Modelling and testing of a wave energy converter based on dielectric elastomer generators

Implementation and optimization of hydraulic wave energy generation system

Wave energy is one of the primary sources of marine energy, representing a readily available and inexhaustible form of renewable clean energy. In recent years, wave energy generation has garnered increasing attention from researchers. To study wave energy generation technology, we have constructed a real wave energy generation system and designed wave simulation and hydraulic energy storage systems. The wave simulation system is mainly composed of a frequency converter and an electric boost pump, while the hydraulic energy storage system consists of a hydraulic control unit and hydraulic motors. Corresponding mathematical models have been established to investigate the characteristics of wave energy generation. Specifically, a mathematical model for wave input using the double-parameter JONSWAP wave spectrum has been created for wave simulation in the wave simulation system. For the hydraulic energy storage system, known as the Power Take Off (PTO) system, mathematical models have been developed for double-acting hydraulic cylinders, energy storage devices, and precise displacement hydraulic motors, taking into consideration fluid Reynolds numbers and leakage. During the generation of wave energy, there is a problem of prolonged power interruption when wave conditions are unfavorable, which hinders continuous power generation. To address this issue, a system structure with an energy storage unit and two parallel generator sets, as well as a power operation optimization scheme, have been proposed. This system structure and optimization approach efficiently and reasonably utilize wave energy, achieving the goal of uninterrupted power supply in the hydraulic wave energy generation system.

Strategies for enhancing low-frequency performances of triboelectric, electrochemical, piezoelectric, and dielectric elastomer energy harvesting: recent progress and challenges

Mechanical energy harvesting transforms various forms of mechanical energy, including ocean waves, wind, and human motions, into electrical energy, providing a viable solution to address the depletion of fossil fuels and environmental problems. However, one major obstacle for the direct conversion of mechanical energy into electricity is the low frequency of the majority of mechanical energy sources (≤5 Hz), resulting in low energy conversion efficiency, output power and output current. Over recent years, a numerous innovative technologies have been reported to enable improved energy harvesting utilizing various mechanisms. This review aims to present an in-depth analysis of the research progress in low-frequency energy harvesting technologies that rely on triboelectric, electrochemical, piezoelectric, and dielectric elastomer effects. The discussion commences with an overview of the difficulties associated with low-frequency energy harvesting. The critical aspects that impact the low-frequency performance of mechanical energy harvesters, including working mechanisms, environmental factors, and device compositions, are elucidated, while the advantages and disadvantages of different mechanisms in low-frequency operation are compared and summarized. Moreover, this review expounds on the strategies that can improve the low-frequency energy harvesting performance through the modulations of material compositions, structures, and devices. It also showcases the applications of mechanical energy harvesters in energy harvesting via waves, wind, and human motions. Finally, the recommended choices of mechanical energy harvesters with different mechanisms for various applications are offered, which can assist in the design and fabrication process.

Niche Applications and Flexible Devices for Wave Energy Conversion: A Review

We review wave energy conversion technologies for niche applications, i.e., kilowatt-scale systems that allow for more agile design, faster deployment and easier operation than utility scale systems. The wave energy converters for niche markets analysed in this paper are classified into breakwater-integrated, hybrid, devices for special applications. We show that niche markets are emerging as a very vibrant landscape, with several such technologies having now achieved operational stage, and others undergoing full-scale sea trials. This review also includes flexible devices, which started as niche applications in the 1980s and are now close to commercial maturity. We discuss the strong potential of flexible devices in reducing costs and improving survivability and reliability of wave energy systems. Finally, we show that the use of WECs in niche applications is supporting the development of utility-scale projects by accumulating field experience, demonstrating success stories of grid integration and building confidence for stakeholders.

Integration of a soft dielectric composite into a cantilever beam for mechanical energy harvesting, comparison between capacitive and triboelectric transducers

Flexible dielectrics that harvest mechanical energy via electrostatic effects are excellent candidates as power sources for wearable electronics or autonomous sensors. The integration of a soft dielectric composite (polydimethylsiloxane PDMS-carbon black CB) into two mechanical energy harvesters is here presented. Both are based on a similar cantilever beam but work on different harvesting principles: variable capacitor and triboelectricity. We show that without an external bias the triboelectric beam harvests a net density power of 0.3 [Formula: see text] under a sinusoidal acceleration of 3.9g at 40 Hz. In a variable capacitor configuration, a bias of 0.15 [Formula: see text] is required to get the same energy harvesting performance under the same working conditions. As variable capacitors' harvesting performance are quadratically dependent on the applied bias, increasing the bias allows the system to harvest energy much more efficiently than the triboelectric one. The present results make CB/PDMS composites promising for autonomous portable multifunctional systems and intelligent sensors.