Nipu Kumar Das

Germanium telluride as a BSF material for high efficiency ultra-thin CdTe solar cell

The polycrystalline cadmium telluride (CdTe) is regarded as one of the leading photovoltaic (PV) materials for its high efficiency and low-cost. The absorber material CdTe has the ideal and direct bandgap of 1.45 eV and it has a high absorption co-efficient over 5×105/cm. In this work, the possibility of ultra-thin absorber layer of CdS/CdTe solar cell was investigated by numerical analysis utilizing AMPS (Analysis of Microelectronic and Photonic Structures) simulator. In the proposed cell, the CdTe layer was reduced and found that 1 μm CdTe layer is enough for acceptable range of cell conversion efficiency. The viability of this ultra-thin CdTe absorber layer was examined, together with 0.1 μm GeTe back surface field (BSF) layer to reduce the barrier height in the valence band and to minimize the recombination losses at the back contact of the CdS/CdTe cell. It was found that the proposed ultra-thin cells have conversion efficiency of 18.68% (Jsc = 21.47 mA/cm2, FF = 0.85, Voc = 1.02 V) without BSF and with 100 nm GeTe BSF conversion efficiency increased to 22.53% (Jsc = 24.28 mA/cm2, FF = 0.875, Voc = 1.06 V) with only 0.8 μm of CdTe layer. Moreover, it was found that the normalized efficiency of the proposed cells linearly decreased with the increasing operating temperature at the gradient of -0.16%/°C, which indicated better stability of the proposed CdTe solar cell.

A review of the state of the art of generators and power electronics for wind energy conversion systems

Energy is the most fundamental sector for the progression of a nation. The production of energy is going on from many years for the need of energy in all around the world but the true scenario is that the whole world is currently facing dreadful energy crisis in spite of numerous energy sources. So the production, distribution and the use of the energy should be as technological efficient as possible and incentives to save energy at the end-user should be set up. Two major technologies will play important roles to solve the future problems. One is to change the electrical power production sources from the conventional, fossil (and short term) based energy sources to renewable energy resources. The other is to use high efficient power electronics in power systems, power production and end-user application. This paper discusses trends of the most emerging renewable energy source, wind energy. With rapid development of wind power technologies and significant growth of worldwide installed capacity of wind power, wind energy conversion system has become a focal point in the research of renewable energy sources. This paper presents the recent developments in wind energy conversion systems with different wind turbine generators with their technical features and converter topologies, their classifications, choice of generators and their social and environmental benefits.

Modeling of Cu 2 ZnSnS 4 solar cells with Bismuth Sulphide as a potential buffer layer

The Cu2ZnSnS4 is a quaternary semiconductor compound has recently been drawn the attention of extensive research as a potential absorber layer since its offers favourable optical and electronic properties along with low cost material. In this research work, the deep level defects on the performance of CZTS solar cells with Bismuth Sulphide (Bi2S3) buffer layer was carried out by numerical analysis using SCAPS 2802 simulator. In the proposed cell, the CZTS absorber layer was reduced that minimized the cost, saving process time and energy required for fabrication. In this study, it was found that the feasibility of this proposed ultra thin CZTS solar cells and showed higher efficiency of 17.89% (Jsc = 31.05 mA/cm2, Voc = 1.03V and FF = 0.562). Moreover, the thermal stability of the CZTS solar cell was examined and found that the normalized efficiency of the proposed cell was linearly decreased with the increased of operating temperature at the gradient of -0.41%/°C.

Study of molybdenum sulphide as a novel buffer layer for CZTS solar cells

The absorber layer of CZTS solar cell is a compound semiconductor which has favourable optical and electrical properties. Researchers are highly interest to investigate the CZTS solar cells for its earth abundant, non-toxic and low cost feature. Consequently, the absorber layer of CIGS is replaced to CZTS absorber layer. In this research work, the potentiality of Molybdenum Sulphide (MoS2) as buffer has been investigated to explore the higher performance of CZTS solar cells. SCAPS 2802 simulator was used to evaluate the performance of CZTS solar cells with prospective MoS2 buffer layer. The possibility of ultra-thin CZTS solar cells was examined and the higher efficiency of 17.03% (Jsc = 29.42 mA/cm2, Voc = 1.01 V and FF = 0.574) was achieved for 1 μm thickness of absorber layer. In addition, the proposed CZTS solar cells had better thermal stability at higher operating temperature also.

Power converters and control of wind energy conversion systems

The rapid increase in global energy consumption and the impact of greenhouse gas emissions has accelerated the transition towards greener energy sources. The need for distributed generation employing renewable energy sources such as wind, solar and fuel cells has gained significant momentum. Advanced power electronic systems, affordable high performance devices, and smart energy management principles are deemed to be an integral part of renewable, green and efficient energy systems. This paper discuss the most emerging renewable energy source, wind energy, which by means of power electronics is changing from being a minor energy source to be acting as an important power source in the energy system and the standard power converter topologies from the simplest converters for starting up the turbine to advanced power converter topologies, where the whole power is flowing through the converter.

Design and implementation of cost effective smart solar charge station

Utilization of Renewable energy resources is the most important field in a developing country like Bangladesh. Development of an effective method for evaluation of alternative energy sources in the automotive industry has always been a necessity for cost efficient design analysis. One viable energy source is electricity. Electric Vehicle (EV) is the application of this energy. In Bangladesh, Electric vehicle powered by rechargeable batteries are popular day by day. But due to redundancies use of electric energy it is needed to think of alternative sources of energy for running this vehicle. This paper proposed the photovoltaic charging station architecture by using a combination of charge controller based on the battery charging strategy with the unidirectional PWM technique based on the grid to vehicle strategy in Smart Grid. This paper makes a brief introduction and calculation on the power quality research object and takes data like power consumption by running EV. This paper also takes a comparative cost analysis of proposed smart charge station. Consequently, this paper could significantly increase the smart grid system and storage intermittent renewable energy from solar.

Design and implementation of real time transformer health monitoring system using GSM technology

With the progress and development of national economy as well as power system, reliability and safety issues of power system have been more important. Development of distribution Transformer Health Monitoring System (THMS) has been done in that reason. Distribution transformer is the most vital asset in any electrical distribution network and therefore it needs special care and attention. This THMS can monitor the health status of the distribution transformer in real time aspect. As a large number of transformers are distributed over a wide area in present electric systems, its difficult to monitor the condition manually of every single transformer. So automatic data acquisition and transformer condition monitoring has been an important issue. This project presents design and implementation of a mobile embedded system to monitor load currents, over voltage, transformer oil level and oil temperature. The implementation on-line monitoring system integrates Global Service Mobile (GSM) Modem, with single chip microcontroller and sensors. It is installed at the distribution transformer site. The output values of sensors are processed and recorded in the system memory. System programmed with some predefined instructions to check abnormal conditions. If there is any abnormality on the system, the GSM module will send SMS (Short Message Service) messages to designated mobile telephones containing information about the abnormality according to the aforesaid predefined instructions. This mobile system will help the utilities to optimally utilize transformers and identify problems before any catastrophic failure occurs. This system will be an advanced step to the automation by diminishing human dependency. As it is a wireless communicating system, there is no need of large cables which are of high cost. Thus THMS offers a more improved transformer monitoring.

Design of ultra-thin CZTS solar cells with indium selenide as buffer layer

The demand of energy is growing rapidly in response of the development of the world. The crucial solution of large amount of energy is to harvest alternative source of energy. Sustainable development can be possible by harvesting solar energy as it is smoke free, clean and environment friendly. For low cost, non-toxic and earth abundant feature, CZTS solar cell is very prominent to generate solar power. During this study, numerical analysis has been done by SCAPS 2802 simulator to examine the performance of CZTS solar cell with Indium Sulphide (InSe) buffer layer. In this research work, the proposed ultra-thin CZTS solar cells showed higher efficiency of 16.30% (FF = 0.584, Jsc = 28.06 mA/cm2 and Voc = 1.00 V). In addition, the cell stability of the proposed cell showed better result.

Performance improvement of highly stable molybdenum telluride solar cells with CZT BSF

Energy consumption is growing rapidly day by day since the development is directly proportional to the use of electricity. The conventional sources of energy are diminishing in response of huge energy consumption. So, the burning question is to explore new non-conventional sources of energy to meet the enormous demand. Solar energy is considered as potential source of alternative energy to build up sustainable development. Molybdenum Telluride (MoTe2) is a very promising solar cell material for its power conversion efficiency and better thermal stability feature. In this study, it was investigated the performance of MoTe2 solar cell to explore the hidden potentiality by adding Cadmium Zinc Telluride (CZT) material used in back surface field between the absorber layer and final back contact metal. It was found in this research work that the possibility of high performance ultra-thin MoTe2 solar cells with better thermal stability. The highest power conversion efficiency of 25.15% was achieved for only 0.8 μm thickness of absorber layer.

Design and implementation of 3-lead ECG machine for rural medification

The number of decease due to Cardiovascular Disease (CVD) in low and middle-income countries has become a major concern. From a clinical standpoint, electrocardiogram is an useful mechanism to diagnose cardiac diseases. Therefore, electrocardiogram based machine design has taken into consideration to create a framework for building a simple, low cost microcontroller based ECG monitoring system. However, most of the machines in current research has high price with bulky shape which deprives the people of remote area to get benefit from it. Therefore, the paper tries to design a smart economical diagnosis system which can maintain reliable diagnosis with better portability. This system has been implemented by instrumentation amplifier with high common mode rejection ration and right leg circuit to remove 50 Hz noise of ac main. Digital and analog filtering of the system has optimized the signal by removing baseline wandering and power frequency noise. The communication between the hardware and software is interfaced through USB port using microcontroller. The implementation of this system shows greater benefits in domestic health monitoring and rural areas medical camp.