4 ms·

Once humanity is able to fuse hydrogen atoms into helium, we'll have more helium than we'll know what to do with. Also, why is everyone measuring helium in vol

• btrettel 6y ago
  > Also, why is everyone measuring helium in volume (litres, cubic feet)? This is highly dependent on temperature and pressure. Why not state quantities in terms of mass? This problem appears way more often than I'd like. In measuring gas flow through valves there's a quantity called "standard cubic feet per minute". The only problem is that there is no uniformly agreed upon standard reference temperature and pressure! https://en.wikipedia.org/wiki/Standard_cubic_feet_per_minute https://en.wikipedia.org/wiki/Standard_cubic_feet_per_minute It's even worse than described on Wikipedia, as I've found at least one valve manufacturer claims that the reference pressure is the pressure they used upstream of the valve, not something near atmospheric as Wikipedia claims is typical: http://btrettel.nerfers.com/archives/72 http://btrettel.nerfers.com/archives/72 Whenever I get a valve I either have to do my own flow tests or call the manufacturer and hope I get someone who knows a thing or two about their testing procedures. As you said, the entire issue can be avoided by simply specifying mass or moles. I don't quite know why people don't do this, but I suppose it speaks to the power of tradition. Far too few people think about if what they are doing makes sense.
  • wrycoder 6y ago
    The number of moles in a liter of liquid helium is essentially constant over the temperature range of the liquid state. LH is bought by the liter.
• gliese1337 6y ago
  No, we won't. The whole point of fusion power is that it takes very little fuel to produce a lot of energy. That means very little helium ash produced. If all of the world's current electric power production were fueled by fusion, the helium produced would be a drop in the bucket compared to the total existing helium market.
  • scythe 6y ago
    To illustrate this point, producing all of the electricity the United States uses in a year by D-T fusion would give around 20-100 kg of helium depending on efficiency.
    • m4rtink 6y ago
      I wonder if you could run the process energy negative to produce a lot of helium instead of energy ?
      • eloff 6y ago
        The answer should be clear from the quantities in the parent comment. No. Not economically viable at any plausible price.
    • TomMarius 6y ago
      Maybe we will start projects with enormous power requirements?
    • vilhelm_s 6y ago
      How do you get this number? Googling a bit, the D-T reaction produces 17.59 MeV per helium atom, so it should yield 17.59 MeV / (helium-4 atomic mass) = 0.117 TWh/kg in thermal energy per kg of helium produced. The U.S. electricity production in 2019 was 4,118 TWh [1] and 4118 TWh / 0.117 (TWh/kg) = 35,196 kg. If we assume some inefficency in the thermal->electricity conversion, I guess it should produce at least 70,000 kg/year. [1] https://www.eia.gov/tools/faqs/faq.php?id=427&t=3 https://www.eia.gov/tools/faqs/faq.php?id=427&t=3
• dylan604 6y ago
  Probably because that's how it is sold. They measure the volume of the container it is being sold in. The mom running up to Party City to buy canisters of Helium to fill balloons for little Johnny's birthday doesn't care about how much mass it is.
• usrusr 6y ago
  > This is highly dependent on temperature and pressure. Probably because they are talking about liquefied helium. A convention to reserve mass as the unit of sale for elements in gaseous form seems reasonable, you would want to receive a Very Large Bladder of gas when ordering supplies for an experiment that needs to be chilled with helium.