Publications:

References
default
J. Lopez-Garcia, T. Sample and A. Casado
Solar Energy 177, 471-482
ISSN: 0038-092X
(2019)

Abstract: Bifacial photovoltaic (PV) modules can increase the performance with respect to traditional PV modules because both sides of the cells, front and rear, absorb solar radiation. To assess their performance and quality, PV modules are characterized using international standards. However, currently only a draft IEC technical specification exists for bifacial PV modules and research needs to be done in order to study the indoor performance testing conditions. One of the issues that need to be addressed is how to measure bifacial PV modules correctly and analyse the different testing approaches proposed. This work outlines the indoor performance testing of c-Si bifacial modules under different module mounting setups including open rack, a structure with baffles and 3 modules. For each mounting method a white reflective rear panel of several dimensions was placed at various distances behind the module as a potential approach for a double-sided illumination characterization method. Electrical performance is also studied with a single-side illumination method with a black rear panel. The rear irradiance measurements and non-uniformity are also studied and the performance measurements are validated with a single-side illumination method. Additional rear irradiance allows Pmax increment up to 20% under certain conditions. However, the rear irradiance non-uniformity needs to be improved in order to fulfil the current requirements of the draft technical specification.

default
R.P. Kenny, J. Lopez-Garcia, B. Haile and E. Garcia Menendez
AIP Conference Proceedings 1999, 020014 (2018) (2018)

Abstract: The crystalline Si bifacial PV module market has grown significantly in recent years due to the opportunity for increased performance in comparison to traditional PV modules because both sides of the cell can absorb solar radiation. Draft technical specification IEC TS 60904-1-2 (Measurement of current-voltage characteristics of bifacial PV devices) sets limits on permissible deviations of operating conditions, e.g. irradiance non-uniformity. One purpose of this work is to ensure correct evaluation of the real outdoor conditions experienced and to understand what is achievable in practice. A second scope is to ensure correct measurement of module operating conditions in long-term outdoor testing where conditions will be highly variable, but nevertheless must be accounted for in energy yield or rating calculations. Two bifacial modules of each of two different types (Type 1: glass-glass and Type 2: glass-foil) are studied. Rear-side albedo is studied for white ground sheets. The specific conditions studied are module temperature, rear-side irradiance non-uniformity and spectral irradiance.

default
J. Lopez-Garcia, D. Shaw, R.P. Kenny, L. Pinero-Prieto and E. Ozkalay
35th European Photovoltaic Solar Energy Conference and Exhibition
Brussels, BE, 24-09-2018 to 27-09-2018
2018
3-936338-50-7

Abstract: Bifacial crystalline Si photovoltaic modules have attracted considerable interest in the last years, since they can enhance the performance in comparison to traditional PV modules because both sides of the cell can absorb solar radiation. To assess their performance and quality, PV modules are measured and characterized under standard test conditions (STC) as defined by the International Electrotechnical Commission (IEC). Since there is currently no standard for bifacial PV modules, one of the main issues that need to be addressed is the standardisation of bifacial measurements for PV devices. The IEC TC82 is currently working on the development of a draft technical specification. Three different approaches are considered in the draft for the electrical performance of bifacial PV modules, that is, natural sunlight, a solar simulator with adjustable irradiance level for single-side illumination and a solar simulator with double-sided illumination. In order to reproduce the real conditions with both front and rear illumination, the latter approach has been used to characterise bifacial solar cells. However, at a module scale, this approach represents a technical and logistical challenge for many due to the associated cost of using two controlled light sources instead of one and it is considered that the current equipment is not suitable for this setup and requires significant and potentially expensive modifications. However, recent advances in high-power Light Emitting Diode (LED) technology have resulted in a number of LED-based sun simulators coming to market. The aim of this work is the design, development and validation of a double-sided solar simulator based on an existing large-area single long pulse flash solar simulator and a low-cost LED-based rear bias light that can fulfil the standard requirements of rear illumination (up to 200 W/m2) and non-uniformity.

default
D. Pavanello, A. Casado, J. Lopez-Garcia and T. Sample
33rd European Photovoltaic Solar Energy Conference and Exhibition
Amsterdam, the Netherlands, 25-09-2017 to 29-09-2017
2017
3-936338-47-7

Abstract: The interest on the n-type crystalline silicon bifacial PV modules has increased in the last years since they can increase the performance in comparison to traditional PV modules. As the PV modules are generally sold according to the nominal power output and efficiency under standard test conditions STC, the lack of standards for bifacial modules leads each manufacturer to claim different amounts for the "added value" of the bifaciality that makes it difficult for customers to directly compare between bifacial manufacturers. In this work, we have compared the electrical performance of framed and frameless c-Si bifacial modules from 5 different manufacturers utilising rear covers of different reflectivity and different measurement methods such as a single-sweep flash simulator, the so-called multi-flash (MF) method, a largearea steady state sun simulator and under natural sunlight for the accurate measurement of the module parameters. It was observed that depending on the measuring method, some modules presented STC front power out of the tolerance range given by the manufacturer. The design of the module also plays an important role on the rear power contribution.

default
George Koutsourakis

Abstract: Accessing the electrical parameters of individual cells in fully encapsulated photovoltaic (PV) modules can be a cumbersome and time-consuming procedure. It usually requires mechanical shading, which is achieved by using meshes. This limits the control and variability of shading, as there is always a limited variety of mesh patterns available. In this work digital projection technology is utilised as the light source to achieve this. Partial shading can be applied rapidly and performance parameters of individual cells in fully encapsulated modules can be acquired. This is demonstrated inthis work using a custom mini module. Individual cells can be accessedeven in the case that bypass diodes are included. Performance information of individual cells acquired with such a system can be used for studying upscaling lossesor degradation mechanismsfor commercial or research PV modules.

default
George Koutsourakis
0
3-936338-50-7

Abstract: Photocurrent mapping can provide useful spatial information about the electrical and optical properties of a photovoltaic (PV) device under actual operating conditions. Although it is a well-established technique for PV cells, direct current mapping measurements of PV modules is impractical and time-consuming to be applied. One has to mechanically shade specific cells of the PV module or destructively access the cell to be measured. In this work, non-destructive, automated current mapping of encapsulated PV modules is demonstrated. A commercial Digital Light Processing (DLP) projector is utilised in order to apply compressive sampling for current mapping of PV modules. This method is non-destructive, cost effective and significantly fewer measurements are needed for acquiring a current map compared to raster scanning methods. When applying compressive sampling, a series of patterns is projected on the sample, the current response is measured for each pattern and the current map is acquired using an optimisation algorithm. Specific shading strategies, voltage bias settings and I-V curve details are investigated for optimised compressive sampling.

default
Michael Rauer, Christian Reise, Max Mittag and Alexandra Schmid
0
Export as:
BibTeX, XML