Apparatus and Method for Storing Energy

• US 20160032783A1
• Filed: 04/02/2014
• Published: 02/04/2016
• Est. Priority Date: 04/05/2013
• Status: Abandoned Application

• Current Assignee: Energy Technologies Institute LLP
• Original Assignee: Isentropic, Ltd.
• Inventors: Howes, Jonathan Sebastian, Macnaghten, James
• Application Number:
  US14/780,358
• Publication Number:
  US 20160032783A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F01K 3/006 Accumulators and steam compressors
• CPC Class Codes: F01K 3/06 the engine being of extraction or non-condensing type F01K3/004 takes precedence
• CPC Class Codes: F01K 3/12 having two or more accumulators

Abstract

In an energy storage and recovery system, working fluid from a first vessel is compressed by power machinery and passes, via a regenerator, into a second vessel, where it is forced to condense, the temperature and pressure of the saturated working liquid/vapour mixture continuously rising during storage. The stored energy is recovered by the vapour returning through the regenerator and power machinery where it expands to produce work before condensing back into the first vessel. The regenerator comprises a gas permeable, solid thermal storage medium which, during storage, stores superheat and some latent heat from the vapour passing through it in respective downstream regions that exhibit continuously increasing temperature profiles during storage and a small temperature difference with the surrounding vapour, thereby minimising irreversible losses during the thermal energy transfers.

Claims

1. An energy storage and recovery system comprising:

a first vessel configured to store a working fluid as a saturated liquid/vapour mixture L₁ having a temperature T_L1;

a second vessel configured to store the working fluid as a saturated liquid/vapour mixture L₂ having a temperature T_L2;

power machinery disposed between the first and second vessels; and

a regenerator disposed between the power machinery and liquid of the working fluid stored in the second vessel,

wherein the system is configured such that;

(i) in a storage mode, working fluid vapour passes from the first vessel to the power machinery where the working fluid vapour is compressed before passing through the regenerator and condensing in working fluid liquid of the mixture L₂ in the second vessel, so as to produce a progressive increase in the temperature T_L2 of the mixture L₂ and in a liquid/vapour equilibrium phase change temperature of the mixture L₂ during the storage mode; and

,

(ii) in a recovery mode, working fluid vapour passes from the second vessel, through the regenerator to the power machinery where the working fluid vapour is expanded to produce power before condensing in working fluid liquid of the mixture L₁ in the first vessel, so as to produce a progressive decrease in the temperature T_L2 of the mixture L₂ and in the liquid/vapour equilibrium phase change temperature of the mixture L₂ during the recovery mode;

wherein;

the regenerator comprises a solid thermal storage medium, the solid thermal storage medium being configured such that the working fluid vapour passes through the solid thermal storage medium for direct heat transfer between the working fluid vapour and solid thermal storage medium so as to store and return superheat during the storage and recovery modes, respectively; and

,

the system is configured such that some condensation takes place in the regenerator during the storage mode.

2. A system according to claim 1, wherein the solid thermal storage medium is in the form of a porous matrix.

3. A system according to claim 1, wherein the system is configured such that condensation takes place in the regenerator for the full running time of the storage mode.

4. A system according to claim 1, wherein the system is configured to cease operating in the storage mode when condensation is only occurring in a last 5% or less of a downstream length of the regenerator.

5. A system according to claim 1, wherein the system is configured to cease operating in the storage mode when condensation is about to finish in the regenerator such that some of the working fluid vapour is about to start exiting the regenerator as a superheated gas.

6. A system according to claim 1, wherein the system is configured such that there is a progressive decrease in the temperature T_L1 of the mixture L₁ and in a liquid/vapour equilibrium phase change temperature of the mixture L₁ during the storage mode, and, a progressive increase in the temperature T_L1 of the mixture L₁ and in a liquid/vapour equilibrium phase change temperature of the mixture L₁ during the recovery mode.

7. A system according to claim 6, further comprising a further regenerator configured such that the further regenerator is disposed between the power machinery and the working fluid liquid stored in the first vessel.

8. A system according to claim 6, further comprising additional thermal ballast in the first vessel or a temperature regulating sub-system associated with the first vessel, the additional thermal ballast or the temperature regulating sub-system being configured to reduce respective rates of the progressive decrease and increase in the temperature T_L1 of the mixture L₁ during the storage and recovery modes, respectively.

9. A system according to claim 1, wherein the regenerator is configured such that the regenerator is located inside the second vessel above the working fluid liquid of the mixture L₂.

10. A system according to claim 1, wherein the system is configured to lose waste heat from the first vessel by allowing the working fluid vapour of the mixture L₁ to vent to atmosphere or to a waste heat recapture sub-system, when a vapour pressure of the working fluid vapour of the mixture L₁ exceeds atmospheric pressure or a pressure in the sub-system, respectively.

11. A system according to claim 1, wherein the system is configured such that the working fluid liquids of the mixtures L₁ and L₂ are each initially preheated or precooled to respective selected temperatures before commencement of the storage mode.

12. A system according to claim 1, wherein the working fluid comprises a water/steam mixture.

13. A system according to claim 1, wherein the system is configured such that, during the storage mode, superheat and latent heat are stored along the solid thermal storage medium of the regenerator in a respective upstream superheat transfer region and downstream latent heat transfer region, and wherein a temperature profile of the solid thermal storage medium progressively increases in temperature in both the upstream superheat transfer region and the downstream latent heat transfer region during the storage mode.

14. A system according to claim 13, wherein during the storage mode a temperature difference Δ

T between the working fluid vapour and the solid thermal storage medium contacted by the working fluid vapour is generally less than 15°

at at least one selected position in the superheat transfer region and/or the latent heat transfer region.

19. A system according to claim 7, wherein the further regenerator is located inside the first vessel above the working fluid liquid of the mixture L₁.

15. A method of operating an energy storage system using a working fluid that undergoes a phase change, the method comprising:

storing energy in an energy storage/charging mode comprising;

evaporating an amount of a saturated liquid L₁ having a temperature T_L1 to form a first vapour;

doing work by compressing the first vapour to a higher temperature and pressure; and

cooling and condensing an amount of the compressed first vapour to a liquid L₂ having a temperature T_L2 so that there is a transfer of thermal energy from the first vapour to the liquid L₂; and

further comprising recovering the energy in an energy recovery/discharging mode comprising;

evaporating an amount of saturated liquid L₂ at a temperature T_L2 to form a second vapour;

heating the second vapour to superheat it;

expanding the second vapour to a lower pressure and temperature to generate work; and

condensing an amount of the expanded second vapour back to the liquid L₁ having the temperature T_L1;

wherein the energy storage system comprises a lower pressure side in which the working fluid is present as a liquid/vapour mixture L₁ at a lower vapour pressure, and a higher pressure side in which the working fluid is present as a liquid/vapour mixture L₂ at a higher vapour pressure, the lower and higher pressure sides being separated by at least one compressor/expander operating so as to transfer vapour between the respective lower and higher pressure sides at the respective lower and higher vapour pressures,

wherein during charging and discharging the temperature TL₂ is greater than the temperature T_L1,

wherein heating the second vapour uses stored thermal energy, and

wherein the stored thermal energy is stored by direct transfer to thermal media in a regenerator through which gas passes for subsequent return, the regenerator comprising a throughflow regenerator having a solid thermal storage medium so as to allow direct heat transfer between the vapour and solid medium,

wherein all sensible heat transfer upon cooling prior to condensing occurs within the regenerator.

16. A method of storing and recovering energy comprising:

in a storage mode, compressing working fluid vapour from a first vessel containing a saturated working liquid/vapour mixture by power machinery;

passing the compressed working fluid, via a regenerator, into a second vessel, where the compressed working fluid condenses into a saturated working liquid/vapour mixture, a temperature and vapour pressure of which increase as more energy is stored therein;

in a recovery mode, recovering stored energy by evaporation of vapour from the saturated working liquid/vapour mixture in the second vessel such that the temperature and vapour pressure of the mixture decrease;

returning the vapour through the regenerator; and

expanding the returned vapour in power machinery so as to produce work before condensing back into the saturated working liquid/vapour mixture of the first vessel,

wherein the regenerator comprises a gas permeable, solid thermal storage medium, and

wherein during the storage mode superheat and latent heat are stored along the solid thermal storage medium in a respective upstream superheat transfer region and downstream latent heat transfer region, and

wherein the temperature profile of the solid thermal storage medium increases in temperature in both the upstream superheat transfer region and the downstream latent heat transfer region during the storage mode.

17. (canceled)

18. (canceled)