3 ms·

That's why all electric heating should be devices that do work or compute. Do not waste the Gibbs free energy of the universe.

andbberger 3y ago
this was the only sane argument for blockchain mining but it was never competitive with heat pumps
- Scoundreller 3y ago
  Depends how cold it is outside, but yes, heat pumps usually win.
Scoundreller 3y ago
I want a cottage industry of aluminum smelters in cold climates. Pick up a pile of aluminum oxide from a depot, electrolyze it into aluminum at home, and drop off the finished aluminum at the depot for a cheque that covers your electricity. "The theoretical minimum energy requirement for this process is 6.23 kWh/(kg of Al), but the process commonly requires 15.37 kWh." https://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_process https://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_proc... That's quite a few kWh of heat per kg of finished product. You're going from Al2O3 to Al, so your returns will weigh less than your pickups. Comparable to coal or oil heat: "With a complete combustion or fission , approx. 8 kWh of heat can be generated from 1 kg of coal, approx. 12 kWh from 1 kg of mineral oil" https://www.euronuclear.org/glossary/fuel-comparison https://www.euronuclear.org/glossary/fuel-comparison
- Retric 3y ago
  Neat idea. Aluminum smelting isn’t really hands off enough to make this viable at home. It might make sense at industrial scale while pumping waste heat to nearby office buildings or something. But even slightly higher electricity costs would be a huge issue.
- leoedin 3y ago
  The problem is that heat pumps exist, so resistive heating is never the best option. An aluminium smelting at home heating solution would have a maximum CoP of 2 (as you're reducing the energy usage of the smelter by the same amount). A heat pump could easily have a CoP of 3 or 4.
  - Scoundreller 3y ago
    That’s a lot more efficient than an industrial aluminum smelter. The use of electricity as an input is inescapable for this process, so may as well use the waste heat as directly as possible.
  - Retric 3y ago
    You have that math backwards. A smelter turns ~1/2 the energy from electricity into chemical energy and releases the remaining 1/2 as heat thus the COP would be 0.5 not 2. However smelting is profitable because aluminum oxide is less valuable than aluminum which more than compensates for the waste heat having zero value at the smelter. Thus various schemes for combined heat and power etc which take the valueless waste heat and use it for some other purposes like warming homes or greenhouses etc. So while the COP would be 0.5 the electricity would be subsidized by the smelling process. https://en.wikipedia.org/wiki/Cogeneration https://en.wikipedia.org/wiki/Cogeneration Where such schemes fail is generally economies of scale.
grvdrm 3y ago
I should mine BTC in my heatless basement! Love it.

andbberger 3y ago

this was the only sane argument for blockchain mining but it was never competitive with heat pumps

Scoundreller 3y ago
Depends how cold it is outside, but yes, heat pumps usually win.

Scoundreller 3y ago

I want a cottage industry of aluminum smelters in cold climates. Pick up a pile of aluminum oxide from a depot, electrolyze it into aluminum at home, and drop off the finished aluminum at the depot for a cheque that covers your electricity. "The theoretical minimum energy requirement for this process is 6.23 kWh/(kg of Al), but the process commonly requires 15.37 kWh." https://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_process https://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_proc... That's quite a few kWh of heat per kg of finished product. You're going from Al2O3 to Al, so your returns will weigh less than your pickups. Comparable to coal or oil heat: "With a complete combustion or fission , approx. 8 kWh of heat can be generated from 1 kg of coal, approx. 12 kWh from 1 kg of mineral oil" https://www.euronuclear.org/glossary/fuel-comparison https://www.euronuclear.org/glossary/fuel-comparison

Retric 3y ago
Neat idea. Aluminum smelting isn’t really hands off enough to make this viable at home. It might make sense at industrial scale while pumping waste heat to nearby office buildings or something. But even slightly higher electricity costs would be a huge issue.
leoedin 3y ago
The problem is that heat pumps exist, so resistive heating is never the best option. An aluminium smelting at home heating solution would have a maximum CoP of 2 (as you're reducing the energy usage of the smelter by the same amount). A heat pump could easily have a CoP of 3 or 4.
- Scoundreller 3y ago
  That’s a lot more efficient than an industrial aluminum smelter. The use of electricity as an input is inescapable for this process, so may as well use the waste heat as directly as possible.
- Retric 3y ago
  You have that math backwards. A smelter turns ~1/2 the energy from electricity into chemical energy and releases the remaining 1/2 as heat thus the COP would be 0.5 not 2. However smelting is profitable because aluminum oxide is less valuable than aluminum which more than compensates for the waste heat having zero value at the smelter. Thus various schemes for combined heat and power etc which take the valueless waste heat and use it for some other purposes like warming homes or greenhouses etc. So while the COP would be 0.5 the electricity would be subsidized by the smelling process. https://en.wikipedia.org/wiki/Cogeneration https://en.wikipedia.org/wiki/Cogeneration Where such schemes fail is generally economies of scale.

grvdrm 3y ago

I should mine BTC in my heatless basement! Love it.