Misplaced fears? What the evidence reveals of the ecological effects of tidal power generation

The potential energy associated with tides presents a sustainable energy resource that remains largely untapped. Uncertainties on the economic case of tidal range power plants are a known obstacle. Research on tidal range structures suggests energy yield may be maximized through operation strategy optimization, and that impacts can be mitigated through design optimization. While instructive, these perspectives alone are insufficient to support the feasibility of individual projects. We integrate operation optimization and hydrodynamic impact analyses within a cost evaluation framework for tidal range structures focusing on capital costs (CAPEX) and levelized cost of energy (LCOE). Once benchmarked against 11 historic proposal cost projections, we perform a redesign of 18 tidal power plants to deliver a comprehensive comparative basis across a diverse range of sites in the UK. Tidal power plant operation is simulated in regional shallow-water equation models, acknowledging tide variability. The cost evaluation framework demonstrates the impact of geospatial variations on key cost components. The redesign process indicates transformative implications in that equivalent and lower LCOE values can be achieved for designs at a substantially lower CAPEX. Given how the latter hinder development, we show how tidal range schemes could be far more economically feasible than commonly perceived.

Tidal energy is one of the most predictable forms of renewable energy. Although there has been much commercial and R&D progress in tidal stream energy, tidal range is a more mature technology, with tidal range power plants having a history that extends back over 50 years. With the 2017 publication of the “Hendry Review” that examined the feasibility of tidal lagoon power plants in the UK, it is timely to review tidal range power plants. Here, we explain the main principles of tidal range power plants, and review two main research areas: the present and future tidal range resource, and the optimization of tidal range power plants. We also discuss how variability in the electricity generated from tidal range power plants could be partially offset by the development of multiple power plants (e.g. lagoons) that are complementary in phase, and by the provision of energy storage. Finally, we discuss the implications of the Hendry Review, and what this means for the future of tidal range power plants in the UK and internationally.

La Rance Tidal Range Power Station in France and Jiangxia Tidal Range Power Station in China have been both long-term successful commercialized operations as kind of role models for public at large for more than 40 years. The Sihwa Lake Tidal Range Power Station in South Korea has also developed to be the largest marine renewable power station with its installed capacity 254 MW since 2010. These practical applications prove that the tidal range energy as one kind of marine renewable energy exploitation and utilization technology is becoming more and more mature and it is used more and more widely. However, the assessment of the tidal range energy resources is not well developed nowadays. This paper summarizes the main problems in tidal range power resource assessment, gives a brief introduction to tidal potential energy theory, and then we present an analyzed and estimated method based on the tide numerical modeling. The technical characteristics and applicability of these two approaches are compared with each other. Furthermore, based on the theory of tidal range energy generation combined with flux conservation, this paper proposes a new assessment method that include a series of evaluation parameters and it can be easily operated to calculate the tidal range energy of the sea. Finally, this method is applied on assessment of the tidal range power energy of the Jiantiao Harbor in Zhejiang Province, China for demonstration and examination.

Tidal stream energy is a reliable and predictable low-carbon energy source. Over the next few years the first arrays of multiple tidal stream turbines will be deployed mostly in UK, French and Canadian waters. The potential environmental effects should first be examined, in order to scale and site them appropriately. Large theoretical arrays of tidal stream turbines were designed for Scottish Waters (UK), to quantify the available power and the ocean response to its extraction. A comprehensive assessment of the tidal energy resource realistically available for electricity generation and the study of the potential environmental impacts associated with its extraction in Scottish Waters, can then lead the way to further development in different countries with potential tidal stream energy sources. In order to examine both local ( 100 km) spatial scales, the Scottish Shelf Model, an unstructured grid three-dimensional FVCOM (Finite Volume Community Ocean Model) implementation, is a useful tool, since it covers the entire NW European Shelf, but with a high resolution where the tidal stream energy is extracted. The arrays of tidal stream turbines were implemented in the model using the momentum sink approach, in which a momentum sink term represents the loss of momentum due to tidal energy extraction. A typical annual cycle of the NW European Shelf hydrodynamics was reproduced by the SSM model and compared with the same period perturbed by tidal stream energy extraction. The power extracted by the tidal stream arrays was estimated, taking into account the tidal stream energy extraction feedbacks on the flow and considering the realistic operation of a generic tidal stream turbine, which is limited to operate in a range of flow velocities due to technological constraints. The ocean response to tidal stream power extraction was then analysed at the temporal scale of a spring-neap tidal cycle and, for the first time, on longer term seasonal timescales. It is shown that the very large tidal stream arrays can introduce detectable changes to the tidal elevation, marine currents and ocean stratification patterns. Tidal elevation mainly increases upstream of the tidal farms locations (considering the direction of propagation of the tidal wave), while a decrease in the mean spring tidal range is observed downstream, along the UK East Coast and also in the Irish Sea. Marine currents, both tidal and residual flows, are also affected. They can slow down due to the turbines' action or speed up due to flow diversion and blockage processes, on both a local and regional scale. The strongest signal in tidal velocities is an overall reduction, which can in turn decrease the energy of tidal mixing and perturb the seasonal stratification on the NW European Shelf. Although the strength of summer stratification has been found to slightly increase, the extent of the stratified region does not greatly change, thus suggesting the enhanced biological and pelagic biodiversity hotspots, e.g. tidal mixing front locations, are not displaced. Such large-scale tidal stream energy extraction is unlikely to occur in the near future, since very large numbers of devices are required, but such potential changes should be considered when planning future tidal energy exploitation. It is likely that large scale developments around the NW European shelf will interact and could, for example, intensify or weaken the changes predicted here, or even be used as mitigation measures (e.g. coastal defence) for other changes, e.g. effects of climate change.

Oceans have significant renewable energy options to provide environmental friendly and clean energy. Technology for ocean energy systems and the feasibility for extraction of the same is an important area on which research is being focused worldwide. This article covers a detailed review of available tidal energy conversion technologies and case studies, with specific focus on tidal power potential in India. The proven option for tidal energy conversion is barraging. Recently, open-type turbine (usually known as tidal stream turbines) has been studied by several researchers and pilot demonstrations have been made. While conventional turbines of 10–20 MW rating are used in barrages, the application of tidal stream turbines of 0.5–2.0 MW has been demonstrated in water depths between 40 and 60 m. A new scale is proposed for categorizing the tidal energy potential in terms of tidal velocity and tidal range which could be used to categorize the potential sites and their ranking. A new systematic approach proposed for the assessment of tidal energy conversion potential can facilitate the suitability of either tidal stream energy or tidal barrage for a location. Within this, one could also decide the site could be developed as a major project or minor project. Therefore, the present work will be useful for engineers and decision makers in technology selection investment potential identification.

With the global trend to exploit more renewable energy sources, tidal range energy has been gaining more attention recently. This power generation technology is expected to reduce the share of fossil fuels and provide flexibility to the power system. With a pioneering tidal range generation project just granted in Wales and more proposals planned in Great Britain, it is important to study how the incorporation of multiple tidal range power stations will affect power system operation. In this paper, the role of tidal range energy generation in the future Great Britain power system is investigated based on a day-ahead scheduling model of power system incorporating multiple tidal range power stations. In the proposed model, tidal range power stations situated at different sites operate flexibly and in coordination, supporting the power system to reach the minimum operating cost. A case study based on the Great Britain electricity transmission system in 2030 with one tidal barrage and one tidal lagoon was investigated. The results showed that the coordination of flexible tidal range power stations can reduce the power system's operating cost. Furthermore, the energy-storage feature of tidal range power stations can act as a stable source of flexibility in the power system.

Nowadays tidal current energy is considered to be one of the most promising alternative green energy resources and tidal current turbines are used for power generation. Prediction of the open water performance around tidal turbines is important for the reason that it can give some advice on installation and array of tidal current turbines. This paper presents numerical computations of tidal current turbines by using a numerical model which is constructed to simulate an isolated turbine. This paper aims at studying the installation of marine current turbine of which the hydro-environmental impacts influence by means of numerical simulation. Such impacts include free-stream velocity magnitude, seabed and inflow direction of velocity. The results of the open water performance prediction show that the power output and efficiency of marine current turbine varies from different marine environments. The velocity distribution should be clearly and the suitable unit installation depth and direction be clearly chosen, which can ensure the most effective strategy for energy capture before installing the marine current turbine. The findings of this paper are expected to be beneficial in developing tidal current turbines and array in the future.

The power consumption is increasing with modernization of infrastructure and with the depleting fossil fuels. The need to look for alternate sources of energy generation has already reached a peak. The production of power from renewable energy sources is considered to be on a large scale in the near future because of the abundant sources across the country. One of the most reliable sources is the tidal energy as it can be extracted both by kinetic and potential means at the tidal inlets. The process of extracting tidal potential energy by storing the water during the high tide and release during low water is a well-established method. However, there are many parameters that are to be considered for the potential energy extraction. Two such important parameters, i.e. tidal range and basin area are considered in this study. The interrelationship between these two parameters and its overall influence on potential tidal energy estimation is studied. Along the four coastal states, excluding the Gulfs, around 250 tidal inlets have been identified (Vikas, M.Tech. thesis, 2015 [8]). Considering the standards of existing tidal power plants, tidal energy sites for energy extraction are estimated and will be presented in this paper.

Sea level rise (SLR) due to climate change is expected to alter tidal processes and energy transport, disproportionately affecting coastal communities. Utilizing a nested hydrodynamics model, we provided an integrated investigation of tidal responses to SLR in the Hangzhou Bay (HZB). The scenarios of SLR in the next hundred years count for both non-uniform trends based on historical altimetry data and uniform trends from the latest IPCC projections. In a comparison of model results under different SLR scenarios, we found that the tidal range is amplified by SLR in HZB with stronger amplification at the shallow southern coast. Tidal range change generally increases with the SLR scale; however, neglecting the heterogeneities in the spatial distribution of SLR tends to overestimate the SLR effects. The harmonic analysis illustrates that SLR exaggerates the dominated semidiurnal tides (M2 and S2) but dampens their overtides and compound tides (M4, M6, and MS4), of which M2 amplitude amplification explains 71.2–90.0% of tidal range change. SLR tends to promote tidal energy entering HZB through the Zhoushan Archipelago (ZA) compared to the prototype, while dampened sea-bed roughness and reduced tidal velocity come with a less dissipative environment in HZB, resulting in 6–18% more tidal energy exported upstream. Numerical experiments indicate ZA has significant effects on tidal responses and energy flux generation, therefore, its quantitative influences and physical mechanism are also discussed in this paper.

Tidal range power is gaining recognition as a globally important power source, replacing unsustainable fossil fuels and helping mitigate the climate change emergency. Great Britain is ideally situated to exploit tidal power but currently has no operational schemes. Schemes are large and expensive to construct, assessment of their costs is usually examined under conditions of commercial confidentiality. A national strategy for delivery needs a more open system that allows cost estimates to be compared between schemes; a model that evaluates the capital cost of major components has been developed. In 1983, Massachusetts Institute of Technology published a simple additive model of the costs of tidal range schemes on the east coast of the United States. Their model has been updated and benchmarked against recent schemes with published costs; the Sihwa Lake Tidal Power Station (South Korea, completed in 2011) was used along with the published costs for the Swansea Bay Tidal Lagoon proposal in South Wales to benchmark the model. There are developments in civil and mechanical engineering that may influence both the costs and speed of deployment. These are discussed along with methods for their inclusion into the model.

Tidal range energy is one of the most predictable and reliable sources of renewable energy. This study’s main aim is to determine potential sites for tidal range power in East Malaysia, by analyzing tidal range distributions and resources and the feasibility of constructing barrages. Investigation was conducted in 34 sites, estimating their potential energy outputs and studying their areas for constructing barrages. Only 18 sites were marked as appropriate for constructing a tidal range energy extraction barrage. The highest potential power was found in Tanjung Manis, and its maximum capacity was calculated as 50.7kW. The second highest potential of tidal power extraction was found in Kuching Barrage at Pending, where an energy harvester could produce electric power up to 33.1kW.

On the potential of linked-basin tidal power plants: An operational and coastal modelling assessment

An energy transition from fossil fuel energy to renewable energy is needed to alleviate global climate change and achieve the Net Zero emission target. While focus has been put on wind and solar energies, they are intermittent and non-dispatchable. Consequently, there will be a significant need for filling the gap between renewable energy supply and energy demand. Tidal energy is potentially capable of contributing to balancing this gap because of its predictability and dispatchability. Tidal range schemes (TRSs) utilise the tidal range to create artificial head differences across the structures. The head differences then drive the turbines to generate electricity. TRSs can also be used as energy storage by controlling the turbine operation and even pumping water into or out of the impoundment. The UK has vast tidal energy resources which are mainly unutilized. While several TRSs have been proposed, there are currently no TRSs developed in the country because of their large initial investment cost and significant impacts on their adjacent coastal areas. Approaches to determine the optimal design and operation of TRSs are needed to improve their cost-effectiveness.            This research studies the optimal number of turbines for TRSs. There have been discrepancies concerning whether an optimal number of turbines exists for any given TRS by merely optimising its annual energy production (AEP).  Several published works (Aggidis and Feather, 2012; Petley and Aggidis, 2016; Vandercruyssen et al., 2022) showed that the AEP increases as more turbines are used until the turbines fully utilise the available tidal energy. Once the tidal energy is fully utilised, adding more turbines does not increase or decrease the AEP. However, other published works (Xue et al., 2021; Hanousek et al., 2023) showed that there is an optimal number of turbines for a given TRS that produces the maximum AEP and using turbines more than the optimal number reduces AEP. This research reconciles the two aforementioned statements by optimising the AEP of a proposed TRS at an unused dock with a 0D model with and without constraining the maximum starting head to 7.5 m, which is lower than the tidal range at the TRS site. Such a constraint would be necessary if the TRS is used as a flood protection measure as well as an energy source. Results showed that AEP increased with an increase in the number of turbines until the entire tidal range was utilised if the constraint was not applied. With the starting head constraint applied, there was an optimal number of turbines beyond which the AEP decreased. The absence of the optimal number of turbines in the unconstrained condition demonstrates the importance of cost models in selecting the optimal number of turbines. Reference: (i) Aggidis and Feather (2012). 10.1016/j.renene.2011.11.045; (ii) Hanousek et al. (2023). 10.1016/j.renene.2023.119149; (iii) Petley and Aggidis (2016).  10.1016/j.oceaneng.2015.11.022; (iv) Vandercruyssen et al. (2022). 10.1016/j.heliyon.2022.e11381; (v) Xue et al. (2021). 10.1016/j.apenergy.2021.116506Figure 1. The annual energy production for Barry Dock Lagoon with an increasing number of turbines with and without the maximum starting head constraint (≤ 7.5m).

Park, Y.H., 2018. The Application of Dynamic Tidal Power in Korea In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1306–1310. Coconut Creek (Florida), ISSN 0749-0208.Tidal power is attractive as a predictable renewable energy, but it requires a high tidal range. The west coast of Korea is a place where the extreme tidal range is observed, so various studies have been conducted. The largest tidal power, Sihwa Tidal Power Station was successfully built and operated there. However, subsequent projects have been postponed or cancelled due to environmental issues. Dynamic Tidal power (DTP) is an alternative way to a conventional tidal barrage system. Because DTP has to be a huge structure to produce diffraction of tides, it was tested by a numerical model. The 2D numerical model ADCIRC was used in the simulation. DTP was simulated in the largest tidal range of the Korean coast and it was examined in various ways. DTP generates power by the phase difference of tide and it is available even in a small tidal range. The tidal difference between the front and back of DTP becomes maximized on 180 degrees out of phase theoretically. Though the phase difference also increased with the length of DTP structure, it could not reach 180 degrees out of phase even at the DTP length of 50 km. Because the length of DTP structure should be longer than tens of kilometers considering the length of tide, it may cause economic and environmental issues. The phase difference was varied along DTP and it was increasing as the location of measurement moved closer to the coast. When the required length of DTP is optimized, it would be more practical. The study focused on the reduction of the DTP length and some shapes were suggested finally.

Chemical selection by the Interagency Testing Committee: use of computerized substructure searching to identify chemical groups for health effects, chemical fate and ecological effects testing