9 v. fakhfouri meyer-burger_ok

Challenges and solutions for the characterization of bifacial PV modules and cellsV. Fakhfouri1, J. Hiller1, N. Rebeaud1, N. Bassi1, Y. Pelet1, M. Despeisse2, C. Ballif3

1. Pasan SA (Meyer Burger Group), Switzerland2. PV-center, CSEM SA, Switzerland3. Ecole Polytechnique Fédérale de Lausanne (EPFL), PV-Lab, Switzerland

BifiPV Workshop 2014, Chambéry

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Pioneer in PV test systemssince 1981

1981: First solar simulator

Scientific partner

2010: 1st

certified

A+A+A+ solar

simulator

2

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Technology powered by 3

How to measure Bifacial cells / modules?

How to measure High-Capacitive Busbarless Bifacial cells / modules?

Other challenges:– Transient effect (particularly in the case of cells)– Contacting– Calibration– PV Laboratory vs. PV production measurements– DUT temperature measurement

Challenges

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Measurement of high-capacitive cells and modules Measurement of busbarless cells Busbarless cells measurement calibration Measurement of bifacial cells and modules Conclusion and open questions

Outline

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Transient effect: >1s of illumination required for the state-of-the-art cells

Steady-State simulators drawbacks:

– Light quality– Thermal effects

Hybrid simulator approach for cellsDragonBack® approach for

modulesDragonBack® + Hybrid approach

for cells

How to measure High-CapacitiveBusbarless Bifacial cells / modules?

Transient effect measured for high-efficiency R&R cells

Pmax<0.5%

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A+A+A+ Xe source combined with a long-pulse monochromatic source

Hybrid simulator approach: SpotLIGHT

ParameterMean rel. dev.

[%]

Max. rel. dev.

[%]

Uncertainty

@ ISE

[%]

Isc 0.27 0.52 1.9

Voc 0.16 0.38 0.3

Pmax 0.38 1.15 2.0

FF 0.05 0.52 0.7

Comparison of the IV key data measured using SpotLIGHT

HighCap with those measured by Fraunhofer ISE CalLab

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Dynamic voltage sweep Selection of stable intervals for I and V

Dynamic sweep approach: DragonBack®

N. Ferretti et al., EU-PVSEC,2013, 4AV.5.4

Manufacturer Technology # of modules Pmax dev.

DragonBack vs.

Multi-flash

A Panda 5 -0.1%

B p-type (std.) 4 0.2%

C n-type

(bifacial)

4 0.1%

D HIT 2 -0.2%

E HIT 2 0.1%

F n-type (IBC) 4 0.1%

G HJT 1 0.1%

H p-type (high eff.)

6 -0.2%

A. Virtuani et al. 38th IEEE-PVSEC, 2012

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Temporary contacting of cells with GridTOUCH

High contact rate Compatible with HJT, PERC,

MWT, IBC and bifacial technologies

Lifetime: >3 million contacts


Left: Output of the microscopy mapping over 44 fingers and 6 wires. Non-contacted regions are labeled with 0 and badly contacted regions with 0.5. Right: evolution of the effective contacts with the number of contacting

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Determination of the optimal number of wires: max FF

𝐼𝑠𝑐 = 𝐽𝑠𝑐 ∙ 𝐴

𝐼𝑚𝑒𝑎𝑠 = 𝐽𝑠𝑐 ∙ 𝐴 ∙ (1 − 𝑆ℎ𝑎𝑑𝑜𝑤)

Extrapolation of Isc vs “number of wires” for shadowing compensation

Shadowing-compensated IV measurement

Applies to Bifacial measurements as well!

GridTOUCH calibration

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Understanding the Bifacial contribution:


𝐼 = 𝐼𝑓𝑟𝑜𝑛𝑡 + 𝐼𝑏𝑎𝑐𝑘 = 𝐸 𝜆 𝑆𝑅𝑓𝑟𝑜𝑛𝑡 𝜆 𝜕𝜆 + 𝐸 𝜆 𝑇𝐶𝑒𝑙𝑙 𝜆 𝑅𝐶ℎ𝑢𝑐𝑘 𝜆 𝑆𝑅𝑏𝑎𝑐𝑘 𝜆 𝜕𝜆

Chuck

Bifacial cellE()

TCell() RChuck()

𝐸 𝜆 : is the irradiance.𝑆𝑅𝑥𝑥 𝜆 : is the spectral response.𝑇𝐶𝑒𝑙𝑙 𝜆 : is the cell’s transmittance.𝑅𝐶ℎ𝑢𝑐𝑘 𝜆 : is the chuck’s reflectivity, (albedo ?)

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Isc vs. Rchuck

– Reflection-compensated Isc determination

Comparability

Need for “Reflective reference surfaces” definition

Bifacial measurement approach

flat reflection

J. Hohl-Ebinger et al. , EU-PVSEC 2010

𝐼𝑏𝑎𝑐𝑘 = 𝐸 𝜆 𝑇𝐶𝑒𝑙𝑙 𝜆 𝑅𝐶ℎ𝑢𝑐𝑘 𝜆 𝑆𝑅𝑏𝑎𝑐𝑘 𝜆 𝜕𝜆

…similar to the busbarlessmeasurement approach

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Modules Cells

PV Laboratories

• Isc = f(Reflection800-1200 [%])• Reflection-compensated IV

assessment with a black sheet Reference module• Pmax@STC for both sides• The underlying area must be

equal to the module’s area.

• Isc = f(Reflection800-1200 [%])• Reflection-compensated IV

assessment with a black chuck Reference cell• Pmax@STC for both sides

PV Production • Irradiance calibration, with a black sheet, using the Reference module; IV measurement

• Isc = f(R) reporting in the datasheet

• Bifaciality (= 𝑃𝑚𝑎𝑥𝑟𝑒𝑎𝑟

𝑃𝑚𝑎𝑥𝑓𝑟𝑜𝑛𝑡) reporting

in the datasheet

• Irradiance calibration, with a black chuck, using the Reference cell; IV measurement

• Isc = f(R) reporting in the datasheet

• Bifaciality (= 𝑃𝑚𝑎𝑥𝑟𝑒𝑎𝑟

𝑃𝑚𝑎𝑥𝑓𝑟𝑜𝑛𝑡) reporting

in the datasheet

12

Bifacial measurement approach

Light baffle

ModuleReflective reference surfaces

1m

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Other challenges besides the Bifacial aspect must be considered. We should differentiate the PV laboratories and PV production

cases:– Different needs– Different possibilities

Reflection-compensated and black-chuck/sheet measurement fulfills the main needs:

– Best-case assessment of bifacial devices– Inter-laboratory/production comparability– Clear Cell-to-module losses

Conclusion

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Albedo or Reflectivity; which one is more relevant? What is the reliable method to measure bifacial cells temperature in

production environments (with high throughputs)?– Bifacial cells are IR transparent– Contact T° probes are not fast enough

What is the relevance of measurements using double-light-sources for bifacial technologies?

Thank you for your attention

Our questions

𝐼 = 𝐼𝑓𝑟𝑜𝑛𝑡 + 𝐸 𝜆 𝑇𝐶𝑒𝑙𝑙 𝜆 𝑅𝐶ℎ𝑢𝑐𝑘 𝜆 ∙ 𝑆𝑅𝑏𝑎𝑐𝑘 𝜆 𝜕𝜆

Presentations & Public Speaking

9 v. fakhfouri meyer-burger_ok