This book describes new energy saving methods and technologies for heat power engineering. The book is devoted to topical issues of energy and related industries. Leading Ukrainian scientists from both scientific institutes and educational universities took part in its creation. The research results are presented in 6 parts: electrical engineering, heat power engineering, nuclear power engineering, fossil fuels, cybersecurity and computer science, environmental safety. Results of regulating of operating modes and applicability of model checking technique in power systems are showed. Separate block of questions regarding the functioning of nuclear power plants, their waste and preventive measures of protection against negative effects on living organisms (including, for example, the Chernobyl nuclear power plant) is considered. The results of the peculiarities of the extraction, purification and use of fossil fuels are presented. In some chapters, presented the results on improving the cybersecurity of energy systems and its resilience to various threats, including the use of 5G technology. Traditionally for this series, issues of ecological safety, the impact of different energy systems on the environment and its protection are considered. A book is for researchers, engineers, as well as lecturers and postgraduates of higher education institutions dealing with energy sector, power systems, ecological safety, etc.