Abstract:
A rugged, long lasting, transparent housing of a domed shape protects an embedded solar panel. More particularly, the solar panel is embedded in a polymer in a utilized, potted construction. The use of polyurethane as the polymer produces a durable product which is transparent and resistant to both thermal and mechanical stresses. The domed top over the solar panel improves the solar panel&#39;s ability to capture light and thus to operate in locations where the incidence of light is at a low angle as is found in northern latitudes.

Description:
FIELD OF THE TECHNOLOGY  
       [0001]     This invention relates generally to durable solar panel capsules that encapsulate solar panels, that provide protection and enhance the solar generation of electricity in conditions where light is incident at low angles to the plane of the solar panel. More particularly, the solar panel is embedded in a polymer in a unitized, potted construction. The use of polyurethane as the polymer produces a durable product that is transparent and resistant to both thermal and mechanical stresses. The solar panel capsule is formed with a generally convex or domed top to improve the panel&#39;s ability to capture light, to facilitate run-off of rain and debris, and to deflect glancing blows.  
       BACKGROUND  
       [0002]     Solar panels are widely used as a convenient and portable supply of electricity. The planar photovoltaic devices in such panels usually comprise a planar array of interconnected delicate semiconductor wafers. Typical wafers generate approximately one-half volt each, and may be connected either serially or in parallel to supply voltages and currents of selected magnitudes.  
         [0003]     In conjunction with a rechargeable battery, solar panels are now used as power sources in locations that would otherwise be difficult to service with electric power. For example, solar panels are an ideal choice for marine, highway or road construction warning signs or lamps, as they do not require the installation of electric power cable and they can be left unattended for long periods of time.  
         [0004]     In many situations, lights attached to batteries powered by solar panels are used for hazard warnings. The public at large come to rely on them and, in the event of failure, the consequences may be very serious. The solar panel assemblies used in these situations need to be reliable.  
         [0005]     To maximize the amount of electricity generated, solar panels are oriented towards the sun; the plane of the wafer array is preferably generally perpendicular to the angle of incidence of the light striking the solar panel. However, where solar panels are left unattended in locations prone to vandalism or they are installed by unskilled personnel or are mounted on a moving object such as a boat or a buoy, it may be impractical to keep the panel pointed at the sun The best that can be done is to have the solar panel face generally upwards towards the sky or towards the expected location of the sun or of the best source of ambient light.  
         [0006]     To be effective in more northerly latitudes or where the sun is otherwise low in the sky, solar panels must make efficient use of the modest amounts of light available. A number of known techniques are used to achieve this:  
         [0007]     (1) Mirrors or lenses are used to capture a relatively large proportion of the available light and direct it onto the solar panel.  
         [0008]     (2) Air gaps and sharp changes in refractive index where materials meet are avoided so that incident light is not reflected away. This problem can be particularly severe where the solar panel is in a location where the sun is low in the sky.  
         [0009]     (3) The materials through which the light passes are selected to be highly transparent, and the path length through lossy material is kept to a minimum.  
         [0010]     (4) The surface of the solar panel is kept free of dust, debris and bird faeces.  
         [0011]     (5) Software and electronics are dedicated to the task of making best use of the energy available.  
         [0012]     The solar panels and the devices they power need to be durable when they are placed in remote locations or are required to operate reliably under difficult conditions. Once installed, they should last without attention for as long as possible—certainly for several years. For example, such devices can be expected to be subject to: 
        mechanical stresses (from vibration, wind or rough handling);     thermal stresses (from extreme temperatures or large fluctuations in temperature);     corrosion (at sea or in industrial applications);     erosion (from wind or water borne particulates); or     vandalism in some locations.        
 
         [0018]     The following patents issued in the United States each address some of the above design challenges:  
         [0019]     (1) U.S. Pat. No. 4,759,735—“Solar cell powered beacon”, Pagnol and others, 1988. 
        The Pagnol design places the solar cells near the outside of a caisson which assists in light capture but leaves the solar panel vulnerable to accidental damage and abuse from vandals. The geometry provides no assistance in gathering light in low-light situations and a centrally placed lamp casts a shadow over a portion of the solar panel.        
 
         [0021]     (2) U.S. Pat. No. 4,999,060—“Solar cell packaging assembly for self-contained light”, Szekely and others, 1991. 
        Szekely describes a packaging assembly suitable for a “light peg” with a flat solar panel and an air gap between the cover and the solar cells. The flatness of the panel make this device unsuitable for use in locations where there is not plenty of illumination from above. The interface between the air gap and the exterior cover forms a surface at which there is a sharp change in refractive index. At low angles of incidence this causes much of the light to be reflected away.        
 
         [0023]     (3) U.S. Pat. No. 5,680,033 “Solar powered warning device”, Cha, 1997. 
        This warning device makes use of a dome-shaped upper surface and a focusing effect to capture extra light. However, it has a hollow casing with an air cavity that may cause reflection of light arriving at low angles of incidence. The case is not of a unitized construction and can thus be expected to be less durable and more prone to failure from mechanical stress        
 
         [0025]     (4) U.S. Pat. No. 4,626,852 “Buoy lantern system”, Dodge, 1986. 
        This lantern has several moving parts and seals. Over time these are bound to deteriorate, allowing seawater to enter and the light to fail. An air gap between the domed cover and the solar cells will cause reflection of incident light at low angles of incidence.        
 
         [0027]     A number of issued patents include descriptions of methods or selections of materials for embedding the fragile solar cell wafers in an encapsulant material. For example, U.S. Pat. No. 4,097,308 (Klein et al.), U.S. Pat. No. 4,224,081 (Kawamura et al.), U.S. Pat. No. 4,380,038 (Anderson et al.), U.S. Pat. No. 4,383,129 (Gupta et al.), U.S. Pat. No. 4,578,526 (Nakano et al.), U.S. Pat. No. 4,625,070 (Berman et al.), U.S. Pat. No. 4,633,032 (Oido et al.), U.S. Pat. No. 4,869,755 (Huschka et al.), U.S. Pat. No. 5,008,062 (Anderson et al.), U.S. Pat. No. 5,252,139 (Schmitt et al.), U.S. Pat. No. 5,252,141 (Inoue et al.), U.S. Pat. No. 5,743,970 (Czubatjy et al.), U.S. Pat. No. 6,114,046 (Hanoka) and U.S. Pat. No. 6,204,443 B1 (Kiso et al.) all disclose methods for protecting solar cells by encapsulation or sandwiching in a flat planar configuration. Such arrangements are of limited utility in more challenging environments, as flat panels must be securely mounted to face the sun. Flat panels of this sort are frequently mounted in frames of the sort shown in U.S. Pat. No. 4,633,032 (Oido et al.). Such frames form a rim which is itself a source of mechanical failure, leakage and debris build-up. Flat panels of this sort are more prone to breakage from vandalism  
         [0028]     In U.S. Pat. No. 5,782,552, Green et al. disclose a light assembly that has its solar panel encapsulated in a potting material with an exterior protective cover. The solar panel is disposed at the top and near the surface of the light assembly. In this position the solar panel suffers from the following problems: 
        the delicate solar cells are near the surface of the assembly and accordingly are subject to damage from shock (vandals) or from thermal stress;     as the solar panel faces upwards, it is unable to capture light at low angles of incidence; and     the exterior protective shell can delaminate from the potting material, causing a gap that reflects light away.        
 
         [0032]     In U.S. Pat. No. 6,013,985, Green et al. disclose a solar-powered light assembly that is permanently sealed using a potted construction. This provides a rugged construction but does not disclose any features, such as a domed upper surface, that make these lamps suitable for low ambient light conditions.  
       SUMMARY OF THE INVENTION  
       [0033]     The object of the present invention is to provide a rugged, durable and reliable solar powered generator in a unitized construction that can be potted with other components to provide a sealed device that is able to resist mechanical and thermal stress and which is able to operate in unfavourable conditions of low ambient light or in northern latitudes. The present invention so provides by potting (embedding) the solar panel in a polymer in a unitized structure that may aptly be termed a capsule. The preferred use of polyurethane as the polymer produces a durable product that is transparent and resistant to both thermal and mechanical stresses. The solar panel capsule is formed with a generally convex or domed top to improve the panel&#39;s ability to capture light, to facilitate run-off of rain and debris, and to deflect glancing blows.  
         [0034]     The preferred embodiment of the invention is an integrated assembly having:  
         [0035]     (1) A conventional solar panel disposed as a planar array of planar wafers mounted on a non-conducting backing, with electrically conductive connections between the wafers and electrically conductive terminal connections for delivering electric power from the entire solar panel when it is illuminated. 
        The selection of the solar panel is governed by conventional factors. A number of suitable solar panel products are available from manufacturers such as Siemens Corporation or BP Solarex Inc.        
 
         [0037]     (2) A capsule for the solar panel made of transparent polymer material composed of a two-part clear aliphatic urethane compound available commercially and manifesting the following desirable characteristics after curing: 
        (a) a Shore hardness index of 45-55;     (b) resistance to abrasion and impact down to −20° F. (for representative temperate zone use);     (c) over a suitable projected lifetime measured in years, no significant surface deterioration, increase in hardness, shrinkage or noticeable color or gloss change after exposure to ultra-violet light or heat;     (d) no surface corrosion after exposure to salt spray, detergents, aliphatic hydrocarbons, denatured alcohol or gasoline;     (e) no discoloration or swelling after exposure to solutions of 5% potassium hydroxide, 5% sodium chloride, 5% potassium chloride, 20% sulphuric acid and 20% hydrochloric acid (these solutions and strengths being considered representative of the greatest expected chemically corrosive exposures).     (f) minimal loss of transmitted light by absorption of the encapsulating material;     (g) a slippery surface to reduce the adhesion of dirt and dust;     (h) a solid mass both hard enough to withstand the cutting action of a knife and resilient enough to absorb the energy of a hammer blow;     (i) low susceptibility to stresses arising from the expansion of the mass with heat which may cause buckling of the solar panel or the tearing apart of the electric connections between the wafers;     (j) strong, permanent bonding to the solar panel so that no delamination occurs under conditions of thermal stress caused by high temperatures or wide fluctuations in temperature.        
 
         [0048]     The preferred process of manufacturing the solar panel capsule is as follows: The solar wafer array and associated electrical connectors are first embedded in a thin layer of the selected polymer material. This step creates a lightly encapsulated solar panel that is protected by the polymer envelope during the remainder of the manufacturing process. The curing of the polymer material is preferably done in a vacuum with heat to encourage bubbles of air to expand and rise to the surface. Due to the high surface tension of the polymer material, some of the bubbles do not burst of their own accord and as many of them as practically possible are eliminated, as by pricking with a pin. This procedure is repeated until the encapsulant material is hardened and acceptably free of bubbles.  
         [0049]     Next, the solar panel and, optionally, connecting portions of the traffic warning lamp assembly (conveniently, the connecting portions may be brackets attached to or integral with a housing for the battery or other electrical storage device and associated electrical components, herein referred to as a “component housing”) are immersed in a thick mass of transparent, non-conducting, liquid polymeric material contained in a suitably shaped mold. The material used should preferably be the same as that used for the envelope formed around the solar wafer array. The material is solidified by a polymerization reaction (“potting”) around the solar panel. The mold is shaped with a concave surface that produces in the finished capsule a convex and preferably a domed surface of the mass of polymer material over the solar panel, so that the domed surface acts as a lens capturing a large amount of the light available and refracting it onto the solar panel. The amount of curvature of the domed surface can be varied to suit different locations.  
         [0050]     A solar panel capsule of the foregoing sort may be conveniently incorporated into a traffic warning lamp assembly or the like. In such assembly, the component housing, preferably shaped approximately as a cylinder, may house batteries, lamp mountings and connections, and other electronic components (e.g. a microcontroller for timing the commencement and duration of the ON cycles of the lamp). The component housing may be joined to the solar panel by immersing a connecting bracket fixed to a selected end of the component housing in the liquid polymer material and then curing the polymer material at room temperature. The component housing is left open while components such as batteries, control circuits, microcontrollers and lamps are suitably mounted. Preferably, the component housing is closed either with a tight fitting cover held in place by tamper proof screws or by securing a closing cover to the open end of the component housing using the polymer material and curing to hardness.  
         [0051]     In a further embodiment, the component housing contains a microprocessor and communications software so that the operation of the device may be controlled by a hand-held computer such as a Palm Pilot™.  
         [0052]     In a further embodiment, reinforcement means such as rods, wire or a lattice of material are embedded in the liquid polymer material prior to curing to provide stiffening and strengthening of one or more walls of the component housing or of a cantilevered flange or the like whereby the component housing is joined to the solar panel. The choice of material for such reinforcement means is governed by conventional factors and depends on the geometry of the finished product and the stresses it is likely to bear.  
         [0053]     In a further embodiment, the solar panel capsule potted together with the component housing is integrated into a container such as a bollard. The solar panel capsule is mounted by conventional means in an aperture made in the upper surface of the bollard. The contours and profile of the outer layer of the solar panel capsule generally merge with the contours and profile of the adjacent portion of the upper surface of the bollard in the vicinity of the solar panel capsule. The curvature of the domed surface over the solar panel is carefully controlled to match that of the bollard as closely as reasonably and economically possible where they meet so as to further increase resistance to vandals and to promote run-off of dust, debris and rain.  
         [0054]     A number of advantages may accrue if the construction of the solar panel capsule is integrated with the construction of the lamp housing, component housing, or other structure in or on which the capsule is mounted.  
         [0055]     For example, the translucent lamp cover may in some cases be advantageously be bonded to the solar panel capsule during the capsule molding process so that the capsule and lamp cover form essentially a single integral bonded piece. If the lamp is to shine in all directions, then the translucent lamp cover may be formed as a hollow cylinder with a peripheral surface shaped for advantageous beam dispersion in accordance with conventional lamp cover design, and the cylinder may be closed at one end by the capsule, forming an integral extension of the cylindrical lamp cover during the molding process, one end of the lamp cover being inserted into the liquid polymer before it is cured to form the capsule. Assuming that the lamp will be mounted so that the cylindrical axis is approximately vertical and that the capsule will be positioned at the top of the integral unit, the peripheral surface of the cylindrical lamp cover is desirably inset slightly from the capsule, forming an annular margin on the underside of the capsule. This annular margin may facilitate mounting of the unit in a housing, and the overhang of the capsule margin relative to the inset generally cylindrical surface of the lamp cover may also help to deflect spray and debris from the lamp cover.  
         [0056]     Further, in many cases it is desirable to integrate the design of the capsule with the design of the lamp housing or component housing on or in which the capsule is to be mounted.  
         [0057]     For example, assuming that the capsule will be positioned at the top of a lamp housing so as to be able to capture a maximum amount of ambient light, and assuming that the upper surface of the solar panel capsule has a generally convex or dome shape, it may be desirable to conform the shape of the upper surface of the solar panel capsule to the general shape of the top surface of the lamp housing, or vice versa.  
         [0058]     If, for example, vandalism is a potentially serious problem, the upper surface of the lamp housing could be generally cylindrical, or similarly arcuate in two dimensions, and could be provided with protruding arcuate protective ribs following the curvature of the housing, the ribs being positioned on either side of the solar panel capsule. The solar panel capsule in that event would be desirably formed to have a generally cylindrical or similarly convex upper surface conforming generally to the upper cylindrical surface of the lamp housing and extending upwardly to a lesser extent than the ribs. The ribs should be positioned offset from the edges of the capsule so as not to interfere with capture of ambient light and not to interfere with run-off of rain and debris from the upper surface of the capsule, but should be sufficiently close to the capsule that they tend to accept the full force of a blow aimed in the general direction of the upper surface of the capsule.  
         [0059]     If on the other hand, capsule surface cleanliness is of major concern, a dome shape or other similar convex surface of revolution can advantageously be used for the upper surface of the capsule, thereby promoting run-off in all directions.  
         [0060]     The manner of mounting the solar panel capsule in the housing also merits careful attention. In many case, the solar panel capsule will be mounted in a mating aperture in the housing. Overlap of the margin of the housing aperture by the capsule edges may be desirable to facilitate run-off of water and debris, in which case the capsule is desirably formed with a marginal undersurface forming a shoulder, the downwardly depending capsule extension fitting more or less snugly into the aperture, and the entire margin of the aperture is overlain and shielded by the capsule margin. Note that a peripheral undersurface margin on the capsule may alternatively be provided by forming the capsule with a completely flat undersurface and embedding into the capsule when it is formed connecting flanges or the like for connecting the capsule to the top of the housing, which flanges may be inset from the capsule periphery, thereby making available the desired marginal undersurface of the capsule so that the capsule margin may overlap the housing aperture. On the other hand, if vandalism is of serious concern, it may be desirable to have the capsule slightly depressed relative to the upper surface of the housing so that the upper surface of the housing takes the brunt of any blow directed generally at the capsule. Note that depressing the capsule relative to the upper surface of the housing may have a deleterious effect on light capture by the solar panel.  
         [0061]     A design trade-off frequently has to be made between serving the objective of facilitating cleanliness and run-off, the objective of maximizing ambient light capture, and the objective of deterring and surviving attacks by vandals. Take for example the choice of the type and degree of the curvature of the upper surface of the solar panel capsule. A short radius of curvature tends to promote run-off and cleanliness. A long radius of curvature tends to promote light capture and may facilitate integration of the capsule profile with the profile of the housing in which the capsule is mounted, especially if the capsule upper surface is not formed as a surface of revolution but rather is generally cylindrical, matching a generally cylindrical housing upper surface. The designer should take into account the applicable environmental factors in the location in which the solar-powered lamp is to be installed, and make a balanced judgment about the design; the design should in many cases be empirically evaluated over a period of years and modified as required if found to be inadequate to meet the demands of particular circumstances.  
         [0062]     While various types of lamp are used as examples in this specification, it is to be understood that the capsule design according to the invention is suitable for use with many types of solar-powered devices, including warning sirens or bells, illuminated information displays, clocks, etc. 
     
    
     SUMMARY OF THE DRAWINGS  
       [0063]      FIG. 1  is a schematic elevation cross-section view of a polymer-encapsulated solar panel, which may be further encapsulated in a capsule of the sort illustrated in  FIG. 2 .  
         [0064]      FIG. 2  is a schematic elevation cross-section view of a mold holding liquid polymer material in which is embedded a solar panel (shown inverted relative to its orientation in  FIG. 1 ) and a portion of a component housing.  
         [0065]      FIG. 3  is a schematic elevation cross-section view of a solar panel capsule potted with a component housing.  
         [0066]      FIG. 4  is a simplified schematic side elevation view of a representative solar-powered traffic warning lamp incorporating a solar panel capsule according to the invention, of the sort formed pursuant to the technique illustrated by reference to  FIG. 2 .  
         [0067]      FIG. 5  is a schematic side elevation view, in section, of a traffic hazard warning lamp with an integrated solar panel capsule made in accordance with the present invention.  
         [0068]      FIG. 6  is an isometric view of the traffic hazard warning lamp illustrated in  FIG. 5 .  
         [0069]      FIG. 7  is an exploded simplified isometric view of a traffic warning lamp of the sort illustrated in  FIG. 6 , as mounted in a traffic bollard.  
         [0070]      FIG. 8  is an isometric view of the traffic warning lamp of  FIG. 6  mounted in a traffic bollard as illustrated in  FIG. 7 .  
         [0071]      FIG. 9  is an exploded simplified isometric view of a traffic warning lamp for use as a crosswalk indicator warning device. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0072]      FIG. 1  shows a cross-section of a solar panel which is a component of the preferred embodiment and is generally indicated as  1 . Within a polymeric cover  5 , planar photovoltaic wafers  2  are mounted by means of spaced adhesive layer deposits  4  to a non-conducting planar backing sheet  8 . The wafers  2 , adhesive mounts  4 , and backing sheet  8  may be selected from among suitable known conventional such items. Electric connections  3  are made between the photovoltaic wafers  2  with solder or other suitable material. Terminal electrical connections are made by attaching electrical wires  6 ,  7  to regions of positive and negative charge on the photovoltaic wafers  2  so as to provide a source of electric power. These wires  6 ,  7  may be connected to a storage device (not shown) such as a battery. When the photovoltaic wafers  2  are illuminated, they supply power to the storage device.  
         [0073]     To manufacture the solar panel  1 , a layer of initially liquid polymer is poured over the photovoltaic wafers  2 , the adhesive  4 , the electric connections  3  and the proximal portions of the terminal electric connections  6 ,  7  so as to cover them. The liquid polymer is cured to hardness at approximately 50° C. in a vacuum, leaving all of the foregoing items sealed within the solid polymer cover layer  5 , from which connecting wires  6  and  7  protrude for connection to the storage device. Bubbles of air expand and rise to the surface where they burst either unaided or with a pin prick.  
         [0074]      FIG. 2  shows a cross-section of the mold and casting arrangement suitable to produce the preferred embodiment of the capsule illustrated in  FIG. 3 . The mold  9  is shaped so as to make a casting with a smooth domed surface. Molds of different shapes and depths can be selected to provide different amounts of material mass and curvature in the finished assembly. The mold  9  is filled with liquid polymer  10  in which is embedded a solar panel  1  of the sort depicted in  FIG. 1  and the wall extension, connecting bracket or flange, or other suitable joining element  12  of a component housing  11 . The liquid polymer is cured to hardness slowly, typically at room temperature for two days, so that the material mass cures hard and free from striations and defects.  
         [0075]     The resulting solar panel capsule  13 , along with embedded connecting flanges  12  for fixing the capsule  13  to the component housing  11  is illustrated in section in  FIG. 3 . The capsule  13  completely surrounds and shields the solar panel  1  of  FIG. 1 , which no longer is identifiable as such, since its polymeric cover layer  5  has completely merged into and bonded to the encapsulating polymeric material of the solar panel capsule  13 , which material, to avoid delamination, should be identical to the material of the solar panel cover layer  5  of  FIG. 1 .  
         [0076]      FIG. 4  shows a side elevation view, partially in section of a traffic hazard warning light  14 , which is one particular embodiment of a complete solar powered lamp assembly constructed in accordance with the invention. Note that the overall configuration and layout, apart from the capsule  13  and its contents, is generally conventional. A solar panel capsule  13  containing a solar panel  1  and the upper portion of a component housing  11  are fastened together by the potting technique described above and illustrated in  FIGS. 1, 2  and  3 . Flanges  12  (as shown in  FIG. 3 ), formed as an extension of the component housing  11 , ensure that the component housing  11  is fastened securely with an airtight seal to the solar panel capsule  13 . The resulting traffic hazard warning light benefits from having a solar panel capsule:  
         [0077]     (1) with a dome shape as this provides a lens effect so that a large portion of the incident light striking the dome is directed to the solar panel  1 ;  
         [0078]     (2) which is formed without a rim to minimize the build up of debris and dust on the surface;  
         [0079]     (3) with a slippery surface to render it unsuitable as a perch for wildlife and to minimize the build-up of debris and dust on the surface;  
         [0080]     (4) of a durable composition resistant to impact and vibrational stresses;  
         [0081]     (5) which is optically clear; and  
         [0082]     (6) which is resistant to thermal deformation which would otherwise cause buckling and tearing of the solar panel or delamination in the region immediately above the solar panel.  
         [0083]     Electrical power generated in the solar panel  1  is conducted to components, typically first to a storage device and thence to other possible components within the component housing  11  and to the lamp (not specifically illustrated). The lamp may be held in the component housing  11  by means of suitable attachment brackets or an attachment socket to which are attached conventional electrical conductors (not shown). A lamp housing  15  with a conventional reflective interior surface is attached by conventional means to the component housing  11 . One or more light emitting diodes or other suitable light sources (not shown) are mounted inside the lamp housing  15  by conventional means and are connected electrically to power generated from the solar panel  1  through an electric storage device and/or other components mounted in the component housing  13 . A translucent lamp cover  16  is mounted by conventional means to the lamp housing  15 . The hazard warning light  14  may be suitably mounted by conventional means, an example of which is shown in  FIG. 3  as two protruding bolts  17 .  
         [0084]      FIGS. 5 and 6  show an alternative embodiment of a traffic hazard warning light displaying additional features to those described above and illustrated in  FIGS. 3 and 4 . An enhanced traffic hazard warning light  19  is shown as a cross section of a side elevation in  FIG. 6 . The enhanced traffic hazard warning light  19  is as described above for the traffic hazard warning light numbered  14  in  FIG. 4  with the following improvements:  
         [0085]     (1) A solar panel capsule  13  extends over a lamp housing  15  and a lamp cover  16  to provide additional shelter from the elements and wildlife for the lamp housing  15  and the lamp cover  16 .  
         [0086]     (2) The solar panel capsule  13  has bevelled edges to lessen the chance of chipping at the periphery from rough handling.  
         [0087]     (3) As the solar panel capsule  13  extends beyond the support provided by the walls of the component housing  11  there is an increased susceptibility to damage from pressure applied to the extreme edge of the solar panel capsule  13 . To counter this, a lattice of wires  18 , comprised of wire of a suitable gauge, suitably woven in a rectangular pattern, the number of wires per unit length and width of which will be dependent in part upon the gauge of wire chosen, is welded by conventional means to the upper ends of the component housing walls  12  and immersed in the liquid polymer  10  (as shown in  FIG. 2 ) prior to curing. Note that this embedding of the reinforcement lattice  18  in the capsule  13  is novel and not found in prior traffic warning light designs.  
         [0088]      FIG. 7  shows an exploded view of an illuminated bollard ( FIG. 8 ) for controlling the flow of traffic, which bollard is a further particular embodiment of a complete solar powered lamp assembly constructed in accordance with the invention. The bollard  21  houses and displays a translucent traffic information sign (here exemplified as a left pointing arrow)  20  which is suitably illuminated from behind by a selected LED or other suitable source of light. A traffic hazard lamp of the type illustrated as lamp  19  in  FIGS. 5 and 6  and described above is mounted by conventional means within a lamp housing  23  which is attached by conventional means to a stand  24  so that the illuminated traffic information sign  20  is at a suitable height to be visible to motorists. The traffic hazard lamp  19  illuminates the traffic information sign  20 . The perimeter of the solar panel capsule  13  is fitted closely into an aperture  22  in the lamp housing  23  so that a watertight seal is made. Various conventional means are used to seal the perimeter solar panel capsule  13  into the aperture  22 . ( FIG. 8  deliberately exaggerates the gap between the solar panel capsule  13  and the edges of the lamp housing aperture  22 . A practical design goal is to minimize that gap.)  
         [0089]     The curvature of the upper surfaces of the solar panel capsule  13  and the lamp housing  23  are selected to balance the objectives of facilitating cleanliness and run-off, which is improved with a steeper higher dome shape, against the objectives of maximizing ambient light capture and deterring and minimizing the effects of attacks by vandals, which are facilitated by having a lower profile which more closely matches that of the surrounding surface. The exact shape is determined by prevailing conditions and expectations in the location where the bollard is to be installed. In all cases, the transition area between the solar panel capsule  13  and the lamp housing  23  is smooth to promote run-off and reduce the build up of debris.  
         [0090]      FIG. 9  shows an exploded view of a crosswalk indicator for controlling the flow of traffic at a crosswalk which is a further particular embodiment of a complete solar powered lamp assembly constructed in accordance with the invention. The crosswalk indicator is shown generally as  25  and comprises:  
         [0091]     (1) a lamp housing  32  having a flange  33  formed across the width of the housing at the top and at right angles to the rear wall of such housing;  
         [0092]     (2) a front cover  30  in which are provided two apertures  31 ;  
         [0093]     (3) two translucent lamp covers  29 , each of which is mounted into one of the apertures  31  and is securely fastened to make a watertight seal by conventional means to the lamp housing  30 ;  
         [0094]     (4) two LED lamps  28 , one or more rechargeable storage batteries  27  and control circuitry  26  all mounted within the lamp housing, the location of the LED lamps being selected so that the LED lamps are close to and directly behind the lamp covers  29 ;  
         [0095]     (5) a solar panel capsule  13  which is potted together with the flange  33  by encapsulation in liquid polymer and curing to hardness;  
         [0096]     (6) terminal electrical connections ( 7  in  FIG. 1 ) from the solar panel (not shown) which pass through holes in the backing sheet of the solar panel and into the interior of the lamp housing where they connect to the rechargeable storage batteries  27 ; and  
         [0097]     (7) electrical connections (not shown) between the rechargeable storage batteries  27 , the control circuitry  26  and the LED lamps  28 .  
         [0098]     The front cover  30  mates with and is fastened to the lamp housing  32  by conventional means and sealed against penetration by water or air.  
         [0099]     The control circuitry  26  employs a conventionally available microcontroller such as the Mototrola PIC 16F873, to monitor the state of the batteries and control at what times of the day the crosswalk indicator is to be activated. The control circuitry has a conventionally available infra-red coupling device, such as a Seiko S8270 AFE, which allows programming instructions or control parameters to be downloaded from hand held devices such as a Handspring™ or a television remote control unit. This has the advantage that the crosswalk indicator does not need to be opened to set a revised illumination schedule thus prolonging the life and maintaining the quality of the seals employed.  
         [0100]     When activated, the microcontroller operates the LED lamps as a “wagger” wherein the two LED lamps  28  are alternately illuminated; when the first lamp is on, the second is off and vice versa.  
         [0101]     When either of the LED lamps is powered on, the control circuitry makes the lamp flicker at a frequency designed to both improve visibility and save electrical energy.  
         [0102]     Much of the detail of the operation of the lamps per se is either conventional or a matter of straightforward design; see Applicant&#39;s previous U.S. Pat. No. 6,013,985.  
         [0103]     The scope of the invention is not limited to the specific embodiments illustrated and described herein but is governed by the appended claims.