Solar Updraft Tower





Solar updraft tower prototype at Manzanares, Spain.

Solar updraft tower prototype at Manzanares, Spain. Image by Copyright: GNU FDL

Solar updraft towers make use of a combination of the chimeny effect and greenhouse effect to power wind turbines. Essentially a large chimney is constructed that opens at the bottom into a solar collector area (greenhouses) which in turn opens at the sides to allow air in. When sunlight enters the greenhouses it gradually heats the air which flows upwards into the chimney passing by wind turbines that generate electricity. Convection creates a cycle where the heated air flows upwards through the chimney drawing fresh air in from around the solar collector and the cycle continues.

One of the major advantages of solar updraft towers or solar chimneys is that the large solar collector area can still be used for agriculture and in fact may be beneficial as it is a greenhouse. This in contrast to technology like photovoltaic cells that require large areas of land to operate that must be solely dedicated to generating electricity. Another advantage over photovoltaics is that energy storage can be accomplished easily using inexpensive methods like large drums of water or other thermal mass that will absorb heat during the day and emit it at night keeping the convection cycle, and wind turbines, moving. Construction of a solar chimney also requries very basic building materials making them an ideal source of electricity in developing countries.

Solar chimney collector area.

Solar chimney collector area. Image by Widakora. Copyright: GNU FDL

There are many adaptations to this basic concept that result in several other advantages. Instead of solar energy providing the heat waste industrial or urban heat could be used. Humidifying the air in the collector and released through the chimney at high altitudes could create clouds causing precipitation in other arid environments possibility resulting in de-desertification. Installing a chimney scrubber could remove particulate air pollution essentially cleaning the air of urban and industrial areas. There are many variations and alterations that can be made to result in higher performance and regional advantages.

Use of the solar updraft tower concept has been limited but a few working prototypes have been built. One of the first was built in Manzanares, Spain and operated for 8 years before being decommissioned after collapsing due to the guy wires rusting away and failing in a storm. It had a chimney height of 185 meters and a collection area of 46,000 square meters (11 acres). Maximum power output was 50 kW. Although only an experimental prototype the project paved the way for other solar updraft towers and proved the concept was valid.

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