Tidal Energy Resource Research Articles

Research on Analysis Method of Tidal Current Energy Resource Characteristics

Abstract In the demonstration and validation of tidal energy converters, analyzing the characteristics of tidal current energy resource in the demonstration sea area of tidal energy converters is a key step to evaluate the economic performance of the tested tidal energy converter. Based on analyzing the research status and the evaluation demands of economic performance indicators of tidal energy converters at home and abroad, the analysis method of tidal current energy resource assessment and characterization was studied, a method for calculating the cumulative frequency of tidal current velocity was proposed, and it was applied in the processing and analyzing the tidal current field test data. Moreover, using the analysis results of tidal current energy resource characteristics, the annual energy production of the tested tidal energy converter was calculated. The results show that the analysis method studied in this technical note can analyze the tidal current energy resource characteristics comprehensively and objectively, and the proposed calculation method of cumulative frequency can reflect the availability of the tidal energy converter in the demonstration sea area. The research results not only provide a reference for analyzing the tidal current energy resource characteristics in the demonstration sea area of tidal energy converters, but also provide a reference for calculating the annual energy production of tidal energy converters.

Study on Critical Factors Affecting Tidal Current Energy Exploitation in the Guishan Channel Area of Zhoushan

As a new type of clean and renewable energy, tidal current energy has attracted more and more attention from scholars. The Zhoushan Guishan Channel area (GCA) is an important part of the East China Sea port area, with strong currents due to its special terrain. In order to more comprehensively evaluate the characteristics of tidal energy development near the GCA, this paper uses the MIKE21 FM hydrodynamic model to simulate the tidal hydrodynamic process in the Zhoushan sea area and verifies the reliability of the model through the measured data. Based on the results of numerical simulations, the energy flow density, frequency of flow rate occurrence, flow asymmetry, flow rotation, and effective flow time that can be exploited are considered as the key factors affecting the development of tidal current energy. The distribution characteristics of each influencing factor in the region and the different influences on tidal current energy development are analyzed. Numerical simulations show that the average high-tide velocity in the GCA is lower than the ebb-tide velocity, and the duration of the high tide is also shorter than that of the ebb tide, which has a higher flow velocity than the surrounding area. The annual average energy flow density in the GCA is the highest at 4520 W/m2, and the spatial distribution is uneven. The resource level in the central part is much higher than that at both ends of the waterway. Three sections, i.e., A-A′, B-B′, and C-C′, with different key influence factors are selected for specific analysis, and it is concluded that the tidal energy development conditions are relatively superior near the B-B’ section in the middle of the GCA, and the exploitable power calculated using the Flux method is about 24.19 MW. The discussion of the results provides a certain reference for the development of local tidal current energy. These key factors affecting tidal current energy development can also be applied to assess the suitability of tidal current energy resource development in other regions.

Numerical Assessments of Tidal Stream and Wave Energy in Coastal Shelf Seas

Tidal stream and wave energy resources may have the potential to complement the exploitation of wind power currently promoted, in industrial countries, as one of the alternatives to fossil fuel energies [...]

A comparative study of methods for calculating the exploitable amount of tidal energy

As a kind of clean renewable energy, tidal current energy has a great prospect of development and utilization in China's coastal areas, but there is no unified method for evaluating tidal current energy resources. This paper firstly simulates the tidal field in Zhoushan sea based on a numerical model, analyzes the overall characteristics of tidal currents in the sea, selects the Guimen Channel with high energy density, and compares four tidal energy calculation methods, namely the Farm method, the Flux method, the Garrett method and the Lidan method, which are widely used at present, to evaluate the exploitable amount of tidal energy in the region. The results show that the results of Farm, Flux, and Lidan methods are in good agreement, while the conclusions of the Garrett method are more different from these three methods, and the differences may be related to their assumptions. The annual average current velocity in this area can reach 1.97 m/s, and the highest current velocity exceeds 4.5 m/s. The average water depth is 40 m. The exploitable tidal current energy is above 40 MW, which is suitable for large-scale installation and provides some reference for the local tidal current energy development and utilization.

Tidal Range Energy Resource Estimation of Khor Kalmat using Geostatistical Modeling

Electrical power generation by tidal energy provides various advantages. The energy is highly predictable, has less impact on ecological pollution and provides an indefinite amount of renewable energy. The countries like Canada, China, Russia, South Korea and France are extensively utilizing tidal sources of energy for the generation of electrical energy. A suitable site (where less construction is required), adequate tidal range and sufficient bathymetry; are the basic requirements for the installation of a tidal power plant however sometimes there is no tidal data available for suitable sites, like Khor Kalmat tidal lagoon in Pakistan. Therefore, the first time study is conducted to assess the tidal energy resources of the naturally blessed lagoon, Khor Kalmat, which is located in the Baluchistan province of Pakistan, by using geostatistical modeling. A geostatistical model is developed to estimate the tidal energy potential at Khor Kalmat by using observed data of five available locations along with the coastal belt of Pakistan. Models are designed by integrating several layers into ArcGIS. These layers include tidal data, satellite metaphors and other physical and socioeconomic layers. After processing of data, digitized models and layers are generated. Five different models have been compared and the best model is carefully chosen to predict the tidal data of Khor Kalmat after validation of the individual model, During the study, it was observed that low head hydro tidal turbine of Venturi-Enhanced Turbine Technology (VETT) is best suited for harnessing tidal energy due to adequate tidal range. Consequently, by means of a bi-directional VETT device, the output power is assessed to be 269.93 MW.

Effects of Tidal Stream Energy Exploitation on Estuarine Circulation and Its Seasonal Variability

Residual flows are of major importance in coastal areas, driving environmental processes such as sediment transport or nutrient dispersion. Consequently, in those areas where a large tidal stream energy resource is available, prior to the installation of a tidal farm, it is imperative to assess how energy extraction affects the residual flows and, in particular, upwelling events. In this paper, the potential effects of different configurations of tidal stream farms on the residual circulation and its seasonality are analysed by means of a case study: Ria de Ortigueira, the westernmost of the Galician Rias Altas (NW Spain). For this purpose, a 3D numerical model was implemented and validated against field measurements. Next, a total of eight case studies, including the operation of bottom-fixed and floating converters under typical summer and winter scenarios, considering upwelling favourable winds, were studied. Overall, when a tidal farm operates, regardless of its configuration and the forcings considered, the resulting general residual flow pattern does not experience significant modifications. This pattern is characterized by a 2D circulation in the inner ria and a positive estuarine circulation in the middle and outer ria. The largest modifications of the residual flow are apparent in the vicinities of the plant, with maximum values of about 0.05 ms−1. Outside this area, the alteration is lower than 0.01 ms−1 and virtually negligible at some distance from the farm where upwelling events develop.

Drone-based large-scale particle image velocimetry applied to tidal stream energy resource assessment

Resource quantification is vital in developing a tidal stream energy site but challenging in high energy areas. Drone-based large-scale particle image velocimetry (LSPIV) may provide a novel, low cost, low risk approach that improves spatial coverage compared to ADCP methods. For the first time, this study quantifies performance of the technique for tidal stream resource assessment, using three sites. Videos of the sea surface were captured while concurrent validation data were obtained (ADCP and surface drifters). Currents were estimated from the videos using LSPIV software. Variation in accuracy was attributed to wind, site geometry and current velocity. Root mean square errors (RMSEs) against drifters were 0.44 m s−1 for high winds (31 km/h) compared to 0.22 m s−1 for low winds (10 km/h). Better correlation was found for the more constrained site (r2 increased by 4%); differences between flood and ebb indicate the importance of upstream bathymetry in generating trackable surface features. Accuracy is better for higher velocities. A power law current profile approximation enables translation of surface current to currents at depth with satisfactory performance (RMSE = 0.32 m s−1 under low winds). Overall, drone video derived surface velocities are suitably accurate for “first-order” tidal resource assessments under favourable environmental conditions.

Monitoring Tidal Currents and Macroturbulence in a High-Flow Tidal Channel Using a Kilometer-Scale Acoustic Travel-Time Instrument

A challenge in exploiting tidal energy resources is to determine the most suitable sites for development, and as the industry grows, to monitor the progressive impacts of tidal farms on the flow field and sediment transport regimes. A feasibility experiment was carried out with the fluvial acoustic tomography (FAT) system to assess the combined effects of irregular bathymetry, horizontal and vertical sound-speed gradients, and macroturbulence on the quality of FAT-estimated velocities. The experiment involved reciprocal transmissions at 30-s intervals for four days with two 7-kHz broadband transceivers. To determine the origin and potential interpretive value of the frequent multiple arrivals in the unstratified, highly-turbulent flow conditions, we performed a series of simulations with the Bellhop3D model. We demonstrate that the multiple arrivals mainly arise from out-of-plane sound propagation paths resulting from the effects of the local bathymetry. The maximum mean difference between FAT-estimated currents and the coincident moving-vessel acoustic Doppler current profiler (ADCP) transects is found to be less than 10%. Comparisons are also made between velocity spectra during the full flood and the ebb determined using the FAT velocities and the vertically-averaged velocities from a bottom-mounted ADCP deployed in a later experiment. The spectra exhibit similar shapes in the frequency and wave number overlap regions, indicating that FAT is able to detect macroturbulence. Good agreement is also obtained between the sound-speed estimates based on the travel time and those from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> temperature and salinity data. Overall, the results demonstrate the potential of shallow acoustic tomography for monitoring environmental conditions in high-flow tidal channels.

Tidal range energy resource assessment and power generation at Hawke’s Bay and Ghizri

Tidal range energy resource assessment and power generation at Hawke’s Bay and Ghizri

Sedimentological data-driven bottom friction parameter estimation in modelling Bristol Channel tidal dynamics

Accurately representing the bottom friction effect is a significant challenge in numerical tidal models. Bottom friction effects are commonly defined via parameter estimation techniques. However, the bottom friction coefficient (BFC) can be related to the roughness of the sea bed. Therefore, sedimentological data can be beneficial in estimating BFCs. Taking the Bristol Channel and Severn Estuary as a case study, we perform a number of BFC parameter estimation experiments, utilising sedimentological data in a variety of ways. Model performance is explored through the results of each parameter estimation experiment, including applications to tidal range and tidal stream resource assessment. We find that theoretically derived sediment-based BFCs are in most cases detrimental to model performance. However, good performance is obtained by retaining the spatial information provided by the sedimentological data in the formulation of the parameter estimation experiment; the spatially varying BFC can be represented as a piecewise-constant field following the spatial distribution of the observed sediment types. By solving the resulting low-dimensional parameter estimation problem, we obtain good model performance as measured against tide gauge data. This approach appears well suited to modelling tidal range energy resource, which is of particular interest in the case study region. However, the applicability of this approach for tidal stream resource assessment is limited, since modelled tidal currents exhibit a strong localised response to the BFC; the use of piecewise-constant (and therefore discontinuous) BFCs is found to be detrimental to model performance for tidal currents.

On nodal modulations of tidal-stream energy resource in north-western Europe

Estimation of tidal-stream turbine loading and energy yield requires a thorough understanding of the hydrodynamic processes that influence tidal currents over a wide range of timescales. In this study, we focus on the long-term variability of the tidal-stream energy resource associated with the 18.6-year lunar cycle. Three sites in north-western Europe, with strong potential for tidal array development, are considered; the Alderney Race (English Channel), the Fromveur Strait (western Brittany) and the Ramsey Sound (Irish Sea). The investigation relies on harmonic analysis and associated predictions of depth-averaged tidal currents. Results show that the variability in predicted annual power densities is comparable at the three measurement locations. This variability reaches +/- 10% over the 18.6-year lunar cycle, and is mainly associated with M2 nodal modulations which dominate the tidal signal in north-western European shelf seas. Maximum and minimum power density occur in 2015 and 2024, respectively. 2015 is characterized by (i) reduced spring-neap variabilities and diurnal inequalities of tidal currents, and (ii) increased tidal asymmetries (between peak ebb and flood), whereas 2024 shows reverse effects. This cycle also influences the annual maximum/mean current magnitudes. The differences in maximum speeds between 2015 and 2024 are of 0.16–0.17 m/s at the three sites, which represents 4-5% of the peak speeds. The simple approach considered here may be applied in broader locations as a preliminary assessment of the long-term variability of the available tidal stream energy resource. The modulations predicted from harmonic analysis are finally expected to be on the high side of the forecasting range. Indeed, the results of an 18-year numerical simulation performed on the Alderney Race suggested a reduced effect of the 18.6-year lunar cycle on the resource.

Hydrodynamic Model and Tidal Current Energy Potential in Lepar Strait, Indonesia

Previous studies have shown the abundance of tidal energy resources in Indonesia. However, some sites have yet to be considered. The Lepar Strait, for example, is located between Bangka and Lepar Islands. This paper describes a field survey and numerical modelling conducted in the Lepar Strait. The modelling was performed using Delft3D, with the aim of determining potential sites for harvesting tidal current energy and estimate the generated power. In the modelling, the domain decomposition method was employed for model downscaling, allowing grid resolution reaching 130 x 130 m2, which is sufficient to represent the narrow gaps between tiny islands in the area of interest. The National Bathymetric (Batnas) from the Geospatial Information Agency (BIG) and the International Hydrographic Organization (IHO) tide constituents were applied for the bathymetry and tide elevation boundaries. The comparison between the surveyed and modelled data showed a good agreement. The RMSE and r for water level are &gt; 0.95 and &lt; 0.15, and the RMSE for velocity was &lt;0.19. Furthermore, an energetic flow reaching 1.5 m/s was found at the Northern part of Lepar Strait, situated at the narrow gaps. The Gorlov Helical Turbine was selected in this study due to shallow water and low mean velocity. In the 2019 model, the power density and power output at the best potential sites were 2,436.94 kWh/m2 and 1,870.41 kWh, respectively. This number is higher than those previously found in Kelabat Bay. Nonetheless, it is still far below the currently promising project in Larantuka and Lombok Straits. Future research is recommended, to conduct a detailed field measurement campaign and assess the impact of energy extraction in more detail.

Design of Offshore Oil and Gas Platform Based on Tidal Energy Turbine Power Generation

The development of offshore oil and gas energy has become the focus of production breakthrough in the oil and gas industry. Due to the rich oil and gas resources in the offshore coast, aiming at the problem of maximization the commissioning of offshore operations in shallow, we can learn from the conventional jacket platform and make full use of the rich tidal energy resources in the marine resources and their strong regularity and predictability. A set of offshore oil and gas platform based on tidal current turbine power generation is designed. The reasonable reliability of the platform is verified by simulating the load stress under four typical simulated environments with two working conditions under current load, sea breeze load and sea ice load. The results show that under extreme conditions, the UC value of the jacket platform is between 0.34 and 0.43, far less than 1. It has good stability and bearing capacity.

The Parametric Estimation of Tidal Potential Power Density using Modeling Strategies at Hajambro Creek of Indus Delta, Pakistan

There are many accessible resources for electricity generation using renewable energy, like, solar, wind, tidal and wave etc. The output of all these resources depend on weather conditions, force of gravity or rotation of the Earth, but tidal energy has a major advantage over many other forms of renewable generation as it is predictable over a long period of time. Pakistan has about 1000 km long coastline with complex network of creeks in the Indus delta region which include 17 major creeks and further divide into a number of estuaries with considerable tidal ranges and tidal current. This research study is carried out at one of these major creeks namely Hajambro (Hajambro river) and extends from Hajambro 24ᵒ 08’N 67ᵒ 22’E (sea mouth) to Keti Bander 24ᵒ 09’N 67ᵒ 27’E (mouth of river Indus). Study area is targeted within creek region where there is a large shortfall of electricity observed and this situation has threaten the community socioeconomically. In this research study, available tidal energy resources of Hajambro creek are assessed, tidal power density models and bathymetry model are developed in Arc-GIS (geographical informationsystem) environment, for the first time. A comprehensive tidal turbine technology review is conducted and based on up-to-date tidal turbine technology review and results achieved from assessment of tidal energy resources, deployment of a turbine at Hajambro creek is proposed. With effective area of 9.46 km2 mean spring estimated power (seasonally) is observed as 14 MW in winter, 12.9 MW in Pre-Monsoon, 13.6 MW in Monsoon and 13.1 MW in Post-Monsoon.

Dispatchability, Energy Security, and Reduced Capital Cost in Tidal-Wind and Tidal-Solar Energy Farms

The global tidal energy resource for electricity generation is small, and converting tidal kinetic energy to electricity is expensive compared to solar-photovoltaic or land-based wind turbine generators. However, as the renewable energy content in electricity supplies grows, the need to stabilise these supplies increases. This paper describes tidal energy’s potential to reduce intermittency and variability in electricity supplied from solar and wind power farms while lowering the capital expenditure needed to improve dispatchability. The paper provides a model and hypothetical case studies to demonstrate how sharing energy storage between tidal stream power generators and wind or solar power generators can mitigate the level, frequency, and duration of power loss from wind or solar PV farms. The improvements in dispatchability use tidal energy’s innate regularity and take account of tidal asymmetry and extended duration low-velocity neap tides. The case studies are based on a national assessment of Australian tidal energy resources carried out from 2018 to 2021.

Tidal stream energy potential in the Shannon Estuary

The tidal and river in-stream energy resource in the Shannon Estuary (W Ireland) is investigated using of high-resolution numerical modelling and spatial analysis. Although freshwater discharges are large, their influence on the available resource is found to be all but negligible, the tide being the main driver of estuarine circulation. The Tidal Stream Exploitability (TSE) index is adapted to the analysis of estuaries with non-depth-limited areas (TSEndl), such as the Shannon Estuary, and then used to select the hotspots with potential for a tidal stream farm. For this purpose, a new depth penalty-limiting function is defined to avoid overestimating the available energy potential in areas with depths greater than those required for tidal energy converter operation. Seven hotspots are identified based on the revised index. The approach followed in this study illustrates the applicability of high-resolution numerical modelling and spatial analysis for identifying the most appropriate areas for tidal stream energy conversion. Finally, the potential of tidal stream energy to contribute to the much-needed decarbonisation of the energy mix in Ireland is emphasized.

A review of tidal energy—Resource, feedbacks, and environmental interactions

The ocean contains a variety of renewable energy resources, little of which has been exploited. Here, we review both tidal range and tidal stream energy, with a focus on the resource, feedbacks, and environmental interactions. The review covers a wide range of timescales of relevance to tidal energy, from fortnightly (spring-neap) and semi-diurnal variability, down to array, and device-scale turbulence. When simulating the regional tidal energy resource, and to assess environmental impacts, it is necessary to account for feedbacks between the tidal array and the resource itself. We critically review various methods for simulating energy extraction, from insights gained through theoretical studies of “tidal fences” in idealized channels, to realistic three-dimensional model studies with complex geometry and arrays of turbines represented by momentum sinks and additional turbulence due to the presence of rotors and support structures. We discuss how variability can be reduced by developing multiple (aggregated) sites with a consideration of the enhanced phase diversity offered by exploiting less energetic tidal currents. This leads to future research questions that have not yet been explored in depth at first-generation tidal sites in relatively sheltered channels (e.g., the interaction of waves with currents). Such enhanced understanding of real sea conditions, including the effects of wind and waves, leads to our other identified primary future research direction—reduced uncertainties in turbulence predictions, including the development of realistic models that simulate the interaction between ambient turbulence and the turbulence resulting from multiple wakes, and changes to system-wide hydrodynamics, water quality, and sedimentation.

A review of the UK and British Channel Islands practical tidal stream energy resource.

This review provides a critical, multi-faceted assessment of the practical contribution tidal stream energy can make to the UK and British Channel Islands future energy mix. Evidence is presented that broadly supports the latest national-scale practical resource estimate, of 34 TWh/year, equivalent to 11% of the UK’s current annual electricity demand. The size of the practical resource depends in part on the economic competitiveness of projects. In the UK, 124 MW of prospective tidal stream capacity is currently eligible to bid for subsidy support (MeyGen 1C, 80 MW; PTEC, 30 MW; and Morlais, 14 MW). It is estimated that the installation of this 124 MW would serve to drive down the levelized cost of energy (LCoE), through learning, from its current level of around to below , based on a mid-range technology learning rate of 17%. Doing so would make tidal stream cost competitive with technologies such as combined cycle gas turbines, biomass and anaerobic digestion. Installing this 124 MW by 2031 would put tidal stream on a trajectory to install the estimated 11.5 GW needed to generate 34 TWh/year by 2050. The cyclic, predictable nature of tidal stream power shows potential to provide additional, whole-system cost benefits. These include reductions in balancing expenditure that are not considered in conventional LCoE estimates. The practical resource is also dependent on environmental constraints. To date, no collisions between animals and turbines have been detected, and only small changes in habitat have been measured. The impacts of large arrays on stratification and predator–prey interaction are projected to be an order of magnitude less than those from climate change, highlighting opportunities for risk retirement. Ongoing field measurements will be important as arrays scale up, given the uncertainty in some environmental and ecological impact models. Based on the findings presented in this review, we recommend that an updated national-scale practical resource study is undertaken that implements high-fidelity, site-specific modelling, with improved model validation from the wide range of field measurements that are now available from the major sites. Quantifying the sensitivity of the practical resource to constraints will be important to establish opportunities for constraint retirement. Quantification of whole-system benefits is necessary to fully understand the value of tidal stream in the energy system.

Sea level rise changes estuarine tidal stream energy

Worldwide, many estuaries have the potential to harness tidal stream energy via the conversion of current velocities into a consumable energy source. However, the effects of future sea level rise on the tidal stream energy resource within different estuary types are largely unknown. To address this knowledge gap, 978 idealised hydrodynamic simulations were carried out to first identify estuary types and the location of hotspots within them that are promising for tidal energy exploitation in present-day conditions, and then provide insights into the altered tidal stream energy of different estuary types under various future sea level rise and river inflow scenarios. The results indicate that, under sea level rise, the tidal stream energy of prismatic estuaries reduces more than that of converging estuaries. This implies that estuaries that are currently worth exploiting for tidal power may cease to be in the future due to accelerating sea level rise. Further, as sea level rise may bring about geomorphic adjustments, the spatial energy patterns within an estuary may shift and optimal energy sites may be eliminated or displaced. These climate change effects pose a serious challenge for the management of tidal energy generation in future. In this context, the findings of this study are of practical significance for decision-makers in designing long-term strategies for the development of tidal energy installations in estuaries under rising mean sea levels.

Medium-term variability of the UK's combined tidal energy resource for a net-zero carbon grid

The small area of the United Kingdom relative to weather systems makes renewable energy sources variable on short time scales. Short term variability is therefore a growing concern with increasing amounts of renewable energy integration. In this work, we address how tidal energy can contribute to reducing medium-term variability in the future UK energy mix. Two tidal integration scenarios are defined for 2050: for each scenario, a 5-min interval generation profile is calculated using an oceanographic model of UK tides, and the medium-term variability is assessed. Here we show that tidal power shows a lower level of variability compared to other resources. During spring tides, a national network of tidal power stations can produce continuous, although variable, electricity. It is then shown that tidal energy and storage can provide year-round continuous and constant power output, i.e. baseload generation. Therefore, we conclude that tidal energy can provide positive contributions and complement other renewable energy sources.