The climate of Houston, classified as a humid subtropical climate with tropical influences, makes the heating, ventilation, and air conditioning (HVAC) systems the largest electricity consumers in buildings. HVAC systems in commercial buildings are usually operated by a centralized control system and/or an energy management system based on a fixed schedule and scheduled control of a zone setpoint, which is not appropriate for many buildings with changing occupancy rates. Lately, as part of energy efficiency analysis, attention has focused on collecting and analyzing smart meters and building-related data, as well as applying supervised learning techniques, to propose new strategies to operate HVAC systems and reduce energy consumption. On the other hand, unsupervised learning techniques have been used to study the consumption information and profile characterization of different buildings after cluster analysis is performed. This paper adopts a different approach by revealing the power... [more]

Proton exchange membrane fuel cells (PEMFCs) have been utilized as a promising power source for new energy vehicles. Their performances are greatly affected by the structural design of the flow field in the bipolar plate. In this paper, we present a novel three-dimensional (3D) bionic cathode flow field, inspired by the small intestinal villi. The structural design and working principle of the 3D bionic flow field units are first described. A 3D numerical model is developed to study the mass transfer and distribution of the reactants and products, as well as the polarization performances of the PEMFC with the 3D bionic cathode flow field. The simulation results indicate that the proposed 3D bionic flow field can significantly improve the reaction gas supply from the flow field to porous electrodes, and thus would be beneficial for the removal of liquid water in the cathode. The mass transfer of gas in the PEMFC can be enhanced due to the increasing contact areas between the gas diffusi... [more]

The relationships between crude oil prices and exchange rates have always been of interest to academics and policy analysts. There are theoretical transmission channels that justify such links; however, the empirical evidence is not clear. Most of the studies on causal relationships in this area have been restricted to a linear framework, which can omit important properties of the investigated dependencies that could be exploited for forecasting purposes. Based on the nonlinear Granger causality tests, we found strong bidirectional causal relations between crude oil prices and two currency pairs: EUR/USD, GBP/USD, and weaker between crude oil prices and JPY/USD. We showed that the significance of these relations has changed in recent years. We also made an attempt to find an effective strategy to forecast crude oil prices using the investigated exchange rates as regressors and vice versa. To this aim, we applied Support Vector Regression (SVR)—the machine learning method of time series... [more]

With the expansion of system scale and the reduction in simulation step size, the design of a power system real-time simulation platform faces many difficulties. The interactive operation of real-time simulation presents the characteristics of phased and centralized. This paper proposes selecting the appropriate simulation method for each sub-network according to the system operation requirements, and the sub-network simulation method can be changed with the change in system operation requirements in the simulation process. In order to change the sub-network simulation method in the simulation process, a high flexibility hybrid architecture real-time simulation platform based on FPGA was designed. The main body of the architecture runs in the high control mode of instruction flow and uses instruction flexibility to realize the requirement of changing methods. The algorithm modularity architecture is used as an auxiliary architecture to reduce the instruction cost and increase the compu... [more]

Using a cross-country dataset covering 9265 observations on 1785 firms representing 53 countries over the period 2004−2019, this study investigates the relation between carbon emissions reduction and corporate financial performance (CFP). We perform OLS regressions with fixed effects. We found that carbon emissions reduction increases the return on assets, the return on equity, and the return on sales, whereas it has no effect on the Tobin’s Q and the current ratio. The positive relationship with the return on assets is stronger for firms with a higher responsibility score. We study country characteristics by modeling GDP growth, overall emissions within a country, and the presence of carbon emissions legislation. Our results indicate that the overall carbon emissions of a country and the presence of carbon emissions legislation are related to both corporate carbon emissions reduction and CFP. Moderating effects of the country’s overall emissions and the presence of carbon emissions le... [more]

This article presents the results of the design of acoustic−magnetic device thermal protection technology based on simulation. The acoustic−magnetic device (AMD) was installed in the heat supply system of a greenhouse complex with a geothermal heat source, developed and patented by the authors of this paper. Simulation was performed to investigate the possibility of maintaining the acoustic transmitter temperature of the acoustic−magnetic device in its operating range. The QuickField Student Edition v 6.4 simulation environment was used for this purpose. Based on the results of the simulation, the optimum thermal mode of the acoustic−magnetic device was developed and implemented. The optimum temporal operating mode of the acoustic−magnetic device is necessary for the optimization of the non-reagent treatment of geothermal water in a heat supply system of a greenhouse complex. It allows for a considerable reduction in the intensity of scale formation in the heat exchanger and equipment... [more]

The Caspian Sea is a region of active hydrocarbon production, where apart from conventional accumulations, gas hydrates (GH) are known to exist. GH are a potential future source of energy, however, currently they pose danger for development of conventional fields. The goal of this research was to determine the area of GH distribution and thickness of their stability zone in the Caspian Sea using numerical modeling and to define how certain parameters affect the calculated thickness. As a result of the research, cartographic schemes were created for the South and Middle Caspian, where GH were predicted. For the South Caspian, conditions for methane hydrates formation exist at depths of more than 419−454 m, and for the Middle Caspian, more than 416−453 m. The maximal thicknesses of methane hydrates stability zones for the South Caspian can reach 900−956 m, and for the Middle Caspian, 226−676 m. Variations of parameters of seafloor depth, geothermal gradient and gas composition can signif... [more]

The discrimination of inrush currents and internal fault currents in transformers is an important feature of a transformer protection scheme. The harmonic current restrained feature is used in conventional differential relay protection of transformers. A literature survey shows that the discrimination between the inrush currents and internal fault currents is still an area that is open to research. In this paper, the classification of internal fault currents and magnetic inrush currents in the transformer is performed by using an extended Kalman filter (EKF) algorithm. When a transformer is energized under normal conditions, the EKF estimates the primary side winding current and, hence, the absolute residual signal (ARS) value is zero. The ARS value will not be equal to zero for internal fault and inrush phenomena conditions; hence, the EKF algorithm will be used for discriminating the internal faults and inrush faults by keeping the threshold level to the ARS value. The simulation res... [more]

The current practice for multi-fractured horizontal well development in low-permeability reservoirs is to complete the full length of the well with evenly spaced fracture stages. Given methods to evaluate along-well variability in reservoir quality and to predict stage-by-stage performance, it may be possible to reduce the number of stages completed in a well without a significant sacrifice in well performance. Provision and demonstration of these methods is the goal of the current two-part study. In Part 1 of this study, reservoir and completion quality were evaluated along the length of a horizontal well in the Montney Formation in western Canada. In the current (Part 2) study, the along-well reservoir property estimates are first used to forecast per-stage production variability, and then used to evaluate production performance of the well when fewer stages are completed in higher quality reservoir. A rigorous and fast semi-analytical model was used for forecasting, with constraints... [more]

Geothermal power plants are excellent resources for providing low carbon electricity generation with high reliability. However, many geothermal power plants could realize significant improvements in operational efficiency from the application of improved modeling software. Increased integration of digital twins into geothermal operations will not only enable engineers to better understand the complex interplay of components in larger systems but will also enable enhanced exploration of the operational space with the recent advances in artificial intelligence (AI) and machine learning (ML) tools. Such innovations in geothermal operational analysis have been deterred by several challenges, most notably, the challenge in applying idealized thermodynamic models to imperfect as-built systems with constant degradation of nominal performance. This paper presents GOOML: a new framework for Geothermal Operational Optimization with Machine Learning. By taking a hybrid data-driven thermodynamics... [more]

The recently issued EN ISO 52016-1 technical standard provides a new simplified dynamic method for the building energy performance assessment. Since an extensive validation of the EN ISO 52016-1 hourly method is still missing, the present work investigates the effect of the main modelling assumptions—related to the heat balance on the outdoor and the indoor envelope surfaces—on the building thermal behaviour. The model validation was carried out by assessing the accuracy variation consequent to the application of the EN ISO 52016-1 modelling assumptions to a detailed dynamic calculation tool (EnergyPlus). To guarantee a general validity of the outcomes, two buildings, two levels of thermal insulation, and two Italian climatic zones were considered, for a total of eight case studies. To explore different applications of the standard method, the analysis was performed both under a free-floating condition—to evaluate the accuracy of the model in predicting the indoor operative temperature... [more]

Mathematical models of induction motor (IM) used in direct field-oriented control (DFOC) strategies are characterized by parametrization resulting from the IM equivalent circuit and model-type selection. The parameter inaccuracy causes DFOC detuning, which deteriorates the drive performance. Therefore, many methods for parameter adaptation were developed in the literature. One class of algorithms, popular due to their simplicity, includes estimators based on the model reference adaptive system (MRAS). Their main disadvantage is the dependence on other machines’ parameters. However, although typically not considered in the respective literature, there are other aspects that impair the performance of the MRAS estimators. These include, but are not limited to, the nonlinear phenomenon of iron losses, the effect of necessary discretization of the algorithms and selection of the sampling time, and the influence of the supply inverter nonlinear behavior. Therefore, this paper aims to study t... [more]

One of the alternatives to reduce CO2 emissions from industrial sources (mainly the oil and gas industry) is CO2 capture. Absorption with chemical solvents (alkanolamines in aqueous solutions) is the most widely used conventional technology for CO2 capture. Despite the competitive advantages of chemical solvents, the technological challenge in improving the absorption process is to apply alternative solvents, reducing energy demand and increasing the CO2 captured per unit of solvent mass. This work presents an experimental study related to the kinetic and thermodynamic analysis of high-pressure CO2 capture using ethylenediamine (EDA) as a chemical solvent. EDA has two amine groups that can increase the CO2 capture capacity per unit of solvent. A non-stirred experimental setup was installed and commissioned for CO2 capture testing. Tests of the solubility of CO2 in water were carried out to validate the experimental setup. CO2 capture testing was accomplished using EDA in aqueous soluti... [more]

This paper presents research on the effects of the multiple injection strategies on the combustion and emission characteristics of a two-stroke heavy-duty marine engine at full load. The ANSYS FLUENT simulation software was used to conduct three-dimensional simulations of the combustion process and emission formations inside the engine cylinder in both single- and double-injection modes to analyze the in-cylinder pressure, temperature, and emission characteristics. The simulation results were then compared and showed good agreement with the measured values reported in the engine’s sea-trial technical reports. The simulation results showed reductions in the in-cylinder pressure and temperature peaks by 6.42% and 12.76%, while NO and soot emissions were reduced up to 24.16% and 68%, respectively, in the double-injection mode in comparison with the single-injection mode. However, the double-injection strategy increased the CO2 emission (7.58%) and ISFOC (23.55%) compared to the single-inj... [more]

The RANS (Reynolds-averaged Navier−Stokes equations) with CFD (Computational Fluid Dynamics) simulation method is used to analyze the head hump formation mechanism in the double-suction centrifugal pump under a part load condition. The purpose is to establish a clear connection between the head hump and the microcosmic flow field structure, and reveal the influence mechanism between them. It is found that the diffuser stall causes a change in the impeller capacity for work, and this is the most critical reason for hump formation. The change in the hydraulic loss of volute is also a reason for hump, and it is analyzed using the energy balance equation. The hump formation mechanism has not been fully revealed so far. This paper found the most critical flow structure inducing hump and revealed its inducing mechanism, and greatly promoted the understanding of hump formation. The impeller capacity for work is analyzed using torque and rotational speed directly, avoiding large error caused b... [more]

This paper introduces a new analytical method for the 3-dimensional analysis of heat sources installed underground. Such sources include primarily electric power cables and steam pipes in urban areas. For complex arrangements of the heat sources, the heat transfer and cable rating calculations require the application of numerical methods, which call for high level of expertise and are generally difficult to use. The computational algorithm presented in this paper uses a point sources approach and is an extension of the work published by the authors based on line source modeling, with the goal of simplifying the numerical calculations. The proposed approach is applicable for all heat sources, which are directly buried in a uniform or a partially dried out soil. The method is illustrated by several numerical examples. These examples are used for comparison with the existing standard approach.

At Université Libre de Bruxelles (ULB), research was performed on a 1 kN lab-scale Hybrid Rocket Motor (the ULB-HRM). It has a single-port solid paraffin fuel grain and uses liquid N2O as an oxidizer. The first Computational Fluid Dynamics (CFD) model of the motor was developed in 2020 and improved in 2021, using ANSYS Fluent software. It is a 2D axisymmetric, two-phase steady-state Reynolds-Averaged Navier−Stokes (RANS) model, which uses the average fuel and oxidizer mass flow rates as inputs. It includes oxidizer spray droplets and entrained fuel droplets, therefore adding many additional parameters compared to a single-phase model. It must be investigated how they affect the predicted operating conditions. In this article, a sensitivity analysis is performed to determine the model’s robustness. It is demonstrated that the CFD model performs well within the boundaries of its purpose, with average deviations between predicted and experimental values of about 1% for the chamber pressur... [more]

Having a photovoltaic (PV) system raises the question of whether it runs as expected. Measuring its energy yield takes a long time and the result still contains uncertainties from varying weather conditions and possible shading of the modules. Here, a free software PVcheck to measure the peak power of the system is announced, using the power data of a single sunny day. The software loads a data file of the generated power as a function of time from this day. This data file is provided by typical inverters. The software then simulates this power curve using known parameters like angle and location of the PV system. The assumed peak power of the simulation can then be adjusted so that the simulated curve matches the measured one. The software runs under Microsoft Windows™ and makes use of the free library pvlib python. The simulation can be refined by importing weather data like temperature, wind speed, and insolation. Furthermore, curves describing the nominal module efficiency as a fun... [more]

Most of today’s water supply systems are based on plastic pipes. They are characterized by the retarded strain (RS) that takes place in the walls of these pipes. The occurrence of RS increases energy losses and leads to a different form of the basic equations describing the transient pipe flow. In this paper, the RS is calculated with the use of convolution integral of the local derivative of pressure and creep function that describes the viscoelastic behavior of the pipe-wall material. The main equations of a discrete bubble cavity model (DBCM) are based on a momentum equation of two-phase vaporous cavitating flow and continuity equations written initially separately for the gas and liquid phase. In transient flows, another important source of pressure damping is skin friction. Accordingly, the wall shear stress model also required necessary modifications. The final partial derivative set of equations was solved with the use of the method of characteristics (MOC), which transforms the... [more]

In solar-thermal adsorption/desorption processes, it is not always possible to preserve equal operating times for the adsorption/desorption modes due to the fluctuating supply nature of the source which largely affects the system’s operating conditions. This paper seeks to examine the impact of adopting unequal adsorption/desorption times on the entire cooling performance of solar adsorption systems. A cooling system with silica gel−water as adsorbent-adsorbate pair has been built and tested under the climatic condition of Iraq. A mathematical model has been established to predict the system performance, and the results are successfully validated via the experimental findings. The results show that, the system can be operational at the unequal adsorption/desorption times. The performance of the system with equal time is almost twice that of the unequal one. The roles of adsorption velocity, adsorption capacity, overall heat transfer coefficient, and the performance of the cooling syste... [more]

A suitable ice slurry fluid with a suitable ice concentration ratio can save operational costs. The design of the optimal ice slurry concentration focuses on finding an evolution strategy, which can further minimize the power consumption of the pump. A theoretical model was established to simulate the effect of different ice concentrations and flow rates on the performance of the pump. The data obtained were fitted by curve-fitting function. The process was modeled in the MATLAB evolutionary strategy algorithm to obtain the configuration scheme of the ice concentration and flow under different refrigeration capacities. The simulation results showed that when the required cooling capacity was 13.889 kWh, ice concentration was set to 19.68%, and flow rate was set to 2.1075 × 10−4 m3/s, the power consumption could be reduced by 23%.

This paper evaluates the performance of coordinated control across advanced distribution management systems (ADMS), distributed energy resources (DERs), and distributed energy resource management systems (DERMS) using an advanced hardware-in-the-loop (HIL) platform. This platform provides a realistic laboratory testing environment, including accurate dynamic modeling of a real-world distribution system from a utility partner, real controllers (ADMS and DERMS), physical power hardware (DERs), and standard communications protocols. One grid service—voltage regulation—is evaluated to show the performance of the coordinated grid automation system. The testing results demonstrate that the coordinated DERMS and ADMS system can effectively regulate system voltages within target operation limits using DERs. The realistic laboratory HIL testing results give utilities confidence in adopting the grid automation systems to manage DERs to achieve system-level control and operation objectives (e.g.,... [more]

The article presents a proposal to reduce energy consumption in a hydraulic system with a single pump and multiple receivers. The proposed Load-Sensing Basic (LSB) solution consists of expanding a typical hydraulic system by using additional logic valves and a dedicated differential valve. The modification is aimed at decrease in operating pressure and, thus, reduction in energy consumption. The LSB system is compact as all components are built on a single ISO plate. A detailed mathematical model of the system was formulated, then a simulation model was built and numerical tests were carried out in the Matlab/Simulink environment. The obtained results indicate that the use of the proposed LSB system for the implementation of typical working cycles with three actuators may reduce energy consumption by 4−30%, and under certain conditions even up to 70%.

Current electric vehicle (EV) charging systems have limited smart functionality, and most research focuses on load-balancing the national or regional grid. In this article, we focus on supporting the early design of a smart charging system that can effectively and efficiently charge a company’s EV fleet, maximizing the use of self-generated Photo-Voltaic energy. The support takes place in the form of the Vehicle Charging Simulation (VeCS) model. System performance is determined by operational costs, CO2 emissions and employee satisfaction. Two impactful smart charging functions concern adaptive charging speeds and charging point management. Simulation algorithms for these functions are developed. The VeCS model is developed to simulate implementation of a smart charging system incorporating both charging infrastructure and local Photo-Voltaics input, using a company’s travel and energy data, prior to having the EVs in place. The model takes into account travel behaviour, energy input a... [more]

Since both ethanol and acetone are the main components in many alternative fuels, research on the burning characteristics of ethanol-acetone blends is important to understand the combustion phenomena of these alternative fuels. In the present study, the burning characteristics of ethanol-acetone fuel blends are investigated at a temperature of 358 K and pressure of 0.1 MPa with equivalence ratios ranging from 0.7 to 1.4. Ethanol at 100% vol., 25% vol. ethanol/75% vol. acetone, 50% vol. ethanol/50% vol. acetone, 75% vol. ethanol/25% vol. acetone, and 100% vol. acetone are studied by the constant volume combustion chamber (CVCC) method. The results show that the laminar burning velocities of the fuel blends are between that of 100% vol. acetone and 100% vol. ethanol. As the ethanol content increases, the laminar burning velocities of the mixed fuels increase. Furthermore, a detailed chemical kinetic mechanism (AramcoMech 3.0) is used for simulating the burning characteristics of the mixt... [more]