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?
Zachary Holman, Arizona State UniversityPVMirror: A Solar Concentrator Mirror Incorporating PV Cells
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
• 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
• Diffuse light is collected by PV cells → broader geographical use than CSP
How does it improve the state-of-the-art?
Zachary Holman, Arizona State UniversityPVMirror: A Solar Concentrator Mirror Incorporating PV Cells
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
• 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
• Diffuse light is collected by PV cells → broader geographical use than CSP• 50% higher annual energy output than trough CSP…
How does it improve the state-of-the-art?
Zachary Holman, Arizona State UniversityPVMirror: A Solar Concentrator Mirror Incorporating PV Cells
455055
6065
7075
80
600 800 1000 1200 1400150200250300350400450500550600650700750
Phoenix
Pass-band cut-off wavelength (nm)
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
Pass-band cut-off wavelength (nm)
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
Pass-band cut-off wavelength (nm)
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
• 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
• 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
How does it improve the state-of-the-art?
Zachary Holman, Arizona State UniversityPVMirror: A Solar Concentrator Mirror Incorporating PV Cells
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
(%)
CSP storage fraction (%)
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
(%)
CSP storage fraction (%)
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
Zachary Holman, Arizona State UniversityPVMirror: A Solar Concentrator Mirror Incorporating PV Cells
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
Zachary Holman, Arizona State UniversityPVMirror: A Solar Concentrator Mirror Incorporating PV Cells
400 600 800 1000 1200 1400 1600 18000
102030405060708090
100
Ref
lect
ance
(%)
Wavelength (nm)
Simulated long-pass Measured long-pass Simulated band-pass