US 4,294,078 A · Method and system for the compact storage of heat and coolness by phase change materials

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.

Claims36

Dependent claims

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.

7 more elements

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.

6 more elements

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.

6 more elements

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.

8 more elements

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.

10 more elements

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.

8 more elements

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.

8 more elements

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.

8 more elements

Dependencies are inferred from the claim text.

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

Life of this patent

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

Life of this patent

Abstract

Claims36