Intellectual Merit: Wind energy presents a renewable, widely distributed, abundant source of clean energy that has been largely untapped due to the high installation cost, environmental impact, and intermittency of the blade-turbine generators. The recent advances in dielectric elastomers provides a unique opportunity to design a new category of wind electricity generators wherein the active transducing material absorbs wind energy and converts it directly into electricity. These electroactive polymers can undergo large deformation and store a large quantity of elastic energy that is transduced into electricity as the deformed polymers relax. The objective of the proposed research is to study the aerodynamics associated with the large deformations in dielectric elastomer films and the corresponding generation of electricity. The PIs will 1) model and experimentally analyze the deformation and energy transduction mechanisms in dielectric elastomer generators (DEGs), 2) use highly accurate numerical simulation to model the aerodynamics of wind-membrane interaction and use the simulated deformation of soft membranes to calculate the maximum wind energy absorption and power generation density in the membrane, 3) design and fabricated DEGs in the form factor of a flag based on the aerodynamic simulation and the material's electro-mechanical characteristics, 4) experimentally measure the generated power at various wind velocities and correlate the results with the simulations and calculations, and 5) synthesize new dielectric elastomers according to the aerodynamic requirements. The research will result in the essential understanding of the wind energy harvesting cycle and methodologies required to efficiently capture and transduce wind energy using dielectric elastomers. Broader Impact: The research will create a radically a new wind energy generator with an attractive and flexible form factor, potentially high conversion efficiency, low-cost fabrication, and scale invariability. The results should benefit other dielectric elastomer applications in such important areas as biomedical devices, robotics, industrial automation, and consumer electronics. The research findings will be disseminated to the public through scientific and patent publications, conference presentations, and education of undergraduate and graduate students. Graduate and undergraduate students will participate in the proposed research and learn techniques ranging from synthesis and characterization of new materials to creating devices and measuring physical properties. As part of our commitment to promote diversity, we plan to particularly encourage junior and senior undergraduate women and minorities to carry out intern research, especially those who show interest in pursuing an academic teaching or research career. We will collaborate with the California NanoSystems Institute at UCLA to host high school students from the Los Angeles Unified School District for 8-week summer intern research in the PI's lab.
We Investigated various materials strategies to increase the energy harvesting capability of dielectric elastomers. These include the use of nanofillers to increase the dielectric constant, synthesis of new dielectric elastomer based on two interpenetrating silicone elastomer networks. The new material exhibits high actuation performance without the need for prestrain. The peak calculated energy density is estimated to be as much as 0.6 J/g, which is significantly higher than previously reported record, and makes the polymers an attractive material for harvesting renewable energy from mechanical sources such as wind and wave. Novel designs for a DE wave energy harvester have been carried out. The wave energy harvesting concept consists of a simple tube design where the tube is partially submerged in water with a DE stack at the open end. As waves pass by they generate a pressure differential between the inside and outside of the tube causing the DE stack to deform. Initial analysis shows that a 2 m wide device should be capable of producing 0.618 kW of power assuming an average wave height of 3 m and a wave period of 10 s. We have applied our new high-order cut-cell method to study fluid flow over solid surface with arbitrary roughness elements and obstacles. We have also validated the numerical results by comparing with linear wave theory for the flow interaction with a hollow cylinder with a flexible membrane. Our computational study has confirmed the effectiveness of ocean waves for energy harvesting. 6 graduate students and 4 undergraduate students, 1 visiting graduate student (University of Michigan), and 4 high school student interns participated in the multidisciplinary project, received education and developed research skills with the project. Made presentations and live demonstrations of dielectric elastomer transducers to a total of about 200 high school students and parents during the department open house.