Abstract:
A flexible solar power assembly ( 2 ) includes a flexible photovoltaic device ( 16 ) attached to a flexible thermal solar collector ( 4 ). The solar power assembly can be rolled up for transport and then unrolled for installation on a surface, such as the roof ( 20, 25 ) or side wall of a building or other structure, by use of adhesive and/or other types of fasteners ( 23 ).

Description:
BACKGROUND OF THE INVENTION  
       [0001]    This is a continuation of U.S. patent application Ser. No. 09/606,657, filed Jun. 28, 2000, now U.S. Pat. No. 6,295,818, issued Oct. 2, 2001.  
         [0002]    Solar thermal collectors have been made in the past in long extruded strips which are then installed by adhering to the surface of a building roof. Recent developments in the manufacturing of photovoltaic(PV) power cells using thin-film photovoltaic material deposited onto a thin sheet of metal or polymer has resulted in the ability to produce a flexible solar-electric power cell. This technique also allows the manufacturing of these power cells in continuous sheets. 
     
    
     
       SUMMARY OF THE INVENTION  
         [0003]    The present invention is directed to the combination of a solar thermal collector and a photovoltaic device, each designed to capture energy in a different way, and to provide an assembly with better performance and economics than may result from the application of the two products separately.  
           [0004]    The first aspect of the invention is directed to a solar power assembly comprising a flexible thermal solar collector and a PV device mounted to the thermal collector to create a solar power assembly. The assembly may have sufficient flexibility so it may be transported in a roll to a use site, unrolled and attached to a support at the use site. The thermal solar collector typically includes a plurality of fluid passageways.  
           [0005]    Another aspect of the invention is directed to a hybrid solar power system including a solar power assembly, comprising a flexible thermal solar collector and PV device creating a flexible solar power assembly. An external heated fluid receiver, such as a heat exchanger, is fluidly coupled to the thermal solar collector. An external device, such as a regulated power supply, is electrically coupled to the PV device.  
           [0006]    A further aspect of the invention is directed to a method for making a solar power assembly. A flexible thermal solar collector and a PV device are joined to create a flexible solar power assembly. The assembly is rolled for transport to a use site.  
           [0007]    A still further aspect of the invention is directed to a method for installing a solar power assembly on a support at a use site comprising unrolling a solar power assembly from a roll, the solar power assembly comprising a flexible thermal collector and a PV device mounted to one another. The solar power assembly is attached to the support with the flexible thermal collector located between the support and the flexible PV device. The attaching step may be carried out using an adhesive and/or clips.  
           [0008]    An additional aspect of the invention is directed to a solar power assembly comprising a polymer thermal solar collector and a PV device mounted thereto. The polymer may be a flexible polymer, such as EPDM.  
           [0009]    Another aspect of the invention is directed to a solar power unit comprising a thermal solar collector and a PV device mounted thereto to create a solar power assembly. A collapsible glazing is mounted to the solar power assembly to overlie the PV device for movement between upright, inflated and collapsed, deflated conditions.  
           [0010]    These various aspects of the invention provide a number of advantages. The invention permits the solar power assembly to be simply and securely mounted to a roof or other support by, for example, attaching the assembly directly to a roof membrane with an adhesive; this reduces or eliminates the need for additional mounting structure and also may eliminate the need for roof membrane-penetrating fasteners. Also, the assembly can take the place of the roof membrane by, for example, mounting strips of the solar power assembly adjacent to one another in a shingled fashion to form what is in essence a roof membrane. The manufacture of a PV device and thermal solar collector as one assembly may result in lower cost as well as simpler transportation and installation. 
       
    
    
       [0011]    Other features and advantages of the invention will appear from the following description which the preferred embodiments have been set forth in detail in conjunction with the accompany drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic view illustrating joining of a length of a flexible thermal solar collector and a flexible PV device laminate to create a roll of a flexible solar power assembly;  
         [0013]    [0013]FIG. 2 is an enlarged view of the roll of the solar power assembly of FIG. 1 with a portion of the PV device laminate broken away to show the thermal solar collector;  
         [0014]    [0014]FIG. 3 is an enlarged view of the outer end of the flexible solar power assembly of FIG. 2 showing the series of fluid pathways formed in the thermal solar collector;  
         [0015]    [0015]FIG. 4 illustrates a length of the solar power assembly of FIGS.  1 - 3  mounted to a shingled roof membrane of a building;  
         [0016]    [0016]FIG. 5 is a schematic representation illustrating the fluid and electrical connections to the solar power assembly of FIG. 4;  
         [0017]    [0017]FIG. 6 illustrates a roof membrane created by a shingled series of adjacent lengths of the power assembly of FIGS.  1 - 5 ;  
         [0018]    [0018]FIG. 7A- 7 C illustrate an alternative embodiment of the invention in which adjacent thermal solar collectors can be joined using fluid couplers between aligned fluid passageways and a clip to secure the joint;  
         [0019]    FIGS.  8 A- 8 C illustrate enlarged cross-sectional views of three embodiments of the PV device laminate of FIGS.  1 - 3 ;  
         [0020]    FIGS.  9 A-B illustrate an alternative embodiment of the invention in which an inflatable cover material is used above the photovoltaic device laminate; and  
         [0021]    FIGS.  10 A-B illustrate the use of clips for attaching a solar power assembly to supporting shingles. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 illustrates in schematic form a roll  2  of a flexible thermal solar collector  4  being joined to a roll  6  of a flexible photovoltaic (PV) device laminate  8 , typically by the use of heat and/or adhesives and/or pressure at position  10 , to create an elongate solar power assembly  12  which is wound into a roll  14 .  
         [0023]    [0023]FIG. 2 is an enlarged view of roll  14  and shows thermal solar collector  4  and PV device laminate  8  which are joined to form solar power assembly  12 . Laminate  8  includes a series of PV devices  16  which are appropriately interconnected to obtain the desired electrical output during use.  
         [0024]    [0024]FIG. 3 illustrates a series of fluid passageways  18  formed through thermal solar collector  4 . An appropriate fluid, such as water, is passed through passageways  18  to collect heat from solar collector  4 . Fluid may be caused to flow through passageways  18  by natural convective flow, by pumping or by a combination thereof.  
         [0025]    In the preferred embodiment of FIGS.  1 - 3 , PV device laminate  8  comprises an amorphous silicon photovoltaic collector material deposited onto a stainless steel substrate  19 , or other PV material, such as copper indium diselinide on substrate of similarly flexible material. While it is preferred that PV devices  16  be flexible, PV devices may be substantially rigid but shaped and sized so as not to impair the desired flexibility of collector  4 .  
         [0026]    Thermal solar collector  4  is made of a polymer, preferably of a flexible plastic or elastomer material such as polypropylene, PEX brand cross-linked polyethylene from Specialty Filaments, Inc. or Ethylene Propylene Diene Monomer (EPDM). Thermal solar collector  4  may be extruded in long sections. Making thermal solar collector  5  of a polymer has several advantages over conventional copper thermal solar collectors: lower cost; there is a better area match between the PV and thermal loads due to the less efficient thermal collection efficiency of polymers; the maximum design stagnation temperature for polymer solar thermal collectors is lower than for conventional copper solar thermal collectors so there is a better match with the maximum operating temperature of the PV device, typically about 80° C.; when the polymer is flexible, the solar power assembly may be flexible to permit the assembly to be stored and transported in rolls.  
         [0027]    Solar power assembly  12  is preferably sufficiently flexible so that it may be wound into a roll having a minimum diameter of about 60 cm (2 foot), preferably about 30 cm (1 foot) and more preferably about 10 cm (4 inches). That is, power assembly  12  is flexible enough to permit it to be wound about a mandrel having a diameter of about 60 cm, preferably about 30 cm and more preferably about 10 cm.  
         [0028]    Assembly  12  may conveniently be transported to a work site as a roll  14 . Once at the work site an appropriate length of assembly  12  may be removed from roll  14  and mounted to the support, such as roof membrane  20  shown in FIG. 4. While various hold-down structures and fasteners may be used to secure assembly  12  to roof membrane  20 , solar power assembly  12  may often be mounted to a roof or other support simply by using an adhesive without the need for specialized mounting structures. Also, the solar power assembly may be formed into the desired lengths to appropriately fit a desired location. The invention facilitates not only the manufacturing of hybrid solar power assembly  12 , it also facilitates transport and installation of the solar power assembly. When adhesives are used, the adhesives may supply all, or at least a majority of, the hold-down strength holding assembly  12  to the support. In an alternate embodiment, see FIGS. 10A and 10B, clips  23  may be used to secure assembly  12  to shingles  25  to supply all, substantially all, or at least a majority of, the hold-down strength to the roof.  
         [0029]    [0029]FIG. 5 illustrates schematically one way in which assembly  12  may be connected for use. FIG. 5 illustrates a heat exchanger  21  connected to opposite ends  22 ,  24  of assembly  12  by a conduit  26 . Ends  22 ,  24  are typically in the form of manifolds to combine and distribute the fluid flow, typically a water-based liquid, from and to fluid passageways  18 . The output from PV devices  16  is provided to a regulated power supply  28 , which typically may include appropriate control electronics, storage batteries, an inverter, etc, by an electrical line  30 . In lieu of heat exchanger  21 , heated water, or other liquid, could be used directly; for example, pre-heated water could be supplied from end  26  of assembly  12  to a water heater with replacement water being directed to the end  24  of assembly  12  from, for example, a municipal water supply, or water could be supplied from end  26  directly into a fluid reservoir, such as a swimming pool. Also, regulated power supply  28  could be replaced, for example, by control electronics which would provide alternating current to a user&#39;s dwelling and/or to a commercial electric power grid. Other uses of heated fluid and electricity can also be made.  
         [0030]    [0030]FIG. 6 illustrates a solar power assembly  12 A in a form of numerous strips of solar power assemblies  12  joined at their adjacent edges, typically in a shingled or other rain-shedding configuration. Alternatively, solar power assembly  12 A could be manufactured as a unitary piece. Solar power assembly  12 A itself could act as a roof-membrane itself. This can result in increasing the life of a roof membrane or it may enable one to forego the use of a separate roof membrane altogether. Solar power assemblies could also be made to act as side wall cladding for buildings. Roof membranes and side wall cladding are layers which protect the structures from the effects of the environment, primarily rain, and will be referred to generally as weather barriers.  
         [0031]    [0031]FIG. 7A- 7 C illustrate an alternative embodiment of the thermal solar collector  4  of FIGS.  1 - 3 . Thermal solar collector  4 A is shown to include fluid passageways  18 A sized to accept fluid couplers  34 . Adjacent ends of two thermal solar collectors  4 A can be joined using fluid couplers  34 ; the joint created can be secured through the use of a clip  36  as shown in FIGS. 7B and 7C. Such a joint may also be secured using additional fasteners and/or adhesives.  
         [0032]    [0032]FIG. 8A is an enlarged cross-sectional view of one embodiment of a PV device laminate  8 A made in accordance of the invention. Laminate  8 A comprises a top layer  40 , typically of glass or a halogenated hydrocarbon film such as Tefzel, from DuPont, or other suitable material. A typical thickness for top layer  40  is on the order of 50 microns for material such as Tefzel while a typical thickness for encapsulant layer  42  is on the order of 0.76 mm (0.03 inch) for a material such as Ethyl Vinyl Acetate (EVA). Next comes an encapsulant layer  42  typically made of EVA film. Third is the PV active layer  44 . Below PV layer  44  is a PV substrate  46 , typically made of stainless steel, aluminum, a polymer or some other suitable material. Next comes a second encapsulant layer  48 , which may or may not be made of the same material as encapsulant layer  42 . Beneath encapsulant layer  48  is a backskin  50 , made of a material such as Tedlar brand polyvinyl fluoride film from DuPont, Tefzel from DuPont, or aluminum foil. Beneath backskin  50  is a third encapsulant layer  52 . The bottom layer is a thermal collector material layer  54 . Encapsulant layers  42 ,  48  and  52  may also be characterized as adhesive layers. Adhesion between the various layers may be accomplished using thermoplastic sheets, such as EVA, polyethylene or other suitable material. The bonding process will typically use a lamination technique or direct adhesive application or both. PV device laminate  8 A illustrates a typical layering sequence. PV device laminate  8 A may also be made by adding or subtracting various layers; for example, thermal collector material layer  54  may constitute thermal solar collector  4 , thus eliminating the need for encapsulant layer  52  and backskin  50 .  
         [0033]    [0033]FIG. 8B illustrates a PV device laminate  8 B which is substantially identical to laminate  8 A with the exception of encapsulant layer  42 B. The thickness of encapsulant layer  42 B is increased to increase the thermal insulation above PV active layer  44 . Doing so allows the solar power assembly to operate at increased temperatures, thus increasing the heat flow to a fluid in the thermal solar collector. To increase the thermal insulation above PV active layer  44 , the thickness of encapsulant layer  42 B may be increased from, for example, about 0.76 mm to as much as 6.4 mm (0.25 inch) causing encapsulant layer  42 B to serve as both an encapsulant and a thermal barrier. The increased thermal insulation may also be achieved by or aided by increasing the thickness of top layer  40 . Increasing the thickness of layer  42 , when made of a material such as EVA, reduces thermal losses by an amount greater than an equivalent thickness of air (see FIG. 8C) due to the lower thermal conductivity of EVA and the lack of convective currents in the EVA. Further, direct contact of encapsulant layer  42 B with top layer  40  and PV active layer  44  reduces incident light losses compared with an equivalent air gap.  
         [0034]    [0034]FIG. 8C illustrates an alternative embodiment of the PV device laminate  8 A of FIG. 8A. Laminate  8 C is similar to laminate  8 A but includes an oversheet  56  mounted to above top layer  40  by spacer  58  to create void spaces  60  therebetween. Oversheet  60  may be of the same material as top layer  40  or a different material suitable for placement above PV active layer  44 .  
         [0035]    FIGS.  9 A-B illustrate, in simplified schematic form, use of a collapsible glazing  62  above a PV device laminate  8 D of assembly  12 D. Collapsible glazing  62  is supported in its expanded, raised condition by the dynamic pressure drop of a circulating operating fluid passing through thermal solar collector, the operating fluid being air, water, or some other fluid. Collapsible glazing  62  inflates during thermal collection and falls slack or collapses during the generation of electricity only. Glazing  62  offers good thermal insulation during thermal collection, and reduced stagnation temperatures during electric only operation because the insulating layer between collapsible glazing  62  and PV device laminate  8 D is greatly reduced when the circulating pump or fan is turned off.  
         [0036]    Collapsible glazing  62  is preferably inflated by blowing air into the region  64  between glazing  62  and assembly  12 D. A fluid, such as air or water, may be forced through passageways formed in assembly  12 D (such as with a fan, a pump or by convective forces); however, the passage of a fluid through region  64  may be sufficiently efficient at removing heat so to eliminate the need for passage of a fluid through passageways in assembly  12 D. Glazing  62  could, for example, incorporate hollow ribs which could be filled with a fluid to cause the glazing to assume its expanded, raised condition shown in FIGS.  9 A-B.  
         [0037]    Modifications and variations can be made to the disclosed embodiments without departing from the subject of the invention as defined in the following claims. For example, PV devices  16  could be mounted directly to thermal solar collector  4 .  
         [0038]    Any and all patents, patent applications and printed publications referred to above are incorporated by reference.