What is a Solar Chimney?

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As solar power becomes more familiar, innovations appear and new ideas are applied to existing technology to either improve output or come up with entirely new ways of harnessing the sun's renewable energy for everyday use. Solar chimneys are one of those innovations that could one day produce power on a grand scale.

A solar chimney is a vertical, open-ended duct that is glazed on the sun-facing side (south in the northern hemisphere) and painted black on the inside. It acts as a solar air collector. When the sun's radiation hits the chimney the air inside is heated and rises, pulling cooler air in at the bottom. As long as the sun shines, air circulates through the chimney.

The question is what to do with the chimney, and this is where the innovation comes in. Here are two examples of how solar chimneys can be used in practical applications:

  • In hot climates, solar chimneys can be used to cool buildings. The bottom of the chimney opens into the top of the building; as the air in the chimney heats and rises, the hot air at the top of the building gets sucked up and new, cooler air enters the building to replace it.
  • On a grand scale, massive solar chimneys could be installed in very hot locations such as desert areas. With a very large, long chimney running up the side of a hill, mesa or mountain, an enormous amount of heat can be gathered and a large volume of air circulated. By placing a propeller-style electric generator inside the chimney, the circulating air can be used to create significant amounts of very low-cost power.

Putting those two ideas together, there may soon be a residential market for solar chimneys in hot climates, including small built-in electricity generators that could be used to run equipment much like a PV panel can today.