Passive solar systems are one of the earliest systems developed for the use of solar energy. It is mainly used in design and architecture for heating and cooling buildings. In solar architecture, it is very important to control and use the solar energy density and duration in order to obtain the desired effects beneficial to heat, light and health, while at the same time, it will damage high temperatures, excessive light and people and materials, and prevent undesirable effects. Solar energy is converted to heat in buildings (normally) without the use of any electromechanical devices. Heat transfer and hot fluid cycle are natural. Passive solar thermal systems also include storage elements such as energy collector elements or building walls, such as windows.