Contents


Preface

The use of energy can be traced back to humans (species of the genus *Homo*) starting about two million years ago when they started cooking their food using firewood. Cooking had a profound evolutionary effect because it increased food efficiency, which allowed humans to spend less time foraging, chewing, and digesting. Modern anthropologists argue that *Homo erectus* developed a smaller, more efficient digestive tract, which freed up body energy to enable larger brain growth. Extended arguments reveal that cooking and control of fire generally affected species development by providing warmth and helping to fend off predators, which helped human ancestors adapt to a ground-based lifestyle. As humans developed new skills with increased activities, energy interaction and usage emerged. Energy was used not only for domestic functions but also for space applications. With industrialization, humans realized that energy was needed to move machines and do other things as well. In this quest, and without understanding the consequences of using fossil fuels extensively, many problems arose. Researchers in energy embarked on a journey to try to solve some of the problems by studying different forms of renewable energy. To understand different needs, researchers have tried to come up with ways in which small-scale energy harvesting can be adapted to different needs that do not require heavy-duty energy production. Technological advancements point directly to this quest where some gadgets have been miniatur-

ized and others developed to help humans live better lives.

that may be helpful in improving the quality of life.

chapter.

This book attempts to present a number of ideas regarding a few selected smallscale energy harvesting methods and techniques as well as theories and products

Chapter 1 outlines the potential of perovskite solar cells (PSCs) as a promising form of new solar cell for power generation due to their simple processing, abundance of materials, and architectural integration, as well as good power conversion efficiencies, which rocketed from 3.8% in 2009 to 23.3% in 2018. It is pointed out in the chapter that the toxic lead (Pb) element containing the chemical composition of typically used organic–inorganic halide perovskites hinders the practical applications of PSCs. The chapter, however, gives a general discussion on perovskite crystal structure along with serious efforts focused on Pb replacement in these devices. Elaborate fundamental features of tin (Sn)-based perovskites together with their performance in PSCs is then presented, and alternative elements, such as copper (Cu), germanium (Ge), bismuth (Bi), and antimony (Sb), are outlined. Last but not least in the chapter is a summary of the challenges and opportunities based on the

In Chapter 2, thermoelectric energy generation of electrical power from temperature gradients or differences in naturally occurring geothermal heat and rocks, or from waste heat in man-made equipment and industrial processes, are discussed. Their commercial applications to replace or recharge batteries in low-power electronic systems are presented. The fundamental thermoelectric theory related to power generation, including the theoretical analysis and numerical calculations required to calculate the thermoelectric efficiency and electrical power generated
