High-Performance Piezoelectric Energy Harvesters and Their Applications

With the rapid advances in wireless sensors, implantable electronics, and wearable devices, the demand for high-power-density and long-lifespan power sources is becoming increasingly stronger. Energy harvesting, emerging as an alternative energy solution to batteries, holds great potential to achieve self-powered autonomous operations of such low-power electronic devices, and thus has recently attracted much attention from both academia and industry. The piezoelectric effect is widely adopted to convert mechanical energy to electrical energy, due to its high energy conversion efficiency, ease of implementation, and miniaturization. This paper presents a comprehensive and critical review of state-of-the-art research on piezoelectric energy harvesting. From the viewpoint of applications, we are most concerned about whether an energy harvester can generate sufficient power under variable excitation. Therefore, here we concentrate on methodologies leading to high power output and broad operational bandwidth. A variety of designs, nonlinear methods, optimization techniques, and harvesting materials are reviewed and discussed in depth. The study also evaluates different figures of merit and presents a systematic performance comparison on recently proposed energy harvesters. Furthermore, we identify four promising applications: shoes, artificial pacemakers, tire pressure monitoring systems, and bridge and building monitoring. The excitation characteristics of each application are analyzed and corresponding harvesting methods discussed. The piezoelectric energy-harvesting technology has experienced significant progress in the past 10 years. However, research on energy harvesters is mostly conducted without specific applications, and reliability and system integration have not been well examined. More research is expected to deal with these issues to facilitate in turning decades of research efforts on energy harvesting into tangible benefits in our daily life. Energy harvesting holds great potential to achieve long-lifespan self-powered operations of wireless sensor networks, wearable devices, and medical implants, and thus has attracted substantial interest from both academia and industry. This paper presents a comprehensive review of piezoelectric energy-harvesting techniques developed in the last decade. The piezoelectric effect has been widely adopted to convert mechanical energy to electricity, due to its high energy conversion efficiency, ease of implementation, and miniaturization. From the viewpoint of applications, we are most concerned about whether an energy harvester can generate sufficient power under a variable excitation. Therefore, here we concentrate on methodologies leading to high power output and broad operational bandwidth. Different designs, nonlinear methods, optimization techniques, and harvesting materials are reviewed and discussed in depth. Furthermore, we identify four promising applications: shoes, pacemakers, tire pressure monitoring systems, and bridge and building monitoring. We review new high-performance energy harvesters proposed for each application. Energy harvesting holds great potential to achieve long-lifespan self-powered operations of wireless sensor networks, wearable devices, and medical implants, and thus has attracted substantial interest from both academia and industry. This paper presents a comprehensive review of piezoelectric energy-harvesting techniques developed in the last decade. The piezoelectric effect has been widely adopted to convert mechanical energy to electricity, due to its high energy conversion efficiency, ease of implementation, and miniaturization. From the viewpoint of applications, we are most concerned about whether an energy harvester can generate sufficient power under a variable excitation. Therefore, here we concentrate on methodologies leading to high power output and broad operational bandwidth. Different designs, nonlinear methods, optimization techniques, and harvesting materials are reviewed and discussed in depth. Furthermore, we identify four promising applications: shoes, pacemakers, tire pressure monitoring systems, and bridge and building monitoring. We review new high-performance energy harvesters proposed for each application.