Methods of hot and cold side charging in thermal energy storage systems
The present disclosure provides pumped thermal energy storage systems that can be used to store electrical energy. A pumped thermal energy storage system of the present disclosure can store energy by operating as a heat pump or refrigerator, whereby net work input can be used to transfer heat from the cold side to the hot side. A working fluid of the system is capable of efficient heat exchange with heat storage fluids on a hot side of the system and on a cold side of the system. The system can extract energy by operating as a heat engine transferring heat from the hot side to the cold side, which can result in net work output. Systems of the present disclosure can employ solar heating for improved storage efficiency.
1. A method comprising:
operating a pumped thermal system in a charging mode, wherein the pumped thermal system is configured to operate in the charging mode in which energy is stored in the pumped thermal system and a discharging mode in which energy is discharged from the pumped thermal system, wherein the pumped thermal system comprises:
a compressor,
a hot side heat exchanger,
a hot thermal storage (“HTS”) medium,
a turbine,
a cold side heat exchanger,
a cold thermal storage (“CTS”) medium,
a working fluid, and
a closed cycle fluid path configured to circulate a working fluid through, in sequence and in the same direction, the compressor, the hot side heat exchanger and in thermal contact with the HTS medium, the turbine, and the cold side heat exchanger and in thermal contact with the CTS medium when the pumped thermal system operates in the charging mode and when the pumped thermal system operates in the discharging mode; and
adding thermal energy from an external thermal energy source to the HTS medium.
2. The method of claim 1 , further comprising transferring thermal energy from the CTS medium to the HTS medium via the working fluid.
3. The method of claim 1 , wherein the external thermal energy source comprises concentrating solar heat as a source of external thermal energy.
4. The method of claim 1 , wherein the external thermal energy source comprises a waste heat stream from a solar energy system.
5. The method of claim 1 , wherein the external thermal energy source comprises combustion as a source of external thermal energy.
6. The method of claim 1 , wherein the pumped thermal system further comprises a recuperative heat exchanger, wherein the closed cycle fluid path is further configured to circulate the working fluid through the recuperative heat exchanger such that the working fluid downstream of the compressor is in thermal contact with the working fluid downstream of the turbine,
wherein, in the charging mode, the working fluid flows through, in sequence, the compressor, the hot side heat exchanger and in thermal contact with the HTS medium, the recuperative heat exchanger, the turbine, the cold side heat exchanger and in thermal contact with the CTS medium, and the recuperative heat exchanger, and
wherein, in the discharging mode, the working fluid flows through, in sequence, the compressor, the recuperative heat exchanger, the hot side heat exchanger and in thermal contact with the HTS medium, the turbine, the recuperative heat exchanger, and the cold side heat exchanger and in thermal contact with the CTS medium.
7. A method comprising:
storing a cold thermal storage (“CTS”) medium inside a first cold storage tank at a first temperature above an ambient temperature of atmospheric air;
pre-cooling the CTS medium below the first temperature via heat exchange with the atmospheric air;
cooling the CTS medium from the ambient temperature to a second temperature below the ambient temperature by flowing the CTS medium from the first cold storage tank through a cold side heat exchanger within which the CTS medium exchanges heat with a working fluid, wherein the working fluid circulates through a pumped thermal system, wherein the pumped thermal system is configured to operate in a refrigerator cycle in which energy is stored in the pumped thermal system and a heat engine cycle in which energy is discharged from the pumped thermal system, wherein the pumped thermal system comprises a closed cycle comprising, in sequence, a compressor, a hot side heat exchanger, a turbine, and the cold side heat exchanger, and wherein the working fluid flows through, in sequence and in the same direction, the compressor, the hot side heat exchanger, the turbine, and the cold side heat exchanger when the pumped thermal system operates in the refrigerator cycle and when the pumped thermal system operates in the heat engine cycle; and
storing the CTS medium in a second cold storage tank.
8. The method of claim 7 , wherein the working fluid further circulates through a recuperative heat exchanger such that the working fluid downstream of the compressor is in thermal contact with the working fluid downstream of the turbine,
wherein, in the refrigerator cycle, the working fluid flows through, in sequence, the compressor, the hot side heat exchanger, the recuperative heat exchanger, the turbine, the cold side heat exchanger, and the recuperative heat exchanger, and
wherein, in the heat engine cycle, the working fluid flows through, in sequence, the compressor, the recuperative heat exchanger, the hot side heat exchanger, the turbine, the recuperative heat exchanger, and the cold side heat exchanger.
9. A method comprising:
storing a hot thermal storage (“HTS”) medium inside a first hot storage tank at a first temperature;
pre-heating the HTS medium from the first temperature to an intermediate temperature by flowing the HTS medium through a first heat exchanger, wherein the HTS medium exchanges heat with an intermediate thermal storage (“ITS”) medium flowing through the first heat exchanger;
heating the HTS medium from the intermediate temperature to a second temperature by flowing the HTS medium from the first heat exchanger through an element configured to transfer external thermal energy to the HTS medium;
storing the HTS medium in a second hot storage tank;
circulating a working fluid through, in sequence, a compressor, a hot side heat exchanger, a turbine, and a cold side heat exchanger, wherein the working fluid circulates through a pumped thermal system that is configured to operate in a charging mode in which energy is stored in the pumped thermal system and a discharging mode in which energy is discharged from the pumped thermal system, and wherein the working fluid flows through, in sequence and in the same direction, the compressor, the hot side heat exchanger, the turbine, and the cold side heat exchanger when the pumped thermal system operates in the charging mode and when the pumped thermal system operates in the discharging mode.
10. The method of claim 9 , wherein the external thermal energy comprises concentrating solar heat as a source of external thermal energy.
11. The method of claim 9 , wherein the external thermal energy comprises thermal energy in a waste heat stream.
12. The method of claim 9 , further comprising:
flowing the HTS medium from the second hot storage tank through the hot side heat exchanger to the first hot storage tank, wherein the HTS medium exchanges heat with the working fluid within the hot side heat exchanger.
13. The method of claim 12 , further comprising circulating the working fluid further through a recuperative heat exchanger such that the working fluid downstream of the compressor is in thermal contact with the working fluid downstream of the turbine,
wherein, in the charging mode, the working fluid flows through, in sequence, the compressor, the hot side heat exchanger, the recuperative heat exchanger, the turbine, the cold side heat exchanger, and the recuperative heat exchanger, and
wherein, in the discharging mode, the working fluid flows through, in sequence, the compressor, the recuperative heat exchanger, the hot side heat exchanger, the turbine, the recuperative heat exchanger, and the cold side heat exchanger.
14. A method comprising:
in a closed cycle fluid path of a pumped thermal system configured to operate in a charging mode in which energy is stored in the pumped thermal system and a discharging mode in which energy is discharged from the pumped thermal system, circulating a working fluid through, in sequence and in the same direction, a compressor, a hot side heat exchanger, a turbine, a cold side heat exchanger when the pumped thermal system operates in the charging mode and when the pumped thermal system operates in the discharging mode; and
circulating an intermediate thermal storage (“ITS”) medium through a thermal bath and the hot side heat exchanger, wherein the ITS medium exchanges heat with the working fluid within the hot side heat exchanger, and wherein the ITS medium exchanges heat with a heat sink medium within the thermal bath.
15. The method of claim 14 , wherein the ITS medium comprises a heat transfer oil.
16. The method of claim 14 , wherein the heat sink medium comprises water.
17. The method of claim 14 , further comprising circulating the working fluid further through a recuperative heat exchanger such that the working fluid downstream of the compressor is in thermal contact with the working fluid downstream of the turbine,
wherein, in the charging mode, the working fluid flows through, in sequence, the compressor, the hot side heat exchanger, the recuperative heat exchanger, the turbine, the cold side heat exchanger, and the recuperative heat exchanger, and
wherein, in the discharging mode, the working fluid flows through, in sequence, the compressor, the recuperative heat exchanger, the hot side heat exchanger, the turbine, the recuperative heat exchanger, and the cold side heat exchanger.
18. A method comprising:
in a closed cycle fluid path of a pumped thermal system configured to operate in a charging mode in which energy is stored in the pumped thermal system and a discharging mode in which energy is discharged from the pumped thermal system, circulating a working fluid through, in sequence and in the same direction, a compressor, a hot side heat exchanger, a turbine, a cold side heat exchanger when the pumped thermal system operates in the charging mode and when the pumped thermal system operates in the discharging mode; and
circulating an intermediate thermal storage (“ITS”) medium through a thermal bath and the cold side heat exchanger, wherein the ITS medium exchanges heat with the working fluid within the cold side heat exchanger, and wherein the ITS medium exchanges heat with a heat sink medium within the thermal bath.
19. The method of claim 18 , wherein the ITS medium comprises a heat transfer oil.
20. The method of claim 18 , wherein the heat sink medium comprises water.
21. The method of claim 18 , further comprising circulating the working fluid further through a recuperative heat exchanger such that the working fluid downstream of the compressor is in thermal contact with the working fluid downstream of the turbine,
wherein, in the charging mode, the working fluid flows through, in sequence, the compressor, the hot side heat exchanger, the recuperative heat exchanger, the turbine, the cold side heat exchanger, and the recuperative heat exchanger, and
wherein, in the discharging mode, the working fluid flows through, in sequence, the compressor, the recuperative heat exchanger, the hot side heat exchanger, the turbine, the recuperative heat exchanger, and the cold side heat exchanger.