| 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. |
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| 3. |
- Goude, Anders, et al.
(författare)
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Forces on a marine current turbine during runaway
- 2017
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Ingår i: International Journal of Marine Energy. - : Elsevier. - 2214-1669. ; 19, s. 345-356
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Tidskriftsartikel (refereegranskat)abstract
- A runaway marine current turbine will typically overshoot the runaway speed significantly before it settles at that speed. Numerical simulations of an experimental turbine indicate that the peak forces experienced by the turbine during runaway are up to 2.7 times those seen during nominal operation, and 2.1 times those at asymptotic runaway speed, making peak runaway force an important consideration in turbine design. The main contribution to the force increase is found to originate from the increased rotational speed, but a significant part is also due to the temporal lag in turbine wake development. A parameter study further shows that turbines with low inertia, turbines that have low losses, and turbines designed for low tip speed ratios will experience larger increases in forces.
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| 4. |
- 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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| 5. |
- Göteman, Malin, 1980-, et al.
(författare)
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Optimizing wave energy parks with over 1000 interacting point-absorbers using an approximate analytical method
- 2015
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Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 10, s. 113-126
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Tidskriftsartikel (refereegranskat)abstract
- Large arrays of wave energy converters of point-absorber type are studied using an approximate analytical model. The model is validated against a numerical method that takes into account full hydrodynamic interactions based on linear potential flow theory. The low computational cost of the analytical model enables parameter studies of parks in the MW range and includes up to over 1000 interacting devices. The model is actuated by irregular wave data obtained at the Swedish west coast. In particular, focus is on comparing park geometries and improving park configurations to minimize the power fluctuations.
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| 6. |
- Isberg, Jan, 1964-, et al.
(författare)
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Control of rapid phase oscillations in the modelling of large wave energy arrays
- 2015
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Ingår i: International Journal of Marine Energy. - : Elsevier. - 2214-1669. ; 11, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Several recently developed concepts for economically viable conversion of ocean wave energy are based on large arrays of point absorbers. Simulations of the hydrodynamic interactions between devices in wave energy parks provide guidelines for optimal configurations with regard to maximizing produced electricity while minimizing fluctuations and costs. Parameters that influence the performance include the geometrical lay-out of the park, the number of wave energy converters and their dimensions and separating distance, as well as the wave climate and the incoming wave spectral characteristics. However, the complexity of the simulations increases rapidly with growing number of interacting units, and simulations become a severe challenge that calls for new methods. Here we address the problem of rapid phase oscillations appearing in the simulation of large arrays of point absorbers using potential theory for the structure–fluid interaction. We do this by analytically integrating out the factors that are causing the oscillations. Our group has successfully utilized this method to model parks with up to 1000 point absorbers.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
- Simas, Teresa, et al.
(författare)
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Review of consenting processes for ocean energy in selected European Union Member States
- 2015
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Ingår i: International Journal of Marine Energy. - : Elsevier BV. - 2214-1669. ; 9, s. 41-59
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Consenting is still generally regarded as a non-technological barrier to the progress of the marine renewable energy industry, caused by the complexity of consenting processes and the lack of dedicated legal frameworks. Existing consenting systems for ocean energy projects tend to be based on procedures designed for other sectors and are seen as inappropriate for the specific needs of ocean energy. Licensing procedures are also viewed by developers as time-consuming because regulators see ocean energy as a new activity with unknown or uncertain effects and consequently often apply strong interpretation of the precautionary principle. Consenting processes for ocean energy are, nevertheless, evolving throughout Europe, driven by national and European policies and incentives on renewables, changing legal and administrative frameworks to facilitate development and more integrated marine governance. This review compares the consenting processes for ocean energy in different European countries, focusing on aspects thought to hamper operation of the process. It shows that different systems of governance across the EU Member States have resulted in diversity in the design of consenting processes, though common features can also be identified. This evidence-based review enables suggestions for streamlining consenting processes for wave energy.
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