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> Suppose you have renewable sources that on average generate 100GW. Well, some weeks they're going to average 90GW Renewables' fluctuations are way, way bigge

> Suppose you have renewable sources that on average generate 100GW. Well, some weeks they're going to average 90GW Renewables' fluctuations are way, way bigger than 10%. Solar, by definition, is going to be producing 0% of output 12 hours a day on average. Wind has fluctuations of over 10x as well: https://ars.els-cdn.com/content/image/1-s2.0-S0306261917308346-gr10.jpg https://ars.els-cdn.com/content/image/1-s2.0-S03062619173083... https://www.sciencedirect.com/science/article/abs/pii/S0306261917308346 https://www.sciencedirect.com/science/article/abs/pii/S03062... It's more like, you have renewable sources that produce 100 GW at their times of peak output. And for a couple months of the year they're producing 10GW. If you built 90 GW of nuclear power, then you could just scrap 90% of your renewables and run your nuclear plants all year round. Again, nuclear power plants are just as cheap to run constantly as it is to run them intermittently.

AnthonyMouse 3y ago
I reiterate that we're talking about the daily average and not the instantaneous generation. You have solar panels that generate 100GW average, i.e. 200GW during sunlight and nothing at night. You have batteries to match this up with the daily load. But then it's more cloudy than usual for a couple weeks, so your average generation from solar is 50GW, or 10GW, or what have you, depending on how cloudy it is. You need something to make up the difference that week or the batteries run down and the power goes out. But because averaging 90GW over a day (when the typical average is 100GW) is a lot more common than averaging 10GW, the first 10GW of peaker plants is economical against nuclear and the last 10GW is not. And the total of nuclear + peaker plants has to add up to ~90GW because there will be times when you only average ~10GW from renewables.
- zozbot234 3y ago
  > the first 10GW of peaker plants is economical against nuclear and the last 10GW is not. I'm not sure how well this works given that peaker plants have to pay for their fuel whereas nuclear - to a first approximation - does not; everything is factored in the building cost. So it's more like the first 10GW of nuclear baseload can displace a lot of gas use, whereas the last 10GW shortfall might still be efficiently covered by peaker plants if they're cheaper to build for the same capacity and almost never have to burn fuel. It works out to mostly the same outcome, though.
  - AnthonyMouse 3y ago
    > I'm not sure how well this works given that peaker plants have to pay for their fuel whereas nuclear - to a first approximation - does not; everything is factored in the building cost. It's not about the cost of nuclear, it's about the utilization of peaker plants. If you build 10GW of nuclear, you generate 10GW 100% of the time. If you build 10GW of peaker plants, do you use it 15% of the time or 0.5% of the time? The answer to which depends on if it's the first 10GW of peaker plants (10GW shortfall happens frequently) or the last 10GW of peaker plants (only needed if the first 80GW of installed capacity was used first; 90GW shortfall happens very rarely).
    - zozbot234 3y ago
      Sure, but a peaker plant is providing capacity even when it sits unused. That's a valuable service, and it gets rewarded by usual electricity-market arrangements. So the relevant question is when can this service be provided more cheaply than the same amount of nuclear-supplied capacity.
      - AnthonyMouse 3y ago
        The value of the service depends on how many other peaker plants there already are. > That's a valuable service, and it gets rewarded by usual electricity-market arrangements. This is the bureaucracy papering over the details like an abstraction layer. You want to look at the underlying economics when you're redesigning a system like this. This is napkin math but it should be directionally accurate. Suppose we assign rates to the relationship between supply and demand in the power grid. The price of electricity set by how much demand exceeds supply. Then you're going to have a base rate, call it R0, essentially what electricity costs off-peak on a typical day. This is the rate which is going to prevail for around two thirds of the time. Then you have your normal day peak rate, R1, this is what it costs in the early evening when there is low renewable generation and high demand, basically the higher cost of intra-day energy storage. This might prevail for 1/6th of the hours in a year. Two thirds plus 1/6th, you still have another 1/6th, that's when something bad is happening. It's a bit cloudy today, rate R2, happens 10% of the time. More cloudy, even higher rate R3, 3% of the time. Overcast for the whole day, rate R4, 2% of the time. Overcast for multiple days, rate R5, 1% of the time. Overcast for multiple days in the summer during peak air conditioning demand, rate R6, <1% of the time. Now you can calculate how much value a nuclear plant has, because it generates all the time: 0.6667 * R0 0.1667 * R1 0.1000 * R2 0.0300 * R3 0.0200 * R4 0.0100 * R5 0.0067 * R6 Solar has to recover its costs from just R0, which is the lowest rate, but it can do that by generating for a large number of hours a year relative to a peaker plant, and because it's cheap. Batteries recover their cost during R1, which isn't as many hours but the rate is higher. The first peaker plant gets R2 through R6, because it gets turned on as soon as you hit R2, i.e. you need more than you get from current generation + energy storage. The second peaker plant only generates at R3 through R6 because it doesn't get turned on until then, since the first one was enough during R2. The last peaker plant only generates during R6 and has to justify its entire cost by operating only 0.67% of the time. Which is why R6 is the highest rate, but even then it's a tough sell -- much harder than the other peaker plants which operate during R6 and R5, R4, etc. Whereas the nuclear plant operates ~100% of the time, R0 through R6, replacing both renewable generation on a normal day and peaker generation during a supply crunch. But it costs more to build. So it should be worth it to replace the peaker plant that only operates during R6, but maybe not worth it to replace the peaker plant that operates from R3-R6, and definitely not worth it to replace the peaker plant that operates from R2-R6.
- Manuel_D 3y ago
  > You have solar panels that generate 100GW average, i.e. 200GW during sunlight and nothing at night. You have batteries to match this up with the daily load. And that amount of batteries is absolutely massive. To put this in perspective, the US uses about 500 GW of electricity, or about 12 TWh per day. That's 6,000 GWh for just the United States. This is an incredible amount of storage, over 10x the annual global battery production. This is why talking about "average production" of intermittent sources is simplistic. You need to dig into the degree of overproduction and storage required to even out that intermittency. But including those factors makes renewables way more expensive, which is why people don't like to talk about these factors.
  - AnthonyMouse 3y ago
    > This is an incredible amount of storage, over 10x the annual global battery production. It's a lot. Battery production would have to increase. But it is increasing, and it's not an impossible amount. You also cut it to less than half by doing the thing mentioned above, because the daytime load is higher anyway. If 40% of the generation comes from nuclear, that's 80% of the nighttime load and now you only need 20% as many batteries.
    - Manuel_D 3y ago
      > It's a lot. Battery production would have to increase. But it is increasing, and it's not an impossible amount. Is it? Global battery production is about 500 GWh per year. A single digit percentage of that is going towards grid storage, it's mostly used for EVs and electronics. Even if we completely halted EV production, and dedicated 100% of global battery production to grid storage it'd take over a decade to just satisfy the United States' grid storage requirements. And that's just for diurnal storage, not seasonal storage. And again, that's dedicating 100% of global battery production to just one country. While battery production is increasing, so is electricity use. As transportation and other industries decarbonized, and as poor countries grow richer, electricity use is going to rise and so will the storage requirements. > because the daytime load is higher anyway Nope, in fact it's the opposite. Load typically peaks after sundown, at around 8pm. This is why solving the duck curve is so hard. Solar produces no energy during peak demand: https://en.m.wikipedia.org/wiki/Duck_curve https://en.m.wikipedia.org/wiki/Duck_curve

AnthonyMouse 3y ago

I reiterate that we're talking about the daily average and not the instantaneous generation. You have solar panels that generate 100GW average, i.e. 200GW during sunlight and nothing at night. You have batteries to match this up with the daily load. But then it's more cloudy than usual for a couple weeks, so your average generation from solar is 50GW, or 10GW, or what have you, depending on how cloudy it is. You need something to make up the difference that week or the batteries run down and the power goes out. But because averaging 90GW over a day (when the typical average is 100GW) is a lot more common than averaging 10GW, the first 10GW of peaker plants is economical against nuclear and the last 10GW is not. And the total of nuclear + peaker plants has to add up to ~90GW because there will be times when you only average ~10GW from renewables.

zozbot234 3y ago
> the first 10GW of peaker plants is economical against nuclear and the last 10GW is not. I'm not sure how well this works given that peaker plants have to pay for their fuel whereas nuclear - to a first approximation - does not; everything is factored in the building cost. So it's more like the first 10GW of nuclear baseload can displace a lot of gas use, whereas the last 10GW shortfall might still be efficiently covered by peaker plants if they're cheaper to build for the same capacity and almost never have to burn fuel. It works out to mostly the same outcome, though.
- AnthonyMouse 3y ago
  > I'm not sure how well this works given that peaker plants have to pay for their fuel whereas nuclear - to a first approximation - does not; everything is factored in the building cost. It's not about the cost of nuclear, it's about the utilization of peaker plants. If you build 10GW of nuclear, you generate 10GW 100% of the time. If you build 10GW of peaker plants, do you use it 15% of the time or 0.5% of the time? The answer to which depends on if it's the first 10GW of peaker plants (10GW shortfall happens frequently) or the last 10GW of peaker plants (only needed if the first 80GW of installed capacity was used first; 90GW shortfall happens very rarely).
  - zozbot234 3y ago
    Sure, but a peaker plant is providing capacity even when it sits unused. That's a valuable service, and it gets rewarded by usual electricity-market arrangements. So the relevant question is when can this service be provided more cheaply than the same amount of nuclear-supplied capacity.
    - AnthonyMouse 3y ago
      The value of the service depends on how many other peaker plants there already are. > That's a valuable service, and it gets rewarded by usual electricity-market arrangements. This is the bureaucracy papering over the details like an abstraction layer. You want to look at the underlying economics when you're redesigning a system like this. This is napkin math but it should be directionally accurate. Suppose we assign rates to the relationship between supply and demand in the power grid. The price of electricity set by how much demand exceeds supply. Then you're going to have a base rate, call it R0, essentially what electricity costs off-peak on a typical day. This is the rate which is going to prevail for around two thirds of the time. Then you have your normal day peak rate, R1, this is what it costs in the early evening when there is low renewable generation and high demand, basically the higher cost of intra-day energy storage. This might prevail for 1/6th of the hours in a year. Two thirds plus 1/6th, you still have another 1/6th, that's when something bad is happening. It's a bit cloudy today, rate R2, happens 10% of the time. More cloudy, even higher rate R3, 3% of the time. Overcast for the whole day, rate R4, 2% of the time. Overcast for multiple days, rate R5, 1% of the time. Overcast for multiple days in the summer during peak air conditioning demand, rate R6, <1% of the time. Now you can calculate how much value a nuclear plant has, because it generates all the time: 0.6667 * R0 0.1667 * R1 0.1000 * R2 0.0300 * R3 0.0200 * R4 0.0100 * R5 0.0067 * R6 Solar has to recover its costs from just R0, which is the lowest rate, but it can do that by generating for a large number of hours a year relative to a peaker plant, and because it's cheap. Batteries recover their cost during R1, which isn't as many hours but the rate is higher. The first peaker plant gets R2 through R6, because it gets turned on as soon as you hit R2, i.e. you need more than you get from current generation + energy storage. The second peaker plant only generates at R3 through R6 because it doesn't get turned on until then, since the first one was enough during R2. The last peaker plant only generates during R6 and has to justify its entire cost by operating only 0.67% of the time. Which is why R6 is the highest rate, but even then it's a tough sell -- much harder than the other peaker plants which operate during R6 and R5, R4, etc. Whereas the nuclear plant operates ~100% of the time, R0 through R6, replacing both renewable generation on a normal day and peaker generation during a supply crunch. But it costs more to build. So it should be worth it to replace the peaker plant that only operates during R6, but maybe not worth it to replace the peaker plant that operates from R3-R6, and definitely not worth it to replace the peaker plant that operates from R2-R6.
Manuel_D 3y ago
> You have solar panels that generate 100GW average, i.e. 200GW during sunlight and nothing at night. You have batteries to match this up with the daily load. And that amount of batteries is absolutely massive. To put this in perspective, the US uses about 500 GW of electricity, or about 12 TWh per day. That's 6,000 GWh for just the United States. This is an incredible amount of storage, over 10x the annual global battery production. This is why talking about "average production" of intermittent sources is simplistic. You need to dig into the degree of overproduction and storage required to even out that intermittency. But including those factors makes renewables way more expensive, which is why people don't like to talk about these factors.
- AnthonyMouse 3y ago
  > This is an incredible amount of storage, over 10x the annual global battery production. It's a lot. Battery production would have to increase. But it is increasing, and it's not an impossible amount. You also cut it to less than half by doing the thing mentioned above, because the daytime load is higher anyway. If 40% of the generation comes from nuclear, that's 80% of the nighttime load and now you only need 20% as many batteries.
  - Manuel_D 3y ago
    > It's a lot. Battery production would have to increase. But it is increasing, and it's not an impossible amount. Is it? Global battery production is about 500 GWh per year. A single digit percentage of that is going towards grid storage, it's mostly used for EVs and electronics. Even if we completely halted EV production, and dedicated 100% of global battery production to grid storage it'd take over a decade to just satisfy the United States' grid storage requirements. And that's just for diurnal storage, not seasonal storage. And again, that's dedicating 100% of global battery production to just one country. While battery production is increasing, so is electricity use. As transportation and other industries decarbonized, and as poor countries grow richer, electricity use is going to rise and so will the storage requirements. > because the daytime load is higher anyway Nope, in fact it's the opposite. Load typically peaks after sundown, at around 8pm. This is why solving the duck curve is so hard. Solar produces no energy during peak demand: https://en.m.wikipedia.org/wiki/Duck_curve https://en.m.wikipedia.org/wiki/Duck_curve