Patent Publication Number: US-9840846-B2

Title: System, method and apparatus for thermal energy management in a roof

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application is a continuation of U.S. patent application Ser. No. 13/440,762, filed Apr. 5, 2012, entitled “SYSTEM, METHOD AND APPARATUS FOR THERMAL ENERGY MANAGEMENT IN A ROOF”, naming inventors Ming-Liang Shiao et al., and claims priority to and the benefit of U.S. Provisional Patent Application No. 61,477,941, filed Apr. 21, 2011, entitled “SYSTEM, METHOD AND APPARATUS FOR THERMAL ENERGY MANAGEMENT IN A ROOF”, naming inventors Ming-Liang Shiao et al. The entire disclosures of these applications are expressly incorporated by reference, in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Disclosure 
     The present invention relates in general to roofing and, in particular, to a system, method and apparatus for thermal energy management in a roof. 
     Description of the Related Art 
     Typical residential roofs in the North America have bitumen-based roofing materials that provide satisfactory water shedding, long term durability and have aesthetic appeal. Most asphaltic roofing materials are colored in traditional dark earth tones. These colors absorb significant amounts of solar heat during hot summer times, which penetrates through the roof deck, attic and ceiling into the house. The heat penetration increases the need for cooling energy for the indoor comfort of residence occupants. 
     On the other hand, these types of roofing products usually have good thermal emittance and low thermal mass. These properties allow them to quickly re-radiate and lose solar heat during the night. This results in the so-called “super cooling” effect that may increase the heating energy need to maintain indoor temperatures during the night. This issue is particularly problematic for cold to moderate climate regions, and for seasons where the day and night temperature differences are significant, such as in the spring or fall seasons. 
     Therefore, it would be advantageous to have a roofing system that can store or manage the solar heat during the day, and then release that heat into the house during the night to improve the energy efficiency of the house. It would be a further advantage to have such a system that is compatible with current asphaltic shingle aesthetics, and can be readily applied with existing roofing techniques and construction practices. 
     Some asphaltic shingles have improved solar reflectance that reduces the absorption of solar heat. Although such products lower cooling energy costs, particularly in warmer climates, they are not designed for managing solar heat during the night or for significant seasonal changes. In colder climates, these products can have heating penalties due to the loss of solar heat. This is also true when radiant barriers are used to reduce solar heat flux into the attic. Radiant barriers do not capture or manage solar heat. 
     Other conventional solutions include ventilated decks and ventilation systems that reduce heat flux into the attic via air flows to expel heat. Again, these systems do not store or manage solar heat for the later cooler times of day. Thus, continued improvements in thermal management are desirable. 
     SUMMARY 
     Embodiments of a system, method and apparatus for thermal energy management of a roof are disclosed. For example, a roof product may comprise a thermal heat storage layer, a vent layer having channels for transferring excess heat through an entire length of the roof product, and a flame retardant to suppress fire through the vent layer. These three materials form a unitary structure. In other embodiments, the roof product combines a radiant layer, the thermal heat storage layer and the vent layer to form the unitary structure. 
     Embodiments of the roof products may be assembled in an abutting configuration on the roof of a building. The vent layer vents excess heat from an eave of the roof up to a ridge of the roof and out to atmosphere. In operation, the roof products may be used to manage thermal energy in the roof. The roof has a roof deck, a roof outer barrier and the unitary roof products located between the roof deck and roof outer barrier. The method comprises storing thermal heat with the unitary product during a heating cycle; venting excess heat through the unitary product; and releasing the stored thermal heat from the unitary product into the building during a cooling cycle. The unitary product may have a flame retardant for blocking venting thereof in the event of a fire. 
     The foregoing and other objects and advantages of these embodiments will be apparent to those of ordinary skill in the art in view of the following detailed description, taken in conjunction with the appended claims and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the features and advantages of the embodiments are attained and can be understood in more detail, a more particular description may be had by reference to the embodiments thereof that are illustrated in the appended drawings. However, the drawings illustrate only some embodiments and therefore are not to be considered limiting in scope as there may be other equally effective embodiments. 
         FIGS. 1 and 2  are isometric views of embodiments of a roof product; 
         FIGS. 3-6  are schematic sectional views of additional embodiments of a roof product; 
         FIG. 7  is a schematic isometric view of an embodiment of a roof product; 
         FIG. 8  is a sectional view of an embodiment of a roof product installed in a roof of a building; 
         FIG. 9  is a partially sectioned, isometric view of another embodiment showing layers of a roof product; 
         FIG. 10  is an enlarged top view of an embodiment of a roof product; 
         FIG. 11  is a partially sectioned, isometric view of an embodiment showing layers of a roof product; 
         FIGS. 12A and 12B  are schematic isometric views of a building having embodiments of roof products; 
         FIGS. 13A and 13B  are schematic sectional views of additional embodiments of a roof product; and 
         FIGS. 14-16  depict plots of performance comparing a conventional roof construction to an embodiment of a roof construction. 
     
    
    
     The use of the same reference symbols in different drawings indicates similar or identical items. 
     DETAILED DESCRIPTION 
     Embodiments of a system, method and apparatus for thermal energy management of a roof are disclosed. For example, a roof product  11  may comprise a sheet or a panel (which may be rigid; see, e.g.,  FIG. 1 ) or a flexible roll of material (see, e.g.,  FIG. 2 ) having a plurality of layers and/or materials. In some embodiments, the roof product  11  comprises a thermal heat storage layer  13 , a vent layer  15  having channels  17  for transferring excess heat through an entire length L of the roof product  11 , and a flame retardant  19  to suppress fire through the vent layer  15 . The thermal heat storage layer  13 , vent layer  15  and flame retardant  19  form a unitary structure as shown. 
     In other embodiments, the roof product further comprises outer skin layers comprising an uppermost layer  21  and a lowermost layer  23 , between which are located the thermal heat storage layer  13 , the vent layer  15  and the flame retardant  19 . As shown in  FIGS. 1 and 2 , the flame retardant  19  is located between the thermal heat storage layer  13  and the vent layer  15 . In  FIG. 3 , the vent layer  15  is located between the thermal heat storage layer  13  and the flame retardant  19 . 
     In the embodiments of  FIGS. 4A-4C , the roof product  11  comprises a radiant layer  20 , the thermal heat storage layer  13 , and the vent layer  15  to form a unitary structure. As shown in  FIG. 4A , the vent layer  15  may be located between the radiant layer  20  and the thermal heat storage layer  13 . Alternatively ( FIG. 4B ), the radiant layer  20  may be located between the vent layer  15  and the thermal heat storage layer  13 . In the embodiment of  FIG. 4C , the thermal heat storage layer  13  is on top, the vent layer  15  is on the bottom, and the radiant layer  20  is in between them. 
     However, alternate embodiments have at least some of the layers combined together. For example, the flame retardant  19  may be combined with the thermal heat storage layer  13  ( FIG. 5 ). The flame retardant  19  and the thermal heat storage layer  13  may each comprise media, and the media may be mixed and combined in a single layer  25  as shown. In some versions, the single layer  25  may comprise less than about 25% of the flame retardant  19 , or less than about 5% to less than about 10% of the flame retardant  19 . 
     In the embodiment of  FIG. 6 , the flame retardant  19  comprises materials used to form a structure for the channels  17  of the vent layer  15 , such that the flame retardant  19  and the vent layer  15  are combined in a single layer. In other embodiments ( FIG. 7 ), the roof product  11  has a planar area A, and the flame retardant  19  comprises an area that is less than the planar area A. Thus, the flame retardant  19  may be located adjacent only a portion of each of the channels  17  in the vent layer  15 , rather than distributed throughout the roof product. For example, the flame retardant  19  may be located along a single edge of the roof product  11 , as shown in  FIG. 7 . 
     In the embodiments of  FIG. 13 , the radiant layer  20  and vent layer  15  may be combined in a single layer ( FIG. 13A ), or the radiant layer  20 , thermal heat storage layer  13  and vent layer  15  may be combined in a single layer ( FIG. 13B ). 
     The flame retardant  19  also may comprise an intumescent that expands into the vent layer  17  at a desired temperature (e.g., about 175° C. to about 280° C.). For example, the flame retardant  19  may comprise media such as expandable clay, expandable graphite, intumescent silicates, hydrated metal silicates, bromated compounds, halocarbons, aluminum hydroxide, magnesium hydroxide, hydromagnesite, antimony trioxide, various hydrates, red phosphorus, boron compounds, phosphonium salts, or combinations thereof. 
     Still other embodiments of the roof product  11  may include an upper radiant barrier  31  ( FIG. 8 ) and a lower moisture barrier  33 , such that the roof product  11  comprises the only material located between a roof deck  35  and a roof barrier  37 . The uppermost layer  31  may be UV resistant. Versions of the roof product  11  may have a thickness T of about 0.75 to 2.5 inches. For example, the thermal storage layer  13  may have a thickness t t  ( FIG. 3 ) of about 0.25 inches to about 1 inch, the vent layer  15  may have a thickness t v  of about 0.25 inches to about 1 inch, and the flame retardant  19  may have a thickness t f  of about 0.25 inches to about 0.5 inches. The drawings are not drawn to scale. 
     In still other embodiments, the intumescent may expand in the presence of fire to about 20 times its original volume. Thus, thickness t f  may comprise a ratio of about 1/20 th  of the thickness t v . For example, for a thickness t v  of about 0.25 inches, the thickness t f  is about 0.01 inches to effectively block air flow through the vent layer  15 . In addition, the roof product  11  may be configured with an overall weight per unit area in a range of about 1 pound per square foot (lbs/ft 2 ), to about 10 lbs/ft 2 , or less than about 10 lbs/ft 2 , or less than about 5 lbs/ft 2 , or less than about 3 lbs/ft 2 . 
     In some embodiments, the thermal heat storage layer  13  may have a heat capacity that stores solar heat during a heating cycle, and have a thermal emittance that re-radiates stored heat during a cooling cycle. For example, the heat capacity may be greater than about 100 kJ/kg, and a heat absorbing range thereof may be about 10° C. to about 50° C. In other versions, the heat capacity may be greater than about 200 kJ/kg, and the heat absorbing range may be about 20° C. to about 40° C. Other versions of the roof product include two or more thermal heat storage materials having different heat capacities and/or heat absorbing ranges. 
     The thermal heat storage layer  13  may comprise a solid, such as one or more phase change materials (PCM), paraffins, hydrated salts, stearic acid, ceramic media, or combinations thereof. The phase change material may comprise calcium chloride hexahydrate, sodium sulfate, paraffin, Na 2 SO 4 .10H 2 O, CaCl 2 .6H 2 O, Na 2 S 2 O 3 .5H 2 O, Na 2 CO 3 .10H 2 O, NaHPO 4 .12H 2 O, a mixture of strontium chloride hexahydrate, potassium chloride and calcium chloride, or any combination thereof. Embodiments of the phase change material may include a mixture of strontium chloride hexahydrate, potassium chloride and calcium chloride. In other embodiments, the phase change material may comprise a supersaturated solution of calcium chloride hexahydrate. 
     The thermal heat storage layer  13  may comprise a powder or be in an encapsulated form with sizes that are less than about 0.5 mm in diameter. As shown in  FIG. 9 , the thermal heat storage layer  13  may comprise media  41  located between skin layers  43 ,  45 , with or without an adhesive  47 . In the example of  FIGS. 9 and 10 , the media  41  may be located in a structure  49  having cavities (e.g., an array of honeycomb cavities with vertical axes).  FIG. 11  depicts an embodiment of the thermal heat storage layer  13  having outer skin layers  50  that contain heat storage media  41  in a binder matrix. Such media may be formed, for example, by extrusion, gel casting, lamination, solvent casting or extrusion coating. 
     Referring again to  FIG. 1 , the channels  17  in the vent layer  15  may have openings along the edges thereof that extend completely through the roof product  11  along length L. Each opening may have an effective area of about 0.01 in 2  to about 1 in 2 , or about 0.05 in 2  to about 0.5 in 2  in other embodiments. 
     As shown in  FIGS. 12A and 12B , a plurality of the roof products  11  is assembled in an abutting configuration on the roof of a building  61 .  FIG. 12A  depicts the roof products  11  in sheet or panel form, while  FIG. 12B  depicts the roof products  11  in roll form. The vent layer  15  of roof product  11  is adapted to vent excess heat from an eave  63  of the roof up to a ridge  65  of the roof and out to atmosphere. The vent layers  15  inside roof products  11  may be positioned to vent excess heat via natural air flow from the lower eave  63  of the roof up to the ridge  65  of the roof. Thus, the channels  17  of the vent layers  15  may form substantially contiguous, uninterrupted air flow paths between abutting products having inlets substantially only adjacent the eave  63  of the roof and outlets substantially only adjacent the ridge  65  of the roof. The openings of channels  17  are large enough to eliminate the need for precise alignment of the inlets and outlets of adjacent, abutting products  11  such that a path for air flow is substantially unimpeded. 
     As shown in  FIG. 12B , the roof product  11  may comprise rolls of material that extend continuously from adjacent the eave  63  to adjacent the ridge  65  to form continuous, uninterrupted air flow paths having inlets only adjacent the eave and outlets only adjacent the ridge, such that there is no air flow communication in the channels  17  between laterally adjacent rolls of the roof product  11 . 
     Alternatively, some embodiments may include the capacity of lateral flow of air between channels with lateral openings. A plurality of roofing products  11  may be laid up on a roof deck ( FIGS. 12A and 12B ) with adjacent roof products  11  being arranged side-by-side, in horizontal and vertical courses (horizontal only in  FIG. 12B ) from a lower end  63  of the roof deck to an upper end  65  thereof. Their vent channels  17  may communicate laterally (side to side) with each other through one or more lateral openings, for providing airflow through successive horizontal courses of the roofing products  11  within in the same vertical course. 
     As depicted in  FIGS. 1 and 8 , the roof product  11  is directly fastenable to the roof deck  35  of a building, and is covered by outer roof barriers  37  (e.g., shingles, tiles, membranes, etc.). Roof barriers  37  may be located on top of the roof products without substantially affecting an overall thickness of the roof products  11 . In the embodiment of  FIG. 10 , the roof product may be provided with a plurality of cells  53  that are adapted to be penetrated by roofing fasteners  55 , such as nails. The cells  53  may be void of a material  41  used to form the thermal heat storage layer  13 . 
     In some embodiments, a kit for equipping a roof for thermal management comprises a plurality of roof products as described herein. The roof products are adapted to form continuous air vents from adjacent an eave of the roof to adjacent a ridge of the roof. Attachment means such as roofing nails or adhesive may be used to secure each of the roof products to a roof deck. At least a portion of the roof products may further comprise an intumescent zone for fire suppression within the roof products. For example, as shown in  FIG. 12A , the roof products  11  may comprise one or more rows of lower edge eave elements  71 , roof plane elements  73 , and upper edge ridge elements  75 . The fire retardant  19  may be located along at least one of the lower edge eave elements  71  and the upper edge ridge elements  75 . In an alternate embodiment, the fire retardant  19  may be located in at least some of each of the lower edge eave elements  71 , roof plane elements  73  and upper edge ridge elements  75 . In still other embodiments, fire retardant  19  may be located at least somewhere in a path of an assembled structure so that, in the event of fire, the vent channels are blocked. 
     In operation, embodiments of a method of managing thermal energy in a roof of a building may comprise providing a roof having a roof deck, a roof outer barrier and a unitary product located between the roof deck and roof outer barrier; storing thermal heat with the unitary product during a heating cycle; venting excess heat through the unitary product; and releasing the stored thermal heat from the unitary product into or out of the building during a cooling cycle. The unitary product may have a flame retardant for blocking venting thereof in the event of a fire. 
     In some embodiments, skin layers may be added to enhance the walkable surface for roofers, particularly in wet conditions. The skin layers may be configured for walkability and may include elements such as synthetic underlayment products. In addition, they may provide some UV resistance for short term exposure (e.g., one year of UV stability) if left unprotected on the roof. Furthermore, the skin layer may be combined with a radiant barrier, such as aluminum foils, metalized films, mirrorized surfaces, etc., to reflect solar heat. 
     The thermal heat storage layer may comprise a desirable heat capacity that can store solar heat over an extended period of time. It may have a desirable thermal emittance that re-radiates stored heat during night time or during extended cold periods to leverage the stored solar heat for greater indoor comfort. In some embodiments, the thermal heat storage layer absorbs heat in a given range of temperatures and releases the stored heat upon cooling in a selected range of temperatures. Moreover, the roof product  11  remains flexible in lower temperatures down to about 0° C., and remains structurally sound for a roof walkable surface in higher temperatures where a roof surface temperature may exceed 70° C. 
     The thermal heat storage layer may perform without leakage even after being penetrated by roofing nails. For example, when a nail penetrates the structure, it goes through only a small number of capsules, leaving the vast majority of them intact over the roof area. 
     For embodiments of the layer with venting channels, the channels may provide sufficient openings for air flow, but not for insect infiltration or infestation. For example, a screen structure may be employed to inhibit such. The openings also are not so small that they are susceptible to clogging from airborne dust or contamination. Suitable materials for this layer may comprise thermoplastics, thermoplastic elastomers, aluminum, thermoset resins, cellulose composite, wood composites, rubbers, or their mixtures. The layer may contain fillers or functional fillers, flame retardants, or intumescent agents to reduce or block the air passages in the event of a fire. The layer may further contain biocides or fungicides to prevent or inhibit microbial growth. The layer may be constructed, for example, by industrial processes such as extrusion, injection molding, compression molding, pultrusion, lamination, or thermal forming. 
     Embodiments of the flame retardant reduce the risk of a fire spreading and penetrating into the underlying roof deck. This material may reduce the size of or block the air passages of the venting layer during a fire. It also may provide a charring or fire suffocating effect to prevent further spreading of fire. For example, it may provide Class A fire protection for the underlying roof deck. Suitable fire retarding media may comprise expandable clay, expandable carbon black, intumescent silicates, hydrated metal silicates, bromated compounds, halocarbons, aluminum hydroxide, magnesium hydroxide, hydromagnesite, antimony trioxide, various hydrates, red phosphorus, boron compounds, phosphonium salts, or their mixtures. 
     In some embodiments, the flame retardant may be combined with the thermal heat storage layer. For example, such a combination may comprise forming the flame retardant as part of the skin layer for the thermal heat storage layer, or by intermingling the flame retarding media with the heat storage media within the layer. Other versions may include a flame retardant applied as a separate accessory to the roofing product. For example, a strip of “fire stop” tape may be applied near the bottom or top of the vent channels to close the channels in the event of fire. 
     In other embodiments, the flame retardant may be combined with the air venting layer by incorporating the flame retardant as a skin layer, or by incorporating the flame retardant media in the materials for construction the venting layer. In addition, the flame retardant media may be dispersed or incorporated into the materials for forming the roof deck composite. Other variations to the construction of the roof deck composite for managing solar heat will become apparent to those who are skilled in the art. 
     An embodiment as described herein was tested against a control or conventional roofing configuration. In the test, two test huts were constructed, including an experimental but and a control hut. The effects on attic temperatures and heat flux into the ceilings were tested on both huts. The huts had identical constructions, other than their roof deck systems. The control but had a conventional roof deck construction. The experimental but had a roof deck system for managing solar heat. A summary of their constructions appears in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Control 
                 Experimental 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Roof Assembly 
                   
                   
               
               
                 shingle 
                 standard black shingle 
                 Energy Star cool shingle 
               
               
                 venting channel 
                 No 
                 ½″ PC board 
               
               
                 radiant barrier 
                 No 
                 yes 
               
               
                 PCM 
                 No 
                 29° C. PCM, 0.66 lb/ft 2   
               
               
                 underlayment 
                 #30 felt 
                 #30 felt 
               
               
                 roof deck 
                  7/16″ OSB 
                  7/16″ OSB 
               
               
                 attic insulation 
                 R-33 fiberglass batt 
                 R-33 fiberglass batt 
               
               
                 rafter 
                 2 × 6 @ 16″ O.C. 
                 2 × 6 @ 16″ O.C. 
               
            
           
           
               
               
            
               
                 Ceiling Assembly 
                   
               
               
                 joist 
                 2 × 6 @ 16″ O.C. 
               
               
                 gypsum board 
                 ½″ 
               
               
                 Wall Assembly 
               
               
                 siding 
                 fiber cement shiplap 5/16″ 
               
               
                 housewrap 
                 DuPont Tyvek 
               
               
                 sheathing 
                  7/16″ OSB 
               
               
                 joists 
                 2 × 4 @ 16″ O.C. 
               
               
                 insulation 
                 R-13 
               
               
                 wall board 
                 gypsum ⅝″ 
               
               
                 window 
                 2′ × 3′ PVC window 
               
               
                 Floor Assembly 
               
               
                 exterior sheathing 
                 Celotex sheathing ½″ 
               
               
                 joists 
                 2 × 6 @ 16″ O.C. 
               
               
                 insulation 
                 R-30 fiberglass batt 
               
               
                 decking 
                 plywood ¾″ 
               
               
                 additional insulation 
                 board insulation R-10 (2″) 
               
               
                 Space Conditioning 
                 through-the-wall AC with GE model AJCQ06LCD 
               
               
                   
                 at capacity of 6400 BTU/hr and 9.9 EER 
               
               
                   
               
            
           
         
       
     
     The experimental but had shingles with increased solar reflectance, an air gap of about ½″, and a layer of phase change materials having a transition temperature at 29° C. The interiors of the huts were kept at constant temperature with the air conditioning and the resultant energy consumption was monitored to provide the energy impact by the two different types of roof deck systems. 
     The huts were placed in an outdoor environment and spaced apart to ensure no shadowing effects on each other. The rooms inside the huts were kept constant at 68° F. with an air conditioning unit during the daytime. The huts were not occupied nor contained any furniture. Each but had a 2′×3′ window to simulate their solar heat gain into the rooms. The roof shingle temperature, roof deck temperature, attic temperature at inner side of the roof deck and at attic floor, ceiling temperature, room temperature, and wall temperatures were measured by thermistors and thermocouples. The energy consumption, start time, and the run duration of the AC units were recorded to determine the energy impact. The data was collected with a data acquisition system and computer located inside each hut. 
     Data was collected in both huts over the course of a continuous week. The results are shown in  FIGS. 14-16 . Comparing the temperatures of the roofing shingles ( FIG. 14 ), a reduction of about 10° C. was achieved by the experimental but with the solar heat management roof deck system. Moreover, the experimental hut&#39;s attic air temperatures ( FIG. 15 ) show a significant reduction of about 20° C. in peak temperatures, and a shift in peak temperatures into evening hours. This reduction and shifting in peak temperatures had a significant delaying effect for reducing the peak hour energy demands, as well as significantly reducing the AC load. The overall AC energy consumption was reduced by 25% from a daily average of 14.6 kWh in the control hut, to 11.1 kWh in the experimental hut. The daily ceiling heat flux results are shown in  FIG. 16 , where a reduction of about 35% in peak heat flux is observed. 
     This written description uses examples to disclose the embodiments, including the best mode, and also to enable those of ordinary skill in the art to make and use the invention. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 
     Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed are not necessarily the order in which they are performed. 
     In the foregoing specification, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     Also, the use of “a” or “an” are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise. 
     Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. 
     After reading the specification, skilled artisans will appreciate that certain features are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, references to values stated in ranges include each and every value within that range.