The radiant heat and light received from the sun is known as solar energy. It is a renewable source of energy that is classified in to active solar and passive solar depending upon how the energy is captured and distributed. Passive solar technologies are those which don't use any external mechanical or electrical device and depends upon natural circulation of air. Whereas, active solar systems use devices such as fans and pumps to circulate air or fluid through solar collectors. Some prominent examples of solar technologies are photovoltaics, solar architecture, solar heating and artificial photosynthesis. Solar energy has undergone rapid developments under the last few decades and is expected to enhance sustainability, reduce air pollution, lower the fuel prices and mitigate the effects of global warming in the coming years. This book attempts to understand the multiple branches that fall under the discipline of solar energy engineering and how such concepts have practical applications. Most of the topics introduced in this book cover new techniques and the applications of solar energy engineering. It will serve as a valuable source of reference for those interested in this field.