scholarly journals Using sea bed roughness as a wave energy dissipater

2012 ◽  
Author(s):  
T. Elgohary ◽  
R. Elgohary ◽  
M. Hagrass
Keyword(s):  
Wave Energy ◽  
Energy Dissipater ◽  
Sea Bed ◽  
Bed Roughness

A submerged cylinder wave energy converter

2013 ◽  
Vol 716 ◽  
pp. 566-596 ◽  
Author(s):  
S. Crowley ◽  
R. Porter ◽  
D. V. Evans
Keyword(s):  
Wave Energy ◽  
Three Dimensional ◽  
Wave Energy Converter ◽  
Wave Crest ◽  
Maximum Efficiency ◽  
Passive Component ◽  
Mooring System ◽  
Energy Converter ◽  
Rotation Rates ◽  
Sea Bed

AbstractA novel design concept for a wave energy converter (WEC) is presented and analysed. Its purpose is to balance the theoretical capacity for power absorption against engineering design issues which plague many existing WEC concepts. The WEC comprises a fully submerged buoyant circular cylinder tethered to the sea bed by a simple mooring system which permits coupled surge and roll motions of the cylinder. Inside the cylinder a mechanical system of pendulums rotate with power generated by the relative rotation rates of the pendulums and the cylinder. The attractive features of this design include: making use of the mooring system as a passive component of the power take off (PTO); using a submerged device to protect it from excessive forces associated with extreme wave conditions; locating the PTO within the device and using a PTO mechanism which does not need to be constrained; exploiting multiple resonances of the system to provide a broad-banded response. A mathematical model is developed which couples the hydrodynamic waves forces on the device with the internal pendulums under a linearized framework. For a cylinder spanning a wave tank (equivalent to a two-dimensional assumption) maximum theoretical power for this WEC device is limited to 50 % maximum efficiency. However, numerical results show that a systematically optimized system can generate theoretical efficiencies of more than 45 % over a 6 s range of wave period containing most of the energy in a typical energy spectrum. Furthermore, three-dimensional results for a cylinder of finite length provide evidence that a cylinder device twice the length of its diameter can produce more than its own length in the power of an equivalent incident wave crest.

On the trapping of wave energy round islands

1967 ◽  
Vol 29 (4) ◽  
pp. 781-821 ◽  
Author(s):  
M. S. Longuet-Higgins
Keyword(s):  
Wave Energy ◽  
Incident Radiation ◽  
Initial Energy ◽  
Trapped Modes ◽  
Macquarie Island ◽  
Long Wave ◽  
Sea Bed ◽  
Rate Of Decay ◽  
Rotation Of The Earth ◽  
The Waves

It is shown that islands can trap long-wave energy in a way similar to the capture of a particle by an atomic nucleus. The frequencies of the captured waves form a discrete set, being determined by the shape of the island and the contours of the surrounding sea bed. If the depth at great distances tends to a constant value, the trapped modes must leak some energy to infinity, though the consequent rate of decay may be exceedingly small. The initial energy of the trapped modes may be absorbed from incident radiation of the same frequency or from a sharp pulse. The particular example of a rectilinear pulse incident on a circular island is discussed in some detail.The effect of the rotation of the Earth is to split the frequencies of a pair of waves progressing in opposite directions round the island. The splitting of the frequencies produces slow beats in the waves as seen at any fixed point. Slight asymmetry in the island induces a slow exchange of energy between each pair of progressive modes.The present investigation was suggested by the occurrence of regular oscillations having a period of 6 min and a beat period of about 3 h in long-wave records taken at Macquarie Island, in the Southern Ocean.

Determining the Service Life of a Steel Wire Under a Working Load in the Wave Energy Converter (WEC)

2009 ◽  
Author(s):  
A. Savin ◽  
O. Svensson ◽  
E. Stro¨mstedt ◽  
C. Bostro¨m ◽  
Mats Leijon
Keyword(s):  
Service Life ◽  
Wave Energy ◽  
West Coast ◽  
Steel Wire ◽  
Ocean Waves ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Swedish West Coast ◽  
Sea Bed ◽  
The Wire

There are different types of energy in nature. Kinetic energy of natural movements like ocean waves is one of them. It is advantageous to convert this energy into a form suitable for use. Ocean waves can play important role in tomorrow’s energy production. At the Swedish Center for Renewable Electric Energy Conversion at Uppsala University, the Wave Energy Converter (WEC) was launched offshore outside the Swedish west coast in March 2006. The WEC consists of the linear generator placed on the sea bed and connected to the buoy via the rope, see Fig.2. Different rope solutions were tested. In May 2008, the steel wire Powerplast (28mm) was connected to the WEC. The steel wire has a shorter service life than other parts of the WEC. The steel wire connects the translator and the buoy. Therefore, the steel wire’s lifetime appears to be very important characteristic for the WEC. It is necessarily to determine the service life of the wire. Aggressive environments reduce the calculated service life which results in corrosion of an ordinary steel wire. A high wave climate and the contact loads can drastically affect wear of the wire. In order to prevent metal-to-metal contact between a steel wire and a funnel, the steel wire was impregnated in a black high density (HD) jacketing compound, that had a good abrasion, scratch resistance and a very good heat deformation resistance. The pulsating nature of waves can cause dramatic transition of the wire from the ductile to brittle fatigue fracture appearance. The residual stresses was also the causes of failures in the wire. The research results and the result from a full-scale experiment of dynamic behavior of a steel wire under a working load in the WEC are considered in this work. The measurements of the dynamic force along the steel wire under a water line were conducted offshore at Lysekil off the Swedish west coast.

scholarly journals Sedimentary Processes and the Holocene Development of Palmyra Atoll, Equatorial Pacific Ocean

2021 ◽  
Author(s):  
◽  
Kim Nicole Owen
Keyword(s):  
Sea Level ◽  
Wave Energy ◽  
Environmental Data ◽  
Equatorial Pacific Ocean ◽  
Central Pacific ◽  
Sedimentary Processes ◽  
The Holocene ◽  
Geological Processes ◽  
Sea Bed ◽  
Reef Islands

<p>Coral atolls are unique landforms in that they are the physical manifestations of the interplay between both biological and geological processes. Prominent amongst these processes is the ability of the reef organisms to produce CaCO3 and its subsequent erosion and dispersal as sediment. Overriding controls on this process are organic productivity, wave energy, and relative sea level. The development and stability of atolls are thus critically dependent on the balance between several processes which may change over time. Atolls are regarded as being particularly vulnerable to environmental change. This study investigates the Holocene geological history of Palmyra atoll, at 5°52’N 162°04’W, in the northern Line Islands. Beachrock is used as an indicator of (a) paleo-sea level and (b) paleo-shoreline conditions from clasts trapped within the beachrock matrix. The study also models annual CaCO3 production and hydrodynamic conditions at the sea bed to provide an integrated assessment of the past and present sedimentary processes and reef island development at Palmyra Atoll. The atoll is currently the focus of intensive scientific study by the Palmyra Atoll Research Consortium and is particularly suited to this study because of the reduced human presence. This allows the examination of the relationship between beachrock, islet development and other processes, in an environment lacking ongoing anthropogenic development. Beachrock was found at 10 locations at Palmyra Atoll and yielded 14C ages ranging from 1249 to 105 cal. yrs BP. Typically, the beachrock contains mostly coral and algal clasts and is thought to form in the intertidal zone. Continual wetting and drying throughout a tidal cycle results in the precipitation of marine phreatic cements, which thus, indicate paleo-shorelines and sea level elevation. The production of CaCO3 sediment at Palmyra was estimated using reef habitat zones from Hopley (1996) and suggests that the most productive areas are reef terraces and the reef edge. An estimate total of 91,500 tonnes of CaCO3 is produced annually on the reefs, although only approximately 9 % of this becomes sediment that remains on the reef islands. Hydrodynamic processes were modelled using the SWAN model, a bathymetric grid from NOAA, and bottom conditions estimated from other studies. Input parameters were determined using a 13 year WAVEWATCHIII hindcast model of the wave climate for the central Pacific, as well as estimations of extreme wave events. Sediment transport was inferred from the modelled bed shear stress and these results show that to form most of the beachrock outcrops on Palmyra extremely strong wave action must be coupled with a higher sea level in order to allow the propagation of wave energy across the reef to some of the island shorelines. Integration of all results suggests that growth of the reef islands at Palmyra Atoll was initiated as the sea level fell from the mid-Holocene Highstand, 1-2 m above present mean sea level. The islands subsequently grew progressively eastward, forming 3-4 island chains which strike north or northeast. The beachrock that formed on these island provided protection from later wave erosion. Despite limitations caused by lack of climatic and other environmental data due to the isolation of the study area, results are reliable and highlight the application of beachrock as a proxy for past climates and sea levels.</p>

scholarly journals Sedimentary Processes and the Holocene Development of Palmyra Atoll, Equatorial Pacific Ocean

2021 ◽  
Author(s):  
◽  
Kim Nicole Owen
Keyword(s):  
Sea Level ◽  
Wave Energy ◽  
Environmental Data ◽  
Equatorial Pacific Ocean ◽  
Central Pacific ◽  
Sedimentary Processes ◽  
The Holocene ◽  
Geological Processes ◽  
Sea Bed ◽  
Reef Islands

<p>Coral atolls are unique landforms in that they are the physical manifestations of the interplay between both biological and geological processes. Prominent amongst these processes is the ability of the reef organisms to produce CaCO3 and its subsequent erosion and dispersal as sediment. Overriding controls on this process are organic productivity, wave energy, and relative sea level. The development and stability of atolls are thus critically dependent on the balance between several processes which may change over time. Atolls are regarded as being particularly vulnerable to environmental change. This study investigates the Holocene geological history of Palmyra atoll, at 5°52’N 162°04’W, in the northern Line Islands. Beachrock is used as an indicator of (a) paleo-sea level and (b) paleo-shoreline conditions from clasts trapped within the beachrock matrix. The study also models annual CaCO3 production and hydrodynamic conditions at the sea bed to provide an integrated assessment of the past and present sedimentary processes and reef island development at Palmyra Atoll. The atoll is currently the focus of intensive scientific study by the Palmyra Atoll Research Consortium and is particularly suited to this study because of the reduced human presence. This allows the examination of the relationship between beachrock, islet development and other processes, in an environment lacking ongoing anthropogenic development. Beachrock was found at 10 locations at Palmyra Atoll and yielded 14C ages ranging from 1249 to 105 cal. yrs BP. Typically, the beachrock contains mostly coral and algal clasts and is thought to form in the intertidal zone. Continual wetting and drying throughout a tidal cycle results in the precipitation of marine phreatic cements, which thus, indicate paleo-shorelines and sea level elevation. The production of CaCO3 sediment at Palmyra was estimated using reef habitat zones from Hopley (1996) and suggests that the most productive areas are reef terraces and the reef edge. An estimate total of 91,500 tonnes of CaCO3 is produced annually on the reefs, although only approximately 9 % of this becomes sediment that remains on the reef islands. Hydrodynamic processes were modelled using the SWAN model, a bathymetric grid from NOAA, and bottom conditions estimated from other studies. Input parameters were determined using a 13 year WAVEWATCHIII hindcast model of the wave climate for the central Pacific, as well as estimations of extreme wave events. Sediment transport was inferred from the modelled bed shear stress and these results show that to form most of the beachrock outcrops on Palmyra extremely strong wave action must be coupled with a higher sea level in order to allow the propagation of wave energy across the reef to some of the island shorelines. Integration of all results suggests that growth of the reef islands at Palmyra Atoll was initiated as the sea level fell from the mid-Holocene Highstand, 1-2 m above present mean sea level. The islands subsequently grew progressively eastward, forming 3-4 island chains which strike north or northeast. The beachrock that formed on these island provided protection from later wave erosion. Despite limitations caused by lack of climatic and other environmental data due to the isolation of the study area, results are reliable and highlight the application of beachrock as a proxy for past climates and sea levels.</p>

The Silicon Detector, and Measurement of Electric Wave Energy

1907 ◽  
Vol 63 (1638supp) ◽  
pp. 26239-26239
Author(s):  
William Maver
Keyword(s):  
Wave Energy ◽  
Silicon Detector ◽  
Electric Wave
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