Khomdram Jolson Singh

Maximum power point tracking controller using P and O algorithm for solar PV array on FPGA

The electrical circuit modelling of a photovoltaic module and the implementation MPPT controller on Field Programmable Gate Array (FPGA) is investigated in this article. The maximum power point location is always unknown at any instant from the PV cells thus necessitate the design of locating this maximum point using some controller. The widely used P and O algorithm is implemented on FPGA system. The design have been written in VHDL language and its simulation is done using Quartus II VHDL tools. Further, the VHDL-modules have also been simulated, synthesized and tested using ModelSim Altera Quartus II. The same algorithm is implemented on generalized PV model developed in MATLAB Simulink software and the outputs are compared with that of Altera. It has been carefully observed that we can satisfactorily extracted the MPP from both the system. The system is further evaluated for different insolation and ambient Temperature in order to analyze the various outputs in these conditions. Simulation results validated the proposed implementation of MPPT algorithm using VHDL program in FPGA.

A wide band gap In 0.5 (Al 0.7 Ga 0.3 ) 0.5 P Back Surface Field layer increases 6% more efficiency in DLAR Dual Junction InGaP solar cell

A wider band gap (2.3eV) material In0.5(Al0.7Ga0.3)0.5P based BSF layer lattice matched with both top In0.49Ga0.51P and bottom GaAs cell is found to increase 6% more efficiency than other widely used Al0.7Ga0.3As material under the same cell configuration because of its high photo generation rate. A numerical simulation analysis of these BSF layer in InGaP/GaAs dual-junction solar cell is investigated using TCAD tool Silvaco ATLAS. The cell is modeled using these two BSF materials both for top and bottom cells and compared all their performance parameters. InAlGaP is found to be a better choice for both window and BSF layer. The cell efficiency and EQE is further optimized by varying BSF layer thickness under current matching condition which is achieved with relatively thinner BSF layer of top cell (30nm) and the thicker BSF layer of bottom cell (1000nm). For this optimized cell structure, a maximum conversion efficiency of 36.67 % (1000 suns) are obtained under AM1.5G illumination. The detail photogeneration rates in this optimized DJ solar cell structure with DLAR of Al2O3-TiO2 are also generated and compared.

Simulation and experimental study of ZnO thin film deposited over p-Si with Al contact

This paper comes with Zinc Oxide (ZnO) thin film deposition over virtually grown p-Si substrate and fabricated using the E-beam evaporation PVD technique. The simulation analysis of ZnO TF/p-Si introduces photo-generation rate, spectral response that has been carried out using the Silvaco ATLAS software. The surface morphology and structural characterization has been done by Field Emission Scanning Microscopy (FESEM) and X-Ray Diffraction (XRD) analysis. The electrical characterization is verified in dark and light condition which shows the rectifying behavior of the Al schottky contact. The turn-on voltage is around 1V for the device.

Study and design of graphene field effect transistor for RF performance

This paper presents the study of RF characteristics of Graphene based Field Effect Transistor (GFET). The study of characteristic curves is carried out using SILVAVO TCAD tools. The RF parameters which determines the performance of the device in the higher frequency and the effect of downscaling of the device channel length is analyzed and parameters are extracted. This work also presents the effective and novel way to model the material graphene in simulator and GFET device simulation using TCAD.

ZnO based homojunction p-i-n solar cell to self-power UV detector

A simple novel and low cost efficient all ZnO based homojunction p-i-n solar cell without any top transparent conductive oxide layer and aback reflector layer are numerically modeled using 2D device simulation tool ATLAS. Optimization of the different layers, doping level and power conversion efficiency of the model has been done. The spectral response such as transmissivity, reflectance, and absorptance under AM1.5 solar illumination is well studied. Although the ZnO material responds to only a small portion of sunlight in UV region of AM1.5, the External Quantum efficiency(EQE) of the model is found to be nearly 70% and efficiency upto 16% for 1000nm thick i-layer ZnO. These optimized results are validated with other reported published experimental works. The wavelength dependent photo response properties of the homojunction are investigated in detail by studying the effect of light illumination on current-voltage (I-V) characteristics, photocurrent and spectral response at room temperature. From the photocurrent spectra, it is observed that the ultraviolet (UV)photons are absorbed in the depleted n-ZnO under positive bias conditions with responsivity of 1.6 mA/V. This indicates that such a model of ZnO p-i-n thin film homojunction can be used to sense UV though the photo response for UV as well as generate a significant energy to self-power this sensor.

Heterogeneous carbon nano-tube window layer with higher sheet resistance improve the solar cell performance

The heterogeneous Carbon Nano-Tube (CNT) layers deposited on the window surface of solar cells that allow better charge carrier collection was numerically analyzed and studied in modern TCAD tools. The quantum efficiency(EQE) as well as power conversion efficiency (η) were found to be improved significantly based on the light transmission capabilities of the CNT layer. Two CNT network models using experimental sheet resistance values of 75 Ω/ and 128 Ω/ as a top conducting layer in a GaAs solar cell were compared. It is found that the CNT networks allow for a greater area of charge collection as well as serve as a lower resistance path for charge carriers with minimum voltage loss to travel to the top contact. This model thus significantly improve the η up to 30% under AM0 with more than 90% EQE. The effect of cell width varying starting from 200 μm to 4000 μm with CNT top layer on Jsc, Voc and Pmax parameters were studied and found that these parameters remain almost constant irrespective of cell width. This work thus shown that a thin CNT top layers of lower sheet resistance with a higher light transmission can greatly improve the efficiency of solar cells.

A performance optimization and analysis of graphene based schottky barrier GaAs solar cell

Performance optimization of Graphene-GaAs schottky barrier solar cell have been performed by considering variables such as substrate thickness, Graphene thickness, dependence between graphene work function and transmittance. The optimized parameter was extensively used to numerically model the design using TCAD Atlas. The results show the enhanced performance of the design with the optimized thickness of Graphene (0.3μm) and GaAs (10μm), resulting in significant increase in power conversion efficiency from 0.732% to 2.581% and reasonable fill factor up to 70%. It was further analysed that maximum potential was developed in the vicinity of the anode, which results in better charge collection hence improving the overall performance of the solar cell. The results are validated with the reported experimental work.

Exploration on low cost and effective EOG bio-potential amplifier design and development

The Cornea-Retinal Potential (CRP) is the main source of the Electrooculogram (EOG) signals. These potential are in small microvolt and required to be amplified upto the applicable and usable level. The place of electrode attachment, the eyeball rotation, the motion of head, the ambient light as well as the conductivity of skin can also vary this signal. These numerous artifacts with power-line interference and other unwanted noise had made the EOG signal quite unattractive for any real biomedical applications. This work thus mainly focuses on the elimination of the above major artifacts while striving to maintain signal linearity. The hardware design part also considers the cost effectiveness without negotiating accuracy. The circuit is then rigorously tested and checked over the varied sample of people. It is found to give an efficient and significantly consistent result with minimum noise level. The development and design of a low cost EOG signal amplifier and acquisition system that counters all the major problems is investigated and achieved making it suitable for both theoretical research analysis as well as for real practical applications.