Energy Reports

Published by Elsevier
Print ISSN: 2352-4847
Publications
For vibration energy harvesting, we propose an inductor-less step-up ac/dc converter in this paper. To realize the inductor-less design, the proposed ac/dc converter consists of two converter blocks: Cockcroft–Walton circuit and charge pump. Unlike existing ac/dc converters for vibration energy harvesting, the proposed ac/dc converter can achieve less electro-magnetic interference (EMI), because no magnetic component is necessary. Furthermore, owing to the Cockcroft–Walton circuit, a full-bridge circuit is not necessary to convert vibration energy. Therefore, small vibration energy, namely, as 0.3 [email protected] MHz, can be converted directly to dc voltage. Through theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulation, the performance of the proposed converter with 6× voltage gain is investigated, where the proposed converter is designed by assuming 0.18μm CMOS process. The proposed converter demonstrates that about 62% power efficiency can be provided, where the output power is 30 μW, the output voltage is about 1.6 V, and the ripple factor is 0.8%. Furthermore, the feasibility of the proposed ac/dc converter is confirmed by breadboard experiments. The inductor-less design provides us to integrate the proposed ac/dc converter into a hybrid IC chip.
 
In this paper, the vortex shedding characteristics been numerically simulated for Re = 1 × 10⁴ by computational fluid dynamics (CFD), which caused by flow separation of NACA0012 airfoil. What is more, the variation of vortex shedding structure and the corresponding frequency characteristics of vortex shedding at different angles of attack are studied. The results reveal that with the increase of the angle of attack, the flow state around the airfoil will change from steady state to unsteady state, the vortex structure of the suction surface will become more and more complex with the increase of the angle of attack. In the periodic wake vortex shedding flow field, according analysis of the vortex structure and vortex shedding frequency, the vortex shedding will show 2S (Single) mode (8°∼15°) - chaotic state (16°∼18°) - 2S (Single) model (19°)- quasi periodic flow (20°∼24°) with the increase of angle of attack for α>7°. The rising section and falling section of airfoil lift and drag coefficient curves correspond to the vortex shedding and formation respectively. The frequency spectrum corresponding to the lift coefficient can be used to analyze the characteristics of vortex shedding from the perspective of frequency domain. With the increase of the angle of attack, the stability of flow field decreases, and the Strouhal number of vortex shedding frequency decreases basically. The order of the Strouhal number in different flow field states is 2S mode > quasi periodic flow > chaotic state. Among them, most of the Strouhal number corresponding to 2S mode fluctuate around 0.2, and the Strouhal number corresponding to chaotic state and quasi periodic flow fluctuate around 0.02 and 0.07 respectively
 
In the present era, eco-friendly green hydrogen production is emerging as a very important technology. Photocatalytic hydrogen generation is a field that must be developed as a future-oriented technology. SnS has a low electron affinity, low enough to generate hydrogen from water, and has a small ionization potential, so it can absorb a wide range of visible light. We successfully synthesized 0D/2D SnS multi structures using hydrothermal methods and demonstrated that when the band gap of SnS is wider and tuned than that of bulk materials, this material can be used for more efficient photocatalytic applications. In addition to the chromium hexavalent (CrVI) reduction and organic dye reduction photocatalysts, the efficiency was improved by about 2 times in the hydrogen generation photocatalyst. Because each dimension shape of SnS has a different bandgap, SnS can act as a donor/acceptor as a heterojunction. This increases the lifetime and reduces the electron–hole recombination rate. Designing and fabricating bandgap energy-matched nanocomposite photocatalysts could provide a fundamental direction to solving future clean energy challenges. Since SnS is composed of safe and abundant elements and SnS QDs and various structures can be synthesized using simple wet chemistry methods applicable to mass production, the SnS material described here is suitable for future solar hydrogen production. In addition, band control and performance improvement through material structuring are expected to be widely applied to other materials.
 
The electricity distribution in a planned way has been a difficult issue that the power supply bureau wishes to solve, and it is the lifeblood of economic development. Forecasting annual electricity consumption is very crucial for the planning of the power supply bureau and for booming economic development. We propose a novel unbiased fractional nonlinear grey Bernoulli model [i.e, UFNGBM (1,1)] to forecast China’s annual electricity consumption based on the nonlinear grey Bernoulli model [i.e, NGBM (1,1)]. First, UFNGBM (1,1) approach is designed to derive calculation formula of the novel model, and validity of the model is proved by the matrix perturbation theory. Second, a novel optimization algorithm is introduced based on the whale algorithm to find the optimal parameters (i.e., order and power) of the proposed model. Third, the accuracy, stability, and effectiveness of our method are verified through three real-world cases in China. Finally, we collect the electricity consumption data of three provinces in China and successfully apply the proposed algorithm to predict the electricity consumption from 2019 to 2024. The experimental results demonstrate that our proposed model is significantly superior to nine alternative models on the electricity consumption data of Jilin and Jiangsu. The performance of our novel method is close to the state-of-the-art deep learning method on the electricity consumption data of Shandong. It is noticed that our method [as an extended version of NGBM(1,1)] is significantly better than NGBM(1,1) on these three real-world datasets, which further shows the effectiveness of the our proposed algorithm. Meanwhile, the electricity consumption of these three provinces in the next six years (2019–2024) is forecasted, which has a very good guiding significance and provides a more reliable reference for the economic and power bureau.
 
The utilization of wind energy can alleviate the problems of fossil energy shortage and environmental pollution. As the core unit of wind power generation systems, improving the design and manufacturing technology of permanent magnet synchronous generator has become the research focus of researchers. In this paper, the key design technology of direct drive permanent magnet synchronous wind turbine, especially the semi-direct drive permanent magnet synchronous wind turbine with primary gear is studied, and a 1.5 MW semi-direct drive permanent magnet synchronous wind turbine is designed. To improve the power factor of the permanent magnet synchronous generator, the reactive power compensation device and filter circuit are added to the control circuit. The results show that after adding the reactive power compensation circuit, the power factor of the circuit can reach 1. In addition, due to the filter circuit, the fifth harmonic is reduced from 5.6% to 3.9%. The scheme of closed slot is used to weaken cogging torque and resistance torque of the permanent magnet synchronous generator. To improve the utilization of permanent magnet, a T-shaped rotor pole structure is proposed in this paper and the pole arc coefficient is selected between 0.65–0.70. Through the comparative analysis of various design schemes, the design scheme of 50 poles-180 slots is determined. The temperature rise of the permanent magnet synchronous generator is calculated by the thermal network method and ANSYS finite element analysis. The results show that the temperature rise of the design scheme is within the normal working range of the motor.
 
Potentially scarce materials play an important role in many current and emerging technologies needed to support a sustainable energy and mobility system. This paper examines the global demand for 25 potentially scarce materials needed in key energy and transport technologies. The starting point is a global energy system scenario that is compatible with the 1.5°C target. To determine the material requirements, an extensive database was built up on the current and expected future specific demand of these materials in the key technologies studied. A second database describes the potential development of sub-technology market shares (e.g. different battery types) within a technology class (e.g. photovoltaics). A material flow analysis model was used to determine the annual and cumulative material requirements as well as the recycling potential. The results show that current production of all materials will have to be increased, in some cases significantly, in a short period of time to meet the anticipated demand for the energy and transportation system. In addition, the cumulative demand for some materials significantly exceeds current reserves and even resources. In particular, lithium, cobalt, and nickel for batteries, dysprosium and neodymium for permanent magnets (e.g. wind turbines and electric motors), and iridium as well as platinum in fuel cells and electrolyzers are affected. The construction of battery electric and fuel cell electric vehicles thus represents a major driver of the growing material demand. Depending on the material, the expected shortages can be reduced or delayed by technology substitution, ambitious material recycling, an extension of technology lifetime, increased material efficiency, and a smaller future vehicle stock, but not entirely avoided. Hence, it can be expected that material bottlenecks will result in increases in material prices, at least in the short to medium term. What impact this will have on the transformation process itself still needs to be investigated in more detail.
 
High-temperature corrosion of boiler water wall is one of the major factors that affect safe and economic operation of large thermal generator sets. For the high-temperature corrosion of right and left water walls of a domestic 1000 MW dual circle tangential boiler during trial operation, this paper studies impact on high-temperature corrosion of water walls from burner height–width ratio and secondary air nozzle swing angle respectively through Fluent numerical simulation. Simulation results show that a burner combination mode with a small height–width ratio shall be used during actual operation of the boiler. In addition, when the secondary air nozzle is swung upward by 15°, the CO concentration at the place close to the wall surface in the combustion zone is less than 3% with adequate oxygen content, which can reduce high-temperature corrosion risk of water walls.
 
Modern offshore wind farms rely on SCADA system to manage information and issue commands. One current interest and the future trend of SCADA is to have openness of working environments. The present paper follows the concept, and proposes the solutions to wind farms DMZ storing the wind data for internet guests and to firewall traffic control by utilizing the advantage of IEC 60870-5-104 protocol. The paper demonstrates the IEC 60870-5-104 protocol packets, routes, and packet structural changes in major octets after passing each network component. Two results are shown. The first result is in the plot, the wind speed value against the packet number. By managing the packet number and selecting proper packets, the classification/privatibility of wind speed values released can be regulated by the wind farm administrators to decide the quantity and batches of packets to be stored in DMZ for internet guest, as well as for the firewall to set up traffic flow. The second result is the figure of all data traffics in the networks. It displays that the proposed solutions for data traffic flow control works effectively under the situation of limited bandwidth but enormous number of packets, and opens out a latitude for future study. The purpose of this paper is to develop the openness of SCADA working environment and to assist wind farm SCADA administrators to optimize the management skills, from the IEC 60870-5-104 protocol packet point of view. The author declares the present paper is invented independently and personally, to avoid any infringement of intellectual properties and patents.
 
In this paper, it is aimed to examine the relationship between biomass energy consumption (BEC) and economic growth (EG) in NEXT-11 countries (except for Vietnam). In this context, panel data analysis was executed using annual data for the 1970-2017 period. According to the findings, it has been found that BEC and EG act together in the long run. In consequence of the causality tests, concluded that the conservation hypothesis is valid for NEXT-11 countries. In the country-specific evaluations, the conservation hypothesis was found to be valid for Indonesia, Nigeria and Bangladesh; the neutrality hypothesis was found to be valid for Turkey, Egypt, Iran, Korea, Mexico, Pakistan, and the Philippines. The findings show that NEXT-11 countries can only realize such a serious, costly biomass energy investment when they achieve EG. These findings provide valuable signals for policymakers.
 
This paper portrays the application of a Partial Discharge (PD) signal combined with the dual-input VGG Convolution Neural Network (CNN) to predict the location of the pollution layer on 11 kV polymer insulators subjected to alternating current for smart grid applications. First, a non-uniform pollution layer artificially created for HV insulator with three straight shed ball end fitting in a laboratory setup and corresponding PD readings are measured. The wavelet transform is employed to represent the measured PD signal as scalogram patterns. In general CNN uses a single input pattern for feature extraction. If the pattern quality is low, it is easy to cause misclassification. Hence in this proposed work, the feature fusion of a dual-input Visual Geometry Group (VGG) based CNN is used for the classification of contamination layer. VGG 19 is a pretrained deep learning network used for extracting the rich features from the patterns. In continuation to that, hyperparameter (HP) play a vital role in deep learning algorithms because they directly manage the behaviours of training algorithms and have a significant effect on the performance of deep learning models. Hence, Bayesian Optimization (BO) is used for tuning the HP. At last, to check the practicality of the proposed algorithm, a new dataset is created for 11 kV polymer insulator with three alternate shed clevis end fitting and different pollution levels—acceptable results obtained by using dual-input CNN with the minimum quantity of data.
 
Meteorological observations of the site.
View of 11.2 kWp rooftop grid interactive solar PV system. 
Performance summary of some selected grid connected PV systems.
Barren land and roof tops of buildings are being increasingly used worldwide to install solar panels for generating electricity. One such step has been taken by Siksha ‘O’Anusandhan University, Bhubaneswar (Latitude 20.24° N and Longitude 80.85° E) by installing a 11.2 kWp grid connected solar power system during February, 2014. This PV system is tilted at an angle of 21° on the top floor of a 25 metre height building. This system was installed This paper presents the results of this grid connected photovoltaic system which was monitored between September 2014 to August 2015. The entire electricity generated by the system was fed into the state grid. The different parameters of the system studied include PV module efficiency, array yield, final yield, inverter efficiency and performance ratio of the system. The total energy generated during this period was found to be 14.960 MWh and the PV module efficiency, inverter efficiency and performance ratio were found to be 13.42%, 89.83% and 0.78 respectively.
 
Insulators are the most crucial part of power systems. The insulation performance of insulators is vital for the sustainability of power systems. Recently, silicone rubber (SiR) insulators are used frequently in all sections of the power systems. In this paper, a SiR insulator currently used in power transmission systems has been analyzed under combined AC–DC voltage using the finite element method. In the analysis, positive and negative DC voltages in different amplitude ratios were superimposed over the phase-earth operating voltage of the insulator. Analyses in the study were made in time-dependent. Only DC voltage was applied to the insulator for the first 60 s, AC + DC voltage was applied between 60 to 120 s. Thus, the electric field behavior of the SiR insulator under combined AC–DC voltage has been obtained. The change of electric field based on positive and negative DC components was investigated. As a result of the study, the effect of the polarity of the DC component in the combined voltage was observed. As a result, effect of the polarity of the DC component in the combined voltage on the maximum electric field intensity was observed.
 
Rigid jumper is usually used in the strained angled tower for the UHV transmission project, which makes the protection angle of the ground wire to the jumper end larger, thus the lightning shielding failure risk of the strained angled tower may increase. In order to study the lightning shielding performance of strained angled tower for the ±1100 kV ultra-high voltage direct current (UHVDC) transmission project, a numerical model for the simulation of lightning attachment to the strained angled tower was established based on the research results in the aspects of lightning downward leader, inception and propagation characteristic of upward connecting leader and so on. The maximum lightning shielding failure current and the shielding failure flashover rate (SFFOR) of rigid jumper were calculated under different line angles and overhead ground wire cross-arm lengths based on the proposed model. Results show that the lightning flashover of rigid jumper mainly occurs on the outer side while the rigid jumper on the inner side is in a good shielding state. When the cross-arm length of overhead ground wire on the outer side of J27104A1 tower with 90° line angle is greater than 21.7 m, the SFFOR of rigid jumper will be below 0.1 times/(100 km a), which can meet the operation requirement. The analysis provides technical references for the lightning protection design of strained angled tower for the UHVDC transmission project.
 
Global warming and energy exhaustion problems are becoming a severe problems, of which energy conservation and carbon reduction are the most critical. Between 40% and 48% of the total electricity used in a building is consumed by air conditioning systems. The development of a supersonic water-misting cooling system with a fuzzy control system is proposed to optimize existing condenser noise, space, and energy consumption, as well as to address problems with cooling capacity resulting from improper control between compressors and condensers. An experimental platform was established for conducting tests, observing cooling efficiencies, and calculating power saving statuses. Comparing the observed cooling efficiency, a temperature difference of 5.4 °C was determined before and after the application; this is significant regarding efficiency. The method produces no pollution or water accumulation. When compared with fixed frequency air-cooled water chillers, an exceptional energy saving of 25% was observed. The newly developed supersonic mist-cooled chiller is an excellent solution to increasing water and electricity fees.
 
To suppress the switching dead-band in the Open-End Winding Permanent Magnet Synchronous Machine with Common DC bus (OW-PMSM-CDCB) drive system, the dual-inverter switch dead-band generates zero-sequence voltage and current during 120°decoupling modulation. The generation mechanism of dead-band voltage is analyzed with the help of Matlab/Simulink and a method to compensate for the zero-sequence voltage resulting from the dead-band of dual-inverter switches is discussed in this study. With the help of current polarity detection, the zero-sequence voltage resulting from the dead-band of the switch is offset by solving the dead-band voltage compensation amount, and an OW-PMSM-CDCB drive system experimental platform is built for experimental verification. Simulation and experimental show that the proposed compensation method can effectively suppress the zero-sequence current of OW-PMSM-CDCB.
 
This paper presents an inductor-less multilevel inverter (MLI) with a 13-level ac output. The proposed MLI consists of only 11 switches, 2 capacitors, and 2 input sources. Owing to the inductor-less symmetrical topology, the proposed MLI can reduce the component count in comparison of conventional MLIs. This leads to reduction of power loss and hardware cost. To clarify the effectiveness of the proposed MLI, the characteristic evaluation is given in detail. Some computer-based simulations in SPICE simulator environment as well as breadboard-based experimental tests are conducted concerning the proposed 13-level inverter. In the performed simulations, the power efficiency of the proposed MLI reaches about 85% and 88% at 1 kW in the case of a sinusoidal output and a triangular output, respectively. The proposed MLI improves power efficiency more than 2.5% comparing with the conventional K-type MLI when the output power is 1 kW. Furthermore, the experimental result proves the physical feasibility of the proposed topology by demonstrating the 13-level ac output.
 
Lightning strikes are one of the main causes of power system trip-outs. When the overhead transmission line (TL) connected to a wind farm is struck by lightning, large currents propagate to the substation, resulting in severe problems. To enhance the performance of wind farm substations, the transient behavior during lightning must be analyzed. The main contribution of this paper is to study the lightning behavior of wind farm substations whose design is different from other conventional substations. The lightning surge overvoltages caused by back flashover and shielding-failure of the 132 kV overhead TL connected to the 33/132 kV air-insulated substation (AIS) of Miramar wind farm are calculated. This wind farm has been built in Argentina to achieve grid connection and power transmission with a total capacity of 98.7 MW. The work investigates the fast-front lightning transient overvoltages in the AIS caused by lightning flashes striking the 132 kV overhead TL. The distributed parameter model of the TL, including towers, phase-conductors, the shielding-wire, insulators, and the span, is investigated using Digsilent Power Factory software. In addition, the AIS apparatus, including surge arresters (SAs), two 60 MVA transformers, and circuit breakers, are also considered in the model. The strike is applied first at the shielding-wire, and the impact on the transient overvoltages at the TL and the substation during the back flashover phenomenon are analyzed. On the other hand, the shielding-failure is studied and the transient overvoltages at the TL and the substation are analyzed. The impact on the transient overvoltages at the TL and the substation is investigated, taking into account the SA protection operation, and its dissipated energy during lightning flashes is calculated. The study results are important for the lightning protection systems design of wind farm substations connected to overhead TLs.
 
Smart grids are one of the most important structures based on cyber–physical devices. Therefore, these grids should be more reliable and efficient when increasing consumption. In recent years, however, with the automation of power grids and data transferring in a telecommunications infrastructure, the possibility of planning cyber-attacks has become a significant threat to systems integrity. Well-planned cyber-attacks can have catastrophic effects on the system to the extent that they may lead to a global blackout. It has been proven that, the optimization of the budgets for attack and defense in a power grid through cyber-attack is so essential. The aim of the present paper is investigate and simulate the most vulnerable operating bus using the state estimation technique through a new algorithm. The false data injection is performed on the data sent from the Phasor Measurement Units in such a way that it is not detectable to the grid dispatching operator under the invasion. In other words, when a cyber-attack occurs, the defender does not notice the attack and thus the estimated modes are destroyed. The proposed algorithm is implemented on a 14 IEEE bus network, and the best bus in terms of exposure under attack is identified. The proposed algorithm is based on the results obtained from state estimating of the grid after occur a cyber-attack on different buses. It was found that, the best bus to carry the attack was bus number 5, which causes the most changes in state variables with the least measurement damage. In addition, the most damage to the grid occurs when a cyber-attack causes the most damage in estimating the state of the most grid state variables.
 
Aiming at the defect that the traditional bearingless switched reluctance motor cannot control the axial suspension force, so that the rotor cannot achieve five-degree-of-freedom suspension by itself, this study presents an innovative 12/14 conical bearingless switched reluctance motor. The structure and principle of suspension force generation is illustrated in detail. Meanwhile, mathematical model of the proposed motor is studied and established. Considering the radial and axial displacement of the rotor, the derived mathematical model could accurately describe the radial force, axial force and electromagnetic torque of the proposed motor. Finally, the effectiveness of the derived mathematical model is verified by finite element simulation.
 
Changes in protease content in natto according to bacteria density and fermentation time . (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Protease content at different fermentation conditions.
The objective of the study to determine the factors affecting the protease content generated during soybean fermentation by Bacillus subtilis. In this study, four factors were investigated during soybean fermentation: (1) pH, (2) fermentation temperature, (3) fermentation time and bacterial density, and (4) added glucose content on steamed soybean. The experimental results showed that at 33 °C temperature, 48 h fermentation time, bacterial density 104 CFU, pH 7, and supplementation of 1 g glucose into 50 g steamed soybean, Bacillus subtilis fermented soybean (another name is natto) had the highest protease activity. This suggests that the fermentation conditions in the study are consistent with the growth of Bacillus subtilis to produce proteases. Moreover, the optimization of fermentation conditions contributes to reducing the energy consumption to obtain the desired product, by increasing the yield in reaction. Therefore, this study is important at an industrial level, while contributing to the rational use of energy. Keywords: Soy, Soybean, Natto, Protease, Nattokinase, Bacillus subtilis
 
Overcharging is one of the most serious safety problems in large-scale application of lithium ion battery (LIB). An in-depth understanding of the failure mechanism of battery overcharge is necessary to guide the safe design of battery system. In this paper, the electrochemical performance of commercial 18650-type cylindrical battery with Li(Ni0.5Co0.2Mn0.3)O2 cathode and graphite anode as the background is evaluated with different state of charge (SOC). The dynamic thermal behavior of overcharge in adiabatic conditions is studied, and the cathode materials, separator and anode materials after long-term overcharge cycle are characterized to identify the side reactions in battery. The results show that the battery impedance increases with the increase of SOC, and thereby greatly accelerating the attenuation of battery capacity. When LIB is charged and discharged in adiabatic conditions, the battery surface temperature of 116% SOC is about 10.03 °C higher than that of 100% SOC. Therefore, the battery with higher SOC has higher heating and is easy to induce the thermal runaway reactions. During the overcharge cycle, electrolyte decomposition, transition metal dissolution and phase transformation occur at the cathode, and serious lithium plating occur at the anode, as a result, increasing battery impedance, accelerating aging and increasing heat production. These results provide feasible support for understanding the overcharge mechanism and battery management system.
 
The spread of the COVID-19 pandemic in 2020 has contributed a large impact on various economic sectors and the energy sector is no exception. In this paper, we analyze the time-varying correlation between COVID-19 shocks (positive and negative) and energy markets (natural gas, gasoil, heating oil, coal, and crude oil) in the time-varying environment. This study adds to the literature by implementing the Markov-switching dynamic copula with Student-t distribution to explore the unexpected COVID-19 pandemic shock effects on energy markets. Our results revealed that (i) there is evidence of correlation between COVID-19 shocks and all energy markets; (ii) the contributions of COVID-19 shocks on energy markets are not constant along 2020. (iii), there is evidence of a similar response of the energy markets to the positive and negative COVID-19 shocks.
 
The number of households experiencing fuel poverty is thought to have risen by at least 600,000 in the UK because of the ongoing Covid-19 pandemic. The concentration of fuel poor households in poor quality, energy inefficient accommodation that they have little power to improve means they are particularly negatively affected by the retreat into the home brought about by successive lockdowns and restrictions. For many such households, the home is not the place of sanctuary that it needs to be at a time like this. However, our empirical research into the lived experiences of fuel poverty reveals additional consequences for fuel poor households, chiefly associated with restricted access to third spaces and other disruptions to their usual coping strategies. Based on our evidence, we highlight three key considerations for policy on fuel poverty in the era of Covid-19: the need to rapidly upgrade the energy performance of the existing housing stock; the need to address the additional financial hardship faced by fuel poor households; and the need to prioritise access to third spaces and high-quality public spaces while restrictions last. This paper develops the concept of energy poverty by considering the role of spaces outside the home as part of the overall experience of energy poverty and the range of ways in which policy makers can mitigate its impacts.
 
Many issues have emerged more clearly than before in multi-storey residential buildings during quarantine and lockdown caused by the global pandemic COVID-19. Among these problems is the deterioration in people’s mental and physical health inside the home caused by quarantine and closure. This deterioration is due to inadequate passive ventilation, natural lighting, and the lack of green open spaces in and around traditional multi-storey residential buildings. Also, one of the most severe problems is the airborne infection transmission from a positive covid-19 person to others due to the lack of control in the entrance of buildings against an infected person. In this paper, we modified the shape of a traditional multi-storey residential building. Using Design-Builder and Autodesk CFD software, we create a simulation to compare the amount of natural ventilation and lighting before and after modifying the building’s shape. This work aims to increase the passive ventilation and daylight inside the building. Also, to achieve the biophilic concept to provide open spaces for each apartment to improve the mental and physical health of the residents. In addition, it protects the building users from infection with the virus. Through this study, we found that passive ventilation and daylight achieved more efficiency in the building that we have modified in its shape, which led to a 38% reduction in energy consumption. In summary, these findings suggest that by modifying the mass of the traditional multi-storey residential building with open green spaces provided for each apartment, the natural connection with the inhabitants of the building was sufficiently provided. Moreover, all this will significantly help improve residents’ mental and physical state, and it will also help prevent the spread of various diseases inside the homes.
 
Isometric view of air speed meter. Source: Patent US 2018/0245954 [19].
Conceptual design of the expired air spirometer. Source: China national phase patent application.
Activation of the dropping of the colorful liquid. Own elaboration.
Meshing of the computational domain of the spirometer, using the Grid technique in the ICEM software. Source: Own elaboration.
Simulation with a blow of 12 l/s. Own elaboration.
The evolution of respiratory capacity in convalescent Covid-19 patients must be monitored over time, which is not feasible due to the lack of personal, portable and low cost spirometers that prevent contamination. Here, we propose the design of a portable and personal spirometer, that uses the parabolic movement of a drop of fluid, driven by exhaled air, to measure respiratory capacity. The distance traveled by the drop is correlated with the air and thus, the exhaled air volume. The mechanical design does not require an external energy source and instead relies on the force of the patient’s exhalation. The position of the drop can be measured directly using an interchangeable ruler within the spirometer. The research methodology consists in three stages: idea generation, concept definition (patent), and concept feasibility. In this third stage a simulation with Modellus X.04.05 is realized. We have patented the conceptual design of the spirometer, and additionally present a simulation and feasibility determination of the environmentally friendly and low-cost design. The novelty of this patented spirometer is the use of a simple physical principle to solve a complex problem, without using external energy. Therefore, this artifact can be implemented and widely used in the prevention and control of bronchopulmonary diseases.
 
Electric load forecasting is a challenging research, which is of great significance to the safe and stable operation of power grid in epidemic period. In this paper, Long-Short-Term-Memory (LSTM) model with simplex optimizer is proposed to forecast the electric load for an enterprise during the COVID-19 pandemic. The forecasting process consists of data processing, LSTM network construction and optimization. Firstly, some data processing steps includes information quantifying, electric load data cleaning, correlation-coefficient-based medical data filtering, clustering-based medical data and electric load data filling. Then LSTM-Based electric load forecasting model of enterprise is established during the COVID-19 pandemic. On this basis, LSTM network is trained and parameters are optimized via simplex optimizer. Finally, an example of the electric load forecasting of an enterprise during the COVID-19 pandemic is investigated. The forecasting results show that the reduced number of iterations is about 25% and the improved forecasting accuracy is about 5.6%. These results can be used as a reference for resuming production of enterprises and planning of electric grid.
 
Carbon dioxide emissions trend in: France, Netherlands, Poland, Portugal, Germany, Italy, Greece, Spain, Sweden and UK, 1960-2018.
Carbon dioxide emissions trend in: Austria, Belgium, Bulgaria, Croatia, Czech Republic, Cyprus, Denmark, Estonia, Finland, Malta, Romania, Slovakia, Hungary, Ireland, Slovenia, Latvia, Lithuania and Luxembourg, 1960-2018.
Yearly CO 2 emissions in EU-28.
The paper analyzes the variation of carbon dioxide emissions produced by burning fossil fuels for energy production in the European Union member states between 1960 and 2018. It was analyzed the evolution of CO2 emissions produced by the combustion of coal, gas, and oil in 28 member states. The analysis showed that Cyprus, Portugal, Greece, and Spain recorded the highest increases in CO2 emissions in 2018 compared to 1960, while the Czech Republic and Latvia recorded the lowest increase in CO2 emissions by only 7% compared to 1960. Only four countries (Germany, Luxembourg, Sweden, and the United Kingdom), out of the 28 countries analyzed, had in 2018, CO2 emissions lower than or equal to those of 1960. In 2018, CO2 emissions generated by burning coal increased in eleven countries and decreased in the other seventeen countries, compared to 1960 emissions. CO2 emissions from gas combustion increased in all 28 countries analyzed, with the mention that in 1960, eleven countries had no gas consumption. Regarding the CO2 emissions generated by oil burning, they have increased in 26 countries and only two countries have registered emissions reduction below the value of 1960. EU’s energy intensity (ratio of gross energy consumption to gross domestic product) decreased by 37% between 1990 and 2017.
 
To meet the requirement of the wind energy resource assessment and utilization, the statistical characteristics of wind climate in the China mainland were analyzed in this study by using observation wind dataset for 1971–2017 from the China Meteorological Administration (CMA). A series of key factors closely related to wind power development were analyzed, systematically including the spatial and temporal characteristic of wind speed, the distribution of wind speed at different density grades, the density of the cumulative distribution, strong wind days and weak wind days. The characteristics of wind patterns in different regions are also compares. Results indicate that: (1) the regions with the highest wind speed in China centrally locate in Northwest China, North China and Northeast China with the highest wind speed occurs in spring. The annual variation of wind speed in northern China is bimodal while in southern China it is unimodal. (2) The wind speed probability density distribution shows a significant spatial–temporal difference. The wind speed probability distribution is the most concentrated in spring for almost all regions. For each season, the concentrated and stable wind speed occurs in Xinjiang region in spring. While it appears in the region from Northwest China to the northern part of North China for summer and autumn, and in the southern part of North China and Central China for winter. In the case of equal cumulative probability, the highest wind speed locates in Northeast China and the lowest in Sichuan Basin. (3) For 1971–2017, the wind speed in all regions of China showed a decreasing trend on the whole. But this trend slowed down since 1990s. It is worth noting that the wind speed in some regions even increased since 2000. (4) The numbers of strong wind day have been decreasing in all regions, but the numbers of weak wind day demonstrate an evolutionary feature of a growth followed by decrease. In most regions, the numbers of weak wind day reached the maximum in the vicinity of 2000 and then decreased rapidly.
 
Solar activity transmitted in energy reaches the Earth, affecting atmospheric temperature and other global weather variables. This research aims to analyze the relationship between solar cycles and meteorological variables in the Central Inter-Andean Valley during the period 1986–2019. Sunspot data were obtained from the Royal Observatory of Belgium for solar cycles 22, 23 and 24, and the meteorological variables of the National Service of Meteorology and Hydrology of Peru from five stations that are distributed in the Valley. For the correlation of the variables, the nonparametric Spearman statistical test with a third-degree polynomial regression was applied. The results show that there is a decrease in the number of sunspots in cycle 24, and that the temperature varies by 3.85 °C in the study period. Of the five stations analyzed, four of them show that there is no relation between the variables and only in the station Viques there is an inverse relation for α<0.05 referring to the variables of maximum temperature and sunspots, obtaining a coefficient of determination of R2=0.619. Therefore, solar activity does not influence the climate variability of the study valley, and this is due to climate change due to the effects of anthropogenic activities.
 
There are four strategies to combating global warming, namely by directly reducing greenhouse gas emissions, or indirectly through expanding renewable energy employment, more efficient use of energy, or a wide range of climate policies. This study reports a bibliometric analysis of direct carbon dioxide emission reduction through carbon capture. The research trend in carbon capture within the three main types of technologies, namely pre-combustion, post-combustion and oxy-fuel combustion, was investigated using publications from 1998 to 2018 retrieved from the Web of Science database. It was found that from 1998–2007 there was little or no research output on carbon capture, until 2008, when legislation on climate change abatement was introduced and public and industry awareness of clean fossil energy options grew. With these motivating factors, 55 countries engaged in carbon capture technologies and related research in which the United States has the most research output followed by the UK and, China. Among the carbon capture technologies commonly studied, the bibliometric analysis based on a network map showed that post-combustion capture is the most referenced carbon capture technology with about 80.9% of total publications retrieved. oxy-fuel combustion had the lowest number of publications (3.4%).
 
In recent years, some countries are facing the problem of energy security. Energy security is an important factor affecting the national economy and environment. There are many investigations about energy security, but few of them are bibliometric analysis, including co-citation analysis, hot topics, burst detection, and emerging trends. Therefore, this paper adopts a bibliometric method to address the above issues and provide a general picture of the research field. By downloading 2845 articles from Web of Science and analyzing the results given by CiteSpace, the main conclusions of the most productive countries, institutions, sources, authors, and interesting research directions in the energy security researches are visually demonstrated. For instance, Energy Policy, Renewable Sustainable Energy Reviews, and Applied Energy are the major sources for energy security researches. The emerging trends in energy security researches are energy security, the exploring proposition, the integrated assessment. This paper provides an overall analysis of energy security researches and gives some inspirations for the researchers in this area to do further investigations.
 
Time plots of the variables in the empirical model. Source: Federal Reserve (2018); EIA (2018b).
CUSUM and CUSUM-Q tests.
Results of unit root tests (ADF, PP, KPSS) a .
NARDL cointegration test. Panel A: Testing the presence of asymmetry
This paper investigates the impacts of non-renewable consumption (NRE) and renewable energy consumption (RE) on industrial production (IP) in the US using monthly data from 2000:01 to 2018:02. To do so, the paper employs the nonlinear autoregressive distributed lag (NARDL) approach to examine asymmetric relationships, thus contributing to the past literature methodologically. The findings show that both non-renewable and renewable energy drive industrial growth in the US and that a certain asymmetric behaviour can be concluded: the impact of an increase in NRE on IP is greater than that of a decrease in NRE on IP, while the influence of an increase in RE on IP seems to be less than that of a decrease in RE on IP. Keywords: Non-renewable energy consumption, Renewable energy consumption, Economic growth, Nonlinear autoregressive distributed lag approach
 
(a) Frequency and rate of forced outages across various levels of operating units; (b) Frequency and rate of forced outage events across voltage levels; (c) Frequency of forced outages by months of year; (d) Frequency of forced outages by days of week; (e) Frequency of forced outage events across various levels of times of day.
In this paper, the authors present a novel approach to the study of the frequency of forced outages in various operating units, or regions of Eskom, using statistical techniques. The forced outage data are summarized in frequencies and rates of forced outages for various levels, providing insight into variations among the levels of variables, and helping to identify levels that could be targeted in forced outage reduction strategies. The chi-squared test was performed to identify variables that had associations with the operating units (OUs), isolating variables that could be focused on to reduce frequencies in OUs. Where dependence was determined, the degree of association was calculated, enabling the ranking of the dependence with OUs in terms of which ones, if targeted, will have the highest impact on the frequency of forced outages in OUs. The paper contributes to the discourse on outages of equipment and provides insight into historical forced outage data. Furthermore, the paper provides a practical approach to studying the frequency of forced outages in regions of a utility. Finally, the insight gained from the study can enhance decision making related to the asset and performance management of power system equipment in general, and subtransmission transformers in particular.
 
Using clean cooking energy is better for people’s health than solid fuel. Studies have focused on the impact of energy types on objective health, but less on subjective or mental health. Based on the 2014 China labor force dynamic survey, this paper found that cooking with clean energy was significantly better for self-assessment of health than solid fuel. (1) For people who use clean energy cooking, the odds of general self-assessment as healthy, physically painless, mental self-assessment as healthy and no physical health impact on work or life were respectively 1.43 times, 1.43 times, 1.34 times, and 1.3 times that of those who use solid fuel. (2) The type of cooking energy has a deeper influence on villagers’ body health than on the psychological level. When other factors remain the same, the type of cooking fuel has nothing to do with whether emotional problems affect work or life. (3) Cooking energy type has a health spillover effect, which has an impact on the health of both the cook and people who do not cook, but the impact on the cook is more extensive. (4) The smoother the smoke in the cooking or the kitchen is open, or the kitchen has a range hood or exhaust fan, the more it is good for the health of the cook. But kitchen type does not affect people who do not cook. Actively promoting clean energy use in cooking, reducing the amount of cooking lampblack, and improving the condition of the kitchen are all important ways for health assessment.
 
The bulk electric power system in New England is fundamentally changing. The representation of nuclear, coal and oil generation facilities is set to dramatically fall, and natural gas, wind and solar facilities will come to fill their place. The introduction of variable energy resources (VERs) like solar and wind, however, necessitates fundamental changes in the power grid’s dynamic operation. VER forecasts are uncertain, and their profiles are intermittent; thus requiring greater quantities of operating reserves. This paper describes the methodology and the key findings of the 2017 ISO New England System Operational Analysis and Renewable Energy Integration Study (SOARES). This study was commissioned by the ISO New England stakeholders to investigate the effect of several scenarios of varying generation mix on normal operating reserves. The project was conducted using the holistic assessment approach called the Electric Power Enterprise Control System (EPECS) simulator. The study finds a minimal impact on current normal operating conditions in the ISO-NE system for scenarios with relatively low penetration of VERs. Nevertheless, for scenarios with a significant presence of VERs, the system may require additional amounts of both upward and downward load following reserves and upward and downward ramping reserves to effectively maintain reliable operations. In these scenarios, the curtailment of semi-dispatchable resources also becomes an integral part of balancing performance; in part to complement operating reserves and in part to mitigate the topological limitations of the system. Indeed, the integration of significant amounts of VERs in relatively remote regions significantly increases the potential of congestion on several key interfaces. In many of these scenarios, the system experiences heavy saturations of regulation reserves and their increase would enhance the response to residual imbalances. The concludes with final insights into the emerging roles of curtailment, energy storage, and demand response as integral parts of normal balancing performance. Keywords: Renewable energy integration, Operating reserves, Unit commitment, Economic dispatch, ISO New England, Enterprise control
 
2019 The Author(s) This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. After a thorough investigation, the Editor has concluded that the acceptance of this article was partly based upon the positive advice of two illegitimate reviewer reports. The reports were submitted from email accounts which were provided to the journal as suggested reviewers during the submission of the article. Although purportedly real reviewer accounts, the Editor has concluded that these were not of appropriate, independent reviewers. This manipulation of the peer-review process represents a clear violation of the fundamentals of peer review, our publishing policies, and publishing ethics standards. Apologies are offered to the readers of the journal that this deception was not detected during the submission process.
 
On the 27th of February 2015, it was published, in Portugal, the Regulation for Sustainability and Efficient Use of Resources (RESEUR). This is one of the thematic areas created of Portugal 2020, a partnership agreement between Portugal and the European Commission, that regulates the access to European Structural and Investment Funds. RESEUR frames different Investment Priorities (IP) and this research focus on the one that respects energy efficiency, intelligent energy management and the use of renewable energy in local government buildings, street lighting and social housing. We concluded that, despite there were, until now, 87 opportunities for proposal submission, only 46 % of the municipalities have approved projects and no more than 35 % of the budget for this IP is allocated. Until now, € 121 million were approved in this IP, with only 4.2 % meant to interventions in public buildings, although it is the intervention axis with a closer approach to Triple Bottom Line (TBL). Defining a “Decision Triangle” and introducing a political dimension in TBL, we verified that most of the approved projects and the funds allocated refer to social housing and street lighting, i.e. based on the available data there is no demand for TBL balance.
 
Distribution of papers presented at ICEER 2020 by topic.
The 7th International Conference on Energy and Environment Research (ICEER 2020) followed six previous successful editions hosted in three European Countries (Portugal, Spain, Czech Republic). This last edition was planned to be held in Italy first, and then in Portugal, due to the pandemic situation. Finally, for safety reasons, it was decided to organize a virtual event, which was held from 14 to 17 September 2020. Despite the limitations imposed by COVID-19 spreading, the online format did not affect the original spirit of the Conference, which was born as “a privileged space to discuss current matters related to energy and the environment research”. This year the Conference main topic was “Driving Energy and Environment in 2020 towards a Sustainable Future”, bringing attention to the dramatic changes that occurred in the energy and environment sectors in the last years, speeded up by the pandemic, and their perspectives for a sustainable future. This paper gives a comprehensive outline of the conference organization as well as of the main research topics addressed in the three keynote speeches and in the dedicated sessions planned to enhance the event effectiveness and boost discussion and interaction among experts in those fields.
 
Based on a two-month simultaneous in-situ wave dataset of two observational sites in the coastal regions of the northern South China Sea, the variabilities and richness of the wave energy (WE) during typhoon Lupit (2021) are studied and the discrepancies in WE responses between the two sites are also discussed. The results show that the WE of the sites mainly consists of the ocean condition whose significant wave height ranges from 0.5 to 1.5 m and energy period ranges from 5 to 8 s. It is suggested that the richness of WE could be significantly enhanced by the passage of the typhoon. For example, the energy density is enhanced by 2–4 times, i.e. from 1.2–4.2 kW/m to 5.9–9.5 kW/m, and the available level frequency maintains as high as 100%. Moreover, the increase in WE caused by typhoons occurs several days before the passage of the typhoon and can maintain for nearly a week after its passage. Further analysis reveals that the variable intensity of the WE responses to typhoons is mainly decided by the wind speed of the typhoon and the distance between the typhoon centers to the location of the sites. Our study highlights the possibility and importance of WE to meet the basic power consumption of equipment in coastal regions, under extreme weather conditions when wind energy and solar energy are both difficult to be utilized.
 
Distribution of authors in ICEER 2020 by country.
Distribution of papers presented at ICEER 2021 by topic.
The World pandemic situation that started in 2020 brought important limitations to live events. In spite of the fast response provided by the scientific community, with researchers from all over the World committed to the development of vaccines to prevent the dissemination and effects of the corona virus, in 2021 it was not yet possible to organize the 8th International Conference on Energy and Environment Research (ICEER) under live mode. Therefore, the ICEER 2021 occurred online for the second consecutive year, from 13–16 September 2021. The Authors, Participants and the Conference organization understood how important it is to discuss matters related to Energy and the Environment Research, as it was demonstrated by the huge changes introduced by travel and work limitations. Not only the energy consumption was affected during the pandemic, but also the environment was positively impacted by the reduction of human individual travel, both for working and for amusement purposes. These facts highlighted even more the importance of the development and use of energy sources and systems that are reliable, affordable and, above all, environment friendly, towards Sustainable Development, which motivated the theme adopted for the current edition of ICEER 2021: “Developing the World in 2021 with clean and safe energy”. The ICEER 2021 recovered some participants who preferred the live version but were committed not to give up on their research in these important topics, and the full three working days demonstrated the resilience of this community. This editorial paper summarizes the ICEER 2021, briefly reporting the main conclusions and the most impacting sessions, presentations and interventions that allowed to strengthen the interaction among experts and young researchers in the energy and environment field.
 
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Kittisak Jermsittiparsert
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Sami Hammami
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