Energy harvesting technologies have been explored by researchers for more than two decades as an alternative to conventional power sources (e.g. batteries) for small-sized and low-power electronic devices. The limited life-time and necessity for periodic recharging or replacement of batteries has been a consistent issue in portable, remote, and implantable devices. Ambient energy can usually be found in the form of solar energy, thermal energy, and vibration energy. Amongst these energy sources, vibration energy presents a persistent presence in nature and manmade structures. Various materials and transduction mechanisms have the ability to convert vibratory energy to useful electrical energy, such as piezoelectric, electromagnetic, and electrostatic generators. Piezoelectric transducers, with their inherent electromechanical coupling and high power density compared to electromagnetic and electrostatic transducers, have been widely explored to generate power from vibration energy sources. A topical review of piezoelectric energy harvesting methods was carried out and published in this journal by the authors in 2007. Since 2007, countless researchers have introduced novel materials, transduction mechanisms, electrical circuits, and analytical models to improve various aspects of piezoelectric energy harvesting devices. Additionally, many researchers have also reported novel applications of piezoelectric energy harvesting technology in the past decade. While the body of literature in the field of piezoelectric energy harvesting has grown significantly since 2007, this paper presents an update to the authors' previous review paper by summarizing the notable developments in the field of piezoelectric energy harvesting through the past decade.

https://iopscience.iop.org/article/10.1088/1361-665X/ab36e4/pdf

A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008–2018)

Review of wearable thermoelectric energy harvesting: From body temperature to electronic systems

The need for energy-efficient and environmentally friendly refrigeration, heat pumping, air conditioning, and thermal energy harvesting systems is currently more urgent than ever. Magnetocaloric energy conversion is among the best available alternatives for achieving these technological goals and has been the subject of substantial basic and applied research over the last two decades. The subject is strongly interdisciplinary, requiring proper understanding and efficient integration of knowledge in different specialized fields. This review article presents a historical and up-to-date account of the energy-related applications of magnetocaloric materials and information about their processing and magnetic fields, thermodynamics, heat transfer, and other relevant characteristics. The article also discusses the conceptual design of magnetocaloric refrigeration and power generation systems and some guidelines for future research in the field.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/aenm.201903741

Energy Applications of Magnetocaloric Materials

Condition monitoring can reduce machine breakdown losses, increase productivity and operation safety, and therefore deliver significant benefits to many industries. The emergence of wireless sensor networks (WSNs) with smart processing ability play an ever-growing role in online condition monitoring of machines. WSNs are cost-effective networking systems for machine condition monitoring. It avoids cable usage and eases system deployment in industry, which leads to significant savings. Powering the nodes is one of the major challenges for a true WSN system, especially when positioned at inaccessible or dangerous locations and in harsh environments. Promising energy harvesting technologies have attracted the attention of engineers because they convert microwatt or milliwatt level power from the environment to implement maintenance-free machine condition monitoring systems with WSNs. The motivation of this review is to investigate the energy sources, stimulate the application of energy harvesting based WSNs, and evaluate the improvement of energy harvesting systems for mechanical condition monitoring. This paper overviews the principles of a number of energy harvesting technologies applicable to industrial machines by investigating the power consumption of WSNs and the potential energy sources in mechanical systems. Many models or prototypes with different features are reviewed, especially in the mechanical field. Energy harvesting technologies are evaluated for further development according to the comparison of their advantages and disadvantages. Finally, a discussion of the challenges and potential future research of energy harvesting systems powering WSNs for machine condition monitoring is made.

Energy Harvesting Technologies for Achieving Self-Powered Wireless Sensor Networks in Machine Condition Monitoring: A Review.

Review of thermoelectric geometry and structure optimization for performance enhancement

Studies concerning the use of thermoelectric effect for the conversion of thermal energy into electricity have become increasingly numerous since applications of the thermoelectric phenomenon can be limitless. Thermoelectric Generators (TEG) have shown promising results in combustion vehicles, with an overall efficiency increment from 33% to 57%, in addition to an increase of 6% in the available power in an automobile. In the aerospace industry, thermoelectric devices have been employed due to the need of making the most of the available energy. Thermoelectric modules are also used in the harvest of waste heat in wood stoves, furnace walls, and industrial chimneys. In Bioengineering, there are applications for small-scale generation including the use of heat from the human body to feed microelectronic devices and autonomous sensors. Therefore, the article shows a review of the use of thermoelectricity for the energy harvesting, beginning with the main concepts and definitions on the subject, followed by the state of the art containing the main methods and advances in science and technology for the development and application of solid-state micro-generators to capture residual energies.

A review of the development and applications of thermoelectric microgenerators for energy harvesting

The conversion of residual thermal energy into electricity using TEGs (Thermoelectric Generators) arises as a promising technological alternative for increasing energy efficiency and power generation. In order to optimize the performance of TEGs, it is known that the maximum output power is obtained by matching the impedances between the TEG and the connected load. Therefore, the objective of this work is to present the development of a numerical and a simplified analytical model to determine the internal resistance (Rint) and predict the open circuit voltage, charge voltage, current and power values of TEGs. The models have used as reference the thermoelectric module TEHP 1263-1.5 (Thermonamic), with the analytical one being based on the classical theory of electrical circuit analysis and, for the numerical one, a three-dimensional geometric model was developed and the set of equations were solved in the COMSOL Multiphysics® tool by the finite element method. The Rint obtained by the analytical and numerical models were, respectively, 3.157 Ω and 6.027 Ω, and the value supplied by the supplier is 3.154 Ω. Therefore, the analytical model is indicated as a reference to estimate Rint of the TEG, allowing optimizing its use by choosing the load resistance that will result in the maximum power.

Analytical and Numerical Study for the Determination of a Thermoelectric Generator’s Internal Resistance

The article presents the results of research that aims at training and consolidation of knowledge and their use for thermoelectric energy harvesting. Therefore, we present a numerical modeling for design and dimensioning of micro electric power generating sources, from theoretical performance curves of thermoelectric modules and temperature gradients for future applications in industrial processes. The final result appears very attractive, since the developed experimental analysis shows promising results, given that many processes generate energy harvesting and, in addition, the cogeneration of power using thermoelectric modules is totally clean, which prevents the emission of gaseous pollute to the environment.

Anderson Luis Oliveira Maran

Papers

A review of the development and applications of thermoelectric microgenerators for energy harvesting

Analytical and Numerical Study for the Determination of a Thermoelectric Generator’s Internal Resistance

Use of the Seebeck Effect for Energy Harvesting