how to build the world’s most reliable solar panel celltech 17/pvcell… · how to build the...

© 2016 SunPower Corporation

PV CellTech Conference, Malaysia, 15th March 2017

Peter Cousins Senior Vice President Research, Development & Deployment

How to build the World’s Most Reliable

Solar Panel

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Still the most efficient after 40yrs in the field

Reliability: Valued by Customers

Comprehensive

Warranty

Economic “End of Life”

?

Product

“End of Life”

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Building on decades of experience. Learning loops.

Building the Most Reliable Solar Panel

New

Design

Process (Hours)

Lab Testing (Months)

Field Performance (Years)

Design

“Physics of Failure” (Design for Reliability)

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Physics of Failure: Mission Profile

In the Field

The life of a solar panel.

Real world stresses.

Installation Logistics

Factory

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Example: Change in Rear Recombination vs 1% change in cell performance.

Physics of Failure: Product Sensitivity

1% Drop in Relative

Cell Efficiency

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Design for Moisture

Mechanism: Low temperature reoxidation of the surface.

Sensitivities: Compensated diffused regions. P-type diffused regions.

Physics of Failure: Mechanism

Emitter Diffusion (p-type) Base Diffusion (n-type)

H2O

Gen 1- 20% Cell Design

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Laboratory Validation: Autoclave Testing (121oC, 100% RH, 168hrs)

Physics of Failure: Design Solution

Initial Post-ACL

Initial Design

20% 22%

Initial Post-ACL

New

Design

22%

Initial Post-ACL

Final Design

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Product Validation: Long Term Humidity Testing

The unique design of the SunPower cell makes

the Panels almost impervious to corrosion.

1 Kohl, “PV Reliability: Accelerated Aging Tests and

Modeling of Degradation.” 2010. 2 Meakin, “PV Durability Initiative for Solar Modules.”

2013. 3 Ferrara, “PV Durability Initiative for Solar Modules:

Part 2.” 2014. 4 Ketola, B., & Norris, A. Degradation Mechanism

Investigation of Extended Damp Heat Aged PV

Modules. EUPVSEC, 26th, Hamburg, Germany,

2011 5 Jahn, U. PV Module Reliability Issues Including

Testing And Certification. 27th EUPVSEC, 2012.

0 1000 2000 3000 4000 0%

20%

40%

60%

Pa

ne

l P

ow

er

100%

5000

Number of Hours at 85°C (185°F) and 85% Humidity

Certification

Standard

1000 Hours

7000

80%

6000 8000 9000

Note: End of line indicates ending of test

SunPower® Panels

Conventional Panels1,2,3,4,5

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PVLife Simulation Model

• Using array configuration, weather data, and pre-evaluated technology

parameters, PVLife computes cell performance and failure probabilities over

time

Physics of Failure: Reliability/Degradation Model

Initial Performance and

PV configuration

Model

Degraded

Performance

Weather Dt=1 hour

© 2014 SunPower Corporation | Confidential |

10 © 2016 SunPower Corporation |

PVLife: Field Validation of Model

Results of an inverter-level degradation

study including 149 sites, 560 inverters

and >800,000 PV modules

G. M. Kimball, Z. Campeau, M. Anderson. SunPower

internal, 2017. unpublished.

Conventional Panels

~ 0.75 %/yr

SunPower Panels

0.2 %/yr

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Accelerated Laboratory Testing: Cell Strength

Apply Stress on “mini-module” to determine the exact load at crack of every cell.

This generates a Weibull distribution

Test Configuration

4

840 mm

420 mm

380 mm

Cell centered and displacement probe at center

160 mm

Cells centered and displacement probe at center

Note: center coupon’s orientation and position on bend fixture

4 Point Bend Coupon tester

Manual

Load at crack(N)

Fai

lure

Rat

e FEA

Peak Stress

Field Stress:

Snow, Wind ⟹ Uniform Load

Stepping ⟹ Local Load

Peak stress under uniform load

Peak stress under local step

FE

A

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Simulation from Accelerated Test Results

Reliability Monitoring Program

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In-line screening to ensure Reliability for our Customers

Metal strength critical to improved

reliability of SunPower Panels

In Process Controls: Critical-to-Reliability

100% Inline Screen of Metal Thickness

Design Cut off

Outliers

Screened

Conventional Panels SunPower Panel

Post mechanical loading

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The unique design of the SunPower cell makes them

exceptionally resilient to mechanical stress.

Product Validation: 90o Drop Test

SunPower Panels Conventional Panels

As Received As Received Post Test Post Test

1 Based on independent testing and analysis

performed by Core Energy Works in 2017.

Post test measurements occur under 17mm

of deflection.

15 © 2016 SunPower Corporation |

How to build the World’s Most Reliable Solar Panel

• SunPower’s back contact panels are the worlds most

reliable and robust panel

• Thinking about Reliability as you think about Efficiency:

– Understanding the “Physics”

– Develop comprehensive simulation tools

– Utilize field data to validate testing and product results

– Develop accurate accelerated testing methods

– Control critical to reliability parameters in the factory

– Feedback loops into new designs

Thank You

Let’s change the way our world is powered.

© 2016 SunPower Corporation