Road energy harvester designed as a macro-power source using the piezoelectric effect

• An energy harvester designed and optimized for a busy roadway.
• Harvester designed to use piezoelectric cantilever beams.
• The natural frequency of the beams tuned by attaching a tip mass.
• Impedance matching conducted to maximize the output power.
• An output power density of 8.19 mW/m2 realized.

While energy harvesting is commonly used for micro-power sources, it could be applied in macro-power sources using a large-scale harvester in a spacious area. We designed and optimized an energy harvester for a busy roadway using piezoelectric cantilever beams. Using the road vibrational frequency under vehicle speeds of 60–80 km/h, we tuned the natural frequency of the beams by attaching a tip mass. Considering the typical vehicle wheel width and the depth of pavement, the designed energy harvester with a volume of 30 × 30 × 10 cm3 contained 48 piezoelectric beams. To optimize the harvester circuit, we rectified the output current from each piezoelectric beam and connected the beams in parallel to avoid phase difference interruptions. Finally, we conducted impedance matching to maximize the output power. As a result, we realized an output power of 736 μW with a power density of 8.19 mW/m2.