8 ms·

That's what I thought as well. Silicon is basically.... well, sand, isn't it?

by caladan 14y ago

kragen 14y ago
In the same way that aluminum and iron are basically sand, yes.
Tuna-Fish 14y ago
Going from sand to pure polysilicon is extremely energy-intensive and expensive.
- debacle 14y ago
  Cu2o is still about 2-3x as expensive, though.
  - mchannon 14y ago
    Silicon wafers (cheap ones) cost about $150/kg. Polysilicon (good luck making a wafer out of it) costs about $30/kg (market has crashed). Copper costs about $7.50/kg.
- Daniel_Newby 14y ago
  It's not terribly energy intensive. You want to see energy intensive, pick up a beer can. Aluminum is electricity in solid form. Silicon is capital equipment intensive. It is processed in batches. While each batch is being processed, it ties up an expensive processing station for a long time.
  - mchannon 14y ago
    1 pound of metallurgical grade silicon takes about 1 pound of coal and 1 pound of wood chips. 1 pound of polysilicon takes about 2 pounds of metallurgical grade and even more energy. 1 pound of wafer takes about 2 pounds of polysilicon and even more energy. Aluminum probably doesn't take as much energy but the difference is Silicon's energy is cheap (coal and wood chips for the first step).
    - Joakal 14y ago
      Isn't the reason that silicon is cheap to process is because there are high-silicon sands at Silicon Valley and other places? By the way, would a solar furnace be feasible to replace your first step, eliminating CO2 result?
      - mchannon 14y ago
        I'm sure you didn't mean it as such, but that's actually kinda funny; no, Silicon Valley did not get its name from the manufacture of Silicon from sand. Most of the sand that is sourced to make your microchips and solar cells comes from quartz mines and sand pits in Appalachia; Alabama, SE Ohio, and West Virginia are probably the top producers. Silicon Valley imports wafers and has historically had very little to do with how those wafers got made. In fact, according to the foreman at one of said plants I talked to, they use pieces of quartzite that are more like pebbles than sand; no point in crushing it further I guess. The function of the carbon is not just to create the heat but also to give the oxygen some way to remove itself. In fact, I believe the oxygen would still rather bond to silicon than carbon but the carbon is able to pull enough physically away as gas to make the reaction work. The resultant gas is mostly CO, carbon monoxide, which somehow becomes CO2 after the plant's done with it.
  - Someone 14y ago
    http://agmetalminer.com/2009/02/26/power-costs-the-production-primary-aluminum/ http://agmetalminer.com/2009/02/26/power-costs-the-productio...: "Although the newest smelters can be closer to 12,500 kWh per ton let’s say most smelters are consuming electricity at 14,500-15,000 kWh/ton of ingot produced." So, that is 12 to 15 kWH per kilogram. Compare that with http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pdf http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pd...: "In making MG-Si, approximately 12 kilowatt-hours of electrical energy are consumed per kilogram of silicon produced." That already is in the same ballpark, for MG = metallurgical grade silicon. Getting from there at the purity needed for chip production is energy intensive. From the same text: "Energy consumption for the Siemens process is ~200 kilowatt hours/kilogram of silicon produced" Even correcting for a potential bias of the author (who has his own patented process that he claims to be more efficient and, I guess, that he wants to sell), I conclude that, per kg, production of silicon-grade silicon is way more energy expensive than production of aluminum. On the other hand, http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pdf http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pd... seems to indicate that chip-quality silicon is overkill for solar cells. A dedicated factory for solar cell silicon would be more energy efficient than what exists now.
forgottenpaswrd 14y ago
Not really. Sand is (among other things) silicon but silicon(crystalline) is not sand.
mchannon 14y ago
It's not just sand. It's sand with the oxygen removed. The oxygen (especially every last atom) doesn't want to leave. Silicon has to be purified to 99.9999% at the very least to make a crappy solar cell. Add four more 9's to get to making decent microprocessors. Getting certain impurities out (that behave exactly like silicon in a chemical sense) is really difficult.
- sukuriant 14y ago
  You're using some interesting numbers. Citation?
  - duaneb 14y ago
    http://www.techradar.com/us/news/computing-components/processors/how-sand-is-transformed-into-silicon-chips-599785 http://www.techradar.com/us/news/computing-components/proces... http://www.cam.ac.uk/research/features/solar-grade-silicon-at-low-cost/ http://www.cam.ac.uk/research/features/solar-grade-silicon-a... That's 30 seconds of Googling. I can't vouch for how accurate they are.
Ingaz 14y ago
And aluminium is basically clay. But 75% of the price of aluminium is electricity.

That's what I thought as well. Silicon is basically.... well, sand, isn't it?

by caladan 14y ago

That's what I thought as well. Silicon is basically.... well, sand, isn't it?

kragen 14y ago

In the same way that aluminum and iron are basically sand, yes.

Tuna-Fish 14y ago

Going from sand to pure polysilicon is extremely energy-intensive and expensive.

debacle 14y ago
Cu2o is still about 2-3x as expensive, though.
- mchannon 14y ago
  Silicon wafers (cheap ones) cost about $150/kg. Polysilicon (good luck making a wafer out of it) costs about $30/kg (market has crashed). Copper costs about $7.50/kg.
Daniel_Newby 14y ago
It's not terribly energy intensive. You want to see energy intensive, pick up a beer can. Aluminum is electricity in solid form. Silicon is capital equipment intensive. It is processed in batches. While each batch is being processed, it ties up an expensive processing station for a long time.
- mchannon 14y ago
  1 pound of metallurgical grade silicon takes about 1 pound of coal and 1 pound of wood chips. 1 pound of polysilicon takes about 2 pounds of metallurgical grade and even more energy. 1 pound of wafer takes about 2 pounds of polysilicon and even more energy. Aluminum probably doesn't take as much energy but the difference is Silicon's energy is cheap (coal and wood chips for the first step).
  - Joakal 14y ago
    Isn't the reason that silicon is cheap to process is because there are high-silicon sands at Silicon Valley and other places? By the way, would a solar furnace be feasible to replace your first step, eliminating CO2 result?
    - mchannon 14y ago
      I'm sure you didn't mean it as such, but that's actually kinda funny; no, Silicon Valley did not get its name from the manufacture of Silicon from sand. Most of the sand that is sourced to make your microchips and solar cells comes from quartz mines and sand pits in Appalachia; Alabama, SE Ohio, and West Virginia are probably the top producers. Silicon Valley imports wafers and has historically had very little to do with how those wafers got made. In fact, according to the foreman at one of said plants I talked to, they use pieces of quartzite that are more like pebbles than sand; no point in crushing it further I guess. The function of the carbon is not just to create the heat but also to give the oxygen some way to remove itself. In fact, I believe the oxygen would still rather bond to silicon than carbon but the carbon is able to pull enough physically away as gas to make the reaction work. The resultant gas is mostly CO, carbon monoxide, which somehow becomes CO2 after the plant's done with it.
- Someone 14y ago
  http://agmetalminer.com/2009/02/26/power-costs-the-production-primary-aluminum/ http://agmetalminer.com/2009/02/26/power-costs-the-productio...: "Although the newest smelters can be closer to 12,500 kWh per ton let’s say most smelters are consuming electricity at 14,500-15,000 kWh/ton of ingot produced." So, that is 12 to 15 kWH per kilogram. Compare that with http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pdf http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pd...: "In making MG-Si, approximately 12 kilowatt-hours of electrical energy are consumed per kilogram of silicon produced." That already is in the same ballpark, for MG = metallurgical grade silicon. Getting from there at the purity needed for chip production is energy intensive. From the same text: "Energy consumption for the Siemens process is ~200 kilowatt hours/kilogram of silicon produced" Even correcting for a potential bias of the author (who has his own patented process that he claims to be more efficient and, I guess, that he wants to sell), I conclude that, per kg, production of silicon-grade silicon is way more energy expensive than production of aluminum. On the other hand, http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pdf http://www.rsi-silicon.com/media/SolarGradeSilicon_050611.pd... seems to indicate that chip-quality silicon is overkill for solar cells. A dedicated factory for solar cell silicon would be more energy efficient than what exists now.

forgottenpaswrd 14y ago

Not really. Sand is (among other things) silicon but silicon(crystalline) is not sand.

mchannon 14y ago

It's not just sand. It's sand with the oxygen removed. The oxygen (especially every last atom) doesn't want to leave. Silicon has to be purified to 99.9999% at the very least to make a crappy solar cell. Add four more 9's to get to making decent microprocessors. Getting certain impurities out (that behave exactly like silicon in a chemical sense) is really difficult.

sukuriant 14y ago
You're using some interesting numbers. Citation?
- duaneb 14y ago
  http://www.techradar.com/us/news/computing-components/processors/how-sand-is-transformed-into-silicon-chips-599785 http://www.techradar.com/us/news/computing-components/proces... http://www.cam.ac.uk/research/features/solar-grade-silicon-at-low-cost/ http://www.cam.ac.uk/research/features/solar-grade-silicon-a... That's 30 seconds of Googling. I can't vouch for how accurate they are.

Ingaz 14y ago

And aluminium is basically clay. But 75% of the price of aluminium is electricity.