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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
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Physical Technical
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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