Self-sensing for robust automatic charge management of dielectric elastomer generators

Dielectric elastomer generators (DEGs) produce electrical energy by converting mechanical into electrical energy. Efficient operation requires an optimal deformation of the DEG during the energy harvesting cycle. However, the deformation resulting from an external load has to be applied to the DEG. The deformation behavior of the DEG is dependent on the type of the mechanical interconnection between the elastic DEG and a stiff support area. The maximization of the capacitance of the DEG in the deformed state leads to the maximum absolute energy gain. Therefore several configurations of mechanical interconnections between a single DEG module as well as multiple stacked DEG modules and stiff supports are investigated in order to find the optimal mechanical interconnection. The investigation is done with numerical simulations using the FEM software ANSYS. A DEG module consists of 50 active dielectric layers with a single layer thickness of 50 μm. The elastomer material is silicone (PDMS) while the compliant electrodes are made of graphite powder. In the simulation the real material parameters of the PDMS and the graphite electrodes are included to compare simulation results to experimental investigations in the future. The numerical simulations of the several configurations are carried out as coupled electro-mechanical simulation for the first step in an energy harvesting cycle with constant external load strain. The simulation results are discussed and an optimal mechanical interconnection between DEG modules and stiff supports is derived.

Dielectric elastomer generators (DEG) produce electrical energy by converting mechanical into electrical energy. Efficient operation requires homogeneous deformation of each single layer. However, by different internal and external influences like supports or the shape of a DEG the deformation will be inhomogeneous and hence negatively affect the amount of the generated electrical energy. Optimization of the deformation behavior leads to improved efficiency of the DEG and consequently to higher energy gain. In this work a numerical simulation model of a multilayer dielectric elastomer generator is developed using the FEM software ANSYS. The analyzed multilayer DEG consists of 49 active dielectric layers with layer thicknesses of 50 μm. The elastomer is silicone (PDMS) while the compliant electrodes are made of graphite powder. In the simulation the real material parameters of the PDMS and the graphite electrodes need to be included. Therefore, the mechanical and electrical material parameters of the PDMS are determined by experimental investigations of test samples while the electrode parameters are determined by numerical simulations of test samples. The numerical simulation of the DEG is carried out as coupled electro-mechanical simulation for the constant voltage energy harvesting cycle. Finally, the derived numerical simulation model is validated by comparison with analytical calculations and further simulated DEG configurations. The comparison of the determined results show good accordance with regard to the deformation of the DEG. Based on the validated model it is now possible to optimize the DEG layout for improved deformation behavior with further simulations.

Dielectric Elastomers (DEs) are a very promising technology for the development of energy harvesting devices based on the variable-capacitance electrostatic generator principle. As compared to other technologies, DE Generators (DEGs) are solid-state energy conversion systems which potentially feature: 1) large energy densities, 2) good energy conversion efficiency that is rather independent of cycle frequency, 3) easiness of manufacturing and assembling, 4) high shock resistance, 5) silent operation, 6) low cost. Envisioned applications for DEGs are in devices that convert ocean wave energy into usable electricity. This paper introduces the Lozenge-Shaped DEG (LS-DEG) that is a specific type of planar DE transducer with one degree of freedom. A LS-DEG consists of a planar DE membrane that is connected along its perimeter to the links of a parallelogram four-bar mechanism. As the mechanism is put into reciprocal motion, the DE membrane varies its capacitance that is then employed as a charge pump to convert external mechanical work into usable electricity. Specifically, this paper describes the functioning principle of LS-DEGs, and provides a comparison between different hyper-elastic models that can be used to predict the energy harvesting performances of realistic prototypes. Case studies are presented which address the constrained optimization of LS-DEGs subjected to failure criteria and practical design constraints.

In this letter, a theoretical framework describing an energy harvesting cycle including the loss of tension (LT) process is proposed to investigate the energy harvesting performance of a dielectric elastomer generator (DEG) with a triangular energy harvesting scheme by considering material viscosity and leakage current. As the external force that is applied to the membrane decreases, the membrane is relaxed. When the external force decreases to zero, the condition is known as LT. Then the membrane undergoing LT can further relax, which is referred to as the LT process. The LT process is usually ignored in theoretical analysis but observed from energy harvesting experiments of DEGs. It is also studied how shrinking time and transfer capacitor affect the energy conversion of a DEG. The results indicate that energy density and conversion efficiency can be simultaneously improved by choosing appropriate shrinking time and transfer capacitor to optimize the energy harvesting cycle. The results and methods are expected to provide guidelines for the optimal design and assessment of DEGs.

Dielectric elastomer generators (DEGs) provide a new solution for vibrational energy harvesting. Currently, a type of impact-based DEGs, which can harvest energy from ambient vibrations, has been proposed and studied through simulations. However, the energy conversion mechanism and the performance evaluation approach of such impact-based DEGs have not been fully studied yet, thus limiting the reliability of the research on the system design/optimization and performance evaluation. In this paper, a single-sided impact (SSI) model is proposed to reveal the impact-based energy conversion mechanism. Based on this model, a complete four-stage impact process is analyzed to reveal the energy conversion mechanism, and the electrical outputs and energy conversion efficiency are derived as the energy harvesting performance evaluation indexes. To use the developed analytical model to predict the system electrical response accurately, some important parameters including the coefficient of restitution (COR) and largest deflection of the membrane at impacts were obtained experimentally, and the system output voltages at impacts were measured to verify the theoretical approaches in calculating the system electrical outputs and studying the parameters' influences. Furthermore, the influences of the pre-stretched ratio, impact velocity, and input voltage on the system energy harvesting performance are studied through simulations. The research results can provide guidelines to improve the energy harvesting performance of the impact-based DEGs in real applications.

The dielectric elastomer generator (DEG) has attracted significant attention in the past decade for harvesting energy from reciprocating mechanical motion owing to its variable capacitance under tension. However, the challenge of conceiving novel DEGs with high energy harvesting performance should be addressed. In this work, azobenzene molecules with strong polarity were synthesized and chemically grafted onto a hydroxyl-terminated polydimethylsiloxane (PDMS) network through a simple one-step process, offering a robust, molecularly homogenous silicone rubber. In addition, dimethyl silicone oil (DMSO) plasticizer was simultaneously added to reduce the mechanical modulus of the composite. The loading content of DMSO was firstly optimized in terms of the mechanical and dielectric properties of the resultant azo-g-PDMS/DMSO elastomers. Then, the effects of azobenzene loading on the morphology, and mechanical, dielectric and electric generation performances were thoroughly investigated. Overall, the dielectric permittivity displayed a rising trend with the increase of the azobenzene content while the breakdown strength increased initially and then decreased. The breakdown strength could reach as high as 73 V μm−1 by grafting with 7 phr of azobenzene while maintaining a relatively low mechanical modulus. Meanwhile, the as-prepared azo-g-PDMS/DMSO films exhibited enhanced energy harvesting density (0.69 mJ cm−3) and electromechanical conversion efficiency (5.01%) at a bias voltage of 1500 V, which were 2 and 2.5 times as much as those of the azobenzene-free matrix. This work provides ideas for future applications of DEG with high energy harvesting performance.

The purpose of this project is to develop a generator called a Galloping Hydroelectric Energy Extraction Device (GHEED). It uses a galloping prism to convert water flow into linear motion. This motion is converted into electricity via a dielectric elastomer generator (DEG). The galloping mechanism and the DEG are combined to create a system to effectively generate electricity. This project has three research objectives: 1. Oscillator development and design a. Characterize galloping behavior, evaluate control surface shape change on oscillator performance and demonstrate shape change with water flow change. 2. Dielectric Energy Generator (DEG) characterization and modeling a. Characterize and model the performance of the DEG based on oscillator design 3. Galloping Hydroelectric Energy Extraction Device (GHEED) system modeling and integration a. Create numerical models for construction of a system performance model and define operating capabilities for this approach Accomplishing these three objectives will result in the creation of a model that can be used to fully define the operating parameters and performance capabilities of a generator based on the GHEED design. This information will be used in the next phase of product development, the creation of an integrated laboratory scale generator to confirm model predictions.

As a new transduction technology, dielectric elastomer generators (DEGs) are capable of converting mechanical energy from diverse sources into electrical energy. However, their energy harvesting performance is strongly affected by the material viscoelasticity. Based on the finite-deformation viscoelasticity theory and the nonlinear coupled field theory for dielectric elastomers, this work presents a theoretical framework to model the performance of DEGs. Motivated by the recent experiments of DEGs with a triangular harvesting scheme, we propose a method to optimize the harvesting cycle, which could significantly improve the conversion efficiency of viscoelastic DEGs. From our simulation results, choosing a higher voltage power source appears to be an effective way to improve the performance of DEGs. In addition, optimizing the period of the discharging process of DEG can markedly increase its efficiency. Also, we have uncovered that the triangular harvesting scheme for DEGs, which is expected to harvest energy close to the maximum achievable energy, could be actually realized by choosing dielectric elastomers with a higher fraction of time-independent polymer networks. The theoretical framework and simulation results presented in this work are expected to benefit the optimal design of DEGs for different applications.

Optimizing energy harvesting performance of cone dielectric elastomer generator based on VHB elastomer

Nonlinear dynamics and chaos control of circular dielectric energy generator

Dielectric elastomer generators (DEGs) offer a means of converting mechanical energy from low-frequency (<1 Hz) reciprocating motion-such as ocean waves-into electricity for low-power sensors. However, current DEG materials exhibit low intrinsic power density. Conventional high-voltage power electronics (HVPE) solutions, such as dual active bridge (DAB) or modular multilevel converters (MMCs), are unsuitable due to their high housekeeping power requirements. This work proposes a compact, low-loss energy harvesting converter tailored for small-scale DEG applications. It integrates a self-priming circuit (SPC) and a single-switch step-down stage. A mathematical model and SPICE simulation of the DEG-SPC system are developed and validated, including a derived expression for the optimal capacitance ratio between the SPC and the DEG. A prototype is built to demonstrate the circuit's functionality.

Energy harvesting from a novel contact-type dielectric elastomer generator

Automating LC–MS/MS mass chromatogram quantification: Wavelet transform based peak detection and automated estimation of peak boundaries and signal-to-noise ratio using signal processing methods.

Dielectric Elastomer Generators (DEGs) are an emerging energy harvesting technology based on a the cyclic stretching of a rubber-like membrane. However, most design processes do not take into account different excitation frequencies; thus limits the applicability studies since in real-world situations forcing frequency is not often constant. Through the use of a practical design scenario we use modeling and simulation to determine the material frequency response and, hence, carefully investigate the excitation frequencies that maximize the performance (power output, efficiency) of DEGs and the factors that influence it.

Dielectric elastomer energy harvesters are an emerging technology that promise high power density, low cost, scalability, and the capability of fitting niche markets that have yet to be exploited. To date, materials issues that limit their overall performance have hampered the full potential of these devices. In order to supplant existing technologies, even in niche markets, dielectric elastomer generators must increase their reliability and energy density. Previous work has indicated that stiffer elastomers should be capable of higher energy densities; the increased stiffness of the elastomer films should results in lower Maxwell pressure induced strains, and thus allow the elastomer to relax further, resulting in a larger swing in capacitance and larger energy gains. In this paper we examine the use of VHB-based acrylic interpenetrating polymer network dielectric elastomers with a trimethylolpropane trimethacrylate additive network for energy harvesting purposes. We test films with varying additive content and compare their performance with highly prestrained VHB acrylic elastomers. We show that by increasing additive content, Maxwell induced strains can be suppressed and larger energy gains can be achieved at higher bias fields. Moreover, the introduction of the additive network stabilizes the highly prestrained acrylic elastomers mechanically, thereby increasing their mechanical robustness. However, the interpenetrating polymer network films suffer from an increase in viscoelastic behavior that hinders their overall performance.