One of the major challenges with the use of solar thermal energy is the intermittent nature. As such, present day research is geared towards energy storage systems in which thermal energy is stored during the day for later use. However, in many engineering applications there is a continuous steady demand for energy. Hence, this book is focused on a system to provide an uninterrupted continuous supply of energy in the absence of or availability of solar energy. A mathematical model was developed from consideration of the basic phenomena of heat transfer to predict the thermal behavior of a simultaneous charging, storage and discharging system during a heating cycle. Experiments were conducted by charging the packed bed system from a flat plate solar collector. The analysis shows that the packed bed thermal storage unit converts the intermittent energy received from the sun, stores and discharge it continuously and that it is possible to have a simultaneous charging, storage and discharging system. The book should be useful for all building and solar/thermal energy professionals as well as students in the field of mechanical engineering.