•A prototype of 1kW traveling-wave thermoacoustic electrical generator was presented.•Maximum electrical power of 1043W with 17.7% efficiency was achieved.•Maximum thermal-to-electrical efficiency of ...19.8% with 970W electric power was obtained.•Impedance coupling rule between the engine and the alternator was first revealed.•System efficiency problem was discussed to provide clues for further improvement.
Traveling-wave thermoacoustic heat engine is a special device capable of converting external heat to acoustic work with high reliability and high potential efficiency. By coupling with a linear alternator, it can be further developed as a new kind of electricity generator called the traveling-wave thermoacoustic electrical generator. In this paper, a prototype of 1kW traveling-wave thermoacoustic electrical generator was designed and tested. In the preliminary experiments, due to the high clearance seal loss caused by the pistons of the alternator, only 638W electric power with 16.6% thermal-to-electrical efficiency was obtained, which was far below our expectation. After further investigation, the acoustic impedance coupling relationship between the engine and alternator was first revealed by means of numerical approach. According to this relationship, the working frequency was decreased in the experiments from 74Hz to 64Hz by charging 4.5% mole fraction argon gas into the system. And a maximum electric power of 1043W with a thermal-to-electrical efficiency of 17.7% and a maximum thermal-to-electrical efficiency of 19.8% with an electric power were of 970W were obtained successfully. Other operating conditions were a mean pressure of 4.0MPa, a heating temperature of 650°C and a cooling temperature of 15°C. So far, the output electric power and efficiency are the highest values for such a thermoacoustic electrical generator. This work presents a new kind of thermal electric power generator, which is believed to be suitable for many applications in the energy area, such as solar energy, industrial waste heat and so on.
The paper presents a detailed analysis of the dynamics and control of air turbines and electrical generators in oscillating-water-columns (OWCs). The aim is to explain the performance of an OWC ...device based on the physical behaviour of each system component. The Mutriku wave power plant was chosen as the test case. The power plant is a breakwater located in the Bay of Biscay, in Basque Country, Spain. The contributions of the work are: i) development of a hydrodynamic model of the power plant in the frequency domain; ii) implementation of a non-linear time-domain wave-to-wire model; iii) real-valued implementation of the Prony method for the computation of the wave-radiation force; iv) a detailed generator model based on experimental data to assess the influence of the generator efficiency on the power take-off performance; v) a critical performance comparison of the Wells and biradial turbines; vi) a sensitivity analysis of the control parameters of the turbine/generator set; and vii) an explanation of the comparative performance of both turbines based on statistical data. The turbine performance curves were taken from developers’ published experimental data. The results were obtained with a simplified model of the wave climate off the Mutriku test site comprising 14 sea states.
•Non-linear time-domain wave-to-wire model of the Mutriku OWC-breakwater was developed.•Experimental electrical generator efficiency was mapped versus rotational speed and shaft torque.•The performances of Wells and biradial turbines were compared based on statistical data.•A sensitivity analysis of the control parameters of the turbine/generator sets was performed.•The biradial turbine was found to be more efficient and less sensitive to the control parameters.
As one special type of sustainable energy source, radioisotopes have extremely high energy densities. Electrical generators using the decay heat from these radioisotopes can provide long-lasting ...power when other types of energy, such as solar or chemical energy, are not available. Starting from the 1960s, radioisotope generators were safely used in numerous space and terrestrial missions, and have powered systems from interstellar spacecraft to lighthouses along the arctic coast. This work reviewed the generator development and critical components that constitute a functional system. Started with a brief generator history, the paper focused on technological aspects including fuel manufacturing, energy conversion elements, thermal insulation, structural materials, prototype measurements, future improvements, and concluded with the safety aspects for both space and terrestrial applications. Radioisotope generators are one example of using nuclear energy in a peaceful way to benefit human be-ings. Plutonium fuel productions were resumed and accelerated in the United States and americium fuel research was actively sponsored by the European Space Agency. It is promis-ing that more and more high performance generators will be used in future land and space missions.
•The history and radioisotope fuel source technology.•The thermal-to-electrical energy conversion methods and devices.•The generators' insulation, structural supports, and radiators.•Measurement results from different technology prototypes and futuristic directions.•The social and political challenges of using the generator in space and terrestrial missions.
The use of generative design as an alternative to typical structural optimization techniques opens the door to new methods of manufacturing. In this study, generative design techniques were used as ...an automated iterative process with an extensive set of control variables and initial models to explore and optimise the stiffness and weight of different configurations for a 3 MW offshore wind turbine electrical generator structure. With this new approach of adding generative design techniques to a structural optimization process, a 4% reduction in structural mass was achieved. The modification in the structural geometry also help to enlarge the machine's operational range with the consequent growth in energy gathering.
•The electrical generator structure of a 3MW wind turbine has been designed and optimized using generative design techniques•The design process was initiated using different configurations that helped identify the most appropriate optimization path•A structural mass and deflection comparison between models revealed that a structure with a central support is the optimum.•Making use of preoptimized structural configurations can significantly help to achieve mass savings
The PLTU monitoring system developed in this study will be in the form of a monitoring system for temperature, current, voltage, turbine speed on a laboratory scale mini PLTU created using the blynk ...application and displayed on a smartphone. The research method used is in the form of testing a monitoring system comparing the prototype with standard gauges to determine the percentage of the measurement error, readings of type K and MAX6675 thermocouples, Lm393 sensors, DC voltage sensors, ACS712 sensors. The results of the measurement of the steam temperature sensor have an average percentage error of 0.03%, the turbine rotation sensor has an average percentage error rate of 0.01%, DC voltage sensor has an average error percentage rate of 0.07%, DC current sensors have an average percentage error rate of 0.10%.
•Thermoacoustic Stirling electrical generator for recovery LNG cold exergy is studied.•The corresponding characteristics for the external load of the alternator are analyzed.•The influence of ...regenerator parameters on the low temperature engine is investigated.•Maximum electrical power of 12.4 kW and maximum efficiency of 37% are obtained.
In recent years, the share of natural gas in total primary energy consumption has gradually increased around the world. In China, almost half of imported natural gas is in the form of LNG. Thus, how to effectively use LNG’s cold energy or exergy has gained increasing attention. In this paper, a double-acting thermoacoustic Stirling heat electrical generator capable of using LNG cold exergy is introduced. The system consists of a four-unit thermoacoustic Stirling engines and four linear alternators connected end-to-end to construct a loop configuration. The engine converts the external thermal energy to acoustic work by completing the thermoacoustic Stirling cycle between the low temperature provided by the LNG and that of the ambient environment. Then, the alternator converts the acoustic work to electrical power. To understand the system’s operating mechanism, numerical simulation is performed based on the classic thermoacoustic theory. Besides the distributions of key parameters, the influences of the electrical parameters on the system performance and the optimization of the regenerator in low temperature are presented in detail. According to the simulation results, the regenerator of the engine prefers a higher porosity to achieve high power and efficiency. The maximum acoustic work of 17.6 kW and electrical power of 12.4 kW for the whole system is obtained with a porosity of 0.9 and a hydraulic radius of 53 μm when the electrical resistance and capacitance are 160 Ω and 80 μF, respectively. The cooling and heating temperatures are 110 K and 303 K. This study presents a new way to efficiently use the cold exergy of LNG and may be especially relevant for distributed small-scale applications.
This work reports a gimbaled-pendulum wave energy converter with a magnetic multistable mechanism to better capture multidirectional irregular excitations. To have a deep insight into the multistable ...effect, the dynamic energy conversion is modeled by taking random excitations from multiple directions into account. Moreover, this work investigates the effect of hull swing on the distribution of equilibrium points and potential wells and analyzes the promotion of energy harvesting performance under different excitations. It is found that the average output power is increased by 6.5% under the sway excitation and by 51.1% under the roll excitation with the help of the multistable mechanism. A scalable prototype occupying a space of 0.029 m 3 in total is fabricated. Field results under mild sea condition show that the wave energy converter can output electrical power with the peak value of 3.83 W and average value of 0.295 W, while the corresponding root mean square amplitudes of the roll and pitch vibrations of the hull are as small as 3.52° and 3.07°. Potential approaches for enlarging the electrical output are also discussed.
Recently, generation of electrical power from the oceanic wave draws incredible attention to the researchers and engineers. Although, oceanic wave energy is gigantic and available to most of the ...earth's surface, it is still unused because of the lack of technological excellence in the past decades. Therefore, research gap is created in this regard specially extraction of electrical power from the oceanic wave. In this paper, wave energy devices and optimization of the linear electrical generator (LEG) that mainly converts the mechanical energy (from the device) into electricity are presented in detail with finite element analysis (FEA). The methodology involves analysis of the design, observation of its electrical and magnetic properties, optimization, different copper windings, enhancement of output power, maximizing the efficiency of the LEG, and power density. To test the proposed method, an LEG is designed using the computer aided design software. Its geometry is then imported to ANSYS software for conducting FEA. The generated power, electrical, and magnetic properties of the LEG are observed for various conditions. Optimization procedure is parallelly conducted with FEA to ensure extracting the maximum output power and efficiency. Various magnetic materials are analyzed for selecting proper magnetic core and the permanent magnet to further increase the output power. Simulation results show that because of applying the proposed design method to the LEG with optimization, approximately 93.9% efficiency and 530 kW/m3 power density are achieved for 2 m/s velocity of the translator, which is the highest among almost all other existing LEGs so far.
•Analysis of linear electrical generator (LEG) by finite element method (FEM)•Design and optimization of the LEG by FEM in stepwise manner with a flow chart•Selection of suitable copper winding and magnetic material to enhance output power•Reduction of core loss with applying advanced ferromagnetic core•Maximization of its efficiency by observing the electrical and magnetic properties
This work investigates integrating vegetation into solar chimney power plants (SCPPs) using numerical simulations of an SCPP prototype in Spain. A 2D axisymmetric computational fluid dynamics model ...with radiation heat transfer was employed to evaluate the impact of vegetation beneath the solar collector roof on system performance. Different SCPP configurations were analyzed: a standard design, one with a secondary collector roof, and another with secondary and tertiary collector roofs. Results indicate the secondary and tertiary roof configuration exhibited the highest annual electricity generation capacity of 34-80 kW. While introducing vegetation under the collector appears feasible, it is likely to reduce the overall energy output. In summary, simulations suggest that vegetation influences SCPP operation, decreasing power production, while incorporating multiple collector roofs enhances the generation capacity.
With an increasing number of wind turbines being erected offshore, there is a need for cost-effective, predictive, and proactive maintenance. A large fraction of wind turbine downtime is due to ...bearing failures, particularly in the generator and gearbox. One way of assessing impending problems is to install vibration sensors in key positions on these subassemblies. Such equipment can be costly and requires sophisticated software for analysis of the data. An alternative approach, which does not require extra sensors, is investigated in this paper. This involves monitoring the power output of a variable-speed wind turbine generator and processing the data using a wavelet in order to extract the strength of particular frequency components, characteristic of faults. This has been done for doubly fed induction generators (DFIGs), commonly used in modern variable-speed wind turbines. The technique is first validated on a test rig under controlled fault conditions and then is applied to two operational wind turbine DFIGs where generator shaft misalignment was detected. For one of these turbines, the technique detected a problem 3 months before a bearing failure was recorded.
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