scholarly journals Hydrodynamic constraints on the energy efficiency of droplet electricity generators

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Antoine Riaud ◽  
Cui Wang ◽  
Jia Zhou ◽  
Wanghuai Xu ◽  
Zuankai Wang
Keyword(s):  
Energy Efficiency ◽  
Kinetic Energy ◽  
Total Energy ◽  
Viscous Dissipation ◽  
Shear Force ◽  
Mechanical Energy ◽  
Electric Energy ◽  
The Past ◽  
Viscous Shear ◽  
Impingement Velocity

AbstractElectric energy generation from falling droplets has seen a hundred-fold rise in efficiency over the past few years. However, even these newest devices can only extract a small portion of the droplet energy. In this paper, we theoretically investigate the contributions of hydrodynamic and electric losses in limiting the efficiency of droplet electricity generators (DEG). We restrict our analysis to cases where the droplet contacts the electrode at maximum spread, which was observed to maximize the DEG efficiency. Herein, the electro-mechanical energy conversion occurs during the recoil that immediately follows droplet impact. We then identify three limits on existing droplet electric generators: (i) the impingement velocity is limited in order to maintain the droplet integrity; (ii) much of droplet mechanical energy is squandered in overcoming viscous shear force with the substrate; (iii) insufficient electrical charge of the substrate. Of all these effects, we found that up to 83% of the total energy available was lost by viscous dissipation during spreading. Minimizing this loss by using cascaded DEG devices to reduce the droplet kinetic energy may increase future devices efficiency beyond 10%.

Maximum Energy-Efficiency Compliant Mechanism Design for Piezoelectric Stack Actuators

Aerospace ◽  
2003 ◽  
Author(s):  
Mostafa M. Abdalla ◽  
Mary Frecker ◽  
Zafer Gu¨rdal ◽  
Terrence Johnson ◽  
Douglas K. Lindner
Keyword(s):  
Energy Efficiency ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Compliant Mechanism ◽  
Mechanical Energy ◽  
Electric Energy ◽  
Energy Conversion Efficiency ◽  
Maximum Energy ◽  
System Level ◽  
Voltage Source

Combined optimization of a compliant mechanism and a piezoelectric stack actuator for maximum energy conversion efficiency is considered. The paper presents a system level analysis in which the actuator and the compliant mechanism are mathematically described as linear two-port systems. The combination of stack and compliant mechanism is used to drive a structure, modeled as a mass-spring system. The analysis assumes all components to be free from dissipation, and the piezoelectric stack is driven by an ideal voltage source. Energy conversion efficiency is defined as the ratio of the output mechanical energy to the input electric energy. Theoretical bounds on the system efficiency are obtained. It is shown that the stack actuator can be optimized separately and matched to the specified structure and an optimally designed complaint mechanism. The optimization problem for the compliant mechanism is formulated to maximize a weighted objective function of energy efficiency and stroke amplification. Optimization results are presented for ground structures modeled using frame elements.

Economic and Ecologic Analysis of Wind Energy as Steps in Starting a New Business

2017 ◽  
pp. 133-159
Keyword(s):  
Energy Efficiency ◽  
Renewable Energy ◽  
Kinetic Energy ◽  
Environmental Impact ◽  
Wind Energy ◽  
Wind Turbine ◽  
Technological Development ◽  
Electric Energy ◽  
Energy Capacity ◽  
New Business

Wind energy has a long history but in the last decades the technological development and the increasing energy efficiency push this business on a top position for the installed renewable energy capacity worldwide. For a better understanding of the economic and ecologic analysis of the business into the wind energy sector, in this chapter, are presented the main principles and energy concepts related to renewable energy, especially for wind energy. The analysis is focused on the importance of the main elements of a wind turbine and its costs structure. The wind turbine is analyzed also along its lifecycle in order to identify the environmental impact from the row material extraction to the end of lifetime. The main objective of this chapter is to understand the importance of wind energy as a renewable energy and how to use the kinetic energy of wind in order to generate electric energy taking into account its efficiency and also its impact on the environment.

An investigation of the relationships between dispersion, power, and mechanical energy using the end-over-end shaking and ultrasonic methods of aggregate stability assessment

Soil Research ◽  
1997 ◽  
Vol 35 (1) ◽  
pp. 41 ◽  
Author(s):  
S. R. Raine ◽  
H. B. So
Keyword(s):  
Kinetic Energy ◽  
Total Energy ◽  
Mechanical Energy ◽  
Initial Period ◽  
Aggregate Stability ◽  
Simple Calculation ◽  
Stability Assessment ◽  
Ultrasonic Probe ◽  
Ultrasonic Methods ◽  
Aggregate Breakdown

The dispersion and energies applied by the end-over-end shaking and ultrasonic methods of assessing aggregate stability were compared. The simple calculation of the kinetic energy of the falling water within the shaking cylinder (0·72 W) was found to underestimate the total energy associated with dispersion, which was estimated as the equivalent energy during the initial period of shaking, as 1·92±0·18 W. A range of mechanical energies up to 24·95 W was applied to suspensions of 2 Vertisols with contrasting stability using the ultrasonic and the end-over-end shaking techniques. Both power and total energy applied was found to affect significantly (P < 0·05) the dispersion of material sized <20 and <2 µm. The results confirmed the presence of aggregate hierarchy, with the end-over-end shaking treatment being unable to disperse completely the <2 µm material for either soil. An increase in the power applied by the ultrasonic probe increased the rate of aggregate breakdown for the stable soil but produced no effect on rate of breakdown in the unstable soil.

scholarly journals Changes in Energy Cost and Total External Work of Muscles in Elite Race Walkers Walking at Different Speeds

2014 ◽  
Vol 44 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Wiesław Chwała ◽  
Andrzej Klimek ◽  
Wacław Mirek
Keyword(s):  
Kinetic Energy ◽  
Total Energy ◽  
Energy Cost ◽  
Direct Method ◽  
Mechanical Energy ◽  
Mass Movement ◽  
Average Energy ◽  
Centre Of Mass ◽  
External Work ◽  
Race Walking

Abstract The aim of the study was to assess energy cost and total external work (total energy) depending on the speed of race walking. Another objective was to determine the contribution of external work to total energy cost of walking at technical, threshold and racing speed in elite competitive race walkers. The study involved 12 competitive race walkers aged years with 6 to 20 years of experience, who achieved a national or international sports level. Their aerobic endurance was determined by means of a direct method involving an incremental exercise test on the treadmill. The participants performed three tests walking each time with one of the three speeds according to the same protocol: an 8-minute walk with at steady speed was followed by a recovery phase until the oxygen debt was repaid. To measure exercise energy cost, an indirect method based on the volume of oxygen uptake was employed. The gait of the participants was recorded using the 3D Vicon opto-electronic motion capture system. Values of changes in potential energy and total kinetic energy in a gate cycle were determined based on vertical displacements of the centre of mass. Changes in mechanical energy amounted to the value of total external work of muscles needed to accelerate and lift the centre of mass during a normalised gait cycle. The values of average energy cost and of total external work standardised to body mass and distance covered calculated for technical speed, threshold and racing speeds turned out to be statistically significant. The total energy cost ranged from 51.2 kJ.m-1 during walking at technical speed to 78.3 kJ.m-1 during walking at a racing speed. Regardless of the type of speed, the total external work of muscles accounted for around 25% of total energy cost in race walking. Total external work mainly increased because of changes in the resultant kinetic energy of the centre of mass movement.

scholarly journals A water-energy balance application with adaptations to a brazilian water supply system

2021 ◽  
Vol 10 (10) ◽  
pp. e380101019039
Author(s):  
Matheus Gonçalves Silqueira ◽  
Fernando das Graças Braga da Silva ◽  
Alex Takeo Yasumura Lima Silva ◽  
Matheus David Guimarães Barbedo
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Energy Balance ◽  
Water Supply ◽  
Total Energy ◽  
Electric Energy ◽  
Pressure Control ◽  
Supply System ◽  
Water Supply System ◽  
Total Energy Consumption

According to the Alliance to Save Energy, between 2 % and 3 % of the total electric energy consumed in the world is used for water pumping in supply systems, with the consumption reduction potential through energy efficiency and conservation measures being estimated at 25 %. In Brazil, the water supply sector corresponds to 2.6 % of the total energy consumed in the country, with pumping systems being responsible for over 90 % of the total energy consumption. It is extremely common to find supersized facilities with pump motor sets operating outside their ideal points, with it being a common practice to perform flow and pressure control through the installation of valves. The use of reducing valves inserts unnecessary pressure drops into the hydraulic system, increasing energy consumption. The objective of this work is to present an energy balance of a study sector of the Autonomous Water and Sewage Service (AWSS) of a municipality in the south of Minas Gerais, Brazil, aiming to elucidate the electric energy consumption of the system and where the reduction in such consumption may occur. For this, we measured data such as the efficiency of the pump motor sets, calculated performance indicators and water loss indices, and applied the energy balance adapted. This work presents an application of a water-energy balance with adaptations to a Brazilian water supply system, under the perspective of the energy efficiency in lift station pump motor sets.

scholarly journals Assessing the Energy Efficiency of an Electric Car

2020 ◽  
Vol 23 (1) ◽  
pp. A1-A13
Author(s):  
František Synák ◽  
Matej Kučera ◽  
Tomáš Skrúcaný
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Mechanical Energy ◽  
Electric Energy ◽  
Driving Cycle ◽  
Batch Production ◽  
Electric Network ◽  
Electric Car ◽  
Points Of View

Electric car does not supply all the electric energy, obtained from the electric network, to the wheels in the form of mechanical energy. During such a transformation, a part of this energy is lost. The article endeavours to determine the energy efficiency of selected electric car. The electric car used for measurements is not from the batch production since that is a vehicle designed at University of Zilina. The efficiency has been observed while driving under the conditions of amended methodology of New European Driving Cycle (NEDC). The measured value of electric car's efficiency is being analyzed from the energy consumption, as well as emission production, points of view.

scholarly journals Energy Assessment of Sorghum Cultivation in Southern Ukraine

Agriculture ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 695
Author(s):  
Oleg Bazaluk ◽  
Valerii Havrysh ◽  
Mykhailo Fedorchuk ◽  
Vitalii Nitsenko
Keyword(s):  
Energy Efficiency ◽  
Total Energy ◽  
Climate Changes ◽  
Field Experiments ◽  
Renewable Energy Sources ◽  
Grain Sorghum ◽  
Mineral Fertilizers ◽  
Efficiency Ratio ◽  
Energy Inputs ◽  
Southern Ukraine

Global climate changes and fossil fuel reserve depletion are drivers for the search for environmentally friendly renewable energy sources. In Europe, biomass represents the main alternative to fossil fuels. Among energy crops, sorghum is a promising crop for arid regions. The biomass yield and energy efficiency of sorghum (both silage and grain) were studied based on field experiments conducted in Southern Ukraine. The following climate changes were identified: an increase in temperature and a decrease in precipitation. The total energy inputs for sweet sorghum were estimated at 11.256 GJ/ha. The main contributors to the energy inputs are mineral fertilizers (56.99%). The experiment showed that a yield of 40.6 t/ha could be achieved with annual precipitation of 350 mm. The energy efficiency ratio was determined to be 11.18. The total energy inputs for grain sorghum was 16.081 GJ/ha. Its yield (grain) varied from 1.92 to 7.05 t/ha. The energy efficiency ratio of grain sorghum ranged from 2.8 to 16.7.

Multi-Stable Magnetic Spring-Based Energy Harvester Subject to Harmonic Excitation: Comparative Study and Experimental Evaluation

2018 ◽  
Author(s):  
Hieu Nguyen ◽  
Hamzeh Bardaweel
Keyword(s):  
Energy Harvesting ◽  
Kinetic Energy ◽  
Comparative Study ◽  
Experimental Evaluation ◽  
Chaotic Motion ◽  
Energy Harvester ◽  
Electric Energy ◽  
Harmonic Excitation ◽  
Jump Frequency ◽  
Piezoelectric Elements

The work presented here investigates a unique design platform for multi-stable energy harvesting using only interaction between magnets. A solid cylindrical magnet is levitated between two stationary magnets. Peripheral magnets are positioned around the casing of the energy harvester to create multiple stable positions. Upon external vibration, kinetic energy is converted into electric energy that is extracted using a coil wrapped around the casing of the harvester. A prototype of the multi-stable energy harvester is fabricated. Monostable and bistable configurations are demonstrated and fully characterized in static and dynamic modes. Compared to traditional multi-stable designs the harvester introduced in this work is compact, occupies less volume, and does not require complex circuitry normally needed for multi-stable harvesters involving piezoelectric elements. At 2.5g [m/s2], results from experiment show that the bistable harvester does not outperform the monostable harvester. At this level of acceleration, the bistable harvester exhibits intrawell motion away from jump frequency. Chaotic motion is observed in the bistable harvester when excited close to jump frequency. Interwell motion that yields high displacement amplitudes and velocities is absent at this acceleration.

Investigation of Thermal Effects in Direct Driven Hydraulic System for Off-Road Machinery

2016 ◽  
Author(s):  
Niko Karlén ◽  
Tatiana Minav ◽  
Matti Pietola
Keyword(s):  
Energy Efficiency ◽  
Hydraulic System ◽  
Energy Savings ◽  
Mechanical Energy ◽  
Hydraulic Model ◽  
Energy Losses ◽  
Total Efficiency ◽  
Ambient Temperatures ◽  
Wheel Loaders ◽  
Save Energy

Several types of off-road machinery, such as industrial trucks, forklifts, excavators, mobile cranes, and wheel loaders, are set to be operated in environments which can differ considerably from each other. This sets certain limits for both the drive transmissions and working hydraulics of these machines. The ambient temperature must be taken into account when selecting the hydraulic fluid since the viscosity and density of the fluid are changing at different operating temperatures. In addition to the temperature, energy efficiency can also be a problem in off-road machinery. In most off-road machines, diesel engines are employed to produce mechanical energy. However, there are energy losses during the working process, which causes inefficiency in produced energy. For better energy efficiency, hybridization in off-road machinery is an effective method to decrease fuel consumption and increase energy savings. One of the possible methods to save energy with hybrids is energy regeneration. However, it means that the basic hydraulic system inside off-road machinery needs to be modified. One solution for this is to utilize zonal or decentralized approach by means of direct driven hydraulic (DDH) system. This paper aims to investigate a DDH system for off-road machinery by means of modelling and analyzing the effect of the temperature. In the direct-driven hydraulic system, the actuator is controlled directly by the hydraulic pump which is operated by the electric motor. Specifically, it is a valveless closed-loop hydraulic system. Thus, there will be no energy losses caused by the valves, and the total efficiency is assumed to be significantly higher. In order to examine the DDH system, a thermo-hydraulic model was created. Additionally, a thermal camera was utilized in order to illustrate the temperature changes in the components of the DDH system. To reproduce the action of the system in different circumstances DDH system was run at different ambient temperatures, and the component temperatures in the system were measured and saved for the analysis. The thermo hydraulic model was proven capable to follow the general trend of heating up.

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