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Solar chimney

A solar chimney is an apparatus for harnessing solar energy by convection of heated air.

In its simplest form, it simply consists of a black-painted chimney. During the daytime, solar energy heats the chimney and thereby heats the air within it, resulting in an updraft of air within the chimney. The suction this creates at the chimney base can be used to ventilate, and thereby cool, the building below. In most parts of the world for most of the time it is easier to harness wind power for such ventilation, but on hot windless days such a chimney can provide ventilation where there would otherwise be none.

This principle has been proposed for electric power generation , using a large greenhouse at the base rather than relying on heating of the chimney itself. The main problem with this approach is the relatively small difference in temperature between the highest and lowest temperatures in the system. Carnot's theorem greatly restricts the efficiency of conversion in these circumstances.

General concept of proposed solar chimney power station
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General concept of proposed solar chimney power station
Contents

Power station designs

See also Solar Tower for a current proposal.

History

One of the earliest descriptions of a solar chimney power station was written in 1931 by a German author, Hanns Günther.

More recently Schlaich, Bergerman and Partner, under the direction of German engineer Prof. Dr. Ing. Jörg Schlaich, built a working model of a solar tower in 1982 in Manzaranes , (Spain), 150 km south of Madrid, which was funded by the German Government. This power plant operated successfully for approximately 8 years. The chimney had a diameter of 10 metres and a height of 195 metres, and the maximum power output was about 50 kW.

It was destroyed by heavy weather and thunderstorms in 1989 and was officially decommissioned. However, during the final 3 years, optimization data was collected on a second-by-second basis. This data has been licensed to EnviroMission and SolarMission Technologies Inc. USA, who plan to manufacture solar chimneys under the brand name Solar Tower.

No patent was ever awarded, and so similar solar chimneys may be built at anytime, anywhere by anyone so long as local laws and official regulations are observed in the respective jurisdictions.

Byproducts

The most significant byproducts from proposed designs are distilled water (made from ocean water or ground water) and produce grown under the solar collector. Fruits and vegetables, as well as medicinal and aromatic essential oils made from herbs and flowers, seaweeds and planktons, blue-green algae, have all been suggested as suitable crops. Residual biomass will create additional heat during composting, as will the various distillation, food processing and manufacturing operations. Other byproducts may include ethanol and methane, bio-diesel and all manner of vegetable and plant derivatives.

It is also suggested that heat produced from the air-conditioning of factories, offices, schools, shopping malls and homes could be funneled to the tower to optimize refrigeration and air-conditioning operations. Thermodynamically, this must of course reduce the power available for power generation at the tower.

Reliability

Another benefit of the solar tower concept is its ability to generate surrogate solar power during cloudy periods and at night. Water vapors rising through the tower during daylight hours are condensed near the top of the solar tower and return to holding tanks situated throughout the structure. The distributed water vessels act collectively as a heat sink. The radiant heat, escaping from the water containers during overcast or cooling periods and at night, continues to drive the turbines. Near dawn, the cooled waters, driven by gravitational pull, return towards the periphery, driving hydroelectric turbines, and perform other kinetic works. Thereafter, the cooled waters may be distributed as irrigation for the tower's gardens, tree farms, reforestation projects and as domestic drinking water. Robustness from storms could be greatly improved by running the chimney up a steep mountain side instead of free standing.

External links

  • Schlaich, Bergerman and Partner website http://www.sbp.de/en/html/home/solar_chimney_quicktime.html .
  • Solar Tower OpenSource Energy Project http://wiki.solartower.com .
  • Environmission International EarthNews Online http://www.enviromission.com .
  • Solar Chimney http://www.globalwarmingsolutions.co.uk/the_solar_chimney.htm .
  • EnviroMission Ltd. of Australia Website http://www.enviromission.com.au
  • Wentworth Shire, NSW - Proposed Site http://www.wentworth.nsw.gov.au/solartower



Last updated: 02-27-2005 12:28:39