The performance of a heat exchanger is directly related to the energy conversion efficiency of the thermal storage system, and its optimal design is an important method to improve the performance of the heat exchanger. This paper uses the distributed parameter method to analyze the effect of the structural parameters and operating parameters of a heat exchanger on the entransy dissipation rate, the entransy dissipation number, the entransy dissipation heat resistance, entropy production rate, and entropy production number in a molten salt−supercritical CO2 concentric tube heat exchanger. The results show that the entransy dissipation rate and entropy production rate have the same trend, with the structural parameters and operating parameters, as well as the changes in the entransy dissipation number and entransy dissipation thermal resistance, jointly affected by the entransy dissipation rate and the heat exchange. Based on the above indicators, single-objective and multi-objective opt... [more]

Based on extremely uneven temperature distribution along the insulated gate bipolar transistor (IGBT) chip vertical path during switching transients, a short-duration transient microsecond-scale prediction model applicable to multi-timescale simulation is presented in this paper. Traditional thermal models often take the chip active area as a uniform heat source to obtain a victual junction temperature (Tvj). In this paper, a discrete distributed heat source model combined with a thermal network model based on the sublayer division strategy is proposed to achieve an accurate temperature distribution description along the chip vertical path. Taking a 1700 V/3600 A IGBT module as an example, the proposed model can evaluate the short-duration transient temperature distribution along the chip vertical path and the error is less than 2 °C compared with the finite element model. Meanwhile, the model is applied to a single short-duration transient timescale and multi-timescale systems separat... [more]

To improve the low aerodynamic efficiency and reduce the high energy consumption of a single-stage circulation control wing, a multistage circulation control wing was designed. By combining force measurement and particle image velocimetry (PIV), the aerodynamic and flow-field characteristics of an aerofoil were investigated with respect to the increase in the number of blowing slots, changes in the blowing coefficient, and different blowing ratios for three slots. The force measurement results revealed that the maximum lift-to-drag ratio resulting from simultaneous blowing into the three slots increased by 95.3% compared with that in the absence of circulation control. With an increase in the blowing coefficient, two stages were observed: separation control and supercirculation control. In the separation control stage, the lift and drag coefficients significantly increased and decreased, respectively. In the supercirculation control stage, the lift coefficient gradually increased with... [more]

Solar energy coupling with energy storage is a popular technology in the energy field. How to achieve the high-efficiency application of solar energy is very important. Energy storage technology is the key issue in this aspect. Latent heat storage is a more efficient energy storage. In this paper, a visualization experimental platform of a latent heat storage system has been designed, and some performance data have been obtained. Hot water has been used as the heat transfer fluid, and paraffin wax has been used as the phase change material. The inclination angle of the tank is varied from the horizontal direction (0°) to the vertical direction (90°) by a step of 30°. The melting performance has been studied for three cases with inlet water temperature of 356 K, 361 K, and 366 K. The result shows that the inclination angle of the tank has a great influence on the melting process of the phase change material, and the temperature distribution of the material is obviously different. The re... [more]

Under active icing conditions, the heat transfer performance of the CPHE has a significant impact on the system’s efficiency and energy consumption. Using the enthalpy-porosity method for describing the solidification process of liquids, the simulation and analysis of the effects of different parameter changes on the CPHE heat transfer performance were conducted to clarify the effects of the changes in the intermediary side inlet water temperature, intermediate water flow rate, and cold water flow rate on the heat transfer process in the CPHE. According to our results, changing the intermediary inlet water temperature has a greater impact on the heat transfer process in the cold-water phase-change heat exchangers. For every decrease of 0.5 °C in the intermediary side inlet water temperature, the average heat transfer coefficient increases by approximately 50 W/m2-K. Changes in the intermediary water flow rate affect the cold water phase-change heat exchanger’s heat transfer process. By... [more]

The application of batteries has become more and more extensive, and the heat dissipation problem cannot be ignored. Oscillating Heat Pipe (OHP) is a good means of heat dissipation. In this paper, the methods to improve the energy conversion and flow thermal performance of micro-channel OHP are studied and summarized. The working principle, heat transfer mechanism, advantages and applications of PHP are also introduced in detail in this study. Proper adjustment of the micro-channel layout can increase the heat transfer limit of PHP by 44%. The thermal resistance of two-diameter channel PHP is 45% lower than that of conventional PHP. The thermal resistance of PHP under uneven heating can be reduced to 50% of the original. PHP pulse heating can alleviate the phenomenon of dryness. Different working fluids have different effects on PHP. The use of graphene nano-fluids as the work medium can reduce the thermal resistance of PHP by 83.6%. The work medium obtained by the mixture of different... [more]

The need for improved energy security in Nigeria cannot be over-emphasized. Currently, energy security is rather poor, while access to energy is fundamental to socio-economic development and poverty alleviation. Renewable energy could potentially contribute to resolving this because renewable sources such as solar radiation are more available and sustainable, and can be set up in small generation units, meaning that it is suitable for community management and ownership. In theory, a community energy approach could well apply. In this paper, the main research question is: In what ways can community energy initiatives contribute to increasing the use of renewable energy sources and improving energy security in Nigeria according to selected stakeholders and households? A mixed methods research approach was used to answer this question, with stakeholder interviews and survey data from 124 residents in two case studies of selected housing estates in Lagos. The results show that 58% of the h... [more]

Active Buildings that allow users to adjust their demands on the grid to the needs of the energy system could greatly assist the transition to net zero, but will not be widely adopted unless the businesses involved can make money from doing so. We describe the construction, flexibility and information supply chains of activities needed to make these buildings work. Drawing on the results of an expert workshop, we set out four possible business models deserving further investigation. Developers may find it profitable to build or upgrade energy-efficient buildings with the monitoring and control equipment needed to adjust demand and energy storage as required, selling them soon after completion. Aggregators monitor the state of the building and communicate with the energy system to adjust the building’s demand while maintaining comfort levels, in return for suitable payments. Energy service companies may sell energy-as-a-service and own the equipment instead of a consumer who wishes to m... [more]

This paper is an experimental characterization of a light-receiving module containing a fly-eye lens system with high tolerance to beam irradiation conditions. The fly-eye lens system, which is tolerant to fluctuations in beam shape, beam size, number of beams, beam incident position, and beam incident direction, was proposed, a light receiver module with a fly-eye lens system was constructed, and its characteristics were evaluated. The effect of the beam size on the fly-eye lens system was evaluated and the tolerance to misalignment of beam incident position was measured. When a GaAs solar cell was irradiated with a laser beam of 450 nm wavelength and 6 W light output through a 90 cm long water tank with tap water, a maximum output of 0.755 W was obtained as underwater OWPT. In addition, a fly-eye lens system with mirrors applied to four surfaces was proposed and fabricated as a light-receiving side module that can receive high incident angles from any direction of up, down, left, and... [more]

The steam generator (SG) is a critical component of the steam supply system in the nuclear power plant (NPP). Hence, it is necessary to control the SG level well to ensure the stable operation of the NPPs. However, its dynamic level response process has significant nonlinearity (such as the ‘swell and shrinks’ effect) and time-varying properties. As most of the SG level control systems (SGLCS) are constructed based on the Proportional-Integral-Derivative (PID) controllers with fixed parameters, the controller parameters should be optimized to improve the performance of the SGLCS. However, traditional parameters tuning methods are generally experience-based, cumbersome, and time-consuming, and it is difficult to obtain the optimal parameters. To address the challenge, this study adopts a knowledge-informed simultaneous perturbation stochastic approximation (IK-SPSA) based on adjacent iteration points information to improve the performance of the SGLCS. Rather than the traditional contro... [more]

Sustainable public transport is an important factor to boost urban economic development, and it is also an important part of building a low-carbon environmental society. The application of driverless technology in public transport injects new impetus into its sustainable development. Road traffic sign recognition is the key technology of driverless public transport. It is particularly important to adopt innovative algorithms to optimize the accuracy of traffic sign recognition and build sustainable public transport. Therefore, this paper proposes a convolutional neural network (CNN) based on k-means to optimize the accuracy of traffic sign recognition, and it proposes a sparse maximum CNN to identify difficult traffic signs through hierarchical classification. In the rough classification stage, k-means CNN is used to extract features, and improved support vector machine (SVM) is used for classification. Then, in the fine classification stage, sparse maximum CNN is used for classificati... [more]

A unified active power control scheme is devised for the grid-integrated permanent magnet synchronous generator-based wind power system (WPS) to follow the Indian electricity grid code requirements. The objective of this paper is to propose control schemes to ensure the continuous integration of WPS into the grid even during a higher percentage of voltage dip. In this context, primarily a constructive reactive power reference is formulated to raise and equalize the point of common coupling (PCC) potential during symmetrical and asymmetrical faults, respectively. A simple active power reference is also proposed to inject a consistent percentage of generated power even during faults without violating system ratings. Eventually, the efficacy of the proposed scheme is demonstrated in terms of PCC voltage enhancement, DC-link potential, grid real, and reactive power oscillation minimization using the PSCAD/ EMTDC software.

Within the policy framework of the energy union strategy started in 2015, the European Union (EU) finalized the “Clean Energy for all Europeans Package” (CEP) in 2019 [...]

Before selecting a proper hydraulic turbine for power generation, conflicting factors frequently emerge from the wide range of available technology alternatives. The preliminary selection of hydraulic turbines (PSHT) has been usually carried out by overlooking and/or overshadowing downstream and upstream processes. The development of a new conceptual framework that allows for including more parameters into the decision-making process at company levels is still required to avoid the danger of engaging in a one-dimensional approach, which would not only result in a reduced and simplistic vision of the choice but would also overlook the trade-offs between individual aspects and the possible unintended side-effects. This paper aims to provide empirical evidence for the PSHT by proposing a well-thought-out framework based on a mixed methodology approach (analytical hierarchy process (AHP) and fuzzy-VIKOR multi-criteria methods) and focused on small hydropower projects. A total of 16 criteri... [more]

The major challenges in sustainable and profitable agriculture are developing high-yielding crop varieties and reducing crop losses. Presently, there are significant crop losses due to weed/bird/insect/animal attacks. Among the various renewable energy sources, solar energy is utilized for different agricultural operations, especially in plant protection applications. Solar photovoltaic (PV) devices present a positive approach to sustainable crop production by reducing crop loss in various ways. This might result in the extensive use of PV devices in the near future. PV-based plant protection equipment/devices are primarily utilized in protecting crops from birds, weeds, or insects. Solar-powered plant protection equipment such as light traps, bird scarers, sprayers, weeders, and fencing are gaining interest due to their lower operational costs, simple design, no fuel requirements, and zero carbon emissions. Most of these PV devices require 12 V rechargeable batteries with different cu... [more]

In recent decades, expansion in urban areas has faced issues such as management of public waste, noise, mobility, and air quality, among others. In this scenario, Internet of Things (IoT) and Wireless Sensor Network (WSN) scenarios are being considered for Smart Cities solutions based on the deployment of wireless remote sensor nodes to monitor large urban areas. However, as the number of nodes increases, the amount of data to be routed increases significantly as well, meaning that the choice of the data routing process has great importance in terms of the energy consumption and lifetime of the network. In this work, we describe and evaluate the energy consumption of routing protocols for WSN-based Smart Cities applications in LoRa-based mesh networks, then propose a novel energy-saving radio power adjustment (RPA) routing protocol. The Cupcarbon network simulator was used to evaluate the performance of different routing protocols in terms of their data package delivery rate, average e... [more]

The share of energy produced by small-scale renewable energy sources, including photovoltaic panels and wind turbines, will significantly increase in the near future. These systems will be integrated in microgrids to strengthen the independence of energy consumers. This work deals with energy management in microgrids, taking into account the volatile nature of renewable energy sources. In the developed approach, Multi-Agent Reinforcement Learning is applied, where agents represent microgrid components. The individual agents are trained to make good decisions with respect to adapting to the energy load in the grid. Training of agents leverages the historic energy profile data for energy consumption and renewable energy production. The implemented energy management simulation shows good performance and balances the energy flows. The quantitative performance evaluation includes comparisons with the exact solutions from a linear program. The computational results demonstrate good generalis... [more]

Despite the fact that in the mass consciousness nuclear power is associated with increased environmental risks, this type of energy today remains one of the cleanest, most efficient and carbon neutral. Further development of nuclear energy is hampered by the problem of appropriate handling of spent nuclear fuel (SNF). A very attractive concept of the closed nuclear cycle has been developed to solve it. A real-life implementation of this concept requires the development of technological processes for the efficient separation of minor actinides from the rest of the SNF components. Recent progress in this area has been closely associated with N,O-hybrid donor ligands for liquid−liquid extraction. This work systematically reviews the available literature on the topic and provides detailed explanations on the behavior of the most perspective ligands. Notably, another important aspect of the application of N,O-hybrid donor ligands in nuclear cycle analytics through their incorporation in che... [more]

The superparamagnetic Fe3O4 nanoparticles as an absorbent with a size distribution of 4.8−6.4 nm were synthesized using a simple one-pot hydrothermal strategy at 200 °C for 24 h, where iron citrate and distilled were the sum total of raw materials. The as-synthesized Fe3O4 powders showed rapid and efficient adsorption for xylenol orange with a saturated adsorption amount of 42.5 mg/g according to Langmuir linear fitting, and the adsorption reaction between xylenol orange adsorbate and Fe3O4 adsorbent was mostly completed within 10 min. The Fe3O4 nanoparticles not only had superparamagnetism with a saturation magnetization value of 54.9 emu/g at 15 kOe but also possessed strong magnetic response, making them easy to separate easily from aqoeous solution under the attraction of magnet. In this work, the Fe3O4 particles can be totally attracted toward the magnet within 15 s, leaving the suspension a clear solution.

This paper studies the multi-level supply chain network equilibrium optimization problem of multi-energy-efficiency products under different government subsidies and demand scales. In the equilibrium optimization problem, manufacturers determine the production volume of the energy-saving products; retailers decide the transaction volume with manufacturers, distribution volume for markets, and marketing efforts of energy-saving products; markets determine the transaction price. Firstly, the optimal decision-making behaviors of manufacturers, retailers, and markets are described. Simultaneously, the global optimization problem is transformed into a finite-dimensional variational inequality formulation. Then, the equilibrium conditions of the whole supply chain network are derived by the Euler method. Finally, a case study verifies the effectiveness of the proposed method. Interestingly, we found that energy-saving subsidies and demand scales were negatively correlated with the marketing... [more]

The central North China Plain (NCP) is one of the rapidly developing regions in China which has a great potential for ground source heat pump (GSHP) system applications. However, the ground thermal property, which is a prerequisite for GSHP system design, has been insufficiently investigated. In this paper, the ground thermal conditions including ground temperature and thermal conductivity are characterized in three representative hydrogeological regions in the NCP area: the piedmont alluvial plain, the central alluvial plain, and the coastal plain. Results show that the geothermal gradient below 40 m in depth in this area ranges from 0.018 °C/m to 0.029 °C/m. Although the thermal conductivity measured by soil samples differs slightly among the three regions, parameters in the piedmont plain have a larger variability than in the central and coastal plain due to the significant heterogeneity of the lithology. Thermal conductivity measured by the thermal response test (TRT) ranges betwee... [more]

With rising electricity demand, heavy reliance on imports, and recent economic downturns due to the negative impact of the COVID-19 pandemic, supply chain bottlenecks, and the Russian invasion of Ukraine, Thailand is suffering severely from energy resilience risks. The government has therefore set a goal of decentralizing energy production through small-scale distributed renewable energy systems. To support their design and the planning process, we simulate multiple scenarios with wind turbines, photovoltaic systems, and battery storage for a model community in rural Nakhon Phanom, Thailand. Using the software NESSI4D, we evaluate and discuss their impact on energy resilience by considering environmental sustainability, economic attractiveness, and independence from the central power grid. To fill the gap of missing data on energy demand, we synthesize high-resolution load profiles from the Thailand Vietnam Socio-Economic Panel. We conclude that distributed photovoltaic systems with ad... [more]

The evolution of fracture zone controls the safety of underground coal gasification (UCG) in terms of gas emission and water leakage. In order to understand the fracture propagation in the confining rock of a UCG cavity with various influence factors, this paper implemented a set of numerical models based on different geological and operating conditions. Analysis was implemented on the mechanism of fracture propagation and its evolution characteristics, suggesting that (a) continuum expansion of the cavity leads a near-field fracture circle in confining rock initially, followed by the roof caving and successive propagation of shear band. (b) The key observed influence factors of fracture propagation are the grade of confining rock, overburden pressure, dimension of the cavity and gasifying pressure, the linear relationships between them, and the fracture height. Additionally, the fracture depth in the base board was mainly caused by tensile fracture. (c) A model was proposed based on t... [more]

Different types of partial discharge (PD) in gas-insulated switchgear (GIS) cause different damage to GIS insulation, correctly identifying the PD type is very important for evaluating the insulation status of GIS. This paper proposes a PD pattern recognition method based on an improved feature fusion convolutional neural network (IFCNN) to fully use the time-frequency features of PD pulses to realize PD pattern recognition. Firstly, the one-dimensional time-domain feature sequence of the PD pulse and the corresponding wavelet time-frequency diagram are applied as inputs. Secondly, the convolutional neural network (CNN) with two parallel channels is used for feature extraction, the extracted fault information is fused, and the shallow features of the wavelet time-frequency diagram are fused to prevent feature loss caused by pooling operation. Finally, the extracted features are sent to the classifier to recognize different types of PD. The discharge data of different types of PD are ob... [more]

Methods for obtaining efficient sorption materials based on highly porous melamine and polyurethane matrices modified with reduced graphene oxide were developed. These materials are promising for solving environmental problems such as water pollution with organic products by sorption treatment. Reduced graphene oxides (rGOs) were synthesized from graphene oxide suspensions using potassium hydroxide, ascorbic acid or hydrazine hydrate. Composites with obtained rGO and melamine and polyurethane foam were produced for further characterization. The composites demonstrate high sorption of organic pollutants (oil, diesel fuel and gasoline) and low sorption of water. The composites were comprehensively analyzed by physicochemical techniques (SEM, XPS, Raman spectroscopy, UV−Vis) to elucidate the mechanism of sorption.