solar concentrator temperature limit

[jabonet]

I want to know how much is the maximun temperature you can achieve with a solar concentrator.

lets say that you have a volume of one cubic millimeter, and that you start concentrating reflected rays from the sun passing through this volume, is it posible to achieve a temperature higher that the surface of the sun (6000K) or is that a assintotic value as you increase the concentration?
thanks!

 

[Compositepro]

The temperature of the sun would be an upper limit that could not be reached. If an object were hotter than the sun it would radiate heat to the sun.

 

[elfgriper]

Hi Jab,
I think the upper limit would be the where the out going energy (in vacuum the backbody radiation) is the same as the incomming energy. You need to know the surface area of the radiating body to calculate it.
-elf

 

[unclesyd]

There is a solar concentrator in Odellio, France that can achieve 33,000° C

Power generating collectors:

A linear parabolic-shaped reflector can achieve operating temperatures over 400°C.

A solar dish concentrator can achieve temperatures of 750°C

 

[btrueblood]

Unclesyd,

While I've seen the 30,000 ^oC number cited on several websites too (most of them mis-spelling Odeillo also), my enjuneer sense tingled when I saw that. Above 10,000 ^oC and we enter the plasma physics realm, where gases like N₂ and O₂ are fully dissociated, may begin to ionize, and temperature becomes a somewhat vague term.

From MS-Encarta entry for solar energy, on this link:

http://encarta.msn.com/text_761554832__1/Solar_Energy.html

the following excerpt comes:

"One important high-temperature application of concentrators is solar furnaces. The largest of these, located at Odeillo in the Pyrenees Mountains of France, uses 63 mirrors with a total area of approximately 2,835 sq m (about 30,515 sq ft) to produce temperatures as high as 3200°C (5800°F). Such furnaces are ideal for research requiring high temperatures and contaminant-free environments—for example, materials research to determine how substances will react when exposed to extremely high temperatures. Other methods of reaching such temperatures usually require chemical reactants that would also react with the substances to be studied, skewing the results."

There's also a link to the Odeillo website, but I can't get much from it, not being much of a French speaker. The link is here:

http://www.imp.cnrs.fr/foursol/index.shtml

5800 °F is still nothing to sneeze at - it is a respectable fraction (90%?) of the thermal solar surface "temperature" (itself a somewhat fuzzy term, and varies depending upon what source you cite). Odeillo's maximum is probably limited to the 5800 °F value more by the fact that almost all known materials will be molten or vaporized at this temperature ("um, M'sr. professor, our probes keep melting, what should we do?...).

 

[unclesyd]

trueblood, et all

I stand corrected by a factor 6. I have three quick references that state the higher values and also misspelled the location name.
A little thought on my part should have caught that since I spent a lot of time and effort trying to control 1700°C.

The English version of the website.

http://www.imp.cnrs.fr/foursol/1000_en.shtml