This document discusses solar air heaters and concentrating solar collectors. It defines solar air heating as a technology that captures solar energy to heat air, which can then be used for space heating, drying processes, or ventilation. The document classifies solar air collectors as either unglazed, with no covering, or glazed, with a glass covering. It lists advantages such as avoiding corrosion and low costs, as well as disadvantages like poor heat transfer properties of air and need for large air volumes. The document also introduces concentrating solar collectors, which use mirrors or lenses to concentrate sunlight onto a receiver, and can achieve higher temperatures than flat-plate collectors.