Conversion Loss Research Articles

Numerical study on a Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler for natural gas liquefaction

Compact heat-driven cryocoolers can harness the thermal energy produced by burning a small quantity of natural gas to accomplish liquefaction. This addresses the requirements of distributed natural gas stations in remote locations. This paper introduces a Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler designed for natural gas liquefaction. It conducts a comparative analysis of the mechanical and electrical systems, focusing on the acoustic field, available energy loss, and performance. Simulation results indicate that the optimized mechanical configuration system achieves peak performance with a piston area ratio of 0.84 and a piston phase angle of 90°. It yields a cooling power of 1964 W@130 K when driven by an 873 K heat source, resulting in an overall system efficiency of 28.3%. This marks a notable enhancement compared to current thermoacoustic systems. While the electrical configuration provides superior stability, the performance is constrained by significant losses in acoustic-electric conversion of linear alternators and compressors. To further enhance efficiency, it is worthwhile to establish direct power transfer between the pistons, for example, by aligning the expansion piston and compression piston coaxially. The evolved duplex configuration eliminates the loss from electrical energy conversion, leading to a remarkable 64.7% increase in overall efficiency. Simultaneously, this evolutionary approach offers a new perspective to elucidate the inherent connections among Stirling heat engines of Franchot double-acting and duplex. It provides valuable theoretical insights for the subsequent analysis and design of Stirling heat-driven refrigerators or cryocoolers.

Review of DC-DC Partial Power Converter Configurations and Topologies

The Partial Power Processing (PPP) concept has garnered attention as it enables the down-sizing of converter and component ratings. Unlike conventional power processing, PPP addresses a portion of the transferred power, leading to a reduction in conversion losses. Throughout this paper, the state of the art of isolated and non-isolated DC-DC converter topologies will be revised. Partial Power Converter (PPC) systems represent one of the main streams of PPP, which, based on isolation requirements and converter connections, can further be divided into isolated converters, such as: Input-Parallel-Output-Series (IPOS), Input-Series-Output-Parallel (ISOP), and, Input-Series-Output-Series (ISOS), or non-isolated converters. This work intends to evaluate and differentiate the characteristics of each type of topology while developing analytically possible connections that may require further research and reviewing metrics that help in fair comparisons of different PPC arrangements, operating under different conditions. A thorough revision is provided for DC-DC converter topologies due to their increased importance in present-day applications, such as energy storage, Electric Vehicles (EVs), and Photo-Voltaics (PVs).

Power quality investigation with multilevel inverter by photovoltaic-fed dynamic voltage restorer

ABSTRACT In this research endeavor, a novel approach has been presented to enhance the power quality through a Photovoltaic (PV)-based Dynamic Voltage Restorer (PV-DVR). The proposed work is designed to address voltage fluctuations, flicker, and harmonics within medium or low voltage micro-grid systems. Unlike existing DVR systems that often neglect injected harmonics and converter losses, in the proposed work there is an integration of a PV-fed multilevel inverter system employing Selected Harmonic Elimination and Moderation-based Pulse Width Modulation (SHEAM-PWM). This innovative configuration, coupled with a DC – DC boost converter and a series injection transformer, not only aims to alleviate voltage stress on devices but also optimizes the number of switches to minimize switching losses. The proposed setup successfully reduces the overall voltage Total Harmonic Distortion (THD) to a significant extent, delivering superior dynamic performance. To determine optimal switching angles for the SHEAM-PWM technique, ensuring the elimination or mitigation of the maximum number of harmonics from the output voltage waveform, we employ the Biogeography-Based Optimization (BBO) approach. The computation of these angles is performed offline to eliminate lower-order harmonics, and the results are stored in the microcontroller’s memory using mixed model equations for online applications. The efficacy of our proposed method is demonstrated through both simulation and experimental validation in a real-time laboratory system. The simulation and experimental results obtained underscore the potential utility of our technique for Dynamic Voltage Restorer (DVR) applications, particularly those requiring low harmonic injection. The proposed method introduces a comprehensive and innovative solution for power quality enhancement, combining PV technology, multilevel inverter systems, and advanced optimization techniques. The proposed PV-DVR system exhibits promising results, showcasing its potential for practical implementation in residential micro-grid systems with a focus on minimizing harmonics and ensuring efficient grid compensation.

Energy-efficient craters detection based on spiking neural network using digital elevation models

Craters are the primary topographic features on celestial bodies and play a vital role in deep space exploration missions. Recently, artificial neural networks (ANNs) have excelled in crater detection. However, when compared to ANNs, spike neural networks (SNNs) have the advantage of low power consumption, making them more suitable for resource-limited deep space environments. To the best of our knowledge, this is the first spiked-based crater detection model. Firstly, two conversion learning algorithms based on cluster neurons and vary-time windows neurons are proposed to address the non-differentiability problem of SNNs. Secondly, a calibration mechanism is introduced to correct the conversion loss between ANNs and SNNs. Thirdly, the experimental results demonstrate that the proposed scheme exhibits sufficient precision, while reducing the energy consumption cost by more than 10 times compared to the previous method. Additionally, this method is expected to offer new insights for segmentation tasks in resource-constrained environments.

An MTPZC for the Integration of RESs using Analysis, Modeling, Control, and Implementation

This article presents a novel approach to enhance the efficiency, control, and power management capabilities of traditional Zeta Converters in renewable energy applications. The proposed particle swarm optimization (PSO)-modified three-port zeta converter (MTPZC) features a multiport structure with dedicated input ports for photovoltaic (PV) and battery sources, along with an output port. The integration of PSO optimization aims to optimize maximum power point tracking to enhance energy extraction. Extensive simulations and experimental validations showcase the MTPZC's superior performance in power extraction from both PV and Battery sources. This innovative design positions the converter as a promising solution for multiport energy conversion systems in renewable energy applications. The article contributes to the advancement of power electronics by offering improved reliability and efficiency. Simulation results, validated in MATLAB and compared with existing methods, demonstrate an impressive efficiency of 97.8%. The MTPZC outperforms existing approaches, indicating lower converter losses and highlighting its potential for practical implementation in diverse renewable energy systems.

A Compact Neural Network-Based Conversion Loss Model With Hard Constraints for Energy Management

A Compact Neural Network-Based Conversion Loss Model With Hard Constraints for Energy Management

Techno-Economic Comparison of Low-Carbon Energy Carriers Based on Electricity for Air Mobility

The decarbonization of air mobility requires the decarbonization of its energy. While biofuels will play an important role, other low-carbon energy carriers based on electricity are considered, such as battery electrification and liquid hydrogen (LH2) or eFuel, a hydrogen-based energy carrier. Each energy carrier has its own conversion steps and losses and its own integration effects with aircraft. These combinations lead to different energy requirements and must be understood in order to compare their cost and CO2 emissions. Since they are all electricity-based, this study compares these energy carriers using the well-to-rotor methodology when applied to a standard vertical take-off and landing (VTOL) air mobility mission. This novel approach allows one to understand that the choice of energy carrier dictates the propulsive system architecture, leading to integration effects with aircraft, which can significantly change the energy required for the same mission, increasing it from 400 to 2665 kWh. These deviations led to significant differences in CO2 emissions and costs. Battery electrification is impacted by battery manufacturing but has the lowest electricity consumption. This is an optimum solution, but only until the battery weight can be lifted. In all scenarios, eFuel is more efficient than LH2. We conclude that using the most efficient molecule in an aircraft can compensate for the extra energy cost spent on the ground. Finally, we found that, for each of these energy carriers, it is the electricity carbon intensity and price which will dictate the cost and CO2 emissions of an air mobility mission.

Modified Broadband Ruthroff-Type Transmission Line Transformer Balun for Isolation-Enhanced Passive Mixer Design.

Generalized broadband operation facilitates multifunction or multiband highly integrated applications, such as modern transceiver systems, where ultra-wideband bidirectional passive mixers are favored to avoid a complex up/down-conversion scheme. In this paper, a modified Ruthroff-type transmission line transformer (TLT) balun is presented to enhance the isolation of the mixer from the local oscillator (LO) to the radio frequency (RF). Compared to the conventional methods, the proposed Ruthroff-type architecture adopts a combination of shunt capacitors and parallel coupled lines to improve the return loss at the LO port, thus effectively avoiding the area consumption for the diode-to-balun impedance transformation while simultaneously providing a suitable point for IF extraction. In addition, a parallel compensation technique consisting of an inductor and resistor is applied to the RF balun to significantly improve the amplitude/phase balance performance over a wide bandwidth. Benefiting from the aforementioned operations, an isolation-enhanced 8-30 GHz passive double-balanced mixer is designed as a proof-of-principle demonstration via 0.15-micrometer GaAs p-HEMT technology. It exhibits ultra-broadband performance with 7 dB average conversion loss and 50 dB LO-to-RF isolation under 15 dBm LO power. The monolithic microwave integrated circuit area is 0.96 × 1.68 mm2 including all pads.

Performance analysis and multi-objective optimization of the offshore renewable energy powered integrated energy supply system

Offshore renewable energy technologies offer a promising prospect for energy supply on offshore islands. However, traditional wind and solar energy sources exhibit strong variability and cannot fully meet the energy demands of users. At the same time, the energy demand of users also has great volatility, so the supply side and demand side of energy cannot match well. Existing renewable energy systems often utilize thermal power generation as a stabilizer for the system, however, this approach is difficult to apply in offshore conditions. This study introduces an innovative multi-energy complementary system that integrates seawater freezing desalination, refrigeration and power-hydrogen-ammonia co-generation, driven by ocean thermal energy, wind energy, and solar energy. The system incorporates the use of a new developed small temperature difference ejector refrigeration cycle to stabilize the entire system and produce low-temperature refrigeration. By utilizing the seawater freezing desalination process to minimize energy conversion losses and balancing fluctuations in multiple energy inputs and user demands through ammonia-hydrogen co-production, this approach effectively minimizes energy waste, enhances energy utilization efficiency, and reduces excess power handling. The purpose is to optimize the configuration of the energy conversion subsystem within the multi-energy complementary multi-effect co-generation system, thus improving the economic feasibility and reliability of the system in providing energy and freshwater supply, ultimately achieving the goals of reducing energy waste, achieving high conversion efficiency, and minimizing equipment investment. This study conducts an economic analysis and optimization of a multi-energy complementary system, utilizing a 2 MW-level OTEC subsystem as a stabilizer. Both equipment investment and operating costs are considered in the economy analysis. The carbon emission reduction performance of this system is evaluated. The performance optimization results show that the system achieves an energy storage efficiency of 65.96 %, and the curtailment rate of this system is only 3.99 %, significantly lower than the 10 % curtailment rate in traditional system. The proposed system can meet the annual electricity demand of 33.09 million kWh, as well as a cooling demand of 546.81 million kWh. Under typical conditions, the ocean thermal energy conversion cycle exhibits a power efficiency of 0.85 % and a refrigeration efficiency of 29.10 %. Meanwhile, it annually reduces CO2 emissions by 2.54 million tons, demonstrating significant environmental benefits. This proposed system is mainly applicable to tropical waters with high surface water temperatures and depths of no less than 600 m worldwide. This study offers a practical and economically beneficial solution for energy and freshwater supply on offshore islands.

Modulation Techniques and Coordinated Voltage Vector Distribution: Effects on Efficiency in Dual-Inverter Topology-Based Electric Drives

The increasing popularity of electric drives employing an isolated dual-inverter (DI) topology is motivated by their superior DC-link voltage and power utilization, fault-tolerant operation, and potential for multilevel operation. These attributes are significant in battery-powered transportation, such as electric vehicles and aviation. Given the considerable freedom in modulation and control of the DI topology, this paper researches the impact of reference voltage vector distribution between the two individual inverters. The study also evaluates the influence of two well-established asynchronous modulation strategies—Space Vector PWM (SVPWM) and Depenbrock’s Discontinuous Modulation (DPWM1). Since simulation tools nowadays play a crucial role in power electronics design and concept verification, the results are based on extensive and detailed models in Matlab/Simulink. Employing the basic field-oriented control of a 12 kW induction motor with precisely parameterized SiC switching devices for accurate loss calculation, this research reveals the possibility of significant energy savings at multiple operating points. Notably, optimal efficiency is achieved when one inverter operates up to half of the nominal speed while the other solely establishes a neutral point for the winding. Moreover, the results highlight DPWM1 as a superior strategy for the DI topology, showcasing reduced converter losses. Overall, it is shown that the system’s losses can be significantly reduced just by the design of the voltage vector distribution in the drive’s operating range and the modulation strategy selection.

Reliable Frequency Regulation Through Vehicle-to-Grid: Encoding Legislation with Robust Constraints

Problem definition: Vehicle-to-grid increases the low utilization rate of privately owned electric vehicles by making their batteries available to electricity grids. We formulate a robust optimization problem that maximizes a vehicle owner’s expected profit from selling primary frequency regulation to the grid and guarantees that market commitments are met at all times for all frequency deviation trajectories in a functional uncertainty set that encodes applicable legislation. Faithfully modeling the energy conversion losses during battery charging and discharging renders this optimization problem nonconvex. Methodology/results: By exploiting a total unimodularity property of the uncertainty set and an exact linear decision rule reformulation, we prove that this nonconvex robust optimization problem with functional uncertainties is equivalent to a tractable linear program. Through extensive numerical experiments using real-world data, we quantify the economic value of vehicle-to-grid and elucidate the financial incentives of vehicle owners, aggregators, equipment manufacturers, and regulators. Managerial implications: We find that the prevailing penalties for nondelivery of promised regulation power are too low to incentivize vehicle owners to honor the delivery guarantees given to grid operators. Funding: This work was supported by the Institut Vedecom. Supplemental Material: The online appendix is available at https://doi.org/10.1287/msom.2022.0154 .

Power Losses Reduction of Stacked Multicell Converter Fed Wind Energy Conversion System (WECS) Using Hybrid Methodology

This paper proposes a hybrid method for reduction of power losses of multicell converter in wind energy conversion system (WECS). The proposed methodology is the Artificial Intelligence (AI) based phase disposition pulse width modulation (PD-PWM). The Artificial Intelligence (AI) is the Gradient Boosting Decision Tree algorithm (GBDT). Hence it is named as GBDT-PD-PWM. Gradient boosting is a machine learning system that creates a prediction model in the group of weak prediction models, often called decision trees. The multicell converter is employed as the grid side converter (GSC) of WECS to attenuate harmonics created by nonlinear load. For stacked multicell converters (SMCs), a method of capacitor voltage balance based on PD-PWM approach is proposed.

Efficiency Comparison of Grid Side Converters for DC Distribution Systems

This paper aims to study the energy losses in Grid Side Converters (GSCs) used for grid connection of DC residential distribution systems, including renewables and storage. Two different electrical architectures have been considered, the former using an H-bridge as GSC and the latter a PFC active rectifier in association with a storage system. An observation time of one year has been fixed. The analysis is based on the same amount of energy generated by renewables and load demand, in both cases. A detailed formulation of the power losses in each component of the power converter is given. A comparison of the energy lost yearly in both the GSCs is presented, considering different sizing of the storage system.

Reduced Losses in PV Converters by Modulation of the DC Link Voltage

The efficiency of a PV system has improved by the fact that the researchers have used different techniques to enhance their efficiency. This paper aims to present how the PV converter losses can be reduced by employing a polypropylene capacitor in the DC link and to modulate that DC voltage. A problem of controllability and stability arises. Two current control methods, constant off time and a PWM type with second order high pass filter DC-link feedback are presented. Polypropylene capacitors in the PV converters do have lower losses and a lower cost. The PV converter simulation and lab experiment is based on a three-phase bridge APTGF50X60T3G, used to combine a step-up/step down and H-bridge in one package.

A Wide-Output-Range DC-DC Converter and Minimum Loss Collaborative Control Strategy

In response to the challenges faced by traditional LLC resonant converters in simultaneously achieving a wide output voltage and high efficiency, this paper proposes a cascaded DC-DC converter. The front stage of the converter adopts a new LLC topology, and it is cascaded with a boost converter through a reutilization of the output-side inductor. The proposed DC-DC converter leverages the electrical isolation and wide output voltage range advantages of LLC and boost converters, enabling the overall system to achieve broad output voltage regulation and high-efficiency operation. The reutilization of the inductor design further enhances the integration density of the DC-DC converter. A minimum loss collaborative control strategy is introduced for the proposed DC-DC converter. When determining the output voltage and operating the circuit in step-up mode, the duty cycles of the switch in the proposed LLC converter and the switch in the boost converter are adjusted to minimize overall circuit losses while ensuring the rated output voltage. Ultimately, the correctness and practicality of the proposed DC-DC converter and its control strategy are validated through a simulation and an experiment. The overall efficiency of the DC-DC converter can reach up to 94% under optimal conditions.

Application of Quasi-Continuous Waveform Coding in Spaceborne Synthetic Aperture Radar

Quasi-continuous wave radar is an attempt to give consideration to the performance of pulse and continuous wave radar signals. However, it also has the shortcomings of both. This paper aims to add a new quasi-continuous-wave coding method to the spaceborne synthetic aperture radar (SAR) system. The technology of improving spaceborne SAR imaging performance by coding quasi-continuous-wave pulses is studied, and some shortcomings of this algorithm are improved. Firstly, the application of quasi-continuous-wave radar in the SAR system is studied, and the coding and reconstruction scheme is provided so that this technology can be successfully applied in spaceborne SAR. Secondly, the effects of different quasi-continuous-wave coding methods on SAR imaging performance are evaluated, including signal-to-noise ratio, resolution, and integration time. Then, several coding schemes are given, and the characteristic changes of the signal after quasi-continuous-wave coding are analyzed. The transmit–receive conversion loss function and azimuth Doppler ambiguity function of the design scheme are analyzed, which proves the advantages of the scheme. Finally, we design the hardware implementation scheme and carry out the practical test.

Pillar[5]arene based artificial light-harvesting supramolecular polymer for efficient and recyclable photocatalytic applications

Photosynthesis is the process through which living plants utilize photosynthetic pigments, such as chlorophyll, to convert CO2 and water into organic compounds and release O2 under visible light. In this study, we have successfully constructed a fluorescent supramolecular polymer (P5Py2/Zn/Gen)n by employing orthogonal pillar[5]arene-based molecular recognition and metal ion coordination. Within the supramolecular polymer, the guest molecule Gen unit acts as a light-harvesting moiety, as the ACQ effect is inhibited by host-guest interactions, while the (Py)2/Zn center serves as a catalytic site. By employing this orthogonal self-assembly strategy, we have enhanced the stability of both the donor and acceptor in catalyzing the reduction of p-nitrophenol to p-aminophenol. Moreover, this photocatalyst can be reused at least 5 times without significant conversion loss. These findings provide a pathway for constructing a recyclable artificial LHS that mimics the entire photosynthesis process.

Tiger Habitat Quality Modelling in Malaysia with Sentinel-2 and InVEST

Deforestation is a threat to habitat quality and biodiversity. In intact forests, even small levels of deforestation can have profound consequences for vertebrate biodiversity. The risk hotspots are Borneo, the Central Amazon, and the Congo Basin. Earth observation (EO) now provides regular, high-resolution satellite images from the Copernicus Sentinel missions and other platforms. To assess the impact of forest conversion and forest loss on biodiversity and habitat quality, forest loss in a tiger conservation landscape in Malaysia is analysed using Sentinel-2 imagery and the InVEST habitat quality model. Forest losses are identified from satellites using the random forest classification and validated with PlanetScope imagery at 3–5 m resolution for a test area. Two scenarios are simulated using InVEST, one with and one without the forest loss maps. The outputs of the InVEST model are maps of tiger habitat quality and habitat degradation in northeast Peninsular Malaysia. In addition to forest loss, OpenStreetMap road vectors and the GLC2000 land-cover map are used to model habitat sensitivity to threats from roads, railways, water bodies, and urban areas. The landscape biodiversity score simulation results fall sharply from ~0.8 to ~0.2 for tree-covered land cover when forest loss is included in the habitat quality model. InVEST makes a reasonable assumption that species richness is higher in pristine tropical forests than in agricultural landscapes. The landscape biodiversity score is used to compare habitat quality between administrative areas. The coupled EO/InVEST modelling framework presented here can support decision makers in reaching the targets of the Kunming-Montreal Global Biodiversity Framework. Forest loss information is essential for the quantification of habitat quality and biodiversity in tropical forests. Next generation ecosystem service models should be co-developed alongside EO products to ensure interoperability.

Effect of dietary β-mannanase supplementation on broiler performance

This study was conducted to investigate the effect of graded levels of β-mannanase supplementation in broiler diets on growth performance, energy digestibility, and lesion scores in d-old birds fed mash, corn-soybean meal-based diets and raised to 42 d. Five dietary treatments were investigated: 1) positive control diet (PC) containing standard energy; 2) negative control (NC) with 100 kcal/kg diet reduction in AME compared to PC; 3) NC supplemented with 30 U/g β-mannanase (NC + 30 U); 4) NC supplemented with 60 U/g β-mannanase (NC + 60 U); and 5) NC supplemented with 90 U/g β-mannanase (NC + 90 U). Each treatment had 6 replicate pens with 52 chicks per replicate. Data was analyzed using 1-way ANOVA, and means were separated by LSMEANS. Reduction of 100 kcal/kg feed (NC) resulted in an overall body weight gain reduction of 51 g (P < 0.05) and feed conversion loss of approximately 4 points (P < 0.05) compared to PC at 42 d of age. At the same time, supplementing β-mannanase at 60 and 90 U/g improved growth performance parameters compared to NC, while 30 U/g did not result in significant improvements beyond NC; body weight gain was improved (P < 0.05) by 87, and 106 g when β-mannanase was supplemented at 60 and 90 U/g, respectively, compared to NC. This corresponded to an improvement by 6 and 7 points in feed conversion for 60 and 90 U/g supplementation, respectively, compared to NC. Furthermore, AMEn was improved (P < 0.05) by 15, 97, and 116 kcal/kg at 42 d when β-mannanase was added to NC at 30, 60, and 90 U/g, respectively. Digesta viscosity measured at 42 d was decreased (P < 0.05) by β-mannanase supplementation of 60 and 90 U/g, compared to NC, while 42 d lesion scores were improved (P < 0.05) by β-mannanase supplementation compared to NC. Data demonstrated that dietary supplementation of β-mannanase improved growth performance, energy digestibility, and reduced viscosity and lesion scores when supplemented with diets with a reduced energy content of 100 kcal/kg compared to a standard energy diet.

Исследование влияния конструкции антипараллельной пары диодов с барьером Шоттки на потери преобразования гармонического смесителя 3-мм диапазона

This paper presents the design and principle of operation of a passive harmonic mixer in the 3-mm range (75-110 GHz), the active element of which is an antiparallel pair of Schottky barrier diodes (SBD). A theoretical analysis of the mixer operation was carried out. A technique for measuring conversion losses using a vector network analyzer is presented. The experimental results of a study of the dependence of the conversion losses of a harmonic mixer on the design of an antiparallel pair of DBSs are presented. The variable parameters of the antiparallel pair of diodes were the distance between the anode leads, the length of the anode lead and the diameter of the Schottky barrier contact. The dynamic range of the mixer is investigated.