WO2013138915A1

WO2013138915A1 - Energy storage and transfer system

Info

Publication number: WO2013138915A1
Application number: PCT/CA2013/000273
Authority: WO
Inventors: Geoffrey T. Sheerin
Original assignee: Sheer Technology Inc.
Priority date: 2012-03-20
Filing date: 2013-03-15
Publication date: 2013-09-26

Abstract

An energy storage and transfer system including a distribution means for distributing thermal energy and a thermal energy storage means including a thermal energy storage medium for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means, as stored thermal energy. The energy storage and transfer system also includes a heat transfer means including a heat transfer medium for transferring at least a part of the stored thermal energy from the thermal energy storage medium to the heat transfer medium.

Description

ENERGY STORAGE AND TRANSFER SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No.

61/613,201 , filed on March 20, 2012, the disclosure of which is incorporated fully herein by reference.

FIELD OF THE INVENTION

[0002] The present invention is an energy storage and transfer system.

BACKGROUND OF THE INVENTION

[0003] As is well known in the art, the rate of emissions of carbon compounds and other air pollutants has become so large that serious consequences are believed to have resulted from such pollution. Different approaches to minimizing carbon emissions have been proposed, however, they generally have significant disadvantages associated therewith.

[0004] For instance, automobiles powered by electricity are now in production.

However, such automobiles would, if used in large numbers, result in a significant increase in electrical energy consumption. In particular, in countries where a large proportion of electricity is generated by coal-fired thermal generating plants, increasing the demand for electricity results in increased carbon emissions.

[0005] Various technological solutions have been proposed. However, the long-term solutions generally require testing and much other work before they can be implemented on a sufficiently broad basis to have a significant impact on carbon emissions. Estimates of the time periods involved range from 25 years and up. Shorter-term solutions (partial or otherwise) are needed to mitigate the serious consequences of the carbon emissions that have occurred to date. [0006] Accordingly, there is a need to reduce the use of and dependency on petroleum- based fuels in transportation applications. The prior art teaches that, in order to utilize renewable energy in transportation applications, renewable energy is converted to electricity, that is stored in batteries and consumed in electrical drive systems to propel vehicles.

[0007] Pure electric and plug-in hybrid electric vehicles rely on rechargeable storage batteries and electrical drive systems and the energy is transferred as electrical power via wires. However, as is well known in the art, the conventional systems have a number of disadvantages. While the gravimetric specific energy density of modern batteries exceeds at least 20 Wh/kg (and for Li-based system can significantly exceed 100 Wh kg and can reach 400 Wh/kg), the use of modern batteries significantly increases the cost of the vehicles and the batteries need to be replaced frequently due to limited cycle lives of the individual battery modules. Also, a number of technical and safety issues are encountered when employing multi-module batteries, including, but not limited to, un-matched battery modules and uneven thermal and electrochemical conditions prevailing within the multi-module battery pack. The volumetric specific energy density of batteries for use in electric and hybrid road vehicles exceeds at least 40 Wh/1 and for modern battery systems is in the range of between 200 Wh/1 and 500 Wh/1.

[0008] In addition, for a number of transportation systems, electrical propulsion systems in which the renewable energy is stored as electrical power in batteries are impractical. Such transportation systems are characterized by at least one of the following features:

(i) a vehicle net or gross weight exceeding five tons;

(ii) a range requirement exceeding 100 km before the energy storage means is depleted;

(iii) engine horsepower requirements exceeding 100 HP. SUMMARY OF THE INVENTION

[0009] For the foregoing reasons, there is a need for an energy storage and transfer system that overcomes or mitigates one or more of the deficiencies of the prior art.

[0010] In its broad aspect, the invention provides an energy storage and transfer system including a distribution means for distributing thermal energy and a thermal energy storage means including a thermal energy storage medium for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means, as stored thermal energy. The energy storage and transfer means also includes a heat transfer means including a heat transfer medium for transferring at least a part of the stored thermal energy from the thermal energy storage medium to the heat transfer medium.

[001 1] In one of its aspects, the invention additionally provides a transportation means including an energy utilizing means for consuming at least said part of the stored thermal energy to effect movement of the transportation means.

[0012] In yet another aspect, the thermal storage medium includes a phase-change material.

[0013] In another of its aspects, the energy storage and transfer system includes a distribution means for distributing thermal energy, and a thermal energy storage means including a thermal storage medium for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means, as stored thermal energy. The energy storage and transfer system also includes a heat transfer means including a heat transfer medium, for transferring at least a part of the stored thermal energy between the thermal storage medium and the heat transfer medium. The heat transfer medium includes one or more inert gases that is directed through the thermal storage medium, when the thermal storage medium is substantially molten.

[0014] In another of its aspects, the invention also provides an energy storage and transfer system including a distribution means for distributing thermal energy and a thermal energy storage means including a thermal storage medium for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means, as stored thermal energy. The energy storage and transfer system also includes a heat transfer means including a heat transfer medium, for transferring at least a part of the stored thermal energy from the thermal energy storage medium to the heat transfer medium. The heat transfer means includes one or more heat transfer tubes through which the heat transfer medium is directed, each heat transfer tube is positioned proximal to the thermal energy storage medium for heat transfer between the thermal storage medium and the heat transfer medium. The heat transfer medium is a liquid metal directed through each heat transfer tube.

[0015] In yet another of its aspects, the heat transfer means additionally includes water directed through the liquid metal, for transfer of at least a portion of the stored thermal energy from the heat transfer medium to the water.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will be better understood with reference to the attached drawings, in which:

[0017] Fig. 1 is a flow chart schematically illustrating elements of an embodiment of an energy storage and transfer system of the invention;

[0018] Fig. 2 is a cross-section of an embodiment of a railway car of the invention including embodiments of a thermal storage means and a heat transfer means of the invention;

[0019] Fig. 3 is a side view of an embodiment of the system of the invention, drawn at a smaller scale;

[0020] Fig. 4 is a top view of the system of Fig. 3, drawn at a smaller scale;

[0021] Fig. 5 is a side view of an embodiment of a steam-driven locomotive and railway cars of the invention, drawn at a larger scale;

[0022] Fig. 6 is a schematic illustration of an embodiment of the heat transfer means of the invention, drawn at a larger scale;

[0023] Fig. 7 is a side view of an embodiment of a railway car of the invention including a partial longitudinal cross-section to show the heat transfer means of Fig. 6, drawn at a smaller scale; [0024] Fig. 8A is a transverse cross-section of the railway car of Fig. 7, drawn at a larger scale;

[0025] Fig. 8B is a transverse cross-section of an alternative embodiment of the railway car of the invention;

[0026] Fig. 8C is a schematic illustration of an alternative embodiment of the system of the invention;

[0027] Fig. 9 is a cross-section of a portion of an embodiment of a tank wall of the invention with part of the heat transfer means of Fig. 6 positioned thereon, drawn at a larger scale;

[0028] Fig. 10 is a cross-section of the tank wall of Fig. 9 and a part of the heat transfer means of Fig. 9, drawn at a larger scale;

[0029] Fig. 1 1 is another embodiment of the railway car of the invention including a partial longitudinal cross-section to show another embodiment of the heat transfer means of the invention, drawn at a smaller scale;

[0030] Fig. 12 is a transverse cross-section of the railway car of Fig. 1 1 , drawn at a larger scale; and

[0031] Fig. 13 is a transverse cross-section of another embodiment of the railway car of the invention showing an alternative embodiment of the heat transfer means of the invention therein.

DETAILED DESCRIPTION

[0032] In the attached drawings, like reference numerals designate corresponding elements throughout. Reference is first made to Figs. 1 A- 10 to describe an embodiment of an energy collection and transfer system of the invention referred to generally by reference numeral 20. In one embodiment, the system 20 preferably includes a distribution means 21 for distributing thermal energy, and a storage means 24 including a thermal storage medium 25 for storing at the least a portion of the distributed thermal energy transferred thereto from the distribution means 21, as stored thermal energy. It is also preferred that the system 20 includes a heat transfer means 26 including a heat transfer medium for transferring at least a part of the stored thermal energy from the thermal energy storage medium to the heat transfer medium, as will be described.

[0033] Preferably, the ultimate source of the thermal energy, whether direct or indirect, is a renewable energy source. For instance, and as will be described, in one embodiment, it is preferred that solar energy directly provides thermal energy. This is an example of an energy source that is considered (for the purposes hereof) to be a "direct" source of thermal energy.

[0034] In another embodiment, wind may be used to generate electricity. As will be described, the electrical power therefrom preferably is directed through resistive elements (i.e., such resistive elements being included in the distribution means, in this embodiment) to generate thermal energy, which is at least partially stored in the thermal storage means. This is an example of a renewable energy source (i.e., the wind) that is considered (for the purposes hereof) to be "indirectly" providing thermal energy. Alternatively, electricity generated by water power may be used to provide thermal energy in the system 20.

[0035] As will be described, in the invention herein, thermal energy is efficiently stored, and efficiently transferred for ultimate utilization. It is preferred that the thermal energy is provided directly or indirectly by a renewable energy source. An energy input 23 is provided to the distribution means 21 , which then distributes the energy input 23 to store thermal energy in the thermal energy storage means. Preferably, the distribution means 21 is adapted to receive energy inputs 23 from one or more energy sources. For instance, if the energy input is electric power, then the distribution means 21 includes resistive elements that generate heat when electric current is passed through them, and the resistive elements are positioned to transfer the thermal energy generated thereby to the thermal energy storage means 24. When the energy input is solar power, the distribution means 21 directs sunlight onto the thermal energy storage means 24, as will be described.

[0036] In summary, thermal energy is distributed in the thermal energy storage means

24 by the distribution means 21. In certain embodiments described herein, the distribution means 21 converts an energy input into thermal energy. It will be understood that, where the energy input is thermal energy, the distribution means alternatively may be configured to distribute the thermal energy. Preferably, the part of the stored thermal energy is transferred to the heat transfer medium, which is utilized as desired.

[0037] In one embodiment, the system 20 preferably also includes a collection means

22 for collecting thermal energy for transmission thereof to the distribution means 21. As illustrated in Figs. 3 and 4, the collection means 22 preferably includes means 28 for converting solar energy to thermal energy. In one embodiment, the collection means 22 preferably includes one or more arrays 30 of primary reflectors 32, and the distribution means 21 preferably includes a number of secondary reflectors 34. As shown in Fig. 3, the primary reflectors 32 preferably are positioned to reflect sunlight onto the secondary reflectors 34, and the secondary reflectors 34 are positioned to reflect the sunlight reflected from the primary reflectors 32 onto the thermal storage medium 25.

[0038] As will be described, the heat transfer means 26 preferably is for transferring part of the stored thermal energy therefrom to an energy utilizing means 36. In one embodiment, it is preferred that the energy storage and transfer system 20 additionally includes a transportation means 38 for transporting the storage means 24 to the energy utilizing means 36. In an alternative embodiment, the energy storage and transfer system 20 preferably includes the transportation means 38 including the energy utilizing means 36 therein, for consuming at least the part of the stored thermal energy to effect movement of the transportation means 38.

[0039] As can be seen in Fig. 8A, in one embodiment, the thermal energy storage means 24 preferably includes an insulated container 40 having a tank 42 in which the thermal storage medium 25 is located. Preferably, the transportation means 38 includes a railway car 44 with a railway car body 46, and the thermal energy storage means 24 includes the insulated container 40 that is mounted on the railway car body 46. As noted above, the insulated container 40 preferably includes the tank 42, in which the thermal storage medium 25 is located. The railway car body 46 preferably includes a conventional undercarriage subassembly 48 (Fig. 8A) adapted for use on a conventional railway track 50 (Fig. 4).

[0040] In use, sunlight (schematically represented by arrow "A" in Fig. 3) is directed onto the primary reflectors 32. The sunlight reflected from the primary reflectors 32 is directed toward secondary reflectors 34, as is schematically represented by arrows "Β - "B₆" in Fig. 3. Preferably, the sunlight is further reflected by the secondary reflectors 34 directly onto the thermal storage medium 25, which is located in the insulated container 40. The sunlight reflected from the secondary reflectors 34 to the thermal storage medium 25 is schematically represented by arrows "Ci" and "C₂" in Fig. 3.

[0041] Those skilled in the art would appreciate that many different arrangements of the primary reflectors 32 in the array(s) 30 may be suitable. As shown in Fig. 4, in one embodiment, the energy collection means 22 preferably includes arrays (identified in Fig. 4 as 30A and 30B for convenience) that are located on both sides of the railway track 50 on which the railway car 44 is temporarily located. As shown in Fig. 3, this arrangement of the arrays 30A, 30B conveniently permits the railway car 44 to be positioned therebetween, so that sunlight is directed onto the thermal storage medium 25 from both sides of the insulated container 40 in which the thermal storage medium 25 is located. When the sunlight is directed onto the thermal storage medium 25, the solar energy is converted to thermal energy.

[0042] The thermal storage medium preferably is any suitable material or materials.

In one embodiment, the thermal storage medium preferably includes a phase-change material. For the purposes hereof, "phase-change material" means a material with a high heat of fusion capable of storing large amounts of thermal energy (i.e., when liquefied) and releasing the large amounts of energy (i.e., upon solidifying). Those skilled in the art would be aware of suitable phase-change materials. Preferably, the phase-change material is a salt hydrate. Those skilled in the art would be aware of suitable salt hydrates.

[0043] In one embodiment, energy (e.g., in the form of sunlight) preferably is directed onto the thermal energy storage medium 25 until the thermal energy storage medium 25 has stored an optimum amount of thermal energy therein. For example, where the thermal energy storage medium 25 is a salt hydrate, it is preferred that sunlight is directed at the salt hydrate 25 at least until the salt hydrate 25 becomes molten. Salt hydrates become molten at various temperatures. For instance, the salt hydrate may become molten at about 600° C.

[0044] Those skilled in the art will appreciate that, once heated until molten, the molten salt hydrate retains heat relatively well, especially if positioned in a closed container with suitable thermal insulation. Once sufficient heat is removed from the thermal storage medium, the thermal storage medium solidifies. The thermal storage medium is then reheated, i.e., thermal energy is again stored therein. In this way, the thermal storage medium can be re-used. [0045] In one embodiment, the transportation means 38 preferably includes the energy utilizing means 36, e.g., a steam-driven locomotive 52 (Fig. 5). As can be seen in Fig. 5, in a train 54 including the locomotive 52 and the railway car 44A with the thermal storage means 24 therein, the heat transfer means 26 preferably is utilized to transfer thermal energy from the thermal storage medium 25 to the locomotive 52. It will be understood by those skilled in the art that the thermal energy thus transferred preferably is used to generate steam in the locomotive 52, to propel the locomotive.

[0046] As noted above, in one embodiment, the transportation means 38 preferably is used to move the railway car 44 to another energy utilizing means 36, e.g., a thermal power generating station. In this embodiment, once the stored thermal energy has been substantially utilized, the balance of the stored thermal energy preferably is utilized in the transportation means 38 to move the train 54 to a location where additional thermal energy may be stored in the thermal energy storage medium 25, to repeat the cycle.

[0047] It will be understood that, although the thermal storage means 24 is illustrated as being positioned in the railway car body 46, the transportation means 38 is optional, i.e., the system 20 may exclude the transportation means 38. For instance, the system 20 may be located where it can both receive energy inputs (e.g., sunlight) and transfer energy to the energy utilizing means 36 (e.g., a thermal power generating station).

[0048] As noted above, the energy inputs into the system 20 preferably are from renewable energy sources. For instance, instead of or in addition to solar power, a geothermal source may be used to provide thermal energy to the system. Alternatively, the energy input to the system 20 may be electricity, e.g., electricity generated by wind or water power. Where the energy input to the system 20 is in the form of electricity, the distribution means 21 preferably includes a number of resistive elements 55 positioned to transfer thermal energy (i.e., generated therein when electric current is passed therethrough) to the thermal energy storage medium (Fig. 8B). Those skilled in the art would appreciate that the resistive elements 55 may be arranged in various configurations, and the configuration shown in Fig. 8B is exemplary only.

[0049] Accordingly, in one embodiment, the distribution means 21 includes one or more resistive elements 55 for generating thermal energy when electric current is passed through the resistive element(s) 55. Each resistive element 55 preferably is configured for transfer of the thermal energy therefrom to the thermal energy storage medium, for storage of the distributed thermal energy in the thermal energy storage medium.

[0050] As can be seen in Figs. 6-8B, one embodiment of the heat transfer means 26 preferably includes one or more heat transfer tubes 56 positioned for engagement with an exterior surface 58 of a tank wall 60 of the tank 42. Preferably, the heat transfer medium is movable through the heat transfer tube 56 for transfer of heat energy between the heat transfer medium and the thermal storage medium. The heat transfer medium may be any suitable fluid. Those skilled in the art would be aware of various suitable fluids. In one embodiment, the heat transfer medium preferably is water. For the purposes hereof, it will be understood that "water" refers collectively to water, steam, and mixtures of water and steam unless the context indicates otherwise.

[0051] Preferably, movement of the heat transfer medium through the heat transfer tube(s) 56 is at least partially controlled by one or more valves 62 controlled by a controller 64 to provide a predetermined volume of the heat transfer medium at a predetermined temperature over a predetermined time period. In this way, the rate at which heat is transferred from the thermal energy storage means 25 can be closely controlled.

[0052] It will be understood that, as schematically illustrated in Fig. 2, the railway car body 46 preferably includes at least a part of the heat transfer means 26, for transferring heat from the thermal energy storage means 24. Although only one heat transfer tube 56 is shown in Fig. 2, it will be understood that the heat transfer means 26 preferably includes a number of heat transfer tubes 56 positioned in the railway car 44, and that only one heat transfer tube 56 is shown in Fig. 2 for clarity of illustration. Preferably, each of the heat transfer tubes 56 extends between an inlet 66 and an outlet 68 thereof.

[0053] For instance, in order for heat to be transferred from the thermal storage medium 25 to the energy utilizing means 36, suitable connections preferably are made between the locomotive 52 and the heat transfer tube(s) 56, and the heat transfer medium is directed through the heat transfer tube 56, i.e., from the inlet 66 to the outlet 68, and subsequently to the locomotive 52. In the locomotive 52, the steam (i.e., the heat transfer medium) is utilized, as is known in the art.

[0054] In Fig. 5, the railway car immediately behind the locomotive 52 is identified by the reference numeral 44A for convenience. As can be seen in Fig. 5, it is preferred that the heat transfer tube 56 of the first railway car 44A is directly connected to the locomotive 52. The transfer of heat energy from the thermal storage medium 25 in the railway car 44A to the boiler in the locomotive 52 is effected via the heat transfer medium.

[0055] In Fig. 5, a first connecting line 70 is shown connected to the inlet 66, to permit the heat transfer medium to be pumped into the heat transfer tube 56 from the locomotive 52, i.e., after the hot heat transfer medium has been utilized in the locomotive 52. A second connecting line 72 connects the outlet 68 to the locomotive 52, to permit the hot heat transfer medium to be directed to the boiler (not shown) in the locomotive 52.

[0056] It will be understood that the heat transfer tube 56 is formed and positioned for optimum efficiency of the heat transfer in relation to the thermal storage medium 25. Those skilled in the art would appreciate that the heat transfer tube 56 may have any suitable configuration. The configuration of the heat transfer tube 56 as illustrated is exemplary only. The direction of travel of the heat transfer medium through the heat transfer tube 56 is generally indicated by arrow "D" in Fig. 2.

[0057] As noted above, in one embodiment, utilizing some of the thermal energy stored in the thermal energy storage means, the railway car 44 preferably is brought to another energy utilizing means 36, e.g., a thermal electric power generating station (not shown). Preferably, at the generating station, thermal energy is transferred to the generating station from the thermal energy storage medium via the heat transfer medium, exiting the heat transfer tube 56 via the outlet 68 and suitable connecting elements.

[0058] In one embodiment, once such heat as is extractable from the thermal storage medium has been extracted, the heat transfer tube 56 in the storage means 24 is disconnected. Preferably, the depleted storage means 24 is returned to the collection means 22 (Fig. 3), where the thermal storage medium 25 is heated again by solar energy, so that the thermal storage medium 25 is re-energized with thermal energy.

[0059] From the foregoing, it can be seen that the system 20, in one embodiment, collects energy (e.g., solar energy) and stores it as thermal energy. The system 20 also provides for transferring part of the stored thermal energy to the heat transfer medium, for utilization of the part of the stored thermal energy in the transportation means 38 for transporting the stored thermal energy to other energy utilization means 36 (e.g., a thermal power plant), where the stored thermal energy is used to generate electricity, subject to losses due to inefficiencies.

[0060] As is well known in the art, electric power may be generated by dynamic braking, e.g., for deceleration of the locomotive 52. As will be described, in one embodiment, the electrical energy resulting from dynamic braking of the locomotive 52 preferably is used in the system 20 to generate thermal energy.

[0061] In one embodiment, the distribution means 21 preferably includes the resistive elements 55, as described above. It is also preferred that the transportation means 38 additionally includes a dynamic braking subsystem 37 for generating electric power. The system 20 preferably also includes transmission means 39 for providing the electric current to the distribution means.

[0062] As schematically illustrated in Fig. 8C, the locomotive 52 preferably includes a prime mover 41 for providing power to move the locomotive 52, a generator or an alternator-rectifier 43, one or more traction motors 45, and a control subsystem 47 for controlling the traction motors. As is known, the prime mover 41 may be a diesel engine, or a steam-driven engine.

[0063] The prime mover 41 provides mechanical power (torque) to the generator/alternator-rectifier 43, which generates electrical power used to drive the traction motors 45. The traction motors 45 (and other elements of the locomotive), are controlled by the control subsystem 47. The dynamic braking subsystem 37 preferably includes the control subsystem 47 and the traction motors 45, configured to generate electricity.

[0064] Dynamic braking is implemented by the dynamic braking subsystem 37, as is known in the art. As schematically illustrated in Fig. 8C, in one embodiment, electric current generated by dynamic braking of the locomotive 52 preferably is transmitted via the transmission means 39 to the railway car 44, such railway car preferably including the resistive elements 55. The electric current from the dynamic braking is passed through the resistive elements 55 to generate thermal energy, which is at least partially stored in the thermal energy storage means 24. As described above, at least part of the stored thermal energy is transferred to the heat transfer medium. The heat transfer medium, preferably steam once it is heated, preferably is transferred to the energy utilizing means 36. [0065] Those skilled in the art would appreciate that the prime mover 41 may be a steam-driven engine, i.e., it is the energy utilizing means. Where the prime mover 41 is a steam-driven engine, the steam generated in the railway car 44 preferably is directed to the steam-driven engine. The movement of the steam from the railway car 44 to the steam- driven prime mover 41 is indicated by arrow "G" in Fig. 8C. In this way, the locomotive's dynamic braking is used to at least partially power its prime mover.

[0066] Accordingly, in one embodiment, where the prime mover 41 in the transportation means is steam-driven, it is preferred that the heated heat transfer medium is directed from the heat transfer means to the prime mover, to power movement of the transportation means.

[0067] Those skilled in the art will appreciate that the system 20 is designed to work with conventional elements (e.g., railways, thermal power plants) of the existing infrastructure. Because of this, it is possible to utilize the system 20 relatively quickly, and thereby to achieve significant reductions in carbon emissions in a relatively short time period.

[0068] It is believed that the overall efficiencies and economics of the system of the invention described above are at least comparable to overall efficiencies of the prior art systems.

[0069] In one embodiment, and as illustrated in Figs. 6-10, the heat transfer means 26 preferably includes one or more heat transfer tubes 56 (Figs. 6, 7) operatively connected to a steam drum 73 (Fig. 6). As shown in Fig. 6, the computer valve controller 64, operationally connected to valves 62, is used to regulate the flow of the heat transfer medium through the heat transfer means 26.

[0070] In one embodiment, it is preferred that each of the heat transfer tubes 56 is connected to the exterior surface 58 of the tank wall 60 of the tank 42 by one or more connectors 74. Each connector 74 is formed to permit movement of the tank wall 60 and the heat transfer tube 56 relative to each other due to thermal expansion and contraction thereof.

[0071] Because of their configuration the connectors 74 take the movement of the loop 56 and the exterior surface 58 relative to each other (i.e., due to thermal expansion and contraction) into account. As will be appreciated by those skilled in the art, the tank wall 60 expands and contracts in response to corresponding changes in its temperature, and the loop 56 also expands and contracts according to changes in its temperature. Those skilled in the art will also be aware that the expansion and contraction of these elements is primarily influenced by the temperature of the salt hydrate inside the tank 42.

[0072] For example, as the salt in the tank 42 is heated, the tank wall 60 is heated, via conduction. As will be described, the thermal energy storage means 24 includes features designed to maintain the salt at a relatively high temperature for as long as possible, e.g., thermal insulation of the railway car body 46. However, after thermal energy is stored in the thermal energy storage means 24, heat is drawn from the molten salt, and as its temperature falls, the temperature of the walls 60 of the tank 42 decrease, causing them to contract. In the same way, the loops 56 expand when hotter water is directed through them. Over time, the water in the loops 56 is not heated as much, because the salt is gradually losing its heat. The loops 56 contract as the temperature of the water is decreased. The connectors 74 are designed to take into account the expansion and contraction of the loops 56 and the tank wall 60 at different times and at different rates.

[0073] It is also preferred that the thermal energy storage means 24 additionally includes one or more impeller subassemblies 76 for mitigation of thermal stratification of the thermal storage medium 25 when molten. Each impeller subassembly 76 preferably includes a blade element 78, for agitating the thermal storage medium 25 when molten, a shaft 80 connected to the blade element 78, and a motor 82 for rotating the shaft 80. Because the blade 78 is securely mounted on the shaft 80, rotation of the shaft 80 results in corresponding rotation of the blade 78.

[0074] It will be understood that a number of impeller subassemblies 76 preferably are positioned so that the blades 78 thereof are inside the tank 42. Only one impeller subassembly 76 is shown in Fig. 8A for clarity of illustration.

[0075] Those skilled in the art would appreciate that a variety of arrangements of the heat transfer tubes 56 are possible. In one embodiment, illustrated in Fig. 6, the heat transfer tubes 56 preferably are divided into three loops identified in Fig. 6 as 56A, 56B, and 56C for convenience. Each of the loops 56A-56C is connected to the steam drum 73 in which steam (or steam and hot water, as the case may be) resulting from water in the loops 56A-56C being heated by the molten salt is accumulated. The valves 62 controlling flow of the heat transfer medium in the loops 56A-56C preferably are controlled by the controller 64 to produce steam (or steam and hot water) having the desired characteristics, as will be described.

[0076] As is known in the art, molten salt hydrate is corrosive to a variety of materials. In one embodiment, the tank wall 60 preferably includes an interior liner element 86 which preferably is substantially resistant to corrosion (Figs. 9, 10). The interior liner element 86 preferably is made of any suitable material. For example, where the thermal energy storage medium 25 is a salt hydrate, the interior liner element 86 preferably is stainless steel. It is also preferred that the tank wall 60 includes an exterior element 88 (i.e., including the exterior surface 58 thereon, facing outwardly) which, in one embodiment, is copper. It is preferred that copper is used as the exterior element 88 because of its superior heat-conducting characteristics.

[0077] For the purposes of discussion, the heat transfer means 26 is schematically illustrated in a simplified form only in Fig. 6. Those skilled in the art would be aware that various numbers of loops of heat transfer tubes may be used to transfer heat to the heat transfer medium.

[0078] As indicated in Fig. 6, the water is pumped into the loop 56A in the direction indicated by arrow "Di ". By controlling the valves, the characteristics of the steam produced are controlled. For example, if the valve "Vj" is open, then water heated in the loop 56A is allowed to flow into the steam drum 73, in the direction indicated by arrow "D₂" in Fig. 6. On the other hand, if the valve "Vi " is closed and the valve "V₂" is open, then the heated water from the loop 56A is directed to the loop 56B, flowing in the direction indicated by arrow "D3". Because the water travels through each of the loops 56A and 56B, it is heated to a higher temperature than water which travels through only the loop 56A. If the valve "V3" is open and the valve "V4" is closed, then hot water heated in the loop 56B is allowed to flow into the steam drum 73, in the direction indicated by arrow "D₄". The steam resulting would be at a higher temperature than steam resulting from the flow of hot water into the steam drum through the valve "Vi ".

[0079] In the same way, when the valve "V₃" is closed and the valve "V₄" is open, hot water flows in the direction indicated by arrow "D₅" in Fig. 6. In this situation, the hot water is heated still further in the loop 56C. As can be seen in Fig. 6, in order to permit the heated water to flow into the steam drum 73 (as indicated by arrow "D₆"), the valve "V₅" is open. It will be understood that, as schematically illustrated in Fig. 6, the valves "Vi"-"Vy preferably are controlled by the computer valve controller 64. In this way, the valves are controllable in order that the steam which flows out of the steam drum as indicated by arrow "D₇" meets the applicable criteria, e.g., temperature and/or volume.

[0080] The water preferably is pumped into the loops 56 from a water accumulator 90 located at an end 92 of the railway car body 46. The release of the steam from the steam drum 73 preferably is effected via a steam valve tree (not shown) located at an opposite end 94 of the railway car body 46.

[0081] As can be seen in Fig. 8A, in one embodiment, the heat transfer means 26 preferably includes two heat transfer subassemblies, identified in Fig. 8A for convenience as Hi and H₂. In one embodiment, the thermal energy storage means 24 preferably also includes thermal insulation 96 in one or more roof elements 98. Such insulation may be any suitable insulation. Also, side walls 101 of the railway car body 46 preferably are insulated. Those skilled in the art would be aware of suitable insulation means. For instance, the railway car side wall 101 may include two walls (i.e., interior and exterior) separated by a small space from which air has generally been removed, i.e., to provide a partial vacuum between the railway car walls. Preferably, the railway car body 46 also includes inner thermal insulation 103 located between the tank 42 and the side walls 101. The inner insulation 103 preferably is any suitable material. For example, in one embodiment, the inner insulation 103 preferably is ceramic wool. It will be understood by those skilled in the art that the thermal insulation is intended to insulate the salt hydrate in the tank (and the water in the heat transfer subassembly), to minimize heat loss therefrom.

INDUSTRIAL APPLICABILITY

[0082] In use, energy inputs to the system 20 are distributed by the distribution means

21 to store thermal energy in the thermal energy storage means 24. At least part of the stored thermal energy is transferred from the thermal energy storage means 24 by the heat transfer means 26. In one embodiment, the heat transfer means provides thermal energy to the energy utilization means 36. [0083] Another embodiment of the energy storage and transfer system 220 of the invention is illustrated in Figs. 1 1 and 12. In one embodiment, the energy storage and transfer system 220 preferably includes a distribution means 221 for distributing thermal energy, and a thermal energy storage means 224 including a thermal storage medium 225 for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means 221 , as stored thermal energy. The system 220 preferably also includes a heat transfer means 226 including a heat transfer medium, for transferring at least a part of the stored thermal energy between the thermal storage medium and the heat transfer medium. As will be described, the heat transfer medium preferably includes one or more inert gases 205 that is directed through the thermal storage medium 225, when the thermal storage medium is substantially molten.

[0084] Preferably, the heat transfer means 226 includes one or more gas distribution manifolds 207 for distributing the inert gas into the molten thermal energy storage medium 225. It is also preferred that the heat transfer means 226 includes one or more gas collection manifolds 209 positioned for collecting the inert gas after the inert gas has moved through the molten thermal storage medium 225.

[0085] In one embodiment, the thermal energy storage means 226 preferably also includes one or more impeller subassemblies 276 for mitigation of thermal stratification of the thermal storage medium 225 when molten. Preferably, each impeller subassembly 276 includes a blade element 278, for agitating the thermal storage medium 225 when molten, a shaft 280 connected to the blade element 278, and a motor 282 for rotating the shaft.

[0086] As can be seen in Figs. 1 1 and 12, the inert gas or gases are used as the heat transfer medium, directly contacting the molten salt hydrate. In this embodiment, tubes in which the heat exchange medium flows are unnecessary, as will be described.

[0087] Specifically, Fig. 1 1 shows a partial longitudinal cross section of a railway car

244 with a railway car body 246 and the storage means 224 containing the thermal energy storage medium 225. The inert gas is pumped into the distribution manifolds 207 (Figs. 1 1, 12) and enters a tank 242 via nozzles 21 1 to supply heat energy to or withdraw heat energy from the molten salt. The inert gas is withdrawn from the energy storage means 224 at the top via the exit (collection) manifolds 209. [0088] Fig. 12 shows a transverse cross-section of the railway car 244. The thermal energy storage medium 225 is contained in the tank 242 that is located on the car body 246. Thermal insulation 203 is provided between the tank 242 and a railway car side wall 201 and additional thermal insulation 296 is also provided in one or more roof elements 298. The impeller subassemblies 276 are provided to improve the temperature uniformity and mitigate any thermal stratification of the molten salt hydrate.

[0089] The heat exchange medium preferably is an inert gas or gas mixture containing at least one gas selected from the group consisting of nitrogen, argon, helium and carbon dioxide. Those skilled in the art would be aware of suitable inert gases. The inert gas or gases (or their mixtures, as the case may be), are injected directly into the thermal storage medium 225, e.g., the molten salt hydrate, and then withdrawn from the thermal energy storage medium 225. The heat transfer means 226 does not include heat exchange tubes. Instead, the heat transfer means 226 directs the heat transfer medium directly into the thermal storage medium 225, and also withdraws the heat transfer medium therefrom.

[0090] For the purposes of illustration, in Fig. 12, the inert gas 205 is shown in the thermal storage medium 225 in the form of bubbles thereof. (It will be understood that the size of the bubbles in Fig. 12 is exaggerated for clarity of illustration.) The bubbles result from the release of the inert gas 205 from the distribution manifold 207, and the bubbles rise generally upwardly through the molten thermal storage medium 225 (i.e., generally in the direction indicated by arrow "E") until the inert gas reaches a head space 208 in the tank 242 above the thermal storage medium 225. Heat is transferred from the thermal storage medium 225 to the inert gas as it rises through the thermal energy storage medium 225, and the heated inert gas in the head space 208 is collected at the collection manifold 209, through which the inert gas is removed, for utilization thereof.

[0091 ] A distribution means 221, in the form of resistive elements 255, is also illustrated in Fig. 12. As described above, the distribution means 221 may be provided in different configurations, depending on the source of the energy inputs. Accordingly, it will be understood that the distribution means 221 of the system 220 may have other configurations, depending on the source of the energy inputs. [0092] Those skilled in the art would appreciate that, in the alternative, heat may be transferred from the inert gas 205 to the thermal storage medium 225. In this way, the thermal storage medium may be recharged.

[0093] It will be understood that the energy input for the system 220 may be electrical power generated by dynamic braking implemented in a locomotive included in the system 220, as described above.

[0094] Another embodiment of the energy storage and transfer means 320 of the invention is illustrated in Fig. 13. The energy storage and transfer system 320 preferably includes a distribution means 321 for distributing thermal energy, a thermal energy storage means 324 comprising a thermal storage medium 325 for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means 321, as stored thermal energy, and a heat transfer means 326 comprising a heat transfer medium, for transferring at least a part of the stored thermal energy from the thermal energy storage medium 325 to the heat transfer medium. In one embodiment, the heat transfer means 326 preferably includes one or more heat transfer tubes 356 through which the heat transfer medium is directed. Each heat transfer tube 356 is positioned proximal to the thermal energy storage medium 325 for heat transfer between the thermal storage medium and the heat transfer medium. Preferably, the heat transfer medium is a liquid metal directed through the heat transfer tube 356.

[0095] In one embodiment, it is also preferred that the heat transfer means additionally includes water directed through the liquid metal, for transfer of at least a portion of the stored thermal energy from the heat transfer medium to the water. Preferably, the water is distributed in the liquid metal in droplets. The heat transfer means 326 preferably includes one or more distribution manifolds 307 for distributing the droplets of water into the liquid metal. The heat transfer medium also includes one or more collection manifolds 309 for collecting the droplets of water after the droplets have moved through the liquid metal.

[0096] A distribution means 321 , in the form of resistive elements 355, is also illustrated in Fig. 13. As described above, the distribution means 321 may be provided in different configurations, depending on the source of the energy inputs. Accordingly, it will be understood that the distribution means 321 of the system 320 may have other configurations, depending on the source of the energy inputs. [0097] The heat transfer tubes 356 preferably are filled with a metal having a low melting point, such as tin, which melts at 231°C and does not boil until reaching temperatures much higher than the salt hydrate's operating range, e.g. 2603°C for tin. When the molten salt hydrate is in its typical operating range, e.g., between 250°C and 600°C, the molten tin in the heat exchanger tubes is heated by the molten salt hydrate. Preferably, water is introduced in the form of small droplets at the bottom of the tin-containing heat exchange tube 356.

[0098] As can be seen in Fig. 13, the liquid metal (identified in Fig. 13 by reference numeral 327) is located in the heat transfer tube 356, and the water droplets (identified by reference numeral 310) are released into the liquid metal 327 from the distribution manifold 307. The droplets 310 rise generally upwardly through the liquid metal 327 (i.e., generally in the direction indicated by arrow "F") until they reach a head space 313 in the heat transfer tube 356 above the liquid metal 327. The heated water (i.e., steam) is removed from the head space 313 via the collection manifold 309.

[0099] It will be understood that heat is transferred from the molten thermal energy storage medium 325 to the liquid metal 327. When the water droplets 310 rise through the liquid metal 327, heat is transferred to them also, primarily from the liquid metal 327.

[00100] The water preferably rapidly evaporates in the molten tin and rises to the surface of the liquid metal, where it is collected from the head space. The steam may be used to do work, e.g., it may be transferred to, and used directly in, a steam engine. This design allows for tubes that are almost equal in temperature (isothermal) and therefore have a long thermal life. The only thermal stress is within the molten tin itself where the water is flashed to steam and rises to the surface where it is collected.

[00101] It will be understood that the energy input for the system 320 may be electrical power generated by dynamic braking implemented in a locomotive included in the system 320, as described above.

[00102] As illustrated above one particularly suitable application for the invention is the harvest and use of renewable energy for use in railways, specifically to propel emission- free locomotives. In one specific aspect the locomotive is a steam locomotive retrofitted to be propelled by renewable energy stored in molten salts to replace the coal-fired system. The tender designated to store the coal can be dislodged if reversibly coupled to but not permanently attached to the locomotive. It can also be converted to receive a thermal energy storage means in addition to the thermal energy storage means contained in the railway cars. The boiler can serve as the heat exchanger for the heat transfer means and in the case of using water/steam as heat transfer means it can be bypassed to supply the steam directly to the piston drive system.

[00103] It will be appreciated by those skilled in the art that the invention can take many forms, and that such forms are within the scope of the invention as described above. The foregoing descriptions are exemplary, and their scope should not be limited to the preferred versions provided therein.

Claims

I claim:

1. An energy storage and transfer system comprising: a distribution means for distributing thermal energy; a thermal energy storage means comprising a thermal energy storage medium for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means, as stored thermal energy; and a heat transfer means comprising a heat transfer medium for transferring at least a part of the stored thermal energy from the thermal energy storage medium to the heat transfer medium.

2. An energy storage and transfer system according to claim 1 additionally comprising a collection means for collecting thermal energy for transmission thereof to the distribution means.

3. An energy storage and transfer system according to claim 2 in which the collection means comprises means for converting solar energy to thermal energy.

4. An energy storage and transfer system according to claim 3 in which: the collection means comprises at least one array of primary reflectors; the distribution means comprises a plurality of secondary reflectors; the primary reflectors are positioned to reflect sunlight onto the secondary reflectors; and the secondary reflectors are positioned to reflect the sunlight reflected from the primary reflectors onto the thermal storage medium.

5. An energy storage and transfer system according to claim 1 in which the heat transfer means transfers said part of the stored thermal energy therefrom to an energy utilizing means.

6. An energy storage and transfer system according to claim 5 additionally comprising a transportation means for transporting the storage means to the energy utilizing means.

7. An energy storage and transfer system according to claim 6 in which the thermal energy storage means comprises an insulated container comprising a tank in which the thermal storage medium is located.

8. An energy storage and transfer system according to claim 6 in which the transportation means comprises a railway car comprising a railway car body and the thermal energy storage means comprises an insulated container mounted on the railway car body, the insulated container comprising a tank in which the thermal storage medium is located.

9. An energy storage and transfer system according to claim 8 in which the heat transfer means comprises at least one heat transfer tube positioned for engagement with an exterior surface of a tank wall of the tank, the heat transfer medium being movable through the heat transfer tube for transfer of heat energy between the heat transfer medium and the thermal storage medium.

10. An energy storage and transfer system according to claim 9 in which the heat transfer medium is water.

11. An energy storage and transfer system according to claim 9 in which movement of the heat transfer medium through said at least one heat transfer tube is at least partially controlled by at least one valve controlled by a controller to provide a predetermined volume of the heat transfer medium at a predetermined temperature over a predetermined time period.

12. An energy storage and transfer system according to claim 9 in which the heat transfer tube is connected to the exterior surface of the tank wall of the tank by at least one connector, said at least one connector being formed to permit movement of the tank wall and the heat transfer tube relative to each other due to thermal expansion and contraction thereof.

13. An energy storage and transfer system according to claim 8 in which the thermal energy storage means additionally comprises at least one impeller subassembly for mitigation of thermal stratification of the thermal storage medium when molten, said at least one impeller subassembly comprising: a blade element, for agitating the thermal storage medium when molten; a shaft connected to the blade element; and a motor for rotating the shaft.

14. An energy storage and transfer system according to claim 1 in which: the distribution means comprises at least one resistive element for generating thermal energy when electric current is passed through said at least one resistive element; and said at least one resistive element is configured for transfer of the thermal energy therefrom to the thermal energy storage medium, for storage of said portion of the distributed thermal energy in the thermal energy storage medium.

15. An energy storage and transfer system according to claim 1 additionally comprising a transportation means comprising an energy utilizing means for consuming at least said part of the stored thermal energy to effect movement of the transportation means.

16. An energy storage and transfer system according to claim 15 in which: the distribution means comprises at least one resistive element for generating thermal energy when electric current is passed through said at least one resistive element; said at least one resistive element is configured for transfer of the thermal energy therefrom to the thermal energy storage medium, for storage of said portion of the distributed thermal energy in the thermal energy storage medium; the transportation means additionally comprises a dynamic braking subsystem for generating electric power; and the system additionally comprising transmission means for providing the electric current to the distribution means.

17. An energy storage and transfer system according to claim 16 in which: the transportation means comprises a prime mover that is steam-driven; and the heat transfer medium is directed from the heat transfer means to the prime mover, to power movement of the transportation means.

18. An energy storage and transfer system according to claim 1 in which the thermal storage medium comprises a phase-change material.

19. An energy storage and transfer system according to claim 18 in which the phase- change material is a salt hydrate.

20. An energy storage and transfer system comprising: a distribution means for distributing thermal energy; a thermal energy storage means comprising a thermal storage medium for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means, as stored thermal energy; a heat transfer means comprising a heat transfer medium, for transferring at least a part of the stored thermal energy between the thermal storage medium and the heat transfer medium; and the heat transfer medium comprising at least one inert gas that is directed through the thermal storage medium, when the thermal storage medium is substantially molten.

21. An energy storage and transfer system according to claim 20 in which the heat transfer means comprises: at least one gas distribution manifold for distributing said at least one inert gas into the molten thermal energy storage medium; and at least one gas collection manifold positioned for collecting said at least one inert gas after said at least one inert gas has moved through the molten thermal storage medium.

22. An energy storage and transfer system according to claim 20 in which the thermal energy storage means additionally comprises at least one impeller subassembly for mitigation of thermal stratification of the thermal storage medium when molten, said at least one impeller subassembly comprising: a blade element, for agitating the thermal storage medium when molten; a shaft connected to the blade element; and a motor for rotating the shaft.

23. An energy storage and transfer system according to claim 20 in which heat is transferred to the thermal storage medium from said at least one inert gas.

24. An energy storage and transfer system comprising: a distribution means for distributing thermal energy; a thermal energy storage means comprising a thermal storage medium for storing at least a portion of the distributed thermal energy transferred thereto from the distribution means, as stored thermal energy; a heat transfer means comprising a heat transfer medium, for transferring at least a part of the stored thermal energy from the thermal energy storage medium to the heat transfer medium; the heat transfer means comprising at least one heat transfer tube through which the heat transfer medium is directed, said at least one heat transfer tube being positioned proximal to the thermal energy storage medium for heat transfer between the thermal storage medium and the heat transfer medium; and the heat transfer medium being a liquid metal directed through said at least one heat transfer tube.

25. An energy storage and transfer system according to claim 24 in which the heat transfer means additionally comprises droplets of water that are directed through the liquid metal, for transfer of at least a portion of the stored thermal energy from the heat transfer medium to the water droplets.

26. An energy storage and transfer system according to claim 25 in which the heat transfer means comprises: at least one distribution manifold for distributing said droplets of water into the liquid metal; and at least one collection manifold for collecting said droplets of water after said droplets have moved through the liquid metal.