This paper presents the concept design, preliminary experimental validation, and performance evaluation of a novel bio-inspired bi-stable piezoelectric energy harvester for self-powered fish telemetry tags. The self-powered fish tag is designed to externally deploy on fish (dorsal fin) to track and monitor fish habitats, population, and underwater environment, meanwhile, harvests energy from fish motion and surrounding fluid flow for a sustainable power supply. Inspired by the rapid shape transition of the Venus flytrap, a bi-stable piezoelectric energy harvester is developed to generate electricity from broadband excitation of fish maneuvering and fluid. A bluff body is integrated to the free end of the bistable piezoelectric energy harvester to enhance the structure-fluid interaction for the large-amplitude snap-through vibrations and higher voltage output. Controlled laboratory experiments are conducted in a water tank on the bio-inspired bi-stable piezoelectric energy harvester using a servo motor system to simulate fish swing motion at various conditions to evaluate the power generation performance. The preliminary underwater experimental results demonstrated that the proposed bio-inspired bi-stable piezoelectric effectively converters fish swing motions into electricity. The average power output of 1.5 mW was achieved at the swing angle of 30° and frequency of 1.6 Hz.
In vibration energy harvesting systems, mechanical damping is reduced to minimum to get large electrical power output. However, small mechanical damping will result in a narrow bandwidth in the frequency domain. This will lead to non-ideal performance when the excitation frequency does not match with the natural frequency. In human body energy harvesting backpack, the human comfort will also have to take into consideration besides harvesting power. In this paper, we proposed an electrical damping tuning method for energy harvesting backpack. The electrical damping will change according to the excitation frequency to achieve high power output at lower frequency. In this way, the frequency bandwidth increases. At resonance and high frequency, the damping will be tuned to control the maximum stroke of the backpack. This will make the wearer feel comfortable while substantial power is harvested. The electrical damping tuning circuit senses the input frequency and tunes the electrical damping accordingly. The circuit design and the control strategy are described in detail. Experiment will be done to validate the design goals.
During trips and outdoor adventures, there are a lot of electric equipment and thus power supply for those devices is critical. At the same time, the burden on shoulders from heavy baggage is substantial. This paper presents a one-way energy harvesting backpack with ball-screw mechanism to generate electricity with high efficiency and reliability, while relieves the burden on shoulders. The one-way energy harvesting method only harvests negative work from human body and potentially reduce metabolic cost while carrying backpack. Simulations show that 4.5W of electrical energy can be obtained from human walking. Bench test results indicate this system can obtain an average power of 7.3 W with excitation of 2Hz and 25mm direct drive. Treadmill test to verify the performance of burden relieve on shoulders indicates this one-way design combing with elastic support strap can reduce the force on shoulders, which reduce fatigue in human.
In this short paper, we report a design of an energy harvesting backpack with a mechanical motion rectifier (MMR). Also, we report the experiment studies conducted on two male subjects who carry two types of energy harvesting backpacks, including the MMR-based and traditional energy harvesting backpack, while walking on a treadmill at 3 and 3.5 mph. The harvested power of the backpacks shunted with different resistors are reported with each walking speed to demonstrate the high efficiency of the MMR-based backpack harvester. During the tests, the MMR-based backpack harvest generated more power regardless of walking speeds and resistor values. Finally, a maximum average power of 4.8 Watts and instant power of 12.8 Watts were obtained by one subject, carrying the MMR-based backpack harvester and walking at 3.5 mph.
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