A converter valve unit, which converts Alternating Current (AC) to Directing Current (DC) and DC to AC, is one of the key elements of high voltage direct current (HVDC) transmission. The insulation design of a converter valve unit should be considered for air clearance according to the DC superimposed overvoltage and the insulator that maintains the insulation performance and the corona shield to suppress DC corona discharge. There is no prescribed standard for the insulation design of a converter valve unit. Moreover, insulation performance under an applied DC voltage has not yet been thoroughly investigated. Therefore, it is necessary to study the insulation design method of the converter valve unit. In this paper, consideration of the insulation design method on a ±200 kV converter valve unit in an HVDC converter hall is performed. The finite element method (FEM) is used to simulate the 3D model. Additionally, the safety factor (SF) is applied in accordance with the dielectric test... [more]

Input uncertainty is one of the major obstacles urban building energy models (UBEM) must tackle. The aim of this paper was to quantify the effects of two of the main sources of stochastic uncertainty, namely building occupants and urban microclimate, on electrical and thermal supply system sizing at the district scale. In order to analyze the effects of the former, three different methods of occupant modeling were implemented in a UBEM. The effects of the urban heat island on system sizing were studied through the use of measured temperature data from a weather station in the case study district compared to measured data from a national weather station. The methods developed were used to assess the sizing and costs of centralized and decentralized technologies for a case study in central Zurich, Switzerland. The choice of occupant modeling approach was found to affect the district’s total annualized costs for space heating and cooling by ±5%, whereas for the costs of electricity the va... [more]

Gasoline produced in Mexico by the productive company of the state Petróleos Mexicanos (PEMEX) mainly uses oil-derived ethers as oxygenators to reach the Mexican Regulatory ‘Framework’s octane number. An alternative to complying with these regulations could be to use bioethanol as an oxygenate. However, as a gasoline component, this could affect ‘Mexico’s food markets since sugar cane, and grains are the primary inputs for local production. The main objective of this study is to evaluate whether the use of bioethanol, produced from corn stubble, as an additive in gasoline produced by Petróleos Mexicanos (PEMEX) is profitable in Mexico, from the perspective of the evaluation of the supply chain and the finances. The purpose of this work is to contribute to the definition of the advantages and limitations for the existence of a second-generation bioethanol market produced from Lignocellulosic corn biomass and integrated into the gasoline market of national production in Mexico. The work... [more]

The interconnection of wind power plants (WPPs) with distribution networks has posed many challenges concerned with voltage stability at the point of common coupling (PCC). In a distribution network connected WPP, the short-circuit ratio (SCR) and impedance angle ratio seen at PCC (X/RPCC) are the most important parameters, which affect the PCC voltage (VPCC) stability. Hence, design engineers need to conduct the WPP siting and sizing assessment considering the SCR and X/RPCC seen at each potential PCC site to ensure that the voltage stability requirements defined by grid codes are provided. In various literature works, optimal siting and sizing of distributed generation in distribution networks (DG) has been carried out using analytical, numerical, and heuristics approaches. The majority of these methods require performing computational tasks or simulate the whole distribution network, which is complex and time-consuming. In addition, other works proposed to simplify the WPP siting an... [more]

The article was motivated by the design of adaptive control algorithms for the control of a a fixed wing unmanned aerial vehicle (UAV). An adaptive system is a system that, with its structure or parameters, adapts to changes in the behavior of the object and based on the knowledge of variable properties, maintains the quality of its regulatory transition. The knowledge gained on this small UAV can be applied to larger aircraft. The creation of the proposed adaptive control into the UAV consisted of the creation of a simulation model of the aircraft based on known physical laws, the properties of the aircraft and a mathematical description. An adaptive PID controller for stabilization with changing coefficients based on the airspeed of the aircraft was designed and simulated. A validated control of the mathematical model of an unmanned aircraft was designed and simulated using the methods of estimation and identification of the UAV model parameter based on measured data from flight test... [more]

The condensation of humid air is a crucial step in air conditioning and process engineering. However, the models that describe the condensation of vapour in the presence of a non-condensable gas require time-consuming numerical calculations that go beyond the Nusselt film theory. Only a small number of publications exist, where simple and computationally effective correlations for the condensation of water vapour in the presence of air are presented for specially designed condenser heat exchangers. Therefore, the objective of this paper is to extend the existing semi-empirical correlations for different geometries and process parameters. For the purpose of the study, an experimental setup with two different condenser heat exchangers based on vertical plates (height 74 mm) and horizontal tubes (3 tubes, diameter 40 mm and 7 tubes, diameter 15 mm) was built. Additionally, based on existing correlations, we developed two semi-empirical models that predict the condensation mass flux for th... [more]

This paper compares the energy economy and vertical vibration characteristics of in-wheel drive electric vehicles (IEVs), in-wheel drive electric hydraulic hybrid vehicles (IHVs) and centralized drive electric vehicles (CEVs). The dynamic programming (DP) algorithm is used to explore the optimal energy consumption of each vehicle. The energy economy analysis shows that the IEV consumes more energy than the CEV due to its relatively lower electric motor efficiency, even with fewer driveline components. The IHV consumes much more energy than the IEV and CEV because of the energy loss in the hydraulic driveline. The vertical vibration analysis demonstrates that both IEV and IHV degrade the vehicle driving comfort due to increased unsprung mass. Taking the advantage of high power density of the hydraulic motor, IHV have less unsprung mass when compared with the IEV, which helps to mitigate the vibration problems caused by increased unsprung mass.

The Digital Product Passport (DPP) is a concept of a policy instrument particularly pushed by policy circles to contribute to a circular economy. The preliminary design of the DPP is supposed to have product-related information compiled mainly by manufactures and, thus, to provide the basis for more circular products. Given the lack of scientific debate on the DPP, this study seeks to work out design options of the DPP and how these options might benefit stakeholders in a product’s value chain. In so doing, we introduce the concept of the DPP and, then, describe the existing regime of regulated and voluntary product information tools focusing on the role of stakeholders. These initial results are reflected in an actor-centered analysis on potential advantages gained through the DPP. Data is generated through desk research and a stakeholder workshop. In particular, by having explored the role the DPP for different actors, we find substantial demand for further research on a variety of i... [more]

In recent years, wind power systems have been used extensively, which not only improve the efficiency of current conventional power generation systems, but also can save traditional fossil fuel resources. However, considering the instability of wind power, after being grid connected, it can easily cause an impact on the stability of the grid operation. Considering the above problems, this paper considers to make full use of the energy storage part of electric vehicles (EVs) to increase the stability of grid operation. Based on the mathematical model, this paper studies the load frequency control (LFC) problem of a multi-region interconnected power system with wind power and EVs. First, since the system states are difficult to be monitored, a state observer is designed to estimate the state. Based on this, the integral sliding mode controller (SMC) is designed to realize the LFC of the interconnected power system. Meanwhile, to obtain better control performance, this paper further analy... [more]

With the rapid increase in the proportion of the installed wind power capacity in the total grid capacity, the state has put forward higher and higher requirements for wind power integration into the grid, among which the most difficult requirement is the zero-voltage ride through (ZVRT) capability of the wind turbine. When the voltage drops deeply, a series of transient processes, such as serious overvoltage, overcurrent, or speed rise, will occur in the motor, which will seriously endanger the safe operation of the wind turbine itself and its control system, and cause large-scale off-grid accident of wind generator. Therefore, it is of great significance to improve the uninterrupted operation ability of the wind turbine. Doubly fed induction generator (DFIG) can achieve the best wind energy tracking control in a wide range of wind speed and has the advantage of flexible power regulation. It is widely used at present, but it is sensitive to the grid voltage. In the current study, the... [more]

The properties and advantages of axial flow cyclones are presented; several dozen of them are already widely used as the first stage of inlet air filtration in internal combustion motor vehicle engines, work machines and helicopters. The necessity to conduct research on cyclones to improve separation efficiency has been demonstrated. Using the commercial engineering software Ansys Fluent, at a constant inlet velocity of 10 m/s, an assessment was made on the effect of the separation length and inlet diameter of the outlet tube on changes in separation efficiency in axial flow cyclone. Each of the examined parameters was variable while maintaining other factors at a constant level. In the numerical calculations, test dust was used, which was the equivalent of AC fine dust, the particle size composition of which was taken into account using the Rosin−Rammler model. Increase in the separation efficiency was observed with an increase in the separation length and a decrease in the diameter o... [more]

To investigate the optimum layouts of small vertical-axis wind turbines, a two-dimensional analysis of dynamic fluid body interaction is performed via computational fluid dynamics for a rotor pair in various configurations. The rotational speed of each turbine rotor (diameter: D = 50 mm) varies based on the equation of motion. First, the dependence of rotor performance on the gap distance (gap) between two rotors is investigated. For parallel layouts, counter-down (CD) layouts with blades moving downwind in the gap region yield a higher mean power than counter-up (CU) layouts with blades moving upwind in the gap region. CD layouts with gap/D = 0.5−1.0 yield a maximum average power that is 23% higher than that of an isolated single rotor. Assuming isotropic bidirectional wind speed, co-rotating (CO) layouts with the same rotational direction are superior to the combination of CD and CU layouts regardless of the gap distance. For tandem layouts, the inverse-rotation (IR) configuration sh... [more]

Flexible AC Transmission Systems (FACTS) are essential devices used for the efficient performance of modern power systems and many developing countries lack these devices. Due to the non-existence of these advanced technologies, the national grid remains weak and vulnerable to power stability issues that can jeopardize system stability. This study proposes novel research to solve issues of an evolving national grid through the installation of FACTS devices. FACTS devices play a crucial role in minimizing active power losses while managing reactive power flows to keep the voltages within their respective limits. Due to the high costs of FACTS, optimization must be done to discover optimal locations as well as ratings of these devices. However, due to the nonlinearity, it is a challenging task to find the optimal locations and appropriate sizes of these devices. Shunt VARs Compensators (SVCs) and Thyristor-Controlled Series Compensators (TCSCs) are the two FACTS devices considered for th... [more]

The increasing world population generates huge amounts of wastewater as well as large energy demand. Additionally, fossil fuel’s combustion for energy production causes the emission of greenhouse gases (GHG) and other pollutants. Therefore, there is a strong need to find alternative green approaches for wastewater treatment and energy production. Microalgae biorefineries could represent an effective strategy to mitigate the above problems. Microalgae biorefineries are a sustainable alternative to conventional wastewater treatment processes, as they potentially allow wastewater to be treated at lower costs and with lower energy consumption. Furthermore, they provide an effective means to recover valuable compounds for biofuel production or other applications. This review focuses on the current scenario and future prospects of microalgae biorefineries aimed at combining wastewater treatment with biofuel production. First, the different microalgal cultivation systems are examined, and the... [more]

Photocatalysis is a classical solution to energy conversion and environmental pollution control problems. In photocatalysis, the development and exploration of new visible light catalysts and their synthesis and modification strategies are crucial. It is also essential to understand the mechanism of these reactions in the various reaction media. Recently, bismuth and graphene’s unique geometrical and electronic properties have attracted considerable attention in photocatalysis. This review summarizes bismuth-graphene nanohybrids’ synthetic processes with various design considerations, fundamental mechanisms of action, heterogeneous photocatalysis, benefits, and challenges. Some key applications in energy conversion and environmental pollution control are discussed, such as CO2 reduction, water splitting, pollutant degradation, disinfection, and organic transformations. The detailed perspective of bismuth-graphene nanohybrids’ applications in various research fields presented herein sho... [more]

This study quantifies the potential of a 4.0 kW air source heat pump (ASHP) unit retrofitted to a 12.0 kW, 1000 L electric boiler coupled to a 1000 L storage tank. A data acquisition system was built to monitor the performance of the electric boiler and the ASHP water heater. The annual electrical energy saving and the load factor reduction from the electric boiler because of the ASHP unit retrofit was 34,805.94 kWh and 0.124. The net present value payback period of the ASHP system was 1.60 years. A Wilcoxon rank sum test was employed to compare both the volumes of hot water and electrical energy consumed by the two systems. Linear regression models of the daily volumes of hot water and electrical energy consumed by both systems were established. The results should be of great value to the management of universities that are considering energy-efficient interventions with a significant return on investment.

Since the introduction of Perovskite Solar Cells, their photovoltaic efficiencies have grown impressively, reaching over 25%. Besides the exceptional efficiencies, those solar cells need to be improved to overcome some concerns, such as their intrinsic instability when exposed to humidity. In this respect, the development of new and stable Hole Transporting Materials (HTMs) rose as a new hot topic. Since the doping agents for common HTM are hygroscopic, they bring water in contact with the perovskite layer, thus deteriorating it. In the last years, the research focused on “dopant-free” HTMs, which are inherently conductive without any addition of dopants. Dopant-free HTMs, being small molecules or polymers, have still been a relatively small set of compounds until now. This review collects almost all the relevant organic dopant-free small-molecule HTMs known so far. A general classification of HTMs is proposed, and structure analysis is used to identify structure−property relationships... [more]

In order to expand the speed range for an indirect matrix converter−surface mounted permanent magnet synchronous motor drive (IMC-SPMSM), a wide speed range operation control strategy based on a flux-weakening control and an over-modulation method is proposed in this paper. In the stage of the inverter, an IMC over-modulation method is designed, which increases the fundamental voltage transmission ratio (VTR) to 1. In addition, considering the variation of the voltage limit boundary of the IMC with motor speed, flux-weakening control is implemented based on the voltage error feedback method, which maximizes the voltage utilization rate by setting the endpoint of the output voltage vector on the voltage boundary during the flux-weakening operation. In the stage of the rectifier, over-modulation is automatically switched on or off according to operation requirements by a modulation depth controller. Finally, experimental results show that the proposed strategy increases the maximum speed... [more]

In this study, we mitigated the harmonic voltage in a power system that contained the roughing mill (RM) and finishing mill (FM) motor drives. AC/DC converter type RM drive is a non-linear, large-capacity varying load that adversely affects power quality, e.g., a flicker, voltage distortion, etc. The voltage drop can be compensated within a certain limit by using the proper capacity of a power capacitor bank. In addition, the voltage distortion can be controlled as per the guidelines of IEEE Std. 519 using the passive harmonic filter corresponding to the characteristic harmonics of the motor drive load. The passive harmonic filter can provide an economical solution by mitigating the harmonic distortion with a proper reactive power supply. However, at the planning level, attention should be paid to avoid system overvoltage that is caused by the leading power under light load conditions and also the problem of parallel resonance between the harmonic filter and the step-down transformer.... [more]

Particle adhesion is of great importance to coating processes due to its effect on fluidization. Currently, Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) has become a powerful tool for the study of multiphase flows. Various contact force models have also been proposed. However, particle dynamics in high temperature will be changed with particle surface properties changing. In view of this, an adhesion model is developed based on approaching-loading-unloading-detaching idea and particle surface change under high temperature in this paper. Analyses of the adhesion model are given through two particle collision process and validated by experiment. Effects of inlet gas velocity and adhesion intensity on spouted bed dynamics are investigated. It is concluded that fluidization cycle will be accelerated by adhesion, and intensity of fluidization will be marginally enhanced by slight adhesion. Within a certain range, increasing inlet gas velocity will lead to strong intensity... [more]

The reverse osmosis method has developed extremely rapidly in recent years and has become the most competitive seawater desalination technology in the world, and it has been widely used in all aspects. Large-scale reverse osmosis desalination plants cannot provide fresh water resources in areas with insufficient water resources and limited space. Therefore, this paper proposes a research plan for a small seawater desalination device based on reverse osmosis, which is mainly suitable for handling emergencies, disaster relief, desert areas and outdoor activities and other needs for timely freshwater resources. It mainly includes pretreatment modules, a reaction infiltration module, a post-processing module and an energy supply module. Detailed design calculations are carried out for the small-scale reverse osmosis membrane system, including the selection and quantity and arrangement of membranes. Subsequently, the one-stage two-stage small-scale reverse osmosis membrane system was modele... [more]

Ancillary services rely on operating reserves to support an uninterrupted electricity supply that meets demand. One of the hidden reserves of the grid is in thermostatically controlled loads. To efficiently exploit these reserves, a new realization of control of voltage in the allowable range to follow the set power reference is proposed. The proposed approach is based on the deep reinforcement learning (RL) algorithm. Double DQN is utilized because of the proven state-of-the-art level of performance in complex control tasks, native handling of continuous environment state variables, and model-free application of the trained DDQN to the real grid. To evaluate the deep RL control performance, the proposed method was compared with a classic proportional control of the voltage change according to the power reference setup. The solution was validated in setups with a different number of thermostatically controlled loads (TCLs) in a feeder to show its generalization capabilities. In this ar... [more]

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]

Co-hydrothermal carbonization (Co-HTC) is an emerging technology for processing multiple waste streams together to improve their fuel properties in the solid product, known as hydrochar, compared to the hydrothermal carbonization (HTC) of those individual streams. Sulfur is considered one of the most toxic contaminants in solid fuel and the combustion of this sulfur results in the emission of SOx. It was reported in the literature that, besides the fuel properties, Co-HTC reduced the total sulfur content in the hydrochar phase significantly. However, the transformation of different forms of sulfur has not yet been studied. Therefore, this study investigated the transformation of different forms of sulfur under the Co-HTC treatment. In the study, the Co-HTC of food waste (FW) and two types of coal wastes (middle bottom (CW1) and 4 top (CW2)) were conducted at 180 °C, 230 °C and 280 °C for 30 min. Different forms of sulfur were measured by using elemental analysis (total sulfur), and a w... [more]

Uninterruptible Power Supplies (UPS) have been demonstrated to be the key technology in feeding either single- and three-phase loads in a wide range of critical applications, such as high-tier datacenters and medical facilities. To increase the overall system power capacity and resilience, UPS systems are usually connected in parallel. When UPS systems are parallel connected, a circulating current can rise, inhibiting correct system operation. Moreover, having a controlled load power distribution is another fundamental requirement in paralleled UPS systems. However, strategies to ensure these two topics have not been explored to date for UPS systems with a load-side neutral connection. This paper proposes an innovative Finite Control Set Model Predictive Control (FCS-MPC) strategy that ensures circulating current elimination and controlled load power distribution for paralleled UPS systems that use an additional inverter leg for load neutral point connection. Additionally, a system top... [more]