High Inertia Research Articles

Simulation of the Hygrothermal Behavior of a Building Envelope Based on Phase Change Materials and a Bio-Based Concrete

Phase Change Materials (PCMs) have high thermal inertia, and hemp concrete (HC), a bio-based concrete, has strong hygroscopic behavior. In previous studies, PCM has been extensively combined with many materials, however, most of these studies focused on thermal properties while neglecting hygroscopic aspects. In this study, the two materials have been combined into a building envelope and the related hygrothermal properties have been studied. In particular, numerical studies have been performed to investigate the temperature and relative humidity behavior inside the HC, and the effect of adding PCM on the hygrothermal behavior of the HC. The results show that there is a high coupling between temperature and relative humidity inside the HC, since the relative humidity changes on the second and third days are different, with values of 8% and 4%, respectively. Also, the variation of relative humidity with temperature indicates the dominant influence of temperature on relative humidity variation. With the presence of PCM, the temperature variation inside the HC is damped due to the high thermal inertia of the PCM, which also leads to suppression of moisture evaporation and thus damping of relative humidity variation. On the second and third days, the temperature changes at the central position are reduced by 4.6% and 5.1%, compared to the quarter position. For the relative humidity change, the reductions are 5.3% and 5.4% on the second and third days, respectively. Therefore, PCM, with high thermal inertia, acts as a temperature damper and has the potential to increase the moisture buffering capacity inside the HC. This makes it possible for such a combined envelope to have both thermal and hygric inertia.

РАЗМЕЩЕНИЕ И СПЕЦИАЛИЗАЦИЯ ПРОИЗВОДСТВА ПРОДУКЦИИ СКОТОВОДСТВА В РЕГИОНАХ СТРАНЫ

The determining factor in the spatial development of agriculture was still natural conditions, however, in many regions there was a constant violation of the interaction of socio-economic and natural factors that form a relatively stable combination of dominant and complementary types of agriculture and its individual sub-sectors. Despite certain positive aspects in the spatial organization of agriculture in a few regions, which has recently begun to take into account the bioclimatic potential of the country's territory to a greater extent, its location and specialization still do not fully meet the requirements of regional systems of industry management, the creation of specialized high-tech production zones on certain types of agricultural products and sustainable development of rural areas. The existing long-term disproportions in the spatial development of agriculture are manifested in almost most regions. Its predominantly spontaneous spatial self-organization is largely a movement towards territorial desertification and economic degradation of a significant part of the country's rural areas, especially the vast but sparsely populated northern and eastern regions of the country. In this regard, when developing a forecast for the spatial development of agriculture and the layout and specialization of production for certain types of agricultural products, it is necessary to take into account not only the existing proportions of the spatial organization of the industry, but also its high inertia, which is due to the long-term nature of most of the factors that form them, since the force of inertia will continue to “shift proportions” towards the west, which predetermines a low probability of a cardinal change in the situation not only in the medium term, but possibly in the long term as well.

Optimization and Transient Analysis of Distributed Asynchronous Condenser

After the high proportion of new energy is connected, the decrease of the proportion of synchronous machine in power system will cause a series of stability hazards, such as the lack of inertia. The distributed asynchronous condenser provides a solution for the above problems because of its high controllability, high inertia and high phase advance ability. In this paper, the performance parameters of the distributed asynchronous condenser are analyzed to further optimize its structure. At the same time, the advantages and disadvantages of different excitation schemes are compared and analyzed, and the best scheme is selected; Secondly, a multi physical domain model is established to analyze the magnetic field distribution in steady-state operation and verify the error between the design value and the simulation value; Finally, the transient characteristics of distributed asynchronous condenser under different fault types and different fault parameters are analyzed. Through the above research, this paper verifies that the distributed asynchronous condenser plays the role of reactive power support and voltage regulation on the stability of new energy system.

Adaptive Sliding Mode Control Method for Onboard Supercapacitors System

Urban rail trains have undergone rapid development in recent years due to their punctuality, high capacity and energy efficiency. Urban trains require frequent start/stop operations and are, therefore, prone to high energy losses. As trains have high inertia, the energy that can be recovered from braking comes in short bursts of high power. To effectively recover such braking energy, an onboard supercapacitor system based on a radial basis function neural network-based sliding mode control system is proposed, which provides robust adaptive performance. The supercapacitor energy storage system is connected to a bidirectional DC/DC converter to provide traction energy or absorb regenerative braking energy. In the Boost and Buck modes, the state-space averaging method is used to establish a model and perform exact linearization. An adaptive sliding mode controller is designed, and simulation results show that it can effectively solve the problems of low energy utilization and large voltage fluctuations in urban rail electricity grids, and maximise the recovery and utilization of regenerative braking energy.

Structural and CFD analyses of a reciprocating-airfoil (RA) driven UAV wing under maximum lift and inertia forces

The reciprocating-airfoil (RA) driven vertical take-off and landing (VTOL) aircraft is a new aircraft concept that utilizes the reciprocating motion of the wings to provide lift for take-off and landing. The RA wings are shaped like the wings of a fixed-wing airplane and work as fixed wings while cruising. The wing undergoes substantial linear motion during take-off and may generate lift similar to a fixed-wing aircraft. The unique structural characteristics of reciprocating wings are their high inertia and lifting force loadings. This study aims to conduct an internal structural analysis of the wing under the maximum lift and inertia force to validate the wing’s performance. The reciprocating motion of the wing in a stroke was analyzed to determine its maximum speed in the stroke and its inertia force loading in conjunction with a reciprocating driver. A 3D computational fluid dynamic (CFD) analysis was conducted at the highest angle of attack (AoA) and the determined maximum speed to obtain maximum lift and drag. The results of a finite element analysis (FEA) revealed acceptable stresses, demonstrating a safe load-carrying capacity of the wing structure, which may ensure the suitability of the wing for integration with the RA UAV module.

Model reference adaptive system-based precise online inertia identification of induction motor with error utilisation technique

Time varying parameters can be estimated using either adaptive control or robust control. Robust control can be used only when the control law is fixed and varying parameters are bounded. Adaptive control is concerned with control law changing itself. Model reference adaptive system (MRAS) is an adaptive control method that can be used to identify initially unknown parameters. Variation in load and machine vibrations affect the control system performance of any motor drive system when it is in operating condition. Estimation of moment of inertia becomes essential to improve the dynamic response characteristics of any high-performance asynchronous machine (ASM) drive system. A novel method using model reference adaptive system (MRAS) with error utilisation technique (EUT) for precise identification of online varying inertia is presented in this article. The proposed method uses an interesting relation between the estimation error and actual inertia, to compensate for the error and provide high precision online inertia identification.

Fixed-time sliding mode attitude control of a flexible spacecraft with rotating appendages connected by magnetic bearing.

This study focuses on the attitude control of a flexible spacecraft comprising rotating appendages, magnetic bearings, and a satellite platform capable of carrying flexible solar panels. The kinematic and dynamic models of the spacecraft were established using Lagrange methods to describe the translation and rotation of the spacecraft system and its connected components. A simplified model of the dynamics of a five-degrees-of-freedom (DOF) active magnetic bearing was developed using the equivalent stiffness and damping methods based on the magnetic gap variations in the magnetic bearing. Next, a fixed-time sliding mode control method was proposed for each component of the spacecraft to adjust the magnetic gap of the active magnetic bearing, realize a stable rotation of the flexible solar panels, obtain a high inertia for the appendage of the spacecraft, and accurately control the attitude. Finally, the numerical simulation results of the proposed fixed-time control method were compared with those of the proportional-derivative control method to demonstrate the superiority and effectiveness of the proposed control law.

Determination of Parameters of Electronic Devices by the Method of Passive Radio-Sensor Technical Diagnostics

Introduction. Technical diagnostics (TD) as a nascent discipline is rapidly developing in the field of both software and hardware. Modern TD methods, such as vibrometry, thermal control, JTAG testing and optical control, either exhibit high inertia, consume processor time, require suspension of the electronic device, or demand a galvanic contact with the study object, which is often unacceptable. These disadvantages can be eliminated by passive radio-sensor TD. To date, little information has been published on the parameters of electronic devices provided by this method.Aim. Determination of the parameters of electronic devices, the assessment of which can be provided by passive radio-sensor TD.Materials and methods. Signal radio profiles were obtained experimentally using metrological equipment and software-numerical methods for modeling radio wave processes. The parameters of the signal radio profile were calculated by a mathematical method for solving differential equations.Results. The main principles and results of radio-sensor TD, as well as the simplest toolkit, are shown. An equation is obtained for the signal radio profile emitted by the electronic unit of the device, as well as an expression for its free components. An approach for assessing the TD correctness based on the number of free components of the received signal radio profile and the reference is described. The possibility of obtaining information about temperature, voltage drop, speed of emitting nodes, as well as the state of its components and modes of operation of p–njunctions is demonstrated. It is shown that this information is carried by the parameters of the basic equation for the signal radio profile.Conclusion. The derived basic equation allows a non-contact, remote passive radio-sensor TD to be conducted by correlation analysis of the received signal, providing a detailed examination of malfunctions in each electronic unit. The described TD method based on the presented parameters is promising for assessing the technical state of electronic devices.

Investigations for efficient design of a new counter flow double-pass curved solar air heater

The aim of this paper is to numerically investigate a new curved design of a counter flow double-pass solar air heater with arched baffles placed in the second duct. Due to high inertia of the flow and curved nature of design, fluid in second channel tend to move away from the absorber plate and thus, reduces the thermal efficiency significantly. In order to overcome this deficiency, new design parameters are introduced in the second duct in terms of arched baffles and their design is optimized for various geometric parameters such as angle of attack, variable pitch ratio etc. for best thermo-hydraulic performance. It was observed that arched baffles accelerate the flow near the absorber and facilitate the formation of large secondary vortices that enables multiple attachment zones at the absorber plate. Enhancement in thermal and hydraulic performances are discussed in terms of flow visualization, local Nusselt number, thermal effectiveness and friction factor ratio. Maximum enhancement of Nu in roughened curve counter double-pass solar air heater with baffle angles α/90 = 0.5 at P/d = 6 are found in the range of 20–28%, higher than without baffles. Moreover, two new regression correlations are developed for prediction of thermo-hydraulic performance in terms of geometrical and flow parameters.

Harmonic Analysis of Electromagnetic Torque in Brushless Direct Current Motors

This study has aimed at establishing and analyzing the causes that produce oscillations of electromagnetic torque developed by brushless direct current motor. The study opportunity is given by the progresses obtained in command and power electronics, which made this motor performant from technical and economic viewpoint. The specialty literature reveals that important torque oscillations occur in this motor in a complete rotation. That is why, this study and the simulations presented here emphasize that there are five classes of slots relatively to the torque magnitude developed and the fact that all the slots are active, that meaning that the average torque developed occurs in the rotation direction. The harmonic analysis reveals that the torque distortion, within the five classes of slots, is variable between 51.03% and 97.63%. The torques computed for the slots classes are between the minimum limit of 0.029 Nm and the maximum one of 0.077 Nm. The low speed torque oscillations can be reduced with a high inertia moment, a speed reaction loop and a performant control system. The importance of the research theme is justified by what we have presented before and is a subject of major interest for engineering.

Influence of Physical and Technical Aspects on Change of Direction Performance of Rugby Players: An Exploratory Study.

We examined the relationships between change of direction (COD) speed and deficit, and a series of speed- and power-related measurements in national team rugby union players and analyzed the influence of movement patterns on COD ability. Eleven male athletes completed the following physical assessments on different days: day 1—anthropometric measurements, and lower-body kinematic parameters (assessed with eight inertial sensors) and completion time in COD tests (pro-agility, 45° cutting maneuver (CUT), and “L” (L-Drill)); day 2—bilateral and unilateral squat and countermovement jumps, 40 m linear sprint, and bar-power output in the jump squat and half-squat exercises. Pearson’s product–moment correlations were performed to determine the relationships between COD velocities, COD deficits, and the speed–power variables. Differences between players with higher and lower COD deficits were examined using magnitude-based inferences. Results showed that (1) greater sprint momentum was associated with higher COD deficits, particularly in drills with sharper angles and multiple directional changes (L-drill and pro-agility); (2) higher unilateral jump heights were associated with greater COD deficits in the pro-agility and L-drill but not in the CUT; (3) faster athletes were less efficient at changing direction and presented greater trunk and knee flexion angles during COD maneuvers, probably as a consequence of higher inertia.

Towards understanding cork concrete behaviour: Impact of considering cork absorption during mixing process

The main objective of this paper to examine the impact of varying the considered level of cork absorption during preparation of cork concrete. For this purpose, experiments were carried out on cork concretes considering three different levels of cork absorption, namely: (i) no water, (ii) water corresponding to 2 h of cork absorption and (iii) cork saturation water. For each level of absorption, three cork percentages (25, 50 and 75%) were studied. Concretes were tested in terms of consistency, density, microstructure and hygro-thermo-mechanical properties. Microstructure’ results highlighted the impact of considering cork absorption on the porosity of concrete, its pore size distribution and the Interfacial Transition Zone (ITZ) between cork and matrix. By increasing the considered level of cork absorption, the hygric performance of cork concretes was substantially improved. For instance, by going from zero to a saturation level, an increase of 20% was recorded on Moisture Buffer Value (MBV) of concrete with 75% of cork. The best thermal conductivity was obtained for concretes incorporating water corresponding to 2 h of cork absorption. However, the highest specific heat (Cp), value that insure high thermal inertia, was recorded for concretes containing cork saturation water. Depending on water amount and cork percentage, thermal conductivity of concretes ranged between 140 and 1230 mW/(m.K). Notwithstanding the decrease of compressive strength with increasing cork absorption water, the produced concretes exhibited good performance for the use as non-structural materials.

Modeling of the tunnel kiln control system taking into account the features of the pid controller and fuzzy logic

Taking into account the non-linear, time-varying temperature characteristics of the tunnel kiln, high inertia and some uncertainty of its parameters, it’s difficult to create an accurate mathematical model and get an acceptable set of the controller of the control system. The asynchronous motor actuator of the system, which regulates the amount of gas and air to change the temperature, gives the system first-order a statism. A conventional PID controller does not provide the required quality parameters of temperature control in the entire possible range of changes in the parameters of the controlled object. Thus, the synthesis of an additional fuzzy PID controller is required to ensure the required quality of regulation. Of course, PID control and fuzzy intelligence will provide effective self-tuning of the parameters of controlled PID controllers. A simulation experiment in Matlab shows that fuzzy PID control reduces the time and magnitude of overshoot, effectively increasing the stability of the system by giving it robustness properties.

Incorporating decadal climate variability information in the operation and design of water infrastructure

Abstract The high thermal and mechanical inertia of the oceans results in slow changes in sea surface temperatures (SSTs). Changes in SSTs, in turn, can impact atmospheric circulation including water vapor transport, precipitation, and temperatures throughout the world. The Pacific Decadal Oscillation (PDO), the tropical Atlantic SST gradient variability, and the West Pacific Warm Pool are patterns of natural climate variability that tend to persist over decadal time periods. There are current efforts to produce decadal climate predictions, but there is limited understanding if this information can be used in water resources management. Understanding the current state of decadal climate variability (DCV) phenomena and the probability of persisting in that state may be useful information for water managers. This information could improve forecasts that aid operations and short-term planning for reservoir management, domestic and industrial water supplies, flood risk management, energy production, recreation, inland navigation, and irrigation. If conditions indicate a higher likelihood of drought, reservoir managers could reduce flood storage space and increase storage for conservation purposes. Improved forecasts for irrigation could result in greater efficiencies by shifting crops and rotational crop patterns. The potential benefits of using a forecast must be balanced against the risk of damages if the forecast is wrong. Seasonal forecasts using DCV information could also be used to inform drought triggers. If DCV indices indicate that the climate has a higher probability of dry conditions, drought contingency plans could be triggered earlier. Understanding of DCV phenomena could also improve long-range water resources planning. DCV can manifest itself in relatively short-term hydrologic records as linear trends that complicate hydrologic frequency analysis, which has traditionally assumed that hydrologic records are stationary.

Virtual Inertia-Based Multipower Level Controller for Inductive Electric Vehicle Charging Systems

A method of modulating the power level of a grid-supplied inductive electric vehicle (EV) charger to provide frequency stabilization to the utility grid is presented. The proposed controller can allow inductive EV charging systems to effectively respond to grid frequency fluctuations by online regulating the charging level and adding high virtual inertia. A new IPT multipower level controller using simplified digital circuits is designed. The virtual inertia control/controller (VIC) is incorporated into the proposed multipower level controller which gets the grid frequency measurement and online adjust the IPT’s charging level. Using the proposed VIC IPT charger, the switching cycles, as a result, the power transfer from the grid to the EV can be regulated in response to the grid frequency change. The simulation results of the proposed VIC IPT power controller are presented to show its effectiveness in response to power grid fluctuations. The proposed virtual inertia based controller is experimentally implemented and verified on an IPT setup connected to an actual small-scale Labvolt testbed.

Long-Term Energy Demand Forecasting Based on a Systems Analysis

—Energy demand forecasting plays a key role in solving the majority of problems connected with determining the economic and energy development prospects. In view of high inertia and capital intensity of energy generation facilities, the changes in the energy consumption structure and rates should be considered for a sufficiently long-term future of no less than 15 years. This adds much difficulty to the development of such forecasts, because it is necessary to take into account the possible results of technological progress in different sectors of the economy and changes in its structure. The suggested approach to energy demand forecasting is based on the systems analysis methods. Energy consumers are disaggregated by economic sectors, country regions, energy carriers, and their utilization areas. As a result, it becomes possible to take into account the possible future technological and structural changes in the economy, its differences in different regions, mutual replacements of energy carriers, and energy saving. The most important feature of the approach is that it involves the separation of economic and energy variables. Economic variables determine the development scales of economic sectors, and energy variables determine the energy consumption intensities in them. The separation of variables helps obtain essentially more accurate forecasts owing to the possibility of taking into account the differences in the variation trends of these variables in the forecast period. For forecasting the economic variables, a nonlinear conditionally dynamic model of interrelations between the economy and energy is used. The energy variables are forecasted on the basis of their links with economic factors, e.g., with cumulative investments in the fixed capital of the considered economic sectors. The discussed approach was implemented as the totality of adaptive simulation models united into the EDFS computing system. The approach was repeatedly and quite successfully used to forecast the energy demand for an up to 10–20-year horizon in solving various problems. The gained experience has demonstrated the correctness of applying the approach for solving long-horizon forecast problems. To illustrate the capacities of the approach, the electric energy demand forecast for the period of up to 2040 for the basic version of the social and economic development of Russia’s economy prepared on the basis of this approach is presented.

A hybrid robust-stochastic approach for unit commitment scheduling in integrated thermal electrical systems considering high penetration of solar power

With increasing environmental concerns, limited oil reserves and governmental incentives, installation of photovoltaic (PV) systems have gained substantial momentum in smart electric distribution systems (EDS), which is considered to be a great success. That said, widespread integration of these PV units, comes with uncertainty issues that puts the flexibility of the system at stake. In this regard, local district heating systems (DHS) are considered to be an effective tool in enhancing the flexibility of the power system on account of their high thermal inertia. In this study, we propose hybrid robust (RO)- stochastic programming (SP) optimization framework for commitment scheduling of distributed generation units and local DHS considering high penetration of PV units. Furthermore, the impact of flexible thermal and electrical loads on total operational cost and overall flexibility of the system is evaluated. The SP is utilized to deal obscurity of solar radiation, and RO is utilized to handle price uncertainties. The uncertainty management via the electrical storage system is also scrutinized. The results are evaluated by different cases studies implemented on an integrated IEEE 33-bus EDS and an 8-node DHS. Eventually, the mixed integer linear problem is solved with a standard CPLEX solver.

A Spatially-Explicit Economic and Financial Assessment of Closed-Loop Ground-Source Geothermal Heat Pumps: A Case Study for the Residential Buildings of Valle d’Aosta Region

Ground Source Heat Pumps (GSHPs) take advantage of the high thermal inertia of the ground to achieve a higher energy efficiency compared to Air Source Heat Pumps. GSHPs, therefore, have the potential to reduce heating, cooling, and domestic hot water costs, however the high installation cost of borehole heat exchangers (BHEs) limits the growth of such installations. Nevertheless, GSHPs can be profitable under certain conditions (climate, expensive fuels, subsidies, etc.), which can be identified using geo-referenced data and Geographical Information Systems (GIS). The proposed work investigates the economic and financial ability of GSHPs to cover the heat demand of the residential building stock of the Italian region Valle d’Aosta. To identify the opportunities offered by GSHPs in the Valle d’Aosta region, more than 40,000 residential buildings were analyzed using a GIS-based method. The return on the investment was then assessed based on the occurrence of two conditions—the Italian subsidies of the “Conto Termico” and the installation of rooftop photovoltaic (PV) systems—which contribute to the reduction of the initial and operation costs, respectively. The life-cycle costs of the four resulting combinations were compared with conventional systems composed of an oil/gas boiler and an air-source chiller. One of the main findings of this study is that subsidies exert a key role in the financial feasibility of GSHPs, especially for replacing gas boilers, whereas the presence of a PV system has a minor influence on the financial analysis carried out.

Impact of High Inertia Particles on the Shock Layer and Heat Transfer in a Heterogeneous Supersonic Flow around a Blunt Body

One of the most important and complex effects associated with the presence of particles in the flow is the gas-dynamic interaction of particles with the shock layer. Of particular interest is the intensification of heat transfer by high inertia particles rebounding from the surface or by the products of erosion destruction, which reach the front of the bow shock wave and violate the gas-dynamic structure of the flow. In this case, according to experimental data, the increase in heat fluxes is much greater than it could be predicted based on the combined action of the kinetic energy of particles and a high-speed flow. The problem is related to the destruction of the flow structure. In this paper, the problem is studied with numerical simulation. We show that the key role in the intensification of heat transfer is played by the formation of an impact jet flowing onto the surface. An area of increased pressure and heat flux is formed in the zone of action of the impact jet. This effect is maintained over time by the successive action of particles.

Transient behaviour and optimal start-up procedure of closed Brayton cycle with high thermal inertia

• Precise dynamic simulation of a closed Brayton cycle with high thermal inertia is achieved based on test data and optimization algorithm. • Thermal inertia of the regenerator is critical to fast and stable full-load operation. • Initial pressure ratio takes great effect on the start-up time and start-up power consumption. • The rotor speed should be accelerated when the compressor inlet pressure arrives at 60%-65% design value. The closed Brayton cycle is promising as a power generation system owing to its output flexibility and compactness. In this study, a small closed Brayton cycle device was developed and its transient characteristics were studied experimentally and numerically. The start-up procedure for a closed Brayton cycle with considerable thermal inertia and heat dissipation was investigated. First, a modelling method based on both test data and an optimisation algorithm was developed to improve the accuracy of the dynamic simulation of the closed Brayton cycle. The optimal values of model parameters describing the thermal inertia and heat dissipation of the components were obtained by matching a group of dynamic test data using a genetic algorithm. The precision of the model was validated against additional experimental data. Then, the Pareto front of the start-up procedure, which was characterised by the time parameters concerning acceleration and injection, pressure coefficient, androtor speed, was acquired using a double-objective genetic algorithm with the goal of obtaining the smallest values for the start-up time and start-up power. Further studies showed that adjusting the sequence of acceleration and injection could help overcoming the thermal inertia of the regenerator, which was critical for fast and stable full-load operation. Firstly, selecting the appropriate initial pressure coefficient, then accelerating and then injecting was a favourable start-up procedure.