Patent Publication Number: US-2015068586-A1

Title: Array of Photovoltaic Cells

Description:
RELATED APPLICATIONS 
     This application is a divisional application of pending U.S. patent application Ser. No. 13/434,837 entitled S OLAR  E NERGY  H ARVESTING AND  S TORAGE  S YSTEM  filed on 29 Mar. 2012 and claims priority of and is related to U.S. Provisional Application 61/469,031 entitled S OLAR  C OLLECTOR AND  S YSTEM FOR  S PATIAL AND  S PECTRAL  C ONCENTRATION OF  S OLAR  P OWER  filed on 29 Mar. 2011, having common inventors and a common assignee, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to field of solar energy and solar collectors and more particularly relates to the efficient spatial and spectral concentration of sunlight throughout daily and seasonal changes. 
     BACKGROUND 
     Communities and individual electrical power users located in cold climates comprise more than twenty-five percent of the North American population. In adverse weather during the months of winter, late fall, early spring months, the availability of electrical power is both a productivity and life-critical requirement and the energy supply chains are vulnerable. Unless long distance power transmission lines are both available and operating, isolated users in northern latitudinal climates depend on fossil fuel generators and stored fuel supplies. Transportation costs for getting fossil fuel into these isolated areas results in high energy costs. Community power organizations and larger end users require installations with continuous average power availability ranging between ten kilowatts for the average single home in the United States in 2006 and ten megawatts representing the legislative limit for many community power distribution cooperatives. 
     Farmers, small rural communities, local power distribution cooperatives and firms in cold climates have increased regulatory and contractual capability for small-scale, renewable power generation. Industrial and military programs must meet power needs of isolated bases without the dangerous trucking and shipment of high volatility fossil fuels. National Science Foundation (NSF) efforts in Antarctica and comparable places now rely on seasonal fuel deliveries at great expense. 
     Conventional renewable energy alternatives to fossil fuel generators depend on water flow, wind or solar illumination. Water flow, hydroelectric power, is cost effective when the users are at a reasonable distance from hydro-power generators so that long distance transmission lines are not required. In cold climates, seasonal variations in the sun&#39;s angle range nearly ninety degrees from just below the horizon to nearly overhead. A stationary lens with convex optical properties is not able to effectively concentrate light. If wind and solar energy are the primary and not the supplementary source of energy, there is the risk of not being able to meet instantaneous power demands. Wind power, moreover, loses efficiency when scaling down, imposes undesirable noise when sited close to load centers, and takes a toll on avian wildlife, preventing implementation on some migratory routes. 
     Solar energy using collectors having thin film cells reduce cost but at the expense of efficiency and area required. Techniques for high efficiency solar cells are known in niche industries such as earth-orbiting spacecraft but at significant cost premium. 
     Communities and electrical power users in cold climates would benefit from solar power systems suited to their climate if the life-cycle cost of continuous power from such renewable sources was cost efficient. Contemporary solar power systems have focused on warm and sunny climates such as the US southwest and Iberia. Such systems lack the conversion efficiency, environmental hardening and long term storage capability needed to provide primary power supply when communities in cold climates most need electrical power. 
     SUMMARY 
     The embodiments of a solar energy harvesting and storage system incorporates a dual-sided solar cell that efficiently harnesses wide swaths of solar bandwidth with a lithographically integrated DC to AC inverter. The embodiments described herein improve on existing solar collectors on: (1) the energy per unit area; (2) the energy per unit cost; (3) long term system durability; and (4) providing integrated wireless data and telephony capability. Energy per unit area is enhanced by harvesting more of the light spectrum and maximizing conversion efficiency for a given wavelength. Many deployment situations have limited land or roof space. Such situations often benefit from generating maximum energy from the available area. Even where land or roof area is abundant, larger deployments consume more structural elements and longer power cables. Even if area is unrestricted, cost seldom is. Greater energy per unit cost is achieved using techniques including concentration of light, use of dual-sided solar cells and making the most efficient use of expensive III/V compounds. Long term durability is enhanced through techniques such as a robust solar tracker, use of dual-sided steel rather than fragile silicon wafers and integration of the solar cell with the DC to AC inverter on a common substrata electrode. The embodiments described herein achieve long term durability and lower cost of operation/maintenance to make solar energy a more attractive energy option. 
     Integrated wireless and data telephony within the panel assembly both improves long term maintainability and facilitates use of panel assemblies in areas lacking physical infrastructure, time or experienced installers. Such enhanced functionality reduces the barrier to deployment of solar energy. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of the major components of the solar energy harvesting and storage system as described herein. It is suggested that  FIG. 1  be printed on the face of the patent. 
         FIG. 2  is a block diagram of a direct solar operating mode of the solar energy harvesting and storage system. 
         FIG. 3  is a block diagram of a supplemented solar operating mode of the solar energy harvesting and storage system. 
         FIG. 4  is a block diagram of a stored energy solar operating mode of the solar energy harvesting and storage system. 
         FIG. 5  is a structural diagram of the light-to electrical energy converter in accordance with an embodiment described herein. 
         FIG. 6  is an illustration of a dual-sided solar cell in accordance with an embodiment described herein. 
         FIG. 7  describes the flow process of seed layer deposition in the creation of the photovoltaic solar cell in accordance with an embodiment described herein. 
         FIG. 8  is an illustration of the semiconductor junction structure of the photovoltaic solar cell in accordance with an embodiment described herein. 
         FIG. 9  is a flow chart of the selection optical fill process. 
         FIG. 10  is a side view of the solar panel assembly in accordance with an embodiment described herein. 
         FIG. 11  is an end view of the solar panel assembly in accordance with an embodiment described herein. 
         FIG. 12  is a plan view of the solar panel assembly in accordance with an embodiment described herein. 
         FIG. 13  is a block diagram of an integrated DC to AC converter in accordance with an embodiment described herein. 
     
    
    
     DETAILED DESCRIPTION 
     These embodiments will best be understood when viewing the FIGS. along with the detail description provided herewith. With reference to  FIG. 1 , a block diagram of the architecture of the solar energy harvesting and storage system  80  is shown. The solar energy harvesting and storage system  80  comprises a plurality of solar panel assemblies  130  connected on a power bus  210  to a persistent energy storage  160 , supplementary energy sources  240 , digital control  180 , an electrical energy distribution interface  170  from which power is distributed to electrical energy consumers(s)  190 . Digital control  180  is connected to the various components, such as the DC to AC inverters  220 , supplementary energy sources  230 , persistent energy storage  160 , the electrical energy distribution interface  170  through a control bus  230 . 
     Although two panel assemblies  130  are shown, preferably there are more panel assemblies, up to hundreds or more, in the solar energy harvesting and storage system  80 . Each panel assembly  130  comprises a light-to-electrical energy converter  110  connected to the power bus  210  and to a DC to AC inverter  220 , also connected to the power bus  210  and the control bus  230 . The panel assembly  130  may also have a wireless base station  200 , also connected to the power bus  210 . The light-to-electrical energy converter  110 , the DC to AC inverter  220  and the wireless base station  200  are mounted on a two axis passive solar tracker  100 . 
     Persistent energy storage  160  retains energy during periods where limited solar illumination does not provide sufficient energy from the light-to-electrical energy converter  110 . Numerous forms of chemical (battery) and thermal storage are known. However most economical alternatives reported in the literature or in common commercial use suffer from use of expensive, hazardous materials as well as leakage. Leakage reduces the energy stored over time. Current adequate design options for the persistent energy storage exist, but are suboptimal. 
     Supplementary energy sources  240  are included to reduce dependence on persistent energy storage  160 . Examples of supplementary energy sources  240  include wind, geothermal, hydro and even conventional sources such as fossil fuel or nuclear. Hybrid installations may share components such as the persistent energy store  160 , DC to AC inverter  220 , electrical energy distribution interface  170  and transmission line assets. 
     The electrical energy distribution interface  170  attaches energy generated by the solar energy harvesting and storage system  80  to local or national scale power grids. The electrical energy distribution interface  170  insures that voltage, frequency and phase of the solar power matches that of the power distribution system; local generation and grid power are isolated from one another; and that the relative flow of energy may be measured and reported for economic reasons. Techniques for implementing such an electrical energy distribution are well understood, commercially available from many vendors and already installed in numerous installations ranging from local fossil fuel generators to alternative energy production facilities. 
     Digital control  180  is required to coordinate and implement functionality among the components of the solar energy harvesting and storage system  80 . Among the functions of digital control  180  are: consistent maintenance of voltage, frequency and phase; ensuring adequate power source; recognition of developing failures and reporting for timely maintenance; partitioning of failed components from the power bus  210  and control bus  230  and economic analysis and reporting. The digital control system  180  is commonly implemented in many situations for industrial control. A wireless control link that could be primary or a backup, requires a wireless base station  200  within the digital control  180 . 
     The solar energy harvesting and storage system  80  has at least three operating modes, whose block diagrams are shown in  FIGS. 2-4 . In a direct solar operating mode shown in  FIG. 2 , incident solar energy is received in the light to electrical energy converter  110 , as shown in block  260 . In block  264 , the photons of the solar energy are converted to electrical energy as direct current within the light to electrical energy converter  110 . The generated DC energy can be transmitted directly over the power bus  210  and stored in persistent energy storage  160 . In addition, the integrated DC to AC inverter  220  converts the direct current energy into alternating current at a voltage, frequency and phase set in the digital control  180  and transmitted on the control bus  230 , as shown in block  268 . In block  272 , the AC electrical energy is transmitted over the power bus  210  to an electrical energy distribution interface  170 . In block  276 , the electrical energy is distributed through the electrical energy distribution interface  170  to energy consumers  190 . 
     An additional operating mode of the solar energy harvesting and storage system  80  is shown in  FIG. 3 . In the supplemented solar operating mode shown in  FIG. 3 , incident solar energy is received in the light to electrical energy converter  110 , as shown in block  260 . In block  264 , the photons of the solar energy are converted to electrical energy as direct current within the light to electrical energy converter  110 . The generated DC energy can be transmitted directly over the power bus  210  and stored in persistent energy storage  160 . The integrated DC to AC inverter  220  converts the direct current energy into alternating current at a voltage, frequency and phase set in the digital control  180  and transmitted on the control bus  230 , as shown in block  268 . In block  272 , the AC electrical energy is transmitted over the power bus  210  to an electrical energy distribution interface  170 . If necessary or desired, supplemental energy from either the persistent energy storage  170  and/or from the supplementary energy sources  240  are also combined with the AC electrical energy output from the DC to AC inverters  220  to maintain a desired voltage, frequency and phase determined by the digital control  180 . As in other operating modes, in block  276 , the electrical energy is distributed through the electrical energy distribution interface  170  to energy consumers  190 . 
       FIG. 4  is a block diagram of the stored energy operating mode of the solar energy harvesting and storage system  80 . Block  320  shows that direct current energy is supplied from the persistent energy storage  160  and/or the supplementary energy sources  240 . The DC to AC inverter  220  converts the direct current energy into alternating current at a voltage, frequency and phase set in the digital control  180  and transmitted on the control bus  230 , as shown in block  268 . In block  272 , the AC electrical energy is transmitted over the power bus  210  to an electrical energy distribution interface  170 . As in other operating modes, in block  276 , the electrical energy is distributed through the electrical energy distribution interface  170  to energy consumers  190 . 
       FIG. 5  is a structural diagram of the light-to-electrical energy converter  110 . The light-to-electrical energy converter  110  receives incident sunlight, concentrates the solar energy and then focuses the solar energy onto a photovoltaic cell for conversion to DC energy. Within a sealed housing (not shown) of aluminum, steel, plastic, or other rigid and durable material is a bent or angular “corrugated” zig-zag structural element  528  forming spaces above  540  and spaces below  550  the bent structural element  528 . The bent structural element  528  may be metal, resin, and other materials sufficient to provide rigid support in varying weather and light conditions. Extending normal or near normal from a planar surface at the troughs of the bent structural element  528  and bisecting the upper space is an arrangement of a plurality of photovoltaic cells  516  electrically connected via a common electrode  535  to another similar arrangement of photovoltaic cells  516 . In typical solar cell construction the silicon substrata represents a significant cost element. Replacing silicon wafers with a common electrode  536  enables both use of a potentially less expensive substrata and doubling area coverage of the substrata or common electrode  536 . 
     At the crests of the bent structural element  528  are pads  512  to eliminate or reduce vibration and mechanical stresses on the bent structural element  528 . The light-to-electrical energy converter  110  can be assembled in at least three configurations. As a first configuration, the photovoltaic cells  515  are assembled on both sides of the common electrode  536  as shown. A second configuration having two single-sided cells simplifies manufacture. A third configuration is that the photovoltaic element  516  is formed on a single side of a conventional wafer using traditional solar cell mounting technology. 
     Mounted in the housing and positioned on the pads  512  is a cover glass  504  having an optional plurality of convex lenses  508  that are spaced with respect to each other and positioned above the bent structural element  528  to focus light onto a reflective or focusing element  524  on the angular sides of the bent structural element  528 . The convex lenses  508  can be formed by masking, etching, molding or grinding. Light received through the convex lenses  508  is directed to the reflective or focusing element  528  that receives and concentrates the light. The cover glass  504  or other suitable material is selected to have good optical transmission properties throughout the widest range of frequencies at which the sun emits optical and near-optical radiation. An anti-reflective coating  500  may be applied to the cover glass  504 . Similarly, an anti-reflective coating, if applied, should have similar optical qualities and may be applied to the cover glass  504  by deposition techniques. In one embodiment, microphotoetched metals can be used instead of a holographic anti-reflective film. In another instance, neither existing wafer technology nor thin films are used. 
     Use of a double-sided common electrode  536  as shown, however, requires introduction of a reflective or focusing element  524 . There are many different ways to fabricate the reflective or focusing element  524 . Glass mirrors, although very stable, tend to be fragile and are subject to degradation of the reflective material. Various plastic materials are more robust to physical stress, weigh less but are more subject to degradation over time. When the bent structural element  528  is metallic, forming a grating directly in the structural element  528  reduces material and assembly cost while having the potential for high durability. Filling the solar energy producing void  540  with an inert gas such as nitrogen further reduces degradation of the reflective surface. In addition, plating material may be applied over the reflective or focusing element  524  to inhibit oxidation and retain high reflectivity over time. The reflective or focusing element  524  can either be used directly as a mirror or ruled to construct a grating that will focus as well as reflect the incident light. By focusing the light, the area covered by the photovoltaic cells  516  is reduced. The increased optical concentration, however, also increases heating. Excess heat can degrade the photovoltaic cells  516  or the DC to AC inverters  220  over time. 
     The spaces  540  above the bent structural element  528  into which the reflective or focusing element  524  and the photovoltaic cells  516  extend may be filled with an inert gas such as dry nitrogen to minimize condensation, corrosion and other degeneration; The spaces  550  below the bent structural element  528  towards the power bus  210  may be void or may be filled other matter useful for wireless base station operation or internal persistent energy storage  532 . 
     Integrated with the array of photovoltaic cells  650  and the common electrode  536  are DC to AC inverters  220  to convert the DC electrical energy generated by the photovoltaic cells  650  into AC energy. The DC to AC inverters  220  connected to the photovoltaic cells  650  provide control and distributed DC to AC conversion to a high frequency multiple of the line frequency and carefully controlled phase. Incorporating DC to AC inverters  220  directly into the photovoltaic cells  650  provides advantages. Because the inverters  220  are distributed throughout the installation, concentrated heat and low-frequency noise generated as with conventional inverters are prevented—an important safety feature, especially in close proximity to human-occupied areas, flammable ground cover or roofing material. The distributed DC to AC inverters  220  yield alternating current output at voltage levels consistent with semiconductor device voltages and frequencies that are a multiple of and in-phase with the power distribution frequencies of the power grids. 
     The DC to AC inverters  220  are also electrically connected to the power bus  210  and to the control bus  230 . The common electrode  516  which extends upward from the trough of the bent structural element  528  is electrically connected to power bus  210  for the transmission of DC electrical energy generated by the photovoltaic cells  516 . Control bus  230  is also electrically connected to the light-to-electrical energy converter  110  and/or the internal persistent energy store  160 . 
     Circuit technology for implementing various kinds of DC to AC inverters is known in the literature. Conventional switching regulators, producing a square wave, are efficient and easily implemented but are incompatible with some kinds of equipment using electrical energy. Sine wave and modified sine wave converters are more complex but increasingly required for unrestricted end use compatibility. 
     Innovatively, the DC to AC inverters  220  are lithographically formed directly on the same substrata as the photovoltaic cells  516 . Techniques for lithographically forming resistors, small capacitors, inductors and transistors are well known and commonly implemented by industry, such as monolithic point of load regulators offered by firms such as National Semiconductor and Linear Devices. Integrating the photovoltaic cells  516  with the DC and AC inverters  220  requires additional processing layers but reduces the assembly required, reduces cost and most importantly eliminates solder or other junctions between the common electrode and discrete devices. Large capacitors, insulators and comparable components are also major sources of failure eliminated by this integrative approach. By distributing the DC to AC inverters  220  throughout the array, heat from the inverters helps to melt snow and ice which may otherwise form on the anti-reflective coating during periods when limited solar illumination allows surface temperature to drop. 
       FIG. 6  is a structural diagram of the photovoltaic cells  516  of the light to electrical energy converter  110 . Light reflected from the reflective or focusing element  524  is incident upon the arrangement of photovoltaic cells  516 . Eight photovoltaic cells  516  are illustrated but in actuality tens, hundreds, or thousands photovoltaic cells can be robotically manufactured to obtain efficiencies of scale and wired in series/parallel with isolating switches. Although illustrated as two linear arrays each having four photovoltaic cells  650 , the photovoltaic cells  650  may be arranged in a two-dimensional array, preferably of up to 256 or more photovoltaic cells per array. Each photovoltaic cell  516  has a convex lens  620  on the order of approximately one centimeter to focus incoming light toward a central optical axis of each photovoltaic cell  516 . Between the convex lens  620  and the optoelectronic junctions  650  are at least two or more different optical materials  630 ,  634 ,  638  wherein at least the outer optical materials  630 ,  638  have a different index of refraction relative to the second material  634 . This arrangement of the optical fill materials  630 ,  634 ,  638  creates a compound optical structure that spatially segregates light into a plurality of different wavelengths both across the illustrated plane and in/out of the plane along central axis of the convex lens. In certain circumstances, it may be preferable that each optical fill material  630 ,  634 ,  638  have a unique index of refraction to achieve the desired separation of wavelengths. Both the indices of refraction of the optical fill material  630 ,  634 ,  638  and the orientation of the optical fill material  630 ,  634 ,  638  determine wavelength separation, an important feature of the photovoltaic cell  517 ; these parameters can be adjusted to achieve a desired result, for example as in separating infrared from visible from ultraviolet wavelengths. Critically, the junctions and the wavelength divisions are formed using integral lithographic techniques. The walls  642  of the cells  516  provide a containment space to deposit and shape the optical fill material  630 ,  634 ,  638  as well as to accommodate thermal expansion allowing the array of photovoltaic cells  516  to match thermal expansion/contraction of the common electrode  537  and the other components. Optical fill material  630 ,  634 ,  638  may be, for example, optical grade silicon, a clear thermoplastic resin, or other material that is transparent and has a high strength, rigidity, is preferably electrically insulating, and has compatible thermal expansion and contraction characteristics. 
     Each photovoltaic cell  516  further comprises a matrix of wavelength-specific light biased junctions  650  with band-gaps matching frequencies of the incident wavelengths on that cell  516 . Each opto-electronic junction is on the order one millimeter. These optoelectronic junctions  650  receive the spatially separated optical output from the optical fill material  638  and convert the optical energy to electrical energy. Thus, particular ones of the opto-electronic junctions  650  are more responsive to particular wavelengths, depending upon the choice of materials comprising the opto-electronic junctions  650 , for instance Type III/V semiconductor materials are responsive to different wavelengths than silicon or Type II/VI semiconductor materials. The bandgap relative concentrations of the dopants in the semiconductor material making up the opto-electronic junction  650  changes the output voltage and the conversion efficiency at a particular wavelength. Preferably, the wavelength-specific light-based opto-electronic junctions  650  comprise a P/N semiconductor junction, preferably a Group III/V composition and more preferably indium phosphide, for high bandwidth data transmission using very narrow band, coherent optical radiation. A plurality of electrodes  640  provide for a current path to the common electrode  536 . 
       FIG. 7  presents the process by which the common electrode  536  is prepared for the formation of the opto-electronic components  650 , surface electrodes and other electrodes  640 , optical fill material  630 ,  634 ,  638 , DC to AC inverters  220  and other components integrated with or otherwise attached to the common electrode  536 . In block  700 , a planar conductive material, such as steel or copper or other supportive conductive material to be used as the common electrode  536  is cleaned, de-oxidized and cut to a required size for the number of photovoltaic cells  516  to be formed. The size will typically be rectangular or a narrow strip for continuous handling and manipulation. At step  704 , one surface of the planar conductive material is scanned, preferably with a laser beam having sufficient energy to briefly melt seed-size points in a two-dimensional grid array and further creating markers to align masks and other subsequent processing stages. In steps  708 - 712 , as each seed-size point in the raster is melted, a seed crystal of, e.g., purified silicon or other semiconductor growth material suitable for the formation of the opto-electronic junction is applied to each seed site and embedded onto the planar conductive surface. 
     To begin the formation of the opto-electronic junction  650 , in step  716 , the planar conductive material, also referred to as the common electrode  536 , is inserted with the seeded surface facing downward into a crucible. The crucible contains a purified crystalline material in a liquid, gaseous or other comparable phase that is also compatible with the seed crystal applied in step  708 . In block  720 , the common electrode  536  is slowly extracted upwards from the crucible to form crystalline towers descending from each seed crystal. This step closely resembles the extraction of a seed crystal to form crystal ingots used in semiconductor wafer production; microscale equivalents of crystal pulling techniques enable formation of the base material for the wavelength-specific light biased opto-electronic junctions  650 . 
     In step  724 , the crystalline towers are planarized and otherwise prepared for subsequent processing steps to form the opto-electronic junctions  650 , the surface electrodes  640 , the optical fill material  630 ,  634 ,  638 , the DC to AC inverter circuits  220  and/or other interconnects to the power bus  210  and the control bus  230 , or other connections and components. In step  728 , the common electrodes are turned over once to repeat steps  704  through  724  to form similar crystalline towers on the other surfaces of the planar conductive material. 
       FIG. 8  is an illustration of the opto-electronic junction  650  used in accordance with an embodiment described herein. Using fabrication resist and deposition techniques the various band-gap materials may be grown onto the seed crystal formed above so that the opto-electronic junction has the appropriate sensitivity of wavelength bands, v 1  to v 2 . From the common electrode  536 , the semiconductor material is grown and doped from a high N dopant concentration to a high P dopant concentration. As mentioned, the material bandgap concentration of the different dopants affect the conversion efficiency and the voltage obtained from the junction at a particular wavelength. The sensitivity to the wavelengths is determined the type of semiconductor materials used, e.g., whether silicon, Type III/V, Type II/VI, etc, and by the spatial distribution of the wavelengths determined by the indices of refraction and the orientation of the optical fill material, as will be described. The relationship between the wavelengths and the bandgaps of the semiconductor materials of the opto-electronic junction is indicated by the subscripts v 1  to v 2 , P 1 to 2  and N 1 to 2 . A voltage potential in applied between the surface electrodes  640  and the common electrode  536 . Incident light onto the opto-electronic junction is absorbed by the high concentration P dopant and is converted to DC electrical energy collected by the high concentration N dopants. Inversion of the P and the N dopant semiconductor materials is possible with an inverted voltage. 
       FIG. 9  is an illustration of the process steps by which the compound optical structures of the photovoltaic cells  516  are formed. After the opto-electronic junctions  650  and the surface electrodes  640  have been fabricated and planarized, in step  910  side walls  642  are fabricated using microelectromechanical system (MEMS) techniques to form a cavity  950 . Side walls  642  are preferably manufactured from a material that is opaque and nonconductive and of sufficient rigidity to contain the optical material  630 - 638 . In step  914  a first optical resin having a first index of refraction is dispensed into cell cavity  950  at the bottom towards the opto-electronic junction  650 . In step  918 , the common electrode assembly is rotated at a first angle α 1 , perhaps 45 degrees, and the first optical resin is cured by heat, light, radio frequency or other curing means to form the optical fill material  638 . In step  922 , a second optical resin having a second index of refraction is dispensed into the cavity  950  onto the cured first optical resin. The common electrode assembly is rotated to a second at a second angle, perhaps α 2 , perhaps −45 degrees, and the second optical resin is thermally, optically or otherwise cured to form the optical fill material  634 , as shown in step  926 . In step  930 , a third optical resin is dispensed into the cavity  950  on top of the cured optical fill material  634 . The third optical resin may be the same as the first optical resin or it may have a different index of refraction as required to spatially separate the incident light. In step  934 , a suitable fourth optical resin is applied onto the third optical resin to form a convex lens  920 . The differences in viscosity, pressure, density will help to keep the third and fourth optical resins distinct. The third and fourth optical resins are appropriately cured by heat, light, ultraviolet radiation, radio frequencies, or other means to form optical fill material  630  and convex lens  620 . Alternatively, convex lens  620  may be formed separately to achieve refractive indices differentiation for the desired wavelength dispersion. Thus, a compound optical structure can be formed on the common electrode  536  for the capture of radiant energy and separation of wavelengths. While the first and second rotated angles α 1  and α 2  are shown and described at  45  and −45 degrees, respectively, the optical fill materials  638 ,  634 ,  630  may be rotated at different angles to create the compound optical structure and each optical fill material may have a unique index of refraction. 
     In step  938  of  FIG. 9 , the common electrode  536  is flipped or turned over to process the other side having the opto-electronic junctions  650  and common electrodes  640  according to steps  910  through  934 . Thus, the integrated light-to-electrical energy converter  110  is manufactured. This light-to-electrical energy converter is then able to receive light, spatially separate the wavelengths. The light output from the compound optical structure is incident upon the opto-electronic junctions  650  that have been doped for efficiently converting photons at a particular range of wavelengths to electrons and a DC current. 
       FIGS. 10 and 11  are a side view and an end view of panel assemblies  130  (shown in  FIG. 1 ) showing the light-to-electrical energy converter assembly  110  mounted on a dual axis passive solar tracker  100 .  FIG. 10  illustrates an optional antenna array  1020  affixed or otherwise mounted onto the panel assembly  130 . Voids  550  of the light-to-electrical energy converter assembly  110  may have an optional persistent energy storage, such as a battery, and/or may have additional electronic or mechanical components of an optional wireless base station  200  in communication with the optional antenna array  1020 . 
     The light-to-energy converter assembly  110 , the DC to AC inverters  220 , and other optional components such as the wireless base station  200 , an antenna array  1020 , and any matter or components within the space  550  are mounted on a dual axis tracking mount  100  comprising a lower leaf-spring assembly  1000  and an upper leaf-spring assembly  1004 . The upper leaf-spring assembly  1004  is mounted on and horizontally rotated ninety degrees from the lower leaf-spring assembly  1000 .  FIG. 10  illustrates the panel assembly  130  wherein the lower leaf-spring assembly  1000  and the spaces between the leaf-springs  1010  are visible to the reader whereas  FIG. 11  illustrates the rotation wherein the upper leaf-spring assembly  1004  and the spaces between the leaf-springs  1010  face the reader. Leaf-springs  1010  are made from steel or other rigid material that can be shaped to provide an elastic spring effect. Leaf-springs  1010  are each approximately ten to twenty centimeters in length and are bent as shown for spring action. The upper side  1014 , i.e., the face of the leaf-spring facing upwards, of each leaf spring  1010  has an energy absorptive coating or is made from a material that absorbs solar energy and thus expands while the underside  1018 , i.e., the face of each leaf spring facing downwards, has a reflective surface applied with a coating or other material and will contract or expand less than the upper side  1014 . Alternatively, the upper side  1014  of the leaf-spring  1010  may be made from a different metal or material having a different coefficient of thermal expansion from the underside  1018  of each leaf spring  1010 . The distance between the upper side  1014  to the underside  1018  of each leaf spring  1010  is on the order of five to ten centimeters. The dual axis tracking mount  100  thus steers the solar panel assembly  130  to track solar illumination. 
     The dual-axis tracking mounts  1000  and  1004  of the panel assembly  130  are able to withstand 130 rotational stress, such as tornadic winds and active loading with lift. Electrical damage from lightening can be minimized with careful site placement. In addition, the mounting base  1008  may be pliant to respond to extreme wind loading as well as provide a high current path for lightening discharge. 
     The solar concentrator and storage system  100  should preferably be incorporated in the initial design or an extensive refit of the entire roof system when installed on a roof to minimize damage and potential liability. Placing the solar concentrator and storage system  100  at ground level reduces the potential for damage resulting from lightening strikes. 
       FIG. 12  is a plan view of a panel assembly  130 . The features of  FIG. 12  are not drawn to scale but are shown to generally illustrate the final assembly of the panel  130 . Generally, the dimensions of the panel assembly  130  along the short edges of the paper are on the order of one to two meters and the dimensions of the panel assembly  130  along the long edges of the paper are on the order of two to three meters. Of course, the panel assembly may be larger or smaller; these dimensions are chosen for maneuverability and ease of handling. The two-axis passive solar tracking mounts  100  of the leaf-springs are illustrated underneath the panel assemblies. Preferably, there are two such two-axis passive solar tracking mounts  100  per panel assembly  130  of this size for rotational integrity and to prevent one tracking mount  100  from blocking the light path of another tracking mount  100 . Positioned along the periphery of the panel assembly  130  are the optional antenna arrays  1020 . The dotted lines  1212  indicate the troughs of the bent structural element  528  (shown in  FIG. 5 ) having the active components of the light-to-electrical energy converter  110 , the DC to AC inverters  220  while the sold lines  1216  of the panel assembly  130  represent the crests of the bent structural element  528  (shown in  FIG. 5 .) having the pads  512  for vibration, shock and mechanical force absorption. 
       FIG. 13  provides a block diagram of the optional integration of the panel assembly  130  and the wireless base station  200 . First the wireless base station  200  integration into the panel assembly  130  provides either a static alternative to or a backup for the control bus  230  in the event that control bus  230  not operational. Integration of the wireless base station  200  having a global position receiver powered by the solar energy harvesting and storage system  80  described herein is particularly useful where installing power lines and wired signal connections to land-based data lines is undesirable or impractical. Examples include isolated rural areas, frozen ground, flooded ground, disasters or situations where trained installers are unavailable. 
       FIG. 13  illustrates the wireless base station option  200 . Functionality in  FIG. 13  must be split between antenna arrays  1020  located on the periphery of the panel assembly  130  and a wireless base station  200  located in or shared between components within the void  550  under bent structural element  528  and/or a module situated under the mounting base  1008  of the panel assembly  130 . Note that in  FIG. 12 , there are four antenna arrays  1020  in each directional orientation at the periphery of the panel assembly  130 ; thus each of the four antenna arrays  1020  is in communication with a wireless base station  200 . In a given panel assembly  130 , then, there need only be an equivalent number of wireless base stations  200  as the number of antenna arrays  1020 . 
     Antenna arrays  1020  serve not only to connect with wireless edge devices such as smart phones and wireless enabled laptops but also to provide back-haul connections routing to and from the wireless base stations  200  to other such stations within relay range, cell towers or comparable routing infrastructure. Digital beam forming and other techniques for improving signal strength are well known in the wireless design community. 
     The wireless base station  200  may either operate at carrier frequencies supporting a wide range of protocols or may mix the wireless carrier frequencies down to base band using additional mixer and local oscillator components in the wireless base station  200 , as shown in block  1304  of  FIG. 13 . The former technique is commonly known as software defined radio. Either approach uses analog to digital converters and digital to analog converters, also shown in block  1304 , to convert incoming and outgoing signals suitable for both a signal processor in block  1304  to, e.g., demodulate the signals, and a processing system, block  1308 , at the heart of the wireless base station  200 . Both the signal processor of block  1304  and the processing system of block  1308  are included as part of the wireless base station  200 . 
     Because the panel assembly  130  may be rapidly installed, perhaps by unskilled personnel, it is useful to include an optional global positioning system (GPS)  1312  with the wireless base station  200 . This GPS system  1312  is also useful to locate particular panel assemblies  130  during field support. Maintenance operations can be paired with panel health indications to direct field support directly to the right panel assembly. An antenna for the GPS  1312  may be included in one or more of the antenna arrays  1020  for improved signal handling. 
     Within the panel assembly  130  wired connectivity is provided among the optional antenna array elements  1020  and the signal processing function  1304  and the processing system  1308  of the wireless base station  200 . These may most conveniently be located underneath the solar panel assemblies  130  as part of the control bus  230  internal to the panel assembly  130 . Power may be derived using AC or DC energy from the power bus  210 . 
     Wireless base stations  200  may be included in some panel assemblies  130  and not others. However this innovative synergy greatly facilitates maintenance, asset tracking as well as providing enhanced wireless communication for other purposes such as data links and telephony. Cost of lower powered base stations such as femtocells makes such integration economically affordable in an increasing application range. 
     The particular embodiment described herein of the panel assemblies  130  mounted on the dual-axis passive solar tracker  100  satisfies reliability criteria for tracking operations up to twenty-five years in very inclement snow and ice-covering environments and minimal preventative/incident repair. The entire solar collector and storage system  80  has a reliable operation, can be maintained by unskilled workers, and satisfies tight environmental requirements associated with long term operation in close proximity to populated structures. Similarly, during seasons having less than ideal illumination, maximum energy from the sun&#39;s daily cycle from sunrise to sunset can be obtained. 
     Such solar collector and energy storage systems as provided herein can provide power for high performance computer systems, e.g., ranging up to four megawatts each, in such locations and circumstances where there is limited available power and processor power efficiency.