This book introduces the main waste heat sources that come from the industrial, electric, commercial, residential and transportation sectors of society. The wide applications of waste heat through heat pumps are then detailed, mainly including gas heating, hot water production, and steam production (for sterilization, distillation, rectification, etc.). A summary of the main findings and trends in the area of ejector-enhanced efficiency of waste heat recovery cycles and systems using low boiling point working fluids. Following a brief overview of the ejector, selected configurations of interest are presented and discussed in a variety of applications. The purpose of the following chapter is to provide a concise overview of waste heat availability and energy capturing potential, and the different technologies available for its recovery as well as their advantages and challenges. In closing, the different types of waste heat recovery technologies that are used in cement plants to produce electricity are reviewed, and the potential for electricity production from heat exhaust gases of three cement plants by using waste heat recovery technology is discussed.