Design Of Conversion Systems Research Articles

Magnetohydrodynamic Enhancement of Biofuel Cell Performance.

Biofuel cells have become an interesting alternative for the design of sustainable energy conversion systems with multiple applications ranging from biosensing and bioelectronics to autonomously moving devices. However, as an electrochemical system, their performance is intimately related to mass transport conditions. In this work, the magnetohydrodynamic (MHD) effect is studied as an easy and straightforward alternative to enhance the performance of a biofuel cell based on the enzymes glucose oxidase (GOx) and bilirubin oxidase (BOD). The synergetic effect between the electric and ionic currents, produced by the enzymatic redox reactions, and a magnetic field orthogonal to the surface of the electrodes, leads to the formation of localized magnetohydrodynamic vortexes. Such an integrated convective regime generates an increase of the bioelectrocatalytic current and its concomitant power output in the presence of the external magnetic field. In addition, by fine-tuning the spatial arrangement of the anode and cathode, it is possible to benefit from the sum of anodic and cathodic MHD vortexes, leading to an enhanced power output of up to 300%.

The Integration of Renewable Energies and Energy Static Converters Courses for Energy Engineering Students in the Framework of the European Higher Education Area (EHEA)

As it is well known, the Bologna Process is a voluntary intergovernmental European cooperation initiative that led to the creation of the named European Higher Education Area (EHEA). EHEA was formed to promote mobility, increase academic recognition and attract students and staff from around the world to Europe. On the other hand, since September 2016, the Technical University of Catalonia - BarcelonaTech (UPC) has a new Campus, the Diagonal-Besòs Campus. In this new Campus appears the Eastern Barcelona School of Engineering (Escuela de Ingeniería de Barcelona Este - EEBE), with new Bachelor’s and Master’s Degrees. In this framework, also since September 2016, the EEBE is offering the new 4-year Bachelor’s Degree in Energy Engineering with a total number of ECTS credits of 240. Current article deals with the inclusion of the sizing and design of renewable energy systems and energy static conversion systems in the context of this degree. In particular, and although this topic was eventually abandoned in the initial degree curriculum, the paper presents the development of a 3rd-year course, Energy Static Converters, and, especially, a 4th-year course, Renewable Energies, that focuses on these two topics.

Wind Speed Modeling under Quasi‐Linear Autoregressive Neural Network Model for Prediction of Production Power

Accurate wind speed modeling is beneficial for the design of wind energy conversion systems. Models of wind speed are used to assess the adequacy and dependability of a power supply. However, precise wind speed modeling is challenging due to the sporadic availability of wind speed. In this note, we propose a wind speed model with an autoregressive (AR) structure. A hybrid model is developed under linear and nonlinear parts based on a quasi‐linear autoregressive exogenous neural network (Q‐ARX‐NN). The model's structure is composed of a regression vector and its coefficients. The coefficients are divided into linear and nonlinear coefficients. A set of linear coefficients is identified under the algorithm of least square error (LSE), and a set of nonlinear coefficients is modeled by using a neural network to refine the residual error of the nonlinear part. Some artificial neural network (ANN) models can be set as nonlinear part sub‐models to sharpen the model's accuracy. The proposed model is tested for wind speed modeling to estimate wind energy production. Various nonlinear parts of the sub‐model are tested, such as neural networks, radial basis function networks, and ANN networks. Moreover, we evaluate the effects of the order of the model by varying hidden and output nodes, which can be summarized as the number of coefficients of the regression vector. Using specific wind turbine performance data, prediction models estimate production power. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Dual photoelectrode-drived Fe–Br rechargeable flow battery for solar energy conversion and storage: A cost-effective approach

The integrated design of solar energy conversion and storage systems has attracted increasing attention, and non-spontaneous redox reactions driven by dual photoelectrodes provide a potential solution to this issue. This study presents a solar rechargeable flow battery (SRFB) that combines dual photoelectrodes (BiVO4 or Mo–BiVO4 as photoanode, polyterthiophene (pTTh) as photocathode) with cost-effective redox pairs (Fe3+/Fe2+ and Br3−/Br−). The system charges under simulated solar illumination (100 mW∙cm−2, AM 1.5G) and releases stored energy controllably as electrical energy. Research indicates the Mo–BiVO4 photoanode and pTTh photocathode achieve an open-circuit voltage of 0.34 V and a short-circuit current density of 0.38 mA cm−2. Using a specially designed Fe3+/Fe2+-Br3−/Br− (Fe–Br) SRFB device made via 3D printing, a charging photocurrent of approximately 1.9 mA cm−2 is attained. In constant current discharge tests, an initial discharge voltage of 0.23 V is observed at 0.1 mA∙cm−2 within the 10 discharge cycles, demonstrating system stability and offering a viable solution for low-cost, large-scale solar energy storage and conversion.

Overcoming Electrostatic Interaction via Pulsed Electroreduction for Boosting the Electrocatalytic Urea Synthesis

AbstractElectrocatalytic urea synthesis under ambient conditions offers a promising alternative strategy to the traditional energy‐intensive urea industry protocol. Limited by the electrostatic interaction, the reduction reaction of anions at the cathode in the electrocatalytic system is not easily achievable. Here, we propose a novel strategy to overcome electrostatic interaction via pulsed electroreduction. We found that the reconstruction‐resistant CuSiOx nanotube, with abundant atomic Cu−O−Si interfacial sites, exhibits ultrastability in the electrosynthesis of urea from nitrate and CO2. Under a pulsed potential approach with optimal operating conditions, the Cu−O−Si interfaces achieve a superior urea production rate (1606.1 μg h−1 mgcat.−1) with high selectivity (79.01 %) and stability (the Faradaic efficiency is retained at 80 % even after 80 h of testing), outperforming most reported electrocatalytic synthesis urea catalysts. We believe our strategy will incite further investigation into pulsed electroreduction increasing substrate transport, which may guide the design of ambient urea electrosynthesis and other energy conversion systems.

Overcoming Electrostatic Interaction via Pulsed Electroreduction for Boosting the Electrocatalytic Urea Synthesis.

Electrocatalytic urea synthesis under ambient conditions offers a promising alternative strategy to the traditional energy-intensive urea industry protocol. Limited by the electrostatic interaction, the reduction reaction of anions at the cathode in the electrocatalytic system is not easily achievable. Here, we propose a novel strategy to overcome electrostatic interaction via pulsed electroreduction. We found that the reconstruction-resistant CuSiOx nanotube, with abundant atomic Cu-O-Si interfacial sites, exhibits ultrastability in the electrosynthesis of urea from nitrate and CO2. Under a pulsed potential approach with optimal operating conditions, the Cu-O-Si interfaces achieve a superior urea production rate (1606.1 μg h-1 mgcat. -1) with high selectivity (79.01 %) and stability (the Faradaic efficiency is retained at 80 % even after 80 h of testing), outperforming most reported electrocatalytic synthesis urea catalysts. We believe our strategy will incite further investigation into pulsed electroreduction increasing substrate transport, which may guide the design of ambient urea electrosynthesis and other energy conversion systems.

(Invited) Case Studies for in-Space Electrochemical Operations

Faraday Technology Inc. is a research, development and electrochemical engineering firm developing electrochemical innovations for terrestrial and space system.[1,2] With that founding basis Faraday has been able to bridge the gap between academic understanding and small-scale demonstrations to commercialization of practical components for over 32 years of operation.This presentation will discuss a broad range of electrochemical approaches to improve the performance of components used in space or to be used for in-space production. We will provide insight into case studies, performed at Faraday, from our four business units of electrodeposition, electrochemical surface finishing, electrochemical conversion, and electrochemical system design. For instances, we will discuss direct print electrodeposition, electrophoretic application of coatings for glare resistance, surface finishing of rocket components, bioelectrochemical treatment of urine, and the generation of peroxide. Each electrochemical process has applications on earth and in space; additionally, each program had to overcome specific challenges that only space can present.

Design of a High-Performance Control Scheme for a Grid-Connected DFIG‐Based Wind Energy Conversion System Using Model Predictive Control and Hysteresis Model

In this paper, we present a novel design and development of wind energy conversion systems (WECS) for a doubly-fed induction generator (DFIG). A hysteresis current control is used to improve the DC bus for rectifier and smart current control by model predictive of three-level-NPC (3L-NPC) inverter. The advantages of this intelligent method are such as fast dynamic answers and the easy implementation of nonlinearities, and that it requires fewer calculations to choose the best switching state. In addition, an innovative algorithm is proposed to adjust the current ripples and output voltage harmonics of the wind energy conversion system. The performance of the system was analysed by simulation using MATLAB/Simulink.

Experimental and Theoretical Analysis of Immersion Cooling of a Li-Ion Battery Module

Abstract Overheating of Li-ion cells and battery packs is an ongoing technological challenge for electrochemical energy conversion and storage, including in electric vehicles. Immersion cooling is a promising thermal management technique to address these challenges. This work presents experimental and theoretical analysis of the thermal and electrochemical impact of immersion cooling of a small module of Li-ion cells. Significant reduction in both surface and core temperature due to immersion cooling is observed, consistent with theoretical and simulation models developed here. However, immersion cooling is also found to result in a small but non-negligible increase in capacity fade of the cells. A number of hypotheses are formed and systematically tested through a comparison of experimental measurements with theoretical modeling and simulations. Electrochemical Impedance Spectroscopy measurements indicate that the accelerated cell aging due to immersion cooling is likely to be due to enhanced lithium plating. Therefore, careful consideration of the impact of immersion cooling on long-term performance may be necessary. The results presented in this work quantify both thermal and electrochemical impacts of a promising thermal management technique for Li-ion cells. These results may be of relevance for design and optimization of electrochemical energy conversion and storage systems.

Experimental study of pressure drop oscillation in a supercritical carbon dioxide natural circulation loop

Pressure drop oscillation (PDO) is a common type of instability in a two-phase system. The PDO may occur in a supercritical fluid system, with limited prior research on the matter. In this study, an experimental study on PDO of supercritical carbon dioxide (S-CO2) in a natural circulation loop has been carried out. The influence of thermal parameters and compressible volume has been investigated. The experimental result shows that PDO occurs in a natural circulation loop of supercritical carbon dioxide. The location and compressibility capacity of the pressurizer greatly impacts the instability characteristics of the natural circulation loop. The large volume pressurizer installed at the outlet of hot section helps to stabilize the system. The amplitude and the period are influenced by the heat flux and the location of the compressible volume. Increasing the heat flux will slightly increase the amplitude and decrease the period. This work helps to clarify the mechanism of PDO of S-CO2 in the natural circulation loop and provides a reference for the safe design and operation of S-CO2 energy conversion systems.

Phytic acid-derivative Co2B-CoPOx coralloidal structure with delicate boron vacancy for enhanced hydrogen generation from sodium borohydride

Application of transition metal boride (TMB) catalysts towards hydrolysis of NaBH4 holds great significance to help relieve the energy crisis. Herein, we present a facile and versatile metal-organic framework (MOF) assisted strategy to prepare Co2B-CoPOx with massive boron vacancies by introducing phytic acid (PA) cross-linked Co complexes that are acquired from reaction of PA and ZIF-67 into cobalt boride. The PA etching effectively breaks down the structure of ZIF-67 to create more vacancies, favoring the maximal exposure of active sites and elevation of catalytic activity. Experimental results demonstrate a drastic electronic interaction between Co and the dopant phosphorous (P), thereby the robustly electronegative P induces electron redistribution around the metal species, which facilitates the dissociation of B-H bond and the adsorption of H2O molecules. The vacancy-rich Co2B-CoPOx catalyst exhibits scalable performance, characterized by a high hydrogen generation rate (HGR) of 7716.7 mL min−1 g−1 and a low activation energy (Ea) of 44.9 kJ/mol, rivaling state-of-the-art catalysts. This work provides valuable insights for the development of advanced catalysts through P doping and boron vacancy engineering and the design of efficient and sustainable energy conversion systems.

Pyrolysis characteristics and kinetic parameters assessment of typical agricultural residues using high heating photothermal TGA

Understanding the complexity of thermal degradation characteristics, kinetic behavior, and thermodynamic parameters is pertinent for the efficient design and process optimization of large-scale conversion systems. Comparative assessment of pyrolysis characteristics and thermodynamic parameters of corn cobs (CC), peanut shells (PS) and sugarcane bagasse (SB) are investigated using high heating rates (100–1000 ℃/min) TGA results. Despite the effect of the heating rate increase on the degradation process of individual samples, increasing heating rates affect pyrolysis characteristics due to compositional differences. With increasing heating rates, the comprehensive pyrolysis index increased sporadically for CC (2.54–44.09 ×104%2/min2 ℃3) and PS (1.36–31.13 ×104%2/min2 ℃3), indicating easier release of volatiles at higher pyrolysis heating rates. The pyrolysis stability index (Rw), which relates to thermal degradation stability, presented an increasing trend (CC>PS>SB) with a heating rate increase (≥106%). Kinetic parameters estimated using model-free methods showed that the activation energies of CC and PS were significantly lower than that of SB. Comparative evaluation of fractional conversions and kinetic parameters using traditional and modified parallel models showed that the double random pore model (DRPM) fitted the best for simulating the experimental results at higher heating rates than other models. The change in Gibbs free energy (ΔG) trend for PS and SB showed a deviation, suggesting reaction difficulties due to higher temperature demands.

Thermal analysis-based design of energy conversion systems

Thermal analysis-based design of energy conversion systems

Design and performance comparisons of power converters for battery energy storage systems

SummaryThe use of grid‐connected battery energy storage systems (BESSs) has increased around the world. In the scenario of high penetration level of renewable energy sources in distributed generation, BESS plays an important role to combine a sustainable power supply with a reliable dispatched energy source. Different power converter topologies are employed to connect the batteries to the grid, generally using single‐stage converters. However, the battery voltage changes according to its state of charge, which can introduce great variations in the dc‐link voltage. Therefore, the dc/ac stage converter must have its power switches designed to support this voltage variation. A controllable dc‐link voltage is achieved by inserting a dc/dc converter stage to connect the batteries to the dc/ac stage. Among the dc/dc converters, the interleaved bidirectional converter has been widely used due to the low input current ripple. However, the trade‐off of the insertion of the dc/dc stage is barely explored in the literature. Therefore, this work presents a methodology of analysis, considering the battery voltage variation and its influence on BESS power conversion system design and efficiency. Furthermore, it is proposed a power conversion system design oriented toward the voltage class of power switches and efficiency. The analysis in this study are conducted through the use of a case study approach, incorporating both simulated and experimental results.

Analyzing the engineering feasibility of the direct fusion drive

The Direct Fusion Drive (DFD) and its terrestrial counterpart, the Princeton Field Reversed Configuration (PFRC) reactor, have seen significant developments in the past decade. Various groups conducted detailed research on the required specifications of the engine and associated technology for power delivery to onboard avionics and payloads. Multiple studies have also addressed the thrust generation mechanism using empirical specific power scaling relations and plasma flow simulations. Recent studies have designed spacecraft for missions to Earth’s second Lagrange point, Mars, transneptunian bodies like Pluto, and the neighboring star systems Alpha Centauri A and B. However, significant work is needed to design the engine components in detail using scientific scaling relations and ab inito calculations to develop the physical systems for prototyping and testing. After critically analyzing the reference design of the DFD and the underlying fusion reactor, this paper addresses the technological gaps and suggests avenues to improve specifications toward targets outlined in previous studies while considering costs. Further, the authors present a prototype engine and magnetohydrodynamic power conversion system design to study the engineering hurdles relevant to the practical implementation of the DFD.

Special issue on “Optimal design and operation of energy systems”

Special issue on “Optimal design and operation of energy systems”

An ultra-broadband and wide-angle absorber based on a TiN metamaterial for solar harvesting.

The efficient absorption of solar spectrum radiation is the most critical step in solar thermal utilization. In this work, a near-perfect metamaterial solar absorber with broadband, wide angle, polarization insensitivity, and high-temperature resistance is proposed and investigated. The absorber takes advantage of the high melting point material, which consists of a TiN reflector, a SiO2 insulating layer, and a TiN ring array. In the spectral range of 300-2500 nm, an average absorption of 97.6% is achieved. The percentage of absorbed energy in the AM1.5 spectral radiation can reach 95.8%. The electric and magnetic field distributions show that the high absorption is attributed to the coupling effect of surface plasmon resonance, guided mode resonance and cavity resonance. Furthermore, the absorber is found to maintain high absorption performance at large angles of solar radiation and to be insensitive to polarization. The designed absorber maintains its broadband absorption performance well within certain geometric tolerances. This reduces the complexity and cost of manufacturing and facilitates practical applications. The research indicates that this work will benefit the design and application of solar thermal conversion and thermophotovoltaic systems.

(Invited) Management Systems for Lithium-Ion Batteries

Battery management systems (BMS) for large Li-ion batteries are, of themselves, complex systems. The complexity starts with voltage measurement for individual cells. Large batteries may have 96, 192, or more, series connected cells, so requiring complex wiring harnesses. The high noise environment provides additional challenges for wiring and also analog front end and analog to digital conversion system design. For safety, and to help with state-of-charge (SOC) estimation, temperature sensors must be located throughout the battery. A computational infrastructure estimates SOC for each cell. The estimate is typically based on cell voltage, measured current, estimated cell resistance, integrated current and temperature. Additionally, cell capacity imbalance, whether present from the start or evolved over time, must be corrected.This talk will attempt to provide some insight into BMS design for mass-produced large batteries. The applications, whether for electric vehicles (EV) or stationary storage, are generally safety critical, so placing additional demands on the BMS. Typically, the BMS also manages the interaction between the battery and the remainder of the system. It sets limits for allowed charge and discharge currents and can interrupt current and disconnect the battery if limits are exceeded. This area will also be addressed, with a particular focus on fusing challenges for EV applications. Power transfer of 500 kW or more may be required. Depending on the application this may be for only a few seconds, or it may be indefinite. In additional to safety, reliability is also critical. For example, the many required cell connections must remain intact for the intended service life of the installation. This will be addressed, touching also on design of the overall battery pack.

(Invited) Management Systems for Lithium-Ion Batteries

Battery Management Systems (BMS) for large Li-ion batteries are, of themselves, complex systems. The complexity starts with voltage measurement for individual cells. Large batteries may have 96, 192, or more, series connected cells, so requiring complex wiring harnesses. The high noise environment provides additional challenges for wiring and also analog front end and analog to digital conversion system design. For safety, and also to help with State of Charge (SOC) estimation, temperature sensors must be located throughout the battery. A computational infrastructure estimates SOC for each cell. The estimate is typically based on cell voltage, measured current, estimated cell resistance, integrated current and temperature. Additionally, the effects of cell capacity imbalance, whether present from the start, or evolved over time, must be mitigated. This paper will attempt to provide some insight into BMS design for mass produced large batteries. The applications, whether for Electric Vehicles (EV) or Stationary Storage, are generally safety critical, so placing additional demands on the BMS. Typically, the BMS also manages the interaction between the battery and the remainder of the system. It sets limits for allowed charge and discharge currents and has the ability to interrupt current and disconnect the battery if limits are exceeded. In additional to safety, reliability is also critical. For example, the many required cell connections must remain intact for the intended service life of the installation. This will be addressed, touching also on design of the overall battery pack.

Heterostructured Ru/Ni(OH)2 Nanomaterials as Multifunctional Electrocatalysts for Selective Reforming of Ethanol.

The electrochemical reforming of ethanol into hydrogen and hydrocarbons can reduce the electric potential energy barrier of hydrogen production from electrochemical water splitting, obtaining high value-added anode products. In this work, Ru/Ni(OH)2 heterostructured nanomaterials were synthesized successfully by an in situ reduction strategy with remarkable multifunctional catalytic properties. In the hydrogen evolution reaction, Ru/Ni(OH)2 exhibits a smaller overpotential of 31 mV to obtain a current density of 10 mA/cm2, which is better than that of commercial Pt/C. Notably, such heterostructured Ru/Ni(OH)2 nanomaterials also perform an outstanding catalytic selectivity toward an acetaldehyde product in the oxidation of ethanol. DFT calculations reveal that abundant Ru(0)-Ni(II) heterostructured sites are the key factor for the excellent performances. As a result, an ethanol-selective reforming electrolyzer driven by a 2 V solar cell is constructed to produce hydrogen and acetaldehyde in the cathodic and anodic part, respectively, via using Ru/Ni(OH)2 heterostructured catalysts. This work provides a forward-looking technical guidance for the design of novel energy conversion systems.