Hybrid energy-harvesting systems that capture both wave and solar energy from the oceans using triboelectric nanogenerators and photovoltaic cells are promising renewable energy solutions. However, ...ubiquitous shadows cast from moving objects in these systems are undesirable as they degrade the performance of the photovoltaic cells. Here we report a shadow-tribo-effect nanogenerator that hybrids tribo-effect and shadow-effect together to overcome this issue. Several fiber-supercapacitors are integrated with the shadow-tribo-effect nanogenerator to form a self-charging power system. To capture and store wave/solar energy from oceans, an energy ball based on the self-charging power system is demonstrated. By harnessing the shadow-effect, i.e. the shadow of the moving object in the energy ball, the charging time shortens to 253.3 s to charge the fiber-supercapacitors to the same voltage (0.3 V) as using pure tribo-effect. This cost-effective method to harvest and store the wave/solar energy from the oceans in this work is expected to inspire next-generation large-scale blue energy harvesting.
The interactions between moisture and materials give rise to the possibility of moisture‐driven energy generation (MEG). Current MEG materials and devices only establish this interaction during water ...sorption in specific configurations, and conversion is eventually ceased by saturated water uptake. This paper reports an asymmetric hygroscopic structure (AHS) that simultaneously achieves energy harvesting and storage from moisture absorption. The AHS is constructed by the asymmetric deposition of a hygroscopic ionic hydrogel over a layer of functionalized carbon. Water absorbed from the air creates wet‐dry asymmetry across the AHS and hence an in‐plane electric field. The asymmetry can be perpetually maintained even after saturated water absorption. The absorbed water triggers the spontaneous development of an electrical double layer (EDL) over the carbon surface, which is termed a hygro‐ionic process, accounting for the capacitive properties of the AHS. A peak power density of 70 µW cm‐3 was realized after geometry optimization. The AHS shows the ability to be recharged either by itself owing to a self‐regeneration effect or via external electrical means, which allows it to serve as an energy storage device. In addition to insights into moisture‐material interaction, AHSs further shows potential for electronics powering in assembled devices.
An unusual route for moisture‐driven energy generation (MEG) is proposed by an asymmetric hygroscopic structure (AHS), which simultaneously achieves MEG and energy storage. The water‐absorption triggered dual function originates from the permanently maintained wet‐dry asymmetry that is formed across the AHS by the asymmetric deposition of a hygroscopic ionic hydrogel over a functionalized‐carbon layer.
As an excellent candidate for lightweight structural materials and nonmetal electrical conductors, carbon nanotube reinforced carbon matrix (CNT/C) composites have potential use in technologies ...employed in aerospace, military, and defense endeavors, where the combinations of light weight, high strength, and excellent conductivity are required. Both polymer infiltration pyrolysis (PIP) and chemical vapor infiltration (CVI) methods have been widely studied for CNT/C composite fabrications with diverse focuses and various modifications. Progress has been reported to optimize the performance of CNT/C composites from broad aspects, including matrix densification, CNT alignment, microstructure control, and interface engineering, etc. Recent approaches, such as using resistance heating for PIP or CVI, contribute to the development of CNT/C composites. To deliver a timely and up-to-date overview of CNT/C composites, we have reviewed the most recent trends in fabrication processes, summarized the mechanical reinforcement mechanism, and discussed the electrical and thermal properties, as well as relevant case studies for high-temperature applications. Conclusions and perspectives addressing future routes for performance optimization are also presented. Hence, this review serves as a rundown of recent advances in CNT/C composites and will be a valuable resource to aid future developments in this field.
An active inductor based on gyrator-
C
structure is proposed in this work. Voltage-controlled oscillator with wide frequency range and significant RF output power based on the proposed active ...inductor is presented in this work. The design of the voltage-controlled oscillator is carried out using UMC 180 nm RFCMOS technology. Post-layout simulations are carried out using Spectre RF in Cadence virtuoso. Voltage-controlled oscillator can be tuned from 500 MHz to 2.8 GHz suitable for multi-band transceiver design. The proposed design attains a frequency tuning range of 139.4%. VCO operates at a supply voltage of 1.8 V with a power consumption of 5.3 mW. Phase noise at a frequency offset of 1 MHz from carrier frequency of 2.4 GHz is − 94 dBc/Hz. VCO occupies an active area of
200
×
150
μ
m
2
. Figure of merit values that take into consideration RF output power and frequency tuning range are comparable to other VCO designs proposed in the literature. PVT analysis of the designed VCO is presented in this work.
Emulation of natural photosynthesis is central to modern photovoltaic research targeting sustainable and economic ways of solar energy harvesting. Natural photosynthetic systems have succeeded in ...efficiently harvesting solar energy which is key to the sustenance of life on earth. With numerous advances in understanding the structure and function of the natural photosystems, the last decade has witnessed new perspectives in developing bioinspired photovoltaics. Interestingly, organic photovoltaics (OPVs) adopting photosynthetic design principles and biophotovoltaics (BPVs) adopting solid‐state device architectures have now converged at a juncture. Several reports in recent years point to a new scope of improvement in OPVs and BPVs stemming from mutual inspiration. At this juncture, there are new perspectives by which a BPV can be designed that were previously limited only to conventional optoelectronics. Treating natural pigment–proteins as optically and electronically functional materials in any photovoltaic design, from the band‐theory viewpoint, is a promising direction for advancing BPVs beyond the boundaries of bioelectrochemistry. This article presents an overview of selected reports on BPVs in the last few years utilizing new design concepts based on band‐theory and its associated principles. In light of this, the scope of the band‐structure approach in BPVs is discussed, eliciting prospective research directions.
The electronic processes in natural photosynthetic systems are reviewed, and a contrast is established with emerging photovoltaic systems, thereby providing insight on how the band‐structure approach can aid in bridging photosynthetic research and emerging photovoltaic technologies by mutual inspiration.
In their comment, Amit et al. propose an alternative working mechanism for the origin of photocurrent and photovoltage in our shadow-effect energy generators (SEG). However, in this reply we have ...elucidated the fundamental difference in the connection pattern of our measurements against Amit et al.' s. This misunderstanding has led them to propose an alternate working mechanism for our device. The working mechanism proposed by the authors does seem appropriate and gives a better performance when both the metallic thin film and the underlying Si are a part of the electrical circuit, whereas our proposed mechanism of the work function shift in the semiconductor-metal system seems appropriate for the connection pattern that we had adopted for our measurements.
The salt fouling issue, which has become the major bottleneck hindering a sustainable solar desalination process in practice. Herein, a fluidic photothermal structure that is able to completely ...prevent salt formation for durable steam generation while achieving electricity generation during the one-way fluid transportation is reported. By continuously navigating the one-way saline fluid through solar absorber, salt rejection can be completely guaranteed during intense steam generation. The proposed strategy was demonstrated by a polyaniline (PANi)/cellulose bilayer and realized ultrahigh solar efficiency (92%) under 1 Sun illumination. We further show that electricity is synchronously generated via asymmetric deposition of functional carbon materials on capillary wicks, and voltage >0.2 V is readily derived with good scalability. This one-way fluidic structure exhibits favorable universality to nearly all the other planar solar absorbers and multistage solar stills, which would be of great practical significance to long-term solar desalination in the future.
The aim of this research is to perform remote sensing scene classification, because it supports numerous strategic research fields like land use and land cover monitoring. However, classifying an ...enormous amount of remote sensing data is a challenging task in scene classification. In this research work, a new model is introduced to improve the feature extraction ability for better scene classification. A multiscale Retinex technique is employed for color restoration, and contrast enhancement in the aerial images that are collected from UC Merced, aerial image dataset, and RESISC45. Further, the feature extraction is carried out using steerable pyramid transform, gray level co-occurrence matrix features, and local ternary pattern. The feature extraction mechanism reduces overfitting risks, improves training process, and data visualization ability. Generally, the extracted features are high dimension, so an unsupervised feature selection based on multi subspace randomization and collaboration with state transition algorithm is proposed for selecting active features for better multiclass classification. The selected features are fed to long short term memory network for scene type classification. The experimental results showed that the proposed model achieved 99.14 %, 98.09%, and 99.25% of overall classification accuracy on UC Merced, RESISC45 and aerial image dataset. The proposed model showed a minimum of 0.03 % and maximum of 18.6 % improvement in classification accuracy compared to the existing models like self-attention based deep feature fusion, multitask learning system with convolutional neural network, multilayer feature fusion Wasserstein generative adversarial networks, and transfer learning model on UC Merced, RESISC45 and aerial dataset, respectively.
Energy harvesting from shadow-effect Zhang, Qian; Liang, Qijie; Nandakumar, Dilip Krishna ...
Energy & environmental science,
08/2020, Letnik:
13, Številka:
8
Journal Article
Recenzirano
Shadows are everywhere. Not much engineering use has been found for shadows, and this ubiquitous effect is strenuously avoided in optoelectronic applications. In this work, we present a shadow-effect ...energy generator (SEG) that scavenges the illumination contrast that arises on the device from shadow castings, and generates a direct current, simply by placing a part of the generator in shadow. The shadow-effect mechanism is experimentally validated by Kelvin Probe Force Microscopy (KPFM). The SEG is capable of harvesting energy from illumination contrasts arising under weak ambient light. Without any optimization, our generator has a power density of 0.14 μW cm
−2
under indoor conditions 0.001 sun, where shadows are persistent. Our SEG performs 200% better than that of commercial silicon solar cells under the effects of shadows. The harvested energy from our generator in the presence of shadows arising at a very low intensity (0.0025 sun) can drive an electronic watch (1.2 V). In addition, the SEG can serve as a self-powered sensor for monitoring moving objects by tracking the movement of shadows. With its cost-efficiency, simplicity and stability, our SEG offers a promising architecture to generate green energy from ambient conditions to power electronics, and as a part of a smart sensor systems, especially in buildings.
We demonstrate an unprecedented mode of energy harvesting from shadows that fall on the shadow-effect energy generator (SEG). Furthermore, a self-powered proximity sensor is also demonstrated using the SEG.
This paper presents the design of gyrator-C active inductor. Current reuse technique reduces the noise of transconductor in gyrator. Bandpass filter and voltage-controlled oscillator (VCO) are ...designed based on the proposed active inductor. Post-layout simulations and PVT analysis are carried out using 180 nm RFCMOS technology at 1.8 V supply voltage. Bandpass filter with center frequency 2.45 GHz attains a noise figure of 6 dB. VCO with a tuning range of 1.5 GHz–2.8 GHz attains a phase noise of −99.86 dBc/Hz. The active area occupied by bandpass filter and VCO are 150 μm × 150 μm and 145 μm × 145 μm respectively.
•Current reuse technique is used to realize the negative transconductor in gyrator-C to reduce the noise contribution.•An additional design freedom to tune self-resonant frequency and Q factor of the active inductor an active resistor is used.•A bandpass filter with tuning range 1.6 GHz-2.9 GHz is designed based on the proposed active inductor that occupies less area.•VCO is designed based on the proposed active inductor with a tuning range and phase noise on a par existing designs.
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