Paper Out of China on Solar Updraft Tower Optimization

If I am interpreting this paper right, the importance to electrical generation of a water vapor condenser downdraft, as proposed in the solar updraft tower algae biosphere, is more than I thought. Essentially, their model predicts that for an extension of the Manzanares prototype, without the latent heat of vaporization there to slow the loss of heat during ascent, the optimal height of a taller Manzanares solar updraft tower is only around 615m with a maximum power output of only 102.2 kW. This is due to cooling of the air column as it ascends.

Title: Analysis of chimney height for solar chimney power plant

Xinping Zhoua, , , Jiakuan Yangb, , Bo Xiaob, Guoxiang Houc and Fang Xingb, School of Civil Engineering and Mechanics, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China bSchool of Environmental Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China cSchool of Traffic Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, PR China

Received 13 May 2007; accepted 13 February 2008. Available online 20 February 2008.

Abstract: Current in solar chimney power plant that drives turbine generators to generate electricity is driven by buoyancy resulting from higher temperature than the surroundings at different heights. In this paper, the maximum chimney height for convection avoiding negative buoyancy at the latter chimney and the optimal chimney height for maximum power output are presented and analyzed using a theoretical model validated with the measurements of the only one prototype in Manzanares. The results based on the Manzanares prototype show that as standard lapse rate of atmospheric temperature is used, the maximum power output of 102.2 kW is obtained for the optimal chimney height of 615 m, which is lower than the maximum chimney height with a power output of 92.3 kW. Sensitivity analyses are also performed to examine the influence of various lapse rates of atmospheric temperatures and collector radii on maximum height of chimney. The results show that maximum height gradually increases with the lapse rate increasing and go to infinity at a value of around 0.0098 K m^−1, and that the maximum height for convection and optimal height for maximum power output increase with larger collector radius.

http://tinyurl.com/4rmtwj