Mathematical Energy Model Research Articles

Artificial Intelligence Enabled Energy-Saving Drive Unit With Speed and Displacement Variable Pumps for Electro-Hydraulic Systems

In this paper, an artificial intelligence enabled energy-saving strategy (AIESS) is proposed to achieve high energy efficiency of hydraulic systems with a speed and displacement variable pump (SDVP). The AIESS, which integrates extreme gradient boosting (XGBoost) and genetic algorithm (GA), can generate the optimum combination of motor speed and pump displacement of SDVP in real time under actual working conditions. The XGBoost-based power model is used to accurately predict the input power of the SDVP considering environmental factors, e.g., oil temperature, then followed by GA for optimization, in which the XGBoost-based power model is the objective function. A test rig with a 16t hydraulic press and a stamping process is applied to validate the effectiveness of the proposed strategy. Compared to four other algorithm models, the XGBoost-based power model has the highest accuracy. The optimum combination can be obtained quickly by GA. The results show that the AIESS can reduce energy consumption by 28.6% during pressure-maintaining operation and by 11.2% during one stamping cycle compared to the previously proposed segmented control energy-saving strategy. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Energy-saving hydraulic system is a topic in the automation industry. The low energy efficiency of electro-hydraulic systems is mainly caused by poor flow rate matching. A speed and displacement variable pump (SDVP) is used to address this problem, but it is difficult to find the matched speed and displacement for the highest energy conversion efficiency of the SDVP due to the inaccuracy energy model and the challenge of coupling variables. This paper presents an energy-saving strategy integrated with machine learning and a genetic algorithm to handle this challenge. Relative variables of the machine learning model are picked through analysis of the mathematical energy model, and the usage of machine learning can fit the high-nonlinear energy model caused by uncertainties in both components and environmental factors. The trained model is then used as an objective function for a GA-based optimization process to generate the optimum motor speed and pump displacement combination. Considering the processing time of GA, this combination can be optimized before the operation for known working conditions. Finally, we have established a 16t hydraulic press to validate this energy-saving strategy and pre-optimized five combinations for a stamping process. The proposed strategy can reduce energy consumption by 11.2% compared with the previous strategy. This energy-saving strategy can also be applied to other automated hydraulic equipment, such as injection machines.

Data Driven Methods for Finding Coefficients of Aerodynamic Drag and Rolling Resistance of Electric Vehicles

This research investigated an alternate method for establishing the complex coefficients used in an electric vehicle’s mathematical energy consumption model. While other methods for creating electric vehicle energy models exist, it would be beneficial to have a rapid and inexpensive technique that remains accurate. Producing a mathematical energy model for such a vehicle has the challenge of determining its aerodynamic drag and rolling resistance coefficients. Currently and most often, expensive and tedious (time-consuming) methods are used to find these coefficients. Computational fluid dynamics (CFD), wind tunnel testing, and extensive mathematics make this objective challenging. For this work, a solar-powered electric vehicle provided the source data to derive its coefficients cost-effectively and efficiently. Data were collected during a road test of the solar electric vehicle from South Africa to Namibia stretching over 2000 km, in which all required energy variables were recorded. The collected data were used in an optimisation routine to establish the two coefficients by minimising the actual and modelled energy consumption error and controlling the driving speed. The outcome of the optimisation routine produced accurate coefficients with a final error value of less than 5% when applied to a validation data set not used during optimisation. With minor modifications, this method may be integrated into any electric vehicle computer system to autonomously identify its two hard-to-find coefficients while driving, which can be used to provide an accurate and realistic driving range estimation to the driver.

Thermodynamic analysis of NH3/CO2 cascade refrigeration system with thermosyphon refrigerant cooling screw compressor motor

The cooling of the motor is one of key factors of keeping higher running efficiency of the refrigeration compressor. Suction refrigerant gas cooling motor is a widely used cooling method but it has poor cooling effect. A novel method of directly cooling screw compressor motor by thermosyphon refrigerant was proposed by authors. In this paper, the refrigeration system with thermosyphon refrigerant cooling motor (RSTRCM) and its basic principle were introduced firstly, then the mathematical model of energy and exergy of the system was built, and the test loop of an NH3/CO2 cascade refrigeration system was set up. Finally, compared with the refrigeration system with compressor suction gas cooling motor (RSCSCM), numerical analysis results showed that as condensation temperature of LTL is 5°C, RSTRCM can get higher exergy efficiency by up to 23.53%, and if condensing temperature of LTL increases from -5°C to 5°C, the power consumption of CO2 compressor and NH3 compressor in RSTRCM were reduced by 4.26% and 5.46% on average, separately. The test results showed that as the condensing temperature of the system is 40°C and the evaporation temperature is -45°C, -35°C, and -30°C, the coefficient of performance (COP) of RSTRCM were higher than that of RSCSCM by 10.42%, 6.61%, and 6.25%, respectively, which verify that the method of thermosyphon refrigerant cooling compressor motors can significantly improve the performance of the NH3/CO2 cascade refrigeration system.

Research on the Precession Characteristics of Hemispherical Resonator Gyro

Hemispherical Resonator Gyro (HRG) is a new type gyro with high precision, high reliability, shock resistance, no need of preheating, short start time, and long life. It is a kind of vibrating gyro with standing wave rotating along the sensitive base of annular precession, has a unique application prospect in the field of high precision inertial sensors, and is widely used in unmanned aerial vehicle control in complex environments. Based on the theory of the structure characteristics of the hemispherical resonator, the mathematical model of energy of the resonator is established to research the rule of resonant frequency when the hemispherical resonator is rotated around the central axis. In this paper, the influence of precession factor, which are the top angle, the bottom angle, and wall unevenness of the hemispherical resonator, are analyzed. A series of hemispherical resonator models are constructed by ANSYS software to prove the results of theoretical research. The simulation results show that precession factor of the hemispherical resonator is more sensitive of the top angle than the bottom angle, and the error of angular velocity which is caused by the change of the top angle is larger than that which is caused by the change of the bottom angle.

Mechanical structure optimization of energy storage tank group in MEES system

The energy storage component of the MEES system is mechanical elastic energy storage tank group. Whether the mechanical structure design of energy storage tank is reasonable or not directly determines the performance of the whole system. In this paper, the structural design scheme of series linkage energy storage tank group is proposed, which can take into account the energy storage capacity and power demand. Firstly, the structural group of energy storage tank group is analyzed. Secondly, the operation mode of energy storage and power generation process of energy storage tank group is described in detail. Finally, the mathematical model of energy storage/generation operation is established, which provides theoretical guidance for the configuration of capacity and power of energy storage tank group.

A comparative study of γAl2O3–C2H6O2 and γAl2O3–H2O near a vertical curved surface having porous medium

The present analysis reveals the impact of porous medium and mixed convection nano-fluid flow near an exponentially curved surface. For this purpose alumina is treated as nano-particles along with two base fluids such as H2O and C2H6O2. Under different assumptions the mathematical model of energy and momentum equations are developed by using curvilinear coordinates. The PDEs are transformed into non-linear differential equations by using similarity transformation variables. The table of skin friction and Nusselt number are drawn by fluctuating the values of different parameters for both fluids. Moreover, the numerical solutions are generated in MATLAB by using Bvp4c. Influence of effective and without effective Pr numbers for an incompressible γAl2O3−C2H6O2 and γAl2O3−H2O are investigated. We observe that the velocity profile increases for increasing values of curvature, mixed convection and volume fraction of nanoparticles for two different cases effective and with-out effective Prandtl numbers. Moreover, in case of effective Pr number, the temperature profile decreases but for with-out effective Pr number temperature profile increases. Furthermore, the graphs are drawn to check the behavior various parameters for effective and with-out effective Pr numbers.

Application of resistance energy model to optimising electric power consumption of a belt conveyor system

Driven by constantly increasing energy demands, prices, environmental impact caused by carbon dioxide emissions and global warming, efficient use of energy is gaining grounds in both public and private enterprises. The energy consumption of belt conveyors can be lowered using energy modelling techniques. In this research, &#x0D; a resistance-based mathematical energy model was utilised in &#x0D; the electrical energy efficiency optimisation of the troughed, inclined belt conveyor system taking into account indentation rolling resistance, bulk solid flexure resistance and secondary resistance as they together contribute 89% resistance to motion. An optimisation problem was formulated to optimise the electrical energy efficiency of the belt conveyor system and subsequently solved using &#x0D; the “fmincon” solver and interior point algorithm of the MATLAB optimisation toolbox. Analysis of simulation results showed that for the same given operating capacities, an average energy saving of about 7.42% and an annual total cost savings of Gh¢ 5, 852, 669.00 (USD 1, 083, 827.59) for a 2592-hour operation can be achieved when the used model and optimisation technique are employed over the constant speed operation.

EXERGY ANALYSIS OF DOUBLE-CIRCUIT FLAT SOLAR COLLECTOR WITH THERMOSYPHON CIRCULATION

In the present work, an exergy analysis was done of two-circuit flat solar collector with thermosiphon circulation. The article presents a mathematical model of energy and exergic analysis of flat solar collectors, as well as calculations of solar radiation efficiency, temperature, flow rate of the fluid, exergy rates and exergy loss rates are done. The significance of the results achieved is high, since experimental studies can detect inefficient components of the solar heating system. The exergetic efficiency of a dual-circuit flat solar collector with a thermosiphon circulation describes irreversibility of the process according to thermodynamic parameters. This is caused by a large the degree of overheating achieved at the end of the processes of compression and evaporation, which leads to large differences in heat exchange temperature based on the heat pump cycle. The exergy efficiency value for the entire system is 70. Maximum values energy efficiency and exergy at noon, 32.5% and 2.23%, respectively. The efficiency of exergy is 4%, and the highest the loss of exergy is the difference between the absorber plates and the sun, accounting for 52.86% of the total exergy rate.

Turkey’s energy planning considering global environmental concerns

Energy and energy policies are the main factors to determine the position of the country in the globalized world. By the year 2023 Turkey’s main aim on the optimal energy distribution is to reduce the cost of energy production, create minimum effect on ecosystem and to use uninterrupted, environmentally friendly energy sources under the lights of UNFCCC and Kyoto protocol which was signed by Turkey also. By considering these facts; in this study a new mathematical energy model is proposed to design the future energy systems of Turkey and by solving it under this aim Turkey’s 15-years electricity generation plan is obtained which is mainly used the renewable energy sources that has minimum effect on ecosystem. Turkey’s energy need in 2030 is solved by a multi-objective mixed integer linear programming model under the Republic of Turkey Ministry of Energy and Natural Resource (MENR)’s objectives/goals by the year 2023 which are stated in the MENR’s “Security of Energy Market and Supply Strategy” document and the scenario model optimizes simultaneously the objectives of energy production cost minimization, within the framework of the UNFCCC responsibilities of Turkey reduction on emissions of greenhouse gases, minimization of the use of power plants that use fossil fuels that has significant impacts on ecosystem, environment and causes of climate change.

Анализ энергетических и магнитных процессов в дросселях импульсных преобразователей электрической энергии

The article presents the analysis of energy and magnetic processes in core of inductors switched-mode AC-AC and DC-DC converters. The mathematical model of energy and magnetic processes in core of inductors is obtained. The mathematical model is generalized to DC-DC and AC-AC converters, to most popular schemes of converters and to transfer, recuperation and idle modes. It is shown that the energy and magnetic processes in core of inductors are identical for DC-DC and AC-AC converters, for buck, boost, buck-boost and fly-back converters, and for transfer, recuperation and idle modes. It is shown that energy processes in converters can be defined by parameters of magnetic flux of inductor core. It is shown that power of converter will be maximal, when value of ripple induction in core is equal the maximum allowable induction of core, and average value of induction in core is equal half of the maximum allowable induction of core. It is shown that maximum power of converter is proportional volume of inductor core.

상수관망의 에너지 평가기법에 관한 연구

The systematic analysis and evaluation of required energy in the processes of drinking water production and supply have attracted considerable interest considering the need to overcome electricity shortage and control greenhouse gas emissions. On the basis of a review of existing research results, a practical method is developed in this study for evaluating energy in water supply networks. The proposed method can be applied to real water supply systems. A model based on the proposed method is developed by combining the hydraulic analysis results that are obtained using the EPANET2 software with a mathematical energy model on the MATLAB platform. It is suggested that performance indicators can evaluate the inherent efficiency of water supply facilities as well as their operational efficiency depending on the pipeline layout, pipe condition, and leakage level. The developed model is validated by applying it to virtual and real water supply systems. It is expected that the management of electric power demand on the peak time of water supply and the planning of an energy-efficient water supply system can be effectively achieved by the optimal management of energy by the proposed method in this study.

Exergy Based Performance Analysis of a Shower Cooling Tower

The present study provides a descriptive mathematical model of energy and exergy for a shower cooling tower (SCT). The model is used to predict the variation in temperature and exergy along the tower length. The validity of the model for predicting variations in gas and liquid characteristics along the tower length was examined against some operating data measured in a cooling tower company. The results show that the exergy of water decreases as tower height increases. The distribution of the exergy loss is high at the bottom and gradually decreases moving up to the top of the tower. Moreover, 1.50 m/s air velocity results in less exergy destruction. With a decrease in the size of the water droplets, the fluids carrying energy have more opportunities for mass and energy transfers.

Immediate assisted solar direct contact membrane distillation in saline water desalination

A direct contact membrane distillation (DCMD) equipped with a solar absorber was designed for saline water desalination and integrated into a small unit, that possesses a combined solar absorber for an energy source and membrane distillation process for desalination. The proposed device performs at middle temperature (about 35–50 °C) using hot saline water at the inlet associated with a constant cold stream inlet. The solar absorber is inserted between the glass cover and membrane to heat the flowing fluid which passes underneath the absorber plate. A two-dimensional mathematical energy model and a general numerical method are presented to obtain the water productivity, absorber plate and flow conduit temperature distributions. The results show that the theoretical predictions agree fairly well with the experimental results using a combination of Knudsen diffusion and viscous flow models for membrane coefficient estimation. The maximum trans-membrane flux increment in this study is obtained as 16.56% and the distillation ability potential is 4.1 kg/(m 2 h) with high purity.

A Novel Energy Saving Approach through Mobile Collaborative Computing Systems

Energy saving has been studied widely in both of computing and communication research communities. For handheld devices, energy is becoming a more and more critical issue because lots of applications running on handhelds today are computation or communication intensive and take a long time to finish. Unlike previous work that proposes computing or communication energy solutions alone, this paper proposes a novel energy savings approach through mobile collaborative systems, which jointly consider computing and communication energy cost. In this work, the authors use streaming video as investigated application scenario and propose multi-hop pipelined wireless collaborative system to decode video frames with a requirement for maximum inter-frame time. To finish a computing task with such a requirement, this paper proposes a control policy that can dynamically adapt processor frequency and communication transmission rate at the collaborative devices. The authors build a mathematical energy model for collaborative computing systems. Results show that the collaborative system helps save energy, and the transmission rate between collaborators is a key parameter for maximizing energy savings. The energy saving algorithm in computing devices is implemented and the experimental results show the same trend.

Small Gas Flow Measurement - Microcomputer Application in Education

This paper is focused on education in the field of small gas flow measurement. Students obtain theoretical knowledge in flow and they acquaint with different types of flowmeters. The Department of Automatic Control of Tomas Bata University is equipped with the thermal mass flowmeter (time - of - flight sensor). The theoretical education is on a basis of the mathematical model of energy and temperature balance simulated in the FEMLAB. Students use various constructional materials for design of the thermal mass flowmeter and they verify the properties of designed flowmeter on laboratory models.

A mathematical integration of energy and amino acid metabolism of lactating sows.

A dynamic mathematical model of energy and protein metabolism of lactating sows is described in this article. The model is designed to contribute to a systematic and quantitative understanding of the biological connection between diet and reproduction. It traces the flow of energy-containing nutrients from absorption through intermediary metabolism, into and out of body stores, and into milk. State variables (pools) include lysine, other amino acids, glucose, fatty acids, acetate, propionate, acetyl-coenzyme A, ATP, oxygen, carbon dioxide, urea, lean-body protein, visceral protein, storage triacylglycerol, milk protein, milk triacylglycerol, and milk lactose. The rate of each transaction is a function of substrate and inhibitor concentrations, assuming saturable kinetics. Protein and fat turnover, substrate cycles, and the energy cost of membrane transport are explicitly considered. Dynamic simulation of a complete lactation is accomplished by iterating the numerical integration of 16 first-order, nonlinear differential equations, each associated with a pool. Most kinetic parameters were estimated indirectly. Preliminary tests suggest the model is sound. It promises to be useful as a research tool and, with further development, as a guide to practical feeding strategies.

Operational strategies for Kuwait's 100 kW e/0.7MW th solar power plant

In March 1981 a 0.7 MW th solar thermal power plant was commissioned at Kuwait's Sulaibiya Solar Complex. The cogeneration of solar power plant was designed to be the main energy supplier for an agricultural desert settlement 35 km south-west of Kuwait City. The power plant produces both the electric and thermal energy needs for its own internal uses and those of the food/water/power complex. The electric users, outside the power plant's own needs, include water pumping from a 110 metre deep water well, an outdoor irrigation network, four desert greenhouses, a walk-in cooler, air conditioning, a reverse osmosis (R.O.) desalination plant, as well as the electric power needs for a multistage flash (M.S.F.) desalination plant, offices, workshop, data acquisition and lighting. The reject thermal energy from the power plant is utilized to power an M.S.F. desalination plant, and the domestic hot water needs. The power plant operational strategies are aimed at satisfying the energy needs for this food/water/power complex under prevailing solar radiation conditions while minimizing the inconvenience to the user (the complex) and maximizing the percent of the total energy derived from the sun (solar fraction). Surplus energy is stored as electric energy, thermal energy, or used to desalinate additional volumes of brackish water which can be stored in strategic water reservoirs. During periods of low solar radiation the power plant may be operated at partial load to supply the essential electric energy needs, charge the thermal storage, or provide the thermal energy needs for the MSF desalination system. An energy cost accounting system was developed to encourage the user to minimize his electric consumption during periods of low solar radiation. A mathematical energy model for the power plant was utilized to predict its output and suggest the optimum operational strategy according to the user's priorities, and predict surpluses or shortages that have to be accommodated by the emergency secondary energy source.