EP2396379A1

EP2396379A1 - Phase change material composition

Info

Publication number: EP2396379A1
Application number: EP10710097A
Authority: EP
Inventors: Mathew Holloway; Karina Torlei; Daniel Becerra; William Linsey Penfold
Original assignee: Artica Technologies Ltd
Current assignee: VKR Holding AS
Priority date: 2009-02-11
Filing date: 2010-02-11
Publication date: 2011-12-21
Also published as: GB2476427A; GB201106185D0; GB2476427B; CN102405270A

Abstract

A transportable PCM (phase change material) module comprises anumber of PCM packs; a housing for thermally insulting said number of PCM packs from a module's surrounding medium; spaces separating said packs and forming one or more channels for the flow of a fluid; said housing incorporating a fluid inlet and a fluidoutlet; whereby, in use, fluid flows through said channels from said inlet to said outlet.A PCM (phase change material) pack comprises a laminate of a first conducting panel and a second conducting panel enclosing a portion formed primarily of PCM; wherein said portion of PCM incorporates thermal conductors. A PCM (phase change material pack) comprises an envelope of relatively highly thermally conductive material enclosing a portion formed primarily of PCM; wherein said PCM portion incorporates a conductive compound mixed into said PCM which comprises carbon black particles.

Description

PHASE CHANGE MATERIAL COMPOSITION

FIELD OF THE INVENTION

[001] The invention relates to phase change material (PCM) packs and/or a phase change material compound suitable for use in phase change material packs. The invention is of particular applicability to the use of PCM for the ambient temperature control, for example within domestic and commercial buildings.

BACKGROUND

[002] Phase change materials use the latent heat property of material to store thermal energy and can be used in methods of controlling temperature. Phase change materials are either organic such as paraffin or non-paraffin compounds, inorganic (salt hydrates and metallics) or eutectic (organic-organic, organic-inorganic, inorganic-inorganic). Despite the wide variety of available phase change materials, the following drawbacks may exist dependent upon the phase change material chosen: • relatively low density which limits the energy stored in a given volume;

• relatively expensive and/or difficult to process;

• inappropriate phase change temperatures;

• inadequate storage of energy;

• inappropriate corrosive effects; • irreversible segregation during phase changes;

• low conductivity limiting the rate of melting and cooling, or the thickness of;

• partial phase changes in a pack of certain sizes i.e. due to the conductivity, size and material choices portions of a pack may not change phase which limits the size of an optimal PCM pack; • suffer from super cooling;

• are flammable.

[003] The following prior art documents are acknowledged: JP200080358, EP1837617, JP2005330484, US2008318050, CN10128961 1 , CN101074854, EP1837385, and KR20060047958. The following prior art documents have also been identified: US2006/0185817, EP1947404, EP1455156, EP1739376, EP1455155, DE20314018 and DE20310593. BRIEF SUMMARY OF THE DISCLOSURE

[004] Viewed from a first aspect the present invention provides a phase change material composition comprising between 50 and 99% by weight of a salt hydrate and between 0 and 45% by weight of carbon black, preferably between 0 and 15% by weight of carbon black. [005] In accordance with the invention, the combination of salt hydrate and carbon black has been found to be particularly effective, especially in climate control applications.

[006] The salt hydrate may comprise a hydrate of sodium sulphate and/or a hydrate of calcium chloride. For example, the salt hydrate may be sodium sulphate decahydrate, calcium chloride hexahydrate, calcium chloride tetrahydrate, calcium chloride dehydrate or a mixture of two or more of these. Other suitable salt hydrates are hydrates of sodium thiosulphate, sodium acetate, disodium hydrogen phosphate or sodium carbonate or suitable mixtures of these and other salt hydrates.

[007] The composition may comprise a hydrate of sodium sulphate and between 0 and 15% by weight of sodium chloride. The sodium chloride can be used to lower the melting point of the sodium sulphate hydrate to the required level. Similarly, the composition may comprise a hydrate of calcium chloride and between 0 and 15% by weight of potassium chloride, sodium chloride and/or ammonium chloride. The composition may comprise between 0 and 15% paraffin or another organic material to create a eutectic mixture.

[008] Optionally, the composition may comprise between 0 and 10% of a thickening agent. Optionally, the composition may comprise between 0 and 10% of a nucleating agent.

[009] Typically, the composition has a melting point between -15 and 100 degrees centigrade, preferably between 15 and 40 degrees centigrade, more preferably between 20 and 30 degrees centigrade. Typically, the phase change material has a latent heat at least ten times that of the specific heat of the material. [010] The invention extends to a phase change material pack comprising the composition in an envelope of material of relatively high thermal conductivity. In this context "relatively high thermal conductivity" means that the envelope facilitates heat flow between the composition and its surroundings, for example for effective operation of a climate control system. Suitable materials for the envelope are metals such as aluminium and stainless steel which have good corrosive properties, but plastics material or metal / plastics composites may also be used.

[011] The invention extends to a climate control system utilising the composition.

[012] In a broad aspect, the invention provides a PCM (phase change material) pack comprising an envelope of relatively highly thermally conductive material enclosing a portion formed primarily of PCM; wherein said PCM portion incorporates a conductive compound mixed into said PCM which comprises carbon black particles. This configuration allows a PCM pack to be optimised. It improves the conductivity so that larger scale PCM packs may be achieved with improved thermal properties. Improvements to conductivity effectively increases the rate of energy transfer, speeding up melting and freezing cycles, and therefore maximising the cooling or heating power that a heat exchanger using a latent heat store can provide. It allows the phase change material to be operational for a large number of cycles. The carbon black can also reduce the effects of supercooling and improve stability, reducing the need for other agents. It lends itself to relatively straightforward manufacture at reduced costs. It is possible for the PCM portion to comprise a mixture of paraffin and carbon black particles, but this is not preferred.

[013] The PCM portion may incorporate an agent to reduce supercooling, such as lithium fluoride.

[014] In a subsidiary aspect, said PCM portion comprises a mixture of salt-based material and carbon black particles. This mixture is particularly advantageous as it further improves the effects mentioned above. It allows the salt-based material to undergo the necessary phase change substantially without being impeded by the particles. To the contrary, the particles improve the thermal conductivity in order to improve the properties of the PCM pack.

[015] In a further subsidiary aspect, said salt is a hydrated sodium sulphate salt. This configuration further optimises the PCM pack properties. [016] In a further subsidiary aspect, said carbon black particles have a fluffy outer surface. The fluffy outer surface may take the form of a large number of uneven protruding points. In this form the carbon black particles have a relatively low density which optimises the conductivity whilst improving the properties of integration into the phase change material. In this context, "fluffy" can be considered to mean that the carbon black has a significantly greater effective surface area than smooth particles of carbon black.

[017] In a further subsidiary aspect, the width of a majority of said particles is between 1 and 10 μm. This configuration is also particularly advantageous in terms of improving the mixture between the carbon black and the PCM. It allows for advantageous dispersion throughout the material. [018] In a further subsidiary aspect, the density of said carbon black particles is in a range of 100 to 250 kg/m³. Within this range an optical mixture is obtained. It also reduces the risk of segregation during phase changes.

[019] In a further subsidiary aspect, ihe PCM portion incorporates an agent to improve the stability and life of the mixture by preventing segregation, this could be a silicate additive such as Laponite (RTM), a gum such as Xanthan, a clay e.g. bentonite. In a further subsidiary aspect, said clay mineral is selected from or is a combination of any clay mineral of the following group: kaolinite, montmorillonite and/or bentonite. These further improve the material by thickening the material. [020] In a further broad independent aspect, the invention provides a phase change material (PCM) compound comprising a thermally conductive compound mixed into said PCM which comprises carbon black particles. In a further subsidiary aspect, the compound comprises a mixture of a salt-based material and carbon black particles.

[021] Viewed from a further broad aspect, the invention provides a transportable PCM (phase change material) module comprising a number of PCM packs; a housing for thermally insulting said number of PCM packs from a module's surrounding medium; spaces separating said packs and forming one or more channels for the flow of a fluid; said housing incorporating a fluid inlet and a fluid outlet; whereby, in use, fluid flows through said channels from said inlet to said outlet. [022] This configuration is particularly advantageous because it allows systems to be built up from a number of modules for variable energy requirement. It may also reverse conventional thinking when it is configured without any driven or powered component in the module. It may thus allow for retrofitting to existing air flow systems. It also improves energy usage effectiveness. [023] In a subsidiary aspect, said inlet and/or said outlet incorporates one or more flow regulating valves. If the module consists of these components only it further reduces the number of components necessary and allows for particularly compact modules compared to module incorporating power components per module.

[024] In a further subsidiary aspect, said PCM packs are arranged substantially side by side. In this configuration, the cooling is advantageous.

[025] In a further subsidiary aspect, said PCM packs are separated by one or more thermal conductors extending transversely and forming said channels. This allows the PCM portion to be of greater effective volume and therefore improves its effectiveness.

[026] Further aspects improve one or more of the following: the effectiveness of the PCM, the turbulence of the flow, the compactness of the system relative to its effectiveness, its overall packaging weight and its manufacturing requirements.

[027] In a further subsidiary aspect, said thermal conductors take the form of a corrugated sheet. [028] In a further subsidiary aspect, at least one of said PCM pack incorporates a corrugated wall forming a channel for the flow of fluid.

[029] In a further subsidiary aspect, a number of projections are provided in at least one of said channels. [030] In a further subsidiary aspect, at least one of said PCM pack incorporates a wall from which projections project into said channel.

[031] In a further subsidiary aspect, the or each PCM pack comprises a laminate of a first conducting panel and a second conducting panel enclosing a portion formed primarily of PCM; wherein said portion of PCM incorporates thermal conductors. In a further subsidiary aspect, said thermal conductors extend in a transverse direction from one or both of said conducting panels.

[032] In a further subsidiary aspect, said thermal conductors form hexagonal cells when viewed in plan.

[033] In a further subsidiary aspect, said laminate further incorporates a corrugated thermally conductive panel.

[034] In a further subsidiary aspect, said laminate incorporates a third conductive panel and a fourth conductive panel enclosing a second portion formed primarily of PCM; and a corrugated thermally conductive panel located between said second and third conductive panels. [035] In a further subsidiary aspect, said laminate incorporates a plurality of projections on said panels.

[036] In a further subsidiary aspect, said thermally conductive panels are selected from the group comprising aluminium based material, steel based material, and plastics material.

[037] In a further subsidiary aspect, said PCM is selected from the group comprising a salt, a salt based hydrate, a mixture of salt, and/or salt based hydrate, and/or an organic material.

[038] In a further subsidiary aspect, said salt based hydrate are selected from the group comprising hydrated calcium chloride or hydrated sodium sulphate.

[039] In a further subsidiary aspect, said salt based hydrate incorporates a thickening agent selected from the group comprising Xanthan and/or Laponite. [040] In a further subsidiary aspect, said organic material is paraffin based.

[041] In a further subsidiary aspect, said thermal conductors incorporate a conductive compound mixed into said PCM. In a further subsidiary aspect, said thermal conductor is a carbon based compound mixed into said PCM.

[042] In a further subsidiary aspect, said carbon based compound is carbon black.

[043] In a further subsidiary aspect, said thermal conductors incorporate wire wool or chemical carbon nanotubes. [044] In a further subsidiary aspect, said module further incorporates a pettier cooler.

[045] In a further subsidiary aspect, said module further incorporates an evaporative cooler.

[046] In a yet further broad independent aspect, the invention provides an air conditioning arrangement, comprising:

• one or more transportable PCM modules according to any of the preceding claims; and • at least one transportable control module incorporating a housing with an inlet and an outlet; and a pump for causing, in use, the flow of fluid from said inlet to said outlet;

• wherein said arrangement incorporates a conduit for linking said transportable control module to said transportable PCM modules.

[047] In a subsidiary aspect, said control module incorporates a first and a second inlet located on separate sides of said housing and a valve configured to regulate the intake between said inlets.

[048] In a further subsidiary aspect, said control module incorporates an internal conduit between said inlet and said outlet; said internal conduit comprising two adjacent paths, one of which incorporates a pump and a second of which incorporates a non-return valve. [049] In a further subsidiary aspect, said arrangement further comprises a transportable backup module incorporating one of a heat pump, an inverter, a peltier cooler, or an evaporative cooler; and further incorporating means for linking said backup module to said PCM module.

[050] In a further broad independent aspect, a PCM (phase change material) pack comprises a laminate of a first conducting panel and a second conducting panel enclosing a portion formed primarily of PCM; wherein said portion of PCM incorporates thermal conductors.

[051] In a subsidiary aspect, said thermal conductors extend in a transverse direction from one or both of said conducting panels.

[052] In a further subsidiary aspect, said thermal conductors form hexagonal cells when viewed in plan.

[053] In a further subsidiary aspect, said laminate further incorporates a corrugated thermally conductive panel.

[054] In a further subsidiary aspect, said laminate incorporates a third conductive panel and a fourth conductive panel enclosing a second portion formed primarily of PCM; and a corrugated thermally conductive panel located between said second and third conductive panels.

[055] In a further subsidiary aspect, said laminate incorporates a plurality of projections on said panels.

[056] In a further subsidiary aspect, said thermally conductive panels are selected from the group comprising aluminium based material, steel based material, and plastics material. [057] In a further subsidiary aspect, said PCM is selected from the group comprising a salt, a salt based hydrate, a mixture of salt, and/or salt based hydrate, and/or an organic material.

[058] In a further subsidiary aspect, said salt based hydrate are selected from the group comprising hydrated calcium chloride or hydrated sodium sulphate. In a further subsidiary aspect, said salt based hydrate incorporates a thickening agent selected from the group comprising Xanthan and/or Laponite.

[059] In a further subsidiary aspect, said organic material is paraffin based.

[060] In a further subsidiary aspect, said thermal conductors incorporate a conductive compound mixed into said PCM.

[061] In a further subsidiary aspect, said thermal conductor is a carbon based compound mixed into said PCM.

[062] In a further subsidiary aspect, said carbon based compound is carbon black.

[063] In a further subsidiary aspect, said thermal conductors incorporate wire wool or chemical carbon nanotubes.

[064] Further aspects of the invention include: • A cooling device that uses the 24 hour daily cycle to store cooling energy from outside night time air and releases it during the day, which comprises a thermally insulated PCM, an electric fan and a control system to control the flow of air through the PCM.

• A device that is portable and moved outside at night time to cool the PCM, with a battery pack to provide power to a fan and optional docking station to charge it. • A device that can be retrofitted to a building by mounting to the wall or ceiling, or that rests on the floor with the option of rollers, and connects to the outside air through a duct. • A control system which controls the flow of air over the PCM with a valve or a fan, by using a timer and optional sensors to measure the temperature inside, outside, of the PCM or its electrical resistance.

• A control system which pulls cool air over the PCM to freeze it when either the outside air temperature is lower than the phase change temperature, at a preset time, or when the user manually sets it to 'night' mode.

• A control system that when in 'night' mode shuts off the air when the PCM has reached the desired temperature or the electrical resistance has changed to indicate that it is completely frozen. • A user interface for the control system that can be part of the main unit or separate to allow the user to turn the units on and off, change the mode, set the timer, or select the amount of cooling. - A user interface that can connect using wireless protocols, infrared, or that is physically wired so that a single user interface can control individual or multiple units at once. • A control system that either when set by the user, when a preset tie is reached, as the indoor temperature rises, or with a combination of inputs provides cooling by activating the fan or valve to pull air from inside or outside over the PCM and releasing it into the room.

• A control system that controls the ratio of air from outside to inside to ensure a minimum of fresh air is provided for breathing, but increases the proportion of outside air if the temperature outside is lower than inside.

• A control system and interface that monitors the batteries to indicate the power remaining to the user, and controls their charging when connected to a power source.

• A control system and interface that feeds back to the user how much cooling energy remains in the unit.

• An optional docking station that the units can be mounted in to charge their batteries and holds the units securely on a window sill, wall or elsewhere.

• Vents to allow air in and out of the units.

• A valve to control the flow of air from inside or outside over the PCM. • An optional valve to control the flow of air from the unit into the room or back outside.

• Attachment points to connect ducting or multiple units together.

• A modular series of ducting or a flexible hose and fittings that individual or multiple units can connect to and in turn is connected to the outside to carry air in or out, through a window, ceiling or wall unit.

• An end unit where the ducting connects to the outside air and is mounted to the window, ceiling or wall, with the option for an air filter and separate valve to let excess air from the room back outside.

• An optional air filter in the unit.

• Mounting the PCM inside the ducting.

• Fittings to attach or embed an optional lighting system.

• In a further aspect, the system incorporates a low energy cooling module as a freestanding, portable, ceiling or wall mounted device that can be retrofitted to a building. The unit contains a suitable PCM that will provide the user with a comfortable indoor temperature according to local climatic conditions. The unit will rely on fluctuating 24 hour temperature cycles.

BRIEF DESCRIPTION OF THE DRAWINGS [065] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[066] Figure 1 shows a cross sectional view of a PCM module with a single upper opening.

[067] Figure 2 shows a cross sectional view of a PCM module with two upper openings and two lower openings of differing directions. [068] Figure 3 shows a PCM module adapted to fit to a false ceiling.

[069] Figure 4 shows a PCM module in cross section adapted to be fitted to a false ceiling with the PCM packs provided in series.

[070] Figure 5 shows a heat exchanger in cross section with a plurality of PCM packs separated by corrugated plates. Figure 6 shows an exploded view in a perspective of the embodiment of Figure 5.

[071] Figure 7 shows in perspective view the combination of a PCM pack with a corrugated plate.

[072] Figure 8 shows in perspective view a portable PCM pack.

[073] Figures 9A and B show a PCM pack incorporating a thermally conductive corrugated plate.

[074] Figure 10 shows in perspective view the assembly of a PCM pack with a corrugated plate with a plurality of holes.

[075] Figure 1 1 shows a perspective view of the assembly of a hexagonal array.

[076] Figure 12 shows a perspective view of the assembly of a PCM pack with a hexagonal array with perforations. [077] Figures 13A and B show in cross section and in perspective view PCM packs incorporating a corrugated wall.

[078] Figures 14A and 14B show respectively in cross section and in perspective a PCM pack whose envelope may be formed by extrusion.

[079] Figure 15 shows a perspective view of a heat exchanger incorporating a number of PCM packs of the kind shown in Figure 14.

[080] Figure 16 shows a perspective view of a heat exchanger incorporating a number of PCM packs of the embodiment of Figures 14.

[081] Figure 17 shows a schematic cross sectional view of a control unit with a lateral valve.

[082] Figure 18 shows a schematic cross sectional view of a control module with a valve located between two inlets. Figure 19 shows a schematic cross sectional view of a control module employing a nonreturn valve.

[083] Figure 20 shows a control unit incorporating a fan.

[084] Figure 21 shows a schematic cross sectional view of a heat exchanger which may be used in conjunction with a PCM module. [085] Figure 22 shows a schematic cross sectional view of a further embodiment of a heat exchanger.

[086] Figure 23 shows a cross sectional view of a heat exchanger incorporating a pettier cooler.

[087] Figure 24 shows a heat exchanger in cross sectional view incorporating PCM packs. [088] Figure 25 shows in cross section a heat exchanger incorporating hexagonal ducts as part of a pettier cooler.

[089] Figure 26 shows a control unit incorporating a number of heat exchangers.

[090] Figure 27 shows a schematic cross sectional view of a backup module incorporating an evaporative unit. [091] Figure 28 shows a further embodiment of a backup unit with an evaporative system. [092] Figure 29 shows a further embodiment of a backup unit.

[093] Figure 30 shows a schematic cross sectional view of a further embodiment of the invention.

[094] Figure 31 shows a PCM pack laminate with bi-directional channels in perspective view.

[095] Figure 32 shows a further evaporative system in schematic cross sectional view. Figure 33A and Figure 33B shows a perspective view and a cross sectional view of a plate and PCM pack combination.

[096] Figure 34 shows a schematic cross sectional view of a PCM unit. [097] Figure 35 shows a plurality of PCM modules.

[098] Figure 36 shows a further embodiment of a PCM module.

[099] Figure 37 shows a combination of a controlled unit, and PCM modules in cross sectional view.

[0100] Figure 38 shows a combination of a plurality of PCM modules. [0101] Figure 39 shows a further embodiment of a combination of PCM modules in cross sectional view.

[0102] Figure 40 shows a further embodiment of the combination of PCM modules, a control unit and a recirculation unit.

[0103] Figure 41 shows a portable unit with a rechargeable battery to drive a fan. [0104] Figure 42 shows a docking station suitable for charging the PCM module of Figure 41.

[0105] Figures 43 to 52 show plan views of arrangements of PCM modules for a given room.

[0106] Figure 53 illustrates the selected "fluffy" particles of carbon black.

[0107] Figure 54 illustrates the selected relatively "smooth" particles of carbon black.

[0108] Figure 55 illustrates a phase change material pack in accordance with the invention. DETAILED DESCRIPTION

[0109] Figure 1 shows a transportable PCM (phase change material) module with a plurality of PCM packs such as PCM pack 2. The PCM packs are secured to a module housing 3. The PCM packs are provided side by side and parallel to one another. Between two neighbouring packs such as pack 2 and pack 4, there is provided a channel 5 through which an appropriate fluid may circulate. The fluid may be a gas or a liquid, however in preferred embodiments of the invention the fluid is selected to be a gas. The housing 3 incorporates a neck 6 forming an inlet /outlet to the housing. In this description the terms inlet /outlet are to be understood as interchangeable since as soon as the direction of flow is changed the inlets become outlets and vice versa. The module incorporates a valve or damper 7 for restricting the flow of gas which would typically be air through neck 6. In a system where multiple modules are employed in a network, damper 7 may be used to balance the flows to cope with differences in pressures in a given network configuration. At the opposite end of module 1 , a vent 8 is provided with a number of blades such as blade 9 which is typically mounted to housing 3 in order to allow manual and/or automatic adjustment of the angle at which air would exit the housing. Housing 3 may have relatively high insulation properties so as to effectively create a thermal barrier between the PCM packs located in the housing and the housing's surrounding environment.

[0110] Figure 2 shows a further embodiment of a PCM module. PCM module 10 incorporates a plurality of PCM packs such as PCM pack 1 1. The module incorporates a housing 12 with releasable attachment means for securing the PCM packs in spaced apart configurations in order to provide channels such as channel 13 between neighbouring packs. A number of turning valves such as turning valve 14 are provided above the PCM packs' array in order to control the flow. Integral with the housing 12, there is provided a duct portion 15 with a first lateral opening 16 and a second lateral opening 17. Duct 15 is shaped at said lateral openings to allow for the attachment of a duct or a further module of the kind shown in any of the embodiments of the invention. Beneath the PCM packs' array, two openings 18 and 19 are configured to allow the flow of air in two separate directions as indicated by arrows 20 and 21 which are approximately 90 degrees apart. A divider 22 is provided between openings 18 and 19 to channel the flow in the desired directions. As in figure 1 a number of vents are provided in the openings. These vents may be pivotable to allow a user to control the exact direction of the air. Whilst air may be drawn through the module in both directions, the embodiment of figure 2 shows air flowing in the opening 16 as indicated by arrow 23, passing through the channels formed between the PCM packs and out through openings 18 and 19.

[0111] Figure 3 shows a further PCM module generally referenced 24 with a separable duct 25 sealed to the module's upper opening 26 which is neck shaped. The module 24 incorporates an array of PCM packs such as pack 27 arranged in a parallel configuration within an insulative housing 28. A false ceiling tile 29 is sealed to bottom opening 30 of PCM module. The false ceiling tile 29 incorporates lateral grooves 31 corresponding in shape to tongue 32 of a false ceiling frame member 33. A number of openings 34 and 35 are provided to allow air circulating from duct 25 through PCM module 24 to exit the ceiling tile into the area beneath the ceiling tile. [0112] Figure 4 shows a PCM module generally referenced 36 with an array of PCM packs such as pack 37 located in a housing 38. The housing incorporates a lateral opening 39 allowing the circulation of air to and/or from module 36. The PCM packs are provided in series in a path between opening 39 and opening 40. Module 36 is located against ceiling tile 41 in order to allow the flow of air through the false ceiling tile to the area beneath the tile. An arrangement of pivotable and/or adjustable vents is provided to allow a user to control and interact with them as appropriate. The ceiling tile is attached to false ceiling supports as described with reference to figure 3. The configuration of the figure provides for a longer air flow path in a heat exchanger when compared to the previous embodiments.

[0113] In each of the preceding PCM modules, it is preferred and particularly advantageous for there to be no active components for example for driving the flow of air. A separate module or control module is described subsequently.

[0114] Figure 5 shows a PCM module in cross-section which takes the form of a heat exchanger 42 with an insulating housing 43. The housing wall may be selected to hold 80 to 90% of the "coolth" over 8 hours. It may be of approximately 25mm in thickness with a conductivity of 0.01 to 0.02 W/mK. On the inside of housing 43, a conductive metal frame 44 forms a lining. A succession of layers of corrugated plates such as plate 45 alternate with PCM pack layers such as layer 46. Figure 6 shows the components of figure 5 in an exploded view. The corrugated plate may instead be replaced by a number of transverse fins or links which in a similar fashion as the corrugated plate would increase the surface area in contact with air flowing through the channels left between the PCM packs. Since the surface area in contact with air is increased, the PCM packs may be thicker thus allowing greater cooling to be achieved. In a preferred embodiment, the gap between the PCM packs is slightly smaller than the height of the corrugated fins to ensure optimum thermal contact. In order to support the weight of the PCM packs, there is provided rails on the inside of the frame (not shown in the figures). Figure 7 shows a corrugated plate 47 with a number of projections such as projection 48. Alternatively, these projections may be holes or a combination of holes and projections in order to break up laminar flow by creating turbulence in order to increase heat transfer. The corrugated plate 47 may be disposed as shown in figure 5 adjacent to a sealed PCM pack 49. The corrugated plate 47 may preferably be made of sheet metal preferably less than 1 mm thick. For optimum structural strength and thermal conductivity, a range of 0.1 to 0.2 mm is envisaged. A number of known techniques are envisaged to form the plate such as pressing or folding. Instead of employing sheet metal, a thermally conductive plastics material may also be selected.

[0115] Figure 8 shows a PCM pack 50 with an impermeable outer layer 51 for containing the PCM. A handle 52 is provided which may take the form of an oblong opening. A number of recesses 53 and 54 are provided on opposite lateral sides of the pack. These may be employed in order to lock the pack into releasable attachment means provided in a heat exchanger for example. This embodiment illustrates how the PCM pack may be rendered readily portable. [0116] Figure 9A shows a PCM pack formed with an upper wall 55 and a lower wall 56 for trapping PCM. Between walls 55 and 56, there is provided a plate 57 formed as a succession of V-shaped portions when viewed in cross-section. The components of figure 9A are shown in figure 9B as glued or sealed together in order to prevent any escape of PCM during use.

[0117] The PCM is one of an organic, a salt based hydrate, or a combination of both. A paraffin-based PCM is envisaged with a melt temperature preferably within the range of 21 to 24 degrees Celsius. In order to achieve an optimal melt temperature, the different types of available paraffins are mixed in the appropriate proportions.

[0118] Salt hydrates which are suitable for use may for example be hydrated forms of calcium chloride or sodium sulphate. The invention also envisages employing a thickening agent as an addition to the salt hydrates to maintain the salt in its hydrated form. Suitable thickening agents may be selected from the group comprising: Xanthan or Laponite. In addition to the transverse conductive fins of the corrugated plate 57 or instead of such transverse fins, a conductive element may be suspended in the mixture of PCM. An appropriate compound for suspension may be carbon black. [0119] Figure 10 shows an alternative construction of a PCM pack generally referenced 58. The configuration of the PCM pack differs from the preceding embodiment in that a number of holes 59 are provided in the fins 60 of the corrugated plate generally referenced 61. Such holes allow molten PCM to distribute evenly and to keep air out. The corrugated panel may be glued to improve strength. [0120] The corrugated panels may be pressed and mainly made of very thin wall thicknesses such as less than 1 mm in order to keep weight to a minimum whilst the profile /ridges /pattern adds a strength. The transverse fins allow the thickness of the PCM pack to be increased by improving conductivity. It allows the PCM to be at an optimal maximum distance of between 4 to 16 mm (or 10 to 20 mm) from the links throughout the pack. Alternative thermal conductors are envisaged to be located in the PCM such as wire wool, chemical carbon nano-tubes, suspended carbon black which may be randomly distributed throughout the material.

[0121] The transverse links may be made of thin metal /plastic which would preferably be less than 1 mm in thickness. The shape and configuration of the plate may be obtained by pressing, stamping and/or folding processes. [0122] Figure 1 1 shows a PCM pack 62 in an exploded view with an array of closely contiguous cylinders 63 for receiving PCM. The cylindrical tubes may take the form of a hexagonal mesh. The array may be formed from a single sheet which is laser cut and pulled apart to result in an array with walls of a thickness of approximately 0.1 mms. Secured to the top and bottom of the array, there is provided top and bottom plates respectively referenced 64 and 65. The process of assembling may incorporate the following steps: a) attaching the array of hexagonal receptacles to one of the top or bottom plates, b) filling the tubes with PCM in its molten phase allowing sufficient clearance for its expansion as it freezes before c) gluing to attach the remaining panel. [0123] An alternative PCM pack 66 is shown when compared to the embodiment of figure 11. PCM pack 66 incorporates a shallow walled plateau 67 into which an array of hexagonal receptacles 68 is located. The array of receptacles is sealed between lid 69 and plateau 67. Holes such as hole 70 are provided through each of the hexagonal receptacles in order to allow PCM to distribute. The panel 69 may be attached to the plateau 67 by ultrasonic welding or by gluing.

[0124] If the PCM is selected to be salt based the material for the pack is preferably selected to be a coated aluminium or a conductive plastics material (for example K greater than 5W/mK) or stainless steel in order to prevent corrosion.

[0125] One of the key advantages of transverse links is that it allows PCM packs to be made of a greater thickness than would otherwise be possible. For example packs with material thicknesses of 20 to 50 mm may be achieved with effective conductivity.

[0126] Figures 13A and 13B a PCM pack (figure 13A) and a stack of PCM packs (figure 13B). In this embodiment, the PCM pack is generally referenced 71 and is formed only of two plates 72 and 73 allowing for the filling of PCM in an array of cavities such as cavity 74. The cavities are formed in cross-section in a V-shape. The portions such as portion 75 would be exposed to air flow. In addition, it is envisaged for the external surface exposed to the flow to incorporate knurling and/or bumps. This kind of relief may be used in any of the preceding embodiments in order to increase the flow turbulence and therefore the heat transfer properties of the pack. The undulated or corrugated plate 73 is formed for example by pressing or folding. As indicated in the stack of packs 76 and 77 air may flow in the cavities provided as indicated by the arrows. This embodiment allows an increase in surface area in contact with the air and a reduction of the maximum distance between the PCM and the conductive material. In other words, it combines the function f the PCM packaging with the transverse links inside as well as the corrugated heat exchanger in touch with the air. [0127] Figures 14A and 14B show a PCM pack 78 in two separate views. The PCM packs 78 incorporate a single peripheral wall 79 with a number of inwardly projecting webs such as web

80 and outwardly projecting webs such as web 81. In other embodiments only externally projecting webs may be provided and/or only internally projecting webs. Within the envelope formed by peripheral wall 79, PCM 82 is placed to fill the space. In order to enclose the PCM pack, end pieces (not shown in the figures) may be provided and secured onto lateral edges 83 and 84. The materials used for these PCM packs may be a relatively low permeable plastics material. Alternatively, coated aluminium is also advantageous. Preferably, a conductive of plastics material would be selected with a thermal conductivity factor greater than 1 W/mK. An option of achieving this kind of conductive of plastics material for the PCM pack material would be to add carbon nanotubes or particles to the plastics material. The process envisaged in order to produce wall 79 would be to form the wall by extrusion.

[0128] Figure 15 shows a PCM pack module generally referenced 85. Module 85 incorporates an insulating outer layer 86 formed by side walls 87, 88, a base wall 89 and a lid 90. Within the insulation, there is provided a frame 91 with a number of ledges such as ledge 92 for supporting a stack of PCM packs in a spaced apart relationship. Gaps such as gap 93 are provided to allow the circulation of fluid. The links 80 and 81 extend in this embodiment only partially towards a neighbouring PCM pack plate.

[0129] As shown in figure 16, during assembly, a side 94 may be fully open in order to allow the insertion of the successive packs in similar fashion to a drawer sliding into its case. [0130] Figure 17 shows a control module generally referenced 95. The control module may be employed in communication with a number of PCM modules which may be of the kind described in the previous embodiments. The control module 95 incorporates it own housing 96 which contains a fan 97 causing the circulation of air as shown in the figure by the arrows. In an alternative embodiment, the fan may be driven in an opposite direction. The control module incorporates an inlet duct 98 which is split between a first opening 99 and a second opening 100. The first and second openings are located on different sides of the housing 96. In a particular configuration, the module may be placed within a building in order to draw air in from the room through opening 100 and to draw air in from outside or fresh air from an appropriate source through opening 99. Within opening 100 a valve and/or a vent and/or a sliding door 101 may be provided to regulate the proportion of air drawn from within the room with the proportion of air drawn from outside or from a fresh source of air. Optionally, a filter 102 is provided upstream from the fan.

[0131] In addition to these components, there may be provided circuitry for controlling the operation of the fan. The circuitry may be in communication with one or more sensors or monitors which monitor carbon dioxide and/or room temperature. Appropriate sensors may be provided within a room or outside of a room. In addition sensors or monitors may be provided to assess the PCM exit temperature where appropriate. In a preferred embodiment, the sensors may be configured to assess the electrical resistance of PCM to determine the amount of cooling remaining in a given pack. [0132] Figure 18 shows an alternative module generally referenced 103 with a control valve 104 located between first opening 105 and second opening 106. Optimally a number of filters 107 and 108 are provided downstream from openings 105 and 106. The duct beneath the valve 104 may be configured to widen out towards fan 1 10 leading to opening 1 1 1.

[0133] Figure 19 shows a further embodiment of a separable control module 1 12. This control module incorporates an opening 1 13 for drawing in air from a room or from outside. The duct 1 14 is split into two paths 1 15 and 116 which are respectively fitted with a fan 1 17 and a non-return valve 1 18. This allows an external forced air system to be used since the non-return valve allows the air to bypass the fan. If re-circulated air from the room is required then the fan is operated creating a high pressure in order to draw the air through. [0134] Figure 20 shows a further separate control module 1 19 with an upper opening 120 in a housing 121. It optimally incorporates an air filter 122 downstream from opening 120. A lateral opening 123 is provided with a vent. Around the fan 123 there are provided baffles such as baffle 124 which provide sound insulation. In this embodiment, the simple vent 123 can open /close - this is because the air from outside has further to travel than when the vent is open. There is less resistance and more air is re-circulated. As the vent closes it creates more resistance so a smaller proportion of air is taken from inside. In practice, the vent may have greater cross-sectional area for example up to twice the area of the fresh air duct which incorporates opening 120.

[0135] In addition to the PCM module and the control module a further module may be provided. In a preferred embodiment, the backup module would be provided upstream from the PCM module. Figure 21 shows a backup module 125 which incorporates a heat exchanger with a hot side 126 and a cold side 127. Cooling liquid may for example circulate between the hot and cold side. Housing 128 incorporates a duct 129 suitable for connection to a further duct or a further module. An opening 130 is provided to allow air in from inside and/or outside. The control module of the kind described in figures 17 to 20 may be used to cause the flow of air through the cold side 127 of the heat exchanger. An exit duct 131 is provided with an opening 132 to allow air to circulate towards a PCM module. An opening 133 allows air which may be for example stale room air to circulate through the hot side of the heat exchanger and towards opening 134. A pump 135 or a fan is employed to draw the air through in the direction shown in the figure. [0136] Figure 22 shows a further backup module 136 with a housing 137 accommodating a hot and cold side of a heat exchanger. The cold side is referenced 138 and the hot side is referenced 139. Two openings 140 and 141 are provided on either side of a valve 142. Fan 143 powers air out of a room to remove heat from the hot side. The backup module may incorporate a heat pump and/or an inverter and/or a pettier cooler in order to cool air going to a PCM module with waste heat taken away. Alternatively, an evaporative arrangement may be used where the hot side would become an evaporator cooler and enables the wet waste air to be removed whilst "coolth" is transferred to incoming air.

[0137] A number of advantages arise from combining a module of the kind described in figures 21 and 22 with a PCM module as described previously, it allows the backup modules to be kept compact as compared to a conventional heat exchanger only system. It is also particularly advantageous since it allows operation during night time when the heat exchanger is in any event more efficient. There is therefore particular energy savings for evaporative, heat pump and/or pettier cooling systems. It also allows the use of night time electricity which is cheaper. The module arrangements allow for the backup unit to be specified separately to the PCM and control system to suit the local climate and heat loading of the room. It also allows easier maintenance.

[0138] The backup system may ideally be controlled so that it enters a night freezing mode if the temperature assessed by the control module is not cool enough then it would turn on the backup system to freeze the PCM. In this configuration, the heat pump is virtually not required during the day time since by combining the PCM module and the backup module during the night cycle most of the cooling is achieved.

[0139] Figure 23 shows in further detail how a peltier backup module may be formed. A peltier may be located between its hot side 145 and its cold side 146. A cold side duct 147 and a hot side duct 148 are provided. As in the previous embodiments, the cold side duct may be in communication with a PCM module. Insulation is provided as a wall for the ducts.

[0140] Figure 24 shows a further PCM module 149 with an outer housing 150 and an inner housing 151. One or more peltiers are provided such as peltier 152. The pettier 152 has a hot side 153 provided in a duct through which air is drawn. Within housing 151 there is provided a conductive frame 154 in which layers of corrugated plates and PCM packs alternate as in for example figure 5. PCM module acts as the cold side of the heat exchanger as well as incorporating the PCM packs. One of the benefits of this configuration is that it is particularly compact.

[0141] An alternative to the embodiment of figure 23 is shown in figure 25 where a further peltier based backup module 155 is shown. The peltier 156 incorporates a mesh of hexagonal tubes such as tube 157. The hexagonal arrays each form a side of the heat exchanger. In this embodiment, side 158 is a cold side whilst side 159 is a hot side. The cool side 158, in use, may be in communication with a PCM module for backup cooling when necessary. The hexagonal configurations form a relatively light weight configuration due to the wall thickness. Improved thermal conductivity is also achieved due to the high surface area it provides.

[0142] Figure 26 shows a further backup module 160 with one side in communication with a PCM module and/or a room and a second side 162 through which air is drawn and forced out by a fan (not shown). The module incorporates three peltiers located in a series. Advantages exist from incorporating two or more arrangements in series. The air circulation is similar to the preceding embodiments where a duct 163 may be in communication with a PCM module and/or a room.

[0143] It is preferred to use an insulated housing for a heat pump or peltier backup system to separate the hot and cold sides. In an evaporative cooler the two chambers are preferably thermally connected to transfer the cold from the wet to the dry side. [0144] Figure 27 shows an evaporative cooler module generally referenced 164. The module

164 creates a housing 165 with a first opening 166 through which air may be drawn. Housing

165 incorporates two adjacent chambers 167 and 168. In chamber 167 a heat exchanger array transfers the "coolth" from the evaporative chamber to the incoming air. A second opening 169 is provided to allow air to exit - this may be cool air which is then channelled to a PCM module or to the room. In chamber 168, a mesh or wicking is envisaged for the evaporative cooler. Air is drawn in through opening 170 due to the action of fan 171. The air exits as wet air through opening 172.

[0145] Figure 28 shows a further evaporative cooler module 173 with a first opening 174 though which air is drawn in. A fan 175 and a filter 176 are provided downstream from the opening 174. A heat exchanger 177 and an evaporative cooler 178 are located side by side. The air drawn in through opening 174 is split by a splitter or a valve 179 which controls the amount of air going to either the evaporative cooler 178 or to the heat exchanger. In the circumstances when the evaporative cooler is not required all the air is directed to a PCM unit 180 which is in communication with the heat exchanger 177 by a duct 181. Air exits the PCM unit to a room via opening 182. The exhaust air exits through opening 183.

[0146] Figure 29 shows a further evaporative cooler module generally referenced 184 with a fresh air intake 185 and a secondary intake 186 which may be in communication with a room. A valve may be optionally fitted between intakes 185 and 186 to control proportions of air. If the valve is not used then the air can only be drawn from outside. A cross flow evaporative chamber 187 exhausts wet air through opening 188. Air is drawn through opening 189 whilst air to a further PCM module or to the room exits the module through opening 190.

[0147] In the preceding Figures 27 to 29 the evaporative chamber incorporates separate paths for the evaporative wet air used to create cooling and for the dry air taken into the room. This prevents the conditioned air and the room becoming too humid. Further examples of indirect evaporative coolers that transfer "coolth" from the wet to dry chamber are well known, see for example US6581402. Whilst the use of evaporative coolers is well known, by using them in conjunction with latent heat storage and PCM modules, the evaporative cooler can be used at night when they are more efficient and when the night air is cooler. This substantially increases the effectiveness and/or reliability of a PCM cooling module when compared to a PCM module operating on its own. The two chambers 167 and 168 are thermally connected. Figure 30 shows a further evaporative system generally referenced 191. In this embodiment the air is drawn through opening 192 by a fan 193. It then flows through an evaporative chamber 194. Warm dry air goes into the evaporative chamber and cool wet air comes out. A heat exchanger 195 transfers the "coolth" from the wet exhaust air to the dry air going into the room. Opening 196 provides for the outlet of exhaust air whilst opening 197 provides for the cool dry air to room. A second fan 198 draws fresh air from outside or separately sourced fresh air through the system. Valve 199 which is again optional allows the proportions between air drawn from outside and air drawn from the room to be regulated.

[0148] Figure 31 shows a combined PCM and evaporative module 200. The laminate of PCM and air channels is formed in layers of in succession a PCM pack 201 , a layer of air channels in a first direction and a layer of air channels in a second direction 203. One of the directions is for dry air and is indicated by arrow 204 whilst the second direction is for wet air as indicated by arrow 205.

[0149] The heat exchanger of Figure 30 may also incorporate a PCM/evaporative arrangement of the kind shown in Figure 31.

[0150] Figure 32 shows a further PCM/evaporative arrangement where fresh air flows through opening 206. Optionally, a second opening 207 is provided to allow air in from the room. An optional valve 208 is provided between the two openings. A fan 209 draws the air through the arrangement. A combined PCM and evaporative chamber 210 is located downstream from the fan and exits either outside through opening 21 1 or into room through opening 212. A valve 213 is provided between the two openings 211 and 212.

[0151] Figures 33A show a further embodiment of a heat exchanger with a PCM pack and an evaporative cooler. The heat exchanger as shown in Figure 33B may be built from a stack of combined heat exchanger and a PCM pack. It is envisaged that the PCM pack layer thickness would be greater than that illustrated. The heat exchanger may be formed as a corrugated arrangement with conductive wicking on its surface. These may be knurls on an aluminium plate. The advantages of the combined PCM and evaporative modules are that they are more compact than the side by side combinations of such modules. At night, air is taken from outside, circulated over the PCM. If the air is not cold enough then water is added so that the evaporation provides additional cooling. The wet air is dumped outside as the PCM packs are frozen. During the day the cooling is provided by the PCM whilst no water is added and air is simply taken inside.

[0152] The heat exchanger is preferably conductive for example a metal, a conductive plastics material or a composite to increase the surface area in contact with the air to increase the heat transfer when the PCM is working. It also acts as a wicking to create a fine layer of water over it as it breaks down surface tension. In order to achieve this, grooves, channels and/or knurling on the metal surface or another form of mesh, fabric, or wicking may be envisaged.

[0153] The control system consists of a microcontroller and sensors to measure the time and temperature. Preferably the temperature in the room, the temperature or electrical resistance of the PCM and the outside temperature are measured.

[0154] When the outside air temperature has dropped, or the timer indicates it is the coldest time of the night, cool air from outside is pulled over the PCM. A temperature sensor in the PCM, or a measure of the electrical resistance of the material, tells the control system whether it is frozen or has reached the desired temperature. The PCMs typically exhibit low electrical resistance when liquid and high electrical resistance when frozen.

[0155] During the day the system circulates air over the PCM to provide cooling either when the temperature rises above a certain level or when the user requires it. Preferably a timer is provided to allow the user to set when the system is to be active. If the outside air is cooler than the inside air then a greater proportion of the air is taken from outside.

[0156] Figure 34 shows how the unit works. A valve 214 determines whether air is taken from inside 215 or outside 216, it is then pulled through the PCM by a fan 217 and back into the room 218. Preferably a simple removable air filter 219 removes dust and particles. A layer of insulation around the PCM 220 allows the cooling energy to be stored until required. Figure 35 shows how one or more units 221 can be connected to the outside air through a series of ducting 222. The units are mounted inside the room 223 and the ducting connects the units to an exterior wall 224 and the outside through a hole in the wall, door or window. Preferably an additional vent or valve 225 at the wall allows excess air from inside to escape, when the air is being pulled inside through the units and an additional air filter is placed here. [0157] The unit described previously can be mounted in a number of ways. The unit 221 can be ceiling or wall mounted, or left on the floor and moved by rollers. The units can be connected to a series of ceiling or wall mounted ducting, or by a flexible hose through a window to the outside. [0158] Figure 36 shows an additional valve 226 to the system described in Figure 34. This allows the air leaving the unit to be sent outside 227 via a second duct or hose, or into the room 228. When the cool night time air is used to cool the PCM it can be returned outside should the room temperature become too low. By returning the excess air outside the room temperature can be regulated without effecting the cooling of the PCM. [0159] The units can be combined with lighting. They may have a sound/acoustic absorbing panel fitted to the PCM module in order to absorb sound from the room. Preferably fittings are provided to attach the lights if required.

[0160] Preferably a control interface is provided that is either part of the unit or separate to it. The control interface may have a wireless, infrared or wired connection allowing it to control individual or multiple units. The control interface provides feedback to the user on how much cooling energy is remaining in the unit, as well as allowing them to activate or deactivate the units.

[0161] A further system is shown in Figure 37 where the PCM is mounted inside the ducting that connects to a supply of outside air. A central control unit 229 at one end contains the valve 230 to control whether air enters the units from outside 231 or inside 232, a fan 233, and preferably an air filter 234. The modules connecting to the control unit are insulated and contain the PCM 235. Air travels all the way along the duct and out the end 237. To ensure the air does not stall the cross-sectional area for air flow will need to vary with the total length of the duct, or if the duct is split into multiple paths. This can be achieved by varying the overall diameter of the duct or by changing the density of the PCM inside the duct. For example if the resistance to the air is too great at the end of the duct then less PCM may be placed here. Valves may be placed along the length of the duct to allow air out, and balance the air flow.

[0162] Figure 38 shows the PCM 238 mounted inside the duct along the fan 239. During the day the two valves 240 and 241 allow the air to pass through each unit individually, allowing air from in the room 242 and back out again. At night these valves allow air to travel along the entire length, from outside 224 and out of the last unit 245. The air is allowed into the room or the last unit is also connected to the outside and the flow into the room is controlled by the valve 241 only.

[0163] The units can be connected directly to each other or separated with additional pieces as shown by 246, which may perform additional functions such as turning a corner.

[0164] Figure 39 shows a central control system 247 that consists of a fan 248 and filter 249 to push or pull night time air through the whole system (from A to H) as described. Each PCM 250 contains two valves 251 and 252 controlling the air flow so that during the day time, air is circulated through the PCM 253 individually (from E to I), via a fan 254 and filter 255.

[0165] Figure 40 shows a plurality of modules I, C, E and F located in a series. A channel is provided to bypass the series of PCM packs. A fan drawn air through the PCM packs in the PCM modules and out towards a plurality of rooms. Each outlet incorporates a valve to regulate the flow. Module F is simply a recirculation module. [0166] Figure 41 shows a portable system which works in a similar way to the system shown in Figure 34, but provides local cooling rather than cooling for a whole room. Air enters 256 through some vents 257 and passes over the PCM 258, pulled by a fan 259, and out towards the user 260. An interface and control system 261 is provided to allow the user to activate the unit. Feedback is provided to the user to show the amount of cooling energy remaining. A rechargeable battery powers the fan when it is not connected to a power supply. Sensors monitor the air temperature coming into the unit and the temperature or state of the PCM to control the air flow during the 'night' cycle.

[0167] Preferably a docking system 262 as shown in Figure 42 holds one or more units 263, while the batteries are charged, either though a direct electrical contact or induction charging. The docking station may have window, window sill or wall mountings to hold the units outside securely, while both the batteries are charged and the PCM is cooled overnight. Alternatively the docking station may be used inside on a desk or similar.

[0168] The unit can be manually placed outside during the night, so ducting is not required to connect the units up to a supply of outside air. During the day the units can be placed inside whenever they are required. The PCM pack in the portable unit is also separable form the control unit or fan unit. This means different PCM batteries can be used, when one runs out another can be taken. These packs may be stored/frozen in the fridge or if using water the freezer. For additional cooling, when the night cooling is not sufficient.

[0169] Figure 43 shows an arrangement of modules. In this embodiment there is a single control module 264 drawing fresh air from outside. The fresh air is circulated through duct 265 which is provided with a number of laterally extending channels such as channel 266 which terminate with a PCM module. Duct 265 is preferably insulated. Stale air may be drawn through control module 264 out of the room.

[0170] Figure 44 shows a duct 267 which draws air from outside. The duct incorporates two laterally extending channels 268 and 269. A control unit is attached to respective laterally extending channels. The control modules 270 and 271 draw stale air from the room and fresh air through two adjacent PCM modules 272 and 273. An additional vent for drawing stale air out from the room is provided as module 274. [0171] The configuration of Figure 45 is similar to the configuration of Figure 43 but with six laterally extending channels each leading to their respective PCM modules. The various modules may be individually attached to a false ceiling framework formed by a number of support members such as support member 275. Figure 46 shows an embodiment of the kind shown in Figure 44, but incorporated into a false ceiling. In addition, the two laterally extending channels 276 and 277 form a "V" shape, whilst each control unit is in communication with four adjacent PCM modules.

[0172] Some of the advantages of the preceding Figures 43 to 46 are that the arrangements are easily scalable since they allow the simple addition of more PCM modules to meet a particular room air conditioning requirement. Since the PCM modules in a preferred embodiment have no powered bits these may be readily retrofitted to existing powered units. These can use existing ventilation, ducts and forced ventilation systems. As shown in Figure 46, for example, a single control system can drive many units. A single control system may also be employed to drive multiple units in multiple rooms.

[0173] The efficiencies are of the order of 10 times better than ordinary heat pumps. More specifically, the ratio of heat energy to electrical energy is ten times better (COP rating). For heat pump this is about 3 whilst for the arrangements presented herein about 30.

[0174] Figure 47 shows an arrangement incorporating a backup system inside a room. The backup unit 278 draws fresh air into the room whilst exhausting air through a separate duct. A duct is provided to channel air to respective control units 279 and 280. Each control unit is attached to two separable PCM modules such as modules 281 and 282. The backup unit may be of the kind described in previous embodiments.

[0175] Figure 48 shows a further arrangement incorporating a backup unit in the form of a pettier or heat pump. In this configuration the control unit is located on a duct 283 instead of being adjacent to PCM modules 284 and 285. In this configuration the backup system may have an additional valve to allow it to either function in the backup mode or simply function with air being directly pumped to the PCM modules during the cooling phase.

[0176] A further backup arrangement is provided in Figure 49. In this configuration the air into the control unit 286 determines the amount of air inside/outside. The backup unit 287 draws stale air in from the room. [0177] As a further backup system, it may be incorporated into the PCM module. A further modification of the arrangement would be to have the backup system after the PCM units or in them so as to provide a boost to air going into the room during the day.

[0178] In the arrangements of Figures 47 to 49, the PCM provides "free" cooling most of the year but a backup system is available if the night time temperature is not cold enough.

[0179] Alternatively, these arrangements can allow the systems to be more powerful but with a reduction of energy usage of for example 20 to 40%. The reduction in energy usage is typically 60-80%.

[0180] Figures 50 to 52 show an arrangement of the kind shown in Figure 43 associated with: a forced air system 288 (as shown in Figure 50), a forced air system 289 in conjunction with a backup system providing a cooling boost 290 (Figure 51 ) and a configuration where the control unit 291 is located outside the room (Figure 52). This control unit may have the ability to use/re-circulate internal air.

[0181] During the day enough fresh air is sent through the system for breathing. [0182] At night air is forced through the system from outside to freeze the PCM.

[0183] In the embodiment of Figure 51 it is possible to use an existing ventilation system plus the configuration of any of the preceding embodiments fitted onto it.

[0184] One of the advantages of external forced air systems is that a single more powerful control unit with a fan is mounted outside where noise is not a problem. Another advantage of the system is that in combination with a forced air system when these are already installed, it takes advantage of the existing ventilation system rather than duplicating it with the modular units. It allows the addition of PCM modules to the ventilation system and nothing else.

[0185] An optional internal control unit can be used inside to control the room temperature for individuals and allow recirculation of air inside. [0186] In a winter mode, by the end of the day warm stuffy air is passed over the PCM melting it. The heat is then stored in the PCM encased with insulation for the following day. As the system provides fresh air during the day this is passed over the PCM so warming it as it enters the room.

[0187] The PCM material itself has thermal conductive properties of the order of 0.5 to 1 W/mK. A thermal conductor is added to the material or located adjacent to the material which has a greater conductive property than the PCM material on its own. A particularly beneficial level of thermal conductivity would be for the conductors to have a conductivity of at least 5 W/mK. A range of 5 to 20 is envisaged for plastics material conductors whilst a greater range of say 100 to 250 is envisaged for metals.

[0188] In an embodiment of the invention a PCM pack comprising an envelope of relatively highly thermally conductive material enclosing a portion formed primarily of PCM is proposed. The PCM is selected to be a hydrated sodium sulphate salt. The hydrated sodium sulphate salt has a melting/freezing temperature of 21° Celsius in a first embodiment or 24° Celsius in a second embodiment. In each of the first and second embodiments, the carbon black may be sourced from Cabot Corp (USA). For a first embodiment of the invention the carbon black selected is a so-called "Black Pearl L" and for the second embodiment the carbon black sample is a so-called "Mogul L". The carbon black of the first embodiment has a relatively smooth outer surface. The particles take the form of pellets. With regard to the second embodiment the carbon black particles are generally termed "fluffy". An example of the fluffy outer surface is shown in Figure 53 whilst the relatively smooth outer surface of the pellets of the first embodiment is shown in Figure 54. The PCM portion of either of these two embodiments incorporates hydrated sodium sulphate in combination with the carbon black particles. The sodium sulphate may be "sodium sulphate 10 - hydrate" (obtained from Fisher Scientific, UK).

[0189] The size distribution for the carbon black of the first and second embodiment may have a D₅₀ of around 4μm. Advantageous effects have been found for percentages by mass of carbon black between 1 and 45%. As the percentage of carbon black is increased, the consistency of the PCM also changes. The mixture becomes viscous after heating at high percentages. A proportion of 3% in weight of carbon black is particularly advantageous. It would also appear to be a granular system. The carbon black also forms around crystals.

[0190] Advantages are achieved when incorporating minerals such as montmorillonite or kaolinite, which can act as viscosity modifiers. The first and second embodiments also envisage the incorporation of a viscosity modifier such as Xanthan gum to prevent settling.

[0191] Kaolinite may be obtained from lmeris Minerals which has a content of 88% kaolinite. The addition of the kaolinite may be obtained by heating the PCM, mixing it in and then allowing it to cool. The kaolinite which is preferred is a plate-like mineral with very fine particles of the order of 1 μm in diameter. The proportion of kaolinite may be 5/40 by mass relative to the sodium sulphate.

[0192] In a further embodiment, the PCM mixture may be preferably 80%_w/_w sodium sulphate, 10% w/w kaolinite and 10% _w/w fluffy carbon black. [0193] In a further embodiment, the PCM consists of:

• a hydrated salt based PCM such as sodium sulphate decahydrate, sodium thiosulphate pentahydrate, or calcium chloride hexahydrate; • 1-10% addition of clay based thickening agent such as kaolinite or bentonite;

• 1-10% addition of a conductivity additive, such as carbon black in a preferred embodiment;

• 1-3% addition of supercooling preventative such as lithium fluoride;

[0194] The following benefits may be achieved:

• Improvement in conductivity and therefore speed at which melting and solidification occurs, increasing the thickness of the packaging (or layers of the material), further reducing costs, or maximising energy transfer and therefore cooling and heating power of a heat exchanger incorporating a latent heat store; • Improvement in the stability and life of salt based PCMs, preventing separation and moisture escaping;

• Reduction in supercooling;

• Reduction in phase change temperature, typically by 3-5 degrees Celsius, reduction in the amount of other salts used to lower the phase change temperature; • Improvement in energy storage density compared to alternative methods;

• Less likely to leak as mixture increases viscosity.

[0195] In a preferred mode of manufacture, kaolinite and carbon black are mixed together in a dry state. Thereafter, the sodium sulphate is heated at an elevated temperature such as 40° Celsius to produce the anhydrous suspension. Then, the powdered mix of carbon black and kaolinite is added to the mixture and agitated. The resulting mixture is then inserted into an oven for a heat treatment of for example, 30 minutes at 40° Celsius before further agitation or stirring.

[0196] In a preferred mode of preparation, the compound is mixed at a temperature above the phase change temperature but below the temperature at which water vaporizes (< 100 degrees Celsius).

[0197] In broad terms the PCM may be organic, eutectic or a salt hydrate. Organic PCM is not presently preferred. Organic PCMs are typically either fatty acids or paraffin based waxes.

They are stable, have high latent heat properties and are available in a wide range of useful phase change temperatures, but tend to have problems of flammability, low conductivity, high cost, sustainability, and can attract parasites due to their organic nature. Examples include: Paraffin C16-C18 (phase change at 20-22C) and Paraffin C13-C24 (phase change at 22-24C) which have latent heat of fusion of approx 150-200KJ/Kg, but relatively low conductivity of 0.2 W/mK; fatty acids such as a Mistiric-capric acid (34%-66%, phase change at approx 24C) or Capric-lauric acid (45%-55%, phase change at approx 21 C), with latent heats of fusion of approx 150KJ/Kg and low conductivity of approx 0.1-0.2 W/mK.

[0198] Carbon black can be added to these mixtures, ideally around 5-15% to improve conductivity, while maximizing energy storage. At approximately 12% a conductive path is formed across the material. [0199] Salt hydrate based PCMs are less expensive, non-flammable, sustainable alternatives to organics. Salt hydrate based PCMs can exhibit problems with segregation, limiting their life, and supercooling, where they freeze at lower temperatures than they melt. In accordance with the invention, adding carbon black increases thermal conductivity while acting as a nucleating agent (reducing the effect of supercooling) and a thickening agent (limiting the segregation while extending the life). [0200] In general terms, a composition according to an embodiment of the invention comprises (by weight):

• Salt Hydrate-based PCM, 50 - 99%

• Carbon Black, 0 - 45% (preferably 5-15%, around 12% is optimum for conductivity as it forms a continuous link across the material) • Optional 0-10% Thickening / Gelling Agent

• Optional 0-10% Nucleating Agent

[0201] The two preferred salt based PCMs for use in space heating and cooling of buildings use sodium sulphate and calcium chloride. The thermal conductivity is also low, typically 0.5 to 1 W/m.K depending on the additives used. [0202] Sodium sulphate decahydrate (Na2SO4^«10H2O, also known as Glauber's Salt), has a phase change temperature of 32.4 ⁰C and a latent heat of 241 KJ/Kg. Sodium chloride is added to the mixture to lower the phase change temperature, e.g. 9% sodium chloride and 91 % sodium sulphate decahydrate would result in a phase change temperature around 25C. Thus, the salt hydrate based PCM may comprise: • Sodium Sulphate Decahydrate, 85% - 100%

• Sodium Chloride, 0-15%

[0203] Calcium Chloride Hexahydrate (CaCI2 ^«61-120) has a phase change temperature of approximately 29C and a latent heat of approx 190 KJ/Kg. Potassium Chloride, Sodium Chloride and/or Ammonium Chloride can be added to lower the phase change temperature. For example 48% CaCI2 + 4.3% NaCI + 0.4% KCI + 47.3% H2O, results in a phase change temperature of 26-27C and a latent heat of approximately 180-190KJ/Kg. Thus, the salt hydrate based PCM may comprise:

• Calcium Chloride Hexahydrate, 85% - 100%

• Potassium Chloride, and/or Ammonium Chloride, 0 - 15% [0204] Potassium nitrite or potassium nitrate have also been used to reduce the phase change temperature below 23C.

[0205] Calcium Chloride Tetrahydrate (CaCI2 ^«41-120) and Calcium Chloride Dihydrate (CaCI2 •2H2O) have phase change temperatures of 43.3 C and 130 C respectively. [0206] The two salts, sodium sulphate and calcium chloride above can be combined into the same PCM mixture to get the desired temperature and energy storage.

[0207] Other possible salt hydrates include sodium thiosulphate pentahydrate (Na2S2O3^«5H2O), sodium acetate trihydrate (CH3COONa^«3H2O), disodium hydrogen phosphate dodecahydrate (Na2HPO4^«12H2O), and sodium carbonate (Na2CO3^«10H2O). [0208] There is a wide range of possibilities for thickening agents, which can be selected from one of the following groups:

• Clay based - bentonite, kaoynite, kaolinite, montmorillonite, attapulgite clay or sodium bentonite to create a gel;

• Laponite - trade name, used to thicken paints;

• Silica, silica gel, & related derivatives; • Natural / vegetable gums and gels, e.g. Xanthan;

• Cellulose based gums and gels, e.g. carboxymethyl cellulose;

• Polyethylene glycol;

• Carbomer; or

• Water-insoluble hydrogel [0209] Paraffin waxes have also been used as thickening agents which has the benefit of improving both stability and the effect of supercooling.

[0210] Sodium tetraborate decahydrate (borax), silicates, calcium carbonate, cryolite, sodium borate decahydrate and lithium fluoride have successfully been used as nucleating agents to prevent supercooling in PCMs. However there are many other alternatives depending on the PCM used. In reference to calcium chloride hydrates, nucleating agents may include calcium hydroxide and barium and strontium carbonates, chlorides and fluorides, which may be in the form of hydrates.

[0211] Example compositions are shown in the table below.

Carbon black Gelling / NaCI H2O Na2SO4 Phase (mass %) Nucleating (mass %) (mass %) (mass %) Change agent (m %) Temp (C)

Typically a nucleating / thickening agent would be present at lower concentrations e.g. 1-5%. [0212] Figure 55 shows a phase change material pack 300 according to an embodiment of the invention. The pack is made from two pressed panels 301 which are joined at their edges and at two locations 302 in the middle of the pack surface for strength. The surface of the pack is textured to induce turbulent flow in the fluid (air) passing over it.

[0213] A conductive PCM material allows the PCM packs to be thicker, reducing manufacturing costs. Currently the PCM packs / panels are 10-15mm thick. Where salt based hydrates are used then the pack material must be non-corrosive, non-permeable and robust. Preferably, depending on the thickness, the material should be thermally conductive. [0214] Preferably metals are used to form the panels 301 as they are non-permeable and highly conductive. Those with the best corrosive properties are aluminium and stainless steel.

Further coatings may be needed to reduce the effects of corrosion depending on the salt.

Suitable techniques are anodizing, E-Coat or Electro Coat, silane coating, PTFE.

Depending on the method of manufacture there are many processes which allow the protective layer to form naturally during the manufacturing process. Aluminium alloys 5052 &

5251 have good formability and very good corrosion resistance, reducing the need for the level of coatings.

[0215] Many plastics have poor permeability and their mechanical properties degrade over time due to the effects of the salt hydrate weakening the plastic, this means that plastics generally need higher wall thickness, ie 1-5mm rather than 0-1 mm with metals. HDPE is one of the best off the shelf plastics. Additives / processes used to make plastics more conductive also have a positive effect on plastics permeability.

[0216] A composite material may be used. As used commonly in the food industry this may consist of a film of a number of different materials, e.g. aluminium foil for permeability reasons, plastic for corrosive reasons.

[0217] The typical method of manufacture is using superforming / hydroforming or stamping two sides of the pack, and then epoxy gluing or welding the edges shut. A preferably resealable opening is left to fill / refill the pack.

[0218] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. [0219] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A phase change material composition comprising between 50 and 99% by weight of a salt hydrate and between 0 and 45% by weight of carbon black.

2. A composition as claimed in claim 1 , wherein the salt hydrate comprises a hydrate of sodium sulphate or a hydrate of calcium chloride.

3. A composition as claimed in claim 2, wherein the salt hydrate is sodium sulphate decahydrate.

4. A composition as claimed in claim 2, wherein the salt hydrate is calcium chloride hexahydrate, calcium chloride tetrahydrate or calcium chloride dehydrate.

5. A composition as claimed in claim 1 , wherein the salt hydrate comprises a hydrate of sodium thiosulphate, sodium acetate, disodium hydrogen phosphate or sodium carbonate.

6. A composition as claimed in any preceding claim, wherein the salt hydrate comprises a mixture of at least two salt hydrates.

7. A composition as claimed in any preceding claim comprising a hydrate of sodium sulphate and between 0 and 15% by weight of sodium chloride.

8. A composition as claimed in any preceding claim comprising a hydrate of calcium chloride and between 0 and 15% by weight of potassium chloride, sodium chloride and/or ammonium chloride.

9. A composition as claimed in any preceding claim comprising between 0 and 15% by weight of carbon black.

10. A composition as claimed in any preceding claim comprising between 0 and 10% of a thickening agent.

1 1. A composition as claimed in any preceding claim comprising between 0 and 10% of a nucleating agent.

12. A composition as claimed in any preceding claim with a melting point between -15 and 100 degrees centigrade.

13. A composition as claimed in claim 12 with a melting point between 15 and 40 degrees centigrade.

14. A composition as claimed in claim 13 with a melting point between 20 and 30 degrees centigrade.

15. A phase change material pack comprising a composition as claimed in any preceding claim in an envelope of material of relatively high thermal conductivity.

16. A climate control system utilising a composition as claimed in any of claims 1 to 15.