Hydrostatically compensated compressed gas energy storage system

1. A compressed gas energy storage system comprising:

a) an accumulator having a primary opening, an upper wall, a lower wall and an accumulator interior at least partially bounded by the upper wall and lower wall, the accumulator containing a layer of compressed gas atop a layer of liquid;

b) a gas compressor and expander subsystem having a least a first compression stage that is spaced apart from the accumulator and a first expansion stage,

c) a first gas supply conduit having an upper end in communication with the first compression stage and a lower end in communication with a first location in the accumulator interior for conveying compressed gas into the compressed gas layer;

d) a shaft having a lower end adjacent the primary opening, an upper end spaced apart from the lower end, and a shaft sidewall extending upwardly from the lower end to the upper end and at least partially bounding a shaft interior containing a quantity of a liquid, the shaft being fluidly connectable to a liquid source/sink via a liquid supply conduit and wherein at least the first gas supply conduit passes through the shaft interior and is at least partially submerged in the quantity of the liquid; and

e) a partition positioned at the lower end of the shaft and covering the primary opening and separating the accumulator interior from the shaft interior, the partition having an outer surface in communication with the shaft interior and an opposing inner surface in communication with the accumulator interior;

wherein at least one of the layer of compressed gas and the layer of liquid bears against and exerts an accumulator force on the inner surface of the partition and the quantity of liquid within the shaft bears against and exerts a counter force on the outer surface of the partition, whereby a net force acting on the partition while the compressed gas energy storage system is in use is a difference between the accumulator force and the counter force and is less than the accumulator force.

2. The compressed gas energy storage system of claim 1 , further comprising a second gas conduit that is spaced apart from the first gas conduit, the second gas conduit having a lower end in communication with a second location in the accumulator interior and an upper end that is spaced apart from the upper end of the first gas conduit and is in fluid communication with the first expansion stage.

3. The compressed gas energy storage system of claim 2 , further comprising a third gas conduit that is spaced apart from the first gas conduit and the second gas conduit, the third gas conduit having a lower end in communication with a third location in the accumulator interior and an upper end that is spaced apart from the upper end of the first gas conduit and the upper end of the second gas conduit and is in fluid communication with a second expander that is spaced apart from the first expansion stage.

4. The compressed energy storage system of claim 1 , wherein only the first gas conduit extends through the shaft interior and is submerged in the quantity of liquid contained in the shaft, and the second gas conduit and third gas conduit are external to the shaft.

5. The compressed gas energy storage system of claim 1 , further comprising a liquid conduit providing fluid communication between the liquid in the shaft interior and the layer of liquid in the accumulator, whereby liquid can flow between the shaft interior and the layer of liquid in the accumulator in response to changes in the pressure of the layer of compressed gas.

6. The compressed gas energy storage system of claim 5 , wherein an upper end of the liquid conduit is proximate the upper wall of the partition.

7. The compressed gas energy storage system of claim 5 , wherein the liquid conduit passes through the partition.

8. The compressed gas energy storage system of claim 5 , wherein a lower end of the liquid conduit is submerged in the layer of liquid within the accumulator and remains fluidly isolated from the layer of gas within the accumulator when the compressed gas energy storage system is in use.

9. The compressed gas energy storage system of claim 1 , wherein when a pressure of the layer of compressed gas is increased by conveying additional gas into the layer of compressed gas a magnitude of the gas force is increased and liquid is conveyed through the liquid conduit from the layer of liquid in the accumulator to the shaft interior, and when the pressure of the layer of compressed gas is decreased by releasing gas from the layer of compressed gas, the magnitude of the gas force is decreased and liquid is conveyed through the liquid conduit from the shaft interior to the layer of liquid in the accumulator.

10. The compressed gas energy storage system of claim 1 , wherein at least the first gas supply conduit passes through the partition.

11. The compressed gas energy storage system of claim 1 , further comprising a thermal storage subsystem provided in fluid communication downstream from the gas compressor and expander subsystem and upstream of the accumulator, whereby compressed gas exiting the gas compressor and expander subsystem at an exit temperature passes through the thermal storage subsystem whereby thermal energy is extracted from the compressed gas and stored in the thermal storage subsystem and the temperature of the gas exiting the thermal storage subsystem is reduced to a storage temperature that is less than the exit temperature.

12. A compressed gas energy storage system comprising:

a) an accumulator having a primary opening, an upper wall, a lower wall and an accumulator interior at least partially bounded by the upper wall and lower wall, the accumulator containing a layer of compressed gas atop a layer of liquid;

b) a gas compressor and expander subsystem having a least a first compression stage that is spaced apart from the accumulator and a first expansion stage,

c) a first gas supply conduit having an upper end in communication with the first compression stage and a lower end in communication with a first location in the accumulator interior for conveying compressed gas into the compressed gas layer;

d) a shaft having a lower end adjacent the primary opening, an upper end spaced apart from the lower end, and a shaft sidewall extending upwardly from the lower end to the upper end and at least partially bounding a shaft interior containing a quantity of a liquid, the shaft being fluidly connectable to a liquid source/sink via a liquid supply conduit and wherein at least the first gas supply conduit is external to the shaft;

e) a partition positioned at the lower end of the shaft and covering the primary opening and separating the accumulator interior from the shaft interior, the partition having an outer surface in communication with the shaft interior and an opposing inner surface in communication with the accumulator interior;

wherein at least one of the layer of compressed gas and the layer of liquid bears against and exerts an accumulator force on the inner surface of the partition and the quantity of liquid within the shaft bears against and exerts a counter force on the outer surface of the partition, whereby a net force acting on the partition while the compressed gas energy storage system is in use is a difference between the accumulator force and the counter force and is less than the accumulator force.

13. The compressed gas energy storage system of claim 12 , further comprising a liquid conduit providing fluid communication between the liquid in the shaft interior and the layer of liquid in the accumulator, whereby liquid can flow between the shaft interior and the layer of liquid in the accumulator in response to changes in pressure of the layer of compressed gas.

14. The compressed gas energy storage system of claim 13 , wherein an upper end of the liquid supply conduit is proximate the outer surface of the partition.

15. The compressed gas energy storage system of claim 13 , wherein the liquid supply conduit passes through the partition.

16. The compressed gas energy storage system of claim 13 , wherein a lower end of the liquid supply conduit is submerged in the layer of liquid within the accumulator and remains fluidly isolated from the layer of gas within the accumulator when the compressed gas energy storage system is in use.

17. The compressed gas energy storage system of claim 12 , wherein when a pressure of the layer of compressed gas is increased by conveying additional gas into the layer of compressed gas a magnitude of the gas force is increased and liquid is conveyed through the liquid supply conduit from the layer of liquid in the accumulator to the shaft interior, and when the pressure of the layer of compressed gas is decreased by releasing gas from the layer of compressed gas the magnitude of the gas force is decreased and liquid is conveyed through the liquid supply conduit from the shaft interior to the layer of liquid in the accumulator.

18. The compressed gas energy storage system of claim 12 , further comprising a thermal storage subsystem provided in fluid communication downstream from the gas compressor and expander subsystem and upstream of the accumulator, whereby compressed gas exiting the gas compressor and expander subsystem at an exit temperature passes through the thermal storage subsystem whereby thermal energy is extracted from the compressed gas and stored in the thermal storage subsystem and a temperature of the gas exiting the thermal storage subsystem is reduced to a storage temperature that is less than the exit temperature.

19. The compressed gas energy storage system of claim 12 , further comprising a second gas conduit that is spaced apart from the first supply gas conduit, the second gas conduit having a lower end in communication with a second location in the accumulator interior and an upper end that is spaced apart from the upper end of the first supply gas conduit and is in fluid communication with the first expansion stage.

20. The compressed gas energy storage system of claim 19 , further comprising a third gas conduit that is spaced apart from the first supply gas conduit and the second gas conduit, the third gas conduit having a lower end in communication with a third location in the accumulator interior and an upper end that is spaced apart from the upper end of the first supply gas conduit and the upper end of the second gas conduit and is in fluid communication with a second expander that is spaced apart from the first expansion stage.