Abstract:
A transportable PCM (phase change material) module comprises a number of PCM packs; a housing for thermally insulting said number of PCM packs from a module&#39;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. 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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application under 35 U.S.C. §371 of International Application No. PCT/GB2009/000377, titled PCM MODULES/PACKS/PCM ARRANGEMENTS, filed Feb. 11, 2009, which claims priority to Great Britain Application No. 0802445.7, filed Feb. 11, 2008, both of which are hereby incorporated by reference in their entireties. 
     FIELD OF THE INVENTION 
     The invention relates to PCM modules, PCM packs and arrangements. 
     BACKGROUND TO THE INVENTION AND PRIOR ART KNOWN TO THE APPLICANT(S) 
     The following prior art documents have been identified: US2006/0185817, EP1947404, EP1455156, EP1739376, EP1455155, DE20314018 and DE20310593. 
     SUMMARY OF THE INVENTION 
     In a first broad independent 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&#39;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. 
     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. 
     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. 
     In a further subsidiary aspect, said PCM packs are arranged substantially side by side. In this configuration, the cooling is advantageous. 
     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. 
     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. 
     In a further subsidiary aspect, said thermal conductors take the form of a corrugated sheet. 
     In a further subsidiary aspect, at least one of said PCM pack incorporates a corrugated wall forming a channel for the flow of fluid. 
     In a further subsidiary aspect, a number of projections are provided in at least one of said channels. 
     In a further subsidiary aspect, at least one of said PCM pack incorporates a wall from which projections project into said channel. 
     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. 
     In a further subsidiary aspect, said thermal conductors form hexagonal cells when viewed in plan. 
     In a further subsidiary aspect, said laminate further incorporates a corrugated thermally conductive panel. 
     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. 
     In a further subsidiary aspect, said laminate incorporates a plurality of projections on said panels. 
     In a further subsidiary aspect, said thermally conductive panels are selected from the group comprising aluminium based material, steel based material, and plastics material. 
     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. 
     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. 
     In a further subsidiary aspect, said organic material is paraffin based. 
     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. 
     In a further subsidiary aspect, said carbon based compound is carbon black. 
     In a further subsidiary aspect, said thermal conductors incorporate wire wool or chemical carbon nanotubes. 
     In a further subsidiary aspect, said module further incorporates a pettier cooler. 
     In a further subsidiary aspect, said module further incorporates an evaporative cooler. 
     In a second 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. 
     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. 
     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. 
     In a further subsidiary aspect, said arrangement further comprises a transportable backup module incorporating one of a heat pump, an inverter, a pettier cooler, or an evaporative cooler; and further incorporating means for linking said backup module to said PCM module. 
     In a third 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. 
     In a subsidiary aspect, said thermal conductors extend in a transverse direction from one or both of said conducting panels. 
     In a further subsidiary aspect, said thermal conductors form hexagonal cells when viewed in plan. 
     In a further subsidiary aspect, said laminate further incorporates a corrugated thermally conductive panel. 
     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. 
     In a further subsidiary aspect, said laminate incorporates a plurality of projections on said panels. 
     In a further subsidiary aspect, said thermally conductive panels are selected from the group comprising aluminium based material, steel based material, and plastics material. 
     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. 
     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. 
     In a further subsidiary aspect, said organic material is paraffin based. 
     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. 
     In a further subsidiary aspect, said carbon based compound is carbon black. 
     In a further subsidiary aspect, said thermal conductors incorporate wire wool or chemical carbon nanotubes. 
     Modules and/or arrangements and/or PCM packs substantially as herein described and/or illustrated in any appropriate combination of the accompanying text and/or figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a cross sectional view of a PCM module with a single upper opening. 
         FIG. 2  shows a cross sectional view of a PCM module with two upper openings and two lower openings of differing directions. 
         FIG. 3  shows a PCM module adapted to fit to a false ceiling. 
         FIG. 4  shows a PCM module in cross section adapted to be fitted to a false ceiling with the PCM packs provided in series. 
         FIG. 5  shows a heat exchanger in cross section with a plurality of PCM packs separated by corrugated plates. 
         FIG. 6  shows an exploded view in a perspective of the embodiment of  FIG. 5 . 
         FIG. 7  shows in perspective view the combination of a PCM pack with a corrugated plate. 
         FIG. 8  shows in perspective view a portable PCM pack. 
         FIGS. 9A  and B show a PCM pack incorporating a thermally conductive corrugated plate. 
         FIG. 10  shows in perspective view the assembly of a PCM pack with a corrugated plate with a plurality of holes. 
         FIG. 11  shows a perspective view of the assembly of a hexagonal array. 
         FIG. 12  shows a perspective view of the assembly of a PCM pack with a hexagonal array with perforations. 
         FIGS. 13A  and B show in cross section and in perspective view PCM packs incorporating a corrugated wall. 
         FIGS. 14A and 14B  show respectively in cross section and in perspective a PCM pack whose envelope may be formed by extrusion. 
         FIG. 15  shows a perspective view of a heat exchanger incorporating a number of PCM packs of the kind shown in  FIG. 14 . 
         FIG. 16  shows a perspective view of a heat exchanger incorporating a number of PCM packs of the embodiment of  FIG. 14 . 
         FIG. 17  shows a schematic cross sectional view of a control unit with a lateral valve. 
         FIG. 18  shows a schematic cross sectional view of a control module with a valve located between two inlets. 
         FIG. 19  shows a schematic cross sectional view of a control module employing a non-return valve. 
         FIG. 20  shows a control unit incorporating a fan. 
         FIG. 21  shows a schematic cross sectional view of a heat exchanger which may be used in conjunction with a PCM module. 
         FIG. 22  shows a schematic cross sectional view of a further embodiment of a heat exchanger. 
         FIG. 23  shows a cross sectional view of a heat exchanger incorporating a pettier cooler. 
         FIG. 24  shows a heat exchanger in cross sectional view incorporating PCM packs. 
         FIG. 25  shows in cross section a heat exchanger incorporating hexagonal ducts as part of a pettier cooler. 
         FIG. 26  shows a control unit incorporating a number of heat exchangers. 
         FIG. 27  shows a schematic cross sectional view of a backup module incorporating an evaporative unit. 
         FIG. 28  shows a further embodiment of a backup unit with an evaporative system. 
         FIG. 29  shows a further embodiment of a backup unit. 
         FIG. 30  shows a schematic cross sectional view of a further embodiment of the invention. 
         FIG. 31  shows a PCM pack laminate with bi-directional channels in perspective view. 
         FIG. 32  shows a further evaporative system in schematic cross sectional view. 
         FIG. 33A  and  FIG. 33B  shows a perspective view and a cross sectional view of a plate and PCM pack combination. 
         FIG. 34  shows a schematic cross sectional view of a PCM unit. 
         FIG. 35  shows a plurality of PCM modules. 
         FIG. 36  shows a further embodiment of a PCM module. 
         FIG. 37  shows a combination of a controlled unit, and PCM modules in cross sectional view. 
         FIG. 38  shows a combination of a plurality of PCM modules. 
         FIG. 39  shows a further embodiment of a combination of PCM modules in cross sectional view. 
         FIG. 40  shows a further embodiment of the combination of PCM modules, a control unit and a recirculation unit. 
         FIG. 41  shows a portable unit with a rechargeable battery to drive a fan. 
         FIG. 42  shows a docking station suitable for charging the PCM module of  FIG. 41 . 
         FIGS. 43 to 52  show plan views of arrangements of PCM modules for a given room. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 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&#39;s surrounding environment. 
       FIG. 2  shows a further embodiment of a PCM module. PCM module  10  incorporates a plurality of PCM packs such as PCM pack  11 . 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&#39; 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&#39; 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  FIG. 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  FIG. 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 . 
       FIG. 3  shows a further PCM module generally referenced  24  with a separable duct  25  sealed to the module&#39;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. 
       FIG. 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 are 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  FIG. 3 . The configuration of the figure provides for a longer air flow path in a heat exchanger when compared to the previous embodiments. 
     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. 
       FIG. 5  shows a PCM module in cross-section which takes the form of a heat exchanger  42  with an insulative housing  43 . The housing wall may be selected to hold 80 to 90% of the “coolth” over 8 hours. It may be of approximately 25 mm 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 .  FIG. 6  shows the components of  FIG. 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). 
       FIG. 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  FIG. 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. 
       FIG. 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. 
       FIG. 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  FIG. 9A  are shown in  FIG. 9B  as glued or sealed together in order to prevent any escape of PCM during use. 
     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. 
     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. 
       FIG. 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. 
     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 KM 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. 
     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. 
       FIG. 11  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. 
     An alternative PCM pack  66  is shown when compared to the embodiment of  FIG. 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. 
     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 5 W/MK) or stainless steel in order to prevent corrosion. 
     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. 
       FIGS. 13A and 13B  a PCM pack ( FIG. 13A ) and a stack of PCM packs ( FIG. 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. 
       FIGS. 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 nano-tubes or particles to the plastics material. The process envisaged in order to produce wall  79  would be to form the wall by extrusion. 
       FIG. 15  shows a PCM pack module generally referenced  85 . Module  85  incorporates an insulative 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. 
     As shown in  FIG. 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. 
       FIG. 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. 
     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. 
       FIG. 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  110  leading to opening  111 . 
       FIG. 19  shows a further embodiment of a separable control module  112 . This control module incorporates an opening  113  for drawing in air from a room or from outside. The duct  114  is split into two paths  115  and  116  which are respectively fitted with a fan  117  and a non-return valve  118 . 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. 
       FIG. 20  shows a further separate control module  119  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 . 
     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.  FIG. 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  FIGS. 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. 
       FIG. 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. 
     A number of advantages arise from combining a module of the kind described in  FIGS. 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 nighttime 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. 
     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. 
       FIG. 23  shows in further detail how a pettier backup module may be formed. A pettier 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. 
       FIG. 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 pettier  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  FIG. 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. 
     An alternative to the embodiment of  FIG. 23  is shown in  FIG. 25  where a further pettier based backup module  155  is shown. The pettier  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. 
       FIG. 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 exists 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. 
     It is preferred to use an insulated housing for a heat pump or pettier 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. 
       FIG. 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 channeled 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 . 
       FIG. 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 . 
       FIG. 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 . 
     In the preceding  FIGS. 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 U.S. Pat. No. 6,581,402. 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. 
       FIG. 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. 
       FIG. 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 . 
     The heat exchanger of  FIG. 30  may also incorporate a PCM/evaporative arrangement of the kind shown in  FIG. 31 . 
       FIG. 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  211  or into room through opening  212 . A valve  213  is provided between the two openings  211  and  212 . 
       FIG. 33A  show a further embodiment of a heat exchanger with a PCM pack and an evaporative cooler. The heat exchanger as shown in  FIG. 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. 
     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. 
     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. 
     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. 
     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. 
       FIG. 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. 
       FIG. 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. 
     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. 
       FIG. 36  shows an additional valve  226  to the system described in  FIG. 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. 
     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. 
     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. 
     A further system is shown in  FIG. 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. 
       FIG. 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. 
     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. 
       FIG. 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 . 
       FIG. 40  shows a plurality of modules I, G, 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. 
       FIG. 41  shows a portable system which works in a similar way to the system shown in  FIG. 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. 
     Preferably a docking system  262  as shown in  FIG. 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. 
     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. 
       FIG. 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. 
       FIG. 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 . 
     The configuration of  FIG. 45  is similar to the configuration of  FIG. 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 . 
       FIG. 46  shows an embodiment of the kind shown in  FIG. 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. 
     Some of the advantages of the preceding  FIGS. 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  FIG. 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. 
     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. 
       FIG. 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 separatable PCM modules such as modules  281  and  282 . The backup unit may be of the kind described in previous embodiments. 
       FIG. 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. 
     A further backup arrangement is provided in  FIG. 49 . In this configuration the air into the control unit  286  determines the amount of air inside/outside. The backup unit  287  draws state air in from the room. 
     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. 
     In the arrangements of  FIGS. 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. 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%. 
       FIGS. 50 to 52  show an arrangement of the kind shown in  FIG. 43  associated with: a forced air system  288  (as shown in  FIG. 50 ), a forced air system  289  in conjunction with a backup system providing a cooling boost  290  ( FIG. 51 ) and a configuration where the control unit  291  is located outside the room ( FIG. 52 ). This control unit may have the ability to use/re-circulate internal air. 
     During the day enough fresh air is sent through the system for breathing. 
     At night air is forced through the system from outside to freeze the PCM. 
     In the embodiment of  FIG. 51  it is possible to use an existing ventilation system plus the configuration of any of the preceding embodiments fitted onto it. 
     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. 
     An optional internal control unit can be used inside to control the room temperature for individuals and allow recirculation of air inside. 
     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. 
     Further Descriptive Aspects
         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.       

     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.