Abstract:
An enhanced solar heating device comprising multiple arrays of lenses enclosed in a housing configured to receive solar rays and concentrate the rays into multiple hot spots located on the outer surface of a water conduit is disclosed. The solar ray collection system is supplemented by a reflector attachment used to increase the solar light fed into the device. The water conduit is configured with multiple sections to increase exposure to solar light and increased surface area for formation of hot focal points.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to a solar heating device for heating water. More specifically, the present invention relates to arrays of lenses configured for concentrating solar rays into a plurality of focal points disposed on the surfaces of water conducting tubes to enhance the water heating capacity of the device. 
       BACKGROUND OF THE INVENTION 
       [0002]    Solar heating systems for heating water circulating through pipes achieved through focusing the sun&#39;s rays onto the surface of the pipes is well known in the art. A fair number of prior art references teach magnifying lenses and arrays of magnifying lenses arranged to collect solar rays and configured such that focal points formed by these rays and lenses fall on the surfaces of water conducting pipes. The focal points concentrate the solar rays onto the surfaces of these pipes causing the surfaces of these pipes to heat up. The pipes and the magnifying lens arrays may be contained inside a housing configured to reduce heat losses to the environment. This is illustrated in the examples below. 
         [0003]    U.S. Pat. No. 1,672,750 discloses sections of lenses enclosed inside a housing arranged at different angles positioned to direct sunlight through a receptacle containing water. 
         [0004]    Likewise U.S. Pat. No. 2,277,311 provides a lens construction for picking up the sun&#39;s rays from various angles and for concentrating and intensifying them onto a confined area containing water. 
         [0005]    U.S. Pat. No. 4,319,560 relates to a solar heating system comprising a heat accumulating structure for heating both air and water in which both the heated air and water are directed to an object to be heated such as a commercial building or private residence. The heat accumulating structure is below ground and includes a magnifying glass forming the roof thereof and protruding above ground, the magnifying glass concentrating the rays of the sun into the heat accumulating structure which includes a lower portion containing water and an air space there above. The solar heating system includes a piping arrangement whereby heated water can be directed to the object to be heated and piped away. 
         [0006]    U.S. Pat. No. 4,601,282 describes an automatic solar collector system useful for heating and storing a heating fluid such as, for example, water. The automatic solar collector system of this invention is characterized by its construction including a photo cell-actuated hydraulic cylinder whereby the collector panel may be positioned at an angle to focus the sun&#39;s rays onto the fluid conduit disposed within the collector panel. Overall operation of the automatic solar collector system of this invention is regulated by a clock timer, and the entire system is essentially self-contained so that it may easily be moved from one location to another, or put in parts to be attached to a home or a building with the tank and controls below the roof. 
         [0007]    U.S. Pat. No. 4,611,576 refers to an automatic solar collector system useful for heating and storing a heating fluid such as, for example, water. The automatic solar collector system of this invention is characterized by its construction including a photo cell-actuated hydraulic cylinder whereby the collector panel may be positioned at an angle to focus the sun&#39;s rays onto the fluid conduit disposed within the collector panel. Overall operation of the automatic solar collector system of this invention is regulated by a clock timer, and the entire system is essentially self-contained so that it may easily be moved from one location to another, or put in parts to be attached to a home or a building with the tank and controls below the roof. 
         [0008]    U.S. Pat. No. 5,143,051 is for an apparatus for heating of a body of water. The collector includes a housing formed with an interior cavity containing aluminum oxide crystals in communication with collector tubes extending orthogonally downwardly relative to the housing also filled with the aluminum oxide crystals. A lens assembly plate is mounted above the cavity, with the lens assembly including a matrix of magnification lens members coextensively directed throughout the plate above the cavity. 
         [0009]    U.S. Pat. No. 5,941,239 discloses a multiple lens solar heating unit consisting of a piping component, a housing component with a transparent housing cap, holes within the housing component for entry and exit of the piping component, multiple lens mounting braces affixed parallel wise to inner walling of the housing component, a plurality of external lens holders mounted to the braces by mounting pins and rotatably pivotable in an XY plane, an equivalent plurality of internal lens holders mounted one each to each external lens holder by mounting pins and rotatably pivotable in an XZ plane and an equivalent plurality of magnifying lens mounted one each within each internal lens holder. 
         [0010]    U.S. Pat. No. 6,630,622 teaches an apparatus for converting solar energy to thermal and electrical energy including a photovoltaic grid for converting the concentrated solar energy into electrical energy mounted on a copper plate that provides even temperature dispersion across the plate and acts as a thermal radiator when the apparatus is used in the radiant cooling mode; and a plurality of interconnected heat transfer tubes located within the enclosure and disposed on the plane below the copper plate but conductively coupled to the copper plate for converting the solar energy to thermal energy in a fluid disposed within the heat transfer tubes. Fresnel lenses are affixed to the apparatus on mountings for concentrating the solar energy on to the photovoltaic grid and functioning as a passive solar tracker. 
         [0011]    A configuration of a single array of lenses forms focal points that concentrate the heat produced by these focal points only through the center points of each lens. The number of such focal points is therefore limited by the space between lens centers. Additionally, where the magnifying lenses are circular or oval in shape, the joining of the lenses creates gaps between the lenses that allow light to pass through without producing additional focal points. For these reasons, a single array of lenses does not efficiently utilize solar light for heating in a given space configuration. 
         [0012]    U.S. Pat. No. 2,277,311 describes a lens made of an upper bulb and a lower bulb. The upper bulbs are convex and are used to intercept the rays of the sun irrespective of their angle of the sun. These condensing lenses act to concentrate the heat effect from the sun&#39;s rays and direct the rays to the lower bulbs. The lower bulbs are also convex but are offset relative to the upper bulbs and therefore act as diffusing bulbs. Thus, although a second array of lenses is added, the disclosure in this prior art reference does not solve the problem of achieving only a limited number of focal points in a given space. 
       SUMMARY OF THE PRESENT INVENTION 
       [0013]    The present invention provides a solar heating device comprised of multiple arrays of lenses enclosed in a housing configured to collect solar rays and concentrate the rays into multiple hot spots located on the outer surface of a water conduit. The heat from these spots is transferred to water circulating through the conduit. The number of heat producing focal points formed on the water conduit by solar rays passing through multiple arrays of lenses is significantly higher compared to the number provided by a single array. 
         [0014]    It is therefore the object of the present invention to provide a high capacity solar heating device configured to efficiently utilize existing space. 
         [0015]    In an aspect of the present invention, a solar device for heating circulating water comprises: a housing having a bottom, side walls having an inner portion and an outer portion, the housing also containing a substantially transparent top; a water conduit system disposed on the bottom of the housing, the water conduit system having an inlet and an outlet; a first planar array of magnifying lenses that is substantially parallel with the bottom of the housing, the first planar array of magnifying lenses being disposed between the transparent top and the water conduit system; and a second planar array of magnifying lenses that is substantially parallel with the bottom of the housing, the second planar array of magnifying lenses being disposed between the first planar array of magnifying lenses and the water conduit system. 
         [0016]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, descriptions and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a top view of the lens array assembly according to an embodiment of the present invention; 
           [0018]      FIG. 2  is an illustration of a focal point pattern formed by solar rays propagating through a lens according to an embodiment of the present invention; 
           [0019]      FIG. 2A  is a depiction of the lens dimensions that affect the formation of the focal lengths according to an embodiment of the present invention; 
           [0020]      FIG. 3  is an illustration of focal point formation by multiple arrays of lenses according to an embodiment of the present invention; 
           [0021]      FIG. 4  is a cross sectional side view of the solar heating device having four planar arrays of lenses according to an embodiment of the present invention; 
           [0022]      FIG. 5  is a top exploded view of the solar heating device having three planar arrays of lenses and enclosed water circulating tubes according to an embodiment of the present invention; 
           [0023]      FIG. 6  is a top exploded view of the solar heating device having four planar arrays of lenses according to an embodiment of the present invention; 
           [0024]      FIG. 7  is a side exploded view of the solar heating device having four planar arrays of lenses according to an embodiment of the present invention; 
           [0025]      FIG. 8  is a side exploded view of the solar heating device having four planar arrays of lenses and enclosed water circulating tubes according to an embodiment of the present invention; and 
           [0026]      FIG. 9  is an illustration of the path of a solar ray entering the lens system of the device as shown in  FIG. 4  through the reflector attachment according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
         [0028]    The present invention relates to a device for heating water circulating through pipes that may be used in a number of applications such as domestic water heating, indoor and outdoor pool water heating and industrial water heating. 
         [0029]    The device comprises of three systems: 1) a solar ray collection system configured for providing solar energy to be converted to heat, 2) a solar ray processing system for concentrating the solar energy into multiple focal points, and 3) a system for efficiently transferring the heat produced by the solar rays to heat water in a water conduit system that winds through the device. 
         [0030]    In the preferred embodiment of the present invention, all three systems are enclosed in a rectangular shaped housing having a bottom, four side walls and a top. The top is transparent allowing solar light to enter the housing. In order to minimize heat losses to the environment, it would be desirable to limit the size of the housing. This however necessitates the efficient utilization of the available space in the housing for converting solar energy to heat. The design of the present invention provides enhanced solar light input into the housing. It also provides for a system of lenses for concentrating the light into multiple focal points that produce heat that may be transferred to the water. The water conduit contains a floor section and four side wall sections having enhanced length and surface area to allow for high exposure time of the water to the heat from the focal points. Each focal point provides an additional heating source for the water and contributes to the increase in water temperature. 
         [0031]    The preferred embodiment for the solar ray processing system comprises three or four planar arrays of magnifying lenses; however, two arrays as well as more than four also fall within the scope of the present invention. In this context, each planar array is constructed with circular or oval lenses attached to three or four adjacent magnifying lenses, depending on the location of the lenses, such that the lenses in each array substantially define an x-y plane. The arrays are preferably disposed in parallel with the bottom of the housing and with each other; however non parallel arrangements also fall within the scope of the present invention. 
         [0032]    Each array is supported by a frame attached to the side walls of the housing. The frames may be installed on railings attached to the side walls of the housing and adapted to slide alongside the inside of the walls. The arrays may be separated from each other by a distance determined by the characteristics of the lenses as described below. 
         [0033]    A magnifying lens is typically characterized by the shape of the top and bottom surfaces, refractive index, and the radii of curvature of the top and bottom surfaces. A magnifying lens is further characterized by an optical center which is the point where light passes through the lens in a straight line and is not bent by the lens. The shape of the lenses in the thickness, or z-direction, which is perpendicular to the arrays&#39; x-y plane may be convex or concave. The index of refraction typically varies from about 1 to about 2. The most common types of magnifying lenses used for concentrating solar rays and most suitable in the context of the present invention are ordinary convex glass lenses and Fresnel lenses. 
         [0034]    In an embodiment of the present invention, three or four planar arrays of convex lenses are disposed in parallel with the bottom of the housing. Each array is separated from the next array by a distance ranging from about 1 inch to about 12 inches depending on the design of the device and the characteristics of the lenses. In order for each lens to form a focal point on the surfaces of the water conduit tubes which are in a fixed position, the focal lengths of each array of lenses must be progressively smaller going from the higher to the lower magnifying glass arrays. To accomplish this, the arrays of lenses may be configured according to the equation used for calculating the focal length of a convex lens as follows: 
         [0000]    
       
         
           
             
               
                 1 
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             , 
           
         
       
     
         [0035]    Where: 
         [0036]    f is the focal length of the lens, 
         [0037]    n is the refractive index of the lens material, 
         [0038]    R 1  is the radius of curvature of the lens surface closest to the light source, 
         [0039]    R 2  is the radius of curvature of the lens surface farthest from the light source, and 
         [0040]    d is the thickness of the lens (the distance along the lens axis between the two surface vertices). 
         [0041]    Lens thicknesses, in the range of about 0.1 to about 0.5 inches, are typically small relative to the radii of curvature that may range between about 4 inches to about 12 inches. The refractive index of a lens ranges typically between 1 and 2. For this configuration, the equation simplifies to: 
         [0000]    
       
         
           
             
               1 
               f 
             
             ≈ 
             
               
                 
                   ( 
                   
                     n 
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         [0042]    The table below illustrates exemplary combinations of refractive indexes and radii of curvature which produce decreasing focal lengths for the first through the fourth array of lenses. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 R2, inches 
                 R1, inches 
                 n, dimensionless 
                 f, inches 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 First array 
                 4 
                 2.4 
                 1.4 
                 15 
               
               
                 Second array 
                 4.4 
                 3 
                 1.7 
                 13.5 
               
               
                 Third array 
                 4.4 
                 2.9 
                 1.7 
                 12.2 
               
               
                 Forth array 
                 4.5 
                 2.8 
                 1.7 
                 10.6 
               
               
                   
               
             
          
         
       
     
         [0043]    Thus, arranging the arrays of lenses such that their respective lens centers are positioned approximately 15 inches, 13.5 inches, 12.2 inches and 10.6 inches respectively from the surface of the water tubes produces focal points from each of the four arrays. 
         [0044]    It will be understood to those skilled in the art that multiple combinations of refractive indexes and radii of curvature values may be used to vary the focal length of the lens. Small adjustments that allow more accurately pinpointing the focal points onto the desired spots on the water tubes may be made by moving the frames of the lens arrays along the side walls of the housing. 
         [0045]    As a general rule, solar rays projected onto the x-y plane of a convex magnifying lens&#39; top surface form a focal point at a distance below the bottom surface of the lens determined by the characteristics of the lens and a line passing through the center of the lens and perpendicular to the lens x-y plane. Other lenses placed between the center of a lens and the location of its focal point do not impede the formation of the focal point except if the ray line passes through two lens centers. Thus it would be desirable to design the lens arrays such that the lineup of any two lens centers is minimized. 
         [0046]    In a preferred embodiment of the present invention, the lengths, or radii in case of circular or oval shaped lenses, of the lenses in any array are equal and are progressively smaller going from the first array to the fourth array. This configuration minimizes lens center overlap and generally provides at least one lens center in the path of light passing through gaps in the lens arrays. 
         [0047]    The present invention is illustrated in  FIGS. 1-9 . The solar heating device  10  is enclosed in a housing  15  of rectangular shape having a top  22 . Four arrays of magnifying lenses are disposed inside the housing  15 . The first array of magnifying lenses  11  that is closest to the top has the longest lenses. The arrays of lenses below the first array include the second array  14 , the third array  17  and the fourth array  29 . The radii of the lenses of each of the successive arrays below the first array have progressively smaller magnifying lenses. Except for the end lenses, each lens in the arrays is attached to four adjacent lenses at four points in its circumference. Alternatively, the lens edges may be combined using edge holders. In a top view of the lens system  20  shown inside the housing  15  in  FIG. 1 , the top array of circular lenses  11  has gaps between the lenses that are filled by the lower arrays  14  and  17 . Thus light passing through these gaps is picked up by magnifying lenses from the lower arrays which then form additional focal points.  FIG. 2  shows the formation of focal points by solar rays passing through convex magnifying lenses.  FIG. 2A  shows the dimensions of a convex lens. If the bottom surface radius of curvature R 2  of the magnifying lens is equal to or greater than that of the top surface, a focal point is formed below the bottom surface of the lens.  FIG. 3  illustrates the formation of additional focal points by adding arrays of magnifying lenses below that of the first array. The end lenses in each array are held by frames  23  as shown in  FIGS. 4 and 6 . Also shown are the inlet  27  to the water conduit system and the outlet  33 . The water conduit comprises a floor section  37  and a side wall section  21 . A pole  34  attached to the bottom of the housing  15  provides pivot capability to tilt the housing in the direction of the sun. A handle  35  may also be attached to the housing  15  that allows for convenient transportation of the device  10  as needed. The reflector surface attachment  44  comprises a first reflecting surface  32  angled outwardly relative to the top  22  of the housing  15  for collecting the solar light and reflecting it onto the second surface  31  angled inwardly relative to the top  22  of the housing  15  for reflecting the rays into the housing  15 . 
         [0048]    The side wall section of the water conduit system provides additional surface area for focal point and heat formation that enhance water temperature. The geometry of the reflector is such that the reflected rays are directed substantially to form focal points on the side wall section  21  of the water conduit system.  FIG. 9  shows a path for an incidental ray  39  collected by the first reflecting surface  32  and reflected through the second surface  31  onto the side wall section  21  of the water conduit. A transparent enclosure  25  shown in  FIGS. 5 and 8  enclosing water conduit system helps keep the heat generated by the focal points from dissipating away from the water tubes. 
         [0049]    It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention.