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  • 1
    Publication Date: 2016-06-01
    Description: Due to the dynamic process of maximum power point tracking (MPPT) caused by turbulence and large rotor inertia, variable-speed wind turbines (VSWTs) cannot maintain the optimal tip speed ratio (TSR) from cut-in wind speed up to the rated speed. Therefore, in order to increase the total captured wind energy, the existing aerodynamic design for VSWT blades, which only focuses on performance improvement at a single TSR, needs to be improved to a multi-point design. In this paper, based on a closed-loop system of VSWTs, including turbulent wind, rotor, drive train and MPPT controller, the distribution of operational TSR and its description based on inflow wind energy are investigated. Moreover, a multi-point method considering the MPPT dynamic process for the aerodynamic optimization of VSWT blades is proposed. In the proposed method, the distribution of operational TSR is obtained through a dynamic simulation of the closed-loop system under a specific turbulent wind, and accordingly the multiple design TSRs and the corresponding weighting coefficients in the objective function are determined. Finally, using the blade of a National Renewable Energy Laboratory (NREL) 1.5 MW wind turbine as the baseline, the proposed method is compared with the conventional single-point optimization method using the commercial software Bladed. Simulation results verify the effectiveness of the proposed method.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 2
    Publication Date: 2018-08-30
    Description: Sustainability, Vol. 10, Pages 3077: Political Cycles and the Mix of Industrial and Residential Land Leasing Sustainability doi: 10.3390/su10093077 Authors: Li Fang Chuanhao Tian Xiaohong Yin Yan Song This paper studies how political cycles change the mix of industrial and residential land in urban land leasing. The mixture of different types of land leasing in cities affects urban landscape, resident welfare, and economic sustainability. Using prefecture-level panel data from China and statistical regressions, this paper finds that cities lease out 3% more industrial land, as a percentage of total annual urban land leasing, when their party committee secretaries have been in office for no more than two years. In the same period, they lease out 2% less residential land. This is explained by the strategic behaviors of party committee secretaries to increase their chances of political promotion. Urban land leasing fuels local economic performance and increases the chance of city leaders’ promotion. While the economic benefits of residential land are immediate, those of industrial land cannot be reaped until two years later. This divided timeline results in more aggressive leasing of industrial land early on in party committee secretaries’ service terms, and that of residential land later on. Mayors’ service terms do not have the same effect. This political cycle distorts the temporal and spatial distributions of industrial and residential land in cities, and results in inefficient land use and unstable real estate markets.
    Electronic ISSN: 2071-1050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 3
    Publication Date: 2016-12-04
    Description: Because of the slow dynamic behavior of the large-inertia wind turbine rotor, variable-speed wind turbines (VSWTs) are actually unable to keep operating at the design tip speed ratio (TSR) during the maximum power point tracking (MPPT) process. Moreover, it has been pointed out that although a larger design TSR can increase the maximum power coefficient, it also greatly prolongs the MPPT process of VSWTs. Consequently, turbines spend more time operating at the off-design TSRs and the wind energy capture efficiency is decreased. Therefore, in the inverse aerodynamic design of VSWTs, the static aerodynamic performance (i.e., the maximum power coefficient) and the dynamic process of MPPT should be comprehensively modeled for determining an appropriate design TSR. In this paper, based on the inverse design method, an aerodynamic optimization method for VSWTs, fully considering the impacts of the design TSR on the static and dynamic behavior of wind turbines is proposed. In this method, to achieve higher wind energy production, the design TSR, chord length and twist angle are jointly optimized, which is structurally different from the conventional separated design procedure. Finally, the effectiveness of the proposed method is validated by simulation results based on the Bladed software.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 4
    Publication Date: 2017-11-25
    Description: Sensors, Vol. 17, Pages 2717: A Functionalized Tetrakis(4-Nitrophenyl)Porphyrin Film Optical Waveguide Sensor for Detection of H2S and Ethanediamine Gases Sensors doi: 10.3390/s17122717 Authors: Gulimire Tuerdi Nuerguli Kari Yin Yan Patima Nizamidin Abliz Yimit The detection of hydrogen sulfide (H2S) and ethanediamine, toxic gases that are emitted from industrial processes, is important for health and safety. An optical sensor, based on the absorption spectrum of tetrakis(4-nitrophenyl)porphyrin (TNPP) immobilized in a Nafion membrane (Nf) and deposited onto an optical waveguide glass slide, has been developed for the detection of these gases. Responses to analytes were compared for sensors modified with TNPP and Nf-TNPP composites. Among them, Nf-TNPP exhibited significant responses to H2S and ethanediamine. The analytical performance characteristics of the Nf-TNPP-modified sensor were investigated and the response mechanism is discussed in detail. The sensor exhibited excellent reproducibilities, reversibilities, and selectivities, with detection limits for H2S and ethanediamine of 1 and 10 ppb, respectively, and it is a promising candidate for use in industrial sensing applications.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by MDPI Publishing
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