CONCENTRACION FOTOVOLTAICA - 2009 03 12 CPV Webinar
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Transcript of CONCENTRACION FOTOVOLTAICA - 2009 03 12 CPV Webinar
POLITÉCNICA
Webinar in Photovoltaic ConcentrationMarch 12, 2009
Webinar in Photovoltaic ConcentrationWebinar in Photovoltaic ConcentrationMarch 12, 2009March 12, 2009
High concentration photovoltaics: potentials and challenges
High concentration photovoltaics: potentials and challenges
J.C. Miñano, P. Benítez
LPI-LLC, USAUniversidad Politécnica de Madrid, Spain
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1. Why high concentration photovoltaics (HCPV)?
2. Concentrator optics fundamentals
3. Advanced HCPV optics
4. Comparing HCPV systems
5. HCPV versus 2-axis tracked flat-plates
6. Summary
Outline
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FhG-ISE
monolithic multijunction tandem III-V solar cells in concentration
Why high concentration photovoltaics (HCPV)?Record cell efficiencies
• From ~30% to 40% during the last decade• III-V cells are very expensive (~$50,000/m2-$200,000/m2) • HCPV purpose is to decrease cell cost by reducing its area
41.1%
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FPPV=Flat panel PVHCPV=High Concentration Photovoltaics
(High) concentration factor(High) concentration factor
Solar cell
area
A /Cg
Area A
sunlight
sunlight
HCPV
FPPV
electricity
electricity
Area A
What is HCPV?
Cg
Webinar in Photovoltaic ConcentrationMarch 12, 2009
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solar radiation
cell cost other costs+
efficiency×
cost
energy=
1. Concentration to decrease cell cost2. Efficiency=(optical efficiency) x (cell efficiency)3. optics, tracker Tolerance4. only direct radiation is useful for concentration (90-65%)
Why high concentration photovoltaics (HCPV)?
Webinar in Photovoltaic ConcentrationMarch 12, 2009
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1. Why high concentration photovoltaics (HCPV)?
2. Concentrator optics fundamentals
3. Advanced HCPV optics
4. Comparing HCPV systems
5. HCPV versus 2-axis tracked flat-plates
6. Summary
Outline
Webinar in Photovoltaic ConcentrationMarch 12, 2009
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Classic imaging PV concentrators
Example: Flat Fresnel lens
Cell
Rays tilted at the acceptance angle α: rays focus approximately on the edge of the cell
±α
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θ
(degs)
100
75
50
25
0.5 1 1.5
T(θ) (%)
α
90%
α
Geometrical and chromaticaberrations
Formal definition of acceptance angle α: Angle at which transmission drops to 90% of maximum
Ideal lens
Real lens
Classic imaging PV concentrators
Webinar in Photovoltaic ConcentrationMarch 12, 2009
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Classic imaging PV concentrators
For a given optical design concept:
sin α ≈
constant × cell side
Such “constant” strongly depends on the optical design concept
Modifying the geometrical concentration
L’
α’ α
L
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Some examples of CPV systems based on flat
Fresnel lens
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Illumination non-homogeneity in imaging concentrators
Cell
Fresnel lens
Therefore, imaging concentrators have to compromise uniformity and
pointing tolerance
Sun image on the cell
Perfect aiming Misspointing
Sun angular diameter= 0.53º (r=±0.27º)
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Classic non-imaging secondary optical elements (SOE)
Prism homogenizer
α
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Classic non-imaging secondary optical elements (SOE)
CPC-type non- imaging
concentrator(reduces cell area)
Compare cost and efficiency!
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Other imaging concentrator designs
Cell
Cassegrian two-mirrorsParabolic mirror
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Other imaging concentrator designs
Cassegrian two-mirrorsParabolic mirror
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1. Why high concentration photovoltaics (HCPV)?
2. Concentrator optics fundamentals
3. Advanced HCPV optics
4. Comparing HCPV systems
5. HCPV versus 2-axis tracked flat-plates
6. Summary
Outline
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1. Higher Efficiency
2. Higher Tolerance
3. Higher Concentration?
Why advanced HCPV optics?
• To be achieved without increasing the number of optical elements.
• Each optical surface must perform as many functions (concentration, homogenization, etc.) as possible.
• The highest Tolerance for a given Concentration will maximize Efficiency at system level.
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Symptomatology:
1. Optics surfaces require high accuracy
2. Assembling is expensive because fine adjustments become
compulsory.
3. Efficiency decreases significantly from single unit to array.
Optical mismatch
4. Efficiency increases significantly when the cells are bigger.
5. The electricity production waves in moderate windy
conditions
6. The efficiency decrease due to dirt accumulation is more
severe than in flat modules
Do you need more tolerance?
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Tolerance
Tolerance budget has to be shared among:
1. Sun’s angular extension ±0.27°2. Optical component manufacturing
(shape and roughness)3. Module assembling4. Array assembling5. Tracker structure stiffness6. Tracking accuracy
0.1°-0.5° present automotive industry standards
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Advanced HCPV optics: Free-form designs
• Free-form: surfaces with no prescribed symmetry
• New degrees of freedom to the design: A single optical element can perform multiple functions
• The SMS 3D design method of Nonimaging Optics is the most advanced method to design free-forms
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Free-form XR for HCPV (Boeing-LPI)
Homogenizing prism
Free-form lens
A. Plesniak et al. “Demostration of high performance concentrating photovoltaic module designs for utility scale power generation”, ICSC – 5, (Palm Desert, CA, USA, 2008)A. Cvetkovic, M. Hernández, P. Benítez, J. C. Miñano, J. Schwartz, A. Plesniak, R. Jones, D. Whelan, “The Free Form XR Photovoltaic Concentrator: a High Performance SMS3D Design”, Proc. SPIE Vol. 7043-12, 2008
Free-form mirror
Solar cell
Free-form lens
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Secondary lens (R)
Solar cell
Primary lens (R)
RR free-form Kohler design for HCPV
A. Cvetkovic et al. “High Performance Köhler Concentrators with Uniform Irradiance on Solar Cell”, ICSC – 5, (Palm Desert, CA, USA, 2008)
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RR free-form Kohler design for HCPV
A. Cvetkovic et al. “High Performance Köhler Concentrators with Uniform Irradiance on Solar Cell”, ICSC – 5, (Palm Desert, CA, USA, 2008)
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Other free-form designs (for SSL)Free-form RXI Free-form RXI with Kohler
integration
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1. Why high concentration photovoltaics (HCPV)?
2. Concentrator optics fundamentals
3. Advanced HCPV optics
4. Comparing HCPV systems
5. HCPV versus 2-axis tracked flat-plates
6. Summary
Outline
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What should be the criterion to compare CPV systems?
• Final merit function = cost of electricity
• It is difficult to evaluate before product is very mature
• Several parameters are usually selected as merit functions to compare
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Some parameters for CPV systems comparison
1. Module electrical efficiency at nominal conditions
2. Concentration
3. Tolerance angle (in degs)
4. Nominal power per unit area of the module, Pmodule (in Wp /m2)
5. Nominal power per unit area of the cell, Pcell (in Wp /cm2)
6. Estimated yearly energy production in certain reference locations (in kWh/(m2 year))
7. Others: Mounting complexity, numbers of parts per unit area of the module, materials cost, weight, depth, thermal design, etc
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Electrical efficiency η (%)
The efficiency-concentration-tolerance (ECT) space
Tolerance α (degs)
Concentration Cg
η
= 27%Cg =400xα
= ±0.5 degs
Example: Fresnel lens concentrator with
27%
0.5 degs
400
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Boundaries of the ECT space
Thermodynamic limits:• Electrical efficiency (for infinite junctions) limited to: η < 86%
• Concentration × Tolerance2 < n2 ≈
2.25 (n=refractive index of encapsulant)
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Electrical efficiency η
(%)
Boundaries of the ECT space
Tolerance (degs)
Concentration
η < 86%
Concentration × Tolerance2 < n2 ≈
2.25
Tolerance > sun radius = 0.26ºη
= 27%
Cg =400xα
= ±0.5 degs
Example: Fresnel lens concentrator with
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Comparing CPV systems in the ECT space
η
= 27%Cg =400xα
= ±0.5º
η
= 27%Cg =1,000xα
= ±1.8º
Fresnel lens concentrator XR free-form concentrator
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Comparing CPV systems in the ECT space
Electrical efficiency (%)
Tolerance (degs)
Concentration
1,000400
±0.5º
±2.8ºConcentration × Tolerance2 ≈
constant
±1.8º
Fresnel lens concentrator
XR free-form concentrator
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Comparing CPV systems in the ECT space
Electrical efficiency (%)
Tolerance (degs)
Concentration
2,000400
±0.5º±1.3º
Concentration × Tolerance2 ≈
constant
±2.8º
Fresnel lens concentrator
XR free-form concentrator
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Comparing CPV systems in the ECT space
A. Plesniak et al. “Demostration of high performance concentrating photovoltaic module designs for utility scale power generation”, ICSC – 5, (Palm Desert, CA, USA, 2008)
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Comparing CPV systems in the ECT space
Target Target
Advanced XR HCPV
Advanced XR HCPV
Target ≈
±2.0º 31% 1,200xTarget ≈
±2.8º 33% 600x
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1. Why high concentration photovoltaics (HCPV)?
2. Concentrator optics fundamentals
3. Advanced HCPV optics
4. Comparing HCPV systems
5. HCPV versus 2-axis tracked flat-plates
6. Summary
Outline
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solar radiation
cell cost other costs+
efficiency×
cost
energy=
HCPV versus 2-axis tracked flat-plates
• Solar radiation: Diffuse radiation can add 15-30% more for flat-plates.
• Efficiency for flat-plates use to be rated at 25ºC cell temperature while the efficiency is rated at 20ºC ambient temperature for concentrators.
• Efficiency vs temperature coefficients are different for Si and MJ cells
• Flat plate trackers don’t need accuracy
Concentration-tolerance-efficiency comparison is not possible because technologies are quite different.
solar radiation efficiency
other costs
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Conventional silicon
High efficiency
silicon
HCPV for equal
output
High performance
HCPVGoal
Module efficiency at STC (%)
12.0 19.3 - - -
Average efficiency in operation (%)
10.6 17.5 22.4 27.0 30.0
Annual solar irradiation (kWh/(m2·year))
2580 2580 2012 2012 (78%)
2012 (78%)
Nominal annual DC electrical energy density (kWh/(m2·year))
274 451 451 543 (198%)
604 (220%)
(100%) (78%)
(164%) (164%)
HCPV versus 2-axis tracked flat-plates
Example: Seville (Spain)
(100%)
(100%)
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FhG-ISE
41.1%
Record cell efficiencies
HCPV versus 2-axis tracked flat-plates
• The derivatives of efficiencies for MJ and Si cells vs time are significantly different.
• Si cells are more mature (less risk and less expected improvements)
• The same considerations affects to cell cost of both technologies
The most important advantages of HCPV vs flat-plates come from the comparison of recent time evolution of efficiencies
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1. Why high concentration photovoltaics (HCPV)?
2. Concentrator optics fundamentals
3. Advanced HCPV optics
4. Comparing HCPV systems
5. HCPV versus 2-axis tracked flat-plates
6. Summary
Outline
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Summary
1. The potential of HCPV relies on the fast increase of MJ cells
efficiency
2. The near-term challenge is beating 2-axis tracking flat-panels
3. To succeed, HCPV needs high efficiency, sufficient high
concentration and as much tolerance as possible
4. The best Efficiency-Concentration-Tolerance is being achieved by
Advanced Optics.
5. Scaling-up HCPV will need the synergy with present high-
throughput low-cost industries (such as automotive or solid state
lighting)
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LEGAL NOTICE
Devices shown in this presentation are protected by the following US and International Patents and Patents Pending:
Patents Issued
HIGH EFFICIENY NON-IMAGING US 6,639,733 October 28, 2003COMPACT FOLDED-OPTICS ILLUMINATION LENS US 6,896,381 May 24, 2005COMPACT FOLDED-OPTICS ILLUMINATION LENS US 7,152,985 December 26, 2006COMPACT FOLDED-OPTICS ILLUMINATION LENS US 7,181,378 February 20, 2007DEVICE FOR CONCENTRATING OR COLLIMATING RADIANT ENERGY US 7,160,522 January 9, 2007DISPOSITIVO CON LENTE DISCONTINUA DE REFLEXIÓN TOTAL INTERNA Y DIÓPTRICO ESFÉRICO PARA CONCENTRACIÓN O COLIMACIÓN DE ENERGÍA RADIANTE Spain ES P9902661 December 2, 1999 OPTICAL MANIFOLD FOR LIGHT-EMITTING DIODES US 7,380,962OPTICAL MANIFOLD FOR LIGHT-EMITTING DIODES US 7,286,296THREE-DIMENSIONAL SIMULTANEOUS MULTIPLE-SURFACE METHOD AND FREE-FORM ILLUMINATION- OPTICS DESIGNED THEREFROM US 7,460,985 December 2, 2008
Patents Pending
DEVICE FOR CONCENTRATING OR COLLIMATING RADIANT ENERGY - a continuation of US 7,160,522FREE-FORM LENTICULAR OPTICAL ELEMENTS AND THEIR APPLICATION TO CONDENSERS AND HEADLAMPS PCT/US2006/029464 July 28, 2006MULTI-JUNCTION SOLAR CELLS WITH A HOMOGENIZER SYSTEM AND COUPLED NON-IMAGING LIGHT CONCENTRATOR PCT/US07/63522 March 7, 2007OPTICAL CONCENTRATOR, ESPECIALLY FOR SOLAR PHOTOVOLTAICS PCT/US08/03439 Mar 14, 2008
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Further reading
R. Winston, J.C. Miñano, P. Benítez, NonImaging Optics, Elsevier Academic Press, 2005, ISBN 0127597514
J. Chaves, Introduction to Nonimaging Optics, CRC Press, 2008, ISBN: 9781420054293
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ContactsLPI EUROPE SLRamón F. de Caleya, Managing [email protected] Dross, Technology [email protected]
Edificio CedintCampus de Montegancedo UPM28223, Madrid, SPAINFax: (+34) 91 452 4892 www.lpi-europe.com
LPI LLCRoberto Alvarez, [email protected] Falicoff, Exec. [email protected]
2400 Lincoln Ave. Altadena, CA 91001, USAFax: (949) 265-0547www.lpi-llc.com
LPI POBill Tse, General Manager [email protected]
Unit 02, G/F, Photonics Centre, Science Park East Ave., Hong-Kong, CHINAFax: +852 2144 2566
www.lpi-po.com
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LPI Overview
LPI-LLCHeadquartersAltadena, California, USA
LPI-LLCHeadquartersAltadena, California, USA
LPI-POHong Kong, China
LPI-POHong Kong, China
LPI-EuropeCologne, GermanyMadrid, Spain
LPI-EuropeCologne, GermanyMadrid, Spain
Thank you!Thank you!
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Acknowledgements
The authors thank the support under the project PIE521/2008,“Investigación en nuevos concentradores FV 1000x con células solares de alta eficiencia” given by the Instituto Madrileño de Desarrollo and the Fondo Europeo de Desarrollo regional