Among novel technologies for producing electricity from renewable resources, a new class of wind energy converters has been conceived under the name of Airborne Wind Energy Systems (AWESs). This new generation of systems employs flying tethered wings or aircraft in order to reach winds blowing at atmosphere layers that are inaccessible by traditional wind turbines. Research on AWESs started in the mid seventies, with a rapid acceleration in the last decade. A number of systems based on radically different concepts have been analyzed and tested. Several prototypes have been developed all over the world and the results from early experiments are becoming available. This paper provides a review of the different technologies that have been conceived to harvest the energy of high-altitude winds, specifically including prototypes developed by universities and companies. A classification of such systems is proposed on the basis of their general layout and architecture. The focus is set on the hardware architecture of systems that have been demonstrated and tested in real scenarios. Promising solutions that are likely to be implemented in the close future are also considered

Dielectric elastomer generators (DEGs) are a class of capacitive solid-state devices that employ highly stretchable dielectrics and conductors to convert mechanical energy into high-voltage direct-current electricity. Their promising performance in terms of convertible energy and power density has been mostly proven in quasi-static experimental tests with prescribed deformation. However, the assessment of their ability in harvesting energy from a dynamic oscillating source of mechanical energy is crucial to demonstrate their effectiveness in practical applications. This paper reports a first demonstration of a DEG system that is able to convert the oscillating energy carried by water waves into electricity. A DEG prototype is built using a commercial polyacrylate film (VHB 4905 by 3M) and an experimental campaign is conducted in a wave-flume facility, i.e. an artificial basin that makes it possible to generate programmed small-scale waves at different frequencies and amplitudes. In resonant conditions, the designed system demonstrates the delivery of a maximum of 0.87 W of electrical power output and 0.64 J energy generated per cycle, with corresponding densities per unit mass of dielectric elastomer of 197 W kg ⁻¹ and 145 J kg ⁻¹ . Additionally, a notable maximum fraction of 18% of the input wave energy is converted into electricity. The presented results provide a promising demonstration of the operation and effectiveness of ocean wave energy converters based on elastic capacitive generators.

This article introduces and describes an electrically powered full-body (FB) exoskeleton, called the body extender (BE), intended as a research platform for the study of the transport and handling of heavy loads up to 50 kg, with one hand at worst-load conditions (WLCs). The machine features a 22-degrees-of-freedom (DoF) quasi-anthropomorphic kinematic scheme and a modular hardware/software architecture that made it possible to manage the complexity of the system design. Besides providing a context and some general guidelines, which have driven the design of the BE, this article presents the hardware and software developments that have been achieved and implemented in the machine. The experimental results are shown that prove the functionalities of the BE in common operating conditions such as walking, squatting, and handling loads. The one-of-a-kind system demonstrates, in relevant laboratory settings, the feasibility of a complex, electrically powered full-body exoskeleton with such a target payload.

Dielectric elastomer generator systems (DEGSs) are a class of electrostatic soft‐transducers capable of converting oscillating mechanical power from different sources into usable electricity. Over the past years, a diversity of DEGSs has been conceived, integrated, and tested featuring diverse topologies and implementation characteristics tailored on different applications. Herein, the recent advances on DEGSs are reviewed and illustrated in terms of design of hardware architectures, power electronics, and control, with reference to the different application targets, including large‐scale systems such as ocean wave energy converters, and small‐scale systems such as human motion or ambient vibration energy harvesters. Finally, challenges and perspectives for the advancement of DEGSs are identified and discussed.

The discovery of an innovative class of thermally activated actuators based on twisted polymeric fibres has opened new horizons toward the development of effective devices that can be easily manufactured using inexpensive materials such as fishing lines or sewing threads. These new devices show large deformations when heated together with promising performance in terms of energy and power densities. With the aim of providing information and data useful for the future engineering applications, we present the results of a thermo-mechanical characterization conducted on a specific type of twisted polymeric fibre (i.e. nylon-made coiled actuators) that is considered particularly promising. A custom experimental test-bench and procedure have been developed and employed to run isothermal and isometric tensile tests on a set of specimens that are fabricated with a simple and repeatable process. The results of the experiments highlight some important issues related to the response of these actuators such as hysteresis, repeatability, predictability and stored elastic energy.

This paper compares the performance of commercially available membranes made of styrenic rubber, natural rubber and acrylic elastomer for dielectric elastomer transducers (DETs) operating in the large strain regime. Following a detailed description of the adopted experimental set-up and procedures, the results of a comprehensive electro-mechanical characterization of the three materials are reported to highlight the following dependencies: dielectric strength versus stretch, electrical conductivity versus electric field, dielectric constant versus stretch, stress versus stretch and strain rate. This includes the fitting of the experimental data with constitutive equations which provide material property values that can be used for model-based analysis, design and control of dielectric elastomer actuators and generators operating at large levels of strain amplitudes (like, for instance, transducers featuring actuation and generator strains over 50%) or in the presence of large pre-strains (over 50%). Performance metrics relying on the identified constitutive parameters are introduced in order to discuss the specific pros and cons of the considered elastomers for the development of practical DETs.