Single-stage Configuration Research Articles

Numerical thermal analysis and structural optimization of cascaded PCM heat sinks for thermal management of electronics

In the present study, an innovative cascaded phase change material (PCM) heat sink using organic PCMs was proposed for electronic thermal management. The design arranges multiple PCMs with progressively lower melting points along the heat transfer path, allowing active control of the melt front. A numerical model with 5 % accuracy was developed to evaluate thermal performance. Based on the validated model, the effects of PCM stage numbers, PCM volume fractions, fin types, and fin volume fractions were analyzed. The fin volume fractions were further optimized using a support vector machine (SVM) and genetic algorithm (GA) methods. Results showed that a three-stage PCM heat sink with pin fins and increasing configurations outperformed single-stage PCM heat sinks, enhancing heat transfer by up to 36.7 %. Additionally, the innovative cascaded PCM heat sink with a uniform 20 % fin volume fraction across the three stages achieved a 38.8 % improvement compared to single-stage configurations. When the fin volume fractions were set to 24.1 %, 17.6 %, and 13.0 % for the three stages, thermal performance of the innovative cascaded PCM heat sink was enhanced by up to 39.8 % compared to single-stage configurations. The findings provide valuable insights for the design and application of PCM-based thermal management systems, potentially leading to more efficient solutions for various engineering fields.

Numerical investigation on non-linear streaming effects in a two-stage coaxial pulse tube cryocooler

Stirling pulse tube cryocoolers (PTC) are widely used in aerospace applications for the cooling of infrared sensors and for filtering background thermal noise in the astro-imaging devices, etc. Present investigation aims to use numerical methods to demonstrate the nonlinear fluid flow, heat transfer, and vortex generation phenomena in a two-stage coaxial type inertance pulse tube cryocooler. The numerical simulation is conducted using commercially available Fluent® code for both single-stage and multi-stage configurations to show nonlinear processes with varying heat load conditions. It has been noticed that the width of the vortex produced inside the pulse tube grows with an increase in heat load capacity. This undesirable flow conditions yields an adverse effect in the cooling behavior and reduces overall performance of cryocooler with higher heat load. Additionally, streamlines, stream function, pressure and temperature variation plots are given for both stages with different heat load capacity to substantiate our results.

Single-Stage Standalone Photovoltaic Water Pumping System Using Predictive Torque Control (PTC) of Induction Machine

Solar energy is widely utilized for water pumping systems, particularly in remote areas. However, such systems have different configurations and strategies, each with its own advantages and drawbacks. To design a suitable system, this paper proposes a method that utilizes a single-stage conversion system with hydraulic storage. In this method, the predictive torque controller (PTC) adjusts the inverter switching while the electrical storage in batteries is replaced by the potential energy of water in tanks. The PTC works side-by-side with a maximum power point tracking (MPPT) technique to supply the optimal power to the water-pumping Induction Motor (IM). This maximum power tracking is maintained during the day hours to provide and store water, whereas the water supply is guaranteed due to the gravity at night. The effectiveness of the proposed system is evaluated through MATLAB/Simulink-based results, demonstrating that the single-stage configuration outperforms the double-stage configuration in terms of power optimization, torque ripples, and power loss reduction. Furthermore, the suggested system offers the advantage of cost-effective installation due to its simple structure.

Performance evaluation of a solar humidification dehumidification desalination system employing a multistage bubble column dehumidifier

In humidification-dehumidification desalination (HDD) system, conventional dehumidifiers require a large condensing area due to the additional thermal resistance to the heat transfer caused by high concentrations (60–95% by mass) of non-condensable gases present in the air. In a bubble column dehumidifier (BCD), condensation of humid air via direct contact with cold water in a column can significantly decrease condensing area and cost. Hence, in this study, a solar-powered HDD using a multistage BCD is designed and tested in the climatic conditions of Kerala, India. Single-stage and two-stage configurations are investigated in BCD. A mathematical model based on the energy and mass balance of each component is also developed. The model results are observed to be in good agreement with experimental measurements. The results showed that the daily freshwater yield, day average gain output ratio (GOR), and average BCD effectiveness of HDD system with two-stage BCD are 4.571 kg/m2, 0.79, and 0.9, respectively. Furthermore, upgrading the single-stage configuration of BCD to a two-stage configuration increases freshwater yield, day average GOR, and BCD effectiveness by about 6.24%, 6.75%, and 17%, respectively. Detailed water quality analysis revealed that freshwater quality is well within drinking water standards. The cost of freshwater is about 0.0716 $/liter.

A 79.2-μW 19.5-kHz-BW 94.8-dB-SNDR Fully Dynamic DT ΔΣ ADC Using CLS-Assisted FIA With Sampling Noise Cancellation

This brief proposes a fully dynamic discrete-time (DT) Σ ADC using a correlated level shifting (CLS)-assisted floating inverter amplifier (FIA) with a sampling noise cancellation (SNC) technique. The CLS-assisted FIA improves amplifier gain with a single-stage configuration, which has lower input-referred noise than the cascaded one. In combination with the proposed SNC, the noise contribution of the 1st-stage integrator can be minimized. We also propose a novel passive integrator cascaded with a passive adder that avoids unwanted inter-stage loading without a speed penalty. The prototype of the proposed ADC fabricated in a 65 nm bulk CMOS process realizes a fully dynamic operation and achieves 94.8 dB SNDR with an OSR of 256 for 19.5 kHz bandwidth while consuming 79.2 W from a 1.2V supply at a 10 MHz sampling frequency. The Schreier and Walden FoMs are respectively 178.7 dB and 45.2 fJ/conv.-step, which are the best among recent fully dynamic DT Σ ADCs with similar bandwidth.

Continuous polyhydroxybutyrate production from biogas in an innovative two-stage bioreactor configuration.

Biogas biorefineries have opened up new horizons beyond heat and electricity production in the anaerobic digestion sector. Added-value products such as polyhydroxyalkanoates (PHAs), which are environmentally benign and potential candidates to replace conventional plastics, can be generated from biogas. This work investigated the potential of an innovative two-stage growth-accumulation system for the continuous production of biogas-based polyhydroxybutyrate (PHB) using Methylocystis hirsuta CSC1 as cell factory. The system comprised two turbulent bioreactors in series to enhance methane and oxygen mass transfer: a continuous stirred tank reactor (CSTR) and a bubble column bioreactor (BCB) with internal gas recirculation. The CSTR was devoted to methanotrophic growth under nitrogen balanced growth conditions and the BCB targeted PHB production under nitrogen limiting conditions. Two different operational approaches under different nitrogen loading rates and dilution rates were investigated. A balanced nitrogen loading rate along with a dilution rate (D) of 0.3 day-1 resulted in the most stable operating conditions and a PHB productivity of ~53 g PHB m-3 day-1 . However, higher PHB productivities (~127 g PHB m-3 day-1 ) were achieved using nitrogen excess at a D = 0.2 day-1 . Overall, the high PHB contents (up to 48% w/w) obtained in the CSTR under theoretically nutrient balanced conditions and the poor process stability challenged the hypothetical advantages conferred by multistage vs single-stage process configurations for long-term PHB production.

Metabolic Functional Profiles of Microbial Communities in Methane Production Systems Treating Winery Wastewater

This study investigated the impact of process configuration and conditions on microbial communities and metabolic pathways in the anaerobic digestion of winery effluents. Four system configurations were analyzed for taxonomic and functional profiles using 16S rRNA gene sequencing and Tax4Fun2. Sporolactobacillus, Prevotella, and Acetobacter dominated (> 70%) in the acidogenic reactor with 5277 conserved functions across configurations. In the methanogenic reactor, methane production relied on Methanosaeta in the single-stage configuration (13%) and five archaea genera in the two-stage configuration (18%). Thermophilic conditions favored syntrophic acetate oxidation and hydrogenotrophic methanogenesis by Methanothermobacter (65%), significantly changing due to temperature. The two-stage configuration exhibited 3.0 times higher functional redundancy than the single-stage configuration. Mesophilic conditions displayed 2.5 times greater functional redundancy than thermophilic conditions. High organic loading rate and short hydraulic retention time reduced functional redundancy by 1.5 times. Assessing microbial functionality beyond their composition is crucial to understand stability and performance of anaerobic digestion systems.

Design and optimization of reverse osmosis unit for vinasse purification of Moroccan distillery

The aim of this work is to design and optimize a RO unit that can be integrated into a Moroccan distillery, for vinasse purification. The RO membrane was chosen, for its efficiency to remove acetic acid and glycerol. Based on water flux calculations, the RO unit design was carried out, proposing a single-stage configuration with modules grouped in series. Subsequently, Artificial neural network (ANN) and Non-dominated sorting genetic algorithm-II (NSGA-II) are applied to optimize the rejections depending on the operating parameters of the proposed process. The effect of these parameters on the two rejections was conducted by numerical experiments using physical model. The resulting data are exploited to develop a reliable ANN model allowing a satisfactory prediction of the rejections. By coupling this model to the NSGA-II the optimal rejections are 99.8% for acetic acid and 98.8% for glycerol. The cost of vinasse purification is evaluated to 0.48 US$/m3.

An improved reduced order model for bladed disks including multistage aeroelastic and structural coupling

To assess the influence of mistuning on the vibration amplitudes of turbomachinery rotors, reduced order models (ROMs) are widely used. A variety of methods are available for single-stage configurations and mostly aeroelastic effects can be taken into account. More recent research focusses on extending these methods to include multiple stages. However, due to the significantly increased computational effort of the aeroelastic simulations when adding more stages to the models, these ROMs are rarely applied with the inclusion of multistage aeroelastic effects. It is therefore desirable to develop reduction methods which minimize the number of these simulations to reduce the computational cost and thereby enable analyses of rotors with multiple stages including aeroelastic effects. In this paper, a cyclic Craig-Bampton reduction method with an a priori interface reduction for multistage rotors is extended with an additional a posteriori interface reduction to reduce the number of aeroelastic simulations necessary for a given accuracy level of the ROM. The interface degrees of freedom between stages are reduced using a modified version of Characteristic Constraint Modes, to yield a more efficient representation of their displacements while retaining their monoharmonic nature. The method is applied to a two-stage axial compressor with full aeroelastic coupling between the stages and its reduced computational effort is demonstrated. Additionally, two sorting methods for the degrees of freedom (DOFs) of the ROM are compared.

Economic and thermal performance analysis of two-stage thin-film solar thermoelectric power generator

One of the performance enhancement strategies in thermoelectric technology is application of two-stage leg instead of normal single stage leg structure. However, for a thin-film solar thermoelectric generator applying this strategy requires many in-depth considerations including economic -cost and reliability aspects. In this research, attempts are made to identify the economic and performance characteristics of a two-stage thin-film solar thermoelectric generator under various geometrical conditions and then compare with normal single stage configuration. Generally, in addition to being cost-effective compared to the single-stage design, the double-stage design can produce more power if the appropriate material is selected. The results of numerical simulations show that the use of bismuth tellurides in single stage thermoelectric generator (SATEG) legs improves the performance of the system in terms of power generation. But the use of skutterudites in the lower layer and bismuth tellurides in the upper layer of the two-stage case, in addition to increasing the output power, significantly reduces the dollar/watt value. Furthermore, the highest output power and exergy efficiency are obtained in the lower layer angle ratio of 0.8–1 and in the upper layer angle ratio of 2. Among the geometrical parameters, the radius of heated area (Rh) has the greatest effect on the performance of double-stage solar annular thermoelectric generator (DSATEG). The highest power output is obtained at Rh = 1.5, which is equal to 1.323W.

Development of continuous spatially distributed diafiltration unit operations

The objective of this study is to develop an operation that can conduct separations based on diafiltration using semipermeable nanofiltration or ultrafiltration membranes in a fully continuous manner in a single stage configuration.

Increasing the efficiency of the use of oil fuel in thermal power stations and boilers

An organization can achieve good results by properly managing the supply of fuel, ensuring the desired intensity of combustion, and optimizing the volume of the combustion process to promote complete combustion. Additionally, the mixing of fuel with secondary air, provided by combustion devices, is crucial for achieving efficient combustion. Experimental studies conducted on boilers in thermal power plants have demonstrated that heating the secondary air can enhance energy efficiency. This improvement is particularly relevant for fuel oil and gas burning. To optimize the combustion of fuel oil, steam-mechanical nozzles are commonly utilized. These nozzles excel in prolonging the combustion process, leading to more efficient fuel oil burning. When burning gas and fuel oil, a two-stage arrangement of burners in the boiler is more effective than a single-stage configuration, regardless of whether the burners are positioned in opposite directions or in a one-sided frontal arrangement. To mitigate the emission of nitrogen oxides, several measures can be taken. It has been observed that recirculating flue gases from the heat is more effective than solely utilizing flue gas. Additionally, the strategic placement of boilers with furnace gases and the optimization of turning parameters can also contribute to reducing harmful nitrogen oxide emissions.

A comparative sustainability evaluation of alternative configurations of an urban nitrogen removal solution targeting different pathways

Limiting the introduction of excess nitrogen to natural water sources is a growing priority for water security and environmental health. This poses particular difficulties in urban environments where available land for potential solutions is limited. A promising option is the integrated fixed-film activated sludge (IFAS) process that requires only a small footprint and is capable of high total nitrogen (TN) removal through multiple pathways. In light of the sustainable development goals set out by the United Nations, the present work has sought to compare the sustainability of two TN removal pathways by comparing the technical, economic and environmental performance of their optimum configurations. Through modelling, a single-stage configuration demonstrated the capacity to achieve an effluent TN concentration of 8.7 mg/L by the simultaneous nitrification denitrification pathway when a dissolved oxygen concentration of 3.5 mg/L was provided. Addition of a post-anoxic stage at equal volume to the aerobic stage (1:1 aerobic to anoxic ratio) to target conventional nitrification denitrification could realise an effluent TN concentration of 4.2 mg/L when DO was increased to 4.5 mg/L, although 5.8 mg/L of effluent TN could be achieved with only a 5:1 ratio. In terms of environmental burden and economic costs, analysis of the system's life-cycle under these different configurations indicated considerable asymmetry of the two pathways during the operational phase due mainly to the increased aeration. However in spite of this, the two conventional configurations were ultimately both shown to be more sustainable than that of the simultaneous pathway due to the greater TN removal capacity afforded.

Common-Ground Grid-Connected Five-Level Transformerless Inverter With Integrated Dynamic Voltage Boosting Feature

A single-phase common-ground five-level (5L) inverter with a dynamic voltage conversion gain and capability of operating in a wide input voltage range and a single-stage energy conversion configuration is presented in this article. The proposed topology requires nine active power switches and is comprised of an integrated switched-boost (SB) module connected in series to a switched-flying-capacitor (SFC) cell. Two self-balanced capacitors with a single boost inductor in the integrated SB module are employed to generate a 5L output voltage waveform with a dynamic voltage conversion gain. The current stress profile of all the active and passive elements is kept within a permissible input current range. By adopting an extra diode-capacitor-inductor network into the integrated SB module and with the utilization of the same SFC cell, the proposed topology is extended to achieve a quadratic voltage conversion gain while retaining the quality of ac voltage waveform. Theoretical analysis, closed-loop control/modulation principles, design guidance, comparative study, and relevant experimental results obtained from a 1.5-kW laboratory-built prototype are presented to ascertain the operation and feasibility of the proposed system.

Flexible Active Power Control of Distributed Photovoltaic Systems With Integrated Battery Using Series Converter Configurations

Flexible active power control (FAPC) is becoming mandatory for PV systems, which is to limit/reserve the PV power below certain constraints as commanded, including the power ramp-rate control (PRRC), power limiting control (PLC), and power reserve control (PRC). In practice, energy storage (ES) such as batteries can be adopted to reduce the PV energy discarding in such cases. On the other hand, concerning the system overall cost, single-stage series power converter configurations are becoming attractive. Such configurations bring more flexibilities by integrating PV systems and batteries. However, the implementation of FAPC functions in series power converter configurations has not been systematically investigated. To fill this gap, the PRRC, PLC, and PRC strategies for series-PV-battery systems are developed in this article. With the proposed strategies, the power ramp-rate/limiting/reserve constraints are maintained by the coordinated control of individual converters. The reserved power is then distributed among all converters depending on the available power of individual PV converters, battery power, and state-of-charge (SoC) conditions. Experimental tests performed on a 1.6-kW system have validated the effectiveness of the proposed solution.

Design of radio frequency power amplifier for 2.45 GHz IoT application using 0.18 µm CMOS technology

PurposeThe purpose of this study is to show that due to the emergence of the Internet of Things (IoT) industry in recent years, the demand for the higher integration of wireless communication systems with a higher data rate of transmission capacity and lower power consumption has increased tremendously. The radio frequency power amplifier (PA) design is getting more challenging and crucial. A PA for a 2.45 GHz IoT application using 0.18 µm complementary metal oxide semiconductor (CMOS) technology is presented in this paper.Design/methodology/approachThe design consists of two stages, the driver and output stage, where both use a single-stage common source transistor configuration. In view of performance, the PA can deliver more than 20 dB gain from 2.4 GHz to 2.5 GHz.FindingsThe maximum output power achieved by PA is 13.28 dBm. As the PA design is targeted for Bluetooth low energy (BLE) transmitter use, a minimum of 10 dBm output power should be achieved by PA to transmit the signal in BLE standard. The PA exhibits a constant output third-order interception point of 18 dBm before PA becomes saturated after 10 dBm output power. The PA shows a peak power added efficiency of 17.82% at the 13.24 dBm output power.Originality/valueThe PA design exhibits good linearity up to 10 dBm out the PA design exhibits good linearity up to 10 dBm output power without sacrificing efficiency. At the operating frequency of 2.45 GHz, the PA exhibits a stability k-factor, the value of more than 1; thus, the PA design is considered unconditional stable. Besides, the PA shows the s-parameters performance of –7.91 dB for S11, –11.07 dB for S22 and 21.5 dB for S21.

Dual-Boost Inverter for PV Microinverter Application—An Assessment of Control Strategies

Photovoltaic (PV) microinverters have grown rapidly in the small-scale PV market, where typical two-stage converters are used to connect one PV module to the single-phase AC grid. This configuration achieves better performance in terms of energy yield compared with other PV configurations. However, the conversion efficiency of a two-stage system is the main drawback, especially when a high-voltage gain effort is required. In this context, single-stage microinverter topologies have been recently proposed since only one power conversion stage is required to extract the maximum power of the PV module and inject the AC power to the grid. This single-stage configuration allows considerable improvement of the overall efficiency of microinverters by reducing the number of elements in the system. However, the main challenge of these topologies is their control, since all variables of the converter are composed by the AC waveform with DC-bias. In this paper, four control strategies are analyzed for the mainstream single-stage topology, which is the dual-boost inverter (DBI). Classical linear control and three non-linear strategies, namely finite control set–model predictive control, flatness-based control, and sliding mode control, are detailed. The main contribution of this work is a complete comparison of the control strategies, to give insights into the most suitable control strategy for the DBI in PV microinverter application.

Compact CMOS Wideband Instrumentation Amplifiers for Multi-Frequency Bioimpedance Measurement: A Design Procedure

The design of an instrumentation amplifier (IA), based on indirect current feedback and suited to electrical bioimpedance spectroscopy, is presented. The IA consists of two transconductors and a summing stage, featuring a single-stage configuration process that allows the maximum achievable bandwidth to be extended. The transconductors are linearized by means of resistive source degeneration, whereas the use of super source followers allows a reduction in the values of the source degeneration resistors. This fact leads to a decrease in the overall noise and the silicon area, thus resulting in a compact implementation. A thorough analysis of the proposed solution, accompanied by a design procedure and verified by means of electrical simulations, is also provided. Two versions of the IA, i.e., a single-ended (SE) and a pseudo-differential (PD) structure, were designed and fabricated using 180 nm CMOS technology to operate with a 1.8 V supply. The experimental results, including a BW of 5.2 MHz/8.0 MHz, a CMRR higher than 72 dB/80 dB, a DC current consumption of 139.0 μA/219.3 μA and a silicon area equal to 0.0173 mm2/0.0291 mm2 for the SE/PD implementation, validate the suitability of the approach.

Palm biodiesel spray and combustion characteristics in a new micro gas turbine combustion chamber design

Micro gas turbine (MGT) is one of the main candidates for green distributed cogeneration since it allows the utilization of wider range of renewable fuel sources. A new chamber geometry was designed and optimized for liquid biofuels combustion. Prior to the testing of the chamber, a cold-flow fuel atomization test rig was tested with different fuel injector sizes covering flow range of 50–200 ml/min. Spray characteristics of palm biodiesel were investigated and compared to diesel as the benchmark. The chamber was then tested with diesel fuel followed by biodiesel in a single-stage MGT configuration. Turbine inlet temperature (TIT) was limited below 900 °C to avoid damaging turbine blades, thus, limiting the operating gauge pressure below 0.6 bar. A Power turbine with high-speed alternator and heat recovery unit (HRU) were then added to the test rig in a combined heat and power (CHP) configuration. The lab-scale MGT-CHP system was fully characterized in the pressure range of 0.1–0.4 bar and achieved overall efficiency of 24.7% and total NOx emissions range of 22–70 ppm with palm biodiesel.

Downscaling reverse osmosis for single-household wastewater reuse: towards low-cost decentralised sanitation through a batch open-loop configuration

Abstract There is a significant demand for water recycling in low-income countries. However, wastewater infrastructure is primarily decentralised, necessitating the development of affordable household-scale reclamation technology. In this study, a batch open-loop reverse osmosis (RO) system is therefore investigated as a low-cost clean water reclamation route from highly saline concentrated blackwater. In a single-stage configuration, increasing feed pressure from 10 to 30 bars improved selective separation at water recovery exceeding 85%, whereas lower cross-flow velocity improved product recovery, reducing specific permeate energy demand from 21 to 4.8 kWh m−3. Rejection achieved for total phosphorous (99%), chemical oxygen demand (COD, 96%), and final pH (8.7) of the RO permeate was compliant with the ISO30500 reuse standard for discharge. However, the rejection of total nitrogen in the RO permeate was non-compliant with the reuse standard due to the transmission of low-molecular weight (MW) uncharged organic compounds. It is suggested that rejection may be improved by increasing feed pressure to rebalance selectivity but may also be controlled by reducing fluid residence time (storage) to constrain the hydrolysis of urea. The economic analysis identified that a high-pressure 1812 element cost of ∼US$30 meets the sanitation affordability index of US$0.05 capita−1 day−1. However, the unit cost of a high-pressure feed pump must be reduced to ∼US$500 to obtain an affordable system cost. These unit costs can be achieved by manufacturing 1812 elements at economies of scale, and by adopting pumping solutions that have been developed for other applications requiring high pressures and low flows. Overall, our findings suggest that RO in the batch open-loop configuration has the potential to deliver affordable and safe water production from blackwater in a decentralised (single-household) context.