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Evaluation of a model for predicting the tidal velocity in fjord entrances
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Strömkraft)
Norwegian University of Science and Technology.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2013 (English)In: Energies, ISSN 1996-1073, Vol. 6, no 4, 2031-2051 p.Article in journal (Refereed) Published
Abstract [en]

Sufficiently accurate and low-cost estimation of tidal velocities is of importance when evaluating a potential site for a tidal energy farm. Here we suggest and evaluate a model to calculate the tidal velocity in fjord entrances. The model is compared with tidal velocities from Acoustic Doppler Current Profiler (ADCP) measurements in the tidal channel Skarpsundet in Norway. The calculated velocity value from the model corresponded well with the measured cross-sectional average velocity, but was shown to underestimate the velocity in the centre of the channel. The effect of this was quantified by calculating the kinetic energy of the flow for a 14-day period. A numerical simulation using TELEMAC-2D was performed and validated with ADCP measurements. Velocity data from the simulation was used as input for calculating the kinetic energy at various locations in the channel. It was concluded that the model presented here is not accurate enough for assessing the tidal energy resource. However, the simplicity of the model was considered promising in the use of finding sites where further analyses can be made.

Place, publisher, year, edition, pages
2013. Vol. 6, no 4, 2031-2051 p.
National Category
Oceanography, Hydrology, Water Resources Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
URN: urn:nbn:se:uu:diva-197317DOI: 10.3390/en6042031ISI: 000318030700013OAI: diva2:612525
Available from: 2013-03-22 Created: 2013-03-22 Last updated: 2014-01-10Bibliographically approved
In thesis
1. Hydrokinetic Resource Assessment: Measurements and Models
Open this publication in new window or tab >>Hydrokinetic Resource Assessment: Measurements and Models
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The conversion of kinetic energy in water currents into electricity has gained great attention the past years. The conversion systems are stand-alone units that typically consist of a turbine, driven by the water stream, with a generator connected to it. At the Division of Electricity at Uppsala University, research on a hydrokinetic energy conversion system is ongoing. In March 2013, a full-scale prototype was deployed in the river Dalälven at Söderfors.

This thesis is based on seven papers where the aim has been to assess the resource for hydrokinetic energy conversion. The existing hydrokinetic energy resource assessments in Scandinavia have been limited to the tidal energy found along the coast of Norway. The results from these assessments were unreliable, due to the lack of velocity data and the simple methodology used. One objective of this thesis was thus to measure the velocity in both tidal current and rivers, and evaluate models for predicting these values. Another objective was to study implications of the conversion of hydrokinetic energy, such as the degree of utilisation and the conversion efficiency, and effects on the surrounding flow and water level.

River discharge data was shown to give a good approximation of the velocity. However, non-linear behaviour of the velocity upon changing discharge cannot be approximated with discharge data. A model using tidal level data to estimate the velocity in fjord entrances was evaluated, and the model was shown to adequately estimate the cross-sectional average velocity. However, the maximum velocity in the horizontal cross-sectional profile was significantly higher than the cross-sectional average, and the model, in its current form, was not recommended to be used for resource estimations.

A high degree of utilisation, around 50%, was shown to be possible to achieve in both tidal and river currents, provided that the rated velocity is chosen properly. It was concluded that the rated velocity should be higher than the mean value, but lower than the value giving optimal conversion efficiency. Converting the kinetic energy of the flow to electricity in a river was shown to alter the water level upstream of the turbine. However, the increase in water level, caused by a hydrokinetic energy converter, was shown to be negligible compared to background friction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 70 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1038
National Category
Oceanography, Hydrology, Water Resources
urn:nbn:se:uu:diva-197834 (URN)978-91-554-8654-9 (ISBN)
Public defence
2013-05-24, Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Available from: 2013-05-03 Created: 2013-04-04 Last updated: 2013-08-30

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