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The High Concentration Photovoltaic Systems V.D. Rumyantsev, V.M. Andreev Ioffe Physical Technical Institute Ioffe Physical Technical Institute, PV Laboratory 26 Polytechnicheskaya str., St.-Petersburg, 194021 Russia tel.: +7-812-2927394, e-mail: [email protected] High concentration solar PV concept at the Ioffe Institute 1985 “Normal” Fresnel lenses 1981 Large mirrors 1980 First HCPV installation 1990 Small-aperture area smooth-surface lenses 1 cm 1970s- AlGaAs/GaAs cells for space applications Ioffe Institute From 1999 to presentHCPV modules with InGaP/(In)GaAs/Ge cells and silicone-on-glass Fresnel lens panels 1977-1978: Measurements of the internal quantum efficiency (ηi) of radiative recombination in III-V heterostructures by records of the spectral response curves InGaP/InGaAsP/GaAs* AlGaAs/GaAs** (first photosensitive lattice-matched heterostructures) slightly p-doped (prototypes of the cells with intermediate conversion of radiation) heavily p-doped ηi =60% at room temperature and illumination intensity of 10-4 W/cm2 Ioffe Physical Technical Institute ηi =96% at room temperature and illumination intensity of 10-5 W/cm2 *I.N.Arsent’ev, D.Z.Garbusov, V.D.Rumyantsev “Internal quantum efficiency of radiative recombination in heterostructures based on wide-gap InGaAsP solid alloys”. Abstracts of the IInd All-USSR Conf. on physical processes in heterostructures. Ashkhabad, 1978, v.2, pp. 107-109 (in Russian). **Zh.I.Alferov, V.M.Andreev, D.Z.Garbuzov, V.R.Larionov, V.D.Rumyantsev, V.B.Khalfin "Heterophotocell with intermediate conversion of radiation". Sov.Phys.Semicond., 1977, v.11, N 9, p.1765-1770. 1980: Solar cells with intermediate conversion of sunlight into luminescencebeginning of a HCPV concept at the Ioffe Institute Cell structure for operation at 2500 suns* First electroluminescent characterization of the AlGaAs/GaAs solar cells of 10 mm in diameter (IR picture at forward current of 20 A) * Zh.I.Alferov, V.M.Andreev, D.Z.Garbuzov, V.R.Larionov, V.D.Rumyantsev. "Photocells with intermediate conversion of radiation operating at increased concentration ratio (k = 2500) of solar radiation". PZhTF, 1977, v.3, N 20, p.1090- 1093. Ioffe Physical Technical Institute First HCPV AlGaAs/GaAs solar installation** **Zh.I.Alferov, V.M.Andreev, Kh.K.Aripov, V.R.Larionov, V.D.Rumyantsev. "A model of autonomous solar installation with heteroface solar cells and sunlight concentrators". Geliotekhnika, 1981, N 2, p.3-6. Advantages of the small-aperture area HCPV modules - On the left- comparison of the “large”- and “small”-aperture area approaches to HCPV module design. - On the right- operation of “larger”- and “smaller”-in-area multijunction cells of the same structure under highly concentrated solar illumination of the same concentration ratio. Ioffe Physical Technical Institute Silicone-on-glass Fresnel lenses (SoG lenses) A section of the composite Fresnel lens structure with sunrays Focal plane Conc. ratio x1000, suns Silicone Focal distance (F) Glass 6 F=65 mm 5 4 Blue light 3 Red light 2 Infrared light 1 0 0 Ioffe Physical Technical Institute 0.2 0.4 0.6 0.8 Distance along receiver radius, mm 1.0 Thermal regimes of the Fresnel lenses and cells in ”all-glass” HCPV modules Lens area is 40x40mm2; SC diameter is 1.7 mm Calculated dependences of the optical efficiency on operation temperature for lenses with different focal distances F. Ioffe Physical Technical Institute Overheating of a cell, ∆T, in dependence on position and surface treatment of the heatdistributing copper plate “All-glass” HCPV module design Primary Fresnel lens of 40x40 or 60x60 mm2 Front glass base Silicone microprisms Rear base (integral cover glass) Solar cell Ioffe Physical Technical Institute Secondary plane-convex lens 12 mm in diameter Cell panel with integral cover glass Heat sink Assembled HCPV module Advantages of the modules with secondary lenses: - a wider misorientation curve; - or saving the cell materials. But: problems connected with use of the secondary lenses: A very high local concentration Limited peak current density in tunnel junctions 7500 0.14 7000 0.12 H=65 mm (opt.) 6000 0.10 5500 5000 f = 5 mm 4500 4000 f = 8 mm 3500 3000 2500 without f = 25 mm 2000 secondary 1500 lens H=63 mm H=62.5 mm 0.08 Current, A Local sun concentration ratio 6500 0.06 0.04 0.02 0.00 1000 -0.02 500 -0.04 0 -1.0 -0.5 0.0 0.5 1.0 Distance along cell surface, mm Local light concentration along the cell surface measured by scanning the focal spot in a PV system with a primary 40x40 mm2 Fresnel lens and a secondary lens of different focal distances f. Ioffe Physical Technical Institute -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Voltage, V Illuminated I-V curves of a triple-junction cell with a primary Fresnel lens and a secondary flat-convex lens under illumination from flash solar tester. A distance H between primary and secondary lenses was varied. Shortening the distance resulted in defocusing of light (improvement of the fill factor). The results on misorientation angle measurements for a PV sub-module with 40x40 mm2 primary Fresnel lens and secondary lenses of different focal distances f 1.0 f = 5 mm 0.8 0.6 f = 8 mm 0.4 f = 11 mm without 0.2 secondary lens f = 25 mm f = 20 mm Receiver photocurrent, rel. units Receiver photocurrent, rel. units 1.0 f = 5 mm 0.8 0.6 f = 25 mm f = 8 mm 0.4 without 0.2 f = 11 m m secondary lens f = 20 mm 0.0 0.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 Misorientation angle, degrees For a solar cell 1.7 mm in diameter Ioffe Physical Technical Institute -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 Misorientation angle, degrees For a solar cell 2.3 mm in diameter 2.5 Characterization equipment for multijunction concentrator cells and modules Installation for Spectral Response Measurements of MJ solar cell InGaP GaAs Flash Tester for Solar Cells (3000 X) with I-V processing (up to 30 A) Ioffe Physical Technical Institute Ge Flash Tester for assembled HCPV modules Technical parameters of the module tester: - Output area of a collimating system 0.5x1.0 m2 - Output corresponds to 1 sun AM 1.5D spectrum; - Ray divergence 32 minutes of arc; - Nonuniformity of light intensity distribution +/-4%; Evaluation of the solar cell internal resistance components in I-V measurements under flash illumination Light, voltage and current pulses at I-V measurements of the concentrator solar cells under flash illumination. Light plateau is 1 ms in duration. Dark and illuminated I-V curves as well as the curves for p-n junctions and internal resistance curves for an InGaP/GaAs/Ge triple-junction cell. On the left: GaSb-based cell demonstrating merely lumped character of internal resistance. Ioffe On the right: AlGaAs/GaAs one-junction cell demonstrating “classical” configuration Physical Technical of the resistance curve in the case of presence of both lumped and distributed resistance components. Institute LEDs and MJ cells: genetic similarity (not only in physical principles) Contact-less photo-electro-luminescent (PL-EL) characterization of the MJ cells under photoexitation Array of the red LEDs Defect (current leakage) Lateral current flow (distributed resistance) HCPV module with MJ cells *Material – AlGaInNPAs (III-V) *Growth method – MOCVD *Chip size – 0.5-1-2 mm *Operation with optical elements *High current density *Amount of heat to be dissipated *Arranged as large panels *EL intensity at photoexitation is a cumulative factor characterizing collection efficiency of the photogenerated carriers and voltage at maximum power point *Mounted automatically *Very large or extremely large potential scaling of production (for lighting and for energy generation) Ioffe Physical Technical Institute 1990: Contactless characterization of the solar cells based on direct band-gap materials by comparison of the photoluminescence (PL) and electroluminescence (EL) signals at shorter-wavelength photoexitation And recent proposal: Overall illumination with shadowed strip To characterize the top and middle sub-cells in a 3-junction cell with respect to voltage at maximum power point (under strip- or point-like illumination) PL+EL EL EL photocurrent VOC Relating to the AlGaAs/GaAs solar cells: see the book V. M. Andreev, V. A. Grilikhes, V. D. Rumyantsev, “Photovoltaic Conversion of Concentrated Sunlight”, John Wiley & Sons, Chichester, 1997, Chapter 4. 0.150 0.125 Current, A Revealing and measurements: - Leakage-active defects in the p-n junction; - Sheet resistance (varied strip width); - Internal collection efficiency of photogenerated carriers; - Open circuit voltage. At Jsc of 10 A/cm2 Jph could be only 0,5 A/cm2 Photocurrent necessary to characterize voltage at maximum power point 0.100 0.075 0.050 0.025 0.000 0.0 0.5 1.0 1.5 2.0 Voltage, V 2.5 3.0 3.5 Optical scanner for contactless characterization of the top and middle sub-cells in an InGaP/(In)GaAs/Ge cell with respect to voltage at maximum power point Cross-section of a triple-junction cell and the conditions of the photoexitation and electroluminescent signals’ generation For injection component of the forward current at room temperature, ten-fold difference in EL intensity corresponds to 59 mV difference in voltage applied to a p-n junction External view of the scanner and wafer map with a black/white cell classification. Each circle represents one solar cell. The brighter the area, the higher is a photoinduced EL-signal from the top InGaP sub-cell and the higher is expected voltage at maximum power point in working regime 0.0 1.0 Ioffe Physical Technical Institute Comparison of the illuminated I-V curves for the cells with different photoinduced EL-signals (PEL-signals) ∆V is appr. 30 mV ∆V is appr. 30 mV Illuminated I-V curves of the InGaP/GaAs/Ge cells, PEL-signals of which differ from 0.34 to 1.00 (in units presented in the wafer map). Illuminated I-V curves for the same cells at photoexitation level corresponding to operation conditions of the concentrator solar cells. The curves were recorded with the help of a flash solar simulator. Ioffe Physical Technical Institute Sun trackers and HCPV installations Stair-like module array and its position at tracking to the Sun during a day Solar installations with HCPV modules on the roof of the Ioffe Institute Ioffe Physical Technical Institute Solar HCPV installations for “in field” and “on roof” deployment (partially equipped with 0.5x1.0 or 0.5x0.5 m2 modules) 3 kWp Ioffe Physical Technical Institute 10 kWp …A dream of a HCPV researcher… Thank you for your attention! Ioffe Physical Technical Institute