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Renewable Energy Research that Work for You
Renewable Energy Research
that Work for You
About Us
"Energy Research for Africa for Tomorrow“
The Centre for Energy Research (CER) comprises
energy research activities from the Faculty of Science,
the Faculty of Engineering, the Built Environment and
Information Technology, and the Faculty of Business
and Economic Sciences at the NMMU.
Mission
The CER is a research based entity that strives to serve
the energy research needs of Africa by means of
training students and conducting applied
energy research.
Heading
Heading
At present there is research activity in the
following areas:
Photovoltaics (PV)
PV materials development
Solar thermal
Renewable Energy Systems
Energy storage and battery chemistry
Energy Economics
Wind energy
Energy efficiency
Resource assessment
Energy Meteorology
Outline:
• PV Research Group activities (Science Faculty).
• Introduction to new Photovoltaic Testing Laboratory (PVTL).
• RE Research Group (Engineering Faculty).
Heading
Photovoltaics Research
Equipment and General Research Activities.
Diagnostic Imaging and Characterisation.
Concentrator Photovoltaics (CPV).
PV Systems Research.
Equipment and General Research Activities • Class AAA solar simulator.
− Standardised current-voltage (I-V) characterisation.
− MPPT measurement.
− Determination of temperature coefficients.
− Module shading experiments.
• Outdoor I-V measurement system. − Real outdoor PV performance.
− Determination temperature coefficients.
• Dark I-V measurement system.
• Portable I-V array tester. − On-site PV string and array performance testing.
• Various solar resource measurements. − Variety of pyranometer and pyrheliometer classes.
− Two secondary class pyranometers and pyrheliometer on accurate
tracker, part of SAURAN network (www.sauran.net).
• Various PV energy yield test platforms. − Two-axis and single axis tracker platforms.
− A variety of general data logging systems.
− 3kW grid tie PV system.
− 1.6kW grid assist PV system with battery storage.
− Dedicated system to determine the location-specific power of
different PV module technologies.
0.0
1.0
2.0
3.0
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5.0
6.0
7.0
8.0
9.0
10.0
0 100 200 300 400 500 600 700 800
Cu
rre
nt
(A)
Voltage (V)
Inverter: WRS_2
String 1 String 2 String 3 String 4 Ideal (20) Ideal (8)
Equipment and General Research Activities
PV module energy yield test platform layout. Papendorf Software Engineering GmbH
Equipment and General Research Activities
• Micro inverter test equipment. − Simulated PV I-V power supply.
− AC power analyser.
− Programmable electronic load.
• Thermal imaging cameras. − Hot-spot imaging
− Reverse bias and Ohmic heating.
• Electroluminescence (EL) cameras. − Micro cracks
− Defect areas with low carrier recombination.
− Outdoor, on-site imaging of module strings.
• Various Light Beam Induced Current
(LBIC) imaging systems. − ID defect areas with low photo generated current.
− PV parameter maps.
− HR-LBIC for cells
− Solar-LBIC for CPV
− LA-LBIC with micro Raman for whole module.
Diagnostic Imaging
Light Beam Induced Current (LBIC) and cell parameter
mapping
• High Resolution LBIC
• Solar LBIC
• Large Area LBIC
Challenge: Extract diode cell
parameters from spot illuminated
I-V in seconds.
7mW, 633 nm Laser LBIC at Isc Beam
intensity 5.0 × 105 W/m2 Solar-LBIC at Isc Beam intensity 106 W/m2
A B
Illuminated current map Saturation current map
Diode ideality map Series resistance map
LBIC parameter maps of Si solar cell. Source: Lucian Bezuidenhout, presented at the 58th SAIP Conference, UniZul, July 2013.
Diagnostic Imaging
Electroluminescence (EL)
• Result from radiative carrier recombination processes.
• Complete Module High Resolution EL.
• Bias dependence and defect Identification.
Diagnostic Imaging
EL and dark current system. (Source , diagram and images: J Crozier)
Dark current-voltage curve. (Source , diagram and images: J Crozier)
EL images of a module defects such as degradation of encapsulant, anti-reflective and micro cracks. Source: Jacqui Crozier, MSc thesis, NMMU 2011.
Diagnostic Imaging
High Resolution EL Results (acknowledgement: Jacqui Crozier)
Diagnostic Imaging
• Outdoor Electroluminescence (EL) camera. − Can image module strings up to 1000V dc.
− Image defect areas with low carrier recombination.
− Micro cracks
Source: Dr. Martin Regehly, GreatEyes Product Presentation, www.greateyes.de
Development of a Large Area LBIC scanner
Module encapsulant browning and delamination.
Source: John Pern, National Centre for Photovoltaics(NCPV)
National Renewable Energy Laboratory (NREL), APP
International PV Reliability Workshop Dec. 4-5, 2008, SJTU,
Shanghai, China
LA-LBIC Raman scanning of PV module
Three-string series connected PV module
Concentrator Photovoltaics (CPV)
Objective: Lower the cost/kWh for electricity produced while
maximising durability.
• Methodology: Optimise the operating conditions for the CPV cell
material to deliver the highest possible Energy Yield.
• Factors that can be controlled when optimising cell operating
conditions:
• Optics (determines the characteristics of on-cell irradiation).
• Electrical Configuration (defines the current-voltage characteristics
and operating point).
• Thermal Management (governs generation losses and lifetime of
the PV material).
• These factors are somewhat interlinked.
• As with all RE technologies; a) Durability, b) Specific Energy Yield
and c) Manufacturing Cost need to be optimized simultaneously.
Low Concentrator Photovoltaics (L-CPV)
Optical design 2 (acknowledgement: Mario Benecke)
Six-facet Intensity distribution Horizontal absorber design
Absorber cell configuration and performance
EL of 8-cell string
X = 1 X = 5.3
Isc 0.55 A 2.76 A
Voc 4.79 V 4.84 V
Imp 0.49 A 2.31 A
Vmp 3.81 V 3.05 V
Pmax 1.89 W 7.07 W
Temp 26⁰ C 32⁰ C
Data of 8 cell string
High Concentrator Photovoltaics (H-CPV)
Main Characteristics
• Maximum efficiency, more than 300 X.
• Higher tracking accuracy.
• Very small manufacturing tolerances.
• PV material generally expensive.
First commercial point focus Fresnel CPV system in deployed in 1998
p n
collection
surface recomb
generation
Bulk
recomb
high I0
low I0
contacts
Si back point contact CPV cell structure
Si CPV cell and mounted secondary lens
High Concentrator Photovoltaics (H-CPV)
I-V characteristics for a CTJ cell for optically misaligned unit . I-V characteristics for a CTJ cell for thermally stressed unit .
Device parameters for two optimally aligned CTJ cells after 2 month operation.
2nd Prototype Results (acknowledgement: Ross Schultz)
High Concentrator Photovoltaics (H-CPV)
New H-CPV module.
The variation of solar spectrum during a day for one sun.
InGaP InGaAs Ge
15%
17%
14%
15.94mA10.48mA10.45mA
500 1000 15000.0
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Wavelength nm
Curr
entD
ensi
tyAm
2.n
m
The reduction in the current density spectrum due to
absorption by the optical system.
3rd Prototype Results (acknowledgement: Ross Schultz)
PV Systems Research
Grid Integrated PV System Operation
• Optimize Grid inverter operation.
• MPPT Algorithm Characterization.
(Source: Warren Allistoun)
PV Array Power dependencies. (Source: Warren Allistoun)
Laboratory established to conduct performance
testing of PV modules in collaboration with Enertis Solar
according IEC standards,
as well as in-house tests:
1. Visual Inspection.
2. Maximum Power using a class AAA in indoor solar simulator.
3. Electrical Insulation.
4. Reverse Bias Thermography.
5. Electroluminescence Imaging.
Details of the tests are found on the next page.
Photovoltaic Testing Laboratory (PVTL)
Tests done in collaboration with Enertis Solar
Test Description Procedure/Standard
Visual Inspection
Crystalline Silicon PVTL-VIS-SI: according to IEC 61215:2005
(section 10.1)
Thin Film PVTL- VIS–TF: according to IEC 61646:2008
(section 10.1)
Maximum Power
Determination
Class AAA Solar Simulator
Crystalline Silicon PVTL-MP-SI: According to IEC 61215 :2005
(section 10.2)
Thin Film PVTL-MP-TF: According to IEC 61646:2008
(section 10.2)
Low Irradiance: Crystalline
Silicon
PVTL-LI-SI: According to IEC 61215:2005
(section 10.7
Low Irradiance: Thin Film PVTL-LI-TF: According to IEC 61646:2008
(section 10.7)
Electrical Insulation
Crystalline silicon PVTL-HP-SI: According to IEC 61215:2005
(section 10.3)
Thin film PVTL-HP-TF: According to IEC 61646:2008
(section 10.3)
Reverse Bias Thermography PVTL-TI: In-house procedure
Electroluminescence Imaging PVTL-EL: In-house procedure
Additional tests that can be performed on-site
at any large PV installation include:
In-situ outdoor (low light) electroluminescence imaging of module
strings up to 10kW.
In-situ outdoor current voltage (I-V) measurement of large module
strings.
In-situ thermographic inspection.
Outdoor Exposure test (according to IEC 61215:2005 and IEC
61646:2008).
Additional Photovoltaic Module Testing
Project Pictures - PVTL
Due Diligence from Academic Perspective
In Situ Module Thermography.
Due Diligence from Academic Perspective
Test Lab Reverse Bias Thermography.
Temperature distribution resistive heating from on a 60 cell PV module. Close-up temperature distribution from
on a single cell.
Due Diligence from Academic Perspective
Test Lab Electroluminescence.
Acceptable module Abused module showing micro cracks
Acceptable module showing processing artefacts Acceptable module showing processing artefacts
RE Research Group: Engineering
Micro Wind Energy
• Twerly hybrid streetlight powered by wind and solar.
Licenced to Twerly Streetlights (Pty) Ltd
• Patented segmented blade wind turbine.
• Large 3D printer under development.
RE Research Group: Engineering
Solar Thermal
• Parabolic concentrated solar collector system.
• Dolerite rock thermal energy storage system.
• Organic Rankin cycle electricity generator.
• Solar Cooker.
Photovoltaics
• Off-grid PV system powering Engineering Lab.
• Novel cellphone and laptop charging system.
• One-axis solar tracking system under development.
THANK YOU !
Acknowledgements: • Ross Schutltz (PhD student)
• Jacqui Crozier (PhD student)
• Nicholas Kwarankunda (PhD student)
• Mario Benecke (MSc student)
• Warren Allistoun (MSc student)
• Brendon Mac Leod
• Lucian Bezuidenhout (MSc student)
• Prof Russell Phillips
• Prof Ernest van Dyk
Acknowledgements
Acknowledgements
CSIR National Laser Centre, Rental Pool Programme
www.nmmu.ac.za/energy
