In the contemporary world, where energy efficiency and sustainability are paramount, exergy analysis has emerged as a crucial tool for addressing the complex challenges of energy use and environmental impact. Unlike traditional energy analysis, which focuses solely on the quantity of energy, exergy analysis considers the quality of energy, providing a more nuanced understanding of how energy is utilized within systems. This distinction is critical in a world where maximizing resource efficiency is not just desirable but necessary. Within the aforementioned information, the book has several topics related to exergy trying to provide the reader with a deeper understanding of this field. In this sense, a deep introduction talking about the theoretical background will be presented and subsequently the exergy evaluation in the energy field and fluids. In summary, exergy analysis is a vital tool in the contemporary world, enabling more sustainable and efficient use of energy resources. By focusing on energy quality and the irreversibility in energy systems, exergy analysis contributes significantly to the design and optimization of processes that are essential for a sustainable future.