• Energy Research

E-Motions is a low-cost and versatile/adaptable wave energy converter conceived towards harnessing energy from wave/wind-induced roll oscillations of floating platforms. This paper focuses on a recently conducted parametric physical modelling stage with three hull designs (half-cylinder, half-sphere and trapezoidal prism), which features a disruptive Power Take-Off reproduction. Free decay, inclining and free-fall tests denoted a good agreement between the physical model's properties and the estimates. Parametric regular waves tests yielded data regarding reflection and transmission coefficients, while large peak-to-peak roll amplitudes (nearly 80) were measured for the half-cylinder and, to a lesser extent, the half-sphere. Peak reduction was observed under resonant conditions, with the introduction of the Power Take-Off, to which adds a motion phase difference between it and the floating platform. On power output, the half-cylinder and half-sphere yielded the highest capture width ratios and power values per metre of device (nearly 0.8 kW/m, in prototype values) and per displaced volume (up to 0.08 kW/m3). Albeit sufficient for supporting some marine activities, these values can be bolstered, in the future, either through alternative mass/damping combinations or stacking various rows of generators. Maximum mean-to-max power ratios reached a value of 11, within the standard literature range, from literature.

Abstract E-Motions wave energy converter is a promising device capable of harnessing energy from wave/wind induced roll oscillations onto a generic floating platform, whose development was initiated with an experimental proof-of-concept study that, despite demonstrating the potentialities of the device, also highlighted the need for further developments, aimed at improving its performance and efficiency. This justified a new phase of numerical modelling, where E-Motions was reproduced within the ANSYS® AQWA™ environment, a potential theory-based numerical model widely used in the field of wave energy converter development. The model was setup (first stage) and calibrated (second stage) with experimental data from a proof-of-concept study, carried out on a 1:40 geometric scale, with a good agreement being obtained for the hydrostatic properties (difference below 5%) and hydrodynamic roll response (minimum average error of 2.83°). From a follow-up third stage, focused on comparing eight different hull solutions with similar natural roll periods, it was determined that the half-sphere and trapezoidal prism geometries produced the highest power outputs for the studied conditions (maximum average outputs of nearly 5 kW/m and 8 kW/m, respectively). These two designs were then adapted to a 1:20 geometric scale alongside an updated version of the half-cylinder, which served as a “control” case, and subjected to a final stage of numerical modelling centered on assessing the Power Take-Off’s influence (namely through variable damping and mass) in their performance. Outcomes from this stage denote the necessity of a careful selection of Power Take-Off mass/damping combinations, as a disproportionate relationship could lead to scenarios where the conversion system would stall on one of the superstructure’s sides, moving within a very limited range of the available sliding amplitude. Maximum average power output values reach nearly 24 kW, 30 kW and 18 kW for the half-cylinder, half-sphere and trapezoidal prism, respectively, with a follow-up experimental study being planned for the near future, in order to evaluate the validity of these results.

Seaports are highly energy demanding infrastructures and are exposed to wave energy, which is an abundant resource and largely unexploited. As a result, there has been a rising interest in integrating wave energy converters (WEC) into the breakwaters of seaports. The present work analyzes the performance of an innovative hybrid WEC module combining an oscillating water column (OWC) and an overtopping device (OWEC) integrated into a rubble mound breakwater, based on results of a physical model study carried out at a geometrical scale of 1:50. Before the experimental tests, the device’s performance was numerically optimized using ANSYS Fluent and WOPSim v3.11. The wave power captured by the hybrid WEC was calculated and the performance of the two harvesting principles discussed. It was demonstrated that hybridization could lead to systems with higher efficiencies than its individual components, for a broader range of wave conditions. The chosen concepts were found to complement each other: the OWEC was more efficient for the lower wave periods tested and the OWC for the higher. Consequently, the power production of the hybrid WEC was found to be less dependent on the wave’s characteristics.

This review details the groundwork made in the most recent years on the development of TENGs for wave energy conversion systems and discusses future perspectives in the scope of autonomous, self-powered sensor buoys and other offshore floating platforms.

Seaports are at the forefront of global trade networks, serving as hubs for maritime logistics and the transportation of goods and people. To meet the requirements of such networks, seaport authorities are investing in advanced technologies to enhance the efficiency and reliability of port infrastructures. This can be achieved through the digitalization and automation of core systems, aimed at optimizing the management and handling of both goods and people. Furthermore, a significant effort is being made towards a green energy transition at seaports, which can be supported through marine renewable sources. This promotes energy-mix diversification and autonomy, whilst reducing the noteworthy environmental footprint of seaport activities. By analyzing these pertinent topics under the scope of a review of container-terminal case studies, and these ports’ respective contexts, this paper seeks to identify pioneering smart seaports in the fields of automation, real-time management, connectivity and accessibility control. To foster the sustainable development of seaports, from an energy perspective, the potential integration with marine renewable-energy systems is considered, as well as their capabilities for meeting, even if only partially, the energy demands of seaports. By combining these fields, we attempt to construct a holistic proposal for a “model port” representing the expected evolution towards the seaports of the future.

This paper seeks to identify promising sites and technologies, in Portugal, for co-located wave energy conversion and offshore aquaculture, whilst providing benchmark implementation references and guidelines to researchers. Accordingly, two case study sites are considered for deployment of five wave energy devices and up to six aquaculture species. A thorough analysis in terms of power ratios, efficiency, redundancy, species viability, device survivability and costs is performed, seeking to find viable co-located solutions. It is found that the Wave Dragon device yields the most promising energy demand coverage and energy output (5 226 to 6 817 MWh/ year). Nevertheless, it may require rescaling towards optimal operation, while the OCECO 4 excels in terms of capacity factor (0.24-0.29) and default adaptation to the deployment sites. The WaveRoller (R) has the lowest single-unit cost (125 euro/MWh) but requires up to nine units to cover all the energy demand targets. Larger wave farms are required for the BBDB and AquaBuOY, albeit with potentially greater economies of scale and single-unit redundancy. These sites also enable cultivation of most of the considered species, even under ideal condi-tions. Lastly, it is recommended that the devices enter survivability mode at a significant wave height threshold of 5.5 m.

Abstract Ocean waves constitute an abundant source of clean and predictable energy, with the potential to partly replace carbon intensive energy sources. At present, several technologies to convert wave energy into electricity are being developed, but those suitable for integration into port breakwaters present additional advantages. This paper presents a novel concept that combines two well-known wave energy conversion principles, an oscillating water column and a multi-reservoir overtopping system. This hybrid concept was designed to be integrated in rubble-mound breakwaters, having as case study Leixoes’ northern breakwater, Portugal. The performance and efficiency of the single components were assessed separately as well as that of the hybrid module as a whole, to demonstrate the advantages of their combination into a single unit. Furthermore, the annual energy production was estimated for a 20 m wide hybrid module considering the local metocean conditions. Results showed that overall efficiency amounted to circa 44.4%, the wave-to-wire efficiency to 27.3% and the annual electricity production was estimated at 35 MWh/m. Considering that 240 m of the reference breakwater are used, the developed hybrid module could provide approximately 50% of the electricity consumption of the Port of Leixoes, which demonstrates the potential and interest of the developed technology.