Method and system for the compact storage of heat and coolness by phase change materials

• US 4,294,078 A
• Filed: 07/12/1978
• Issued: 10/13/1981
• Est. Priority Date: 04/26/1977
• Status: Expired due to Term

• Current Assignee: Calmac Manufacturing Corp. (Trane Technologies plc)
• Original Assignee: Calmac Manufacturing Corp. (Trane Technologies plc)
• Inventors: MacCracken, Calvin D.
• Primary Examiner(s): DAVIS JR, ALBERT
• Application Number:
  US05/923,984
• Time in Patent Office: 1,189 Days
• Field of Search: 165/104 S, 165/163, 165/109, 165/18, 165/DIG. 8, 126/430, 126/436, 62/430, 62/434, 62/59, 62/435, 29/157.3 R
• US Class Current: 62/59
• CPC Class Codes: F28D 20/021 the latent heat storage material and the heat-exchanging means being enclosed in one container F28D20/023 - F28D20/028 take precedence
• CPC Class Codes: Y02E 60/14 Thermal energy storage
• CPC Class Codes: Y02E 70/30 Systems combining energy storage with energy generation of non-fossil origin
• CPC Class Codes: Y10S 165/905 Materials of manufacture
• CPC Class Codes: Y10T 29/4935 Heat exchanger or boiler making

Abstract

While many materials and additives which will melt and freeze at various temperature levels for storing and releasing large amounts of heat thereby per unit volume have been disclosed, the packaging of these materials with suitable non-corrodible long-lasting heat exchange structures has been cumbersome and expensive. The present invention provides an inexpensive, high performance, non-corrodible thermal storage method and system adapted for use with heat storage materials of various compositions and adapted for use over a wide range of temperatures, including a heat exchanger which provides for phase change to occur approximately simultaneously throughout the volume of the entire storage mass and provides for the sites at which the phase change is occurring to be approximately uniformly distributed throughout the volume of the heat storage material. Problems of thermal expansion, stratification and sub-cooling are eliminated. Thermal storage methods and systems embodying the present system may advantageously be used for off-peak storage of electric refrigeration, cooling and heating as well as solar heating and other applications.

Claims

1. In a heat exchange system capable of transferring the heat of fusion between a moving liquid and a stationary liquid/solid phase change material:

A. a tank formed of a material capable of withstanding constant temperatures above and below the melting point of any phase change material within said tank;

B. a grid of closely-spaced, small-diameter flexible plastic tubes arranged to give multiple parallel liquid circuits with opposite direction of flow of the liquid in adjoining tubes;

C. said grid including a plurality of vertical layers of said closely-spaced flexible plastic tubes, said liquid flowing in the opposite direction in adjoining tubes in each layer;

D. spacer means to provide generally uniform horizontal spacing of said layers of plastic tubes throughout said tank;

E. a phase change material substantially filling said tank and surrounding said grid of uniformly spaced tubes;

;

F. liquid supply and return headers connected to said grid of plastic tubes;

G. heat supply means for adding heat to said system;

H. heat removal means for withdrawing heat from said system; and

I. pumping means for recirculating a liquid through said tubing grid, headers, heat supply means and heat removal means, whereby said phase change material may be alternately melted and frozen uniformly throughout the mass of said phase change material as heat is added to and withdrawn from said system.

2. In a heat exchange system capable of transferring the heat of fusion between a moving liquid and a stationary liquid-solid phase change material as claimed in claim 1, in which the plastic tank is cylindrical with a top opening.

3. In a heat exchange system capable of transferring the heat of fusion between a moving liquid and a stationary liquid-solid phase change material as claimed in claim 1, in which the phase change material is pumped into the tank in liquid phase after the tank has been located for its position of use.

4. In a heat exchange system capable of transferring the heat of fusion between a moving liquid and a stationary liquid-solid phase change material as claimed in claim 1, in which the spacer means consists of a noncorrodible loose light-weight matting rolled up with the grid of plastic tubes into a spiral roll.

5. In a heat exchange system capable of transferring the heat of fusion between a moving liquid and a stationary liquid-solid phase change material as claimed in claim 1, in which the outer surface of the tank is insulated.

6. In a heat exchange system capable of transferring the heat of fusion between a moving liquid and a stationary liquid-solid phase change material as claimed in claim 5, in which the phase change material extends in a narrow projection out through the outer wall and outer insulation so that some of the phase change material will not melt when heat is added to the system thus preserving frozen crystals for nucleation purposes when heat is being extracted from the system.

7. The method of storing thermal energy and withdrawing it at a later time comprising the steps of:

A. providing a plastic open-top container;

B. uniformly spacing a grid of small diameter plastic tubes within and substantially throughout said container;

C. arranging said tubes to give multiple parallel circuits with opposite direction of flow in adjoining tubes;

D. connecting said tubes to supply and return headers;

E. substantially filling said container and surrounding said tubes with a phase change material in its liquid state while leaving a region in the top of said container which is free of said phase change material for accommodating the expansion and contraction of said material during its change of state;

F. connecting said headers through pumping and heat exchange means;

G. recirculating a liquid through said tubes at a temperature below the phase change temperature causing the phase change material to solidify; and

H. alternately adding heat energy to and withdrawing heat energy from the recirculating liquid causing said material to melt and solidify simultaneously throughout the mass of said phase change material, whereby heat of fusion will be stored simultaneously throughout the phase change material during solidification and then released to the recirculating liquid simultaneously throughout the phase change material during melting.

8. The method of storing thermal energy and withdrawing it at a later time as claimed in claim 7, in which the plastic tank is cylindrical and said grid has a spiral configuration as seen from above with generally uniformly spaced vertical layers of vertically spaced tubes and the direction of flow is opposite in neighboring tubes in each layer of said spiral configuration for providing generally uniform temperature averaging throughout the mass of phase change material.

9. The method of storing thermal energy and withdrawing it at a later time as claimed in claim 8, in which the spacer means consists of a non-corrodible loose light-weight matting rolled up with the grid of plastic tubes into a spiral roll.

10. The method of storing thermal energy and withdrawing it at a later time as claimed in claim 7, in which the outer surface of the tank is insulated.

11. The method of storing thermal energy and withdrawing it at a later time as claimed in claim 10, in which the phase change material extends in a narrow projection out through the outer wall and outer insulation so that some of the phase change material will not melt when heat is added to the system thus preserving frozen crystals for nucleation purposes when heat is being extracted from the system.

12. The method of storing coolness and subsequently releasing it for use at a later time in air conditioning, refrigeration, and process functions comprising the steps of:

A. providing an open-top container;

B. uniformly spacing a grid of small diameter flexible plastic tubes within and substantially throughout said container;

C. substantially filling said container and surrounding said tubes with a phase change material (PCM) in its liquid state while leaving a region in the top of said container free of PCM for allowing room for expansion and contraction of the PCM during its change of phase;

D. arranging said tubes to give multiple parallel circuits with opposite direction of flow in adjoining tubes in said tank for providing generally uniform heat energy transfer into and out of said grid of flexible plastic tubes throughout the volume of said PCM;

E. connecting said tubes to supply and return headers;

F. connecting said headers through pumping and heat exchange means;

G. recirculating a liquid through said tubes at a temperature below the phase change temperature of said PCM causing the PCM to solidify; and

H. at a later time when cooling is desired recirculating a liquid through said tubes at a temperature above said phase change temperature causing said liquid to be cooled and said PCM to melt, whereby the latent heat of fusion will be withdrawn from the PCM, enabling the storing of coolness in the solid state, and subsequently the heat of fusion will flow from the recirculating liquid to the PCM thereby cooling said liquid.

13. The method of storing coolness and subsequently releasing it for use at a later time in air conditioning, refrigeration, and process functions as claimed in claim 12, in which the tank is cylindrical and has the multiple parallel circuits lying horizontally.

14. The method of storing coolness and subsequently releasing it for use at a later time in air conditioning, refrigeration, and process function as claimed in claim 13, in which the spacer means consists of a noncorrodible loose light-weight matting rolled up with the grid of plastic tubes into a spiral roll.

15. The method of storing coolness and subsequently releasing it for use at a later time in air conditioning, refrigeration, and process function as claimed in claim 12, in which the outer surface of the tank is insulated.

16. In a heat exchange system capable of transferring the heat of fusion of a stationary liquid/solid phase change material between a moving liquid in said system and said phase change material, apparatus comprising:

A. an insulated tank formed of a material capable of withstanding temperatures above and below the melting point of any phase change material within said tank;

B. at least one grid of closely-spaced small diameter flexible synthetic conduits arranged within said tank to give multiple parallel liquid circuits through which said liquid can flow;

C. a phase change material substantially filling said tank and surrounding said grid of synthetic conduits with a region at the top of said tank being free of said phase change material for accommodating expansion and contraction thereof in the tank;

D. said grid of flexible synthetic conduits being arranged for flow of liquid in opposite directions in neighboring pairs of conduits in said grid for providing generally uniform transfer of heat energy between the liquid in the respective pairs of conduits and the phase change material throughout said tank;

E. spacer means in said tank associated with said grid for providing substantially uniform horizontal spacing of said synthetic conduits and permitting free flow of the phase change material in its liquid state throughout said tank;

F. liquid supply and return headers connected to said grid of synthetic conduits for conducting said liquid into and out of said conduit grid;

G. heat supply means for adding heat to said liquid in said system;

H. heat removal means for withdrawing heat from said liquid in said system; and

I. pumping means for recirculating said liquid through said conduit grid, headers, heat supply means and heat removal means;

whereby said phase change material may be alternately melted and frozen uniformly throughout the mass of said phase change material as heat is added to and withdrawn from the recirculating liquid in said system.

17. In a heat exchange system capable of transferring the heat of fusion of a stationary liquid/solid phase change material between a moving liquid in said system and said phase change material, apparatus as claimed in claim 16, in which:

more than one grid of closely-spaced small diameter synthetic conduits are arranged within said tank to give multiple parallel liquid circuits through which said liquid can flow;

whereby in case of a leak in one such grid of conduits rendering the heat exchange system inoperable and thereby causing the phase change material to cool and solidify, said leaking grid can be closed off and another grid in said tank can be used to circulate said liquid for heating and melting the phase change material so that the liquefied phase change material can be pumped out of the tank as a liquid to allow repairs to be carried out on said leaking grid.

18. In a heat exchange system capable of transferring the heat of fusion of a stationary liquid solid phase change material between a moving liquid in said system and said phase change material, apparatus as claimed in claim 16, in which:

said spacer means is fibrous and low density and has sufficiently large spaces therein for permitting said free flow of the phase change material in its liquid state.

19. In a heat exchange system capable of transferring the heat of fusion of a stationary liquid-solid phase change material between a moving liquid in said system and said phase change material, apparatus as claimed in claim 18, in which:

said spaces in said spacer means are also sufficiently small for preventing crystals of the solidified phase change material from falling through to the bottom of the tank.

20. In a heat exchange system capable of transferring the heat of fusion of a stationary liquid-solid phase change material between a moving liquid in said system and said phase change material, apparatus as claimed in claim 16, in which:

said insulated tank is at least two feet in diameter and at least four feet high.

21. In a heat exchange system capable of transferring the heat of fusion of a stationary liquid-solid phase change material between a moving liquid in said system and said phase change material, apparatus as claimed in claim 20, in which:

said insulated tank is sufficiently large to hold 12 cubic feet of the phase change material.

22. The method of storing thermal energy and withdrawing it at a later time comprising the steps of:

A. providing an open-top container insulated on its outer surfaces;

B. outside of said container, fabricating a flexible grid containing a multiplicity of closely and uniformly spaced flexible small diameter conduits of synthetic material arranged to provide multiple parallel circuits for liquid flow;

C. connecting said conduits to supply and return headers;

D. positioning said flexible grid within said open-top container with said grid substantially uniformly spaced horizontally within said container and located throughout substantially the entire volume of said container;

E. providing a phase change material outside of said container and having a phase change temperature above the ambient temperature, and heating said material for causing said material to be in its liquid state;

F. substantially filling said container and surrounding said conduits with the phase change material in its liquid state while leaving a space in the top of said container for expansion and contraction of said phase change material;

G. covering said container with a tightly fitting top cover;

H. connecting said headers to pumping and heat exchange means;

I. filling said conduits, headers, pumping and heat exchange means with suitable heat exchange liquid;

J. recirculating the liquid through said conduits at a temperature below the phase change temperature causing the phase change material to solidify;

K. alternately adding heat to and withdrawing heat from the recirculating liquid causing said material alternately to melt and solidify around said multiplicity of conduits throughout the mass of said phase change material, whereby heat of fusion will alternately be stored in the phase change material and then released to the recirculating liquid; and

whereby when the liquid is not flowing, the heat lost from the phase change material through the outer insulated wall of the tank will cause the phase change material adjoining said wall to solidify, thus preventing convection adjacent to the tank wall and creating additional insulation effect by the solidified material for impeding heat flow from the interior region of the material out through the solidified material adjacent to the insulated wall of the container.

23. The method of storing thermal energy and withdrawing it at a later time as claimed in claim 22, in which:

said step (E) of substantially filling said container and surrounding said conduits with a phase change material in its liquid state is carried out by the further steps of;

delivering the phase change material in its liquid state in a heated tank truck to the site where said container is located, and

pumping the phase change material in its liquid state from the heated tank truck through a hose into said container.

24. Heat storage tank apparatus for temporarily storing heat energy comprising:

A. a thermally insulated tank providing convenient access to its interior;

B. liquid supply and return headers extending within said tank;

C. at least one grid of closely-spaced small diameter conduits of flexible plastic material connected at their ends to the respective headers and arranged within said tank to give multiple parallel liquid circuits through which a heat-transfer liquid can flow;

D. said grid being a rolled-up grid of closely-spaced parallel flexible parallel conduits having a vertical axis and the respective layers of said rolled-up grid having a spiral configuration as seen from above;

E. said liquid flow being in opposite directions in neighboring conduits in each respective layer of said spiral configuration;

F. a liquid/solid phase change material substantially filling said tank and surrounding said grid of closely-spaced small diameter conduits;

G. spacer means in said tank associated with said grid for providing substantially uniform horizontal spacing of said small diameter conduits of plastic material and permitting free flow of the phase change material in its liquid state throughout said tank;

H. said spacer means being a plurality of elongated members extending transversely to the conduits in said grid for holding said flexible plastic conduits in their closely-spaced parallel relationship in said rolled-up grid, and said elongated spacer members extending vertically in said tank; and

I. said insulated tank, said flexible plastic conduits and said headers being formed of materials capable of withstanding temperature above and below the melting point of said liquid/solid phase change material;

whereby said phase change material may be alternately melted and frozen throughout the interior of the mass thereof as heat is added thereto or withdrawn therefrom by circulating heat-transfer liquid through said conduit grid.

25. Heat storage tank apparatus as claimed in claim 24, in which:

G. said grid is rolled into a spiral roll configuration as seen in cross section looking downwardly.

26. Heat storage tank apparatus as claimed in claim 25, in which:

H. said spacer means is low density matting having multiple spaces therein which has been rolled into said spiral roll configuration together with said grid, said matting and said grid being in alternate spiral layers as seen in cross section.

27. Heat storage tank apparatus as claimed in claim 25, in which:

I. said liquid supply and return headers extend generally vertically within said tank, and each of said conduits extends generally in a horizontal plane in a spiral having a reversal of direction near the center of said spiral roll configuration with the liquid flow in each conduit travelling generally in a horizontal plane from the supply header along an inward spiral path through the phase change material to said reversal of direction and then travelling in a generally horizontal plane along an outward spiral path through the phase change material, said outward spiral path being near to and vertically aligned with said inward spiral path.

28. Heat storage tank apparatus as claimed in claim 24, in which:

the density of the phase change material is greater than the rolled-up grid of plastic conduits together with said elongated spacer members whereby the grid and elongaged spacer members will tend to float up vertically when the phase change material is in its liquid state in said tank; and

a rigid tank cover in retaining relationship with said elongated spacer members,

whereby said rolled-up grid is prevented from rising up in spite of the buoyancy effect of the phase change material when it is in its liquid state.

29. Heat storage tank apparatus for temporarily storing heat energy comprising:

A. a thermally insulated tank providing convenient access to its interior;

B. liquid supply and return headers extending within said tank;

C. at least one grid of closely-spaced small diameter conduits of flexible plastic material connected at their ends to the respective headers and arranged within said tank to give multiple parallel liquid circuits through which a heat-transfer liquid can flow;

D. a liquid/solid phase change material substantially filling said tank and surrounding said grid of closely-spaced small diameter conduits;

E. spacer means in said tank associated with said grid for providing substantially uniform horizontal spacing of said small diameter conduits of plastic material and permitting free flow of the phase change material in its liquid state throughout said tank;

F. means for preserving a small portion of the phase change material in its solid state in contact with the main body of the phase change material, when the phase change material is being changed into its liquid state by adding heat energy thereto, thereby preserving frozen crystals of the phase change material for serving nucleation purposes when the phase change material is later being changed into its solid state by extracting heat energy therefrom;

G. said insulated tank, said flexible plastic conduits and said headers being formed of materials capable of withstanding temperature above and below the melting point of said liquid/solid phase change material;

whereby said phase change material may be alternately changed into a liquid state and changed into a solid state throughout the interior of the mass thereof as heat energy is added thereto or withdrawn therefrom by circulating heat-transfer liquid through said conduit grid.

30. Heat storage tank apparatus for temporarily storing heat energy comprising:

A. a thermally insulated tank providing convenient access to its interior;

B. liquid supply and return headers extending within said tank;

C. at least one grid of closely-spaced small diameter conduits of flexible plastic material connected at their ends to the respective headers and arranged within said tank to give multiple parallel liquid circuits through which a heat-transfer liquid can flow;

D. a liquid/solid phase change material substantially filling said tank and surrounding said grid of closely-spaced small diameter conduits;

E. circulating means for causing circulation of the phase change material in its liquid state in said tank for preventing stratification of the phase change material in said tank when in its liquid state;

F. spacer means in said tank associated with said grid for providing substantially uniform horizontal spacing of said small diameter conduits of plastic material and permitting free flow of the phase change material in its liquid state throughout said tank;

G. said insulated tank, said flexible plastic conduits and said headers being formed of materials capable of withstanding temperature above and below the melting point of said liquid/solid phase change material;

whereby said phase change material may be alternately changed into a liquid state and changed into a solid state throughout the interior of the mass thereof as heat energy is added thereto or withdrawn therefrom by circulating heat-transfer liquid through said conduit grid.

31. Heat storage tank apparatus for temporarily storing heat energy comprising:

A. a thermally insulated tank providing convenient access to its interior;

B. liquid supply and return headers extending within said tank;

C. at least one grid of closely-spaced small diameter conduits of flexible plastic material connected at their ends to the respective headers and arranged within said tank to give multiple parallel liquid circuits through which a heat-transfer liquid can flow;

D. a liquid/solid phase change material substantially filling said tank and surrounding said grid of closely-spaced small diameter conduits;

E. spacer means in said tank associated with said grid for providing substantially uniform horizontal spacing of said small diameter conduits of plastic material and permitting free flow of the phase change material in its liquid state throughout said tank;

F. said insulated tank, said flexible plastic conduits and said headers being formed of materials capable of withstanding temperature above and below the melting point of said liquid/solid phase change material;

whereby said phase change material may be alternately melted and frozen throughout the interior of the mass thereof as heat is added thereto or withdrawn therefrom by circulating heat-transfer liquid through said conduit grid;

G. means for preventing stratification of the phase change material when in its liquid state including;

H. impelling means for circulating the liquid in the tank; and

I. motor means connected to said impelling means for driving the impelling means whenever the phase change material is in its liquid state.

32. Heat storage tank apparatus as claimed in claim 31, in which:

said motor means is a relatively low power electric motor having a relatively low starting torque; and

electric power is continuously fed to said motor for automatically causing the impelling means to operate whenever the phase change material surrounding the impelling means is liquid.

33. Heat storage tank apparatus as claimed in claim 31 or 32, in which:

said impelling means has a conduit associated therewith extending in an upright direction in the tank;

said conduit having an opening at its lower end near the bottom of the tank communicating with the interior of the tank, and said impelling means being arranged to impel liquid phase change material downwardly through said conduit for causing the liquid phase change material to exit from the lower end of said conduit and then to rise throughout the tank so as to return to the impelling means to be recirculated.

34. Heat storage tank apparatus as claimed in claim 31 or 32, in which:

said tank is generally cylindrical in configuration and has its axis upright;

said impelling means has a recirculation conduit associated therewith extending upright along the axis of the tank;

said conduit communicates at its upper and lower ends with the phase change material in the top and bottom of the tank, respectively;

said impelling means is arranged to impel liquid phase change material downwardly through said conduit for causing the liquid PCM to rise through the volume of the tank surrounding said conduit for producing recirculation thereof back to the upper end of said conduit;

said grid of closely spaced small diameter flexible conduits arranged in a roll surrounding said recirculation conduit with many spiral turns; and

said spacing means approximately uniformly horizontally spaces the respective spiral turns of said grid.

35. The method of making thermal energy storage apparatus comprising the steps of:

A. providing an open-top container insulated on its outer surfaces;

B. outside of said container, forming a rectangular flexible grid containing a multiplicity of flexible small diameter conduits of synthetic plastic material, arranged in spaced parallel relationship;

C. connecting said conduits to supply and return headers extending transversely across said grid to provide multiple parallel circuits for liquid flow through said conduits from said supply to said return header;

D. positioning a plurality of rigid support members transversely of said mat and and engaging said conduits for holding the conduits in their spaced parallel relationship;

E. rolling up said grid together with said support members forming said grid into a spiral roll configuration with said conduits and support members being in alternate layers as seen in the axial direction of the spiral roll and with said support members and said supply and return headers extending in the axial direction;

F. placing said spiral roll configuration in said container with the axis of said spiral roll configuration extending vertically within the container;

G. supplying a liquid/solid phase change material at a temperature to be in its liquid state and flowing said material into the container for filling the container and surrounding said grid; and

H. covering said container with a tightly fitting top cover.

36. The method for freezing ice solid in a vertical cylindrical plastic tank without creating lateral expansion forces in the tank for cooling storage for use in air conditioning a building using electrical energy at "off peak" rates including the steps of:

uniformly spacing a grid of small diameter spaced flexible plastic tubes within and substantially throughout the tank in the main lower portion of said tank;

arranging said tubes to give multiple parallel circuits with opposite direction of liquid flow in adjoining tubes;

connecting said tubes to supply and return headers;

filling said tank with water in the main lower portion of said tank while leaving the top portion of the tank free of water to accommodate expansion as the water is frozen into solid ice in the tank;

connecting said headers through electrically energized pumping and refrigeration means located outside of said tank and arranged for refrigerating anti-freeze liquid;

electrically energizing said pumping and heat exchange means during "off peak" hours of a 24 hour day for recirculating the anti-freeze liquid through said tubes at a temperature below the freezing point of water for causing the water in said plastic tank to freeze to solid ice around all of said adjoining tubes uniformly throughout the whole volume of water in said tank during said "off peak" hours;

said freezing of the water to solid ice around all of said adjoining tubes throughout the whole volume of water in said tank squeezing the extra water volume upwardly due to expansion of the freezing ice and thereby preventing rupture of the plastic tank as the whole volume of water freezes to solid ice;

during daylight hours when air conditioning is desired in the building recirculating the anti-freeze liquid through said tubes embedded in said solid ice and through second heat exchange means;

blowing building air past said second heat exchange means for cooling the building air by transferring heat energy from the building air into said recirculating liquid and for transferring heat energy from said recirculating liquid into the ice in said tank;

thereby providing air conditioning in the building while avoiding the use of electrical energy during hours of "peak" rates, and

thereby advantageously avoiding rupture of the tank even though the water is frozen solid therein.