In the past, fossil fuels have been considered a reliable source of energy by many countries. Despite the current measures to reduce the use of fossil fuels for electricity generation, the use of this type of energy source will continue for the foreseeable future. This book examines how, if this situation does not change in the future, then all types of fossil fuels, particularly oil, will be exhausted before the end of the current century. The use of microholes may potentially enhance the applications of fossil fuels in various energy fields, especially in thermal power plants. Therefore, the morphology variation of micropunch and microhole during the punching with WC/Co micropunches is investigated in this compilation through scanning electron microscopy, energy dispersive spectrometer and confocal laser studies. Following this, the authors provide a review on experimental and modeling studies performed with direct fuel cells, starting with the fundamentals and main drawbacks of these systems, followed by an exhaustive review on the different studies performed regarding the effects of operating conditions and design parameters. In the penultimate chapter, a new method for determining the cohesion potential energy in solids is described, and fundamental factors such as internal energy, entropy, temperature and time are examined, in particular the connection of entropy and time to potential energy. The method concerns molecular solids and rests upon measurable thermodynamic quantities: heat of sublimation, heat capacity, and entropy as derived from the latter. The closing chapter provides an overview of three methods (retarded osmosis method, forward osmosis-electrokinetic method, and diffusio-osmotic method) for sustainable power generation from the salinity gradient energy by using osmosis-based processes.