Pig farming in mechanically ventilated barns requires much electricity for ventilation or exhaust air purification. Furthermore, thermal energy is needed to fulfill the animals’ temperature requirements, especially in piglet rearing. Electrical and thermal energy input leads to CO2 emissions and operating costs. Up to 90% of heat losses are due to the exhausted air. Heat exchangers can recover thermal energy from the warm exhaust air and transfer it to the cold fresh air. This study aimed to investigate energy consumption, efficiency, CO2 emissions, and energy costs when using heat exchangers in a German piglet rearing barn under practical conditions in combination with exhaust air purification. The following parameters were obtained for a two-year period: air temperatures, air flow rates, and electricity and liquefied natural gas consumption; the latter were used to calculate CO2 emissions and energy costs. In total, 576,042 kWhel,th and 616,893 kWhel,th (years 1 and 2) of energy were... [more]

In electrical power engineering, elements such as reliability analysis, modeling, and optimization for complex systems are of the utmost importance. Although there exist myriad studies regarding reliability optimization with conventional methods, researchers are still seeking to find more efficient and accurate methods to address the issue of the redundancy allocation problem. To that effect, an ideal power energy management approach is put forward for the operation of a hybrid microgrid system with different kinds of productions. In the present study, we suggest three algorithms in order to optimize the series-parallel power energy system: the Firefly (FA), Bat (BA), and Interior Search (ISA) algorithms. Moreover, the reliability estimate of the system is solved with the Ushakov algorithm (UMGF). The components may completely fail, which decreases their performance rate. Furthermore, the optimization results are achieved using objective functions that include the total cost of the sys... [more]

The hydrothermal behavior in a helical double-tube heat exchanger is numerically estimated. A new type of swirl generator with two sections, including; outer curved blades and a semi-conical section with two holes in the inner section, is employed. Two geometrical factors, containing the length (L1) and the position of the swirl generator (S), are used for investigation. The calculations were performed by a commercial FVM code, ANSYS FLUENT 18.2. The numerical outcomes show that a shorter length of the swirl generator leads to a better hydrothermal behavior. Accordingly, the model with L1 = 100 mm at m˙ = 0.008 kg/s achieves the maximum thermal performance by about 17.65, 53.85, and 100% enhancement compared to the models L1 = 200, 300 mm, and without swirl generator. Among the different studied positions of the swirl generator, the maximum heat transfer coefficient and average Nusselt number in entire mass flow rates belong to the case with position S = 0.3π mm. Moreover, the thermal... [more]

As a result of growing interest in the thermal treatment of sewage sludge with methods such as combustion, gasification or pyrolysis, and also in processes that aim to recover precious components such as phosphorus from this waste, a growing demand has been observed for Computational Fluid Dynamics (CFD) models that provide solutions rapidly and accurately for efficient application in research and development. This study was carried out to develop a computationally inexpensive modelling approach for the combustion of pulverized sewage sludge in entrained flow furnaces. Sewage sludge is a very volatile-rich fuel. Therefore, the Steady Diffusion Flamelet model (SFM), in combination with a validated skeletal reaction mechanism, was applied to consider the pulverized firing of sewage sludge. It was possible to represent the complex composition of volatiles emitted from the sludge particles by releasing surrogate fuels. In addition, the influence of limestone additive (calcination reaction)... [more]

The increasing demand for flexibility in hydropower systems requires pumped storage power plants to change operating modes and compensate reactive power more frequently. In this work, we demonstrate the potential of applying reinforcement learning (RL) to control the blow-out process of a hydraulic machine during pump start-up and when operating in synchronous condenser mode. Even though RL is a promising method that is currently getting much attention, safety concerns are stalling research on RL for the control of energy systems. Therefore, we present a concept that enables process control with RL through the use of a digital twin platform. This enables the safe and effective transfer of the algorithm’s learning strategy from a virtual test environment to the physical asset. The successful implementation of RL in a test environment is presented and an outlook on future research on the transfer to a model test rig is given.

The extent of fracture development is associated with the degree of enrichment of a natural gas reservoir and its productivity. Based on numerical simulation results of the paleotectonic stress field, a set of evaluation methods for determining the degree of development of reservoir tectonic fractures were established using rock rupture criteria. Taking the fourth member of the Leikoupo Formation in the Pengzhou area of western Sichuan as an example, a finite element (FE) method was employed to simulate the paleo-tectonic stress field during the period of fracture development, and the degree of tectonic fracture development was further evaluated using the above methods. The results indicated that effective fractures were created in the Himalayan period. In this time, mainly NE−NEE and nearly E−W strike tectonic fractures were developed in the target layer. The fractures were mainly low-angle and oblique fractures, while the high-angle fractures were less developed. According to the int... [more]

This paper presents the study and detailed analysis of converter losses at different stages together with the series-series (S-S) compensating coils in wireless power transfer (WPT) systems, via two distinct approaches to control the power converters. The two approaches towards wireless DC−DC power flow control are termed as the Single Active High-Frequency Wireless Power Transfer (SAHFWPT) system and the Dual Active High-Frequency Wireless Power Transfer (DAHFWPT) system. The operation of converters in SAHFWPT and DAHFWPT are controlled by the extended phase shift (EPS) and dual phase shift method respectively. The general schematic of the SAHFWPT system consists of an active bridge and a passive bridge, while the schematic of the DAHFWPT system consists of both active bridges. The efficiency evolutions of ideal SAHFWPT and DAHFWPT are far away from the real ones. Moreover, this article analyzes the operation and losses of the uni-directional power flow of the WPT system, i.e., from t... [more]

The global energy and environmental crisis promotes the development of electric vehicles (EVs), and the rational planning of EV fast charging stations is an important influencing factor for their development. In this paper, for the EV fast charging station capacity planning problem, a joint-optimization model for optimal planning of EV fast charging stations and the economic operation of a distribution network is constructed, considering the impact of user preference selection and EV access on the regional distribution network. To address the problems of low efficiency and local convergence found in traditional heuristic optimization algorithms, an improved krill swarm optimization algorithm (CKHA) that introduces chaotic optimization parameters to make the initial population as uniformly distributed as possible is proposed to find the optimal planning scheme for EV fast charging stations. The case results show that the optimal planning model and its solution method are effective.

Energy consumption is increasing rapidly; hence, the energy demand cannot be fulfilled using traditional power resources only. Power systems based on renewable energy, including solar and wind, are effective and friendly for the environment. Islanded hybrid microgrid systems (IHMS) are relatively new in this industry and combine two or more sustainable sources, such as wind turbines, solar photovoltaic (PV), and other renewable alternatives, ocean, wave, and geothermal energy, etc. While sustainable, long-lasting power sources are the best choice to satisfy the growing energy demands, they are still not yet ready to be used on a large scale due to their stochastic characteristics. Furthermore, integrating these sources into the existing energy system can cause high technical difficulties, due to the stochastic nature of solar and wind in the conventional grid system and common stand-alone framework. A review of research and applications of the effective hybridization of renewable energ... [more]

The economic operation of an electric vehicle (EV) parking lot under different cases are explored in the paper. The parking lot is equipped with EV charging stations with a vehicle-to-grid (V2G) function, renewable energy sources (RESs), and energy storage system (ESS). An optimisation problem is formulated to maximise the profit of the parking lot from EV charging and feed-in energy to the grid under various charging modes while considering the uncertain factors, ESS degradation, and diverse EV parking conditions. The electricity market price, solar radiation and wind speed are considered as uncertain factors, and the scenred toolbox of MATLAB is used to generate scenarios. Based on the parking time of different EVs, the model classifies the EVs entering the charging station and dynamically determines the charging price according to their charging demand through a linear price-demand relationship. The efficacy of the proposed model is verified by the comparison with two other models u... [more]

This paper mainly studies the optimal control problem of turbine-based combined cycle (TBCC) engines in the mode-transition stage. Based on the TBCC scheme proposed by Xiamen University, an aerothermodynamic model is established as a verification model for the validity of control laws. To reduce the complexity of control design, a control-oriented linear parameter-varying (LPV) model with Mach number as a scheduling variable is established under a given flight path. The design of mode-transition points and distribution of air-flow-rate among paths during the mode-transition process are transformed into linear quadratic (LQ) optimal control problems for an LPV system under the initial and terminal as well as process constraints. By optimizing the opening of the splitters of the inlet and the fuel flow in each channel, the optimal mode-transition points are found to achieve coordinated control and complete the high-precision thrust tracking during the mode-transition process.

Gas and downhole water sink-assisted gravity drainage (GDWS-AGD) is a new process of enhanced oil recovery (EOR) in oil reservoirs underlain by large bottom aquifers. The process is capital intensive as it requires the construction of dual-completed wells for oil production and water drainage and additional multiple vertical gas-injection wells. The costs could be substantially reduced by eliminating the gas-injection wells and using triple-completed multi-functional wells. These wells are dubbed triple-completion-GDWS-AGD (TC-GDWS-AGD). In this work, we design and optimize the TC-GDWS-AGD oil recovery process in a fictitious oil reservoir (Punq-S3) that emulates a real North Sea oil field. The design aims at maximum oil recovery using a minimum number of triple-completed wells with a gas-injection completion in the vertical section of the well, and two horizontal well sections—the upper section for producing oil (from above the oil/water contact) and the lower section for draining wat... [more]

The synchronous generators (SGs) supplying non-linear loads have harmonically distorted terminal voltages. Hence, these distorted terminal voltages adversely affect the performance parameters of the supplied loads such as the power factor, current distortion, losses, and efficiency. To mitigate the harmonic voltages and currents, passive and active filters are generally employed. However, passive filters cause resonance problems, while active filters can cause high costs. On the other hand, in several recent studies to reduce the SG’s terminal voltage harmonic distortion, which depends on the constructional design under the no-loading condition, the conventional DC excitation current has been modulated with AC harmonic components. These field current modulation methods have high computational complexity, and require extra hardware for their implementation. In the present paper, firstly, for the reduction of the terminal voltage harmonic distortion of the SG under non-linear loading con... [more]

The application of additive manufacturing in the field of aviation hydraulics greatly improves the design freedom of hydraulic valve internal flow channels. Pressure loss in hydraulic valve internal flow channels is a primary factor that designers need to consider, and the rapid prediction of pressure loss is very helpful for flow channel design. At present, most studies only focus on how much the pressure loss in an additive manufacturing (AM) hydraulic channel is reduced compared with an original hydraulic channel, and a mathematical model of pressure loss in an AM curved channel is still lacking. In this paper, the pressure loss in a curved flow channel was firstly studied, and the main parameters affecting the pressure loss were determined using the dimensionless analysis method. Using computational fluid dynamics simulation, the relationships between the flow channel diameter, the flow channel length, the flow channel curvature radius, the fluid velocity and pressure loss were stu... [more]

In grid-connected operations, a microgrid can solve the problem of surplus power through regeneration; however, in the case of standalone operations, the only method to solve the surplus power problem is charging the energy storage system (ESS). However, because there is a limit to the capacity that can be charged in an ESS, a separate energy management strategy (EMS) is required for stable microgrid operation. This paper proposes an EMS for a hybrid AC/DC microgrid based on an artificial neural network (ANN). The ANN is composed of a two-step process that operates the microgrid by outputting the operation mode and charging and discharging the ESS. The microgrid consists of an interlinking converter to link with the AC distributed system, a photovoltaic converter, a wind turbine converter, and an ESS. The control method of each converter was determined according to the mode selection of the ANN. The proposed ANN-based EMS was verified using a laboratory-scale hybrid AC/DC microgrid. Th... [more]

The use of fossil-fueled power stations to generate electricity has had a damaging effect over the years, necessitating the need for alternative energy sources. Microgrids consisting of renewable energy source concepts have gained a lot of consideration in recent years as an alternative because they use advances in information and communication technology (ICT) to increase the quality and efficiency of services and distributed energy resources (DERs), which are environmentally friendly. Nevertheless, microgrids are constrained by the outbreaks of faults, which have an impact on their performance and necessitate dynamic energy management and optimization strategies. The application of artificial intelligence (AI) is gaining momentum as a vital key at this point. This study focuses on a comprehensive review of applications of artificial intelligence strategies on hybrid renewable microgrids for optimization, power quality enhancement, and analyses of fault outbreaks in microgrids. The us... [more]

Although highly developed countries are trying to diversify away from coal-based energy, many economies rely on this resource. Its consumption results in the production of carbon dioxide, which promotes global warming, necessitating its sequestration. This paper presents the sorption−dilatometric relationships of hard coal samples differing in vitrinite and inertinite content. The studies were carried out under isothermal conditions (298 K) at a free pressure drop complemented by measurements under non-isothermal conditions (298 K to 323 K). The tests were performed on an original apparatus, based on the operation of an Arduino microcontroller. For the natural porosity to be preserved and for a better representation of the behaviour of the coal−gas system, samples in the form of cuboidal blocks were used, making this apparatus unique worldwide. Based on the study, it appears that the difference in petrographic composition affects the behaviour of the coal structure, influencing differe... [more]

With the emergence of the electric vehicle (EV) era in which the vehicle’s embedded batteries can be exploited for grid support purposes, the role of EVs participating in ancillary services via vehicle-to-grid (V2G) technology cannot be disregarded. Although there are many forms of ancillary services, the most common services delivered by EVs are frequency regulation, frequency contingency, inertia, and voltage regulation. Numerous research studies have been conducted to propose the most effective control strategies for electric vehicle ancillary services (EVASs). In this paper, a comprehensive review is carried out on various control strategies for EVs with respect to their participation in ancillary services. The methodology applied for this review comprises a combination of thematic and historical reviews. The review explores the benefits and limitations of these control strategies and provides a clear understanding of the research gaps in the EVAS area. This review will provide a u... [more]

Among so many fault basins around Ordos presenting good geothermal background, Yinchuan Plain is the key development and protection area of the Ecological and Economic Belt along the Yellow River in Ningxia and Yinchuan Metropolitan Area. The study of geothermal resources in this region is of great significance to the sustainable economic development of Yinchuan Plain. Most scholars suggested that Yinchuan Plain geothermal resources are low-to-medium temperature geothermal resources and have high value in terms of development and utilization due to their large reserves, good water quality conditions, and wide distribution. However, there is much controversy over the geothermal mechanism of this region. As an effective means to study geothermal mechanism, geophysical methods can be used to study regional basement uplift and structural distribution characteristics. Based on the discussion of regional geothermal geology background, this paper studies the distribution rules of Moho and Cur... [more]

Aspects related to the growing pollution of the natural environment and depletion of conventional fossil fuels have become the motive for searching for ecofriendly, renewable, and sustainable alternative energy sources. Particular attention is paid to industrial waste, especially waste of biomass materials, which can be converted into biofuels and energy that meets the growing needs of humanity. The use of biomass for energy purposes is less damaging to the environment, the materials are low-cost, locally available in large quantities, and create employment opportunities for workers in suburban and rural areas around the world. This article discusses issues related to the use of waste biomass materials as renewable energy sources. The current energy situation in the world is analyzed in terms of production, consumption, and investments in green energy. Types of biomass and individual physicochemical and energy properties of waste plant materials obtained for energy purposes are describ... [more]

In this work, a DC microgrid consists of a solar photovoltaic, wind power system and fuel cells as sources interlinked with the utility grid. The appropriate sizing and positioning of electric vehicle charging stations (EVCSs) and renewable energy sources (RESs) are concurrently determined to curtail the negative impact of their placement on the distribution network’s operational parameters. The charging station location problem is presented in a multi-objective context comprising voltage stability, reliability, the power loss (VRP) index and cost as objective functions. RES and EVCS location and capacity are chosen as the objective variables. The objective functions are tested on modified IEEE 33 and 123-bus radial distribution systems. The minimum value of cost obtained is USD 2.0250 × 106 for the proposed case. The minimum value of the VRP index is obtained by innovative scheme 6, i.e., 9.6985 and 17.34 on 33-bus and 123-bus test systems, respectively. The EVCSs on medium- and large... [more]

Various techniques are implemented to reduce odor emission due to their potential multi-source nature. One modern approach is the use of thermochemically processed biomass to eliminate odors. Compared with raw biomass, processed biomass is characterized by greater porosity and an expanded specific surface. In these laboratory experiments, adsorption tests for a mixture of indole, 2,3-dimethylpyrazine, and 2,3,5-trimethylpyrazine are carried out using torreficates produced from biomass from the agri-food industry (walnut shells, orange peels, peach stones, and apple wood chips). This research is focused on the determination of the correlation between the physical-hydraulic properties of the torreficates and their ability to reduce the odors simulated by the selected compounds. The results indicate that 2,3-dimethylpyrazine and 2,3,5-trimethylpyrazine are not detected in any of the investigated low-temperature biochars. However, indole is detected in most materials, and its most signific... [more]

The Kingdom of Saudi Arabia’s (KSA) microgrids must make significant progress during the next five years, since the Saudi government published the Saudi Vision 2030 and the National Transformation Program 2020. In order to implement renewable energy and microgrid technologies in the Saudi Electric Power System(EPS), King Abdullah City for Atomic and Renewable Energy (K.A.CARE) started developing an energy mix program in 2016. To achieve the intended goals, this program will unquestionably need to adhere to practical and technical criteria. In the past five years, the Saudi government has made significant investments in renewable energy technology. In order to keep up with the growth of microgrid systems globally, the Saudi Water and Electricity Regulatory Authority (WERA) is now working to update and define a standard for microgrids. The IEEE 2030 standard, which includes guidelines for understanding smart grid interoperability the integration of communication architectures and power s... [more]

Sustainability is a strategic approach to develop a more sustainable economy to support the environment and socio-economic development. Literature on sustainability has been concerned mainly with global warming and environmental degradation issues, whereas the Circular Economy (CE) concept has recently been suggested as an alternative solution to support market sustainability and deal with both environmental and socio-economic challenges. In order to tackle these challenges, countries must switch from linear economies that follow the “take-make-dispose” principle to circular and sustainable economies. This study applies a structural and conceptual literature review to elucidate the most decisive determinants in the formation of circular strategies, particularly in the context of the energy sector. This study examines obstacles that hinder CE adoption and formulates drivers and measures to overcome them. The strategic literature review shows that the circular approach is critical in ach... [more]

The presence of potentially toxic elements (PTEs) in soils can upset the natural balance and increase the risk of PTE incorporation into the food chain. The use of composite biochar with municipal sewage sludge compost (MSSC/C) can be an effective way of both managing waste, such as sewage sludge, and providing an effective additive-supporting phytostabilization processes. The effectiveness of D. glomerata and MSSC/C in the technique of assisted phytostabilization of industrially contaminated soils was determined under the pot experiment conditions. The PTE contents in D. glomerata and the soil were determined using the spectrophotometric method. The addition of MSSC/C to PTE-contaminated soil contributed to an 18% increase in plant biomass and increased the soil pH by 1.67 units, with the PTE concentration being higher in the roots than in the above-ground parts of D. glomerata. The MSSC/C addition had the strongest effect on the reduction in Cd, Cr, and Ni contents in the soil follow... [more]