Patent Application
20070095388
The present invention relates to photovoltaic roof-top components, photovoltaic roof-top assemblies, and photovoltaic systems that convert solar energy directly into electricity.
BACKGROUND ART
Roof-top assemblies that utilize solar energy are well known, and photovoltaic roof-top components that convert solar energy directly into electrical energy are increasingly common, especially on large commercial, essentially flat roofs. Such photovoltaic roof-top assemblies generally include photovoltaic panels on top of a roofing membrane that overlies a top surface of a roof deck.
A well known roofing system includes use of a roofing membrane, and then a loosely laid insulation layer above the roofing membrane, and then a layer of ballast material, such as stone or concrete layers on the insulation layer to secure the insulation against wind disruption, etc. Such roofing systems are often referred to as “inverted roofing membrane assemblies”, or by the acronym IRMA or PMR. By having the insulation on top of the roofing membrane, instead of under the membrane, IRMA systems protect the membrane from deterioration due to exposure to ultraviolet light and thermal stress. However, the ballast materials add a substantial weight load to the roof, and also require substantial cost and effort in applying the ballast materials to the roof. Each IRMA roofing system requires a predetermined minimum weight per unit area to adequately secure against disruption by wind or other weather events. The minimum weight per unit area cannot exceed a maximum design weight load for the underlying roof structure.
For example, a common predetermined weight per unit area for an IRMA roofing system could be about five to about twelve pounds per square foot. Consequently, such newly constructed buildings must design for the additional loads and existing IRMA roofs may present weight limitation challenges if it is desired to add a photovoltaic roofing system to the IRMA roof. In addition the buildings underlying roof structure must be analyzed for reserve load capability when it is desired to replace an existing conventional membrane over insulation roofing system with an IRMA roofing system or a photovoltaic IRMA roofing system.
Other problems associated with roof-top assemblies using photovoltaic roofing components include efforts to minimize penetration and related possible leakage through the roofing membrane by apparatus used to secure the panels to the roof membrane; resistance to wind forces that may rip photovoltaic panels off of a roof deck; stabilizing temperatures experienced during operation of the photovoltaic panels; drainage of rain and melt water under such photovoltaic components; and a number of related challenges.
For example, U.S. Pat. No. 4,886,554 to Woodring et al. shows a solar roofing system that uses tapered insulation blocks to generate flow of rain water off of surfaces of the photovoltaic cells and then between the insulation blocks and adjacent pavers to direct rain water over the roofing membrane and away from the system. U.S. Pat. No. 5,316,592 to Dinwoodie discloses use of a plurality of insulation blocks between a roofing membrane and a photovoltaic module wherein rainwater flows off of the module surfaces and between insulation blocks of adjacent modules to then flow onto the roofing membrane away from the photovoltaic modules. These patents indicate that the types of flat roofs appropriate for use of such photovoltaic modules include modest slopes for drainage of rain water, which is well understood.
As a further example of problems addressed in the field of photovoltaic roofing modules, U.S. Pat. No. 5,505,788 to Dinwoodie shows elaborate means for regulating temperature of the photovoltaic modules, including use of phase change materials and fluid flow conduits adjacent back sides of the modules. This patent also points out that rain water will drain between joints between the modules. Additionally, U.S. Pat. No. 5,746,839 to Dinwoodie discloses use of pre-formed spacers supporting photovoltaic modules above a roofing membrane, or above an insulation block, to support photovoltaic modules, wherein geometry of the spacers is configured to reduce the force of wind uplift on the overall system.
These and other known patents endeavor to resolve a number of beguiling issues related to installation of photovoltaic modules on essentially flat roofs. However, no known patent or known photovoltaic roofing system efficiently resolves major challenges that have become more pressing with the development of modern, stringent building codes. In particular, new “IBC” codes call for at least a one-quarter inch per foot of run slope for positive drainage on all commercial flat roofs. By requiring such significant drainage slope, known photovoltaic modules are essentially incapable of effectively dealing with a substantial flow of water from upstream of the module in all types of flat or moderately sloped roof conditions. In some circumstances, a sudden, high rain-fall rate may lead to such a flow of water from areas upstream of the modules and then onto the modules, so that the modules may be damaged dislodged from their positions on the roof and also causing damage to the membrane.
Additionally, it has been determined that standardized insulation layers beneath photovoltaic modules may give rise to unacceptable dew points below roofing membranes in certain roofing structures, thereby leading to unacceptable condensation of moisture below a roofing membrane upon a roofing deck. Such condensation may lead to corrosion of metal roofing decks and/or rotting of wooden deck materials & membrane.
Other problems associated with such roofing systems using photovoltaic roof-top components include excessive weight of such known systems, and difficulties associated with repair or upgrading of the photovoltaic panel components of the roofing assemblies. Some older flat roofs are only capable of supporting between four to five pounds per square foot, and most known photovoltaic roofing systems weigh substantially more. Hence, there is a need for a lightweight photovoltaic roofing system.
Moreover, typical and known solar roofing assemblies, such as those disclosed in the aforesaid U.S. Pat. Nos. 5,316,592 and 5,505,788 to Dinwoodie, show that for convenience of manufacture and installation, photovoltaic panels are manufactured to be integral with insulation layers and/or with spacers between the panels and insulation layers below the photovoltaic panels. While that may facilitate manufacture and installation, it is know that frequently only one photovoltaic panel may fail or be damaged by accidental impact by debris resulting from severe weather, falling installation tools, and/or misuse etc.
It is also known that large, flat roofs may have photovoltaic roofing systems with literally hundreds of photovoltaic panels. To remove and replace one or only several photovoltaic panels of such a system is extremely difficult where the photovoltaic panels are integral with spacers and/or an insulation layers below the panels. Removal and disruption of a section of the insulation layer raises risks of damage to the underlying roofing membrane, and adjacent panels. Additionally, environmentally friendly technology such as photovoltaics is developing rapidly, and the quality of photovoltaic panels is changing and is expected to continually change as the panels become more efficient. However, to upgrade known photovoltaic roofing systems may require removal of the entire system because the photovoltaic panels are known to be integral with insulation layers and spacers below the panels.
Accordingly, there is a need for a photovoltaic roofing system that may be easily manufactured and applied to essentially flat roofs that provides for efficient and effective drainage of rain water and/or snow-melt water, and that also allows for variable insulation of a photovoltaic roof panel to prevent deterioration of the roof deck or membrane. There is also a need for a photovoltaic roofing system that facilitates removal of system components for repair and/or upgrading, and that also provides flexibility in weight of system components so that the photovoltaic roofing system may be installed on roofs capable of supporting modest loads.
The invention includes improved photovoltaic roof-top components that may be used alone or as part of photovoltaic roofing assemblies or systems. An improved photovoltaic insulation layer includes a top surface and an opposed bottom surface, wherein the bottom surface defines a predetermined number of drainage channels, and includes a predetermined insulation layer thickness between a top surface and the opposed bottom surface. The photovoltaic roofing system includes a roofing membrane overlying a top surface of a roof deck; the improved photovoltaic insulation layer above the roofing membrane; and a photovoltaic panel above the insulation layer. The predetermined number of drainage channels between the insulation layer and the roofing membrane is a function of variable drainage requirements of the roofing system that are appropriate for a specific roof deck to which the system is installed. Additionally, the predetermined insulation layer thickness between opposed top and bottom surfaces is a function of variable insulation requirements of the insulation layer to address dew point and thermal design issues.
The invention also includes a photovoltaic IRMA roofing system for application to a traditional inverted roofing membrane assembly (“IRMA”) roof system. The photovoltaic IRMA roofing system includes a roofing membrane overlying a top surface of a roof deck; an insulation layer above the roofing membrane; ballast material installed above the insulation layer; and a photovoltaic panel secured above the ballast material. The combined weight of the ballast material and the photovoltaic panel are equal to or greater than a predetermined minimum weight per unit area for the roofing system. The preferred ballast material in the photovoltaic IRMA roofing system is a concrete topping secured to the top of the insulation layer.
By replacing a traditional layer of ballast material in an IRMA roofing system with the photovoltaic panel and concrete topping on the insulation layer, the photovoltaic IRMA roofing system efficiently satisfies the predetermined minimum weight per unit area requirement of any specific roofing system while minimizing any risk of exceeding a maximum weight load of the roof. This is particularly valuable when improving an existing IRMA roof by removing existing ballast materials and replacing them with the combined weight of the concrete layer and the photovoltaic panels. This also adds insulation to enhance the energy efficiency of the building. The photovoltaic IRMA roofing system also minimizes a weight load, cost of materials and assembly for any new roof that is to include photovoltaic panels.
(For purposes herein, use of the word “above” with respect to adjacent components is to mean with respect to a direction of gravity. In other words, where an “insulation layer is secured above a roofing membrane”, that is to means the roofing membrane is closer the center of the earth than is the insulation layer.)
An alternative embodiment of the photovoltaic roofing system of the present invention is referred to for convenience as a “dew-point sensitive roofing system”, and includes the above described roofing membrane, insulation layer and photovoltaic panel above the insulation layer, and also includes a sub-membrane insulation layer secured between the top surface of the roof deck and the roofing membrane such as would occur in an installation of photovoltaic panels over an existing roof or as part of an engineered combination of photovoltaic panels and a new roofing system having a membrane above insulation and decking. The sub-membrane insulation layer defines a predetermined sub-membrane insulation layer thickness between the top surface of the roof deck and the roofing membrane. The above membrane insulation layer in this dew-point sensitive roofing system must define a predetermined thickness that is a function of the sub-membrane insulation layer thickness so that the above membrane insulation layer has a greater “R” (resistance to movement of heat) value than the sub-membrane insulation layer. This dew-point sensitive roofing system alternative embodiment of the invention provides advantages of a protected membrane (“inverted roofing membrane assemblies”, or by the acronym “IRMA”, or “PMR”) roofing system in all applications by combining the dew point sensitive system insulation with a ballast layer consisting of the weight of the photovoltaic glass panel and the weight of a cementitious face of an uppermost layer of insulation. The advantages include longer membrane life due to a more constant membrane temperature and preventing damaging ultraviolet rays from reaching the membrane.
In use of the improved photovoltaic roofing components and system, the area of the roof deck covered by the system would be measured, and the particular position of the system with respect to potential upstream to downstream flow would also be determined so that potential upstream flow through the system could then be measured. With at least these two variables, a user could then determine the variable drainage requirements of the roofing system for a particular installation, including direction and volume of flow. Measurement of the total volume of water that must be moved from the top surface of the photovoltaic system through the system, as well as through the system from flow of water on the roof deck upstream of the system, determines the total flow capacity of the drainage channels defined within the insulation layer above the roofing membrane. The insulation layer would then be selected and/or manufactured to have defined drainage channels that provide adequate flow and directionality for the measured drainage requirements of that particular installation of the present photovoltaic roofing system.
Additionally, prior to installation, the thickness of the insulation layer of the photovoltaic panel would be selected based upon the insulation layer of a particular existing or new roofing system upon which the photovoltaic panels are being installed. The thickness of the insulation layer would be selected based upon variable insulation requirements of a particular roofing system being installed on a particular roof. Determination of a predetermined thickness of the insulation layer would include measurement of the “R” factor of the particular existing or new roof deck or roofing system to which the photovoltaic roofing system is being installed.
Perhaps more importantly, for certain roof decks, such as metal roofs that employ an insulation layer (the “sub-membrane insulation layer” referred to above) under the roofing membrane over metal ribs of a metal deck, it is critically important that the R factor of the sub-membrane insulation layer, and therefore the thickness of the sub-membrane insulation layer, be selected to make sure that the “R” value above the roofing membrane is greater than the “R” factor below the roofing membrane so that condensation between the roofing membrane and the roof deck is avoided. This involves not only a measurement of the R factor and hence thickness of the sub-membrane insulation layer, but also a measurement of the R factor of the roof deck itself, as well as the R factor of the insulation layer between the roofing membrane and the photovoltaic cell. It is to be understood that the “dew point sensitive” embodiment of the roofing system may include retrofitting an existing roof-top system that employs sub-membrane insulation layers and is not limited to newly applied photovoltaic roofing system. In such existing roof-top assemblies having sub-membrane insulation layers, the “R” value of the sub-membrane insulation may simply be measured by taking a core sample by drilling, etc. That sub-membrane “R” factor is then one of the variables used to determine the thickness of the insulation layer above the roofing membrane. Therefore, the present photovoltaic roofing components and roofing systems provide for application of insulation layers of predetermined thicknesses that are appropriate for the specific insulation requirements of the roof deck to which the roofing system is to be installed.
Preferred embodiments of the improved photovoltaic roofing components and photovoltaic roofing system and improved photovoltaic insulation layer also include drainage channels that are both parallel to an axis of gravity flow of water draining through the system, and that are also not parallel to the axis of gravity of flow and that intersect with the channels parallel to the gravity axis of flow. This may appear as the insulation layer having an approximately checked appearance on a surface closest to the roofing membrane including gravity flow drainage channels and channels perpendicular to and intersecting with the gravity flow channels. Such various drainage channels enhance lateral movement of water to thereby provide for even more rapid movement of water through the system, so that, for example, snow-melt water, or water backed up above a temporary snow damn may readily move through the photovoltaic roofing system.
The photovoltaic roofing system invention also includes a photovoltaic roofing system with quick-disconnect photovoltaic panels. The system includes an insulation layer positioned above a roofing membrane of a roof deck. Two or more spacers are positioned above the insulation layer so that the spacers define cooling voids between the spacers and above the insulation layer. A quick-disconnect photovoltaic panel is positioned above the spacers, and the quick-disconnect photovoltaic panel defines a plurality of quick-disconnect throughbores adjacent the cooling voids between the spacers. A quick-disconnect fastener-receiving sleeve is secured to the insulation layer and is also dimensioned to pass through one of the cooling voids and to also pass through a quick-disconnect throughbore of the photovoltaic panel.
A fastener having a flared end and a stem secured to the flared end is dimensioned so that the stem passes through the panel throughbore and into the quick-disconnect fastener-receiving sleeve to be secured within the sleeve by standard mechanical methods, such as a threaded sleeve and screw, etc. The flared end of the fastener is dimensioned to have a diameter greater than any diameter of the throughbore defined within the photovoltaic panel. Therefore, the flared end secures the photovoltaic panel to the insulation layer whenever the fastener is secured within the quick-disconnect fastener-receiving sleeve and the fastener permits disconnection of the photovoltaic panel from the insulation layer whenever the fastener is removed from the fastener-receiving sleeve.
Any quick-disconnect photovoltaic panels may therefore be readily removed from a photovoltaic roofing system without disrupting the insulation layer below the photovoltaic panels, and without risk of damage to adjacent photovoltaic panels, to repair or to replace the removed panel, etc. Additionally, all of the quick-disconnect panels may be removed to be replaced with upgraded photovoltaic panels without disrupting the insulation layer thereby minimizing any risk of damage to the roof membrane, and further minimizing cost of such repairs or upgrades.
The invention also includes a lightweight photovoltaic roofing system. The system includes a plurality of photovoltaic panels secured adjacent each other to define a photovoltaic region. Each photovoltaic panel is secured above a lightweight insulation panel so that each photovoltaic panel and insulation panel have a combined weight of between about 4 and about 5 pounds per square foot. The photovoltaic region defines an exterior perimeter extending around the entire photovoltaic region. A plurality of the lightweight insulation panels completely surrounds and interlocks with the exterior perimeter of the photovoltaic region and interlocks with each other to define a lightweight insulation panel ballast region. At least one insulation panel extends between the exterior perimeter of the photovoltaic region and an exterior perimeter of the lightweight insulation panel ballast region.
Each lightweight insulation panel weighs between about 4 and about 5 pounds per square foot. The lightweight system also includes a paver ballast perimeter that overlies lightweight insulation panel ballast region. The paver ballast perimeter weighs between about 12 and about 17 pounds per square foot, and the width of the paver ballast perimeter is less than half of a width of a photovoltaic panel, or preferably about 16 inches. (For purposes herein, the word “about” is to mean plus or minus 20 percent.)
Accordingly, it is a general purpose of the present invention to provide improved photovoltaic roofing components and a photovoltaic roofing system that overcomes deficiencies of the prior art.
It is a more specific purpose to provide improved photovoltaic roofing components and a photovoltaic roofing system that may be customized for particular conditions of a specific roof deck to thereby enhance performance, service and longevity of the photovoltaic roofing system.
These and other purposes and advantages of the present photovoltaic roof-top components, photovoltaic IRMA roofing system, and photovoltaic roofing system will become more readily apparent when the following description is read in conjunction with the accompanying drawing.
Referring to the drawings in detail, an improved photovoltaic roofing system is shown in
The photovoltaic insulation layer 18 may, and typically does, include a concrete topping 28 that provides ballast weight for the assembly or system 10 and other benefits well known in the art. This provides for “securing” described components to the roofing membrane 12. The insulation layer 18 defines a predetermined number of drainage channels 30, wherein only one drainage channel 30 is shown in
The photovoltaic roofing system 40 of
As is apparent in
As shown in
It is also pointed out that, the third alternative photovoltaic IRMA roofing system 72 may be secured to a metal or a non-metal roof deck 74. The third alternative photovoltaic IRMA roofing system 72 shows, similarly to the second embodiment in
An additional advantage of the present photovoltaic assemblies or system 10 and its individual components is shown in
The present invention also includes the described insulation panel 18 as an improved photovoltaic insulation layer 18 for a photovoltaic roofing system 10. 40, 72. The improved photovoltaic insulation layer 18 has a top surface 19 and an opposed bottom surface 21 (see
As is well known in the art, the schematics of
While the vast majority of photovoltaic roof-top assemblies or systems 10, 40, 72 applies to use of panels 20 that directly convert solar energy into electrical energy, it is to be understood that for purposes herein, the phrases “photovoltaic roofing system”, “photovoltaic roof-top assemblies” or “roofing systems” are to include systems that convert solar energy directly to electrical energy, as well as any roofing system that captures solar energy for any purposes, including for capture of heat energy, etc. Additionally, the phrase “insulation layer defines drainage channels” means that the drainage channels permit flow of liquids from opposed edges of the insulation layer so that the liquids flowing through the photovoltaic roofing system 10 flow from an upstream end of the system through to and out of a downstream end of the system, or out of sides of the system 10. The phrase “insulation layer defines drainage channels” may also mean that drainage channels simply lie between insulation sheets of the insulation layer 18 and the roofing membrane 12, such as by application of fluid conduits (e.g., pipes, hoses, lines, carved tunnels, carved channels, etc.) to or in the insulation sheets 50, 52.
The photovoltaic roofing system of the present invention also includes a quick-disconnect photovoltaic roofing system 100 with a quick-disconnect photovoltaic panel 102 that is shown in
A quick disconnect photovoltaic panel 102 is positioned above the spacers 108A-108D, and the quick-disconnect photovoltaic panel 102 defines a plurality of quick-disconnect throughbores 126A, 126B, 126C, 126D, 126E, 126F adjacent the cooling voids 120A, 120B between the spacers 108A-108D. A plurality of quick-disconnect fastener-receiving sleeves 128A, 128B, 128C (shown best in
For purposes of clarity in explanation, this description will describe one fastener 132, while it will be understood by those skilled in the art that virtually identical fasteners are deployed within each of the quick-disconnect throughbores 126A-126F and fastener-receiving sleeves 128A-128D. The fastener 132 has a flared end 134 and a stem 136 that is secured to the flared end 134, and the fastener 132 is dimensioned so that the stem 136 passes through the panel throughbore 126C and into the quick-disconnect fastener-receiving sleeve 128C to be secured within the sleeve by standard mechanical methods, such as a threaded sleeve and screw, etc. The flared end 134 of the fastener 132 is dimensioned to have a diameter greater than any diameter of the throughbore 126C defined within the photovoltaic panel 102. Therefore, the flared end 134 secures the photovoltaic panel 102 to the insulation layer 104 whenever the fastener 132 is secured within the quick-disconnect fastener-receiving sleeve 128C and the fastener 132 permits disconnection of the photovoltaic panel 102 from the insulation layer 104 whenever the fastener 132 is removed from the fastener-receiving sleeve 128C. The insulation layer 104 may be secured to an adjacent roof membrane 105 by any means known in the art.
While the fastener 132 and corresponding receiving sleeve 128C have been described as a conventional threaded sleeve and threaded bolt, it is to be understood that any quick-disconnect fastening means may be utilized that is known in the art and that is capable of securing the photovoltaic panel 102 to the insulation layer 104 above the cooling voids 120A, 120B, such as bolts and nuts, instead of sleeves, washer-defined sleeves, securing rods with pivot latches at terminal ends, etc. As shown in
As described above, the quick-disconnect photovoltaic panel 102 may therefore be readily removed from the quick-disconnect photovoltaic roofing system 100 without disrupting the insulation layer 104 below the photovoltaic panel 102, and without risk of damage to any adjacent photovoltaic panels (not shown), to repair or to replace the removed panel 102, etc.
As shown best in
The photovoltaic region 154 defines an exterior perimeter 160 extending around the entire photovoltaic region 154. A plurality of the lightweight insulation panels 156 completely surrounds and interlocks with the exterior perimeter 160 of the photovoltaic region 154 and interlocks with each other 156 to define a lightweight insulation panel ballast region 162. At least one insulation panel 156 extends between the exterior perimeter 160 of the photovoltaic region 154 and an exterior perimeter 164 of the lightweight insulation panel ballast region 164. Additional insulation panels 156 may extend between the exterior perimeter 160 of the photovoltaic region and the exterior perimeter 164 of the lightweight insulation panel ballast region 164 if the area of the roof permits, and if additional ballast is needed.
Each lightweight insulation panel 156 weighs between about four and about five pounds per square foot. The lightweight photovoltaic system 150 also includes a paver ballast perimeter 166 that overlies the lightweight insulation panel ballast region 162. In varying embodiments, the paver ballast perimeter 166 may overlie the exterior perimeter 160 of the photovoltaic region 154 and simultaneously overlie an interior perimeter 168 of the lightweight insulation panel ballast region 164 (as shown in
Use of the word “interlocks” in the above description: “A plurality of the lightweight insulation panels 156 completely surrounds and interlocks with the exterior perimeter 160 of the photovoltaic region 154 and interlocks with each other 156 to define . . . ” will now be described. By stating that a plurality of the insulation panels 156 . . . “interlocks”, it is meant to include the type of “tongue and groove” mechanical interlocking shown in
Use of the lightweight photovoltaic roofing system 150 provides a more efficient system 150 that may be used on roofs that would prohibit use of known systems because of weight restrictions of the roof 106′. Use of the quick-disconnect photovoltaic panels 102 provides for rapid removal of damaged panels, or of outdated panels with minimal risk of damage to the roof membrane 105, 105′, roof deck 106, 106′ and/or adjacent panels, and minimizes cost of such replacement by retaining an existing insulation layer 104 and any ballast components 156, 166. The quick-disconnect photovoltaic panels 102 may be used in known photovoltaic systems, or the photovoltaic systems 10, 40, 72, 150 of the present invention described above.
While the present invention has been disclosed with respect to the described and illustrated embodiments, it is to be understood that the invention is not to be limited to those embodiments. Accordingly, reference should be made primarily to the following claims rather than the foregoing description to determine the scope of the invention.
This Application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/732,501 that was filed Nov. 2, 2005, entitled “Photovoltaic Roof-Top Components, Photovoltaic Roof-Top Assemblies, and Photovoltaic Roofing Systems”.
| Number | Date | Country | |
|---|---|---|---|
| 60732501 | Nov 2005 | US |
