Microthrusters are special category of propulsion device used to propel micro sized satellites. It is designed as per the mission requirements. There are various kinds of propulsion requirements such as continuous mode operation for orbit transfer (from one planet to another), orbit shift or adjustment for asteroid mining, pulsed mode operation for attitude control of satellites, and gravitation or solar drag compensation in orbit. Continuous mode operation is a high propellant consuming operation and designed cautiously to reach the destination with onboard available propellant. While pulsed mode operation is widely used for LEO (Low earth orbit) applications, where gravitation drag, atmospheric drag and solar drags are dominating. This paper focuses on the pulsed mode operation of vaporization liquid microthruster in vacuum operating condition. The pulsed mode operation involves timely thrust generation for the fine tuning of the positioning of the microsatellites. The operational timing in this mode of operation ranges from milliseconds to a few seconds at maximum. The operating time is decided based on the adjustment requirement for the positioning of the microsatellites. Vaporizing liquid microthrusters use green propellant to produce thrust. Tests are conducted under vacuum condition to simulate the actual space conditions and corresponding results are plotted. Results has shown a maximum thrust value of 290 μN at 1 sec of valve operating time, 335 μN at 2 seconds, 413 μN at 3 seconds, 524 μN at 4 seconds and 590 μN at 5 seconds of valve operating time for 200°C of a constant VLM temperature respectively. The effect of the dibble volume has also been discussed for the vaporization liquid microthruster using di-ionized water as liquid propellant.
In this paper, the performance of the moving average and moving median load estimation techniques is investigated using aggregated measurements of domestic smart meters. The load estimation techniques were tested using forward and backward walk approaches. Forward walk aims to estimate future load measurements using past measurements while backward walk estimates missing past measurements of the load using more recent measurements. Simulation results show that the moving average combined with forward walk produces load estimates with higher accuracies than the moving median and backward walk.
Electricity thefts in connivance with employees of electricity distribution companies, remain the Achille’s heel of power sector, addressing which continue to be the holy grail. The lackluster performance of technological measures to curb electricity thefts highlights the need to investigate the human aspectstoo. That’s what this study aims at. The findings, grounded in the responses of the nineteen employees of the Indian electricity distribution companies, detail the factors that induce employees to collude with consumers in electricity theft.
Omnipresent charging infrastructure is a requisite for ensuring smooth transition to e-mobility. Reliable, sustainable, cost-effective and photovoltaic (PV) panel based charging of EV batteries could be befitting solution. This paper presents a PV module-integrated converter for EV charging station which can track maximum power point besides providing requisite high gain boost in voltage to a usable value even under intermittent conditions, i.e. insolation variation and partial shading conditions. The current control scheme evacuates the maximum available power amidst intermittent conditions. The performance of the system is evaluated under Matlab/Simulink environment. Presented simulation results show close conformity with design and validates the effectiveness of the system proposed.
In the past four decades, oil sands production in Canada has increased dramatically. More recently, Canada has developed carbon emission reduction targets to meet its Nationally Determined Contributions and Mid-Century Strategy to reduce GHG emissions. Quantification and assessment of GHG emissions from the oil sands industry – a high emitter – is necessary to track progress toward meeting emissions reduction and technology development. This study uses GCAM, an integrated assessment model, to examine the energy consumption of oil sands extraction and upgrading. Five traditional and cogeneration extraction technologies are compared in model simulations for energy cost and nonenergy (operating) cost. Results show that energy consumed by oil sands production will triple by 2050 because of the expected increase in oil sands production. Cogeneration technologies result in reduced CO2 emissions.
Most of phase change materials have an obvious density change during solid-liquid phase change, which is along with the volume change of phase change materials, and results in the formation or disappearance of the void cavities based on the encapsulation methods. Void cavities play ignorable roles in the phase-change process, while their influence in the composite porous phase change materials were hardly taken into account in the literatures. In this work, the effect of void cavities on the heat transfer of the porous phase change material has been studied for the first time by a two-dimensional lattice Boltzmann method. The high thermal diffusion coefficient and low conductivity of void cavities show significant influence on not only the temperature distribution but also the energy storage performance. This simulation model gets closer to the real application, which holds great promising for being applied in the guidance on the thermal management system design.
Contactless slip-ring provide a safe, non-contact, high efficiency, wear-free and reliable power transfer solution with low maintenance for rotary applications. In this paper, a novel magnetic coupler of wireless power transfer (WPT) system is designed. Compared with the traditional slip ring power supply, it can be applied to the rotating condition. To realize light-weight and small-volume of the WPT, the magnetic coupler and circuit have been optimized from both compensation topology and coil configuration. Experimental results are demonstrating that transfer power is 280W at efficiency of 91.7%.
Increasing the share of renewable energy in buildings sector is essential. While the dynamic nature of the renewables is an obstacle for improving its efficiency. In this context, thermal energy storage technologies are to store the renewables and supply it to meet building’s demand. Thermochemical energy storage stands out in advantages including high energy storage density and low thermal loss. However, for a thermochemical energy storage system, the thermochemical reactor is critical. To tackle drawbacks of the reactor, this paper proposes an innovative three-phase thermochemical reactor and investigates its performance through an experimentally validated numerical model. The reactor is integrated with fins and air gaps to enhance heat and mass transfer. Key parameters and the related heat and mass transfer efficiency of the reactor in both charging and discharging processes have been investigated. According to the analysis, the integration of fins has increased the reactor performance by 129% in charging and by 77% for COP in discharging. The effect of fin pitch has been examined and the results show that reducing the fin pitch can increase the reactor performance by up to 14% in charging and 7.5% in discharging. However, the enhancement is not sensitive for fin pitch lower than 30 mm. Additionally, increase the gap size can enhance the charging performance but may reduce discharging efficiency and the optimal gap size range is 3 mm to 5 mm.
In this paper, a transient preventive control method for wind power system, based on the information of generator power angle, angular velocity and voltage, is proposed. The objective function is the minimum of the total control amount. The required preventive control action can be efficiently solved via a linear programming model with the phase trajectory sensitivities-based constraints. The method aims to keep the online preventive transient stability with the wind power integration. The validity of the method is verified through 2DC system.
Source reduction or process control of fuel-N conversion into reactive NOx precursors (NH3 and HCN) during pyrolysis process was fundamental and essential for clean thermal utilization of straw wastes. In this study, three typical straw wastes (bean, rice and wheat) were employed to probe formation characteristics and regulatory mechanisms of two target NOx precursors via stage pyrolysis method with the help of XPS and chemical absorption-spectrophotometry analytic techniques. Results demonstrated that consistent formation pathways of NOx precursors were elucidated by direct and indirect conversion of similar fuel-N types – amide-N/amine-N/amino-N (N-A) in straw wastes. Specifically, two NOx precursors were hardly linked with primary pyrolysis of N-A types (direct conversion) while dominantly determined by secondary reactions of subsequent nitrogen intermediates in chars and tars (indirect conversion); secondary reactions referring to hydrogenation of heterocyclic-N in chars and dehydrogenation of amine-N in tars were more responsible for NH3-N and HCN-N, respectively, leading to a maximal total yield of 45-50 wt.%. Consequently, compared to single-stage pyrolysis uniformly, two-stage pyrolysis could manipulate intensities of formation pathways at different pyrolysis stages through employing differential intermediate feedstocks for re-pyrolysis, minimizing the ratio of total yield by about 60 % with a greater effect on HCN-N yield (76-83 %) than NH3-N yield (44-50 %), which exhibited an excellent regulatory capacity on NOx precursors formation for straw wastes. These findings were favorable for developing some insights into emission control of N-containing gaseous pollutants during their thermo-chemical conversion processes.