Solar Chimney - Description

Description

In its simplest form, the solar chimney consists of a black-painted chimney. During the day solar energy heats the chimney and the air within it, creating an updraft of air in the chimney. The suction created at the chimney's base can be used to ventilate and cool the building below. In most parts of the world it is easier to harness wind power for such ventilation as is done with a Badgir (بادگیر), but on hot windless days a Solar chimney can provide ventilation where otherwise there would be none.

There are however a number of solar chimney variations. The basic design elements of a solar chimney are:

• The solar collector area: This can be located in the top part of the chimney or can include the entire shaft. The orientation, type of glazing, insulation and thermal properties of this element are crucial for harnessing, retaining and utilizing solar gains
• The main ventilation shaft: The location, height, cross section and the thermal properties of this structure are also very important.
• The inlet and outlet air apertures: The sizes, location as well as aerodynamic aspects of these elements are also significant.

A principle has been proposed for solar power generation, using a large greenhouse at the base rather than relying solely on heating the chimney itself. (For further information on this issue, see Solar updraft tower.)

Solar chimneys are painted black so that they absorb the sun's heat more easily and efficiently. When the air inside the chimney is heated, it rises and pulls cold air out from under the ground via the heat exchange tubes.