Browsing by Author "Ranaweera, A. L. A. K."

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Comparison of different methods for generating SPWM signal for the development of a pure Sine wave inverter
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Hemal, S. B. N. H.; Dilshan, G. K. D.; Karunarathna, M. A. D. D. S.; Morawakaarachchi, K. N.; Senanayake, S. V.; Premasiri, R. H. M. D.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.
An inverter is an electronic device which is used for converting Direct Current (DC) to Alternating Current (AC) because AC is the predominant form of electrical power used in homes, businesses, and most electrical appliances. Inverters can be categorized based on the type of waveform that they produce, such as Pure Sine Wave Inverters, Modified Square Wave Inverters and Square Wave Inverters. This paper discusses the development of a Pure Sine Wave Inverter with an output voltage of 230 VRMS and a frequency of 50 Hz using the Sinusoidal Pulse Width Modulation (SPWM) technique. Three SPWM signal generation methods, including analogue comparator, microcontroller, and SPWM driver module methods, were tested. This study presents a method to obtain a 230 VRMS, 50 Hz output sine wave in three steps. The first step involves the generation of an SPWM signal with frequency control, utilizing the DC source supply. The analogue comparator method uses op-amps as the analogue comparator. Then, it compares a reference sinusoidal wave with a high-frequency (in kHz range) carrier triangular wave. The output of the op-amp comparator is SPWM. The frequency of this reference sinusoidal wave is chosen based on the required inverter output frequency (50 Hz). In that process, the comparator gives out a pulse when the voltage of the sine waveform is greater than the triangular voltage, and this pulse is used to trigger the respective inverter switches. When designing a circuit that involves op-amps, the slew rate of the op-amp is a critical consideration. To generate an SPWM signal using an ATmega328p microcontroller, the microcontroller was used to generate a series of PWM signals by digital high and digital low. The corresponding time of each pulse's delay is added using the microsecond function. Increasing and decreasing duty cycle, and then a series of PWM signals. As the pure sine wave inverter SPWM driver module EGS002 was used and, that method was the more accurate method, and a clean SPWM signal was generated with less harmonics. Although this type of inverter board has more features, the circuitry was not complex because of the module. Secondly, we employ the MOSFET H-bridge stage to obtain the desired sine wave output. Finally, the third step focuses on supplying a high DC voltage to the H-bridge circuit, which the DC-DC PWM boost converter generates. Several circuit protections were included to ensure the device's safety and reliability. In the process of SPWM generation, although in the analogue comparator method, op-amps offer a low-cost option, a microcontroller is favoured for its superior precision and ability to handle high-power applications effectively. However, the EGS002 module stands out as the preferred method due to its user-friendly nature, comprehensive protection features, and ability to provide valuable feedback, making it a more economically efficient choice in the overall design.
Design and characterization of a tunable metamaterial absorber for efficient RF energy harvesting in the Wi-Fi frequency band
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Sahasrika, S. L. S. D.; Ranaweera, A. L. A. K.; Seneviratne, J. A.; Jayathilaka, K. M. D. C.
The pursuit of miniaturization and connectivity in semiconductor technology has led to the development of compact, interconnected devices. However, the reliance on batteries for power presents limitations. Ambient energy harvesting, particularly from radio frequency (RF) waves, offers a promising solution. This study explores the feasibility of wireless energy harvesting, especially in the context of the saturated frequency spectrum due to wireless communications. Building upon recent advancements in metamaterial technology, this study focuses on the design, fabrication, and characterization of a tunable metamaterial absorber unit cell for efficient RF energy harvesting. The aim is to exploit metamaterials, specifically tunable metamaterial absorbers (MMA), to harvest RF energy, particularly in the widely utilized Wi-Fi frequency band. To design a novel unit cell structure, simulations were conducted using the commercially available EM simulation tool CST Microwave Studio software. A novel MMA unit cell consisting of E-shaped split ring resonators, copper reflector, and FR-4 substrate layer in the middle was designed and simulated. Results demonstrated its RF energy harnessing ability, achieving peak absorptivity of 98% of incident RF energy at 2.4 GHz. The designed unit cell was fabricated using the standard PCB fabrication method. Experimental results were obtained using a network analyzer through non-contact measurement method. Results closely mirrored the simulation results, confirming a high absorptivity of 99% at 1.44 GHz. To achieve frequency tunability, an external capacitor switching circuit was integrated into the MMA unit cell. Simulation and experimental results were obtained confirming its frequency tunability. The proposed tunable metamaterial absorber unit cell offers advantages over conventional RF energy harvesting systems, including ease of implementation, a wider range of RF energy absorption, and cost-effectiveness paving the way for integration into various applications. In conclusion, this study contributes to the development of energy harvesting technologies by leveraging tunable MMA to harness ambient RF energy.
Design and implementation of automated heat shrink cutting process for industrial usage
(proceedings of the 4th International Research Symposium on Pure and Applied Sciences 2019, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Rajapaksha, R. M. D. M.; Dhananjaya, S.S.; Wijesuriya, M. W. A. S. H.; Fernando, K. M. S.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
An automated heat shrink cutting process for industrial usage has been designed and a prototype model implemented. The designed system consists of a microcontroller, a keypad, a stepper motor, and an ac synchronous motor. The inputs such as the length of the heat shrink and number of pieces required to be cut are given to the system through a keypad and entries are displayed in an LCD panel. That information is fed into the microcontroller, which is the main controller of the designed system. Roller pack of heat shrink is inserted into a socket formed by a rubber shaft attached to the stepper motor. Length measurement of the inserted heat shrink is done by the stepper motor using a simple calculation and heat shrink is pulled into the system for the calculated length. Then a cutting blade powered by the synchronous ac motor connected to the microcontroller cuts the heat shrink at the required length. The process will be repeated until it cuts the required number of pieces. The operation of the process is verified by cutting different number of pieces with different lengths. The designed system can measure a 0.2 mm least count and is better than required accuracy of 1 mm for normal industrial wire harness based product lines. The speed of the designed process is between 25-30 pieces per minute and is well above the speed of a trained human in the same task. It is expected that the cost effectiveness of this designed heat shrink cutting process will be found very useful in the automation of industrial wire harness production lines.
Design of an auto disconnecting regulator and a safety switch to prevent domestic gas leakages
(IEEE, 2020) Rajapaksha, R. M. I. U.; Perera, P. S. H.; Nandasena, P. K. D. M.; Gunarathna, P. S. T. K.; Gihan Kanishka, P. P. D.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
There is a growing demand for research in various aspects of smart homes. Automated security systems are an integral part of smart homes. Liquid Petroleum Gas (LPG) is one of the popular fuels used in domestic cooking. Therefore, there is a very high demand for LPG fire security systems. In this study, an automated LPG fire security system for domestic gas leakages has been designed and a prototype model is constructed. The designed system automatically takes preventive measures in case of gas leakage. It includes a newly designed automatically disconnecting regulator from the cylinder which shuts OFF gas supply from commercially available gas cylinders, a control circuit for switching OFF the power supply of nearby area of gas leakage and transceiver unit for sending SMS to the corresponding people. It has been designed to operate automatically when LPG concentration reaches to 200 PPM, a value well below the LPG gas inflammable concentration. LPG concentration is sensed by the MQ-5 gas sensor and fed into the microcontroller. The commercially available gas regulator is modified by attaching a spring and solenoid valve. The spring is compressed when the regulator is ON. Once an LPG leakage of appropriate PPM is detected, a pulse is sent to the solenoid valve such that the attached spring gets rest by removing the regulator from the cylinder. At the same time, a warning message will automatically send to the corresponding users and security personnel through a GSM module attached to the circuit. The circuit is embedded with a rechargeable battery to work even in power outage. Additional gas sensors are installed in electrical switches located near to the gas cylinder and kept in connection with the microcontroller through the Bluetooth module to cutoff electrical power to prevent any spark.
Design of novel perfect metamaterial absorber for Radio Frequency energy harnessing
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Karunathilaka, M. G. M. T.; Ranaweera, A. L. A. K.; Jayathilaka, K. M. D. C.; Seneviratne, J. A.
Due to the rapidly growing wireless communications and sensing applications, the frequency spectrum has already been saturated. Consequently, the abundance of Radio Frequency (RF) signals in the ambient environment made the concept of wireless energy harnessing to be emerged as an attractive solution to energize low-power wireless devices. In this study, a novel tuneable perfect metamaterial absorber (PMA) unit cell was designed by combining two C-shaped split-ring resonators (SRR) embedded with simple electronics circuitry. The feasibility of harnessing energy from 1.8 GHz signals was investigated through electromagnetic (EM) simulations. The design and numerical analysis of the proposed PMA structure is carried out with the aid of the commercially available EM simulation software, High Frequency Structure Simulator (HFSS). The proposed structure’s capability to absorb EM energy as a perfect metamaterial absorber is studied. According to the simulation results, it shows a high absorption coefficient of around 99%. This verifies that the proposed tuneable PMA structure encompasses a high absorption of RF energy. It can be used for the harnessing of RF energy to power up low-power devices and wireless sensor networks.
Designing a high-performance parametric speaker system: simulation and Optimization
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Gurusinghe, T. N.; Seneviratne, J. A.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
The parametric speaker is designed to direct omnidirectional sound waves towards a specific target. Over the past two decades, numerous research studies have been conducted to optimize parametric speaker systems, with a focus on enhancing audio quality and extending the range of sound propagation. The objectives of this research include the enhancement of the audio quality, the reduction of total harmonic distortion through modulation techniques, and the amplification of the modulated output to increase the effective hearing distance. These goals were pursued alongside the development of a properly designed ultrasonic transducer array circuit, a critical component of a parametric speaker system. Prior to the conception of the novel parametric speaker system, a comprehensive simulation study was conducted using the commercially available COMSOL Multiphysics software. For this study, the Pressure Acoustics, Frequency Domain (acpr) interface, the Solid Mechanics (solid) interface, and the Electrostatics interface were utilized. The principal aim of this simulation study was to analyse the minimal electric potential required for an ultrasonic transducer element to generate a directional sound wave capable of propagating over a one-metre distance. To achieve this, a PZT-5H piezoelectric element with a stacked aluminium metal diaphragm was constructed. The electric potential across the piezoelectric plate was step by step varied from 5 V to 100 V. Polar plots illustrating the sound pressure level of ultrasound propagation in the air domain at a distance of one-thousand-fourhundred millimetres from the source were generated for each simulation. The simulation model of the piezoelectric element was meticulously constructed after a thorough examination of a crosssectional cut of an ultrasonic transducer and the arrangement of layers within the metal cover. This model adopted a two-dimensional (2D) axially symmetric space dimension. This approach leveraged the rotational symmetry of the elements to simulate in 3D, thereby reducing simulation complexity. The analysis revealed that when the electric potential was below 10 V, the sound pressure remained below 60 dB. However, upon increasing the electric potential to above 60 V, although the expected directionality was achieved, distortions adversely affected the output signal. Such sound propagation characteristics were deemed unsuitable for a parametric speaker system. Upon analysing the polar graphs generated for a 30 V electric potential, it was evident that directionalized sound pressure levels in the air were achieved with minimal distortions compared to other simulated systems. Consequently, a 30 V electric potential was selected as the amplified signal voltage peak-to-peak for application to the designed ultrasound speaker. This approach was undertaken to ensure optimal performance and minimize distortion in the parametric speaker system.
Development of a cost-effective real-time commuter counting system for public transportation in Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Premasiri, R. H. M. D.; Koralage, K. G. S. D.; Hasaranga, J. P. K.; Alawaththa, A. K. N. A.; Seneviratne, J. A.; Ranaweera, A. L. A. K.
The use of smart systems in public transportation is relatively new in the Sri Lankan context. This study introduces a cost-effective solution for accurately counting the number of bus passengers at any given time. Current passenger counting systems in Sri Lanka often suffer from inaccuracies and inefficiencies, hindering the effective management of public transportation and addressing problems including long bus queues, ticketing fraud, long waiting times, etc. Precise passenger count is essential for optimising services and resources, ultimately enhancing the efficiency of public transportation in the country. The proposed system is designed to be installed in buses and includes an online platform where users can enter the bus number and check the passenger occupancy in real-time. The proposed system comprises several key components: two input sensors, a microcontroller, a wireless connectivity module, an in-built display, an input panel, and an output display. The two sharp IR sensor modules employed as input sensors are connected to a microcontroller. An inbuilt display connected to the microcontroller provides output information, including passenger count, number of vacant seats, GPS signal strength, and data transmitting capability. Data is wirelessly sent to a cloud database for storage, retrieval, and processing, enabling users to access relevant information via a web application. The algorithm employed in this system ensures precise passenger count by detecting specific sequences of readings from the two IR sensors. To increment the passenger count, the system requires the following sequence: "0-0, 1-0, 1-1, 0-1, 0-0." This sequence corresponds to the detection of a passenger boarding the bus. Each step in the sequence represents the state of the two IR sensors, with "0" indicating no obstacle and "1" indicating an obstacle (i.e., the presence of a passenger). The algorithm recognizes this sequence as an entry event and increments the passenger count accordingly. Conversely, the algorithm relies on the following sequence to accurately decrease the passenger count when a passenger exits the bus: "0-0, 0-1, 1-1, 1-0, 0-0." This sequence represents a passenger leaving the bus. The algorithm reduces the passenger count by monitoring the sensor readings and identifying this sequence. These specific sequences in the algorithm ensure reliable and accurate passenger counting. By requiring a particular order of sensor readings, false positives or negatives caused by noise or temporary obstacles are minimised, leading to a more precise passenger count. The online platform allows users to access passenger occupancy in a particular bus, which aids in real-time service optimization for public transportation management. The system achieves precise real-time passenger occupancy tracking using two Sharp IR sensors and a finely tuned algorithm. Tested results of the pilot system show that data empowered public transportation management in Sri Lanka by optimising routes, efficiently allocating resources, and significantly improving the overall commuter experience. In conclusion, the combination of affordability, reliability, and user-friendliness makes this proposed solution suitable for efficiently managing public transportation systems.
Development of an off-grid solar PV system with battery-supercapacitor hybrid energy storage
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Pitigala, P. A. S. P.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
In off-grid photovoltaic (PV) systems, the charge controller is a significant device since the system's end-to-end efficiency depends on its efficiency. Currently, the commercially available MPPT charge controllers have an average efficiency of 90%. Supercapacitors' (SCs’) high energy density compared to traditional capacitors makes them used as energy storage devices. But theoretically, 50% of energy loss will occur in the capacitor charging loop if we charge it directly connecting to a power supply. According to the supercapacitor-assisted loss management (SCALoM) theory, inserting a useful resistive load into the capacitor charging loop, a portion of the above wasted 50% of energy can be utilised for beneficial work. This paper proposes a novel off-grid PV system with a battery-SC hybrid energy storage. This system utilises the SCALoM theory using the combination of a charge controller and battery as the useful load in the capacitor charging loop, while PV panels are used as the external power source. To achieve maximum use of the SCALoM theory, the SC must be kept under partially charged condition. An electronic switching network consisting of nine electronic switches was designed to realise this. Two SC banks, SC-1 and SC-2 were embedded in the prototype system. The proposed system operates in four different modes: SC-1 charging mode, SC-2 charging mode, SC bypass mode, and night mode. These modes are defined by the state of each switch in the switching network and the voltage of both SC banks. In SC-1 and SC-2 charging modes, the relevant SC bank is connected in series with the PV panels and charge controller while a DC load is connected in parallel to the SC bank. In this mode, the remaining SC bank is discharged through another DC load. In SC bypass mode, the operation of the system is the same as the typical off-grid PV system because both SC-1 and SC-2 are disconnected from the system so that the PV panels are connected in parallel with the charge controller. In this mode, DC loads are connected to the battery. In night mode, an SC bank is connected in series to the PV array and the charge controller and DC loads are connected to the battery again. For maximum utilisation, this system must be operated in SC- 1 and SC-2 charging modes as much as possible throughout the day. The overall operation of the system is controlled by microcontroller-based control circuitry. This system achieved end-to-end efficiencies of 87.36%, 87.50%, 75.68%, and 93.28%, respectively, for SC-1 charging, SC-2 charging, SC bypass, and night modes, respectively. Therefore, it can be concluded that the endto- end efficiency of an off-grid PV system can be increased by implementing a supercapacitor in a series configuration to the solar panel and to the charge controller.
Enhancing UPS battery life through C-rate control with a supercapacitor-assisted battery management system
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Ramesh, J. M. D. A.; Gunawardana, K. D. B. H.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
Battery management systems (BMS) are essential for optimizing the efficiency and dependability of batteries. BMS employs various methodologies and techniques for state of health (SOH) determination, state of charge (SOC) estimation, cell balancing, voltage regulation, current regulation, and overload prevention. This study aims to create a Supercapacitor Assisted Battery Management System (SCABMS) to enhance battery performance and lifespan using a C-rate controlled system by analyzing battery dynamics and load demands. The suggested Battery Management System (BMS) incorporates supercapacitors (SCs) to effectively handle sudden increases in power demand, thereby lessening stress on the main battery and improving its overall lifespan. Previous research indicates that reducing the Crate extends battery lifespan. The C-rate control method is used to manage battery discharge, with the system functioning in two modes depending on the load current. The first is when the load is drawing less than the set current where the load current is completely drawn from the battery without the SC assistant. When the load current exceeds the set current value, the current control circuit begins to limit the battery current for the selected value. In this scenario, the load voltage drops, and the parallel connected buck-boost converter is used to fix the load voltage into the rated value by supplying the rest of the load current. The buck-boost converter output voltage is fixed for the load voltage. The implemented prototype incorporates supplementary functionalities encompassing cell balancing, voltage regulation, current regulation, and overload protection within its BMS. The real-time current and voltage monitoring system was integrated into BMS to ensure a constant C-rate in charging/discharging cycles. Also, the battery's operating periods with and without the Battery Management System (BMS) under the same load circumstances should be compared. This technology successfully reduces power fluctuations and guarantees safe equipment shutdown in case of a power outage. The results indicate a well-maintained c-rate and show the potential of integrating SCABMS in high-power-demanding situations, subject to improvements in efficiency and practicality.
Fabrication and characterization of electrodeposited nano structured copper oxide-based supercapacitors
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Anjalika, B. R. L.; Jayathilaka, K. M. D. C.; Ranaweera, A. L. A. K.; Wijesundera, L. B. D. R. P.; Kalingamudali, S. R. D.
The increasing consumption of limited energy sources, primarily based on fossil fuels, and the resulting environmental issues, such as global warming and climate change, drive researchers to develop environmentally friendly and renewable energy conversions and storage systems. Supercapacitors (SCs) have emerged as a promising solution to meet the increasing global demand for efficient energy storage. The performance and efficiency of a supercapacitor depend directly on the electrode materials used. Nanostructured materials provide new and exciting approaches to developing supercapacitor electrodes for high-performance electrochemical energy storage applications. Interest in pseudocapacitive materials, particularly copper oxide, has grown due to its advantageous properties and application as electrode materials in energy storage devices. In this research, nano cuprous oxide thin films were used as supercapacitor electrodes, and Polyvinyl Alcohol-Potassium Hydroxide (PVA-KOH) gel polymer was used as both the electrolyte and separator for supercapacitors. The nano cuprous oxide films were synthesized on Ti substrates using the electrodeposition technique by controlling the pH of the deposition bath. For comparison, microstructured cuprous oxide thin films were also deposited on Ti substrates as electrodes using the electrodeposition technique. Structural and surface morphological properties of the fabricated electrodes were investigated using high-energy X-ray diffraction (HEXRD) and scanning electron microscopy (SEM). The HEXRD analysis showed the formation of a singlephase polycrystalline cuprous oxide film on the Ti substrate. The SEM revealed that the morphology of the electrodeposited cuprous oxide thin films strongly depends on the pH value of the deposition bath. The performance of cuprous oxide as an electrochemical supercapacitor electrode was analysed using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. In comparison to microstructured electrodes, the nano cuprous oxide electrodes demonstrate better electrochemical performance in terms of specific capacitance, energy density, and power density. The Cu2O//Cu2O supercapacitor with nano-Cu2O electrodes, prepared at pH 7.9, exhibited the highest specific capacitance of 176.02 mF/g, energy density of 61.4 mWh/kg, and power density of 44.23 W/kg. In contrast, the supercapacitor with microstructured electrodes, prepared at pH 6.3, exhibited a specific capacitance of 7.37 mF/g, energy density of 2 mWh/kg, and power density of 1.4 W/kg. The significant improvement is mainly attributed to the increased film surface area associated with cuprous oxide nanostructures. Therefore, nano copper oxide-based supercapacitor electrodes show great potential for supercapacitor applications.
Fabrication and characterization of sulfur-treated cuprous oxide-based supercapacitors
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wijesinghe, W. A. N. D.; Jayathilaka, K. M. D. C.; Ranaweera, A. L. A. K.; Wijesundara, L. B. D. R. P.; Kalingamudali, S. R. D.
Supercapacitors are crucial for modern energy storage, offering high power density, fast charging, and life spans. They are widely used in various applications, meeting the need for lightweight, flexible, and eco-friendly energy solutions. Cuprous oxide (Cu2O) holds significant promise as an electrode material for supercapacitors owing to its distinctive properties. However, electrodeposited Cu2O films often have high resistivity and surface defects, hampering their electrochemical performance. To address this issue, sulfur treatment was employed to modify the surface properties of Cu2O electrodes, aiming to enhance their electrochemical performance. In this research, sulfur-treated Cuprous-oxide thin films were used as the supercapacitor electrodes, and PVA-KOH gel polymer was employed as the supercapacitor separator and electrolyte. The Cu2O films were synthesised on a Ti substrate via electrodeposition, followed by Ammonium Sulfide (NH4)2S vapour treatment for surface modification, with varying exposure times. Untreated Cu2O thin films were analysed for comparison. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to examine their structural and surface morphological characteristics. The XRD analysis showed that the Cu2O deposited on the Ti substrate treated with (NH4)2S vapour did not yield distinct CuxS peaks, indicating the formation of a very thin or amorphous CuxS layer on the film surface. SEM revealed an altered morphology of the electrodeposited Cu2O thin films after the (NH4)2S vapour treatment, with the development of a non-uniform additional layer on the surface. The electrochemical performance of sulfur-treated Cu2O electrodes for supercapacitors was studied using Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS). Sulfur-treated electrodes exhibited enhanced performance, showing higher specific capacitance, energy density, and power density compared to untreated electrodes. The supercapacitor utilising sulfur-treated Cu2O deposited on the Ti electrodes, treated for 10 s, demonstrated superior performance with a specific capacitance of 773.81 mF/g, energy density of 154.76 mWh/kg, and power density of 111.43 W/kg. Conversely, the untreated electrode-based supercapacitor exhibited lower values, with a specific capacitance of 23.34 mF/g, energy density of 4.67 mWh/kg, and power density of 3.38 W/kg. In summary, this study explored the impact of sulfur treatment on the electrochemical performance of electrodeposited Cu2O. CV, GCD, and EIS analyses revealed improved electrochemical performance due to the reduction of surface defects with (NH4)2S surface treatment. The results indicated that the best performance can be obtained in Cu2O with a 10 s (NH4)2S exposure duration for application in supercapacitors.
Harvesting energy from human-body movements for ultra-low power appliances
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Gunarathna, T. G. L.; Rupasingha, U. S. D. B. M.; Gunasekara, H. S.; Thennakoon, S. E. R. T. M. M. I.; Senanayake, S. V.; Leanage, H. B.; Kumarage, W. G. C.; Ranaweera, A. L. A. K.
Energy harvesting from human body movements presents a promising approach to sustainably power wearable devices and sensor nodes. This study explores the potential of capturing energy from footsteps using piezoelectric technology. A critical aspect of this technology involves designing an efficient interface between the piezoelectric elements and the electrical load to maximize energy conversion. The irregular and low-frequency nature of human footsteps poses a significant challenge, resulting in low energy extraction. Moreover, achieving a self-powered circuit adds another layer of complexity. To address these challenges, a novel Parallel-Synchronous Switching Harvesting on Inductor (P-SSHI) circuit is proposed. This circuit increases the energy extraction efficiency of piezoelectric elements. Since the output of a piezoelectric element is in the form of alternating current (AC), a MOSFET-based full-bridge rectifier circuit is proposed to convert AC to direct current (DC). As proof of concept, a shoe insole integrated with multiple piezoelectric elements connected in parallel was developed, and the energy conversion circuit was rigorously validated. The system was tested at a frequency of 1 Hz, which corresponds to the typical walking frequency, using a person weighing 60 kg. Under these conditions, the proposed system achieved an average power output of 550 µW per step with a 10 kΩ resistive load and a 10 µF storage capacitor. The effectiveness of the system was further validated by demonstrating its ability to charge a 1 mF capacitor to 2.1 V in 18 steps and a 10 µF capacitor to 7.0 V in a single step. Notably, the circuit is self-powered and capable of initiating operation without the assistance of an external battery, highlighting its potential for autonomous use. The circuit was prototyped using simple discrete components, emphasizing its practicality and feasibility for real-world applications. The proposed MOSFET-based rectifier circuit offers a significant advantage in converting AC to DC with minimal voltage drop, compared to conventional diode full-bridge rectifiers. Furthermore, the system's capability to charge a Li-ion battery (3.7 V, 300 mAh) was demonstrated, showcasing the potential of the wearable piezoelectric energy harvesting system to provide a sustainable power supply for wearable wireless sensors. Future studies will focus on optimizing energy harvesting under different walking conditions, integrating energy storage devices, and enhancing durability. The proposed technology also shows promise for applications in diverse fields such as healthcare, fitness monitoring, and environmental sensing, where reliable, self-sustaining wearable power solutions are in high demand.
Investigation of a multi-hop wireless power transfer based on repeater coils
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Jayasekara, R. S. N.; Ranaweera, A. L. A. K.; Piyumal, P. L. A. K.
Traditional wireless power transmission systems have limitations in distance and efficiency. The proposed multi-hop wireless power transmission systems (Multi-Hop WPT systems) address these issues with the use of intermediate repeater coils as power hop nodes. A multi-hop wireless power transmission system (Multi-Hop WPT) works by using a series of repeater coils where power is hopping between nearby nodes. The initial source transmits power in the form of electromagnetic waves and the first node captures it. This first node gathers the power and retransmits toward the next hop or the final destination. The methodology involved several key steps. The methodology of this study followed a systematic approach in designing, constructing, and evaluating a multi-hop wireless power transmission (Multi-Hop WPT) system. Two resonator coils were designed as the transmitter and receiver, with their dimensions and material properties optimized for efficient wireless power transfer. The system was tuned to operate within the ISM frequency band, ensuring regulatory compliance. Intermediate hop nodes were strategically placed to enhance range and efficiency. The system's performance was tested using a vector network analyzer (VNA), and power transfer efficiency was verified against theoretical expectations, confirming both accuracy and effectiveness. The experimental results demonstrated that the multi-hop wireless power transmission (WPT) system effectively addressed the distance and efficiency limitations of traditional wireless power transmission systems. By employing intermediate repeater nodes, the system successfully transmitted power over extended distances with minimal loss. Moreover, the design exhibited significant potential for scalability and flexibility, paving the way for future advancements. The study proposed further improvements through the development of an advanced multi-hop node, incorporating a power receiver coil, RF to DC converter (Radio Frequency to Direct Current Converter), power amplifier, and re-transmitter coil, which could enhance system efficiency, range, and scalability, positioning multi-hop wireless power transmission systems as a promising alternative for various applications.
Investigation of MPPT in photovoltaic systems with step-down DC-DC converter and supercapacitor energy storage
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Premasiri, R. H. M. D.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
This study explores the implementation of Maximum Power Point Tracking (MPPT) in photovoltaic (PV) systems integrated with a step-down DC-DC converter and supercapacitor (SC) based energy storage. The integration of renewable energy sources, particularly solar power, necessitates highly efficient energy conversion and storage mechanisms to maximise the utility of the harvested energy. MPPT techniques play a pivotal role in optimising the power output of PV systems by dynamically adjusting the operating point to extract the maximum possible power under varying environmental conditions. SCs, with their high charge and discharge rates and high power density, emerge as a promising storage solution to manage the intermittent and variable energy output characteristic of PV systems. A Constant Voltage (CV) MPPT algorithm is employed to fine-tune the power output and ensure maximum energy efficiency. The experimental setup comprises a Solar Array Simulator simulating the PV array, interfaced with a step-down DC-DC converter, and an SC configured as the load. The system's performance is analysed by observing the available, actual and output power using a power analyser and evaluated to ascertain the robustness and effectiveness of the MPPT algorithm. The research distinguishes itself by utilising SCs as the primary load, an approach not commonly adopted in previous studies. Few studies have investigated the use of SCs exclusively as the load, and those that have indicated that MPPT is not efficiently achieved under such conditions. However, the analysed results affirm that the system proficiently tracks the maximum power point, attaining an average MPPT efficiency of 94.88% when the system is integrated with the CV MPPT algorithm. The average conversion efficiency attained was 75.62% with a basic DC-DC step-down converter constructed on a solderless board. It is anticipated that this MPPT efficiency will further improve with the application of more sophisticated MPPT algorithms such as Perturb and Observe (P&O), Incremental Conductance (IncCond), and Hill Climbing (HC). The average conversion efficiency can be increased by fine-tuning the converter and implementing more advanced topologies of DC-DC stepdown converters. This research makes a substantial contribution to advancing high-efficiency and dependable PV energy storage systems, underscoring the practical viability of SCs as an energy storage device. Furthermore, these findings have significant implications for SC-assisted Heating, Ventilation, and Air Conditioning (HVAC) systems integrated with PV systems, where efficient MPPT can enhance overall system performance as MPPT can be tracked when using the SC as the storage. Prospective studies will examine the long-term stability and scalability of this innovative approach in larger-scale PV installations, paving the way for more resilient and efficient renewable energy systems.
Investigation of multi-functional metamaterial unit cell operating at SHX-X Band Frequencies
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Saraph, A. K.; Ranaweera, A. L. A. K.; Jayathilaka, K. M. D. C; Senevirathne, J. A.
Metamaterials are man-made materials having unique and distinct properties which are not available in natural materials. In this study, a metamaterial unit cell is fabricated with a squarecircular- hexagonal split ring resonator. The feasibility of the fabricated unit cell as a perfect absorber, sensor, and antenna is investigated. The proposed unit cell structure is initially simulated, numerically analysed, and optimized using High Frequency Structure Simulator (HFSS), a commercially available EM simulation software. First, the potential of the designed unit cell to be functioned as highly efficient metamaterial absorber in the Super High Frequency (SHF) – X band is verified. Simulations revealed that the reflection coefficient S11 is lower than 10 dB across the whole test frequency range around 9.2 GHz and the absorptivity is 99.8%. Unit cell has been fabricated with standard PCB fabrication process. The fabricated unit cell is composed of alternate layers of Cu and FR4 dielectric medium in which a Cu split ring absorbs all incident electric and magnetic fields within a single planar layer that is only 0.6 mm thick. Experimental characteristics of the designed unit cell were analysed using the Vector Network Analyzer (VNA). To observe the resonant behaviour a non-contact measurement was performed with home-made copper ring due to the increased accuracy. Experimental results showed relatively high Q-factor revealing that the designed unit cell has lower energy dissipation as compared to the energy stored. By replacing the FR4 layer in the metamaterial absorber (MMA) unit cell with a sensor layer made of air, a design for a metamaterial sensor is suggested liquid density sensing applications. The liquids with different densities were inserted to the air layer and the respective resonance frequencies were obtained. A change in the resonant frequency shifting of the metamaterial unit cell show that it can be used as a liquid density sensor. The proposed sensor can be employed in microwave frequency range for chemical, biological, agricultural, and medical applications. Finally, a design for a metamaterial patch antenna is proposed using the same unit cell. It is made of three layers consisting of the patch and the ground layer made of Cu and the substrate with FR4 dielectric material in between. The patch antenna was found to resonate at several frequencies between 0 and 15 GHz, with the lowest S11 reflection coefficient measured at 7.52 GHz and -21.2456 dB. We envision that this antenna will find application in the miniaturization and integration of various telecommunication equipment functions, particularly for items that are used frequently in daily life such as mobile communication systems, smart phones, portable tablets, GPS receivers, wireless Internet devices, etc.
Maximum Power Point Tracking of an Off-grid Photovoltaic System Consisting of a Series Connected Supercapacitor with a Step-down Converter
(The Electrochemical Society, 2022) Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.; Kularatna, N.
An off-grid photovoltaic (PV) system's PV array is connected with a charge controller as the first power conversion stage. The average efficiency of the power stage of charge controllers is around 90%. Supercapacitor (SC) - battery hybrid PV system is a novel PV system that utilizes some of the wasted energy of a typical system and enhances the system's efficiency up to 98%. However, the feasibility of maximum power point tracking (MPPT) for this system is yet to be validated. This paper presents a comparative study to adapt MPPT for the proposed system consisting of a series- connected SC bank with PV array and step-down DC-DC converter. The step-down converter is used as the impedance matching network. Different solar irradiance profiles were emulated to check the feasibility and efficiency of MPPT. Experimentally, it was shown that the typical MPPT could be adapted to the proposed PV system with very high MPPT efficiency.
Mosquito detection and repellent system using acoustics signals for household use.
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Senanayake, S. V.; Warnakulasooriya, C. B.; Ranaweera, A. L. A. K.; Jayathilaka, K. M. D. C.
There are over 130 mosquito species in Sri Lanka, and this abundance may be the reason for the spread of several critical diseases. Therefore, an effective mosquito repellent system, including a mosquito detection mechanism, is essential for daily life. Using acoustic signals is a harmless and cost-effective method for detecting and repelling pests compared to other visual or thermal processes. Therefore, this research investigates a novel approach for detecting mosquitoes and creating an effective mosquito-repellent mechanism based on acoustic signals. A system capable of distinguishing mosquitoes from other sound sources based on their unique wing flapping frequency was built and repelling them using specific ultrasonic frequencies was realized. The system consists of several components, including microphones, amplifiers, and filters, tested in both simulations and experiments. The methodology involved in determining the wing flapping frequency of mosquitoes by concentrating mosquitoes in a soundproof container, which was found to be within the 800-900 Hz range, with slight differences between male and female mosquitoes. Additionally, the effect of ultrasound in repelling mosquitoes was explored, discovering an effective frequency range of 42 kHz to 44 kHz. The system was subjected to numerous iterations and improvements to enhance mosquito detection sensitivity and the band of repellent frequencies. The final design includes an instrumentation amplifier for cancelling the noises and a second order Sallen-Key bandpass filter for filtering the flapping frequency of mosquitoes. However, due to the limitations of conventional condenser microphones, the discrepancy between simulations and physical implementations appeared. Further, the interference from surrounding noise caused some complications. Despite these obstacles, the results showed the system's potential in detecting and repelling mosquitoes. The system can be improved further by incorporating more sensitive microphones and filter circuits. By providing power with rechargeable batteries, it can be made portable. The flexibility and adaptability of the system design offer exciting possibilities for future enhancements and optimizations. In conclusion, this research advances the field of mosquito detection and repellence, providing new insights into the potential of acoustic signal processing in pest detection and control. Future improvements to the system could significantly contribute to mitigating the risks associated with mosquito-borne diseases.
Novel slow switching technique for efficient solar energy harnessing for off grid photovoltaic systems
(proceedings of the 4th International Research Symposium on Pure and Applied Sciences 2019, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.; Kularatna, N.
Electricity consumers in remote areas where the grid connection is not available rely on diesel generators or off grid photovoltaic (P V) systems. These PV systems uses battery banks as backup energy storage. Those battery banks are charged by using a battery charge controller connected to a PV array. Because of the recent advances in solar charge controllers, they can reach maximum of 90% charging efficiency, where 10% will be unutilized. Since the efficiency of conventional solar panels lies around 20-25% which is relatively low as compared to other energy generation methods, it is important to utilize as much energy as possible produced by the solar panels. Also, when driving loads, energy stored in the battery bank again goes through a converter or inverter by wasting considerable amount of useful energy. Hence, the purpose of this study is to minimize the energy loss of the charging process of the battery bank while using the energy produced by the PV array in an effective manner. In previous publications, it was introduced a novel way of using supercapacitors (SCs) in an off grid PV system. When charging an empty capacitor in parallel with a source, 50% of energy is wasted irrespective of the value of total loop resistance. In contrast, by connecting a SC bank in series with a typical solar charge controller, it was shown that the energy loss of the combined system is less than the energy loss of parallelly connected SC bank and the battery bank in their individual systems. Experimentally, it has been shown that a 9% increment in overall charging efficiency of the combined system when a charge controller having 80% of efficiency is used to charge the battery bank in typical off grid PV system. The present study introduces a possible method of utilizing the energy stored in SC bank in an effective manner using an intelligent electronic switching scheme. The proposed method uses a second SC bank along with the existing one along with a smart electronic switching circuitry which is able to switch each SC bank between charging or discharging stages when necessary. When one SC bank is in its charging state, the other SC bank will be in its discharging state through a proper load. After that, when the first SC bank is fully charged or the second SC bank is fully discharged, positions of each SC bank is swapped so that the second SC bank will start its charging process while the first SC bank is now discharging through the load. This way both charging and discharging of SC bank can be done efficiently while charging the battery bank in the system by the same manner.
Optimising energy efficiency in a PV-enabled base transceiver station
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Jayasooriya, J. A. T. D.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.
The need for green energy sources has become paramount in the modern world due to the environmental hazards of non-green alternatives. Essential services, including the telecommunication industry, must also align with this goal. As foundational elements of the telecommunications network, base transceiver stations offer a ripe opportunity to integrate green energy solutions. However, the prevalent scenario reveals that many of these stations continue to rely on conventional grid-based power sources, with only a limited fraction equipped with standalone photovoltaic (PV) systems. This study addresses a pressing challenge in integrating standalone PV systems with base transceiver stations. Central to this challenge is the conundrum of power generation backups, specifically during the morning hours, when the battery reserves charged by the PV systems are frequently depleted. This operational gap necessitates the deployment of supplementary power generators, imposing substantial operational costs that diminish the cost-efficiency advantages anticipated with the introduction of PV systems. The methodology involved a detailed analysis of the selected base transceiver station's total DC power consumption patterns from 15th May 2023 to 21st May 2023. These insights guided the design of an efficient energy harvesting system enriched with a supercapacitor-battery hybrid energy storage arrangement. A Maximum Power Point Tracking (MPPT) controller was acquired to optimise system performance; its effectiveness was verified through efficiency calculations and PV array emulator Irradiance Profiles, and its efficiency exceeded 90%. An intelligent power management strategy was implemented, automatically switching to consume supercapacitor (SC) energy when the voltage level exceeds a threshold, conserving battery bank energy, ensuring uninterrupted operation, and extending battery lifespan. The prototype's operational modes, including neutral, SC charge recovery, and SC bypass, have been successfully demonstrated. Results indicate that the suggested photovoltaic system prototype effectively tracks the PV array's maximum power point (MPP), comparable to standard systems using traditional MPPT algorithms. This novel system promises to not only obviate the need for extensive generator backups but also potentially reduce their capacity compared to conventional configurations. Realising a green energy-powered telecom network is a vast and complex process, demanding guaranteed performance and cost-effectiveness for a period of at least about 15 years. This research marks a significant milestone in advancing green energy solutions and highlights the crucial role of base transceiver stations in establishing a sustainable telecommunication infrastructure. Embracing eco-friendly technologies is essential in safeguarding our planet and ensuring a brighter future for generations to come.
Supercapacitor assisted LED (SCALED) lighting system with grid connection
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Kumara, W. R.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.
Photovoltaic (PV) systems are increasingly popular as the world shifts to sustainable energy. Generally, there are three main types of PV systems. The SCALED system consists of a PV panel, a Supercapacitor (SC) bank, and an LED. Utilizing the Supercapacitor-Assisted Loss Management (SCALoM) theory, the SCALED system integrates an SC bank and LED bulb to reduce energy loss during charging. Solar energy is stored in the SC bank and released to ensure the LED remains powered. However, the current SCALED system, with oversized solar panels and SC banks, is inefficient if it can't power LEDs at night or in adverse weather. To address this, an innovative approach is proposed by integrating the SCALED system with the grid for reliable energy storage and continuous LED illumination. In this innovative method, the SC bank and LED are connected in series with PV panels or grid connection in the SC charging loop. The system has two identical loops connected in parallel with the PV panels or grid. One SC bank charges while the other discharges, ensuring the LED bulbs remain powered. An electronic switching network with two SC banks manages four operational modes to optimise energy utilisation. These modes include alternating charging and discharging loops. A microcontroller-based control circuitry operates the system, which connects to the grid via a Switch Mode Power Supply (SMPS). A current sensor measures the current of the solar panel output. During adverse weather, the system switches to the grid when the output current drops solar panels below a threshold, isolating the solar panel. In the Developed SCALED system, MOSFETs efficiently manage power flow between the SC bank and LEDs, minimizing losses. Microcontrollers optimize energy use by controlling MOSFETs and monitoring voltage, and current levels, ensuring reliable LED operation even in adverse conditions. This improves overall system efficiency and reliability. When the solar panel output current exceeds the threshold value, the system will connect the solar panels and isolate the SMPS from the system. The system achieves a high charging efficiency of around 95%. Operational in all weather conditions and at night, the system ensures consistent LED illumination, enabling normal user operation regardless of weather during day and night.