BASIC PRINCIPLES FOR DESIGN ANDCONSTRUCTION OF PHOTOVOLTAIC PLANTS

Ing. Salvatore CastelloENEA - Renewable Energy Technical Unit - Photovoltaic Lab

TRAINING COURSE TRAINING COURSE

Summary

• Criteria for selecting PV modules• Strings and PV generator• Supporting structures• Fire prevention • Power conditioning unit• The connection to the grid• Design documentation

GRID CONNCTED PLANT

POWER CONDITIONING UNITPV GENERATOR

string

string

Energy to/from the

grid

DC side

protections

DC/AC

inverter

Grid

Interface

protection

modules

USER LOADS

UTILITY GRID

Production counter

String box

THE CHOICHE OF THE PV MODULES

• Most suitable technology for PVPS applications• Electrical and mechanical features• Specific requirements (BIPV)• Quality of modules• Compliance with norms• Terms of warranty• Recovery and recycling possibility

TECHNOLOGY OPTIONS

CRISTALLINE•Mature and reliable

technology (useful life tested in the field for 30 years)• Good values of efficiency (14-

19%)• Appearance is not entirely

satisfactory

THIN FILMS• Useful life not tested yet in real

operating condition• Degradation in the first days of

exposure• Lower efficiency (7-13%)•More suitable in architecture• Greater yield

TECNOLOGIES AND YIELD

p = - 4,6% / 10 °C c-Sip = - 2,1% / 10 °C a-Sip = - 2,5% / 10 °C CdTep = - 3,66% / 10 °C CIS

Low irradiance

Artificial or diffused lightTemperature effect

solar light

C-Si

a-Si

C-Si

a-Si

Spec

tral

resp

onse

MODULE REQUIREMENTS

In some application (BIPV) modules should be chosen in order to meet the requirements:• Functional

• Waterproofing• Thermal insulation• Mechanical safety• Transparency

• Architectural• particular dimensions• Colors• Aesthetic appearance and forms

• Electrical• must be able to withstand a maximum permissible voltage

MECHANICAL SAFETY IN BUILDINGS

Reference standards specify the glass typologies for each part of the building

Glass roofs• Stratified glasses• tempered and laminated

(greater strength against thermal stress)

Facades• tempered and laminated

(in case of fall off risk: below 1 meter from the floor level)

MODULE WARRANTY

The manufacturer provide:• Product warranty: 10 years against manufacturing defects• Performance warranty :

• P (10 years)> 90% * Pi• P (25 years)> 80% * Pi

It is advisable that the year of fabrication is clearly documented (running of warranty period)

Excluded from warranty damages and failures resulting from misuse

ENEA has carried out a measurement campaign to evaluate the performance degradation of PV modules

Sample under test: 80 PV modules installed in 1980

Measurements over the years: IV curve of each module

Efficiency degradation: 0.4% / year (constant over the years)

MODULE DEGRADATION RATE

MODULE DEGRADATION RATE

Dates of installation prior and after to the year 2000The crossbars denote the mean for each categoryThe diamond represent the 95% confidence interval

Results of tests conducted by laboratories worldwide

Detachment of Tedlar

The defects found did not result in further efficiency degradation compared to the natural one (0.4% / year)

This experience shows that the life time of the modules (glass-tedlar) can be estimated superore to 30 years.

PHYSICAL DEGRADATION OF MODULES

Tedlar cracking collecting grid oxidation

Defects observed during 33 years

TYPICAL SEQUENCE OF EVENTS

0

2

4

6

8

10

12

14

0 5 10 15 20 25 30 35

Pla

nt e

ffic

ien

cy (%

)

Years

Inve

rter

repl

acem

ent

module efficiency degradation (0,4%/a)

Module failure

(infiltration, oxidation,

delamination)

Faul

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er o

r PV

gene

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Dev

elop

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tuni

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f th

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Faul

t

MODULE QUALITY CONTROL

• To ensure a long time outdoor operation, PV modules must have suitable electrical, thermal and mechanical characteristics

• Such features are verified by tests described in the norms• IEC 61215 C-Si• IEC 61646 thin film• IEC 62108 PV concentration

• Further test are foreseen in IEC 61730 part 1 and 2• Allow to assess the safety requirements in the construction and

qualification phases• to check the insulation levels of the modules: Class I and II• to affix the CE marking (compliance with this standard implies conformity

to the essential requirements of the EU Directive for Low Voltage appliances)

COMPLIANCE WITH THE NORMS

Is documented by:

• Type approval Certificate• is issued by an Accredited Laboratory• is accompanied by a Test report

• Conformity Certificate• is issued by a Certification body, as a result of tests performed by an

Accredited laboratory• is accompanied by a test report

• Test report• is issued by an Accredited laboratory, following tests according to the

relevant standards• contains the results of measured characteristics and details of defects

TYPE APPROVAL CERTIFICATE

Minimum information contained• Name and Accreditation number of the

Laboratory• Date and number of the test• Name and address of the module

manufacturer• Model and acronym of the module• Main features of the module:

technology, number and size of the cells, rated power

• Adopted rules to test the modules (indication of not performed tests)

• Time validity

ACCREDITED LABORATORY

must be accredited by organizations belonging to the EA (European Accreditation Agreement) for specific tests listed in the norms or

have established mutual recognition agreements in the framework of EA or ILAC (International Laboratory Accreditation Cooperation)

CONFORMITY CERTIFICATE

Minimum information contained– Name of certification body– Date and number of the Certificate– Name and address of PV module

manufacturer– Module model and acronym – Main features of the module– Adopted rules to test the modules– References of the Test Report– Name of the testing laboratory– Indication of the control in the factory

(factory inspection)– Time validity

CERTIFICATION BODIES

Must be:1) accredited by organizations

belonging to EA (European Accreditation Agreement) and

2) member of the IECEE (IEC for Conformity Testing and Certification of Electrotechnical Equipment) within photovoltaic sector.

List at:http://www.iecee.org/pv/html/pvcntris.htm

CERTIFICATION OF NON STANDARD MODULES

• if are not commercially available certified products that could realize the type of integration designed, could be used PV modules not certified according IEC standards

• In this case the manufacturer typically provide a:

• Declaration about the capability of the product to pass the tests required by the norms

• Conformity Certificate of standard modules fabricated with the same process phases

FACTORY INSPECTION CERTIFICATE

• Is a further demonstration of the module quality

• is issued by a Certification body as a result of periodic checks conducted at the factory, to verify that remain constant over time • manufacturing process and• materials used

• may be • included in the Certificate of Conformity (single certificate) or • recall the Certificate of Conformity

FACTORY INSPECTION ATTESTATION

• Is aimed at identifying the origin of the product

• issued by a Certification body

• contains the following information:• indication of the of the process phases

that are carried out• identification code and address of the

site• the identification code of the site and

the logo of the Certification body must be shown on the label of the module

MODULE CERTIFICATION

• Original Equipment Manufacturer Certificate• is issued by a Certification body if the company that label the module is

not the manufacturer• indicates the name and address of the manufacturer and the company

that markets the module• is accompanied by a test report

• Quality system within operate the manufacturers is evidenced by the certification on: • Quality management system (ISO 9001:2008) • Management system of health and safety at work (OHSAS 18001) • Environmental Management System (ISO 14001)

RECOVERY AND RECYCLING OF PV MODULES

• Each module producer shall adhere to a Consortium that guarantees the collection and recycling of the modules at the end of life.• Producer: Manufacturer / Importer / Distributor under its own brand• Consortium: Subject supported by one or more Producers that on

behalf of their members:• operates in compliance with the “National environmental code“

for the Electrical and Electronic Equipment category

CONSORTIUM REQUIREMENTS

• Must ensure all phases of the life cycle of the modules• Collect the module from the installation site • transport to a storage area• Recover the materials at the recycling plant

• Reporting on • amount collected and sent for recycling• quantity and quality of recovered materials;

• Absolve the Producer from possible liability forms resulting from violations of the rules

• Dispose of appropriate (and authorized)• treatment and recycling plants• collection and transport network • storage areas for the delivery of modules to the recycling plants

CONSORTIUM REQUIREMENTS

• Must operates on modules• removed from plants• from production waste• broken during transport or installation

• Achieve the traceability in order to bring the single module to• the manufacturer or importer and• to the plant in which was installed

• activates a financial instrument• fed for at least 2/3 by modules producers

RECOVERY OF MODULE MATERIALS

CdTe• Cd and Te separated by fragments

of modules using dilute solution of H2SO4

• These products can be reused if treated with hydrogen peroxide

• Separation coefficient = 99%

Si-C• Separation of the silicon:

thermal decomposition of the EVA in gas atmosphere of nitrogenous

• The silicon wafers may be used for the fabrication of new modules

Collected modules 2011 1.500 ton. (23 MW) 2012 6.000 ton. (90 MW)

Typical methods for material recovery

MODULE CERTIFICATION (IEC 61215)

• Describes the requirements for the design qualification and type approval of terrestrial photovoltaic modules suitable for long-term outdoor operation

• Visual inspection for defect detection• misalignment or contact between cells• broken cells• discoloration• air bubbles

• Measurements• Pmax at STC characteristic I-V• Pnom low Irr. (<200 W/m2)• temperature coefficientsof Isc, Voc and Pm• NOCT (Irr. 800 W/m2, T = 20 ° C)

MODULE TEST

TESTS• insulation resistance > 40 M (Vtest=1.000V + 2 Vmax sys)• immersion in water insulation measurement• Exposure > 60h to 1 kW/m2• Partial shadowing exposures of 1 has 1000 W/m2• UV exposure > 15h to 1 kW/m2• thermal cycles 200 from -40 ° C to +85 ° C• diode thermal cycles 1h Isc = T = 75 ° C• humidity exposure 1000 h to +85 ° C and 85% RH• connectors resistance stress simulating screw tightening

operations• mechanical load: uniform load simulating wind speed 130 km/h• Hail resistance balls of ice 25 mm shoot 23 m/s in different

points of module

IEC 61730-1

• describes the construction requirements of PV modules in order to provide safe electrical and mechanical operation

• Module application classes• Class A

• general access, • hazardous voltage, current and power• double /reinforced insulation

• Class B• Restricted access, • hazardous voltage, current and power • basic insulation only

• Class C• general access • limited voltage, current and power

IEC 61730-1

Construction and property requirements• Metal parts (resistance to corrosion)• Polymer Material for

• enclosure of live parts• support live parts• electrical barrier or pottant

• Encapsulants• Frames• Wiring and current-carrying parts• Output Wiring Connectors• Junction Boxes• Creepage and clearance distances• Mechanical securement

IEC 61730-2TEST PROCEDURES

IEC

6121

5IE

C 6

1215

IEC 61730-2 and 61215

IEC

6173

0-2

IEC 60554

IEC 61730• Application class A:

Vtest = 2.000 V + 4 Vmax sys

• Application class B: Vtest = 1.000 V + 2 Vmax

sys• Application class C:

Vtest = 500 V

DIELECTRIC WITHSTAND TEST

FIRE TEST

Burning brand Test

Spread-of-Flame Test

Conditions of acceptanceAt no time during the spread-of-flame or burning-brand tests shall any portion of the module be blown off or fall off the test deck in the form of flaming or glowing brands.

FIRE TEST

Fire test performed: is documented in the Confomity Certificate

ACCEPTANCE TESTS

in order to verify the compliance of modules to design specifications, even before their installation, are carried out factory tests :• visual inspection aimed to highlight any macroscopic defects• electroluminescence test to detect any possible fractures of cells

(with an infrared camera when cells are crossed by a current: damaged cells appear dark)

• Measure of the IV curve and Pnom, after sun simulator calibration (with reference module previously calibrated by a Accredited laboratory)

STANDARD DEVELOPMENTS FOR BIPV• The standard distinguishes among

• modules like glass • accessible or not from inside the building• on roofs or facades

• with polymer sheets or Tedlar

• on metal foil

• on other materials (tiles, roofing elements)

• Defines the essential requirements relating to building aspects:

• Protection from weather conditions

• Mechanical resistance and stability

• Safety in case of fire

• safety in use

• Protection against noise

• energy saving

MECHANICAL RESISTANCE AND STABILITY

• Double glass module

• The increase in temperature of glass with PV cells inside compared to normal glasses affects the structural requirements (mechanical load and stiffness of the laminate must be verified 75 °C)

• Components for roofs

• test load of snow and hail: IEC 61215

• Test of resistance to lifting: required subdivision into classes (wide variety of types, shapes and sizes)

Mechanical fixed elastically fixed

PROTECTION FROM WEATHER CONDITIONS

WATERPROOFING Test

• characterizes the degree of penetration of rain with different

• rain intensity

• Roof pitch

• Wind speed and climate zone

• Is assessed through the presence (and amount) on the back of the module

• Humidity

• Drops of water

• Infiltration of water

THANK YOU FOR YOUR KIND ATTENTION

for information:

salvatore.castello@enea.it