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Water-solid triboelectric nanogenerators (TENGs), as new energy collection devices, have attracted increasing attention in ocean energy harvesting and self-powered sensing. Polyacrylic acid (PAA) coating, usually used on the surface of marine equipment, has the property of anti-aging and anti-wear but limits triboelectrical output when used with TENGs. In this paper, polyacrylic acid coating was modified with fluorinated polyacrylate resin (F-PAA) to increase its triboelectrical output, by 6 times, and also to increase its anti-corrosion property. In addition, the corrosion resistance property can be further enhanced by cathodic protection using the electrical output generated by the water-flow triboelectrical energy transfer process. Given their easy fabrication, water-flow energy harvesting, and corrosion resistance, PAA/F-PAA coating-based TENGs have promising applications in river and ocean energy collection and corrosion protection.

Ocean can provide an inexhaustible amount of energy. Many marine energy converters have been developed but most of them have not surpassed the experimental phase due to the high costs in installation, operation, and maintenance. Since 2002 Uppsala University has developed and deployed several units of wave energy converters of various designs. The Uppsala University wave energy converter concept consists of a linear generator directly connected to a point absorber buoy that is mounted on a concrete gravity foundation. Uppsala University deployments have been carried out using different deployment vessels and methods. Three main methods were utilized for these deployments that are discussed in terms of cost, manpower, and time efficiency. Depending on the desired outcome—multiple- or single-device deployment, low budget, etc.—one of the proposed methods can be used for the optimal outcome.

Object and purpose of research. This paper discusses uninterruptable power supplies (UPS) developed by TSNII SET for marine power systems. The purpose of the study is to compare the results of UPS developments and outline the directions of their further improvement. Materials and methods. The study included analysis and computer-based simulation of electromagnetic and heat processes in the UPS units developed by TSNII SET for marine power systems. Main results. Comparative assessment of performance parameters for developed UPS units. Development of calculation procedures and computer-based models for UPS. Demonstration of the ways for further improvement of UPS technology for marine power systems. Conclusion. This study identifies possible ways of further improvement in UPS technology, as well as discusses how to speed up the introduction of UPS units to marine power systems.

Object and purpose of research. This paper studies current status of Russian marine engine building. The purpose is to estimate the capabilities of Russian mechanical engineering to provide engines for Russian naval and commercial ships, as well as for various floating platforms for Ocean developments. Materials and methods. This paper analyses the state of the art in Russian power engineering for the main types of marine engines (main and auxiliary): diesels, gas turbines, boiler-turbine plants, nuclear reactors, fuel cells and air-independent propulsion plants. Main results. The paper estimates the capability of Russian mechanical engineering industry to ensure advanced developments of naval and commercial ships in the environment of current sanctions against cooperation with leading foreign companies. Conclusion. The paper highlights the efforts made by Russia to restore its capability to produce modern marine diesels and gas turbines, as well as fuel-cell based air-independent propulsion plants. Russia maintains its leadership in nuclear power for icebreakers and other marine objects.

The offshore wind is the sector of marine renewable energy with the highest commercial development at present. The margin to optimise offshore wind foundations is considerable, thus attracting both the scientific and the industrial community. Due to the complexity of the marine environment, the foundation of an offshore wind turbine represents a considerable portion of the overall investment. An important part of the foundation’s costs relates to the scour protections, which prevent scour effects that can lead the structure to reach the ultimate and service limit states. Presently, the advances in scour protections design and its optimisation for marine environments face many challenges, and the latest findings are often bounded by stakeholder’s strict confidential policies. Therefore, this paper provides a broad overview of the latest improvements acquired on this topic, which would otherwise be difficult to obtain by the scientific and general professional community. In addition, this paper summarises the key challenges and recent advances related to offshore wind turbine scour protections. Knowledge gaps, recent findings and prospective research goals are critically analysed, including the study of potential synergies with other marine renewable energy technologies, as wave and tidal energy. This research shows that scour protections are a field of study quite challenging and still with numerous questions to be answered. Thus, optimisation of scour protections in the marine environment represents a meaningful opportunity to further increase the competitiveness of marine renewable energies.

Since ancient times, to provide vessel traffic men persistently searched the way to replace the unpredictable in strength and direction of wind.

The movement of water in the oceans generates a vast store of kinetic energy, which has led to the development of a wide variety of offshore energy harvesters all over the world. In our energy harvester, we used ionic polymer-metal composites (IPMCs) to convert the ocean energy into electricity. This paper presents a simulated model of an IPMC-based electrochemical kinetic energy harvesting system installed in the ocean and produced using the computational fluid dynamics (CFD) method. The simulation processes focused on the movement and structural stability of the system design in the ocean for the protection of the IPMC module against possible damage, which would directly affect the power output. Furthermore, the experimental tests under real marine conditions were also studied to analyze the electrical harvesting performance of the IPMC system. These results showed that the use of IPMC materials has many advantages as they are soft and durable, as a result, they can respond faster to wave parameters such as frequency, amplitude, and wavelength.

In the scientific study, the offshore oil and gas production platforms were considered after the exhaustion of hydrocarbon reserves. An alternative to dismantling is the possibility of refitting and retrofitting prospective structures for the function of energy production. The general problem of determining the climatic offshore oil and gas fields is also considered. For the development of maritime infrastructure, a design development was added to complement the functionality of offshore platforms for energy production. The chosen methods for developing.The subject of the study: the subject of the study are offshore oil and gas production platforms, marine power plants for power generation and bioenergy objects.Objectives: the purpose of the study is to identify options for the use of offshore hydraulic installations in marine offshore platforms for generating energy and locating bioenergetic facilities.Materials and methods: in the course of the work, various options for the use of offshore platforms in the field of renewable energy sources are considered, without the need for disposal of objects.Results: as a result of the work, the project of the experimental energy complex of bioreactor and biocultivator EECBB and RES.Conclusions: the energy sector has the opportunity to be environmentally friendly and rely on the principles of sustainable development.

In this paper, a wave energy converter (WEC) is designed for a wave climate condition and its interior permanent magnet (IPM) generator is dimensioned for minimum life cycle cost (LCC). The single point absorber movement is simulated and the harnessed annual energy is determined to be 325 MWh. Possible IPM generator sizes are investigated using finite element calculations. Tradeoffs between the generator cost and the annual energy efficiency is performed in order to find the best economical solution. For the economical evaluation, the net present value method is utilized in order to obtain the LCC of the electric generation system of the WEC. Increasing the axial length of the machine 1.6 times results in the lowest LCC, with a $2.5\%$ efficiency increase, which means an increment of approximately 1000 € in the investment cost. Despite the higher investment cost, the LCC of the WEC generator decreases from 8070 € to 6450 €, due to the lower losses.

Tidal range power plants represent an attractive approach for the large-scale generation of electricity from the marine environment. Even though the tides and by extension the available energy resource are predictable, they are also variable in time. This variability poses a challenge regarding the optimal transient control of power plants. Here we consider simulation methods which include the main modes of operation of tidal power plants, along with algorithms to regulate the timing of these.This paper proposes a framework where simplified power plant operation models are coupled with gradient-based optimisation techniques to determine the optimal control strategy over multiple tidal cycles. The optimisation results in turn inform coastal ocean simulations that include tidal power plants to gauge whether the benefits of an adaptive operation are preserved once their hydrodynamic impacts are also taken into consideration. The combined operation of two prospective tidal lagoon projects within the Bristol Channel and the Severn Estuary is used as an example to demonstrate the potential benefits of an energy maximisation optimisation approach.For the case studies considered, the inclusion of pumping and an adaptive operation is shown to deliver an overall increase in energy output of 20-40 % compared to a conventional two-way uniform operation. The findings also demonstrate that smaller schemes stand to gain more from operational optimisation compared to designs of a larger scale.

Ocean waves are a promising source of renewable energy. In this paper, we briefly introduce the characteristics of ocean wave energy and summarize the principles of harvesting ocean energy by wave ...

Marine energy harvesting and offshore structures for marine renewable energy exploitation rise as a trending topic of both research and industrial activities. However, many challenges are yet to be tackled and solved when it comes to place such equipment and structures at sea. Over the past years the Marine Energy Group at FEUP has been tackling some of those challenges aiming at a better competitiveness of marine renewable energy in comparison to traditional oil & gas sector, which is more mature and developed at this point in time. Additionally, recent findings of this research team have also been applicable to several offshore oil & gas infrastructures. In this work, the latest contributions, projects and research outcomes developed by the team are reviewed and presented towards the enhancement of future research lines and industrial opportunities.

The marine energy industry is in its early stages but has a large potential for growth. One of the most significant challenges is the reduction of operation and maintenance costs. Magnetic gears (MGs) offer the potential for long periods between maintenance intervals due to their frictionless torque transmission which could reduce these costs. This study presents a summary of the state of the art in MG technology and then investigates its potential for marine energy applications. A brief overview is given of the state of the marine energy industry and the environment in which marine energy converters (MECs) operate. A short history of MG development over the past century is then presented followed by a discussion of the leading MG technologies and their relative advantages. In order to demonstrate the potential of MGs in marine applications, the current technologies, i.e. mechanically geared and direct drive machines, are examined in terms of sizing, reliability and economic value using previous studies on a similar technology, namely wind. MGs are applied to four types of MECs to demonstrate how the technology can be incorporated. The potential to deploy at scale and potential obstacles to this are then discussed.

Quantifying and mitigating environmental risks presented by marine energy conversion systems requires a variety of sensors (active acoustic, passive acoustic, and optical). The operation of these sensors must satisfy three directives to be effective: (1) do not alter the environment through operation of sensors; (2) capture rare events; and (3) do not accrue unmanageable volumes of low-value data. This requires integrating sensors into a single package, rather than operating them independently. The Adaptable Monitoring Package is an integrated instrumentation package that combines a multibeam sonar, acoustic camera, current profiler, optical cameras, and an array of hydrophones. The capabilities and limitations of the AMP sensors were benchmarked using cooperative targets, and real-time target tracking and detection was used to detect opportunistic targets (e.g., diving birds, seals). During an initial deployment, automatic detection of opportunistic targets achieved a 58% true positive rate and a 99% true negative rate (100% corresponding to an ideal system in both cases). In post-processing, target tracking data were used to evaluate automatic target classification capabilities using a k-nearest neighbor algorithm. Results suggest that real-time target classification should be possible and enable integrated instrumentation systems to meet the monitoring needs of marine energy deployments.

Reducing local and global emissions is one of the drivers behind the promotion of renewable energy technologies (RETs). Some RET projects (e.g. solar, marine power, and some biomass and wind) usually require supplemental income from carbon credits in order to make them economically viable. This paper presents the mathematical development of nodal marginal CO2 emission metrics for hydrothermal systems. These metrics are obtained from optimal power flow and hydrothermal dispatch models considering hydro uncertainty. The proposed model allows a more accurate assessment of the emission reduction effect of RET projects and the provision of efficient carbon signals to the system. Modeling of hydro reservoirs and intertemporal constraints also allows incorporating the emission mitigation potential of water storage. The concepts of marginal CO2 emissions for hydrothermal systems are first exemplified using a small test system, and then simulations on a real hydrothermal system illustrate how these metrics can inform investment and operational decisions. Theoretical and simulation results show that transmission and hydro storage constraints neglect may provide wrong signals for RET investors, missing the incentives to install in areas where the potential for emissions reduction is higher (where renewable energy displaces a larger amount of coal or diesel). Policy makers can use the proposed model to assess the cost-effectiveness of emission reduction policies.

Fishes are easy to be gathered around fish aggregating devices (FADs), which is an environment-friendly artificial ocean infrastructure. This study has proposed and developed a new type of FAD with a current turbine to generate an independent electric power for navigational and environmental sensors, especially at archipelago areas with fishery and aquaculture. A mooring type of FAD with a horizontal axis turbine (HAT) or a vertical axis turbine (VAT) was designed to avoid an unexpected collision with fishes. The characteristics of fluid force on FAD were investigated by numerical and theoretical works assuming steady state in time and the motions of FAD were also examined by experimental works. The proposed FAD can achieve 15% reduction for averaged snap load and 30% for maximum one. The amplitudes of surge, sway and heave motions excited by vortex-induced vibration (VIV) in wave-current conditions can be reduced up to 50%. The current flow around FAD and designed turbine was computed by CFD to estimate hydrodynamic force and vortex field. The numerical results in the fluid force are in overall agreement with the experimental and theoretical ones. Moreover, generated electric power by the optimized turbine was estimated at a typical archipelago area in Indonesia. The first model of FAD without turbine was built up and has been installed in real ocean field.

The potential of generating electricity from marine tidal currents is enormous. Tidal energy is a renewable source that has an additional value in a future energy market with regard to other renewable energy sources thanks to its high predictability. Moreover, tidal energy technologies are characterized by CO 2 emission-free power, thus enabling energy security and contributing to economic growth and job creation in coastal and remote areas. Substantial progress is currently being made by the European Union as regards the reduction of greenhouse gas emissions, renewable energy and energy efficiency, in order to fulfil the target of an installed capacity of 3.6 GW of ocean energy by 2020, and to achieve a future installed capacity of 188 GW of ocean energy in 2050. This paper presents a comprehensive review of the current status of tidal energy conversion technologies and describes the costs incurred in the development of tidal energy projects so as to study their economic viability. The study also identifies the principal current risks and the role of each of the stakeholders involved in the successful development of tidal energy projects. Finally, future challenges in tidal technologies that will influence the increase in their current potential are briefly presented along with the current developments of our research group in the field of tidal energy converters design.

The effect of the idealized design parameters, the natural period of oscillation and damping, on the performance of a generic Wave Energy Converter (WEC) model is investigated. Other studies have been conducted on specific WEC technologies, overlooking the impact of these design parameters. Australia has been used as a case study. The consequences of the damping parameter are highlighted. A broad range of ocean wave climates are investigated across different seasons to determine the idealized values of the parameters appropriate for a location, to assist planning for extensive WEC deployments. Swell and wind-sea wave systems were studied; the response of generic model was used to determine the theoretical power generated. It was found that WECs should be selected for a location based on their damping as well as their natural period of oscillation so that the ocean wave resource is optimally utilized.

The existence of sunlight, air and other resources on earth must be used in an appropriate way for human welfare while still protecting the environment and its living creatures. The exploitation of sunlight and air as a substantial Renewable Energy (RE) source is an important research and development domain over past few years. The present and future overtaking in RE mainly comprises of (i) the development of novel technology for optimum production from the available natural resources (ii) environmental awareness, and (iii) the better management and distribution system. Like other domains (food, health, accommodation, safety, etc.), Artificial Intelligence (AI) could assist in achieving the future goals of the RE. Statistical and biologically inspired AI methods have been implemented in several studies to achieve common and future aims of the RE. The present study summarizes the review of reviews and the state-of-the-art research outcomes related to wind energy, solar energy, geothermal energy, hydro energy, ocean energy, bioenergy, hydrogen energy, and hybrid energy. Particularly, the role of single and hybrid AI approaches in research and development of the previously mentioned sources of RE will be comprehensively reviewed.

The slider crank is a proven mechanical linkage system with a long history of successful applications, and the slider-crank ocean wave energy converter (WEC) is a type of WEC that converts linear motion into rotation. This paper presents a control algorithm for a slider-crank WEC. In this study, a time-domain hydrodynamic analysis is adopted, and an AC synchronous machine is used in the power take-off system to achieve relatively high system performance. Also, a rule-based phase control strategy is applied to maximize energy extraction, making the system suitable for not only regular sinusoidal waves but also irregular waves. Simulations are carried out under regular sinusoidal wave and synthetically produced irregular wave conditions; performance validations are also presented with high-precision, real ocean wave surface elevation data. The influences of significant wave height, and peak period upon energy extraction of the system are studied. Energy extraction results using the proposed method are compared to those of the passive loading and complex conjugate control strategies; results show that the level of energy extraction is between those of the passive loading and complex conjugate control strategies, and the suboptimal nature of this control strategy is verified.

This chapter gives an overview of research activities carried out at NTNU AMOS in relation to hybrid marine power plants enabling safer, smarter and greener ships. Recently electrical power plants with a set of diesel-generator sets segregated on several power buses have become the preferred solution for ships with a variation in operational profile and corresponding power demands. Examples of such ships are dynamically positioned (DP) vessels with electric power plants in the range of 10-80 MW used in the offshore oil and gas industry for various service, drilling, intervention and production operations, see Figure 1. The operations are characterised as safety-critical and will take place all-year with large variations in the environmental loads acting on the ship due to wind, waves, ocean currents, and recently more operations in sea-ice. Electrical power plants have also become the preferred solution for cruise ships, ferries, navy ships, LNG tankers, and icebreakers. The electric energy production may be powered by a hybrid marine power plant constituting of diesel engines, gas engines, and integrated with energy storage devices (ESD) such as banks of batteries. By proper design and control systems significant fuel savings can be achieved making the ships greener and safer. © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This is the authors' manuscript to the article (preprint).

With the rapid development of photovoltaic power generation technology, photovoltaic power generation system has gradually become an important component of the integrated energy system of marine. High precision short-term photovoltaic power generation forecasting is becoming one of the key technologies in ship energy saving and ship energy efficiency improving. Aiming at the characteristics of marine photovoltaic power generation system, we designed a highprecision power forecasting model (WT+ESN) for marine photovoltaic power generation system with anti-marine environmental interference. In this model, the information mining of the photovoltaic system in marine environment is carried out based on wavelet theory, then the forecasting model basing on echo state network is construct ed. Lastly, three kinds of error metrics are compared with the three traditional models by Matlab, the result shows that the model has high forecasting accuracy and strong robustness to marine environmental factors, which is of great significance to save fuel for ships, improve the energy utilization rate and assist the power dispatching and fuel dispatching of the marine power generation system.

The higher requests concerning the large scale implementation of the renewable energy imposed by the EU directives implies a substantial enhancement of the renewable energy extraction all over Europe. Wind turbines entered in the last decades gradually in the common landscape and the success of the wind power industry renewed the interest in discovering what might work in the sea. On the other hand, it becomes quite obvious nowadays that wave power will play an important role in the global energy portfolio. Combined offshore wind-wave projects, also known as hybrids, hold great potential down the line when wave technologies will become more established. At that point, wave production might compensate for the intermittent offshore wind, while economies of scale developed from offshore wind could accelerate cost reduction for wave components. Despite a certain degree of uncertainty related to the variability in the wave-wind climate, improvements in the accuracy of evaluating the environmental data in coastal areas would also enhance the accuracy of the predictions that future energy convertors yield. Another important problem that arises together with the implementation of the energy farms in the coastal environment is related to the correct assessment of their impact on the littoral dynamics. From this perspective, the proposed work presents the main challenges related to the wave energy extraction in the nearshore. This includes also the identification of the best European locations from the point of view of the synergy between the wind and the wave power.

Technological advances in marine renewable energy allow for various methods of extracting energy in the form of electrical power from the ocean. One method is through the process of ocean thermal energy conversion (OTEC). This study assesses the distributions of electrical power that can be extracted from the ocean around the state of Florida. The OTEC resource is analyzed with the combination of a state-of-the-art ocean circulation model, the Hybrid Coordinate Ocean Model, along with a state-of-the-industry OTEC plant model in order to predict the attainable power values offshore Florida. The power predictions are then constrained by local cold deep sea water replenishment to provide an upper limit to the sustainable OTEC resource. The thermal resource is used as input to the plant model to predict the potential power production. The resource data is then validated through the comparison against in situ oceanic measurements to safeguard the quality of the predicted power values.

This paper proposes an analytic dispatch for tidal power plants that centralizes the discharge period in the tides extremes. Since the tide cycles are well predicted by a sinusoidal function, this method provides an accurate power generation as shown in the comparative tests. Furthermore, an optimal generation estimation method is derived considering that all stored water is discharged during the tides extremes, i.e., discharging at maximal water head. This method calculates a more realistic maximal power generation, which is especially simple in double-effect operation mode (power production in ebb and flood tides), since the reservoir geometry is not explicitly considered. The proposed methods are compared with a classical analytic solution and an optimal dispatch formulation.

There have been an increasing number of government policies and research activities aimed at the exploitation of renewable energy resources to diversify power supply and meet the growing demand for electricity. In the context of Brazil, an example of this is tidal energy, which has a significant potential and is mainly concentrated on the coast of the States of Maranhao, Para, and Amapa. However, only a few studies have been conducted to evaluate and take advantage of this energy source. One of the works in progress involves the study of a tidal power plant installation at the dam situated at Bacanga. This paper outlines and analyzes the configuration management of a tidal power plant, which is suited to the current physical conditions of the dam and complies with operational and physical constraints. In specific terms, the study takes account the reservoir operating restrictions and available physical space for installing turbines. A recent assessment has been carried out that involves bathymetry, high-resolution photos, and 3-D scanning to evaluate the potential value of the reservoir. This allowed a complete reservoir characterization and the designing of its digital model. Annual studies of optimal operation are reported, as well as factors, such as the technical and economic benefits and drawbacks of the plant

The immense energy potential of the oceans is being increasingly recognized the world over, at the same time the integrity of marine ecosystems is challenged by pressure from multiple human activities. For good reasons environmental licensing procedures are precautionary and new industries must declare their detrimental impacts and provide mitigation measures. New ocean energy industries target renewable energy sources thus, on a grand scale, partly mitigating climate change. However, on-site environmental impacts are yet to be established. In this review we compare ocean energy industries with a wide range of conventional, better understood, human activities and outline environmental risks and research priorities. Results show that ocean energy systems are thought to incur many pressures, some familiar and others with yet unknown effects. Particular uncertainties regard ocean thermal energy conversion (OTEC) and large fast-moving turbines. Ocean energy industries should not be considered in isolation because the significance of environmental impacts depend on the full spectra of human activities in each area. Marine spatial planning provides a platform for holistic assessments and may facilitate the establishment of ocean energy industries, as long as risk-related uncertainties are reduced.

To aid deployment and recovery of tidal stream generators, gravity-based foundations rather than fixed-foundation alternatives are being considered in areas where the foundation may be placed directly onto an exposed rock seabed. Horizontal loading is usually critical in such applications, therefore specific knowledge of the interface friction between the foundation (made of steel or concrete) and seabed is important for design. This paper presents results of an interface testing programme of chalk–steel interfaces carried out utilising a computer-controlled interface shear tester under constant normal stress conditions against steel of different roughness. Results indicate that interface strength is significantly affected by the normal stress applied, as interface strength degrades for normal stress levels in excess of 30% of the chalk's tensile strength (∼300 kPa). Large-displacement tests revealed a tendency of the ultimate interface frictional resistance to drop to values very similar to that of the basic chalk–chalk interface at normal stresses up to 300 kPa, whereas substantial additional degradation was noticed for normal stresses above 700 kPa. At low normal stresses and displacements the behaviour of the chalk–steel interface was captured by an alpha type approach related to the rock unconfined compressive strength, which has been developed for other higher strength rock types.

This paper deals with an energy characterization method of tidal sites. This method is illustrated by the study of a typical tidal site close to the Ouessant (Ushant) Island of the Bretagne region in France. The main objective of this study is to find the optimal location of a tidal turbine including the effect of using or not a yaw drive system. After presenting the different data used in this work, the marine current velocity is first evaluated at different specific locations and times of the studied zone. Afterwords, the tidal energy is evaluated for different systems (tidal turbine with a yaw and bidirectional tidal turbine with fixed axis) and presented in terms of energy distribution maps.

Ocean energy is abundant in China, and the utilization of ocean energy could improve current energy structure and contribute to energy security. If tidal power is harnessed efficiently, it could help China reach its renewable energy goals. A suitable model for solving the multi-criteria decision-making problem is proposed in this paper. The model incorporates the fuzzy analytic network process (FANP) and the fuzzy goal programming (FGP). The FANP can consider various factors, the interrelationships among the factors, and the impreciseness and vagueness of the problem more thoroughly based on expert opinions. The FGP can help select dam sites to maximize the satisfaction of the system when resources are limited. A case study in an east-coast province in China is presented to demonstrate the practicality of the proposed model.

Developing ocean energy extraction, including ocean thermal energy conversion (OTEC), has been of interest to researchers for many decades. OTEC is a free fuel technology and could be used as a baseline power generation. These advantages plus the engineering challenge have resulted in researchers striving to design and construct prototype devices. Making use of worldwide experience, all sections of a conceptual design including site selection, technical specifications and cost estimation were carried out for an Iranian OTEC power plant. A 5 MW closed cycle floating plant with an annual average temperature difference of 22°C was chosen at a 33 km distance from Chabahar harbour. Deep seawater would be extracted from 1000 m depth and would result in 3.52 MW of net power. According to cost calculations, the levelised cost of electricity of the plant has been estimated to be approximately 0.117 $/kWh, which is an acceptable level compared to other renewables. The conceptual OTEC design presented in thi...

The objective of this study was to improve the power captured in heaving wave energy converters using a simple robust hierarchical control strategy (HCS). A HCS comprises a higher level controller (HLC) and a lower level controller (LLC). The HLC provides a reference velocity for the buoy, which is in-phase with the wave’s excitation force. The LLC follows the reference despite the uncertainties in the model. We propose a new HCS called bottom-up HCS (BU-HCS), where the LLC is designed before the HLC. The LLC is implemented using a feedback controlled system with a simple lead-lag compensator as its controller. The lead-lag compensator is designed using H ∞ theory with the objectives of maximizing the robustness and tracking properties of the LLC while minimizing the control force of the power take-off (PTO) device. A set of optimization problem is obtained for designing the parameters of the lead-lag compensator, which are solved using a genetic algorithm. The HLC in the BU-HCS provides the velocity reference, which satisfies a constraint on the control force and the PTO’s utilization index. The HLC is implemented by designing the value of an intrinsic resistance constant, which can be found using the Bode magnitude plot of a transfer function. Based on the plot, a look-up table for the intrinsic resistance constant is generated as a function of the significant height and the peak period of the wave. We tested the proposed method in various scenarios and its performance was compared with existing control techniques.

In this paper, five most emerging renewable energy sources are analyzed. These emerging renewables are either special or advanced forms of the mainstream energy sources (solar, wind, geothermal, biofuels, biomass, and hydro) or brand new technologies. The five emerging renewable technologies discussed in this paper include marine energy, concentrated solar photovoltaics (CSP), enhanced geothermal energy (EGE), cellulosic ethanol, and artificial photosynthesis. Marine energy is divided into wave energy, tidal energy, tidal/ocean currents, salinity gradient, and ocean thermal energy conversion. CSP technologies are divided into parabolic troughs, linear Fresnel reflectors, parabolic dishes, and solar towers. The process for developing EGE reservoirs is also explained in detail. Cellulosic ethanol energy extraction is explained for both cellulolysis and gasification. Artificial photosynthesis is explained by considering semiconductor particles, electrolyzers, artificial leaves, and dye-synthesized solar cells. Each emerging renewable source's explanation is followed by its market share, challenges, implications for increased adoption, future prospects, and drawbacks.

Ocean tidal currents, water waves and thermal gradients are a great source of renewable energy. Ocean tidal, osmotic, wave and thermal sources have annual potentials of 800, 2,000, 8000–80,000 and 10,000–87,600 TWh, which are more than global 16,000 TWh/y electricity demand. Ocean wave generators produce relatively lower output, however, four to eleven meters tidal range stations have large power generation capacities. Abundant ocean heat energy potentially harvested using ocean thermal energy conversion (OTEC) devices and ocean thermo-electric generators (OTEG). Tidal stations may be tidal range or current types, but a wave energy converter (WEC) may be an oscillating water column (OWC), overtopping, heaving, pitching and surging devices. Ocean thermal energy can be harnessed by open, close Rankine cycles, thermo-electric generators and osmotic power plants. Large bays like Turnagain (USA), Annapolis/Minas Passage (Canada), Seven Barrages/Pentland Firth (UK), La Rance (France), Garorim (South Korea) and Mezen/Penzhin (Russia) have huge tidal current power generation capacities. Power Potential from tidal current stations is more than WEC devices which in turn is more than osmotic, OTEC and OTEG technologies. This paper reviews the current state-of-the-art of tidal, wave, OTEC and OTEG ocean energy technologies.

This paper describes a new maximum power point tracking (MPPT) algorithm developed to control a wave energy converter (WEC) in random seas. This algorithm, named the cycling MPPT algorithm, is compared to a perturb and observe algorithm described in numerous literature. Both algorithms were initially tested during 2012 ocean tests of the half-scale prototype Wave Energy Technology – New Zealand (WET-NZ) WEC off the Oregon coast. During these sea trials the perturb and observe algorithm failed to provide effective control of the WET-NZ, while the cycling algorithm was observed to give effective control. More complete investigations were later carried out using MATLAB-Simulink simulations of an autonomous WEC (AWEC) being developed at Oregon State University. The results of the AWEC simulations also showed the cycling algorithm provided better control than the perturb and observe algorithm. The operation of the cycling algorithm was fully characterized during the AWEC simulations and these results are presented.

Wave energy is a nascent industry characterized by high capital costs, which impede technological development and industry expansion. For this reason, new strategies are required to improve sustainability, reduce cost and enable wave energy harnessing even in low energy seas. Six new strategies that can make commercialization of wave energy more appealing are studied. These comprise the integration of wave energy converters (WECs) in coastal defence; tourism; desalination technology; offshore aquaculture; energy security; and power plants. WECs can axe erosion by half, or even more, in sandy beaches by creating wave shadows in their lee. Therefore, an innovative way to offset WEC high initial capital expenditure is their incorporation in coastal defence, with the added benefit of electricity production. Also, WECs can directly provide pressurized seawater for reverse osmosis desalination plants, thus achieving significant energy, cost and environmental footprint reductions. The touristic trade could also benefit from educational and interpretive displays of the wave energy technology, whilst ecotourism opportunities may arise that could address tourism seasonality. Combined offshore aquaculture facilities with WECs would benefit for reduced installation, operation, and maintenance costs, as well as addressing fossil fuel dependence in aquaculture. Moreover, WECs could be used for mitigating the intermittency of established renewables (solar and wind) and advance their penetration; while a combined WEC- pump hydropower storage scheme could secure the energy supply in remote coastal areas and islands. Finally, WECs could directly supply cooling water intake structures, such as power plants, with the huge amounts of seawater they require for cooling purposes. WEC are also able to provide high purity sterile water for core cooling in nuclear reactors and also support its circulation. For example, WECs can be introduced in coastal nuclear power plants, as to minimize the loss of coolant accident and prevent disasters similar to Fukushima’s 2011.

Marine energy is one of the most promising solutions to attempt the ambitious renewable energy target of 20% by 2020 due to its very substantial energy resource. However, it is often considered uneconomical and difficult, and this may hinder its development. Combined energy systems, such as co-located offshore wind turbines and wave energy converters, have recently emerged as a solution to increase the competitiveness of marine energy by taking advantage of the synergies between renewables; which would lead to reductions in the energy cost and improvements in the power output variability and security. On this basis, finding viable locations for combined offshore renewable energies is fundamental to boosting their development. The objective of this paper is to determine suitable locations for deploying a co-located wind and wave energy farm in the North Sea - an area with several characteristics that make large-scale integration of renewable energy sources attractive. In this assessment we investigate not only the existing resource but also other parameters such as its variability and the correlation between waves and winds by means of the CLF index. In addition, inter- and intra-national user conflicts are considered, while balancing environmental conservation and economic development.

In 2018, we were approached by the editorial team of the Journal of Marine Science and Engineering (MDPI editorial) to act as guest editors of a Special Issue related to offshore wind energy [...]

The chapter deals with the basic concepts of installation, operation and maintenance of offshore renewable energy systems. Whilst focus is given to the offshore wind industry, the extension to ocean energy (wave and tidal) offers a wider perspective on the major issues concerning the installation and maintenance. A reliability-based approach has been adopted for the analysis of the failures, providing an overview about the most common functional decomposition methodologies as well as logistic requirements for the different operations at the various stages of the lifetime of an offshore renewable project. The economic modelling of the operations, based on strategies for their planning, briefly completes the chapter.

Tidal range renewable power plants have the capacity to deliver predictable energy to the electricity grid, subject to the known variability of the tides. Tidal power plants inherently feature advantages that characterise hydro-power more generally, including a lifetime exceeding alternative renewable energy technologies and relatively low Operation & Maintenance costs. Nevertheless, the technology is typically inhibited by the significant upfront investment associated with capital costs. A key aspect that makes the technology stand out relative to other renewable options is the partial flexibility it possesses over the timing of power generation. In this study we provide details on a design methodology targeted at the optimisation of the temporal operation of a tidal range energy structure, specifically the Swansea Bay tidal lagoon that has been proposed within the Bristol Channel, UK. Apart from concentrating on the classical incentive of maximising energy, we formulate an objective functional in a manner that promotes the maximisation of income for the scheme from the Day-Ahead energy market. Simulation results demonstrate that there are opportunities to exploit the predictability of the tides and flexibility over the precise timing of power generation to incur a noticeable reduction in the subsidy costs that are often negotiated with regulators and governments. Additionally, we suggest that this approach should enable tidal range energy to play a more active role in ensuring security of supply in the UK. This is accentuated by the income-based optimisation controls that deliver on average more power over periods when demand is higher. For the Swansea Bay tidal lagoon case study a 23% increase is observed in the income obtained following the optimisation of its operation compared to a non-adaptive operation. Similarly, a 10% increase relative to an energy-maximisation approach over a years operation suggests that simply maximising energy generation in a setting where power prices vary may not be an optimal strategy.

An underwater profiler is one of the popular platforms for ocean observation. Due to energy limitations, conventional underwater vehicles have a short life span, which cannot meet the needs of long-term ocean exploration. Therefore, there is a growing interest in using ocean energy such as ocean thermal energy and wave energy for driving. This study aimed to investigate an energy-saving and ocean thermal energy (OTE)-powered buoyancy driving system of the ocean profiler. The purpose of this study was to explore an ocean profiler buoyancy driving system powered by ocean thermal energy (OTE). According to the seawater profile temperature gradient, an OTE-powered electro-hydraulic control system was designed, and the dynamic characteristics of this system are simulated and analyzed by using the power bonding diagram method. Based on the results conducted from lake tests, this profiler possesses the self-driving capability for using OTE perfectly. This research can provide important guidance for the design of the buoyancy drive system of underwater vehicles.

For ships, the total loss of electrical power, ‘blackout’, is a critical failure. The failure of the marine power supply system not only results in loss of ability to perform tasks, but also poses ...

Ocean (wave and tidal) energy is still in the prototype testing stage, with several challenges standing between the sector’s current status and the goal of commercial deployment. The study of how to reduce the cost of energy, to a level competitive with renewable energy alternatives, is an important aspect of sector development. A comprehensive PESTLE (Political, Economic, Social, Technological, Legal and Environmental) analysis has been carried out to reveal the risks and uncertainties that face wave and tidal energy technology within identified themes. The purpose of the PESTLE analysis was to ascertain the factors most relevant to the reduction of the Levelised Cost of Energy (LCOE), and the wider commercialisation of wave and tidal energy technology. It has been shown that two separate case studies are required in order to more accurately assess the needs of the ocean energy sector. Firstly the suitability of different geographic locations for technology deployment and secondly the progress of the technology in the development cycle; the areas that require the focus of research and development activity. With the completion of both case studies, the paths towards sector development and cost effective energy production has been presented.