ALBERT

Description: The issues of mathematical and numerical simulation of an electrical complex of a power plant based on hydrogen fuel cells with a voltage step-down converter were considered. The work was aimed at developing a mathematical model that would provide for determining the most loaded operation mode of the complex components. The existing mathematical models do not consider the effect of such processes as the charge and discharge of the battery backup power supply on the power plant components. They often do not consider the nonlinearity of the fuel cell output voltage. This paper offers a mathematical model of an electrical complex based on the circuit analysis. The model combines a well-known physical model of a fuel cell based on a potential difference and a model of a step-down converter with a battery backup power supply developed by the authors. A method of configuring a fuel cell model based on the experimental current–voltage characteristic by the least-squares method has been proposed. The developed model provides for determining currents and voltages in all components of the power plant both in the nominal operating mode and in the mode of limiting the power consumed from the fuel cell when the battery backup power supply is being charged. The correctness of the calculated ratios and the mathematical model has been confirmed experimentally. Using the proposed model, a 1300 W power plant with a specific power of 529.3 W∙h/kg was developed and tested.

Description: The introduction of a complex electrical vehicle charging (EVC) infrastructure consisting of an electrical vehicle (EV) charger and renewable energy source (RES) in the distribution system has been required as an important countermeasure for global environmental issues. However, the problems for hosting capacity and power stability of the distribution feeder can be caused by the penetration of lager scaled RES and EVC infrastructure. Further, it is required for the efficient operation method to prevent congestion and to ensure hosting capacity for the distribution feeder due to the increase of variable RES and EVC infrastructure in the distribution systems. In order to solve these problems, it is necessary to develop a technology which is capable of stably introducing an EVC infrastructure without reinforcing the existing distribution system. Therefore, to maintain the existing hosting capacity of distribution feeder and allowable limits, this paper presents a virtual power line (VPL) operation method using Energy Storage System (ESS) based on the power and voltage stabilization control to ensure hosting capacity of the EVS infrastructure. The proposed operation method is determined by optimal power compensation rate (PCR) and voltage compensation rate (VCR). Specifically, ESS for VPL is controlled according to the charging and discharging mode is operated according to the comparison value of the PCR and VCR. From the test results, it is verified that hosting capacity of the distribution system can be maintained using the proposed control method of ESS for VPL operation.

Description: This study proposes a novel modified Cuk converter. The proposed converter attempts to resolve the limitations of the conventional converters, such as voltage gain limitations of a canonical Cuk converter. Therefore, the mentioned improvement has made the proposed converters more compatible for renewable energy applications. Moreover, the increase of the voltage gain in the proposed converter has not impacted the efficiency or the voltage stress of the switches, which is common in other voltage boosting techniques, such as cascading methods. Furthermore, the advantages of a Cuk converter, such as continuity of the input current, have been maintained. The average voltage/current stresses of the semiconductor devices and various types of power losses have been calculated and compared with the existing topologies. Moreover, the non-ideal voltage gain of the proposed converters was compared with the other high step-up topologies. Eventually, the simulation results with PLECS, along with the experiments on an 120 W prototype, have been presented for validation.

Description: A double-bridge shape is proposed as a novel flow channel cross-sectional shape of a membraneless microfluidic fuel cell, and its electrochemical performance was analyzed with a numerical model. A membraneless microfluidic fuel cell (MMFC) is a micro/nano-scale fuel cell with better economic and commercial viability with the elimination of the polymer electrolyte membrane. The numerical model involves the Navier–Stokes, Butler–Volmer, and mass transport equations. The results from the numerical model were validated with the experimental results for a single-bridge channel. The proposed MMFC with double-bridge flow channel shape performed better in comparison to the single-bridge channel shape. A parametric study for the double-bridge channel was performed using three sub-channel widths with the fixed total channel width and the bridge height. The performance of the MMFC varied most significantly with the variation in the width of the inner channel among the sub-channel widths, and the power density increased with this channel width because of the reduced width of the mixing layer in the inner channel. The bridge height significantly affected the performance, and at a bridge height at 90% of the channel height, a higher peak power density of 171%was achieved compared to the reference channel.

Description: Twin-screw compressors are widely used in aerodynamics, refrigeration and other fields. The screw rotors are the core component of the screw compressor and affect the performance of the compressor. This paper focuses on variable-lead rotors. A thermal process simulation model considering leakage is established to calculate the efficiency of the compressor. Different lead change methods are compared by evaluating the contact line, exhaust port and simulation results. The results show that the compressor obtains better performance when the lead decreases rapidly on the discharge side. Furthermore, the effects of the wrap angle and internal volume ratio on variable-lead rotors are studied. The work provides a reference for the design of the screw compressor rotor.

Description: With regard to safety, efficiency and lifetime of battery systems, the thermal behavior of battery cells is of great interest. The use of models describing the thermoelectric behavior of battery cells improves the understanding of heat generation mechanisms and enables the development of optimized thermal management systems. In this work, a novel experimental approach is presented to determine both the irreversible heat due to ohmic losses and the reversible heat due to entropy changes directly via heat flow measurements. No additional information about thermal properties of the battery cell, such as heat capacity or thermal conductivity, are required. Thus, the exothermic and endothermic nature of reversible heat generated in a complete charge/discharge cycle can be investigated. Moreover, the results of the proposed method can potentially be used to provide an additional constraint during the identification process of the equivalent circuit model parameters. The described method is applied to a 23 Ah lithium titanate cell and the corresponding results are presented.

Description: Non-cooperative scheduling games can be used to coordinate residential loads in order to achieve a common goal while accounting for individual consumer’s interests, privacy, and autonomy. However, a significant portion of the residential flexibility—Thermostatically Controlled Loads (TCLs) such as water and space heating/cooling appliances—has not been fully addressed under this game theoretic approach: their comfort constraints and integer control were not considered. This paper presents a method for properly including TCLs in this framework and discusses its application in energy communities. Specifically, we propose a general mathematical formulation for considering users’ comfort in non-cooperative games. We model the integer nature of the TCLs control with binary variables and show that optimal or close to optimal (less than 1%) solutions are reached. Moreover, different total cost functions can be used depending on the market context and the objective of the demand management program. To illustrate and discuss these aspects in practical applications, we used a case study of an energy community in Spain. The results show that the TC solutions are optimal or only 0.80% worse than optimal; different total cost functions result in different results (load curve smoothing or peak load reduction); consumers’ comfort is respected; and the proposed game model cooperates with consumers in order to minimize community’s costs.

Description: Microgrid (MG) is a novel concept for a future distribution power system that enables renewable energy sources (RES). The intermittent RES, such as wind turbines and photovoltaic generators, can be connected to the MG via a power electronics inverter. However, the inverter interfaced RESs reduce the total inertia and damping properties of the traditional MG. Consequently, the system exhibits steeper frequency nadir and the rate of change of frequency (RoCoF), which may degrade the dynamic performance and cause the severe frequency fluctuation of the system. Smart loads such as inverter air conditioners (IACs) tend to be used for ancillary services in power systems. The power consumption of IACs can be regulated to suppress frequency fluctuation. Nevertheless, these IACs, regulating power, can cause the deviation of indoor temperature from the temperature setting. The variation in indoor temperature should be controlled to fulfill residential comfort. This paper proposes a multi-objective decentralized model predictive control (DMPC) for controlling the power consumption of IACs to reduce MG frequency fluctuation and control the variation in indoor temperature. Simulation results on the studied microgrid with the high penetration of wind and photovoltaic generator demonstrate that the proposed DMPC is able to regulate frequency deviation and control indoor temperature deviation as a user preference. In addition, the DMPC has a superior performance effect to the proportional-integral (PI) controller in terms of reducing frequency deviation, satisfying indoor temperature preferences, and being robust to the varying numbers of IACs.

Description: This article presents an analysis of the reliability of the power grid using data on the failure rate of the medium voltage (MV) power grid from the last five years. The analysis of the state of the power grid was based on the data provided by the grid operator. The purpose of this article is to analyze the reliability assessment of the medium voltage (MV) power connections using various analytical methods, a simulation model and reliability indicators. The analysis was performed based on the defined categories of power outages in terms of their duration. This made it possible to determine the energy quality indicators in a selected power grid. Then, a more complex analysis was carried out to assess the convergence of the applied analytical models of reliability assessment with the actual results obtained for the power grid. Moreover, using ANSYS Multiphysics, a numerical model of the cable head was developed to analyze the processes taking place in this element of the power grid for various exploitation cases.

Description: The aim of this work is to design a piezoelectric power generation system that extracts power from the vibration of a cantilever beam. A semi-cylinder placed in a water stream and attached to the beam is excited into vortex-induced vibrations (VIV), which triggers the piezoelectric deformation. The mechanical system is modelled using parametric equations based on Hamilton’s extended principle for the cantilever beam and the modified Van der Pol model for the bluff body (the semi-cylinder). These equations are simulated using the MATLAB software. The dimensions of the model, the flow velocity and the resistance are treated as design parameters and an optimization study is conducted using MATLAB to determine the combination of optimal values at which maximum power is extracted. The key findings of this research lie in the identification of the effect of changing the design parameters on output power. In addition to the numerical simulation, a finite element analysis is carried out on the bluff body and the hydrodynamic forces and velocity profiles are observed. It is determined that the vibration amplitudes increase with increasing diameter of the bluff body, length of the bluff body and water velocity.

Description: Fiscal policy is a crucial government tool for influencing and managing the national economy and creating a strong incentive for low carbon investment. Previous literature has reputable evidence that improving fiscal policy enhances environmental quality. However, the literature fails to classify the exact turning level (threshold point) below/above which the association may be negative or positive. In this regard, this research investigates the nexus between fiscal policy, foreign direct investment, financial development, trade openness, urban population, gross capital formation, labour force, and CO2 emissions in the era of globalization. The panel data set contained 105 countries over the period from 1990 to 2016. The empirical findings are estimated through linear and nonlinear panel data approaches such as fully modified ordinary least square and panel threshold regression. The subsequent findings are established: first, fiscal policy and globalization significantly increase environmental pollution. Second, the empirical results confirm the existence of the pollution haven hypothesis (PHV). Third, financial development and gross fixed capital formation are also considered some of the most crucial indicators to increase pollution levels. Fourth, trade openness, urban population, and labour force improve environmental quality. Fifth, panel threshold regression discovers that countries maintain a minimum level of fiscal policy at −1.2889. Based on these empirical findings, this study suggests that policymakers and governments of these countries should take steps to restructure their industrial sector and design macroeconomic-level carbon-free policies to support the implementation of low-energy-intensive and lower carbon production technologies.

Description: This study aims to examine the impact of green transition and globalization processes on changes in the labour share. The study covers 76 national economies diversified in development, global production share and energy transition stage from 2000 to 2018. Based on the Total Economy Database data, panel models of the relationship between green transition, globalization and the labour share in the national income were estimated. The conducted Breusch–Pagan and Hausman tests proved the validity of using fixed-effects models. We confirmed the research hypothesis that the openness of the economy contributes to a decline in the labour share. The openness of the economy resulting from globalization reduces the labour share in the national income. We do not confirm hypotheses that suggest energy transition contributes to a reduction in the labour share and that the labour share will decline in the post-crisis period due to the lower bargaining power of workers. Changes in the labour share should be of interest to government representatives who influence the shape and implementation of economic policy, especially in employment policy, education, and investment policy, mainly aimed at the green transformation.

Description: Short-term load forecasting predetermines how power systems operate because electricity production needs to sustain demand at all times and costs. Most load forecasts for the non-residential consumers are empirically done either by a customer’s employee or supplier personnel based on experience and historical data, which is frequently not consistent. Our objective is to develop viable and market-oriented machine learning models for short-term forecasting for non-residential consumers. Multiple algorithms were implemented and compared to identify the best model for a cluster of industrial and commercial consumers. The article concludes that the sliding window approach for supervised learning with recurrent neural networks can learn short and long-term dependencies in time series. The best method implemented for the 24 h forecast is a Gated Recurrent Unit (GRU) applied for aggregated loads over three months of testing data resulted in 5.28% MAPE and minimized the cost with 5326.17 € compared with the second-best method LSTM. We propose a new model to evaluate the gap between evaluation metrics and the financial impact of forecast errors in the power market environment. The model simulates bidding on the power market based on the 24 h forecast and using the Romanian day-ahead market and balancing prices through the testing dataset.

Description: Real-time monitoring of energetic-environmental parameters in wastewater treatment plants enables big-data analysis for a true representation of the operating condition of a system, being still frequently mismanaged through policies based on the analysis of static data (energy billing, periodic chemical–physical analysis of wastewater). Here we discuss the results of monitoring activities based on both offline (“static”) data on the main process variables, and on-line (“dynamic”) data collected through a monitoring system for energetic-environmental parameters (dissolved oxygen, wastewater pH and temperature, TSS intake and output). Static-data analysis relied on a description model that employed statistical normalization techniques (KPIs, operational indicators). Dynamic data were statistically processed to explore possible correlations between energetic-environmental parameters, establishing comparisons with static data. Overall, the system efficiently fulfilled its functions, although it was undersized compared to the organic and hydraulic load it received. From the dynamic-data analysis, no correlation emerged between energy usage of the facility and dissolved oxygen content of the wastewater, whereas the TSS removal efficiency determined through static measurements was found to be underestimated. Finally, using probes allowed to characterize the pattern of pH and temperature values of the wastewater, which represent valuable physiological data for innovative and sustainable resource recovery technologies involving microorganisms.

Description: The calorific value of household refuse (HR) is greatly improved after classification, which includes the implementation of sufficient pyrolysis conditions. Therefore, a better pyrolysis effect can be achieved by co-pyrolysis with industrial solid waste (ISW) with high calorific value. In this work, HR and ISW were used as raw materials for co-pyrolysis experiments. The influence on the distribution of three-phase products after co-pyrolysis, the concentration of heavy metals and dioxins in the flue gas, and the distribution of PCDD/Fs isomers were studied. The results showed that, at a temperature of 600 °C and H/C = 1.3, of the formed material, the quantity of pyrolysis gas was approximately 27 wt.%, and the quantity of pyrolysis oil was approximately 40.75 wt.%, which mainly contained alkanes, olefins, and aromatic hydrocarbons. When S/C = 0.008, pyrolysis gas accounted for 25.95 wt.% of the formed material, and pyrolysis oil for 41.95 wt.% of the formed material. The ignition loss rate of pyrolysis coke was approximately 20%, and the maximal calorific value was 14,217 KJ/kg. According to the thermogravimetric experiment, the co-pyrolysis of HR and ISW can promote the positive reaction of pyrolysis, and the weight loss reached 62% at 550 °C. The emission of gaseous heavy metals was relatively stable, and the concentration of heavy metals slightly decreased. The main heavy metals in the ash were Cu, Fe, and Zn. The emission of dioxins could be effectively reduced by the pyrolysis of HR with ISW, and the produced dioxins were mainly synthesized from de novo synthesis. After pyrolysis, the toxic equivalent of dioxins in the flue gas was reduced from 0.69 to 0.29 ng I-TEQ/Nm3, and the distribution of dioxin isomers in the flue gas had little influence. The experimental results provide a theoretical basis for the application of co-pyrolysis technology with HR and ISW.

Description: The knowledge of the ground thermal properties, and in particular the ground thermal conductivity is fundamental for the correct sizing of the Ground Coupled Heat Pump (GCHP) plant. The Thermal Response Test (TRT) is the most used experimental technique for estimating the ground thermal conductivity. This paper presents an experimental setup aimed to realise a suitable scale prototype of the real borehole heat exchanger (BHE) and the surrounding ground for reduced scale TRT experiments. The scaled ground volume is realised with a slate block. Numerical analyses were carried out to correctly determine suitable geometric and operational parameters for the present setup. The scaled heat exchanger, inserted into the block, is created with additive technology (3D printer) and equipped with a central electrical heater along its entire depth and with temperature sensors at different radial distances and depths. Present measurements highlight the possibility to reliably perform a TRT experiment and to estimate the slate/ground thermal conductivity with an agreement of about +12% with respect to measurements provided by a standard commercial conductivity meter on proper cylindrical samples of the same material and onto 10 different portions of the slate block.

Description: A superconducting fault current limiter (SFCL) for medium voltage networks cooled by a cryocooler was designed, built and tested by the current author. For the construction of this limiter, a high-temperature second generation superconducting tape (HTS 2G)—SF12100—was used. In this limiter, it is possible to change the working temperature. The possibility of changing the operating temperature allows for adjusting the parameters of the limiter to the electric power needs. Adjusting the parameters of the limiter to the power needs is a key problem to solve, resulting from the ambiguous characteristics of HTS tapes. Cooling with a cryocooler is the only solution in the case of a limiter for power industry applications. The electric power mechanism does not tolerate any liquids. After analyzing the experimental results and after analyzing the results from the numerical models of the limiter, the concepts of using superconductors to limit current in the power industry were changed: the transition from a superconducting fault current limiter (SFCL) to a superconducting surge current limiter (SSCL). Transition to the limiter operation system—surge current limitation—is associated with the reduction in the limiter operation time. The advantages of the transition from the SFCL to SSCL work system are presented.

Description: In the literature, different authors attribute between 15% to 30% of a wind farm’s costs to logistics during the installation, e.g., for vessels or personnel. Currently, there exist only a few approaches for crew scheduling in the offshore area. However, current approaches only satisfy subsets of the offshore construction area’s specific terms and conditions. This article first presents a literature review to identify different constraints imposed on crew scheduling for offshore installations. Afterward, it presents a new Mixed-Integer Linear Model that satisfies these crew scheduling constraints and couples it with a scheduling approach using a Model Predictive Control scheme to include weather dynamics. The evaluation of this model shows reliable scheduling of persons/teams given weather-dependent operations. Compared to a conventionally assumed full staffing of vessels and the port, the model decreases the required crews by approximately 50%. Moreover, the proposed model shows good runtime behavior, obtaining optimal solutions for realistic scenarios in under an hour.

Description: Carbon capture, utilization, and storage (CCUS) is an attractive technology for the decarbonization of global energy systems. However, its early development stage makes impact assessment difficult. Moreover, rising popularity in carbon pricing necessitates the development of a methodology for deriving carbon abatement costs that are harmonized with the price of carbon. We develop, using a combined bottom-up analysis and top-down learning curve approach, a levelized cost of carbon abatement (LCCA) model for assessing the true cost of emissions mitigation in CCUS technology under carbon pricing mechanisms. We demonstrate our methodology by adapting three policy scenarios in Canada to explore how the implementation of CO2-to-diesel technologies could economically decarbonize Canada’s transportation sector. With continued policy development, Canada can avoid 932 MtCO2eq by 2075 at an LCCA of CA$209/tCO2eq. Technological learning, low emission hydroelectricity generation, and cost-effective electricity prices make Quebec and Manitoba uniquely positioned to support CO2-to-diesel technology. The additional policy supports beyond 2030, including an escalating carbon price, CO2-derived fuel blending requirements, or investment in low-cost renewable electricity, which can accelerate market diffusion of CO2-to-diesel technology in Canada. This methodology is applicable to different jurisdictions and disruptive technologies, providing ample foci for future work to leverage this combined technology learning + LCCA approach.

Description: The influences of superellipse shapes on natural convection in a horizontally subdivided non-Darcy porous cavity populated by Cu-water nanofluid are inspected in this paper. The impacts of the inner geometries (n=0.5,1,1.5,4), Rayleigh number (103≤Ra≤106), Darcy number (10−5≤Da≤10−2), porosity (0.2≤ϵ≤0.8), and solid volume fraction (0.01≤∅≤0.05) on nanofluid heat transport and streamlines were examined. The hot superellipse shapes were placed in the cavity’s bottom and top, while the adiabatic boundaries on the flat walls of the cavity were considered. The governing equations were numerically solved using the finite volume method (FVM). It was found that the movement of the nanofluid upsurged as Ra boosted. The temperature distributions in the cavity’s core had an inverse relationship with increasing Rayleigh number. An extra porous resistance at lower Darcy numbers limited the nanofluid’s movement within the porous layers. The mean Nusselt number decreased as the porous resistance increased (Da≤10−4). The flow and temperature were strongly affected as the shape of the inner superellipse grew larger.

Description: This paper provides empirical evidence on the relationship between the increasing-block-rate (IBR) pricing of electricity and the propensity of households to buy major electrical appliances. I use a variation from a natural experiment in Russia that introduced IBR pricing for residential electricity in a number of experimental regions in 2013. The study employs household-level panel data, which records, among others, whether the household has purchased any major electrical appliances during the last three months. Using a difference-in-differences specification, I show that the purchase of major electrical appliances in the regions with IBR pricing has increased by more than 20% (or more than two percentage points). The findings suggest that price-based energy policies may be an effective tool in shaping the behaviour of households.

Description: This paper proposes a methodology for plant root system and soil moisture analysis through the geoelectrical prospecting method. Overall, bench and field experiments are implemented to analyze the behavior of electrical conductivity of the soil in relation to moisture content and plant root system growth. Specifically, Wenner array and lateral profiling technique are used to stratify the soil in horizontal layers, performing in-depth analysis. Millet (Pennisetum glaucum L.), bean (Phaseolus vulgaris L.) and sorghum (Sorghum bicolor L. Moench) are used to analyze the root system behavior. Results show that the soil water dynamics can be observed through soil stratification in horizontal layers and the plant root system is correlated with apparent electrical conductivity of the soil. Thus, geoelectric prospecting methods can be used as an analysis tool, both of soil moisture dynamics and of plant roots, to support decision making regarding soil and crop management.

Description: The accuracy of a predictive system is critical for predictive maintenance and to support the right decisions at the right times. Statistical models, such as ARIMA and SARIMA, are unable to describe the stochastic nature of the data. Neural networks, such as long short-term memory (LSTM) and the gated recurrent unit (GRU), are good predictors for univariate and multivariate data. The present paper describes a case study where the performances of long short-term memory and gated recurrent units are compared, based on different hyperparameters. In general, gated recurrent units exhibit better performance, based on a case study on pulp paper presses. The final result demonstrates that, to maximize the equipment availability, gated recurrent units, as demonstrated in the paper, are the best options.

Description: Resource recovery from biodegradable waste is essential in order to reach the goals of zero circular economy waste generation and zero greenhouse gas emissions from the waste sector. Waste whose management is a real challenge is sewage sludge, mainly because of high concentrations of heavy metals. The aim of this study was to compare the effectiveness of material stabilization during aerobic stabilization of two feedstocks with sewage sludge obtained from different sources, namely, digestate from a municipal wastewater treatment plant and digestate from a co-digestion process. Moreover, the goal of the experiment was to assess the quality of compost in terms of remediation potential. The composting process was carried out for four different mixtures consisting of the mentioned digestates, municipal solid waste, and grass. A better composting efficiency with digestate from the co-digestion process was observed. In that case, a higher temperature in the thermophilic phase (〉55 °C) and a higher organic matter loss ratio (60%) were obtained as compared to the process with digestate from wastewater treatment plant. Taking into account the fertilizing properties and the concentration of heavy metals, all obtained composts met the requirements set out in the Polish Regulation for organic fertilizers. Only the content of Helminth eggs in the composts produced with the digestate from the wastewater treatment plant was above the acceptable level. The research also proved that the produced composts can be used in the phytoremediation process of the degraded area. It was found that all composts caused a significant increase in fescue biomass. The highest yield was achieved for compost produced from a mixture with the addition of 30% sewage sludge from the co-digestion process.

Description: Remote communities are increasingly adopting renewable energy, such as wind, as they transition away from diesel energy generation. It is important to understand the benefits and costs of wind energy to isolated systems so that decision-makers can optimize their choices in these communities. There are few examples of valuation of wind energy as a distributed resource and numerous differences in valuation approaches, especially in the inclusion of environmental and economic impacts. We apply a distributed wind valuation framework to calculate the benefits and costs of wind in St. Mary’s, Alaska, to the local electric cooperative and to society, finding that the project does not have a favorable benefit-to-cost ratio unless societal benefits are included, in which case the benefit-to-cost ratio is nearly double. Government funding is important to reducing the initial capital expenditures of this wind project and will likely be the case for projects with similar characteristics. Additional fuel savings benefits are potentially possible for this project through technological additions such as energy storage and advanced controls.

Description: Passivhaus EnerPHit is a rigorous retrofit energy standard for buildings, based on high thermal insulation and airtightness levels, which aims to significantly reduce building energy consumption during operation. However, extra retrofit materials are required to achieve this standard, which raises a contradiction between how to balance the environmental impacts of the retrofitting material inputs and extremely low energy consumption after retrofit. This motivated the analysis in this paper, which aimed to evaluate the possibilities of reducing the required retrofitting material inputs when trying to achieve the EnerPHit energy standard using a typical suburban dwelling in China’s hot summer–cold winter climate region as a case study. Firstly, how the insulation performance of each envelope component affected the building’s energy consumption was analysed. Based on this, sensitivity simulations of combinations of different insulation levels with different fabric components were investigated under four scenarios of insulation levels, airtightness and glazing choice. The final proposed retrofitting plans achieved the EnerPHit standard with insulation materials’ savings between 18% to 58% compared to a baseline retrofit plan, and this led, in turn, to 3.9 to 12.6 tonnes of carbon reductions. Moreover, an energy-saving of 87% in heating and 70% in cooling was achieved compared with the pre-retrofit dwelling.

Description: In line with the assumptions of the European Green Deal, it is planned to allocate 25% of agricultural land to organic farming by 2030. However, the question arises: what share of organic farming and under what additional conditions is it able to feed the population of a given country? The aim of the article is to try to answer the above question for the example of Poland. In particular, the authors analyze: the problem of satisfying people’s nutritional needs, reducing food wastage, and finally the relationship between sustainable consumption and increasing the share of organic farming in Poland. Attention was also paid to possible potential changes in the agricultural land area with the growing share of organic farming. The proposed scenarios for the transition to organic farming concern the year 2030. We propose to increase the share in 20%, 40% and 60%, imposing them on changes in sustainable consumption of +/−25%, +/−50% and +/−75%. The available FAOSTAT (Statistic Data of the Food and Agriculture Organization of the United Nations) and Statistics Poland data from 2008–2018 were used for the analysis. The model scenario analysis showed that the total food demand will be met in most of the scenarios. It has also been shown that with a higher level of transition to organic farming, it becomes necessary to reduce food wastage. Changing the consumption style not only creates opportunities for a wider development of organic farming in Poland but can also generate free areas on arable land (e.g., even more than 26% of free area in the +/−75% scenario). This may create potential opportunities for their use in the production of consumer crops, but also in the protection of the natural and agricultural environment.

Description: Throughout the world, wind energy is widely distributed as one of the most universal energy sources in nature, containing a gigantic reserve of renewable and green energy. At present, the main way to capture wind energy is to use an electromagnetic generator (EMG), but this technology has many limitations; notably, energy conversion efficiency is relatively low in irregular environments or when there is only a gentle breeze. A triboelectric nanogenerator (TENG), which is based on the coupling effect of triboelectrification and electrostatic induction, has obvious advantages for mechanical energy conversion in some specific situations. This review focuses on wind energy harvesting by TENG. First, the basic principles of TENG and existing devices’ working modes are introduced. Second, the latest research into wind energy-related TENG is summarized from the perspectives of structure design, self-power sensors and systems. Then, the potential for large-scale application and hybridization with other energy harvesting technologies is discussed. Finally, future trends and remaining challenges are anticipated and proposed.

Description: This paper aims to explore torque optimization control issue in the turning of EV (Electric Vehicles) with motorized wheels for reducing energy consumption in this process. A three-degree-of-freedom (3-DOF) vehicle dynamics model is used to analyze the total longitudinal force of the vehicle and explain the influence of torque vectoring distribution (TVD) on turning resistance. The Genetic Algorithm-Particle Swarm Optimization Hybrid Algorithm (GA-PSO) is used to optimize the torque distribution coefficient offline. Then, a torque optimization control strategy for obtaining minimum turning energy consumption online and a torque distribution coefficient (TDC) table in different cornering conditions are proposed, with the consideration of vehicle stability and possible maximum energy-saving contribution. Furthermore, given the operation points of the in-wheel motors, a more accurate TDC table is developed, which includes motor efficiency in the optimization process. Various simulation results showed that the proposed torque optimization control strategy can reduce the energy consumption in cornering by about 4% for constant motor efficiency ideally and 19% when considering the motor efficiency changes in reality.

Description: The purpose of this study is to design a business model that generates profits by developing eco-friendly convergent products. This study proposes a new concept of solar signage in the digital signage system that helps carbon emission reduction. This study developed a solar signage business model using the eco-science methodology specialized in manufacturing servitization. Following the ecosystem platform service strategy (EPSS) framework of eco-science optimized for convergent industry service design, this study implemented service derivation, convergent ecosystem definition, and business model development. The developed business model was evaluated by 10 experts in the field. The business model obtained 43 points, which exceeded the standard commercialization decision cutoff of 35 points. This study’s results imply that the business model is developed from an integrative perspective and defines the convergent industry ecosystem, a convergent knowledge service methodology, in digital signage. Moreover, through the business model, the perspectives on technological development can be expanded and the model can play an important role in carrying out new industry commercialization based on convergent technologies.

Description: The increasing amount of Internet of Things (IoT) devices and wearables require a reliable energy source. Energy harvesting can power these devices without changing batteries. Three-dimensional printing allows us to manufacture tailored harvesting devices in an easy and fast way. This paper presents the development of hybrid and non-hybrid 3D printed electromagnetic vibration energy harvesters. Various harvesting approaches, their utilised geometry, functional principle, power output and the applied printing processes are shown. The gathered harvesters are analysed, challenges examined and research gaps in the field identified. The advantages and challenges of 3D printing harvesters are discussed. Reported applications and strategies to improve the performance of printed harvesting devices are presented.

Description: Solid-state plastic crystal electrolytes (SPCEs) have attracted much attention due to their high ionic conductivity at room temperature and polymer-like plasticity. Herein, we made a LiFePO4||Li solid state battery based on SPCEs. A SPCE film is made up of glass fiber, succinonitrile (SN), lithium bis (triflu-romethanesulphonyl) imid (LiTFSI), and LiNO3. Glass fiber is introduced to improve the mechanical property, and LiNO3 served as an additive to stabilize electrolyte/Li interface. The SPCE film delivers a high ionic conductivity of 7.3 × 10−4 S cm−1 at room temperature and has excellent stability with Li-metal anode. SPCE is also infused into cathode electrode and used as the interface with cathode particles, which can access a large interface contact area and deform reversibly with volume change. The LiFePO4||Li solid state battery based on SPCE can work well at ambient temperature, which shows a high initial specific capacity of 121.4 mAh g−1 and has 86.9% retention after 90 cycles at 0.5 C.

Description: Hydrogen and its energy carriers, such as liquid hydrogen (LH2), methylcyclohexane (MCH), and ammonia (NH3), are essential components of low-carbon energy systems. To utilize hydrogen energy, the complete environmental merits of its supply chain should be evaluated. To understand the expected environmental benefit under the uncertainty of hydrogen technology development, we conducted life-cycle inventory analysis and calculated CO2 emissions and their uncertainties attributed to the entire supply chain of hydrogen and NH3 power generation (co-firing and mono-firing) in Japan. Hydrogen was assumed to be produced from overseas renewable energy sources with LH2/MCH as the carrier, and NH3 from natural gas or renewable energy sources. The Japanese life-cycle inventory database was used to calculate emissions. Monte Carlo simulations were performed to evaluate emission uncertainty and mitigation factors using hydrogen energy. For LH2, CO2 emission uncertainty during hydrogen liquefaction can be reduced by using low-carbon fuel. For MCH, CO2 emissions were not significantly affected by power consumption of overseas processes; however, it can be reduced by implementing low-carbon fuel and waste-heat utilization during MCH dehydrogenation. Low-carbon NH3 production processes significantly affected power generation, whereas carbon capture and storage during NH3 production showed the greatest reduction in CO2 emission. In conclusion, reducing CO2 emissions during the production of hydrogen and NH3 is key to realize low-carbon hydrogen energy systems.

Description: This article introduces an application of the recently developed hunger games search (HGS) optimization algorithm. The HGS is combined with chaotic maps to propose a new Chaotic Hunger Games search (CHGS). It is applied to solve the optimal power flow (OPF) problem. The OPF is solved to minimize the generation costs while satisfying the systems’ constraints. Moreover, the article presents optimal siting for mixed renewable energy sources, photovoltaics, and wind farms. Furthermore, the effect of adding renewable energy sources on the overall generation costs value is investigated. The exploration field of the optimization problem is the active output power of each generator in each studied system. The CHGS also obtains the best candidate design variables, which corresponds to the minimum possible cost function value. The robustness of the introduced CHGS algorithm is verified by performing the simulation 20 independent times for two standard IEEE systems—IEEE 57-bus and 118-bus systems. The results obtained are presented and analyzed. The CHGS-based OPF was found to be competitive and superior to other optimization algorithms applied to solve the same optimization problem in the literature. The contribution of this article is to test the improvement done to the proposed method when applied to the OPF problem, as well as the study of the addition of renewable energy sources on the introduced objective function.

Description: Wastewater treatment plants designed to meet the requirements of discharging wastewater to a receiving water body are often not energy optimised. Energy requirements for conventional activated sludge wastewater treatment plants are estimated to range from 0.30 to 1.2 kWh/m3, with the highest values achieved using the nitrification process. This article describes the energy optimisation process of the wastewater treatment plant in Gubin (Poland) designed for 90,000 PE (population equivalent) using renewable energy sources: solar, biogas, and geothermal. At the analysed wastewater treatment plant electricity consumption for treating 1 m3 of wastewater was 0.679 kWh in 2020. The combined production of electricity and heat from biogas, the production of electricity in a photovoltaic system, and heat recovery in a geothermal process make it possible to obtain a surplus of heat in relation to its demand in the wastewater treatment plant, and to cover the demand for electricity, with the possibility of also selling it to the power grid.

Description: In this paper, testing and diagnosis methods for the static excitation systems of power plant synchronous generators using Hardware-In-the-Loop technology are described. These methods allow a physical excitation system to be connected to a real-time model of a power plant unit. A feature of a static excitation system is the presence of generator self-excitation—that is, when the input voltages of the excitation system are defined by a synchronous generator. These voltages are determining by the digital model, which creates additional difficulties with combining a digital model with a real excitation system. Various ways to solve this problem are described in this article; in particular, we focus on the option in which the gate-impulses of a thyristor converter are applied to the digital model by a real static excitation system. The real-time models are based on the method of average voltages in the integration step. This method is effective for providing numerical stability for the models of power schemes and their functioning in real time mode over a long period. A synchronization method for the calculation time of the model with real time is described. The adequacy of the described method is proved by the results of the static excitation system of synchronous generators testing in operating and fault modes.

Description: Rockburst is a dynamic rock mass failure occurring during underground mining under unfavorable stress conditions. The rockburst phenomenon concerns openings in different rocks and is generally correlated with high stress in the rock mass. As a result of rockburst, underground excavations lose their functionality, the infrastructure is damaged, and the working conditions become unsafe. Assessing rockburst hazards in underground excavations becomes particularly important with the increasing mining depth and the mining-induced stresses. Nowadays, rockburst risk prediction is based mainly on various indicators. However, some attempts have been made to apply machine learning algorithms for this purpose. For this article, we employed an extensive range of machine learning algorithms, e.g., an artificial neural network, decision tree, random forest, and gradient boosting, to estimate the rockburst risk in galleries in one of the deep hard coal mines in the Upper Silesian Coal Basin, Poland. With the use of these algorithms, we proposed rockburst risk prediction models. Neural network and decision tree models were most effective in assessing whether a rockburst occurred in an analyzed case, taking into account the average value of the recall parameter. In three randomly selected datasets, the artificial neural network models were able to identify all of the rockbursts.

Description: This paper is the companion paper of Remote Microgrids for Energy Access in Indonesia “Part I: scaling and sustainability challenges and a technology outlook”. This part II investigates the issues of photovoltaic (PV) systems with respect to the planning, design, and operation, and maintenance phases in microgrids in Indonesia. The technology outlooks are also included as PV has an important role in providing electricity in the underdeveloped, isolated, and border areas. The data in this paper are from PV microgrids located in Maluku and North Maluku, which are two provinces where there is barely any grid connection available and thus very dependent on remote microgrids. The data are obtained from interviews with Perusahaan Listrik Negara (PLN) and NZMATES, which are an Indonesian utility company and a program for supporting role for the PV systems in Maluku funded by New Zealand respectively. Common issues with respect to reliability and sustainability are identified based on the provided data. Advanced technologies to increase reliability and sustainability are also presented in this paper as a technology outlook. Among these solutions are online monitoring systems, PV and battery lifetime estimation, load forecasting strategies, and PV inverters technology.

Description: The Smart Energy Research Lab (SERL) Observatory dataset described here comprises half-hourly and daily electricity and gas data, SERL survey data, Energy Performance Certificate (EPC) input data and 24 local hourly climate reanalysis variables from the European Centre for Medium-Range Weather Forecasts (ECMWF) for over 13,000 households in Great Britain (GB). Participants were recruited in September 2019, September 2020 and January 2021 and their smart meter data are collected from up to one year prior to sign up. Data collection will continue until at least August 2022, and longer if funding allows. Survey data relating to the dwelling, appliances, household demographics and attitudes were collected at sign up. Data are linked at the household level and UK-based academic researchers can apply for access within a secure virtual environment for research projects in the public interest. This is a data descriptor paper describing how the data were collected, the variables available and the representativeness of the sample compared to national estimates. It is intended to be a guide for researchers working with or considering using the SERL Observatory dataset, or simply looking to learn more about it.

Description: In this study, the effects of the mixing chamber diameter (Dm), mixing chamber length (Lm) and pre-mixing chamber converging angle (θpm) were numerically investigated for a two-throat nozzle ejector to be utilized in a CO2 refrigeration cycle. The developed simulated method was validated by actual experimental data of a CO2 ejector in heat pump water heater system from the published literature. The main results revealed that the two-throat nozzle ejectors can obtain better performance with Dm in the range of 8–9 mm, Lm in the range of 64–82 mm and θpm at approximately 60°, respectively. Deviation from its optimal value could lead to a poor operational performance. Therefore, the mixing chamber structural parameters should be designed at the scope around its optimal value to guarantee the two-throat nozzle ejector performance. The following research can be developed around the two-throat nozzle geometries to strengthen the ejector performance.

Description: This paper has tried to execute accurate demand forecasting by utilizing big data visualization and proposes a flexible and balanced electric power production big data virtualization based on a photovoltaic power plant. First of all, this paper has tried to align electricity demand and supply as much as possible using big data. Second, by using big data to predict the supply of new renewable energy, an attempt was made to incorporate new and renewable energy into the current power supply system and to recommend an efficient energy distribution method. The first presented problem that had to be solved was the improvement in the accuracy of the existing electricity demand for forecasting models. This was explained through the relationship between the power demand and the number of specific words in the paper that use crawling by utilizing big data. The next problem arose because the current electricity production and supply system stores the amount of new renewable energy by changing the form of energy that is produced through ESS or that is pumped through water power generation without taking the amount of new renewable energy that is generated from sources such as thermal power, nuclear power, and hydropower into consideration. This occurs due to the difficulty of predicting power production using new renewable energy and the absence of a prediction system, which is a problem due to the inefficiency of changing energy types. Therefore, using game theory, the theoretical foundation of a power demand forecasting model based on big data-based renewable energy production forecasting was prepared.

Description: The prevalent use of the Internet of Things (IoT) devices over the Sea, such as, on oil and gas platforms, cargo, and cruise ships, requires high-speed connectivity of these devices. Although satellite based backhaul links provide vast coverage, but they are inherently constrained by low data rates and expensive bandwidth. If a signal propagated over the sea is trapped between the sea surface and the Evaporation Duct (ED) layer, it can propagate beyond the horizon, achieving long-range backhaul connectivity with minimal attenuation. This paper presents experimental measurements and simulations conducted in the Industrial, Scientific, and Medical (ISM) Band Wi-Fi frequencies, such as 5.8 GHz to provide hassle-free offshore wireless backhaul connectivity for IoT devices over the South China Sea in the Malaysian region. Real-time experimental measurements are recorded for 10 km to 80 km path lengths to determine average path loss values. The fade margin calculation for ED must accommodate additional slow fading on top of average path loss with respect to time and climate-induced ED height variations to ensure reliable communication links for IoT devices. Experimental results confirm that 99% link availability of is achievable with minimum 50 Mbps data rate and up to 60 km distance over the Sea to connect offshore IoT devices.

Description: The prediction of solar radiation has a significant role in several fields such as photovoltaic (PV) power production and micro grid management. The interest in solar radiation prediction is increasing nowadays so efficient prediction can greatly improve the performance of these different applications. This paper presents a novel solar radiation prediction approach which combines two models, the Auto Regressive Moving Average (ARMA) and the Nonlinear Auto Regressive with eXogenous input (NARX). This choice has been carried out in order to take the advantages of both models to produce better prediction results. The performance of the proposed hybrid model has been validated using a real database corresponding to a company located in Barcelona north. Simulation results have proven the effectiveness of this hybrid model to predict the weekly solar radiation averages. The ARMA model is suitable for small variations of solar radiation while the NARX model is appropriate for large solar radiation fluctuations.

Description: A significant body of research has emerged for adapting diverse intelligent distributed energy resources to provide primary frequency reserves (PFR). However, such works are usually vague about the technical specifications for PFR. Industrial practitioners designing systems for PFR markets must pre-qualify their PFR resources against the specifications of the market operator, which is usually a transmission system operator (TSO) or independent system operator (ISO). TSO and ISO requirements for PFR have been underspecified with respect to real-time performance, but as fossil-fuel based PFR is being replaced by various distributed energy resources, these requirements are being tightened. The TSOs of Denmark, Finland, Norway, and Sweden have recently released a joint pilot phase specification with novel requirements on the dynamic performance of PFR resources. This paper presents an automated procedure for performing the pre-qualification procedure against this specification. The procedure is generic and has been demonstrated with a testbed of light emitting diode (LED) lights. The implications of low bandwidth Internet of Things communications, as well as the need to avoid abrupt control actions that irritate human users, have been investigated in the automated procedure.

Description: The paper’s main purpose is to identify the differentiation and variation of electricity prices for households in EU countries. The specific objectives are to highlight the directions and differentiation of price changes in EU states, determine the degree of volatility (or stability) of electricity rates, and establish the correlation between electricity prices for household consumers and economic and energy parameters. All members of the European Union were chosen for this project as of 31 December 2019 (28 countries). The analyzed period covered the years 2008–2019. The source of collected information was the thematic literature review and the data from Eurostat. Descriptive, tabular and graphical methods, constant-based dynamics indicators, coefficient of variation, Kendall’s tau correlation coefficient, and Spearman’s rank correlation coefficient were used to analyze and present the materials. It was determined that higher electricity prices for households in the EU states were associated with better economic parameters. Developed countries must have higher energy rates because they will ensure energy transformation, i.e., implementing energy-saving technologies. In the EU, electricity prices for household consumers showed little volatility, but that variability increased in line with the surge of the volume of household energy consumption.

Description: The issues of renewable energy, energy crisis, and carbon reduction have caught people’s attention all over the world, and governments have put forth greater effort to proactively solve these problems. Electric transportation not only benefits the environment, but can also utilize renewable energy to prevent an energy crisis. Based on previous theoretical strands of the literature, this research integrates the technology readiness and acceptance model (TRAM) into the norm activation model (NAM) and proposes an integrated model denoted as TRA-NAM. It takes TRA-NAM as our theoretical foundation and aims to explore the effect of technology readiness and awareness of consequence on the intention toward using an electric scooter (ES). The results display that technology readiness positively influences perceived usefulness and perceived ease of use and further improves consumers’ intention toward adopting ES. In addition, personal norm mediates the relationship between awareness of consequence and intention to adopt ES. This study offers the integrated TRAM-NAM model in order to understand the crucial factors affecting consumers’ intention to adopt electric vehicles (EVs). Overall, this research fills the gap in the field of government policies and transportation and proposes ponderable suggestions, in particular that if they want to encourage or attract consumers to drive an ES, they should not overlook the effect of technology readiness and awareness of consequence.

Description: Detrimental effects exerted by biomass-based traditional cookstoves on health, environment, hygiene, and the soaring price of gas makes it imperative to investigate the feasibility of electric cooking as a promising clean cooking fuel in the context of Bangladesh. However, the adoption of electric cooking is unlikely to be welcomed if the monthly cost of electricity consumed by the electric cooking appliances is not comparable to traditional cooking fuels. So far, no study has been reported in this respect. Therefore, this paper is aimed to assess the energy consumption of available electric cooking appliances for cooking typical Bangladeshi dishes. Estimated monthly electricity cost of electric cooking is also reported and then compared to that of traditional cooking fuels. For the study purpose, three respondent families were provided with a rice cooker, hot plate, induction cooker and electric pressure cooker for cooking their daily meals. After four months of use, data related to dish cooked, amount of food, cooking time, and energy consumption were collected which shows that hot plate and rice cooker were the least preferred appliances due to their poor workmanship and limited use respectively. On the contrary, despite the fact that electric pressure cookers cannot perform all types of frying, it was the most preferred appliance owing to its ability to significantly reduce the cooking time and its less energy consumption. Induction cooker was less preferred for the additional requirement of compatible cook pots. The study also reveals that monthly energy requirements for electric cooking varied from 72–87 kWh corresponding to a cooking electricity bill ranging from BDT 504–609 per month (USD 6–7.5) which is less expensive as compared with biomass and LPG based cooking. This paper also highlights the prospects and challenges associated with the adoption of electricity as the primary cooking fuel in Bangladesh.

Description: A hybrid photovoltaic-thermal collector (PV-T) with the capability to produce thermal energy and electrical energy simultaneously has attracted the attention of researchers, especially in terms of improving PV-T performance. This study analyses the work of four model installations with PV-T and other devices built in the transient systems simulation program. The novelty of this article lies in a long-term approach to the operation of PV-T panels under selected climatic conditions. Influence of the installation’s configuration on the obtained temperatures of solar cells, and, in consequence, on electric power generated by PV-T and the amount of heat produced during one year in a selected location is presented. Among others, the impact of the temperature coefficient of photovoltaic cells for long-term PV-T operation was analyzed in the paper. The results showed that the type of cell used may decrease the yearly electric energy production from PV-T even by 7%. On the other hand, intensification of the process of heat reception from PV-T using a heat pump increased this production by 6% in relation to the base model. The obtained research results indicate possible methods for improving the effectiveness of PV-T operation in a long-term aspect.

Description: Real-time transient stability studies are based on voltage angle measures obtained with phasor measurement units (PMUs). A more precise calculation to address transient stability is obtained when using the rotor angles. However, these values are commonly estimated, which leads to possible errors. In this work, the kinetic energy changes in electric machines are used as a criterion for evaluating and correcting transient stability, and to determine the precise time of insertion of a special protection system (SPS). Data from the PMU of the wide-area measurement system (WAMS) are used to construct the SPS. Furthermore, it is assumed that a microcontroller can be located in each generation unit to obtain the synchronized angular velocity. Based on these measurements, the kinetic energy of the system and the respective control action are performed at the appropriate time. The results show that the proposed SPS effectively corrects the oscillations fast enough during the transient stability event. In addition, the proposed method has the advantage that it does not depend on commonly proposed methods, such as system models, the identification of coherent machine groups, or the structure of the network. Moreover, the synchronized angular velocity signal is used, which is not commonly measured in power systems. Validation of the method is carried out in the New England power system, and the findings show that the method is helpful for real-time operation on large power systems.

Description: The effects of doping manganese ions into a cerium oxide lattice for a thermochemical two-step water-splitting cycle to produce oxygen and hydrogen and new synthesis methods were experimentally investigated. In order to comparison of oxygen/hydrogen producing performance, pristine CeO2, a coprecipitation method for Mn-CeO2, and a direct depositing method for Mn-CeO2 with different particle sizes (50~75, 100–212, over 212 μm) and doping extents (0, 5, 15 mol%) were tested in the context of synthesis and fabrication processes of reactive metal oxide coated ceramic foam devices. Sample powders were coated onto zirconia (magnesium partially stabilized zirconia oxide, MPSZ) porous foam at 30 weight percent using spin coating or a direct depositing method, tested using a solar reactor at 1400 °C as a thermal reduction step and at 1200 °C as a water decomposition step for five repeated cycles. The sample foam devices were irradiated using a 3-kWth sun-simulator, and all reactive foam devices recorded successful oxygen/hydrogen production using the two-step water-splitting cycles. Among the seven sample devices, the 5 mol% Mn-CeO2 foam device, that synthesized using the coprecipitation method, showed the greatest hydrogen production. The newly suggested direct depositing method, with its contemporaneous synthesis and coating of the Mn-CeO2 foam device, showed successful oxygen/hydrogen production with a reduction in the manufacturing time and reactants, which was lossless compared to conventional spin coating processes. However, proposed direct depositing method still needs further investigation to improve its stability and long-term device durability.

Description: Common-Mode Voltage (CMV) induces shaft voltage and bearing current due to the electrical interaction with the parasitic capacitance of the motor. CMV, shaft voltage, and bearing current are considered the major causes of bearing fault. Motor fault in a traction system poses a risk of accidents. Therefore, it is necessary to reduce the CMV and the shaft voltage to ensure the reliability of the bearing. However, some existing CMV reduction methods are based on asynchronized space vector pulse width modulation (SVPWM), which will cause unacceptable harmonic distortion at a low switching frequency. Alternatively, some CMV reduction methods based on synchronized SVPWM burden the processor because they require a lot of calculation. In this paper, the method to reduce CMV and shaft voltage is proposed using carrier wave phase shift in SVPWM. CMV is explained in traditional SVPWM, and CMV is reduced by shifting the carrier wave phase of one phase. The simulation model is constructed through MATLAB/SIMULINK and Maxwell 2D/Twin Builder. Considering the proposed method, CMV, shaft voltage, and bearing current are analyzed by an equivalent circuit model. Moreover, the output torque behaviors with different input currents are analyzed through the simulation.

Description: Plasma spraying and magnetron sputtering were used to form graphite–copper films on an n-type silicon surface. The main objective of this work was to compare the properties of the obtained graphite–copper Schottky photodiodes prepared using two different layer formation methods and to evaluate the influence of copper content on the surface morphology, phase structure, and photovoltaic characteristics of the graphite–copper films. Surface morphology analysis shows that the surface of the formed layers using either plasma spraying technology or the magnetron sputtering method consists of various sphere-shaped microstructures. The X-ray diffraction measurements demonstrated that the graphite–copper coatings formed by plasma spraying were crystalline phase. Meanwhile, the films deposited by magnetron sputtering were amorphous when the copper concentration was up to 9.7 at.%. The increase in copper content in the films led to the formation of Cu crystalline phase. Schottky diodes formed using magnetron sputtering technology had a maximum current density of 220 mA/cm2 at 5 V. Meanwhile, the maximum electric current density of Schottky photodiodes formed using plasma spraying reached 3.8 mA/cm2. It was demonstrated that the efficiency of Schottky diodes formed using magnetron sputtering was up to 60 times higher than Schottky diodes formed using plasma spraying.

Description: A major challenge in the development of multi-vendor HVDC networks are converter control interactions. While recent publications have reported interoperability issues such as persistent oscillations for first multi-vendor HVDC setups with AC-side coupling, multi-terminal HVDC networks are expected to face similar challenges. To investigate DC-side control interactions and mitigate possible interoperability issues, several methods based on the converters’ and DC network’s impedances have been proposed in literature. For DC network’s impedance modelling, most methods require detailed knowledge of all converters’ design and controls. However, in multi-vendor HVDC networks, converter control parameters are not expected to be shared due to proprietary reasons. Therefore, to facilitate impedance-based stability analyses in multi-vendor MTDC networks, methods that do not require the disclosure of the existing converter controls are needed. Here, detailed impedance measurements can be applied; however, they are time-consuming and require new measurement for a single configuration change. This paper proposes an equivalent impedance calculation method suitable for multi-vendor DC networks, which for available black-box models or converter impedance characteristics can be modularly applied for various network configurations, including different control settings and operating points, while significantly reducing the required time for obtaining an equivalent DC network impedance.

Description: Blankets are a difficult problem for fusion engineering design. Because of the complex flow channels, the design, production, processing, and accident maintenance of blankets are all huge challenges for traditional water/gas-cooled blankets. Blankets are the bridge for heat transfer and tritium production. A high-performance blanket with simplified structure is obviously beneficial for engineering, safety, and the economy. In this study, gravity heat pipes instead of coolant flow channels are adopted to remove the heat. Compared with coolant-cooled systems, heat pipes may be simpler and more reliable. The in-vessel and in-box loss of coolant accident (LOCA) will not occur because there is no coolant in the blanket. Moreover, a damaged heat pipe may be replaced easily compared to a damaged water-cooled blanket. In this study, a hypothetical heat pipe-cooled blanket for the China Fusion Engineering Test Reactor (CFETR) was proposed and one module of the blanket was analyzed by numerical simulation. The results were compared with those of a water-cooled blanket, and the temperature distribution of the heat pipe-cooled blanket is more uniform. This study verified the preliminary feasibility of heat pipe-cooled blankets and provided a fresh idea for blanket design.

Description: While extensive research has gone into demand response techniques in data centers, the energy consumed in edge computing systems and in network data transmission remains a significant part of the computing industry’s carbon footprint. The industry also has not fully leveraged the parallel trend of decentralized renewable energy generation, which creates new areas of opportunity for innovation in combined energy and computing systems. Through an interdisciplinary sociotechnical discussion of current energy, computer science and social studies of science and technology (STS) literature, we argue that a more comprehensive set of carbon response techniques needs to be developed that span the continuum of data centers, from the back-end cloud to the network edge. Such techniques need to address the combined needs of decentralized energy and computing systems, alongside the social power dynamics those combinations entail. We call this more comprehensive range “carbon-responsive computing,” and underscore that this continuum constitutes the beginnings of an interconnected infrastructure, elements of which are data-intensive and require the integration of social science disciplines to adequately address problems of inequality, governance, transparency, and definitions of “necessary” tasks in a climate crisis.

Description: In coal mines that are exploiting methane-saturated seams, high-level emission of methane is often the basic limitation for modern and high-efficiency longwall complexes. This paper presents selected observations and tests carried out in the Cw-4 longwall in seam 364/2 of the Budryk mine, which belongs to JSW SA. To observe the methane levels in the Cw-4 longwall, additional sensors were installed at the end section of the longwall from the side of the gobs, and the air velocity and methane concentration were registered in a multi-point system that were built in the selected longwall cross-section. The air parameters were recorded in the monitoring system. The use of multi-point simultaneous measurements of the local velocities and concentrations of methane in the longwall cross-section allowed for the precise determination of the air and methane volume flow using the velocity field method. This allowed us to perform a comparative analysis of the obtained records of the air parameters using special software to determine the distribution of the parameters in the cross-section of the excavation. An important element of the study was the simultaneous registration of the methane concentration in the longwall, information on the operating times, the direction of shearer operation, and the type of work being done (i.e., mining/cleaning).

Description: In this work, a smart solar still prototype for water desalination is designed. It consists of a basic solar still, a solar preheater and a remote monitoring system based on the Internet of Things (IoT) technique. The monitoring system is developed and integrated into the hybrid solar still in order to control its evolution online, as well the quality of the freshwater provided by checking measured parameters such as pH. Thanks to the IoT technique, parameters collected by the monitoring system (e.g., air temperatures, relative humidity, etc.) are uploaded to the cloud for online remote monitoring. The users are notified by an SMS about the status of the system (e.g., water level in the basin, water in the tank, etc.), using an GSM module. The whole system, including the preheater, water pump, valve, sensors and an electronic board, is powered by a photovoltaic module of 75 Wp. The results showed that by adding a solar preheater system, the evaporation process is accelerated and, consequently, the daily yield is improved and reaches the value of 12.165 L/m2/day. The saline concentration of the tested ground water is 3.9 g/Kg (0.39%), and, after desalination, the salinity is 0.1 g/Kg (0.01%).

Description: This work presents a thermohydraulic analysis of a postulated accident involving the rupture of the breeder primary cooling loop inside a heat exchanger (once through steam generator). After the detection of the loss of pressure inside the primary loop, a plasma shutdown is actuated with a consequent plasma disruption, isolation of the secondary loop, and shutoff of the pumps in the primary; no other safety counteractions are postulated. The objective of the work is to analyze the pressurization of the primary and secondary sides to show that the accidental overpressure in the two sides of the steam generators is safely accommodated. Furthermore, the effect of the plasma disruption on the FW, in terms of temperatures, should be analyzed. Lastly, the time transients of the pressures and temperatures in the HX and BB for a time span of up to 36 h should be obtained to assess the effect of the decay heat over a long period. A full nodalization of the OTSG was realized together with a simplified nodalization of the whole PHTS BB loop. The code utilized was MELCOR for fusion version 1.8.6. The accident was simulated by activating a flow path which directly connected one section of the primary with the parallel section of the secondary side. It is shown here that the pressures and the temperatures inside the whole PHTS system remain below the safety thresholds for the whole transient.

Description: The rapid growth of aquaculture production has required a huge power demand, which is estimated to be about 40% of the total energy cost. However, it is possible to reduce this expense using alternatives such as renewable energy (i.e., solar energy) instead of non-renewable energy. Solar energy is one of the cleanest energy sources and is touted as a potential renewable energy source for the world with benefits such as reducing CO2 emissions, reversing global warming by being eco-friendly, and bringing innovation to sustainable aquaculture and potential cost-efficiency for manufacturing. In this review, we present an overview of using non-renewable and renewable energy sources for aquaculture by reviewing several articles and applications of solar energy at many companies in the world. Moreover, this review shows potential and future trends using solar energy for aquaculture.

Description: The underlying effect of preflush salinity and silica nanofluid (Si-NF) on oil production is examined. The influence of salinity on the stability of Si-NFs is studied. A series of sand-pack floodings evaluating oil production was conducted at different concentrations of preflush salinity (0 to 4 wt.%), followed by the injection of a Si-NF (0.5 wt.%) at the trail of which postflush water was injected. The effluent water and solids were collected and analyzed using X-ray fluorescence (XRF). Interfacial tension (IFT) and contact angle measurements were conducted on the Si-NF in the presence of salinity to confirm the effect. The Si-NF became unstable and formed precipitate in the presence of salinity. The sand-pack flooding showed that when the preflush salinity was increased, the displacement efficiency (ED) using the Si-NF and postflush injection was increased (ED = 44%). The XRF of the precipitated effluent revealed that the preflush salinity and Si-NF caused mineral leaching, which triggered pore clogging. The IFT value reduced from 13.3 to 8.2 mN/m, and the wettability was altered to be more strongly water-wet when the salinity increased. The primary mechanisms of oil recovery using the Si-NF after preflush salinity is attributed mainly to the clogging mechanism. This clogging helps block the high-perm area, shift the fluid flow to the oil-trapped zone, and free the oil out. Other contribution mechanisms are IFT reduction and wettability alteration.

Description: This paper deals with pore-scale two-phase flow simulations in carbonate rock using the pore network method (PNM). This method was used to determine the rock and flow properties of three different rock samples, such as porosity, capillary pressure, absolute permeabilities, and oil–water relative permeabilities. The pore network method was further used to determine the properties of rock matrices, such as pore size distribution, topological structure, aspect ratio, pore throat shape factor, connected porosity, total porosity, and absolute permeability. The predicted simulation for the network-connected porosity, total porosity, and absolute permeability agree well with those measured experimentally when the image resolution is appropriate to resolve the relevant pore and throat sizes. This paper also explores the effect of the wettability and fraction of oil-wet pores on relative permeabilities, both in uniform and mixed wet systems.

Description: When the state of the wind turbine sensors, especially the anemometer, appears abnormal it will cause unnecessary wind loss and affect the correctness of other parameters of the whole system. It is very important to build a simple and accurate fault diagnosis model. In this paper, the model has been established based on the Random Walk Improved Sparrow Search Algorithm to optimize auto-associative neural network (RWSSA-AANN), and is used for fault diagnosis of wind turbine group anemometers. Using the cluster analysis, six wind turbines are determined to be used as a wind turbine group. The 20,000 sets of normal historical data have been used for training and simulating of the model, and the single and multiple fault states of the anemometer are simulated. Using this model to analyze the wind speed supervisory control and data acquisition system (SCADA) data of six wind turbines in a wind farm from 2013 to 2017, can effectively diagnose the fault state and reconstruct the fault data. A comparison of the results obtained using the model developed in this work has also been made with the corresponding results generated using AANN without optimization and AANN optimized by genetic algorithm. The comparison results indicate that the model has a higher accuracy and detection rate than AANN, genetic algorithm auto-associative neural network (GA-AANN), and principal component analysis (PCA).

Description: Roughness is an important factor affecting the engineering stability of jointed rock masses. The existing roughness evaluation methods are all based on a uniform sampling interval, which changes the geometrical morphology of the original profile and inevitably ignores the influence of secondary fluctuations on the roughness. Based on the point cloud data obtained by 3D laser scanning, a non-equal interval sampling method and an equation for determining the sampling frequency on the roughness profile are proposed. The results show that the non-equal interval sampling method can successfully maintain the morphological characteristics of the original profile and reduce the data processing cost. Additionally, direct shear tests under constant normal load (CNL) conditions are carried out to study the influence of roughness anisotropy on the shear failure mechanism of joint surfaces. It is found that with the increase in shear displacement, the variations in the shear stress are related to the failure mechanisms of dilatancy and shear fracture of the joint. Finally, the distributions of shear stress, dilatancy and fracture areas on the rough joint in different shear directions are calculated theoretically. Results show that the anisotropy and failure mechanism of rough joint can be well characterized by the modified root mean square parameter Z2′.

Description: All over the world, the vehicles introduced now into the market are usually provided with EDRs (Event Data Recorders), intended to measure and record the parameters that characterise the vehicle motion in the pre-, during-, and post-accident phases. The EDRs are to facilitate the description and reconstruction of possible road accidents. They are patterned on aircraft “black boxes” (flight recorders). Many of them have simplified design, disregarding three (of six) vector components that describe the motion of the vehicle body solid. In the paper presented, the authors used simulation models built by themselves to represent motor vehicle dynamics and the reconstruction of vehicle trajectory and velocities based on records obtained from two EDR types: “aircraft” one (EDR1) and “simplified” one (EDR2). Using a simulation method, they examined the impact of the said simplifications mentioned above on the quality of reconstruction of vehicle motion for four typical manoeuvres in road traffic. The calculation results obtained for input data adopted to rep-resent a medium-class passenger car have shown that the simplifications may cause considerable reconstruction errors. This particularly applies to the manoeuvres where significant changes took place in the roll and pitch angles of the vehicle body solid (to which the EDR was fixed) or where the changes were characterised by absence of symmetry in the parameters that describe the manoeuvre and by the constant sign of the vehicle body roll angles.

Description: Estimating the probability of the occurrence of hazardous winds is crucial for their impact in human activities; however, this is inherently affected by the shortage of observations. This becomes critical in poorly sampled regions, such as the northwestern Sahara, where this work is focused. The selection of any single methodological variant contributes with additional uncertainty. To gain robustness in the estimates, we expand the uncertainty space by applying a large body of methodologies. The methodological uncertainty is constrained afterward by keeping only the reliable experiments. In doing so, we considerably narrow the uncertainty associated with the wind return levels. The analysis suggest that not necessarily all methodologies are equally robust. The highest 10-min speed (wind gust) for a return period of 50 years is about 45 ms−1 (56 ms−1). The intensity of the expected extreme winds is closely related to orography. The study is based on wind and wind gust observations that were collected and quality controlled for the specific purposes herein. We also make use of a 12-year high-resolution regional simulation to provide simulation-based wind return level maps that endorse the observation-based results. Such an exhaustive methodological sensitivity analysis with a long high-resolution simulation over this region was lacking in the literature.

Description: Performance degradation is, in general, regarded as a power quality problem. One solution to recover grid performance is through the application of a unified power quality conditioner (UPQC). Although these devices are multi-input/multi-output (MIMO) systems, the most common control strategies consist of two decoupled controllers, which neglect the coupling effects and add uncertainty to the system. For this reason, this paper proposes a multivariable resonant observer-based control strategy of a UPQC system. This method includes all significant coupling effects between this system and the grid. This strategy results in a stability-based compensator, which differs from recently proposed strategies that are based on signal calculation and cannot assure closed-loop stability. In addition, this paper introduces a simplified controller tuning strategy based on optimal conventional methods without losing closed-loop performance. It implies that the controller can be easily tuned, despite the complexity of the MIMO dynamic model. The UPQC with the resonant observer is verified on an experimental setup for a single-phase system, obtaining three relevant results for power quality improvement: (1) harmonics compensation tested with a total harmonic distortion limit of 5%; (2) sags and swells mitigation; and (3) power factor correction, achieving a unitary value on the grid side.

Description: As more countries seek solutions to their de-carbonization targets using renewable energy (RE) technologies, interconnection standards and national grid codes for distributed energy resources (DER) are being updated to support higher penetrations of RE and improve grid stability. Common grid-code revisions mandate DER devices, such as solar inverters and energy storage systems, ride-through (RT) voltage and frequency disturbances. This is necessary because as the percentage of generation from DER increases, there is a greater risk power system faults will cause many or all DER to trip, triggering a substantial load-generation imbalance and possible cascading blackout. This paper demonstrates for the first time a methodology to verify commercial DER devices are compliant to new voltage, frequency, and rate of change of frequency (ROCOF) RT requirements established in IEEE Std. 1547-2018. The methodology incorporates a software automation tool, called the SunSpec System Validation Platform (SVP), in combination with a hardware-in-the-loop (HIL) system to execute the IEEE Std. 1547.1-2020 RT test protocols. In this paper, the approach is validated with two commercial photovoltaic inverters, the test results are analyzed for compliance, and improvements to the test procedure are suggested.

Description: To obtain the knowledge that contributes to the safer operation of nuclear power plants and their prompt recovery and termination in the event of an accident, soft epoxy resins with rubber-based additives—used as insulators and airtight sealants in electrical penetrations in nuclear power plants—were aged under several simulated severe accident environments with different conditions of heat, gamma rays, and exposure to superheated steam containing no oxygen. Then, changes in structural, dynamic mechanical, mechanical, and dielectric properties were examined. It has been found that this resin becomes hard as a result of cross-linking if aged by irradiation with gamma rays. Since the cross-linking slows down the molecular motions, the glass transition temperature increases, whereas the dielectric permittivity and the dielectric loss factor decrease unless the steam penetrates the sample. Although the sample melts and disappears if directly exposed to superheated steam at 171 °C or 200 °C, the irradiation with gamma rays conducted prior to the steam exposure can mitigate the hydrolysis induced by the steam. Although the soft epoxy resin shows drastic changes in various properties, its properties after the aging approach or exceed the corresponding ones of the non-degraded ordinary hard epoxy resin. Therefore, it seems that using soft epoxy resin according to its purposes would not be a problem.

Description: In this article, we propose a mathematical model using the port-Hamiltonian formalism for a satellite’s three-axis attitude system comprising fluid rings. Fluid rings are an alternative to reaction wheels used for the same purpose, since, for the same mass, they can exert a greater torque than a reaction wheel as the fluid can circulate the periphery of the satellite. The port-Hamiltonian representation lays the foundation for a posterior controller that is feasible, stable, and robust based on the interconnection of the system to energy shaping and/or damping injection components, and by adding energy routing controllers. The torques exerted by the fluid rings are modeled using linear regression analysis on the experimental data got from a prototype of a fluid ring. Since the dynamics of turbulent flows is complex, the torques obtained by the prototype lead to a simpler first approach, leaving its uncertainties to a controller. Thus, the attitude system model could be tested in a future prototype before considering a spatial environment.

Description: The heterogeneous and interoperable nature of the cyber-physical system (CPS) has enabled the smart grid (SG) to operate near the stability limits with an inconsiderable accuracy margin. This has imposed the need for more intelligent, predictive, fast, and accurate algorithms that are able to operate the grid autonomously to avoid cascading failures and/or blackouts. In this paper, a new comprehensive identification system is proposed that employs various machine learning architectures for classifying stability records in smart grid networks. Specifically, seven machine learning architectures are investigated, including optimizable support vector machine (SVM), decision trees classifier (DTC), logistic regression classifier (LRC), naïve Bayes classifier (NBC), linear discriminant classifier (LDC), k-nearest neighbor (kNN), and ensemble boosted classifier (EBC). The developed models are evaluated and contrasted in terms of various performance evaluation metrics such as accuracy, precision, recall, harmonic mean, prediction overhead, and others. Moreover, the system performance was evaluated on a recent and significant dataset for smart grid network stability (SGN_Stab2018), scoring a high identification accuracy (99.90%) with low identification overhead (4.17 μSec) for the optimizable SVM architecture. We also provide an in-depth description of our implementation in conjunction with an extensive experimental evaluation as well as a comparison with state-of-the-art models. The comparison outcomes obtained indicate that the optimized model provides a compact and efficient model that can successfully and accurately predict the voltage stability margin (VSM) considering different operating conditions, employing the fewest possible input features. Eventually, the results revealed the competency and superiority of the proposed optimized model over the other available models. The technique also speeds up the training process by reducing the number of simulations on a detailed power system model around operating points where correct predictions are made.

Description: Office buildings built before the pre-1960 age constitute a relevant group for analyzing the energy performance of the Portuguese building sector. A dynamic energy simulation was used to assess the energy performance of an existing office building located in the town of Bragança, Portugal. By using a staged renovation approach, two passive technologies applied to the building envelope and an efficient domestic hot water system were selected and a financial evaluation through the net saving (NS) method was undertaken to choose the best efficiency measures/packages for improving the building’s energy performance. Real discount rates of 3% and 1% were used in the financial evaluation. Considering the real discount rate of 3%, the results showed that only two out seven retrofit options had a positive financial return. By using the real discount rate of 1%, all retrofit options were found to be financially efficient. The results of the study corroborated those of earlier works that found that the financial profitability of energy renovation investments is very sensitive to the discount rate used in the analysis. The results of the study also suggested that the staged renovation approach used in the analysis is economically feasible, and that this approach is an alternative to one-step renovation approach to help to achieve the country´s energy and climate targets by 2030. Suggestions for future research conducted for office buildings in the different climate zones and other age groups in Portugal are proposed.

Description: The circulating cooling water system is widely used in various industrial production fields, and its operating cost largely depends on external factors, such as ambient temperature and working medium flow. Considering the relative elevation of the heat exchanger, this study establishes a total system operation cost analysis and optimization model based on the superstructure method. The model uses ambient dry bulb temperature, ambient wet bulb temperature, and working medium flow as random variables. Water supply temperature is adopted as the decision variable, and the minimum operating cost of the system is used as the objective function. An analysis of the effect of the three random variables on the operation cost shows that the effect of ambient dry bulb temperature on the operation cost is negligible, and the effect of ambient wet bulb temperature and working medium flow on the operation cost is significant. In addition, a control equation of water supply temperature is established to determine the “near optimal” operation, which is based on the correlation among ambient wet bulb temperature, working medium flow, and optimal water supply temperature. Then, the method is applied to a case system. The operating cost of the system is reduced by 22–31% at different times during the sampling day.

Description: An integrated energy system that consists of a centralized refrigeration unit can deliver the entire HVAC&R (heating, ventilation, air conditioning, and refrigeration) demand for a supermarket. CO2 (R744) is a natural refrigerant that is becoming increasingly popular for these centralized units due to significant energy and cost savings, while also being sustainable, safe, and non-toxic. This study focuses on the fully integrated CO2 refrigeration system configuration for a supermarket in Porto de Mos, Portugal, which was equipped and fully monitored through the EU-funded project MultiPACK. A dynamic system model was developed in Modelica and validated against measurement data from the site recorded for one week. The model is used to provide additional ejector performance data supporting the obtained measurement data and to evaluate the system configuration at equivalent boundary conditions. The simulation results show that the installation of a vapor ejector (high-pressure lift) is sufficient to improve the efficiency of the unit compared to an ejector-less (high-pressure valve) system. However, more notable enhancements are achieved by including additional flooded evaporation with liquid ejectors and smart regulation of the receiver pressure, adding up to a global efficiency increase of 15% if compared to the high-pressure valve system during the validation week.

Description: Instability and high permeability are two of the problems facing tunnelling excavations in soils with high fines content. Among the different techniques used to improve these soils, the injection of cement grouts stands out. In this work, a grouting treatment is designed to ensure the stability of the ground during the construction of two tunnels linking two municipalities in the north of Spain in Biscay, and to reduce the inflow of water from the aquifer located in the vicinity of these tunnels. First of all, the rock mass is analysed and the material to be injected is selected on the basis of the authors’ experience as well as setting time and compressive strength. Subsequently, with a test device designed by the DinRock research group of the University of Oviedo, two types of laboratory tests are carried out in order to analyse the effect of fines migration and washing on the water flows and the effect of re-injections of grouts with different densities on the permeability value. The results show that, in sandy materials, obtaining high degrees of waterproofing together with large stable zones can only be achieved by a combination of treatments and stages with different materials and densities. In addition, maximum values for both injection pressure and flow rate must be established depending on the type of grout and the permeability of the soil. Once the problem has been analysed, the injection treatment is designed and executed. The treatment consists of one pre-injection in four stages with 30 boreholes drilled in the top heading, 19–20 boreholes drilled in the bench, and one post-injection with boreholes drilled around the perimeter of the tunnel in those areas where the pre-injection does not achieve the desired degree of waterproofing.

Description: Renewable energy sources are an environmentally attractive idea, but they require a proper control scheme to guarantee optimal operation. In this work, we tune different controllers for an Interleaved Boost Converter (IBC) powered by a photovoltaic array using three metaheuristics: Genetic Algorithm, Particle Swarm Optimization, and Gray Wolf Optimization. We also develop several controllers for a second simulated scenario where the IBC is plugged into an existing microgrid (MG) as this can provide relevant data for real-life applications. In both cases, we consider hybrid controllers based on a Linear Quadratic Regulator (LQR). However, we hybridize it with an Integral action (I-LQR) in the first scenario to compare our data against previously published controllers. In the second one, we add a Proportional-Integral technique (PI-LQR) as we do not have previous data to compare against to provide a more robust controller than I-LQR. To validate our approach, we run extensive simulations with each metaheuristic and compare the resulting data. We focus on two fronts: the performance of the controllers and the computing cost of the solvers when facing practical issues. Our results demonstrate that the approach proposed for tuning controllers is a feasible strategy. The controllers tuned with the metaheuristics outperformed previously proposed strategies, yielding solutions thrice faster with virtually no overshoot and a voltage ripple seven times smaller. Not only this, but our controllers could correct some issues liaised to the IBC when it is plugged into an MG. We are confident that these insights can help migrate this approach to a more diverse set of MGs with different renewable sources and escalate it to real-life experiments.

Description: Making full use of wind energy can effectively alleviate the global energy shortage and environment contamination problems. Nevertheless, how to significantly improve the performance of the wind turbine airfoil and blade is a crucial issue. As the novel flow control method, the co-flow jet (CFJ) technology is one of the most potential methods to solve this problem. Thus, the effects of the CFJ technology on the performance enhancement of the S809 airfoil and Phase VI wind turbine blade are explored in this study. Furthermore, the effects of the injection location and jet momentum coefficient are studied, and an adaptive jet momentum coefficient strategy of the CFJ technology is proposed. Results demonstrate that the CFJ technology can significantly improve the maximum lift coefficient and maximum corrected lift-to-drag ratio of the S809 airfoil. Moreover, the power coefficient of the Phase VI wind turbine blade at the low tip speed ratio is greatly enhanced as well. In particular, the maximum lift coefficient and maximum corrected lift-to-drag ratio of the typical S809 CFJ airfoil with adaptive Cμ are improved by 119.7% and 36.2%, respectively. The maximum power coefficient of CFJ blade can be increased by 4.5%, and the power coefficient of CFJ blade can be boosted by 226.7% when the tip speed ratio is 1.52.

Description: Groundwater-filled boreholes are a common solution in Scandinavian installations of ground source heat pumps (GSHP) due to the particular hydro-geological conditions with existing bedrock, and groundwater levels close to the surface. Different studies have highlighted the advantage of water-filled boreholes compared with their grouted counterparts since the natural convection of water within the borehole tends to decrease the effective thermal resistance Rb*. In this study, several methods are proposed for the evaluation and modeling of the effective thermal resistance of groundwater-filled boreholes. They are based on distributed temperature sensing (DTS) measurements of six representative boreholes within the irregular 74-single-U 300 m-deep borehole field of Aalto New Campus Complex (ANCC). These methods are compared with the recently developed correlations for groundwater-filled boreholes, which are implemented within the python-based simulation toolbox Pygfunction. The results from the enhanced Pygfunction simulation with daily update of Rb* show very good agreement with the measured mean fluid temperature of the first 39 months of system operation (March 2018–May 2021). It is observed that in real operation the effective thermal resistance Rb* can vary significantly, and therefore it is concluded that the update of Rb* is crucial for a reliable long-term simulation of groundwater-filled boreholes.

Description: Nanoparticles are frequently used to enhance the thermal performance of numerous materials. This study has many practical applications for activities that have to minimize losses of energy due to several impacts. This study investigates the inclusion of ternary hybrid nanoparticles in a partially ionized hyperbolic tangent liquid passed over a stretched melting surface. The fluid motion equation is presented by considering the rotation effect. The thermal energy expression is derived by the contribution of Joule heat and viscous dissipation. Flow equations were modeled by using the concept of boundary layer theory, which occurs in the form of a coupled system of partial differential equations (PDEs). To reduce the complexity, the derived PDEs (partial differential equations) were transformed into a set of ordinary differential equations (ODEs) by engaging in similarity transformations. Afterwards, the converted ODEs were handled via a finite element procedure. The utilization and effectiveness of the methodology are demonstrated by listing the mesh-free survey and comparative analysis. Several important graphs were prepared to show the contribution of emerging parameters on fluid velocity and temperature profile. The findings show that the finite element method is a powerful tool for handling the complex coupled ordinary differential equation system, arising in fluid mechanics and other related dissipation applications in applied science. Furthermore, enhancements in the Forchheimer parameter and the Weissenberg number are necessary to control the fluid velocity.

Description: The reduction of unwanted heat losses across the buildings’ envelope is very relevant to increase energy efficiency and achieve the decarbonization goals for the building stock. Two major heat transfer mechanisms across the building envelope are conduction and radiation, being this last one very important whenever there is an air cavity. In this work, the use of aerogel thermal break (TB) strips and aluminium reflective (AR) foils are experimentally assessed to evaluate the thermal performance improvement of double-pane lightweight steel-framed (LSF) walls. The face-to-face thermal resistances were measured under laboratory-controlled conditions for sixteen LSF wall configurations. The reliability of the measurements was double-checked making use of a homogeneous XPS single panel, as well as several non-homogeneous double-pane LSF walls. The measurements allowed us to conclude that the effectiveness of the AR foil is greater than the aerogel TB strips. In fact, using an AR foil inside the air cavity of double-pane LSF walls is much more effective than using aerogel TB strips along the steel flange, since only one AR foil (inner or outer) provides a similar thermal resistance increase than two aerogel TB strips, i.e., around +0.47 m2∙K/W (+19%). However, the use of two AR foils, instead of a single one, is not effective, since the relative thermal resistance increase is only about +0.04 m2∙K/W (+2%).

Description: The energy efficiency gap is known as the difference between optimal level of energy efficiency and the actual level of achieved energy efficiency. Energy management has proven to further close the energy efficiency gap. Energy management may differ depending on whether it concerns a large, energy-intensive company or small and medium-sized enterprises (SMEs). SMEs are of high interest since they form a large share of the economy today. For SMEs, a lighter form of energy management, in the form of energy efficiency network participation, has proven to deliver sound energy efficiency impact, while for larger, energy-intensive firms, a certified energy management system may be more suitable. However, various barriers inhibit adoption of energy efficiency measures. While there is an array of research on barriers to and driving forces for energy efficiency in general, research on barriers to, and driving forces for, energy management is rare, one exception being a study of energy-intensive pulp and paper mills. This holds even more so for industrial SMEs. This paper aims to identify the barriers to, and drivers for, energy management in manufacturing SMEs. Results of this explorative study show that the top four barriers to energy management are lack of time/other priorities, non-energy-related working tasks are prioritized higher, slim organization, and lack of internal expert competences, i.e., mainly organizational barriers. The top four drivers for energy management are to reduce production waste, participation in energy efficiency networks, cost reduction from lower energy use, and commitment from top management. Furthermore, results show that energy management among the studied SMEs seems to not be as mature, even though the companies participated in an energy management capacity building program in the form of energy efficiency networks, which, in turn, shows a still largely untapped potential in the societal aim to reduce the energy efficiency and management gaps. The main contribution of this paper is a first novel attempt to explore barriers to, and drivers for, energy management among SMEs.

Description: Pore-scale studies of premixed gas combustion in a packed bed is conducted to study the flow and thermal non-equilibrium phenomenon in packed bed. The 3D random packed bed is generated using the EDEM software and solid surface radiation is computed using Discrete Ordinates (DO) model. The simulations are carried out using a commercial software package based on the finite volume method. It is shown that the local variation of species mass fraction, reaction rate et al. in pores near the flame front is significant, the radiation heat flux is transferred layer-by-layer. Cold flow simulation without reaction reveals that flow non-equilibrium is one of the essential characteristics of packing bed and increase in flow velocity leads to intensify non-equilibrium phenomenon. The distributions for content of axial velocity and gas temperature are wave-like shape in the burner and vary with time.

Description: The increasing use of lithium batteries and the necessary integration of battery management systems (BMS) has led international standards to demand functional safety in electromobility applications, with a special focus on electric vehicles. This work covers the complete design of an enhanced automotive BMS with functional safety from the concept phase to verification activities. Firstly, a detailed analysis of the intrinsic hazards of lithium-based batteries is performed. Secondly, a hazard and risk assessment of an automotive lithium-based battery is carried out to address the specific risks deriving from the automotive application and the safety goals to be fulfilled to keep it under control. Safety goals lead to the technical safety requirements for the next hardware design and prototyping of a BMS Slave. Finally, the failure rate of the BMS Slave is assessed to verify the compliance of the developed enhanced BMS Slave with the functional safety Automotive Safety Integrity Level (ASIL) C. This paper contributes the design methodology of a BMS complying with ISO 26262 functional safety standard requirements for automotive lithium-based batteries.

Description: As the global diesel generator market grows and generators gain wider use, various methods are being developed to increase their energy efficiency. One of these methods entails integrating a Li-ion battery with diesel generators (DGs). This method did not attract attention until recently because it was economically unappealing. A significant decrease in the price of Li-ion batteries in recent years has made hybrid diesel generator/Li-ion battery systems more viable. We present a model-based economic analysis of a hybrid DG/Li-ion battery system with the aim of increasing the energy efficiency of diesel power generators. Special blocks were developed for calculations and comparisons with a MATLAB Simulink model, including 457 kW DG operating modes with/without a Li-ion battery. We simulated the system in order to calculate the conditions required to achieve savings in fuel and the level of savings, in addition to the payback time of the Li-ion battery. Furthermore, we present the additional savings gained by postponing the investment in a new diesel generator thanks to the Li-ion battery. Based on our findings, the payback period of the Li-ion battery system varies between 2.5 and 4 years. According to our 12-year economic analysis, the cost savings resulting from postponing new investments can reach 40% of the profit gained from the savings during such a period.

Description: Many hydrocarbon-rich countries have recognized the global shift towards renewable energy sources, and Russia is not an exception. Drawing on two strands of literature—technological innovation systems and the advocacy coalition framework—we investigate the roles of actors and coalitions in shaping the Russian renewable energy policy and explore why particular renewable energy sources have progressed more than others, and what the main reasons are for their sudden development. The results show that the more successful renewable energy industries are those that were promoted by influential actors from traditional energy industries. Moreover, these actors also promoted the specific design of support schemes for renewable energy policy in Russia. We discuss the importance of policy process theories for understanding energy transition studies and provide specific policy recommendations for policy creation in the renewables industry.

Description: This paper proposes a full-hybrid driveline based on an electric continuously variable transmission (e-CVT), which is inspired by the car industry’s most successful solution. The paper describes the operating principle, the system architecture, and the control scheme of the proposed driveline. An analysis of four possible operating modes shows that the e-CVT driveline leads to a performance similar to that of conventional tractors, as well as unusual features such as power boost, full-electric mode, optimized auxiliary drive and electric power delivery capability. The compact layout proposed for the e-CVT also makes it possible to simplify the overall layout of the tractor, particularly during the installation of both the thermal engine and the cooling system.

Description: Shared mobility based on cars refers to a transportation mode in which travelers/drivers share vehicles to reduce the cost of the journey, emissions, air pollution and parking demands. Cost savings provide a strong incentive for the shared mobility mode. As cost savings are due to cooperation of the stakeholders in shared mobility systems, they should be properly divided and allocated to relevant participants. Improper allocation of cost savings will lead to dissatisfaction of drivers/passengers and hinder acceptance of the shared mobility mode. In practice, several schemes based on proportional methods to allocate cost savings have been proposed in shared mobility systems. However, there is neither a guideline for selecting these proportional methods nor a comparative study on effectiveness of these proportional methods. Although shared mobility has attracted much attention in the research community, there is still a lack of study of the influence of cost saving allocation schemes on performance of shared mobility systems. Motivated by deficiencies of existing studies, this paper aims to compare three proportional cost savings allocation schemes by analyzing their performance in terms of the numbers of acceptable rides under different schemes. We focus on ridesharing based on cars in this study. The main contribution is to develop theory based on our analysis to characterize the performance under different schemes to provide a guideline for selecting these proportional methods. The theory developed is verified by conducting experiments based on real geographical data.

Description: The research was a response to the search for alternative energy sources and the assessment of their profitability and legitimacy of use. The assessment used combined energy sources in the form of wind, solar, and natural gas energy. The research was carried out in various locations with varying degrees of sunlight and in various wind zones, which was motivated by the adopted strategy of increasing the importance of non-conventional energy sources and reducing greenhouse gas emissions. The evaluation was performed using the Homer Grid software. The studies showed the justification for the use of hybrid energy sources, combining renewable and non-renewable sources, at the current stage of development. In the conditions of the Lubuskie Voivodeship, the level of insolation was more important than the more favourable wind zone in such a model. Higher economic efficiency of the hybrid model was obtained in the southern location, with slightly less favourable conditions for wind installations. At the same time, the investments were economically profitable and allowed for their return in the perspective of at least eleven years, even at current prices.

Description: The abandonment of the built heritage, as a result of functional or technological obsolescence or as a consequence of cultural, social, and economic trends, is steadily increasing. This great number of buildings, worldwide spread, offers a huge opportunity to reduce the environmental impacts related to the construction industry. Nonetheless, the recovery and reuse interventions that require the implementation of residual technological performance, to accommodate new uses, are not always environmentally neutral. Therefore, a new design approach needs to be developed so as to improve the buildings’ technological performance and enhance resources and energy already incorporated in buildings. The circular economy principles in the building sector, performance-based building design together with downcycling and upcycling theories are applied to develop a methodology aiming to reduce the environmental impacts within the rehabilitation and refurbishment design process. Starting from the building analysis phase (historical, material, construction) residual performance is evaluated; then the design phase demonstrates that, according to downcycling and upcycling design strategies applied on building components and materials, it is possible improving the building to the required new uses while minimizing transformations and effectively reducing related environmental impacts. The reduction of environmental impacts depends on a careful assessment of the residual technological and structural performance that the building still provides, by involving limited performance implementations to balance rehabilitation needs and environmental protection goals.

Description: The transformation of our energy system toward zero net CO2 emissions correlates with a stronger use of low energy density renewable energy sources (RES), such as photovoltaic (PV) energy. As a source of flexibility, distributed PV systems, in particular, are oftentimes installed in combination with battery storage systems. These storage systems are dispatchable, i.e., controllable by the operating owners, who can thereby take over an active market role as energy prosumers. The particular battery operation modes are based on the individual prosumer decisions, which, in turn, are strongly affected by the regulatory framework in place. Regulatory frameworks differ from country to country, but almost all regulatory frameworks feature a network charge mechanism, which allocates network infrastructure and operating costs to the end customers. This raises the question of the extent to which different network charges lead to different prosumer decisions, i.e., battery operation modes, and thus different energy system configurations (system costs). In order to evaluate this question we apply (a) a fundamental linear optimization model of the energy wholesale market, which we stringently link to (b) an analysis of peak-coincident network capacity utilization as well as (c) an evaluation of the complete costs of energy for prosumers and consumers. This stringent cycle of analysis is applied to two prototypical network allocation schemes. We demonstrate that network allocation schemes that are orientated to peak-coincident network capacity utilization could both better incentivize a distribution network-oriented behaviour and better share financial burdens between prosuming and purely consuming households than would be the case for volumetric network charge designs. This paper further demonstrates that network-oriented battery operation does not, per se, result in optimal RES integration at the wholesale market level and CO2 emissions reduction. To identify effects from increasing sector integration, an analysis is both performed for a setting without and with consideration of widespread e-mobility. As a broader conclusion, our results demonstrate that future regulatory frameworks should have a stronger focus on prosumer integration by means, among other things, of an adequate network charge design reflecting the increasingly distributed nature of our future energy system.

Description: At present, vortex generators have been extensively used in radiators to improve the overall heat transfer performance. However, there is no research on the effect of vortex generators on the ends of motor coils. Meanwhile, the current research mainly concentrates on the attack angle, shape and size, and lacks a detailed study on the transverse and longitudinal distance and arrangement of vortex generators. In this paper, the improved dimensionless number R is used as the key index to evaluate the overall performance of enhanced heat transfer. Firstly, the influence of the attack angle on heat transfer enhancement is discussed through a single pair of rectangular vortex generators, and the results demonstrate that the vortex generator with a 45° attack angle is superior. On this basis, we compare the effects of different longitudinal distances (2 h, 4 h, and 6 h, h meaning the height of vortex generator) on enhanced heat transfer under four distribution modes: Flow-Up (FU), Flow-Down (FU), Flow-Up-Down (FUD), Flow-Down-UP (FDU). Thereafter, the performances of different transverse distances (0.25 h, 0.5 h, and 0.75 h) of the vortex generators are numerically simulated. When comparing the longitudinal distances, FD with a longitudinal distance of 4 h (FD-4 h) performs well when the Reynolds number is less than 4000, and FU with a longitudinal distance of 4 h (FU-4 h) performs better when the Reynolds number is greater than 4000. Similarly, in the comparison of transverse distances, FD-4 h still performs well when the Reynolds number is less than 4000, and FU with a longitudinal distance of 4 h and transverse distance of 0.5 h (FU-4 h–0.5 h) is more prominent when the Reynolds number is greater than 4000.

Description: This paper focuses on magnetorheological clutches (MR clutches) with a disc structure that can be designed as one-disc or multi-disc clutches (number of discs: N = 1, N 〉 2). The main goal of the paper is to compare their overall dimensions (lengths and radii), masses, volumes, and characteristic factors—torque per mass ratio and torque per volume ratio for MR clutches that develop the same given clutching torque Tc but differ in the number of discs (it is assumed that the number of discs of the primary member varies from one to four). This analysis develops charts and guidelines that will allow designers to choose the appropriate number of discs from the view point of various criteria, and with various limitations regarding geometry, geometric proportions, mass, volume, or restrictions on the amount of active materials used in the manufacturing process. The limitations on the active materials used are of particular importance in the case of mass production. Our methodology uses a comparative study, which can also be used when comparing design solutions of other electromechanical converters.

Description: The behavior of convective boundary conditions is studied to delineate their role in heat and mass relegation in the presence of radiation, chemical reaction, and hydro-magnetic forces in three-dimensional Powell–Eyring nanofluids. Implications concerning non-Fourier’s heat flux and non-Fick’s mass flux with respect to temperature nanoparticle concentration were examined to discuss the graphical attributes of the principal parameters. An efficient optimal homotopy analysis method is used to solve the transformed partial differential equations. Tables and graphs are physically interpreted for significant parameters.

Description: The transport sector powered by internal combustion engines (ICE) requires novel approaches to achieve near-zero CO2 emissions. In this direction, using CO2 capture and storage (CCS) systems onboard could be a good option. However, CO2 capture in mobile sources is currently challenging due to the operational and space requirements to install a CCS system onboard. This paper presents a systematic review of the CO2 capture in ICE driven transport to know the methods, techniques, and results of the different studies published so far. Subsequently, a case study of a CCS system working in an ICE is presented, where the energy and space needs are evaluated. The review reveals that the most suitable technique for CO2 capture is temperature swing adsorption (TSA). Moreover, the sorbents with better properties for this task are PPN-6-CH2-DETA and MOF-74-Mg. Finally, it shows that it is necessary to supply the energy demand of the CCS system and the option is to take advantage of the waste heat in the flue gas. The case study shows that it is possible to have a carbon capture rate above 68% without affecting engine performance. It was also found that the total volume required by the CCS system and fuel tank is 3.75 times smaller than buses operating with hydrogen fuel cells. According to the review and the case study, it is possible to run a CCS system in the maritime sector and road freight transport.

Description: This paper discusses the simulation framework developed for an in-campus pilot micro-grid at MCAST, Malta, to enhance its efficiency and reliability. One year of real-time metered data were used to arrive at the load curves, categorize the loads as essential and non-essential ones, and decide the micro-grid domain within MCAST. The potential scenarios were modeled to observe the behavior of the present status of the micro-grid, with an increased photovoltaic (PV) generation capacity, by using an optimum battery storage system with a diesel generator of suitable capacity and finally integrating electric vehicles (EVs) to discuss the potential of vehicle to grid (V2G) operation modes. The existing building management system (BMS) of MCAST was interfaced within the micro-grid to introduce the geographic information system (GIS) and Building Information Modeling (BIM) for developing an intelligent 3D model of the micro-grid. The results of the simulation framework for various potential case scenarios were obtained in a MATLAB/Simulink environment to assess the performance of the micro-grid. Previously formulated key performance indices (KPIs) that describe the financial aspects of micro-grid operation and ecological benefits of the investigated micro-grid were evaluated. A sensitivity analysis of these KPIs shows encouraging results with the potential of cost-competitiveness.

Description: Most of today’s water supply systems are based on plastic pipes. They are characterized by the retarded strain (RS) that takes place in the walls of these pipes. The occurrence of RS increases energy losses and leads to a different form of the basic equations describing the transient pipe flow. In this paper, the RS is calculated with the use of convolution integral of the local derivative of pressure and creep function that describes the viscoelastic behavior of the pipe-wall material. The main equations of a discrete bubble cavity model (DBCM) are based on a momentum equation of two-phase vaporous cavitating flow and continuity equations written initially separately for the gas and liquid phase. In transient flows, another important source of pressure damping is skin friction. Accordingly, the wall shear stress model also required necessary modifications. The final partial derivative set of equations was solved with the use of the method of characteristics (MOC), which transforms the original set of partial differential equations (PDE) into a set of ordinary differential equations (ODE). The developed numerical solutions along with the appropriate boundary conditions formed a basis to write a computer program that was used in comparison analysis. The comparisons between computed and measured results showed that the novel modified DBCM predicts pressure and velocity waveforms including cavitation and retarded strain effects with an acceptable accuracy. It was noticed that the influence of unsteady friction on damping of pressure waves was much smaller than the influence of retarded strain.

Description: A detailed analysis and validation of the DC-DC boost converter based on the three-state switching cell (3SSC) type-A are presented in this paper. The study of this topology is justified by the small amount of research that employs 3SSC-A and the advantages inherent to 3SSC-based converters, such as the division of current stresses between the semiconductors, the distribution of thermal losses, and the high-density power. Therefore, a complete static analysis of the converter is described, as well as the study of all voltage and current stresses in the semiconductors, the development of a loss model in all components, and a comparison with other step-up structures. Additionally, the small-signal model validation is accomplished by comparing the theoretical frequency response and the simulated AC sweep analysis. Finally, implementing a simple controller structure, the converter is experimentally validated through a 600 W prototype, where its overall efficiency is examined for various load conditions, reaching 96.8% at nominal load.

Description: The article presents selected problems related to an analysis of damage to wind turbine planetary gear. It is the most vital element installed in wind turbines, affecting the operational costs (prolonged downtime), and costs of repairs and servicing including delivery of required components. The authors have analyzed the wear/failure of planetary gear. The process initiating fatigue wear, different from similar devices in other industries, can be easily observed in wind turbine gear. This establishes a specific direction of research into the causes, and early detection of ‘gas spots’ on gear teeth as they seem to trigger fatigue wear.

Description: The self-preservation property of CH4 hydrates is beneficial for the transportation and storage of natural gas in the form of gas hydrates. Few studies have been conducted on the effects of chemicals (kinetic and thermodynamic promoters) on the self-preservation properties of CH4 hydrates, and most of the available literature is limited to pure water. The novelty of this work is that we have studied and compared the kinetics of CH4 hydrate formation in the presence of amino acids (hydrophobic and hydrophilic) when the temperature dropped below 0 °C. Furthermore, we also investigated the self-preservation of CH4 hydrate in the presence of amino acids. The main results are: (1) At T 〈 0 ℃, the formation kinetics and the total gas uptake improved in the presence of histidine (hydrophilic) at concentrations greater than 3000 ppm, but no significant change was observed for methionine (hydrophobic), confirming the improvement in the formation kinetics (for hydrophilic amino acids) due to increased subcooling; (2) At T = −2 °C, the presence of amino acids improved the metastability of CH4 hydrate. Increasing the concentration from 3000 to 20,000 ppm enhanced the metastability of CH4 hydrate; (3) Metastability was stronger in the presence of methionine compared to histidine; (4) This study provides experimental evidence for the use of amino acids as CH4 hydrate stabilizers for the storage and transportation of natural gas due to faster formation kinetics, no foam during dissociation, and stronger self-preservation.

Description: In this article, we aim to identify the determinants that profoundly impact renewable energy sources development in Poland. To this end, the authors have conducted qualitative and quantitative analyses of Poland’s renewable energy sector. In this paper, we demonstrate an original approach considering the different development levels of the given sector across provinces (voivodeships). It uses panel data from the Local Data Bank of the Statistics Poland on electricity production from renewable energy sources in individual voivodeships in Poland from 2005 through 2019. The study confronts the results of previous studies and sheds light on the situation in Poland—specifically, upon the changes that have happened over the ten years (2010–2019). The qualitative analysis shows a negative correlation between energy consumption and the share of renewable energy sources in total energy production. Evidence shows that favorable changes are underway in the energy production structure: RES share is growing and by degrees satisfying energy demand, and there is growing potential of energy entities in Poland. Furthermore, the analysis shows that R&D and total expenditures on environmental protection and water management investments do not significantly affect the development of RES. A dynamic panel data model has been used to analyze the group and time effects on the dependent variable. The findings confirm the existence of the persistency effect and indicate positive effects of total installed electric capacity (IEC) and household electricity consumption (HEC). Nonhousehold electricity consumption (NHEC) has a negative effect on the endogenous variable, i.e., the renewable energy sources share in the gross final energy consumption (RESS). The research results may be applicable as recommendations for energy efficiency policy development based on renewable energy sources depending on the RES development level in the regions of Poland.

Description: Renewable Energy Sources provide a viable solution to the problem of ever-increasing climate change. For this reason, several countries focus on electricity production using alternative sources. In this paper, the optimal positioning of the installation of wave energy converters is examined taking into account geospatial and technical limitations. Geospatial constraints depend on Land Use classes and seagrass of the coastal areas, while technical limitations include meteorological conditions and the morphology of the seabed. Suitable installation areas are selected after the exclusion of points that do not meet the aforementioned restrictions. We implemented a Deep Neural Network that operates based on heterogeneous data fusion, in this case satellite images and time series of meteorological data. This fact implies the definition of a two-branches architecture. The branch that is trained with image data provides for the localization of dynamic geospatial classes in the potential installation area, whereas the second one is responsible for the classification of the region according to the potential wave energy using wave height and period time series. In making the final decision on the suitability of the potential area, a large number of static land use data play an important role. These data are combined with neural network predictions for the optimizing positioning of the Wave Energy Converters. For the sake of completeness and flexibility, a Multi-Task Neural Network is developed. This model, in addition to predicting the suitability of an area depending on seagrass patterns and wave energy, also predicts land use classes through Multi-Label classification process. The proposed methodology is applied in the marine area of the city of Sines, Portugal. The first neural network achieves 98.7% Binary Classification accuracy, while the Multi-Task Neural Network 97.5% in the same metric and 93.5% in the F1 score of the Multi-Label classification output.