The growing scarcity of conventional energy sources and its rapidly increasing cost makes it mandatory to look for alternative sources of energy. There is also fear of possible environmental risks associated with the use of conventional fuels and the nuclear energy. This concern has focused worldwide attention on the potential of harnessing renewable energy resources. Solar energy which is one of the most prominent source of energy which has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar energy technologies include solar heating, solar photovoltaics, solar thermal electricity and solar architecture, which can make considerable contributions to the energy sector. Solar Collector is the heart of any solar energy related system. This book describes performance and evaluation of double pass solar air collector with and without porous absorber material.