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Latest Updates of Single-Junction Organic Solar Cells up to 20% Efficiency
Boudia Mohamed El Amine, Yi Zhou, Hongying Li, Qiuwang Wang, Jun Xi, Cunlu Zhao
May 24, 2023 (v1)
Keywords: bulk-heterojunction, organic solar cells, power conversion efficiency, ternary configuration
Single-junction organic solar cells have reached a power conversion efficiency of 20% with narrow bandgap non-fullerene electron acceptor materials such as Y6, as well as with large band gap electron donor materials and their derivatives. The power conversion efficiency improvement of single-junction organic solar cells is a result of highly efficient light harvesting in the near-infrared light range and reduced energy losses with the most promising active layer layout currently available, Bulk-Heterojunction. Ternary blending is known to be the most advanced strategy to construct Bulk-Heterojunction structures in organic solar cells at present. In this review, we examine different devices based on Bulk-Heterojunction structures with efficient electron donors and acceptors. Then, we review the performance of binary and ternary organic solar cells with high power conversion efficiency, in conjunction with different anode and cathode interfaces used in recent studies of high-power conver... [more]
Prospects of Controlled Auto-Ignition Based Thermal Propulsion Units for Modern Gasoline Vehicles
Abdullah U. Bajwa, Felix C. P. Leach, Martin H. Davy
May 24, 2023 (v1)
Keywords: advanced compression ignition, dedicated hybrid engines, gasoline compression ignition, HCCI, low temperature combustion
Gasoline engines employing the spatially distributed auto-ignition combustion mode, known as controlled auto-ignition (CAI), are a prospective technology for significantly improving engine efficiency and reducing emissions. This review paper provides an overview of developments in various gasoline CAI technologies and discusses their attendant strengths and weaknesses. Hybrid propulsion systems powered by high-efficiency gasoline CAI engines can provide a low-carbon pathway for mobility sector decarbonisation. Therefore, this paper focuses on the challenges and opportunities of CAI implementation, especially for electrified powertrains. Different control actuators that can extend the CAI operating range are discussed, and opportunities for synergistic operation between thermal and electric components of hybridised powertrains are identified. Such synergies can remove impediments in the way of CAI system adoption and can, thus, support CAI adoption and maximise efficiency gains from its... [more]
Gallium Nitride Power Devices in Power Electronics Applications: State of Art and Perspectives
Salvatore Musumeci, Vincenzo Barba
May 24, 2023 (v1)
Keywords: cascode, depletion mode, enhancement mode, GaN FET, HEMT, LIDAR, SiC MOSFET, super-junction MOSFET, WBG
High-electron-mobility transistors based on gallium nitride technology are the most recently developed power electronics devices involved in power electronics applications. This article critically overviews the advantages and drawbacks of these enhanced, wide-bandgap devices compared with the silicon and silicon carbide MOSFETs used in power converters. High-voltage and low-voltage device applications are discussed to indicate the most suitable area of use for these innovative power switches and to provide perspective for the future. A general survey on the applications of gallium nitride technology in DC-DC and DC-AC converters is carried out, considering the improvements and the issues expected for the higher switching transient speed achievable.
Assessment of Wind Speed Statistics in Samaria Region and Potential Energy Production
Sergei Kolesnik, Yossi Rabinovitz, Michael Byalsky, Asher Yahalom, Alon Kuperman
May 24, 2023 (v1)
Keywords: Rayleigh distribution, Weibull distribution, wind statistics assessment
Statistical characteristics of the wind speed in the Samaria region of Israel have been analyzed by processing 11 years of wind data provided by the Israeli Meteorological Service, recorded at a 10 m height above the ground. The cumulative mean wind speed at a measurement height was shown to be 4.53 m/s with a standard deviation of 2.32 m/s. The prevailing wind direction was shown to be characterized by a cumulative mean azimuth of 226° with a standard deviation of 79.76°. The results were extrapolated to a 70 m height in order to estimate wind characteristics at the hub height of a medium-scale wind turbine. Moreover, Weibull distribution parameters were calculated annually, monthly, and seasonally, demonstrating a good match with histogram-based statistical representations. The shape parameter of the Weibull distribution was shown to reside within a narrow range of 1.93 to 2.15, allowing us to assume a Rayleigh distribution, thus simplifying wind turbine energy yield calculations. Th... [more]
A Comparative Study of the Performance of Different Particle Models in Simulating Particle Charging and Burden Distribution in a Blast Furnace within the DEM Framework
Huaqing Ma, Xiuhao Xia, Lianyong Zhou, Chao Xu, Zihan Liu, Tao Song, Guobin Zou, Yanlei Liu, Ze Huang, Xiaoling Liao, Yongzhi Zhao
May 24, 2023 (v1)
Keywords: blast furnace, DEM, multi-sphere model, polyhedral model, super-ellipsoid model
There has been growing interest in applying the DEM (discrete element method) to study the charging and burden distribution in a BF (blast furnace). In practice, the real particles in a BF are non-spherical. However, spherical particles have mostly been used in previous DEM investigations. Furthermore, various particle models have been developed to describe non-spherical particles. However, the effects of using different particle models on particle behavior in a BF are still unclear. Therefore, a comparative study of how the particle shape model impacts the burden charging in a BF was conducted. Specifically, the DEM using a multi-sphere model, polyhedral model, and super-ellipsoid model was first established. Then, experiments and DEM simulations of the charging and burden distribution of non-spherical quartz sand particles in a lab-scale bell-less top BF were performed. The results indicated that the number of sub-spheres, the principle of creating the particle for multi-spheres, the... [more]
Research on Wake Field Characteristics and Support Structure Interference of Horizontal Axis Tidal Stream Turbine
Jiayan Zhou, Huijuan Guo, Yuan Zheng, Zhi Zhang, Cong Yuan, Bin Liu
May 24, 2023 (v1)
Keywords: Computational Fluid Dynamics, horizontal axis tidal stream turbine, support structure, turbine power coefficient, wake flow
The harnessing and utilization of tidal current energy have emerged as prominent topics in scientific inquiry, due to their vast untapped resource potential, leading to numerous investigations into the efficacy of hydrokinetic turbines under various operational conditions. This paper delineates the wake field characteristics and performance of horizontal axis tidal stream turbines under the influence of support structures, using a comprehensively blade-resolved computational fluid dynamics (CFDs) model that employs Reynolds-averaged Navier−Stokes (RANS) equations in combination with the RNG k-ε turbulence model. To achieve this, the study utilized experimental tank tests and numerical simulations to investigate the distribution characteristics and recuperative principles of the turbine’s wake field. The velocity distribution and energy augmentation coefficient of the wake field showed strong agreement with the experimental results. To further assess the effect of support structures on... [more]
Long-Term Self-Discharge Measurements and Modelling for Various Cell Types and Cell Potentials
Mohamed Azzam, Moritz Ehrensberger, Reinhard Scheuer, Christian Endisch, Meinert Lewerenz
May 24, 2023 (v1)
Keywords: 18650, anode overhang, filtering, float current analysis, graphite, LFP, Modelling, NCA, NMC, potentiostatic hold, self-discharge rate
Self-discharge of lithium-ion cells leads to voltage decay over time. In this work, the self-discharge was measured at 30 ∘C for three cell types at various voltage levels for about 150 days in a constant voltage mode determining the current at a high precision (float current). All cells exhibit a transient part leading to a steady-state, which is no longer influenced by reversible effects. To study the effect of the check-ups on the steady-state float current, the cells, interrupted and not interrupted by check-ups, were compared. The results indicate that both the transient processes and steady-state currents are highly reproducible. In the first period of the float current, the polarization dominates the measured current, followed by the anode overhang effect dominating the process for a period of 5−30 days. After the decline of both processes, a mostly constant steady-state in the order of μA is observed. The check-up interruption generally shows no apparent effect on the reached s... [more]
A Comprehensive Evaluation of Different Power Quantities in DC Electric Arc Furnace Power Supplies
Pegah Hamedani, Cristian Garcia, Jose Rodriguez
May 24, 2023 (v1)
Keywords: DC electric arc furnace, feeding system, harmonic distortion, power quality, total harmonic distortion, unbalance
Conventionally, DC arc furnaces are fed by thyristor rectifiers to control the level of current or power transferred to the load. With the advancement of high-power transistors, other structures such as diode rectifiers and DC choppers have been introduced and developed for the feeding system of DC electric arc furnaces. In this paper, the effect of different power supply systems on power quality indexes is discussed. In this regard, two types of feeding systems are considered, including a power supply system based on thyristor rectifiers and a power supply system based on diode rectifiers and DC choppers. In addition, different control methods, including constant current control (CCC) and constant power control (CPC), on DC electric arc furnaces are applied. For evaluating the power quality indexes, voltage and current harmonic distortion, unbalance of voltage and current, and power factor on the AC side are investigated for different power supply systems. Simulation results were perf... [more]
Feasibility Study of Scheme and Regenerator Parameters for Trinary Power Cycles
Vladimir Kindra, Igor Maksimov, Ivan Komarov, Cheng Xu, Tuantuan Xin
May 24, 2023 (v1)
Keywords: Brayton cycle, Carbon Dioxide, combined cycle power plant, efficiency, heat exchanger, Kalina cycle, organic Rankine cycle
Natural gas-fired combined cycle plants are nowadays one of the most efficient and environmentally friendly energy complexes. High energy efficiency and low specific emissions are achieved primarily due to the high average integral temperature of heat supply in the Brayton−Rankine cycle. In this case, the main sources of energy losses are heat losses in the condenser of the steam turbine plant and heat losses with the exhaust gases of the waste heat boiler. This work is related to the analysis of the thermodynamic and economic effects in the transition from binary to trinary cycles, in which, in addition to the gas and steam−water cycles, there is an additional cycle with a low-boiling coolant. A method for the feasibility study of a waste heat recovery unit for trinary plants is proposed. The schematic and design solutions described will ensure the increased energy and economic performance of combined cycle power plants. Based on the results of the thermodynamic optimization of the st... [more]
Possibilities and Limitations of Anaerobic Co-Digestion of Animal Manure—A Critical Review
Anna Jasińska, Anna Grosser, Erik Meers
May 24, 2023 (v1)
Keywords: anaerobic digestion, animal manure, biogas, co-digestion, methane, Renewable and Sustainable Energy
Anaerobic digestion is a well-known and long-used biological method for stabilizing organic materials. Among the benefits of this process in waste management are the reduction of greenhouse gases, the production of alternative energy, and the acquisition of valuable digestate that can be used in the form of biogas, thereby closing the cycle of elements in nature. For some materials, such as manure, which is heterogeneous in terms of morphology and chemical composition, digestion of a single substrate may not be very efficient. Therefore, more and more studies on the co-digestion process are appearing in the literature. This solution allows higher biogas production and the possibility of processing several wastes simultaneously. The prospect of the future effective application of anaerobic co-digestion depends on regulations, work regime, and access to raw materials. Therefore, there is a need to systematize the available knowledge and results, as well as to identify the possibilities a... [more]
Household Carbon Footprint Characteristics and Driving Factors: A Global Comparison Based on a Dynamic Input−Output Model
Xi Chen, Yingying Zhen, Zhanming Chen
May 24, 2023 (v1)
Subject: Environment
Keywords: household carbon footprint, household consumption expenditure, input–output model, LMDI method
Carbon emissions are rapidly increasing with continuing global economic development, necessitating an urgent energy revolution. Often, when calculating carbon footprint, analysts have failed to account for changes in capital stock and the impact of indirect emissions caused by the consumption of imported products. Furthermore, the homogenization of industrial and resident sectors has reduced our understanding of the specific driving forces behind carbon emissions. To avoid such locational and temporal biases, this study employs a dynamic input−output model to re-estimate the carbon footprint of only residents. We deconstruct residential emissions into different consumption categories and conduct a comparative analysis between developed and developing countries from across the world. To this end, data from 44 global economies were obtained from the World Input−Output Database for the period from 2000 to 2014. For developing countries, food consumption had the highest share of embodied c... [more]
Application of Leather Waste Fractions and Their Biochars as Organic Fertilisers for Ryegrass Growth: Agri-Environmental Aspects and Plants Response Modelling
Ksawery Kuligowski, Adam Cenian, Izabela Konkol, Lesław Świerczek, Katarzyna Chojnacka, Grzegorz Izydorczyk, Dawid Skrzypczak, Paulina Bandrów
May 24, 2023 (v1)
Subject: Environment
Keywords: agronomic effectiveness, biochar, nitrogen uptake, ryegrass growth, tanned leather waste
The automotive upholstery industry, which processes bovine leathers, has struggled with vast amounts of solid waste, of which the majority are fractions, such as shavings and splits and offcuts, both containing chromium (Cr) and free of Cr. In this work, a novel leather waste-to-fertiliser approach has been tested: four lightly processed (incubation with effective microorganisms) and three aggressively processed (using pyrolysis or hydrolysis processes) tanned leather waste fractions were used. They were applied as organic nitrogen-based fertilisers in two separate glasshouse experiments, consisting of four subsequent harvests, under spring−autumn conditions in northern Poland. The Cr stressing effect caused by bovine shavings containing Cr and splits and offcuts containing Cr stimulated an increase in ryegrass growth after 30 days, providing twice the dry matter yield than bovine shavings free of Cr and splits and offcuts free of Cr, then (after 90 and 120 days) it inhibited growth. T... [more]
Experimental Analysis and Simulation of Mixed Storage with Lithium-Ion Batteries and Supercapacitors for a PHEV
Leone Martellucci, Mirko Dell’Aria, Roberto Capata
May 24, 2023 (v1)
Keywords: hybrid storage, Li-ion batteries, mixed storage, PHEV vehicle, supercapacitors
This work focuses on the simulation and testing of an innovative storage system for a PHEV vehicle, investigating the possibility of replacing the car’s original storage system with a mixed-storage system with lithium-ion batteries and supercapacitors connected in direct parallel without the use of an intermediate DC/DC converter. The aim is to evaluate the behavior of the supercapacitors’ branch compared with that of the Li-ion cells, both in the discharge/charge transients and over an entire WLTP cycle (Worldwide harmonized Light vehicles Test Procedure). The analysis started with the definition of the digital models of a lithium cell and a supercapacitor. The parameters of the models were tuned through experimental characterization of the two storage cells, Li-ion and supercapacitor. Subsequently, the overall models of the branch with the lithium cells and the branch with the supercapacitors were constructed and connected. The overall storage system was sized for application to a PH... [more]
The Role of Direct Air Capture in EU’s Decarbonisation and Associated Carbon Intensity for Synthetic Fuels Production
Rocio Gonzalez Sanchez, Anatoli Chatzipanagi, Georgia Kakoulaki, Marco Buffi, Sandor Szabo
May 24, 2023 (v1)
Subject: Environment
Keywords: carbon footprint, decarbonisation, direct air capture, Hydrogen, Renewable and Sustainable Energy, Synthetic Fuels
Direct air capture (DAC) is considered one of the mitigation strategies in most of the future scenarios trying to limit global temperature to 1.5 °C. Given the high expectations placed on DAC for future decarbonisation, this study presents an extensive review of DAC technologies, exploring a number of techno-economic aspects, including an updated collection of the current and planned DAC projects around the world. A dedicated analysis focused on the production of synthetic methane, methanol, and diesel from DAC and electrolytic hydrogen in the European Union (EU) is also performed, where the carbon footprint is analysed for different scenarios and energy sources. The results show that the maximum grid carbon intensity to obtain negative emissions with DAC is estimated at 468 gCO2e/kWh, which is compliant with most of the EU countries’ current grid mix. Using only photovoltaics (PV) and wind, negative emissions of at least −0.81 tCO2e/tCO2 captured can be achieved. The maximum grid inte... [more]
A Modeling Framework to Develop Materials with Improved Noise and Vibration Performance for Electric Vehicles
Seyed Jamaleddin Mostafavi Yazdi, Seongchan Pack, Foroogh Rouhollahi, Javad Baqersad
May 24, 2023 (v1)
Subject: Materials
Keywords: damping, electric vehicles, finite element analysis, lightweight, NVH, vibration
The automotive and aerospace industries increasingly use lightweight materials to improve performance while reducing fuel consumption. Lightweight materials are frequently used in electric vehicles (EVs). However, using these materials can increase airborne and structure-borne noise. Furthermore, EV noise occurs at high frequencies, and conventional materials have small damping. Thus, there is an increasing need for procedures that help design new materials and coatings to reduce the transferred and radiated noise at desired frequencies. This study pioneered new techniques for microstructure modeling of coated and uncoated materials with improved noise, vibration, and harshness (NVH) performance. This work uses the microstructure of materials to study their vibration-damping capacity. Images from an environmental scanning electron microscope (ESEM) show the microstructure of a sample polymer and its coating. Tensile tests and experimental modal analysis were used to obtain the material... [more]
Temporal Stability of Attitudes towards Climate Change and Willingness to Pay for the Emissions Reduction Options in Queensland, Australia
Galina Williams
May 24, 2023 (v1)
Subject: Energy Policy
Keywords: attitudes, climate change, contingent valuation, emissions reduction, Queensland, temporal stability, willingness to pay
Citizens’ attitudes towards and their perceptions of climate change are widely believed to influence citizens’ actions related to climate change. Knowledge of these attitudes and willingness to pay (WTP) for environmental improvement can be useful in designing an environmental policy. Although citizens’ attitudes and perceptions are likely to affect their WTP, they are rarely included in the non-market valuation. Furthermore, over time, attitudes and perceptions of environmental issues are likely to change. An understanding of temporal stability of attitudes towards climate change could shed the light on changes in citizens’ WTP for environmental quality over time. This study examined changes in perceptions, attitudes, and actions towards climate change using two surveys in Queensland, Australia. The surveys were administered 10 years apart (2009 and 2018). The effect of attitudes over time on WTP was analysed using a contingent valuation (CV) method. The results confirmed that attitud... [more]
Influence of Changes in Stiffness and Damping of Tyre Wheels on the Outcome of the Condition Assessment of Motor Vehicle Shock Absorbers
Andrzej Zuska, Jerzy Jackowski
May 24, 2023 (v1)
Keywords: shock absorber tests, tire energy properties, tire radial stiffness, tired wheel, vehicle dynamics control, vehicle testing and diagnostics
This article deals with the influence of the elastic-damping properties (energy losses) of tired wheels on the results of the evaluation of the technical condition (dynamic properties) of automotive suspensions carried out on the diagnostic line. The purpose of this paper is to point out the inadequacies of test stands for assessing the technical condition of vehicle suspensions. The diagnostic line used in the testing featured two testing stations. The test object was a passenger car with hydro-pneumatic suspension. This enabled the conducting of suspension tests for two settings (comfort and dynamic positions). The tests were conducted for four different air pressures in the tyres of tired wheels. This made it possible to determine, for each wheel, four graphs of the load versus tyre deflection (radial stiffness characteristics). These graphs were used to determine the values of the stiffness coefficients, energy loss, and damping characteristics as well as to identify the correlatio... [more]
The Design and Processor-In-The-Loop Implementation of a Super-Twisting Control Algorithm Based on a Luenberger Observer for a Seamless Transition between Grid-Connected and Stand-Alone Modes in Microgrids
Ali Aillane, Karim Dahech, Larbi Chrifi-Alaoui, Aissa Chouder, Tarak Damak, Abdelhak Hadjkaddour, Pascal Bussy
May 24, 2023 (v1)
Keywords: digital Luenberger observer, grid-connected mode, islanding mode, microgrid, processor-in-the loop (PIL), smooth transition, super-twisting sliding mode controller
The abrupt transfer from grid-connected (GC) to stand-alone (SA) operation modes is one of the major issues that may threaten the stability of a distributed generation (DG) system. Furthermore, if the islanding mode happens, it is vital to take into consideration the load voltages or load current waveforms as soon as feasible. This paper develops an advanced control technique based on a super-twisting sliding mode controller (ST-SMC) for a three-phase inverter operating in both the GC and SA modes. This control scheme is proposed to ensure a smooth transition from the GC to SA mode and enhance the load voltage waveforms under the islanding mode. In addition, to minimize the operational costs of the system and the complexity of the studied model, a digital Luenberger observer (DLO) with a proper design is adopted for estimating the inverter-side current. The control scheme of the whole system switches between a current control mode during the GC mode and a voltage control mode during th... [more]
Experimental Study on Spray Cooling Heat Transfer of LN2 for a Large Area
Jinhong Zhao, Yanming Guo, Qing Ai, Jiaming Gong, Yong Shuai
May 24, 2023 (v1)
Keywords: liquid-nitrogen, micro-grooved surface, porous surface, spray cooling, temperature control
Spray cooling has been considered one of the most promising thermal control methods of high-heat flux devices. Most of the spray cooling research focuses on electronic components as the main application object to achieve higher heat dissipation heat flow in ambient temperature regions for small areas. Water is the most common cooling medium. This paper investigates the application of spray cooling thermal control over large areas. In this study, the heat-transfer characteristics of liquid nitrogen (LN2) for large areas was investigated by conducting experiments. The test surface is 500 mm × 500 mm, which was cooled by a nine-nozzle array. The spray nozzles used in the experiment were conical nozzles with an orifice diameter of 1.6 mm, a spray angle of 120°, and a spray height of 42 mm. Liquid nitrogen was forcefully ejected from nozzles by the high pressure of a liquid storage tank to cool the test surface. According to the cooled surfaces, spray directions, and spray pressures, three... [more]
Using Artificial Neural Networks to Gather Intelligence on a Fully Operational Heat Pump System in an Existing Building Cluster
Fredrik Skaug Fadnes, Reyhaneh Banihabib, Mohsen Assadi
May 24, 2023 (v1)
Keywords: artificial neural network (ANN), coefficient of performance (COP), monitoring and fault detection, operational data, sewage heat pump
The use of heat pumps for heating and cooling of buildings is increasing, offering an efficient and eco-friendly thermal energy supply. However, their complexity and system integration require attention to detail, and minor design or operational errors can significantly impact a project’s success. Therefore, it is essential to have a thorough understanding of the system’s intricacies and demands, specifically detailed system knowledge and precise models. In this article, we propose a method using artificial neural networks to develop heat pump models from measured data. The investigation focuses on an operational heat pump plant for heating and cooling a cluster of municipal buildings in Stavanger, Norway. The work showcases that the network configurations can provide process insights and knowledge when detailed system information is unavailable. Model A predicts the heat pump response to temperature setpoint and inlet conditions. Except for some challenges during low-demand cooling mo... [more]
Quasi-Resonant Single-Switch High-Voltage-Gain DC-DC Converter with Coupled Inductor and Voltage Multiplier Cell
Giordano Luigi Schiavon, Eloi Agostini Jr, Claudinor Bitencourt Nascimento
May 24, 2023 (v1)
Keywords: coupled inductor, DC–DC converter, high voltage gain, voltage multiplier cell
This paper introduces a quasi-resonant high-efficiency high-step-up DC−DC converter requiring a reduced number of components. The proposed circuit uses a coupled inductor associated with voltage multiplier cells to ensure high-voltage-gain operation without the necessity of an extremely high number of turns ratio. Quasi-resonant operation guarantees zero current switching (ZCS) for some diodes of the converter. A detailed steady-state analysis is carried out aiming at the adequate design of the circuit. Experimental results taken from the testing of a 400 W prototype operating in closed loop with an input voltage range of 25−48 V, output voltage of 400 V and switching frequency of 100 kHz validate the analysis carried out and demonstrate the feasibility of the proposed converter.
Bioprocessing of Waste for Renewable Chemicals and Fuels to Promote Bioeconomy
Gayathri Priya Iragavarapu, Syed Shahed Imam, Omprakash Sarkar, Srinivasula Venkata Mohan, Young-Cheol Chang, Motakatla Venkateswar Reddy, Sang-Hyoun Kim, Naresh Kumar Amradi
May 24, 2023 (v1)
Keywords: biohydrogen, biomethane, organic waste, volatile fatty acids, waste biorefinery
The world’s rising energy needs, and the depletion of fossil resources demand a shift from fossil-based feedstocks to organic waste to develop a competitive, resource-efficient, and low-carbon sustainable economy in the long run. It is well known that the production of fuels and chemicals via chemical routes is advantageous because it is a well-established technology with low production costs. However, the use of toxic/environmentally harmful and expensive catalysts generates toxic intermediates, making the process unsustainable. Alternatively, utilization of renewable resources for bioprocessing with a multi-product approach that aligns novel integration improves resource utilization and contributes to the “green economy”. The present review discusses organic waste bioprocessing through the anaerobic fermentation (AF) process to produce biohydrogen (H2), biomethane (CH4), volatile fatty acids (VFAs) and medium chain fatty acids (MCFA). Furthermore, the roles of photosynthetic bacteria... [more]
CO2 Adsorption Performance of Activated Coke Prepared from Biomass and Coal
He Gao, Shaohua Wang, Miaomiao Hao, Wei Shao, Shuhui Zhang, Lei Zhang, Xiaohan Ren
May 24, 2023 (v1)
Keywords: activation, active coke, Adsorption, Carbon Dioxide, nitrogen-containing functional groups
CO2 adsorption is one of the promising CCS technologies, and activated coke is a solid adsorbent with excellent adsorption properties. In this study, activated coke was prepared by using bituminous coal and coconut shells activated with KOH or CaCl2 in a physically activated atmosphere and modified with ammonia. The effect of the active agent impregnation ratio on the physicochemical properties of activated coke was investigated by N2 adsorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The CO2 adsorption performance of activated coke was tested, and the effect of nitrogen-containing functional groups on CO2 adsorption was investigated by experiments and simulations. The results showed that the specific surface area of activated coke reached 629.81 m2/g at a KOH impregnation ratio of 0.5 and 610.66 m2/g at a CaCl2 impregnation ratio of 1. The maximum CO2 adsorption capacity of activated coke reached 71.70 mg/g and 90.99 mg/g for c... [more]
Carnot Battery Based on Brayton Supercritical CO2 Thermal Machines Using Concentrated Solar Thermal Energy as a Low-Temperature Source
José Ignacio Linares, Arturo Martín-Colino, Eva Arenas, María José Montes, Alexis Cantizano, José Rubén Pérez-Domínguez
May 24, 2023 (v1)
Keywords: Brayton supercritical CO2 thermodynamic cycle, Carnot batteries, high-temperature heat pump, pumped thermal energy storage, renewable energies dispatchability, thermal energy storage
Carnot batteries store surplus power as heat. They consist of a heat pump, which upgrades a low-temperature thermal energy storage, a high-temperature storage system for the upgraded thermal energy, and a heat engine that converts the stored high-temperature thermal energy into power. A Carnot battery is proposed based on supercritical CO2 Brayton thermodynamic cycles. The low-temperature storage is a two-tank molten salt system at 380 °C/290 °C fed by a field of parabolic trough collectors. The high-temperature storage consists of another two-tank molten salt system at 589 °C/405 °C. Printed circuit heat exchangers would be required to withstand the high pressure of the cycles, but shell and tube heat exchangers are proposed instead to avoid clogging issues with molten salts. The conventional allocation of high-temperature molten salt heat exchangers is then modified. Using solar energy to enhance the low-temperature thermal source allowed a round-trip efficiency of 1.15 (COP of 2.46... [more]
Energy-Saving Control for Asynchronous Motor Motion System Based on Direct Torque Regulator
Stanimir Valtchev, Viktor Meshcheryakov, Elena Gracheva, Alexey Sinyukov, Tatyana Sinyukova
May 24, 2023 (v1)
Keywords: alternating current, asynchronous motor, direct torque control, frequency control, squirrel-cage rotor
Energy saving issues occupy a leading position in all control systems. This article provides a detailed analysis of control systems and is conducted by considering the complexity of implementation and response to the control action. The implementation of energy-saving control systems is directly related to the selected control system and the proposed energy-efficient algorithm. A system with direct torque control is proposed, which provides energy savings in the mechanisms for moving goods. A detailed analysis of the implementation of systems with direct torque control is carried out. New methods to save energy in the control system by minimizing the stator current have been proposed.
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