Abstract:
A device, system, and method for harvesting solar energy from an artificial turf field or other area exposed to sunlight. An array of solar collectors may be placed in a sports stadium or other open field, each solar collector having an artificial turf structure including simulated grass and an open support structure capable of supporting human foot traffic, the artificial turf structure overlying a resilient bed supporting photovoltaic panels. Light falling on the structure at incident angles of 30 degrees from the artificial turf surface normal may be transmitted from the open support structure to the photovoltaic panels, and the panels may convert the transmitted light to electricity. The photovoltaic panels may be oriented to maximize an amount of captured light responsively to latitude. The turf structure support members may be angled responsively to an average direction of the sun at an installation latitude.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Application No. 61/444,523, filed Feb. 18, 2011, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    Artificial turf is used in athletic fields such as football pitches and baseball fields as well as golf courses. It is also used for landscaping. Artificial turf provides benefits including durability, consistent appearance, environmental advantages such as avoidance of the need for polluting fertilizers, polluting maintenance equipment such as mowers, and rapacious consumption of water. The solar energy that normally bathes artificial and natural turf areas is a wasted resource. It would be of significant value to exploit areas covered by turf as a low impact solar resource, as proposed by University of Florida Research Foundation which has filed for a PCT application published as WO/2009/070706. This application describes an artificial turf structure of solar blades each defining a photovoltaic component. The system proposes a structure for collectors that mimic grass and has various specific requirements and associated potential advantages and disadvantages. There remains a need for new approaches that can exploit the energy resource represented by artificial turf and efficiently harvest the solar electricity. 
       SUMMARY 
       [0003]    A solar collector in accordance with one or more exemplary embodiments of the present invention may include an artificial turf structure including simulated grass and an open support structure capable of supporting human foot traffic, the artificial turf structure overlying a resilient bed supporting photovoltaic panels, the open support structure transmitting to the photovoltaic panels at least 30% of light falling thereon at incident angles of 30 degrees from the artificial turf surface normal. The support structure may be a truss layer of polymer or polyurethane, and the simulated grass may include tufts supported by stems depending from a level below a top surface of the support structure. Additionally, the tufts may be made of transparent material. The photovoltaic panels may be spaced apart to permit drainage through a resilient bed, and the resilient bed may be porous. The photovoltaic panels may include cells embedded or encapsulated in polymer to form a unitary ruggedized unit. A system in accordance with one or more exemplary embodiments of the present invention may include an array of solar collectors in accordance with one or more exemplary embodiments of the present invention, arranged in a sports stadium or other open field. 
         [0004]    A solar collector in accordance with one or more exemplary embodiments of the present invention may include a support structure supporting an artificial turf structure in spaced relation to a ground surface, and an array of photovoltaic panels disposed below the turf structure, the turf structure being substantially open to permit an amount of light to pass through the turf structure to the array of photovoltaic panels. The amount of light permitted to pass through may be at least 30%. The turf structure may include an artificial turf with simulated grass and an open support structure capable of supporting human foot traffic. The turf support structure may be a truss layer of polymer or polyurethane, or both. The simulated grass may include tufts supported on stems that extend from a level below a top surface of the support structure. The simulated grass may include tufts of transparent material supported on stems that extend from a level below a top surface of the support structure. The photovoltaic panels may be spaced apart to permit drainage through a resilient bed, and the resilient bed is porous. The photovoltaic panels may include cells embedded or encapsulated in polymer to form a unitary ruggedized unit. The simulated grass may include tufts attached to a web layer that is separate from the support structure, for allowing the web layer and tufts to be replaced separately from the support structure. The collector may include a sheet, screen, mesh, or veil fixed above the photovoltaic panels and below the support structure, and the sheet, screen, mesh, or veil is may optionally be tinted, translucent, and/or perforated. 
         [0005]    A system in accordance with one or more exemplary embodiments of the present invention may include an array of solar collectors in accordance with one or more exemplary embodiments of the present invention, arranged in a sports stadium or other open field. 
         [0006]    A component for a functional ground system in accordance with one or more exemplary embodiments of the present invention may include an artificial turf structure including simulated grass and an open support structure capable of supporting human foot traffic, the artificial turf structure overlying a resilient bed supporting light emitting panels, the open support structure permitting at least 30% of light from the light emitting panels to pass through the artificial turf structure. The support structure may be a truss layer of polymer or polyurethane, or both. The simulated grass may include tufts supported on stems that extend from a level below a top surface of the support structure. The simulated grass may include tufts of transparent material supported on stems that extend from a level below a top surface of the support structure. The light emitting panels may be spaced apart to permit drainage through the resilient bed, and the resilient bed may be porous. The light emitting panels may include cells embedded or encapsulated in polymer to form a unitary ruggedized unit. 
         [0007]    A device in accordance with one or more exemplary embodiments of the present invention that include a photovoltaic panel, may include the photovoltaic panel such that the photovoltaic panel is oriented to maximize an amount of captured light responsively to a latitude. The turf structure support members may be angled responsively to an average direction of the sun at an installation latitude. 
         [0008]    A method for efficiently harvesting solar energy in accordance with one or more exemplary embodiments of the present invention may include placing an array of solar collectors in a sports stadium or other open field, each solar collector including an artificial turf structure including simulated grass and an open support structure capable of supporting human foot traffic, the artificial turf structure overlying a resilient bed supporting photovoltaic panels; transmitting from the open support structure to the photovoltaic panels at least 30% of light falling on the structure at incident angles of 30 degrees from the artificial turf surface normal; and converting the light transmitted to the photovoltaic panels to electricity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The utility, objects, features and advantages of the disclosed subject matter will be readily appreciated and understood from consideration of the following detailed description of the embodiments of this disclosed subject matter, when taken with the accompanying drawings, in which same numbered elements are identical. 
           [0010]      FIG. 1  shows a cross-section of a portion of an artificial turf structure according to an embodiment of the disclosed subject matter and illustrating features that may be combined with those of other embodiments. 
           [0011]      FIG. 2  shows a cross-section of a portion of an artificial turf structure according to another embodiment of the disclosed subject matter and illustrating features that may be combined with those of other embodiments. 
           [0012]      FIG. 3  shows a cross-section of a portion of an artificial turf structure according to yet another embodiment of the disclosed subject matter and illustrating features that may be combined with those of other embodiments. 
           [0013]      FIG. 4  shows a porous bed with wells for functional panels according to an embodiment of the disclosed subject matter. 
           [0014]      FIG. 5  shows functional panels arranged in the wells of the porous bed of  FIG. 4  according to an embodiment of the disclosed subject matter. 
           [0015]      FIG. 6  shows a completed artificial turf structure according to an embodiment of the disclosed subject matter. 
           [0016]      FIG. 7  shows a top of view of artificial turf modules with irregular boundaries according to an embodiment of the disclosed subject matter. 
           [0017]      FIG. 8  shows a cross-section of a portion of an artificial turf structure according to yet another embodiment of the disclosed subject matter and illustrating features that may be combined with those of other embodiments. 
           [0018]      FIG. 9  shows another embodiment of an artificial turf structure which may be used with any of the embodiments. 
           [0019]      FIGS. 10 and 11  show a portion of an artificial turf structure according to an embodiment of the disclosed subject matter and illustrating features that may be combined with those of other embodiments, with  FIG. 10  showing a cross section and  FIG. 11  showing a plan view of a supporting portion of the structure of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Referring to  FIG. 1 , a solar collecting artificial turf structure  100  has a porous bed  102  of resilient material that supports encapsulated functional panels  104  arranged in an array. Overlying the panels  104  and bed  102  is a simulated turf mat  101 . The turf mat  101  includes an open lattice mat  108  with attached blade tufts  106  which simulate grass. The blade tufts  106  may be welded to, for example, or otherwise attached to the lattice mat  108 . The lattice mat can be configured to provide support for foot traffic and resist shear and wear due to downward pressure from foot traffic. By arranging the blade tufts  106  within the open lattice mat  108 , the lattice mat can protect the blade tufts  106  to a large degree and ensure the blade tufts remain erect to simulate natural or live grass. The open structure of the lattice mat  108  allows a good proportion of incident light to pass through to the functional panels  104  positioned below the lattice mat. 
         [0021]    The functional panels  104  may include solar collectors (e.g. photovoltaic cells and panels) or light-emitting devices such as lamps, photodiodes or light-emitting diode (LED) arrays. They may include multiple types of functional panels  104  among other types including light and/or pressure sensors, voltage regulators, control panels, voltage boosters, inverters, rectifiers, transformers, voltage and/or current regulators or energy storage devices such as batteries, ultracapacitors, etc. The functional panels  104  may also include communications devices such as wireless relay stations or wireless control devices. The functional panels are preferably ruggedized by enclosing in polymer boxes or encapsulating in a resin block. 
         [0022]    In an exemplary embodiment, the functional panels  104  are arranged in an array covering a recreational field or landscape such as a football field, golf course, or baseball field. In this embodiment, the functional panels  104  may be mostly photovoltaic converters that are interconnected by a suitable mechanism. Other functional panels  104  may provide electrical service functions such as voltage regulation, safety switching, insolation measurement, and other functions. The turf mat  101  protects the functional panels  104  by distributing impact and/or pressure over a wide area of the functional panels. The turf mat  101  is configured into a truss-like structure of resilient material that bends under impact and deforms under shear and pressure loading followed by recovery. The functional panels  104  are further protected by being fitted into the porous bed  102 . 
         [0023]    The blade tufts  106  and the open lattice mat  108  can be formed of a polymer. The blade tufts  106  are preferably formed of a material that allows transmittance of as much solar energy as possible. For example, they may be transparent with a tint to give the appearance of grass. The blade tufts and open lattice mat may also be coated with UV-screening material and be fitted with optimally sited optical elements that can modify the turf appearance or scatter/direct light onto the photovoltaic elements beneath. In embodiments in which at least some of the functional panels  104  include photovoltaic converters, the tinting may be selected to pass light of a range of wavelengths that best overlaps the range of wavelengths over which the photovoltaic converter is most efficient. The blade tufts  106  may also be configured with a minimum number/density of blades required to provide the desired appearance. Preferably, the open lattice  108  is of a material that matches the blade tufts  106  in appearance. The open lattice and blade tufts may also have properties that provide yield and springiness of the turf. 
         [0024]    The porous bed  102  may be of any suitable material such as, for example, material used in modern playgrounds. For example, elastomers such as sintered shredded rubber waste (e.g. tires), open cell foam, or an open truss-structure may be used. Referring for the moment to  FIG. 4 , the porous bed  102  may be laid down and simultaneously molded with recesses  180  impressed therein. Busses  172  or other kinds of wiring such as signal wiring or cabling, appropriately insulated, may be laid down in the porous bed  102 . Anchor points  184  may be distributed as required for securing the lattice mat  108 . Then, as illustrated in  FIG. 5 , the functional panels  104  are then laid down into the recesses  180  and as necessary, interconnected or connected to a buss  172 . In order to avoid a bluish appearance of the turf from such an open structure (since for example, silicon cells can have a blue shiny appearance), panels may be encapsulated or covered with materials having a greenish tint. As shown in  FIG. 6 , the lattice mat  108  may then be laid over the functional panels and anchored to the anchor points  184 . 
         [0025]    The open lattice  108  may include spokes  110  of a strong and resilient material with low creep. For example, polyurethane, polyethylene, polypropylene, rubber and the like. The structure of the spokes may be designed to provide resistance to shear and a yield that mimics natural turf. The truss-like structure of the open lattice  108  may be configured to permit as much light to pass through it as possible, with consideration of a wide range of apparent angles of the sun during the course of a day. For example, the spokes  110  may be near vertical and have a low aspect ratio in cross-section. Alternatively, the spokes may be flat but their primary surface may be aligned in the North-South direction to ensure that the sunlight is minimally blocked during midday. 
         [0026]    Referring now to  FIG. 2 , a solar collecting artificial turf structure  120  also has a porous bed  102  of resilient material that supports encapsulated functional panels  104  as in the embodiment of  FIG. 1 . The present embodiment shows features that may be combined with any of the features of the other embodiments. For example, on top of, and overlying the panels  104  and bed  102 , a simulated turf mat  121  has an open lattice mat  128  with a non-flat surface  116 . The surface  116  may improve the purchase of athletes using the artificial turf structure  120 , thus increasing the ability to apply or exert power against the turf during athletic activity. The undulations in the surface  116  may be regular or irregular and may include dense (high frequency) components (not shown) to ensure that the top surface has desired properties in terms of its appearance and mechanical performance, in addition to, or instead of gradual undulations. 
         [0027]    The blade tufts  112  may be welded to, for example, or otherwise attached to the open lattice mat  128 . As above, by arranging the blade tufts  112  within the open lattice mat  128 , the latter can protect the blade tufts  112  to a large degree and ensure that the latter remain erect to simulate real or natural grass. Another feature shown in  FIG. 2  is that the blade tufts  112  are attached to a web  114  which is separate from the open lattice mat  128 . This may allow the web  114  and blade tufts  112  to be replaced separately from the open lattice mat  128 . The web  114  may include a thin tinted or translucent sheet, screen, mesh or veil with periodically located drain holes if necessary, that allows for water drainage and avoids dust or dirt collecting on the panels below. The web could be maintained and cleaned for relatively minimal cost. 
         [0028]    Referring now to  FIG. 3 , a solar collecting artificial turf structure  140  also has a porous bed  102  of resilient material that supports encapsulated functional panels  104  as in the embodiments of  FIGS. 1 and 2 . The present embodiment shows features that may be combined with any of the features of the other embodiments. Blade tufts  134  are attached onto stems  132 . This configuration can provide a greater open area below the top  143  and surface  116 , while providing a similar appearance as viewed from the top  143  of the open lattice mat  128 . 
         [0029]    The artificial turf structures shown above may be made from modules that are tiled or fit together to form a macroturf structure. In an exemplary embodiment, the modules may be configured with irregular boundaries as indicated at  100  in  FIG. 7  to give an installed system a more natural appearance. Alternatively, the modules may be configured with varying geometric boundaries (not shown) to give an installed system a specific patterned or logo-based appearance. 
         [0030]    Additional layers may be provided in an installed system according to suitable methods and structures. For example, a gravel, limestone or supplementary elastomeric bed may be installed to support the porous bed  102 . Drainage conduits may be provided within or beneath the gravel bed. Also, power and communications wiring may be provided below the porous bed  102 . Electrical components may be provided outside the array of functional panels  104  such as terminals, junction boxes, controllers, inverters, voltage boosters, and monitoring systems. 
         [0031]    Referring now to  FIG. 8 , another feature that may be combined with any of the foregoing embodiments, or replace features thereof, is a blade tuft support  192  that stems from a level above the base of the open lattice mat  196 . The support  192  may support blade tufts (e.g.,  194 ) as in any of the foregoing embodiments. The blade tufts can be shortened as needed to ensure a proper fit within the artificial turf structure  190 . 
         [0032]    In other exemplary embodiments (not shown), blade tufts may stem from the top of an open lattice mat. For example, as shown in  FIG. 9 , tufts  234  may be integral or attached to an open lattice  238 . In this embodiment, the tufts maybe form a mat or tile that is attached to the open lattice. 
         [0033]    Referring to  FIGS. 10 and 11 , the artificial turf support  220  has vertical  222  and horizontal  224  supports forming square sections (aligned horizontally and extending into the plane of the page so that they intersect as a line with the plane of the page of  FIG. 1  and as viewed from above in  FIG. 11 ) closed by a mesh or screen  226 . The mesh or screen  226  supports an open lattice mat  202 . The lattice mat  202  has truss elements  218  that are shaped and angled to minimize blocking of light when oriented appropriately. A variety of structures may be devised to satisfy the condition of low light blocking with sun angle, and various tradeoffs may be employed in optimizing their shape and orientation for different climates, latitudes, and desired functional criteria to be optimized. 
         [0034]    As in previous embodiments, blade tufts  204  may be provided as a separate mat or may be made integral to the open lattice mat  202 . A porous supporting bed  212  made, for example, of gravel may be provided. Conventional methods and structures may be employed as are suitable to provide for drainage and solid support. Functional panels  208 , for example photovoltaic panels, can be supported and oriented by a panel support  210 . The panel support  210  may include a porous bed as discussed in other embodiments. Since the support  220  is able to handle the load applied to the artificial turf structure  200 , the panel support  210  may also be a lightweight molded support such as, for example, a vacuum molded tray. The functional panel  208  may be covered by a clear cover  206 . Gutters  216  may also be provided and drain holes as required may be provided in the panel support  210 . The support  220  may have triangulation provided by additional structural members according to suitable devices for forming support structures. 
         [0035]    In another embodiment (not shown) the open lattice mat may not have horizontal stringers (such as that indicated at  198 ) and may include only upwardly directed pillars. Spokes may be arranged in any suitable fashion to create a desired support and performance. In further embodiments, the open lattice mats may be transparent or translucent as are the blade tufts. In yet other embodiments, the blade tufts may be sufficiently sparse that they may be opaque (e.g. being formed of an opaque material or coated with an opaque substance). 
         [0036]    Bladed tufts may be attached by welding, weaving, or other suitable securement means. The tufts may have round cross-sections or other cross-section shapes, and may have a cross-section that differs from that of natural turf blades. The components may be formed as modular units, as tiles, as rolls, or as large mats as desired. Where components are in abutting arrangement, they may be interconnected by any suitable mechanism such as, for example, by clips, studs, a continuous polymer seam such as on a baseball, or screw, rivet, nut and bolt, or other fasteners with appropriate interlinking bosses stemming from the components, such as the open lattice mat, the blade tuft mat, the support structure (support  220  in  FIG. 10 ), etc. 
         [0037]    In exemplary embodiments, the functional panels may be photovoltaic panels or modules between 10 and 30 cm square or alternatively, rectangular with edges in the range of 10 to 30 cm. Such sizes are illustrative only and not intended to be limiting of the scope of the claimed invention. In exemplary embodiments, the functional panels include individual cells providing typically 0.5V and 2 W in full unshaded sunlight or up to 5 W at 12V in larger sized panels such as 30 cm×30 cm. Preferably, the aggregate efficiency of the artificial turf structure is at least 5% at peak solar conditions. This may be achieved using photovoltaic cells having 15% efficiency with the artificial turf above the functional panels permitting passage of about a third of the solar light in cases where the incoming light forms an angle of 30 degrees from the vertical or the top surface normal (e.g., incident angle for horizontal surface). Alternatively, lower cost cells/panels with lower efficiencies may be used. 
         [0038]    Potential applications for the artificial turf embodiments include golf courses, football stadiums, parks, highway mediums, open-air theaters including stage and seating/walking areas, sport fields, parking lots, sidewalks, driveways, residential landscaping and other applications. Functional panels that include light-emitting devices may be used to generate digital displays and light shows, for example at sports stadiums. 
         [0039]    It will be apparent to those skilled in the art that various changes may be made in the above-described embodiments of the present invention. However, the scope of the present invention should be determined by the following claims.