Session: Research Posters

Paper Number: 166125

Miniature Multi-Phase Electrical Generator for Energy Harvesting 

The use of mobile electronics keeps growing, while battery technology has not yet kept pace with portable electronics technology. Such systems comprise a variety of technologies, from powering low-power electronics in structural health monitoring and tracking of goods or animals to biomedical applications and smart devices. As a result, regular battery replacement or battery charging has become ingrained in daily activities. However, servicing batteries might not be possible for some applications. Hence, power generation for portable electronics presents a challenge. Portable power sources have had a constant tradeoff between device capabilities, physical volume, and energy capacity for the intended final application. One such example is the cardiac pacemaker, where a relatively large battery is incorporated in a design that lasts for years. 

Energy harvesting can ease this problem since it can harness energy from the surroundings to complement or even replace batteries for some applications, such as solar-powered calculators or self-winding wristwatches. Energy can be extracted primarily from motion, photovoltaics, wind, and thermal gradients. Kinetic energy is an attractive option where solar cells or thermoelectric generators have limited use. Electromagnetic, piezoelectric, or electrostatic generation comprise the main transduction techniques in use. Traditional electromagnetic generators use a combination of a stator and a rotor with multiple coils and permanent magnet configurations for single-phase energy generation systems. The single-phase generator produces a non-constant power output. Three-phase generation systems create a more uniform power output, increasing the efficiency of the energy conversion. This paper reports on a miniature three-phase axial flux electromagnetic generator combining photolithographic techniques for stator manufacturing and additive manufacturing for the fabrication of the rotor.

The stator has copper windings and is manufactured by stacking several layers. This is done by having two layers per phase, for six layers comprising three phases, and manufactured by photolithography with 200 µm linewidth. Each layer was fabricated on flexible copper-clad polyimide, 18 µm thick copper, and 25 µm thick polyimide layers, containing eight coils. Two layers per phase helped minimize the interconnects between the top and bottom layers by having wave windings rather than individual coils per magnet pair. Using stereolithography additive manufacturing, a 30 mm rotor was manufactured to encase sixteen neodymium magnets (6 mm x 3 mm x 2 mm) for a total of eight pole pairs in a single permanent magnet disc. The setup was then mounted on an experimental testing platform with up to 20,000 RPM to evaluate induced voltage for energy generation at a constant speed. The generator was tested for performance evaluation at 20%, 30%, 40%, 50%, and 100% of the maximum speed (open circuit).  The windings were placed 0.5 mm from the rotor surface, and the system produced up to 10.2 V at maximum speed for the three-phase design during the preliminary setup. This shows the potential of developing miniature three-phase electrical generators for power generation on portable generators that can be integrated into rotational electrical generators.

Presenting Author: Brandon Harkhu Florida Polytechnic University

Presenting Author Biography: Brandon Harkhu is a graduate student at Florida Polytechnic University.

Authors:

Brandon Harkhu Florida Polytechnic University
Edwar Romero Florida Polytechnic University
Walter Ward Florida Polytechnic University
Gerardo Carbajal Florida Polytechnic University
Christos Tsetsekas Florida Polytechnic University
Alejandro Rolan Blanco Technical University of Catalonia