5 ms·

500MW from half a gram of hydrogen: The hunt for fusion power heats up

22 points by ukdm 15y ago

ntoshev 15y ago
They probably mean MW/h ...
- pieter 15y ago
  ITER won't produce any stable power at all, so they most likely mean something like "A single run of ITER will consume about half a gram of hydrogen while having a peak output of 500MW (for a few seconds).
  - mrsebastian 15y ago
    Yeah, the plan for ITER is to produce 500MW over 1,000 seconds, with an input power of 50MW (and 0.5 grams of deuterium-tritium fuel). The current record is, like, 10 seconds and no one has broken even on input/output power... Edit: Ah, actually the current record is less than 1 second: http://en.wikipedia.org/wiki/ITER#Background http://en.wikipedia.org/wiki/ITER#Background
- DanWaterworth 15y ago
  I thought that, but I now think it means in a single run, using just half a gram of hydrogen, the peak output power is 500MW, it would be helpful if it also mentioned how much usable energy was generated too.
  - mrsebastian 15y ago
    I don't think anyone knows how much 'usable' energy ITER will generate (plus, ITER won't be a power plant -- the heat produced will actually be thrown away -- so I guess we won't ever know.)
deleted 15y ago
[deleted]
tocomment 15y ago
Fusion idea that I've always had. Why can't we scale up a something like a car engine's piston and cylinder to be 1000's of times bigger and explode hydrogen bombs in it to move the piston up and down? I know it sounds kind of absurd to think about but it seems like it would work to me. Can anyone explain why it wouldn't work? Is it just a cost issue?
- bradleyland 15y ago
  Lots of great answers here, but only a couple really get down to brass tacks. TGFlynn answers the question of why we can't use fusion bombs: "Thermonuclear bombs require a fission explosion to trigger them (in fact I believe most produce more energy from fission than from fusion)." So in short, even setting off "fusion" bombs produces lots of bad byproducts. The other part of your question is, "why not a big piston and cylinder?" Car engines are heat engines as well. They convert heat in to kinetic energy (motion). The problem is that they're relatively inefficient when compared to the typical means of heat/motion conversion used in a power plant. They're also far more complex and require more maintenance than other, simpler designs. The design of a car engine has advantages that suit it well to use in an automobile. Namely that it's power output is easily variable. You don't need peak horsepower when sitting at a stoplight, so you throttle the engine back and generate far less power. This requirement is almost nonexistent in power plants. There is some variability, but you're dealing with average power consumption from thousands of households. The rate of increase/decrease is much, much slower than you find in an automobile. Because of this, power plants use heat engines that might require a lot of energy to get started, but are more efficient once operating. Steam generators coupled with turbines are most common. The heat is used to boil water, which creates steam, which is used to drive some type of turbine. Turbines are wildly efficient if they're designed properly. The primary inefficiency in a steam/turbine power plant is startup and shutdown, but plant operators try to minimize this impact by employing operation strategies that distribute load in a way that can scale up and down minimally. So, why not use a large piston in cylinder design? Because it's less efficient, more complex, requires more maintenance, and requires more materials to construct.
- rbarooah 15y ago
  What use would this have?
zerostar07 15y ago
Looks like those sun gamma rays haven't been following their diet.
GiraffeNecktie 15y ago
I'm not sure why we're still pursuing the incrediblly difficult and expensive route of fusion when thorium is simple, safe, inexpensive and incredibly abundant.
- JumpCrisscross 15y ago
  Because the fusion route is cheaper and more abundant not to mention more powerful. It's not an either or.
- torstesu 15y ago
  I completely agree, especially since Norway has large reserves of the stuff. One challenge though, is that uranium is also abundantly available and still much cheaper to mine than thorium. Another challenge is that it is not the fuel which drives the cost, as in conventional power plants; it is the capital cost concerned with building the reactors themselves. Therefore, a thorium-fueled reactor has to be considerably cheaper to build than a uranium-fueled reactor and it is easy to pose the question if this will ever be true. There has to be some serious subsidizing to incentivize commercial development, adaption and investment.
  - DanBC 15y ago
    People are scared of "Nuclear" - mention uranium and many people will panic. There's the problem of allowing some countries to have a Uranium energy programme which gives them access to the beginnings of nuclear weapons technology.
  - drucken 15y ago
    1. Thorium is a natural by-product, in fact it is in the waste slurry, from rare earth mineral mining. 2. Tiny amounts are required relative to uranium for electricity production. We have already mined in the West more than we will need for a hundred years, if we had production Molten Salt Reactors today. 3. It is far more electrically efficient than uranium. So, there is no comparison purely based on which is the better fuel for fission. Thorium wins by multiple factors if not magnitude across many aspects, including fission waste prodcuts. However, that said, the trust cost of fission is, as you mentioned, the upfront cost of the nuclear reactors. Since this quasi-government industry has seen little innovation in practice for 70+ years, conventional nuclear power plants have remained enormous capital sinks and risky endeavours. There is now some serious research going into MSRs (including thorium) and other nuclear tech. But it is mainly being led by China, excluding sidetracking efforts like the Travelling Wave Reactors of Bill Gates et. al, who need as much energy as they can get.
aqme28 15y ago
This article talks about tokamaks like they're the only magnetic confinement technology out there. Things like stellarators and dipoles have been gaining a lot of ground lately and could one day overtake tokamaks as the standard magnetic confinement tech. http://en.wikipedia.org/wiki/Wendelstein_7-X http://en.wikipedia.org/wiki/Wendelstein_7-X http://en.wikipedia.org/wiki/Levitated_dipole http://en.wikipedia.org/wiki/Levitated_dipole

22 points by ukdm 15y ago

ntoshev 15y ago

They probably mean MW/h ...

pieter 15y ago
ITER won't produce any stable power at all, so they most likely mean something like "A single run of ITER will consume about half a gram of hydrogen while having a peak output of 500MW (for a few seconds).
- mrsebastian 15y ago
  Yeah, the plan for ITER is to produce 500MW over 1,000 seconds, with an input power of 50MW (and 0.5 grams of deuterium-tritium fuel). The current record is, like, 10 seconds and no one has broken even on input/output power... Edit: Ah, actually the current record is less than 1 second: http://en.wikipedia.org/wiki/ITER#Background http://en.wikipedia.org/wiki/ITER#Background
DanWaterworth 15y ago
I thought that, but I now think it means in a single run, using just half a gram of hydrogen, the peak output power is 500MW, it would be helpful if it also mentioned how much usable energy was generated too.
- mrsebastian 15y ago
  I don't think anyone knows how much 'usable' energy ITER will generate (plus, ITER won't be a power plant -- the heat produced will actually be thrown away -- so I guess we won't ever know.)

deleted 15y ago

[deleted]

tocomment 15y ago

Fusion idea that I've always had. Why can't we scale up a something like a car engine's piston and cylinder to be 1000's of times bigger and explode hydrogen bombs in it to move the piston up and down? I know it sounds kind of absurd to think about but it seems like it would work to me. Can anyone explain why it wouldn't work? Is it just a cost issue?

bradleyland 15y ago
Lots of great answers here, but only a couple really get down to brass tacks. TGFlynn answers the question of why we can't use fusion bombs: "Thermonuclear bombs require a fission explosion to trigger them (in fact I believe most produce more energy from fission than from fusion)." So in short, even setting off "fusion" bombs produces lots of bad byproducts. The other part of your question is, "why not a big piston and cylinder?" Car engines are heat engines as well. They convert heat in to kinetic energy (motion). The problem is that they're relatively inefficient when compared to the typical means of heat/motion conversion used in a power plant. They're also far more complex and require more maintenance than other, simpler designs. The design of a car engine has advantages that suit it well to use in an automobile. Namely that it's power output is easily variable. You don't need peak horsepower when sitting at a stoplight, so you throttle the engine back and generate far less power. This requirement is almost nonexistent in power plants. There is some variability, but you're dealing with average power consumption from thousands of households. The rate of increase/decrease is much, much slower than you find in an automobile. Because of this, power plants use heat engines that might require a lot of energy to get started, but are more efficient once operating. Steam generators coupled with turbines are most common. The heat is used to boil water, which creates steam, which is used to drive some type of turbine. Turbines are wildly efficient if they're designed properly. The primary inefficiency in a steam/turbine power plant is startup and shutdown, but plant operators try to minimize this impact by employing operation strategies that distribute load in a way that can scale up and down minimally. So, why not use a large piston in cylinder design? Because it's less efficient, more complex, requires more maintenance, and requires more materials to construct.
rbarooah 15y ago
What use would this have?

zerostar07 15y ago

Looks like those sun gamma rays haven't been following their diet.

GiraffeNecktie 15y ago

I'm not sure why we're still pursuing the incrediblly difficult and expensive route of fusion when thorium is simple, safe, inexpensive and incredibly abundant.

JumpCrisscross 15y ago
Because the fusion route is cheaper and more abundant not to mention more powerful. It's not an either or.
torstesu 15y ago
I completely agree, especially since Norway has large reserves of the stuff. One challenge though, is that uranium is also abundantly available and still much cheaper to mine than thorium. Another challenge is that it is not the fuel which drives the cost, as in conventional power plants; it is the capital cost concerned with building the reactors themselves. Therefore, a thorium-fueled reactor has to be considerably cheaper to build than a uranium-fueled reactor and it is easy to pose the question if this will ever be true. There has to be some serious subsidizing to incentivize commercial development, adaption and investment.
- DanBC 15y ago
  People are scared of "Nuclear" - mention uranium and many people will panic. There's the problem of allowing some countries to have a Uranium energy programme which gives them access to the beginnings of nuclear weapons technology.
- drucken 15y ago
  1. Thorium is a natural by-product, in fact it is in the waste slurry, from rare earth mineral mining. 2. Tiny amounts are required relative to uranium for electricity production. We have already mined in the West more than we will need for a hundred years, if we had production Molten Salt Reactors today. 3. It is far more electrically efficient than uranium. So, there is no comparison purely based on which is the better fuel for fission. Thorium wins by multiple factors if not magnitude across many aspects, including fission waste prodcuts. However, that said, the trust cost of fission is, as you mentioned, the upfront cost of the nuclear reactors. Since this quasi-government industry has seen little innovation in practice for 70+ years, conventional nuclear power plants have remained enormous capital sinks and risky endeavours. There is now some serious research going into MSRs (including thorium) and other nuclear tech. But it is mainly being led by China, excluding sidetracking efforts like the Travelling Wave Reactors of Bill Gates et. al, who need as much energy as they can get.

aqme28 15y ago

This article talks about tokamaks like they're the only magnetic confinement technology out there. Things like stellarators and dipoles have been gaining a lot of ground lately and could one day overtake tokamaks as the standard magnetic confinement tech. http://en.wikipedia.org/wiki/Wendelstein_7-X http://en.wikipedia.org/wiki/Wendelstein_7-X http://en.wikipedia.org/wiki/Levitated_dipole http://en.wikipedia.org/wiki/Levitated_dipole