5 ms·

At those temperatures, Carnot efficiency is between 80 and 90 percent. The comparison to steam engines is misleading, but there’s an important distinction. Ste

At those temperatures, Carnot efficiency is between 80 and 90 percent. The comparison to steam engines is misleading, but there’s an important distinction. Steam or gas turbines would reach very high efficiencies at these temperatures too, but won’t because of material properties and limitations thereof. These limitations don’t seem to exist for this new technology. Hence, reaching very high efficiencies becomes possible. In theory… In practice, I don’t see how heat sources with temperatures that high are feasible or could stem from renewable sources. (something with the thermal battery? Wasn’t explained much in the article) In any case, in comparison to steam turbines, the technology presented here does absolutely nothing in terms of decarbonising the grid, as claimed. It’s just potentially more efficient. But what’s the source for the primary energy?

intrepidhero 5y ago
I think the (unstated) idea is to use an arc furnace, during peak solar/wind output to heat graphite and recover the energy later using their fancy new TPV cell. That's going to require some really good insulation, since your heat source is intermittent and your temperature difference is huge. My first thought was let's use it in fission (and later fusion) reactors.
- marcosdumay 5y ago
  It's too hot for a fission reactor. Probably for fusion too, but that's not clear. I got the impression they would heat the graphite with concentrated solar power.
- MisterTea 5y ago
  The problem is it only generates electricity when the input temperature is 1900-2400 C whereas uranium melts at 1132.2 C.
  - klyrs 5y ago
    Passively slurping the heat off a critical puddle of molten uranium is the disruptive startup pitch I'd make to secretly record audience reactions.
    - marcosdumay 5y ago
      With unmoderated fast neutrons, and critical geometry your startup will be always exceptionally close to booming and taking over a huge flank of the market.
    - MisterTea 5y ago
      You can use this as an inspirational soundtrack for the presentation: https://sentientruin.bandcamp.com/album/wormboiler https://sentientruin.bandcamp.com/album/wormboiler
  - the8472 5y ago
    Most civilian reactors use uranium dioxide, which has a melting point of 2865°C. Or uranium carbide, which melts at 2350°C
- 13of40 5y ago
  I think they're talking about something like this: https://www.theverge.com/2022/2/22/22945975/rondo-energy-decarbonize-steel-cement-making-renewable https://www.theverge.com/2022/2/22/22945975/rondo-energy-dec... Basically, in their words, "a large insulated shoebox full of brick". And I could be wrong, but I think you should be able to scale the amount of "brick" up to whatever size and keep the insulation the same thickness, so the storage capacity would increase by the cube of the scale and the amount of insulation would only increase by the square of the scale. That would allow you to minimize the fluctuation in temperature - i.e. if it takes 10 days to get up to temperature, because it's big, you don't have to cool it all the way back to room temperature when you take an afternoon worth of energy back out.
sroussey 5y ago
Heliogen for solar, and Quaise for geothermal. Both have high temperatures to deal with.
fsloth 5y ago
"in comparison to steam turbines, the technology presented here does absolutely nothing in terms of decarbonising the grid, as claimed" I understood the claim to be that this would have close to no moving parts. That sounds it's cheaper to mass manufacure and operate?
- walnutclosefarm 5y ago
  The actual generator has no moving parts. The "tanks" for storing the heat can be made from graphite, but the thermal battery made by combining the storage tank with the generator that they propose has to pump heat around using liquid tin (or perhaps liquid silicon) as the working fluid, at temperatures up to 2400C. That requires not just moving parts, but some pretty far out engineering. All of the metals we commonly build things like pumps out of are liquid at those temperatures, after all. And of course, you want pumps that run reliably for years in that hostile environment.
- diarrhea 5y ago
  Of all things keeping the energy transition back, steam turbine manufacturing is probably very low on the list. I’m not aware it’s an issue. It’s an old and proven technology.
whimsicalism 5y ago
Not to beat a dead horse, but nuclear?
biomcgary 5y ago
For non-mobile storage, it seem that the waste heat (from cooling the TPV) would still be at such a high temperature that it can be used for co-generation to improve total system efficiency. Do existing technologies exists to make optimal use of this "temperature bandgap"? Would direct to steam work efficiently?

intrepidhero 5y ago

I think the (unstated) idea is to use an arc furnace, during peak solar/wind output to heat graphite and recover the energy later using their fancy new TPV cell. That's going to require some really good insulation, since your heat source is intermittent and your temperature difference is huge. My first thought was let's use it in fission (and later fusion) reactors.

marcosdumay 5y ago
It's too hot for a fission reactor. Probably for fusion too, but that's not clear. I got the impression they would heat the graphite with concentrated solar power.
MisterTea 5y ago
The problem is it only generates electricity when the input temperature is 1900-2400 C whereas uranium melts at 1132.2 C.
- klyrs 5y ago
  Passively slurping the heat off a critical puddle of molten uranium is the disruptive startup pitch I'd make to secretly record audience reactions.
  - marcosdumay 5y ago
    With unmoderated fast neutrons, and critical geometry your startup will be always exceptionally close to booming and taking over a huge flank of the market.
  - MisterTea 5y ago
    You can use this as an inspirational soundtrack for the presentation: https://sentientruin.bandcamp.com/album/wormboiler https://sentientruin.bandcamp.com/album/wormboiler
- the8472 5y ago
  Most civilian reactors use uranium dioxide, which has a melting point of 2865°C. Or uranium carbide, which melts at 2350°C
13of40 5y ago
I think they're talking about something like this: https://www.theverge.com/2022/2/22/22945975/rondo-energy-decarbonize-steel-cement-making-renewable https://www.theverge.com/2022/2/22/22945975/rondo-energy-dec... Basically, in their words, "a large insulated shoebox full of brick". And I could be wrong, but I think you should be able to scale the amount of "brick" up to whatever size and keep the insulation the same thickness, so the storage capacity would increase by the cube of the scale and the amount of insulation would only increase by the square of the scale. That would allow you to minimize the fluctuation in temperature - i.e. if it takes 10 days to get up to temperature, because it's big, you don't have to cool it all the way back to room temperature when you take an afternoon worth of energy back out.

sroussey 5y ago

Heliogen for solar, and Quaise for geothermal. Both have high temperatures to deal with.

fsloth 5y ago

"in comparison to steam turbines, the technology presented here does absolutely nothing in terms of decarbonising the grid, as claimed" I understood the claim to be that this would have close to no moving parts. That sounds it's cheaper to mass manufacure and operate?

walnutclosefarm 5y ago
The actual generator has no moving parts. The "tanks" for storing the heat can be made from graphite, but the thermal battery made by combining the storage tank with the generator that they propose has to pump heat around using liquid tin (or perhaps liquid silicon) as the working fluid, at temperatures up to 2400C. That requires not just moving parts, but some pretty far out engineering. All of the metals we commonly build things like pumps out of are liquid at those temperatures, after all. And of course, you want pumps that run reliably for years in that hostile environment.
diarrhea 5y ago
Of all things keeping the energy transition back, steam turbine manufacturing is probably very low on the list. I’m not aware it’s an issue. It’s an old and proven technology.

whimsicalism 5y ago

Not to beat a dead horse, but nuclear?

biomcgary 5y ago

For non-mobile storage, it seem that the waste heat (from cooling the TPV) would still be at such a high temperature that it can be used for co-generation to improve total system efficiency. Do existing technologies exists to make optimal use of this "temperature bandgap"? Would direct to steam work efficiently?