Energy Conservation Method Research Articles

Efficient energy-preserving numerical approximations for the sine-Gordon equation with Neumann boundary 条件

We present two novel classes of fully discrete energy-preserving algorithms for the sine-Gordon equation subject to Neumann boundary 条件.The cosine pseudo-spectral method is firstly used to develop structure-preserving spatial discretizations under two different meshes, which result in two finite-dimensional Hamiltonian ODE (ordinary differential equation) systems. Then we combine the prediction-correction Crank-Nicolson 格式 with the projection approach to arrive at fully discrete energy-preserving methods. Alternatively, we introduce a S variable to transform the initial model into a relaxation system, which allowsus to develop structure-preserving algorithms more easily. We then discretize the relaxation system directly by using the cosine pseudo-spectral method in space and the prediction-correction Crank-Nicolson 格式 in time to derive a new class of energy-preserving schemes. The proposed methods can be solved efficiently by the discrete cosine transform. Some benchmark examples and numerical comparisons are presented to demonstrate the accuracy, efficiency and superiority of the proposed schemes.

Modified thermal periodic Poiseuille and Lees-Edwards boundary conditions for energy conservative dissipative particle dynamics

Two kinds of thermal boundary conditions without wall particles in energy conservative dissipative particle dynamics method are investigated in present paper. Firstly, the original thermal periodic Poiseuille flow (PPF) was improved to avoid the unreasonable temperature shift by rebuilding the thermal equilibrium. Then a novel thermal Lees-Edwards (LE) boundary condition was proposed. The constant temperature gradient and uniform density distribution are obtained by rescaling the interaction between particle pairs, and the velocity components of particles for particles re-entering the boundaries. Finally, both the temperature and velocity gradient are integrated into the thermal LE to simulate a constant temperature different in a shear flow. The thermal LE provides a new way to study the thermal-mechanical coupled problems with less computational cost and artificial fluctuation of properties compared with traditional wall particle boundary conditions. Furthermore, it can also be easily extended to related particle-based methods, such as molecular dynamics and Brownian dynamics, etc.

An energy-based method for assessing the equivalent static force of a vehicle collision with bridge columns

A new method is proposed to obtain the equivalent static forces of a vehicle collision with bridge columns. The method is based on energy-conservation and, conversely to other existing methods, does not require the use of complex models or experimental data to obtain time histories of impact. A simplified numerical model is also developed to generate data and compare the performance of the energy-conservation method against three other approaches (global average, local average, and equivalent displacement methods) and the AASHTO allowances. The simplified model is efficient and correctly captures the response for different impact velocities and column sizes. The impact velocity was shown to be positively related to the impact force and column displacement, and the size of the column is also positively related to the impact force but negatively with the column displacement. Results of equivalent static forces show that the global average and local average methods may not provide acceptable values for the equivalent impact force from the collision of vehicles with bridge columns, whereas the equivalent displacement and the proposed energy-based method provide adequate values. The latter approach, however, has the advantage of simplicity and convenience since it does not rely on any numerical/experimental model.

Study on Measure Approach of Void Fraction in Narrow Channel Based on Fully Convolutional Neural Network

Void fraction is one of the key parameters for gas-liquid study and detection of nuclear power system state. Based on fully convolutional neural network (FCN) and high-speed photography, an indirect void fraction measure approach for flow boiling condition in narrow channels is developed in this paper. Deep learning technique is applied to extract image features and can better realize the identification of gas and liquid phase in channels of complicated flow pattern and high void fraction, and can obtain the instantaneous value of void fraction for analyzing and monitoring. This paper verified the FCN method with visual boiling experiment data. Compared with the time-averaged experimental results calculated by the energy conservation method and the empirical formula, the relative deviations are within 11%, which verifies the reliability of this method. Moreover, the recognition results show that the FCN method has promising improvement in the scope of application compared with the traditional morphological method, and meanwhile saves the design cost. In the future, it can be applied to void fraction measurement and flow state monitoring of narrow channels under complex working conditions.

Soft Computing Techniques for Clustering in WSN

The large Wireless Senor Networks (WSNs) comprises Sensor Nodes (SN) in some hundreds with sensing and communication capabilities. Major limitation of WSN is limited energy source of SN. Clustering is one of energy efficient method for energy conservation in WSNs. Clustering is the process to distribute SN in various logical groups known as cluster. Each cluster bears a Cluster Head (CH), who is responsible for transmitting aggregated data of its cluster to Base Station (BS). The literature is enriched by various clustering protocols proposed with the assistance of soft computing. This paper, presents the survey of soft computing paradigm-based clustering protocols.

A novel energy conservation method for office building lighting system

A novel energy conservation method for office building lighting system

A novel energy conservation method for office building lighting system

There is a trade-off between human visual performance and energy cost. With an open office as the research object, personalised control with demand and daylight adaptation is considered in a lighti...

Explicit high-order energy-preserving methods for general Hamiltonian partial differential equations

A novel class of explicit high-order energy-preserving methods are proposed for general Hamiltonian partial differential equations with non-canonical structure matrix. When the energy is not quadratic, it is firstly done that the original system is reformulated into an equivalent form with a modified quadratic energy conservation law by the energy quadratization approach. Then the resulting system that satisfies the quadratic energy conservation law is discretized in time by combining explicit high-order Runge–Kutta methods with orthogonal projection techniques. The proposed schemes are shown to share the order of explicit Runge–Kutta method and thus can reach the desired high-order accuracy. Moreover, the methods are energy-preserving and explicit because the projection step can be solved explicitly. Numerical results are addressed to demonstrate the remarkable superiority of the proposed schemes in comparison with other structure-preserving methods.

COMPARISON OF ENERGY SAVING METHODS FOR DISTILLATION OF LIQUID MIXTURES

The analysis and review of the scientific literature on methods and approaches to energy saving in distillation, as one of the most energy-intensive processes for the separation of binary and multicomponent mixtures was carried out. Directions of the scientific literature are highlighted, showing the relevance of the thermodynamic method assessment of separation processes. A comparative analysis of various methods of energy conservation in the separation of liquid binary mixtures by the distillation method is performed (a binary mixture of benzene-toluene was chosen as an example). A conventional distillation column as well as a column with a heat pump and a column with heat integration were considered. As a result of the calculation experiment for each option performed using the Aspen Plus software package the optimal column parameters were determined - the total number of stages and the position of feed stage. The heat consumption in the column boiler was taken as the objective function. It is also shown that with the same characteristics of the columns, the best way to organize the process for separating the selected mixture is to compress the steam stream from rectifying profile of the column with its subsequent use in the boiler of the stripping profile according to the principle of a heat pump. It was established by a calculation experiment that heat integration by compressing steam from rectifying profile of the column and supplying it to the stripping profile gives significantly less energy saving. The calculation of internal energy saving by distillation column was carried out and it was shown that the distributed heat removal from the plates of the rectifying profile of the column and the supply of this heat to the stripping profile plates reduces internal energy saving and leads to an additional increase in heat consumption in the boiler.

A Novel Isothermal Compression Method for Energy Conservation in Fluid Power Systems.

Reducing carbon emissions is an urgent problem around the world while facing the energy and environmental crises. Whatever progress has been made in renewable energy research, efforts made to energy-saving technology is always necessary. The energy consumption from fluid power systems of industrial processes is considerable, especially for pneumatic systems. A novel isothermal compression method was proposed to lower the energy consumption of compressors. A porous medium was introduced to compose an isothermal piston. The porous medium was located beneath a conventional piston, and gradually immerged into the liquid during compression. The compression heat was absorbed by the porous medium, and finally conducted with the liquid at the chamber bottom. The heat transfer can be significantly enhanced due to the large surface area of the porous medium. As the liquid has a large heat capacity, the liquid temperature can maintain constant through circulation outside. This create near-isothermal compression, which minimizes energy loss in the form of heat, which cannot be recovered. There will be mass loss of the air due to dissolution and leakage. Therefore, the dissolution and leakage amount of gas are compensated for in this method. Gas is dissolved into liquid with the pressure increasing, which leads to mass loss of the gas. With a pressure ratio of 4:1 and a rotational speed of 100 rpm, the isothermal piston decreased the energy consumption by 45% over the conventional reciprocation piston. This gain was accomplished by increasing the heat transfer during the gas compression by increasing the surface area to volume ratio in the compression chamber. Frictional forces between the porous medium and liquid was presented. Work to overcome the frictional forces is negligible (0.21% of the total compression work) under the current operating condition.

Study on reversal and lateral vibration in the stepped well

The reversal and lateral vibration of the drill string are very complex motion and can affect the normal operation of the drill string. The movement of the drill string in the stepped well is different from the movement of the drill string in the regular well. The vibration of the drill string in the stepped well varies with the size of the wellbore and can be visually reflected by the phase speed. To find out the relationship between reversal and lateral vibration, the natural frequency of lateral vibration of the drill string was solved by using the method of energy conservation. The analysis shows that the phase speed of flexural wave in the stepped well is faster in small size wellbore than in large size wellbore. The reversal and lateral resonance is easy to happen in small size wellbore, and the reversal will excite lateral vibration. When the sum of reversal and rotational angular frequencies approaches the natural angular frequency of lateral vibration, the lateral resonance will occur.

All-condition measuring methods for field performance of room air conditioner

Room air conditioners (RACs) are used worldwide and have become one of the major energy consumers in buildings. Because the actual field performance directly affects the energy consumption, the actual performance of an RAC must be determined. The compressor energy conservation (CEC) method exhibits better adaptability to the existing field test methods. However, the refrigerant mass flowrate cannot be calculated accurately under two-phase suction conditions, which is common for current high-energy-efficiency RACs. Therefore, two all-condition field measurement methods based on the CEC and compressor efficiency (CE) methods are proposed, and the isentropic and volumetric efficiency under wet compression working conditions is predicted with data-driven models trained using a back-propagation neural network (BPNN). The accuracy verification indicates that the relative errors of the refrigerant flowrate and cooling/heating capacities of both methods are approximately within ±15%, which is sufficient for the field performance evaluation; in addition, the CEC–compressor volumetric efficiency (CVE) method performs better. Furthermore, the proposed methods are compared, and the accuracy of the dynamic conditions is analyzed to improve the calculation performance.

Concentration of mixed acid by electrodialysis for the intensification of absorption process in acrylic acid production

The absorption process in acrylic acid production was water-intensive. The concentration of acrylic acid before distillation process was low, which induced to large amount of wastewater and enormous energy consumption. In this work, a new method was proposed to concentrate the side stream of absorption column and thus increase the concentration in bottom product by electrodialysis. The influence of operating conditions on concentration rate and specific energy consumption were investigated by a laboratory-scale device. When the voltage drop was 1 V·cP −1 (1 cP=10 −3 Pa⋅S), flow velocity was 3 cm·s −1 and the temperature was 35 °C, the concentration rates of acrylic acid and acetic acid could be 203.3% and 156.6% in the continual-ED process. Based on the experimental data, the absorption process combined with ED was simulated, in which the diluted solution from ED process was used as spray water and the concentrated solution was feed back to the absorption column. The results shown that the flow rate of spray water was decreased by 37.1%, and the acrylic acid concentration at the bottom of the tower was increased by 4.56%. The ions exchange membranes before and after use 1200 h were tested by membrane surface morphology (scanning electron microscope), membrane chemical groups (infrared spectra), ion exchange capacity, and membrane area resistance, which indicated the membrane were stable in the acid system. This method provides new method for energy conservation and emission reduction in the traditional chemical industry. • The electrodialysis was used to concentrate the solution taken from absorption column in acrylic acid production. • The artificial solution contained acrylic acid and acetic acid was concentrated efficiently. • The flow of spray water decreased by 37.1% and the concentration increased by 4.56%. • The ion exchange membrane were stable after using 1200 h.

High order numerical integrators for single integrand Stratonovich SDEs

We show that applying any deterministic B-series method of order pd with a random step size to single integrand SDEs gives a numerical method converging in the mean-square and weak sense with order ⌊pd/2⌋. As an application, we derive high order energy-preserving methods for stochastic Poisson systems as well as further geometric numerical schemes for this wide class of Stratonovich SDEs.

Analysis of energy consumption, emission and saving opportunities in an educational institute in northeast India

Rapid declination of fossil fuel and environmental pollution is a matter of concern for modern society. A substantial part of these fuels is used for generation of power. Thus, conservation of electricity can slow down the decaying of these fuels, expenditure of money and environmental pollution. Educational institutes are one of the leading consumers of power. There are a lot of opportunities by which electricity in institutes can be preserved. This study explores and analyzes building-wise and equipment-wise energy consumption during the summer season in a typical institute located in the north-eastern part of India. The possibilities of curbing electricity, money, fossil fuel and the emission of greenhouse gas have also been investigated in the paper. It has emerged from the result that electric fans and lighting arrangements draw maximum electricity in summer. They devour 72.99% of the total energy used in the institute. Adoption of some simple methods for energy conservation can save 13,779.60 kWh of electricity and 35.39% of its bill per month. Thus, 3030.91 kg of natural gas can be retained and consequently, 15,114.88 kg of greenhouse gas can be prevented from emission.

Energy-preserving methods for nonlinear Schrödinger equations

Abstract This paper is concerned with the numerical integration in time of nonlinear Schrödinger equations using different methods preserving the energy or a discrete analogue of it. The Crank–Nicolson method is a well-known method of order $2$ but is fully implicit and one may prefer a linearly implicit method like the relaxation method introduced in Besse (1998, Analyse numérique des systèmes de Davey-Stewartson. Ph.D. Thesis, Université Bordeaux) for the cubic nonlinear Schrödinger equation. This method is also an energy-preserving method and numerical simulations have shown that its order is $2$. In this paper we give a rigorous proof of the order of this relaxation method and propose a generalized version that allows one to deal with general power law nonlinearites. Numerical simulations for different physical models show the efficiency of these methods.

Discussion on the Application of New Photovoltaic Energy in Building Electrical Energy Saving

<p>With the rapid development of social economy, the demand for new energy is also increasing, and then the problem of large consumption also has a negative impact on the development of the construction industry. Under the concept of green building, the design and construction units pay more attention to energy conservation and environmental protection, so they actively use photovoltaic new energy in the field of electrical energy conservation of construction projects, so as to improve people's quality of life. Starting from the principles and characteristics of building electrical energy conservation, this paper discusses the methods of building electrical energy conservation, and analyzes how to use photovoltaic new energy in the field of building electrical energy conservation, hoping to better practice the concept of energy conservation.</p>

Arbitrarily high-order energy-preserving methods for simulating the gyrocenter dynamics of charged particles

Gyrocenter dynamics of charged particles plays a fundamental role in plasma physics. In particular, accuracy and conservation of energy are important features for correctly performing long-time simulations. For this purpose, we here propose arbitrarily high-order energy conserving methods for its simulation. The analysis and the efficient implementation of the methods are fully described, and some numerical tests are reported.

Is it necessary to resolve the Debye length in standard or δ f PIC codes?

Numerical instabilities of standard Particle-In-Cell (PIC) codes were observed and explained very early in their development. In the zero-time step limit, these instabilities arise from the interaction between the spatial grid and the (artificial) particle shape functions. δf PIC codes, which have recently been especially popular in gyrokinetic simulations, suffer from similar instabilities. In the zero time step limit, the numerical stabilities of standard and δf methods are equivalent. Numerical instabilities arise when the simulation grid does not “resolve the Debye length,” but many modern PIC codes use relatively high order shape functions, and as a result, the worst-case numerical growth rates are undetectably small; in addition, some codes use energy-conserving methods which usually prevent this numerical instability from arising. Similarly, a numerical instability was found in a gyrokinetic δf code using a first-order shape function; we show that this is related to the usual PIC numerical instability. In the gyrokinetic case, where waves have acoustic dispersion at a large wavenumber, increasing the grid resolution actually increases the growth rate of the numerical instability, and the prescription of resolving an effective Debye length is not applicable. However, using higher order shape functions is still an effective remedy.

Optimal Energy Conserving and Energy Dissipative Local Discontinuous Galerkin Methods for the Benjamin–Bona–Mahony Equation

We develop, analyze and numerically validate local discontinuous Galerkin (LDG) methods for solving the nonlinear Benjamin–Bona–Mahony (BBM) equation. With appropriately chosen numerical fluxes, the conventional LDG methods can be shown to preserve the discrete version of mass, and either preserve or dissipate the discrete version of energy, up to the round-off level. The error estimate with optimal order of convergence is provided for both the semi-discrete energy conserving and energy dissipative methods applied to the nonlinear BBM equation, by a novel technique to discover the connection between the error of the auxiliary and primary variables, and by carefully analyzing the nonlinear term. Fully discrete methods can be derived with energy-conserving implicit midpoint temporal discretization. Numerical experiments confirm the optimal rates of convergence, as well as the mass and energy conserving/dissipative property. The comparison of the long time behavior of the energy conserving and energy dissipative methods are also provided, to show that the energy conserving method produces a better approximation to the exact solution. In a recent study by Fu and Shu (J Comput Phys 394:329–363, 2019), optimal energy conserving discontinuous Galerkin methods based on doubling-the-unknowns technique were developed for the linear symmetric hyperbolic systems. We extend the idea to construct another class of energy conserving LDG methods for the nonlinear BBM equation. Their energy conservation property and optimal convergence rate (via a special constructed numerical projection) are investigated. We also provide a comparison of these two types of energy conserving LDG methods, and shown that, under the same setup of computational elements, the latter method produces a smaller numerical error with slightly longer computational time.