Solar-To-Electricity Conversion System Using Cascaded Architecture of Photovoltaic and Thermoelectric Devices

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US 2009/025.0099 A1 Oct. 8, 2009

SOLAR-TO-ELECTRICITY CONVERSION induced by thermal expansion mismatch induce defects and SYSTEMUSING CASCADED degrade conversion efficiency and occur in both lattice ARCHITECTURE OF PHOTOVOLTAC AND matched and metamorphic (lattice-mismatched) epitaxial THERMOELECTRIC DEVICES layered multi-junction Solar cell structures. 0008 Examples of solar to electrical conversion systems

RELATED APPLICATION DATA can be seen in the following, all of which are hereby incor 0001. The present application claims the benefit under 35 porated by reference herein:

U.S.C. 119(e) of the priority date of Provisional Application 0009 U.S. Pat. No. 4,710,588 Ellion Ser. No. 61/043014 filed Apr. 7, 2008 which is hereby incor 0010 U.S. Pat. No. 6,281,426 Olson, et al. porated by reference. The application is further related to the 0011 U.S. Pat. No. 7,109,408 KucheroV, et al. following applications, all of which are filed on this same date 0012 U.S. Pat. No. 7,322,156 Rillie, et al. and incorporated by reference herein: 0013 U.S. Pat. No. 5,009,719 Yoshida 0002 Solar-To-Electricity Conversion Sub-Module: Ser. 0014 U.S. Pat. No. 7,335,835 Kukulka, et al. No. (attorney docket number 2009-1) 0.015 U.S. Pat. No. 4,776,893 McLeod et al. 0003 Solar-To-Electricity Conversion System: Ser. No. (0016 Ortiz, Estibalizet al., “A high-efficiency LPEGaAs (attorney docket number 2009-2) solar cell at concentrations ranging from 2000 to 4000 suns.” 0004 Method for Solar-To-Electricity Conversion: Ser. 0017 Progress in Photovoltaics: Research and Applica No. (attorney docket number 2009-3) tions, volume 11, issue 3 (Jan. 30, 2003), pp. 155-163. 0018. The most significant obstacle to wide deployment of

FIELD OF THE INVENTION solar electricity has been the figure of merit in cost per watt or kilo-watt-hour generated by a given Solar-to-electricity con 0005. The present invention relates to the field of solar version method. Current methods for manufacturing the Solar electricity and, more particularly, to the collection and con power generation require significant capital investment to version of Solar energy into electricity using a concentrated realize Volume production. Final products remain high in cost optical system and other components such as light tubes, light which has prevented penetration into the large utility and guides, light fibers, or a light pipe for Solar energy collection consumer markets as well as other niche markets. Contribut and solid state devices for Solar energy conversion. ing factors to cost include the conversion cell and its material, fabrication, package and assembly, frame and assembly,

BACKGROUND applicable Solar ray collection apparatus such as concentrator 0006. The collection of solar energy including photonic and tracker, electrical system, transportation, and installation. and thermal energies within the Solar spectrum and Subse 0019. A key parameter is the conversion efficiency-the quent conversion to electric power have been explored for ratio of electrical power output over Solar powerimpinging on many applications including, but not limited to, photovolta the Solar cell or module. Higher conversion efficiency means ics, concentrating photovoltaics, thermophotovoltaics, Solar higher power output per unit collection area and lower cost thermal power, concentrating Solar thermal power, active per output power. Another key parameter is the concentration Solar heating, and passive Solar heating, cooling, Solar factor-the ratio of the concentrated Solar radiation intensity at thermo-electrochemical, and daylighting. In Solar collection, the focal area to the flux at its collector aperture or, equiva there are a number of optical systems demonstrated for long lently, the ratio of the concentrated area at the focal point to term reliability such as flat-plates, flat-plates with side reflec the collector aperture area provided negligible loss of Solar tors, tubular collectors, paraboloids, parabolic troughs, flux along the path of concentration optics. Higher concen Fresnel lens or reflectors, heliostats with a central receiver, tration factor means Smaller footprint of the conversion and Stirling dishes with a refractance or a reflectance solar device and thus lower cost per output power. loss of typically 10%. These optical systems may or may not 0020. Accordingly there is clearly a long-felt need for be integrated with a one-axis or two-axes solar tracking sys Solar-to-electrical conversion systems (and components tem.

thereof) which are capable of addressing these deficiencies in 0007. The selection of an optical system depends on cost the prior art.

effectiveness, maintainability, cell materials, cell device and SUMMARY OF THE INVENTION assembly, conversion efficiency, the degree of Solar concen tration, and the methods to collect and/or track the sun. The 0021. An object of the present invention, therefore, is to concentration factor of these optical system collectors is pri overcome the aforementioned limitations of the prior art. It marily limited by the temperature-dependent efficiency and will be understood from the Detailed Description that the thermal stability of solar conversion method whether it is a inventions can be implemented in a multitude of different working fluid in Solar thermal or a conversion device in Solar embodiments. Furthermore, it will be readily appreciated by photovoltaic. Among the top system performers at the time of skilled artisans that such different embodiments will likely this invention, Stirling dish that uses a gas has operated with include only one or more of the aforementioned objects of the a conversion efficiency at about 40% and a concentration over present inventions. Thus, the absence of one or more of Such 2,000x for solar thermal power and a lens-based concentrator characteristics in any particular embodiment should not be that uses a multi-junction Solar cell has performed at about construed as limiting the scope of the present inventions. 40% conversion efficiency and 240x concentration factor. For 0022. A first aspect of the invention is directed to a solar multi-junction concentrator Solar cells, it is found that con to-electricity conversion Submodule comprising: a photon version efficiency peaks out at about 600x before the thermal to-electricity conversion device; a heat sink/pipe coupled to expansion mismatch and associated thermal effects of mul the photon-to-electricity conversion device; a multi-layer tiple stacking junctions or monolithically grown epitaxial board having a light cavity for receiving or transmitting radia layers become problematic. In particular, residual stresses tion flux associated with the photon-to-electricity conversion

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device; one or more conductive leads coupled to the photon tricity conversion device, thermionic and/or thermoelectric to-electricity conversion device for providing an electrical device, heat sink/pipe and electrical combiner circuit are output in response to radiation flux impinging on the photon located on and housed by the multi-layer board. to-electricity conversion device; wherein the photon-to-elec 0029. In preferred embodiments a position of the thermi tricity conversion device, heat sink/pipe and conductive leads onic and/or thermoelectric device can be automatically are located on and housed by or attached to the multi-layer adjusted. Also, the multi-layer board preferably has a thermal board. expansion characteristic matching the photon to electricity 0023 The photon-to-electricity device is preferably based conversion device.

on a single junction cell adapted to convert only a first portion 0030. A further aspect of the invention is directed to a of an insolation flux spectrum into electrical energy based on Solar-to-electricity conversion Submodule comprising: at a first band gap energy. The module is further preferably least one photon-to-electricity conversion device having a adapted to be stacked into a cascade with one or more second single junction cell for converting only a first portion of an modules having one or more photon-to-electricity devices incident radiation spectrum into electricity; a heat sink/pipe based on single junction cells adapted to convert a second coupled to the photon-to-electricity conversion device; a different portion of the insolation flux spectrum into electrical multi-layer board having a light cavity for receiving or trans energy based on one or more second band gap energies. The mitting radiation flux associated with the photon-to-electric cascade is arranged in a linear arrangement such that the ity conversion device; wherein the multi-layer board is insolation flux travels in a straightline, or in an offset arrange adapted to have a thermal expansion characteristic that Sub ment such that the insolation flux is refracted and reflected stantially matches the photon-to-electricity conversion between different photon-electricity devices as it travels. device; one or more conductive leads coupled to the photon 0024. The multi-layer board is further preferably adapted to-electricity conversion device for providing an electrical to mounta thermionic orthermoelectric device in lieu of or in output in response to radiation flux impinging on the photon addition to the photon-to-electricity device, and is comprised to-electricity conversion device; wherein the photon-to-elec of a co-fired ceramic and conducting thermal vias, thermal tricity conversion device, heat sink/pipe and conductive leads diodes, bypass and/or blocking diodes, and embedded sen are located on and housed by the multi-layer board. sors and related electronic circuitry. In some embodiments 0031. Other aspects of the invention are directed to a larger the multi-layer board is further adapted to couple to a light Solar-to-electricity conversion system, in which the improve tube, a light guide or light pipe to receive the radiation flux. ment comprises a photovoltaic Subsystem including a plural 0025. In some embodiments the photon-to-electricity ity of photovoltaic cells having different band gaps to convert device includes reflector or a single or more reflection coat concentrated ultraviolet, visible, and infrared solar flux into ings are for reflecting a remaining radiation flux that is not electrical energy; and wherein the plurality of photovoltaic converted into electricity. cells are configured in a cascade arrangement for processing 0026. In other embodiments a plurality of photon-to-elec the concentrated ultraviolet, visible, and infrared solar flux. tricity devices having the same spectrum conversion capabil 0032 Preferably the cascade arrangement includes at least ity are arranged within the same plane and in a line to receive two photovoltaic cells arranged linearly such that the flux the radiation flux in a broad focal line. The focal line can be travels substantially in a straight line through the photovoltaic created by, among other things, a slit or light cavity mounted Subsystem, or they are arranged with an offset Such that the on the multi-layer board. flux is refracted and reflected between successive cells in the 0027. In some embodiments the photon-to-electricity con photovoltaic Subsystem.

version devices are situated and paired in a plane with other 0033 Each of the plurality of photovoltaic cells preferably matching photovoltaic cells, while other devices are situated is made from liquid phase epitaxy or gas diffusion, and and paired in a plane with respective matching photovoltaic includes an anti-reflection coating and/or a reflection coating cell, such that the concentrated insolation flux is converted by for spectrum selectivity of solar flux impinging on the device, a a two dimensional array into electrical energy. The devices one or more p-n junctions, one or more front conductor con can be paired with cells orthogonally positioned as well Such tacts, and one or more back conductor contacts for electrical, that the concentrated insolation flux is converted by a three as well as contacts for heat conduction. The p-n junctions of dimensional array into electrical energy. the photovoltaic cells are preferably made of crystalline mate rials.

0028. Another aspect of the invention concerns a solar-to electricity conversion Submodule comprising: a photon-to 0034. The cells can also include a single layer or multilay electricity conversion device adapted to convert insolation ers of absorptive or anti-reflection costings for raising the flux into electricity; a thermionic and/or thermoelectric absorption of a selective spectrum of the radiation flux that is device with a single or multiple anti-reflection and/or reflec converted into electricity.

tion coatings for spectrum selectivity situated along the path 0035. In preferred embodiments a heat to electrical con of solar flux to convertheat energy into electricity or adjacent version subsystem is situated in a path of the ultraviolet, to the photon-to-electricity device and adapted to convertheat visible, and infrared solar flux and adapted to convertheat to energy associated with Such photon-to-electricity device into electricity. The invention can be paired with tracking sensors electricity; a heat sink/pipe coupled to both the photon-to and motor drives that orient the conversion system toward the electricity conversion device and the thermionic and/or ther Sun. Automated positioning mechanisms can be employed for moelectric device; a multi-layer board having a light cavity adjusting a spacing of the photon-to-electricity conversion for receiving or transmitting insolation flux: an electrical devices.

combiner circuit coupled to both the photon-to-electricity 0036 Further aspects of the invention concern a solar-to conversion device and the thermionic and/or thermoelectric electricity conversion system comprising: a photovoltaic Sub device and adapted to generate an electrical output in system including at least two photovoltaic cells having dif response to the insolation flux: wherein the photon-to-elec ferent band gaps to convert concentrated insolation flux into

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electrical energy; at least two circuit boards for mounting and 0042. The thermionic cells in the heat to electrical conver housing the at least two photovoltaic cells; wherein respective sion Subsystem preferably include: a single or multiple anti junctions of the at least two photovoltaic cells are on separate reflection and/or reflection coatings on the hot side for spec substrates or thin films situated on a respective circuit board; trum selectivity; an array of alternating n-type and p-type a frame adapted for Supporting the at least two circuit boards thermal diodes; wherein the thermal diodes are shaped into and maintaining a first separation there between; wherein an columns using a via structure embedded in a multilayer electrical output can be generated based on the concentrated board; a hot side conductor contact; a cold side conductor insolation flux. contact; and electrical interconnect to couple the thermal 0037. In preferred embodiments of this type of system a diodes and electrical contacts.

light cavity can be coupled to one or more of the at least two 0043 Embodiments of the invention can be used to form a circuit boards, the least two circuit boards are thermally Solar energy power generating plant. matched to the respective at least two photovoltaic cells, have 0044) Other aspects of the invention concern a photon-to embedded thermal conduction components, and diodes and/ electricity Subsystem comprising: a cascade of photovoltaic or other electrical circuitry to optimize Voltage and current cells of different band gaps and each of one or more p-n maximums of electricity generated by the system. junctions absorbing ultraviolet, visible, and infrared solar 0038. Furthermore at least one of the least two photovol flux; the photovoltaic cells including optical coatings, p-n taic cells can have a reflector for transmitting a remaining junctions, and conductor contacts for electrical and heat con unconverted spectrum of the concentrated insolation flux to a duction; wherein the p-n junctions of the photovoltaic cells Subsequent separate photovoltaic cell. The concentrated inso are made of crystalline materials; and the photovoltaic cells lation flux can received as a focal beam of a defined shape. being mounted on a multilayer board of cofired ceramic. 0039. Another aspect of the invention addresses a solar 0045 Another aspect of the invention is directed to a solar to-electricity conversion system comprising: a first photon to-electricity conversion system configured in a modular plat to-electricity conversion device adapted to convert a first form and comprising: a photon-to-electricity Subsystem spectrum portion of a concentrated insolation flux to electric including an array of Successive spaced photovoltaic cells ity; the first photon-to-electricity conversion device being having different band gaps to convert concentrated insolation situated in a first position within a path of the concentrated flux within a flux path into electrical energy; a heat-to-elec insolation flux: a second photon-to-electricity conversion tricity conversion subsystem also situated within the flux path device situated adapted to convert a second spectrum portion and including at least one of an array of thermoelectric cells or of a remainder of the concentrated insolation flux to electric thermionic cells to covert heat into electric energy; a heat ity; the second photon-to-electricity conversion device being sink/pipe coupled to the photon-to-electricity Subsystem and/ situated in a second position separated from the first position or the heat-to-electricity conversion Subsystem; a plurality of within the path of the concentrated insolation flux: a heat to thermal expansion matched multilayer boards for integrating electrical conversion Subsystem situated in a third position the photon-to-electricity subsystem, the heat-to-electricity within the path of the concentrated insolation flux and includ conversion Subsystems and heat sink/pipe; a light cavity situ ing at least one of an array of thermoelectric cells and/or ated within the flux path and adapted to direct the concen thermionic cells to covertheat associated with a third spec trated insolation flux between the Successive spaced photo trum portion of the concentrated insolation flux into electric Voltaic cells; and an assembly for mounting the photon-to energy; a frame adapted for Supporting the first and second electricity Subsystem, the heat-to-electricity conversion photon-to-electricity conversion devices and the heat to elec Subsystem, the heat sink/pipe, the plurality of thermal expan trical conversion Subsystem; wherein electrical power can be sion matched multilayer boards and the light cavity. derived from at least the first spectrum portion, the second 0046. A further aspect concerns a solar-to-electricity con spectrum portion and the third spectrum portion of the con version system configured in a modular platform and com centrated insolation flux. prising: a photon-to-electricity Subsystem including a linear 0040. The heat to electrical conversion subsystem can be cascade arrangement of two or more successive spaced pho situated in a variety of locations, including before the first tovoltaic cells, each of the cells having a different bandgap to photon-to-electricity conversion device and/or after a lastone convert concentrated insolation flux within a flux path into of the photon-to-electricity conversion devices within the electrical energy; a heat-to-electricity conversion Subsystem concentrated insolation flux path. As alluded to above the first also situated immediately before or after the photon-to-elec photon-to-electricity conversion device, the second photon tricity Subsystem within the linear cascade arrangement and to-electricity conversion device, and the heat to electrical flux path and including at least one of an array of thermoelec conversion Subsystem can be configured or in an offset tric cells or thermionic cells to convert heat into electric arrangement such that the concentrated insolation flux is energy; a heat sink/pipe coupled to the photon-to-electricity refracted and reflected between one or more successive cells Subsystem and/or the heat-to-electricity conversion Sub and/or the heat to electrical conversion Subsystem. system; a plurality of thermal expansion matched multilayer 0041. The thermoelectric cells in the heat to electrical boards, one for each of the photovoltaic cells and the array of conversion Subsystem preferably include: a cascade of crys thermoelectric or thermionic cells; and a casing assembly for talline thermoelectric cells of one or multiple types of junc mounting the photon-to-electricity Subsystem, the heat-to tion materials absorbing infrared radiation or heat; and the electricity conversion Subsystem, the heat sink/pipe, the plu thermoelectric cells further including a single or multiple rality of thermal expansion matched multilayer boards and anti-reflection and/or reflection coatings for spectrum selec the light cavity.

tivity, p-n junctions, front conductor contacts, and back con 0047. In preferred embodiments the two or more succes ductor contacts for electrical and, separate heat conduction; sive spaced photovoltaic cells include the following: a first and the p-n junctions of the thermoelectric cells are made of photovoltaic cell of band gap at about 2.54 eV; a second crystalline materials. photovoltaic cell of band gap at about 1.47 eV; and a third

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photovoltaic cell of bandgap of about 0.7 eV. Furthermore the photon-to-electricity subsystem and/or the heat-to-electricity first photovoltaic cell is AlGaAs; the second photovoltaic cell conversion Subsystem; a plurality of thermal expansion is GaAs; and the third photovoltaic cell is GaSb or Ge. matched multilayer boards, one for each of the photovoltaic 0048. Yet another aspect concerns a solar-to-electricity cells and the array of thermoelectric or thermionic cells; and conversion system configured in a modular platform and a casing assembly for mounting the photon-to-electricity Sub comprising: a photon-to-electricity Subsystem including an system, the heat-to-electricity conversion Subsystem, the heat offset cascade arrangement of two or more Successive spaced sink/pipe, and the plurality of thermal expansion matched photovoltaic cells, each of the cells having a different band multilayer boards.

gap to convert concentrated insolation flux within a flux path 0051. A further aspect of the invention is directed to a into electrical energy; wherein the concentrated insolation Solar-to-electricity conversion system configured in a modu flux is reflected between successive photovoltaic cells as it lar platform and comprising: a photon-to-electricity Sub traverses the offset cascade arrangement; a heat-to-electricity system including a first linear cascade arrangement of two or conversion subsystem situated immediately before the pho more Successive spaced photovoltaic modules, each of the ton-to-electricity Subsystem for reflecting the concentrated modules having a different band gap to convert concentrated insolation flux into the offset cascade arrangement and insolation flux within a focal line into electrical energy; including at least one of an array of thermoelectric cells or wherein the photovoltaic modules each include one or more thermionic cells to convert heat into electric energy; a heat photovoltaic cells situated in a planar arrangement within the sink/pipe coupled to the photon-to-electricity Subsystem and/ focal line; a heat-to-electricity conversion Subsystem situated or the heat-to-electricity conversion Subsystem; a plurality of immediately before or after the photon-to-electricity sub thermal expansion matched multilayerboards, one for each of system within the focal line and including at least one of an the photovoltaic cells and the array of thermoelectric or ther array of thermoelectric cells or thermionic cells to convert mionic cells; a casing assembly for mounting the photon-to heat from the concentrated insolation flux into electric electricity Subsystem, the heat-to-electricity conversion Sub energy; a heat sink/pipe coupled to the photon-to-electricity system, the heat sink/pipe, and the plurality of thermal Subsystem and/or the heat-to-electricity conversion Sub expansion matched multilayer boards. system; a plurality of thermal expansion matched multilayer 0049. Another aspect of the invention is directed to a solar boards, one for each of the photovoltaic cells and the array of to-electricity conversion system configured in a modular plat thermoelectric or thermionic cells; a casing assembly for form and comprising: a first light directing means for receiv mounting the photon-to-electricity Subsystem, the heat-to ing concentrated insolation flux; a photon-to-electricity electricity conversion subsystem, the heat sink/pipe, the plu Subsystem including an offset cascade arrangement of two or rality of thermal expansion matched multilayer boards and more Successive spaced photovoltaic cells, each of the cells the light cavity.

having a different band gap to convert the concentrated inso 0.052 Still another aspect concerns a solar-to-electricity lation flux within a flux path into electrical energy; second conversion system configured in a modular platform and pro light directing means positioned between the two or more cessing concentrated Solar insolation flux incidence into the Successive spaced photovoltaic cells; wherein the concen Solar-to-electricity conversion system with a concentration trated insolation flux is reflected between the successive pho factor between 250x and 5,000x comprising: a photovoltaic tovoltaic cells within the second light directing means as it subsystem including an array of photovoltaic cells of differ traverses the offset cascade arrangement; a heat-to-electricity ent band gaps and each cell having an area between about 300 conversion subsystem situated immediately before the pho hundred square microns to 30 square centimeters to convert ton-to-electricity Subsystem for reflecting the concentrated concentrated solar visible, ultraviolet, and infrared radiation insolation flux into the linear cascade arrangement and into electrical energy; a thermoelectric or a thermionic Sub including at least one of an array of thermoelectric cells or system including a plurality of thermoelectric or thermionic thermionic cells to convert heat into electric energy; a heat cells to convert at least the concentrated solar infrared radia sink/pipe coupled to the photon-to-electricity Subsystem and/ tion and/or a temperature gradient into electrical energy; a or the heat-to-electricity conversion Subsystem; a plurality of frame adapted to Support and function as an environmental thermal expansion matched multilayerboards, one for each of shield and which is integrated as part of the hot side and/or the photovoltaic cells and the array of thermoelectric or ther cold side (heat sink) in the heat-to-electricity conversion; a mionic cells; and a casing assembly for mounting the photon first light directing means for directing the concentrated Solar to-electricity Subsystem, the heat-to-electricity conversion insolation flux incidence and any reflectance unto the photo Subsystem, the heat sink/pipe, the plurality of thermal expan Voltaic and thermoelectric or thermionic Subsystems; a ther sion matched multilayer boards and at least the second light mal expansion matched multilayer board adapted to integrate directing means. components (a) and (b) and to transfer heat among Such 0050 Still another aspect concerns a solar-to-electricity components by thermal vias; and a second light directing conversion system configured in a modular platform and means in the multilayer board adapted to direct concentrated comprising: a photon-to-electricity Subsystem including a solar insolation flux between photovoltaic cells. linear cascade arrangement of two or more successive spaced 0053 Other aspects of the invention concern methods of photovoltaic cells, each of the cells having a different band converting concentrated ultraviolet, visible, and infrared gap to convert concentrated insolation flux within a flux path Solar flux to electrical energy using the above architectures into electrical energy; a heat-to-electricity conversion Sub and configurations. In addition the Solar insolation flux can be system situated immediately before the photon-to-electricity collected by one or more of: a dome of a Fresnel lens system, Subsystem for reflecting the concentrated insolation flux into a parabolic trough parabolic trough, a linear Fresnel lens, a the linear cascade arrangement and including at least one of hemispherical bowl collector, a flat absorbing plate, a cylin an array of thermoelectric cells or thermionic cells to convert drical collector, oran active steering or a motion-free tracking heat into electric energy; a heat sink/pipe coupled to the collector with concentration or spectrum splitting function.

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From there it is presented to a cascade of photon-to-electricity ity devices such as Solid-state thermionic and thermoelectric devices and/or heat-to-electricity devices. The electrical devices, each of which is made of specific composition. energy generated can be used to charge an electric Storage 0068 Embodiments of the present invention thus provide apparatus, or be delivered to a balance-of-system for deliver a conversion system that is scalable for the photovoltaic ing electricity. device of area from a few hundreds of micron square to a few 0054) Other aspects of the invention concern a production tens of centimeter square with the corresponding optical col method for making crystalline photovoltaic cells and/or ther lection area that gives a concentration factor from 250x to moelectric or thermionic cells the improvement comprising 5,000x. The overall conversion efficiency of the solid-state forming the crystalline photovoltaic and/or thermoelectric or Solar engine module of the present invention has potential to thermionic cells and interfaces by liquid-phase epitaxial growth, gas diffusion, or some other equivalent process. The achieve 50% or more of which the conversion from photon to process further preferably includes a step of growing a seed electricity is greater than 40% and the conversion from heat to layer and/or a sacrificial layer using metalorganic chemical electricity is greater than 10%.

vapour deposition (MOCVD) or an epitaxy growth method. 0069. The present disclosure describes an alternative solu 0055 While described in the context of a solar conversion tion to the prior-art multi-junction Solar cell or photovoltaic system, it will be apparent to those skilled in the art that the cell. The problem of thermal expansion mismatch in the present teachings could be used in any number of other sys multi-junction solar cell occurs between different constituent tems in which it is desirable to improve efficiency of a radia layers under elevated temperature that leads to thermal tion conversion process. Embodiments of the invention are residual stresses, which affect the integrity and lifetime of the expected to be used for both terrestrial and extra-terrestrial photovoltaic cells, under high concentrated Solar flux. It is applications where it is desired to make use of Solar power— known for a single-crystal cell under no external influence, its Such as part of a satellite, a space transport, robotic explora coefficient of thermal expansion (CTE) is complaint with the tion vehicle, a housing unit, a building, a Solar power plant, crystal symmetry.

space station, a Solar powerplant, off-grid and grid-connected 0070 A single-crystal photovoltaic cell as used in pre facilities, etc. ferred embodiments of the present invention can, therefore, handle higher concentrated Solar flux and temperature than

DESCRIPTION OF THE DRAWINGS the prior-art multi-junction photovoltaic cells. The modular platform described herein arranges the single-crystal photo 0056 FIG. 1 is a simplified diagrammatic view of a pre voltaic cells to absorb solar flux in a cascade such that the first ferred embodiment of a solid-state solar engine system of the cell absorbs a portion of the solar flux with energy above its present invention; band gap and the second cell absorbs, with energy above the 0057 FIG. 2A is an illustrative configuration of a pre second cell's band gap, a portion of the Solar flux that is not ferred embodiment of a solar-to-electricity converter module: absorbed by the first cell, and so on. For semiconductor-based 0058 FIG. 2B is an illustrative configuration of an alter photovoltaic materials, the band gap generally refers to the nate embodiment of a solar-to-electricity converter module in energy difference between the top of the valence band and the which athermoelectric/thermionic device is coupled to one or bottom of the conduction band.

more photoelectric device: 0071. Furthermore, preferred embodiments exploit the 0059 FIG. 3A is a diagrammatic view of common com conversion of thermal energy to electric energy using ther ponents of a preferred embodiment of a packaged cell; moelectric and thermionic converters. In particular, a prior art 0060 FIG. 3B is an illustrative configuration of an alter Solid-state thermionic converter using semiconductor diode nate embodiment of a cell in which a thermoelectric/thermi has sufficient high power densities and efficiencies and can onic device is coupled to a photoelectric device; operate attemperature range for a broad scope of application 0061 FIG. 3C is a cross sectional view of a packaged potentials. In some embodiments the Solar energy converter Sub-module: comprising the aforementioned cascading single crystal pho 0062 FIG. 4 is a diagrammatic view of a converter module tovoltaic cells and the solid-state thermionic devices utilizes according to one embodiment of the present invention; and transfers heat from the interaction between solar flux and 0063 FIG. 5 is a diagrammatic view of a second embodi a solid-state matter to a solid-state thermionic device for ment of a converter module: heat-to-electricity conversion.

0064 FIG. 6 is a diagrammatic view of a third embodi 0072 Another advantage of certain preferred embodi ment of a converter module: ments is that a single crystal cell of high quality can be 0065 FIG. 7 is a diagrammatic view of a fourth embodi fabricated with a method that forms a layer interface of true ment of a converter module: thermodynamic equilibrium Such as by using a prior-art liq 0066 FIG. 8 is a diagrammatic view of a fifth embodiment uid-phase epitaxy method that is not currently used for the of a converter module: mass production of Solar cells. The liquid phase epitaxy method may be improved for mass production with active

DETAILED DESCRIPTION epitaxy growth control and high throughput layer formation mechanism. Among other aspects the present invention pro 0067. A novel modular platform integrates solid-state poses a new application by using an improved liquid phase photovoltaic and thermionic or thermoelectric devices with epitaxy method for the mass production of high quality single the Solar collection and concentration optics for the Solar-to crystal Solar cells with low dislocations and defects and uni electricity conversion. Both the conversion efficiency and the form layers and interface. High crystal quality yields signifi heat handling capability under a focal area of high Solar cant advantage with high conversion efficiency because of concentration are increased by cascading photon-to-electric low defect density and exceptional optical quality because of ity devices such as photovoltaic devices and heat-to-electric high degree of homogeneity and interfacial uniformity.

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0073 Finally, another useful aspect of embodiments of the certain current conventional examples of Such components invention is that the the solar energy converter can be fabri have been described, it will be understood that the present cated with a method that is fully compatible with conven invention can be used with other variants, advances, etc. of tional low-temperature cofired ceramic process technology Such components which are not yet well known and/or undis for assembling the cells into packages. The coefficient of covered.

thermal expansion of low-temperature cofired ceramic can be I0081. In addition solar conversion system 100 can be inte matched to that of the solar-to-electricity conversion die grated into a conventional balance-of-system typically com attached to it for thermal stability under high solar concen posed of charge control, storage, inverter, electrical cabling, tration. A customized light cavity can be incorporated into the and protection circuitry for off-grid and on-grid applications. low-temperature cofired ceramic process for special module Energy storage (not shown) may use prior-art direct electric configurations. storage Such as ultracapacitors or electrochemical energy 0074 Referring initially to FIG. 1 a preferred embodiment storage such as batteries.

of a solar-to-electricity conversion system 100 according to I0082. A preferred embodiment of a solar-to-electricity the present invention is shown. It will be understood by those converter module 250 is illustrated in FIG. 2A. The converter skilled in the art that the depiction provided is not intended to module 250 provides a novel method and apparatus to show exact dimensions, shapes, and/or proportions as may be improve conversion efficiency, concentration factor, and ther used in a commercial application. mal handling capability. Again for illustrative purposes the 0075. The system 100 generally includes a collector 110, a present diagram and discussion is simplified and skilled arti concentrator 120, a frame 130, a light tube/guide/fiber/pipe sans will appreciate that other components could be 140, and a converter module 150 which is the subject of employed in deployed application.

substantial discussion below. It will be apparent to those I0083 Radiation 205 (preferably solar flux) falls on the skilled in the art that the present discussion is simplified in converter module as a source of photons to be converted to order to elaborate the main aspects of the invention, and that electricity. Preferably the converter module 250 comprises a other elements could be employed as well in other embodi cascade arrangement of one or more photon-to-electricity ments depending on system requirements. devices 210, one more heat-to-electricity devices 220, a first 0076 Collector 110 is preferably one of a conventional power control circuit 230 for photon-to-electricity charge dome of a Fresnel lens system with high optical conversion to control, a second power control circuit 240 for heat-to-elec collect low and high angle Solar rays (or other radiation tricity charge control, and a circuit combiner 245 as part of the source). Alternatively a combined optical system can be used balance-of-system that may be placed external to a unit mod for the dual purposes of a collector and a concentrator Such as ule.

an active steering collector or a motion-free tracking collector I0084. The first power controller circuit 230 can be with concentration or spectrum splitting function. arranged such that the photocurrent and photovoltage from 0077 Concentrator 120 is preferably one of the following: each photon-to-electricity device 210 can be combined a conventional parabolic trough/reflector, a set of two reflec within a Solar-to-electricity converter module or connected in tors, a linear Fresnel lens, a hemispherical bowl collector, a parallel or series with devices of other modules (shown in cylindrical collector, a focusing lens, a tapered light tube, a FIG. 1) to form the next levels of integration as in a panel and light guide, a light fiber, or a light pipe for directing all the an array (not shown) for desired electrical characteristics. The photons collected after the collector 110 to a focal area such Solar radiation 205, consisting of a first spectrum of energetic as a focal spot or a focal line that is reduced from the collector photons, impinges on the cascade of photovoltaic devices 210 aperture area by approximately the concentration ratio. and a thermoelectric or thermionic device 220. 0078 Frame 130 is preferably comprised of planks, I0085. Thethermoelectric orthermionic device 220 is pref frames, conduits, enclosures, racks or other Suitable struc erably placed within the cascading order So that Solar radia tures and is mounted on a roof-top, a stand, a tracking mount, tion incidence can be extracted from a position before the first a cladding, or any Supporting structure for optimal Solar col photovoltaic device 210, after the last such device, or in both lection and structure support of the entire system 100. The locations. Coatings such as that absorb infrared and/or ultra frame 130 may be configured to serve to shield the light violet and reflect visible may be applied on the surface of the tube/guide/fiber/pipe 140 and the converter module 150 from thermoelectric or thermionic device upon which solar radia environmental factors such as air temperature, air humidity, tion incidence hits. The thermoelectric or thermionic device water, wind, etc. The frame 130 may also be configured as a thus captures and converts thermal energy from that portion part of heat sinks/pipes for the photovoltaic conversion. The of the spectrum which would otherwise not be sufficient to frame 130 may further serve in a preferred modular configu activate electrons from the valence band to the conduction ration to be integrated into the thermionic and thermoelectric band across a band gap in a photovoltaic device. It will be conversion as part of a hot side or a cold side. In some understood of course that the heatenergy converteris optional embodiments frame 130 may even further consist of separate and will not be necessary or required in many installations. layers or regions as a hot side and a cold side for the thermi 0086. An alternative embodiment for the conversion mod onic and thermoelectric conversion. ule 250 is shown in FIG. 2B. In this configuration the ther 0079 Light tube 140 is preferably a conventional appara moelectric/thermionic devices 220 are directly physically/ tus for guiding light rays from the concentrator 120 to the mechanically coupled to the photovoltaic devices 210, and converter module 150. extract heat that is associated with Such devices, rather than 0080. Other examples will be apparent to those skilled in deriving directly from within the solar flux beam. In some the art for components 110 - 140, and it is expected that the embodiments the positioning of the thermoelectric orthermi particular components and configuration will vary Substan onic device 220 can be adaptively varied (by an automated tially from application to application depending on perfor mechanical positioning system) in accordance with an opti mance requirements, cost constraints, etc. Moreover while mal behavior observed at a particular location/installation/

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time of year. It will be understood by those skilled in the art flux incidence impinges first on a AlGaAs photovoltaic cell of that other embodiments may utilize features from both of band gap at about 2.54 eV for the absorption and conversion these approaches, and the invention is not so limited. of solar photons of wavelengths from blue/green to near ultra 0087 Although the solar spectrum and photonic device violet and then on to a second GaAs photovoltaic cell of band physics are well known in the art and many prior-art photo gap at about 1.47 eV for the absorption and conversion of Voltaic cells with various compositions and band gaps have photons of wavelengths from orange/red to green/yellow and been fabricated, the present invention provides further further on to a third GaSb or Ge photovoltaic cell of band gap improvement to the photon-to-electricity conversion effi close to 0.7 eV for the absorption and conversion of photos of ciency and the concentration factor through a modular plat wavelengths from medium infrared to red/near infrared. It form capable of integrating the photon-to-electricity and will be apparent to those skilled in the art that other materials heat-to-electricity conversion devices. Unlike a conventional of elemental (including silicon), binary, ternary, quaternary, prior-art multi-junction solar cell that operates with limited or higher number of elements in compositions may be utilized concentration factor and operating temperature because of to optimize the number of sub-modules and the order of thermal expansion mismatches between the dissimilar con cascading Sub-modules and to maximize the Solar-to-electric stituent layers in a monolithic die and other thermal effects ity conversion efficiency.

associated with temperature-dependent material properties 0092. While the present discussion provides an example Such as series resistance, band gap, and built-in Voltage, the of three (3) cascaded sub-modules, it will be apparent to those present invention uses multiple single crystal cells of differ skilled in the art that the principles of the invention can be ent compositions and thicknesses that the combined scheme generally applied to any number of stages depending on the can absorb equal or larger amounts of solar spectrum than the desired cost and performance requirements. Furthermore in prior art multi-junction Solar cells under significantly higher some embodiments it may be desirable to have overlap in concentration. band gap coverage between one or more successive Sub 0088 Prior-art single-junction solar cells made of single modules or stages. Still further, in some embodiments where crystal, polycrystalline, or amorphous layers are limited to the thermal management of cells under concentration is able wavelengths within a portion of the Solar spectrum corre to maintain cells below each cell's junction temperature, the sponding to their respective band gaps for Solar absorption photovoltaic cells in the cascade may be made of single and conversion. The present invention preferably arrange junction, double-junction, and/or multi-junction. single junction, single crystal devices to absorb solar flux in a 0093. A preferred embodiment of a packaged sub-module cascade arrangement. In a simple example of such configu 300 according to the present invention is illustrated in FIG. ration a first cell absorbs wavelengths within a first portion of 3A. The packaged sub-module 300 is a building block of the the Solar flux with energy above its first band gap, a second converter module as in FIG. 1 and preferably includes a cell absorbs energy above its respective second band gap, and conductor 330 preferably made of indium tin oxide, gold, so on. The cells are configured so that a portion of the Solar copper, or other materials of high electrical conductivity, a flux that is not absorbed by the first cell is nonetheless heat-to-electricity conversion device 320 and/or a photon-to absorbed by one or more Subsequent cells in the cascade. In electricity conversion device 310, a heat sink/pipe 335, a this fashion, a larger portion (a greater number of wave multilayer board 360, a light cavity 370, as appropriate, for lengths) of the entire radiation spectrum can be utilized and radiation transmission, and another conductor 380 which is converted to electrical form. preferably set to an opposite polarity from conductor 330 or a 0089. Prior-art tandem cells are typically made of two bias voltage between conductors 330 and 380 forming an different photovoltaic cells mechanically stacked on top of electrical circuit under normal operating conditions. Note each other. Preferred embodiments of the invention increase that the size, shape and configuration of the components is the number of cascading cells and add a variety of modular merely illustrative, and no assumptions or limitations should configurations. Different modular configurations may be drawn from these specific depictions. include photovoltaic cells of single p-n junction or a combi 0094. The photon-to-electricity conversion device 310 is nation of single-junction cells with double-junction cells or preferably connected with two electrical conductors 330 and even multi-junction cells to maximize full Solar spectrum 380 of opposite polarity for the collection of photocurrent and utilization and to optimize among cost, concentration factor, the generation of a DC photovoltage when photons in the thermal management, and reliability. solar flux, S. are absorbed. The photon-to-electricity conver 0090 Preferred embodiments of the invention also pro sion device 310 preferably is a photovoltaic cellor an array of vide a novel scheme to transfer the heat from the interaction photovoltaic cells. The photon-to-electricity conversion of solar flux 205 with the hot side of a thermionic or thermo device 310 is preferably positioned in the direct path of the electric device 220 arranged along the solar ray path of the radiation in this case solar rays from a light tube? guide/ cascade. While FIG. 2A shows the solar flux travelling in a fiber/pipe 140 (as in FIG. 1) and again is preferably a photo straight line for ease of illustration, it will be understood that Voltaic device adapted to absorb a partial range of Solar spec the actual route may vary according to design constraints. By trum or energy, S, and to convert Such to electricity. converting both photonic energy 230 and heat 240 and com 0095. In fact, for a given semiconductor material, the solar bining the two into converted electricity 245, the present flux (or other radiation source) of photons of different ener invention achieves higher overall conversion efficiency under gies penetrate different distances as a function of solar energy high Solar concentration. The compositions of the photon-to or wavelength-dependent absorption coefficient. Different electricity conversion devices 210 in the present invention are semiconductor materials exhibit different absorption coeffi preferably chosen to realize desired band gaps for absorbing cient curves and usually have an abrupt edge in their absorp all or most of Solar spectrum of radiation. tion coefficient curves, corresponding to the photons of 0091 For example, a simple cascading arrangement of energy below the band gap that do not have sufficient energy photovoltaic cells is preferably structured so that the solar to raise an electron across the band gap. Consequently these

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photons are not absorbed and are instead transmitted through 0101. As shown in FIG. 3A, the hot side of the heat-to the material. Thus photons having energy above the band gap electricity conversion device 320 is preferably positioned in have sufficient energy to raise an electron across the bandgap the direct path of Solar flux, and has a single layer or multi and are absorbed. layers of absorptive and reflective coatings (not shown). The 0096. Therefore, for a photovoltaic device, photons in the cold side of the heat-to-electricity conversion device 320 is impinging Solar flux, S. of energy, in eV, greater than or equal connected to a heat sink/pipe 335 that is preferably coupled to to the band gap of the active p-n junction will be absorbed so the multilayerboard 360 and the frame 130 (shown in FIG.1). that an amount of Solar energy equal to the band gap is 0102) The heat sink/pipe 335 may be embodied with a converted to electricity. Some photons of energies greater number of different materials, dimensions, shapes, propor than the band gap are re-emitted as heat or light, and it may be tions, densities, and configurations depending on cost/perfor desirable to capture this type of heat energy as well as men mance requirements. As such, heat from the Solar interaction tioned herein. Photons of energy less than the band gap of the with the hot side of device 320 is preferably not wasted but active p-n junction will mostly transmit (not be absorbed) instead used for electricity generation. through the active p-n junction. 0103 Photon-to-electricity conversion device 310 and 0097. Preferred embodiments of the present invention pro heat-to-electricity device 320 are preferably constructed from vide a new type of converter module that, in addition to the one or more p-n junctions. The p-n junctions can beformed by conversion of solar flux of photons, preferably also converts a low-cost material growth method Such as prior-art liquid heat into electricity. Heat is usually generated from the sub phase epitaxy (LPE), gas diffusion, or an equivalent method sequent interactions between transmitted light and device on a crystalline Substrate material; of course other techniques materials and is typically associated with the transfer of known in the art can also be used if desired. While LPE has absorbed light energy into heat through atomic vibration in been used in the past for LED manufacture, the Applicant is the lattice structure. This can occur when incident photons unaware of any prior implementation for Solar cell technol have energy in excess of that of the bandgap of the material in ogy. This technique is expected to be particularly useful for question. In preferred embodiments of the invention, a ther this type of device, and can result in Substantially greater mal conversion can be done for those portions of the concen wafer throughput figures. The solid-state p-n junction orther trated solar insolation spectrum situated both below and mal diodes in the thermoelectric/thermionic devices can also above the bandgaps covered by the photovoltaic devices. be made using such technology.

0098. As noted earlier, the heat-to-electricity conversion 0.104 FIG. 3B shows another embodiment for the conver device is preferably positioned in the direct path of the solar sion sub-module 305. The hot side of the heat-to-electricity flux, S, and preferably is a thermoelectric or thermionic conversion device 320 is preferably connected to the front device 320. Thus as seen in FIG. 3A, the sub-module can side of the photon-to-electricity conversion device 310 with a accommodate either a photovoltaic device 310 or a thermi heat conductor 337 that is preferably one of the following: onic or thermoelectric device 320 within the radiation path. conducting ribbons, wires, and/or thermal vias. While shown However, as noted earlier in some embodiments (see FIG. as a single structure, it will be understood that multiple indi 3B) the thermoelectric or thermionic device 320 may not lie vidual members may be used for the heat conductor. The heat directly within the flux, and, instead, may be extracting heat conductor 337 is preferably not connected electrically to the primarily from the photovoltaic device 310 instead. In FIG. front side electrical conductor 330. The heat conductor 337 3B athermoelectric or thermionic device 320 is coupled by a may optionally connect one or multiple heat-to-electricity heat extraction member 337. An additional heat sink/pipe 336 conversion devices 320 to the photon-to-electricity conver can be employed as well if desired depending on the relative sion device 310. The heat sink/pipe 336 connected to the cold heat dissipation needs/characteristics of devices 310 and 320. side of the heat-to-electricity conversion device 320 is pref 0099. A prior-art thermoelectric device responds to a tem erably separate from the heat sink/pipe 335 for the photon perature gradient or the absorption of infrared radiation (heat) to-electricity conversion device 310. with a Voltage at the interface of dissimilar semiconductors 0105. Furthermore, in a novel scheme, columns of n- and that creates a current flow through the circuit (the external p-type thermal diodes for the thermoelectric or thermionic load) via the Seebeck effect. A prior-art thermionic device, by devices 320 are preferably formed and shaped using a via adding solid-state p-n junctions (as emitter-base and collec structure (not shown) which is on or embedded in multilayer tor-base junctions) to conventional thermoelectric semicon board.

ductor (as base), responds to a temperature gradient between 0106. As shown in a cross section in FIG.3C, a multilayer an emitter (hot) side and a collector (cold) side and Fermi board 360 is preferably used to house the packaged sub level discontinuities at the interfaces between the emitter and module that may include the the heat-to-electricity conver a semiconductor barrier and the semiconductor barrier and a sion device 320, the photon-to-electricity conversion device semiconductor gap material with a potential difference, 310, the light cavity 370 in configurations that use light trans which may drive current flow through the circuit (the external mission, thermal or conducting vias 323, other circuit com load). ponents 325 Such as diodes, tracking sensors, and other 0100 More specifically, preferred embodiments of the devices, and conductors and pads 327. The thermal vias 323 invention provide a novel heat transferring mechanism that can make contacts, preferably using thermal interface mate preferably uses a thermal expansion matched low-tempera rials or solder, to heat sinks and/or heat pipes. ture cofired ceramic, high-temperature cofired ceramic (oran 0107 The multilayer board 360 is preferably made of a equivalent) multilayer board 360 to the solar-to-electricity prior-art low-temperature cofired ceramic, high-temperature conversion device with metal-filled or other conducting ther cofired ceramic, or printed circuit board or a similar board mal vias (not shown) to transfer heat. This heat can then also configuration and may contain multiple module components. be converted into electricity to supplement the overall radia In some embodiments of the converter module 300, a novel tion conversion operation. light cavity 370 may be formed on the multilayer board 360

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and positioned directly below the photon-to-electricity con proper Solar flux incidence and transmittance. The particular version device 310. Bypass and blocking diodes (not shown) material/structure is not critical, and it will be understood that are preferably designed and incorporated to prevent the com a variety of implementations will be possible depending on plete loss of power (which may occur in case a photon-to the particular components chosen for the conversion system. electricity conversion cell fails or is shadowed). These can be The packaged sub-modules 300 are preferably intercon embedded into the photon-to-electricity conversion device nected by ball grids, interposers, micro tubes, or similar con 310 or multilayer board 360 or panel of modules. tact mechanisms within the casing. The placement and con 0108. A first exemplary embodiment of a full converter nection of the packaged sub-modules 300 to the casing 440 module 400 is illustrated in FIG. 4 which includes a linear may be achieved through slots, sockets, sliders, anchoring arrangement of multiple and separate sub-modules 300 at fasteners, tensioned springs, or similar contact mechanisms different positions in the flux path. This particular embodi and, if necessary, through means of adjustment of Sub-mod ment of a full converter module 400 thus includes multiple ule positions.

thin-layer photon-to-electricity devices 410 (each with its 0113. Furthermore, while not shown specifically in FIG.4, distinct junctions from other devices) and at least one heat it will be apparent to those skilled in the art that a conventional to-electricity device 420. In this configuration the latter is mechanized control system can be implemented to physically shown at the end of the cascade. Again, it will also be apparent adjust/altera relative position and spacing between Sub-mod to those skilled in the art that different numbers of such ules. This can be done by any conventional motorized/me Sub-modules could be employed depending on cost/perfor chanical means attached to frame 440, so that the entire mance requirements. conversion module's behavior can be adjusted/optimized as 0109 The incidence and reflectance of radiation (solar necessary based on an observed output. The output can be flux) 405 to the components 420 and 410 (of packaged sub monitored by a conventional computing system (not shown) modules 300) is preferably at a right angle (90 degrees). which analyzes the solar/electrical data and then provides Packaged sub-modules 300 shown in FIG. 4 are preferably appropriate feedback to the mechanical positioner. the sub-modules of FIG.3A having photon-to-electricity con 0114. A second embodiment of a converter module 500 is version cells of different band gaps and one or more heat-to illustrated in FIG. 5. This embodiment is similar to the pre electricity devices within the flux path. The sub-modules are vious embodiment 400 and has a number of corresponding preferably positioned/arranged in a linear fashion to be in a components with the following exceptions. Instead of a direct transmission path of Solar rays (but not in one monolithic die Solar ray transmission arrangement, the Sub-modules 300 are as in prior-art multi-junction cells or mechanically-stacked arranged offset and opposite/facing each other. The incidence tandem cells) and the solar flux 405 is preferably transmitted and reflectance of solar flux (or other radiation source) 505 to from one packaged Sub-module to the next one through a light the packaged Sub-modules of a heat-to-electricity conversion cavity 415. In this arrangement, a photovoltaic device 410 in device 510 and photon-to-electricity conversion devices 520 a first top packaged sub-module in a first position in the flux are at oblique angles.

path absorbs photons of energy above its band gap from the 0115 There is no light cavity required for solar transmit incident solar flux and each subsequent device 410 in a dif tance and the module is adapted with reflectors (not shown, ferent position preferably absorbs, in like manner, from the but which can be of any conventional form suitable for the portion of the solar flux that is not absorbed by a previous sub-modules including a metallic layer within the cell) to device. The photon-to-electricity conversion devices 410 as guide the light between the Sub-modules so as to impinge on noted above are of thin layers and are preferably mounted to devices 520 and 510. A back side of each photon-to-electric a multilayer board (not shown) on an edge Surface around the ity or heat-to-electricity conversion device is preferably light cavity 415 that may be further supported by narrow grids mounted entirely to a respective multilayer board and a heat (not shown) formed at the opening of the light cavity 415. sink/pipe.

0110. One main apparent advantage of the present inven 0116 Casing 540 is again an assembly adapted to hold and tion over the prior art therefore lies in the fact that there is position the packaged sub-module 300 components 520 and preferably some physical separation on the order of about a 510 together for proper solar flux incidence, transmittance, half of a millimeter to a centimeter between the conversion and reflectance. As with the other embodiments described cells which results in increased overall module efficiency and herein, the number of sub-modules in this particular form the ability to handle larger flux concentrations. This physical factor may be varied in accordance with the particular separation will be a function of the particular application and arrangement.

can be tailored as required depending on specific system 0117. A third embodiment of a converter module 600 is cost/performance requirements. illustrated in FIG. 6. This embodiment is similar to the pre 0111. The cells also preferably are sized to have an area vious embodiment 500 with the following exceptions. The that is between a few hundred square microns to a few tens of incidence and reflectance of solar flux 605 to the packaged centimeter squared depending on concentration factor and sub-module 300 components 620 and 610 are guided by one heat handling capability. The sequence of the packaged Sub or more light tubes/guides/fiber/pipes 670. Again there is no modules, the selection of the p-n junction cell materials, and light cavity required for Solar transmittance. As before a back the cell layer thicknesses is preferably chosen such that the side of the photon-to-electricity 610 or heat-to-electricity 620 photovoltaic cells absorb and convert solar radiation (visible conversion devices is preferably mounted entirely to an asso and maybe portions of infrared and ultraviolet) into electric ciated multilayer board and a heat sink/pipe. ity and the thermoelectric (or the thermionic cells) convert 0118 Casing 640 is again an assembly adapted to hold and solar infrared and ultraviolet radiation and heat into electric position the packaged sub-modules together for proper Solar ity to maximize the overall conversion efficiency. flux incidence, transmittance, and reflectance. The light tube? 0112 Casing 440 is a preferably a rigid assembly adapted guide/fiber/pipe 670 may be prior arts of a tube, a guide, a to hold and position the packaged Sub-modules in position for fiber, or a pipe in any shape or form with reflective or micro

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scopic prisms coating oran optical guide or fiberin any shape figurations such that the majority of the photons in the Solar or form for transporting light with minimal loss of Solar light. spectrum and some of the heat generated from the interac 0119. A fourth embodiment of a converter module 700 is tions between photons and matters (e.g. non-radiative recom illustrated in FIG. 7. This embodiment preferably receives the bination, excess energy) are used in the conversion to elec concentrated solar flux in a broad focal line 705 instead of a tricity:

focal spot as in the previous embodiments. The focal line of I0127 2) improved concentration factor by using photovol solar flux 705 can be formed by a prior-art parabolic trough taic cells of a single crystal to avoid thermal stress and by collector, a linear Fresnel lens, a hemispherical bowl collec enhancing thermal management using the integration scheme tor, a cylindrical collector, or other known and contemplated in (1):

equivalents. The focal line of solar flux 705 preferably enters I0128. 3) can provide a true low-cost mass production with the module through a slit or light cavity (not shown) guided consistent yield by:

with or without a light tube/guide/fiber/pipe in any shape or I0129 a) combining both high conversion efficiency (1) form. and high concentration factor (2) into a single conversion 0120. The packaged sub-modules are preferably arranged system, with the thin-layer photon-to-electricity conversion devices 0.130 b) using a low cost liquid-phase epitaxy method, gas 710 and a heat-to-electricity conversion device 720 aligned diffusion, or similar material growth methods for the forma adjacent to each other and placed directly under slit (not tion of materials in the conversion devices, shown) to receive the focal line of solar flux 705. This allows I0131 c) using the cofired ceramic or similar multilayer for a matrix of sub-modules 300 of any desired size, such as boards for the packaging of the photovoltaic and thermoelec with N sub-modules in a width direction, and M sub-modules tric or themionic devices into a unit module. deep (with differing absorption characteristics as noted I0132) d) using solar collectors, light tubes/guides/fibers/ above) which results in a two dimensional array. Furthermore pipes, and standard components which are readily available it will be understood as well that in this arrangement addi for day-lighting, optical communication, and other applica tional cells can be placed and paired orthogonally in a plane to tions, a line connecting two more Sub-modules So that the concen 0.133 e) using proven wafer processing and packaged trated insolation flux is converted by a a three dimensional assembly methods developed and manufactured in the semi array into electrical energy. Other examples will be apparent conductor, microelectronics, and/or Solar industry. to those skilled in the art. 0.134 4) provides flexibility in design configurations that 0121. As above casing 740 is an assembly adapted to hold may encompass different types of conversion devices that and position the packaged sub-modules together for proper may be made of single p-n junction, double p-n junctions, or Solar flux incidence, transmittance, and reflectance. multiple p-n junctions, Solar collectors, Solar concentrators, 0122. A fifth embodiment of a converter module 800 is light tubes/guides/fibers/pipes, and heat sinkS/pipes to meet a illustrated in FIG. 8. This embodiment is similar to the pre given set of Solar power generation requirements. vious embodiment 500 with the following exceptions. The I0135) It is expected that embodiments of the present incidence of solar flux 805 to the packaged sub-module of a invention can result in newer generations of power facilities heat-to-electricity conversion device 820 is reflected to and that can achieve greater than 0.4 MW per acre. transmitted through multiple packaged sub-modules of thin 0.136. It will be apparent to those skilled in the art that the layer photon-to-electricity conversion devices 810 mounted above is not intended to be an exhaustive description of every to an associated multilayered board with light cavity with the embodiment which can be rendered in accordance with the exception of the terminating Sub-module of a photon-to-elec present teachings. Other embodiments could be constructed tricity conversion device 825 which does not have a light whichusea combination of features from the above described cavity. exemplary forms, such as an embodiment which uses a mix 0123. While not shown in FIG. 8, a heat-to-electricity ture of focal lines/focal spots, direct transmission and reflec conversion device 820 may be placed at the first incident tance, and varying combinations of light tubes/guides/fibers/ position or the last terminating position, or at both first inci pipes, light cavities, etc.

dent and the last terminating positions. Casing 840 is again an 0.137 Accordingly the present disclosure will be under assembly adapted to hold and position the packaged Sub stood by skilled artisans to describe and enable a number of modules 820, 810, and 825 together for proper solar flux such variants as well. While the present invention is depicted incidence, transmittance, and reflectance. using Solar flux as a radiation Source, it will be apparent that 0124 All of the aforementioned embodiments of conver the present teachings could be used in any environment where sion modules can be implemented within large scale Solar it is desirable to optimize a radiation/electrical conversion power generation plants using concentrated light collection process, particularly those involving high intensity radiation. techniques. The present embodiments can also be mounted as part of an intelligent Solar tracking system Such as depicted in What is claimed is:

US Publication No. 2007/0227574 to Cart incorporated by 1. A Solar-to-electricity conversion system configured in a reference herein. This latter system is for the most part cell/ modular platform and comprising:

module agnostic and could benefit from incorporating the a. a photon-to-electricity Subsystem including an array of conversion modules of the present invention. Successive spaced photovoltaic cells having different 0.125. The embodiments described herein provide a num band gaps to convert concentrated insolation flux within ber of benefits including at least the following for solar elec a flux path into electrical energy; tricity generation: b. a heat-to-electricity conversion Subsystem also situated 0126 1) improved conversion efficiency resulting from within said flux path and including at least one of an integrating specially arranged photovoltaic and thermionic or array of thermoelectric cells orthermionic cells to covert thermoelectric devices into different conversion module con heat into electric energy;

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c. a heat sink/pipe coupled to said photon-to-electricity 10. The system of claim 9, wherein said first photovoltaic Subsystem and/or said heat-to-electricity conversion cell is AlGaAs; said second photovoltaic cell is GaAs; and Subsystem; said third photovoltaic cell is GaSb or Ge. d. a plurality of thermal expansion matched multilayer 11. A Solar-to-electricity conversion system configured in a boards for integrating the photon-to-electricity Sub modular platform and comprising:

system, said heat-to-electricity conversion Subsystems a. a photon-to-electricity Subsystem including an offset and heat sink/pipe; cascade arrangement of two or more Successive spaced e. a light cavity situated within said flux path and adapted photovoltaic cells, each of said cells having a different to direct said concentrated insolation flux between said band gap to convert concentrated insolation flux within Successive spaced photovoltaic cells; a flux path into electrical energy; wherein said concen f, a rigid assembly for mounting said photon-to-electricity trated insolation flux is reflected between successive Subsystem, said heat-to-electricity conversion Sub photovoltaic cells as it traverses said offset cascade system, said heat sink/pipe, said plurality of thermal arrangement;

expansion matched multilayer boards and said light cav b. a heat-to-electricity conversion Subsystem with a single ity. or multiple anti-reflection and/or reflection coatings for 2. The system of claim 1 further including a light directing spectrum selectivity situated immediately before said means adapted to direct said concentrated insolation flux unto photon-to-electricity subsystem for selectively absorb said photon-to-electricity and/or heat-to-electricity conver ing and reflecting said concentrated insolation flux into sion Subsystems. said offset cascade arrangement and including at least 3. The system of claim 1, wherein said photon-to-electric one of an array of thermoelectric cells or thermionic ity and heat-to-electricity Subsystems are arranged in a cas cells to convertheat into electric energy; cade. c. a heat sink/pipe coupled to said photon-to-electricity 4. The system of claim 1 further including one or more Subsystem and/or said heat-to-electricity conversion diodes and/or other electrical circuitry embedded in said cells Subsystem;

or plurality of multilayer boards to optimize Voltage and d. a plurality of thermal expansion matched multilayer current maximums of electricity generated by said system. boards, one for each of said photovoltaic cells and said 5. The system of claim 1 further including tracking sensors array of thermoelectric or thermionic cells; embedded in said cells or plurality of multilayer boards to e. a casing assembly for mounting said photon-to-electric control motor drives that orient the solar-to-electricity con ity Subsystem, said heat-to-electricity conversion Sub version system toward the Sun. system, said heat sink/pipe, and said plurality of thermal 6. The system of claim 1 wherein said photovoltaic cells are expansion matched multilayer boards. made from liquid phase epitaxy and/or gas diffusion. 12. The system of claim 11 wherein said concentrated 7. The system of claim 1 wherein said thermal expansion insolation flux can be directed through a path that first matched multilayer boards are made of cofired ceramic. includes partial absorption by said heat-to-electricity conver 8. A Solar-to-electricity conversion system configured in a sion Subsystem, and then Subsequent reflection from said modular platform and comprising: Subsystem to a first photovoltaic cell, and then to a second a. a photon-to-electricity Subsystem including a linear cas photovoltaic cell, and then to a final third photovoltaic cell. cade arrangement of two or more Successive spaced 13. The system of claim 11 further including a positioning photovoltaic cells, each of said cells having a different mechanism for orienting said Successive photovoltaic cells band gap to convert concentrated insolation flux within and heat-to-electricity conversion Sub System relative to each a flux path into electrical energy; other and the Sun.

b. a heat-to-electricity conversion Subsystem with a single 14. The system of claim 1 wherein said photovoltaic cells or multiple anti-reflection and/or reflection coatings for are made from liquid phase epitaxy and/or gas diffusion. spectrum selectivity also situated immediately before or 15. The system of claim 1 wherein said thermal expansion after said photon-to-electricity subsystem within said matched multilayer boards are made of cofired ceramic. linear cascade arrangement and flux path and including 16. A Solar-to-electricity conversion system configured in a at least one of an array of thermoelectric cells or ther modular platform and comprising:

mionic cells to convertheat into electric energy; a. a first light directing means for receiving concentrated c. a heat sink/pipe coupled to said photon-to-electricity insolation flux:

Subsystem and/or said heat-to-electricity conversion b. a photon-to-electricity Subsystem including an offset Subsystem; cascade arrangement of two or more Successive spaced d. a plurality of thermal expansion matched multilayer photovoltaic cells, each of said cells having a different boards, one for each of said photovoltaic cells and said band gap to convert said concentrated insolation flux array of thermoelectric or thermionic cells; within a flux path into electrical energy; e. a casing assembly for mounting said photon-to-electric c. Second light directing means positioned between said ity Subsystem, said heat-to-electricity conversion Sub two or more Successive spaced photovoltaic cells; system, said heat sink/pipe, said plurality of thermal wherein said concentrated insolation flux is refracted expansion matched multilayer boards and said light cav and reflected between said successive photovoltaic cells ity. within said second light directing means as it traverses 9. The system of claim 8 wherein said two or more succes said offset cascade arrangement sive spaced photovoltaic cells include the following: a first d. a heat-to-electricity conversion Subsystem with a single photovoltaic cell of band gap at about 2.54 eV; a second or multiple anti-reflection and/or reflection coatings for photovoltaic cell of band gap at about 1.47 eV; and a third spectrum selectivity situated immediately before said photovoltaic cell of band gap of about 0.7 eV. photon-to-electricity subsystem for selectively absorb

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US 2009/025.0099 A1 Oct. 8, 2009

ing and reflecting said concentrated insolation flux into photovoltaic modules, each of said modules having a said linear cascade arrangement and including at least different band gap to convert concentrated insolation one of an array of thermoelectric cells or thermionic flux within a focal line into electrical energy; cells to convertheat into electric energy; wherein said photovoltaic modules each include one or e. a heat sink/pipe coupled to said photon-to-electricity more photovoltaic cells situated in a planar arrange Subsystem and/or said heat-to-electricity conversion ment within said focal line; Subsystem; a heat-to-electricity conversion Subsystem situated f a plurality of thermal expansion matched multilayer immediately before or after said photon-to-electricity boards, one for each of said photovoltaic cells and said Subsystem within said focal line and including at least array of thermoelectric or thermionic cells; one of an array of thermoelectric cells or thermionic g. a casing assembly for mounting said photon-to-electric cells to convert heat from said concentrated insolation ity Subsystem, said heat-to-electricity conversion Sub flux into electric energy;

system, said heat sink, said plurality of thermal expan c. a heat sink/pipe coupled to said photon-to-electricity sion matched multilayer boards and at least said second Subsystem and/or said heat-to-electricity conversion light directing means. Subsystem;

17. The system of claim 16 wherein said first light directing . a plurality of thermal expansion matched multilayer means is one of a tapered light tube, a light guide, a light fiber, boards, one for each of said photovoltaic cells and said or a light pipe. array of thermoelectric or thermionic cells; 18. The system of claim 16 wherein said second light e. a casing assembly for mounting said photon-to-electric directing means is one of a tapered light tube, a light guide, a ity Subsystem, said heat-to-electricity conversion Sub light fiber, or a light pipe. system, said heat sink/pipe, said plurality of thermal 19. A Solar-to-electricity conversion system configured in a expansion matched multilayer boards and said light cav modular platform and comprising: ity.

a. a photon-to-electricity Subsystem including a linear cas 22. The system of claim 21 further including a light slit for cade arrangement of two or more Successive spaced generating said focal line.

photovoltaic cells, each of said cells having a different 23. The system of claim 21 wherein multiple focal lines are converted in said planar arrangement by photovoltaic cells band gap to convert concentrated insolation flux within arranged in a two dimensional array. a flux path into electrical energy; 24. A Solar-to-electricity conversion system configured in a a heat-to-electricity conversion subsystem situated modular platform and processing concentrated solar insola immediately before said photon-to-electricity sub tion flux incidence into the said solar-to-electricity conver system with a single or multiple anti-reflection and/or sion system with a concentration factor between 250x and reflection coatings for spectrum selectivity for selec 5,000x comprising:

tively absorbing and reflecting said concentrated insola a. a photovoltaic Subsystem including an array of photo tion flux into said linear cascade arrangement and Voltaic cells of different band gaps and each cell having including at least one of an array of thermoelectric cells an area between about 300 hundred square microns to 30 or thermionic cells to convertheat into electric energy; square centimeters to convert concentrated Solar visible, c. a heat sink/pipe coupled to said photon-to-electricity ultraviolet, and infrared radiation into electrical energy; Subsystem and/or said heat-to-electricity conversion . a thermoelectric or a thermionic Subsystem including a Subsystem; plurality of thermoelectric or thermionic cells to convert d. a plurality of thermal expansion matched multilayer at least said concentrated Solar infrared radiation and/or boards, one for each of said photovoltaic cells and said a temperature gradient into electrical energy; array of thermoelectric or thermionic cells; c. a frame adapted to Support and function as an environ e. a casing assembly for mounting said photon-to-electric mental shield and which is integrated as part of the hot ity Subsystem, said heat-to-electricity conversion Sub side and/or cold side (heat sink) in the heat-to-electricity system, said heat sink/pipe, and said plurality of thermal conversion;

expansion matched multilayer boards. . a first light directing means for directing said concen 20. The system of claim 19 wherein said concentrated trated Solar insolation flux incidence and any reflectance insolation flux can be directed through a path that first unto said photovoltaic and thermoelectric or thermionic includes partial absorption by said heat-to-electricity conver Subsystems;

sion Subsystem, and then reflection so that said flux passes in e. a thermal expansion matched multilayer board adapted a Substantially straight line from said Subsystem to a first to integrate components (a) and (b) and to transfer heat photovoltaic cell, and then to a second photovoltaic cell, and among Such components by thermal vias; then to a final third photovoltaic cell. f, a second light directing means in the multilayer board 21. A Solar-to-electricity conversion system configured in a adapted to direct concentrated Solar insolation flux modular platform and comprising: between photovoltaic cells. a. a photon-to-electricity Subsystem including a first linear cascade arrangement of two or more Successive spaced c c c c c