8 ms·

It seems to be around the wrong way. We need the nuclear reactors providing constant reliable power day and night to the grid, whereas variable renewables such

by erentz 7y ago

It seems to be around the wrong way. We need the nuclear reactors providing constant reliable power day and night to the grid, whereas variable renewables such as solar are better for creating synthetic fuels since to be viable on a large scale they need to be combined with a form of storage anyway, which is what the synthetic fuels would be.

danans 7y ago
From the article: "Reactors that could power the hydrogen extraction are small enough to be transported by truck and would occupy a building one-10th the size of a nuclear power station." They are talking about a specific type of small nuclear reactor tightly coupled with the synthetic fuel generation. Just speculating, but the waste heat from the nuclear reactor itself could be fed into the fuel synthesis process, making it a sort of combined cycle system. That could be more efficient than trying to use renewables, which generate very little in the way of waste heat.
- darksaints 7y ago
  Fischer Tropsch is typically what people are talking about when they talk about synthetic fuels, and when that is the case, extra heat doesn't help, apart from starting the reaction. You need enough heat to get it to about 250-300C, but once the reaction has started, you need to aggressively remove heat from the reactor, as the reaction is highly exothermic.
- wffurr 7y ago
  Even so, seems like pricing would work out better with the reactors attached to the grid. Lock in a rate for providing baseline power, and then bid for renewable energy to power the facility when spot prices are low enough at times of peak production, and ramp up synthetic fuel production at the same time. You can keep using process heat from the reactor since it's already operating anyway, but get much cheaper electricity (sometimes even negative prices!) from peak renewable generation and turn that into synthetic fuels for storage.
  - greggyb 7y ago
    The challenge with many environmentally-powered renewables is specifically that they can't be used for spot production. Nuclear tends to share this. Most nuclear reactor technology is not optimized for rapid swings in production. A reactor is a very expensive thing to not run most of the time. The two technologies aren't terribly compatible. The first tend to be intermittent (not great for on demand needs) and the second are best suited for base load. What you need is something that is relatively cheap to maintain, and can be ramped up quickly. This is where you typically see natural gas peakers in a fossil-fuel based system. Wikipedia summarizes these well: https://en.wikipedia.org/wiki/Peaking_power_plant https://en.wikipedia.org/wiki/Peaking_power_plant https://en.wikipedia.org/wiki/Base_load https://en.wikipedia.org/wiki/Base_load For peaking demand you need something that can store energy and can adjust to load rapidly. Batteries do this (I include mechanical solutions as batteries, e.g. a flywheel or pumped hydroelectric). Natural gas plants tend to fill this role now. These are not the only options, just common examples.
    - craftinator 7y ago
      Could the excess energy be fed into the local grid during non productive times, help balance out the cost of keeping it running?
      - greggyb 7y ago
        In short, yes, but there are limits. A really (really) rough analogy would be filling a tank of water. If you fill it faster than it can drain, eventually it will overflow. If it is sealed, it may burst. The grid equivalents of an overflowing or bursting tank are not great scenarios. And with intermittent energy sources, there are additional problems. We only get energy sometimes. We want energy always. It basically inverts the idea of base load and peak load sources. If your source is intermittent, then you do want to be able to over-produce at certain times, with an ability to capture the energy. Think batteries, but know that they need not be chemical batteries. Energy storage can then cover the valleys of production or the peaks of demand. Add coordination to the challenges as well. Much (most?) solar is distributed. It's much easier to ramp generation up or down in a few centralized plants. If every home has a solar panel array, then you need to be able (either at the local or the grid level) be able to store excess energy or turn off production. None of this is insurmountable, but there are many challenges that are non-trivial by nature and some that are difficult d/t the way energy grids are typically set up.
Aloha 7y ago
Clean energy seems wildly impractical for airplanes. There is no battery tech approaching kerosene for power density, and unlike fuel, the battery doesn't get lighter as it's used up.
- sitkack 7y ago
  It is already taking over the light plane market. Short haul flights will all be electric in less ten years.
  - Aloha 7y ago
    I think you're being wildly optimistic here about the state and future of the technology
- loeg 7y ago
  The article suggests compressed hydrogen. Although that has obvious problems (at some point there is probably a tradeoff between increased density and the weight of the storage tank required to safely hold that density, which directly related to energy density) and probably more subtle problems, it would be clean-burning. Edit: Random wikipedia page[1] gives energy density of "jet fuel" as 35 MJ/L and liquid (i.e., about as compressed as you're going to get) hydrogen as ... 8.5 MJ/L. Yeah, that's not even close, nevermind. LNG gets you to 22 MJ/L, which is still 2/3 of the density and requires storage at -160°C, which costs more energy, etc, and isn't clean-burning (but maybe slightly better than kerosene). [1]: https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density
  - joe_the_user 7y ago
    The article mentions hydrogen at the start but then says the hydrogen would be used to produce synthetic jet fuel with the properties of regular fuel.
    - loeg 7y ago
      So the idea being: if you pull the carbon out of the air to make your kerosene, burning it again is carbon neutral? That makes sense.
jerrysievert 7y ago
from the article: > The plants, costing 1.8 billion pounds ($2.4 billion) apiece, would feed the national grid and come online from the 2030s, with all complete by 2050.
hokkos 7y ago
An electrolyser is CAPEX expansive based on power usage, so you wouldn't want to run it at 10% to 40% charge factor.
stjohnswarts 7y ago
I agree, replace all the current coal/natural gas/etc factories with nuclear. It's here, it's well understood and it can be done. It will serve us well until fusion is perfected. It will end the global warming issues and we can even take older more fallible reactors offline.
DennisP 7y ago
That depends on the capital expense of the fuel plant. If it's a high percentage of the fuel cost, then it needs power 24/7. On the other hand if energy is the dominant cost, then it's best to take cheap low-cost energy and shut down fuel production other times. That would apply in a nuclear grid as well; you could keep your nukes running 24/7 and run the fuel plants when demand is low.
8bitsrule 7y ago
Nuclear reactors must be periodically shut down for days to months at a time for maintenance. That fact often fails to be mentioned when the 'constant reliable' claim is raised. The Sun, on the other hand, rises each day. Renewables 'on a large scale' become less reliant on storage. Their 'viability' depends on the grid connecting them. On a continent-sized grid the wind is very likely to be blowing. Coupled with full-scale decentralized storage, the viability question blows away.

by erentz 7y ago

danans 7y ago

From the article: "Reactors that could power the hydrogen extraction are small enough to be transported by truck and would occupy a building one-10th the size of a nuclear power station." They are talking about a specific type of small nuclear reactor tightly coupled with the synthetic fuel generation. Just speculating, but the waste heat from the nuclear reactor itself could be fed into the fuel synthesis process, making it a sort of combined cycle system. That could be more efficient than trying to use renewables, which generate very little in the way of waste heat.

darksaints 7y ago
Fischer Tropsch is typically what people are talking about when they talk about synthetic fuels, and when that is the case, extra heat doesn't help, apart from starting the reaction. You need enough heat to get it to about 250-300C, but once the reaction has started, you need to aggressively remove heat from the reactor, as the reaction is highly exothermic.
wffurr 7y ago
Even so, seems like pricing would work out better with the reactors attached to the grid. Lock in a rate for providing baseline power, and then bid for renewable energy to power the facility when spot prices are low enough at times of peak production, and ramp up synthetic fuel production at the same time. You can keep using process heat from the reactor since it's already operating anyway, but get much cheaper electricity (sometimes even negative prices!) from peak renewable generation and turn that into synthetic fuels for storage.
- greggyb 7y ago
  The challenge with many environmentally-powered renewables is specifically that they can't be used for spot production. Nuclear tends to share this. Most nuclear reactor technology is not optimized for rapid swings in production. A reactor is a very expensive thing to not run most of the time. The two technologies aren't terribly compatible. The first tend to be intermittent (not great for on demand needs) and the second are best suited for base load. What you need is something that is relatively cheap to maintain, and can be ramped up quickly. This is where you typically see natural gas peakers in a fossil-fuel based system. Wikipedia summarizes these well: https://en.wikipedia.org/wiki/Peaking_power_plant https://en.wikipedia.org/wiki/Peaking_power_plant https://en.wikipedia.org/wiki/Base_load https://en.wikipedia.org/wiki/Base_load For peaking demand you need something that can store energy and can adjust to load rapidly. Batteries do this (I include mechanical solutions as batteries, e.g. a flywheel or pumped hydroelectric). Natural gas plants tend to fill this role now. These are not the only options, just common examples.
  - craftinator 7y ago
    Could the excess energy be fed into the local grid during non productive times, help balance out the cost of keeping it running?
    - greggyb 7y ago
      In short, yes, but there are limits. A really (really) rough analogy would be filling a tank of water. If you fill it faster than it can drain, eventually it will overflow. If it is sealed, it may burst. The grid equivalents of an overflowing or bursting tank are not great scenarios. And with intermittent energy sources, there are additional problems. We only get energy sometimes. We want energy always. It basically inverts the idea of base load and peak load sources. If your source is intermittent, then you do want to be able to over-produce at certain times, with an ability to capture the energy. Think batteries, but know that they need not be chemical batteries. Energy storage can then cover the valleys of production or the peaks of demand. Add coordination to the challenges as well. Much (most?) solar is distributed. It's much easier to ramp generation up or down in a few centralized plants. If every home has a solar panel array, then you need to be able (either at the local or the grid level) be able to store excess energy or turn off production. None of this is insurmountable, but there are many challenges that are non-trivial by nature and some that are difficult d/t the way energy grids are typically set up.

Aloha 7y ago

Clean energy seems wildly impractical for airplanes. There is no battery tech approaching kerosene for power density, and unlike fuel, the battery doesn't get lighter as it's used up.

sitkack 7y ago
It is already taking over the light plane market. Short haul flights will all be electric in less ten years.
- Aloha 7y ago
  I think you're being wildly optimistic here about the state and future of the technology
loeg 7y ago
The article suggests compressed hydrogen. Although that has obvious problems (at some point there is probably a tradeoff between increased density and the weight of the storage tank required to safely hold that density, which directly related to energy density) and probably more subtle problems, it would be clean-burning. Edit: Random wikipedia page[1] gives energy density of "jet fuel" as 35 MJ/L and liquid (i.e., about as compressed as you're going to get) hydrogen as ... 8.5 MJ/L. Yeah, that's not even close, nevermind. LNG gets you to 22 MJ/L, which is still 2/3 of the density and requires storage at -160°C, which costs more energy, etc, and isn't clean-burning (but maybe slightly better than kerosene). [1]: https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density
- joe_the_user 7y ago
  The article mentions hydrogen at the start but then says the hydrogen would be used to produce synthetic jet fuel with the properties of regular fuel.
  - loeg 7y ago
    So the idea being: if you pull the carbon out of the air to make your kerosene, burning it again is carbon neutral? That makes sense.

jerrysievert 7y ago

from the article: > The plants, costing 1.8 billion pounds ($2.4 billion) apiece, would feed the national grid and come online from the 2030s, with all complete by 2050.

hokkos 7y ago

An electrolyser is CAPEX expansive based on power usage, so you wouldn't want to run it at 10% to 40% charge factor.

stjohnswarts 7y ago

I agree, replace all the current coal/natural gas/etc factories with nuclear. It's here, it's well understood and it can be done. It will serve us well until fusion is perfected. It will end the global warming issues and we can even take older more fallible reactors offline.

DennisP 7y ago

That depends on the capital expense of the fuel plant. If it's a high percentage of the fuel cost, then it needs power 24/7. On the other hand if energy is the dominant cost, then it's best to take cheap low-cost energy and shut down fuel production other times. That would apply in a nuclear grid as well; you could keep your nukes running 24/7 and run the fuel plants when demand is low.

8bitsrule 7y ago

Nuclear reactors must be periodically shut down for days to months at a time for maintenance. That fact often fails to be mentioned when the 'constant reliable' claim is raised. The Sun, on the other hand, rises each day. Renewables 'on a large scale' become less reliant on storage. Their 'viability' depends on the grid connecting them. On a continent-sized grid the wind is very likely to be blowing. Coupled with full-scale decentralized storage, the viability question blows away.