5 ms·

There is a strong possibility that even fusion reactors will use turbines. They are a very efficient way of converting heat into electricity.

bryanlarsen 4y ago
I argue the opposite, a steam turbine maxes out at about 37% efficiency. The inefficiency and massive capital costs of of steam turbines is a major reason why natural gas is so much cheaper than coal or fission -- natgas uses a combined cycle turbine rather than a steam turbine.
- AtlasBarfed 4y ago
  I believe modern heat --> electric conversion systems use the turbine and several other additional heat --> electricity recapture systems to approach 50-60% efficiency at large scales so they can beat the Carnot Limit of just the turbine engine. https://www.powermag.com/efficiency-improvements-mark-advances-in-gas-turbines/ https://www.powermag.com/efficiency-improvements-mark-advanc... That claims 64% for a gas turbine. LFTR presentations said they could use the brayton cycle I think due to high temps, I'd imagine a fusion would also have the temps to enable brayton cycle and several other tricks to achieve good efficiency. Remember, what matters at scale is cost cost cost. Turbines might not be sexy, but if they are cheap, then that is what you use.
  - aordano 4y ago
    For anyone curious, check out https://en.wikipedia.org/wiki/Rankine_cycle https://en.wikipedia.org/wiki/Rankine_cycle
  - bryanlarsen 4y ago
    > Remember, what matters at scale is cost cost cost. Turbines might not be sexy, but if they are cheap, then that is what you use. Exactly. Turbines (along with the accompanying water treatment, condensers, generators, power transformation) aren't cheap. A 600MW coal plant costs $2B.
- joak 4y ago
  Wind and photovoltaics just skip the heat part in the cycle. Electricity is generated without converting heat to kinetic energy. This is also the case of helion energy fusion solution. Aneutronic fusion with direct energy conversion. No heat in the cycle. The issue with these thermal power solutions is the waste heat. It means you need water nearby to cool down your reactor. Side effect: thermal pollution, raising the temp of rivers and/or coastals water is detrimental to ecosystems. Plus: how do you deal with droughts?
  - depressedpanda 4y ago
    The waste heat needs not be 'waste'; it can effectively be used for district heating. This makes fission quite attractive in colder climates. https://www.powermag.com/district-heating-supply-from-nuclear-power-plants/ https://www.powermag.com/district-heating-supply-from-nuclea...
epistasis 4y ago
There's a difference between "best possible efficiency" and "efficient," and I would argue that anything <75% efficiency is not "very efficient." Especially since a lot of people look to nuclear for applications in space, where it's hard to dissipate all that waste heat.

bryanlarsen 4y ago

I argue the opposite, a steam turbine maxes out at about 37% efficiency. The inefficiency and massive capital costs of of steam turbines is a major reason why natural gas is so much cheaper than coal or fission -- natgas uses a combined cycle turbine rather than a steam turbine.

AtlasBarfed 4y ago
I believe modern heat --> electric conversion systems use the turbine and several other additional heat --> electricity recapture systems to approach 50-60% efficiency at large scales so they can beat the Carnot Limit of just the turbine engine. https://www.powermag.com/efficiency-improvements-mark-advances-in-gas-turbines/ https://www.powermag.com/efficiency-improvements-mark-advanc... That claims 64% for a gas turbine. LFTR presentations said they could use the brayton cycle I think due to high temps, I'd imagine a fusion would also have the temps to enable brayton cycle and several other tricks to achieve good efficiency. Remember, what matters at scale is cost cost cost. Turbines might not be sexy, but if they are cheap, then that is what you use.
- aordano 4y ago
  For anyone curious, check out https://en.wikipedia.org/wiki/Rankine_cycle https://en.wikipedia.org/wiki/Rankine_cycle
- bryanlarsen 4y ago
  > Remember, what matters at scale is cost cost cost. Turbines might not be sexy, but if they are cheap, then that is what you use. Exactly. Turbines (along with the accompanying water treatment, condensers, generators, power transformation) aren't cheap. A 600MW coal plant costs $2B.
joak 4y ago
Wind and photovoltaics just skip the heat part in the cycle. Electricity is generated without converting heat to kinetic energy. This is also the case of helion energy fusion solution. Aneutronic fusion with direct energy conversion. No heat in the cycle. The issue with these thermal power solutions is the waste heat. It means you need water nearby to cool down your reactor. Side effect: thermal pollution, raising the temp of rivers and/or coastals water is detrimental to ecosystems. Plus: how do you deal with droughts?
- depressedpanda 4y ago
  The waste heat needs not be 'waste'; it can effectively be used for district heating. This makes fission quite attractive in colder climates. https://www.powermag.com/district-heating-supply-from-nuclear-power-plants/ https://www.powermag.com/district-heating-supply-from-nuclea...

epistasis 4y ago

There's a difference between "best possible efficiency" and "efficient," and I would argue that anything <75% efficiency is not "very efficient." Especially since a lot of people look to nuclear for applications in space, where it's hard to dissipate all that waste heat.