4 ms·

What are you going to make your crucible out of that is transparent, won’t contaminate the contents and is strong enough at high temperatures to withstand regul

What are you going to make your crucible out of that is transparent, won’t contaminate the contents and is strong enough at high temperatures to withstand regular use? Also if it wasn’t available 20 years ago there’s your reason.

zackmorris 8y ago
My first thought was maybe silicon carbide, since it can be made with readily available silicon and carbon. But there are other caramics which have much higher melting points. Who wants a little hafnium carbide at 3958 C haha: https://en.wikipedia.org/wiki/Ultra-high-temperature_ceramics#Physical_properties https://en.wikipedia.org/wiki/Ultra-high-temperature_ceramic... I'm having trouble finding infrared conductivities: https://global.kyocera.com/fcworld/charact/heat/thermalcond.html https://global.kyocera.com/fcworld/charact/heat/thermalcond.... So looks like aluminum nitride might be best (first made in 1877 so we have the technology!) with a melting point of 2200 C: https://en.wikipedia.org/wiki/Aluminium_nitride https://en.wikipedia.org/wiki/Aluminium_nitride Portland cement (the basic ingredient of concrete) is made at 1450 C: https://en.wikipedia.org/wiki/Portland_cement#Manufacturing https://en.wikipedia.org/wiki/Portland_cement#Manufacturing And looks like any aluminum from the crucible wouldn't contaminate the concrete. Not sure about the nitrogen, but since the air is nitrogen/oxygen, it should be ok: https://www.tandfonline.com/doi/pdf/10.3130/jaabe.10.217 https://www.tandfonline.com/doi/pdf/10.3130/jaabe.10.217 But I think it's important to flip the problem on its head. Since solar thermal energy is essentially free after the solar furnace is manufactured, then we might as well scale it up to provide 2-10x more heat than we need, and then choose a ceramic with the material properties we want, even if its thermal conductivity isn't as efficient as we'd like. Keep in mind that any heat we get from this will be roughly 4 times cheaper than from photovoltaics (running at 25% efficiency) since we avoid the light->electricity->heat conversions.
- Armisael16 8y ago
  You seem to have a fundamental misunderstanding about how crucibles operate. The outside of the crucible is not supposed to get particularly hot. Heat is applied to the inside; the crucible contains both the material and the heat. If you don’t do this then all the air in the room is also heated up to ludicrous temperatures, and that tends to be bad for any other equipment or people nearby.

zackmorris 8y ago

My first thought was maybe silicon carbide, since it can be made with readily available silicon and carbon. But there are other caramics which have much higher melting points. Who wants a little hafnium carbide at 3958 C haha: https://en.wikipedia.org/wiki/Ultra-high-temperature_ceramics#Physical_properties https://en.wikipedia.org/wiki/Ultra-high-temperature_ceramic... I'm having trouble finding infrared conductivities: https://global.kyocera.com/fcworld/charact/heat/thermalcond.html https://global.kyocera.com/fcworld/charact/heat/thermalcond.... So looks like aluminum nitride might be best (first made in 1877 so we have the technology!) with a melting point of 2200 C: https://en.wikipedia.org/wiki/Aluminium_nitride https://en.wikipedia.org/wiki/Aluminium_nitride Portland cement (the basic ingredient of concrete) is made at 1450 C: https://en.wikipedia.org/wiki/Portland_cement#Manufacturing https://en.wikipedia.org/wiki/Portland_cement#Manufacturing And looks like any aluminum from the crucible wouldn't contaminate the concrete. Not sure about the nitrogen, but since the air is nitrogen/oxygen, it should be ok: https://www.tandfonline.com/doi/pdf/10.3130/jaabe.10.217 https://www.tandfonline.com/doi/pdf/10.3130/jaabe.10.217 But I think it's important to flip the problem on its head. Since solar thermal energy is essentially free after the solar furnace is manufactured, then we might as well scale it up to provide 2-10x more heat than we need, and then choose a ceramic with the material properties we want, even if its thermal conductivity isn't as efficient as we'd like. Keep in mind that any heat we get from this will be roughly 4 times cheaper than from photovoltaics (running at 25% efficiency) since we avoid the light->electricity->heat conversions.

Armisael16 8y ago
You seem to have a fundamental misunderstanding about how crucibles operate. The outside of the crucible is not supposed to get particularly hot. Heat is applied to the inside; the crucible contains both the material and the heat. If you don’t do this then all the air in the room is also heated up to ludicrous temperatures, and that tends to be bad for any other equipment or people nearby.