Academic scholars are increasingly confronted with the complex challenges of understanding and optimizing heat transfer processes, particularly in the areas of cavities and Phase Change Materials (PCM). These issues are central to a range of crucial applications, including building systems, electronic equipment, and the harnessing of solar energy. The need for innovative solutions to enhance heat transfer efficiency is more pressing than ever, and a comprehensive resource to guide scholars through these complexities is essential. FlexPDE and Finite Element Method Applications in Thermal Energy Storage and Cavities is research book specifically designed to provide scholars with the knowledge and expertise necessary to navigate the complexities of heat transfer issues. With a strong emphasis on practical application, the book leverages the capabilities of the Finite Element Method (FEM) through the FLEXPDE software, making it a valuable resource for those seeking innovative solutions to problems in heat transfer. From the application of FEM in understanding cavities to its role in optimizing thermal energy storage, this book offers a comprehensive and in-depth exploration of these critical subjects. By providing not only the theoretical framework but also the practical codes required for research, it equips scholars to make tangible contributions to the field. Moreover, the book does not stop at addressing these fundamental issues; it also delves into the pressing global challenge of Energy Storage Systems (TESS), making it a holistic resource for scholars looking to make a meaningful impact in the academic world and beyond.