the “pv system doctor” a comprehensive “health check” for ... · eirr: 18.0%. pirr: 12.1%....
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SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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The “PV System Doctor” A comprehensive “Health Check” for PV systemsVijay KrishnamurthyProject Manager
Solar Energy Research Institute of Singapore (SERIS)National University of Singapore (NUS)
SERIS INDUSTRY DAY on “PV Quality and Asset ManagementNUS, University Hall14 August 2017
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
Motivation
The “PV System Doctor”
Case study
3SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
Results from analytical monitoringShowing a wide range of system performance
82.6 82.2 81.9 81.7 79.9 79.873.5 70.0 69.5
62.558.1
A B C D E F G H I J K0
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Perfo
rman
ce R
atio
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SiteSource: SERIS, Solar Energy Systems’ research
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Financial losses from reduction in PRUsing returns under the “most-likely” future electricity price scenario
Note: PR = performance ratio, NPV = net present value, EIRR = equity internal rate of return, PIRR = project internal rate of return
Under optimum PR condition:
EIRR: 18.0%PIRR: 12.1%NPV: ~USD 500k
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
Motivation
The “PV System Doctor”
Case study: PV diesel hybrid system
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
The “PV System Doctor”
Real time monitoring and analysis
Advanced On-site Diagnostics
Visual field inspections
Electrical measurements
Optical measurements
Financial evaluations
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Analysis of PV monitoring data Performance Ratio calculation based on irradiance and inverter data
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Analysis of PV monitoring data Performance Ratio calculation based on irradiance and inverter data
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
The “PV System Doctor”
Real time monitoring and analysis
Advanced On-site Diagnostics
Visual field inspections
Electrical measurements
Optical measurements
Financial evaluations
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Source (pictures): IEA-PVPS T13-01:2014
Documentation & Visual Inspections Examples of typical activities and findings
General review of system documents Electronic filings (prior to site visit) On-site documentation for both system
operation and safety Visual inspection of BOS (balance of
systems), strings and arrays Typical flaws include (but are not limited to):
Burn marks De-lamination Browned EVA
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
The “PV System Doctor”
Real time monitoring and analysis
Advanced On-site Diagnostics
Visual field inspections
Electrical measurements (IV Curve)
Optical measurements
Financial evaluations
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Steps/Notches in the I-V curve
Typically caused by partial shading of string.
Depth of current step tells us how much the most shaded module is affected.
Width of voltage step tell us how many “cell groups” are affected. Typically, a module has three of such “cell groups”, one for each bypass
diode installed in the junction box at the back of the module
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Source (pictures): Solmetric
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Low short circuit current Isc
Typically caused by uniform soiling and dirt dams across a string.
Could be caused by lower irradiance experienced by a particular string, and notaccurately adjusted back to match STC.
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Source (pictures): Solmetric
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Low open circuit voltage Voc
Strings are slightly mismatched in voltages (usually small deviations).
Temperature variations between measurements, or between strings in an array.
If Voc is suppressed by approximately a module’s �𝑉𝑉𝑜𝑜𝑜𝑜N, it may indicate dropped “cell
groups”, likely caused by shorted bypass diode(s). [N is typically between 1 to 3]
Potential induced degradation (PID). PID is driven by high voltage stress - more likelyto occur at higher voltages and negative polarity, and in modules with poorencapsulation.
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Source (pictures): Solmetric
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Rounder knee in IV curve
Typically caused by a combination of high series resistance and low shuntresistance in a string.
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Source (pictures): Solmetric
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Increased series resistance Rs
PV string’s wiring is incorrectly sized (too small diameter)
Interconnections are more resistive than expected. Corrosion damage due to poor aging. Test leads are not plugged in properly, or test lead diameters are too small.
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Source (pictures): Solmetric
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Decreased shunt resistance Rsh
Shunt paths may exist within the cells in one or more of the PV modules. Typically associated with highly localized cell defects within the solar cell. Infra-red imaging may be able to identify these shunts.
A worse shunt can result in localized temperature rises in the module that can reach the melting point of encapsulant material or the module backsheet. Modules that fail in this manner may show burn spots.
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Source (pictures): Solmetric
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
The “PV System Doctor”
Real time monitoring and analysis
Advanced On-site Diagnostics
Visual field inspections
Electrical measurements
Optical measurements
Financial evaluations
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Optical Measurements InfraredImages (IR)
Daytime Electroluminescence Images (DEL)
OpticalImages (OI)
Daytime Photoluminescence Images (DPL)
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Visual image
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Infrared image (IR)
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Visual image
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Electroluminescence image (EL)
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Electroluminescence image (EL)Close-up view
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Image AnalysisCollected at same time and outdoor light conditions for image analysis
DPL
OI DEL
IR
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Source: Solarzentrum
Luminescence Imaging in Daylight
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Luminescence Imaging in Daylight
Source: Solarzentrum
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
The “PV System Doctor”
Analysis of monitoring data
On-site assessments
Electrical measurements
Optical measurements
Financial evaluations
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Example: Faulty modules In year 5, 25% of the module underperform by 50%
In year 5 PR drops to 67%, -12.5% drop in annual output If left unchanged, NPV loss: USD -126k, 34% of initial investment System Doctor diagnostic services would help to restore the losses
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Agenda
Motivation
The “PV System Doctor”
Case study: PV diesel hybrid system
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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PV system specifications
Chinaland modules 240 Wp poly crystalline 12 modules in 1 string Total of 6 strings System Size -17 kWp
SMA inverters 3 Sunny Boy 5000 TL 2 Sunny Island 6.0H
Ritar battery bank Lead acid 48 V 48 cells : 490 Ah
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Historical Performance dataDaily performance ratio 65%-70%
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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No visual cracks were noticed on the PV modules
Inverter 2 – Not Working
No proper earthing of PV module frames – Non Conformance
Connector for Inverter 3, String 2 broken – FIRE HAZARD
AC Isolator used instead of DC Isolator - FIRE HAZARD
Visual Inspection Results
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Inverter String Name plate Measured power(STC corrected)
% Generation loss
11 2880 W 2.5 kW 11%
2 2880 W 2.1 kW 26%
21 2880 W 2.1 kW 26% (in fact 100%)
2 2880 W 1.2 kW 57% (in fact 100%)
31 2880 W 1.8 kW 37%
2 2880 W 2.2 kW 25%
Significantly less generation
The modules connected to inverter 2 do not generate energy atall as the inverter is not operable
IV curve Electrical Measurements
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Yellow = functional and energy generated
Black = non-functional and no energy generated
Test string
Test string
Daytime Luminescence Images
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Daytime Luminescence Scan
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Daytime Luminescence scan
Lightning strikes mighthave caused short-circuitedbypass diodes
Platform
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Background: PV module
In-built bypass diodes One bypass diode for 20 cells
(2 columns) Why are there bypass diodes?
Higher performance when partly shaded
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Earth PV modules - Provide Equipotential boding and construct a Earth Pit to earth all frames
Actions
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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ActionsReplace inverter 2 and earth all inverters
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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ActionsReplace faulty connector and AC isolator with DC Isolators
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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ActionsReplace bypass diodes
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Inverter String Name Plate
Measured power before
Measuredpower after
CA
Percentageimprovement
11 2880 W 2.5 kW 2.4 kW -4%
2 2880 W 2.1 kW 2.2 kW 5%
21 2880 W 2.1 kW (in fact 0 kW) 2.1 kW 0%
2 2880 W 1.2 kW (in fact 0 kW) 2.0 kW 67%
31 2880 W 1.8 kW 2.4 kW 33%
2 2880 W 2.2 kW 2.4 kW 9%
PV String improvement: 11.6 kW 13.5 kW (16%)PV system improvement: 8.3 kW 13.5 kW (63%)
Confirmatory tests after rectification (I)IV curve results
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Confirmatory tests after rectification (II)Electroluminescence imaging
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Water
Platform
Inv1 Str1
Inv2 Str2
Inv2 Str1
Inv3 Str1
Inv3 Str2
Inv1 Str2
Confirmatory tests after rectification (III)Electroluminescence plot
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Outcome after rectification
All modules functional again
All inverters functional
All modules earthed
DC disconnect switches safe
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Underperformance: -10% outputInternal rate of return (IRR) falls by 2.5%
If the owner needs to pay faulty modules/inverter, output can be restored, however, IRR remains sub-optimal
If the warranty can be claimed successfully, output restored and IRR almost back to expected levels
*includes an administrative fee of ~USD 500
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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The “PV System Doctor” - summary Applicability:
Regular health checks
Preventive maintenance
Suspected under-performance
Methodology:
Remote monitoring
On-site assessments (Visual, electrical, optical, incl. DEL/DPL)
Financial assessments
Benefits:
Timely identification of under-performing PV systems
Replacement of degraded / failing system components
Maximise revenues and reduce financial risks
SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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SERIS is a research institute at the National University of Singapore (NUS). SERIS is sponsored by the National University ofSingapore (NUS) and Singapore’s National Research Foundation (NRF) through the Singapore Economic Development Board (EDB).
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Don‘t hesitate to contact us:
More information at www.seris.sgwww.solar-repository.sg