New solar dish from MIT concentrates sunlight intensely enough to melt steel | Hacker News Reader

New solar dish from MIT concentrates sunlight intensely enough to melt steel

dailytech.com

10 pointssah8 comments

I walked past this the other day when they were building it out in front of MIT. What was amazing to me was not that it can melt steel, but that the mirrors they used were built to such perfect concavity with insanely smooth surfaces. The article suggests a possible application of the technology is bringing heat and solar electricity to poorer countries, but I have a hard time believing those perfect mirrors are really that inexpensive.

To compare this thing to anything Archimedes could have made is laughable.

> To compare this thing to anything Archimedes could have made is laughable.

Agreed. The quote about Archimedes was because I think he was ahead of his time (and technology). The idea of concentrating and focusing, not the implementation (and not necessarily the use - burning ships)

Is it really that impressive compared to the mirror in any of the world's largest telescopes? I mean, good work being built by students at low cost and all, but any serious observatory will have a mirror which is larger and a lot smoother.

On the other hand, I just got back from my first trip to Chicago where I was insanely impressed by the giant mirrored jellybean in Millennium Park, so I don't deny the impressiveness of big shiny objects.

From their website:

> "RawSolar's patented design flexes flat mirror into precisely the right shape without any special tooling or skilled labor"

So I think they just use plain flat mirrors and flex them with the frame, which would keep the cost down.

"When Marcellus withdrew them [his ships] a bow-shot, the old man [Archimedes] constructed a kind of hexagonal mirror, and at an interval proportionate to the size of the mirror he set similar small mirrors with four edges, moved by links and by a form of hinge, and made it the center of the sun's beams – its noon-tide beam, whether in summer or in mid-winter. Afterwards, when the beams were reflected in the mirror, a fearful kindling of fire was raised in the ships, and at the distance of a bow-shot he turned them into ashes. in this way did the old man prevail over Marcellus with his weapons."

"Archimedes and his Burning Mirrors, Reality or Fantasy?" http://www.mlahanas.de/Greeks/Mirrors.htm

Wonder what its efficiency is compared to a Fresnel lens:

http://www.youtube.com/watch?v=DGtA8E5iw3k

http://images.google.com/imgres?imgurl=http://www.terrypeppe...

What is patentable about this? I don't understand what is novel about it.

I was wondering the same thing. I wish the article would have focused on what was novel about this design compared to other solar-thermal dishes like Sterling Energy Systems, (http://www.stirlingenergy.com/) which is putting up 850MW worth of dishes in the desert.

Also I have to wonder if they could benefit by using a different working fluid than water. A lot of solar thermal projects use low melting point salts as the working fluid, since they hold heat for a long time. You can heat the salt all day, then hold vast amounts of superheated salt in holding tanks, and heat exchange it with water to drive steam turbines. This allows you to produce power well into the night.

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