Heat exchange with compressed gas in energy-storage systems
In various embodiments, compressed-gas energy storage and recovery systems include a cylinder assembly for compression and/or expansion of gas, a reservoir for storage and/or supply of compressed gas, and a system for thermally conditioning gas within the reservoir.
1. A method for improving efficiency of a compressed-gas energy storage and recovery system, the method comprising:
(i) receiving energy from a power source comprising an electric generating plant or a source of renewable energy, receiving gas from an ambient atmosphere, storing the received energy in the form of compressed gas by compressing the gas within a cylinder assembly, and transferring compressed gas to a compressed-gas reservoir to store the compressed gas; and
(ii) transferring compressed gas from the compressed-gas reservoir to the cylinder assembly, expanding the compressed gas within the cylinder assembly to recover energy from the compressed gas, venting expanded gas to an ambient atmosphere, and converting the recovered energy into electricity; and
outside of the cylinder assembly, thermally conditioning the gas, via heat exchange with a heat-exchange fluid, during at least one of transferring compressed gas from the compressed-gas reservoir or transferring compressed gas to the compressed-gas reservoir.
2. The method of claim 1 , wherein thermally conditioning the gas comprises at least one of (i) heating compressed gas during the transfer from the compressed-gas reservoir or (ii) cooling compressed gas during the transfer to the compressed-gas reservoir.
3. The method of claim 1 , wherein the thermal conditioning of the gas is performed within the compressed-gas reservoir.
4. The method of claim 1 , wherein the thermal conditioning of the gas is performed within a conduit connecting the cylinder assembly to the compressed-gas reservoir.
5. The method of claim 1 , wherein thermally conditioning gas comprises circulating the heat-exchange fluid around the compressed-gas reservoir to exchange heat through a wall thereof with gas in the compressed-gas reservoir.
6. The method of claim 5 , further comprising thermally conditioning the heat-exchange fluid to maintain the heat-exchange fluid at a substantially constant temperature.
7. The method of claim 6 , wherein thermally conditioning the heat-exchange fluid comprises exchanging heat between the heat-exchange fluid and a separate liquid.
8. The method of claim 6 , wherein thermally conditioning the heat-exchange fluid comprises exchanging heat between the heat-exchange fluid and a separate gas.
9. The method of claim 1 , wherein thermally conditioning gas comprises submerging the compressed-gas reservoir in heat-exchange liquid.
10. The method of claim 1 , wherein thermally conditioning gas comprises spraying the heat-exchange fluid into the gas during the at least one of transferring gas from the compressed-gas reservoir or transferring gas to the compressed-gas reservoir.
11. The method of claim 10 , wherein the heat-exchange fluid is sprayed into the compressed-gas reservoir.
12. The method of claim 1 , wherein thermally conditioning gas comprises circulating the heat-exchange fluid through the gas, the heat-exchange fluid not in fluid communication with the gas.
13. The method of claim 12 , wherein the heat-exchange fluid is circulated (i) from a fluid reservoir containing heat-exchange fluid at a substantially constant temperature, (ii) into the gas, and (iii) back to the fluid reservoir.
14. The method of claim 1 , further comprising thermally conditioning the gas within the cylinder assembly during at least one of the compression or the expansion, thereby increasing efficiency of the energy storage and recovery.
15. The method of claim 14 , wherein the thermally conditioning the gas during at least one of the compression or the expansion renders the at least one of the compression or the expansion substantially isothermal.
16. The method of claim 1 , wherein (i) energy stored during compression of the gas originates from an intermittent renewable energy source of wind or solar energy, and (ii) energy is recovered via expansion of the gas when the intermittent renewable energy source is nonfunctional.
17. The method of claim 1 , wherein the expansion results in reciprocal motion of a boundary mechanism within the cylinder assembly, and further comprising converting the reciprocal motion into rotary motion.
18. The method of claim 1 , further comprising, outside the cylinder assembly, at least one of (i) heating gas prior to the expansion thereof or (ii) cooling gas after the compression thereof.
19. The method of claim 18 , wherein the at least one of (i) heating gas prior to the expansion thereof or (ii) cooling gas after the compression thereof is performed within the compressed-gas reservoir.
20. The method of claim 1 , wherein:
(i) the gas is compressed within the cylinder assembly to a first pressure, and further comprising, prior to transfer to the compressed-gas reservoir, transferring the gas to a second cylinder assembly and compressing the gas within the second cylinder assembly from the first pressure to a second pressure larger than the first pressure; or
(ii) the gas is expanded within the cylinder assembly to a first pressure, and further comprising, prior to venting expanded gas to the ambient atmosphere, transferring the gas to a second cylinder assembly and expanding the gas within the second cylinder assembly from the first pressure to a second pressure smaller than the first pressure.