In the wireless power transfer systems, a coupling coefficient is one of the measures of performance. In particular, the coupling coefficient at critical coupling does not ensure maximum system ...energy efficiency but guarantee maximum output power to the load. As the coupling coefficient goes beyond the critical-coupled state, output power begins to decline. In this letter, we propose a method to maximize output power even in an overcoupled state as in the critical-coupled state by adjusting the capacitance of the resonator. Our proposal is verified by comparing the calculations and simulations with measurements, and they are in good agreement.
Interfacial solar steam generation offers a sustainable and affordable technology for seawater desalination and water treatment. During solar steam generation the temperature of the solar evaporation ...surface is generally higher than the bulk water, which results in energy loss to the bulk water by heat conduction. While many strategies have been developed to minimize and/or eliminate the conductive heat loss, this study focuses on completely reversing conductive heat loss and turning it into an energy extraction from the bulk water to enhance the evaporation during solar steam generation. This was achieved by introducing a certain area of cold evaporation surface between the solar evaporation surface and the bulk water, which led to the conductive heat loss from the solar evaporation surface being completely absorbed and consumed by the cold evaporation surface before reaching the bulk water. Meanwhile, due to its lower surface temperature, the cold evaporation was also able to extract energy from the bulk water, turning the heat conduction loss from the evaporator to the bulk water into the energy harvest from the bulk water. When the surface area of the cold evaporation surface was increased to a certain point (50.3 cm2 in this work), heat flow was reversed, and energy was extracted from the bulk water by the evaporator to enhance solar evaporation. Theoretical simulations agreed well with the experimental results. In addition, as parasitic effects, the cold evaporation surface was also able to gain energy from the ambient air and lower the temperature of the solar evaporation surface, reducing both radiation and convection energy loss. As a result, the evaporation rate and the light-to-vapor energy efficiency of the evaporator were far beyond the theoretical limits, confirming that this strategy has great potential for further practical applications.
During solar steam generation, by introducing a certain area of cold evaporation surface between the solar evaporation surface and bulk water, the heat conduction energy loss from the solar evaporation surface to bulk water can be eliminated and even reversed, thus extracting energy from bulk water to enhance solar evaporation. Display omitted
•A new strategy is developed to completely eliminate and even reverse heat conduction loss during solar steam generation.•Cold evaporation surface between the solar evaporation surface and bulk water can extract energy from both sides.•A new energy input channel other than incident light energy is introduced for solar steam generation.•An extremely high evaporation rate of 2.95 kg m−2 h−1 and an energy efficiency beyond theoretical limit were achieved.
Unmanned aerial vehicles (UAVs) have found numerous applications and are expected to bring fertile business opportunities in the next decade. Among various enabling technologies for UAVs, wireless ...communication is essential and has drawn significantly growing attention in recent years. Compared to the conventional terrestrial communications, UAVs' communications face new challenges due to their high altitude above the ground and great flexibility of movement in the 3-D space. Several critical issues arise, including the line-of-sight (LoS) dominant UAV-ground channels and induced strong aerial-terrestrial network interference, the distinct communication quality-of-service (QoS) requirements for UAV control messages versus payload data, the stringent constraints imposed by the size, weight, and power (SWAP) limitations of UAVs, as well as the exploitation of the new design degree of freedom (DoF) brought by the highly controllable 3-D UAV mobility. In this article, we give a tutorial overview of the recent advances in UAV communications to address the above issues, with an emphasis on how to integrate UAVs into the forthcoming fifth-generation (5G) and future cellular networks. In particular, we partition our discussion into two promising research and application frameworks of UAV communications, namely UAV-assisted wireless communications and cellular-connected UAVs, where UAVs are integrated into the network as new aerial communication platforms and users, respectively. Furthermore, we point out promising directions for future research.
Energy consumption and thermal comfort in buildings are heavily affected by weather conditions. This study investigated the impact of climate change on thermal comfort conditions and on heating and ...cooling energy demand in dwellings in three cities in Brazil. Scenario A2 of the Intergovernmental Panel on Climate Change was selected to be used in the study. To quantify the impact, the Climate Change World Weather File Generator was used to produce weather data for future typical meteorological years, such as 2020, 2050 and 2080. The EnergyPlus computer programme was used to estimate the indoor air temperature and the annual heating and cooling energy demand in the future. In order to maintain the energy consumption in the houses at the level it is nowadays, passive design strategies such as solar shading, low absorptance and thermal insulation were assessed. Results show that there will be an increase in the annual energy demand ranging from 19%–65% among the three cities in 2020; 56%–112% in 2050; and 112%–185% in 2080. In the coldest city, the annual heating energy demand will decrease by 94% in 2080 due to an increase in the average temperature and global solar radiation. The use of passive design strategies may reduce up to 50% the future annual cooling and heating energy demand in houses in Brazil.
In recent years, artificial neural networks have become the flagship algorithm of artificial intelligence
. In these systems, neuron activation functions are static, and computing is achieved through ...standard arithmetic operations. By contrast, a prominent branch of neuroinspired computing embraces the dynamical nature of the brain and proposes to endow each component of a neural network with dynamical functionality, such as oscillations, and to rely on emergent physical phenomena, such as synchronization
, for solving complex problems with small networks
. This approach is especially interesting for hardware implementations, because emerging nanoelectronic devices can provide compact and energy-efficient nonlinear auto-oscillators that mimic the periodic spiking activity of biological neurons
. The dynamical couplings between oscillators can then be used to mediate the synaptic communication between the artificial neurons. One challenge for using nanodevices in this way is to achieve learning, which requires fine control and tuning of their coupled oscillations
; the dynamical features of nanodevices can be difficult to control and prone to noise and variability
. Here we show that the outstanding tunability of spintronic nano-oscillators-that is, the possibility of accurately controlling their frequency across a wide range, through electrical current and magnetic field-can be used to address this challenge. We successfully train a hardware network of four spin-torque nano-oscillators to recognize spoken vowels by tuning their frequencies according to an automatic real-time learning rule. We show that the high experimental recognition rates stem from the ability of these oscillators to synchronize. Our results demonstrate that non-trivial pattern classification tasks can be achieved with small hardware neural networks by endowing them with nonlinear dynamical features such as oscillations and synchronization.
The rise of intelligent matter Kaspar, C; Ravoo, B J; van der Wiel, W G ...
Nature (London),
06/2021, Letnik:
594, Številka:
7863
Journal Article
Recenzirano
Odprti dostop
Artificial intelligence (AI) is accelerating the development of unconventional computing paradigms inspired by the abilities and energy efficiency of the brain. The human brain excels especially in ...computationally intensive cognitive tasks, such as pattern recognition and classification. A long-term goal is de-centralized neuromorphic computing, relying on a network of distributed cores to mimic the massive parallelism of the brain, thus rigorously following a nature-inspired approach for information processing. Through the gradual transformation of interconnected computing blocks into continuous computing tissue, the development of advanced forms of matter exhibiting basic features of intelligence can be envisioned, able to learn and process information in a delocalized manner. Such intelligent matter would interact with the environment by receiving and responding to external stimuli, while internally adapting its structure to enable the distribution and storage (as memory) of information. We review progress towards implementations of intelligent matter using molecular systems, soft materials or solid-state materials, with respect to applications in soft robotics, the development of adaptive artificial skins and distributed neuromorphic computing.
The drive to design modern low-environmental impact buildings with high-energy efficiency has led to an increase in unfired earth masonry studies reflecting the rising trend of earth used in passive ...buildings. This paper deals with the efficacy of incorporating biosourced earth in the building envelope. Firstly, the development and the hygro-thermo-mechanical characterization of earth blocks biosourced with local agro-aggregates (Alfa fibers and sawdust) were conducted. An aggregate-to-earth replacement ratio of 8 wt% was adopted. Mechanical tests show that earth blocks alone have a compressive strength of about 1.7 MPa. The hygrothermal tests reveal that biosourced blocks exhibit excellent hygrothermal properties, especially specimens with short Alfa fibers. A twofold decrease in the thermal conductivity value and a significant increase of the time lag and sorption capacities were achieved. The moisture buffering tests show that Alfa fibers improve the buffering capacity of earth from 1.9 to 2.3 g/(m2.%RH), leading the blocks to be classified as “Excellent” humidity regulators. Following the laboratory tests, and to overcome the low mechanical strength of earth, a double hollow brick wall integrating biosourced earth was studied. Building-scale benefits during summer were identified using a validated PMV-PPD model, implemented in EnergyPlus, based on real-time monitoring of an existing building. The findings show that the proposed wall increases thermal comfort by regulating indoor temperature and humidity, reducing 24.6% in dissatisfied occupants compared to typical walls. It is concluded that the use of earth presents a sustainable practice for constructing eco-efficient buildings with enhanced occupant satisfaction in hot regions.
•Bio-based earth blocks used for the design of modern eco-efficient building envelopes.•Sorption isotherms, moisture buffering values (MBV) and thermophysical properties were experimentally characterized.•Field assessment of summer thermal comfort of an existing office building was conducted.•Calibrated PMV-PPD-based model was implemented for simulating the occupant dissatisfaction in buildings.•Hybrid walls (adobe/red bricks) improve the occupant satisfaction in buildings in hot climates.
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•Hydrogen production pathways via renewable and non-renewable sources.•Renewable energy sources gaining potential as clean energy source to produce H2.•Plasmolysis is competitive to ...electrolysis for H2 production.•Plasmolysis is beneficial for its low power consumption and reduced equipment size.•Solar integrated plasmolysis with zero carbon footprints is the proposed strategy.
Hydrogen as an energy carrier can provide a long term solution to the problem of sustainable supply of cleaner and environmentally friendly fuel. Hydrogen finds extensive use s in petroleum, chemical synthesis and treated as a zero-emission fuel for transportation as well. It could also be used to produce power. Especially, in the remote areas away from main cities where electrification cost would be significantly higher. A hydrogen based decenteralized system could be developed where the “surplus” power generated by a renewable source could be stored as chemical energy in the form of hydrogen. 80% of the whole hydrogen produced is by steam methan reforming at an energy efficiency of 74–85%. However, steam methane reforming and other fossil fuel based technologies are neither green nor sustainable. Hydrogen, could only be counted as a renewable and clean fuel if the required power to produce hydrogen comes from a renewable source such as wind or solar power. Using a renewable source, hydrogen could be produced by electrolysis, biohydrogen, thermochemical cycles, photocatalysis, and plasmolysis. Amongst hydrogen production technologies, electrolysis contributes the highest 4% of the total world’s energy demand. The production cost and energy efficiency estimated for electrolysis are 10.3 $/kg and 52%, respectively. Electrolysis, an energy-intensive process for hydrogen production, is still confronting challenges to manifest itself economically. While, the production rate of 20 g/kWh with predicated cost and efficiency 0.09 €/kWh or 6.36 $/kg and 79.2%, respectively, has been reported that depicts plasmolysis competitive on par with electrolysis with the advantage of low power consumption, reduced equipment size and principle cost. This review highlights the current status, potential, and challenges of both renewable and non-renewable hydrogen production. A new strategy for simultaneous hydrogen production and separation by microplasmas and microbubble mediated mass transfer has been proposed. A decenterlaized system for hydrogen generation by combining the proposed strategy with solar energy has been suggested to reduce the carbon footprints.
Intelligent buildings have drawn considerable attention due to rapid progress in communication and information technologies. These buildings can utilize current and historical data, collected from ...occupancy detection and monitoring networks, to predict occupancy profiles and adjust heating, ventilating, and air conditioning (HVAC) operations accordingly. This adjustment aims to minimize the energy consumption of HVAC systems while maintaining an acceptable level of thermal comfort and indoor air quality. To provide a trade-off between these conflicting objectives, a variety of occupancy-based control strategies have been proposed in the literature. The present article aims to review the research works concerning occupancy-based control systems, classify them based on the integration of occupancy information with control systems and identify their strengths and limitations. Finally, research gaps in this field are discussed from different aspects, including performance evaluation metrics, control methods, occupancy models and buildings types. Future research directions are also proposed to fill the identified gaps.
•HVAC control systems are classified based on their integration with occupancy information.•Occupancy-based HVAC control systems are reviewed.•The limitations of occupancy models and control systems are discussed.•Research gaps are identified by reviewing occupancy-based control systems from different viewpoints.•Future research directions are proposed to fill the current gaps.
Zinc‐iodine batteries (Zn‐I2) are extremely attractive as the safe and cost‐effective scalable energy storage system in the stationary applications. However, the inefficient redox kinetics and ...“shuttling effect” of iodine species result in unsatisfactory energy efficiency and short cycle life, hindering their commercialization. In this work, Ni single atoms highly dispersed on carbon fibers is designed and synthesized as iodine anchoring sites and dual catalysts for Zn‐I2 batteries, and successfully inhibit the iodine species shuttling and boost dual reaction kinetics. Theoretical calculations indicate that the reinforced d‐p orbital hybridization and charge interaction between Ni single‐atoms and iodine species effectively enhance the confinement of iodine species. Ni single‐atoms also accelerate the iodine conversion reactions with tailored bonding structure of I─I bonds and reduced energy barrier for the dual conversion of iodine species. Consequently, the high‐rate performance (180 mAh g−1 at 3 A g−1), cycling stability (capacity retention of 74% after 5900 cycles) and high energy efficiency (90% at 3 A g−1) are achieved. The work provides an effective strategy for the development of iodine hosts with high catalytic activity for Zn‐I2 batteries.
Ni single atoms highly dispersed on carbon fibers is designed and synthesized as iodine anchoring sites and dual catalysts for Zn‐I2 batteries, and successfully inhibit the iodine species shuttling and boost dual reaction kinetics. Consequently, the high‐rate performance (180 mAh g−1 at 3 A g−1), cycling stability (capacity retention of 74% after 5900 cycles) and high energy efficiency (90% at 3 A g−1) are achieved.
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