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Solar Tower, sometimes called Central Receiver System, has rings of small individual flat mirrors (heliostats) surrounding a central power tower (up to 100-200 m), on top of which sits a receiver that gathers the reflected radiation. The receiver contains a kind of fluid medium, be it water, air, mineral oil, liquid metal, molten salt or diluted salt. The heated fluid goes to a hot fluid storage tank (where excessive heat is stored) and then to a steam generator to engender electricity. The medium is then reused, returning to a cold fluid storage tank and being pumped up to the tower again. Solar tower can reach the highest temperature of all concentrator designs. The scheme of a solar tower plant is shown below.


power tower schematic.bmp
Scheme of Solar Two, a molten-salt power tower system


Solar tower possesses a higher efficiency than parabolic trough power plants (approximately 20% vs. 15%) resulting from its higher concentrating ratio and higher temperature. Therefore they are expected to be more cost efficient than parabolic trough power plants when producing at a large scale (100-200 MW) in a longer run. Pilot projects, Solar One (later converted into Solar Two) in the Mojave deserts in the U.S have demonstrated well-maintained functionality. They use molten/diluted salt which could maintain the heat energy for several days. A big challenge for solar tower now is the high cost of the overall construction and operation, with the heliostat and the rest of the system each accounting for half of the total cost. , Several more solar tower plants are scheduled for installation in the Mojave Desert, California


America¡¯s pilot solar tower project that has been proven to operate functually--Solar Two, In Daggett, CA, 10 MWe, HTF/Storage Molten Nitrate Salt, 30 Acres in size

 


 

 

 

A fully operation PS10 solar tower plant near Seville, Spain that can generate 10MW of electricity. Expansion into 20 MW will be completed January 2009, enough to power 11,000 homes.(guardian.co.uk)
http://www.det.csiro.au/science/r_h/nsec.htm

 


Bibliography


SolarPaces.org http://www.solarpaces.org/CSP_Technology/docs/solar_tower.pdf

¡°Learning About Renewable Energy: Concentrating Solar Power¡± NREL http://www.nrel.gov/learning/re_csp.html

Farret, F.A.; Simoes, M.G. Integration of Alternative Sources of Energy IEEE Press 2006 pp.112-127

 

Copyright Yiting Wang 2008