Sea-state modification and heaving float interaction factors from physical modelling of arrays of wave energy converters (original) (raw)
Related papers
Physical modelling of wave energy converter arrays in a large-scale wave basin: the WECwakes project
Tests have been performed in the Shallow Water Wave Basin of DHI (Hørsholm, Denmark), on large arrays of up to 25 heaving point absorber type Wave Energy Converters (WECs), for a range of geometric layout configurations and wave conditions. WEC response and modification of the wave field have been measured to provide data for the understanding of WEC array interactions and for the evaluation of array interaction numerical models. Each WEC consists of a buoy with a diameter of 31.5 cm and power take-off is modelled by realizing friction based energy dissipation through damping of the WEC's motion. Wave gauges were located within and around the WEC array. Wave conditions studied include regular, polychromatic, long-and short-crested irregular waves. A rectilinear arrangement of WEC support structures has been employed such that several array configurations could be studied. The experimental arrangement and the obtained database are presented. Results have been obtained for power a...
Water Wave Basin of DHI, in Denmark, on large arrays of up to 25 heaving point absorbers for a range of layout configurations and wave conditions. Float response and modification of the wave field are measured to provide data suitable for the evaluation of array interaction models and environmental scale models. Each wave energy converter unit has a diameter of 0.315 m and power absorption is due to friction of both a power take off system and bearings. Response is measured on all floats and surge force on five floats. Wave gauges are located withinand around the array. Wave conditions studied include regular waves and both long-and short-crested irregular waves. A rectilinear arrangement of support structures is employed such that several float configurations can be studied. A summary is presented of the experimental arrangement with particular emphasis on the individual wave energy converters and wave conditions employed. Reasonable agreement is observed between measured response for single floats and power output and float response predicted using a linear time domain model. For an array of 25 floats, up to 16.3% reduction of significant wave height is observed down-wave and 10.8% increase observed upwave for unidirectional irregular waves due to wave radiation by the heaving WECs. Spectra at different locations within and around the array show the wave field modifications.
A Review of Numerical Modelling of Wave Energy Converter Arrays
Volume 7: Ocean Space Utilization; Ocean Renewable Energy, 2012
Large-scale commercial exploitation of wave energy is certain to require the deployment of wave energy converters (WECs) in arrays, creating ‘WEC farms’. An understanding of the hydrodynamic interactions in such arrays is essential for determining optimum layouts of WECs, as well as calculating the area of ocean that the farms will require. It is equally important to consider the potential impact of wave farms on the local and distal wave climates and coastal processes; a poor understanding of the resulting environmental impact may hamper progress, as it would make planning consents more difficult to obtain. It is therefore clear that an understanding the interactions between WECs within a farm is vital for the continued development of the wave energy industry. To support WEC farm design, a range of different numerical models have been developed, with both wave phase-resolving and wave phase-averaging models now available. Phase-resolving methods are primarily based on potential flo...
An overview of the WECwakes project: physical modeling of an array of 25 wave energy converters
Experiments have been performed in the DHI Shallow Water Wave Basin (Denmark), on large arrays of up to 25 heaving point absorber Wave Energy Converters (WECs), for a range of geometric layout configurations and wave conditions. WEC response, surge forces on the WECs and modification of the wave field are measured to provide data for the understanding of WEC array interactions/effects. Wave conditions studied, include regular, polychromatic, long- and short-crested irregular waves. The experimental arrangement and the obtained database are presented. For irregular long-crested waves, up to 18.1% attenuation of significant wave height is observed downwave a rectilinear array of 25 heaving WECs.
A review of hydrodynamic investigations into arrays of ocean wave energy converters
arXiv (Cornell University), 2015
Theoretical, numerical and experimental studies on arrays of ocean wave energy converter are reviewed. The importance of extracting wave power via an array as opposed to individual wave-power machines has long been established. There is ongoing interest in implementing key technologies at commercial scale owing to the recent acceleration in demand for renewable energy. To date, several reviews have been published on the science and technology of harnessing ocean-wave power. However, there have been few reviews of the extensive literature on ocean wave-power arrays. Research into the hydrodynamic modelling of ocean wave-power arrays is analysed. Where ever possible, comparisons are drawn with physical scaled experiments. Some critical knowledge gaps have been found. Specific emphasis has been paid on understanding how the modelling and scaled experiments are likely to be complementary to each other.
Coastal Engineering Proceedings, 2014
Experiments have been performed in the Shallow Water Wave Basin of DHI (Hørsholm, Denmark) within the EU FP7 Hydralab Programme, on large farms of up to 25 heaving point absorber type Wave Energy Converters (WECs). For a range of geometric layout configurations and wave conditions (regular, polychromatic, long-and short-crested irregular waves), WEC response and modification of the wave field have been measured to provide data for the understanding of WEC farm interactions and for the evaluation of farm interaction numerical models. A first extensive wave farm database is established. The experimental arrangement and the obtained database are presented, as well as results for wave height attenuation downwave of the farms. For long-crested irregular waves, up to 18.1 % and 20.8 % reduction in significant wave height is observed downwave of the 5x5-WEC rectilinear and staggered farm, respectively. Wave height attenuation is expected to be larger, since in practical wave farm applications WECs will be controlled to extract a large amount of power from the waves, and therefore the array will cause larger wave height dissipation. These findings present the ability to combine the harvesting of energy from sea waves with coastal defence systems, resulting in cost reduction for both applications when WECs operate as multipurpose devices.
Performance of ocean wave-energy arrays in Australia
2016
Wave energy converters (WEC) range significantly in respect of concept, technologies and design maturation, with the majority of devices at an early-commercial stage. To date, most large scale deployments have been conducted with a single WEC, however there is a necessity to expand this to ‘arrays’ or ‘farms’ in the future. With this, there are complex hydrodynamic implications which require consideration in the evolution from single device to arrays. This paper considers two main issues in array designs, the positioning and coupling effects, which can be directly related to the diffraction property of the waves and the radiation properties of WECs respectively. The work conducted comprises both theoretical and experimental modelling, the latter a novel approach utilising Australia’s most technically advanced wave basin at the Australian Maritime College. The aim is to address a critical knowledge gap: understanding the performance of ocean WEC arrays, and to develop a software tool...
Analysis of the Impacts of Wave Energy Converter Arrays on the Nearshore Wave Climate
This study analyzes the impacts of offshore Wave Energy Converter (WEC) arrays on far-field waves and on nearshore wave-induced hydrodynamic forcing for a variety of array designs and incident wave conditions. The main objective of the study is to provide general conclusions on the nearshore impacts of WEC arrays in order to facilitate the assessment of future field test sites. The study utilizes the spectral wave model SWAN. Two array configurations are simulated, and WEC arrays are located either 5, 10, or 15 km offshore. Input conditions include parametric JONSWAP spectra with a range of offshore wave heights and periods. Trials are conducted with a directional wave field with the dominant direction being shore normal in all cases. Arrays are represented in SWAN through the external modification of the wave spectra at the device locations based on an experimentally-determined Power Transfer Function. Based on an analysis of existing field data, a new threshold for nearshore hydrodynamic impact is also established. The threshold represents an empirical relationship between radiation stress and longshore current magnitude. This threshold value is subsequently used as an indicator of when significant changes in the nearshore forcing are induced by WEC arrays. Results show that the changes in nearshore forcing parameters decrease as the distance between the array and the shore increases. Additionally, a more significant change in nearshore forcing parameters is seen in cases with larger input wave heights and periods and with low directional spread. The incident wave conditions, array configurations, and array locations that lead to nearshore impact are identified and assessed.
HAL (Le Centre pour la Communication Scientifique Directe), 2012
Wave energy from ocean waves is absorbed by using Wave Energy Converters (WECs). In order to extract a considerable amount of wave power at a location, in a cost-effective way, large numbers of WECs have to be arranged in arrays using a particular geometric configuration. Interactions between the individual WECs ("near field effects") affect the overall power production of the array. In addition, the wave height reduction behind an entire WEC array ("far field effects") may affect other users in the sea, the environment or even the coastline. Several numerical studies on large WEC arrays have already been performed, but large scale experimental studies, focussing on "near-field" and "far-field" wake effects of large WEC arrays are not available in literature. Within the HYDRALAB IV FP7 European programme, the WECwakes research project has been introduced, in order to perform experiments on large arrays of point absorber WECs, using different geometric configurations and inter-WEC spacings. The selected facility is the Shallow Water Wave Basin of the Danish Hydraulic Institute (DHI), in Denmark. The results from the WECwakes experimental tests will be useful in the validation and extension of the recently developed numerical models, as well as in providing insight to optimizing the geometric configurations of WEC arrays for real applications. The latter, also, aims at cost-effective configurations of WEC arrays for power production, and at quantifying the related environmental impact. The present paper focuses on the preparation of the WECwakes project and the development of the used WEC models.