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Eigen Frequencies of A Vertical Axis Wind Turbine Tower Made of Laminated Wood and the Effect Upon Attaching Guy Wires
Halmstad University, School of Business, Engineering and Science, Biological and Environmental Systems (BLESS), Energiteknik.ORCID iD: 0000-0001-9982-5317
Halmstad University, School of Business, Engineering and Science, Biological and Environmental Systems (BLESS), Energiteknik.
Halmstad University, School of Business, Engineering and Science, Biological and Environmental Systems (BLESS), Energiteknik.
Uppsala Universitet.
2014 (English)In: Wind Engineering: The International Journal of Wind Power, ISSN 0309-524X, E-ISSN 2048-402X, Vol. 38, no 3, 277-290 p.Article in journal (Refereed) Published
Abstract [en]

Eigen frequencies of a vertical axis wind turbine tower made out of laminated wood which are both bolted to the ground and supported by guy wires are studied and compared. Using beam theory, an analytical model taking the guy wires into account for calculating the first mode eigen frequency of the tower has been derived. The analytical model is then evaluated by comparing with FEM-simulations and measurements performed on the actual tower. The model is found to be reasonably accurate keeping in mind that the estimated masses and second moments of area are somewhat rough. Furthermore the model can be used to give an indication of the magnitude of change in eigen frequency when modifying a tower or guy wire property.

Place, publisher, year, edition, pages
Brentwood, United Kingdom: Multi-Science Publishing, 2014. Vol. 38, no 3, 277-290 p.
Keyword [en]
VAWT, Vertical Axis Wind Turbine, Semi-guy-wired, Natural frequency, Eigen frequency, Resonance
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:hh:diva-25467DOI: 10.1260/0309-524X.38.3.277ScopusID: 2-s2.0-84901792518OAI: oai:DiVA.org:hh-25467DiVA: diva2:720731
Funder
StandUp
Available from: 2014-06-02 Created: 2014-06-02 Last updated: 2017-05-10Bibliographically approved
In thesis
1. Vertical Axis Wind Turbines: Tower Dynamics and Noise
Open this publication in new window or tab >>Vertical Axis Wind Turbines: Tower Dynamics and Noise
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Vertical axis wind turbines (VAWTs) have with time been outrivaled by the today common and economically feasible horizontal axis wind turbines (HAWTs). However, VAWTs have several advantages such as the possibility to put the drive train at ground level, lower noise emissions and better scaling behavior which still make them interesting for research.

The work within this thesis is made in collaboration between the Department of Construction and Energy Engineering at Halmstad University and the Division for Electricity at Uppsala University. A 200 kW VAWT owned by the latter and situated close to Falkenberg in the southwest of Sweden has been the main subject of the research even if most learnings has been generalized to fit a typical vertical turbine. This particular turbine has a wooden tower which is semi-guy-wired, i.e. the tower is both firmly attached to the ground and supported by guy-wires.

This thesis has two main topics both regarding VAWTs: eigenfrequency of the tower and the noise generated from the turbine. The eigenfrequency of a semi-guy-wired tower is studied and an analytical expression describing this is produced and verified by experiments and simulations. The eigenfrequency of the wire itself and how it is affected by wind load are also studied.  The noise characteristics of VAWTs have been investigated, both theoretically and by noise measurement campaigns. Both noise emission and frequency distribution of VAWTs has been studied.

The work has resulted in analytical expressions for tower and wire eigenfrequency of a semi-guy-wired tower as well as recommendations for designing future towers for VAWTs. The noise emission of VAWTs has been studied and proven low compared to HAWTs. The noise frequency distribution of the 200 kW VAWT differs significantly from that of a similar size HAWTs with for example lower levels for frequencies below 3000 Hz.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2015. 61 p.
Series
UURIE / Uppsala universitet, Institutitionen för teknikvetenskaper, ISSN 0349-8352 ; 340-15L
Keyword
VAWT, H-rotor, eigenfrequency, semi-guy-wired tower, noise emission, sound power level
National Category
Energy Engineering
Identifiers
urn:nbn:se:hh:diva-27526 (URN)
Presentation
2015-01-16, Polhemsalen, Ångströmlaboratoriet, Uppsala, 13:43 (English)
Opponent
Supervisors
Funder
StandUp
Available from: 2015-01-22 Created: 2015-01-19 Last updated: 2015-02-18Bibliographically approved
2. Noise, eigenfrequencies and turbulence behavior of a 200 kW H-rotor vertical axis wind turbine
Open this publication in new window or tab >>Noise, eigenfrequencies and turbulence behavior of a 200 kW H-rotor vertical axis wind turbine
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vertical-axis wind turbines (VAWTs) have with time been outrivaled by the today more common and economically feasible horizontal-axis wind turbines (HAWTs). However, VAWTs have several advantages which still make them interesting, for example, the VAWTs can have the drive train at ground level and it has been argued that they have lower noise emission. Other proposed advantages are suitability for both up-scaling and floating offshore platforms.

The work within this thesis is made in collaboration between Halmstad University and Uppsala University. A 200-kW semi-guy-wired VAWT H-rotor, owned by Uppsala University but situated in Falkenberg close to Halmstad, has been the main subject of the research although most results can be generalized to suit a typical H-rotor.

This thesis has three main topics regarding VAWTs: (1) how the wind energy extraction is influenced by turbulence, (2) aerodynamical noise generation and (3) eigenfrequencies of the semi-guy-wired tower.

The influence from turbulence on the wind energy extraction is studied by evaluating logged operational data and examining how the power curve and the tip-speed ratio for maximum Cp is impacted by turbulence. The work has showed that the T1-turbine has a good ability to extract wind energy at turbulent conditions, indicating an advantage in energy extraction at turbulent sites for VAWTs compared to HAWTs.The noise characteristics are studied experimentally, and models of the two most likely aerodynamic noise mechanisms are applied. Here, inflow-turbulence noise is deemed as the prevailing noise source rather than turbulent-boundary-layer trailing-edge noise (TBL-TE) which is the most important noise mechanism for HAWTs. The overall noise emission has also been measured and proven low compared to similar sized HAWTs.

The eigenfrequencies of a semi-guy-wired tower are also studied. Analytical expressions describing the first-mode eigenfrequency of both tower and guy wire has been derived and verified by experiments and simulations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 89 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1485
Keyword
VAWT, H-rotor, eigenfrequency, semi-guy-wired tower, noise emission, sound power level, microphone array, turbulence intensity, power curve
National Category
Energy Engineering
Identifiers
urn:nbn:se:hh:diva-33834 (URN)978-91-554-9834-4 (ISBN)
Public defence
2017-04-28, Häggsalen, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Funder
StandUp
Available from: 2017-05-11 Created: 2017-05-10 Last updated: 2017-05-17Bibliographically approved

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