Zachary Holman, Arizona State UniversityZachary Holman, Arizona State University PVMirror: A Solar Concentrator Mirror Incorporating PV Cells width Cut-off PV cell spectral efficiency

What is the technology?

1

• Hybrid solar-power-plant technology combining the high efficiency of photovoltaics (PV) with the energy storage benefits of concentrating solar thermal power (CSP)

• CSP perspective: A trough mirror that steals some of the light and spits out DC electricity• PV perspective: Strange four-terminal tandem in which the top cell is under one-sun illumination and

the bottom cell, which happens to be a thermal absorber, is under concentration

Zachary Holman, Arizona State UniversityPVMirror: A Solar Concentrator Mirror Incorporating PV Cells

Glass

Silicon PV cellBacksheet

Spectrum-splitting film

Visible view

Near-infrared view

2

• Spectrum-splitting film directs the solar spectrum to location of best use; VIS & IR reflected to the CSP receiver tube, NIR transmitted to the PV cells

How does it improve the state-of-the-art?


width Cut-off

PV cell spectral efficiency CSP efficiency to direct light Filter reflectance Filter transmittance

Pass-band

400 800 1200 1600 20000

102030405060708090

100

PV cell spectral efficiency CSP efficiency to direct light

Effic

ienc

y, re

flect

ance

, tra

nsm

ittan

ce (%

)

Wavelength (nm)

3


• Diffuse light is collected by PV cells → broader geographical use than CSP



Dag

get,

CA

Las

Vega

s, N

VTu

cson

, AZ

Phoe

nix,

AZ

Albu

quer

que,

NM

Pres

cott,

AZ

Flag

staf

f, AZ

Ren

o, N

VG

rand

Jun

ctio

n, C

OFr

esno

, CA

Hon

olul

u, H

IBo

ulde

r, C

OLo

s An

gele

s, C

ASa

n Fr

anci

sco,

CA

Tam

pa, F

LM

iam

i, FL

Atla

nta,

GA

New

Orle

ans,

LA

Min

neap

olis

, MN

Wilm

ingt

on, N

CBo

ston

, MA

New

Yor

k C

ity, N

YC

hica

go, I

LD

etro

it, M

IPo

rtlan

d, O

RSe

atle

, WA

3

4

5

6

7

8

9

10

Glo

bal s

olar

inso

latio

n (k

Wh/

m2 /d

ay)

15

20

25

30

35

40

45

Diff

use

fract

ion

(%)

600 800 1000 1200 1400150200250300350400450500550600650700750

Phoenix

Pass-band cut-off wavelength (nm)

1011121314151617181920212223

Pass

-ban

d w

idth

(nm

)

PV-C

SP ta

ndem

sys

tem

effi

cien

cy (%

)

4


• Diffuse light is collected by PV cells → broader geographical use than CSP• 50% higher annual energy output than trough CSP…



455055

6065

7075

80

600 800 1000 1200 1400150200250300350400450500550600650700750

Phoenix


1011121314151617181920212223

PV/CSP split (%)

Pass

-ban

d w

idth

(nm

)

PV-C

SP ta

ndem

sys

tem

effi

cien

cy (%

)

455055

6065

7075

80

600 800 1000 1200 1400150200250300350400450500550600650700750

Phoenix


1011121314151617181920212223

PV/CSP split (%)

Pass

-ban

d w

idth

(nm

)

PV-C

SP ta

ndem

sys

tem

effi

cien

cy (%

)

5055

60

70

45

40

35

30

75

80

85

600 800 1000 1200 1400150200250300350400450500550600650700750

Miami


1011121314151617181920212223

PV/CSP split (%)

Pass

-ban

d w

idth

(nm

)

PV-C

SP ta

ndem

sys

tem

effi

cien

cy (%

)

0 20 40 60 80 1008

10

12

14

16

18

20

22

Phoenix

PV only

CSP only

Syst

em e

ffici

ency

(%)

CSP storage fraction (%)

5


• Diffuse light is collected by PV cells → broader geographical use than CSP• 50% higher annual energy output than trough CSP… but with the same storage capacity• Only 10% more $$$ than trough CSP



0 20 40 60 80 1008

10

12

14

16

18

20

22

PV/C

SP ta

ndem

Phoenix

PV only

CSP only

40%50%

Syst

em e

ffici

ency

(%)


PV/CSP split: 70%

0 20 40 60 80 1008

10

12

14

16

18

20

22

20.2%

17.7%16.4%

PV/C

SP ta

ndem

Phoenix

PV only

CSP only

40%50%

Syst

em e

ffici

ency

(%)


PV/CSP split: 70%

Solana13.2%

6

• Silicon solar cells with enhanced NIR efficiency designed and fabricated• Dichroic mirror down-selection

Status and achievements of the project to date


500 1000 1500 2000

Wavelength (nm)

500 1000 1500 20000.0

0.2

0.4

0.6

0.8

1.0

1-R

Wavelength (nm)

500 1000 1500 2000

Wavelength (nm)

500 1000 1500 2000

Wavelength (nm)

TiO2/SiO2on glass

TiO2/SiO2 on polished cell

3M long-pass film on polished cell

3M band-pass film on textured cell

PV: 297CSP:257

System:554[kWh/m2/yr]

281266547

256269527

321218539

7

• Silicon solar cells with enhanced NIR efficiency designed and fabricated• Dichroic mirror down-selection• Light reflected from prototype measured to be highly specular (

8

• Silicon solar cells with enhanced NIR efficiency designed and fabricated• Dichroic mirror down-selection• Light reflected from prototype measured to be highly specular (

9

• Larger-than-expected FF losses after tabbing cells• 3M does not presently manufacture a band-pass film with the desired optical properties• Conformal lamination of 3M films is challenging; also simultaneously need good shear strength

Challenges that the team has encountered


400 600 800 1000 1200 1400 1600 18000

102030405060708090

100

Ref

lect

ance

(%)

Wavelength (nm)

Simulated long-pass Measured long-pass Simulated band-pass

Documents

Zachary Holman, Arizona State UniversityZachary Holman, Arizona State University PVMirror: A Solar Concentrator Mirror Incorporating PV Cells width Cut-off PV cell spectral efficiency