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Advanced and Customized Test

Techniques for Photovoltaic Applications14 April 2009

Professor Y.C. ChanPhD, FIEEE, FHKIE, FIEE, CEngChair Professor of Electronic Engineering,City University of Hong KongDirector, EPA Centre

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Acknowledgements

HKSTPMr. Ricky Ma, Dr. W.C. Wong & Mr.Stephen IpCityU

Dr. Jun Shen & Dr. Daniel K. Lau

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What are Photovoltaics?

Photovoltaics: To generate electric power by using solar cells packaged in photovoltaic modules to convert solar energy into electricity.

Photovoltaic Applications

Power stations In buildings In transport Standalone devices Rural electrification Solar roadways

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Market demand

Solarbuzz Report: world solar photovoltaic market installations reached a record high of 5.95 gigawatts (GW) in 2008.

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Cost-efficiency

The prices for high power band (>125 watts) solar modules has dropped from around $27/Wp(Watt-Peak) in 1982 to around $4/Wp today.

However, solar energy prices are still several times more expensive than the cheapest source of conventional electricity generation.

Source:Source: Solarbuzz Report

For a solar electric generating device, its power in watts-peakis defined as the peak output of the device, measured in watts.

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Improve the Cost-efficiency

1. To Develop Advanced Materials and Devicesfor Low Cost and High Conversion EfficiencyPhotovoltaic Cells

2. To Produce Highly Reliable PhotovoltaicDevices

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Roadmap of improvement in solar cell efficiency from 1976 to 2004

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3 generations of solar cells

1st generation: silicon-basedphotovoltaic cells

2nd generation: thin-film solar cells

3rd generation: polymer solar cells,quantum dot solar cells,multi-junction cells,hot-carrier cells,dye-sensitized solar cells,etc.(Still in the research phase)

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Reliability challenges

Hence, photovoltaic manufacturers must build extremely reliable PV systems!

1. Despite declining production costs and increasing cell conversion efficiencies, cost-efficiency remains a significant issue.

2. Only over a long period of time, the high initial producting costs will be amortized.

3. However, photovoltaic modules/arrays always are deployed in harsh service environment.

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Case: reliability problem of packagingCase: reliability problem of packagingThe operation of a basic solar cell

Packaging costs about 50% of the photovoltaic devices and photovoltaic devices and most most of the of the damages/failures of PV damages/failures of PV devicesdevices occur in occur in packaging part..

Packaging part

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Advanced and Customized test techniques

To improve the reliability of photovoltaic devices, 5 types of tests are needed as follows:1. Indoor Environmental Tests2. Indoor Accelerated Tests3. Outdoor Tests4. Failure Analysis5. Module Characterization .

Source: National Renewable Energy Laboratory, USAhttp://www.nrel.gov/

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Indoor Environmental Tests

To evaluate electrical insulation and moisture intrusionthat can cause corrosion, ground faults, or pose anelectrical safety hazard, specialized chambers areused to test the performance of PV devices in varyingweather conditions: 1. Heat; 2. Cold;3. Humidity;4. Moisture;5. Ultraviolet light, etc..

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Indoor Accelerated Tests

In these tests, the relative and absolute performance of PV devices is determined for samples exposed to

different accelerated conditions:1. Continuous light;2. Intense simulated lighting conditions;3. Elevated levels of temperature and humidity;4. Accelerated cycles of temperature and humidity.

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Equipment for indoor tests

1.Temperature/Humidity Oven2.Solar Simulator—Accelerated

Weathering Machine3.Sun test Chamber4.Rapid Thermal Shock Oven5.Thermal Moisture Cycles Oven

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Outdoor Tests

For Outdoor Test Facility Arrays (OTFA), thePerformance of PV devices are tested at differentfield conditions:1. Performance and Energy Ratings Test;2. High-Voltage Stress Test;3. PV array testing;4. Real-Time Meteorological and Irradiance

Monitoring.

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Failure AnalysisSeveral destructive and non-destructive analysisto determine Failure Mechanisms of PV devices.e.g.:1. Module leakage current tests;2. Materials Analysis technologies• High-resolution X-ray system for non-destructive detection.• AFM (atomic force microscopy) for high-resolution detection• ESEM (environmental scanning electron microscope) for non-

destructive and gaseous environment test without need for special sample preparation

• EFTEM (energy-filtered transmission electron microscopy) for both chemical analysis and crystallography analysis at nanoscale

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Module characterization

The electrical output performance of modules is determinedunder simulated conditions using different current versusvoltage measurements systems. They include:1. Open-circuit voltage of the module;2. Short-circuit current;3. Fill factor;4. Maximum power output of the module;5. Voltage at maximum power;6. Current at maximum power;7. Module's conversion efficiency.

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A consortium to be established in HKSTP

University/institute partners:University/institute partners:

••City university of Hong Kong (EPA)City university of Hong Kong (EPA)••Georgia Institute of TechnologyGeorgia Institute of Technology••University of Hong KongUniversity of Hong Kong••Hong Kong Polytechnic UniversityHong Kong Polytechnic University••Chinese University of Hong KongChinese University of Hong Kong••University of GlasgowUniversity of Glasgow••HuazhongHuazhong University of Science & University of Science & Technology Technology ••Chongqing universityChongqing university

Industry partners:Industry partners:

••DuPontDuPont Apollo Limited•Golden Regent Electronics Industrial Limited •Top Brilliant Technology•Beghelli Asia Pacific Limited•Vedbaek Concepts Limited

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Photovoltaic innovations

The largest solar panel arrayThe largest solar panel array

New low temperature screenprintable pastes for all majorthin film PV applications

Pioneer Waimea research center

Source: DuPont companyhttp://www2.dupont.com/Photovoltaics/en_US/index.html

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Products

Front Sheet Materials Front Sheet Materials

Photovoltaic EncapsulantsMetallization Pastes

Back Sheet Materials

Junction Box & StructuralSupport Materials

Thin Film Substrates

High Performance Sealsfor Cell Manufacturing Equipment

Source: DuPont companyhttp://www2.dupont.com/Photovoltaics/en_US/products_services/index.html

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Summary

1.1. Need for Dedicated Support in PV:Need for Dedicated Support in PV:•• Provide dedicated total solutions on site for PV Provide dedicated total solutions on site for PV

applications applications •• Customize the PV products for local Customize the PV products for local

environment and usesenvironment and uses

2. Advantages of having a dedicated PV support:2. Advantages of having a dedicated PV support:•• Fast turn around time and round the clock Fast turn around time and round the clock

supportsupport•• Full support of consortium formed by university Full support of consortium formed by university

and industry alliance, including the EPA Center and industry alliance, including the EPA Center at at CityUCityU

•• One stop shop full services in FA and One stop shop full services in FA and Reliability for PV applications in HKSTPReliability for PV applications in HKSTP