56 research outputs found
Grid Interaction of Electrolysers and Fuel Cells for Utilisation of Renewable Energy Surplus
No full textThis thesis investigates the grid interaction of electrolysers (ELs) and fuel cells (FCs) combined as green hydrogen storage for utilisation of renewable energy surplus. The integration of renewable energy sources (RESs), such as solar PV and wind, with power grids is becoming increasingly popular to reduce greenhouse emissions and mitigate climate change. However, integrating RESs with power grids can produce challenges, such as the impacts of sudden variations in weather conditions including say cloud passing and wind gusts on PV and wind systems respectively, and sudden variations in load demands. These sudden variations are usually accompanied by high ramp rates, where the power outputs of renewable energy sources or the load demands can ramp up or down at a very high rate. Besides these, the harmonic distortions caused by modern power electronic loads can threaten the power quality and reliability. To minimise above mentioned problems, a hybrid energy storage system (HESS) is considered for the future power grid infrastructure. HESS can mitigate not only the system challenges but also, with sufficient capacity, the fast-rising energy demand, by storing surplus when there is excess generation and discharging the energy when there are insufficient power outputs from renewables to meet the load demand. Traditionally, battery energy storage (BES) is considered to supplement uncertain renewable generation. However, BES alone may have unanticipated environmental and financial consequences. Recently, with the increasing global interest in producing green hydrogen energy (GHE) to transition to a zero-carbon economy, several research papers in the literature have proposed to convert any surplus output from RES (whenever the electricity marginal price is zero or negative) to hydrogen using an EL. The produced hydrogen gas is transferred and stored in a controlled manner. Whenever there is a need for energy say due to unavailability of supply from renewables, the stored hydrogen gas is used to produce electrical energy using a FC to supply to the grid. To make the integrated power system including RESs, and HESS comprising ELs and FCs, an optimal, efficient, reliable, and cost-effective power management control strategy (PMCS) with advanced control decisions needs to be formulated. The main aim is to utilise the surplus RES to generate and store hydrogen gas and convert the stored hydrogen gas into electrical power with the aid of FC. Furthermore, it is important to optimally share the energy between the grid and HESS.This thesis conducts a detailed review on FCs/ELs comprising GHE storage technologies for utilising the RES surplus because the state of the art is still limited in terms of topologies integrated with different types of grids (i.e., AC or DC), multiple types of FCs/ELs, and a variety of power electronic interfaces with appropriate PMCS. The thesis proposes a mathematical and novel electrical equivalent circuit model of proton exchange membrane electrolyser (PEMEL) where the dynamic cell performance has been evaluated by considering the fluctuations in the external current profile. To demonstrate its adaptive feature, the proposed electrical equivalent circuit model is then scaled up to a 1 MW array by series and parallel connections, and the resulting system is validated by comparing it with the other reported experimental results of a 1 MW stack.Furthermore, the dynamic features of the PEMEL stack are used to investigate the impact of introducing the PEMEL stack's control loop into a single-area power system populated with solar PV units, while accounting for the communication time lag during the control signal transfer process. The dynamic performance of the proposed power system as well as steady-state errors are subsequently investigated to demonstrate the PEMEL stack's effective contribution to frequency regulation services. Furthermore, the potential resilience benefits of frequency control services and frequency sensitivity analysis for a modified IEEE-13-bus distribution system have been investigated. The results show that the system with PEMEL control loop responds to frequency changes faster than standard synchronous generators, implying the proposed PEMEL stack has a significant potential for enhancing frequency stability, resilience, and robustness.The thesis also includes a system modelling and performance analysis of a renewable hydrogen energy hub (RHEH) connected to an AC/DC hybrid microgrid. When power is in excess, a coordinated power flow control strategy minimises generation and demand mismatches while also producing green hydrogen. A modified hybrid approach involving perturb and observe, and particle swarm optimization techniques is suggested for tracking maximal power points. The thesis also presents a novel compensation technique for reducing intermittencies in a PV-powered microgrid that employs a hybrid multilevel energy storage system. This method solves memory and temporal delays through improved storage capacity. Simulations using a 24-hour solar irradiance profile are used to evaluate the technique on a 100-kW grid-interactive PV-dominated microgrid system.The thesis presents a grid-integrated analytical model for the co-production of hydrogen from an offshore hybrid energy system. The system supplies a percentage of its capacity to the onshore grid facility while producing hydrogen. The electricity is quantified based on a market price and total offshore generation. A case study is presented for a hypothetical 10 MW hybrid offshore energy system in NSW, Australia. The thesis proposes a probabilistic approach to size the HESS and a two-layer distributed energy management strategy for the HESS. Simulation results show that the supercapacitor bank can handle high-frequency fluctuations and avoid round-trip losses associated with HESS. The two-layer distributed energy management strategy extends operating lifetime and reduces operation costs of HESS, and also, maximizes the utilization HESS by avoiding excessive switching between FCs and Els, and maintaining an equal number of ON/OFF operations by ELs and FCs.</p
Design and Performance Analysis of a Triple-band Rectangular Slot Microstrip Patch Antenna for Wi-Fi, Wi-MAX and Satellite Applications
No full textA triple-band microstrip patch antenna is presented in this article with detail investigation of its working mechanism and performance characteristics. The antenna consists of a rectangular slot on the patch to achieve multiband operation. Three distinct frequencies of 2.4 GHz, 5.5 GHz and 7.5 GHz are achieved with return losses of 27 dB, 29 dB and 29 dB respectively. The Impedance Bandwidths are 70 MHz (2.52 GHz-2.44 GHz) at 2.4 GHz, 220 MHz (5.65 GHz-5.43 GHz) at 5.5 GHz and 250 MHz (7.57 GHz-7.32 GHz) at 7.5 GHz, which satisfy the requirements of Wi-Fi, Wi-MAX and satellite communications bands. The fabricated prototype of the antenna has total dimension of 53×53×1.6 mm3 over FR4 substrate. The antenna is simple and has sensible radiation characteristics with considerable gain. This work also focuses on developing a Link Budget model for its application in satellite communication. Most notably, it examines overall system efficiency and optimum path loss, distance analysis, system noise temperature, signal to noise power ratio, the size of antenna and the overall customer satisfactions. The highest gain of the antenna is achieved as 3.5 dB in the band (5.65 GHz-5.43 GHz), while the highest directivity and bandwidth are found as 8.7 dBi and 250 MHz respectively in the higher operating band. The affordable agreement between the simulated and measuring outcomes justifies that the antenna is often applicable for Wi-Fi (2.4 GHz), Wi-MAX (5.25 – 5.85 GHz) and satellite (7.24 – 7.57 GHz) communications
Design of a Triple Band Rectangular Slot Microstrip Patch Antenna for Wireless Applications
No full textTaking strides towards decarbonization: The viewpoint of Bangladesh
No full textOver the past two decades, Bangladesh has experienced a rapid increase in access to electricity. Bangladesh has become more dependent on the burning of furnace oil for electricity generation instead of increasing the generation of renewable energy sources. There are a variety of energy resources in the country to achieve a carbon-neutral energy which have not yet been explored to their fullest potential. A lack of proper strategies would lead to the country failing to meet its emissions reduction target, for example lack of energy diversification policy. In order to reduce carbon emission, a country should have a well-defined relationship between economic growth to the energy diversification. In this paper a relationship between economic growth and energy diversification (Energy Mix Concentration Index) has been developed for the year of 200–2020. From this relationship, it is observable that most diversified outcome can be achievable for the next fiscal year by analyzing the past year reports. The of Effort has given in this review to assess the current state of the energy sector in Bangladesh with a specific focus on energy diversification and initiatives for clean energy production. The potential for clean energy sources and technologies to reduce carbon emissions were discussed. The evolution of energy diversification was evaluated using the energy mix concentration index. Providing empirical evidence for energy policies to enhance innovation skills in the renewable energy industry might help Bangladesh achieve long-term development in energy sector.Full Tex
The growth and contemporary challenges of Islamic microfinance in Bangladesh
No full textMicrofinance industry is one of the a sectors of Bangladesh which has been experienced a
tremendous growth in last three decades. The aim of developing microfinance schemes is to provide business
opportunities for the poor in order to promote their financial health. Initially, the conventional model has only
been used to give financing. With the passage of time, Islamic model of financing is also included under
microfinancing programs. Nowadays, both conventional and Islamic models are currently being used to provide
financing. However, several researchers believe that the Islamic model of financing is more effective as it
considers basic human needs. But, the growth of Islamic microfinance is not as it is expected. At present,
Islamic Microfinance Institutions (IMFIs) in Bangladesh are facing a number of challenges due to its nature,
lack of resources and regulatory support. Therefore, this study is going to deliberate rationales behind the
growth of Islamic microfinance industry in Bangladesh. Moreover, current challenges and possible suggestions
of this industry are also discussed. The article has been mainly designed based on secondary data. It is expected
that the output of this study might be beneficial for microfinance practitioners, learners and researchers
especially those who have interest on this issue
Superior Performance of Surface Plasmon Resonance Biosensor for Recognizing of DNA Hybridization
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