Energies

We developed a Parsimonious Multi-dimensional Moving Window (PMMW) algorithm that only requires Digital Elevation Model (DEM) data of a watershed to efficiently locate potentially optimal hydropower sites. The methodology requires only open source DEM data; therefore, it can be used even in remotest watersheds of the world where in situ measurements are scarce or not available at all. We used three parameters in this algorithm, and tested the method using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar Topography Mission (SRTM) derived DEMs. Our case study on the Morony Watershed, Montana, USA shows that (1) along with 6 out of the 7 existing hydropower plants being successfully located, 12 new potential hydropower sites were also identified, using a clearance of 1 km, diversion of 90 m, and Hydropower Index (HI) threshold of 10⁹ m as the criteria. For the 12 new potential hydropower sites, 737.86 Megawatts (MW) ± 84.56 MW untapped hydropower potential in the Morony Watershed was also derived; (2) SRTM DEM is more suitable for determining the potential hydropower sites; (3) although the ASTER and SRTM DEMs provide elevation data with high accuracy, micro-scale elevation differences between them at some locations may have a profound impact on the HI. Full article

The determination of the critical ventilation flow rate is significant for risk control and standard development during accidental hydrogen leakage in a confined space with hydrogen-related equipment. This paper presents an analytical model for calculating the critical ventilation flow rate through the quantification and constraint solution of the ventilation effect and ventilation cost. The experimental method was used to investigate the effects of nozzle diameter and stagnation pressure on the diffusion and ventilation of horizontal hydrogen leakage in a cuboid chamber. Ventilations from 30 to 180 m³/h were carried out through the rectangular vent. It was shown that the peak concentration of the measuring point was positively correlated with the stagnation pressure and the nozzle diameter. The experimental data were used to verify the analytical model by calculating the effective ventilation time. This study demonstrates that the critical ventilation flow rate can be increased significantly at higher stagnation pressures and larger nozzle diameters. Furthermore, the discrepancy of critical ventilation flow rates under different nozzle diameters will be enhanced with the increase of stagnation pressure. For a stagnation pressure of 0.4 MPa, the critical ventilation flow rate under a 4 mm nozzle even increased by 52% relative to the 2 mm nozzle. Full article

At the end of 2020, the Chinese government announced the pledge to become carbon neutral in the year 2060. Simultaneously, quality growth objectives were established, which were environmentally friendly and promoted the health and wellbeing of the population. The first objective of this study is to assess the gains in energy efficiency and the savings in energy demand that this commitment implies. Secondly, the feasibility of achieving these objectives of savings and efficiency increases is discussed based on an international analysis. The method is based on a quantitative estimate of the primary energy demand throughout the period from 1965 up to the year 2060. For this purpose, long historical series taken from reliable international sources are analyzed. The methodology applied to estimate and project future energy demand is new and based on several steps: The first consists of analyzing the trends of the series and estimating the relationships between them using a robust procedure. Secondly, equilibrium relationships are estimated, which avoids the eventual instabilities involved in the estimation of dynamic models. The third characteristic is based on the bootstrap, estimating and simulating the model by selecting random samples of different sizes from the available dataset. The simulations generate a complete probability distribution for the expected energy demand, which also allows for carrying out a risk analysis, assessing the risk of the demand becoming significantly larger than the expected average. The first result obtained is that the primary energy demand forecast for 2060 is much higher than the demand of the official forecasts by almost three times. However, taking into account the objective to replace 85% of fossil sources with renewables, this discrepancy is greatly reduced and becomes approximately 50% higher than the official forecast. If the savings analyzed in relevant international references are accounted for, then an additional reduction of even up to 40% of this demand could be achieved, so that the final demand would fall further, close to official forecasts. The main and final conclusion is that although the objective of making the Chinese economy carbon neutral by 2060 is feasible, it implies a radical transformation that will necessarily require a determined and unwavering political commitment throughout the entire period considered. Full article

There has been a recent surge in interest toward thin film-based solar cells, specifically new absorber materials composed by Earth-abundant and non-toxic elements. Among these materials, antimony selenide (Sb₂Se₃) is a good candidate due to its peculiar properties, such as an appropriate bandgap that promises a theoretical maximum power conversion efficiency of 33% and an absorption coefficient of around 10⁵ cm⁻¹, enabling its use as a thin film absorber layer. However, charge carrier transport has been revealed to be problematic due to its cumbersome structure and the lack of a doping strategy. In this work, we aim to provide a clear picture of the state-of-the-art regarding research on Sb₂Se₃-based solar cells and its prospects, from the successful achievements to the challenges that are still to be overcome. We also report on the key parameters of antimony selenide with a close focus on the different characteristics associated with films grown from different techniques. Full article

This paper aims to investigate and compare the fuel consumption data obtained from on-board fuel consumption meters (OBFCMs) from approximately 1000 vehicles through field testing. Furthermore, this research aims not only to compare the OBFCM readings but also to juxtapose them against the fuel consumption specifications provided by the respective vehicle manufacturers. To collect data, a cost-effective on-board diagnostics (OBD) reader and a user-friendly mobile app were employed, providing an accessible and efficient method for fuel consumption analysis. Field testing involved a diverse range of vehicles, covering various makes, models, and years of production. The OBCFM readings were recorded over a 9-month period, probably capturing a wide range of driving conditions and patterns. In order to ensure the reliability of the OBCFM readings, the fuel consumption measurements obtained from the manufacturers specifications were utilized as a reference benchmark. Preliminary data analysis indicates that there are noticeable variations in the fuel consumption data obtained from the OBCFM and the manufacturer specifications. These differences can be attributed to various factors. The novelty of the presented data lies in using a new feature implemented in EU cars since 2019. The study capitalizes on this feature, allowing for the collection of data from a broad spectrum of vehicles throughout the country under genuine driving conditions. Full article

The serious problem of wind power curtailment in northern China has created a pressing need to enhance the peak-shaving ability of the power system. As the main source of power supply in northern China, combined heat and power (CHP) units have significant potential for peak-shaving. Currently, the Chinese government encourages CHP plants to increase their peak-shaving capacity by installing power-to-heat (P2H) equipment. In addition, the government has implemented auxiliary service market policies to encourage CHP plants to provide peak-shaving services. In order to maximize economic benefits for CHP plants, this paper proposes an optimal configuration method of P2H equipment with the static payback time (SPT) as the objective function. Cost and income models of installing the P2H equipment are constructed by taking into account the auxiliary service market policies. The peak-shaving income model of the CHP plant is derived emphatically as a key part of the proposed method. Finally, the district heating region in Jilin province is used as a case study example. The results show that adding the P2H equipment is significantly effective in improving the peak-shaving ability of CHP units, and investing in heat pumps is more cost-effective than electric boilers. The proposed method can be applied to other northern regions relying on CHP units for central heating, providing a valuable solution to the problem of wind power curtailment in these regions. Full article

This article utilizes the research method of the Life Cycle Assessment (LCA) to scrutinize Lithium Iron Phosphate (LFP) batteries and Ternary Lithium (NCM) batteries. It develops life cycle models representing the material, energy, and emission flows for power batteries, exploring the environmental impact and energy efficiency throughout the life cycles of these batteries. The life cycle assessment results of different power battery recycling process scenarios are compared and analyzed. This study focuses on retired LFP batteries to assess the environmental and energy efficiency during the cascade utilization stage, based on a 50% Single-Cell Conversion Rate (CCR). The findings of the research reveal that, in terms of resource depletion and environmental emission potential, LFP batteries exhibit lower impacts compared to NCM batteries. The use of hydrometallurgy in recovering LFP power batteries leads to minimal life cycle resource consumption and environmental emission potential. During the cascade utilization stage of LFP batteries, significant benefits are noted, including a 76% reduction in mineral resource depletion (ADP e) and an 83% reduction in fossil energy depletion (ADP f), alongside notable reductions in various environmental impact factors. Simultaneously, considering the sensitivity of life cycle assessment indicators and their benefit percentages to different CCRs, it is observed that ODP exhibits the highest sensitivity to CCR changes, while evaluation indicators such as HTP, AP, and GWP show relatively lower sensitivity. This study can provide an effective reference for the establishment of an energy saving and emission reduction evaluation system of power batteries. Full article

Background: This study examines the relationship between energy usage, health issues, and pro-environmental behaviour (PEB) in Kyrgyzstan amidst the country’s commitment to transition from coal-based energy to renewable sources, in line with the Paris Agreement. The purpose is to investigate citizens’ attitudes towards PEB and their intentions to engage in environmentally friendly actions, focusing on gas, electricity, and coal. Methods: Drawing upon the Theory of Planned Behaviour (TPB) framework, a survey was conducted among 1455 respondents to explore attitudes towards PEB and energy sources’ impact on health issues. Results: Decarbonization efforts in Kyrgyzstan and Central Asia are in their early stages, with coal remaining a primary energy source. The study emphasizes the importance of governmental policies and citizen action in achieving decarbonization goals. Rising electricity costs outweigh the increase in indirect energy costs for food, posing challenges for households adapting to changing energy dynamics. Conclusions: Targeted interventions and communication strategies are crucial to promote pro-environmental behaviour and facilitate the transition to sustainable energy sources. Understanding the relationships between health concerns, air pollution awareness, PEB, and energy source choices can inform policymakers and organizations to ensure a sustainable and healthy future for Kyrgyzstan and other Central Asian countries. Full article

Activities related to the planning and operation of power systems use premise load forecasting, which is responsible for providing a load estimative for a given horizon that assists mainly in the operation of an electrical system. Hierarchical short-term load forecasting (STLF) becomes an approach used for this purpose, where the overall forecast is performed through system partition in smaller macro-regions and, soon after, is aggregated to compose a global forecast. In this context, this paper presents a bottom-up STLF approach for macro-regions. The main innovation is the Average Consumption per Meteorological Region (CERM) index, used to weigh the importance of each station meteorological (EM) in total load demand. Another index, the Variation of Load and Temperature (IVCT), based on historical temperature and demand changes, is proposed. These indexes are incorporated into an ANN model of the multi-layer perceptron type (MLP). The results showed a higher average performance of the index CERM and variable IVCT in relation to the other combinations performed, and the best results were used to compose the prediction of the MTR. Finally, the proposed model presented a Mean Absolute Percentage Error lower than 1%, presenting superior performance compared to an aggregate model for MTR, which shows the efficiency and contribution of the proposed methodology. Full article

Nowadays, the penetration of inverter-based energy resources is continuously increasing in low-voltage distribution grids. Their applications cover traditional renewable energy production and energy storage but also new applications such as charging points for electric vehicles, heat pumps, electrolyzers, etc. The power ratings range from a couple of kW to hundreds of kW. Utilities have, in the last few years, reported more challenges regarding power quality in distribution grids, e.g., high harmonic content, high unbalances, large voltage and frequency excursions, etc. Phase-Lock-Loop (PLL) algorithms are typically used for grid synchronization and decoupled control of power converters connected to the grid. Most of the research within PLLs is mainly focusing on grid voltage angle estimation while the byproducts of the algorithms, e.g., frequency and voltage magnitude, are often overlooked. However, both frequency and voltage magnitude estimations are crucial for grid code compliance. Practical considerations for implementation on microcontroller boards of these algorithms are also missing in most of the cases. The present paper proposes a modified PLL algorithm based on a Synchronous Reference Frame that is suitable for both grid synchronization and frequency monitoring, i.e., the estimation of RMS phase voltages and frequencies in highly distorted distribution grids. It also provides the tuning methodology and practical considerations for implementation on commercial DSP boards. The performance of the proposed approach is assessed through simulation studies and laboratory tests under a wide range of operational conditions, showing that the proposed PLL can estimate the grid frequency, for all considered grid events, with an accuracy of less than ±5 mHz, which is a significant improvement on the current state-of-the-art solutions, having an accuracy of at least ±20 mHz or more. Full article

As a type of airtight equipment, vertical gas tanks are prone to accumulations of toxic and harmful gases due to their poor ventilation and narrow space. This poses many safety hazards. Therefore, we conducted a FLUENT simulation for vertical gas tanks with different diameters. The results indicated that the larger the diameter, the longer the required ventilation time. It was necessary to monitor the gas concentration after ventilation for at least 6 h when the tank diameter was 2.6 m, after ventilation for at least 24 h when the tank diameter was 5.2 m, and after ventilation for at least 80 h when the tank diameter was 7.8 m. To ensure comprehensive monitoring, at least one monitoring point was required to be placed at the upper and lower ends of the vertical gas tank, respectively. Monitoring was initiated after these requirements were reached. A theoretical numerical analysis and an experimental verification analysis were conducted on the simulation results. The variation trend of the simulation value, the theoretical value, and the experimental test value were the same. The measured value of the ventilation duration was greater than the theoretical value of the ventilation duration and the simulation value of the ventilation duration. Therefore, the simulation results and theoretical analysis could be used for a risk analysis of gas tanks. The determination of ventilation characteristics via a simulation of vertical gas tanks has a practical significance when guiding on-site operations. Full article

During microbial-enhanced oil recovery (MEOR), surfactant-producing microorganisms are reported to improve displacement efficiency. However, the sweep efficiency could be improved by emulsified droplets or be reduced by low-IFT (interfacial tension)-induced fingering flow. Therefore, whether sweep efficiency can be improved by surfactant-producing microorganisms is currently unclear. To reveal the EOR mechanisms by surfactant-producing microorganisms, a 2D micro-model was used to conduct a long-term pore-scale experiment. In the results, 19.4% of the original oil in place (OOIP) was recovered, and surfactant-producing microorganisms can improve not only displacement efficiency (16.9% of the OOIP in the main stream) but also sweep efficiency (27.7% of the OOIP in the margin). Furthermore, the sweep efficiency was improved during flooding and shut-in periods. For instance, 19.5% of the OOIP in margins migrated to the main stream during the 1st shut-in period. Regarding mechanisms of sweep, it was improved by Jamin’s effect during the flooding period, while during the shut-in period, the oil migration was attributed to the spontaneously spreading biomass and their wettability altering the biosurfactant. This long-term experiment revealed that the dominant oil recovery mechanisms were altering with declining oil saturation, based on which sweep efficiency contributed to oil recovery only at oil saturation higher than 40.5%. While at lower oil saturation, only displacement efficiency could be improved. Full article

Nearly 60% of commercial customers are connected to a low-voltage network in Poland with a contractual capacity of more than 40 kW and are assigned a fixed tariff with flat prices for the whole year, no matter the usage volume. With smart meters, more data about how businesses use energy are becoming available to both energy providers and customers. This enables innovation in the structure and type of tariffs on offer in the energy market. Customers can explore their usage patterns to choose the most suitable tariff to benefit from lower prices and thus generate savings. In this paper, we analyzed whether customers’ electricity usage matched their optimal tariff and further investigated which of them could benefit or lose from switching the tariff based on the real dataset with the hourly energy readings of 1212 commercial entities in Poland recorded between 2016 and 2019. Three modelling approaches, i.e., the k-nearest neighbors, classification tree and random forest, were tested for optimal tariff classification, while for the benchmark, we used a simple approach, in which the tariff was proposed based on the customers’ previous electricity usage. The main findings from the research are threefold: (1) out of all the analyzed entities, on average, 76% of them could have benefited from the tariff switching, which suggests that customers may not be aware of the tariff change benefits, or they had chosen a tariff plan that was not tailored to them; (2) a random forest model offers a viable approach to accurate tariff classification; (3) the policy implication from the research is the need to increase the customers’ awareness about the tariffs and propose reliable tools for selecting the optimal tariff. Full article

Given its adaptable and efficient energy consuming devices during peak hours, the residential building sector is urged to take part in demand response (DR) initiatives with the use of a building energy management system (BMS). The residents of buildings with BMS enjoy secure, pleasant, and fully managed lifestyles. Although the BMS helps the building consume less energy and encourages occupant engagement in energy-saving initiatives, unwelcome interruptions and harsh instructions from the system are inconvenient for the inhabitants, which further discourages their participation in DR initiatives. Building automation control is a crucial factor for improving buildings’ energy efficiency and management, as well as improving the electricity grid’s reliability indices. Smart houses that use the right sizing procedure and energy-management techniques can help lower the demand on the entire grid and potentially sell clean energy to the utility. Recently, smart houses have been presented as an alternative to traditional power-system issues including thermal plant emissions and the risk of blackouts brought on by malfunctioning bulk plants or transmission lines. This paper describes the necessary technology requirements and presents the methodology and the decentralized building automation novel algorithm for efficient demand side management in a building management system. Human comfort aspects including thermal comfort and visual comfort were taken into consideration when selecting heating and lighting controls. The suggested BMS relies primarily on a load-shifting technique, which moves controllable loads to low-cost periods to avoid high loading during peak hours. The model aims to minimize the individual household electricity consumption cost while considering customers’ comfort and lifestyle. All these are applied in an experimental university microgrid, and the results are presented in terms of energy saving in kWh, money in €, and working hours. The results demonstrated that the proposed approach might successfully lower energy use during the DR period and enhance occupant comfort. Full article

In a world facing increasing environmental and energy challenges, anaerobic digestion of agrifood by-products and food waste could contribute to the production of green energy while reducing greenhouse gas emissions into the atmosphere. Anaerobic digestion is a biological process capable of breaking down and stabilising organic matter in the absence of oxygen and converting it into a renewable source of energy, known as biogas. Biomethane production also enables the generation of electricity and produces digestate, a by-product of the digestion process that can be used as a soil conditioner or fertiliser. This review aims to highlight how substrate pretreatment, together with the optimisation of operating parameters, application of additives, recirculation of digestate and frequent feeding, can increase biogas production. An overview of the basics of the anaerobic digestion of agrifood by-products and food waste is provided, including feedstock characteristics (nutrient content, particle size and inhibitory compounds) and process parameters (process configuration, pH, temperature, total and volatile solids, total Kjeldahl nitrogen, ammonium, chemical oxygen demand, carbon/nitrogen ratio, retention time, organic loading rate, etc.). In addition, recent studies in the field of processes, equipment and pretreatments that can significantly improve the anaerobic digestion process of agricultural and food wastes were classified and discussed. Finally, the challenges and future perspectives of biogas production from the agrifood sector are addressed. Full article

Continental delta deposits are characterized by strong heterogeneity in the lateral direction; meanwhile, reservoir development is challenged by rapid changes in rock properties. Thus, it is critical to use proper methods for fine characterization to confirm the distributions of thin interbedded reservoirs. The aim of this study was to propose a novel workflow for integrated research on the 3D geomodeling of thin interbedded reservoirs, using the Triassic T₂a¹ formation in the Tahe Oilfield B9 area of the Tarim Basin as a case study. The complicated representation of thin interbeds in a 3D geomodel was simulated using a multiscale joint controlling strategy, based on wells (Points), 2D geological cross-sections (Lines), and horizontal wells (Surfaces). The resistivity inversion results from the horizontal wells validated the proof of the plane distribution of the thin interbeds within the drilled area, and this quantitative statistic provided effective parameters and guidance for 3D interbed geomodeling. In this study, comprehensive 3D facies modeling was divided into 3D interbed geomodeling and 3D sedimentary facies modeling. An optimized interbed geomodel was picked out from multiple stochastic simulation realizations, and the drilled horizontal well data were used to constrain the simulation process, so the simulation results were more consistent with the real distribution of the thin interbed morphology. Classical two-point geostatistical methods, the multipoint simulation (MPS) geostatistical method, and the hierarchical mindset were integrated for the microfacies simulation. This procedure demonstrated a good ability to characterize thin interbed reservoirs in continental delta deposits. An MPS training image obtained from a high-resolution satellite photo was used to fix the issue of the relationships between the distributions and configurations of all microfacies within the spatial distribution. A 3D lithofacies interbed model was embedded into the 3D facies model. This comprehensive facies model served as a constraint condition in the property modeling process. A porosity model was simulated using separate stratigraphy and individual microfacies controls, as facies-controlled property modeling has been used as a prior foundation for field development planning in the Tahe Oilfield B9 case. The porosity model was then used as a basis for permeability modeling, and a water saturation model was created using the J function and all of the constraints from the other two property models. Finally, all the results were validated using dynamic production data from the Tahe Oilfield B9 wells, with good matching observed between the geological models. There was only a 0.92% difference in reservoir volume between the reservoir simulation results and the static geological model results using our solution. Full article

Thermal heat storage is becoming important in systems with renewable energy sources. Their largest benefit is smoothing the intermittent production and reduction in the site peak demand. The advantages of thermal energy storage with phase-change material are storing energy at a lower temperature for reduction in thermal losses, and enabling energy transfer at a constant temperature, which reduces the risk of equipment damage. In this paper, a low-order model of latent thermal energy storage, derived in a state-space form by using the mixed logical dynamical approach, is proposed. The model is compared to a stratified model and shows significant improvements of physical accuracy and execution time. Finally, a model predictive control algorithm suited for the real case study is designed, implemented and compared to classical rule-based control. The obtained results show significant energy savings of 8.43%, and improvements in user comfort and equipment duration. Full article

The energetic assessment of biomass conversion processes is important for evaluating their application potential. Process energy efficiency is often evaluated based on simulation results for processes under idealized conditions. The present work uses data from a laboratory plant to perform an evaluation of the supercritical water gasification (SCWG). For this purpose, experiments were conducted with two types of feedstock, Reed Canary Grass and ethanol. Under the present lab-plant configuration, a cold gas efficiency of up to 79% could be reached, which is comparable to the gasification of biomass in fluidized-bed gasifiers or entrained-flow gasifiers. Based on the obtained data on the produced substances and their distribution, a scale up to pilot plant size was conducted. A model was derived from the available data to energetically assess different SCWG plant sizes based on real laboratory results. This model can be transferred to other feedstocks and other process designs to approximate the optimal size for the used biomass feedstock. The importance of heat recuperation in this process is described in detail based on pilot-scale data. Full article

The aim of this article is to propose methods for obtaining the aerodynamic characteristics of a flying object in a turbulent atmosphere. This article presents static aerodynamic characteristics of an unmanned aerial vehicle (UAV), which have been obtained during experimental examinations and during numerical calculations. The results have been compared with each other in order to validate the numerical model and methods. The method for modeling gusts using state-of-the-art CFD software (i.e. ANSYS Fluent Release 16.2) has been proposed and applied to obtain the aerodynamic characteristics of a UAV including during gusts. Two cases have been analyzed. In the first case, a downburst was modeled. In the second case, a single oblique gust was modeled (i.e., changing the angle of attack and the angle of sideslip), that had a complicated time course in regard to its velocity. Although this article is focused on the assessment of the vulnerability of a UAV model to gusts, the practical implications of the proposed methodology are applicable to a wide selection of objects, including wind turbines. Full article