AbstractsPhysics

Investigation of inflow wind conditions and load performance of small wind turbines in the built environment

by Amir Bashirzadeh Tabrizi




Institution: Murdoch University
Department:
Year: 2016
Posted: 02/05/2017
Record ID: 2064754
Full text PDF: http://researchrepository.murdoch.edu.au/32913/


Abstract

One of the fastest growing renewable electricity technologies has been wind energy, in both large-scale wind farms as well as in smaller distributed and community wind applications. Small wind turbines have traditionally been designed for rural areas over open terrain as off-grid system. There has, however, been an increasing trend towards the installation of wind turbines in non-open terrain, such as in urban areas and in mountainous regions as on-grid system, where the turbulence levels are higher and wind speeds are lower. The design, installation and performance of small wind turbines in urban areas are areas lacking in guidelines and procedures, despite evidence of failure of small wind turbines at urban sites and concerns over reliability and safety. This thesis is designed to address this lack of guidelines and procedures and can be considered as an investigation in two distinct but related parts. Firstly, it is an investigation of aspects related to wind resource assessment in urban areas through both wind monitoring programs and computational flow simulation. This research was designed in order to make a contribution to a document planned by the International Energy Agency (IEA Task 27) entitled ‘Recommended Practice for Design of Small Wind Turbines in the Built Environment’. Secondly, it is an investigation of the turbulence models currently used in the design standard for small wind turbines (IEC61400-2), their relevance for urban sites and their prediction of small wind turbine loads. This research was designed in order to make a contribution to the next revision of IEC61400-2, planned for 2019. In the first part of the study, the impact of sampling rate and averaging period on a study of the turbulent wind regime in the built environment was investigated. It was shown that choice of sampling rate did not significantly influence the values of turbulence intensity and power spectral density. Unlike sampling rate, changing the parameter of averaging period significantly affected the results of calculated turbulence intensity, including the value of the characteristic intensity I15. Generally, the results of this study showed that the turbulence intensity and power spectra of the longitudinal and lateral components of wind over a rooftop are sensitive to the choice of averaging period. Due to this sensitivity, an averaging period of at least 10 minutes was suggested for rooftop wind monitoring to avoid underestimating values of turbulence intensity and turbulence power spectra. In summary, a 10 Hz sampling rate and a 10 minute averaging period yield upper estimates for values of turbulence intensity and turbulent power spectral density. Taking this conservative approach may be the best strategy if looking to ensure that the wind resource assessment accurately captures the inflow to the wind turbine so that the turbine can be designed to handle both the loading and resonance due to turbulent gusting. The first part of the study also focused on the assessment of the combination of a ANSYS CFX… Advisors/Committee Members: Whale, Jonathan, Urmee, Tania, Lyons, Tom.