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In-stream energy converters in a river: Effects on upstream hydropower station
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2011 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, no 1, 399-404 p.Article in journal (Refereed) Published
Abstract [en]

The use of in-stream energy converters in rivers is an area of research that is still in its preliminary stages. The driving force of river flows is the potential energy the water gains when it precipitates on mountainsides, and this energy is traditionally converted by hydropower stations, where dams are used to create a larger head. Using an in-stream energy converter would be advantageous in areas restricted by regulation. In this paper the effects of using these converters on the upstream water level in a river are studied. This has been done both with an analytical model and with a numerical model. The analytical model described the water level increase due to energy capture to depend on how large fraction of the channel that is blocked by the turbine. It was also shown that as the converter induces drag on the flow, and as energy is lost in wake mixing, the total head loss will be a sum of energy capture and energy losses. The losses correspond to a considerable fraction of the total head drop. The numerical model was used to evaluate these results. The model used was the 3D numerical model MIKE from the DHI Group in Sweden. Turbines were modelled with an inbuilt function in the program. The results from the model did not correspond to the analytical results, as the energy capture was equal to the head drop in the program. (c) 2010 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
2011. Vol. 36, no 1, 399-404 p.
Keyword [en]
Numerical model, In-stream energy converters, Hydrokinetic energy, Hydropower
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
URN: urn:nbn:se:uu:diva-133581DOI: 10.1016/j.renene.2010.05.019ISI: 000282845000047OAI: oai:DiVA.org:uu-133581DiVA: diva2:370310
Available from: 2010-11-16 Created: 2010-11-11 Last updated: 2016-04-19Bibliographically 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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