Patent Publication Number: US-2015083190-A1

Title: Coatings for aircraft fuselage surfaces to produce electricity for mission-critical systems and maintenance load on commercial aircraft

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. 119(e) of U.S. Provisional Application No. 61/841,243, filed on Jun. 28, 2013 (Attorney Docket No. 7006/0141PR01), U.S. Provisional Application No. 61/842,355, filed on Jul. 2, 2013 (Attorney Docket No. 7006/0141PR02), U.S. Provisional Application No. 61/841,244, filed on Jun. 28, 2013 (Attorney Docket No. 7006/0142PR01), U.S. Provisional Application No. 61/842,357, filed on Jul. 2, 2013 (Attorney Docket No. 7006/0142PR02), U.S. Provisional Application No. 61/841,247, filed on Jun. 28, 2013 (Attorney Docket No. 7006/0143PR01), U.S. Provisional Application No. 61/842,365, filed on Jul. 2, 2013 (Attorney Docket No. 7006/0143PR02), U.S. Provisional Application No. 61/841,248, filed on Jun. 28, 2013 (Attorney Docket No. 7006/0144PR01), U.S. Provisional Application No. 61/842,372, filed on Jul. 2, 2013 (Attorney Docket No. 7006/0144PR02), U.S. Provisional Application No. 61/842,796, filed on Jul. 3, 2013 (Attorney Docket No. 7006/0145PR01), U.S. Provisional Application No. 61/841,251, filed on Jun. 28, 2013 (Attorney Docket No. 7006/0146PR01), U.S. Provisional Application No. 61/842,375, filed on Jul. 2, 2013 (Attorney Docket No. 7006/0146PR02) and U.S. Provisional Application No. 61/842,803, filed on Jul. 3, 2013 (Attorney Docket No. 7006/0147PR01); the entire contents of all the above identified patent applications are hereby incorporated by reference in their entirety. This application is related to Applicants&#39; co-pending U.S. applications, which are filed concurrently herewith on Jun. 27, 2014, 7006/0141PUS01, 7006/0142PUS01, 7006/0143PUS01, 7006/0145PUS01, 7006/0146PUS01 and 7006/0147PUS01; each of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to the use of organic photovoltaic devices—cell or modules—as coatings for commercial aircraft fuselage, wing, tail, and strut surfaces, to provide electricity for mission-critical systems and/or maintenance loads on-board the aircraft. 
     BACKGROUND OF THE INVENTION 
     Modern commercial aircraft are becoming increasingly technologically advanced vehicles that must operate effectively under demanding conditions. Energy efficiency and energy consumption are of increasing importance in such vehicles, as airlines and society become more concerned with both the economics and the climate impact of air travel. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes that one way to increase energy efficiency is to incorporate renewable energy sources, but of the traditional renewable energy sources, photovoltaics (PV) is the only one that makes sense for aircraft. Electricity from PV could be used to help power mission-critical systems and/or maintenance loads on-board commercial aircraft to offset the energy needs of the many electrical systems present in modern aircraft. Traditional inorganic PV makes little sense for aircraft applications for a number of reasons, however, including excessive weight and potentially bulky structures that could increase wind resistance, both of which would reduce fuel efficiency, and poor aesthetics. 
     Organic PV (OPV) has a number of features that makes it potentially attractive for application in commercial aircraft including low specific weight (W/g), flexibility, and thickness of the thin films. An important feature is the very low specific weight of OPV, as compared to other PV technologies, which could minimize any impact on fuel efficiency. Additionally, because OPV is inherently flexible, this device architecture potentially allows unique application methods for non-planar surfaces, such as curved fuselage surfaces. Furthermore, the tunable nature of the absorption in OPV materials allows for customized surface appearances, which can be desirable for power production, and aesthetic and branding reasons. 
     The present invention recognizes that conventional commercial aircraft surfaces, such as fuselage, wing, tail, and strut surfaces (hereafter referred to simply as fuselage surfaces), are generally large passive surfaces that do not contribute in any way to help increase energy efficiency of the aircraft. 
     These problems and others are addressed by the present invention, a first exemplary embodiment of which comprises an OPV device, comprising one or more cells connected in series and/or parallel, applied as a film to conventional commercial aircraft surfaces. In this embodiment, the OPV coating is applied as a completed device onto the aircraft surface using a thin, flexible substrate with pressure-sensitive adhesives, which is described in detail in Applicants&#39; related applications. In such a fashion, the OPV device can be fabricated in a high-throughput manner via roll-to-roll or sheet-to-sheet manufacturing processes onto a flexible planar substrate (with backing material, if necessary) that is then applied to both planar and curved aircraft surfaces. The OPV device can then be wired into the electrical systems via small connection terminals in, or below, the aircraft surface, and any necessary power electronics, such as inverters, batteries, and the like can be located inside the aircraft body. The top surface of the OPV device-coated aircraft is then protected via a hard clear-coat, (e.g. a clear epoxy coating), to protect the OPV device from physical damage and environmental stresses, and from moisture and oxygen ingress, ensuring a superior lifetime. In such a way, the surfaces of the aircraft can be turned into electricity-generating surfaces to help power mission-critical systems and/or maintenance loads, while adding minimal weight, and resulting in a smooth, hard, low-drag surface, to minimize any loss of fuel efficiency. Furthermore, by selecting appropriate OPV material absorption properties, the surface visual effect can be customized for specific levels of power production, and aesthetic or branding reasons, while still generating power. 
     Another exemplary embodiment of the invention comprises an OPV device—comprising one or more cells connected in series and/or parallel—fabricated directly on the conventional aircraft surfaces, before assembly of the aircraft. In this embodiment, the surfaces are coated via one or more of a number of coating techniques, such techniques as: spray, curtain, slot-die, gravure, etc. depending on the curvature of the aircraft surface requiring OPV. Spray and curtain coating can be utilized for curved surfaces, while slot-die and gravure coating can be used for planar surfaces. First, an insulating layer is deposited to allow isolation of the individual cells from each other and from the metal aircraft surfaces, to prevent electrification of the entire aircraft body. Then, the rest of the OPV device is deposited as usual via the appropriate coating and patterning techniques, as know to those skilled in the art of OPV, to produce a completed device directly on the aircraft surface. Again, wiring is accomplished via small terminals on, or below, the aircraft surface, and a hard top-coat, such as an epoxy, is applied to provide a hard, low-drag surface that protects the OPV device. Such completed OPV-coated aircraft surface panels can then be assembled directly on the aircraft body, with wiring and any necessary power electronics such as inverters and batteries placed inside the aircraft body, to produce a commercial aircraft with electricity-producing surfaces to help power mission-critical systems and/or maintenance loads on-board, increasing energy efficiency of the aircraft. 
     Other features and advantages of the present invention will become apparent to those skilled in the art upon review of the following detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and features of embodiments of the present invention will be better understood after a reading of the following detailed description, together with the attached drawings, wherein: 
         FIG. 1  is a cross-sectional view of a pressure-sensitive adhesive-coated organic photovoltaic device, itself coated on a thin flexible substrate with a transfer release layer and rigid backing layer, which can be used to prepare planar and curved organic photovoltaic device-covered commercial aircraft fuselage surfaces, according to an exemplary embodiment of this invention. 
         FIG. 2  is a cross-sectional view of an organic photovoltaic device coated onto a planar commercial aircraft fuselage surface using the pressure-sensitive adhesive method according to an exemplary embodiment of the invention. 
         FIG. 3  is a cross-sectional view of an organic photovoltaic device coated onto a curved commercial aircraft fuselage surface using the pressure-sensitive adhesive method according to an exemplary embodiment of the invention. 
         FIG. 4  is a cross-sectional view of an organic photovoltaic device coated directly onto a planar commercial aircraft fuselage surface using conventional coating methods according to an exemplary embodiment of the invention. 
         FIG. 5  is a cross-sectional view of an organic photovoltaic device coated directly onto a curved commercial aircraft fuselage surface using conventional coating methods according to an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION 
     The present invention now is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Referring now to the drawings,  FIGS. 1-5  illustrate exemplary embodiments of electricity-generating coatings for commercial aircraft fuselage surfaces ( FIGS. 4-5 ) and their manufacture ( FIG. 1 ). 
     Referring to  FIG. 1 , which provides a cross-sectional view of an intermediate film stack produced for the eventual fabrication of electricity-generating coatings for commercial aircraft fuselage surfaces, the film is prepared upon a temporary base layer  101 , in order to provide sufficient rigidity to allow conventional manufacturing techniques, including high-speed roll-to-roll coating. The base layer can include of thick polymer foils, metal foils, or any convenient substrate material, depending on the chosen manufacturing methods. On top of the base layer is a transfer release layer  102  that allows easy removal of the base layer and transfer layer from the thin flexible substrate  103 , which are all laminated together as known to those skilled in the art. The thin flexible substrate is any appropriate substrate material that is highly flexible and transparent, such as very thin polymer foils, including but not limited to polyethyleneterephthalate (PET). On top of this is coated an OPV device, comprising one or more cells connected in series and/or parallel, which is inherently flexible and thus contains no highly crystalline materials. The multi-layered OPV device is coated and processed according to standard methods known to those skilled in the art, such as slot-die coating and laser scribing, which are compatible with high-throughput manufacturing techniques, including high-speed roll-to-roll or sheet-to-sheet production methods. Finally, the OPV device is coated on top with a semitransparent pressure-sensitive adhesive according to methods know to those skilled in the art. The resulting film comprising layers  101 - 105  can be used to transfer the OPV device comprising layers  103 - 105  onto commercial aircraft fuselage surfaces to convert them into electricity-generating fuselage surfaces. 
     Referring to  FIG. 2 , which provides a cross-sectional view of a planar electricity-generating commercial aircraft fuselage surface produced via the pressure-sensitive adhesive method, the base layer  206  includes a conventional commercial aircraft fuselage panel. Laminated onto the fuselage panel using stretching and press-forming, with or without vacuum assistance in removing entrained air, is the electricity-generating OPV device  204 , which is adhered to the panel using the pressure-sensitive adhesive layer  205 , and is supported by the thin flexible substrate layer  203 . Finally, the whole OPV device is protected via a clear hard-coat  207  (e.g. a clear epoxy), which can be applied via a variety of techniques known to those skilled in the art, such as spray coating. While, in this exemplary embodiment, the method is necessarily a discrete object process for the fabrication of each individual fuselage panel, the intermediate transfer film (see  FIG. 1 ) used to transfer the completed OPV device onto the panel can be produced in a continuous, high-throughput methodology. Not shown are any wires or other electrical contacts, or any power circuitry (e.g. inverters), which would be contained largely within the aircraft body. 
     Referring to  FIG. 3 , which provides a cross-sectional view of a curved electricity-generating commercial aircraft fuselage surface produced via the pressure-sensitive adhesive method, the base layer  306  includes a conventional curved commercial aircraft fuselage surface. Laminated onto the fuselage panel using stretching and press-forming, with or without vacuum assistance in removing entrained air, is the electricity-generating OPV device  304 , which is adhered to the panel using the pressure-sensitive adhesive layer  305 , and is supported by the thin flexible substrate layer  303 . Finally, the whole OPV device is protected via a clear hard-coat  307  (e.g. a clear epoxy), which can be applied via a variety of techniques known to those skilled in the art, such as spray coating. The unique and inherent flexibility of OPV devices allows lamination onto curved surfaces without significant disruption of device performance, and enables production of three-dimensional OPV devices that would be difficult to produce via conventional coating techniques due to realities of capillarity flow on curved surfaces. This method enables OPV devices to be laminated onto surfaces of arbitrary and changing curvature, which would be impossible via conventional solution coating techniques. While, in this exemplary embodiment, the method is necessarily a discrete object process for the fabrication of each individual fuselage panel, the intermediate transfer film (see  FIG. 1 ) used to transfer the completed OPV device onto the panel can be produced in a continuous, high-throughput methodology. Not shown are any wires or other electrical contacts, or any power circuitry (e.g. inverters), which would be contained largely within the aircraft body. 
     Referring to  FIG. 4 , which provides a cross-sectional view of a planar electricity-generating commercial aircraft fuselage surface produced via the conventional coating method, the base layer  406  includes a conventional commercial aircraft fuselage surface. First, the fuselage surface is coated with an insulating layer  408  using methods known to those skilled in the art, to allow isolation of the individual cells from each other and from the aircraft body, preventing electrification of the entire aircraft body. The OPV device  404  is then coated onto the insulating layer using conventional coating techniques such as known to those skilled in the art. Finally, the whole OPV device is protected via a clear hard-coat  407  (e.g. a clear epoxy), which can be applied via a variety of techniques known to those skilled in the art, such as spray coating. While this method has the advantage of having less extraneous layers and materials involved as compared to the laminated processes (see  FIG. 2 ), in this exemplary embodiment, it is necessarily a sheet-to-sheet coating process performed on a panel-by-panel basis for every individual layer in the OPV device, which can limit throughput and increase defects, compared to producing the OPV device in a continuous process (see  FIG. 1 ). Not shown are any wires or other electrical contacts, or any power circuitry (e.g. inverters), which would be contained largely within the aircraft body. 
     Referring to  FIG. 5 , which provides a cross-sectional view of a curved electricity-generating commercial aircraft fuselage surface produced via the conventional coating method, the base layer  506  includes a conventional commercial aircraft fuselage surface. First, the fuselage surface is coated with an insulating layer  508  using methods known to those skilled in the art, to allow isolation of the individual cells from each other and from the aircraft body, preventing electrification of the entire aircraft body. The OPV device  504  is then coated onto the insulating layer using conventional coating techniques such as spray or curtain coating. Finally, the whole OPV device is protected via a clear hard-coat  507  (e.g. a clear epoxy), which can be applied via a variety of techniques known to those skilled in the art, such as spray coating. While the realities of capillarity flow make precision coating of the very thin layers in OPV devices very difficult, it is possible to overcome these limitations, as least for surfaces with relatively uniform curvature. Doing so repeated for the several layers in an OPV device remains a significant challenge, however, and it is currently impossible for surfaces with varying or very high curvature. As such, the pressure-sensitive adhesive lamination method presents an attractive alternative for the production of curved fuselage surfaces (see  FIG. 3 ). 
     The present invention has been described herein in terms of several preferred embodiments. However, modifications and additions to these embodiments will become apparent to those of ordinary skill in the art upon a reading of the foregoing description. It is intended that all such modifications and additions comprise a part of the present invention to the extent that they fall within the scope of the several claims appended hereto.