The earth provides a vast resource of groundwater from aquifers a few meters beneath the surface. Thus, buildings that use underground space must be equipped with dewatering wells to drain the permeated groundwater to the sewage pipelines to ensure the structural stability of the building. Although the inflowing groundwater temperatures and flow rates are stable enough for groundwater to be used as an energy source, 79% of the permeated groundwater is discarded through the sewers, generating significant sewerage expenses. This study introduced a novel heat exchanger module to utilize the permeated groundwater as an unused energy source using heat pumps, and the performance of the system was evaluated by TRNSYS simulations. First, the sizing of the unit heat exchanger module was proposed according to the mean inflow rate of the permeated groundwater. Second, the heat pump system was configured using multiple modules in the source-side loop. Finally, the performance of the proposed heat... [more]

This work presents a review of the main topologies of switched capacitors (SCs) used in DC-DC power conversion. Initially, the basic configurations are analyzed, that is, voltage doubler, series-parallel, Dickson, Fibonacci, and ladder. Some aspects regarding the choice of semiconductors and capacitors used in the circuits are addressed, as well their impact on the converter behavior. The operation of the structures in terms of full charge, partial charge, and no charge conditions is investigated. It is worth mentioning that these aspects directly influence the converter design and performance in terms of efficiency. Since voltage regulation is an inherent difficulty with SC converters, some control methods are presented for this purpose. Finally, some practical applications and the possibility of designing DC-DC converters for higher power levels are analyzed.

At present, electrical network stability is of the utmost importance because of the increase in electric demand and the integration of distributed generation deriving from renewable energy. In this paper, we proposed a static reactive power compensator model with common direct current voltage sources. Converter parameters were calculated and designed to fulfill specifications. In order to ascertain the device response for different operating modes as reactive power consumer and generator, we developed the model’s power and control circuits in Matlab Simulink. Simulations were performed for different conditions, and as a result, the current and voltage waveforms and the circular power chart were obtained. This paper has theoretically proven it is possible to achieve the consumption or generation of purely active or reactive power by implementing a static reactive power compensator with common DC voltage sources.

Energy access and waste management are two of the most pressing developmental and environmental issues on a global level to help mitigate the accelerating impacts of climate change. They are particularly relevant in Sub−Saharan Africa where electrification rates are significantly below global averages and rural areas are lacking a formal waste management sector. This paper explores the potential of integrating solar energy into a biomass pyrolysis unit as a potentially synergetic solution to both issues. The full design of a slow pyrolysis batch reactor targeted at biochar production, following a strict cost minimization approach, is presented in light of the relevant considerations. SPEAR is powered using a Cassegrain optics parabolic dish system, integrated into the reactor via a manual tracking system and optically optimized with a Monte-Carlo ray tracing methodology. The design approach employed has led to the development an overall cost efficient system, with the potential to achi... [more]

In the carbon-neutral scenarios fixed by most developed countries, wind and solar resources play a significant role due to their substantial potential. Their instability can be mitigated through smarter designs of energy systems, including sector coupling and cross-border interconnections, which require detailed information on the spatial and temporal evolution of these intermittent resources. The present study aims at estimating the spatial−temporal energy potential of wind in Japan based on meteorological weather data. These data allow to analyze the potential of resources sharing to reduce power generation’s lack and excess, even in such an isolated country due to its variety of climate conditions and local energy demand. The correlation skewness is introduced as a measure of the sites’ uniqueness to identify important sites for the spatial distribution of capacity toward the efficient stabilization of supply at a national scale in a model-free fashion.

This study examined the current state of water demand and associated energy input for water supply against a projected increase in water demand in sub-Saharan Africa. Three plausible scenarios, namely, Current State Extends (CSE), Current State Improves (CSI) and Current State Deteriorates (CSD) were developed and applied using nine quantifiable indicators for water demand projections and the associated impact on energy input for water supply for five Water Service Providers (WSPs) in Kenya to demonstrate the feasibility of the approach based on real data in sub-Saharan Africa. Currently, the daily per capita water-use in the service area of four of the five WSPs was below minimum daily requirement of 50 L/p/d. Further, non-revenue water losses were up to three times higher than the regulated benchmark (range 26−63%). Calculations showed a leakage reduction potential of up to 70% and energy savings of up to 12 MWh/a. The projected water demand is expected to increase by at least twelve... [more]

With the constant increase in energy demand, using renewable energy has become a priority. Geothermal energy is a widely available, constant source of renewable energy that has shown great potential as an alternative source of energy in achieving global energy sustainability and environment protection. When exploiting geothermal energy, whether is for heating or cooling buildings or generating electricity, a ground heat exchanger (GHE) is the most important component, whose performance can be easily improved by following the latest design aspects. This article focuses on the application of different types of GHEs with attention directed to deep vertical borehole heat exchangers and direct expansion systems, which were not dealt with in detail in recent reviews. The article gives a review of the most recent advances in design aspects of GHE, namely pipe arrangement, materials, and working fluids. The influence of the main design parameters on the performance of horizontal, vertical, and... [more]

In wastewater, nutrient concentrations and salinity vary substantially, however, the optimal N:P ratio for the treatment using microalgae is not well described. In this study, the effects of higher and lower nitrate and phosphate contents and N:P ratios on growth, nutrient removal ability and halotolerance of the common green alga Coelastrum morus were investigated in model solutions. The results suggest that high nitrate content (above 100 mg L−1) with a similarly high phosphate concentration (resulting low N:P ratio) is not favorable for growth. The studied isolate can be considered as a halotolerant species, showing remarkable growth up to 1000 mg L−1 NaCl and it seems that despite the negative effects on growth, higher nutrient content contributes to higher halotolerance. A significant amount of nitrate removal was observed in media with different nutrient contents and N:P ratios with different salt concentrations. High N:P ratios favor phosphate removal, which is more inhibited by... [more]

Due to high efficiency and low cost, hydrate-based desalination is investigated as a pretreatment method for seawater desalination. To improve the formation rate of hydrates, the effect of sodium dodecyl sulfate (SDS) on CO2 hydrate formation from a 3.5 wt.% NaCl solution was measured at 275 K and 3 MPa. X-ray diffraction (XRD) and cryo-scanning electron microscopy (cryo-SEM) were used to measure the crystal structure and micromorphology of the formed hydrates. The results showed that the induction time of CO2 hydrate formation reduced from 32 to 2 min when SDS concentration increased from 0.01 to 0.05%, the hydrate conversion rate increased from 12.06 to 23.32%, and the remaining NaCl concentration increased from 3.997 to 4.515 wt.%. However, as the SDS concentration surpassed 0.05 wt.%, the induction time increased accompanied by a decrease in the hydrate conversion rate. XRD showed that the CO2 hydrate was a structure I hydrate, and SDS had no influence on the hydrate structure. How... [more]

This study investigated the applied methods for the collection and treatment of an organic fraction of municipal solid waste with anaerobic digestion (AD), including the effects of selective waste collection system introduction. As the research area, data from a waste treatment plant, which collects waste from about 260,000 inhabitants, was used as the selected waste management plan. Biowaste stream management was emphasized. Thus, research on energy recovery and the characteristics of digestate (nutrient and heavy metals content) obtained from biowaste AD was performed. The results of the studies and their quantitative data were interpreted. A significant discrepancy between the assumptions and the actual situation was revealed (up to 20% year-on-year regarding biowaste). An underestimation of the amount of waste when planning was noted. AD ensures energy recovery from biowaste, which can cover facility electricity needs and material recovery. The digestate might find agricultural usa... [more]

Accuracy of hydrogeological and geotechnical investigation in place of shaft sinking is a key factor for selection of sinking method and design of the shaft lining. The following work presents the influence of the rising level of accuracy of geological data gathered in the area of shaft sinking in the Silesian Coal Basin and technical projects of shaft lining and technology of its sinking, which have been changing over the years. The initial project of the shaft was repeatedly modified. Each modification eventuated in rising requirements for the shaft lining, such as increasing its thickness or changing concrete class. It has become necessary to use additional methods of reinforcing rock mass around the shaft.

The reliability of pumping units at nuclear power plants (NPPs) is critical in terms of their energy efficiency and safety. Remarkably, WWER-1000 reactors at Ukrainian NPPs are equipped with outdated pumping units that have already served their full-service life. This fact leads to an urgent need to develop a new, more efficient pump. In the article, a promising pump, ACNA 600-35, was developed. It was designed to increase the energy efficiency of pumps TX 800/70/8-K-2E, applied at the holding pool and the industrial circuit of the nuclear reactor. Since these pumps should be imported from the monopoly suppliers, this affects both the energy efficiency of pumping equipment and the energy independence of Eastern Europe. The proposed pump ACNA 600-35 is characterized by an increased efficiency of up to 0.12−0.13 compared with the TX 800/70/8-K-2E pump. In general, the life cycle cost of the proposed pump is 15−20% lower than for the analog TX 800/70/8-K-2E. The design of the developed pu... [more]

Silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) have many advantages compared to silicon (Si) MOSFETs: low drain-source resistance, high thermal conductivity, low leakage current, and high switching frequency. As a result, Si MOSFETs are replaced with SiC MOSFETs in many industrial applications. However, there are still not as many SiC modules to customize for each application. To meet the high-power requirement for custom applications, paralleling discrete SiC MOSFETs is an essential solution. However, it comes with many technical challenges; inequality in current sharing, different switching losses, different transient characteristics, and so forth. In this paper, the detailed MATLAB®/Simulink® Simpscape model of the SiC MOSFET from the datasheet and the simulation of the half-bridge circuit are investigated. Furthermore, this paper proposes the implementation of the four-paralleled SiC MOSFET half-bridge circuit with an improved symmetric gate driv... [more]

In this paper, a study on creep-fatigue evaluation on the cladded nuclear component subjecting to low pressure and high temperature services is carried out. To do this, the codes and standards presented by ASME-III Division 5 are reviewed, and a detailed evaluation procedure is presented step by step for practical applications. As an example of practical design application, a molten salt reactor vessel with a cladding thickness of 10% of the base material thickness is designed and four representative operation cycle types are established. The stress cycle types based on finite element stress analysis are determined from the operation cycle types having coolant temperature and pressure time history loads, and results of the creep-fatigue evaluation are described step by step according to the evaluation procedure. From the result of the creep-fatigue evaluation, it is found that the creep-fatigue evaluation for reactors such as molten salt reactor, sodium-cooled reactor, and so on, which... [more]

Currently, biofuels represent a solution for the European Union in the transportation sector in order to reduce the greenhouse gas (GHG) emissions and the dependency of fossil fuels. Biodiesel from vegetable oils is a solution for countries with low GDP per capita to strengthen the internal agriculture, provide jobs, and reduce the use of fossil fuels. In this study, we model and simulate a temperature regulator designed for the biodiesel transesterification process in a discontinuous batch reactor, using methanol and a homogenous basic catalyst. The simulation was based on the kinetical model of the transesterification reaction and the mathematical model of the reactor. We considered molar ratios of alcohol/oil of 6:1 and 9:1, respectively, to shift the reaction equilibrium towards the production of fatty acid methyl esters. In the design of the simulation, the methanol boiling point was considered a restriction, therefore, temperatures below 65 °C were imposed. The results demonstrat... [more]

The anaerobic digestion of New Zealand low-input dairy farms has previously been evaluated for energy production, but farming systems have recently become more intensive with increased feed supplementation and feed replacement; therefore, we are studying how these changes affect the overall energy production for water heating. A combination of literature review, surveys, chemical analyses, biomethane potential analysis, and modeling were used for this study. On a case study farm with a solid separator, it was found that 558 MJ/day and 176−861 MJ/day could be produced with the solid and liquid portions of effluent, respectively. There is enough biogas to satisfy the dairy farm’s water heating requirements with a tankless water heater.

In Europe, the recast of Directive 2018/2001 defined Renewable Energy Communities as innovative configurations for renewable energy sharing between different end user types. In this regard, this work aims to assess the benefits following the constitution of a Renewable Energy Community in the industrial area of Benevento (South of Italy), involving a mixed-use building and an industrial wastewater treatment plant. The alternative single end users’ configuration has been also examined, and both solutions have been compared with the current state where the users’ electric energy requests are fully met by the power grid. The users have been equipped with a 466 kWp photovoltaic plant, modelled in HOMER Pro®, providing in input experimental meteorological data (global solar radiation and air temperature) collected by one of the weather control units in Benevento. Real data about users’ electric energy demand have been gathered from their electricity bills, and when unavailable their electri... [more]

Heating ventilation and air conditioning (HVAC) systems represent one of the main noise sources inside classrooms. This explain why HVAC systems require careful design, competent installation and balancing, and regular maintenance. Many factors influence the classroom acoustical design, such as air handlers or fans, the velocity of air inside the classroom, as well as the size and acoustical treatment of ducts, returns, and diffusers. Acoustic parameters, including background-noise levels, reverberation time, and intelligibility, were analyzed in 17 classrooms at the Università Politecnica in the Marche region. The study of intelligibility was performed by measuring the objective parameters in situ and using prediction methods to determine the intelligibility score. The relationship between speech intelligibility measurements and speech intelligibility calculation has been studied. The relationship between the STI values with the background-noise levels and the reverberation time was a... [more]

The anaerobic digestion of the organic fraction of municipal solid waste and the biogas production obtained from its stabilization are becoming an increasingly attractive solution, due to their beneficial effects on the environment. In this way, the waste is considered a resource allowing a reduction in the quantity of it going to landfills and the derived greenhouse gas emissions. Simultaneously, the upgrading process of biogas into biomethane can address the issues dealing with decarbonization of the transport. In this work, the production of biogas obtained from the organic fraction of municipal solid wastes in a plug flow reactor is analyzed. In order to steer the chemical reactions, the temperature of the process must be kept under control. A new simulation model, implemented in the MatLab® environment, is developed to predict the temperature field within the reactor, in order to assess how the temperature affects the growth and the decay of the main microbial species. A thermal m... [more]

The well pattern and boundary shape of reservoirs determine the distribution of the remaining oil distribution to a large extent, especially for small-scale reservoir blocks. However, it is difficult to replicate experiences from other reservoirs directly to predict the remaining oil distribution because of the variety of irregular boundary shapes and corresponding well patterns. Meanwhile, the regular well pattern can hardly suit irregular boundary shapes. In this paper, we propose a well placement method for undeveloped irregular reservoirs and a multi-step prediction framework to predict both oil saturation and pressure fields for any reservoir shape and well pattern. To boost the physical information of input characteristics, a feature amplification approach based on physical formulae is initially presented. Then, 3D convolution technology is employed for the first time in 3D reservoir prediction to increase the spatial information in the vertical direction of the reservoir in the... [more]

In the framework of the EUROfusion Horizon Europe Programme, ENEA and its linked third parties are in charge of the conceptual design of the steam generators belonging to EU DEMO WCLL Breeding Blanket Primary Heat Transfer Systems (BB PHTSs). In particular, in 2021, design activities and supporting numerical simulations were carried out in order to achieve a feasible and robust preliminary concept design of the Once Through Steam Generators (OTSGs), selected as reference technology for the DEMO Balance of Plant at the end of the Horizon 2020 Programme. The design of these components is very challenging. In fact, the steam generators have to deliver the thermal power removed from the two principal blanket subsystems, i.e., the First Wall (FW) and the Breeding Zone (BZ), to the Power Conversion System (PCS) for its conversion into electricity, operating under plasma pulsed regime and staying in dwell period at a very low power level (decay power). Consequently, the OTSG stability and con... [more]

To effectively provide the handicapped with mobility aids, studies on the shared autonomy of robotic systems have been widely cultivated. This study proposes an adaptive shared control strategy to realize reliable and safe driving assistance on an intelligent electric wheelchair with protection against human errors. The theoretical framework of the system is analyzed by the linearized reference wheelchair model and stable characteristics of obstacle avoidance behavior can be subsequently derived according to the Lyapunov analysis and Liénard-Chipart criterion. Based on the convex analysis, the relationships between human input and robot control are investigated to determine shared control weights. As such, safety and reliability can be guaranteed. To verify the performances of the proposed approach, human errors including skill-based errors, decision errors, and violations are considered in the experiments. The experimental results based on a comprehensive study show that the proposed... [more]

One of the most important environmental and safety concerns in nuclear fusion plants is the confinement of radioactive substances into the reactor buildings during both normal operations and accidental conditions. For this reason, hydrogen build-up and subsequent ignition must be avoided, since the pressure and energy generated may threaten the integrity of the confinement structures, causing the dispersion of radioactive and toxic products toward the public environment. Potentially dangerous sources of hydrogen are related to the exothermal oxidation reactions between steam and plasma-facing components or hot dust, which could occur during accidents such as the in-vessel loss of coolant or a wet bypass. The research of technical solutions to avoid the risk of a hydrogen explosion in large fusion power plants is still in progress. In the safety and environment work package of the EUROfusion consortium, activities are ongoing to study solutions to mitigate the hydrogen explosion risk. T... [more]

A numerical study estimated the mixed convection around a sinusoidal cylinder inside a rectangular cavity. The key parameters for sinusoidal circular cylinders were the wavelength and Reynolds number (Re = 100, 500, and 1000) with a fixed Prandtl number of 0.7. The flow regimes were greatly affected by these parameters. The unsteadiness of the flow pattern was also affected by λ and Re. The results were analyzed by the thermal structure, vortical structure, and Nusselt number. Furthermore, the orthogonal enstrophy was used to quantify the three-dimensional flow characteristics, and the frequency of the surface-averaged Nusselt number for the heated bottom wall was used to analyze the unsteady characteristics. The heat transfer performance was enhanced by 6.6% at Re = 100 for λ = 3 compared to the circular cylinder. In addition, the heat transfer performance was enhanced by 6.6% and 2.6% at Re = 500 for λ = 2 and Re = 1000 for λ = 1, respectively, compared to the circular cylinder.

Iron additives are effective in the anaerobic sewage sludge digestion process, but the composition and dosage of these additives are not precisely defined. This research investigates the effects of three iron oxides-based additives on the destruction of volatile solids, the production and quality of biogas, as well as the quality of the supernatant. Additive No 1 contained >41.5% of FeO and >41.5% of Fe2O3, additive No 2 contained ≥86% of Fe3O4, and additive No 3 contained ≥98% of Fe3O4. The best results were obtained by applying an iron oxides-based additive with a higher content of divalent iron oxide. The increase in efficiency of the VSs destruction was not significant and on average 2.2%. The increase in biogas production was on average 20% while the average increase in the content of methane in the biogas was 6.3%. Applying the additive, the reduction in the concentration of ammonium nitrogen in the supernatant was up to 28%, as well as a reduction in the concentration of phospha... [more]