Freeform optics applications in photovoltaic concentration

(1)

Print

Submitted

on August 23, 10:54 AM for energy12 Proof

ABSTRACT FINAL ID: SM2A.3 CONTROL ID: 1464611

TITLE: Free form Optics Applications in Photovoltaic Concentration

Abstract (35 Word Limit): Freeform surfaces are the key of the state-of-the-art nonimaging optics to solve the challenges in concentration photovoltaics. Different families (FK, XR, FRXI) will be presented, based on the SMS 3D design method and Köhler homogenization.

AUTHORS/INSTITUTIONS: J.C. Minano, , Universidad Politecnica de Madrid, Madrid, SPAIN; KEYWORDS: General: 000.0000, General: 000.0000.

Follow ScholarOne on Twitter

Terms and Conditions of Use

(2)

Juan C. Miñano, Pablo Benítez, Pablo Zamora, João Mendes-Lopes,

Marina Buljan, Asunción Santamaría

Universidad Politécnica de Madrid (UPM), Spain

LPI , Altadena, California, USA

(3)

Index

1. Introduction

2. Free-forms in asymmetric systems

3. Freeform Köhler array concentrators



The VENTANA optical train



Daido Steel’s DFK

(4)

PV technologies

Triple-junction

III-V cells

(

C

>>1

)

III-V cells are very expensive (

~$

50,000/m

2

-

$

150,000/m

2

)!!!!!

Silicon cells (

C

= 1

)

(5)

HCPV optical specs

1. Geometrical concentration: 500-1,500

2. Low cost of optics (<$100/m

2 )

3. High optical efficiency (~80-90%), spectrally

balanced

4. Good irradiance uniformity, spectrally balanced

(6)

θ

(degs)

100

75

50

25 0.5 1 1.5

T(

θ

) (%)

α

90%

α

Geometrical

and chromatic

aberrations

Angle at which transmission drops to 90% of maximum

Ideal lens

Real lens

(7)

Tolerance budget has to be shared among:

1. Sun’s angular extension

±

0.27°

2. Optical components manufacturing

(shape and roughness)

3. Module assembling

4. Array assembling,

series connection mismatch

5. Tracker structure stiffness

6. Tracking accuracy

Tolerance budget

(8)

(9)

Concentration Acceptance Product

• CAP

=

• CAP

≈ constant for a given architecture

• CAP

is an important merit function

sin

(10)

Classic homogenization scheme

Prism

homogenizer

CAP~0.45

CAP~0.18

(11)

Classical mirror based designs

Cell

(12)

Cassegrian aplanat

Parabolic mirror

(13)

Why freeforms in CPV?

• Freeforms provide more freedom to improve

performance and functionality

• Nonimaging freeforms are not more expensive

than symmetric surfaces

• Symmetric optics cannot solve satisfactorily

(14)

Index

1. Introduction

2. Free-forms in asymmetric systems

3. Freeform Köhler array concentrators



The VENTANA optical train



Daido Steel’s DFK

(15)

Solar cell

Homogenizing

prism

Free-form

_primary

mirror (X)

Free-form

secondary

lens (R)

• Light blocking is avoided

• Wide space for heat-sink

(16)

The SMS3D design method

• SMS3D is an advanced optical design method

• SMS3D is capable to design two freeform

surfaces without optimization

• SMS3D deals with extended sources and

receivers

(17)

XR SMS 3D design

A. Cvetkovic et al. Proc. SPIE Vol. 7043-12, 2008

(18)

(19)

XR SMS 3D design procedure

(20)

* The XR700 module developed by BOEING Co. and LPI (A.Plesniak et all. 34th IEEE PV Specialist Conference, 2010)

The freeform XR concentrator

33.2%

Freeform mirror

Freeform

lens

A. Cvetkovic, M. Hernández, P. Benítez, J. C. Miñano, J. Schwartz, A. Plesniak, R. Jones, D. Whelan, Proc. SPIE Vol. 7043-12, 2008

C = 1,000x

α

=±1.8º

Glass cover

(21)

(22)

Index

1. Introduction

2. Free-forms in asymmetric systems

3. Freeform Köhler array concentrators



The VENTANA optical train



Daido Steel’s DFK

(23)

The simplest Köhler CPV design

L. W. James, Contractor Report SAND89–7029, (1989)

Images the Fresnel

lens on the cell!

2.83451 1.874190.913859 -0.0464674-1.00679 -1.96712 0 0.000005 0.00001 0.000015 0.00002 0.000025 0.00003 0.000035 0.00004 -2. 834 51 -2. 245 93 -1. 657 34 -1. 068 75 -0. 480 163 0. 10842 4 0. 69701 1 1. 2856 1. 87419 2. 46277

(24)

LPI’s Köhler array concentrators

S

S'

T

T’ O

I

I’

O’

M

_i

M

_o

(25)

The Fresnel-Köhler (FK) concentrator

(26)

0.0 0.2 0.4 0.6 0.8 1.0 0.59 0.45 0.36 0.30 0.28 0.18 3 5 7 No SOE Spherical dome SILO XTP RTP Fresnel Kohler (FK)

No SOE Spherical dome SILO XTP RTP Fresnel Kohler (FK)

sin

g

CAP

=

C

×

α

25

Comparison

Fresnel-RTP

0 5 10 15 20 25 -10 -5 -15 -25 -20 5 10 15 25 20 35 30 40 45 50 (mm) 55 Spherical Dome FK concentrator Fresnel-XTP SILO

Fresnel (no SOE)

Since (0.59/0.45)

2

_{=1.7, the FK 1,000x is equivalent to an 580x RTP!}

(27)

Freeform secondary lens

Fresnel lens

(28)

FK acceptance angle

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0 -1.6

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6 Isc

(A

)

Tracker angle (º)

Measured =

_±

1.24

o

Simulated =

±

1.25

o

(29)

FK irradiance uniformity

-5 5 0 100 200 300 400 500 600 -5 5 -5 5 0 100 200 300 400 500 600 -5 5

Measured

Peak irradiance = 595 suns

Peak irradiance = 575 suns

Simulated

Su

ns

Su

(30)

The Ventana

TM

Optical Train

• A complete off-the-shelf optics solution by Evonik and LPI

• Based on the best-in-class design: The FK concentrator

POE

= primary optical element

SOE

= secondary optical element

6x6 Fresnel

lens parquet

(31)

0

0.5

1

1.5

2

2.5

3

0

0.5

1

1.5

2

2.5

3 Cu

rr

en

t (

A)

Voltage (V)

LPI-Evonik Ventana

TM

optical train

Pm

Efficiency =

32.8%*

Fill Factor =

83.6%

Pm =

6.97 W

Isc =

2.80 A

Voc =

2.95 V

Irradiance =

847 W/m

2

Entry Aperture =

256 m

2

*No AR coatings; @Tcell=25ºC

C

= 1,024x

(32)

• Daido Steel present CPV system:

• UPM and Daido Steel are developing

a new Köhler technology,

DFK

, within

the NGCPV project

*Over illuminated cell area

CAP = Cg x sin

α

• Cg* = 950

• α

= ±0.92º

CAP = 0.49

• Higher concentration without compromising

acceptance angle is desired.

• LPI, in collaboration with UPM, has developed

high-performance Köhler freeform concentrators.

(33)

Index

1. Introduction

2. Free-forms in asymmetric systems

3. Freeform Köhler array concentrators



The VENTANA optical train



Daido Steel’s DFK

(34)

DFK optics

• Cg = 1,234

• α

> ±1.1º

• Module efficiency > 35%

Daedo Steel

module

& system

technology

LPI Köhler

optical

technology

CAP > 0.67

CAP = Cg x sin

α

(35)

POE (4 sectors Fresnel lens)

Flat FK (FK)

Dome-shaped FK (DFK)

(36)

17.3

13.8

5.5

5 

C

_g

=1,234x



f/ 0.81



SOE material: B270-equiv. glass



POE material: PMMA

cell side

design area side

0.25mm

wide frame around

the cell for assembly tolerances

All dimensions

in mm

(37)

Irradiance uniformity

0 200 400 600 800 1000 1200 1400 suns 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Ef fi ci e n cy

Angle (deg)

Transmission curve

1.18 deg

90%

(38)

AR coating on

SOE

efficiency

Optical

Acceptance

angle

NO

85.6%

±1.18º

YES

87.5%

±1.18º

AR coating

50 55 60 65 70 75 80 85 90 95 100

300 500 700 900 1100 1300 1500 1700

Tr an sm is sion (% ) Wavelength (nm) α=0deg α=10deg α=20deg α=30deg α=40deg α=50deg α=60deg α=70deg

(39)

ISSUE

FLAT FK

DOME-SHAPED FK

Acc. angle (α)

1

_{±1.03 deg}

_{±1.18 deg}

CAP

0.63

0.72 Optical efficiency

2

_86.5%

_87.5%

Irr. uniformity

Excellent

Very good

F-number

1.07

0.81

1

_C

_{= 1,234x for both concentrators}

(40)

SILO

XTP

RTP

esnel Kohler (FK)

SILO

XTP

RTP

esnel Kohler (FK)

FK

r

0.63 DFK

0.72 SILO

XTP

RTP

FK

DFK

(41)

Practical problems with RTP secondaries

Köhler SOE

Classical SOE

Lost ray

Every surface is

optically active

Total

Internal

Reflection

(TIR)

(42)



POE mold has a

9-part molding die



3 different demolding movements



Only central part (red) needs

positive draft angles

(43)

Index

1. Introduction

2. Free-forms in asymmetric systems

3. Freeform Köhler array concentrators



The VENTANA optical train



Daido Steel’s DFK

(44)

Conclusions

• Freeform optics is a proven technology for higher

performance CPV designs

• Highly asymmetric CPV problems can optimally solved

with freeforms, as the SMS3D XR design

• Köhler array concentrators, as the FK, solve practical

issues and outperform classical designs

(45)

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, 2003

COMPACT FOLDED-OPTICS ILLUMINATION LENS US 6,896,381 May 24, 2005

COMPACT FOLDED-OPTICS ILLUMINATION LENS US 7,152,985 December 26, 2006

COMPACT FOLDED-OPTICS ILLUMINATION LENS US 7,181,378 February 20, 2007

DEVICE FOR CONCENTRATING OR COLLIMATING RADIANT ENERGY US 7,160,522 January 9, 2007

DISPOSITIVO CON LENTE DISCONTINUA DE REFLEXIÓN TOTAL INTERNA Y DIÓPTRICO ESFÉRICO PARA CONCENTRACIÓN O COLIMACIÓN DE ENERGÍA RADIANTE Spain ES P9902661December 2, 1999

OPTICAL MANIFOLD FOR LIGHT-EMITTING DIODES US 7,380,962

OPTICAL MANIFOLD FOR LIGHT-EMITTING DIODES US 7,286,296

THREE-DIMENSIONAL SIMULTANEOUS MULTIPLE-SURFACE METHOD AND FREE-FORM ILLUMINATION-OPTICS DESIGNED THEREFROM US 7,460,985 December 2, 2008

Partial List of Patents Pending

DEVICE FOR CONCENTRATING OR COLLIMATING RADIANT ENERGY - a continuation of US 7,160,522

(46)

• This work is under the

NGCPV EU-Japan project,

funded by EU Commission

(ENERGY,2011,2,1-1 Grant

agreement no. 283798) and

Japanese NEDO.

• Devices shown in this presentation are protected

under US patent 8,000,018 & International patent

applications 0905286.3, 200980154626.5,

(47)

(48)

0.76 0.77 0.78 0.79 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88

0 10 20 30 40 50

O pt ic al Ef fic ie nc y

Edge Radius (μm)

Only Rounded Outer Corners

Equally Rounded Inner and Outer

Corners

Outer

corners

Inner

corners

Outer

corners

LENS

No rounded

corners

ciency drop due to teeth rounded edges

83.4%

87.5%

30μm

87.0%

0.78 0.79 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.90 0.89

(49)

(50)

Top view

Bottom view

(51)