Electrical Energy Efficiency Research Articles

Efficient absorption cooling for low district heating return temperatures

In the past years scientists of Technische Universität Berlin, developed a new generation of single stage H2O/LiBr absorption chillers in the range of 50 to 500 kW nominal cooling capacity. In 16 installations 25 absorption chillers have been monitored within a broad field test (FeldtestAbsorptionskälte für Kraft-Wärme-Kälte-Kopplung-Systeme, FAkS, funded by BMWi as project FKZ 03ET1171a-d) in the years 2013 to 2018. Annual performance figures of thermal coefficient of performance (COPth) in the range of 0.7 kWh 0/kWh 2 and electrical coefficient of performance (COPel) superior to 20 kWh 0/kWh el have been proven, serving district heat (DH) return line temperatures in the range of 62 °C to 68 °C.While the FAkS project focused on installation and operation of absorption chillers themselves, the follow-up project called ReKs (Regelungenergie-aufwandsoptimierterKälteerzeugungssysteme, FKZ 03ET1583), concentrates on overall system control and efficiency. Controlling absorption chiller cooling supply at low district heat return line temperatures is extended to an energy efficient control of all participating components including hot water, chilled water, heat sink pump and cooling tower fans. Models and strategies have been developed on thermal science theory and implemented in industrial control software. Proof of concept has been evaluated by monitoring field test installations while in parallel particular field test related parameters have been varied. Without diminishing quality of chilled water temperature and/or cooling capacity, electrical energy efficiency can at least be doubled, compared to the figures of FAkS installations. Moreover, new strategies enable efficient absorption cooling with DH return line temperatures in the range of 50 °C during moderate weather conditions periods. Field test results from 2020 and 2021 are presented here.

Rancang Bangun Hidroponik Dengan Bantuan Pompa Bertenaga Surya

Agriculture traditionally still uses large areas of land with relatively large amounts of water. The application of solar energy is one of the uses of new and renewable energy. This research uses a 50 Wp photovoltaic cell, battery, solar charge controller, DC stepdown, DC pump and hydroponic frame. The stages of the research are the design of the tools, the calculation of the power required by the tools, the manufacture of the tools, the collection of data and the analysis of the data. The data collected is temperature, sunlight intensity, electric power, electrical energy, water discharge, and photovoltaic efficiency. The data were processed and analyzed in an exploratory manner. Based on the results of the research conducted, the lowest average temperature was 25.33 C and the highest was 33.70 C with the highest average light intensity of 920.26 w/m2 at 12.00 WIB. The relationship between temperature and light intensity with a value of R2 of 0.7594. The highest average electrical energy obtained by polycrystalline is 30.44Wh. The water lost from the hydroponic system is 0.03%. The efficiency of photovoltaic cells is 10.09%–15.72%. Keywords: DC pump, hydroponics, light intensity, photovoltaic

Experimental and numerical analysis of energy and exergy performance of photovoltaic thermal water collectors

The aim of this paper is the investigation and comparison of PV (Photovoltaic) module and PV/T (Photovoltaic/Thermal) collectors regarding the energetic and exergetic point of view. A reference PV module and two different flow pattern PV/T collector was experimentally observed and evaluated results were compared concerning first and second law of thermodynamics. Experimentation results are also compared with the numerical results that were obtained by ANSYS Fluent software. Experimentation proceeded in Karabuk, Turkey. As a result, it was concluded that the PV module electrical efficiency is equal to its overall efficiency and is approximately 7.96%. Thermal, electrical, and overall energy efficiency values are 29.08%, 9.74%, and 38.82% for PV/T1, and PV/T2 are 49.68%, 10.19%, and 59.88%. The exergy efficiency of PV, PV/T1, and PV/T2 are determined at approximately 4.63%, 10.64%, and 11.53%. When the exergy efficiency values are compared, solar energy utilization in the renewable energy class for both PV/T collectors formed with the cooling units integrated with the PV panel has been almost doubled.

A New Arrangement of Active Coils for Wireless Charging of UAV

This paper presents the design and optimization of a wireless power transfer (WPT) charging system based on magnetically coupled resonant technology, applied to an Unmanned Aerial Vehicle (UAV). In this paper, a charging system, including dual active transmitter coils and a single receiver coil, is proposed. The dual transmitting coils adopt a coaxial structure with different radii. This structure simplifies the calculation of the complex mutual inductance between the coils to a function of mutual inductance only related to the value of the radial misalignment. Aiming toward a constant charging power, the optimal transmission efficiency of electric energy is achieved by controlling the input voltages of the active coils, which are solved via a set of equations defined as Lagrange multipliers. The simulation results of the 570 V and 85,000 Hz system verified the validity of the proposed wireless UAV charging scheme.

Fruit peels pigment extracts as a photosensitizer in ZnO-based Dye-Sensitized Solar Cells

Two of the most serious problems that we encounter today are the energy crisis and global warming. It has, therefore, become essential for a quest for clean and renewable energy sources, as the lasting solution for these problems. This paper presents the natural pigments from the facile extraction of fruit peels of Musa paradisiaca, Mangifera indica, Punica granatum, and Ananas comosus and their conversion efficiency in dye-sensitized solar cells (DSSCs). The zinc oxide (ZnO) photo-anode film was prepared and its properties were analyzed. Natural extracts were used as photosensitizers for constructing DSSCs. Characteristics of the natural Pigments were analyzed by various spectroscopy techniques. Solar to electrical energy efficiencies of natural dye-based on ZnO DSSCs were evaluated for Musa paradisiaca, Mangifera indica, Punica granatum, and Ananas comosus to be 0.009%, 0.024%, 0.010%, and 0.002%, respectively. The conversion of visible light into electricity resulting in improved photoelectric characteristics was achieved.

Power and Energy Rating Considerations in Integration of Flow Battery with Solar PV and Residential Load

Integration of renewable energy sources such as solar photovoltaic (PV) generation with variable power demand systems like residential electricity consumption requires the use of a high efficiency electrical energy system such as a battery. In the present study, such integration has been studied using vanadium redox flow battery (VRFB) as the energy storage system with specific focus on the sizing of the power and energy storage capacities of the system components. Experiments have been carried out with a seven-day simulated solar insolation and residential load characteristics using a 1 kW VRFB stack and variable amounts of electrolyte volume. Several scenarios have been simulated using power and energy scale factors. Battery response, in terms of its power, state of charge and efficiency, has been monitored in each run. Results show that the stack power rating should be based on peak charging characteristics while the volume of electrolyte should be based on the expected daily energy discharge through the battery. The PV source itself should be sized at about 25% more energy rating than the average daily load. The ability to design a VRFB with a high power-to-energy ratio makes it particularly attractive for PV-load integration.

Energy and exergy analysis of hybrid photovoltaic thermal solar system under climatic condition of North Iraq

Present study involves an exhaustive analysis on hybrid photovoltaic thermal (PVT) system to display the actions of climate and operating conditions on its thermal and electrical efficiencies. The performances of the system have been evaluated based on energy and exergy analysis using the experimental data for the purpose of comparison. Experimental data have been measured for three different days in 2019 in Dohok city/north of Iraq under active mode. The results displayed that the climatic conditions have significant effect on the energy and exergy outputs. The results of energy analysis indicate that the maximum thermal and electric efficiencies in the range of (25%–58%) and (12%–16%), respectively. The results of exergy analysis displayed that the optimum thermal and electric efficiencies in the range of (2%–7%) and (10%–18%), respectively. The results also displayed that the solar panel temperature has a significant impact on the electrical energy and exergy efficiencies. The total solutions illustrated that the employ of PVT water system under active mode provides an obvious advantages and hence, the current work provides an interesting information for evaluating the performances of PVT system. As consequence, it can be advised for using in household applications at north of Iraq.

Applicability of photoelectrical solar units inside domical structures in northern conditions

The possibility of installing photoelectrical solar units inside domical structures with the maintenance of their power generation level was investigated; an optimal distance between a photoelectrical solar unit and the transparent walls of the respective domical structure was determined. The experiments were carried out at the North-Eastern Federal University in the central part of the Republic of Sakha (Yakutia) by determining reduction in the electrical energy efficiency of photoelectrical solar units when changing their location. An optimal distance for installing such units within transparent domical structures was found based on graphical interpretations and gradients. The authors obtained reference parameters for light flux reduction, the generation power of a photoelectrical solar unit when changing the operation medium, and the optimal distance of a photoelectrical solar unit inside a domical structure for reducing the surface contamination of the unit. It was found that, when photoelectrical solar units are operated within a transparent domical structure, the power generation falls by 25.61% as compared to actual results in open space. It was found that an increase in the distance between the transparent walls of the domical structure and the unit led to a decrease in the power generation by ~23.01% and the light flux power by 5.224% at 1.5 m. This method of installing photoelectrical solar units can be used in the construction and designing of smart home systems and autonomous power generation facilities in northern regions of Russia.

ORGANIZATION OF THE ENERGY MANAGEMENT SYSTEM ON THE BASIS OF THE UNIVERSITY KNOWLEDGE HUB

BACKGROUND AND OBJECTIVES. Energy efficiency and energy saving are the priority direction of science, technology and engineering development in Ukraine. The policy of energy saving, carried out all over the world, is directed to all branches and scientific researches in all spheres. The big consumer of energy resources is the higher school. Updating of normative-legal and technical base aimed at design and operation of buildings with low energy consumption and high energy efficiency class shows the necessity of short-term solution of the problem. At the same time, there is a lack of a systemic view of energy efficiency, which does not allow evaluating the level of energy costs throughout the life cycle of higher education institutions, which shows the need to find effective solutions to the problem.METHODS. Multiple regression equation was used to assess the influence of factors on electricity consumption and energy efficiency of Kyiv National University of Technologies and Design, statistical analysis of the obtained data was performed.FINDINGS. As a result it was found out that the data of electricity consumption do not obey the law of normal distribution, so it is difficult to build an accurate prediction of electricity consumption. The use of HAB knowledge on energy efficiency allowed a more qualitative analysis and highlighted the main factors affecting electricity consumption. The university has unregulated central heating, individual air conditioning systems, and central and individual lighting. In this regard, we selected the following main factors: average outdoor air temperature, average duration of daylight hours, heating period, average number of people working per day, during the month to conduct energy monitoring and energy audit of university buildings.CONCLUSION. Implementation of suggested scheme of structural organization of typical system of automatic accounting of university energy consumption on the basis of university HUB of energy efficiency knowledge: server, allowing to collect, store and process data; routers by means of various wire and wireless communication technologies; hubs, installed on the objects of energy consumption; workstations, which are personal computers with installed software of used HUB will allow to optimize energy consumption.

The Efficient Implementation of Hybrid Power Plants in Indonesia

The energy crisis is a serious issue that all countries around the world are dealing with, particularly the energy sources used to generate electricity. There are numerous alternative energy sources available in nature, such as solar energy, wind energy, and so on. Wind and solar energy as hybrid energy sources are thought to be promising in electric generation technology. Hybrid Power Plants can also be used to address the issue of limited electrical energy supply in Indonesia's remote areas. The purpose of this study is to describe the effectiveness of the hybrid power plants implementation in Indonesia. The study was conducted using the narrative literature review method. It can be inferred that the purpose of developing this hybrid technology, among others, is to obtain more efficient electrical energy generation by combining the advantages of two or more types of power generation systems that work in an integrated manner as a compact system. The produced electric energy can be stored in the battery. In terms of use, the produced direct current (DC) is converted into alternating current (AC) using the inverter system prior to distribution to consumers. Therefore, this hybrid power plant is suitable to be implemented in Indonesia.

Arched snap motor: power flow analysis

Impulse force is effective for purposes such as system analysis, mobile robots, and haptic devices. However, the most popular DC motor actuator is not suitable for generating an impulse force. Thus, the lack of a compact impulse force generator has become a problem. We propose a snap motor that is a compact and rapid impulse force generator. In this paper, we propose a slider mechanism for the arched snap motor to increase the durability of the frame. This paper shows a reasonable explanation the function of the slider mechanism on an arched snap motor with simulation. Then, experiments showed that the energy conversion efficiency of the input electric energy to the buckling energy is about 60%. This paper provides a design method for a simple and compact impulse force generator.

Thermodynamic performance analysis and optimization for a novel full-spectrum solar-driven trigeneration system integrated with organic Rankine cycle

Solar-driven trigeneration systems do not consume any fossil fuels and can output cooling, heating, and electricity independently, which effectively reduces environmental pollution and improves solar energy utilization. However, the traditional solar-driven trigeneration system only utilizes part of the solar spectrum, resulting in significant heat losses. Therefore, a new full-spectrum solar-driven trigeneration system integrated with an organic Rankine cycle is proposed to improve solar energy utilization efficiency. Applied the Engineering Equation Solver, the thermodynamic models of the trigeneration system are established, and the effects of some key parameters on thermodynamic performance are discussed. Additionally, the thermal allocation ratio is optimized to maximize the environmental benefits of the system. The simulation results indicate that solar to electric efficiency, energy efficiency, and exergy efficiency are positively correlated with the cut-off wavelength of norbornadiene. When the thermal allocation ratio is 0.3, the system has the most significant environmental benefit. The annual solar to electric efficiency, annual energy and exergy efficiencies reach 3.80%, 66.97%, and 8.27%, respectively. Compared with the reference system, both the carbon dioxide emission and primary energy consumption are reduced by 41.75%, demonstrating that the proposed system effectively improves the utilization of solar energy.

Energetic and exergetic performances of a nanofluid-based photovoltaic/thermal system equipped with a sheet-and-grooved serpentine tube collector: Indoor experimental tests

In this experimental investigation, an effort is executed to evaluate and compare the energetic and exergetic performances of three nanofluid-based photovoltaic/thermal (PVT) systems, namely a PVT system with a sheet-and-serpentine tube collector (case-I), a PVT system with a sheet-and-grooved serpentine tube type collector with a groove pitch of 8 mm (case-II), and a PVT system with a sheet-and-grooved serpentine tube type collector with a groove pitch of 5.4 mm (case-III). The water-Fe3O4 nanofluid was considered as the working fluid. The influences of nanoadditive concentration (Ø) (0–1%) and flow rate (mf) of nanofluid (10–40 kg/h) on the performance features were then examined. It was found that at any given Ø, the overall energy, overall exergy, and electrical performances of the case-I, II, and II improved with an increase in nanofluid mf (10–40 kg/h) and vice versa. Thus, the case-III yielded 15% and 6% better overall energy efficiency, 4.6% and 2.3% better overall exergy efficiency, and 3.3% and 1.9% better electrical energy efficiency than the case-I and II at a Ø and nanofluid mf of 1.0% and 40 kg/h. The maximum electrical energy of case-I, II, and III is 9.5%, 11%, and 13.1% higher than those achieved by the PV panel in absence of cooling. The findings obtained from this study can be used to design photovoltaic systems with significant energetic and exergetic performance.

Research on Energy Storage and Hydrogen Production System of Offshore Wind-solar Hybrid Power Generation Based on 3D Finite Element Method

At present, hydrogen, as a fuel, has the characteristics of high efficiency and no pollution, which can replace traditional fossil energy and be used in various fields to a certain extent. Using clean energy such as wind and light to electrolyze water to prepare hydrogen can realize zero pollution in the whole process from hydrogen preparation to use. Such energy conversion and use can reduce air pollution, improve air quality and solve the problem of abandoning wind and light. In this paper, a simulation model is established by using threedimensional finite element method, and meteorological parameters are input into the model, so as to obtain the power generation, hydrogen production rate and the efficiency of converting solar energy, wind energy and electric energy into hydrogen energy under different capacity configurations of each part of the system. Using the model established in this paper, the parameters of wind and solar energy resources, environmental factors and load power in different regions are input. By changing the battery capacity, observing the battery operation and DC bus output, the battery equipment suitable for the whole system can be selected.

Inside Front Cover

By fusion of superhydrophobic surface with transistor‐inspired architecture for high‐frequency water kinetic energy harvesting, we report the design of a superhydrophobic surface‐based droplet electricity generator, which allows for timely water droplet shedding at high impact frequency without the formation of unwanted liquid film and is capable of efficient electrical energy harvesting without compromising output performance. This work represents Harvesting energy from high‐frequency impinging water droplets by a droplet‐based electricity generator. image

Optimization of a three‐dimensional electrochemical process with granular activated carbon for diclofenac removal using response surface methodology

AbstractIn this study, a three‐dimensional electrochemical process with aluminum electrodes in the presence of granular activated carbon derived from walnut shell (WGAC) was employed to remove Diclofenac from synthetic water. Optimum operating conditions were determined using response surface methodology, also, an empirical relationship was established between response and independent variables (activated carbon amount, contact time, pH, and electrolyte concentration). The results showed that activated carbon amount and NaCl concentration were the most influential factors on the removal efficiency, and the most significant factor affecting electrical energy was NaCl concentration. Additionally, three‐dimensional electrochemical process with granular activated carbon has the potential to work in the pH range from 1 to 9. The optimal conditions to gain maximum removal efficiency and minimum electrical energy were determined to be 4.36 g granular activated carbon, 40 min contact time, and 4390 ppm of NaCl. In addition, to show the physical characteristics of activated carbon, the field emission scanning electron microscopy and BET analysis were applied, and Spectrophotometric technique was used to determine diclofenac concentration. Considering high removal efficiency and low electrical energy consumption, the three‐dimensional electrochemical process with WGAC can be considered a cost‐effective and practicable method to remove diclofenac from water and wastewater.

Long gap spark discharge ignition using a boron-doped diamond electrode

A long gap discharge offers an efficient method for achieving stable ignition in lean fuel/air mixtures, because it can reduce the heat loss to the electrodes, achieve efficient electrical energy transfer from the ignition coil to the discharge plasma, and reduce the initial flame curvature by converting the geometry of the ignition from a point to a line. However, the formation of such discharge requires increased discharge voltage to compensate for the reduction in the electric field between the electrodes, and this is not easily achieved in practice. Since the Townsend discharge criteria depend not only on the electron multiplication coefficient (α coefficient) but on the secondary electron emission (γ-process), we focused on the latter to reduce the discharge threshold voltage. In the present study, for the first time, B-doped diamond (BDD), which has a larger secondary electron emission coefficient than the metals used in conventional spark discharge ignition, was utilized as the cathode material, and its discharge and ignition characteristics were investigated. Under the same conditions, use of a BDD cathode resulted in a lower discharge threshold, greater discharge energy, less discharge energy variation, and more rapid flame development, than in the case of a metal cathode. The influence of the cathode material on discharge threshold suggests that the breakdown mechanism of ignition-coil spark discharge is based on Townsend discharge. To elucidate the effect of gap length, the temporal development of flame growth, using the same discharge energy in methane and propane mixtures, was compared between ignition with a short gap discharge with a metal cathode and long gap discharge with a BDD cathode. With a long gap discharge, only the flame growth of lean propane-air mixtures was accelerated, while no difference was observed in the case of lean methane or relatively rich propane mixtures, suggesting the effectiveness of long gap discharge ignition for mixtures with a large Lewis number, due to the small curvature of the initial flame kernel.

Efficiency of light electric vehicles in last mile deliveries – Szczecin case study

City users gladly apply comfortable and time-saving e-commerce solutions as an alternative to traditional purchase. The present pandemic crisis made this issue even more important. It significantly increased the number of transport operations within the city area, as each order has to be delivered directly to the purchaser. Consequently, city authorities are confronted with the important challenge: how to fulfil the expectations and needs of city users in the context of transport system functioning in view of reducing the negative impacts of urban freight transport in terms of safety, air pollution or noise. This is one of the most important elements of social sustainability in cities. One of the solutions that help reduce the negative environmental impacts of urban freight transport is making use of vehicles that produce less air pollution, such as electric vans. It proved to be very effective in decreasing transportation footprint by reducing local emissions of e.g. PM or NOx. However, one of the key limitations is the potential short driving range of such vehicles, which results from the battery capacity and charging infrastructure availability. In recent years, some analyses related to that issue have been made. Nevertheless, the studies have taken into account passenger cars only. This paper presents the results of the research study aimed at verification of electric vans energy efficiency in real-life conditions, i.e. when delivering courier consignments. The electric van used for the purposes of the experiment was Nissan eNV200. This paper fulfils the important knowledge gap and could be helpful from both theoretical and practical perspectives. It should be emphasised that the experiment was carried out in real-life conditions, i.e. in the course of performing business processes in one of the worldwide known CEP companies. The research study was carried out under the EUFAL international project, funded under the Electric Mobility Europe programme. The results of the research shown high potential of electric vehicles and usefulness of electromobility in last mile deliveries. The business partner of the research is now on the stage of electric freight vehicles implementation into vehicles fleets.

Robust fractional‐order super‐twisting sliding mode control to accurately regulate lithium‐battery / super‐capacitor hybrid energy storage system

One of the main challenges in front of the inventors and researchers to compensate the power quality problems is the existence of an efficient and reliable electric energy source for dynamic voltage restorer (DVR). Recent advances in the technologies of lithium-battery (LB) and super-capacitor (SC) have made them possible to be used as hybrid energy storage system (HESS) for DC-power supply of DVR. But then, a robust and efficient controller must be essentially designed to compensate the intricate correlation between system components, unknown nonlinearities, parameter uncertainties related to the HESS. Hence, fractional-order super-twisting sliding mode control (FOSTSMC) is proposed for LB/SC-HESS to smoothly and accurately smoothly track the current reference and control the DC-link voltage of the asymmetric half-cascaded multilevel inverter of DVR during different compensation conditions. As the primary controller, FOSTSMC has compensated the unknown nonlinear parts and parameter uncertainties related to LB/SC-HESS through the real-time disturbance estimation using sliding mode state and disturbance observer (SMSDO). Both the battery current and DC-link voltage due to the physical measurability are chosen to design the control scheme based on the proposed FOSTSMC. The proposed controller has been compared with the proportional integral derivative and the sliding mode control under different probable scenarios to evaluate and validate its observability and controllability. To better present the effects of FOSTSMC, AHCMLI, and HESS-based DVR, they have been quantified as follows: Three real-time stability benchmarks that is, overshoot, undershoot and settling time are respectively attained for FOSTSMC: 0.6, 0.4, and 0.03; for sliding mode control: 1.1, 0.7 and 0.019; for proportional integral derivative: 0.9, 2, and 0.117. That is to say, FOSTSMC can smoothly and accurately track the current reference and control the DC-link voltage during different compensation conditions as compared with other controllers. Asymmetric half-cascaded multilevel inverter can provide 33 steps with consideration of 12 unidirectional switches, whereas binary, trinary, and other multilevel structures can provide less than 27 steps with consideration of 12 switches. The quasi-AC voltage synthesizer-based DVR can completely and accurately compensate the voltage sag and swell with THD of 2.12 and 2.35, respectively. The THD of mal-compensation voltage sag and swell using the conventional DVR are respectively 11.57 and 13.86.

Evaluation of New PCM/PV Configurations for Electrical Energy Efficiency Improvement through Thermal Management of PV Systems

Photovoltaic modules during sunny days can reach temperatures 35 °C above the ambient temperature, which strongly influences their performance and electrical efficiency as power losses can be up to −0.65%/°C. To minimize and control the PV panel temperature, the scientific community has proposed different strategies and innovative approaches, one of them through passive cooling with phase change materials (PCM). However, further investigation, including the effects of geometric shape, insulation, phase change temperature, ambient temperature, and solar radiation on the PV module power output and efficiency, needs further optimization and research. Therefore, the current work aims to investigate several system configurations and different PCMs (RT42, RT31, and RT25) and compare the system with and without insulation through computational fluid dynamic (CFD) tools. The final goal is to optimise and control the temperature of PV modules and evaluate their system efficiency and energy generation. The results showed that compared with a rectangular shape of the PCM container, the trapezoid-one exhibits a considerably better cooling performance with a negligible variation of the PV temperature, even when the melting temperature of the PCM was lower than the average ambient temperature. Moreover, the study showed that having insulation in the PCM container increases the amount of PCM needed, compared with no insulation case, and the increased amount depends on the PCM type. The newly proposed PV/PCM system configuration shows an efficiency and power generation enhancement of 17% and 14.6%, respectively, at peak times.