Electrical Input Research Articles

Thermodynamic analysis of mechanical booster pump-assisted sorption thermochemical heat transformer driven by low-grade heat for building applications

Thermochemical heat transformers (THT) can offer the potential for efficient energy storage and upgrade based on a reversible solid-gas reaction. A mechanical booster pump (MBP)-assisted water-based sorption thermochemical heat transformer driven by low-grade solar thermal energy is proposed to handle variations in the heat demand of buildings. The MBP operates during the discharging process to adjust the magnitudes of temperature lift by compression ratio depending on the user’s demands. The performances of the proposed cycle employing three different reactive salts are investigated and compared with the conventional THT cycle under various operating conditions. Results indicate that compared to the conventional THT cycle, the proposed cycle achieves a maximum temperature lift of 15–17°C, 17–19°C, and 23–26°C for SrBr2, LiOH, and CaCl2 in the evaporating temperature range of 20–40°C, respectively. In the same operating conditions, SrBr2 demonstrates the highest energy and exergy efficiencies, while CaCl2 is inferior to the others due to its greater sensible heat consumption and lower reaction heat under the studied conditions. A suggestion is put forth for enhancing the temperature lift by employing a two-stage MBP-assisted cycle that utilizes the reactive salt SrBr2. Compared to the single-stage MBP-assisted cycle, the heat output temperature can be further increased by up to 3–16°C at the expense of a maximum decrease of 6.6%, 84.4%, and 9.0% in coefficient of performance (COP) based on total energy input, COP based on electricity input, and exergy efficiency, respectively, at 30°C evaporating temperature. The economic and environmental analysis indicates that the proposed system is economically and environmentally feasible and could be a promising alternative to residential water heaters.

Comprehensive Characterization of Energy Saving and Environmental Benefits of Campus Photovoltaic Buildings

The development of campus photovoltaic buildings is a promising way to solve the problem of high energy consumption in colleges and universities. However, comprehensive study on their energy saving and environmental benefits is still insufficient. In this study, a theoretical model of a photovoltaic building roof system was preliminarily built, and the main factors affecting the power generation of campus photovoltaic buildings were analyzed. Furthermore, an experimental test platform for the campus photovoltaic building system was built, and a dynamic grid-connected strategy of “spontaneous self-use, surplus electricity connected to the grid” was creatively proposed, which points out that the grid connection rate in winter and summer vacations are about 15% and over 40%, respectively, and the annual grid connection rate is 25%. The result shows that the electricity input of the campus photovoltaic building can bear nearly 30% of the school’s annual electricity supply, which reduces the comprehensive energy consumption per unit area and per capita comprehensive energy consumption of the campus by more than 20%. The economic and environmental benefits of the 130,000 square meter campus photovoltaic building in the article are 38.8 million CNY and 20.12 million CNY, respectively, and the static investment payback period is about 7 years. The results show considerable reference value to the upgrading of campus photovoltaic buildings.

Optimization assessment and performance analysis of an ingenious hybrid parabolic trough collector: A machine learning approach

Parabolic Trough Collector (PTC) is a solar unit that can convert solar radiation into thermal energy at moderate efficiency. Researchers attempted to increase the output of the PTC units by implementing multiple methods including using helical inserts, transparent aerogel, and reflective mirrors. Nevertheless, the output of this system still is not high enough. The proficiency of the PTC unit can improve by integrating it with Thermoelectric Generator (TEG) and Proton Exchange Membrane (PEM) electrolysis cell, which is studied in the current paper for the first time. In the present study, the efficiency in both PTC-TEG and PTC layouts are poked to demonstrate the consequence of the TEG on the denoted unit efficiency. Besides, the sensitivity study is carried out to assess the influence of operating parameters. Also, extensive data collection is generated and employed to train the designed machine learning models to anticipate the performance of the units in countless operating conditions. Based on the results, the highest accuracy in predicting the performance of the units belongs to the adaptive network-based fuzzy inference system. Also, the results show that the highest entropy generation rate for the PTC and PTC-TEG-PEM units is approximately 11.0 W/m.K and 16.9 W/m.K, respectively. In addition, the highest hydrogen production rate of the PTC-TEG-PEM unit is around 21 mol/h; in fact, the electrical input of the PEM electrolyzer is maintained by the TEG module, which its electrical efficiency calculated to be 3%.

Residential water and energy consumption prediction at hourly resolution based on a hybrid machine learning approach

Predicting water and energy consumption at high resolution over a short-term horizon is critical for water and energy resource management. Water and energy are shown to be closely interlinked in household consumption. However, hourly predictions are often based only on historical consumption data for the resource being predicted, with activity or appliance information and household attribution as additional information. Few studies have used aggregated water and energy consumption for predictions. Within this context, the current study proposed a novel hybrid machine learning model based on the Prophet time-series model, Gated Recurrent Unit network, and self-adaptive weights, called the Prophet-GRU model, which could jointly include historical water and electricity consumption as inputs for hourly water or electricity prediction. Data on hourly water and electricity consumption in six households in Beijing during January–March 2020 were used to train and validate the Prophet-GRU model. The goodness of fit indicator (R2) and prediction accuracy (mean squared error and mean absolute error) for the water and electricity predictions were evaluated. Compared with the single input of water or electricity, with the combined input of data of these two resources, the proposed Prophet-GRU model achieved improvements of 29.2 % and 48.5 % in R2, for water and electricity consumption prediction, respectively. Our results could help better understand water-energy linkages and promote collaborative water and energy management practices.

White light emitting devices with high color rendering index and electrically adjustable color temperature

Herein, we report a rare earth-free white light emitting composite for applications in solid-state lighting, which is made up of carbon nitride (CN) and Mn2+-doped perovskite quantum dots (PQDs). The correlated color temperature (CCT) is adjustable from 18 088 to 2926 K by varying the ratio of the two components. When the PQDs content is 2.88%, the white light emitting diode (W-LED) based on the CN/PQDs composite shows a competitive color rendering index of 88, a CCT of 5737 K, and a chromaticity coordinate of (0.327, 0.33), which is close to the standard white light. The light conversion efficiency of the composite is around 10%, which is attributed to the high photoluminescence efficiencies of the two components and weak photon reabsorption between them. Moreover, the CCT can be tuned from 4750 to 7315 K by changing the repetition frequency of the electrical input.

Co-optimisation of power-gas networks connected to industrial energy hubs with high penetration of storage systems

With proliferation of gas-fired generators and increase in the number of interconnected power-gas networks, co-optimisation of power-gas nexus has become a hot research area. Energy hubs (EHs) are efficient and reliable multi-carrier energy systems which typically take in electricity and natural gas and supply different forms of energy demands. As EHs typically import electricity and gas, their connection into a power-gas nexus may be an interesting option; their electricity input may be connected into an electric bus and their gas input may be connected into a gas node. This research focuses on the operation of power-gas nexus connected to industrial EHs. The Belgian network connected to a 24-bus power system has been used as case study and the studied EH includes boiler, combined heat and power unit, battery and thermal storage and supplies electricity and heat demands. The changes in shadow prices at different electric buses and gas nodes as well as congestion in both networks are investigated. The effect of connection points of EH on total operation cost, electric system cost and gas network cost is investigated and the optimal connection points are determined. According to the results, about 49.4 % of total cost belongs to electric system and the remaining 50.6 % belongs to gas system and a large portion of electric system cost belongs to demand shed cost. According to the results, the electric system is severely congested. At some buses and some hours, due to demand shed, the shadow price of electricity soars 10,000$/MWh which equals value of lost electric load.

Reconstituting Cu0/Cu+ synergy with heterostructured CeO2 enabling energy-efficient bipolar hydrogen generation

The establishment of electrocatalytic hydrogen (H2) production system with low energy consumption is of great significance for sustainable development. Herein, a groundbreaking achievement is presented by development of a bifunctional electrocatalyst (CeO2@Cu NRAs) on Cu foam, enabling simultaneously efficient catalysis of both hydrogen evolution reaction (HER, −0.18 VRHE at 10 mA cm−2) and furfural oxidation reaction (FFOR, 0.10 VRHE at 10 mA cm−2). The synergistic effect between Cu0 and Cu+ is investigated by density functional theory calculation, as well as the role of the heterostructured CeO2 played. Accordingly, subtle integration of such two half-reactions, the catalyst-assembled hydrogen system only requires an electrical input of 1.02 kWh per m3 of H2, which is one fifth of the energy consumed by conventional water electrolysis (5 kWh per m3 H2), signifying a compelling strategy for reducing energy consumption and improving the overall efficiency for hydrogen production.

A new type of supercontinuum generation in hexagonal lattice C6H6-core PCF with broadband and low-power pump

Most of the spectral bandwidths of previous publications are still limited by high input powers making them economically less than ideal. By using a benzene core (C6H6) photonic crystal fiber (PCF) as a new supercontinuum (SC) light source, it is possible to achieve a very large spectral broadening with hundreds of times lower peak power. Due to the change in the diameter of air holes in the first ring near the core, near-zero flattened dispersion, high nonlinearity and small attenuation can be achieved for spectral broadening. The structural geometries of two C6H6-PCFs are optimized to generate wide SC at low input energy. The SC spectrum produced in 1[Formula: see text]cm long of all dispersion fiber extends from a part of visible light to the near-infrared range at 1.3[Formula: see text][Formula: see text]m wavelength and a small pulse energy of 18[Formula: see text]pJ (or 450[Formula: see text]W of electrical input). The second PCF shows wide soliton-induced SC from 0.8 to 4.2[Formula: see text][Formula: see text]m with 71[Formula: see text]pJ pulse energy (or input power approximately 790[Formula: see text]W) at 1.5[Formula: see text][Formula: see text]m wavelength within a fiber of 12[Formula: see text]cm. The proposed structures have the potential to become a new class of microstructured optical fibers for low-cost, broad-spectrum SC generation.

Synergistic engineering of heteroatom doping and heterointerface construction in V-doped Ni(OH)2/FeOOH to boost both oxygen evolution and urea oxidation reactions

The exploitation of cost-effective and abundant non-noble metal electrocatalysts holds great significances in enhancing the efficiency of oxygen evolution reaction (OER) and/or urea oxidation reaction (UOR). Herein, we report an electrocatalyst with co-existing V-dopants and Ni(OH)2/FeOOH interfaces (referred to as A-NiFeV/NF, with “A” indicating “activated”). The electron coupling between Ni, Fe and V, analyzed through X-ray photoelectron spectroscopy, indicates that Ni and Fe both receive electrons from the V. Additionally, the Fe can also lead to a bias toward a lower valence of the Ni centers in Ni(OH)2. Further in situ Raman spectroscopy reveals that Ni2+(OH)2 inevitably undergoes transformation into amorphous Ni3+OOH during the activation process, however, the synergistic effects of V-dopants and Ni(OH)2/FeOOH interfaces keep the Ni centers mostly in a lower oxidation state of +2 even at high potential ranges. These low-valence Ni centers are proposed to be positively correlated with the optimized OER activity of the Ni-based electrocatalysts. As a result, the designed A-NiFeV/NF electrocatalyst exhibits low overpotentials of 234 and 313 mV to propel current densities of 10 and 100 mA/cm2, and a small Tafel slope of 37.8 mV/dec for OER in 1.0 M KOH. The catalyst demonstrates a stable OER activity for over 100 h at 100 mA/cm2. Additionally, it can be integrated with a solar cell to construct a solar-driven electrolytic OER device without additional electric input. Similarly, for the small molecule oxidation, UOR, only ∼1.33 and ∼1.39 V vs. RHE (RHE: reversible hydrogen electrode) are required to achieve 10 and 100 mA/cm2, respectively, in an electrolyte composed of 1.0 M KOH with 0.33 M urea.

Wireless electrical–molecular quantum signalling for cancer cell apoptosis

Quantum biological tunnelling for electron transfer is involved in controlling essential functions for life such as cellular respiration and homoeostasis. Understanding and controlling the quantum effects in biology has the potential to modulate biological functions. Here we merge wireless nano-electrochemical tools with cancer cells for control over electron transfer to trigger cancer cell death. Gold bipolar nanoelectrodes functionalized with redox-active cytochrome c and a redox mediator zinc porphyrin are developed as electric-field-stimulating bio-actuators, termed bio-nanoantennae. We show that a remote electrical input regulates electron transport between these redox molecules, which results in quantum biological tunnelling for electron transfer to trigger apoptosis in patient-derived cancer cells in a selective manner. Transcriptomics data show that the electric-field-induced bio-nanoantenna targets the cancer cells in a unique manner, representing electrically induced control of molecular signalling. The work shows the potential of quantum-based medical diagnostics and treatments.

Fully coupled electric-thermo-mechanical model for predicting the response of a SMA wire activated by electrical input

Shape Memory Alloys (SMAs) are becoming increasingly used in actuator technologies thanks to the generation of high specific power and reliability. These features are obtained by extremely simple architecture and actuation mechanisms that exploit the thermal-induced shape recovery properties of SMAs. Thanks to the high specific power, small diameter wires can be directly used as linear actuators whose activation can be obtained by electric currents, exploiting the Joule effect. Despite the simplicity of the actuator, the complex constitutive behaviour of such material does not allow to easily model its mechanical behavior due to the interdependency of the alloy parameters, especially when electric-thermal phonemena are also involved. In this paper, a fully coupled electric-thermo-mechanical model is proposed to predict the thermal and mechanical response of Shape Memory Alloy (SMA) wires when electrically actuated with the aim to provide user guidelines for properly design/select SMA based wire actuators for engineering applications. The model takes into account the latent heats linked to phase transformations, conduction and convective heat exchanges phenomena as well as the dependency of the resistivity from the thermo-mechanical parameter of the alloy. The implementation consists in two submodels: the electric-thermal and the thermo-mechanical one. Because of the marked dependence of the volume fraction of martensite with both temperature, generated by Joule effect, and mechanical stress, the submodels were coupled. Due to the complexity of the problem, a Matlab/Simulink code was implemented to numerically solve the governing equations. Temperature evolution, generated by the electric input, was investigated during both the heating and cooling stage and its effect on the mechanical response of the SMA actuator was studied. Results were validated with experimental measurements carried out on nickel-titanium (NiTi) wires. It was shown that the proposed model is suitable in predicting the temperature evolution of the wire, even catching phase transitions, as well as the actuation response for different loading conditions. Finally, the SMA actuators performances, in terms of input current to use, actuation time and efficiency, were investigated.

A calibration method for bone conduction transducers using electrical input impedance

The output energy transferred from bone conduction devices (BCDs) highly depends on the impedance match between the BCDs and their loads. However, current clinical calibration methods normally ignore individual impedance differences and therefore do not accurately assess the output force of the BCDs at the subject’s stimulation position. To address this issue, this study proposes a non-invasive BCD calibration method integrating electromechanical modeling and electrical input impedance measurement. The lumped-parameter model subtly fuses the models of demagnetized electrical impedance and mechanical impedance, leading to a better description of BCD’s physical properties. Once these model parameters are determined, measurements of the electrical input impedance can be used to determine the mechanical load impedance, and further the BCD’s output force. Experiments on the Radio Ear B71 showed that this new calibration method can accurately estimate the mechanical load impedance and the output force of B71 in the frequency range of 300–2000 Hz with an average error of 0.7 and 1.0 dB, respectively. It was also found that the B71 wearing status can be monitored by measuring the electrical input impedance. In conclusion, the proposed BC calibration method provides a promising way to calibrate the output and monitor the status of the BCDs non-invasively.

Operating strategy investigation of a solid oxide electrolysis cell under large scale transient electrical inputs

The solid oxide electrolysis cell technology can be integrated with intermittent power sources such as wind to produce hydrogen by water electrolysis for electrical energy storage. However, the fluctuation of wind power may induce transient variations in the electrochemical and thermal performances of the solid oxide electrolysis cell. Applying active operation strategies helps improve the transient performances of the electrolysis cell under large-scale dynamic electrical inputs. In this study, a three-dimensional electrochemical-mass-heat coupling dynamic model of the solid oxide electrolysis cell with voltage-current curve and electrochemical impedance validation is developed to investigate the effects of different active operation strategies. The mechanism and feasibility of the fuel and air operation strategies in the current fluctuation are examined based on the electrochemical, concentration, and temperature responses. The optimized active fuel operating strategy is capable of achieving a dynamic range of 0–163 %. The effectiveness of the air operating strategy depends on the preheating temperature and flow rate of the air, and their selection requires a balance between temperature control ability and temperature gradient. Integrating the advantages of both fuel and air operation strategies, a fuel–air hybrid operating strategy is proposed to further increase the dynamic range to 0–170 %.

Dual Hardware-In-the-Loop (DHIL) platform for testing and validation of WEC subsystems

This paper presents the design process and application of a dual hardware hardware-in-the-loop (DHIL) testing platform targeting components and subsystems of wave energy conversion devices. The DHIL testing methodology combines two HIL-equipped test rigs allowing to simultaneously test components mounted on each rig and connected to the same simulation loop. The platform was therefore developed combining a HIL test rig for drivetrains with a HIL test rig for structural components.The DHIL testing platform has the capability to address multiple types of tests on critical subsystems and components within a WEC: characterization tests, for defining key performances of the equipment under test; accelerated tests, to assess qualitative and quantitative reliability features; and ultimate load testing, for survivability purposes. The overall aim of these tests is to identify weaknesses in an early design phase of device design or as a qualification activity prior the deployment of an ocean prototype. Additionally, HIL and DHIL tests can be used to assess the influence of a design update on the overall WEC model and to track failure interdependencies at a relevant scale. Finally, all of the above-mentioned activities can inform the development of a more accurate global numerical model, potentially at sub-system / critical component level, to be validated based on the test results.The definition of the test rig mechanical and electrical input specifications is dependent on the understanding of the load envelope each subsystem / component will be subject to during its lifetime. To define such envelope, a research activity modelling three different device types, three deployment sites and multiple design situations (e.g. power production, parked, shut-down etc.) led to the creation of a load database that was combined with information from WEC developers.After defining the input specifications, the rigs were designed by identifying the optimal layout, the key components and the setup of the overall test area. Analyses on mechanical, electrical and hydraulic parameters were completed to ensure the required performance of each rig could be achieved, while guaranteeing the safety during their operation.The signal processing of each rig was also analysed, with the aim of defining the minimum rig latency to allow HIL and DHIL tests to be performed. This analysis took into account the possible interface characteristics of the simulator, the sensors and the main features of the models used for real-time tests.An overview of the testing activities to be conducted within the IMPACT project will be presented in this paper. Such activities aim to de-risking the technologies at early stages and increasing their maturity through a structured process. The proposed approach has the final goal of demonstrating that the DHIL testing platform is capable to reduce capital-intensive activities, often associated with the development of large-scale prototypes, which is a critical factor for the successful development and time-to-market of a WEC.

Development, calibration, and validation of a novel gray-box energy model for residential split air conditioners

Energy models for vapor compression refrigeration in residential air conditioners have been developed through white-box, gray-box, and black-box methods in decades. However, existing white-box and gray-box models require complicated equations with detailed geometries while black-box models require substantial experimental data. This paper aims to develop and validate a simple gray-box steady-state energy model without the need for detailed geometries, which can accurately predict the cooling capacity and electrical power input based on outdoor and indoor air conditions, and supply airflow rates. First three state variables, including the evaporation and condensation temperatures, and refrigerant mass flowrate, are applied to develop the energy model and are solved by three physical equations, including the energy conservations at the evaporator and condenser, and the refrigerant volume-mass flow correlation of the compressor. Secondly, seven performance property functions related to three state variables and three physical equations are identified and calibrated by simple temperature and power measurements. Finally, field experiments are conducted on a residential air conditioner to calibrate these performance property functions and validate the developed model. The validated results reveal the model can accurately predict the cooling capacity and electrical power input, with the normalized root mean square errors of 2.3% and 0.87% respectively.

Soft magnetic thin film deformation with a bistable electropermanent magnet

Physically soft magnetic materials (PSMMs) represent an emerging class of materials that can change shape or rheology in response to an external magnetic field. However, until now, no studies have investigated using an electropermanent magnet (EPM) and magnetic repulsion to magnetically deform PSMMs. Such capabilities would enable the ability to deform PSMMs without the need for continuous electrical input and produce PSMM film deformation without an air gap, as would be required with magnetic attraction. To address this, we introduce a PSMM-EPM architecture in which the shape of a soft deformable thin film is controlled by switching between bistable on/off states of the EPM circuit. We characterized the deflection of a PSMM thin film when placed at controlled distances normal to the surface of the EPM and compared its response for cases when the EPM is in the ‘on’ and ‘off’ states. This work is the first to demonstrate a magnetically repelled soft deformable thin film that achieves two electronically-controlled modes of deformation through the on and off states of an EPM. This work has the potential to advance the development of new magneto-responsive soft materials and systems.

The influence of electric circuit parameters on NOx generation by transient spark discharge

Nitrogen fixation, production of NO and NO2 from N2 and O2 in air, has been investigated with transient spark self-pulsing DC discharges. NO production is boosted by the addition of capacitors and an inductor to the electrical circuit which drives the discharge. The quantity of NO produced per joule of electrical input energy is doubled, though the quantity of NO2 produced drops. The yield of NO is also increased because the modified circuit enables higher discharge currents to be used. NO concentrations as high as 2000 ppm were obtained with input energy densities of around 300 J per liter of input gas, whilst NO2 concentrations were around 150 ppm. This simple modification of the driving circuit may have potential for optimizing the plasma chemistry with other input gas mixtures and for scaling up nitrogen fixation from air.

An Integrated Analytics of PEM Electrolyzer and Steel Making

It is widely accepted that the hydrogen-water couple can elevate the green economy circuit if powered by renewable sources of energy. Proton-exchange membrane water electrolyzer (PEMWE) being a clean electrochemical device is expected to provide an amenable solution to the hydrogen-water nexus and act as an enabler to achieving decarbonization of the steel-making industry. In this work, we throw light on the performance of a PEMWE that feeds target hydrogen volumes to a direct iron ore reduction process. The response of the electrolyzer under the presence of a host of operational stressors and variable electricity input is delineated through a macroscale modeling framework. The techno-economics associated with specific energy consumption of the downstream steel-making pathways will be further discussed based on insights from a process cost model.

Electrowetting-driven liquid lens for ultrasound: Enabling controllable focal length and flexible beam steering

Focused ultrasound is an increasingly popular non-invasive treatment modality. Still, its fixed focal point requires an array ultrasound transducer or scanning system to cover different therapeutic scenarios. To address this limitation, we developed an electrically-controlled liquid lens that enables dynamic beam focusing and steering of the incident plane ultrasound beam. The lens was carefully optimized for low-energy attenuation and low-voltage driving. We evaluated the performance of the lens using a homemade 5.5-MHz planar transducer with a 7.5-mm aperture. Our results demonstrate that the planar ultrasound beam can be adjusted to a focused beam with a focal length from 27 mm to 32 mm within 1 s by increasing the electric input (0–60 V) to the lens. Additionally, the beam angle of the ultrasound is tunable from −5 to 5° by adjusting the charge distribution on the lens. Our design enables real-time, fast-response, on-demand changing of focal length and beam angle for a single-element planar transducer. Our study presents a promising technology for altering the ultrasound beam of a planar single-element transducer for different ultrasound applications. The development of this electrically-controlled liquid lens has the potential to enhance the efficacy of focused ultrasound treatment and improve patient outcomes.

Experimental study on acoustic-induced microbubbles fusion

Droplets/microbubbles fusion technology is a key technology for many biochemical medical applications. Here, an acoustic-controlled approach to drive microbubble fusion based on focused surface acoustic wave (FSAW) is presented. When passing through the arc-shaped channel, adjacent microbubbles will decelerate, contact, and fuse induced by the FSAWs. Due to the cooperation of the FSAW and the arc-shaped flow channel structure, the microbubbles are more easily captured and fused with the adjacent microbubbles. The effects of input voltage and pressure input parameters on the microbubble fusion are studied. Relying on electrical input parameters, microbubble fusion can be effectively achieved, providing a new idea for precise gas fuse control. The regulation of the microbubbles fusion by FSAW is revealed, showing potential in the applications of the precise control of gases on a microfluidic chip.