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Thermodynamic limits to energy conversion in solar thermal fuels
摘要： Solar thermal fuels (STFs) are an unconventional paradigm for solar energy conversion and storage which is attracting renewed attention. In this concept, a material absorbs sunlight and stores the energy chemically via an induced structural change, which can later be reversed to release the energy as heat. An example is the azobenzene molecule which has a cis-trans photoisomerization with these properties, and can be tuned by chemical substitution and attachment to templates such as carbon nanotubes, small molecules, or polymers. By analogy to the Shockley–Queisser limit for photovoltaics, we analyze the maximum attainable efficiency for STFs from fundamental thermodynamic considerations. Microscopic reversibility provides a bound on the quantum yield of photoisomerization due to fluorescence, regardless of details of photochemistry. We emphasize the importance of analyzing the free energy, not just enthalpy, of the metastable molecules, and find an efficiency limit for conversion to stored chemical energy equal to the Shockley–Queisser limit. STF candidates from a recent high-throughput search are analyzed in light of the efficiency limit.
关键词： energy storage,thermodynamics,solar energy conversion,photoisomerization
更新于2025-09-19 17:15:36
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Stabilization of GaAs photoanodes by in-situ deposition of nickel-borate surface catalyst as hole trapping sites
摘要： Although semiconducting gallium arsenide (GaAs) possesses an ideal band gap for efficient solar-driven fuel synthesis, it is extremely unstable in aqueous media, undergoing facile photocorrosion and therefore is seldom used. We have addressed this stability problem to some extent using a strategy of introducing a Ni-B surface catalyst onto p/n junction GaAs by in-situ photoassisted electrodeposition. A monolithic layer of Ni-B/Ga(As)Ox was generated during the Ni-B deposition process, resulting in a Ni-B/Ga(As)Ox/GaAs photoanode structure. Such structure was optimized by varying the GaAs surface architecture, electrolyte pH value and Ni-B deposition time to achieve optimal photoelectrochemical performance, together with improved stability. The optimized photoanode (Ni-B/Ga(As)Ox/shallow GaAs with 0.5 h Ni-B deposition time (~ 900 nm thickness of Ni-B/Ga(As)Ox layer) exhibited a very high photocurrent, leading to a nearly 22 hour stable photocurrent density of 20 mA/cm2, while the bare GaAs represents 60 % photocurrent loss after three hours under continuous one sun illumination (100 mW/cm2) in an alkaline media (pH=14). This remarkable performance in both photocurrent and stability directly address the current severe limitations in the application of GaAs photoanodes for solar fuel synthesis, and maybe applicable to other unstable photoelectrodes.
关键词： Nickel borate,Photoanode stabilization,Gallium arsenide,Solar energy conversion
更新于2025-09-19 17:15:36
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Plasmon Ag Promoted Solar-Thermal Conversion on Floating Carbon Cloth for Seawater Desalination and Sewage Disposal
摘要： Using solar energy to achieve seawater desalination and sewage disposal has received tremendous attention for its potential possibility to produce clean freshwater. However, the low solar-thermal conversion efficiency for solar absorber materials obstacles their practical applications. Herein, Ag nanoparticles (NPs) modified floating carbon cloth (ANCC) are firstly synthesized via wet-impregnation, photoreduction and low temperature drying strategy, which could float on the water and absorb the solar energy efficiently. It is worth noting that vaporization rate of ANCC with a high wide-spectrum absorption (92.39%) for the entire range of optical spectrum (200 - 2500 nm) is up to 1.36 kg h-1 m-2 under AM 1.5, which corresponds to solar-thermal conversion efficiency of ~92.82% with superior seawater desalination and sewage disposal performance. Plasmon Ag promotes the conversion efficiency obviously compared to the pristine carbon cloth because the surface plasmon resonance (SPR) effect could increase the local temperature greatly. After the desalination, the ion concentrations (Mg2+, K+, Ca2+ and Na+ ions) in water are far below the limit of drinking water. Such high-performance floating ANCC material may offer a feasible and paradigm strategy to manage the global water contamination and freshwater shortage problem.
关键词： seawater desalination,surface plasmon resonance,plasmon Ag,Solar-thermal energy conversion,floating carbon cloth
更新于2025-09-19 17:15:36
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A New Fabrication Method for Serpentine-Folded Waveguide Slow Wave Structure at W-Band
摘要： Thermionic energy converter (TEC) is a heat engine that generates electricity directly using heat as its source of energy and electron as its working fluid. Despite having a huge potential as an efficient direct energy conversion device, the progress in vacuum-based thermionic energy converter development has always been hindered by the space charge problem and the unavailability of materials with low work function. It is only recently that researchers have started to look back into this technology as recent advances in manufacturing technology techniques have made it possible to solve these problems, making TECs a viable option in replacing current energy production systems. The focus of this paper is to review the challenges of producing efficient and practical TECs, along with recent findings and developments in mitigating these challenges. Furthermore, this paper looked into potential applications of TECs, based on recent works and technologies, and found that, with certain improvements, it can be applied in many sectors.
关键词： nanowires,work function,thermionic energy conversion (TEC),space charge,Energy conversion efficiency
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Simulation of Lateral Near- and Far-Field Profiles of Gain-Guided High-Power Semiconductor Lasers
摘要： The conversion of electrical to mechanical power on a sub-centimeter scale is a key technology in many microsystems and energy harvesting devices. In this paper, we present a type of a capacitive energy conversion device that uses capillary pressure and electrowetting to reversibly convert electrical power to hydraulic power. These microhydraulic actuators use a high surface-to-volume ratio to deliver high power at a relatively low voltage with an energy conversion efficiency of over 65%. The capillary pressure generated grows linearly with shrinking capillary diameter, as does the frequency of actuation. We present the pressure, frequency, and power scaling properties of these actuators and demonstrate that power density scales up as the inverse capillary diameter squared, leading to high-efficiency actuators with a strength density exceeding biological muscle. Two potential applications for microhydraulics are also demonstrated: soft-microrobotics and energy harvesting.
关键词： electrowetting,Microhydraulics,porous materials,energy conversion,electrocapillary,microsystems,soft robotics,energy harvesting,microrobotics,actuator,microfluidics,PDMS
更新于2025-09-19 17:13:59
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Defects controlled doping and electrical transport in TiS <sub/>2</sub> single crystals
摘要： TiS2 has been intensively studied as an electrode material and a thermoelectric material for energy storage and conversion applications due to its high electrical conductivity. Understanding the influence of defects on electrical transport is of importance not only to resolve the long-standing question concerning the nature of TiS2, but also for the rational design of TiS2 based devices for energy scavenging applications. In this study, we integrate photoemission spectroscopy, Raman spectroscopy, and electrical transport measurements to determine the chemical compositions dominated by defects and their influence on the doping and electrical properties. Our results demonstrate that TiS2 is a heavily self-doped semiconductor with the Fermi level close to the conduction band, which serves as the conclusive experimental evidence regarding the semiconducting nature of TiS2. The doping effect is sensitive to the (subtle) changes in the chemical composition. The electron donation from the Ti interstitials (Tii) to the TiS2 host explains the high carrier concentration. The Ti Frenkel pair (TiF) acting as the acceptor is responsible for the decrease in the electron carrier concentration and electrical conductivity. High conductivity maintains upon partial oxidization, indicating the oxidization-tolerance in terms of the electronic structure. Our results provide valuable insight into the evolution of electronic properties modulated by defects that reveal unambiguously the self-doped semiconducting nature of TiS2 and chemical- and environment-tolerance of TiS2 as an advanced energy scavenging material.
关键词： TiS2,doping,defects,electrical transport,energy storage,energy conversion,photoemission spectroscopy,thermoelectric material,Raman spectroscopy
更新于2025-09-19 17:13:59
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Time resolved and time integrated analysis of the AXUV photodiode diagnostics for EUV and soft X-ray emission of nanosecond-laser-produced plasma
摘要： This paper addresses the experimental results and analysis of the time-resolved and time-integrated of AXUV (absolute extreme ultraviolet) photodiode diagnostics. These results are obtained by the measurement of EUV and soft X-ray (SX) power radiation of plasma-produced under the interaction of laser pulse (intensity ～5 × 1011 W/cm2, pulse durations in the range of 10?30 ns and wavelength 1064 nm) with one steel-316 target. The EUV and SX signals with the three speci?c peaks are detected by AXUV photodiode. From the analysis of time resolved of the AXUV signal, it is inferred that the ?rst signal peak can dominantly be related to the free-free transition mechanism of radiation and also the latter related to the free-band and bond-bond transitions respectively. The energy of EUV and SX pulse emission is observed to be approximately linear, proportional to the laser pulse energy. The time integrated results show that, the average energy conversion e?ciency is determined to be about 3.7 %.
关键词： Free-free transition,AXUV photodiode,EUV and soft X-ray,Energy conversion e?ciency,Laser induced plasma,Free-bond transition
更新于2025-09-19 17:13:59
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Cubic AgBiS <sub/>2</sub> Colloidal Nanocrystals for Solar Cells
摘要： Recent progress in colloidal quantum dot (CQD) based solar cells indicates that low toxic materials such as AgBiS2 nanocrystals (NCs) show potential in replacing toxic PbS and CdS CQDs in solar cell applications. In this study, an investigation on the importance of the composition and sensitivity toward synthesis conditions was performed by adjusting concentrations and ratios of Ag and Bi precursors. Firstly, by varying the ratio of Ag towards Bi precursors, and secondly by varying the concentration of Ag with a constant ratio towards Bi precursors in the solution. Furthermore elemental XPS studies and TEM imaging, together with solar cell analysis indicated a strong correlation between the concentration of Ag precursor and the NC properties, and moreover the solar cell properties based on these NCs. In short, a large amount of Ag precursor resulted in smaller Ag rich NCs, which resulted in solar cells with high photovoltage but low photocurrent density, while a lower amount of Ag precursor resulted in larger NCs, and solar cells with a lower photovoltage. The Ag:Bi:S ratio of 0.72:0.9:1 resulted in almost stoichiometric NCs but with a slight excess of Ag, which in turn resulted in solar cells with the highest performance. This work therefore gives insight in how the elemental composition and size of the NCs can be tuned by the precursor ratios, and how this in turn affects the performance of the solar cell devices.
关键词： Quantum Dots,Solar Cells,Energy Conversion,Low-toxic,AgBiS2
更新于2025-09-19 17:13:59
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Graphene Fabrication by Using Femtosecond Pulsed Laser and Its Application on Passively Q-Switched Solid-State Laser as Saturable Absorber
摘要： This paper presents an independent operation of the rotor-side converter (RSC) and grid-side converter (GSC) for a doubly fed induction generator (DFIG)-based wind energy conversion system under unbalanced grid voltage conditions. In this paper, the RSC is controlled to achieve four different control targets, including balanced stator current, sinusoidal rotor current, smooth stator active and reactive powers, and constant DFIG electromagnetic torque. The GSC is commanded to keep the dc voltage at a constant value. Additional feedback compensators using resonant regulators for the RSC are employed, and the decompositions of the positive and negative sequence components and calculations of the rotor negative current references can be avoided. Another similar compensator is used in the GSC to suppress the dc voltage ?uctuates and remove the GSC reactive power oscillations without the stator or rotor power information. The proposed method can make the RSC and GSC available to an independent operation with a simple implementation for higher reliability. The experimental results demonstrate the effectiveness of the proposed control strategy for both the RSC and GSC under unbalanced grid voltage conditions.
关键词： wind energy conversion system (WECS),independent operation,unbalanced grid voltage,resonant regulator,Doubly fed induction generator (DFIG)
更新于2025-09-19 17:13:59
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High Responsivity and High Rejection Ratio Self-Powered Solar-Blind Ultraviolet Photodetector Based on PEDOT:PSS/β-Ga2O3 Organic/Inorganic p-n Junction
摘要： A high responsivity self-powered solar-blind deep UV (DUV) photodetector with high rejection ratio was proposed based on inorganic/organic hybrid p-n junction. Owing to the high crystalized β-Ga2O3 and excellent transparent conductive polymer PEDOT:PSS, the device exhibited ultrahigh responsivity of 2.6 A/W at 245 nm with a sharp cut off wavelength at 255 nm without any power supply. The responsivity is much larger than that of previous solar-blind DUV photodetectors. Moreover, the device exhibited an ultrahigh solar-blind/UV rejection ratio (R245 nm /R280 nm) of 103, which is two orders of magnitude larger than the average value ever reported in Ga2O3-based solar-blind photodetectors. In addition, the photodetector shows a narrow band-pass response of only 17 nm in width. This work might be of great value in developing high wavelength selective DUV photodetector with respect to low cost for future energy-efficient photoelectric devices.
关键词： Self-Powered,PEDOT:PSS/β-Ga2O3,Plasmonics and Optoelectronics,Organic/Inorganic p-n Junction,Energy Conversion and Storage,High Rejection Ratio,High Responsivity,Solar-Blind Ultraviolet Photodetector
更新于2025-09-19 17:13:59