Siyu Guo

A Quantitative Analysis of Photovoltaic Modules Using Halved Cells

In a silicon wafer-based photovoltaic (PV) module, significant power is lost due to current transport through the ribbons interconnecting neighbour cells. Using halved cells in PV modules is an effective method to reduce the resistive power loss which has already been applied by some major PV manufacturers (Mitsubishi, BP Solar) in their commercial available PV modules. As a consequence, quantitative analysis of PV modules using halved cells is needed. In this paper we investigate theoretically and experimentally the difference between modules made with halved and full-size solar cells. Theoretically, we find an improvement in fill factor of 1.8% absolute and output power of 90 mW for the halved cell minimodule. Experimentally, we find an improvement in fill factor of 1.3% absolute and output power of 60 mW for the halved cell module. Also, we investigate theoretically how this effect confers to the case of large-size modules. It is found that the performance increment of halved cell PV modules is even higher for high-efficiency solar cells. After that, the resistive loss of large-size modules with different interconnection schemes is analysed. Finally, factors influencing the performance and cost of industrial halved cell PV modules are discussed.

Comparison of Glass/Glass and Glass/Backsheet PV Modules Using Bifacial Silicon Solar Cells

Bifacial solar cells can be encapsulated in modules with either a glass/glass or a glass/backsheet structure. A glass/backsheet structure provides additional module current under standard test conditions (STC), due to the backsheet scattering effects, whereas a glass/glass structure has the potential to generate additional energy under outdoor conditions. In this study, we quantify the current contributions due to various mechanisms in both module structures under STC. The current contributions due to different mechanisms are calculated by measuring the reflectance and transmittance of mini-modules with both structures, together with a MATLAB-based simulation. Our results show that under STC, glass/backsheet modules provide approximately 2.2% more power, as compared with glass/glass modules using the same bifacial solar cells with a standard cell gap of 2.0 mm. Using module optimization, we demonstrate that the maximum possible cost reduction benefit in

On the spectral response of PV modules

/WP of glass/backsheet modules over glass/glass modules under STC is limited to 3.3%. Due to the potential outdoor energy yield advantages of glass/glass modules reported in the literature, we recommend a glass/glass module structure for bifacial solar cells. Furthermore, in order to compensate for the lower performance of glass/glass modules under STC, we propose a methodology to measure and fairly rate bifacial glass/glass photovoltaic (PV) modules.

Modelling of an integrated standalone streetlamp PV system

The spectral response of silicon wafer based and thin-film photovoltaic (PV) modules is studied using simulation and experimental methods. Circuit simulations show that the module spectral response (SR) depends on (1) the SR of the cells, (2) the shunt resistance Rshunt of the cells, and (3) the bypass diodes of the module. For realistic Rshunt values, the module SR is significantly higher than the minimal SR of the individual cells (which would be the module SR in the case of infinite Rshunt). Round-robin tests using different experimental methods (partial illumination and full-area illumination) to determine the SR of a wafer-based module and a thin-film silicon module were conducted. Both SR methods are found to agree reasonably well. However, circuit simulations indicate that if only one cell, or a few cells, within the module have significantly different characteristics but not known, the results may differ considerably. The partial illumination method can access the SR of the individual cells within a module, but it possibly requires a long measurement time in order to measure the SR and Rshunt of each cell for confirming the SR of the whole module. In contrast, full-area illumination methods measure the module SR directly, but they cannot access the cell SRs if problematic cells exist. An uncertainty analysis of the full-area illumination method is conducted, which reveals that?if the calibrated reference cell is chosen properly?the calibration uncertainty of the reference cell itself is the main source of uncertainty.

Analysing partial shading of PV modules by circuit modelling

In this work, the operation of a standalone streetlamp PV system is modeled considering actual outdoor operation conditions. The model integrates all components required in a stand-alone PV system: PV panel, battery, charge controller and load. Electrical characteristics of each component are based on those of a streetlamp PV system, currently tested in Singapore. Using measured irradiance data, the model is able to predict the real-time current flow, battery operating voltage and state of charge. The simulations of the streetlamp system are done using real-measured irradiance data from Singapore and Boston. We find that for a long-term, uninterrupted operation of a standalone PV system actual meteorological conditions need to be considered. The real-time simulation method presented in this work allows better defining the size of the required solar panel and the battery capacity.