Adiabatic salt electric energy storage

• US 9,932,830 B2
• Filed: 08/12/2013
• Issued: 04/03/2018
• Est. Priority Date: 03/04/2010
• Status: Active Grant

• Current Assignee: Malta, Inc.
• Original Assignee: X Development LLC (Alphabet Inc.)
• Inventors: Laughlin, Robert B.
• Primary Examiner(s): Jules, Frantz
• Assistant Examiner(s): Tadesse, Martha
• Application Number:
  US13/965,048
• Publication Number:
  US 20160298495A1
• Time in Patent Office: 1,695 Days
• CPC Class Codes: F01D 1/02 with stationary working-fluid guiding means and bladed or like rotor, e.g. multi-bladed impulse steam turbinesF01D1/24 takes precedence; without stationary working-fluid guiding means F01D1/18
• CPC Class Codes: F01K 25/00 Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
• CPC Class Codes: F01K 25/10 the vapours being cold, e.g. ammonia, carbon dioxide, ether
• CPC Class Codes: F01K 3/12 having two or more accumulators
• CPC Class Codes: F01K 5/00 Plants characterised by use of means for storing steam in an alkali to increase steam pressure, e.g. of Honigmann or Koenemann type
• CPC Class Codes: F01L 1/02 Valve drive transmitting-gear between valve drive and valve F01L1/12
• CPC Class Codes: F02C 1/04 the working fluid being heated indirectly in a fluidised-bed combustor F02C3/205
• CPC Class Codes: F02C 6/14 Gas-turbine plants having means for storing energy, e.g. for meeting peak loads
• CPC Class Codes: F25B 11/02 as expanders F25B9/06 takes precedence
• CPC Class Codes: F25B 9/004 the refrigerant being air
• CPC Class Codes: F25B 9/06 using expanders F25B9/10 takes precedence
• CPC Class Codes: Y02E 10/46 Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines
• CPC Class Codes: Y02E 60/14 Thermal energy storage

Abstract

Efficient energy storage is provided by using a working fluid flowing in a closed cycle including a ganged compressor and turbine, and capable of efficient heat exchange with heat storage fluids on a hot side of the system and on a cold side of the system. This system can operate as a heat engine by transferring heat from the hot side to the cold side to mechanically drive the turbine. The system can also operate as a refrigerator by mechanically driving the compressor to transfer heat from the cold side to the hot side. Heat exchange between the working fluid of the system and the heat storage fluids occurs in counter-flow heat exchangers. In a preferred approach, molten salt is the hot side heat storage fluid and water is the cold side heat storage fluid.

Claims

1. A method for storing and releasing energy, the method comprising:

(a) increasing a pressure of a working fluid operating in a closed cycle from a first pressure to a second pressure with the aid of a compressor, thereby increasing a temperature of the working fluid;

(b) using a first heat storage unit downstream of the compressor and in thermal communication with the working fluid for (i) in a storing mode, removing heat from the working fluid and decreasing the temperature of the working fluid, which decrease in temperature is at substantially the second pressure, or (ii) in a releasing mode, supplying heat to the working fluid and increasing the temperature of the working fluid, which increase in temperature is at substantially the second pressure;

(c) decreasing the pressure of the working fluid from the second pressure to the first pressure with the aid of a turbine, thereby decreasing the temperature of the working fluid;

(d) using a second heat storage unit downstream of the turbine and in thermal communication with the working fluid for (i) in the storing mode, supplying heat to the working fluid and increasing the temperature of the working fluid, which decrease in temperature is at substantially the first pressure, or (ii) in the releasing mode, removing heat from the working fluid and decreasing the temperature of the working fluid, which decrease in temperature is at substantially the first pressure,

wherein, during use, entropy generation in the first and second heat storage units is less than the entropy generated by the compressor,

wherein the working fluid flows in a same direction in the closed cycle when in the storing mode as when in the releasing mode, and

wherein the working fluid flows through the compressor, the first heat storage unit, the turbine, and the second heat storage unit in both the storing mode and the releasing mode.

2. The method of claim 1, wherein the second heat storage unit has a range of operating temperatures that is lower than the range of operating temperatures of the first heat storage unit.

3. The method of claim 1, wherein the first and second heat storage units have comparable total heat capacities.

4. The method of claim 1, wherein the first heat storage unit comprises a heat storage fluid that includes molten salt.

5. The method of claim 4, wherein the molten salt comprises sodium nitrite and/or potassium nitrate.

6. The method of claim 1, wherein the first and/or second heat storage unit comprises a heat storage fluid that is liquid at a range of operating temperatures of the heat storage fluid.

7. The method of claim 1, wherein the second heat storage unit comprises a heat storage fluid that is at ambient pressure.

8. The method of claim 1, wherein a radiator is operationally coupled to the first heat storage unit.

17. The method of claim 1, wherein the working fluid is Argon.

9. A system for storing and releasing electrical energy, comprising an electrical energy input and an electrical energy output, wherein the system is capable of storing and releasing electrical energy using two heat exchangers, each heat exchanger comprising a thermal storage fluid that directs thermal energy into or extracts thermal energy from a circulatory fluid flow path, wherein the circulatory fluid flow path comprises a working fluid that flows in a same direction in the circulatory fluid flow path when storing electrical energy as when releasing electrical energy, wherein the working fluid flows through a compressor, a first heat exchanger, a turbine, and a second heat exchanger in both a storing mode and a releasing mode, and wherein the system comprises a controller that is programmed to regulate (i) a temperature difference between any two thermally coupled fluid elements of the heat exchangers, and/or (ii) one or more fluid properties of the fluid elements of the heat exchangers such that entropy generation in the heat exchangers is minimized during operation of the system.

10. The system of claim 9, wherein the electrical energy input is stored as thermal energy.

11. The system of claim 9, wherein the electrical energy output is extracted from thermal energy.

12. The system of claim 9, wherein the electrical energy use comprises a transformation to thermal energy.

13. A method for storing and releasing energy, the method comprising:

(a) providing a system comprising a closed cycle comprising, in sequence, a compressor, a first heat storage unit, a turbine, and a second heat storage unit, wherein the first and second heat storage units comprise fluid elements that exchange heat with a working fluid flowing through the closed cycle; and

(b) alternately and sequentially operating the system in a refrigerator mode and a heat engine mode, wherein in the refrigerator mode, mechanical work is used to transfer thermal energy from the second heat storage unit to the first heat storage unit, wherein, in the heat engine mode, thermal energy transferred from the first heat storage unit to the second heat storage unit is used to provide mechanical work, wherein the working fluid flows through the compressor, the first heat storage unit, the turbine, and the second heat storage unit in both the refrigerator mode and the heat engine mode, and wherein the working fluid flows in a same direction in the closed cycle when operating in the refrigerator mode as when operating in the heat engine mode.

14. The method of claim 13, further comprising controlling a temperature difference between fluid elements exchanging heat such that entropy generation in the first and second heat storage units is minimized.

15. The method of claim 13, wherein, during operation, the entropy generated in the first and second heat storage units is less than the entropy generated by the compressor.

16. The method of claim 13, wherein the compressor and the turbine are operably coupled such that they rotate together.