Distribution Of Tidal Energy Research Articles

Response of tidal dynamics to successive land reclamation in the Lingding Bay over the last century

Globally, many estuaries are suffering from land reclamation that drastically influences estuarine hydrodynamics. It has been reported that reclamation may induce tidal regime shifts in small converging estuaries, but it is not clear whether such regime shifts can also occur in wide estuarine bays. Lingding Bay (LDB) in Pearl River Estuary, southern China has a sufficient width (ca. 60 km) and a long history of reclamation (approximately 3.99 × 10 8 km 2 over the past century), forming an ideal area to study the mechanism of tidal regime shift in wide bays. Based on a state-of-the-art modeling tool (Delft3D Flexible Mesh), tidal propagation pattern in 1917, 1964, 1989 and 2016 was reproduced accounting for reclamation-induced shoreline changes. Our results reveal a prominent shift in tidal amplitude, residual current, and tidal energy flux in the period of 1989–2016, even though the reclamation area in this period was the smallest among the three studied periods. The reason for such shift is that reclamation of key areas amplified the imbalanced tidal energy distribution between the western and eastern LDB, and such imbalance exceeded a tipping point around 1989. This regime shift may increase the relative tidal forcing in the eastern LDB, which means stronger saltwater intrusion and higher flooding risk. Our findings indicate that tidal dynamics of LDB has been greatly altered over the last century in the LDB, where the scale and location of the reclamation are of key importance. The insights obtained from this study are valuable to the future management of LDB and other estuaries that are under reclamation stress. • The continuous land reclamation triggered a different response of the tidal dynamics in the Lingding Bay (LDB) around 1989. • The increased lateral difference resulted in regime shifts in the tidal motion in the LDB. • The tidal motion in the LDB showed threshold behavior in response to reclamation. • The altered tidal motion may lead the morphology to a new pattern as a snow ball effect requiring further studies.

High-resolution numerical survey of potential sites for tidal energy extraction along coastline of China under sea-level-rise condition

Many coastal countries are concerned with sustainable energy generation to meet their current and future energy needs. Tidal energy is an attractive resource as in-stream turbines can generate electricity even at moderate flow velocities. However, not all coastal areas are equally well-suited for tidal energy development. The survey of potential locations and their power densities is a crucial step in evaluating the potential cost-benefit of tidal energy. This research surveys the intensity and distribution of offshore tidal energy along whole coastline of China based on a high-resolution numerical simulation with a minimum mesh spacing of 80 m. The Finite Volume Community Ocean Model (FVCOM) has been used to carry out the numerical simulation work. Since FVCOM uses an unstructured mesh, it can accurately identify complex coastlines, such as those along islands, waterways, and estuaries. The simulation period for this numerical survey is 30 days. The accuracy of the simulation results is validated using 8-days in-situ measurements obtained at 17 coastal stations in the region of study. Research results indicate that the total mean tidal energy is 1.19 × 1014 J along the coastline of China. The tidal energy is mainly distributed in the south and southeast of the coastline of China. This study also identifies 45, 23 and 9 top sites, where the averaged tidal energy density is greater than 500, 1000, and 1500 W/m2, respectively, suitable for tidal energy extraction and utilization. Considering the long development cycle of tidal energy and global climate change, this study also investigates the impact of sea-level rise (SLR) on tidal energy distribution in the region of study using a 50-year (0.5 m) and 100-year (1.0 m) SLR scenarios. It is found that the total mean tidal energy increases by 3.0% and 6.5% for 50-year and 100-year SLR scenarios, respectively. It is believed that the findings drawn from this study could be instructive for future utilization of tidal energy along the coastline of China.

Energetics of internal tides over the Sangihe-Talaud ridge - Sulawesi sea

An estimate of energetic barotropic and baroclinic tides over Sangihe-Talaud ridge (STR) - Sulawesi Sea is carried out by using a three-dimensional ROMS (Regional Ocean Modeling System) ocean model. The model is validated with satellite data. The estimate of tidal energy consists of generation, radiation, and dissipation. The model identified the generating internal tide area with strong barotropic-to-baroclinic conversion (above 10 kW/m) over S-T ridge. Away from this generating internal tides area that is in deep Sulawesi Sea basin, energy conversion is very weak (below 10−3Wm−2). Baroclinic energy is mostly dissipated in area near the coast. From the total of 9.45 GW (100%) of barotropic-to-baroclinic energy conversion, about 7.19 GW (76%) is converted into baroclinic energy through the generation of internal tide and about 4.13 GW (57%) of this baroclinic energy radiate to deep open sea. Distribution of tidal energy is highly dependent on topographic features. Estimate of strong vertical eddy diffusivity (KV) over the steep S-T ridge varies between 10−3 and 10−2 m2/s, in contrast to the weak KV in deep flat Sulawesi basin of about 10−4 m2/s.

Evaluation of tidal stream energy and its impacts on surrounding dynamics in the Eastern Region of Pingtan Island, China

Using an improved FVCOM numerical model, combined with the momentum-sinking scheme based on the structural characteristics of specific turbines, this study analyzed the temporal and spatial distributions of tidal energy resources before and after the deployment of tidal turbines near Pingtan Island, China. Considering factors such as the distribution of tidal stream energy, bathymetry, topography, and the design parameters of the turbines, an appropriate location for a demonstration tidal turbine was selected and the corresponding energy resource was evaluated. Several sites with strong tidal streams were considered: south of the northern cape, east of the southern cape, and the southern end of Haitan Bay. The former was thought most suitable for the deployment of a tidal energy turbine, with projected power generation for approximately 470 h per month. The average power of this demonstration was about 2.4 kW, and the annual electricity output was approximately 17.47 MWh. The intervention of the turbine device had little influence on the near-field tidal stream or water level. The tidal stream was reduced slightly in the area south of the northern cape, although the effect weakened further from the turbine. Conversely, the velocity increased slightly on both sides of the demonstration site. The difference in current speed with and without the turbine was greater at slack tide than still tide. The influence of turbine operation on water level was minor. The method adopted in this study can be considered a reference for the selection of sites for the demonstration of tidal stream energy. However, the method is unable describe the dynamic characteristics of the turbulent flow surrounding the deployed turbines, which has an important role regarding the optimal designs of the turbine blade and pile foundations. Therefore, we will continue to work to improve this model in future research.

A system shift in tidal choking due to the construction of Yangshan Harbour, Shanghai, China

Tidal choking is a geometric feature caused by a narrowed channel. Construction of the Yangshan Harbour, Shanghai, China obstructed three key channels and intensively changed the local geometry and topography. In this study nine numerical experiments based on the Finite-Volume Community Ocean Model are conducted to study the project's influence on tidal characteristics. Results show that stronger tidal choking happened at the East Entrance after project, mainly due to the jet induced water-level drop forced by Bernoulli law and the longer and narrower geometry. The stronger tidal choking forces a faster flow and larger tidal energy flux at the choked channel while reducing the tidal amplitude in the Inner Harbour Area (IHA). The scouring on this channel reduces the choking effect but further enlarges tidal energy flux.Moreover, damming the channels decrease the tidal amplitude at the lee side of tidal propagating direction while increasing the amplitude on the stoss side. The dams also decrease the tidal current on both sides, and meanwhile develop two patches with stronger current aside the dam. The project induced changes in tidal characteristics are complex in space, and perturbations in bathymetry increase this complexity. Yangshan Harbour's construction induces little changes in the total tidal energy density in the IHA, but induces obvious changes in the spatial distribution of tidal energy. Although this study is site-specific, the findings may be applicable to tidal dynamics in land reclamation close to open seas, such as the dramatic reclamation of islands in the South China Sea.

Widespread infilling of tidal channels and navigable waterways in the human-modified tidal deltaplain of southwest Bangladesh

Since the 1960s, ~5000 km2 of tidal deltaplain in southwest Bangladesh has been embanked and converted to densely inhabited, agricultural islands (i.e., polders). This landscape is juxtaposed to the adjacent Sundarbans, a pristine mangrove forest, both well connected by a dense network of tidal channels that effectively convey water and sediment throughout the region. The extensive embanking in poldered areas, however, has greatly reduced the tidal prism (i.e., volume of water) transported through local channels. We reveal that >600 km of these major waterways have infilled in recent decades, converting to land through enhanced sedimentation and the direct blocking of waterways by embankments and sluice gates. Nearly all of the observed closures (~98%) have occurred along the embanked polder systems, with no comparable changes occurring in channels of the Sundarbans (<2% change). We attribute most of the channel infilling to the local reduction of tidal prism in poldered areas and the associated decline in current velocities. The infilled channels account for ~90 km2 of new land in the last 40–50 years, the rate of which, ~2 km2/yr, offsets the 4 km2/yr that is eroded at the coast, and is equivalent to ~20% of the new land produced naturally at the Ganges-Brahmaputra tidal rivermouth. Most of this new land, called ‘khas’ in Bengali, has been reclaimed for agriculture or aquaculture, contributing to the local economy. However, benefits are tempered by the loss of navigable waterways for commerce, transportation, and fishing, as well as the forced rerouting of tidal waters and sediments necessary to sustain this low-lying landscape against rising sea level. A more sustainable delta will require detailed knowledge of the consequences of these hydrodynamic changes to support more scientifically-grounded management of water, sediment, and tidal energy distribution.

Tidal energy redistribution among vertical modes in a fluid with a mid-depth pycnocline

We modeled internal tide generation above a high sinusoidal ridge in a fluid with a mid-depth pycnocline and developed an original method to quantify internal tide vertical mode amplitude in two-dimensional-vertical simulations. Since lowest modes can propagate over considerable distances, while high modes are more likely to dissipate locally, estimating the tidal energy distribution among vertical modes is necessary to investigate the spatial redistribution of the tidal energy. Our numerical approach allows expansion and verification of previous analytical studies over a larger range of configurations. The tidal energy distribution among vertical modes is shown here to be dependent on the topographic resonance criterion and the topographic blocking parameter.

High-resolution survey of tidal energy towards power generation and influence of sea-level-rise: A case study at coast of New Jersey, USA

Abstract The first and a crucial step in development of tidal power, which is now attracting more and more attention worldwide, is a reliable survey of temporal and spatial distribution of tidal energy along coastlines. This paper first reviews the advance in assessment of tidal energy, in particular marine hydrokinetic (MHK) energy, and discusses involved challenges and necessary approaches, and then it makes a thorough survey as an illustrative case study on distributions and top sites of MHK energy within the Might-Atlantic-Bight (MAB) with emphasis on the New Jersey (NJ) coastlines. In view of the needs in actual development of tidal power generation and sensitivity of tidal power to flow speed, the former being proportional to the third power of the latter, a high-resolution and detailed modeling is desired. Data with best available accuracy for coastlines, bathymetry, tributaries, etc. are used, meshes as fine as 20 m and less for the whole NJ coast are generated, and the unstructured grid finite volume coastal ocean model (FVCOM) and high performance computing (HPC) facilities are employed. Besides comparison with observation data, a series of numerical tests have been made to ensure reliability of the modeling results. A detailed tidal energy distribution and a list of top sites for tidal power are presented. It is shown that indeed sea-level-rise (SLR) affects the tidal energy distribution significantly. With SLR of 0.5 m and 1 m, tidal energy in NJ coastal waters increases by 21% and 43%, respectively, and the number of the top sties tends to decrease along the barrier islands facing the Atlantic Ocean and increase in the Delaware Bay and the Delaware River. On the basis of these results, further discussions are made on future development for accurate assessment of tidal energy.

A numerical study of the barotropic tides and tidal energy distribution in the Indonesian seas with the assimilated finite volume coastal ocean model

The tides and tidal energetics in the Indonesian seas are simulated using a three-dimensional finite volume coastal ocean model. The high-resolution coastline-fitted model is configured to better resolve the hydrodynamic processes around the numerous barrier islands. A large model domain is adopted to minimize the uncertainty adjacent to open boundaries. The model results with elevation assimilation based on a simple nudge scheme faithfully reproduced the general features of the barotropic tides in the Indonesian Seas. The mean root-mean-square errors between the observed and simulated tidal constants are 2.3, 1.1, 2.4, and 1.5 cm for M2, S2, K1, and O1, respectively. Analysis of the model solutions indicates that the semidiurnal tides in the Indonesian Seas are primarily dominated by the Indian Ocean, whereas the diurnal tides in this region are mainly influenced by the Pacific Ocean, which is consistent with previous studies. Examinations of tidal energy transport reveal that the tidal energy for both of the simulated tidal constituents are transported from the Indian Ocean into the IS mainly through the Lombok Strait and the Timor Sea, whereas only M2 energy enters the Banda Sea and continues northward. The tidal energy dissipates the most in the passages on both sides of Timor Island, with the maximum M2 and K1 tidal energy transport reaching about 750 and 650 kW m–1, respectively. The total energy losses of the four dominant constituents in the IS are nearly 338 GW, with the M2 constituent dissipating 240.8 GW. It is also shown that the bottom dissipation rate for the M2 tide is about 1–2 order of magnitudes larger than that of the other three tidal components in the Indonesian seas.

潮流エネルギーの平面及び鉛直分布の特徴

潮流エネルギーの平面及び鉛直分布の特徴

Sedimentology models from activity concentration measurements: application to the “Bay of Cadiz” Natural Park (SW Spain)

A previous study on seabed sediments of the Bay of Cadiz (SW of Spain) enabled us to identify several relations between sedimentological variables and activity concentrations of environmental radionuclides such as 137Cs, 226Ra, 232Th and 40K. In this paper the study has been extended to a large neighbouring inter-tidal area in order to establish if the above mentioned models can be generalized. As a result we have determined that the measured activity concentrations are closely to the values predicted by the theoretical models (correlation coefficient range = 0.85–0.93). Furthermore, the proposal model for granulometric facies as a function of activity concentrations of the abovementioned radionuclides provides for the sediments distribution a representation which agrees with the values of the tidal energy distribution obtained using numeric models calibrated with experimental data from current meters and water level recorders.

Internal Tides in the Southwestern Japan/East Sea

Abstract This paper investigates the internal tidal energy distribution in the southwestern Japan/East Sea using vertical round-trip travel time (τ) data from 23 pressure-sensor-equipped inverted echo sounders (PIES). The τ records are analyzed by bandpass filtering to separate time-dependent variability of the semidiurnal and diurnal bands. The semidiurnal internal tides exhibit a horizontal beam pattern of high energy, propagating into the open basin. They originate from a restricted portion of the shelf break where the Korea Strait enters the Ulleung Basin. The generation appears to occur at ∼200-m water depth near 35.5°–35.7°N and 130°–131°E, where the slope of bottom topography matches that of the wave characteristics, coinciding with the location where the semidiurnal barotropic cross-slope tidal currents are strongest. Maximum vertical displacement of the thermocline interpreted as a long-wave first baroclinic mode from the measured τ is about 25 m near the generation region. Annual and monthly variations of the propagation patterns and generation energy levels are observed, and these are closely associated with changes in the mesoscale circulation and stratification. Eastward (westward) refraction is observed when a warm (cold) eddy crosses the path of internal tide propagation. Moreover, when the generation region is invaded by cold eddies that spoil the match between shelf break and thermocline depth, the internal tidal energy level decreases by a factor of about 2. A simple geometric optics model is proposed to explain the observed horizontal refraction of the beam of semidiurnal internal tides in which stratification and current shear play essential roles. In contrast, diurnal internal tides are observed to be trapped along the continental slope region around 36°N.

Internal Tides Observed by an Acoustic Doppler Current Profiler

Abstract Previous studies of Knight Inlet, British Columbia, revealed the presence of a strong internal M2 tide. Most of the energy was found to be in either the first or second dynamic modes. Due to difficulties in sampling of the surface layer, objective estimates of the distribution of tidal energy and reflection coefficients, until now, have been impossible to obtain. During June and July 1989, an intense acoustic Doppler current profiler (ADCP) sampling of the inlet was conducted. These results are used to show the existence of a strong semidiurnal flow in the baroclinic field. The authors propose that the horizontal phase information inherent in the spatial sampling by the ADCP can be used to resolve the distribution of energy between dynamic modes. Through a least squares fit of the data to a simple free wave propagation model of the inlet, the authors arrive at objective estimates of the distribution of M2 internal tide energy. The fitting procedure is found to be sensitive to fluctuations in the ...