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]

Covalent organic frameworks (COFs) are emerging crystalline polymeric materials with highly ordered intrinsic and uniform pores. Their synthesis involves reticular chemistry, which offers the freedom of choosing building precursors from a large bank with distinct geometries and functionalities. The pore sizes of COFs, as well as their geometry and functionalities, can be pre-designed, giving them an immense opportunity in various fields. In this mini-review, we will focus on the use of COFs in the removal of environmentally hazardous metal ions and chemicals through adsorption and separation. The review will introduce basic aspects of COFs and their advantages over other purification materials. Various fabrication strategies of COFs will be introduced in relation to the separation field. Finally, the challenges of COFs and their future perspectives in this field will be briefly outlined.

The air filters applied in utility terrain vehicles (UTVs), which are usually driven on dust-prone unpaved roads, employ a two-stage air cleaner that increases the lifespan of the filter element by using a pre-cleaner stage in the air filter intake housing to centrifugally separate any dust particles contained in the intake air before sending the cleaned air to the primary filter. Thus, maximizing the centrifugation capacity by properly modifying the geometry of the intake air passage in the filter housing is important to ensure engine performance and filter lifespan. The geometry of the pre-cleaner air passage was therefore optimized in this study in terms of the inclination angle and air passage location angle using a computational flow analysis to maximize the centrifugal removal of dust particles. The resulting overall pre-cleaner efficiency and overall pre-cleaner efficiency per pressure drop were then used as the objective functions to maximize the dust particle removal capacity... [more]

This paper aims to improve the stability and robustness of the state-of-charge estimation algorithm for lithium-ion batteries. A new internal resistance-polarization circuit model is constructed on the basis of the Thevenin equivalent circuit to characterize the difference in internal resistance between charge and discharge. The extended Kalman filter is improved through adding an adaptive noise tracking algorithm and the Kalman gain in the unscented Kalman filter algorithm is improved by introducing a dynamic equation. In addition, for benignization of outliers of the two above-mentioned algorithms, a new dual Kalman algorithm is proposed in this paper by adding a transfer function and through weighted mutation. The model and algorithm accuracy is verified through working condition experiments. The result shows that: the errors of the three algorithms are all maintained within 0.8% during the initial period and middle stages of the discharge; the maximum error of the improved extensio... [more]

Extracting ethanol by steam directly from fermented solid-state bagasse is an emerging technology of energy-efficient bioethanol production. With continuous solid-state distillation (CSSD) approach, the vapor with more than 25 wt% ethanol flows out of the column. Conventionally, the vapor was concentrated to azeotrope by rectification column, which contributes most of the energy consumption in ethanol production. As an alternative, a process integrating CSSD and vapor permeation (VP) membrane separation was tested. In light of existing industrial application of NaA zeolite hydrophilic membrane for dehydration, the prospect of replacing rectification operation with hydrophobic membrane for ethanol enriching was mainly analyzed in this paper. The separation performance of a commercial PDMS/PVDF membrane in a wide range of ethanol−water-vapor binary mixture was evaluated in the experiment. The correlation of the separation factor and permeate flux at different transmembrane driving force... [more]

The Internet of Things (IoT) is a technology that allows every object or item to become part of the Internet and interact with each other. One of the technologies based on the IoT is Long Range (LoRa). Apart from the increasing number of IoT services, security aspects become a separate issue in the development of the IoT. One of the solutions is to utilize blockchain technology in the IoT topology to secure the data and transactions that occur in the IoT network. The blockchain can take minutes to compute a cryptographic chain. It also needs sufficient computing resources. This problem gave rise to the idea of establishing a lightweight blockchain platform with low latency that could run on devices with low computing resources as well as IoT devices. We offered a technology called Lightweight Multi-Fog (LMF) in our previous publication that is implemented using the Lightweight Scalable Blockchain (LSB) algorithm and the fog network on the IoT to solve the problem of integrating a block... [more]

The quality of the indoor environment has become a vital component for buildings due to the time spent indoors. To this extent, the performance of the indoor environment is considered as part of the greenery criteria by green rating schemes such as the Green Building Index in Malaysia. This study aims to investigate and assess the quality of the indoor environment of Platinum-certified office buildings in a tropical climate. This research applied a case study approach over two Platinum-certified office buildings. Post-occupancy evaluation is employed integrating full-scale measurement with an occupants’ survey. The measurement was carried out from May to August, and 112 questionnaires were retrieved to evaluate occupants’ satisfaction with aspects of the indoor environment. Thermal comfort, indoor air quality, acoustic, lighting, furniture, and cleanliness are considered as the main study variables. The findings of full-scale measurement indicated high relative humidity, and low air ve... [more]

The risk of environmental pollution is a consequence of every kind of energy, including fossil fuels, nuclear power plants, and thermoelectric power plants. For the purpose of reducing the use ratio of such energy, research on eco-friendly energy is being actively carried out, and has shown that among all kinds of energy, solar energy has an advantage: it can supply us with inexhaustible clean energy. However, since solar energy depends on sunlight, the output may be unstable as it is influenced by weather or surrounding structures. In this paper, there is presented a control system which transmits power to a storage device, in a specific state, after the energy of the low-illumination section is charged in a supercapacitor using the accumulation-type controller by use of a supercapacitor. Feedback from the power output of photovoltaic panels (PVs) demonstrates that the power of the low-illumination section can be charged without being discarded. The charging rate was compared with oth... [more]

In this study, an inter-continental agricultural pellet supply chain is modeled, and the production cost and price of agricultural pellets are estimated and compared against the recent cost and price of wood pellets in the global marketplace. The inter-continental supply chain is verified and validated using an integration of an interactive mapping application and a simulation platform. The integrated model is applied to a case study in which agricultural pellets are produced in six locations in Canada and shipped and discharged at the three major ports in Western Europe. The cost of agricultural pellets in the six locations is estimated to be in the range of EUR 92−95/tonne (CAD 138−142/tonne), which is comparable with the recent cost of wood pellets produced in small-scale pellet plants (EUR 99−109/tonne). The average agricultural pellet price shipped from the six plants to the three ports in Western Europe is estimated to be in a range of EUR 183−204 (CAD 274−305/tonne), 29−42% more... [more]

This study proposes a multi-objective approach for the optimal design of a sustainable Integrated Biodiesel/Diesel Supply Chain (IBDSC) based on first- (sunflower and rapeseed) and second-generation (waste cooking oil and animal fat) feedstocks with solid waste use. It includes mixed-integer linear programming (MILP) models of the economic, environmental and social impact of IBDSC, and respective criteria defined in terms of costs. The purpose is to obtain the optimal number, sizes and locations of bio-refineries and solid waste plants; the areas and amounts of feedstocks needed for biodiesel production; and the transportation mode. The approach is applied on a real case study in which the territory of Bulgaria with its 27 districts is considered. Optimization problems are formulated for a 5-year period using either environmental or economic criteria and the remainder are defined as constraints. The obtained results show that in the case of the economic criterion, 14% of the agricultur... [more]

Cognitive radio is expected to be implemented in smart grids since it presents high reliability, high accuracy and low transmission time by utilizing licensed bands opportunistically. Shadowing environment affects the performance of channel availability detection of local spectrum sensing since it occurs occasionally. Therefore, the cooperative spectrum sensing is encouraged to be used for addressing shadowing issues. The principle cooperative spectrum sensing techniques suffer from unreliable local information from secondary users (SUs) who are encountered by the shadowing effect. Then, several alternative methods, adaptive majority rule and improved weight algorithm (IMA) is proposed by taking the SUs reliability into account. However, the unreliable SUs are still considered according to the algorithm. Therefore, in this paper, we propose an adaptive multi-criteria thresholding (AMT) to determine the channel availability according to the SUs reliability. The main contribution of AMT... [more]

The paper presents the combustion profile of selected fuels as a result of thermogravimetric analysis. The main purpose of this study was to investigate a mixture of different types of fuel and the influence of the use of a fuel additive on the combustion process profile. As a fuel additive, halloysite was used to investigate the thermogravimetric profiles. It was confirmed that the main combustion parameters such as ignition temperature, burnout temperature, and maximum peak temperature correlated accordingly with different combustibility indices such as the ignition index, the burnout index, and the combustion indices. Furthermore, the present study provided a comparison of selected methods for analyzing non-isothermal solid-state kinetic data and investigated the kinetics of thermal decomposition to describe the ongoing process. Two non-isothermal model methods (Kissinger and Ozawa) were used to calculate the Arrhenius parameters. The effect of heating rate and the addition of hallo... [more]

Energy communities (EC) are among the new actors in the energy market, playing an important role in the uptake of photovoltaics (PV) in European markets. This paper estimates their aggregate contribution to the low-carbon energy transition in terms of installed capacities for PV and evaluates their economic performance comparing with market prices. We compiled a database of PV facilities with 3672 entries for Germany and 64 entries for Italy. Our statistical analysis does not support an economic under-performance of EC. The aggregate contribution of EC currently amounts to 600−838 MWp installed capacity in Germany and 10.6 MWp installed capacity in Italy, which makes 1.2−1.7% and 0.07% of all PV installations in Germany and Italy, respectively.

Due to the particularity of the synchronous reluctance motor (SynRM) structure, a novel high-performance model predictive torque control (MPTC) method was proposed to reduce the high torque ripple and improve the performance and efficiency of the motor. First, the precise parameters of the SynRM reflecting the magnetic saturation characteristics were calculated using finite element analysis (FEA) data, and the torque and flux linkage maximum torque per ampere (MTPA) trajectory was derived by considering the saturation characteristics. Then, an MPTC model of a SynRM with duty cycle control was established, the MTPA trajectory stored in a look-up table was introduced into the control model, and the duration of the active voltage vector in one control cycle was calculated by evaluating the torque error. Finally, an experimental platform based on a SynRM prototype was built, and various performance comparison experiments were carried out for the proposed MPTC method. The experimental resul... [more]

In this article, a novel wavelet collocation method based on Fibonacci wavelets is proposed to solve the dual-phase-lag (DPL) bioheat transfer model in multilayer skin tissues during hyperthermia treatment. Firstly, the Fibonacci polynomials and the corresponding wavelets along with their fundamental properties are briefly studied. Secondly, the operational matrices of integration for the Fibonacci wavelets are built by following the celebrated approach of Chen and Haiso. Thirdly, the proposed method is utilized to reduce the underlying DPL model into a system of algebraic equations, which has been solved using the Newton iteration method. Towards the culmination, the effect of different parameters including the tissue-wall temperature, time-lag due to heat flux, time-lag due to temperature gradient, blood perfusion, metabolic heat generation, heat loss due to diffusion of water, and boundary conditions of various kinds on multilayer skin tissues during hyperthermia treatment are brief... [more]