Applied Mechanics and Materials Vols. 479-480

Abstract: Small and efficient energy harvesters, as a renewable power supply, draw lots of attention in the last few years. This paper presents a planar rotary electromagnetic generator with copper coils fabricated by using printed circuit board (PCB) as inductance and Nd-Fe-B magnets as magnetic element. Coils are fabricated on PCB, which is presumably cost-effective and promising methods. 28-pole Nd-Fe-B magnets with outer diameter of 50 mm and thickness of 2 mm was sintered and magnetized, which can provide magnetic field of 1.44 Tesla. This harvester consists of planar multilayer with multi-pole coils and multi-pole permanent magnet, and the volume of this harvester is about 50x50x2.5 mm³. Finite element analysis is used to design energy harvesting system, and simulation model of the energy harvester is established. In order to verify the simulation, experiment data are compared with simulation result. The PCB energy harvester prototype can generate induced voltage 0.61 V and 13.29mW output power at rotary speed of 4,000 rpm.

Abstract: The main objective of this paper is to report the small signal stability analysis of Vietnam Power System which has a longitudinal network structure with the consideration of power system stabilizer (PSS) in operation to enhance the damping of inter-area oscillation by using local as well as remote feedback signals via phasor measurement unit (PMU). Both methods of frequency domain and time domain analyses are used to investigate the performance of the power system. The study results show that by proper selection of PSS installation locations and remote feedback signals, power oscillations on the tie-line will be reduced and the system stability is thus improved.

Abstract: In this paper, a novel high step-up DC-DC converter has been designed for fuel cell applications. The proposed high step-up converter can be used for various portable energy storage components such as fuel cells which are used for hybrid electric vehicles (HEV), and light electric vehicles (LEV).The proposed converter is integrated by boost circuit, voltage lift capacitor, and coupled-inductor techniques to achieve high step-up voltage and has several advantages. First, the circuit is controlled by one single pulse width modulation (PWM). Second, the converter consists of active clamp circuit to recycle the leakage inductance and send to output capacitor so that the voltage spike on active switch is suppressed and efficiency is also improved. Third, by using the winding of secondary boost circuit, and voltage lift capacitor techniques, the high voltage gain can be achieved without more than 50% duty ratio, and the slope compensation circuit can also be simplified.Finally, a 1k W prototype converter is implemented, to verify the performance of the proposed converter with input voltage 48V, output voltage 400V, and output power 1k W is also achieved. The highest efficiency is 92.96% at 400W, and the full-load efficiency is up to 90.48%.

Abstract: In the nuclear power plant (NPP) safety, the safety analysis of the NPP is very important work. In Fukushima NPP event, due to the earthquake and tsunami, the cooling system of the spent fuel pool failed and the safety issue of the spent fuel pool generated. In this study, the safety analysis of the Chinshan NPP spent fuel pool was performed by using TRACE and FRAPTRAN, which also assumed the cooling system of the spent fuel pool failed. There are two cases considered in this study. Case 1 is the no fire water injection in the spent fuel pool. Case 2 is the fire water injection while the water level of the spent fuel pool uncover the length of fuel rods over 1/3 full length. The analysis results of the case 1 show that the failure of cladding occurs in about 3.6 day. However, the results of case 2 indicate that the integrity of cladding is kept after the fire water injection.

Abstract: This research aims at investigating the instability phenomena on the power-flow operating map of Lungmen nuclear power plant (NPP). Lungmen NPP is the first ABWR (Advanced Boiling Water Reactor) and under construction in Taiwan. It consists of two identical units with 3926 MWt rated thermal power and 52.2×10⁶ kg/hr rated core flow. In this research, decay ratios (the stability index) are calculated by LAPUR6. LAPUR6 is an analyzing core instability computer code based on the frequency domain approach. Before investigating the stability on Lungmen NPP operating map, some additional state points are carried out for validating with the SIRIUS-F experimental data. LAPUR6 results are consistent with the SIRIUS-F experimental data. Besides, LAPUR6 results of Lungmen NPP operating map show that the Lungmen NPP will not encounter core-wide or regional instability under normal operating or RIP trip event.

Abstract: Energy is an important element in human life. Previous study discovered that buildings consumed more than 40% of global energy mainly electricity and emit 1/3 of global greenhouse gas through combustion of fossil fuels for generating electricity. Nowadays, global warming come to be a major issue facing the world and it leads to a better awareness about renewable energies as alternatives in generating electricity. In certain countries, solar farm has been adopted as an alternative in producing electricity. UTM spent millions of money every year for electricity bills and UTM could consider solar farm as an energy option in generating green electricity due to suitable climate and huge land bank. Governments incentives and decreasing PV panel price are opportunities to be appreciated for UTM to implement solar farm. However, high initial investment is needed to construct the solar farm. Additionally, decision will be based on financial benefits of the solar farm development. The aim of this study is to identify potential of solar farm implementation in generating green electricity. Data will be acquired via literature review, questionnaire survey, record review, and expert interview. Calculations on payback period and net present value were made based on interview data to identify potential of investment for solar farm. The study outlines the suitability factors for UTM to implement solar farm, at the same time financial benefits of solar farm implementation is portrayed.

Abstract: This paper investigates the impact of photovoltaic generation system (pvgs) on the distribution system. The installations of various types of distributed generators (dgs) on the distribution system have significantly changed the operating, planning and maintaining strategies of the utility. In this paper, one practical Taiwan Power Company (taipower) distribution system with a large-scale of pvgs is selected for study. Many power quality issues like steady state voltage variation, reverse power, voltage unbalance, short-circuit current and harmonic are analyzed by considering many different operation scenarios of the distribution system and pvgs. The simulation results are compared with the related standards and it is found that the pvgs impact on the concerned power quality and reliability issues are all within the limits. It is concluded that the simulation results of the paper are very helpful to the electric utilities and pv producers for providing better power quality as well as increasing photovoltaic (pv) penetration in distribution grids.

Abstract: In this paper, an intelligent solar panel cleaning system that monitors the output of solar panels is designed. The output voltage of the solar panel is used to decide if the solar panel needs to clean or not. The control system is developed using Lab-VIEW. The direction and position of the system is set by the light sensor, which is parallel to the direction of sunlight. The data from the light sensors, along with the fuzzy logic control software developed using Lab-View determines the control commands for the stepper motors controlling the cleaning process. The commands are stop, forward or reverse and the cleaning process is repeated until the generated power output of the solar panels is sufficient. The cleaning process is performed in real-time to maintain the power generating capacity of the solar cells.

Abstract: This paper presents Elman neural network for the dynamic control strategies of a hybrid power system that include wind/photovoltaic/diesel system. Wind and PV power are the primary power sources of the system to take full advantages of renewable energy, and the diesel-engine is used as a backup system. A simulation model for the hybrid energy system has been developed using MATLAB/Simulink. To achieve a fast and stable response for the real power control, the intelligent controller consists of a Radial Basis Function Network (RBFN) and an modified Elman Neural Network (ENN) for maximum power point tracking (MPPT). The pitch angle of wind turbine is controlled by ENN, and the PV system uses RBFN, where the output signal is used to control the DC / DC boost converters to achieve the MPPT.

Abstract: In this paper, a 20kW design capacity solar parabolic dish concentrator hybrid solar/gas dish Stirling system (HS/GDSS) is proposed. To ensure a steady operation of an electricity power plant, HS/GDSS uses gas as complement when solar radiation is weak. Thermodynamic models were made to conduct design of system parameters. After detail characteristics were chosen, analysis was carried out to evaluate this system. The results show that within design condition, overall efficiency of the system is 27.58% at daytime and 33.94% at night, which has advantages over single-energy solar dish Stirling electricity power plant.