Piezoelectric Energy Harvesting

Mohammad Adnan Ilyas

• Publisher: Momentum Press
• Year: 2018
• ISBN:
  9781945612718
• Topic: Technology & Engineering
• Subtopic: Renewable Power Resources
• Index: Technology & Engineering

Environmental pollution has been one of the main challenges for sustainable development. Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy to power devices. The focus is on an alternative approach to scavenge energy from the environment. This book presents harvesting methodologies to evaluate the potential effectiveness of different techniques and provides an overview of the methods and challenges of harvesting energy using piezoelectric materials. Piezoelectric energy harvesters have many applications, including sensor nodes, wireless communication, microelectromechanical systems, handheld devices, and mobile devices. The book also presents a new approach within piezoelectric energy harvesting using the impact of raindrops. The energy-harvesting model presented is further analyzed for single-unit harvester and an array of multiple harvesters to maximize the efficiency of the device.

CHAPTER 1

INTRODUCTION

Governments around the world look for ways to boost economies, with an emphasis on multidisciplinary research and business–academic collaboration. This involves investment that will be focused on science, research, and innovation, with development of a number of priority technologies. The focus for governments and legislators will be on delivering affordable and clean energy growth. The growth in the energy sector is constantly under review to ensure new technologies are developed locally. As an example, the UK government identified smart, flexible, and clean energy technologies as one of the key areas in which to become the global lead by solving the energy challenge of supplying clean, affordable energy securely to ever more-demanding societies around the world.

Over the next few decades, making better use of energy resources will be just as important as finding alternative sources of supply. Development of new technologies becomes more important as the country’s demand for energy keeps growing. Conventional technologies may have high efficiencies in meeting the demand, but have a significant impact on the environment and resources. The use of fossil fuels in conventional technologies is likely to continue for the foreseeable future, but significant progress has been made in decreasing the carbon dioxide emission. The need for novel energy harvesting technologies within the renewable energy sector has become important than ever. Research within the field of energy harvesting has attracted a lot of attention in recent years by scavenging low-grade ambient energy sources, such as environmental vibrations and human power into usable electrical energy. Such devices are, therefore, potentially attractive as replacements for primary batteries in low-power electronics.

This book has been put together for students, researchers, and scientists working in the field of energy harvesting systems. It brings together a review of energy harvesting methods, with a focus on piezoelectric energy harvesting. The book demonstrates the current progress within piezoelectric energy harvesting and challenges faced within the field. This introductory chapter presents the rationale and emphasis of the book.

Chapter 2 lays out the fundamental concept of autonomous energy systems, with a focus on energy harvesting. The chapter further gives a brief overview of various harvesting techniques and technologies widely used ranging from vibrational to photovoltaic.

Chapter 3 introduces the background theory with piezoelectricity and gives the reader an overview of various fabricated or commercially available piezoelectric materials for energy harvesting systems.

Chapter 4 looks at the various techniques and empirically models a piezoelectric energy harvester. It also discusses different circuit topologies and efficiency of such systems. The study of piezoelectric energy harvesting is the focal point of the book.

Chapter 5 introduces a novel technique to harvest energy using raindrop impacts on a piezoelectric device. The chapter gives an in-depth review of publications within the field of raindrop energy harvesting, which only has a handful researchers currently work on this theme.

CHAPTER 2

ENERGY HARVESTING

2.1 CONTEXT

Batteries are in wide use for many devices or systems depending on their functionality, which makes us highly dependent on batteries as the power source to power such devices. Even though batteries have proven to be a good source of power, they have a few weaknesses mainly due to size, weight, safety, and life. Emerging applications like wireless micro-sensor networks [1] and micro electromechanical systems (MEMS) [2] are a couple of examples of such emerging technologies that could integrate energy harvesting technologies to provide power. Replacing batteries in such devices becomes difficult because of the complexity and size. A favorable solution to power-up such devices would be to have a battery-less operation. We can scavenge energy from the environment through energy harvesting concepts to support such battery-less operations.

Many portable or handheld devices, such as MP3 players, hearing aid, and pacemaker, are all operated by batteries. Types of batteries used in such devices vary from lithium-ion batteries to alkaline batteries. In many cases, the battery life is limited to days or months, which is not always ideal. Table 2.1: Power consumption of various battery-operated devices shows the typical power consumption of such devices that generally can be as little as in the µW range [3].

Table 2.1. Power consumption of various battery-operated devices

Device	Power consumption
Smartphone	1W
MP3 player	50mW
Hearing aid	1mW
Wireless sensor node	100µW
Cardiac pacemaker	50µW
Quartz watch	5µW

Energy harvesting is a renewable form of power generation, which has the potential to power handheld devices, implantable medical devices, health monitoring devices, and sensors. Recently, research on energy harvesting has attracted tremendous attention as green energy becomes a hot issue. The challenge is to provide efficient and clean power for micro- to macro-level applications. Solar, vibrational, or thermal energy is the most common source of energy used for harvesting. There are many energy fields available from which to harvest energy:

• Radiation (light, solar, electromagnetic radiation)

• Thermal (temperature gradient)

• Mechanical (potential, kinetic)

• Chemical (battery, fuel cell)

• Nuclear

• Magnetic

• Electric

Benefits of energy harvesting can be summarized as:

• Clean and regenerative source of energy

• Long-lasting operability

• Cost saving

• Flexibility

• Maintenance free

2.2 AUTONOMOUS ENERGY SYSTEMS

An autonomous energy system can be defined as consisting of three stages: generation, conversion, and consumption. The energy generation stage requires an energy harvesting device along with an energy source or storage technology that could be used to accumulate energy in excess from the harvester and provide it to the system in its place whenever energy is sufficient. The energy conversion stage requires power management circuitry and system that trades and optimizes the energy harvested in the energy generation block to the energy consumption stage. Figure 2.1 represents the stages of an autonomous energy harvesting system.

Various approaches of energy harvesting can be made to power various electronic devices with low power consumption. Table 2.2 represents a comparison of harvested power densities using different ambient energy sources as experimentally conducted by various researchers [4, 5, 6].

Figure 2.1. Block diagram for an autonomous energy harvesting system.

Table 2.2. Energy sources with their harvested power density

Source	Harvested power density
Light
Indoor	10µW/cm^2
Outdoor	10mW/cm^2
Vibration/Motion
Human	4µW/cm^2
Industrial	100µW/cm^2
Thermal
Human	25–30µW/cm^2
Industrial	5–10mW/cm^2

A significant amount of research has been devoted to developing and understanding power harvesting systems. The idea to develop portable devices and sensors that rely on regenerative source has put the focus of research in the area of power harvesting. Solar, vibrational, or thermal energy is the most common source of energy used for harvesting. Vibrational energy is available just about everywhere in the urban and industrial environment, but it is often overlooked as a source of power to be scavenged. The vibrational harvesters use one of the three methods: electromagnetic, electrostatic, or piezoelectric to harvest energy. Researchers have been successful in testing such generators and transducers, for converting mechanical energy into electrical energy.

Autonomous electrical devices are increasingly being commercialized due to low-power electronics and energy harvesting. Piezoelectric energy harvesting (PEH) is one of the most promising technologies that can harvest ambient vibration or motion. PEHs are well suited to isolated applications where there are sufficient vibrations, but lack of access to power suppli...

Table of contents

• Cover
• Half-title Page
• Title Page
• Copyright
• Contents
• List of Figures
• List of Tables
• 1 Introduction
• 2 Energy Harvesting
• 3 Piezoelectricity
• 4 Piezoelectric Energy Harvesting Techniques
• 5 Raindrop Energy Harvesting
• 6 Conclusion
• References
• About the Author
• Index
• Other Titles in Our Energy Physics and Engineering Collection
• Backcover