact the working fluid circulating through the cold side heat exchanger with a cold side thermal storage (“CTS”) medium;

expelling working fluid from the closed cycle fluid path; and

thermally contacting the expelled working fluid with at least a portion of the CTS medium.

10. The method of claim 9 , further comprising circulating the working fluid through the closed cycle system in the same direction in both a charge mode and a discharge mode.

11. The method of claim 9 , wherein expelling the working fluid from the closed cycle fluid path is performed in response to a demand for decreased power generation.

12. The method of claim 9 , wherein expelling working fluid from the closed cycle fluid path comprises expelling working fluid from the low pressure leg.

13. A system comprising:

a first compressor;

a hot side heat exchanger;

a turbine;

a cold side heat exchanger;

a working fluid circulating in a closed cycle fluid path through, in sequence, the first compressor, the hot side heat exchanger, the turbine, and the cold side heat exchanger, wherein the closed cycle fluid path comprises a high pressure leg and a low pressure leg;

a second compressor coupled to the low pressure leg and configured to, upon demand, compress environmental air and inject the compressed environmental air into the low pressure leg; and

a cold side thermal storage (“CTS”) medium, wherein the system is configured to thermally contact the working fluid circulating through the cold side heat exchanger with the CTS medium, wherein the system is configured to thermally contact the environmental air with at least a portion of the CTS medium.

14. The system of claim 13 , further comprising:

a dehumidifier configured to dehumidify the environmental air using at least a portion of the CTS medium,

wherein the dehumidifier supplies dehumidified environmental air to the second compressor for compressing.

15. The system of claim 13 , further comprising:

a dehumidifier configured to dehumidify the environmental air using at least a portion of the CTS medium,

wherein the second compressor supplies compressed environmental air to the dehumidifier for dehumidification.

16. The system of claim 13 , further comprising a working fluid storage tank containing working fluid at a pressure greater than a pressure of the working fluid in the low pressure leg, wherein the system is configured to, upon demand, inject working fluid from the working fluid storage tank into the low pressure leg simultaneously with the compressed environmental air.

17. The system of claim 13 , wherein the working fluid circulates through the system in the same direction in both a charge mode and a discharge mode.

18. A system comprising:

a compressor;

a hot side heat exchanger;

a turbine;

a cold side heat exchanger;

a working fluid circulating in a closed cycle fluid path through, in sequence, the compressor, the hot side heat exchanger, the turbine, and the cold side heat exchanger, wherein the closed cycle fluid path comprises a high pressure leg and a low pressure leg; and

a cold side thermal storage (“CTS”) medium, wherein the system is configured to thermally contact the working fluid circulating through the cold side heat exchanger with the CTS medium,

wherein the system is configured to expel working fluid from the closed cycle fluid path and thermally contact the expelled working fluid with at least a portion of the CTS medium.

19. The system of claim 18 , wherein the working fluid circulates through the system in the same direction in both a charge mode and a discharge mode.

20. The system of claim 18 , further comprising an auxiliary heat exchanger configured to thermally contact the expelled working fluid with at least the portion of the CTS medium.