Katherine Baker, Jason Karp, Justin Hallas, and Joseph Ford

UCSD Photonics

11/21/201

1 PHOTONIC SYSTEMS INTEGRATION LABORATORY – UCSD JACOBS SCHOOL OF ENGINEERING Photo: Kevin Walsh, OLR

University of California San Diego

Jacobs School of Engineering

Photonic Systems Integration Lab

Reactive Self-Tracking Solar

Concentration

Katherine Baker, Jason Karp, Justin

Hallas, and Joseph Ford

November 3, 2011

OSA Optics for Solar Energy (SOLAR)

UCSD Photonics Concentrator Tracking - Motivation

11/21/201

1 PHOTONIC SYSTEMS INTEGRATION LABORATORY – UCSD JACOBS SCHOOL OF ENGINEERING

Calculations are for a flat collector in San Diego, CA, tilted at latitude. Calculations based on A. Rabl. Active Solar

Collectors and Their Applications.(Oxford University Press, New York, 1985)

2D Mechanical Tracking

UCSD Photonics Concentrator Tracking - Motivation

11/21/201


12/21

6/21

3/20

12/21

6/21

3/20

Static Collector 1D Mechanical Tracking

Calculations are for a flat collector in San Diego, CA, tilted at latitude. Calculations based on A. Rabl. Active Solar

Collectors and Their Applications.(Oxford University Press, New York, 1985)

2D Mechanical Tracking

Goal: Use a material with a nonlinear response to light to minimize mechanical tracking needs.

UCSD Photonics Planar Micro-Optic Solar Concentration

J. H. Karp et al, “Planar micro-optic solar concentrator,”

Optics Express, 18(2) (2010).

J. H. Karp et al, “Radial coupling method for orthogonal

concentration within planar micro-optic solar collectors,”

OSA Optics for Solar Energy (2010)

Thousands of individual

apertures couple to a

common waveguide

Thickness

1.7mm

1.0

mm

41μm

Fabrication Results

1mm

4m

m

Co

nc

en

trate

d

Ou

tpu

t C

on

ce

ntr

ate

d

Ou

tpu

t

120 Reflective Prisms

“Couplers”

“Injection Features”

Coupled light striking

another prism will

decouple – dominant

loss

UCSD Photonics Passive Prototype Performance

11/21/201


Xe arc lamp solar simulator

Ph

oto

vo

lta

ic

Lens Array

Concentrated Output

Optimized

Current

91.0%

76.2%

52.3% (measured)

37.5x concentration (2 edges)

Optimized

Current

UCSD Photonics Mechanical Tracking

11/21/201


Aligned

Misaligned - Loss

Large Scale Mechanical

Tracking

• Typical for CPV systems

• High accuracy requirements

• Wind-Loading problems

Mechanical Micro-Tracking

• Moving one optical element

relative to the other allows tracking

of large angle with small motions

• J. Hallas et al, “Lateral translation

micro-tracking of planar micro-optic

solar concentrator,” Proc. SPIE

7769, 776904 (2010).

UCSD Photonics New approach: Reactive Tracking

Create nonlinear

response to focused

sunlight

11/21/201


Reactive Tracking

– Coupler relocates in response to sunlight

– Cladding index material response

– Spot moves less than 60 um/minute for a 4mm lenslet/slab distance

Continuous Coupling Facets

Tilted Incoming

Sunlight

Shifted High

Index Region

Incoming

Sunlight

High Index

Region

Coupled

Light

Coupled

Light

UCSD Photonics Angle-range Optimized Lens Design

11/21/201


• Acrylic asphere lens

• F2 Glass Waveguide

• Off-Axis performance falls off

• Easy to fabricate

• Acrylic and polycarbonate aspehere lenses

• F2 Glass Waveguide

• Improved off-axis performance; smaller spot sizes

overall

• More difficult to fabricate

• Vignetting at Extreme Angles

0° 10° 20° 30° 35° 0° 10° 20° 30° 35°

UCSD Photonics

At 128x geometric

concentration

Singlet: 65% On-Axis

Efficiency – 83x effective

concentration

Doublet: 86% On-Axis

Efficiency – 110x

effective concentration

Simulated Results – On-Axis

11/21/201


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0 100 200 300

Op

tica

l E

ffic

ien

cy

Geometric Concentration

0

0.2

0.4

0.6

0.8

1

1.2 1.4 1.6 1.8 Op

tica

l E

ffic

ien

cy

Index of Refraction of High Index

Spot

Bulk Fluid

Index = 1.20 1.25 1.30 1.35

Singlet

Doublet

Singlet Lenses Doublet Lenses

UCSD Photonics Simulated Results – Off-Axis

11/21/201


Accepted Annual Energy:

25% - Static Panel

60% - 1D Polar Tracking

28% - Static Panel

83% - 1D Polar Tracking

Passive Design Reactive Singlet Reactive Doublet

1D Polar

Tracking

Static

Panel

UCSD Photonics Nanofluidic design concepts

11/21/201


Optical Gradient: High Particle

Concentration Low-Index Suspension

Focused Sunlight

Direct Trapping Design

Optical trapping of particles

Ideal solution since no

extra components are

needed

Index response can be achieved through

localized trapping of high index particles

in a low index suspension

Optical Tweezers

K.C. Neuman and S.M. Block, “Optical trapping.,” The Review of

scientific instruments, vol. 75, Sep. 2004, pp. 2787-809.

• As light refracts through a sphere, it changes

angle. Through conservation of momentum, the

particle will move in the opposite direction

•Particles large enough for the needed index

change would cause scattering and fail to stay in

suspension

UCSD Photonics Nanofluidic design concepts

11/21/201


Organic Photovoltaic

Optical Gradient: High Particle

Concentration Low-Index Suspension

Focused Sunlight

Direct Trapping Design

Optical trapping of particles

Ideal solution since no

extra components are

needed

Won’t work

Photovoltaic Design

Electro-optical trapping of

particles

Requires photovoltaic layer

and additional processing,

but no external power

Photoconductor Design

Electro-optical trapping of

particles

Requires photoconductor

layer and external power

P.Y. Chiou et al “Massively parallel manipulation of single

cells and microparticles using optical images.,” Nature, vol.

436, Jul. 2005, pp. 370-2.

Index response can be achieved through

localized trapping of high index particles

in a low index suspension

Optically-induced dielectrophoresis

Same trapping force with 100,000 times less

optical intensity compared to optical trapping

UCSD Photonics Reactive Materials Testing

11/21/201


80 μm

Patterned ITO Slide

Colloid Under Test

Solid ITO Slide

Patterned Indium Tin Oxide Electrodes

(a Transparent Conducting Oxide)

Induced Non-Uniform Electric Field attracts

high index particles

ITO Coated Slides

~30 Ω/ sheet resistance

Mach-Zehnder

Interferometer

UCSD Photonics

11/21/2011 PHOTONIC SYSTEMS INTEGRATION LABORATORY – UCSD JACOBS SCHOOL OF ENGINEERING

Results

60 nm Polystyrene Spheres in

Water

(10% by volume)

2 Volts rms 60 Hz Square

Wave

Applied for 60 seconds

Fast, Reversible Index Change

Demonstrated

Signal

Applied

Signal

Removed

UCSD Photonics

11/21/2011 PHOTONIC SYSTEMS INTEGRATION LABORATORY – UCSD JACOBS SCHOOL OF ENGINEERING

Results

Average change in index = .033

2.3x increase in concentration (10% to 23%)

Equivalent increase for titanium dioxide in perfluorotriamylamine (FC-70 from

3M) would result in a .141 change

0

0.5

1

1.5

2

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

0 0.5 1 1.5 2 2.5

Measu

red

nu

mb

er o

f fr

inge

shif

ts

Delt

a n

Voltage (rms); 60 Hz Square Wave

UCSD Photonics Conclusions

• Self-tracking reactive concentration could enable a wide acceptance angle for

concentrator systems without precision tracking requirements.

• Wide-angle lenslet design works, given sufficient change in index of refraction

• While direct optical trapping won’t work, DEP trapping can

• Initial experiments with aqueous polystyrene demonstrate DEP-induced change in

index of refraction

• Additional materials work must be done in collaboration with industry and/or academic

partners to produce the necessary change in index of refraction

11/21/201


This research is supported by

National Science Foundation under SGER award #0844274

California Energy Commission as part of the California Solar Energy

Collaborative

Special thanks to Robert Norwood and Palash Gangopadhyay of the University of Arizona for materials

information and preparation and to Eric Tremblay for assistance with optical design

UCSD Photonics

Thank you,

[email protected]

psilab.ucsd.edu

11/21/201


mailto:[email protected]

Documents

Katherine Baker, Jason Karp, Justin Hallas, and Joseph Ford