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

2 © 2016 SunPower Corporation |

Still the most efficient after 40yrs in the field

Reliability: Valued by Customers

Comprehensive

Warranty

Economic “End of Life”

?

Product

“End of Life”


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)


Physics of Failure: Mission Profile

In the Field

The life of a solar panel.

Real world stresses.

Installation Logistics

Factory


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

Physics of Failure: Product Sensitivity

1% Drop in Relative

Cell Efficiency


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


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


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


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 |


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


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


Simulation from Accelerated Test Results

Reliability Monitoring Program


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


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.


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

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

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