The Solar constant [1] is more than 1kW/m^2. So if you collect enough Solar light and do concentrante it on a small enough surface you can reach very rapidely very high temperatures. At Odeillo [2] températures as high as 3500° have been reached in a few seconds. You have to make sure that the object to be heated does highly absorb Solar light and that it is isolated enough from its surrounding as not to dissipate to fast the incomming energy.

Now from the movie "Farenheit 451" you know that the self ignition of papier takes place at this temperature (233°). When I was a boy it was one of my pleasures during summer time to ignite paper by foccusing Solar light with my father's magnifying glass. So it is very easy to reach 200°C by concentrating Solar light.

[1] http://en.wikipedia.org/wiki/Solar_constant

[2]http://fr.wikipedia.org/wiki/Four_solaire_d'Odeillo

Dear Charles, thank you for your answer

the problem is how to get a uniform 200°C for a surface of 1m2?. As I can reach more, may be using divergent mirror (lentil) to have a uniform 200°C for 1m2?

Thank you

I think the best way to do would be to use a set of flat mirrors a little bit larger than the surface you want to heat up (to avoid edge effects). The number of mirrors strongly depends on parametres such as: the reflectivity of the mirrors, the absorbance, reflectance, and heat capacity of the object to be heated. Some experimentation is clearly needed.

Again thank you for your clear answers,

what are generally the used materials? covering a steel dish with aluminium is it enough? Thanks

For the collector? From my experience stainless steel is a cheap and good enough heat collector for your purpose. Black anodized aluminium would probably stand 200°C.

You can use a concentrating collector (parabolic dish) which can help you in achieving temp up to 200 degrees. For this you have to use a good reflective material (aluminium, glass) with less transmittance losses. The receiver can be coated with nickle chrome or better absorber material to absorb more radiation being concentrated at the receiver's end

Thanks Chaitanya for your suggest. The problem that I have is I would like to get this 200 deg for a large surface and not just for a point as it is for a parabolic dish.

Thank you

Salut Lyes

Je ne sais pas ce que tu veux faire exactement mais il y a moyen de tout d'abord chauffer un gas (air) ou mieux un liquide (oil) que tu fais ensuite passer dans une double enveloppe sous ta plaque de 1 m2. Pour les matériaux, l'acier inox est le mieux.

Thierry