Innovative Approach to Assess

Solar Plant Health

24th of April 2020

Dr. Lucie Garreau-iles

Regional Technical Manager, EMEA

DuPont Photovoltaic Solutions

Lucie.garreau-iles@dupont.com

DuPont Photovoltaic Solutions

DuPont global field reliability program

• Quantitative analysis: components, materials, age,

failure mode

• Post-inspection analytical characterization

• Collaborative: field partners, developers, government

labs, universities

6.5 Mmodules

355Installations

1.8 GWmodules

Improved accelerated

tests and informed

materials selection

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1.8 GW of fields inspected

Total module defects observed: 32%

resulting from

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Detecting panel degradation: a multimodal approach

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Thermal

Anomalies

Electrical IV:

String/Panel Level

Historical/Trend

Power Data

Visual & Lab

Analysis/Safety

Power & Safety

Performance

Visual inspection & lab

analysis can determine

and confirm the nature of

degradations and safety

risks

Panels affected by

thermal anomalies are

a large contributor to

power loss

Gradual loss can be

quantified by IV

measurements,

compared to nameplate

power

Power data analysis

can shed light on

quantitative

historical losses and

trends

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In-field assessment of 40 PV plants

Basic assumption: The plants are performing…

Question: How do you know? How much is underperformance costing you?

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Expected degradation rates

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Source: Photovoltaic degradation rates –

an analytical review, D.C. Jordan, S.R.

Kurtz, NREL, 2012

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How is the portfolio performing?

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13 different panel manufacturers, installations all in the

Mediterranean region

Green: rooftop installations

Red: thin film

Blue: crystalline silicone, ground mounted

Black line: expected normal degradation

About 4 installations out of 40 fulfill normal

degradation criteria (0.7% average).

Potential reasons:

Soiling

Vegetation growth

Broken panels

Broken cells

Potential induced degradation

Light induced degradation (LID + LeTiD)

Disconnected panels

Cell degradation

Panel materials degradation (light

obscuration)

RISO problems

Inverter problems

Cables problems

Network availability

Curtailment

Sys

tem

los

se

s

Pan

el

losses

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Disconnected panels

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Green: rooftop installations

Red: thin film

Blue: crystalline silicone, ground mounted

Many disconnected strings.

Potential reasons:

Blown fuses

Faulty connecters

Riso problems

Fire damage

Weather damage

Faulty panels

Let’s discount the disconnected strings…

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How does it look without disconnected panels?

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Now 8-9 installations out of 40 fulfill normal

degradation criteria (0.7% average per year).Green: rooftop installations

Red: thin film

Blue: crystalline silicone, ground mounted

Black line: expected normal degradation

Excluding

disconnects

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Illustrations of panel level degradation

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Broken cells

String end

String end

Early PID

Optical losses

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What we learned

1. The installations delivered revenue (feed-in-tariff)

2. The installations were reported as having backsheet problems which do not yield power

losses outside late inverter starts or tripping in bad weather (times of minimal production).

But backsheet issues still constitute a major safety matter to be resolved.

3. Why was this amount of power loss not detect-ed/able earlier?

a. PR (performance ratio) relies on the accurate assessment of irradiance and panel temperature.

Weather stations may suffer from misalignment, soiling, breaking, degradation, drift

b. Multiple system malfunctions/dysfunctions and inverter optimization provide a complex system to

analyze

c. Multiple (and changing) conditions of vegetation, soiling and shading issues complicate analysis

d. These plants are between 6-11 years with old monitoring systems (missing data, corrupted data).

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O&M Contractor KPIs

Reflect the performance of the

service provided by the O&M

Contractor. O&M Contractor KPIs

are both quantitative and

qualitative indicators:

• Acknowledgment Time

• Intervention Time

• Response Time

• Resolution Time

• Reporting

• O&M Contractor Experience

• Schedule Attainment

• Preventive vs Corrective

• Maintenance Ratio

What about expanding KPIs?

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PV Plant KPIs

Directly reflect the performance of

the power plant. PV plant KPIs are

quantitative indicators:

• Reference Yield

• Expected Yield

• Specific Yield

• Performance Ratio (PR)

• Temperature-corrected PR

• Energy Performance Index

• Technical Availability (Uptime)

• Tracker Availability

Source: Operation and Maintenance Best Practices Guidelines 4.0, SolarPower Europe, 2019

PV Plant and O&M Contractor

KPIs

Reflect both plant and O&M

Contractor KPIs measuring at the

same time plant performance and

ability of the O&M provider to keep

the power plant ready to produce:

• Contractual Availability

• Contractual Tracker Availability

• Energy-Based Availability

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