What is the highest temperature you can create by using concaved mirros to focus the sunlight on one spot?

Question

Multiple mirrors not just one. Is there a limit to how high you can get the temperature? Can anyone give me an example like, "It would take 233 mirrors focussing on the same spot to make the temperature on teh spot 1000 degrees C"...?

Thanks for your answers ;)

But what would be the highest possible temperature that could be made?

Answer 1

The sun's surface temperature isn't necessarily a limit. Other stars are hotter. The obvious upper limit would be focusing the entire solar output (3.83×10^26 W) on a small black body. That temperature could be much much higher than 6000F.

Solar insolation at the earth but outside the atmosphere is 1366 watts per square meter. You could calculate the power that could be focused by a mirror the size of earth. "Ignoring clouds, the average insolation for the Earth is approximately 250 watts per square meter." (from second reference). That would let you do some calculations about more practical mirror configurations.

Practical examples include Solar One and Solar Two in the California Mojave Desert. They raised molten salts to just over 1000F, but their main purpose was electric power generation, not high temperatures.

Answer 2

The highest theoretically possible temperature that can be achieved by focusing sunlight is the same as that of the surface of the sun, or about 6000° F. That's the blackbody radiation temperature corresponding to white light. In practice, a much milder temperature is achieved by design, because otherwise things would just melt.

Addendum: No, the temperature cannot be infinite, or anything close to it, because the sun is an extended object, and so therefore its image cannot be made into a point without also reducing the total energy flux. The limit is still the same as the surface of the sun, or about 6000° F.

Answer 3

This is a very interesting question. I think that the consideration of 'multiple mirrors' is an irrelevance.
Assuming that the light from the sun is parallel (because of the sun's distance) and that a perfectly parabolic mirror could be used, then -theoretically- the collected radiation would focus down to a point of zero dimensions. This means that the temperature at that focus would be infinite!

Answer 4

It depends on the size of the mirrors, or how many in your array. The sun belts out a *lot* of energy. If you could focus that to a point *and* keep track of the sun while the earth rotates then I think you could easily achieve 1000 deg C. However, it would be just at that point.

Answer 5

check out discovery mythbusters they tried to recreate i think it was pythagraus' mirror weapon which was foot soldiers with highly polished shields. their version was a huge concave mirror made from a lot of individual mirrors. it barely managed to set the mock up boat alight.