In recent years, the investment in the wind energy sector has increased in the context of producing green electricity and saving the environment. The installation of small wind turbines (SWTs) represents an actual strategy for meeting energy needs for off-grid systems and certain specialized applications. SWTs are more expensive per kilowatt installed as compared to large-scale wind turbines. Therefore, the main objective of this study is to produce an economical technology for the wind power market offering low-cost SWTs. The idea consists of considering a simple structure of the wind turbine using direct-drive permanent magnet synchronous generator (DDPMSG). DDPMSGs are the most useful machines in the wind energy field thanks to several advantages, such as elimination of noise and maintenance cost due to suppression of the gearbox and absence of the rotor circuit excitation barriers by the presence of the permanent magnets (PMs). Their major downside is the high cost of active materi... [more]

The need for accurate measurements and for estimating the uncertainties associated with measures are two pillars for researchers and metrologists. This is particularly true in distribution networks due to a mass deployment of new intelligent electronic devices. Among such devices, phasor measurement units are key enablers for obtaining the full observability of the grid. The phasor measurement unit performance is mostly evaluated by means of the total vector error, which combines the error on amplitude, phase, and time. However, the total vector error is typically provided merely as a number, that could vary within an unknown interval. This may result into the phasor measurement unit incompliance with the final user expectancies. To this purpose, and with the aim of answering practical needs from the industrial world, this paper presents a closed-form expression that allows us to quantify, in a simple way, the confidence interval associated with the total vector error. The input requir... [more]

This article presents the research results related to the methodology of threat analysis to implement in energy security. In the conducted studies, the world’s output in scenario planning and the most famous cases of global security and technology scenarios were analysed. These projects were the Lisbon Group analysis, Shell’s scenario planning concepts, and the US National Intelligence Council’s long-term analysis. In this way, I demonstrated the limitations of a scenario-based view of the issues under study, resulting mainly from considering only one type of environment. The formulated conclusions made it possible to build the author’s model of the strategic analysis process for the energy security sector. It goes beyond scenario analysis, complementing it with the sector, portfolio, and integrated analysis methods. The strategic analysis built in this way takes into account the achievements of many scientific disciplines, namely, technology, security, strategic management, foresight,... [more]

A revolution of the global energy industry is without an alternative to solving the climate crisis. However, renewable energy sources typically show significant seasonal and daily fluctuations. This paper provides a system concept model of a decentralized power-to-green methanol plant consisting of a biomass heating plant with a thermal input of 20 MWth. (oxyfuel or air mode), a CO2 processing unit (DeOxo reactor or MEA absorption), an alkaline electrolyzer, a methanol synthesis unit, an air separation unit and a wind park. Applying oxyfuel combustion has the potential to directly utilize O2 generated by the electrolyzer, which was analyzed by varying critical model parameters. A major objective was to determine whether applying oxyfuel combustion has a positive impact on the plant’s power-to-liquid (PtL) efficiency rate. For cases utilizing more than 70% of CO2 generated by the combustion, the oxyfuel’s O2 demand is fully covered by the electrolyzer, making oxyfuel a viable option for... [more]

The importance of corporate social responsibility, especially in the environmental domain, continues to grow in an era of mounting climate urgency. This study is based on original, empirical, survey-based research in two post-communist European countries and seeks to add a geographical viewpoint and to investigate the influence of innovative constructs (environmental reporting, environmental strategy, environmental management control system) on environmental and economic performance. Data are analysed through partial least squares structural equation modelling, which enables the use of a complex model with several links between constructs. Findings reveal that environmental strategy has a positive impact on the use of an environmental management control system and an indirect positive impact on environmental performance. The environmental management control system has been shown to have a positive influence on environmental performance and, ultimately, on economic performance.

Aiming at the problem of end structure heating caused by the excessive eddy current loss of large synchronous condensers used in ultra-high voltage (UHV) power transmission, combined with the actual operation characteristics of the synchronous condenser, a three-dimensional transient electromagnetic field physical model is established, and three schemes for adjusting the end structure of the condenser under rated condition are researched. The original structure has a copper shield and a steel clamping plate. Scheme 1 has no copper shield but has a steel clamping plate. Scheme 2 has no copper shield but has an aluminum clamping plate. By constructing a three-dimensional fluid−solid coupling heat transfer model in the end of the synchronous condenser, and giving the basic assumptions and boundary conditions, the eddy current loss of the structure calculated by the three schemes is applied to the end region of the synchronous condenser as the heat source, and the velocity distribution of... [more]

Utility-sponsored residential energy reduction programs have seen rapid advancement in the Unites States (US) over the past decade. These programs have particularly emphasized investments in energy efficient appliances and enveloped improvements. They have generally required co-investment by residents and, as a result, have mostly reached medium to high-income residents, with low income residences, in effect, supporting the utility investments through higher energy costs. Additionally, utility initiatives directed toward behavior-based energy reduction have reached residences with more advanced technologies, such as smart meters and smart Wi-Fi thermostats linked to phone apps, technologies generally not present in low-income residences. This research seeks to inform development of behavior-based energy reduction programs aimed specifically at low-income residences, premised on peer-to-peer energy education and support. It focuses on the design and implementation of a pilot program for... [more]

In a scenario in which the climate changes subject urban centres and large cities to high levels of environmental vulnerability and criticality underway, it is evident the need to define operational and straightforward decision-making tools capable of prefiguring and verifying the effectiveness of urban transformation climate-adaptive regeneration processes. The Climate Adaptive Design Index for the Built Environment (CADI-BE) tool has been developed to assess the adaptive capacity and level of performance of open urban spaces to the stresses due to the increase in global average temperatures. The repercussions of these phenomena cause the occurrence of heatwaves and the urban heat island effect (UHI), bringing out the inability of cities to cope with changes in the climate, making urban open spaces unlivable and no longer the ideal habitat for everyday life and social interactions.

This paper proposes a high step-up high-efficiency converter, comprised of an active switched coupled-inductor cell. The secondary windings are integrated into a rectifier voltage multiplier cell in a boost-flyback configuration, allowing the operation with high voltage gain with low switches duty cycle and low turn-ratios on the coupled-inductors. Both coupled-inductors are integrated into a single core due to the parallel operation of the switches. The leakage inductances of the coupled-inductors are used to mitigate the reverse recovery currents of the diodes, while regenerative clamp circuits are used to protect the switches from the voltage spikes caused by the leakage inductances. The operation of the converter is analyzed both quantitatively and qualitatively, and the achieved results are validated through experimentation of a 400 W prototype. A 97.1% CEC efficiency is also reported.

The paper analyses the mechanical properties of shales from the Baltic Basin, focusing on creep strain in conditions of variable stress and elevated temperature (85 °C). Rock samples were collected from drill cores from various depths between 3600−4000 m. A series of creep tests was performed using a triaxial apparatus in simulated pressure and temperature conditions in the reservoir. The creep tests were conducted at variable levels of differential stress in variable time intervals. The laboratory experiments were performed in order to study brittle and viscoelastic creep proceeding in time in shales rich in organic matter and clay minerals. Creep compliance of shale formations rich in organic matter influences the success of hydraulic fracturing procedures, as well as migration of natural gas during exploitation. Laboratory characteristics of geomechanical properties (compressive strength, strain and elastic moduli) is crucial for planning natural gas exploitation from unconventional... [more]

Contractors responsible for the whole execution of engineering, procurement, and construction (EPC) projects are exposed to multiple risks due to various unbalanced contracting methods such as lump-sum turn-key and low-bid selection. Although systematic risk management approaches are required to prevent unexpected damage to the EPC contractors in practice, there were no comprehensive digital toolboxes for identifying and managing risk provisions for ITB and contract documents. This study describes two core modules, Critical Risk Check (CRC) and Term Frequency Analysis (TFA), developed as a digital EPC contract risk analysis tool for contractors, using artificial intelligence and text-mining techniques. The CRC module automatically extracts risk-involved clauses in the EPC ITB and contracts by the phrase-matcher technique. A machine learning model was built in the TFA module for contractual risk extraction by using the named-entity recognition (NER) method. The risk-involved clauses col... [more]

The aim of this study was to identify the preferences of final purchasers regarding the environment of cooperation with offerors and the benefits of cooperation, as well as to identify dependencies between two groups of preferences, taking into account the age of purchasers. The results of an analysis of the global literature on the subject indicate that so far these issues have not been studied, either in relation to the energy market or other areas of the consumer market. Therefore, we can talk about a cognitive and research gap in this area. In order to reduce the gap, seven research hypotheses were formulated and primary research was carried out on 1196 adult representatives of final purchasers in Poland to verify the hypotheses. The collected data were subjected to quantitative analysis, the results of which made it possible to state that most respondents preferred the parallel use of the online and offline environments as a place of interaction with offerors. More than half of th... [more]

Integration of wind energy resources into the grid creates several challenges for power system dynamics. More specifically, Type-3 wind turbines are susceptible to subsynchronous control interactions (SSCIs) when they become radially connected to a series-compensated transmission line. SSCIs can cause disruptions in power generation and can result in significant damage to wind farm (WF) components and equipment. This paper proposes an approach to mitigate SSCIs using an online frequency scan, with optimized phase angles of voltage harmonic injection to maintain steady-state operation, to modify the controllers or the operating conditions of the wind turbine. The proposed strategy is simulated in PSCAD/EMTDC software on the IEEE second benchmark model for subsynchronous resonance. Simulation results demonstrate the effectiveness of this strategy by ensuring oscillations do not grow.

This study models the frequency use of wood, charcoal, liquid gas, electricity, and kerosene in urban households in Ghana and supplements the literature on cooking fuel choices. The modeling is based on survey data collected in several major Ghanaian cities. Survey results indicate that charcoal and liquid gas are frequently used in meal preparation, while the frequency use of firewood, kerosene, and electricity is limited. Frequency use is estimated using the ordered probit technique. Five cooking fuel use equations identify income, socio-demographic characteristics, and location of urban residents as influencing the frequency use. Statistically significant effects measure probability changes in each of the four fuel categories. Income and education increase the probability of often or very often of using liquid gas or electricity to cook. The effect of being employed by the government is similar but less consistent. Age, household size, and marital status are linked to frequency use,... [more]

The potential-induced degradation (PID) mechanism in Cu(In,Ga)(Se,S)2 (CIGS) thin-film solar cells, which are alternative energy sources with a high efficiency (>23%) and upscaling possibilities, remains unclear. Therefore, the cause of PID in CIGS solar cells was investigated in this study at the cell level. First, an appropriate PID experiment structure at the cell level was determined. Subsequently, PID and recovery tests were conducted to confirm the PID phenomenon. Light current−voltage (I−V), dark I−V, and external quantum efficiency (EQE) analyses were conducted to determine changes in the cell characteristics. In addition, capacitance−voltage (C−V) measurements were carried out to determine the doping concentration and width of the space charge region (SCR). Based on the results, the causes of PID and recovery of CIGS solar cells were explored, and it was found that PID occurs due to changes in the bulk doping concentration and built-in potential at the junction. Furthermore, b... [more]

A fire can pose a significant threat to a building’s occupants and leads to property damage. The burning characteristics usually determine the severity of the accident. Environments in high-altitude areas feature low oxygen content and ambient pressure, which can influence the burning characteristics of combustibles. In this paper, a series of field experiments were conducted to investigate the burning characteristics of gasoline at different altitudes considering heat release rate (HRR), flame height, and smoke release rate. Results show that the combustion process can be divided into three stages: initial stage, stable stage, and attenuation stage. Lower oxygen content and ambient pressure reduce the HRR; for example, the HRR at an altitude of 4150 m is nearly half at an altitude of 500 m, contributing to a lower smoke release rate. The HRR is proportional to 1.3 power of atmospheric pressure, and a fitting equation was brought out in this paper. Flame height increases with the incre... [more]

In this paper, we perform a literature review on the current state of knowledge about homeowners in the context of the adoption of renewable heating systems. Despite a considerable number of studies about homeowners, homeowner−installer interactions, and ways to improve the effectiveness of renewable heating programs, based on homeowner knowledge, have not yet been studied in much detail. To address these knowledge gaps, we conduct a qualitative study on single-family house owners who installed heat pumps and took part in a renewable heating program in Geneva, Switzerland. We cover homeowner practices in choosing installers and heating system types, homeowners’ feedback about heat pump installation and use, as well as their experience in participation in the renewable heating program. Based on the literature review and the findings from the interviews, we provide the following recommendations on how to increase the effectiveness of renewable heating programs: (a) support for homeowners... [more]

Many researchers in industry and academia are showing an increasing interest in the definition of fuel surrogates for Computational Fluid Dynamics simulation applications. This need is mainly driven by the necessity of the engine research community to anticipate the effects of new gasoline formulations and combustion modes (e.g., Homogeneous Charge Compression Ignition, Spark Assisted Compression Ignition) to meet future emission regulations. Since those solutions strongly rely on the tailored mixture distribution, the simulation and accurate prediction of the mixture formation will be mandatory. Focusing purely on the definition of surrogates to emulate liquid phase and liquid-vapor equilibrium of gasolines, the following target properties are considered in this work: density, Reid vapor pressure, chemical macro-composition and volatility. A set of robust algorithms has been developed for the prediction of volatility and Reid vapor pressure. A Bayesian optimization algorithm based on... [more]

In this paper, the dynamic experimental identification of an inductive energy harvester for the conversion of vibration energy into electric power is presented. Recent advances and requirements in structural monitoring and vehicle diagnostic allow defining Autonomous Internet of Things (AIoT) systems that combine wireless sensor nodes with energy harvester devices properly designed considering the specific duty cycle. The proposed generator was based on an asymmetrical magnetic suspension and was addressed to structural monitoring applications on vehicles. The design of the interfaces of the electric, magnetic, and structural coupled systems forming the harvester are described including dynamic modeling and simulation. Finally, the results of laboratory tests were compared with the harvester dynamic response calculated through numerical simulations, and a good correspondence was obtained.

Current climate change threats and increasing CO2 emissions, especially from the building stock, represent a context where action is required. It is necessary to provide efficient manners to manage energy demand in buildings and contribute to a decarbonised future. By combining new technologies, such as artificial intelligence, Internet of things, blockchain, and the exploitation of big data towards solving real life problems, the way could be paved towards smart and energy-aware buildings. In this context, the aim of this paper is to present a critical review and an in-detail definition of the big data value chain for the built environment in Europe, covering multiple needs and perspectives: “policy”, “technology” and “business”, in order to explore the main challenges and opportunities in this area.

Series-winding topology (SWT) could improve the DC-link voltage utilization, as open-winding topology does. Meanwhile, it can greatly reduce the number of power devices. Firstly, for the half-bridge power modules (HBPMs)-based inverter, an N-phase series-winding motor only requires N + 1 HBPMs for driving. On the other hand, such SWT also brings new challenges to the drive system. A zero-sequence loop is introduced into the motor windings due to SWT. The generated zero-sequence current would degrade the total harmonic distortion of the phase currents and produce the additional torque ripple. Moreover, current sensors are typically integrated with the HBPMs. However, in SWT, their measured results are the leg currents of the inverter, not the phase currents of the motor, which is crucial to the motor control. Thus, this paper mainly focuses on the aforementioned problems in a three-phase series-winding permanent-magnet synchronous motor (TPSW-PMSM) drive with HBPM-based inverter. Firstl... [more]

In the current work, an effort is made to study the influence of injection timing (IT) and injection duration (ID) of manifold injected fuels (MIF) in the reactivity controlled compression ignition (RCCI) engine. Compressed natural gas (CNG) and compressed biogas (CBG) are used as the MIF along with diesel and blends of Thevetia Peruviana methyl ester (TPME) are used as the direct injected fuels (DIF). The ITs of the MIF that were studied includes 45° ATDC, 50° ATDC, and 55° ATDC. Also, present study includes impact of various IDs of the MIF such as 3, 6, and 9 ms on RCCI mode of combustion. The complete experimental work is conducted at 75% of rated power. The results show that among the different ITs studied, the D+CNG mixture exhibits higher brake thermal efficiency (BTE), about 29.32% is observed at 50° ATDC IT, which is about 1.77, 3.58, 5.56, 7.51, and 8.54% higher than D+CBG, B20+CNG, B20+CBG, B100+CNG, and B100+CBG fuel combinations. The highest BTE, about 30.25%, is found for... [more]

The prediction and pre-evaluation of the thermal properties and combustion-related problems (e.g., emissions and ash-related problems) are critical to reducing emissions and improving combustion efficiency during the agricultural crop residues combustion process. This study integrated the higher heating value (HHV) model, specific heat model, and fuel indices as a new systematic approach to characterize the agricultural crop residues. Sixteen linear and non-linear regression models were developed from three main compositions of the ultimate analysis (e.g., C, H, and O) to predict the HHV of the agricultural crop residues. Newly developed HHV models have been validated with lower estimation errors and a higher degree of accuracy than the existing models. The specific heat of flue gas during the combustion process was estimated from the concentrations of C, H, O, S, and ash content under various excess air (EA) ratios and flue gas temperatures. The specific heat of agricultural crop resi... [more]

Overtopping-type wave power conversion devices represent one of the most promising technology to combine reliability and competitively priced electricity supplies from waves. While satisfactory hydraulic and structural performance have been achieved, the selection of the hydraulic turbines and their regulation is a complex process due to the very low head and a variable flow rate in the overtopping breakwater set-ups. Based on the experience acquired on the first Overtopping BReakwater for Energy Conversion (OBREC) prototype, operating since 2016, an activity has been carried out to select the most appropriate turbine dimension and control strategy for such applications. An example of this multivariable approach is provided and illustrated through a case study in the San Antonio Port, along the central coast of Chile. In this site the deployment of a breakwater equipped with OBREC modules is specifically investigated. Axial-flow turbines of different runner diameter are compared, propo... [more]

Electric Vehicles (EV) and Hybrid EV (HEV) use Lithium (Li) ion battery packs to drive them. These battery packs possess high specific density and low discharge rates. However, some of the limitations of such Li ion batteries are sensitivity to high temperature and health degradation over long usage. The Battery Management System (BMS) protects the battery against overvoltage, overcurrent etc., and monitors the State of Charge (SOC) and the State of Health (SOH). SOH is a complex phenomenon dealing with the effects related to aging of the battery such as the increase in the internal resistance and decrease in the capacity due to unwanted side reactions. The battery life can be extended by estimating the SOH accurately. In this paper, an extensive review on the effects of aging of the battery on the electrodes, effects of Solid Electrolyte Interface (SEI) deposition layer on the battery and the various techniques used for estimation of SOH are presented. This would enable prospective re... [more]