Solar Tower
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Submitted by: butchz4paul  Subscribe to this Author Paste this code into your site to promote this story! |
Created 20 weeks 4 hours ago
Made popular 19 weeks 6 days ago |
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This plant is a heat engine and uses direct solar heating of air to power the turbines. The theoretical maximum efficiency of any heat engine is related to the maximum temperature it achieves. According to their video it only gets to 70C. By comparison the parabolic trough types, used in the American southwest, concentrate the sunlight using mirrors and can achieve temperatures as high as 390C.
http://www.nrel.gov/csp/troughnet/power_plant_data.html#saguaro
That makes the parabolic trough type much more efficient. The big question for solar is how much will the plant cost. The trough units are more complicated which increases cost, but because of their higher efficiency they require less collector area for a given amount of power, so that reduces cost.
A big problem for either type is keeping the glass or mirrors clean. That might sound easy but in a dry dusty desert with little water it's a problem, especially considering how huge these puppies are. The SEGS VIII plant alone has a collector area of 464,340 square meters (114. acres).
Actually I think the solar tower harnesses it's energy from air movement. The 200MW plant in the video is based on air movement of 49 ft/sec though the turbines.
"Freedom without emotion is like a car without gas."
That would be correct if it was just using wind. But then there would be no need for the strange structure. Just put up windmills. But this device uses solar power to heat the air. The warm air rises in the chimney and produces a suction at the base which draws air through the turbines. That makes it a heat engine and its efficiency is limited by the maximum temperature it achieves. The maximum efficiency possible is = (Th-Tc)/Th. Where Th is the high temperature. Tc is the low temp which in this case is the ambient. (All temps are absolute, either degrees Kelvin or degrees Rankine.) That's just the thermodynamic efficiency. There will be additional losses because the turbine is not 100% efficient and neither is the generator. And there will be friction losses of the air flowing through the structure too.
I suppose you're right but some might call it a "heat differential". I think I'm right too in that the turbines run on moving air for the most part rather than expanding air. Now the Stirling engine would definitely be known as a heat differential engine.
"Freedom without emotion is like a car without gas."
Utility solar power plants like this and like the SEGS plants in California http://www.fplenergy.com/portfolio/solar/index.shtml require huge tracts of land and still need power transmission lines.
My hope for solar power is that someone develops a low cost solar electric cell that people could put on their roofs instead of shingles. That way no additional land is needed. No transmission lines are required and people can say adios to high electric bills. And installation costs are partially offset by eliminating shingles.
http://tectonicforces.blogspot.com/2007/09/tower-of-power.html
"Freedom without emotion is like a car without gas."