Abstract:
An access floor panel is provided that includes a support frame that supports a phase change material. The phase change material changes phases at a certain temperature. The support frame may form a shell having a cavity. The cavity may be filled with the phase change material or with a mixture of the phase change material and a fill material. The access floor panels can be every panel in an access floor system or selected panels in the system.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to access floor panels and systems. In particular, this invention relates to access floor panels and systems that save energy by absorbing thermal (heat) energy during high thermal load (high temperature) periods, thus reducing the cooling requirements for facilities including the panels and systems during those high thermal load periods. 
         [0003]    2. Background of the Invention 
         [0004]    Sunlight entering office spaces, other places of business, and public buildings through windows and other fully or partially transparent building components often causes excess heat in those facilities. That sunlight usually increases the heat load in those facilities as the work day progresses, often taxing air conditioning systems during peak work hours, which are also peak energy usage hours. 
         [0005]    In addition, a typical office space or data center includes multiple pieces of electronic equipment as well as associated peripheral equipment and cables that generate a relatively high amount of heat. The use of that electronic equipment generally increases during a work day, thus increasing the heat generated in an office space or a data center as a work day progresses. 
         [0006]    Providing adequate cooling of office spaces, data centers, other places of business, and public buildings is of paramount importance to maintain a comfortable working environment, to prevent damage to equipment, and to create a welcome environment for visitors. Those facilities must be maintained at appropriate temperatures, including during high thermal load periods. 
         [0007]    It is desirable that those facilities be cooled as efficiently as possible. For example, the energy costs to cool an office space or a data center may approach a large percentage of the energy costs to operate the office space or the data center. One way to render the cooling systems for those facilities more efficient is by reducing the cooling demands during high thermal load periods. 
         [0008]    Many data centers and some office spaces, other places of business and public buildings have a raised floor system, often called an access floor system. An access floor system is usually comprised of a continuous array of floor panels, arranged edge-to-edge, and supported above the sub-floor by support structure. The array of access floor panels usually extends wall-to-wall in the office space or data center. 
       SUMMARY OF THE INVENTION 
       [0009]    The access floor panels and systems of this invention contribute to the efficient cooling of office spaces and data centers by absorbing thermal energy during high thermal load periods, thus reducing cooling demands during those high thermal load periods. 
         [0010]    In some embodiments of this invention, the access floor panels include a support frame and a phase change material supported by the support frame. The phase change material changes phases at a certain temperature. 
         [0011]    In other embodiments of this invention, the support frame may form a shell having a cavity, with the cavity being filled with the phase change material or a fill mixture that includes the phase change material. The fill mixture may include a mixture of the phase change material and a fill material. The phase change material may be dispersed within the fill material. 
         [0012]    In yet other embodiments of this invention, the cavity formed by the shell may be partially filled with the phase change material and partially filled with the fill material. 
         [0013]    In further embodiments of this invention, the shell formed by the support frame may have a plurality of cavities, and some of the cavities may be filled with the phase change material and other of the cavities may be filled with the fill material. 
         [0014]    In yet other embodiments, the phase change material may be provided in a laminate that is attached to the top of the support frame. The phase change material may be embedded within the laminate. 
         [0015]    In further embodiments, the phase change material may be provided in an enclosure or casing that forms the underside of the support frame. 
         [0016]    According to some access floor system embodiments of this invention, all of the system&#39;s access floor panels may include phase change material. In other access floor system embodiments of this invention, only selected panels include phase change material. 
         [0017]    In yet other access floor system embodiments of this invention, the systems include a plurality of access floor panels that do not include phase change material and one or more thermal dampers intermixed with those access floor panels that include phase change material. The one or more thermal dampers include a box-shaped shell that contains the phase change material. The top surfaces of the dampers may be substantially aligned with the top surfaces of the access floor panels. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a partial view of an access floor system embodiment of this invention. 
           [0019]      FIG. 2  is a cross-sectional view of one access floor panel embodiment of this invention. 
           [0020]      FIG. 3  is a cross-sectional view of another access floor panel embodiment of this invention. 
           [0021]      FIG. 4  is a cross-sectional view of yet another access floor panel embodiment of this invention. 
           [0022]      FIG. 5  is a partial view of another access floor system embodiment of this invention. 
           [0023]      FIGS. 6-8  are embodiments of a thermal damper according to this invention. 
           [0024]      FIG. 9  is a schematic diagram illustrating one embodiment of providing an access floor panel with a fill mixture of phase change material and a fill material. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  is a partial view of access floor system  1 , which, as stated, is an access floor system embodiment of this invention. Access floor system  1  includes multiple access floor panels  10  arranged edge-to-edge in an array that usually extends wall-to-wall in a room. 
         [0026]      FIG. 2  illustrates access floor panel  10 , which, as stated, is an access panel embodiment of this invention. Access floor panel  10  includes shell  15  filled with fill mixture  50 . More specifically, shell  15  includes lower shell  40  and top plate  70 , which define a cavity or multiple cavities that contain fill mixture  50 . In the embodiment illustrated in  FIG. 2 , fill mixture  50  substantially fills the cavity or cavities formed by lower shell  40  and upper plate  70 . 
         [0027]    Lower shell  40  and top plate  70  can be made of any material that is capable of providing the structural rigidity required for a given application. Preferably at least part of lower shell  40  and top plate  70  is made of a metal. Lower shell  40  and/or top plate  70  can be made entirely of metal. 
         [0028]    Lower shell  40  has a plurality of longitudinally and laterally spaced peak portions  16  and valley portions  17  for structural rigidity. The number of peaks and valleys may vary depending on the size of the access floor panel  10  and other considerations. Top plate  70  is usually welded to lower shell  15  at one or more of the valley portions  17 , i.e., at the areas where lower shell  15  is adjacent top plate  70 . In addition to providing structural integrity to the panel, those welds provide for additional heat transfer through panel  10 . 
         [0029]    In the embodiment illustrated by  FIG. 2 , fill mixture  50  includes phase change material  60  dispersed within fill material  130 . That is, fill mixture  50  is comprised of a mixture of phase change material  60  and fill material  130 . Phase change material  60  can be homogeneously or heterogeneously mixed with fill material  130 . 
         [0030]    In other embodiments, the cavity or cavities of shell  15  can be filled with only phase change material  60 . In yet other embodiments, part or parts of the cavity of shell  15  (if shell  15  has one cavity) can be filled with phase change material  60  while the other part or parts of the cavity are empty and/or are filled with fill material  130 . If shell  15  has multiple cavities, one or more of the cavities can be filled with phase change material  60 , while the remaining cavities are empty and/or filled with fill material  130 . 
         [0031]    When dispersed within fill material  130 , phase change material  60  may be provided in either a micro-encapsulated form, as illustrated in  FIG. 2 , or a non-encapsulated form. When phase change material  60  is in the micro-encapsulated form, particles or clumps of particles of phase change material  60  are encased in casings  65  that can be formed of PVC or any other suitable plastic or non-plastic material. 
         [0032]    Fill material  130  can be, for example, any one of, or a combination of, concrete, cement, calcium sulfate and wood particles. Preferably, fill material  130  is cement. 
         [0033]    The percentages of fill material  130  and phase change material  60  in fill mixture  50  may be anywhere from 1% phase change material  60  and 99% fill material  130  to 99% phase change material  60  and 1% fill material  130 , depending, at least in part, on the thermal load that is desired to be absorbed. Moreover, the ratios can be by weight or by volume. One preferred mixture is approximately 12.5% phase change material  60  and approximately 87.5% fill material  130  (by weight). As stated, in some embodiments, phase change material  60  may be the only material in the cavity or cavities of shell  15 , to the exclusion of fill material  130 . 
         [0034]    Phase change material  60  can be comprised of any acceptable material that changes from a solid to a liquid and vice versa at the desired temperature. An example is Microtek Laboratories, Inc.&#39;s microencapsulated phase change material sold under the designation MPCM 24-D. In one embodiment, phase change material  60  changes phase at approximately 75° F. That is, the phase change material transitions (i.e., melts) from a solid to a liquid at approximately 75° F. 
         [0035]    In this embodiment, when phase change material  60  changes from a solid to a liquid, each panel  10  can absorb upwards of  220  BTU thermal energy, which would otherwise be reflected back into the facility and/or transferred into the airstream. Thus, by providing phase change material  60  in access floor panels  10  of access floor panel system  1 , temperature fluctuations and cooling demands can be reduced during high thermal load periods, because phase change material  60  melts and absorbs thermal energy during those high thermal load periods. The absorbed thermal energy can then be “held” within access floor panels  10  until access floor panels  10  are exposed to cooler temperatures during the off peak hours, such as during the night, at which time phase change material  60  resolidifies and releases thermal energy. In that regard, access floor panels  10  function as a thermal damper in the office space or data center in which they are installed. 
         [0036]    Panels  10  can be every panel in access floor system  1 , as illustrated in  FIG. 1 , or select panels in access floor panel system  1  can be panels  10  and the other panels in the system can be access floor panels of other types. For example, access floor panels  10  may be selectively provided in locations of access floor panel system  1  that are adjacent to or otherwise subjected to high thermal loads, such as direct exposure to sun light or a high concentration of electronics equipment. 
         [0037]      FIG. 3  illustrates another access floor panel embodiment of this invention, access floor panel  10 A. In access floor panel  10 A, instead of phase change material  60  being in a cavity formed by a shell, phase change material  60  is embedded in a laminate material  80  that is adhered or otherwise affixed to top plate of the access floor panel  10 A. Preferably, laminate material  80  is made of Formica® Melaminetop or Paper Product Core. 
         [0038]      FIG. 4  illustrates another access floor panel embodiment of this invention, access floor panel  10 B. In access floor panel  1013 , phase change material  60  is provided in an enclosure  90  that is the bottom portion of access floor panel  10 B. Enclosure  90  can be filled with 100% phase change material  60  or with any of the fill mixtures  50  described above. Enclosure  90  can be formed of metal or any other suitable material. 
         [0039]      FIG. 5  illustrates another access floor system embodiment of this invention, access floor system  1 A. Access floor system  1 A includes one or more thermal dampers  120  that are interspersed among access floor panels  10 C. That is, access floor system  1 A includes access floor panels  10 C (with no phase change material  50 ) and one or more thermal dampers  120 . The embodiment illustrated in  FIG. 5  has thermal damper  120  next to a window  20  so as to be able to dampen solar heat from sunlight  30 . However, thermal damper  120  can be provided in other portions of access floor panel system  1 A, as desired. 
         [0040]    The top surface of the one or more thermal dampers  120  can be at the same height or below the height of the top surfaces of access floor panels  10 C in access floor system  1 A. 
         [0041]      FIGS. 6-8  are cross-sectional views of different embodiments of thermal damper  120 . In the embodiment illustrated in  FIG. 6 , a concrete or other structural bearing material  100  is provided on top of lower pan  95 , and phase change material  60  or fill mixture  50  is provided in a cavity defined by bearing material  100  and lower pan  95 .  FIG. 7  illustrates an embodiment in which metal pan  150  completely encases phase change material  60 .  FIG. 8  illustrates an embodiment similar to that illustrated in  FIG. 6 , except that laminate material  110  is provided as the top surface instead of the bearing material  100 . 
         [0042]      FIG. 9  is a schematic diagram illustrating one embodiment of the process of mixing phase change material  60  with fill material  130  to produce fill mixture  50 , which, in this embodiment, is then transferred to the access floor panel  10  via a fill line  150 . 
         [0043]    Use of access floor panels  10 ,  10 A and/or  10 B and/or thermal dampers  120  in access floor panel systems  1  and/or  1 A in an office space or data center should reduce temperature fluctuations and save energy in the office space or data center. Panels  10 ,  10 A and  10 B and thermal dampers  120  add thermal building mass to an office space or data center, and store thermal energy during high thermal load periods. That should result in energy savings during high thermal load periods due to lower HVAC demands during those periods. Those thermal loads during high load periods are essentially shifted to off peak hours, such as during nights. Shifting the thermal load to off peak hours may also result in an energy cost savings because unit energy costs may be lower in off peak hours. 
         [0044]    What has been described and illustrated herein are preferred embodiments of the invention along with some variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention, which is intended to be defined by the following claims—and their equivalents—in which all terms are meant in their broadest reasonable sense unless otherwise indicated.