WO2012123738A1

WO2012123738A1 - Thermal energy store

Info

Publication number: WO2012123738A1
Application number: PCT/GB2012/050557
Authority: WO
Inventors: Thomas Lipinski
Original assignee: Green Structures Limited
Priority date: 2011-03-15
Filing date: 2012-03-14
Publication date: 2012-09-20
Also published as: GB201200659D0; GB2511392A; GB2489069A; GB201322180D0; GB201104346D0; GB2489011A

Abstract

A thermal energy store comprising a vessel (2) having at least one fluid flow path (3) extending therethrough, the fluid flow path (3) arranged to carry a heat transfer fluid for transferring energy to and/or from the thermal energy store (1), wherein the fluid flow path (3) is constructed and arranged in the vessel such that the fluid flow path defines at least one cartridge aperture (5) to receive a thermal energy storage cartridge (20) containing a heat storage material.

Description

THERMAL ENERGY STORE

This invention relates to a thermal energy store. In particular, it relates to a thermal energy store having removable heat storage cartridges. It also relates to a thermal energy store in combination with a cartridge and also relates to a cartridge. Further, it relates to a heating or cooling system incorporating the thermal energy store.

Heating and cooling systems that use heat storage materials such as phase change materials (PCM) are known. A phase change material is one that is able to store relatively large amounts of energy as latent heat during a phase transition. The use of PCMs is attractive as they improve the thermal capacity of a heating or cooling system, or a system that stores energy to be used for electricity generation. A range of PCMs are available with different transition temperatures. For example, using a PCM having a transition temperature of around 40°C, heat could be stored during the day for use in space heating at night. Alternatively, using a PCM having a transition temperature of around 10 to 15°C, the PCM could be cooled at night, when the ambient temperature is lower, which can be used to provide cooling, such as cool air during the day. The use of PCM can substantially improve the efficiency of heating and cooling systems. Further, thermal energy stores that use PCM can be used to maintain a comfortable environment in an office or home or can be used to store energy for use later. This is advantageous if the store is used in combination with an electricity generation system, which can be arranged to generate electricity at the most advantageous times and the thermal energy can be stored until those times.

Known energy stores comprise large tanks that are typically buried underground. Many discrete containers that house the PCM are housed inside the tanks. Air or other working fluid can then be flowed through the tank to "charge" the PCM and also to "discharge" the PCM. Depending on the required use, "charging" the PCM may comprise heating the PCM and therefore "discharging" will involve removing the heat from the PCM for use in space heating or hot water, for example. Alternatively, "charging" may involve cooling the PCM and therefore "discharging" will involve using the PCM to cool air or working fluid, for use in air conditioning, for example. The installation of such large tanks is cumbersome and expensive, especially when retrofitting. Further, maintenance of the system is problematic as the tank may need to be excavated. For instance, if the PCM has separated out of solution it is a major job to remove the containers from the tank.

According to a first aspect of the invention we provide a thermal energy store comprising a vessel having at least one fluid flow path extending therethrough, the fluid flow path arranged to carry a heat transfer fluid for transferring energy to and/or from the thermal energy store, wherein the fluid flow path is constructed and arranged in the vessel such that the fluid flow path defines at least one cartridge aperture to receive a thermal energy storage cartridge containing a heat storage material. This is advantageous as it provides a flexible arrangement for storing heat. The system is particularly suited to retrofit applications as the vessel can be mounted and secured in position and the cartridges slotted into the cartridge aperture adjacent the fluid flow path. As the cartridges are removable, installation is straightforward and the device is easy to customise. The vessel can be relatively lightweight and a cartridge with an appropriate temperature phase change material therein can be selected and slotted into the cartridge aperture.

Preferably the fluid flow path is arranged to define a plurality of cartridge apertures to receive a stack of cartridges, wherein the fluid flow path extends between the cartridges in the stack. This is advantageous as a substantially vertical stack of cartridges is easy to load into the vessel. Further, as the fluid flow path can extend between each of the cartridges in the stack, good thermal contact between the fluid flow path and the heat storage material in the cartridges can be achieved.

The fluid flow path may be arranged to define at least one platform, and preferably a plurality of platforms, that form part of the or each cartridge aperture. Preferably, the or each platform forms the base of a cartridge aperture for receiving the cartridge(s) thereon. Alternatively, the or each platform may be arranged to extend within a hollow portion of the or each cartridge.

Preferably the fluid flow path comprises a single conduit arranged to form the platforms in series. Alternatively, the fluid flow path may comprise a main conduit and the plurality of platforms are formed by lengths of branch conduits, arranged in parallel, that branch from the main conduit. Further, the fluid flow path may be arranged in a combination of the series and parallel arrangement. The platforms may include a support structure in addition to the fluid flow path for supporting the fluid flow path and/or the cartridge when loaded into the cartridge aperture.

Preferably, the cartridge apertures comprise slots for receiving substantially plate shaped cartridges, the slots arranged such that the plates shaped cartridges stack one above the other with the fluid flow path arranged to extend between the cartridges.

Preferably the at least one fluid flow path is arranged to form a plurality of tines that form the platforms, wherein the cartridge aperture is formed between the tines. Preferably, each platform comprises a plurality of tines. This is particularly advantageous as the tines or "prongs" provide a convenient structure in which to slot the thermal energy storage cartridges. The tines provides support for the cartridges and the gaps between the tines allow cartridges in adjacent cartridge apertures to abut and thus support their weight but also to provide close thermal contact between the cartridges and fluid flow path.

Preferably the tines are formed by portions of the fluid flow path having a substantially U-shaped arrangement.

Preferably the tines extend from a back wall of the vessel towards the mounting opening in the vessel. Preferably the vessel is insulated. Preferably the vessel includes a mounting opening through which the cartridge(s) can be mounted in the cartridge aperture(s). Preferably the mounting opening is closed by a removable door to provide access to the at least one cartridge aperture. This makes the thermal energy store easy to service. Preferably the vessel includes external connectors connected to the fluid flow path to enable further conduits to be connected to the thermal energy store.

Preferably the store includes a first fluid flow path and a second, separate fluid flow path. This is advantageous as the first fluid flow path can be used to charge the thermal energy store and the second fluid flow path can be used to discharge the thermal energy store. Thus, the heat in the store can be used at the same time it is being fed into the store for storage. Preferably the first and second fluid flow paths are aligned with one another and may follow substantially the same path in defining the cartridge apertures.

According to a second aspect of the invention we provide a thermal energy store in combination with a heat storage cartridge, the store comprising a vessel having at least one fluid flow path extending therethrough, wherein the fluid flow path is constructed and arranged in the vessel such that the fluid flow path defines at least one cartridge aperture for receiving the heat storage cartridge, wherein the cartridge contains a heat storage material.

This is advantageous because the thermal energy store is easy to assemble as the vessel can be mounted in position and then the cartridges slotted into the cartridge apertures.

Preferably the heat storage material is a phase change material. The fluid flow path may be arranged to define at least one platform, and preferably a plurality of platforms, that form part of the or each cartridge aperture. Preferably, the or each platform forms the base of a cartridge aperture for receiving the cartridge(s) thereon. Alternatively, the or each platform may be arranged to extend within a hollow portion of the or each cartridge. The platforms may include a support structure in addition to the fluid flow path for supporting the fluid flow path and/or the cartridge when loaded into the cartridge aperture.

Preferably, the cartridge apertures comprise slots and the heat storage cartridges are substantially plate shaped, the slots arranged such that the cartridges stack one above the other, in use, with the fluid flow path arranged to extend between the cartridges. This is advantageous as the relatively flat cartridges arranged such that the plane of the cartridge is parallel to the ground helps to prevent stratification of the heat storage material in the cartridge, as the cartridges have a relatively small height.

Preferably the at least one fluid flow path is arranged to form a plurality of tines that comprise the platforms, wherein the cartridge aperture is formed between the platforms. Preferably, each platform comprises a plurality of tines. Preferably the tines are formed by portions of the fluid flow path having a substantially U- shaped arrangement. Preferably the cartridge comprises a sealed container having the heat storage material therein.

Preferably the cartridge includes a groove in its external surface that is complimentary to the fluid flow path, and in particular a tine, the groove arranged to receive the fluid flow path therein when the cartridge is mounted in the cartridge aperture. This is advantageous as the cartridges can be constructed to fit closely together and in close thermal contact with the fluid flow path for efficient heat transfer between the fluid flow path and the cartridges. According to a third aspect of the invention we provide a heat storage cartridge to be used in the thermal energy store of the first aspect of the invention, the cartridge containing a heat storage material and constructed and arranged to slide into a cartridge aperture in the thermal energy store and contact a fluid flow path such that thermal energy can be transferred between the cartridge and the fluid flow path.

According to a fourth aspect of the invention, we provide a heating or cooling system including the thermal energy store of the second aspect of the invention.

According to a fifth aspect of the invention, we provide an electricity generation system comprising the thermal energy store of the second aspect of the invention and an electricity generation device, the electricity generation device adapted to generate electricity from thermal energy received via the thermal energy store.

There now follows by way of example only a detailed description of the present invention with reference to the accompanying drawings, in which; Figure 1 shows a perspective view of an embodiment of a thermal energy store without the cartridges loaded therein;

Figure 2 shows a perspective view of a heat storage cartridge; Figure 3 shows a perspective view of a thermal energy store when fully loaded with heat storage cartridges;

Figure 4 shows a plan view of the tines of a platform of a fluid flow path in situ with a cartridge;

Figure 5 shows a close up view of a plurality of cartridge stacked together with the fluid flow path extending between each of them;

Figures 6a and 6b shows a perspective view and side view respectively of a fluid flow path forming a plurality of platforms in series; and

Figures 7a and 7b shows a perspective view and side view respectively of a fluid flow path forming a plurality of platforms in a parallel arrangement. Figure 1 shows an embodiment of a thermal energy store 1. The thermal energy store 1 of this embodiment is for use in a solar heating system. However, it will be appreciated that the thermal store could be integrated into a hot water system, an air or water cooling systems, a space heating system or electricity generation system or the like. The thermal store has utility in any system where heat or "cold" needs to be used at a different time to when it is generated. Thus, it could be used to store excess energy generated by a turbine, concentrated solar power unit, photovoltaic solar cell or waste heat from another device, such as an industrial machine, for example, for use later. It is becoming popular to generate energy locally by using domestic solar panels or a domestic wind turbine or by a commercial Decentralised Generation arrangement. Any excess energy can be sold to electricity companies. Thus, the thermal energy store could be used to store the energy until a time that was most advantageous to feed electricity to the electricity supplier or electricity grid, such as at peak time.

The thermal energy store 1 comprises a vessel 2 and a fluid flow path 3 that extends within the vessel 2. The fluid flow path is arranged to carry a heat transfer fluid for transferring heat (or "cool") into the store 1 and/or extracting heat (or "cool") from the store 1. The fluid flow path 3 comprises a continuous conduit extending from an input to an output. The fluid flow path 3 is arranged into a plurality of rows or platforms 4. Only four platforms 4 are shown in Figure 1 for clarity, but Figures 3, 6a, 6b, 7a and 7b show an embodiment with many more platforms 4.

In the present embodiment, the vessel 2 includes a first fluid flow path 3a and a second, separate, fluid flow path 3b. The first and second flow paths 3a, 3b run side by side. The first fluid flow path 3a may receive a heat transfer fluid from a heat generating source, such as a solar panel. The second fluid flow path 3b may be connected to a domestic hot water system for taking heat from the thermal energy store 1 to heat the water in the hot water system. Thus, the fluid flow paths typically connect to further conduits to form heat transfer loops with other equipment. In this embodiment, each platform 4 defines a base of a cartridge aperture 5. The cartridge apertures 5 are each arranged to receive a cartridge 20 (as shown in Figure 2) that contains a heat storage material. The cartridge apertures 5 comprise slots arranged to receive plate shaped cartridges. The plane of the slots is substantially horizontal in use. This is advantageous because using a heat storage material that is compartmentalised into a plurality of cartridges 20 of relatively low vertical height helps to prevent stratification and separation of the heat storage material. This is particularly important when the heat storage material is a PCM, such as a eutectic salt solution. The width and/or length of the cartridge may be 3, 4, 5, 6, 7 or more times the vertical height of the cartridge. Further, the thermal energy store is easy to install as the vessel can be positioned and secured and then the cartridges slotted into the cartridge apertures, which ensures the weight of each particular component of the store 1 is relatively low. The vessel 2 comprises an insulated box 6 having a cartridge mounting opening 7. The opening 7 is formed in one side of the box 6 and is closed by an insulated closure (not shown). The closure may be hinged to the box 6 or may be separate. The closure includes a securing element to secure it to the vessel 2 and close the cartridge mounting aperture 7. The vessel 2 includes an input aperture 8 and an output aperture 9 through which the fluid flow path conduits or connectors to the fluid flow paths extend. This allows the fluid flow path 3 to be connected to further conduits for conveying heat transfer fluid through the store 1. Thus, the input aperture 8 comprises the input to the first and second fluid flow paths 3a, 3b and output aperture 9 comprises the output to the first and second fluid flow paths 3a, 3b. However, it will be appreciated that the apertures could be arranged differently depending on the particular set up of the thermal energy store 1.

Figure 2 shows a cartridge 20 comprising a hollow, substantially rectangular plate shaped container. The cartridge contains a heat storage material such as a phase change material. The heat storage material can be chosen to suit the desired application for the thermal energy store 1. For example, for space heating a PCM having a transition temperature of 30-40°C may be used. Alternatively, for high temperature storage, granular salt may be used. It will be appreciated that the materials used to fabricate the vessel, fluid flow path(s) and cartridge will need to be appropriate to the desired operating temperature.

The cartridge 20 comprises a first face 21 and a second face 22, opposite the first face 21. The faces 21 and 22 are separated by four side walls 23. A filling aperture 24, closed by a cap (not shown), is located in one of the side walls 23. The filling aperture 24 provides access to the inside of the container for filling, emptying or refilling (partially or fully) the cartridge 20 with heat storage material. The cap for the filling aperture 24 is removable but could be permanently affixed over the filling aperture once the cartridge has been filled.

The first face 21 includes four spaced parallel grooves 25. The second face 22 also includes four grooves in a corresponding position to those on the first face 21. The grooves 25 extend from one of the side walls to an opposed side wall. The grooves 25 result in the cartridge having a plurality of thinner portions 26 and a plurality of thicker portions 27. The grooves 25 have a depth that is substantially half that of the diameter (or width if not of circular cross- section) of the fluid flow path conduit 3a, 3b. The number of grooves 25 is dependent on the arrangement of the fluid flow path 3a, 3b. Thus, the grooves provide means to receive the flow path for close thermal contact. In a further embodiment (not shown), the grooves 25 are deeper, to receive the whole width of the fluid flow path conduit 3a, 3b. Accordingly, the grooves are only provided on one face 21 , 22 of the cartridge 20. It will be appreciated that combinations of these alternative arrangements could be provided.

As shown in Figures 3 and 5, the cartridges 20 slot into the cartridge apertures 5 between the platforms 4. Thus, the vessel 2 receives a stack of cartridges 20 which abut one another over the thicker portions 27 and the fluid flow paths 3a, 3b extend into the gap formed between the thinner portions 26.

Figure 4 shows a plan view of a cartridge 20 when slotted into the cartridge aperture 3 into contact with a platform 4. The platform 4 comprises four tines 41 , 42, 43 and 44. The tines are formed by substantially U-shaped portions of the fluid flow path 3a and 3b. The fluid flow paths 3a and 3b are arranged to form the tines 41 , 42, 43, 44 in series and then extend to the next adjacent platform 4 where they are arranged to form the four tines of that platform. It will be appreciated that more or less tines may be provided, depending on the size of the vessel, the fluid flow path or the energy density of the heat storage material in the cartridges 20. The width of the tines 41 , 42, 43, 44 correspond to the width of the grooves 25 so that the tines and cartridges 20 are in close thermal contact.

Figures 6a and 6b show the arrangement of the fluid flow paths 3a and 3b when in a "series" arrangement. The vessel 2 has been omitted from these Figures for clarity. The fluid flow paths 3a and 3b include an input/output section 60 and an output/input section 61. The section 60 comprises an input for flow path 3a and an output section for flow path 3b. The section 61 comprises an output section for flow path 3a and an input section for flow path 3b. The input/output section 60 extends to the base of the vessel 2 and the fluid flow paths 3a, 3b form the four tines of the first, lowermost, platform 4a. The fluid flow path then turns upward at point 62 to form the tines of the second platform 4b. The fluid flow path then turns upward once more at point 63, but on an opposite side to upward turn 62, to form the third platform 4c. This continues to the uppermost platform 4y, where the fluid flow paths 3a and 3b meet the output/input section 61.

Figures 7a and 7b show an alternative "parallel" arrangement. In this arrangement, the fluid flow paths 3a and 3b each comprise a main input conduit 70, a main output conduit 71 and a plurality of branch conduits 73. The plurality of branch conduits extend between the main input conduit 70 and the main output conduit 71 to form the platforms 4a to 4y. Thus, each branch conduit 73 branches from the main input conduit 70 and extends to form the tines of one of the platforms 4 and then joins the main output conduit 71. It will be appreciated that the fluid flow paths 3a, 3b may be arranged in a combination of the "series" and "parallel" arrangement described above. In particular, the arrangement may include a main input conduit 70 and a main output conduit 71 and the branch conduit may form a plurality of platforms 4 in the manner of the "series" arrangement before joining the main output conduit 71. In use, the vessel 2 is put into position and the necessary conduits connected to the input and output of the fluid flow paths 3a, 3b. A plurality of cartridges having an appropriate heat storage material therein are selected. The same heat storage material may be selected for all of the cartridges, or the heat storage material may be selected based on where in the vessel the cartridge will be loaded. The cartridges 20 are then slotted into the cartridge apertures 5. When the thermal store is in use, heat transfer fluid is flowed through the first fluid flow path 3a and transfers its energy to the heat transfer material contained in the cartridges 20. Heat transfer fluid flowed through the second fluid flow path 3b can extract heat from the heat storage material of the cartridges or directly from the first fluid flow path 3a.

In a further embodiment, the thermal energy store 1 may be connected to an energy source, such as a concentrated solar panel by the fluid flow path 3a. The store 1 may also be connected to a steam turbine electricity generation device (not shown) by the second fluid flow path 3b. Thus, the store 1 will receive thermal energy from the solar panel and store it. When required, the stored thermal energy can be pumped to the electricity generation device for boiling water to generate steam which turns the electricity generation turbine, as will be known to those skilled in the art. The thermal energy store 1 provides an efficient and convenient means to store energy for when it is most worthwhile to utilise it for electricity generation.

Claims

1 . A thermal energy store comprising a vessel (2) having at least one fluid flow path (3) extending therethrough, the fluid flow path (3) arranged to carry a heat transfer fluid for transferring energy to and/or from the thermal energy store ( 1 ), wherein the fluid flow path (3) is constructed and arranged in the vessel such that the fluid flow path defines at least one cartridge aperture (5) to receive a thermal energy storage cartridge (20) containing a heat storage material.

2. A thermal energy store according to claim 1 , in which the fluid flow path (3) is arranged to define a plurality of cartridge apertures (5) to receive a stack of cartridges, wherein the fluid flow path extends between the cartridges in the stack.

3. A thermal energy store according to claim 1 , in which fluid flow path is arranged such that it defines a plurality of cartridge apertures (5), each for receiving a thermal energy storage cartridge (20), wherein the cartridge apertures comprise slots for receiving substantially plate shaped cartridges and the plane of the slots is substantially horizontal in use.

4. A thermal energy store according to any preceding claim, in which the fluid flow path (3) is arranged to define a plurality of platforms (4) that form part of each cartridge aperture (5) wherein each platform forms the base of a cartridge aperture for receiving the cartridges (20) thereon.

5. A thermal energy store according to claim 4, in which the fluid flow path comprises, at least in part, a single conduit (3a or 3b) arranged to form the platforms in series.

6. A thermal energy store according to claim 4, in which the fluid flow path comprises a main input conduit (70) and a main output conduit (71 ) and the plurality of platforms are formed by lengths of branch conduits (73), arranged in parallel, that branch from the main input conduit and join the main output conduit.

7. A thermal energy store according to any of claims 4 to 6, in which the platforms (4) include a support structure in addition to the fluid flow path for supporting the fluid flow path and/or the cartridge when loaded into the cartridge aperture.

8. A thermal energy store according to any of claims 4 to 7, in which the at least one fluid flow path (3) is arranged to form a plurality of tines (41 , 42, 43, 44) that form the platforms, wherein the cartridge aperture is formed between the tines.

9. A thermal energy store according to claim 8, in which each platform comprises a plurality of tines.

10. A thermal energy store according to claim 8 or claim 9, in which the tines (41 , 42, 43, 44) are formed by portions of the fluid flow path having a substantially U- shaped arrangement.

1 1. A thermal energy store according to any of claims 8 to 10, in which the tines extend from a back wall of the vessel towards a mounting opening (7) in the vessel.

12. A thermal energy store according to any of claims 1 to 10, in which the vessel includes a mounting opening (7) through which the cartridge(s) (20) can be mounted in the cartridge aperture(s), wherein the mounting opening is closed by a removable closure to provide access to the at least one cartridge aperture.

13. A thermal energy store according to any preceding claim, in which the store (1 ) includes a first fluid flow path (3a) and a second, separate fluid flow path (3b).

14. A thermal energy store according to claim 13, in which the first and second fluid flow paths (3a, 3b) are aligned with one another and follow substantially the same path in defining the cartridge apertures.

15. A thermal energy store in combination with a thermal energy storage cartridge, comprising a vessel (2) having at least one fluid flow path (3) extending therethrough, the fluid flow path arranged to carry a heat transfer fluid for transferring energy to and/or from the thermal energy store, wherein the fluid flow path (3) is constructed and arranged in the vessel such that the fluid flow path defines at least one cartridge aperture (5) to receive the thermal energy storage cartridge (20), wherein the cartridge contains a heat storage material.

16. A combination according to claim 15, in which the fluid flow path is arranged to define a plurality of cartridge apertures (5) to receive a stack of the cartridges (20), wherein the fluid flow path extends between the cartridges in the stack.

17. A combination according to claim 15, in which the fluid flow path is arranged to define a plurality of platforms that form part of the or each cartridge aperture (5).

18. A combination according to claim 15, in which fluid flow path is arranged such that it defines a plurality of cartridge apertures (5), each for receiving a thermal energy storage cartridge (20), wherein the cartridge apertures comprise slots for receiving substantially plate shaped cartridges and the plane of the slots is substantially horizontal in use.

19. A combination according to claim 17, in which the at least one fluid flow path is arranged to form a plurality of tines (41 , 42, 43, 44) that comprise the platforms, wherein the cartridge aperture (5) is formed between the platforms.

20. A combination according to claim 15, in which each platform comprises a plurality of tines (41 , 42, 43, 44).

21. A combination according to claim 19 or 20, in which the tines (41 , 42, 43, 44) are formed by portions of the fluid flow path having a substantially U-shaped arrangement.

22. A combination according to any of claims 15 to 21 , in which the cartridge (20) comprises a sealed container having the heat storage material therein.

23. A combination according to claim 15, in which the cartridge includes a groove (25) in its external surface that is complimentary to the fluid flow path, the groove (25) arranged to receive the fluid flow path (3) therein when the cartridge is mounted in the cartridge aperture.

24. A heat storage cartridge to be used in the thermal energy store of any of claims 1 to 14, the cartridge (20) containing a heat storage material and constructed and arranged to slide into a cartridge aperture (5) in the thermal energy store (1 ) and contact a fluid flow path such that thermal energy can be transferred between the cartridge and the fluid flow path (3).

25. A heating or cooling system including the thermal energy store in combination with a cartridge of claims 15 to 23.

26. An electricity generation system comprising the thermal energy store of claims 15 to 23 and an electricity generation device, the electricity generation device adapted to generate electricity from thermal energy received via the thermal energy store.