VARIABLE THERMAL INSULATION ASSEMBLY
A variable thermal insulation assembly includes at least one array comprising a plurality of sheets of film, wherein the plurality of sheets are in a stacked arrangement and each sheet is bonded to an adjacent sheet along a plurality of longitudinally extending regions such that each pair of adjacent sheets form a plurality of longitudinally extending cavities between adjacent regions of the adjacent sheets, a support frame comprising end elements, wherein the support frame frames the plurality of sheets, wherein support frame is coupled to the array to support the array such that the array may transition between an expanded state in which the array is expanded, and a compressed state in which the array is compressed, within the plane of the frame along the direction perpendicular to the longitudinal axis such that the longitudinally extending cavities are expanded or compressed, wherein in the expanded state, the front edge conforms to one of the second end of the support frame or a second front edge of a second array to form a seal that inhibits air flow between the front edge and the one of the second end of the support frame or the second front edge of the second array.
The present disclosure relates to a variable thermal insulation assembly that includes a plurality of thermal cell arrays that are adjustable between an expanded state and a compressed state.
BACKGROUNDDuring sunny weather conditions it is often desirable to maximize the transmission of sunlight into a building to assist with both lighting and heating of the interior of the building. By contrast, during dark, cloudy, or cold weather conditions it is often desirable to maximize the thermal insulation of a building to minimize heat loss from the building. Windows are typically employed in buildings to facilitate the transmission of sunlight into the building while also providing a sealed barrier against the entry of wind, rain, snow and other undesirable elements. While windows typically provide a relatively high degree of optical transmission which may be advantageous for sunny weather conditions, they also typically provide a relatively low degree of thermal insulation which may be undesirable for dark, cloudy, or cold weather conditions.
Attempts have been made to develop solutions that provide both a high degree of optical transmission and a high degree of thermal insulation. However, many of these solutions have failed to provide sufficient sunlight transmission or thermal insulation, require frequent adjustment throughout the day, are costly, or are overly complex.
SUMMARY OF THE INVENTIONThe disclosure provides a variable thermal insulation assembly that includes an array of air-enclosing cavities or pockets, referred to herein as thermal cells, that is adjustable between an expanded state and a compressed state. In the expanded state, the variable thermal insulation assembly provides a thermally insulating layer, whereas in the compressed state, the variable thermal insulation assembly retracts such that the thermal insulation provided is reduced relative to the expanded state. In some embodiments, the variable thermal insulation assembly may be installed in association with a window such that, in the expanded state, light transmission through the window may be reduced relative to the compressed state, in which light is transmitted through the window. The array of thermal cells is referred to herein as a thermal cell array.
One aspect of the disclosure provides a variable thermal insulation assembly that includes a frame that circumscribes a thermal actuation region having a gas, one or more thermal cell array units positioned within the thermal actuation region, each thermal cell array unit including a first surface sheet and a second surface sheet, wherein the first and second surface sheets are similarly shaped and define a thermal cell array region therebetween, a thermal cell array positioned within each thermal cell array region and coupled to the first and second surface sheets such that the thermal cell array substantially fills the thermal cell array region, wherein each thermal cell array comprises a plurality of sheets and at least two of the sheets in each thermal cell array are flexible sheets, wherein adjacent pairs of said flexible sheets are bonded together along at least one pair of bonding regions that extend substantially parallel to each other such that each pair of flexible sheets defines at least one substantially longitudinally symmetrical cavity between each pair of bonding regions, each longitudinally symmetrical cavity being one of a plurality of thermal cells, wherein a distance between each pair of bonding regions is sufficiently small that the total heat loss arising from convective gas flow within the thermal cells is less than total heat loss arising from thermal conduction of the gas present within the thermal actuation region, wherein the distance between each pair of bonding regions is sufficiently large, and the thermal conductivity of the sheets is sufficiently low, such that heat transfer due to thermal conduction within the sheets is less than the heat loss due to thermal conduction of the gas of the thermal actuation region, wherein each of the plurality of thermal cells is bonded to another thermal cell or a sheet in order to form a connected thermal cell array unit, a position controller coupled to at least one of the first and second surface sheets for applying a control force on at least one of the first and second surface sheets to expand the thermal cell array into an expanded state and compress the thermal cell array into a compressed state within the thermal actuation region to vary a volume of the thermal actuation region that is occupied by the thermal cell array units, wherein the plurality of sheets are sufficiently thin and formed of one or more materials that are sufficiently compliant such that, for each first and second sheet, when the thermal cell arrays are in the expanded state by the applied control force, a gap between each surface sheet and the adjacent frame surface or surface sheet, is made sufficiently small that the total heat loss that is attributable to gas flow through the gap is less than the total of the heat loss due to thermal conduction through the thermal cells.
In a further aspect, the position controller is coupled to the one of the first and second sheets such that, when the control force is applied, the at least one of the first and the second surface sheets move in a direction that is normal to the one of the first and second surface sheet such that, during the moving the first and second surface sheets are maintained substantially parallel to each other.
In a further aspect, the position controller is coupled to the one of the first and second surface sheets such that, when the control force is applied, the one of the first and second surface sheets pivots whereby a first end of the one of the first and second surface sheet is substantially fixed relative to a corresponding first end of the other of the first and second surface sheets, and a second end of the one of the first and second surface sheets, opposite the first end, moves relative to the second end of the other of the first and second surface sheets.
In a further aspect, at least some of the plurality of sheets comprising the thermal array are coated on at least a first side by a layer of material having a thermal emissivity of less than 0.2.
In a further aspect, the material is aluminum.
In a further aspect, each of the plurality of sheets comprising the thermal array has a curved shape, and the plurality longitudinally extending regions follow the curved shaped such that the formed longitudinally extending cavities have the curved shape.
In a further aspect, the support frame further comprises a front panel and a back panel coupled to the edge elements to form an enclosed panel that encloses the array.
In a further aspect, the front panel and back panel are light-transmitting window elements fabricated that are fabricated from one of glass, mylar, acrylic, polycarbonate, polyethylene, or ethylene tetrafluoroethylene.
In a further aspect, light-transmitting window elements are diffusely light-transmitting elements.
In a further aspect, the front panel and the back panel are each formed from a thin, light-transmitting material, wherein the front panel and the back panel are bonded together in a periphery region to define a pillow-shaped cavity within the enclosed panel.
In a further aspect, the thin, light transmitting material is one of polyethylene, polycarbonate, or ethylene tetrafluoroethylene.
In a further aspect, the enclosed panel further includes a vent utilized for increasing a pressure within the enclosed panel for increasing a structural rigidity of the enclosed panel.
In a further aspect, a volume defined by the enclosed panel is filled with an inert gas.
In a further aspect, the inert gas is argon gas.
In a further aspect, an inner surface of at least one edge element has a reflectivity of at least 80%.
In a further aspect, the inner surface of the at least one edge element has a convex profile.
In a further aspect, edge elements comprise a first end element at the first end, a second end element at the second end, and a pair of side elements that connect the first and second end elements, wherein at least one of the side elements includes a seal element for inhibiting airflow through an opening of the plurality of longitudinally extending cavities adjacent to the side element when the array is in the expanded state.
In a further aspect, the seal element is a first inflatable bladder.
In a further aspect, one of the first end element and the second end element includes a second inflatable bladder coupled to the first inflatable bladder by an air-transfer connection to transfer air between the first inflatable bladder and the second inflatable bladder, wherein the air-transfer connection is configured to inflate the first inflatable bladder and deflate the second inflatable bladder when the array is in the expanded state, and inflate the second inflatable bladder and deflate the first inflatable bladder when the array in the compressed state.
In a further aspect, the variable thermal insulation assembly includes a position controller for transitioning the array between the expanded state and the compressed state.
In a further aspect, the position controller is an electrostatic system wherein the plurality of sheets of the thermal cell array are formed of an electronically insulative material that is coated on one side with an electrically conductive material such that, for each pair of sheets, the electrically conductive material coating of each flexible sheet of the pair are separate by at least one layer of the electrically insulative material, the
the variable thermal insulation assembly further including a controller to apply an electric potential difference between each adjacent pairs of sheets such that the electrically conductive coatings of the adjacent pair of sheets attract each other to cause the array to be in the compressed state, and a plurality of biasing elements located with the plurality of longitudinally extending cavities to bias adjacent pairs of sheets away from each other to cause the array to be in the expanded state in the absence the controller applying an electrical charge.
In a further aspect, the plurality of biasing elements are provided by forming the plurality of flexible sheets from an elastomeric material, wherein the elastomeric material is deformed such that the plurality of flexible sheets are biased into the expanded state.
In a further aspect, the light-transmitting window elements have a first portion that is diffusely light transmitting and a second portion that is non-diffusely light transmitting such that the diffusion characteristics of the transmitted light can be controlled.
In a further aspect, each thermal cell consists of two flexible film elements, each flexible film element having two edge-bond zones that comprise less than 20% of a surface area of the flexible film element, each edge-bond zone extending in a direction parallel to the longitudinal direction of the flexible film element, and a central bond zone comprising less than 20% of the surface area and extending parallel to the longitudinal direction along the center of the flexible film element, each thermal cell is formed by bonding two flexible film elements along the edge bond zones, thermal cells are oriented into stacks for which each thermal cell is bonded to an adjacent thermal cell along the central bond zone, and a plurality of said stacks are oriented within the thermal cell region such that the stacks do not make contact with one another even when thermal cell array unit is in the compressed state.
In a further aspect, additional thin sheets similar in size and shape to the first and second surface sheets, are positioned within said stacks and bonded there along the film element central bond zones, in order to stabilize the stacks against lateral motion within the stack during controlled movement of the first and/or second sheets.
In a further aspect, the plurality of sheets are sufficiently thin and formed of one or more materials that are sufficiently compliant such that an average size of the gap, when the thermal cell array is in the expanded state, is less than 5 mm.
In a further aspect, the plurality of sheets are sufficiently thin and formed of one or more materials that are sufficiently compliant such that the average size of the gap, when the thermal cell array is in the expanded state, is less than 0.5 mm.
Another aspect of the present disclosure provides a variable thermal insulation assembly that includes at least one array comprising a plurality of sheets of film, wherein the plurality of sheets are in a stacked arrangement and each sheet is bonded to an adjacent sheet along a plurality of longitudinally extending regions such that each pair of adjacent sheets form a plurality of longitudinally extending cavities between adjacent regions of the adjacent sheets, a support frame comprising end elements, wherein the support frame frames the plurality of sheets, wherein support frame is coupled to the array to support the array such that the array may transition between an expanded state in which the array is expanded by extending a front side of the array within a plane of the supporting frame in a direction from a first end of the support frame to a second end of the support frame, the direction being perpendicular to a longitudinal axis of the longitudinally extending regions, such that the longitudinally extending cavities are expanded to provide thermal insulation over the support frame, and a compressed state in which the array is compressed within the plane of the frame along the direction perpendicular to the longitudinal axis such that the longitudinally extending cavities are compressed, wherein in the expanded state, the front edge conforms to one of the second end of the support frame or a second front edge of a second array to form a seal that inhibits air flow between the front edge and the one of the second end of the support frame or the second front edge of the second array.
In a further aspect, one end of the plurality of longitudinally extending cavities are fixed in a closed position such that a transition between the compressed state and the expanded state is a pivoting motion.
In a further aspect, each of the plurality of sheets comprise a plurality of separate portions such that adjacent portions of a sheet are bonded together at the longitudinally extending region.
In a further aspect, wherein the thickness of the array in the compressed state is less than 20% of the thickness of the array in the expanded state.
In a further aspect, the thickness of the array in the compressed state in less than 5% of the thickness of the array in the expanded state.
In a further aspect, the front side of the array is sufficiently compliant such that the front edge conforms to form a seal between the array and adjacent elements at low pressure.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached figures, in which:
The embodiments described in the present disclosure relate to a variable thermal insulation assembly that includes an adjustable thermal cell array unit. In some embodiments the variable thermal insulation assembly is configured such that the thermal cell array unit may be adjustable between a thermally insulative expanded state and an optically transmissive compressed state.
Referring to
The thermal cell array 115 is positioned in a region 145 between the first and second surface sheets 140 and 150, which may be described herein as the “thermal cell array region 145”. As described in more detail below, the thermal cell array unit 100 is generally positioned in a thermal actuation region in order to provide variable thermal insulation within that thermal actuation region. Generally speaking, the thermal actuation region will contain air or other gases or gas mixtures.
Surface sheets 140 and 150 are similarly shaped such that when surface sheets 140 and 150 are positioned as close as possible to one another in the maximally compressed state, both the gaps between sheets 140 and 150 and the distances between adjacent edges of surface sheets 140 and 150 are small relative to the overall size of surface sheets 140 and 150. When surface sheets 140 and 150 are aligned as such, gaps between surface sheets 140 and 150 and the distances between adjacent edges of surface sheets 140 and 150 are preferably less than 1/10 of the overall dimension of the sheet. As an example, for a rectangular sheet with a length and width dimension, where the width is smaller than the length, surface sheets 140 and 150 are considered similarly sized if gaps between surface sheets 140 and 150 and the distances between adjacent edges of surface sheets 140 and 150 are preferably less than 1/10 of the sheet width dimension. As described in more detail below with reference to
The flexible sheets 120a-k, which may alternatively be referred to herein simply as sheets, may be formed of layers of thin, flexible reflective film. The sheets 120a-k may be any suitable thin, flexible film material including, for example a metallic film, aluminized polyester film, aluminized Mylar, or any low thermal conductivity or low cost reflective films. Sheets 120a-k may be coated on one or both sides by a thin metallic coating or other low emissivity coating. It may be desirable that the thermal emissivity of the material coating the sheets 120a-k is less than 0.2, and more desirably less than 0.05, recognizing that investments made in reducing this ratio will have diminishing economic terms because of the very minimally changing loss associated with thermal conduction of the gas.
Surface sheets 140 and 150 may be formed of the same material and coated in the same manner as sheets 120a-k, or they may be formed from a different flexible film material. Each sheet 120a-k is bonded to an adjacent sheet 120a-k along a plurality of longitudinally extending bonding regions 130. For example, sheet 120a is bonded to sheet 120b, as shown in
In the example shown in
Adjacent thermal cells 110 formed from the same pair of sheets 120a-k are sealed from adjacent thermal cells 110 along the longitudinal edge by the bonding in bonding regions 130. Each thermal cell 110 is bonded either to at least one other thermal cell 110 or is bonded to an adjacent sheet 120a-k that is also bonded to at least one other adjacent thermal cell to form a connected thermal cell array.
The sealing between adjacent thermal cell 110 need not be hermetically sealed. Additionally, the ends of the thermal cell 110, along the edges of the sheets 120a-k extending perpendicular to the longitudinal axis of the bonding regions 130, may also be sealed closed. The width of each air-enclosing thermal cell 110, i.e., the spacing between bonding regions 130, may be less than 5 cm, and more desirably less than 1 cm such that an insignificant amount of thermally-induced convective flow occurs within each thermal cell 110.
The thermal cell array 115 is attached to surface sheets 140 and 150 in such a manner that as the distance between surface sheets 140 and 150 is increased by means of an applied control force applied by a position controller (not shown) coupled to at least one of the surface sheets 140 and 150, the shape of the thermal cells 110 expand so that the thermal cell array 115 substantially fills the thermal cell array region 145 between the surface sheets 140 and 150. In this expanded state of the array, the array fully occupies the thermal actuation region.
Expanding the array unit 100 causes the thermal cells 110 to expand, as shown in
The size of the thermal cells is determined by the distance between each pair of bonding regions 130 comprising the thermal cell array 115. This distance between bonding regions 130 is sufficiently small that the total heat loss arising from convective gas flow within the thermal cells 110 is less than total heat loss arising from thermal conduction of the gas present within the thermal actuation region. Furthermore, the distance between each pair of bonding regions 130 is sufficiently large, and the thermal conduction of the sheets is sufficiently low, that heat transfer due to thermal conduction within the sheets is less than the heat loss due to thermal conduction of the gas. Accordingly, the procedure for determining the acceptable range for the distance between each pair of bonding regions 130 is either by experimental testing and thermal loss measurements, or by thermal modeling software. In either case, it will be found that if this distance is too large, thermal convection will be enabled within the thermal cells and will contribute excessively to thermal loss, and in contrast, if the distance is too small, the conductivity of the sheets will contribute excessively to thermal loss, because the distance along the sheet that heat must flow becomes smaller and this allows greater heat loss. Ideally, it will be possible to ensure that the heat loss from thermal convection and from thermal conduction of the sheets will be less than 25% of the intrinsic heat loss associated with thermal conduction of the gas present in the thermal cells. In typical applications, the ideal range for the distance between the bond regions is greater than 10 mm and less than 50 mm.
As described in more detail below, the array unit 100 in the expanded state may be expanded to cover a window, for example, to provide insulation when desired, and may be compressed into the compressed state when insulation is not desired, such that the array is compressed so that it no longer covers the window, allowing light to enter a building.
When compressed, the array unit 100 generally possesses a thickness that is significantly less than when the array unit is in the expanded state. In many applications, the overall thickness of the array unit in the compressed state is about 25% or less, and desirably less than 5%, of the thickness of the array unit 100 in the fully expanded state.
Generally, the array unit 100 is supported within a support frame 300 to form a variable thermal insulation assembly 350. Support frame 300 circumscribes a thermal actuation region in which the array unit 100 is positioned. Referring to
The support frame 300 includes edge elements 302, 304, 306, and 308. Elements 302 and 306 may be referred to as side elements, element 304 may be referred to as a top element, and element 308 may be referred to as a bottom element. The support frame 300 may optionally include a front window 310 and a back window 312 to form an enclosed panel that fully enclose the thermal actuation region, as described in more detail below. The enclosed panel may be suitable for providing, for example, a multi-paned window or a skylight structure. The terms side, top, bottom, front, and back are utilized herein to refer to the orientation shown in the particular figures referred to, and are not intended to be otherwise limiting.
The array unit 100 shown in
When the array unit 100 is expanded, it may press against any of the edge elements 302, 304, 306, and 308, or against adjacent similarly expanded array units 100 in the case that multiple array units are provided within the support frame 300, such that the array unit and the support frame or adjacent array unit against which it expands forms an air flow attenuation structure that that sufficiently reduces air flow through the gap, thus sufficiently reducing heat loss caused by air exfiltration and/or convective air flow. The plurality of sheets are sufficiently thin and formed of one or more materials that are sufficiently compliant that no additional pressure is required to achieve the desired air flow attenuation than that which is already needed to reliably expand the array unit. This air flow attenuation structure achieved by the sufficiently compliant array is required to achieve the desired insulation targets using practical methods for controlling the expansion and compression of the array unit. The desired airflow attenuation structure is achieved when the average, or effective, physical size of the gap between the expanded array unit and the adjacent support frame element or array unit has a dimension less than 5 mm and ideally less than 0.5 mm. The force per unit area of the surface sheets of the thermal cell array units that is required to reliably expand the array unit depends on the dimensions (in particular the thickness of sheets 120a-k and the dimensions of air-enclosed pockets 110) and material composition (in particular the Young's modulus of sheets 120a-k) of the array. Typically, the value of this desired pressure per unit area will be in the range 1,000 to 10,000 Pa.
An example of an enclosed panel 500 utilized to form a variable thermal insulation assembly 501 is shown in
The diffusion characteristics of the transmitted light are determined by the degree of diffusion caused by the light-transmitting panes as the light passes through the pane. A diffusing pane, for example one made from glass or plastic having a milky-white appearance, causes substantially collimated light to become substantially un-collimated as it passes through the pane. A non-diffusing pane, for example one made from highly transparent glass or plastic, causes substantially collimated light to maintain its collimation as it passes through the pane. The desired diffusion characteristics of the transmitted light can be achieved by selecting appropriate optical characteristics for the light-transmitting panes of the panel housing the thermal cell array unit, and appropriately expanding and compressing selected array units within the overall variable thermal insulation assembly. For example, for a greenhouse structure incorporating multiple panels, a portion of the light-transmitting panels may incorporate diffusing panes and another portion of the light-transmitting panels may incorporate non-diffusing panes. In this example, if it is desirable for the transmitted light to be diffused, the array units adjacent the diffusing panes can be compressed and the array units adjacent the non-diffusing panes can be expanded. This will cause light to enter predominately through the diffusing panes only. Similarly, if it is desirable for the transmitted light to be non-diffused, the array units adjacent the diffusing panes can be expanded and the array units adjacent the non-diffusing panes can be compressed. This will cause light to enter predominately through the non-diffusing panes only.
Frame elements 501a, 501b, 502a, and 502b need not be optically transparent and may desirably be fabricated using materials with low thermal conductance. The frame elements 501a, 501b, 502a, 502b, which may be substantially similar to elements 306, 302, 308, and 304, respectively, of support frame 300 described previously, and the window elements 503a and 503b of the enclosed panel 500 define a thermal actuation region, that houses a thermal cell array unit 504, such as the array unit 100 described above. As shown in
For a given application, the desired thermal insulation value of the array unit 100 or the enclosed panel 500 can be achieved by adjusting a number of parameters, including, for example, the number of layers of thin, flexible film used to fabricate the thermal cell array unit, choice of whether the thin, flexible film is coated on one side or on both sides with a thin layer of low thermal emissivity material, by enclosing an appropriate gaseous medium (such as argon) within the thermal cells of the array unit 504, and by adjusting the degree to which the 504 array unit forms a barrier or air flow attenuation structure with the adjacent frame elements 501a, 501b, 502a, and 502b in the enclosed panel 500 at all points along the array unit's 504 periphery to prevent transfer of heat through either exfiltration of air or gas or convective flow. Air flow is attenuated by sufficiently reducing the size of the gap between the surface sheet and the adjacent frame surface or surface sheet of an adjacent thermal cell array unit. The gap is reduced to a sufficiently small amount such that the amount of heat loss caused by air flow through the gap around the edges of the thermal cell array unit 504 is less than, and ideally much less than, the heat loss due to thermal conduction through the thermal cell array unit 504.
In the case where a gaseous medium is used, the air inside the enclosed panel 500 would be replaced with this gaseous medium. The enclosed panel 500 may or may not be pressurized. In some applications it may be appropriate for the panel 500 to be pressurized and in other applications it may be necessary to incorporate a pressure release valve (not shown) in such a way that the heat transfer associated with the pressure adaptation is reduced.
When the array unit is in an expanded state, the insulation value achieved is greater than when the array unit is in the compressed state. In many applications, in the expanded state it is desirable that the insulation value is at least R-5 (RSI 0.88) and preferably at least R-15 (RSI 2.64).
In some applications, it may be desirable to increase the transmission of light through the enclosed panel 500. In many applications, it is desirable that in the compressed state preferably at least 70%, and ideally at least 90%, of the incident light is transmitted through the panel 500. There are a number of features which can be incorporated into an enclosed panel 500 in order to increase light transmission through the enclosed panel 500 when the array unit 504 is in the compressed state. Referring to
In some applications, it may be desirable to minimize the length of edge 510 of the thermal cell array unit 504. Referring to the embodiment depicted in
Light transmission may also be increased by causing interior frame elements 502a and 502b to have a curved profile in order to cause the light reflected by frame elements 502a and 502b to transmit through window element 503b within a desirable angular range.
The enclosed panel 600 shown in
It may be desirable for the variable thermal insulation assembly to achieve high thermal insulation characteristics, and high thermal insulation characteristics are achieved by reducing heat transfer across the thermal cell array unit. When the thermal cell array unit is arranged in the expanded state, it is preferable that there be minimal air gaps between the edges of the thermal cell array unit and the support frame elements of the enclosing panel, in order to reduce heat loss by air exfiltration through these gaps. The degree of required air flow attenuation depends in part on the desired application and characteristics of the enclosed panels. For example, the enclosed panels may or may not be well sealed, and a building structure itself may or may not be well sealed. Note that it may not be necessary to minimize air gaps at all edges of the thermal cell array unit. Depending on the physical orientation of the array unit (that is, whether it is oriented with the window elements parallel to the horizon, perpendicular to the horizon, or at some intermediate angle in between parallel and perpendicular to the horizon) it may be preferable to reduce air gaps at, for example, three of four edges of the thermal cell array unit. For example, a larger air gap along one edge of the array unit 504 would allow for differential thermal expansion of components comprising an enclosed panel according to, for example, the example enclosed panel 500 shown in
An example for reducing the air gap between the thermal cell array unit and the enclosing panel elements is shown in in
Surface sheet 703 may be fabricated from a thin and/or flexible sheet material such as mylar, polycarbonate, acrylic, or polyethylene. In the compressed state, surface sheet 703 conforms to the shape of frame element 701b. Note that while
Dotted lines 704a, 704b, 704c, 704d, and 704e depict the different profile and position of surface sheet 703 over time, as thermal cell array unit 702 is expanded to fill the cavity within enclosed panel 700. When thermal cell array unit 702 is fully expanded, and therefore in the expanded state, the flexible surface sheet 703 may substantially conform to the curved shape of frame element 701a, reducing the air gap between the thermal cell array unit 702 and the frame element 1001a, forming an air flow attenuation structure.
As described earlier, the array unit is sufficiently compliant that no additional pressure is required to achieve the desired air flow attenuation than is already needed to expand the array unit. This air flow attenuation structure achieved by the sufficiently compliant array unit is required to achieve the desired insulation targets using practical methods for controlling the expansion and compression of the array unit. The desired airflow attenuation structure is achieved when the average or effective physical gap between the expanded array unit and the adjacent support frame element or array unit has a dimension less than 5 mm and ideally less than 0.5 mm. The pressure required to expand the array depends on the dimensions (in particular the thickness of the sheets comprising the array and the dimensions of air-enclosed pockets) and material composition (in particular the Young's modulus of sheets comprising the array) of the array. As mentioned previously, well known techniques for experimentally measuring heat loss for modelling heat loss using available software make it readily possibly to determine the acceptable values for the sheet parameters in order to comply with the requirements stated.
In another example, an air gap between the thermal cell array unit and the frame components may be reduced using a seal element. This seal element may be an inflatable bladder located on an inner surface of a support frame element and that expands when the array unit is in the expanded state.
In this example, the array unit, such as array unit 100 shown in
Referring to
Inflatable bladders 902 and 903 may share an air-transfer connection (not shown) such that air can transfer between the two bladders. When the array unit 901 is in the compressed state as shown in
In some applications, it may be desirable to have a particular configuration of one or more thermal cell array units contained within an enclosed panel.
In another example, shown in
In another example, shown in
Referring now to
Films 1101a and 1101b may be formed from any suitable material including, for example, polyethylene, polycarbonate, and ethylene tetrafluoroethylene. Films 1101a and 1101b are bonded in bond region 1102 by any suitable means including, for example, adhesive tape, epoxy, ultrasonic bonding, and thermal bonding. Thermal cell array unit 1103 may be substantially similar to the array unit 100 described above. The pillow-shaped air cavity 1104 may be formed by using air pressure to inflate enclosure 1100 after the films 1101a and 1101b are bonded together. The enclosure 1100 may include, for example, a vent (not shown) to facilitate adjusting the amount of pressure within the cavity 1104, and thereby adjusting the corresponding degree of inflation of enclosure 1100. For example, in an embodiment where enclosure 1100 forms the exterior structure of the building structure, rather than being supported by the exterior structure of the greenhouse, it may be desirable to increase the degree of inflation of enclosure 1100 to provide more structural rigidity in the event of inclement weather. For example, the pressure within the enclosure 1100 may in increased by pumping air into a vent (not shown) in advance of inclement weather to provide greater rigidity, and may be decreased, by removing air through the vent, to reduce rigidity once the inclement weather has passed.
In order for the assembly to transition between the compressed state and the expanded state, it is necessary to have a means of causing the thermal cell array unit to expand and compress. While particular methods of expanding and compressing the thermal cell array unit are described here, other methods may be apparent to a person skilled in the art.
One example of a position controller for expanding and compressing the thermal cell array unit is a mechanical system using drive wires that are attached to either the thermal cell array unit or attached to a surface sheet which is further attached to the thermal cell array unit. These drive wires are subsequently attached to a mechanical drive assembly such that the drive wires can be moved in one direction to cause the thermal cell array unit to expand and the drive wires can be moved in a second, opposite direction to cause the thermal cell array unit to compress.
The mechanical drive assembly may include a rotating drive rod, preferably having a circular cross-section, upon which the drive wires can be wound and unwound.
A detailed view of connection screws 1205 are shown on
A rotating drive rod as described above is one example of a mechanical method of expanding and compressing the thermal cell array unit.
The appropriate method of causing the thermal cell array unit to expand and compress may be different than as described in the preceding examples, depending on a number of factors, including but not limited to: the size and shape of the enclosed panel, the orientation of the enclosed panel within a building structure, the intended purpose of the panel, and the desired operational characteristics of the panel.
In some applications, it may be preferred for the expansion and compression of the thermal cell array unit to occur with a smooth, predictable and repeatable motion. There are a number of methods by which the thermal cell array unit can be physically positioned and/or supported in order to result in the desired smooth, predictable and repeatable motion. While particular methods of physically positioning and/or supporting the thermal cell array unit have been described here, it is to be understood that other methods of physically positioning and/or supporting the thermal cell array unit are possible and are intended to be included herein.
In a first example,
In another example,
In another example,
In another example,
In some applications, it may be preferred for the front plate attached to the thermal cell array to have a particular shape or configuration, depending on desired operational or orientational characteristics.
Alternatively, rather than utilizing a mechanical position controller to transition the array unit between the compressed and expanded states, an electrostatic position controller may be utilized. Example electrostatic position controller are described with reference to
Films 2201 and 2203 may have a thickness of less than 40 microns and desirably the thickness may be less than 10 microns. The films 2201 and 2203 may be layers of thin, flexible film material formed from, for example, polyester film, Mylar, or any highly electrically insulative film. Films 2201 and 2203 are coated on one side by a thin electrode coating 2202 and 2204. Thin electrode coating 2202 and 2204 may be made of a metal or other low emissivity and electrically conductive material, such as, for example, aluminum. The thermal emissivity of the material desirably is less than 0.2 and more desirably is less than 0.05. Thin electrode coatings 2202 and 2204 are separated by at least one of low electrical conductivity films 2201 and 2203 such that the coatings do not contact each other when the cavity 2200 is in the compressed state, as shown in
The electrostatic position control or actuation system shown in
The electrostatic position control or actuation system described above takes advantage of the so-called Paschen effect, whereby the breakdown of the electric field of air in gaps that have a thickness comparable to the mean free path of an ion in the air is up to ten times higher. In other words, a very thin air gap (for example, less than 0.5 microns thick) can withstand an electric field of 107 V/m. Referring to the example shown in
Removing the electrical potential difference previously applied between thin electrode coatings 2202 and 2204 restores the expanded state. There are a number of mechanisms by which the expanded state shown in
The fully compressed state shown in
In some embodiments, the adjacent thin, flexible films forming thermal cell array unit may exhibit a high sticking force in the compressed states shown in
The appropriate method of causing the thermal cell array unit to expand and compress with a smooth, predictable, and repeatable motion may be different than as described in the preceding examples, depending on a number of factors, including but not limited to: the size and shape of the enclosed panel, the orientation of the enclosed panel within a building structure, the intended purpose of the panel, and the desired operational characteristics of the panel.
While the embodiments described above illustrate the thermal cell array units or assemblies and enclosed panels having particular shapes or operational or structural features, the skilled person will understand that the thermal cell array units or assemblies may have any number of suitable shapes or operational or structural features sufficient to perform the operations described above.
In addition, while not shown in the figures, it is to be understood that the transition of the foregoing thermal cell array units between compressed and expanded states can be achieved by any suitable mechanical, electro-mechanical, or other position transitioning device. For example, the thermal cell array units may be coupled to each other and actuated by a control rod to transition the thermal cell array units between compressed and expanded states. In another example, an electro-mechanical actuator could be employed to automate the transitioning of the thermal cell array unit between compressed and expanded states. In another example, the thermal cell array units could be positioned by means of a manual or physical control element.
It is noted that the various embodiments of the thermal cell array unit or system, as described above, and their combinations, can be used in a greenhouse, glasshouse, or other building structure. Further, the thermal cell array unit may also be expanded or compressed either by manual operation or by automatic control in response to the output of a sensor detecting a selected parameter, such as a sunlight or temperature measurement sensor.
The thermal cell array units and assemblies described above can be used in a greenhouse, glasshouse, solarium, or other building structure, to increase the thermal insulation to reduce heat loss from the building. The thermal cell array units and assemblies described above can further be used in walls and doors of refrigeration units or other cold-storage appliances where it is desirable to have a high degree of visual transparency in some instances and a high degree of thermal insulation in other instances. The thermal cell array units and assemblies can further be used in walls or roofs of building structures where variable thermal insulation may be desired or required. The thermal cell array units and assemblies described above can further be used in conjunction with thermal storage units, assemblies, or assemblies. Thermal cell array units and assemblies described above can further be used in solar heat capture structures.
While in this embodiment, only sections 2502a and 2502b of the roof 2502 is integrated with the thermal cell array unit, one or more thermal cell array units/assemblies can be formed as part of the walls 2501.
While in this embodiment, only section 2702b of the roof 2702 is integrated with the thermal cell array unit, one or more thermal cell array units/assemblies can be formed as the entire roof 2702. Further, one or more thermal cell array units/assemblies may also be formed as part of the walls 2701.
While in this embodiment, the roof 2802 forms both the roof 2802 and the walls 2801 of the structure. The roof 2802 and walls 2801 are integrated with the thermal cell array unit, and one or more thermal cell array units/assemblies can be formed as the entire roof 2802. In other embodiments, the thermal cell array unit may not be integrated into walls 2801.
According to some other embodiments, one or more above-described thermal cell array units/assemblies can be positioned below a transparent roof structure or adjacent one or more transparent walls, such that the thermal cell array units/assemblies can be opened to allow the transmission of sunlight into the structure and closed to prevent the transmission of sunlight into the structure and also to increase the thermal insulation property of the roof or walls. The thermal cell array units can be attached to the support structure of the greenhouse, glasshouse, or other building structure. For example, when positioned below the roof, the thermal cell array unit/system can be suspended horizontally near the roof However, it is noted that the orientation of the thermal cell array unit/system can be adjusted depending on various factors, such as the structure and layout of the building, or maximum receipt of sunshine. Alternatively, the thermal cell array units/assemblies can also be positioned near the roof and/or walls from outside of the building.
As described earlier with reference to
One example of thermal cell array units arranged to move in a pivoting motion is depicted in
As described earlier with regard to
In
In the example shown in
While particular embodiments have been described in the foregoing, it is to be understood that other embodiments are possible and are intended to be included herein. It will be clear to any person skilled in the art that modifications of and adjustments to the foregoing embodiments, not shown, are possible. Further, it is to be understood that the foregoing embodiments may be applied in a variety of applications, such as, for example, greenhouses, solar heat capture structures, commercial or residential skylights and windows, walls and doors of refrigeration units or other cold-storage appliances, or for other suitable structures and applications.
Claims
1. A variable thermal insulation assembly comprising:
- a frame that circumscribes a thermal actuation region having a gas;
- one or more thermal cell array units positioned within the thermal actuation region, each thermal cell array unit comprising: a first surface sheet and a second surface sheet, wherein the first and second surface sheets are similarly shaped and define a thermal cell array region therebetween;
- a thermal cell array positioned within each thermal cell array region and coupled to the first and second surface sheets such that the thermal cell array substantially fills the thermal cell array region; wherein each thermal cell array comprises a plurality of sheets and at least two of the sheets in each thermal cell array are flexible sheets;
- wherein adjacent pairs of said flexible sheets are bonded together along at least one pair of bonding regions that extend substantially parallel to each other such that each pair of flexible sheets defines at least one substantially longitudinally symmetrical cavity between each pair of bonding regions, each longitudinally symmetrical cavity being one of a plurality of thermal cells; wherein a distance between each pair of bonding regions is sufficiently small such that the total heat loss arising from convective gas flow within the thermal cells is less than total heat loss arising from thermal conduction of the gas present within the thermal actuation region; wherein the distance between each pair of bonding regions is sufficiently large, and the thermal conductivity of the sheets is sufficiently low, such that heat transfer due to thermal conduction within the sheets is less than the heat loss due to thermal conduction of the gas of the thermal actuation region; wherein each of the plurality of thermal cells is bonded to another thermal cell or a sheet in order to form a connected thermal cell array unit;
- a position controller coupled to at least one of the first and second surface sheets for applying a control force on at least one of the first and second surface sheets to expand the thermal cell array into an expanded state and compress the thermal cell array into a compressed state within the thermal actuation region to vary a volume of the thermal actuation region that is occupied by the thermal cell array units;
- wherein the plurality of sheets are sufficiently thin and formed of one or more materials that are sufficiently compliant such that, for each first and second sheet, when the thermal cell arrays are in the expanded state by the applied control force, a gap between each surface sheet and the adjacent frame surface or surface sheet, is made sufficiently small such that the total heat loss that is attributable to gas flow through the gap is less than the total of the heat loss due to thermal conduction through the thermal cells.
2. The variable thermal insulation assembly of claim 1, wherein the position controller is coupled to the one of the first and second sheets such that, when the control force is applied, the at least one of the first and the second surface sheets move in a direction that is normal to the one of the first and second surface sheet such that, during the moving the first and second surface sheets are maintained substantially parallel to each other.
3. The variable thermal insulation assembly of claim 1, wherein the position controller is coupled to the one of the first and second surface sheets such that, when the control force is applied, the one of the first and second surface sheets pivots whereby a first end of the one of the first and second surface sheet is substantially fixed relative to a corresponding first end of the other of the first and second surface sheets, and a second end of the one of the first and second surface sheets, opposite the first end, moves relative to the second end of the other of the first and second surface sheets.
4. The variable thermal insulation assembly of claim 1, wherein at least some of the plurality of sheets comprising the thermal array are coated on at least a first side by a layer of material having a thermal emissivity of less than 0.2.
5. The variable thermal insulation assembly of claim 4, wherein the material is aluminum.
6. The variable thermal insulation assembly of claim 1, wherein each of the plurality of sheets comprising the thermal array has a curved shape, and the plurality longitudinally extending regions follow the curved shaped such that the formed longitudinally extending cavities have the curved shape.
7. The variable thermal insulation assembly of claim 1, wherein the frame comprises edge elements that circumscribe the thermal actuation region, and a front panel and a back panel coupled to the edge elements to form an enclosed panel that encloses the array.
8. The variable thermal insulation assembly of claim 7, wherein the front panel and back panel are light-transmitting window elements that are fabricated from one of glass, mylar, acrylic, polycarbonate, polyethylene, or ethylene tetrafluoroethylene.
9. The variable thermal insulation assembly of claim 8 wherein light-transmitting window elements are diffusely light-transmitting elements.
10. The variable thermal insulation assembly of claim 1, wherein the front panel and the back panel are each formed from a thin, light-transmitting material, wherein the front panel and the back panel are bonded together in a periphery region to define a pillow-shaped cavity within the enclosed panel.
11. The variable thermal insulation assembly of claim 10, wherein the thin, light transmitting material is one of polyethylene, polycarbonate, or ethylene tetrafluoroethylene.
12-14. (canceled)
15. The variable thermal insulation assembly of claim 7, wherein an inner surface of at least one edge element has a reflectivity of at least 80%.
16. (canceled)
17. The variable thermal insulation assembly of claim 1, wherein the frame comprises a first end element at the first end, a second end element at the second end, and a pair of side elements that connect the first and second end elements, wherein at least one of the side elements includes a seal element for inhibiting airflow through an opening of the plurality of longitudinally extending cavities adjacent to the side element when the array is in the expanded state.
18. The variable thermal insulation assembly of claim 17, wherein the seal element is a first inflatable bladder.
19. (canceled)
20. (canceled)
21. The variable thermal insulation assembly of claim 1, wherein the position controller is an electrostatic system wherein:
- the plurality of flexible sheets of the thermal cell array are formed of an electronically insulative material that is coated on one side with an electrically conductive material such that, for each pair of flexible sheets, the electrically conductive material coating of each flexible sheet of the pair are separate by at least one layer of the electrically insulative material;
- the variable thermal insulation assembly further comprising:
- a controller to apply an electric potential difference between each adjacent pairs of sheets such that the electrically conductive coatings of the adjacent pair of sheets attract each other to cause the array to be in the compressed state; and
- a plurality of biasing elements located with the plurality of longitudinally extending cavities to bias adjacent pairs of sheets away from each other to cause the array to be in the expanded state in the absence the controller applying an electrical charge.
22-53. (canceled)
54. The variable thermal insulation assembly of claim 8, wherein the light-transmitting window elements have a first portion that is diffusely light transmitting and a second portion that is non-diffusely light transmitting such that the diffusion characteristics of the transmitted light can be controlled.
55. The variable thermal insulation assembly of claim 1, wherein each thermal cell consists of two flexible film elements, each flexible film element having two edge-bond zones that comprise less than 20% of a surface area of the flexible film element, each edge-bond zone extending in a direction parallel to the longitudinal direction of the flexible film element, and a central bond zone comprising less than 20% of the surface area and extending parallel to the longitudinal direction along the center of the flexible film element, wherein
- each thermal cell is formed by bonding two flexible film elements along the edge bond zones, and wherein
- thermal cell are oriented into stacks for which each thermal cell is bonded to an adjacent thermal cell along the central bond zone,
- and wherein a plurality of said stacks are oriented within the thermal cell region such that the stacks do not make contact with one another even when thermal cell array unit is in the compressed state.
56. The variable thermal insulation assembly of claim 55, wherein additional thin sheets similar in size and shape to the first and second surface sheets, are positioned within said stacks and bonded there along the film element central bond zones, in order to stabilize the stacks against lateral motion within the stack during controlled movement of the first and/or second sheets.
57. The variable thermal insulation assembly of claim 1, wherein the plurality of sheets are sufficiently thin and formed of one or more materials that are sufficiently compliant such that an average size of the gap, when the thermal cell array is in the expanded state, is less than 5 mm.
58. The variable thermal insulation assembly of claim 3, wherein the frame further comprises edge elements that circumscribe the thermal actuation region, and a front panel and a back panel coupled to the edge elements to form an enclosed panel that encloses the array.
59. The variable thermal insulation assembly of claim 3, wherein the position controller is an electrostatic system wherein:
- the plurality of flexible sheets of the thermal cell array are formed of an electronically insulative material that is coated on one side with an electrically conductive material such that, for each pair of flexible sheets, the electrically conductive material coating of each flexible sheet of the pair are separate by at least one layer of the electrically insulative material;
- the variable thermal insulation assembly further comprising:
- a controller to apply an electric potential difference between each adjacent pairs of sheets such that the electrically conductive coatings of the adjacent pair of sheets attract each other to cause the array to be in the compressed state; and
- a plurality of biasing elements located with the plurality of longitudinally extending cavities to bias adjacent pairs of sheets away from each other to cause the array to be in the expanded state in the absence the controller applying an electrical charge.
60. The variable thermal insulation assembly of claim 7, wherein the position controller is an electrostatic system wherein:
- the plurality of flexible sheets of the thermal cell array are formed of an electronically insulative material that is coated on one side with an electrically conductive material such that, for each pair of flexible sheets, the electrically conductive material coating of each flexible sheet of the pair are separate by at least one layer of the electrically insulative material;
- the variable thermal insulation assembly further comprising:
- a controller to apply an electric potential difference between each adjacent pairs of sheets such that the electrically conductive coatings of the adjacent pair of sheets attract each other to cause the array to be in the compressed state; and
- a plurality of biasing elements located with the plurality of longitudinally extending cavities to bias adjacent pairs of sheets away from each other to cause the array to be in the expanded state in the absence the controller applying an electrical charge.
61. A variable thermal insulation assembly comprising:
- at least one array comprising a plurality of sheets of film, wherein the plurality of sheets are in a stacked arrangement and each sheet is bonded to an adjacent sheet along a plurality of longitudinally extending regions such that each pair of adjacent sheets form a plurality of longitudinally extending cavities between adjacent regions of the adjacent sheets;
- a support frame comprising end elements, wherein the support frame frames the plurality of sheets, wherein support frame is coupled to the array to support the array such that the array may transition between:
- an expanded state in which the array is expanded by extending a front side of the array within a plane of the supporting frame in a direction from a first end of the support frame to a second end of the support frame, the direction being perpendicular to a longitudinal axis of the longitudinally extending regions, such that the longitudinally extending cavities are expanded to provide thermal insulation over the support frame; and
- a compressed state in which the array is compressed within the plane of the frame along the direction perpendicular to the longitudinal axis such that the longitudinally extending cavities are compressed;
- wherein in the expanded state, the front edge conforms to one of the second end of the support frame or a second front edge of a second array to form a seal that inhibits air flow between the front edge and the one of the second end of the support frame or the second front edge of the second array.
Type: Application
Filed: Sep 9, 2016
Publication Date: Sep 27, 2018
Inventors: Lorne WHITEHEAD (Vancouver), Michele MOSSMAN (Vancouver), Jon SCOTT (Salt Spring Island), Namamrta MUSTERER (Vancouver), Wesley BOWLEY (Victoria), Debbie EELTINK (Vancouver), Laura Megan OGILVIE (Campbell River)
Application Number: 15/758,690