Waste-based feedstocks and bioenergy intermediate carriers are key issues of the whole bioenergy value chain. Towards a circular economy, changing upcycling infra-structure systems takes time, while energy-from-waste (EfW) technologies like waste pyrolysis and gasification could play an integral part. Thus, the aim of this study is to propose a circular economy pathway for the waste to energy (WtE) thermochemical technologies, through which solid biomass waste can be slowly pyrolyzed to biochar (main product), in various regionally distributed small plants, and the pyro-oils, by-products of those plants could be used as an intermediate energy carrier to fuel a central gasification plant for syngas production. Through the performed review, the main parameters of the whole process chain, from waste to syngas, were discussed. The study develops a conceptual model that can be implemented for overcoming barriers to the broad deployment of WtE solutions. The proposed model of WtE facilities... [more]

Increased pressure is being applied to industrial wastewater treatment facilities to adhere to more stringent regulations for the discharge of treated wastewater and to improve energy efficiency of the process. Nitrogen and phosphorous removal can be challenging to achieve efficiently, and in the case of phosphorous removal, can often necessitate the use of chemicals. There is a major drive globally to improve wastewater treatment infrastructure, whilst simultaneously reducing the carbon footprint of the process. The intermittently aerated sequencing batch reactor offers a modification of the well-known sequencing batch reactor process that can enable lower energy requirements than conventional sequencing batch reactor processes and can facilitate enhanced nutrient removal capacities. However, to date much of the previous literature has focused on relatively short laboratory-scale trials (often with synthetic wastewater) which may not be representative of larger scale system performanc... [more]

This paper investigates the influence of power semiconductor parasitic components on the ground leakage current in the three-phase Current Source Inverter topology, in the literature called H7 or CSI7. This topology allows reducing converter conduction losses with respect to the classic CSI, but at the same time makes the topology more susceptible to the parasitic capacitances of the semiconductors devices. In the present work, a grid-connected converter for photovoltaic power systems is considered as a case study, to investigate the equivalent circuit for ground leakage current. The same analysis can be extended to applications regarding electric drives, since the HF model of electric machines is characterized by stray capacitance between windings and the stator slots/motor frame. Simulation results proved the correctness of the proposed simplified common-mode circuit and highlighted the need of an additional common-mode inductor filter in case of resonance frequencies of the common-m... [more]

Increasing peak power demand implies the increasing significance of energy storage. Technologies that efficiently store heat and cold are also important for increasing the share of renewables and improving the efficiency of heating, ventilation, and air conditioning (HVAC) systems. The present experimental study investigated the dynamic behavior of a room with suspended thermally activated ceiling panels filled with a material containing 60% paraffin. The purpose of the study was to determine the specific cooling power and the total energy supplied to the phase change material (PCM) during regeneration. Convective heat flux density, radiant heat flux density, and the heat transfer coefficient (convective, radiant) at the ceiling surface were calculated. Analysis shows that shifting system activation to use lower temperatures during the night maintains thermal comfort.

All-solid-state Li-S batteries (use of solid electrolyte LiBH4) were prepared using cathodes of a homogeneous mixture of graphene oxide (GO) and reduced graphene oxide (rGO) with sulfur (S) and solid electrolyte lithium borohydride (LiBH4), and their electrochemical performance was reported. The use of LiBH4 and its compatibility with Li metal permits the utilization of Li anode that improves the vitality of composite electrodes. The GO-S and rGO-S nanocomposites with different proportions have been synthesized. Their structural and morphological characterizations were performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the results are presented. The electrochemical performance was tested by galvanostatic charge-discharge measurements at a 0.1 C-rate. The results presented here demonstrate the successful implementation of GO-S composites in an all-solid-state battery.

An accurate prediction of the interphase behaviors of the vertical gas-liquid subcooled boiling flow is meaningful for the first loop of a nuclear power plant (NPP). Therefore, the interphase behaviors including the bubble size distribution in the first loop of the NPP are analyzed, evaluated, and validated using various wall boiling models coupled with the population balance model (PBM) kernels in this paper. Firstly, nondimensional numbers of the first loop of the NPP and DEBORA (Development of Borehole Seals for High-Level Radioactive Waste) experiment test cases are analyzed with approximation. Secondly, five active nucleation site density models Nn coupled with the PBM kernel combination, four kernel combinations (C1~C4) with the Nn models are calculated and analyzed. Lastly, various behaviors including the bubble size distribution Sauter mean diameter (SMD) dp, void fraction α, gas superficial velocity jg, and liquid superficial velocity jl are compared and validated with the exp... [more]

The scavenging process of two-stroke engines plays a fundamental role in cylinder flow patterns and in the overall engine performance. In this work, 3D CFD simulations of the scavenging in a uniflow, two-stroke, compression ignition engine for general aviation, named GF56, have been performed by using a 3D finite-volume FANS equations solver with k-ϵ closure. The GF56 engine consists of six cylinders, separated into two quasi-symmetric banks. Both the right and the left banks, together with the corresponding cylinders, are carefully analyzed. Charging and trapping efficiencies are computed as a function of the delivery ratio for different mass flow rates entering into the plenum, and the influence of the exhaust pressure and of the cylinder’s location in the bank are analyzed. The results show that the fresh air trapped during the scavenging process is quite similar for each cylinder of the right bank and it is about 92% of the in-cylinder mass. The cylinder’s location in the bank by i... [more]

Ensuring service continuity has become a fundamental issue for companies involved in electricity distribution; in particular, isolating the smallest possible portion of the network as a result of faults has long been a primary objective. To this aim, solutions based on logic selectivity have been defined and implemented for an efficient search for the network branch affected by the fault and its subsequent isolation. The authors have recently presented a proposal for the implementation of logic selectivity that exploits the LoRa transmission protocol, an ideal solution in the case of areas not reachable by the currently exploited communication technologies. The present paper, instead, deals with the optimization of some LoRa parameters, which made it possible to exploit network configurations in terms of coverage range, sensitivity and signal-to-noise ratio. The performance of the new configuration has been assessed through a number of tests conducted in the laboratory and on-field, hi... [more]

Optimal operation of hydropower plants (HP) is a crucial task for the control of several variables involved in the power generation process, including hydraulic level and power generation rate. In general, there are three main problems that an optimal operation approach must address: (i) maintaining a hydraulic head level which satisfies the energy demand at a given time, (ii) regulating operation to match with certain established conditions, even in the presence of system’s parametric variations, and (iii) managing external disturbances at the system’s input. To address these problems, in this paper we propose an approach for optimal hydraulic level tracking based on an Inverse Optimal Controller (IOC), devised with the purpose of regulating power generation rates on a specific HP infrastructure. The Closed−Loop System (CLS) has been simulated using data collected from the HP through a whole year of operation as a tracking reference. Furthermore, to combat parametric variations, an ac... [more]

Design strategies for achieving reliable, affordable, and clean electricity are crucial for energy sustainability. Attaining it requires managing the three core factors (TCF) of the energy trilemma (ET) to increase reliability (energy equity), minimize the levelized cost of electricity (LCOE) (energy equity), and avoid potential CO2 emission (environmental sustainability) simultaneously. This paper aims to present a design strategy for the hybrid energy system microgrid (HESM) model, consisting of a distributed rooftop solar PV (DRSP), battery, and diesel-generator to meet the increasing demand while balancing the TCF of the ET. The design strategy was applied in a cluster of 11 households in Gilutongan Island, Cebu, Philippines, where there is no open land space for a solar PV microgrid system. This study used PVSyst and HOMER Pro software to perform the techno-enviro-economic (TEE) analysis to select all feasible system configurations (FSCs). To identify the optimal FSC, a scoring me... [more]

This paper focuses on two key technical concepts, which may have a tremendous impact on future generations of power electronic converters: the Power Electronic Building Block (PEBB) concept, and the 5G/6G wireless data transfer. It is expected that these two trends may induce development of new cognitive of power electronic converters: Power Electronics 4.0. To investigate this concept, a Proof of Concept (PoC) of PEBB-based power converter integrated with a 5G network, was designed and tested. Study confirmed that power converter assembled from PEBB modules can compete with state-of-the-art devices. Moreover, test results indicates that several challenges related to PEBB and integration of power electronic equipment with 5G network has to be resolved, to enable growth of augmented power electronic converters, especially if wireless data transfer is meant for communication between PEBB modules.

As one of the tasks of the Comprehensive Research Facility for Fusion Technology (CRAFT), a High Heat Flux (HHF) testing device will be built to test the blanket and divertor of Chinese Fusion Engineering Testing Reactor (CFETR). The water loop is a key system of the HHF testing device. The main objective of the water loop is to provide deionized water at specific temperature, pressure, and flow rate for different testing experiments of the water-cooled blanket and water-cooled divertor components. The design of the water loop has been through three major steps. Firstly, the water cooled blanket and divertor were designed and analyzed, in detail, for CFETR. Secondly, thermal hydraulic features of the prototypes were abstracted from the analyses results. Then, the experiment plan was made so that the preliminary design of the water loop was carried out. The third step was the engineering design, which was conducted through cooperation with an industrial enterprise with certifications. A... [more]

The process of cutting rocks with a boom-type roadheader results in extreme dynamic loads and vibrations. Mining, especially in the case of hard rocks, is associated with large energy consumption, which, when combined with low process efficiency, can lead to low drilling performance. These phenomena are undesirable because excessive dynamic load leads to low machine durability, as well as deterioration of work conditions and safety. Low mining efficiency affects the economics of mining works conducted using roadheaders. However, these adverse effects can be minimized by optimizing the cutting process, thanks to the automatic control of the roadheader. The present article discusses the concept of automatic control of a boom-type roadheader’s cutting heads movement. Based on previously conducted computer investigations, it was assumed that reducing the energy consumption of the cutting process and improving the dynamic state of the roadheader (objective functions) are possible only by co... [more]

The solid−electrolyte interphase (SEI), the passivation layer formed on anode particles during the initial cycles, affects the performance of lithium-ion batteries (LIBs) in terms of capacity, power output, and cycle life. SEI features are dependent on the electrolyte content, as this complex layer originates from electrolyte decomposition products. Despite a variety of studies devoted to understanding SEI formation, the complexity of this process has caused uncertainty in its chemistry. In order to clarify the role of the substituted functional groups of the SEI-forming compounds in their efficiency and the features of the resulting interphase, the performance of six different carbonyl-based molecules has been investigated by computational modeling and electrochemical experiments with a comparative approach. The performance of the electrolytes and stability of the generated SEI are evaluated in both half-cell and full-cell configurations. Added to the room-temperature studies, the cyc... [more]

Off-Earth drilling may be assumed as the second phase of space exploration to discover the unrevealed subsurface on the planetary bodies. It accelerates future space objectives such as in-situ propellant production, mineral exploitation, and space tourism. Owing to the rampant progress in modern technology, the new drill tools mounted on the sophisticated robots are capable to drill the planetary regolith dispersed on the celestial objects; however, formidable obstacles such as microgravity, vacuum condition, and temperature fluctuation as well as the weight limitation, lack of real-time drilling analysis, and remote robot-operator communication impose pressing restrictions on the quick development of space drilling tools. In this study, research on the past and present aspects of off-Earth drilling has been implemented to illuminate the horizon of this technology in the near-term future. The context encompasses a detailed description of the limitations, applications and mechanisms of... [more]

Hybrid electric aircraft offer the potential to decrease emissions from air travel. A new hybrid concept is proposed for a fuel cell-battery hybrid aircraft. In contrast to existing hybrids, the proposed concept puts a battery directly on the AC phases of the motor, which together with a suitable switching circuit superimposes the DC voltage from the battery on the AC voltage of the motor phase providing a voltage boost depending on the battery voltage, which can be used during a high-power demand flight phase. The system is also capable of recharging the battery during flight. The necessary switching architecture was developed and modeled in MATLAB/Simulink to verify the concept and an experimental setup was built for demonstrating the functionality. Simulation and experimental results showed a very good agreement which is very promising for the proposed new hybrid topology.

In recent years, ocean current turbines have proven to be a reliable device for renewable energy generation. A crucial element of these turbines are the foundations, since they limit the displacement of the turbine, which is key in achieving efficiency in energy conversion, and can account for up to 26% of the total cost of the project. Most design procedures for foundations focus on sandy and clayey soils, but rock soils often predominate in tropical locations where marine currents are suitable for the installation of this type of turbine. This paper presents a design procedure for steel pile anchors (PAs) and concrete dead weight anchors (DWAs) on weak rock soils, using the assumptions of current technical documents and design codes commonly used in the industry for marine structures. Using specific designs for PA and DWA anchors, the procedure was theoretically assessed for a site off Cozumel Island, Mexico. The results show that the dimensions needed for DWAs are substantially larg... [more]

The oxygen transport membrane reactor technology enables the stable combustion of syngas and reduction in NOx emission. Applying the syngas combustion membrane reactor to fire tube boiler can integrate oxygen separation, syngas combustion, and steam generation in a single apparatus. In this study, a CFD model for oxygen permeation and syngas combustion in a two-pass LSCoF-6428 tubular membrane reactor for fire tube boiler application was developed to study the effects of the inlet temperature, the sweep gas flow rate, and the syngas composition on the reactor performance. It is shown that the inlet temperature has a strong effect on the reactor performance. Increasing the inlet temperature can efficiently and significantly improve the oxygen permeability and the heat production capacity. A 34-times increase of oxygen permeation rate and a doubled thermal power output can be obtained when increasing the inlet temperature from 1073 to 1273 K. The membrane temperature, the oxygen permeati... [more]

Recently, biodigesters have attracted much attention as an efficient alternative for energy generation and organic waste treatment. The final performance of a biodigester depends heavily on the quality of its building process and the selection of its raw material: the geomembrane. The geomembrane is the coat that covers the biodigester used to control the migration of fluids. Therefore, the selection of the proper geomembrane, in terms of thickness, resistance, flexibility, etc., is fundamental. Unfortunately, there are no studies for the selection of geomembranes, and usually, it is an empirical process performed by workers based on their own experience. Such empirical selection might be inaccurate, limited, inconvenient, and even dangerous. In order to assist workers during the building process of a biodigester, this study proposes the use of an Artificial Neural Network (ANN) to classify a geomembrane as appropriate or not appropriate for the manufacture of a biodigester. The ANN is... [more]

Under the Belt and Road concepts of mutual benefit and win−win cooperation, China is strengthening its energy cooperation with other countries. We used several econometric models and social network analysis models to study the impacts of China’s outward foreign direct investment (OFDI) on the host and home countries. We first examined China’s OFDI location preference and analysed the effects of OFDI on energy consumption in host countries. Meanwhile, we observed the impact of the reverse spillover effect of OFDI on China’s energy efficiency. The results indicate that (1) the impact of China’s OFDI on energy consumption in host countries has been lower than that on neighbouring countries, and increased significantly after 2014. (2) The space network of energy consumption in Belt and Road countries has a strict hierarchical structure. However, it was disbanded by the Belt and Road policy in 2014. The network centres are situated primarily in Middle Eastern and European countries, and the... [more]

The present work deals with the study of the electrical behavior of cross-linked polyethylene (XLPE) used for HVDC cable insulation. The aim is to better understand the influences of electrical and thermal stresses on the insulating material in order to provide useful information for designing HVDC cables. This study was carried out on Rogowski samples made of XLPE insulation with semiconductive electrodes, aged for more than 3 years (1220 days) at three different temperatures (70, 80 and 90 °C) under two DC electric fields (30 and 60 kV/mm). Dielectric loss factor, volume resistivity and space charge accumulation were measured. Results are analyzed and cross-correlated, in order to propose possible ageing kinetics.

This study evaluated the energy saving potential of renewable energy generation systems based on integrated solar energy in an urban environment. The solar city concept was implemented using photovoltaic (PV) and solar thermal systems. As a case study, the Sejong national pilot smart city in South Korea was selected to evaluate the renewable energy penetration rate. For evaluating the proposed renewable energy systems, the electrical and thermal loads of the smart city were estimated using field measurement data. Then, the renewable energy penetration rate of the city was evaluated. The HomerPro software was used to analyze the PV generation and operating energy consumption of the natural gas (NG) generator with a district heating network. The thermal load-supporting potential of the solar thermal system was estimated using the TRNSYS software. The results showed that the proposed urban integrated renewable energy system could meet over 30% of the renewable energy penetration rate and... [more]

This paper empirically examined relevant data on BRICS CO2 emissions, financial development, and economic growth in the past 40 years, and analyzed the correlation between them. Using the cointegration test, it found that there is a clear correlation between the variables in China and South Africa, which show that there is a two-way relationship between CO2 emissions, financial development, and economic growth in both countries. Using the quantile regression method in the analysis, the results demonstrated that at the 0.6th quartile, South Africa’s financial development had a negative impact on CO2 emissions, while Brazil’s CO2 emissions had a negative impact on financial development. Economic growth was subsequently added as a control variable, and the quantile-on-quantile regression method was used to test the correlation between the financial development of the BRICS countries and their CO2 emissions. Finally, based on empirical conclusions, this paper proposed that BRICS countries... [more]

Photovoltaic (PV) generation is potentially uncertain. Probabilistic PV generation forecasting methods have been proposed with prediction intervals (PIs) to evaluate the uncertainty quantitively. However, few studies have applied PIs to geographically distributed PVs in a specific area. In this study, a two-step probabilistic forecast scheme is proposed for geographically distributed PV generation forecasting. Each step of the proposed scheme adopts ensemble forecasting based on three different machine-learning methods. When individual PV generation is forecasted, the proposed scheme utilizes surrounding PVs’ past data to train the ensemble forecasting model. In this case study, the proposed scheme was compared with conventional non-multistep forecasting. The proposed scheme improved the reliability of the PIs and deterministic PV forecasting results through 30 days of continuous operation with real data in Japan.

A swirling pulverized coal flame is computationally investigated. A Eulerian−Lagrangian formulation is used to describe the two-phase flow. Turbulence is modelled within a RANS (Reynolds averaged numerical simulation) framework. Four turbulence viscosity- (TV) based models, namely the standard k-ε model, realizable k-ε model, renormalization group theory k-ε model, and the shear stress transport k-ω model are used. In addition, a Reynolds stress transport model (RSM) is employed. The models are assessed by comparing the predicted velocity fields with the measurements of other authors. In terms of overall average values, the agreement of the predictions to the measurements is observed to be within the range 20−40%. A better performance of the RSM compared to the TV models is observed, with a nearly twice as better overall agreement to the experiments, particularly for the swirl velocity. In the second part of the investigation, the resolution of the discrete particle phase in modelling... [more]