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Electric propulsion has emerged as one of the most efficient propulsion arrangements for several vessel types over the last decades. Even though examples can be found in the history at the end of 19th century, and further into the 20th century, the modern use of electric propulsion started in the 1980s along with the development of semiconductor switching devices to be used in high power drives (dc drives and later ac-to-ac drives). This development opened up for full rpm control of propellers and thrusters, and thereby enabling a simplification of the mechanical structure. However, the main reason for using electric propulsion in commercial ship applications is the potential for fuel savings compared to equivalent mechanical alternatives, except for icebreakers where the performance of an electric powered propeller is superior to a combustion engine powered propeller. The fuel saving potential lies within the fact that the applicable vessels have a highly varying operation profile and are seldom run at full power. This favors the power plant principle in which electric power can be produced at any time with optimum running of prime movers, e.g., diesel engines, by turning on and off units depending on the power demand for propulsion and other vessel loads. Icebreakers were among the first vessels to take advantage of this technology later followed by cruise vessel, and the offshore drilling vessels operating with dynamic positioning (DP). The converter technology was rapidly developing and soon the dc drives were replaced with ac drives. In the same period electric propulsion emerged as basic standard for large cruise liners, and DP operated drilling vessels, but also found its way into other segments as shuttle tankers, ferries, and other special vessels. At the same time podded propulsion were introduced, where the electric motor was mounted directly on the propeller shaft in a submerged 360 ^\circ steerable pod, adding better efficiency, improved maneuvering, and reduced installation space/cost to the benefits of electric propulsion. The future trends are now focusing on further optimization of efficiency by allowing multiple energy sources, independent operation of individual power producers, and energy storage for various applications, such as power back up, peak shaving, or emission free operation (short voyages). [ABSTRACT FROM PUBLISHER]

Reports on the technologies that comprise underwater cables, examines their historical development, discusses their deployment, and reports on new areas of technological development to support undersea communciations. [ABSTRACT FROM PUBLISHER]

The articles in this special issue provide a timely and comprehensive review of recent progresses, applications, and challenges spurred by the marine energy generation and transmission technology developments. It is intended for a broad audience interested in gaining comprehensive understanding of technical issues and opportunities that may exist in this important emerging field. [ABSTRACT FROM PUBLISHER]

Marine energy, especially tidal current and ocean wave resources, bear immense potential for generating renewable power toward meeting global electricity needs. A number of conversion technologies have been successfully demonstrated worldwide and precommercial/commercial deployments are expected to appear in the near future. While electric power utilities foresee renewable technologies as a viable alternative to fossil fuels, marine energy technologies are generally excluded in their energy planning processes. Lack of technological preparedness and unavailability of device information are two major obstacles in that regard. This article provides an insight on how such novel schemes of power generation can be analyzed under conventional network planning exercises using generic information. The first study focuses on wave power integration along the coasts of Oregon, USA for the year 2019 and analyzes the Northwest electrical network. The second study considers both tidal current and ocean wave resources in South Korea for the years 2017 and 2022. The primary objective of these high-level grid scenario analysis is to identify the practical potential for longer term large-scale wave and/or tidal power generation, particularly focusing on the transmission networks. Steady-state (overloading and voltage deviations/collapses), time-domain (angular stability and dynamic voltage recovery characteristics), and small-signal (eigenvalue) stability analysis are carried out for these systems. Subsequent to establishing a number of study scenarios, N-1 contingencies and various suitable violation criteria are prepared, which are used in identifying the underlying network bottlenecks, especially within the coastal areas. Simplified generic dynamic models of tidal current and ocean wave devices are developed for the time-domain analysis. It is expected that similar studies, once conducted by the interested utilities, will equip them better toward considering marine energy in their future portfolios. In addition, device manufacturers and project developers will have greater confidence in the emerging marine energy market. [ABSTRACT FROM PUBLISHER]

Due to its higher capacity factor and proximity to densely populated areas, offshore wind power with integrated energy storage could satisfy > 20% of U.S. electricity demand. Similar results could also be obtained in many parts of the world. The offshore environment can be used for unobtrusive, safe, and economical utility-scale energy storage by taking advantage of the hydrostatic pressure at ocean depths to store energy by pumping water out of concrete spheres and later allowing it to flow back in through a turbine to generate electricity. The storage spheres are an ideal complement to energy harvesting machines, such as floating wind turbines (FWTs). The system could provide near-base-load-quality utility-scale renewable energy and do double duty as the anchoring point for the generation platforms. Analysis indicates that storage can be economically feasible at depths as shallow as 200 m, with cost per megawatt hour of storage dropping until 1500 m before beginning to trend upward. The sweet spot occurs when the concrete wall thickness to withstand the hydrostatic pressure provides enough ballast mass, and this will depend on the strength of used concrete and reinforcement. In addition, the required concrete would use significant amounts of fly ash from coal-fired power plants, and the spheres can serve as artificial reefs. [ABSTRACT FROM PUBLISHER]

A number of review articles have synthesized current expert opinion regarding interactions of ocean energy generation technologies with environmental parameters and their potential effects and impacts. Fewer articles have documented such interactions, as operational devices and or demonstration sites at which to make such observations are limited. In this paper, we discuss how the perceived risk or impact of ocean renewable energy development on coastal communities (both the human and marine biological communities) is a function not only of actual physical interactions but also depends on the regulatory environment and how potentially impacted coastal resources are valued by stakeholders. In this paper, we review potential environmental effects of ocean energy, identify applicable federal regulations that address potentially affected ecological components, and highlight observations about stakeholder concerns from experiences in Oregon. Understanding the societal lens through which potential environmental effects are viewed is important for developers to move forward as it will be the regulators and local communities who will determine if projects are permitted. [ABSTRACT FROM PUBLISHER]

This paper gives a historical overview of the development of the U.K. marine energy sector from its academic beginnings in the early 1970s. It includes discussion on government support policies and where the sector might develop up to and beyond the end of this decade. The paper also presents two very different projects: the European Marine Energy Centre in Orkney, U.K., and the forthcoming All Waters Current and Wave Test Facility in Edinburgh, U.K., as examples of capital investment in the sector. [ABSTRACT FROM PUBLISHER]

The rapid increase in renewable energy generation from wind has increased concerns about the impacts that wind arrays have on the marine environment and what these impacts mean for society. One method for identifying the impacts of offshore wind farms (OWFs) on human welfare is through the assessment and valuation of ecosystem services. Using an ecosystem services approach, this paper reviews the impacts of OWFs on the ecosystem services delivered by marine environments. During the construction phase, supporting services such as reduced energy capture and nutrient cycling are changed due to the introduction of hard substrate and the reduction in soft sediment habitat at turbine bases. This may lead to changes in all other ecosystem services, both negative and positive. Quantifying these changes, however, is a challenge partly due to data limitations and a lack of clear understanding of the impacts of OWFs on the marine ecosystems. Scientific effort needs to quantitatively explore the impacts of OWFs on ecosystem functionality and the gathering of data that enables the assessment of changes to ecosystem services. Data needed to better quantify and value the impacts of OWFs on ecosystem services are suggested. The development of methods which integrate socioeconomic valuation of ecosystem services into the evaluation of renewable energy devices compliments efforts in assessing the environmental impacts and should enable a holistic assessment of the impact of renewable energy production and greenhouse gas mitigation technologies on the U.K. carbon footprint. [ABSTRACT FROM PUBLISHER]

The author discusses the role of marine energy in the development of future sustainable energy supply. He states that the increasing role of variable renewable sources in the energy supply has been restricted by the system active power reserve requirements. He mentions that increasing environmental concerns and dependence on energy imports have caused governments to increase their investment and use of wind energy through the construction of offshore wind farms.