Numerical investigation on the use of multi-element blades in vertical-axis wind turbines

The interest in sustainable forms of energy is being driven by the anticipated scarcity of traditional fossil fuels over the coming decades. There is also a growing concern about the effects of fossil fuel emissions on human health and the environment. Many sources of renewable energy are being rese...

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Main Author: Bah, Elhadji Alpha Amadou
Other Authors: Sankar, Lakshmi N.
Format: Others
Language:en_US
Published: Georgia Institute of Technology 2015
Subjects:
CFD
Online Access:http://hdl.handle.net/1853/53501
id ndltd-GATECH-oai-smartech.gatech.edu-1853-53501
record_format oai_dc
spelling ndltd-GATECH-oai-smartech.gatech.edu-1853-535012015-06-27T03:39:48ZNumerical investigation on the use of multi-element blades in vertical-axis wind turbinesBah, Elhadji Alpha AmadouCFDVAWTDMSTDynamic stallMulti-elementsFinancial viabilityThe interest in sustainable forms of energy is being driven by the anticipated scarcity of traditional fossil fuels over the coming decades. There is also a growing concern about the effects of fossil fuel emissions on human health and the environment. Many sources of renewable energy are being researched and implemented for power production. In particular, wind power generation by horizontal- and vertical-axis wind turbines is very popular. Vertical-axis wind turbines (VAWTs) have a relative construction simplicity compared to horizontal-axis wind turbines (HAWTs). However, VAWTs present specific challenges that may hinder their performance. For instance, they are strongly affected by dynamic stall. A significant part of the kinetic energy contained in the oncoming wind is lost in swirl and vortices. As a result, VAWTs have lower power production compared to HAWTs. First, the present work is aimed at the study of the aerodynamics of straight-bladed VAWTs (SB-VAWTs). Empirical calculations are conducted in a preliminary work. Then a two-dimensional double multiple streamtube (DMST) approach supported by a two-dimensional numerical study is implemented. The dynamic stall and aerodynamic performance of the rotor are investigated. A VAWT-fitted dynamic stall model is implemented. Computational fluid dynamics (CFD) simulations are conducted to serve as reference for the DMST calculations. This three-pronged approach allows us to efficiently explore multiple configurations. The dynamic stall phenomenon is identified as a primary cause of performance loss. The results in this section validate the DMST model as a good replacement for CFD analysis in early phase design provided that a good dynamic stall model is used. After having identify the primary cause of performance loss, the goal is to investigate the use to dual-element blades for alleviating the effect of dynamic stall, thereby improving the performance of the rotor. The desirable airfoil characteristics are defined and a parametric analysis conducted. In the present study the parameters consists of the size of the blade elements, the space between them, and their relative orientation. The performance of the rotor is calculated and compared to the baseline. The results highlight the preeminence of the two-element configuration over the single-element provided that the adequate parametric study is conducted beforehand. A performance enhancement is obtained over a large range of tip speed ratios. The starting characteristics and the operation stability are also improved. Finally, an economic analysis is conducted to determine the cost of energy and thus the financial viability of such a project. The Great Coast of Senegal is selected as site of operation. The energy need and sources of this region are presented along with its wind energy potential. The cost evaluation shows the economic viability by comparing the cost of energy to the current energy market prices.Georgia Institute of TechnologySankar, Lakshmi N.Jagoda, Jechiel2015-06-08T18:20:41Z2015-06-08T18:20:41Z2015-052015-01-12May 20152015-06-08T18:20:41ZDissertationapplication/pdfhttp://hdl.handle.net/1853/53501en_US
collection NDLTD
language en_US
format Others
sources NDLTD
topic CFD
VAWT
DMST
Dynamic stall
Multi-elements
Financial viability
spellingShingle CFD
VAWT
DMST
Dynamic stall
Multi-elements
Financial viability
Bah, Elhadji Alpha Amadou
Numerical investigation on the use of multi-element blades in vertical-axis wind turbines
description The interest in sustainable forms of energy is being driven by the anticipated scarcity of traditional fossil fuels over the coming decades. There is also a growing concern about the effects of fossil fuel emissions on human health and the environment. Many sources of renewable energy are being researched and implemented for power production. In particular, wind power generation by horizontal- and vertical-axis wind turbines is very popular. Vertical-axis wind turbines (VAWTs) have a relative construction simplicity compared to horizontal-axis wind turbines (HAWTs). However, VAWTs present specific challenges that may hinder their performance. For instance, they are strongly affected by dynamic stall. A significant part of the kinetic energy contained in the oncoming wind is lost in swirl and vortices. As a result, VAWTs have lower power production compared to HAWTs. First, the present work is aimed at the study of the aerodynamics of straight-bladed VAWTs (SB-VAWTs). Empirical calculations are conducted in a preliminary work. Then a two-dimensional double multiple streamtube (DMST) approach supported by a two-dimensional numerical study is implemented. The dynamic stall and aerodynamic performance of the rotor are investigated. A VAWT-fitted dynamic stall model is implemented. Computational fluid dynamics (CFD) simulations are conducted to serve as reference for the DMST calculations. This three-pronged approach allows us to efficiently explore multiple configurations. The dynamic stall phenomenon is identified as a primary cause of performance loss. The results in this section validate the DMST model as a good replacement for CFD analysis in early phase design provided that a good dynamic stall model is used. After having identify the primary cause of performance loss, the goal is to investigate the use to dual-element blades for alleviating the effect of dynamic stall, thereby improving the performance of the rotor. The desirable airfoil characteristics are defined and a parametric analysis conducted. In the present study the parameters consists of the size of the blade elements, the space between them, and their relative orientation. The performance of the rotor is calculated and compared to the baseline. The results highlight the preeminence of the two-element configuration over the single-element provided that the adequate parametric study is conducted beforehand. A performance enhancement is obtained over a large range of tip speed ratios. The starting characteristics and the operation stability are also improved. Finally, an economic analysis is conducted to determine the cost of energy and thus the financial viability of such a project. The Great Coast of Senegal is selected as site of operation. The energy need and sources of this region are presented along with its wind energy potential. The cost evaluation shows the economic viability by comparing the cost of energy to the current energy market prices.
author2 Sankar, Lakshmi N.
author_facet Sankar, Lakshmi N.
Bah, Elhadji Alpha Amadou
author Bah, Elhadji Alpha Amadou
author_sort Bah, Elhadji Alpha Amadou
title Numerical investigation on the use of multi-element blades in vertical-axis wind turbines
title_short Numerical investigation on the use of multi-element blades in vertical-axis wind turbines
title_full Numerical investigation on the use of multi-element blades in vertical-axis wind turbines
title_fullStr Numerical investigation on the use of multi-element blades in vertical-axis wind turbines
title_full_unstemmed Numerical investigation on the use of multi-element blades in vertical-axis wind turbines
title_sort numerical investigation on the use of multi-element blades in vertical-axis wind turbines
publisher Georgia Institute of Technology
publishDate 2015
url http://hdl.handle.net/1853/53501
work_keys_str_mv AT bahelhadjialphaamadou numericalinvestigationontheuseofmultielementbladesinverticalaxiswindturbines
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