The intended book attempts to depict several ways to increase efficiency of the energy-conversion, which is always needed in order to conserve and more rationally use fossil fuels, some renewables (Solar, biomass) and, more contemporary, to reduce global warming and climate changes on the planet Earth. The book summarizes 6 (six) innovative approaches to a more efficient energy conversion of thermal energy into mechanical energy that can be applied in the field of energy generation (thermal & nuclear power plants; internal combustion engines). The described innovative approaches originate and have evolved either from my completed or uncompleted patent applications or granted patents, either US, Canadian, Serbian or WIPO, in the period 2002-2019. They have also evolved from corresponding technical papers at some ASME Turbo Expo or other ASME or other conferences. The book intends to share all important information to readers, including conference participants, university professors and students, allowing experts or original equipment manufacturers to adopt the concepts presented in the book and to eventually use them in the design & construction of related energy-conversion plants.