3 ms·

Wait, isn't the byproduct of fusion helium anyway?

by 7speter 3y ago

willis936 3y ago
Yeah but you'd power a city for a year for 100 kg of helium.
- ta988 3y ago
  A single MRI needs around 1000 liters, 1L is roughly 130g. For those who wonder prices vary between $15-35 per liter. Recent MRIs have recycling systems that reduce refill needs by 90% when they work properly.
  - willis936 3y ago
    So about $15k for 100 kg?
- Tuna-Fish 3y ago
  Fusion produces much, much less helium than that. D-T fusion that produces 100kg of He-4 would produce something like 25PJ of net primary energy. If you managed to turn 20% of that into electricity, you'd have 5PJ. This is within an order of magnitude of the yearly electricity consumption of the entire world.
  - willis936 3y ago
    I do actually have receipts. For example numbers I picked Washington DC, which has 700k people that each use an average of 600 kWh per month. That's 5 TWh / year, which I rounded up to 10 TWh. This yields 475 m^3 of helium, which is 85 kg. I rounded up to 100. DC is a modest city and all of humanity uses 15000 TWh / year (of heat). This "100 kg / city / year" estimate is even on the lower end since I started with electric consumption and never put in the factor of 3 to convert to thermal. Your mass-energy conversion number is within error of mine, but your estimate of how much power we use is much lower. https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817.59+MeV%29+%2F+%28avogadro%27s+number+1%2Fmol%29+*+%284.002602+g%2Fmol%29+%2F+%280.1786+g+%2F+liter%29 https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817....
  - k8wk1 3y ago
    5PJ is not that large, only 1.4 TWh.
    - pfdietz 3y ago
      In contrast, world primary energy consumption is at a rate of around 20 TW, or five orders of magnitude more than that per year.
      - pas 3y ago
        For anyone else wondering about the five orders of magnitude: https://ourworldindata.org/energy-production-consumption https://ourworldindata.org/energy-production-consumption Yearly total energy consumption 160 PWh (~18 TW of power) 114285 times more than 1.4 TWh

Wait, isn't the byproduct of fusion helium anyway?

willis936 3y ago

Yeah but you'd power a city for a year for 100 kg of helium.

ta988 3y ago
A single MRI needs around 1000 liters, 1L is roughly 130g. For those who wonder prices vary between $15-35 per liter. Recent MRIs have recycling systems that reduce refill needs by 90% when they work properly.
- willis936 3y ago
  So about $15k for 100 kg?
Tuna-Fish 3y ago
Fusion produces much, much less helium than that. D-T fusion that produces 100kg of He-4 would produce something like 25PJ of net primary energy. If you managed to turn 20% of that into electricity, you'd have 5PJ. This is within an order of magnitude of the yearly electricity consumption of the entire world.
- willis936 3y ago
  I do actually have receipts. For example numbers I picked Washington DC, which has 700k people that each use an average of 600 kWh per month. That's 5 TWh / year, which I rounded up to 10 TWh. This yields 475 m^3 of helium, which is 85 kg. I rounded up to 100. DC is a modest city and all of humanity uses 15000 TWh / year (of heat). This "100 kg / city / year" estimate is even on the lower end since I started with electric consumption and never put in the factor of 3 to convert to thermal. Your mass-energy conversion number is within error of mine, but your estimate of how much power we use is much lower. https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817.59+MeV%29+%2F+%28avogadro%27s+number+1%2Fmol%29+*+%284.002602+g%2Fmol%29+%2F+%280.1786+g+%2F+liter%29 https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817....
- k8wk1 3y ago
  5PJ is not that large, only 1.4 TWh.
  - pfdietz 3y ago
    In contrast, world primary energy consumption is at a rate of around 20 TW, or five orders of magnitude more than that per year.
    - pas 3y ago
      For anyone else wondering about the five orders of magnitude: https://ourworldindata.org/energy-production-consumption https://ourworldindata.org/energy-production-consumption Yearly total energy consumption 160 PWh (~18 TW of power) 114285 times more than 1.4 TWh