| 1. |
- Carpman, Nicole, et al.
(författare)
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Tidal resource characterization in the Folda Fjord, Norway
- 2016
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Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 13, s. 27-44
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Tidskriftsartikel (refereegranskat)abstract
- For tidal-stream energy industry to be fully realized, lower velocity sites and fjords should be developed. Finding new prospective sites for in-stream energy extraction from tidal currents is an area of ongoing research. In this paper, the tidal flow at a fjord inlet has been characterized using acoustic Doppler current profiler (ADCP) measurements. This work is based on two survey measurement techniques: transect measurements to map the spatial variability, and seabed measurements to map the temporal variability. The data was analyzed in terms of characterizing metrics, to ensure they are comparable with other resource assessments. Results show that currents exceed 1 m/s for 38% of the time with peak currents of 2.06 m/s at hub height (middle of the water column) and the directional asymmetry is less than 1° between ebb and flood, indicating a truly bi-directional flow. A simple prediction model is proposed which allows peak current speeds to be accurately predicted in the channel center from tidal range data using a linear relationship. The relationship is shown to be strong, with a correlation coefficient of 0.98 at hub height, and a standard variation typically less than 10 cm/s. Furthermore, it is show that a minimum of 9 days of measurements are required to set up the model, although it takes 29 days to reduce the error in peak speed to less than 1%. However, the error is expected to vary depending on where in the monthly tidal cycle the survey begins, it is thus recommended to measure around spring tide if the measurement period is short.
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| 2. |
- Greaves, Deborah, et al.
(författare)
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Environmental Impact Assessment : Gathering experiences from wave energy test centres in Europe
- 2016
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Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 14, s. 68-79
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Tidskriftsartikel (refereegranskat)abstract
- The wave energy industry is an emerging sector and a new user of maritime space that has potential to contribute significantly to the EU renewable energy goals. International and national regulatory frameworks necessitate Environmental Impact Assessments (EIA) that provide important data to inform development consent decisions. Here we have evaluated experience related to the assessment programmes at EU wave energy test centres combined with knowledge gained from EIA produced for other similar renewable energy developments. From this we have identified key receptors of concern, as well as the type and magnitude of impacts which may be expected. The key environmental receptors of concern for wave energy EIA include the physical environment (e.g. morphology, waves and current) and flora and fauna(1) as represented by marine mammals, seabirds, benthos, fish and shellfish. From a review of the EIAs performed at wave energy test centres, we identified several lessons regarding the wave energy EIA process. There is clear evidence that the receptors of primary interest are dependent on factors such as the local environmental characteristics, the presence/absence of protected species and the regulatory authority under which the EIA is performed. Furthermore, it is recommended that concerns relating to cumulative impacts, from an expanding level of wave energy development taking place in a background of growing utilisation of the marine environment, which are largely unknown at this early stage of the industry may be comprehensively addressed at the national level as part of a Strategic Environmental Assessment (EIA) and/or in Maritime Spatial Planning (MSP) and that it should be regularly reassessed.
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| 3. |
- Langhamer, Olivia, 1977-
(författare)
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The location of offshore wave power devices structures epifaunal assemblages
- 2016
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Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 16, s. 174-180
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Tidskriftsartikel (refereegranskat)abstract
- With large-scale development of offshore wave power conversion, artificial structures become more common in the open sea. To examine how wave power devices may be colonized by epifaunal organisms, 21 concrete foundations used for anchoring wave power generators were studied during two years, 2007 and 2008. The foundations were placed in two different clusters, located north and south within the Lysekil test site at the Swedish west coast. The degree to which early recruits covered the foundations and the succession of epibenthic communities were documented during two years. A succession in colonization over time was observed, with a higher degree of cover in the northern location. Furthermore, the northern location showed an increase in number of individuals, number of species and in Shannon-Wiener diversity in 2008. Dominant organisms on the foundations were the serpulid tubeworms (Pomatoceros triqueter) and barnacles (Balanus sp.). This comprehensive large-scale study about succession and colonization patterns on wave power foundations suggests that the location of wave energy devices affects colonization patterns. This gives indications on settlement patterns on already operating and planned offshore wave power parks further off the coasts.
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| 4. |
- Moura Paredes, Guilherme, et al.
(författare)
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Experimental investigation of mooring configurations for wave energy converters
- 2016
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Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 15, s. 56-67
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Elsevier Ltd. Mooring systems are required to keep floating wave energy converters (WECs) on station. The mooring concept might impact the performance of the WEC, its cost and its integrity. With the aim of clarifying the pros and cons of different mooring designs, we present the results from physical model experiments of three different mooring concepts in regular and irregular waves, including operational and survival conditions. The parameters investigated are the tension in the cables, the motions of the device in the different degrees of freedom and the seabed footprint in each case. We can see that the mooring system affects the performance of the wave energy converter, but the magnitude of the impact depends on the parameter analysed, on the mode of motion studied and on the conditions of the sea. Moreover, different configurations have similar performances in some situations and the choice of one over another might come down to factors such as the type of soil of the seabed, the spacing desired between devices, or environmental impacts. The results of our experiments provide information for a better selection of the mooring system for a wave energy converter when several constraints are taken into account (power production, maximum displacements, extreme tensions, etc).
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| 5. |
- Palm, Johannes, 1984, et al.
(författare)
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Coupled mooring analysis for floating wave energy converters using CFD: Formulation and validation
- 2016
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Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 16, s. 83-99
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Tidskriftsartikel (refereegranskat)abstract
- Floating wave energy converters (WECs) operating in the resonance region are stronglyaffected by non-linearities arising from the interaction between the waves, the WECmotion and the mooring restraints. To compute the restrained WEC motion thus requiresa method which readily accounts for these effects. This paper presents a method forcoupled mooring analysis using a two-phase Navier–Stokes (VOF–RANS) model and ahigh-order finite element model of mooring cables. The method is validated againstexperimental measurements of a cylindrical buoy in regular waves, slack-moored withthree catenary mooring cables. There is overall a good agreement between experimentaland computational results with respect to buoy motions and mooring forces. Mostimportantly, the coupled numerical model accurately recreates the strong wave heightdependence of the response amplitude operators seen in the experiments.
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