Shuxian Lun

A new six-parameter model for solar cell parameters based on padé approximants

This paper proposes a six-parameter modeling method to represent parameters of solar cells. The traditional five-parameter model ignores the influence of temperature on series resistance and gives an accurate current-voltage (I - V ) characteristic expression only for mono-crystalline and poly-crystalline silicon solar cells. In this paper, padé approximants is used to express the relationship between series resistance and temperature and thus a new parameter, named temperature coefficient for series resistance, is introduced. The six-parameter modeling method can give a more reasonable description of series resistance about temperature and then provides a more accurate I-V characteristic estimation for silicon solar cells with different technology types, i. e., mono-crystalline, poly-crystalline, thin film, and triple-junction amorphous. Four types of silicon modules with different technology are tested at different solar irradiance and temperature conditions to validate the method proposed in this paper. Experiment results show the proposed six-parameter model is a simple, accurate and effective modeling method for solar cell parameters.

Amorphous silicon-assisted self-catalytic growth of FeSi nanowires in arc plasma

We report the synthesis of FeSi nanowires via a direct current arc discharge method. As material sources, the mixture of Si and Fe powders are put into a graphite crucible that acts as the anode. Free-standing FeSi nanowires are deposited on the iron wires suspended near the cathode without the designed use of any catalyst. The as-grown FeSi nanowires are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The typical size of the FeSi nanowires is 1-3 μm in length and 10-20 nm in diameter. Based on the traditional vapor-liquid-solid (VLS) growth model, a so-called amorphous silicon-assisted self-catalytic growth process is put forward to explain the growth mechanism of the FeSi nanowires. A photoluminescence emission peak with a maximum at about 600 nm is observed at room temperature. Magnetic characterization is carried out and the results show that the FeSi nanowires exhibit ferromagnetic characteristics at room temperature.

The cooling system design and performance analysis of the disc type permanent magnet synchronous motor

To extremely improve high power density of a disc type permanent magnet synchronous motor (PMSM), the results are simulated with finite element method considering the electromagnetic, fluid and thermal. Motor output power and temperature rise with different water are calculated by flow analysis. The rationality of thermal conductivities of materials are proved by comparing the calculated results with the test data, which could be referred in the design of this kind of motor.

Design of GaAs solar cell front surface anti-reflection coating

Based on a variety of dielectric film materials are of different refractive rate, design anti-reflection coating structure applying on the GaAs solar cell front surface in transfer matrix method (TMM), the optical absorption effect showed by different coating structure are analyzed and evaluated. Results show that: the three-layer anti-reflection film structure composed of three different dielectric film material has a smaller reflection loss than single-layer coating and double coating in GaAs cells absorb spectrum (300 nm ~ 867 nm wavelength range), for different incident angles, the reflectivity of incident light can be reduced to less than 5%.

Parameters relation of the Leaky integrator echo state network for time series

The leaky integrator echo state network (Leaky-ESN), an improved echo state network (ESN), has been proved to be useful for learning very low dynamic systems. However, the Leaky-ESN exists a complex nonlinear relationship between parameters, and then setting parameter values is very difficult because of lacking effective guiding principles. It is difficult for beginners to give suitable values of the parameters. Therefore, in order to further enhance modeling ability, in this paper, we study the relationship between the size, sparsity of the reservoir and the modeling accuracy through the simulation experiment. This paper not only gives the qualitative description of relationship between them, but also gives the quantitative description by the least squares fitting method. It is worth mentioning that this paper gives an effective principle about how to choose the size and the sparsity of the reservoir.

Optimize state equation of leaky-integrator ESN based on extend kalman filtering

Recently, a novel recurrent neural network (RNN) called leaky-integrator echo state network (Leaky-ESN) was proposed. Standard Leaky-ESN has showed the good prediction ability for time series. In this article, we introduce a new method called Leaky-ESN based on Extend Kalman Filtering (LEKF). The LEKF method uses the merits of extend kalman filtering (EKF) to improve Leaky-ESN. The reservoir state equation of standard Leaky-ESN ignores output feedback during the recursive process. Thus, to a certain extent, the deficiency of standard Leaky-ESN affects its prediction accuracy and make it expend more computing time. We find that the state update equation of EKF not only is similar with the reservoir state equation but also has the output feedback participating in the state equation updating, which inspires a new thought into us, thus, we propose the LEKF method. In LEKF method, we regarded the reservoir state equation and output mapping of Leaky-ESN as the nonlinear system model of EKF, and conduct derivation of the nonlinear model to obtain the important parameters like Jacobian matrix, Kalman gain and others of EKF recurrent equations. The LEKF method not only obtains a more smaller test error but also makes training error has a faster convergence due to adding the output feedback during the state update process, and shows good prediction ability than standard Leaky-ESN. We use two different time series to further validate the effectiveness of the method.

Reflecting filters based on one dimensional photonic crystal with large lattice constant

We change the optical thicknesses of different layers in one dimensional photonic crystals (1DPCs) by introducing sine and cosine functions into transfer matrix method and find that the changes of 1DPCs optical thicknesses from regular periodic structures to sine and cosine function structures, will make the reflection spectrums of 1DPCs appear multiple reflection peaks and these peaks widths and positions can be easily modulated by changing the fundamental parameters of sine and cosine functions. In this paper, we use this method to design two types of narrow band reflecting filters based on 1DPCs with large lattice constant.

Preparation and characterization of Cu 2 ZnSnS 4 thin films by solvothermal method

The Cu2ZnSnS4 thin films have been deposited onto FTO glass substrates by a simple solvothermal method. The films were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analyzer, and optical absorption spectroscopy technique, respectively. The influence of the annealing temperature on the structure, morphology, and composition of the films has been studied. The polycrystalline Cu2ZnSnS4 thin films crystallized in the tetragonal structure with nearly stoichiometric after annealing at 550 °C in Ar atmosphere for 1h. The analysis of the optical absorption data gave the bandgap energy to be 1.5 eV. The photoelectrochemical characterization showed that the annealed CZTS thin films behaved as p-type semiconductor photoelectrodes.

Preparation and characterization of CdIn 2 S 4 wedgelike thin films

Cadmim Indium sulfide (CdIn₂S₄) thin films composed of wedgelike crystals were prepared on fluorine-doped tin oxide substrate by a tartaric acid assisted hydrothermal method. The tartaric acid was found to play an important role in the formation of the final product. The formation mechanism of the CdIn₂S₄ film was also discussed. The optical properties and microstructure of the CdIn₂S₄ films were characterized by X-ray diffraction, field-emission scanning electron microscopy, and UV-vis absorption spectroscopy. The results revealed that the wedgelike CdIn₂S₄ thin films were crystallized in the cubic spinel structure. The analysis of optical absorption data shows bandgap energy to be 2.46 eV which is optimal for photovoltaic applications.