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Ocean renewable energy, such as wave and tidal energies, is important for energy supply and decarbonization of offshore platforms and ships. However, the intermittent and non-dispatchable nature of wave and tidal energy remains a significant challenge. The hybrid wave-tidal energy conversion presents a potential solution to enhance output power and stability by leveraging their complementary characteristics. This paper reviews the current state of hybrid wave-tidal energy conversion technology, focusing on device design, modeling methods and testing methods. Many current hybrid wave-tidal energy converters (HWTEC) have not considered effective coupling among the modules of sub-systems to maximize efficiency. Modeling and simulation methods are mainly based on studies of single wave or tidal energy conversion, and non-linear system modeling is rare. The assumption of continuous functions in most models can lead to discrepancies from real-life conditions. Advancement of modeling approaches, co-simulation algorithms, and dedicated dry lab and pool tests for HWTEC are desired. While HWTEC is potential for improving ocean energy conversion, addressing key challenges of device design, modeling, testing and economic evaluation are essential for realizing its full potential in contributing to decarbonization. • Wave and tide are compared from the perspective of hybrid energy conversion. • Hybrid wave-tidal energy converters are classified and reviewed. • Analysis methods for hybrid wave-tidal energy converters are summarized. • Technology gaps in hybrid wave-tidal energy conversion are identified. • Potential research directions of hybrid wave-tidal energy conversion are proposed. [ABSTRACT FROM AUTHOR]

Abstract Current narrative on biofuels is backed up by a large number of studies published in the scientific literature that address second-generation bioethanol only through a single topic approach, nonetheless in the vast majority of cases transition to this energy carrier is evaluated as a generally 'promising' technology. This paper presents a first attempt in proposing an integrated evaluation of the actual benefits expected from bioethanol in the transport sector, by applying the Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM) to the prospective realization of a local system of bio-refinery in Campania Region (Southern Italy). MuSIASEM is a multi-criteria analysis enabling to deal with the complexity of a territorial energy system. Since the unavoidable intrinsic uncertainty, the study does not focus on predictions, but adopts a strategy of Quantitative Story-Telling about some relevant results underlying the limits and critical issues about the energy converter fabric, the economic profitability, environmental constraints and the questionable concept of marginal land. The findings suggest concluding toward falsification of key points in the current narrative: (i) the system is not an efficient solar energy converter; (ii) it fails to realize many of the expectations for a renewable energy carrier producer; (iii) the contribution to decarbonization strategies is not as high as desired and other environmental impacts could not be neglected; (iv) the very large land requirement is hardly compatible with conversion of truly marginal land in Campania region; (v) compared to alternate land uses it does not seem an actually promising strategy to regain value from rural economy. Graphical abstract Image 1 Highlights • Single topic studies are not useful for comprehension of a territorial biorefinery. • Multi-scale and multi-dimensional approach to face the ambiguity of energy concept. • Performance's comparison of two distinct energy production systems is misleading. • Decarbonization and marginal lands concepts are a simplification of the problem. [ABSTRACT FROM AUTHOR]

Harvesting energy from nature have attracted much attentions especially the direct energy conversion from other power sources (e.g. light, heat, mechanical movement, moisture) into practical electricity. However, many of existing devices always rely heavily on external metal electrodes, and their rigid structure restrains further applications in portable touchless electronics or perceptual artificial skins. Herein, we demonstrate flexible in-plane moisture-electric converter (IPMEC) based on graphene oxide (GO) film for novel touchless interactive platform. An appreciable electric output voltage (~70 mV) and high electrical current density (12 mA cm −2 ) can be autonomously generated with ambient moisture variation on this IPMEC. The planar configuration and integrative laser reduced GO electrodes of IPMEC renders it highly flexibility, and greatly promotes the touchless interface formation between this device and biological moisture sources (e.g., human finger). Based on this, diverse touchless devices have been developed including finger position annunciator for smart artificial skin, touchless switches and even handwriting panel. This work will provide a new pathway for the development of flexible moisture-electric converters and applications in touchless interactive platform for biomimetic or smart electronics. [ABSTRACT FROM AUTHOR]

Energy from ocean waves remains largely an untapped resource. This is also highly consistent in comparison to other alternate sources of energy such as wind and solar. Present study deals with the design and development of innovative wave energy converter (WEC) that uses a buoy-type point absorber. The device is proposed to be mounted on an offshore platform and be used to produce electric output for meeting the operational energy demands, partially. The device employs lever arm and gear boxes to obtain the mechanical work from the heave energy of the floating buoy. Subsequently, electric energy is generated from the mechanical work harnessed from the waves by deploying a generator. Design Failure Mode and Effect Analysis is carried out on system to identify effects of failure modes. [ABSTRACT FROM AUTHOR]

The application of high-temperature superconducting (HTS) equipment faces challenges that thick current leads connecting superconducting devices with external power sources will generate huge thermal load loss and the difficulty in persistent current operation for a long period. In this work, we have proposed the mechanism of a novel mechanically operated HTS energy converter based on the electromagnetic coupling of the permanent magnet and the HTS coil. The proposed HTS energy converter can charge and discharge a closed superconducting coil without electrical contact, and convert mechanical energy to electromagnetic energy efficiently. However, its working mechanism is theoretically controversial, as it seems to violate Lenz's law. An analytical method based on the method of equivalent circuit is proposed to explain its working mechanism and replicate all experimental electrical behaviour of the HTS energy converter. Experimental results have verified the theoretical analysis. The proposed mechanically operated HTS energy converter is easily controllable, making it promising in various of applications, including superconducting magnetic energy storage (SMES), high field magnets, energy harvesting of urban rail transportation and electromagnetic propulsion. • An analytical model is proposed to explain the phenomenon seeming against Lenz's law. • A novel wireless HTS energy converter with promising applications is proposed. • Factors that could affect working performance of the proposed device are discussed. • Experiments were carried out to verify the proposed analytical model. [ABSTRACT FROM AUTHOR]

• Dual-pump confluence achieves easily the power aggregation. • Dual-pump confluence reduces operating pressure while motor speed is kept constant. • The operating pressure depends not only on load but on the turbine shaft speed. • Distributed HST system can be applied to deep-sea by aggregating dispersed energy. It is well known that generating electricity in the deep-sea has always been a very challenging problem. Aiming at the power demand of the underwater observation system, this paper presents a novel distributed ocean current energy hydrostatic transmission (HST) power generation solution, which can generate electricity efficiently and continuously in large depth and low flow velocity environment. The proposed solution adopts a dual-pump confluence design. According to this, the working pressure of the HST is reduced to avoid overflow compared to the single pump design, and therefore the dispersed micro-energy in deep-sea can be aggregated together to convert continuously to active power rather than to the heat. Furthermore, the solution employs an energy-saving strategy involving constant pressure pump and seawater cooling and improves effectively the efficiency to some extent. Besides, it was found that the working pressure of the system depends not only on load torques but also on turbine speeds reversely, while the speed of hydraulic variable displacement motor maintains constant. Therefore, dual-pump confluence implies power aggregation and plays a key role in generating electricity in deep-sea. Simulation results and the tests based on the 5 kW prototype verifies the feasibility of the proposed distributed HST solution. Accordingly, at the current status, the distributed HST power generation is the most probable solution applied to the deep ocean. [ABSTRACT FROM AUTHOR]