Solar energy provides abundant energy to Earth, with 120 trillion kWh intercepted hourly, meeting global energy demand every 20 minutes. There are two types of solar thermal technologies - passive systems without moving parts that use sunlight for heating, cooling, and lighting, and active systems that require components to transport and transform solar energy into heat and electricity. Solar air heating systems can be classified based on collector type as porous or non-porous, with applications including space heating, crop drying, process heating, and refrigeration.