Experimental Prototype Research Articles

A fuel cell powered rack prototype for data center application with waste heat recovery: design consideration and experimental verification

The combination of data center and PEMFC has been a promising data center zero-carbon emission solution. However, the relevant experimental studies are very rare and most work only solved the simple electrical coupling. This paper proposed a new in-rack data center servers and PEMFC coupling design scheme considering both the electrical coupling and thermal management coupling of the servers and PEMFC, and built a cabinet prototype for the first time. The complete multi-condition continuous experiment on the PEMFC system fully demonstrates the servers power supply stability of the prototype with the fast tested power response capability of 4.9 kW in 0.1 s. The experiments under rated condition (when the servers power is 5 kW) were conducted and the carbon emission level and efficiency performance of the prototype are analyzed. Under the rated condition, the highest prototype CHP efficiency is 64.1 % while the prototype can provide 41.6 ℃ hot water with 3.04 L·min-1 and the lowest prototype CHP efficiency is 59.8 % while the prototype can provide 61.1 ℃ hot water with 1.33 L·min-1. The prototype maintains the zero-carbon (or negative carbon) emission of servers. The average operation carbon emission rate is -35 g·h-1. Compared with the full grid supporting data center, the power average prototype operation carbon reduction rate is 0.13 g·s-1·kW-1. The application potential of the proposed data center and PEMFC coupling scheme is demonstrated with the prototype experiment results from the advantage of carbon emission and heat recovery potential.

Levelized Cost and Carbon Intensity of Solar Hydrogen Production from Water Electrolysis Using a Scalable and Intrinsically Safe Photocatalytic Z-Scheme Raceway System

The realization of an environmentally sustainable and widely-adopted hydrogen economy may require lowering hydrogen production costs of production pathways with ultra-low greenhouse gas emissions to $1/kg H2. The allocation of new or existing renewable electricity generation solely to hydrogen production remains contentious due to disputes regarding emissions accounting. Photoelectrochemical (PEC) hydrogen production technologies offer a unique solution, as hydrogen is produced directly from solar energy and water, without the need for electricity generation. However, cost projections for past photoelectrochemical designs have suggested that they are not cost competitive compared to conventional electrolysis systems manufactured at scale. Herein, we offer the first illustrative benchmark of cost and carbon intensity of hydrogen produced in a Type 2 Z-scheme photocatalytic reactor design that employs suspended semiconducting nanoparticles organized in two stacked baggies in a raceway design.To explore the near-term and future cost projection for hydrogen production via Type 2 photocatalytic Z-scheme raceways, the authors developed a bottom-up total installed capital cost model. This project cost model incorporates: 1) raceway reactor cost, derived from a Design for Manufacturing and Assembly (DFMA) process-based cost model, 2) mechanical balance of plant, including process equipment, piping, valves, and instrumentation, derived from equipment quotes, scaling, database values, and Aspen estimates; 3) electrical balance of plant, including wiring, derived from time and material cost correlations; 4) Site Preparation, focused on green field installation; and 5) Construction Overhead, including engineering, procurement, and construction (EPC) costs and project contingency. The capital cost model is fed into a Levelized Cost of Hydrogen (LCOH) discounted cash flow model that accounts for electricity and water consumption, in addition to other operating costs, including labor, maintenance, and raceway replacements.A hybrid life-cycle approach was used to develop an inventory of greenhouse gas emissions from all materials and energy flows associated with the facility life cycle. These flows are converted to emissions based on specific emission factors, or by using physical units-based input–output LCA models associated with the broader economic impacts of fuel and materials production, use, and end use.Estimates for levelized cost of hydrogen suggest that a 50 metric ton H2 per day (MTD) raceway plant can approach $2.50/kg H2 at an 8% solar-to-hydrogen efficiency with further cost improvements possible through increased performance and larger plant scales. Carbon intensity is estimated to be well under clean hydrogen targets for global warming potential of <2-4 kg CO2e/kg H2 produced. The results suggest a highly competitive and scalable technology, that justifies further experimental validation and prototyping in the field. Figure 1

A multi-stable rotational energy harvester for arbitrary bi-directional horizontal excitation at ultra-low frequencies for self-powered sensing

A rotational multi-stable energy harvester has been presented in this paper for harnessing broadband ultra-low frequency vibrations. The novel design adopts a toroidal-shaped housing to contain a rolling sphere magnet which absorbs mechanical energy from bidirectional base excitations and performs continuous rotational movement to transfer the energy using electromagnetic transduction. Eight alternating tethering magnets are placed underneath its rolling path to induce multi-stable nonlinearity in the system, to capture low-frequency broadband vibrations. Electromagnetic transduction mechanism has been employed by mounting eight series connected coils aligned with the stable regions in the rolling path of the sphere magnet, aiming to achieve greater power generation due to optimized rate of change of magnetic flux. A theoretical model has been established to explore the multi-stable dynamics under varying low-frequency excitation up to 5 Hz and 3 g acceleration amplitudes. An experimental prototype has been fabricated and tested under low frequency excitation conditions. The harvester is capable of operating in intra-well, cross-well, and continuous rotation mode depending on the input excitation, and the validated physical device can generate a peak power of 5.78 mW with 1.4 Hz and 0.8 g sinusoidal base excitation when connected to a 405 Ω external load. The physical prototype is also employed as a part of a self-powered sensing node and it can power a temperature sensor to get readings every 13 s on average from human motion, successfully demonstrating its effectiveness in practical wireless sensing applications.

Analysis and design of a three‐coil IPT system with independent dual output ports

AbstractIndustrial applications tend to involve a substantial assemblage of electronic devices, and it is imperative to consider diverse charging requirements while charging these devices. This paper proposes a three‐coil single‐input‐and‐dual‐output (SIDO) inductive power transfer (IPT) system to meet the charging requirements of different devices. The system includes two independent output ports, providing constant voltage (CV) output and constant current (CC) output for different loads, respectively. In addition, the zero‐phase angle (ZPA) operation can be achieved, thus avoiding injection of reactive power and improving energy transfer efficiency. Unlike previous related studies, the receiver of the proposed SIDO IPT system only includes one receiving coil to pick up energy, eliminating unnecessary cross‐coupling and complex decoupling circuits in traditional IPT systems with multiple outputs. This study first analyzes the CC/CV output theory of the proposed SIDO IPT system in detail, and designs and optimizes the parameters by establishing an equivalent model. Then, the conditions for achieving zero‐voltage switching (ZVS) operation of the inverter are obtained by analyzing the sensitivity of CC/CV performance to the variation of the compensation capacitors. Finally, a verification experimental prototype with 2.5A CC output and 72 V CV output is established to verify the effectiveness of the proposed IPT system.

Variable-Frequency Control for Totem-Pole Bridgeless Power Factor Correction Converter to Achieve Zero-Voltage Switching Without Zero-Crossing Detection Circuits

The totem-pole bridgeless power factor correction (PFC) converter, known for its advantages including simple topology, capability for zero-voltage switching (ZVS), and low common mode interference, presents an opportunity to enhance the efficiency and environmental friendliness of power systems. However, these converters have issues such as ZVS, requiring zero-crossing detection (ZCD) under circuits’ critical continuous mode (CRM) or additional auxiliary resonant circuits, resulting in increased circuit costs and control complexity. Therefore, this paper proposes a variable switching frequency digital control method to achieve ZVS under a wide operating range without ZCD circuits. At the same time, under the premise of ZVS, an interleaved parallel scheme is adopted to further minimize the current ripple and enhance the quality of the current waveform. Finally, an experimental 2 kW two-phase interleaved totem-pole bridgeless PFC converter prototype is designed to verify that the proposed method is correct and effective. The experimental prototype can reach an efficiency of 97.78%.

Enhanced Energy Transfer in Cavity QED Based Phototransistors.

We leveraged strong light-matter coupling, a quantum process generating hybridized states, to prepare phototransistors using donor-acceptor pairs that transfer energy via Rabi oscillations. In a prototype experiment, we used a cyanine J-aggregate (TDBC; donor) and MoS2 monolayer (acceptor) in a field effect transistor cavity to study photoresponsivity. Energy migrates through the newly formed polaritonic ladder, with enhanced device efficiency when the cavity is resonant with donors. A theoretical model based on the time-dependent Schrödinger equation helped interpret results, with polaritonic states acting as a strong energy funnel to the MoS2 monolayer. These findings suggest novel applications of strong light-matter coupling in quantum materials.

A novel arc‐shaped magnetic coupler with dual‐channel receiver for rotational misalignment tolerance in AUV underwater wireless power transfer systems

AbstractTraditional wet plug charging for autonomous underwater vehicles (AUVs) limits its application. Inductive power transfer (IPT) is an effective solution to this problem. This paper proposes an arc‐shaped magnetic coupler incorporated with solenoid coils to achieve a stable and efficient output against rotational misalignment for charging AUV. The novel magnetic coupler consists of two solenoid coils and an arc‐shaped coil with a reverse winding, guaranteeing a relatively constant total mutual inductance and decoupling from each other. This magnetic coupler has the characteristics of a compact structure, an ultra‐wide coupling range, and a relatively stable equivalent mutual inductance. The experimental IPT prototype can deliver 1.29 kW with a dc–dc efficiency of 93% under the fully aligned case and 1.2 kW with a dc–dc efficiency of 91% under the misaligned case.

Effect of blade length on unsteady cavitation characteristics of hydrodynamic torque converter

Hydrodynamic torque converters (HTC), as power transmission component for high-power machinery, achieve flexible and energy saving transmission by circulating viscous oil through multi-stage impellers, involving cavitation at high flow speeds. To achieve cavitation suppression and performance enhancement, this study analyzed the mechanism of HTC blade length on cavitation effects. The Computational Fluid Dynamics (CFD) model of cavitation in the internal flow field of HTCs with different blade length were established, a hydraulic performance and flow-induced vibration test system was set up, and experimental prototypes with different blade lengths were designed and manufactured. The macroscopic and microscopic transient cavitation characteristics of different blade length were studied. The results show that shortening the length of pump and turbine blades has a significant suppression effect on cavitation. Due to changes in the impeller outlet flow field and circulation flow, the cavitation attachment range has changed significantly. Additionally, the significant impact of blade length on the flow-induced vibration influent the evolution characteristics of transient cavitation. Shorter blades reduce the amplitude of pressure oscillations, improving the attachment stability of cavitation. This study has important implications for improving the performance of HTCs and reducing the occurrence of cavitation.

Experimental investigation of a novel hybrid solar-geothermal desalination process

The widespread application of renewable energy, particularly in water desalination, is critical for addressing global water scarcity. This paper proposes a novel hybrid sustainable desalination method that harnesses both solar and shallow geothermal energy through evaporation and condensation processes. The desalination device under consideration uses a parabolic trough solar collector to evaporate saline water, and then transports the generated water vapor to an underground vertical conduit. The vapor cools as a result of the underground low temperature, leading to condensation and the formation of fresh water. To assess the freshwater production capacity of the proposed system, a simple lab-scale prototype was developed. The experimental prototype's findings emphasize the substantial influence of temperature and velocity of water vapor at the inlet of the buried pipe on the efficiency of freshwater production. Despite its small scale, the prototype outperforms other solar desalination methods, producing a remarkable output of 740 ml/h of fresh water under specific conditions (temperature: 53 °C, velocity: 1.4 m/s) With an estimated productivity of 90 l m−2 day−1,the present desalination prototype is more effective when compared with other earlier experimental studies of solar desalination systems such as active solar still and humidifier, dehumidifier solar systems, This research contributes to the advancement of sustainable desalination technologies, holding promise for addressing water scarcity challenges globally.

Analytical modeling of cylindrical eddy current brakes and multi-objective optimization based on game theory

With the research and development of eddy current brake (ECB), today ECBs have been applied in a variety of fields including vibration control and braking of strong impact loads.The application of a new cylindrical structure eddy current brake (ECB) for strong impact braking of large machinery has been discussed recently. Its high-speed and high-kinetic-energy braking conditions require different analytical and optimization design models and methods from what has been addressed in previous studies. For subsequent more engineering-oriented research and optimization, modeling methods are needed, as well as analysis and optimization studies for braking forces and critical speeds of interest. In this work, a magnetic equivalent circuit model is established, and the influence of eddy current induced during application is taken into account by considering it as a magnetomotive force in the model. The braking force is calculated with the MEC model and an approximate electric field cross-section method. A small prototype experiment is carried out and proves the correctness of the proposed model. Using the proposed and FEM model, parameters of the ECB are analyzed. Then, aiming at design objectives of the ECB that are somewhat competitive under this special braking condition, a multi-objective optimization model is established using the Stackelberg game strategy. An FEM model is built and assessed based on optimization results. The results indicate that the multi-objective optimization model based on the Stackelberg game is effective for the design of this ECB structure.

Piezoelectric Linear Motors with Alternating Action for Motion Servo System of Probe Station

The development of a piezoelectric linear motor is presented in this paper, based on the principle of alternating motion, to meet the acting stroke and accuracy requirements for the probe station’s motion servo system. By partitioning the stator into tangential and normal components, two tangential actuators are affixed to the base, while two normal actuators are fixed on the preloading mechanism, thereby proposing a novel approach for connecting the stator and base. First, the construction and the working principle of the motor were introduced. Subsequently, the motor’s major components were designed through finite element simulation, followed by modeling the motor dynamics and deriving its displacement transfer function. Finally, an experimental prototype was fabricated, and a prototype test system was constructed. The driving method can realize a large stroke operation at a low frequency. The minimum operating frequency of the motor is 1 Hz, the minimum step is 12.55 μm, and the stroke is 105 mm. The study results will promote the development of high-performance probe systems.

Wideband isolator based on one-way surface magnetoplasmons with ultra-high isolation

In this paper, we present a new type of isolator based on one-way surface magnetoplasmons (SMPs) at microwave frequencies, and it is the first time that an experimental prototype of isolator with wideband and ultra-high isolation is realized using SMP waveguide. The proposed model with gyromagnetic and dielectric layers is systematically analyzed to obtain the dispersion properties of all the possible modes, and a one-way SMP mode is found to have the unidirectional transmission property. In simulation and experiment with metallic waveguide loaded with yttrium–iron–garnet (YIG) ferrite, the scattering parameters and the field distributions agree well with the analysis and verify the one-way transmission property. The isolation is found to be as high as 80 dB and the typical value of insertion loss is 1 dB. Besides, the one-way transmission band can be controlled by changing the magnetic bias. From theoretical analysis and simulation, it is found that with a tiny value of 10 Oe of the magnetic bias, the relative bandwidth can be tuned to be greater than 50%. Compared with conventional isolators, this one-way SMP isolator has the advantages of ultra-high isolation, wide relative frequency band, and requires much smaller bias field, which has promising potential in non-reciprocal applications.

Onopordum platylepis (Murb.) Murb. as a novel source of thistle rennet: First application to the manufacture of traditional Italian raw ewe’s milk cheese

In this study, for the very first time, aqueous extracts obtained from flowers of spontaneously grown or cultivated Onopordum platylepis (Murb.) Murb. thistles were used as coagulating agents for the pilot-scale manufacture of Caciofiore, a traditional Italian raw ewe’s milk cheese. Cheese prototypes were compared to control cheeses curdled with a commercial thistle rennet obtained from flowers of Cynara cardunculus L. After 45 days of ripening under controlled conditions, both the experimental and control cheese prototypes were analyzed for: cheese yield, physico-chemical (pH, titratable acidity, aw, proximate composition), morpho-textural (color and texture), and microbiological parameters (viable cell counts and species composition assessed by Illumina sequencing), as well as volatile profile by SPME-GC–MS. Slight variations in titratable acidity, color, and texture were observed among samples. Based on the results overall collected, neither the yield nor the proximate composition was apparently affected by the type of thistle coagulant. However, the experimental cheese prototypes curdled with extracts from flowers of both spontaneous or cultivated thistles showed 10 % higher values of water-soluble nitrogen compared to the control prototypes. On the other hand, these latter showed slightly higher loads of presumptive lactococci, thermophilic cocci, coliforms, and eumycetes, but lower counts of Escherichia coli. No statistically significant differences were revealed by the metataxonomic analysis of the bacterial and fungal biota. Though most volatile organic compounds (VOCs) were consistent among the prototypes, significant variability was observed in the abundance of some key aroma compounds, such as butanoic, hexanoic, and octanoic acids, ethanol, propan-2-ol, isobutyl acetate, 2-methyl butanoic acid, and 3-methyl butanal. However, further investigations are required to attribute these differences to either the type of coagulant or the metabolic activity of the microorganisms occurring in the analyzed cheese samples. The results overall collected support the potential exploitation of O. platylepis as a novel source of thistle coagulant to produce ewe’s milk cheeses.

Design, modelling and evaluation of a variable inertance bypass fluid inerter

The inerter emerged as a mechanical analogy to the electrical capacitor, completing the force-current analogy. It operates as a one-port, two terminal device, where the equal and opposite forces at its terminals correlate with the relative acceleration between them. This relationship is governed by ‘inertance’, a quantity that bears the unit of mass, allowing inerters to exert inertial forces. Inerters have gained considerable traction, particularly in vibration control applications. Derived from their passive counterparts, variable inertance inerters enable active control of their inertance through integrated control mechanisms. This work presents the design, modelling and evaluation of a variable inertance inerter prototype dubbed the ‘Variable Inertance Bypass Fluid Inerter’ (VIBFI). An experimental prototype of the concept was designed, constructed and tested. Simultaneously, an effort to develop and validate a mathematical model of the VIBFI is thoroughly documented. Experimental results demonstrate the controllability of performance parameters of the device, including inertance and damping coefficients, through modulating the flow restriction of the bypass channel. The mathematical models derived for the device can serve as an estimate for its performance parameters, though further refinement is required.

A novel design of a Wilkinson power divider based on the circular-shape resonator

Abstract This paper describes the general properties of power dividers, in particular matching and isolation. This original works relates to three different divider structures based on the circular-shaped resonator. These prototypes resemble the Wilkinson power divider due to their geometric configuration. These power dividers provide very good isolation between their output ports of −51.26 dB. In fact, the originality of these new structures stems from the idea of minimizing the size of this classic power divider. The required design parameters for the three proposed dividers came from a simulation study using the Ansoft HFSS tool in addition to a design theory. The experimental prototypes are well presented and operate at 2.4 GHz. They demonstrate excellent performance in adaptation, which refers to impedance matching, ensuring consistent impedance at the component terminations. Additionally, they exhibit low insertion losses and high isolation at 2.4 GHz. The measurement results agree well with those of the simulation. The benefits demonstrated by this study are significant, justifying the preference for these components.

Theoretical and experiment optimization research of a frequency up-converted piezoelectric energy harvester based on impact and magnetic force

Harvesting environmental vibrations to power electronic components is an essential approach for addressing the power supply challenge in MEMS. However, conventional vibration energy harvesting systems frequently suffer from limited frequency bandwidth and high-frequency deficiencies. This paper proposes a novel up-frequency structure for piezoelectric vibration energy harvesting (VEH) that relies on both nonlinear magnetic force and piecewise linear force. The proposed VEH’s nonlinear dynamic characteristics are analyzed theoretically, and an experimental prototype machining and vibration test platform are constructed. Theoretical and experimental results are compared and analyzed by conducting basic experiments and key parameter optimization experiments. The research results demonstrate that the proposed VEH can efficiently harvest vibration energy in low-frequency and wide-band environments. Regarding the system parameters, higher vibration acceleration results in increased output voltage and wider working frequency bandwidth. Reducing the gap distance enhances piecewise linear vibration, which broadens the working frequency bandwidth. Furthermore, the proposed VEH’s ability to harvest low-frequency vibrations can be enhanced by reducing the magnet distance, thereby reducing the linear resonance frequency of the system. The findings of this study offer valuable insights for advancing the engineering application of MEMS self-power supply technology.

Research on extreme obstacle–crossing performance and multi–objective optimization of tracked mobile robot

Stability of obstacle–crossing and structural optimization are important issues in the research of tracked mobile robots. In this paper, in order to fully understand the obstacle–surmounting ability of the robot, the relationship between the position of the center of gravity and the posture of the front and rear swing arms is analyzed. Based on the motion mechanism of the robot crossing obstacles, the geometric model and the dynamic model are established for the key states in the obstacle crossing process. Based on these models, a multi-objective optimization problem for the maximum obstacle–crossing height and minimum driving torque is established during the obstacle crossing process of the robot, which must meet geometric, slip, and stability constraints. To effectively handle the optimization problem of tracked mobile robots, an improved non–dominated sorting genetic algorithm with elite strategy version II based on adaptive genetic strategy (NSGA-II-AGS) is proposed in this paper. Some meaningful relationships between the objective function and the design variables are obtained through sensitivity analysis. Finally, the robot's obstacle-crossing ability was verified through virtual simulation and prototype experiments. These excellent performances enable the proposed NSGA-II-AGS to be qualified for dealing with the multi-objective optimization problem.

A single-bridge interleaved three-level LLC resonant converter with current sharing capability for fuel cell system

This paper propose a wide gain single-bridge interleaved three-level LLC resonant converter with current sharing capability. This novel converter offers numerous advantages, including low cost, low current ripple, reduced voltage and current stress, widely gain range, high efficiency, good current sharing capability and versatile application scalability. Utilizing the three-level inverter + full-wave rectifier LLC converter as a representative case, the paper conducts an in-depth analysis and research on the proposed method. Finality, a 600 W experimental prototype was constructed and tested. Experimental results reveal that the proposed converter exhibits lower current ripple and a broader gain range. Moreover, the converter shows good current sharing capability (with a resonant element tolerance of 10%, the current error between the two phases does not exceed 12%) and high efficiency (peaking at 95.8%).

Design and optimization of 30 kW CLLLC resonant converter for vehicle‐to‐grid applications

AbstractThe CLLLC resonant converter is a promising technology for electric vehicles and microgrids due to its ability to operate bidirectionally. This article presents a design of a bidirectional CLLLC resonant converter that is applied in the vehicle‐to‐grid (V2G). The battery side of the converter uses a two‐channel parallel structure to enhance its efficiency and reliability. In contrast, the DC‐bus side uses a transformer series structure to obtain the benefits of passive current sharing on the secondary side and reduce the transformer turns ratio. By utilizing the proposed design method, the converter can achieve a wide input and output voltage range, high efficiency, and high power density. The article analyzes the working principle of the converter and explains the design process, which includes the transformer turns ratio, magnetizing inductance, and resonance parameters. Finally, an experimental prototype is produced to verify the theory's validity and the design's feasibility. The prototype has a DC‐bus side voltage of 660–860 V, a battery side voltage of 250–500 V, and a maximum power output of 30 kW. The peak efficiency of the prototype is 98.2%, and its power density can reach up to 8 kW/L.

Streak artefact removal in x-ray dark-field computed tomography using a convolutional neural network.

Computed tomography (CT) relies on the attenuation of x-rays, and is, hence, of limited use for weakly attenuating organs of the body, such as the lung. X-ray dark-field (DF) imaging is a recently developed technology that utilizes x-ray optical gratings to enable small-angle scattering as an alternative contrast mechanism. The DF signal provides structural information about the micromorphology of an object, complementary to the conventional attenuation signal. A first human-scale x-ray DF CT has been developed by our group. Despite specialized processing algorithms, reconstructed images remain affected by streaking artifacts, which often hinder image interpretation. In recent years, convolutional neural networks have gained popularity in the field of CT reconstruction, amongst others for streak artefactremoval. Reducing streak artifacts is essential for the optimization of image quality in DF CT, and artefact free images are a prerequisite for potential future clinical application. The purpose of this paper is to demonstrate the feasibility of CNN post-processing for artefact reduction in x-ray DF CT and how multi-rotation scans can serve as a pathway for trainingdata. We employed a supervised deep-learning approach using a three-dimensional dual-frame UNet in order to remove streak artifacts. Required training data were obtained from the experimental x-ray DF CT prototype at our institute. Two different operating modes were used to generate input and corresponding ground truth data sets. Clinically relevant scans at dose-compatible radiation levels were used as input data, and extended scans with substantially fewer artifacts were used as ground truth data. The latter is neither dose-, nor time-compatible and, therefore, unfeasible for clinical imaging ofpatients. The trained CNN was able to greatly reduce streak artifacts in DF CT images. The network was tested against images with entirely different, previously unseen image characteristics. In all cases, CNN processing substantially increased the image quality, which was quantitatively confirmed by increased image quality metrics. Fine details are preserved during processing, despite the output images appearing smoother than the ground truthimages. Our results showcase the potential of a neural network to reduce streak artifacts in x-ray DF CT. The image quality is successfully enhanced in dose-compatible x-ray DF CT, which plays an essential role for the adoption of x-ray DF CT into modern clinicalradiology.