Pongpan Vorasayan

Loughborough University, Loughborough, ENG, United Kingdom

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Publications (13)1.44 Total impact

  • P Vorasayan, T R Betts, R Gottschalg
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    ABSTRACT: A new limiting laser beam induced current (li-LBIC) measurement technique is described which allows the recovery of the true signal in an integrated photovoltaic (PV) module. It is a measurement based on optically exciting the device by scanning with a laser, where the probed cell is brought under limiting condition by means of manipulating the background illumination. The signal obtained is directly proportional to the laser strength, which was previously unobtainable by typical LBIC measurements in a module. The advantages are shown to be that it gives an opportunity to measure the real properties of investigated cells and is usable for fully encapsulated, series connected photovoltaic modules. It is also unaffected by non-uniform background illumination. The system provides spatially resolved measurements and has shown to be an effective characterization tool to reveal spatial non-uniformity in the PV devices with sub-millimetre resolution. It can be employed as a characterization tool for commercial modules functioning not only for quality control of newly produced PV devices but also for loss analysis during various stages of their operating lives.
    Measurement Science and Technology 06/2011; 22(8):085702. · 1.44 Impact Factor
  • P. Vorasayan, T.R. Betts, R. Gottschalg
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    ABSTRACT: A 3D distributed model is developed and implemented based on circuit analysis software for the investigation of spatial variation in performance due to the distributed nature and non-uniformity of solar cell properties. This is applied to LBIC measurements where it is used for sensitivity analysis of the measurements with respect to certain parameters in series connected thin film PV modules.The model is used to explain the differences in dark and illuminated measurements, which clearly shows the illuminated LBIC signal is largely dependent on the homogeneity of the background illumination. The dark LBIC is largely affected by the shunt resistance of the neighbouring cells rather than by the signal strength of the cell under test. It is required to bring the cell into limiting conditions, which then gives a signal one order of magnitude stronger than that in the non-limiting case. The simulations are validated against measurements taken in these regimes.
    Solar Energy Materials and Solar Cells. 01/2011;
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    ABSTRACT: Non-destructive spatial characterisation tools are essential for the evaluation of thin film photovoltaic modules; as such distributed variations have a significant effect on the overall device performance. A combination of several techniques (solar simulator, LBIC and thermography) is used in conjunction to identify and investigate performance problems and locate possible defects in thin film silicon photovoltaic modules of different structures. An excellent agreement between the different spatial analysis tools is demonstrated. The LBIC system used here is unusual in that it analyses modules where the cells are interconnected and the signal strength does not give as clear a feedback on the defects as in the case of measuring each cell separately. The choice of lasers used in the system allows the investigation of separate junctions in the most common multi-junction devices. The system characterisation is demonstrated here in order to warranty reliability and repeatability of this tool. A special test module is investigated where all techniques are compared and good agreement is demonstrated. Furthermore, the problem of reducing signal strength with increasing junction number is demonstrated and discussed.
    Solar Energy Materials and Solar Cells. 01/2009;
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    ABSTRACT: This is a conference paper. There is an interest in identifying localised effects when investigating durability of devices. The combination of tests might also have an influence on test results. This is investigated for single junction amorphous silicon modules. The modules were put under accelerated testing including thermal cycling, light soaking and annealing test. I-V measurement and LBIC system as characterisation tools are used to investigate the possible degradation occurring in the devices both before and after certain stages of the test. Results have shown that there is a difference between modules which have experienced light soaking before being exposed to thermal cycling, indicating that the initial light soaking resulted in a UV activation of the material, which then changed the durability of the lamination. Accepted for publication
    Proceedings of the 4th Photovoltaic Science, Application and Technology (PVSAT) Conference, BathProceedings of the 4th Photovoltaic Science, Application and Technology (PVSAT) Conference, Bath; 01/2008
  • Proceedings of the 23rd European Photovoltaic Solar Energy ConferenceProceedings of the 23rd European Photovoltaic Solar Energy Conference; 01/2008
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    ABSTRACT: This work aims to demonstrate the energy production of amorphous silicon devices through long-term monitoring. Some devices have a very high specific energy production while other does not accomplish this. The reasons for seasonal variations are investigated. Assuming that the short circuit current is mainly influenced by spectral changes allows degradation to be attributed to the fill factor. The seasonal variation of this is investigated in more detail, demonstrating differences between single and multi junction devices
    Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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    ABSTRACT: STC efficiencies are not sufficient to compare photovoltaic devices of different semiconductor material or device configurations. The energy yield changes as the variables of STC deviates from their original values when the modules are placed in various climatic conditions. The magnitude of this change for different modules is not always clear and needs to be investigated and modelled. A modeling and analysis method named site specific conditions (SSC) is demonstrated which is a measure-correlate-predict approach. It allows an accurate estimation of the actual energy yield for different sites based on the measurements at one single site. The method takes into account the effect of the physical operating environment and translates this to other meteorological conditions on the basis of physics related formulae. Our results show a large seasonal variation for modules for the different effects. For crystalline modules losses of up to 12% in the summer is due to the temperature effect while the multi-junction thin film losses of more than 30% in the winter is due to spectral changes and incidence angle effect for the UK.
    Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE; 02/2005
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    ABSTRACT: This conference paper was subsequently published in the journal Solar Energy Materials and Solar Cells [© Elsevier], 93 (6-7), 2009, pp. 917-921 [doi:10.1016/j.solmat.2008.10.019]. The definitive version is available at: www.elsevier.com/locate/solmat Several non-destructive characterisation tools - solar simulator, LBIC, thermography - are used together to investigate the performance of and locate possible defects in TF silicon PV modules of different structures. A special module is investigated where all techniques are compared and good agreement is demonstrated. Accepted for publication
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    ABSTRACT: This is a conference paper. Solar cells are currently evaluated under laboratory conditions and not under realistic operating conditions. Amorphous silicon (a-Si) devices exhibit a complicated dependence on operating conditions, with a major concern being the degradation of these devices in realistic operation. Optimising these devices for energy production of the stabilised state is dependent on many factors, with one of the main inputs being the overall thickness of the cell. In this paper, the effect of intrinsic layer (i-layer) thickness on the cell performance, the degradation and also the energy production under realistic conditions are investigated. It is apparent from the experiment that there has to be an optimisation of the i-layer thickness to maximise the light absorption and minimise the degradation, if higher performance and energy production is to be achieved. Accepted for publication
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    ABSTRACT: This is a conference paper. Further details of the conference are available at: http://www.eurosun2006.org/ A laser beam induced current system has been developed for large area thin film technology. Employing a non-destructive laser scanning approach, such a system is used as a characterisation tool that is able to perform local performance investigation and allows efficient defect detection in large scale devices. In this paper, the results are shown for large area single junction amorphous silicon modules. The scanning images reveal an inhomogeneous current signal. Cross-section analysis illustrates that in some modules, there is considerable performance variation between cells. Certain cells are nearly or completely inactive. Interconnection problems, tiny cracks and defects that cannot be detected by visual inspection can also be identified. Accepted for publication
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    ABSTRACT: This is a conference paper. The energy production of a number of single junction amorphous silicon (a-Si) solar modules with different intrinsic layer thicknesses is investigated. This has been carried out through both indoor measurement and real operating condition monitoring outdoors. After 13 months of light exposure, the fully degraded and seasonally annealed states, can be seen. The results indicate that the thinnest devices do not necessarily have the lowest degradation. The thicker devices which have higher initial efficiency, however do suffer greater efficiency degradation. Experiment also shows that energy production does not follow the initial Standard Test Condition (STC) rated efficiency as the highest can be seen in thinner modules, which initially have much lower efficiencies. Accepted for publication
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    ABSTRACT: This is a conference paper. A laser beam induced current (LBIC) system has been used as a non-destructive characterisation tool for photovoltaic (PV) devices. It provides a detailed twodimensional map of the current signal. Each data point in the map is generated by the laser beam scanning over the devices. The signal strength depends on the response of that particular area on which the laser beam is incident, thereby reflecting the absorption and collection characteristics of that local PV area. However, the magnitude of the measured signal, induced by modulated laser, is very small. Adjustment of set parameters, measurement variables and environmental influences may affect the measurement result and thus could lead to misinterpretation. The LBIC system at the Centre for Renewable Energy Systems Technology (CREST) is analysed for reliability and optimised. It is evident that with appropriate settings under controlled environmental conditions, the system can provide a highly repeatable measurement result. Accepted for publication
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    ABSTRACT: This conference paper was presented on the occasion of the 21st European Photovoltaic Solar Energy Conference, Dresden, Germany, September 2006. The spatial variation of key properties of large area silicon thin film PV modules is investigated using a Laser Beam Induced Current (LBIC) system. The system produces a very detailed current mapping of devices, allowing the identification of spatially varying structural defects of photovoltaic modules. It allows for efficient defect detection as well as investigations of localised performance variation. In this paper, the results are shown for large area single junction amorphous silicon modules from different manufacturers that have been installed outdoors for more than two years. Several defects are identified as probable sources of poor performance and low efficiency of some devices. Some of the major contributions to these defects are likely to occur during the production process while some are developed during outdoor exposure. Not specified

Publication Stats

10 Citations
1.44 Total Impact Points

Institutions

  • 2006–2011
    • Loughborough University
      • Centre for Renewable Energy Systems Technology (CREST)
      Loughborough, ENG, United Kingdom
  • 2008
    • University of Valencia
      Valenza, Valencia, Spain