• Energy Research
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4 ".opj" files created and edited by OriginLab 2018 SR1, corresponding to the script of 4 figures in NST-2022-0094.R1.The Data calculated by ImQMD-shaw code. 4 ".opj" files created and edited by OriginLab 2018 SR1, corresponding to the script of 4 figures in NST-2022-0094.R1.The Data calculated by ImQMD-shaw code.

Wind energy continues to grow as a valuable source of renewable energy due to the reduction in the levelized cost of energy over time. To achieve this growth, wind turbine sizes are growing beyond those predicted by conventional rotor designs. The increased turbine size allows for higher tower heights, accessing higher atmospheric wind speeds, and larger rotor diameters, allowing for more power capture. Such turbines are considered extreme-scale turbines (greater than 10 MW rated power) and consist of blades in excess of 100 meters in length. To reduce the gravitational loadings on blades of such sizes, the blades are designed to be lightweight which leads to highly flexible rotors as compared to conventional wind turbine blade designs. While computational methods have been developed and verified for conventional rotors, it is unknown if they are capable of capturing the dynamics of the highly-flexible, extreme-scale turbines. Experimental testing of the rotors can alleviate any uncertainties with simulations in fully understanding the interaction of gravitational, aerodynamic and elastic loads. While full-scale rotor testing is ideal to capture these dynamics, it can be prohibitively expensive in terms of both time and cost. Therefore, a sub-scaling method which captures the full-scale dynamics can prove beneficial to the development of novel extreme-scale designs. In this study, a method for sub-scaling these ‘extreme-scale’ rotors is developed, applied, and verified through three different sub-scale turbine model designs. The scaling methods are based on a gravo-aeroelastic scaling (GAS) method which ensures the gravitational, aerodynamic, and elastic interactions of the full-scale blades are captured at a fraction of the cost in terms of time to build and materials needed. The following study begins with outlining the requirements of a computationally ideally-scaled turbine and describing the desired results of a sub-scale model based upon an extreme-scale rotor. This leads to a 1% additively manufactured blade model utilizing a bio-inspired designs in order to maintain the defined scaling requirements and is verified through structural testing. Finally, this study concludes with a 20% scale manufactured model based on the gravo-aeroelastic scaling method for experimental testing at the National Renewable Energy Laboratory’s Flatirons Campus. This model is then verified and compared against computational results for both parked and operational conditions.

Intermediaries are recognized as influential actors in advancing local bottom-up experimentation and strengthening its impact on urban sustainability transitions. Recent studies have articulated intermediation by listing diverse roles and activities that intermediaries perform and by presenting theory-based typologies of different intermediaries. However, such listings and typologies fail to capture how intermediaries engage, often informally and multi-directionally, in local experimentation. To improve the conceptual clarity of intermediation in this context, we propose a framework of four intermediation modes: brokering, configuring, structural negotiating, and facilitating and capacitating. We employ these modes in two qualitative, ethnography and interview-based studies of intermediation in urban redevelopment and energy transition contexts. The studies demonstrate that intermediation requires simultaneous engagement in multiple modes owing to the intermediaries’ different competencies, remits, and resources. Therefore, the modes are highly relevant for understanding what it takes to effectively intermediate and for preparing support mechanisms for intermediation in different experimentation domains. Peer reviewed

Intercooling the core flow in the compression process using bypass air can potentially reduce fuel consumption in commercial aviation. However, one of the critical challenges with intercooling is the installation and weight penalty due to complex ducting and large surface area for air-to-air heat exchangers (HEX). The recent interest in cryogenic hydrogen (LH2) as a potentially carbon-neutral fuel for commercial aviation expands the propulsive system’s design space due to the vastly different fuel properties between classical Jet-A and LH2. Regarding intercooling, LH2 adds a formidable heat sink with a high specific heat capacity and low storage temperature at 20K and, if utilised in the intercooling process, should allow for increased cooling power density with less installation penalties than an air-to-air HEX. Furthermore, the heat is transferred to the fuel instead of ejected into the bypass air which has potential thermodynamical benefits. The HEX can further be synergistically used to radial turn the core flow in the ICD. This paper presents the integration of a compact air-to-LH2 heat exchanger inside the gas path of the intermediate compressor duct (ICD) as the shape of a truncated cone. Axisymmetric numerical simulations areutilised to evaluate the duct performance and optimise hub and shroud lines for minimal pressure drop andoutlet uniformity. The HEX sizing was based on a preliminary system model of an LH2 commercial aviation engine with 70,000 lbs of thrust.

Ultrathin bilayer heterojunction solar cells using cyanine electron donors and electron acceptor C-60 are used to fabricate monolithically stacked tandem and triple junction devices. Sub-cell stack sequences as well as C-60 layer thicknesses are optimized by optical modeling and maximum efficiency is corroborated experimentally. The highest power conversion efficiency of 4.3% under full sun irradiation is achieved with a tandem cell where heptamethine and trimethine cyanine dyes are used in the front and back cell, respectively. The open circuit voltage matches the sum of the two respective open circuit voltages of the individual single junction solar cells within 3%. Triple junction cells using an additional sub-cell with a pentamethine cyanine suffer from electrical series resistance. At low light irradiation intensity, however, both triple and tandem solar cells reach power conversion efficiencies above 5% in agreement with the performance increase predicted from numerical simulation. (C) 2015 Elsevier B.V. All rights reserved.

The efficiency of a solar cell can be substantially increased by opening new energy gaps within the semiconductor band gap. This creates additional optical absorption pathways which can be fully exploited under concentrated sunlight. Here we report a new approach to opening a sizeable energy gap in a single junction GaAs solar cell using an array of InAs quantum dots that leads directly to high device open circuit voltage. High resolution imaging of individual quantum dots provides experimentally obtained dimensions to a quantum mechanical model which can be used to design an optimised quantum dot array. This is then implemented by precisely engineering the shape and size of the quantum dots resulting in a total area (active area) efficiency of 18.3% (19.7%) at 5 suns concentration. The work demonstrates that only the inclusion of an appropriately designed quantum dot array in a solar cell has the potential to result in ultra-high efficiency under concentration.

AbstractTriboelectric nanogenerators (TENGs) are considered one of the most effective methods for harvesting irregular and low‐frequency raindrop energy. In this work, molybdenum selenide (MoSe2) nanosheets act as intermediate layers for improving droplet‐based TENG performance. Consequently, without surface etching process, the short‐circuit current (Isc) and open‐circuit voltage (Voc) of the TENG can reach as high as 1.2 mA and 120 V, respectively. Furthermore, precise energy analysis based on an optimization model for input energy calculation is carried out, allowing conversion efficiency to be calculated under diverse conditions. Finally, an all‐solid supercapacitor is fabricated for integration with the TENG. An intelligent wireless sensing system, powered by the integrated TENG and capacitor, is demonstrated for monitoring environmental information. This study provides new insights into intermediate‐layer materials' selection and action mechanisms. It fills a gap in the research on a precise model of theoretical energy conversion efficiency calculation. The integrated devices and sensing applications will provide strategies for creating smart cities.

To address the problem that piezoelectric energy harvesters are difficult to apply in certain environments, this paper establishes the theoretical study of the intermediate fixed disc piezoelectric energy harvester (IFDPEH) based on the unimorph under concentrated force. The reliability of the model was indirectly verified by numerical simulation and Computer-Aided Engineering (CAE) simulation. The effects of load, radius ratio (piezoelectric layer/intermediate support), thickness ratio (piezoelectric layer/total thickness), and elastic modulus ratio (substrate/piezoelectric layer) on electrical energy were studied. The results indicate that the radius/thickness ratios of the IFDPEH based on aluminum and beryllium bronze are 0.05/0.31 and 0.05/0.48, respectively. In addition, through parameter comparison, it is found that the most important parameters affecting IFDPEH power are radius ratio and large load. The results are demonstrated to be meaningful for broadening the application of piezoelectric energy harvesters by the derived closed-form equations for the electrical energy along the diameters of the piezoelectric discs in the z-direction.