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Avoidance of resonances in a semi-guy-wired vertical axis wind turbine
Halmstad University, School of Business, Engineering and Science, Biological and Environmental Systems (BLESS), Energiteknik. Division for Electricity, Department of Engineering Sciences, Uppsala University, PO Box 534, SE - 751 21 Uppsala, SwedenDivision for Electricity, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.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.
Division for Electricity, Department of Engineering Sciences, Uppsala University, PO Box 534, SE - 751 21 Uppsala, SwedenDivision for Electricity, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
2014 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Resonance analysis for a vertical axis wind turbine is performed. The turbine may be described as semi-guy wired, being bolted stiffly to the ground as well as supported by guy wires. The influence of the first mode eigen frequency of the guy wires and how it is affected by wind load is examined. Using beam theory, an analytical model for calculating the first mode eigen frequency of the guy wire for different wind loads is derived. The analytical model is verified with FEM-simulations and then used to assemble a diagram showing how to combine the wire size, inclination angle and pre-tension for an eigen frequency range over the 3P load for nominal rotational speed and for a certain effective spring force acting on the tower. This diagram, here called an EA-T diagram, may be used as a quick tool for comparing wire setups and a similar diagram can be used for other guy wired structures.

Place, publisher, year, edition, pages
2014.
Keyword [en]
VAWT, guy wire, semi-guy-wired, resonance, eigen frequency, natural frequency
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:hh:diva-24884OAI: oai:DiVA.org:hh-24884DiVA: diva2:706117
Conference
EWEA 2014 - European Wind Energy Association – Annual Event (Conference), Barcelona, Spain, 10-13 March, 2014
Funder
StandUp
Available from: 2014-03-19 Created: 2014-03-19 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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