Varying Input Power Research Articles

High-efficiency quad-band RF energy harvesting system with improved cross-coupled differential-drive rectifier

Abstract RF energy harvesting technology has garnered significant attention from researchers in recent years. This paper presents a high-efficiency quad-band RF energy harvesting (RFEH) system. It introduces an improved cross-coupled differential-drive rectifier designed for ambient wireless powering, capable of harnessing power from four distinct ambient RF sources: FM-100, DTV-600, GSM-1800, and WiFi-2400 frequency bands. The proposed RFEH system demonstrates notable advancements, achieving a high RF to DC conversion efficiency of over 80 % within an input power range of −5 dB m to +13 dB m, with a 5 kΩ resistance load. This power output is deemed sufficient for energizing low-power micro-devices autonomously, without reliance on external power sources. Notably, the DC output voltage of the proposed RFEH system exhibits a high level of stability against variations in input power, a characteristic not adequately addressed in existing systems.

Numerical and experimental investigation of 12 W/60 K high-efficiency coaxial pulse tube cryocooler

Maintaining a low-temperature environment is paramount in pursuing reliable operation for infrared detectors. To address the rising demand for long-wave infrared detectors functioning in low-temperature environments around 60 K, this study investigates the enhanced efficiency of a 60 K coaxial pulse tube cryocooler (PTC) through both simulation analysis and experimental methods. A PTC model was developed using Sage software to optimize parameters such as cold finger size. Analysis of the internal flow field highlighted that variations in cold head temperature, frequency, and input power significantly impact phase angle distribution within the regenerator. Experimental results yielded the same conclusion and confirmed how these critical factors affect the PTC’s performance. Through systematic optimization of simulations and experiments, a cooling performance of 12.7 W/60 K was achieved with an input power of 300 W. Furthermore, when the input power of the PTC was 200 W, a cooling capacity of 9.2 W/60 K was achieved, demonstrating a relative Carnot efficiency of 18.3 %.

A dual ultra-wideband rectenna with a compact conical antenna for RF energy harvesting from S and C bands

The current research introduces a novel dual ultra-wideband rectenna that has been specifically devised for the S and C bands. The rectenna configuration being presented demonstrates the potential to efficiently capture energy from 1.5 GHz to 4.65 GHz, and 5.55 GHz–7.85 GHz. It is noteworthy to mention that the bandwidths (BW) corresponding to these frequency ranges are 3.15 GHz and 2.3 GHz, correspondingly. The envisioned rectenna is designed to cater to a selection of five distinct commercial bands. The frequencies under consideration include 1.8 GHz, UTMS 2.1 GHz, 5G 3.5 GHz, 4.5 GHz, and 5.8 GHz, which fall within the mid band range for 5G technology. Notably, the extended S-band and C band are also included within this range, catering specifically to 5G applications. For the purpose of rectification, a solitary HSMS 2850 Schottky diode has been selected. The maximum recorded Conversion Efficiency (CE) achieved at 1.8 GHz, 2.1 GHz, 3.5 GHz, 4.5 GHz, and 5.8 GHz corresponds to CE values of 67 %, 65 %, 77 %, 71 %, and 71 %, respectively. These CE measurements were obtained under varying input power levels (IPL) of −6 dBm, 4 dBm, 4 dBm, 2 dBm, and 9 dBm, respectively. The rectenna under consideration is designed to operate across five distinct frequency bands. Notably, the CE exceeds 65 % across all of these frequency bands. Consequently, the rectenna exhibits a higher output power. As a result, this modification makes it appropriate for supplying energy to low-power electronic equipment.

Design and fabrication of a heat pipe and thermoelectric cooler-based food delivery box for vehicles

In recent years, there has been a notable surge in interest regarding the application of heat pipe and thermoelectric cooling technologies to recuperate waste heat, conserve energy, and augment thermal efficiency across diverse commercial and engineering domains. Particularly within the realm of food delivery services reliant on online ordering systems for the conveyance of freshly prepared meals from restaurants to consumers, sustaining the quality of food during transit poses a significant challenge due to heat dissipation from food containers over extended transportation distances. Consequently, maintaining optimal food temperature or beverage warmth in online orders becomes a pressing concern. This investigation's primary goal was to design and construct a portable heating-cooling chamber that would maintain food temperature during transportation. This technological endeavor offers a viable solution to contemporary energy dilemmas by leveraging electricity and waste energy from vehicles to furnish efficient cooling and heating mechanisms. The heating aspect of the chamber is facilitated by a meticulously developed heat pipe system that utilizes deionized water as the working fluid. Experimental results reveal that a 75 % filling ratio engenders optimal heat pipe performance across varying input power levels. The proposed design amalgamates a heating and cooling chamber, integrates a thermosyphon heat pipe within the exhaust gas trajectory to recuperate dissipated heat, and harnesses the vehicle battery to power a thermoelectric cooler. Experimental results substantiate the efficacy of the thermosyphon heat pipe in elevating the heating chamber's temperature to 48 °C within a span of 25 min, while concurrently, the thermoelectric cooler achieves the desired cooling chamber temperature of 5 °C within a mere 8 min.

Empirical Validation of Fuzzy Logic Based Predictive Load Scheduling in Mimic Home Energy Management System

<p>Load scheduling plays a vital role in the home energy management systems. The main objective of this load scheduling is to balance the power demand and supply power without degrading the performance of the loads and consumers tolerance. Though many research works concentrate on load scheduling, very few works concentrated on real time scenario. On the other hand, research work concentrated on optimal load scheduling through fuzzy logic requires incorporation of fuzzy based system in either simulated or real-time home energy management system. Hence, the proposal aims to schedule the loads in a simulated home energy management system through fuzzy logic controller using MATLAB Simscape with required subsystems. The proposed simulated environment considers four different resistive loads. Intelligent scheduling is aimed to achieve efficient load scheduling. A fuzzy controller has three inputs namely integrated source, state of charge of battery, and power demand whereas probability of scheduling is considered as output. The efficiency of the proposed fuzzy-based load scheduling scheme is evaluated under various load conditions for different sub-systems with varying input power. The results exhibit the efficacy of the proposed scheme.</p> <p> </p>

Reconfigurable all-optical logic device based on cross-phase modulation across highly non-linear fiber

All-optical logic gates are the basic building blocks of photonic integrated circuits to be used for signal processing, to ensure high speed signal processing and decreasing complexity of network. In this paper, reconfigurable all-optical logic gate has been proposed and numerical simulations are analysed at a bit rate of 120 Gb/s. Wavelength Converter, NOT, NOR, AND, XOR, XNOR, A¯.B and OR are the all-optical logic gates that has been designed and implemented using single circuit and has minimum quality factor of 27 dB. All the signal processing operations have been implemented by the exploitation of cross-phase modulation in two parallelly placed (Mach-Zehnder Interferometric configuration) highly nonlinear fibers (HNLF). The influence of variation in input power, at different length of HNLF determines that the quality factor increases for increase in power or length of highly nonlinear fiber up to a certain limit. Quality factor increases for decrease in effective area of the highly nonlinear fiber for a certain range of input power and saturates for further increase in input power. Also, the quality factor is not directly affected with increase in bit rate but adversely affected by increase in dispersion.

Impact of Ignition Assistant on Combustion of Cetane 30 and 35 Jet-Fuel Blends in a Compression-Ignition Engine at Moderate Load and Speed

Abstract This study investigates the use of a commercial-off-the-shelf (COTS) ceramic glow-plug to assist ignition of jet fuel blends with cetane numbers of 30 and 35, below the minimum cetane number of 40 for #2 diesel. Experiments were carried out on a single-cylinder compression-ignition engine operating at 1200 RPM for single and dual-injection (pilot + main) timing sweeps. The COTS glow-plug, termed the ignition assistant, was operated at varying input power levels between 0 and 70 W (stock maximum power input is 30 W) at each SOI. Results demonstrate that the use of an ignition assistant at the higher input powers (50 and 70 W) enables operation over a wider range of SOI timings where more advanced times are limited by high pressure-rise rates and more retarded times are limited by rapidly increasing coefficient of variation of gross indicated mean effective pressure. Use of the ignition assistant enables stable combustion at later injection timings increasing the operable range of SOI timings. For the CN 30 fuel, at earlier injection timings, pressure traces, and heat release analysis demonstrated the advancement of start of combustion and combustion phasing with the ignition assistant on. At retarded injection timings where combustion would not otherwise occur completely for the CN 30 fuel, operating the ignition assistant at the higher powers enabled combustion phasing to be advanced and combustion to be stabilized at conditions where, with the ignition assistant off, misfire (flameout) would occur. Furthermore, the ignition assistant enabled combustion phasing to follow an approximately linear response with respect to SOI timing over a wider range of SOI times.

An analytical study of wireless power transmission system with metamaterials

Abstract Computation of transmission system efficiency of electromagnetic radiation becomes inaccurate when Friis formula is used in Fresnel zone (near-field zone) of wireless power transmission (WPT). A novel methodology has been proposed in this paper for estimation of the power density, received power and transmission system efficiency at a particular operating frequency in the near-field zone. The power transfer and transmission system efficiency need to be maximized for minimal dimensions of transmitter and receiver. Utilization of negative refractive index metamaterials (MM) between transmitter and receiver is proposed to achieve maximum power transfer. In the present paper, variation of received power and system efficiency with respect to transmitting distance is computed and compared for WPT system with and without metamaterials. The variation of system efficiency is studied for varied location of metamaterial from transmitter by assuming metamaterial diameter at a given location is greater than or equal to the beam diameter at that location. Different configurations with varied input power and transmitting distances from shorter to longer range are considered in the study to analyse parameters that affect system efficiency. The approach for identifying optimal number of metamaterials and their placement between transmitter and receiver for maximum power transfer has also been discussed.

Effect of microwave drying pretreatment prior to soxhlet extraction of coffee oil

To increase the effectiveness of the coffee oil processing process in drying coffee beans, in this study, pretreatment drying using a microwave was evaluated. The drying method using a microwave was carried out with three power inputs. After the drying process, it was followed by roasting and grinding process of the coffee beans. Then the coffee beans were extracted so that the oil was obtained. From the process of drying coffee beans using a microwave with 3 variations of input power, namely MH, MM, and ML, from the initial moisture content of 56.75%, the moisture content was 7.29% in a row; 8.32%; and 10.32%. Meanwhile, from the results of the extraction of coffee beans in the three variations of the drying process, the yield of coffee oil was 16.936%, 16.448%, and 2.534%, respectively. It can be seen that the input power in the microwave drying process greatly affects the results of decreasing the moisture content of coffee beans and the yield of coffee oil. In addition, from the process that has been carried out, it can be seen that the fatty acid content obtained in coffee oil was high. So that the drying process carried out using a microwave is very effective to do in producing coffee oil with high yields.

Design and off-design performance analysis of a liquid carbon dioxide energy storage system integrated with low-grade heat source

Nowadays, developing the renewable energy has become the worldwide consensus. Nevertheless, the intermittency and volatility of renewable electricity bring great challenges to the stability of the power grid. Liquid carbon dioxide energy storage is recognized as one of the most promising technologies to overcome these difficulties. In this paper, a liquid carbon dioxide energy storage system integrated with the low-grade heat source is proposed. Based on the preliminary geometric parameters of system components, investigations on the system design and off-design performances are carried out. Results of parametric analysis indicate that the pseudo-critical point corresponding to 8 MPa is recommended as the design point for compressor inlet, and the minimum value of LCOE could reach 9.49 cents/kWh. Under design conditions, the system exergy efficiency reaches 48.42% and the roundtrip efficiency is 63.60%. Moreover, 10.70 cents/kWh of the per unit generation cost is advantageous in the large-scale energy storage systems. With the variations of input power (70%∼120%) and output power level (50%∼100%), the surplus water ratio could reach 23.63% at 50% load level, while the variation range of exergy efficiency is 15.56%∼48.42%. Meanwhile, the roundtrip efficiency varies from 22.16% to 63.60% under off-design conditions, and the maximum value is achieved at the design point. All the results identify the feasibility of the integrated energy storage system.

Minimizing FWM Impact in DWDM ROF DP-DQPSK System for Optical

The demonstration of a higher data rate transmission system was a major aspect to be considered by researchers in recent years. The most relevant aspect to be studied and analyzed is the need for a reliable system to handle nonlinear impairments and reduce them. Therefore, this paper examines the influence of Four-Wave Mixing (FWM) impairment on the proposed high data rate Dual polarization–Differential Quadrature phase shift keying (DP-DQPSK) system using the Optisystem software. In the beginning, the impact of varied input power on the proposed system’s performance was evaluated in terms of QF and BER metrics. More power is used to improve system performance. However, increasing power would raise the FWM effects. Accordingly, a −10 dBm input power and the proposed system are used to reduce the impact of FWM. Additionally, a hybrid amplification method is proposed to enhance system performance by utilizing the major amplification methods of erbium-doped fiber amplifier (EDFA): semiconductor optical amplifier (SOA) and Radio optical amplifier (ROA). The evaluation demonstrates that the OA-EDFA outperformed the other two key amplification techniques of (EDFA-SOA) and (EDFA-ROA) in improving Quality factor (QF) and Bit error rate (BER) system results for all distances up to 720 km. Consequently, the method contributes to minimizing the impact of FWM. In the future, other forms of nonlinearity will be investigated and studied to quantify their impact on the proposed system.

Experimental Investigation of Low-Pressure Microwave Plasma with Oxygen and Argon for Internal Sterilization of Medical Devices with Slender Catheters

This study explores the application of microwave plasma sterilization methods to prevent surgical site infections, specifically targeting the challenge of sterilizing slender catheters used in medical devices. An experimental setup was designed to verify the sterilization effectiveness by varying input power levels, treatment times, and the ratio of injected gases. The temperature inside the sterilization setup was closely monitored to ensure that the death of bacterial spores was not caused by thermal effects. The results demonstrate that microwave plasma has a robust sterilization effect when the microwave power is 200 W, the treatment time is 10 minutes, and the ratio of oxygen to argon is higher than 14.45%. The study highlights that the sterilization effect of plasma significantly depends on the composition of the discharge gas. The experimental setup is capable of simulating sterilization inside slender catheters, indicating the potential of microwave plasma sterilization for such medical devices.

The Modified MPPT for PV System with Interleaved Hybrid DC-to-DC Boost Converter

A modified maximum power point tracking control technic for an off-grid photovoltaic system which include the interleaved hybrid DC-to-DC boost converter was presented in this paper. The input voltage was predicted by measured one branch current of the proposed hybrid DC-to-DC boost converter. The proposed control technic consists of maximum power point tracking with the predicted input voltage and PI controller. Thanks to the proposed control technic, the photovoltaic panel was forced to operate at maximum power point and the output voltage of the proposed converter ensured the desired value despite the varying input power. In addition, the interleaved hybrid DC-to-DC boost converter was increased the low output DC voltage of photovoltaic panel to the desired high voltage value and the stresses on the circuit elements was decreased by reducing the input current ripples. As a conclusion, the total cost of the proposed system is reduced by eliminating the sensing of the input voltage and the service lifespan of the proposed system is extended by using the interleave hybrid DC-to-DC boost converter. The simulation and experimental results of the proposed system were obtained by using MATLAB/Simulink and 400 W DSP TMS320F28379D based porotype, respectively.

Increased radiation due to non-coronal effects on DIII-D and MAST-U with varying input power

Through SOLPS-ITER simulations of DIII-D and MAST-U, an X-divertor (XD) on DIII-D and a super X-divertor (SXD) on MAST-U were shown to have increased carbon emissivity (P Rad/n e n I) over corresponding standard divertors (SD) at similar degrees of partial detachment. The reasons behind the increased emissivity in the DIII-D XD and SXD are analyzed using a simple 0D transport model. From the transport model, it is seen that a major cause of the increased emissivity in the XD and SXD over the SDs is a shorter impurity confinement time. An additional cause (for the SXD) is an increase in the ratio of neutral hydrogen to electron density. The input power (P in) was varied and the XD had a higher emissivity at the higher P in, unlike the SDs which had the emissivity decrease with increasing P in. A basic geometrical reason is given to explain both the benefits of the XD over the SD as well as the increase in the XD’s emissivity with P in.

Techno-economic assessment of enhanced Biogas&Power-to-SNG processes with high-temperature electrolysis integration

Biogenic energy sources are essential elements of the decarbonization pathways, but are strongly constrained by the limited availability. In this context, Biogas&Power-to-X technologies are strongly supported as a promising solution to foster renewable power generation and drive sector coupling opportunities. This work investigates enhanced Synthetic Natural Gas (SNG) production processes for the repurposing of biogas plants. As an alternative to combined heat and power applications via internal combustion engines, the Italian legislation is supporting biogas-to-biomethane upgrading, focusing on the transport market. The proposed integrated plant scheme is a flexible solution based on Power-to-Hydrogen and methanation, able to exploit both electric and gas grid connections, enhancing biomethane production. Advanced process schemes are studied combining solid oxide electrolysers that exploit the methanation waste heat as input thermal energy and flexible PEM electrolysers that improve the part-load operation. The calculated efficiency at max load is about 55% for the Power-to-Methane block and nearly 75% for the overall integrated plant. Results show limited sensitivity of efficiency to input power variations, making the system suitable for the recovery of surplus renewable power generation.

Hybrid Digital Pre-Distortion for Active Phased Arrays Subject to Varied Power and Steering Angle

This letter proposes a memory polynomial (MPM)-aided deep neural network (DNN) digital pre-distortion (MaD-DPD) method for active phased arrays (APAs) subject to varied input power and steering angle. This has been challenging for traditional array linearization methods using either MPM or DNN, which rely on the in-phase and quadrature-phase (I/Q) signal as input and output to derive model parameters. In comparison, the proposed method actively incorporates MPM and DNNs to achieve linearization. The model uses only two varied APA state parameters (input power and steering angle) as input and the MPM coefficients as regression target, eliminating the need for model parameter updating. The MaD-DPD method is validated using a four-by-four antenna array at 28 GHz with 21 input power levels and a broad range of steering angles from −78° to 78°, improving up to 13.16% in error vector magnitude (EVM) and 18.21 dBc in adjacent channel leakage ratio (ACLR).

Statistical Digital Predistortion of 5G Millimeter-Wave RF Beamforming Transmitter Under Random Amplitude Variations

The nonlinearity of the fifth-generation (5G) millimeter-wave (mmWave) phased array transmitter (TX) depends on the variations in the beamforming coefficients, e.g., due to unwanted amplitude errors of the phase shifters or purposely introduced amplitude variations to shape the beam, as well as other analog component variations. Therefore, also the digital predistortion (DPD) coefficients depend on the beamforming coefficients and require a continuous update for different beamsteering directions in a conventional DPD. We propose a robust DPD approach that uses the average array response for DPD training. The average array response is estimated using the known experimental histogram of power amplifier (PA) input power variation resulting from the amplitude variations due to beamforming. The DPD training based on the average array response makes the DPD coefficients insensitive to beamforming variations. The proposed DPD strategy requires a shared feedback path for training and only a single set of DPD coefficients to linearize the array response in all beamsteering directions. The performance of the proposed DPD strategy is validated by over-the-air (OTA) measurements of a 28-GHz phased array TX over different steering angles. Experimental results show that the proposed DPD method using one set of DPD coefficients provides similar linearization performance across the steering angles compared with the DPD trained to all steering angles through the OTA reference antenna.

Mapping of cavitation intensity in a novel dual-frequency ultrasonic reactor of capacity 10 L

Mapping of a dual-frequency ultrasonic reactor was performed based on measurements of local cavitation intensity at various horizontal and vertical planes in the reactor for single frequency operation (22 kHz or 44 kHz) and dual-frequency operation (22 + 44 kHz) at varying input power of 250 and 450 W. The average cavitation intensity ranged between 73.6 and 86.7 W/cm2, 38.75 and 64.4 W/cm2, 86.7 and 100.6 W/cm2 for the operating frequencies of 22, 44 and 22 + 44 kHz respectively at maximum input power of 450 W depending on the location. Bubble dynamics simulations at various frequencies were also performed using the Keller-Miksis equation and the trends of bubble radius, collapse temperature and pressure were found to effectively match the experimental findings for cavitation intensity. The work has clearly elucidated the dependency of the cavitational activity on location, power dissipation and operating frequency mode with dual-frequency operating showing higher cavitation intensity.

Study on Impact of Different Electrode Materials on the Collector Performance in TWTs

Attaining good collector performance in terms of high collector efficiency, low backstreaming, and body interception current has been a prime motive for traveling wave tube (TWT) designers. Selection of appropriate electrode material can result in enhancement of collector performance for the same electrical design (with same electrode potentials and electrode geometry). Here, attempts have been made to quantitatively demonstrate the unexplored impact of electrode material selection on the collector performance systematically. The effect of electrode material on collector efficiency, backstreaming current, body interception current, and their fluctuations arising in a practical scenario due to the variations in input power drives and electrode potentials has been studied. This study has been extended for two different types of TWTs–one with high electronic efficiency and another with medium electronic efficiency at different operating frequencies. Five different electrode materials have been studied with precise recommendations provided for each of the two types of TWTs.

Enhancement of dynamic performance of wave energy converter by introducing a flow control

The stabilization of power take-off (PTO) is imperative especially under circumstances of fluctuating input wave energy. In this paper, a flow control valve is introduced to optimize the transient process of the hydraulic PTO, which can contribute to a quicker adjustment and a stronger stability. Under variations of input power and load torque in transient process, an open-loop control method and a closed-loop control method are proposed as the opening law of the above valve, and the hydraulic motor speed, the pressure at the accumulator inlet and the generated power are chosen as indicators to examine the regulation performance. Then, the synergic effect of the flow control valve and the accumulator in the transient process is discussed. The effectiveness of the two presented control methods on the fluctuation suppression is respectively tested and compared in both regular wave and irregular wave situations via simulation. To validate the practical effectiveness of the proposed methods, field experiments are conducted. The results demonstrate that the open-loop control can only improve the damping ability of the hydraulic PTO in the speed raising stage, while the closed-loop control can improve the stability both in the speed raising stage and in the load increasing stage.