high performance double-glass bifacial pv modules through...
TRANSCRIPT
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 1
High performance double-glass bifacial PV
modules through detailed characterization
Yong Sheng Khoo, Jai Prakash Singh, Min Hsian Saw
Solar Energy Research Institute of Singapore
National University of Singapore
29th September 2016
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 2
Outline
Introduction
Loss characterization in double-glass bifacial PV modules
Optical loss
Resistive loss
Approaches for high performance double-glass bifacial module
development
Half-cut cell and multi-busbar cell modules
Bifacial modules with IR reflective coating
Bifacial modules with selective reflective coating
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 3
Introduction
Power
Module Performance
Cost
Reliability
Levelized cost of electricity (LCOE)
Cost/kWh
𝐿𝐶𝑂𝐸 =
𝐿𝑖𝑓𝑒𝑐𝑦𝑐𝑙𝑒 𝑐𝑜𝑠𝑡
𝐿𝑖𝑓𝑒𝑡𝑖𝑚𝑒 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛=𝐶0 +
𝑀𝑡1 + 𝑖 𝑡
𝑛𝑡=1
𝐸𝑡(1 − 𝑑)
𝑡
1 + 𝑖 𝑡𝑛𝑡=1
𝐶0: initial capital cost 𝑀𝑡: annual O&M cost
𝐸𝑡 : annual energy produced
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 4
LCOE study of PV in Singapore Grid parity can be achieved either with aggressive price or innovative
technology strategy
GHI = Global Horizontal Irradiance, PR = Performance Ratio
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 5
Double-glass bifacial PV modules
Diffuse light
Direct light Bifacial module
LCOE can be reduced through
Higher energy yield (10-20% gain is achievable in outdoor
conditions by using Albedo from surroundings)
Improved reliability
Promising future module technology
illumination
EVA
glass
glass
EVA
bifacial cell
front side
rear side
illumination
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 6
Module structures using bifacial cells
air
glass
EVA
bifacial solar cell
backsheet
1 2Glass/backsheet
Power gain under
STC
Sellable module
power (STC
measurements)
Double-glass
More energy generation
in outdoor conditions by
using Albedo from
surroundings
illumination
EVA
glass
glass
EVA
bifacial cell
front side
rear side
illumination
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 7
Outline
Introduction
Loss characterization in double-glass bifacial PV modules
Optical loss
Resistive loss
Approaches for high performance double-glass bifacial module
development
Half-cut cell and multi-busbar cell modules
Bifacial modules with IR reflective coating
Bifacial modules with selective reflective coating
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 8
Optical loss: bifacial cell transmittance
Reflection (1-air-glass, 2-glass-encapsulant, 3-encapsulant-cell)
and Absorption (4-glass, 5-encapsulant): same as standard
glass/backsheet modules
Transmission (6-through bifacial cell and rear glass)
glass
encapsulant bifacial cell encapsulant
1 2 3
4
5
glass
6
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 9
Significant amount of near infrared light passes through bifacial
cells.
Double-glass structure shows a loss of ~ 1.30% compare to the
glass/backsheet structure under STC measurements.
EVA
glass
glass
(b)
EVA
bifacial cell
front side
rear side
Optical loss: bifacial cell transmittance
J. P. Singh, et al. "Comparison of Glass/glass and Glass/backsheet PV Modules Using Bifacial Silicon
Solar Cells," IEEE Journal of Photovoltaics, vol. PP, pp. 1-9, 2015.
-0.45
0.87
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
glass/backsheet
rela
tive c
hange in I
sc [
%]
double-glass
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 10
Double-glass structure:
No current contribution due to
the cell-gap region
Glass/backsheet structure:
Current gain due to the static
concentration effect of the
light incident on the cell-gap
region
Optical loss: cell-gap area
encapsulant
rear cover
air
front glass
encapsulant
bifacial cell
air
glass
EVA
bifacial solar cell
backsheet
1 2
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 11
Double-glass bifacial
modules show 3-4%
power loss compared to
glass/backsheet modules
The loss depends upon
the cell-gap
Optical loss: cell-gap area
J. P. Singh, et al. "Comparison of Glass/glass and Glass/backsheet PV Modules Using Bifacial Silicon Solar
Cells," IEEE Journal of Photovoltaics, vol. PP, pp. 1-9, 2015.
0 5 10 150.98
1.00
1.02
1.04
1.06
1.08
1.10
no
rma
lise
d m
od
ule
cu
rre
nt
cell-gap [mm]
double-glass
glass/backsheet
glass/backsheet_simulated
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 12
Resistive loss in stringed bifacial cells
Mainly caused by the current
flowing through the ribbons
Impact of resistive losses is
more on bifacial modules
Current flow pattern is
different for monofacial and
bifacial cells
High current generation due
to albedo
Higher resistive loss
compared to monofacial
S. Guo, et, al, "Two-dimensional current flow for stringed PV cells and its influence on the cell-to-
module resistive losses," Solar Energy, vol. 130, pp. 224-231, 2016
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 13
Outline
Introduction
Loss characterization in double-glass bifacial PV modules
Optical loss
Resistive loss
Approaches for high performance double-glass bifacial module
development
Half-cut cell and multi-busbar cell modules
Bifacial modules with IR reflective coating
Bifacial modules with selective reflective coating
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 14
Reducing resistive losses
Halved-cell modules
Multi-busbar modules
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 15
Reducing resistive losses
Combining the half-cut and multi-BB concepts, ~ 4% power gain is
achievable compared to standard 3-BB full-cell modules.
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60
1
2
3
4
5
6
4-busbar half-cut
5-busbar half-cut
6-busbar half cut
7-busbar half-cut
3-busbar half-cut
3-busbar full-cell (base-line)
rela
tive
po
we
r g
ain
[%
]
busbar width [mm]
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 16
Improving optical performance: reduce module transmittance loss Minimize the losses which
occurs due to bifacial cell
transmittance
Solution
Using IR reflective coating on the
rear side glass
Reflective coating only reflects
IR and is transparent to other
spectrum
Maintain the bifacial performance
EVA
glass
glass
(b)
EVA
bifacial cell
front side
rear side
IR reflective
coating
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 17
Reflectance measurement of IR reflective coatings
Evaluation of IR reflective coatings: Reflectance
300 400 500 600 700 800 900 1000 1100 12000
20
40
60
80
100
refle
cta
nce
[%
]
wavelength [nm]
coating type A
coating type B
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 18
EQE measurements with and without reflective coating
Current gain contributed by IR reflective coating is calculated using
the bifacial cell transmittance, cell EQE & reflectance of coating
Evaluation of IR reflective coatings: External Quantum Efficiency (EQE)
950 1000 1050 1100 115020
40
60
80
100
no IR-coating
coating type A
coating type B
glass/cell/glass transmittance
wavelength [nm]
exte
rna
l qu
an
tum
eff
icie
ncy [%
]0
5
10
15
20
25
tra
nsm
itta
nce
[%
]
300 400 500 600 700 800 900 1000 1100 12000
20
40
60
80
100
no IR-coating
coating type A
coating type B
glass/cell/glass transmittance
wavelength [nm]
exte
rnal qu
an
tum
effic
iency [%
]
0
5
10
15
20
25
transm
itta
nce
[%
]
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 19
Current gain with IR reflective coating
*double-glass (without coating) is the reference module
calculated current gain in the range of 1 %
0.930.98 1.01
1.07
coating type A coating type B0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
cu
rrent gain
[%
]
EQE-calculated
reflectance-calculated
max. theoretical current gain = 1.36 %
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 20
Improving optical performance: reduce cell-gap loss Minimize the losses which
occurs due to double-glass
design
Solution
Using reflective coating on the
rear side glass
To maintain the bifacial
performance, reflective coating is
applied in the cell-gap region
only
encapsulant
rear cover
air
front glass
encapsulant
bifacial cell
reflective coating
reflective coating
(cell-gap)
IR reflective
coating (cell)
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 21
Current gain from cell-gap area with reflective coating
Current gain for different cell-gap is calculated using the EQE-line
scan and cell-gap area information
*double-glass (without coating) is the reference module
0 2 4 6 80
1
2
3
4
5
6
full-size cell module
half-cut cell module
curr
ent ga
in [%
]
cell-gap [mm]
EQE scan
cell-gap area solar cell
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 22
Current gain from cell-gap area with reflective coating: experiments Mini-module with (9-half-cut cells) were fabricated to measure the
current gain for different cell-gaps.
*double-glass (without coating) is the reference module
0
1
2
3
4
5
6
1.78
2.87
4.18
cell-gap=2mm, string-gap=3mm
cell-gap=3mm, string-gap=5mm
cell-gap=5mm, string-gap=7mm
rela
tive
pow
er
ga
in [%
]
3 mm
5 mm
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 23
*Baseline: standard double-glass, bifacial, 3-busbar, full-size
cell module
Cell-gap= 3 mm, string-gap= 5 mm
Power gain for various module designs
baseline mod-A mod-B mod-C mod-D0
2
4
6
8
10
12 IR-reflective coating
reflective coating on glass
multi-busbar
half-cut
rela
tive
po
we
r g
ain
[%
]
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 24
Double-glass bifacial PV module made @ SERIS
Half-cut
Multi-busbar
Selective
reflective coating
(rear side)
rear
front
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University of
Singapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB). 25
Thank you for your attention!
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