Conference Presentations by Krishnil Ram
The paper presents a simplified nonlinear model for an open cathode Proton Exchange Membrane Fuel... more The paper presents a simplified nonlinear model for an open cathode Proton Exchange Membrane Fuel Cell (PEMFC) and its control by using three different strategies. The model presented uses four state variables. The mass flow of oxygen, hydrogen flow, water and temperature were taken to be the critical dynamics in the system. The unknown parameters were estimated using the experimental data of a 1.2 kW PEMFC. The simplified model showed good agreement with experimental results. Control schemes were implemented to control the stack temperature of the PEMFC. The Proportional (P) and Proportional Integral (PI) Control performed well but had a poorer response compared to the sliding mode control (SMC) scheme. The study of the different control schemes reveals the dangers of singularly controlling either the oxygen excess ratio or the temperature. Results show the best control is achieved when the excess ratio is control through the reference temperature. The study also compares the parasitic losses from the fans caused by the different controllers. Overall the results provide a good insight into designing a robust control system for an Open Cathode PEMFC for faster response and greater durability. I.
AIRFOIL OPTIMIZATION FOR SMALL WIND TURBINES USING MULTI OBJECTIVE GENETIC ALGORITHM, 2012
Small wind turbines are gaining popularity due to their ability to meet community or domestic nee... more Small wind turbines are gaining popularity due to their ability to meet community or domestic needs in isolated areas with relatively easier installation and lower cost than large wind turbines. This study looks at optimizing airfoils for use in small horizontal axis wind turbines. The optimization looks to maximize the lift coefficient (C l) while minimizing or fixing the drag coefficient (C d). To satisfy these two objectives a multi-objective genetic algorithm is used. The airfoil is parameterized using a composite Bezier curve with two Bezier segments and 11 control points. Appropriate curvature conditions are implemented at the leading and trailing edge of the airfoil and geometric constraints are applied to maintain the maximum thickness between 8% to 14% of the chord for structural reasons. An existing genetic algorithm (GA) code is modified in C++ to generate suitable airfoils using the 13 control points and pass the coordinates to a solver for analysis. As a result four new airfoils are generated for application in low Reynolds number (Re) flow. The characteristics and suitability of the four airfoils are discussed while comparing them to the popular SG6043 airfoil.
Papers by Krishnil Ram
Smart innovation, systems and technologies, 2023
This paper studies the concept of Non-linear Predictive Control (NMPC) to micro-grid in remote sm... more This paper studies the concept of Non-linear Predictive Control (NMPC) to micro-grid in remote small islands in Fiji or the Pacific region. A multi-parametric model with a suitable cost function is considered for a microgrid supplied by renewable energy sources and with a flywheel energy storage system The proposed control strategy has been designed for implementation on an Field-Programmable gate array (FPGA) board, for its the great advantages of reducing the overall system cost, size, and realtime operation, making it suitable for easy and cheap application in small islands or villages.
Journal of Ocean Engineering and Science, 2016
A bend-free rectangular cross-section OWC device was designed and constructed for studying the ef... more A bend-free rectangular cross-section OWC device was designed and constructed for studying the effect of inclination on the flow characteristics inside the device. The inclination is meant to reduce reflection of waves and induce higher velocities in the turbine section. Experimental measurements were made in a wave channel where the OWC device was tested. An S-type Pitot tube was used to measure dynamic pressure of air in the turbine section at several inclinations. Particle Image Velocimetry (PIV) was also done to study the flow of both air and water in the OWC device. In order to focus solely on primary energy capture, no turbine was installed in the OWC device. The dynamic pressure readings were analysed for suction and compression stages. Water volume fluctuations inside the capture chamber were also recorded and compared for different inclinations. The result was an increase in the velocity of air flowing in the capture chamber and hence a rise in the kinetic energy available to the turbine. It was found from experimental studies that as the angle of inclination reduced, the velocity of air in the turbine section increased. The lower angles also caused higher run-up and larger volume of water into the capture chamber.
The study examines the feasibility of producing hydrogen for fuel cell buses in Fiji. The paper f... more The study examines the feasibility of producing hydrogen for fuel cell buses in Fiji. The paper focuses on sizing hybrid microgrids comprising solar panels and wind turbines as the primary power source for hydrogen production while considering both off-grid and grid-connected cases. As no fuel cell vehicles exist in Fiji at present, five long-distance buses with daily travel of 380 km are proposed as a pilot scale baseline system, which would operate in the daytime only. Detailed technical and economic modelling was done using the HOMER Pro software with cost inputs derived from literature. A total of 3 cases for the on-grid and 4 cases for the off-grid systems are analyzed based on the various combinations of components. HOMER Pro optimized the grid configurations to minimize the Net Present Cost (NPC) values. All 7 cases were also modelled with and without the effects of hydrogen gas compressors to emulate the production of low-pressure gas without compression and compressed high-pressure hydrogen required for fuel cell buses. It was found that a grid-connected system with solar and wind hybrid was the most feasible configuration and yielded the lowest NPC of $6 million. The grid-connected case also yielded a
Journal of Electrochemical Energy Conversion and Storage
The paper presents a simplified nonlinear model for an open cathode proton exchange membrane fuel... more The paper presents a simplified nonlinear model for an open cathode proton exchange membrane fuel cell (PEMFC) and its control using three different control strategies. The model presented uses four state variables. The mass flow of oxygen, hydrogen flow, water flow, and temperature were taken to be the critical dynamics in the system. The unknown parameters were estimated using the experimental data of a 1.2 kW PEMFC. The simplified model showed good agreement with experimental results. Control schemes were implemented to control the stack temperature and the oxygen excess ratio of the PEMFC. The proportional (P) and proportional–integral (PI) control performed well but had a poorer response compared to the sliding mode control (SMC) scheme. The study of the different control schemes reveals the dangers of solely controlling either the oxygen excess ratio or the temperature. Results show that the best control is achieved when the excess ratio is controlled together with the referen...
Journal of Mechanical Science and Technology, 2010
A fixed type oscillating water column (OWC) device was designed and tested in a 2-D wave channel.... more A fixed type oscillating water column (OWC) device was designed and tested in a 2-D wave channel. The air chamber was converged to its minimum area at the turbine section to obtain the maximum kinetic energy. The variations in the height of water in the water column and in the static pressure of the air caused by the oscillating waves were studied in detail. The airflow in the entire air chamber was documented with particle image velocimetry measurements. No turbine was installed in the device. The experiments were performed by varying the water depth and the wave frequency. It was found that the air velocities in the turbine chamber during the upward motion of water in the column are always larger than during the downward motion. While the airflow was strong most of the time, very low air velocities were recorded during the transition between the upward and downward flows indicating the need of an airflow regulator before the turbine to get a constant flow rate of air. The well-directed flow obtained at the turbine section can be used to drive a Savonius rotor, which is the most appropriate turbine for rectangular cross-section of the chamber.
2022 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM)
The optimization of a low Reynolds number airfoil for use in small wind turbines is carried out u... more The optimization of a low Reynolds number airfoil for use in small wind turbines is carried out using Genetic Algorithm (GA) optimization. With the aim of creating a roughness insensitive airfoil for the tip region of turbine blades, a multi-objective genetic algorithm code is developed. A review of existing parameterization and optimization methods are presented along with the strategies applied to optimize the airfoil in this study. A composite Bezier curve is used to parameterize the airfoil. The resulting airfoil, the USPT2 has a maximum thickness of 10% and shows insensitivity to roughness at the optimized angles and at other angles of attack as well. The characteristics of USPT2 are studies by comparing it against the popular SG6043 airfoil. While a slight loss in lift is noticed for both airfoils, the drag increments due to early transition are noticeable as well. The airfoil is also studied using CFD and wind tunnel experiments during free and forced transition. The USPT2 ai...
2017 4th Asia-Pacific World Congress on Computer Science and Engineering (APWC on CSE), 2017
A study of a tapered wind turbine tower is performed using particle image velocimetry and numeric... more A study of a tapered wind turbine tower is performed using particle image velocimetry and numerical methods. A 1.5 MW wind turbine base was studied and re-designed. A scaled model of a simple tapered tower base was studied in a wave channel using Particle Image Velocimetry (PIV) to understand the flow phenomena at the tower base. Theoreti9cal and experimental results were found using Morrison equations. The diffraction parameter shows that the linear wave theory is not valid for inertial co-efficient calculations. A direct value of 2.0 resulted for the inertial coefficient values while a lower drag influence was noted at coefficient of drag = 0.315. The turbine’s horizontal force profile is improved in this study to yield a 69% reduction in overturning moment by redesigning the turbines submerged tower.
The root region of small wind turbines experience low Reynolds number (Re) flow that makes it dif... more The root region of small wind turbines experience low Reynolds number (Re) flow that makes it difficult to design airfoils that provide good aerodynamic performance and at the same time, provide structural strength. In the present work, a multi-objective genetic algorithm code was used to design airfoils that are suitable for the root region of small wind turbines. A composite Bezier curve with two Bezier segments and 16 control points (11 of them controlled) was used to parametrize the airfoil problem. Geometric constraints including suitable curvature conditions were enforced to maintain the airfoil thickness between 18% and 22% of chord and a trailing edge thickness of 3% of chord. The objectives were to maximize the lift-to-drag ratio for both clean and soiled conditions. Optimization was done by coupling the flow solver to a genetic algorithm code written in C++, at Re = 200,000 and for angles of attack of 4 and 10 degrees, as the algorithm was found to give smooth variation of...
the paper presents a simplified nonlinear model for an open cathode Proton Exchange Membrane Fuel... more the paper presents a simplified nonlinear model for an open cathode Proton Exchange Membrane Fuel Cell (PEMFC) and its control using two different control strategies. The model presented uses only three state variables and is therefore easy to model and control. The mass flow of oxygen, hydrogen and water were taken to be the key dynamics in the system. The unknown parameters were estimated using the experimental data of a 1.2 kW PEMFC. The model showed good agreement with experimental results. With the objective of maintaining a fixed oxygen excess ratio – a Proportional Integral (PI) Control and a Sliding Mode Control (SMC) scheme were applied to the system model. This paper compares the results of a simple PEMFC model without controller, with a PI controller and a Sliding Mode controller. The SMC performs better in terms of maintaining a fixed oxygen excess ratio of 2. The results also show that the simplified model has good use at an early design stage for systems using PEMFC an...
2021 IEEE Energy Conversion Congress and Exposition (ECCE)
2019 International Aegean Conference on Electrical Machines and Power Electronics (ACEMP) & 2019 International Conference on Optimization of Electrical and Electronic Equipment (OPTIM)
Uploads
Conference Presentations by Krishnil Ram
Papers by Krishnil Ram