Solar chimneys against tornados
The meteorological conditions of formation of tornados are complex but there is a constant: lower part of atmosphere is particularly hot and humid some hours before the beginning of a tornado. The thermal contrast between low hot atmosphere and upper cold atmosphere is instable and the mixture of these layers starts abruptly. The tornados are generated during this mixture.
Since the years 80, the German scientist Jorg Schlaich and his team propose an original way to convert solar light in electric energy: the solar chimney. A solar chimney works in three steps:
- solar radiation heats the air under an horizontal glass roof (the collector),
- at the centre of the glass roof, emerges the chimney ; the hot air flows to the chimney and rises, due to its lower density ; the cold air enters from the outer perimeter of collector as hot air is drawn in the chimney,
- at the base of the chimney, some turbines convert the kinetic energy of ascending hot air in electric energy.
In his book “Solar Chimney” (*), Jorg Schlaich describes some cases of solar chimneys:
- power 5MW, collector diameter 1110m, chimney diameter 54m, chimney height 445m,
- power 30MW, collector diameter 2200m, chimney diameter 84m, chimney height 750m,
- power 100MW, collector diameter 3600m, chimney diameter 115m, chimney height 950m,
- power 200MW, collector diameter 4000m, chimney diameter 175m, chimney height 1500m.
The case of the highest chimneys is particularly interesting. The data contained in the book show that these tall chimneys propel great amounts of hot air at altitude about 900m or more. At full power, a 100 MW solar chimney injects each second about 150000 cubic meters of air at altitude greater than 900m.
By its constant injection of hot air at high altitude, a solar chimney could reduce the thermal contrast between hot lower air layer and cold upper air layer. The reducing of this thermal contrast could diminish the power of the tornados in the region where is located the solar chimney.
Besides its electric production, a solar chimney could perhaps help to control tornados, one the most destructive meteorological phenomenon.
(*) Solar Chimney, Jorg Schlaich, Michael Robinson, 1995, Axel Menges GmbH, ISBN: 3930698692