INNOVATION AND COMPUTATIONAL MODELING OF SMALL-SCALE ENERGY HARVESTING WITH ELECTROMAGNETIC INDUCTION WHILE CONVERTING ROTATIONAL INPUT TO LINEAR MOTION WITH A CRANK-SLIDER MECHANISM

Abstract

Ambient power sources such as wind and vibrations are resources harvested to provide clean and renewable energy to offset the use of fossil fuels. Experimental energy harvesting from fluid flow, specifically from airflow, is typically restricted to rotational movement combined with a rotor and stator design or a model that periodically strikes a piezoelectric. Alternatively, energy harvesting from mechanical vibrations routinely uses the linear motion of a magnet passing through a coil or vibrating piezoelectric elements. Although wind harvesting is typically relegated to large-scale production, significant research has gone into creating innovative small-scale wind harvesters. The viability of these harvesting mechanisms, both wind and vibration, are highly dependent upon their power density, which is determined by the amount of voltage generated per device or per volume. Utilizing such an approach, we have designed, developed, and extensively tested rotational to linear harvesting which utilizes a crank-slider mechanism. Our study includes computational modeling utilizing COMSOL, established kinematic and transduction formulas as a method to provide theoretical predictions of the design and validation of our final output. Furthermore, our research highlights the advantages over alternative designs, demonstrating the more consistent and higher average voltage output, lower wind speed operation, and ability to increase output by easily incrementing the number of dynamo cylinders without expanding the overall footprint. At 0.5 Hz, a single crank-slider generated a voltage of 0.176 Vpp with an output power of 0.147 mW, whereas the reference harvester generated 0.14 mW at 1.0 Hz with a 0.432 Vpp. A single crank-slider operating at regulated frequencies of 0.5, 1, 2, and 3 Hz, with a stroke length of 50 mm generated continuous power of 0.147, 0.452, 2.00, and 4.48 mW, respectively. When joining two crank-sliders into the V-Twin formation, we found that under ambient wind speeds of 3.4 and 4.1 m/s, with the optimized configuration, in which the coils and loads were both connected in series, the device generated 27.0 and 42.2 mW, respectively. The multicylinder design incorporates six crank-slider mechanisms into a low profile harvester by modifying the crank portion. This allows the device to output higher power while operating at lower wind speeds. Furthermore, this device included a rectifier to convert from AC to DC, a capacitor to clean the output signal, a 5 V regulator, and a smaller diameter copper wire that allowed for more turns in each coil. Under a regulated low wind speed of 2.4 m/s and across a 305 ohm load, the device had a rotational frequency of 0.76 Hz and a power output of 1.2 mW. At a regulated wind speed of 4.9 m/s the rotational frequency was 7.25 Hz and the output 421.9 mW. Additional tests were performed under real world conditions. First, at a rotational frequency of 6 Hz the device was used to charge a 3.7 V 46 mAh smart watch and a 10,000 mAh 10.5 W power bank charger. The smart watch took approximately 1.4 minutes to charge 1% and the power bank took 1.1 hours. A second real word test was done by placing the device outside in uncontrolled windy conditions. In one scenario, at an average wind speed of 2.39 m/s, the harvester was able to charge the smart watch 1% in approximately 1 hour. The second scenario used a 305 ohm load in wind speeds reaching 10.1 m/s at which point the harvesters output peaked at 1.21 W resulting in a power density of 19.98 W/m3.