High Efficiency Energy Conversion System Research Articles

ODF-based model considering compressive stress for modeling the magnetic properties of Grain-oriented electrical steels

Grain-oriented electrical steels (GOES) are widely used in the manufacturing of high efficiency energy conversion systems thanks to their excellent magnetic properties along the rolling direction. Nevertheless, on the one hand, GOES exhibit strong magnetic anisotropy, resulting in distinct magnetic properties regarding the direction of the applied magnetic field to the rolling direction. On the other hand, GOES undergoes changes in their magnetic properties due to the industrial manufacturing process and mechanical constraints during operation. In general, stress, and particularly compressive stress, deteriorates magnetic properties. This paper deals with the modeling of the magnetic behavior of GOES under compressive stress. The orientation distribution function (ODF) based approach recently applied to describe the B-H first magnetization curves of a conventional GOES without stress as well as under applied uniaxial mechanical tensile stress is extended to account for the effect of compressive stress, with different considerations of modeling. The magnetic properties and the sensitivity of the ODF-based model to the magnetization direction as well as to the applied compressive stress are analyzed. Oscillation issues inherent to the ODF-based model are also discussed.

Comparative analysis on high-efficiency energy conversion system with different working mediums matched with small lead-cooled fast reactor

Nuclear energy is developing toward miniaturization, high security, and efficiency. A new compact and high-efficiency energy conversion system is being developed to match the integrated and natural-circulated lead-cooled fast reactor. This energy conversion system uses a closed Brayton cycle instead of a steam Rankine cycle for its high thermoelectric conversion efficiency and simple and compact cycle arrangement. A recompression cycle is adopted to solve the heat exchanger pinch point problem while maintaining a relatively simple and compact cycle arrangement. Many mediums are used in the various Brayton cycles, including carbon dioxide (CO2), air, nitrogen, and helium, for which qualitative, but rare quantitative, assessments have been performed. In this study, systematical analysis and quantitative comparison are performed. The efficiency of the system is investigated using various typical working mediums at various split and compression ratios within the parameters of the system. According to various comparisons, the highest system conversion efficiency of CO2 in recompression Brayton cycles is 39.36% within the working temperature range of 15–560 °C under three pressure conditions (8 MPa, 13 MPa, 20 MPa), while the efficiencies of air, nitrogen, and helium are only 32.74%, 32.77%, and 32.48%, respectively. However, the efficiency of these last three working mediums will be higher under the optimal conditions of a simple Brayton cycle, which are 32.97%, 33.22%, and 33.59%, respectively. Finally, this paper proposes an energy conversion system scheme for a lead-cooled fast reactor with supercritical carbon dioxide (S–CO2) as the working fluid, a compression ratio of 2.5, a split ratio of 0.65, a maximum temperature of 560 °C, a maximum pressure of 20 MPa, and a system efficiency of 39.36%.

Hybrid Si/SiC Switches: A Review of Control Objectives, Gate Driving Approaches and Packaging Solutions

Hybrid silicon (Si)/silicon carbide (SiC) switches are gaining increased attention for designing high-efficiency and high-power density energy conversion systems. They offer very good conduction and switching power loss performance compared to using only Si insulated gate bipolar transistor (IGBT) or SiC metal–oxide–semiconductor field effect transistor (MOSFET) devices as a result of combining the best properties of both devices. Several Si/SiC gate control strategies, gate driving approaches, and packaging considerations have been proposed in the literature. This article presents a comprehensive review and performance comparison of different Si/SiC gate control strategies, gate driver solutions, and packaging approaches that are already proposed in the literature. In addition, it aims to provide a general guideline for selecting the appropriate Si/SiC gate control approach that is suitable for different applications considering several Si/SiC switch design properties. It also aims to establish a general metrics for evaluating the performance of different Si/SiC gate driver solutions that are proposed in the literature in order to help the designer choose a suitable gate driver solution for different applications. Moreover, it highlights future research and development needs of hybrid Si/SiC switches in terms of gate control techniques, gate driver approaches, and packaging solutions in order to achieve further performance improvements and fully exploit their benefits.

Design of a high-efficiency electrolytic energy conversion system based on equilibrium analysis of electric-field and flow-field through simulation and experiments

In the context of sudden changes in global energy supply patterns, promoting the diversification of energy supply is an important movement for the sustainable development of the economy. Nuclear energy as a green and clean energy source has undergone rapid development. About 60 wt% of the world's fluorine production is used to produce uranium, a fuel for nuclear power plants. However, fluorine as a necessary raw material facing the challenges of high energy consumption and short lifespan of the electrolysis system. To overcome these drawbacks, this study aims to develop a high-efficiency electrolytic energy conversion system. Therefore, to optimize the design of the electrolysis system, the relationships between the electric field, the flow field and the electrode/electrolyzer geometry are simulated. Then, the simulation results are verified and further corrected by corrosion experiments. Subsequently, the key factors affecting the performance of the electrolyzer are obtained from the bubble separation experiment and simulation. Finally, a high-efficient electrolysis system is established and successfully put into industrial operation. In conclusion, in the course of model calculations, the method of reducing energy consumption is put forward, and the energy consumption is reduced from 17,000 to 14,980 kWh/ton by actual production, and the service life of carbon anode is extended from 90 days to 243 days. The breakthrough in fluorine electrolysis provides practical guidance for improving the performance of the electrolysis process.

Survey of 99.9% Class EfficiencyDC‐ACPower Conversion and Technical Issues

This study provides a survey overview of the literatures with the goal of maximizing the efficiency of DC‐AC power conversion from an engineering science perspective. With the advent of wide band gap power semiconductors, the published literature on realizing high efficiency DC‐AC converters has increased. Therefore, a literature survey of high‐efficiency DC‐AC inverters was first conducted. We demonstrated the importance of the measurement accuracy in measuring high efficiency losses, and then presented the literature on new measurement methods, as well as examples of analysis of the breakdown of these losses. Furthermore, we reviewed the literature on high‐efficiency inverters. We presented measurement data (99.83%) on an inverter with a high efficiency energy conversion system circuit topology using Silicon Carbide (SiC) and Gallium Nitride (GaN) devices to demonstrate how the procedure was used to achieve loss minimization. We summarized the challenges hindering high efficiency. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Operando Analysis of Losses in Commercial-Sized Solid Oxide Cells: Methodology Development and Validation

The development of decarbonised systems is being fostered by the increasing demand for technological solutions for the energy transition. Solid Oxide Cells are high-efficiency energy conversion systems that are foreseen for commercial development. They exhibit potential power generation and power-to-gas applications, including a reversible operation mode. Long-lasting high performance is essential for guaranteeing the success of the technology; therefore, it is fundamental to provide diagnosis tools at this early stage of development. In this context, operando analysis techniques help detect and identify incipient degradation phenomena to either counteract damage at its origin or correct operando protocols. Frequent switches from the fuel cell to the electrolyser mode add more challenges with respect to durable performance, and deep knowledge of reverse-operation-induced damage is lacking in the scientific and technical literature. Following on from preliminary experience with button cells, in this paper, the authors aim to transfer the methodology to commercial-sized Solid Oxide Cells. On the basis of the experimental evidence collected on planar square cells under dry and wet reactant feed gases, the main contributions to impedance are identified as being charge transfer (f = 103–104 Hz), oxygen surface exchanged and diffusion in bulk LSCF (f = 102–103 Hz), and gas diffusion in the fuel electrode (two peaks, f = 1–100 Hz). The results are validated using the ECM methodology, implementing an LRel(RctQ)GWFLW circuit.

An Novel Six-Segment Modulation Strategy for Three-Phase Isolated PFC Converter

A three-phase isolated rectifier features bidirectional power conversion and galvanic isolation, and is attractive as a high-efficiency energy conversion system. However, when a conventional modulation is applied to this rectifier, the excessive DC-link current ripple will result in increasing switching losses or the size of DC-link inductance, which is not cost-effective. In order to effectively reduce the current ripple, this paper proposes a “six segment” PWM (Pulse Width Modulation) strategy. It can significantly reduce the current ripple compared with the existing “eight segment” PWM strategy. Meanwhile, the current quality of the grid is improved. Finally, the experimental tests were carried out. The experimental results reveal that, compared to the traditional “eight segment” PWM, the dc-side current ripple significantly reduced from 2 A to 0.8 A, the total harmonic distortion significantly reduced from 5.69% to 2.41%, and the power factor increased from 0.87 to 0.99, verifying the effectiveness of the proposed method.

A rational design of bimetallic PdAu nanoflowers as efficient catalysts for methanol oxidation reaction* *Project supported by the National Natural Science Foundation of China (Grant Nos. 118740271 and 1774124), Technology Development Program of Jilin Province, China (Grant No. 20180101285JC), and the China Postdoctoral Science Foundation (Grant Nos. 2019T120233 and 2017M621198).

Methanol fuel cells have been intensively developed as clean and high-efficiency energy conversion system due to their high efficiency and low emission of pollutants. Here, we developed a simple aqueous synthetic method to prepare bimetallic PdAu nanoflowers catalysts for methanol oxidation reaction (MOR) in alkaline environment. Their composition can be directly tuned by changing the ratio between Pd and Au precursors. Compared with commercial Pd/C catalyst, all of the PdAu nanoflowers catalysts show the enhanced catalytic activity and durability. In particular, the PdAu nanoflowers specific activity reached 0.72 mA/cm2, which is 14 times that of commercial Pd/C catalyst. The superior MOR activity could be attributed to the unique porous structure and the shift of the d-band center of Pd.

Photonic-Plasmonic Nanostructures for Solar Energy Utilization and Emerging Biosensors.

Issues related to global energy and environment as well as health crisis are currently some of the greatest challenges faced by humanity, which compel us to develop new pollution-free and sustainable energy sources, as well as next-generation biodiagnostic solutions. Optical functional nanostructures that manipulate and confine light on a nanometer scale have recently emerged as leading candidates for a wide range of applications in solar energy conversion and biosensing. In this review, recent research progress in the development of photonic and plasmonic nanostructures for various applications in solar energy conversion, such as photovoltaics, photothermal conversion, and photocatalysis, is highlighted. Furthermore, the combination of photonic and plasmonic nanostructures for developing high-efficiency solar energy conversion systems is explored and discussed. We also discuss recent applications of photonic–plasmonic-based biosensors in the rapid management of infectious diseases at point-of-care as well as terahertz biosensing and imaging for improving global health. Finally, we discuss the current challenges and future prospects associated with the existing solar energy conversion and biosensing systems.

New oxy-fuel cascade thermo-photovoltaic energy conversion system: Effect of cascade design and oxygen ratio

In this study, a novel oxy-fuel cascade thermo-photovoltaic (TPV) system concept was proposed and researched. Oxy-fuel combustion was used to reduce NOx emissions and the proposed cascade design and an increase in oxygen ratio were used to enhance the TPV system output. A physical model was established to conduct thermodynamic calculations to determine the influence of the cascade design and oxygen ratio on the system performance under oxy-fuel conditions. Moreover, the optimal area distribution of the cascade TPV and its influencing factors were determined and a preliminary assessment of the emission reduction potential was conducted. The results showed that the cascade design improved the system efficiency and a comprehensive comparison indicated the superiority of the two-stage TPV. An increase in the oxygen ratio under oxy-fuel conditions increased the system efficiency and resulted in considerable NOx emission reduction. Moreover, the multi-stage TPV system has an optimal area distribution, and an increase in the oxygen ratio increased the optimal area of the first stage. This study provides a reference for the design of high-efficiency TPV energy conversion systems.

EV Range Extender in a Two-Battery HEECS Chopper-Based Powertrain

This paper first presents a new powertrain based on a two-battery High-Efficiency Energy Conversion System (HEECS) chopper that is suitable for electric vehicles (EVs). The HEECS chopper is based on the principle of a partial power conversion circuit, and the overall efficiency is over 99% in a wide load range. The efficiency of this powertrain was measured in the steady state by two types of powertrains, a non-chopper powertrain and an HEECS chopper-based powertrain, using a motor test bench. On the basis of these data, several driving tests, such as the Worldwide-harmonized Light vehicles Test Cycle (WLTC), were simulated, and four driving cycle patterns were included. A 6.4% reduction in energy consumption was observed in WLTC low mode compared with the energy consumed by the non-chopper powertrain in the experiments. Thus, the HEECS chopper-based powertrain is more suitable for low-speed driving ranges than high-speed ranges.

Flexible ceramic film capacitors for high-temperature power electronics

Flexible ceramic film capacitors with high dielectric constant and high breakdown strength hold special promise for applications in power electronics. We deposited lanthanum-doped lead zirconate titanate (PLZT) films on aluminum-metallized polyimide films at room temperature by an aerosol deposition (AD) process and examined the electrical and dielectric properties of the PLZT films over a wide temperature range between −55 and 175 °C. The PLZT film capacitors fabricated by high deposition rate AD process not only satisfy X8R temperature rating but also exhibit superior volumetric and gravimetric specific capacitance. At room temperature, we measured a dielectric constant of ≈85, dielectric loss of ≈0.012, energy density of ≈13.2 J/cm3 with an applied voltage of ≈1000 V. A mean dielectric breakdown field strength (EB) of ≈1.25 MV/cm was determined by Weibull analysis for the ≈8-μm-thick PLZT film capacitors fabricated on flexible aluminum-metallized polyimide substrates. These results revealed that the PLZT-based ceramic film capacitors meet the requirements for advanced high-temperature power inverters. Our results demonstrated that AD process offers the greatest potential for producing low-cost, robust, compact and light-weight ceramic film capacitors with enhanced reliability for power inverters of electrical drive vehicles and various power electronic devices that are critical for high-efficiency energy conversion and renewable energy systems.

A Comprehensive Review of Nanomaterials Developed Using Electrophoresis Process for High-Efficiency Energy Conversion and Storage Systems

Research carried out over the last few decades has shown that nanomaterials for energy storage and conversion require higher performance and greater stability. The nanomaterials synthesized by diverse techniques, such as sol-gel, hydrothermal, microwave, and co-precipitation methods, have brought energy storage and conversion systems to the center stage of practical application but they still cannot meet the capacity and mass production demands. Most reviews in the literature discuss in detail the issues related to nanomaterials with a range of structures synthesized using the above methods to enhance the performance. On the other hand, there have been few critical examinations of use of the electrophoresis process for the synthesis of nanomaterials for energy storage and conversion. The nanomaterials synthesized by electrophoresis processes related to colloidal interface science in the literature are compared according to the conditions to identify promising materials that are being or could be developed to satisfy the capacity and mass production demands. Therefore, a literature survey is of the use of electrophoresis deposition processes to synthesize nanomaterials for energy storage and conversion and the correlations of the electrophoresis conditions and properties of the resulting nanomaterials from a practical point of view.

A Novel One-dimensional Reduced Graphene Oxide/Sulfur Nanoscroll Material and its Application in Lithium Sulfur Batteries

One-dimensional (1D) reduced graphene oxides possess unique structure properties in comparison with conventional graphene sheet material and show great potential in application of high-efficiency energy storage and conversion system. Lithium sulfur batteries have been considered as the promising candidates of high-energy rechargeable batteries due to the high theoretical energy density and cost-efficiency. However, their practical application has been hampered by rapid capacity fading during cycling. In this work, one-dimensional reduced graphene oxide/sulfur nanoscrolls show promise for uniformly confining elemental sulfur in their internal cavities and absorbing polysulfide intermediates. The remarkable electrochemical performance of the reduced graphene oxide/sulfur nanoscroll materials is mainly attributed to the desirable structural features, where sulfur is encapsulated into the RGO nanoscrolls and kept close contact with RGO. The RGO nanoscrolls not only provide the electron transport pathway, but effectively alleviate the dissolution and shuttling of the polysulfides during cycling for lithium sulfur batteries.

A dual-electrolyte based air-breathing regenerative microfluidic fuel cell with 1.76 V open-circuit-voltage and 0.74 V water-splitting voltage

The open circuit voltage of a conventional H2-O2 fuel cell is limited to ~1.23V under atmospheric pressure, which limits the efficiency of the system. Here, we reported a dual-electrolyte microfluidic fuel cell system (DEFC), which could stably deliver an open circuit voltage up to 1.76V at room temperature under atmospheric pressure, and a peak power density of 145mW/cm2, improved by 3 times compared with that in single electrolyte mode. When operated in the reverse mode, the microfluidic cell can be used for water electrolysis, demonstrating a water split voltage of ~0.74V and a round trip voltage efficiency of 83.5% at a current density of 100mA/cm2. The neutralization energy of the two electrolytes, which could be wasted as heat, can be directly utilized to produce electricity or split water with high efficiency. Given the DEFC's features of high open-circuit voltage, low water splitting voltage, and room-temperature operation condition, the reported DEFCs technology presents a superior route for high-efficiency energy conversion and storage system that could revolutionize the fields of large-scale energy storage and portable power systems.

A novel concept of Semi-solid, Li Redox Flow Air (O2) Battery: a breakthrough towards high energy and power batteries

Worldwide efforts are being devoted to promote an efficient use of renewable energy sources and sustainable electric transportation. High efficiency energy conversion systems like batteries, which store/deliver high energy and power densities, are under development. While Li-ion batteries (LIBs) are the best performing batteries on the market and redox flow batteries are already used for stationary plants, a drastic step forward is needed to increase energy and power performance and decrease costs. Li/O2 batteries are considered the next generation due to significantly higher energy delivery than LIBs. We demonstrate a radically new battery concept: a non-aqueous Li/O2 battery that operates with a semi-solid, flowable catholyte. The proof-of-concept is proven by a catholyte based on 2% wt. SuperP carbon dispersed in tetraethylene glycol dimethyl ether – lithium bis(trifluoromethane)sulfonimide. Oxygen redox reaction at the semi-solid catholyte is investigated by electrochemical, morphological and spectroscopic analyses. The perfomance of a semi-solid, flow Li/O2 battery prototype operating at high discharge rates (up to 4mAcm−2) with high discharge capacity (>175mAhcm−2), energy (>500mWh cm−2) and power (>7mWcm−2) is reported. The strategies to approach the challenging target of 1kWhkg−1and 2kWhL−1 are also discussed.

High Efficiency Energy Conversion System for Decreaces in Electric Vehicle Battery Terminal Voltage

High Efficiency Energy Conversion System for Decreaces in Electric Vehicle Battery Terminal Voltage

From waste to electricity through integrated plasma gasification/fuel cell (IPGFC) system

The waste management is become a very crucial issue in many countries, due to the ever- increasing amount of waste material, both domiciliary and industrial, generated. The main strategies for the waste management are the increase of material recovery (MR), which can reduce the landfill disposal, the improvement of energy recovery (ER) from waste and the minimization of the environmental impact. These two last objectives can be achieved by introducing a novel technology for waste treatment based on a plasma torch gasification system integrated with a high efficiency energy conversion system, such as combined cycle power plant or high-temperature fuel cells. This work aims to evaluate the performance of an Integrated Plasma Gasification/Fuel Cell system (IPGFC) in order to establish its energy suitability and environmental feature. The performance analysis of this system has been carried out by using a numerical model properly defined and implemented in Aspen Plus™ code environment. The model is based on the combination of a thermochemical model of the plasma gasification unit, previously developed by the authors (the so-called EquiPlasmaJet model), and an electrochemical model for the SOFC fuel cell stack simulation. The EPJ model has been employed to predict the syngas composition and the energy balance of an RDF (Refuse Derived Fuel) plasma arc gasifier (that uses air as plasma gas), whereas the SOFC electrochemical model, that is a system-level model, has allowed to forecast the stack performance in terms of electrical power and efficiency. Results point out that the IPGFC system is able to produce a net power of 4.2 MW per kg of RDF with an electric efficiency of about 33%. This efficiency is high in comparison with those reached by conventional technologies based on RDF incineration (20%).

Fabrication and Characterization of Stacked SOFCs Using Rapid Fabrication Technique

SOFCs technology is important for developing high efficient energy conversion system. The application fields of SOFC system are possible to improve by among the module design, electrochemical properties and manufacturing speed and cost. In addition, compact modules with small SOFCs are interest for mobile power modules in future. For the purpose of developing ceramic manufacturing process of SOFCs, we are carrying out development of rapid-prototyping-like fabrication techniques using computer manipulation of micro-nozzle and ceramic pastes. Gd-doped CeO2 (GDC) based micro cells (<1.0mm) and the stacked modules have been developed with direct assemble techniques. The products and characterization of the prepared GDC-SOFC cells are shown.

A high-efficiency single-phase three-wire photovoltaic energy conversion system

A single-phase three-wire photovoltaic energy conversion system with single-stage structure using a novel maximum power-point tracking (MPPT) algorithm is presented. An equivalent model of the proposed system is derived to analyze the characteristics of the system and to design the controller. Owing to the linear relation of the PV array parameters versus insolation, the model is easy to analyze. The proposed system employs a three-leg inverter to control the MPPT process, the line current, and neutral line current. A current-controlled MPPT algorithm controls the MPPT. A neutral line-mode controller maintains a utility neutral line current of zero. A line-mode controller controls the line current so as to provide power to the utility with a unity power factor. The proposed system acts as a solar generator on sunny days and functions as an active power filter on rainy days. Computer simulation and experimental results demonstrate the accuracy and the superior performance of the proposed technique.