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Odeillo solar furnace can reach 3300°C and melt about any metal. https://en.wikipedia.org/wiki/Odeillo_solar_furnace https://en.wikipedia.org/wiki/Odeillo_solar

by wazoox 4y ago

Odeillo solar furnace can reach 3300°C and melt about any metal. https://en.wikipedia.org/wiki/Odeillo_solar_furnace https://en.wikipedia.org/wiki/Odeillo_solar_furnace However it's hardly "low tech" :)

moffkalast 4y ago
That just looks like a laser furnace with extra steps. A whole lot of extra steps. I suppose you would get higher efficiency from that than if you replaced the mirrors with solar panels and used that to drive the laser, but you also wouldn't be limited to sunny days since you can also just switch to grid power at any time.
- jagged-chisel 4y ago
  What’s the conversion efficiency of solar panels? What are the losses converting that to run a laser? The direct solar setup has what losses between the collection points and the target? I suspect conversion to electricity is not more efficient. It does, however, provide the convenience of switching power sources as desired.
  - moffkalast 4y ago
    Yeah, that's what I'm saying? You'd lose a lot in conversions with the laser setup, but you'd gain flexibility and the setup would be far more compact.
    - vanderZwan 4y ago
      I think the miscommunication stems from the fact that this phrasing: > That just looks like a laser furnace with extra steps. A whole lot of extra steps. ... implies more conversion steps for the direct solar set-up, while the opposite is true.
      - moffkalast 4y ago
        I don't suppose you guys bothered to read the second line then? Regardless, I would still argue that setting up some panels and connecting them to a laser is fewer steps than setting up an array of carefully aligned mirrors and constructing a whole other building of mirrors that focus bounces from those into a point.
        kragen 4y ago
        Typically solar panels are 21% efficient and lasers are 10% efficient, so the panel+laser setup is about 2% efficient. The mirror setup can be 70% efficient, depending mostly on your absorber design. Building a laser normally also requires carefully aligning mirrors, as well as typically other advanced processes like glassblowing and high-voltage arcs (for low-pressure gas lasers) or glassmaking with high transparency and carefully controlled doping (for solid lasers), and in most cases fairly advanced chemistry. You might be able to make a laser out of fluorescein-doped jello, for example, but where do you get your fluorescein? It doesn't grow on trees. Of course you can just buy a laser off the shelf, in which case you don't have to mess with any of this, but you can also just buy a big Fresnel lens off the shelf. People have been polishing metal into mirrors for 6000 years, and as I understand it, the mathematics of parabolic reflectors for burning things was known by Euclid's time, 2300 years ago, which is probably why the English word for the point where the rays meet is "focus", Latin for "fireplace" (though that sense of "focus" may be only 400 years old). Newton was making fairly decent-shaped parabolic mirrors 354 years ago, and interferometry has been good enough to make parabolic mirrors essentially perfect since about 01851. The great limitation on these processes was historically the cost of materials: from Mesopotamia to Newton we're talking about various shades of copper or bronze, which are very expensive materials. For optical concentrators you don't need such optical perfection; gold leaf on something like polished stone would probably be cheaper, but in the Victorian age we learned the art of silvering glass with mercury, and in the early 20th century we learned the art of vacuum-silvering with silver, gold, or aluminum. Ancient Egypt evidently made polished stonework on lathes, but may not have had the mathematical sophistication to make paraboloids of revolution, or to know why they were important. And the compound parabolic concentrators which allow you to not have to track the sun precisely are, I think, from the 20th century. So, you might say, why didn't we have solar furnaces before the Industrial Revolution? Well, actually, before being murdered by the French Revolution, Lavoisier discovered that diamond was a form of carbon by burning diamonds in a solar furnace, in 01772. The solar furnace was crucial for this experiment not only because it allowed him to reach especially high temperatures but because it didn't introduce carbon dioxide. Lavoisier's solar furnace used a lens like Seegers's, but enormously heavy and thick. Fresnel wouldn't build his first Fresnel-lens prototype until 01820.
    - TeMPOraL 4y ago
      > Yeah, that's what I'm saying? Doesn't read that way. Where your first statement was "That just looks like a laser furnace with extra steps", I'd say what you proposed looks like Odeillo with lot of extra steps. Focusing sunlight with mirrors is strictly simpler.
Schroedingersat 4y ago
Rafael Viñoly finally found his niche.
Someone 4y ago
I think that’s fairly low tech. Something like it could have been built hundreds of years ago (with human operators orienting the 63 heliostats to make them reflect the sun’s light into the parabolic part) https://en.wikipedia.org/wiki/Mirror#Middle_Ages_and_Renaissance https://en.wikipedia.org/wiki/Mirror#Middle_Ages_and_Renaiss...: “by the 16th century Venice was a center of mirror production using this technique. These Venetian mirrors were up to 40 inches (100 cm) square.” And those were mirrors for reflecting images. The mirrors for a device like this need not be as good.
ouid 4y ago
This is very low tech. It's just mirrors, and not even particularly precise ones.

by wazoox 4y ago

moffkalast 4y ago

That just looks like a laser furnace with extra steps. A whole lot of extra steps. I suppose you would get higher efficiency from that than if you replaced the mirrors with solar panels and used that to drive the laser, but you also wouldn't be limited to sunny days since you can also just switch to grid power at any time.

jagged-chisel 4y ago
What’s the conversion efficiency of solar panels? What are the losses converting that to run a laser? The direct solar setup has what losses between the collection points and the target? I suspect conversion to electricity is not more efficient. It does, however, provide the convenience of switching power sources as desired.
- moffkalast 4y ago
  Yeah, that's what I'm saying? You'd lose a lot in conversions with the laser setup, but you'd gain flexibility and the setup would be far more compact.
  - vanderZwan 4y ago
    I think the miscommunication stems from the fact that this phrasing: > That just looks like a laser furnace with extra steps. A whole lot of extra steps. ... implies more conversion steps for the direct solar set-up, while the opposite is true.
    - moffkalast 4y ago
      I don't suppose you guys bothered to read the second line then? Regardless, I would still argue that setting up some panels and connecting them to a laser is fewer steps than setting up an array of carefully aligned mirrors and constructing a whole other building of mirrors that focus bounces from those into a point.
      - kragen 4y ago
        Typically solar panels are 21% efficient and lasers are 10% efficient, so the panel+laser setup is about 2% efficient. The mirror setup can be 70% efficient, depending mostly on your absorber design. Building a laser normally also requires carefully aligning mirrors, as well as typically other advanced processes like glassblowing and high-voltage arcs (for low-pressure gas lasers) or glassmaking with high transparency and carefully controlled doping (for solid lasers), and in most cases fairly advanced chemistry. You might be able to make a laser out of fluorescein-doped jello, for example, but where do you get your fluorescein? It doesn't grow on trees. Of course you can just buy a laser off the shelf, in which case you don't have to mess with any of this, but you can also just buy a big Fresnel lens off the shelf. People have been polishing metal into mirrors for 6000 years, and as I understand it, the mathematics of parabolic reflectors for burning things was known by Euclid's time, 2300 years ago, which is probably why the English word for the point where the rays meet is "focus", Latin for "fireplace" (though that sense of "focus" may be only 400 years old). Newton was making fairly decent-shaped parabolic mirrors 354 years ago, and interferometry has been good enough to make parabolic mirrors essentially perfect since about 01851. The great limitation on these processes was historically the cost of materials: from Mesopotamia to Newton we're talking about various shades of copper or bronze, which are very expensive materials. For optical concentrators you don't need such optical perfection; gold leaf on something like polished stone would probably be cheaper, but in the Victorian age we learned the art of silvering glass with mercury, and in the early 20th century we learned the art of vacuum-silvering with silver, gold, or aluminum. Ancient Egypt evidently made polished stonework on lathes, but may not have had the mathematical sophistication to make paraboloids of revolution, or to know why they were important. And the compound parabolic concentrators which allow you to not have to track the sun precisely are, I think, from the 20th century. So, you might say, why didn't we have solar furnaces before the Industrial Revolution? Well, actually, before being murdered by the French Revolution, Lavoisier discovered that diamond was a form of carbon by burning diamonds in a solar furnace, in 01772. The solar furnace was crucial for this experiment not only because it allowed him to reach especially high temperatures but because it didn't introduce carbon dioxide. Lavoisier's solar furnace used a lens like Seegers's, but enormously heavy and thick. Fresnel wouldn't build his first Fresnel-lens prototype until 01820.
  - TeMPOraL 4y ago
    > Yeah, that's what I'm saying? Doesn't read that way. Where your first statement was "That just looks like a laser furnace with extra steps", I'd say what you proposed looks like Odeillo with lot of extra steps. Focusing sunlight with mirrors is strictly simpler.

Schroedingersat 4y ago

Rafael Viñoly finally found his niche.

Someone 4y ago

I think that’s fairly low tech. Something like it could have been built hundreds of years ago (with human operators orienting the 63 heliostats to make them reflect the sun’s light into the parabolic part) https://en.wikipedia.org/wiki/Mirror#Middle_Ages_and_Renaissance https://en.wikipedia.org/wiki/Mirror#Middle_Ages_and_Renaiss...: “by the 16th century Venice was a center of mirror production using this technique. These Venetian mirrors were up to 40 inches (100 cm) square.” And those were mirrors for reflecting images. The mirrors for a device like this need not be as good.

ouid 4y ago

This is very low tech. It's just mirrors, and not even particularly precise ones.