Correct Energy Balance Research Articles

The Behavioural Change of Distribution Networks with Increasing Circuit Length and Load

Purpose: This study investigated the behavioural change of distribution networks with increasing circuit length and load. Design/Methodology/Approach: This study employed a simulation-based experimental design using OpenDSS to model and analyse the behaviour of the distribution network under different scenarios. A combination of varying network lengths and loading levels was chosen to determine the behavioural changes of a network. A total of 100 simulations were conducted, representing 10 different circuit lengths and 10 different loading conditions. Data collection on voltage levels at various points along the circuit, focusing on the voltage at the end of the circuit was carried out. Each scenario will be modelled and analysed to study the voltage drop and stability. The simulation results were validated by comparing them with theoretical calculations and real-world measurements from similar networks. Findings: It has been shown that, for every circuit length there is a maximum load that will result in a linear relationship maintaining the correct energy balance to respond to voltage regulation and power flow. With circuit length increase, capacitive reactance reduces while resistance and inductive reactance increase leading to a more inductive circuit. Research Limitation/Implications: The research considered only changes in circuit length and loading as it was based on a simplified source-load equivalent circuit. Practical implication: It draws the attention of practising engineers and designers to be mindful of the implications of load increase and network expansions on system characteristics. It forms a guide to the limit a circuit could be extended or loaded if system balance is to be maintained. Social Implication: A stable and reliable power supply supports economic growth, public health, and safety, leading to improved quality of life. Ensuring all communities have reliable electricity fosters social equity and inclusion, promoting fairness and improving the quality of life for disadvantaged groups. Originality/Value: The novelty of this research lies in its comprehensive, realistic, and advanced approach to studying the behavioural changes in distribution networks with increasing circuit length and load. By addressing previously overlooked aspects and integrating modern computational and data analysis techniques, the study provides valuable new insights that can significantly improve the design, operation, and management of long distribution networks.

F(Q, T) gravity, its covariant formulation, energy conservation and phase-space analysis

In the present article we analyze the matter-geometry coupled f(Q, T) theory of gravity. We offer the fully covariant formulation of the theory, with which we construct the correct energy balance equation and employ it to conduct a dynamical system analysis in a spatially flat Friedmann–Lemaître–Robertson–Walker spacetime. We consider three different functional forms of the f(Q, T) function, specifically, f(Q,T)=alpha Q+ beta T, f(Q,T)=alpha Q+ beta T^2, and f(Q,T)=Q+ alpha Q^2+ beta T. We attempt to investigate the physical capabilities of these models to describe various cosmological epochs. We calculate Friedmann-like equations in each case and introduce some phase space variables to simplify the equations in more concise forms. We observe that the linear model f(Q,T)=alpha Q+ beta T with beta =0 is completely equivalent to the GR case without cosmological constant Lambda . Further, we find that the model f(Q,T)=alpha Q+ beta T^2 with beta ne 0 successfully depicts the observed transition from decelerated phase to an accelerated phase of the universe. Lastly, we find that the model f(Q,T)= Q+ alpha Q^2+ beta T with alpha ne 0 represents an accelerated de-Sitter epoch for the constraints beta < -1 or beta ge 0.

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena.

Gas-induced geodynamic phenomena can occur during underground mining operations if the porous structure of the rock is filled with gas at high pressure. In such cases, the original compact rock structure disintegrates into grains of small dimensions, which are then transported along the mine working space. Such geodynamic events, particularly outbursts of gas and rock, pose a danger both to the life of miners and to the functioning of the mine infrastructure. These incidents are rare in copper ore mining, but they have recently begun to occur, and have not yet been fully investigated. To ensure the safety of mining operations, it is necessary to determine parameters of the rock–gas system for which the energy of the gas will be smaller than the work required to disintegrate and transport the rock. Such a comparison is referred to as an energy balance and serves as a starting point for all engineering analyses. During mining operations, the equilibrium of the rock–gas system is disturbed, and the rapid destruction of the rock is initiated together with sudden decompression of the gas contained in its porous structure. The disintegrated rock is then transported along the mine working space in a stream of released gas. Estimation of the energy of the gas requires investigation of the type of thermodynamic transformation involved in the process. In this case, adiabatic transformation would mean that the gas, cooled in the course of decompression, remains at a temperature significantly lower than that of the surrounding rocks throughout the process. However, if we assume that the transformation is isothermal, then the cooled gas will heat up to the original temperature of the rock in a very short time (<1 s). Because the quantity of energy in the case of isothermal transformation is almost three times as high as in the adiabatic case, obtaining the correct energy balance for gas-induced geodynamic phenomena requires detailed analysis of this question. For this purpose, a unique experimental study was carried out to determine the time required for heat exchange in conditions of very rapid flows of gas around rock grains of different sizes. Numerical simulations reproducing the experiments were also designed. The results of the experiment and the simulation were in good agreement, indicating a very fast rate of heat exchange. Taking account of the parameters of the experiment, the thermodynamic transformation may be considered to be close to isothermal.

Analysis of Second Order Time Filtered Backward Euler Method for MHD Equations

The present work is devoted to introduce the backward Euler based modular time filter method for MHD flow. The proposed method improves the accuracy of the solution without a significant change in the complexity of the system. Since time filters for fluid variables are added as separate post processing steps, the method can be easily incorporated into an existing backward Euler code. We show that the time filtered backward Euler method delivers better correct energy and cross-helicity balance in comparison with the backward Euler method. Long-time stability, stability and second order convergence of the method are also proven. The influences of introduced time filter method on several numerical experiments are given, which both verify the theoretical findings and illustrate its usefulness on practical problems.

Temporal and spatial variations of energy balance closure across FLUXNET research sites

There is always a discrepancy between available energy and output energy in the surface energy budget of FLUXNET research sites. Using the daily data retrieved from the FLUXNET database, the energy balance closure (EBC) of around 150 sites covering nine land covers and five Köppen climate zones [i.e. tropical area (A), dry area (B), mild temperate area (C), snow area (D) and polar area (E)] was analyzed. The temporal and spatial variations of EBC in different land covers and climate zones were summarized, and the relationships between EBC and environmental variables were explored. The possible differences in the EBCs of sites with open path (OP) and closed path (CP) gas analyzers were also examined at different precipitation levels in various climate zones. The results showed that EBC was positively related to air temperature (Ta) and vapor pressure deficit (VPD) below certain thresholds. Better EBCs were observed in land covers with stable evaporative fraction (i.e. the ratio of latent heat flux to the sum of latent and sensible heat fluxes). For land covers with seasonal varying evaporative fraction, the larger evaporative fraction in summer corresponded with better EBCs. OP systems resulted in better EBCs at various precipitation levels, and EBCs decreased with increasing precipitation for both OP and CP systems. In addition, the relationship between EBC and CO2 fluxes was different among the different land covers. There was a positive relationship for most land covers but not for savannah, shrub land, and evergreen broadleaf forest. The relationships between EBC and CO2 as well as EBC and other environmental variables are cross-influenced, which could be related to the stomata aperture and metabolism of the vegetation. Overall, this study summarized patterns of EBCs that could be used to correct eddy covariance data and energy balance closure related models. It further enhanced our understanding of the potential link between EBC and vegetation physiology that could facilitate the modeling and prediction of biophysical processes related to water, energy, and carbon fluxes from the leaf to ecosystem levels.

Experimental determination of cold water temperature at the inlet to solar water storage tanks

In the present work, results of experimental research on the mains water temperature supplying the Solar Domestic Hot Water system in the period from 2016 to 2018 are shown. The test object is located in the Hotel for Research Assistants on Bialystok University of Technology campus in Poland. One of the elements that will guarantee the correct energy balance of a hot tap-water system is the exact determination of the cold water temperature. The aim of this study is estimation of the temperature of the mains water flowing into the district heating substation and the water feeding directly the heat storage tanks. The research results showed that the average value of the cold water was 14.09°C during the 3 years of measurements. Moreover, it was shown that this temperature increased by about 0.4°C as a result of heat exchange with the air inside the substation. In the article, the author proposed modifications of coefficients in a commonly used model developed by National Renewable Energy Laboratory for determining the temperature of mains water in energy simulations. The proposed changes allow for accurate modelling of the cold water temperature under the climate conditions of north-eastern Poland.

A low-frequency variational model for energetic particle effects in the pressure-coupling scheme

Energetic particle effects in magnetic confinement fusion devices are commonly studied by hybrid kinetic-fluid simulation codes whose underlying continuum evolution equations often lack the correct energy balance. While two different kinetic-fluid coupling options are available (current coupling and pressure coupling), this paper applies the Euler–Poincaré variational approach to formulate a new conservative hybrid model in the pressure-coupling scheme. In our case the kinetics of the energetic particles are described by guiding center theory. The interplay between the Lagrangian fluid paths and phase space particle trajectories reflects an intricate variational structure which can be approached by letting the four-dimensional guiding center trajectories evolve in the full six-dimensional phase space. Then, the redundant perpendicular velocity is integrated out to recover a four-dimensional description. A second equivalent variational approach is also reported, which involves the use of phase space Lagrangians. Not only do these variational structures confer on the new model a correct energy balance, but also they produce a cross-helicity invariant which is lost in the other pressure-coupling schemes reported in the literature.

High efficiency cogeneration: CHP and non-CHP energy

This paper analyses practical procedures for the virtual recognition of CHP (Combined Heat and Power) and non-CHP parts of the plant, and for determining their efficiencies and other parameters required by the regulator. The division of the plant into CHP and non-CHP parts is done on the basis of standard measurements carried out in practice, and the correct thermodynamic energy balance. The Energy efficiency of the CHP part is equal to a pre-set value and that of the non-CHP part is lower than this value. Instead of the Primary Energy Saving (PES) indicator, which compares the efficiency of a CHP plant with a classical plant for the production of heat energy and electricity, here we are analyzing a method that recognizes only the part of the CHP plant that fulfills the preset value of high-efficiency cogeneration. This value is prescribed by the national regulator and depends on the type and age of the plant, operating conditions, etc. Practical calculation procedures rely primarily on rules that are used in the EU (European Union). The impact of a changeable practical operating mode and the sensitivity of the referred efficiency to the attractiveness of cogeneration is particularly evaluated.

Navier–Stokes Hierarchies of Reduced MHD Models in Tokamak Geometry

We study the closure of reduced MHD models, such as the ones which are used in the modeling of Tokamaks and ITER, see Franck et al. (ESAIM: M2AN 49(5), 2015) and Guillard (2015) and references therein. We show how to modify the entropy moment methods to obtain a hierarchy of Navier–Stokes like models in potential formulation with a correct energy balance. Our procedure is well adapted to the complicated geometry of the torus. We obtain mainly two original results. One is a comparison principle between all these models: it explains that the dynamics of a reduced model is a lower bound of the dynamics of the initial model. The other one the existence of a weak solution to some of these complicate models adapted to the Tokamak geometry.

Estimation of energy budget of ionosphere-thermosphere system during two CIR-HSS events: observations and modeling

We analyze the energy budget of the ionosphere-thermosphere (IT) system during two High-Speed Streams (HSSs) on 22–31 January, 2007 (in the descending phase of solar cycle 23) and 25 April–2 May, 2011 (in the ascending phase of solar cycle 24) to understand typical features, similarities, and differences in magnetosphere-ionosphere-thermosphere (IT) coupling during HSS geomagnetic activity. We focus on the solar wind energy input into the magnetosphere (by using coupling functions) and energy partitioning within the IT system during these intervals. The Joule heating is estimated empirically. Hemispheric power is estimated based on satellite measurements. We utilize observations from TIMED/SABER (Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) to estimate nitric oxide (NO) and carbon dioxide (CO2 ) cooling emission fluxes. We perform a detailed modeling study of these two similar HSS events with the Global Ionosphere-Thermosphere Model (GITM) and different external driving inputs to understand the IT response and to address how well the model reproduces the energy transport. GITM is run in a mode with forecastable inputs. It is shown that the model captures the main features of the energy coupling, but underestimates NO cooling and auroral heating in high latitudes. Lower thermospheric forcing at 100 km altitude is important for correct energy balance of the IT system. We discuss challenges for a physics-based general forecasting approach in modeling the energy budget of moderate IT storms caused by HSSs.

Overview of Structural Life Assessment and Reliability, Part IV: Corrosion and Hydrogen Embrittlement of Naval Ship Structures

Overview of Structural Life Assessment and Reliability, Part IV: Corrosion and Hydrogen Embrittlement of Naval Ship Structures

An unconditionally stable semi-implicit FSI finite element method

Abstract The paper addresses the numerical solution of fluid–structure interaction (FSI) problems involving incompressible viscous Newtonian fluid and hyperelastic material. A well known challenge in computing FSI systems is to provide an effective time-marching algorithm, which avoids numerical instabilities due to the loose coupling of fluid and structure motion on the FSI interface. In this work, we introduce a semi-implicit finite element scheme for an Arbitrary Lagrangian–Eulerian formulation of the fluid–structure interaction problem. The approach strongly enforces the coupling conditions on the fluid–structure interface, but requires only a linear problem to be solved on each time step. Further, we prove that the numerical solution to the fully discrete problem satisfies the correct energy balance, and the stability estimate follows without any extra model simplifications or assumptions on the time step. The analysis covers the cases of Saint Venant–Kirchhoff compressible and incompressible neo-Hookean materials. Results of several numerical experiments are included to illustrate the properties of the method and its applicability for the simulation of certain hemodynamic flows. We also experiment with the enforcement of material incompressibility condition in the finite element method via an integral constraint or alternatively letting the Poisson ratio in the compressible model to be close to 1 2 . From these experiments conclusions are drawn concerning the accuracy of flow statistics prediction for incompressible vs. nearly incompressible structure models.

The Einstein–Maxwell-particle system in the York canonical basis of ADM tetrad gravity. Part 2. The weak field approximation in the 3-orthogonal gauges and Hamiltonian post-minkowskian gravity: the N-body problem and gravitational waves with asymptotic background 1This paper is one of three companion papers published in the same issue of Can. J. Phys.

In this second paper we define a post-minkowskian (PM) weak field approximation leading to a linearization of the Hamilton equations of Arnowitt–Deser–Misner (ADM) tetrad gravity in the York canonical basis in a family of nonharmonic 3-orthogonal Schwinger time gauges. The York time 3K (the relativistic inertial gauge variable, not existing in newtonian gravity, parametrizing the family, and connected to the freedom in clock synchronization, i.e., to the definition of the the shape of the instantaneous 3-spaces) is set equal to an arbitrary numerical function. The matter are considered point particles, with a Grassmann regularization of self-energies, and the electromagnetic field in the radiation gauge: an ultraviolet cutoff allows a consistent linearization, which is shown to be the lowest order of a hamiltonian PM expansion. We solve the constraints and the Hamilton equations for the tidal variables and we find PM gravitational waves with asymptotic background (and the correct quadrupole emission formula) propagating on dynamically determined non-euclidean 3-spaces. The conserved ADM energy and the Grassmann regularization of self-energies imply the correct energy balance. A generalized transverse–traceless gauge can be identified and the main tools for the detection of gravitational waves are reproduced in these nonharmonic gauges. In conclusion, we get a PM solution for the gravitational field and we identify a class of PM Einstein space–times, which will be studied in more detail in a third paper together with the PM equations of motion for the particles and their post-newtonian expansion (but in the absence of the electromagnetic field). Finally we make a discussion on the gauge problem in general relativity to understand which type of experimental observations may lead to a preferred choice for the inertial gauge variable 3K in PM space–times. In the third paper we will show that this choice is connected with the problem of dark matter.

A gradient structure for reaction–diffusion systems and for energy-drift-diffusion systems**Dedicated to Herbert Gajewski on the occasion of his 70th birthday.

In recent years the theory of the Wasserstein metric has opened up new treatments of diffusion equations as gradient systems, where the free energy or entropy take the role of the driving functional and where the space is equipped with the Wasserstein metric. We show on the formal level that this gradient structure can be generalized to reaction–diffusion systems with reversible mass-action kinetic. The metric is constructed using the dual dissipation potential, which is a quadratic functional of all chemical potentials including the mobilities as well as the reaction kinetics. The metric structure is obtained by Legendre transform from the dual dissipation potential.The same ideas extend to systems including electrostatic interactions or a correct energy balance via coupling to the heat equation. We show this by treating the semiconductor equations involving the electron and hole densities, the electrostatic potential, and the temperature. Thus, the models in Albinus et al (2002 Nonlinearity 15 367–83), which stimulated this work, have a gradient structure.

Primary Prevention of Type 2 Diabetes is Advancing towards the Mature Stage in Europe

Issues related to the prevention of type 2 diabetes (T2D) have become a major force in health care during the last decade. Although prevention of T2D is almost a matter of course today, the situation was very different only 25 years ago, that is, no serious attempts for T2D prevention existed back then [1]. Yet, diabetes has been one of the best-known chronic diseases during the past 4000 years. Nowadays, while epidemiological transition has resulted in a dramatically improved life expectancy, in particular in developed countries, the prevalence of chronic noncommunicable diseases including T2D has exploded. Previously, daily life activities and the absence of motored transportation ensured the correct energy balance and physical fitness that also guaranteed good metabolic health. This was the situation still about 50 years ago. In addition, due to limited food supply in general, excessive energy intake was uncommon for most people. Therefore, obesity was not a major public health problem until recently. The modern “era of obesity and physical inactivity” really emerged with full might around the 1970s. Every epidemic has its roots. Accordingly, every mass epidemic must be tackled with mass interventions. T2D has its origins in a complex interplay between social, behavioural, genetic, and metabolic factors. These are not easy to control. Nevertheless, the history of public health has a plethora of examples to demonstrate how preventive measures can lead to the reduction of common diseases and their consequences. While today the news headlines manifestly report that some individuals have died from avian or swine flu, deaths due to diabetes that occur every 10 seconds worldwide do not reach the threshold of news coverage. It may not be possible to eradicate chronic noncommunicable diseases, but their burden can be reduced dramatically. Good examples are coronary heart disease, stroke, lung cancer, etc. From

A study of the energy balance and melt regime on Juncal Norte Glacier, semi‐arid Andes of central Chile, using melt models of different complexity

AbstractWe use meteorological data from two automatic weather stations (AWS) on Juncal Norte Glacier, central Chile, to investigate the glacier–climate interaction and to test ablation models of different complexity. The semi‐arid Central Andes are characterized by dry summers, with precipitation close to zero, low relative humidity and intense solar radiation. We show that katabatic forcing is dominant both on the glacier tongue and in the fore field, and that low humidity and absence of clouds cause strong radiative cooling of the glacier surface. Surface albedo is basically constant for snow and ice, because of the scarcity of solid precipitation. The energy balance of the glacier is simulated for a 2‐month period in austral summer using two models of different complexity, which differ in the inclusion of the heat conduction flux into the snowpack and in the parameterization of the incoming longwave radiation. Net shortwave radiation is the dominant component of the energy balance. The sensible heat flux is always positive, while both the net longwave radiation and latent heat flux are negative. Neglecting the subsurface heat flux and corresponding variations in surface temperature leads to an overestimation of ablation of 2% over a total of 3695 mm water equivalent (w.e.) at the end of the season. Correct modelling of incoming longwave radiation is crucial, and we suggest that parameterizations based on vapour pressure and air temperature should be used rather than on computed cloud amount. We also used an enhanced temperature‐index model incorporating the shortwave radiation flux, which has two empirical parameters. We apply it both with values of parameters obtained for Alpine glaciers and recalibrated on Juncal Norte. The model recalibrated against the correct energy balance simulations performs very well. The model parameters respond to the meteorological conditions typical of this climatic setting. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Quantitative Pollutant Modelling: an Essential Prerequisite for Diesel HCCI and LTC Engine Design

To face the demand for efficient and environmentally-friendly engines, the Diesel HCCI (Homogeneous Charge Compression Ignition) and LTC (Low Temperature Combustion) concepts have been developed in order to drastically reduce the pollutant emissions of present Diesel engines at part load while maintaining their fuel consumption attractive. To be useful in the optimisation procedure of such new engine concepts, 3D CFD (Computational Fluid Dynamics) simulation softwares have to be predictive in terms of consumption and pollutants not only qualitatively (emphasising the global trends) but also quantitatively (providing reliable numbers to allow design or strategy comparisons). The implementation of accurate predictive combustion and pollutant models in 3D CFD codes are consequently a prerequisite to the use of these simulation tools to develop new combustion chamber designs or to test unconventional operating strategies. Pollutant modelling is a very difficult task because the pollutant formation and conversion during and after combustion heavily depend on the mixture formation and combustion processes that define the initial conditions for their complex chemical reactions. Furthermore, the occurring complex chemical reactions are far from being totally known. The correct prediction of the mixture formation and combustion processes are therefore essential for a correct pollutant prediction. However, the complex chemistry controlling the pollutant formation needs to be reduced to propose models that give accurate results with a reasonable CPU time consumption. For the HCCI and LTC engine concepts, the operating restrictions are mainly the NOx/soot trade-off and the noise level. The noise level may be related to the pressure rise and its prediction will therefore be a matter of accurate combustion description. On the other hand, the NOx/soot trade-off can only be numerically handled if accurate pollutant models are available. In the present study, the NOx model is the extended Zeldovitch model while the soot model is the PSK (Phenomenological Soot Kinetics) model coupled with the CORK (CO Reduced Kinetics) model to ensure a correct energy balance.

Effect of different fat supplements used during dry period of cows on colostrum physicochemical properties

The results of certain studies indicate that a relation exists between the quality of colostrum and milk and the correct balancing of energy and protein in the diet for cows in particular during the last three weeks before parturition. The aim of this study was to determine the effect of fat additives offered to cows during the dry period on the composition and physico-chemical properties of colostrum and the pre-colostrum secretion. 24 cows were assigned to one of three groups. Group I - control, received no feed additives; II - received feed supplemented by a mixture of fish and rapeseed oil in a 1:1 ratio, III - received feed supplemented by protected fat (Brgafat). In both cases the addition of fat amounted to 360g, i.e. 2% DM. All animals received a PMR concentrate in quantities calculated according to the INRA system. From all the cows samples were taken about 48 hours before parturition of the pre-colostrum secretion and directly after calving of colostrum from the first, complete milking. The samples taken were analyzed for basic composition, for the overall number of microorganisms (ONM), somatic cell count (SSC), content of urea, coagulation time after adding rennet, thermo stability as well as potential (oSH) and active (pH) acidity. The results of the studies conducted indicate that the composition and physico-chemical properties of colostrum and pre-colostrum is differentiated. Offering protected fat as a feed additive for cows during the last three weeks of the dry period had a significant effect on the share of dry matter and crude protein in the colostrum produced. The addition of a mixture of fish and rapeseed oil did not have a similar effect.

Finite element error analysis of a zeroth order approximate deconvolution model based on a mixed formulation

A suitable discretization for the Zeroth Order Model in Large Eddy Simulation of turbulent flows is sought. This is a low order model, but its importance lies in the insight that it provides for the analysis of the higher order models actually used in practice by the pioneers Stolz and Adams [N.A. Adams, S. Stolz, On the approximate deconvolution procedure for LES, Phys. Fluids 2 (1999) 1699–1701; N.A. Adams, S. Stolz, Deconvolution methods for subgrid-scale approximation in large eddy simulation, in: B.J. Geurts (Ed.), Modern Simul. Strategies for Turbulent Flow, Edwards, Philadelphia, 2001, pp. 21–44] and others. The higher order models have proven to be of high accuracy. However, stable discretizations of them have proven to be tricky and other stabilizations, such as time relaxation and eddy viscosity, are often added. We propose a discretization based on a mixed variational formulation that gives the correct energy balance. We show it to be unconditionally stable and prove convergence.

Equivalence between local Fermi gas and shell models in inclusive muon capture from nuclei

Motivated by recent studies of inclusive neutrino nucleus processes and muon capture within a correlated local Fermi gas model (LFG), we discuss the relevance of nuclear finite-size effects in these reactions at low energy, in particular for muon capture. To disentangle these effects from others coming from the reaction dynamics we employ here a simple uncorrelated shell model that embodies the typical finite-size content of the problem. The integrated decay widths of muon atoms calculated with this shell model are then compared for several nuclei with those obtained within the uncorrelated LFG, using in both models exactly the same theoretical ingredients and parameters. We find that the two predictions are in quite good agreement, within 1-7%, when the shell model density and the correct energy balance is used as input in the LFG calculation. The present study indicates that, despite the low excitation energies involved in the reaction, integrated inclusive observables, like the total muon capture width, are quite independent of the fine details of the nuclear wave functions.