The purpose of writing this three volume 'Advances in Solar Energy Technology' is to provide all the relevant latest information available in the field of Solar Energy (Applied as well as Theoretical) to serve as the best source material at one place. Attempts are made to discuss topics in depth to assist both the students (i.e. undergraduate, postgraduate, research scholars etc.) and the professionals (i.e. Consultancy, design, and contracting firms). Chapter 1 starts with a brief history of solar houses (active heating), one of the oldest and still the widely used application of Solar Energy. Various methods of build­ ing heating and other general aspects such as building form and functions are also described. Various components of active solar heating of building like solar collector, storage system, control unit, auxiliary heat source, etc. are discussed very briefly. Three types of solar active heating of buildings like Solar air systems, solar liquid systems, and solar assisted heat pump systems are discussed in detail in this chapter. Design details and performance of nine typical solar houses which are in use in different climatic conditions and using some newer concepts are also discussed in depth in this chapter.