6 ms·

Any power plant on it's own is not reliable (as in running 24x365 without interruption). To provide base load, you need many independent power plants, as this i

by pintxo 7y ago

Any power plant on it's own is not reliable (as in running 24x365 without interruption). To provide base load, you need many independent power plants, as this is the only way to ensure availability. This is independent of the method of power generation. The sun does always shine someplace on the planet[1], and the wind never dies down completely[1], so it is at least theoretically conceivable to provide base load via those sources if you distribute enough solar/wind power plants across the planet. [1] Citation needed

gnode 7y ago
It is inefficient to distribute electricity over very long distances currently, and that inefficiency increases exponentially. Perhaps in the future a global electrical grid backed primarily with solar may be practical with superconducting transmission lines, but for now, generation is relatively local. While a fossil fuel or nuclear plant is not reliable, their unreliability is uncorrelated. Solar and wind have geographically correlated unreliability, which is a major problem. To make them practical, large scale energy storage is necessary. As energy storage is expensive, fossil fuel and nuclear redundant generation is going to be necessary for some time. Scaling demand could also help ease the problem. Electric storage heaters, aluminium smelters, and air conditioning for example can respond dynamically to supply through a real time market, or demand-side response agreement.
- astrodust 7y ago
  > It is inefficient to distribute electricity over very long distances currently... Québec built a 735kV AC very-long-haul transmission system in 1965 to address the efficiency concerns, carrying power over 1000km efficiently and reliably. That's almost the width of Texas. It's also been using renewable hydro-electric power.
- pintxo 7y ago
  True. Today, and probably in the next couple of years. But in 10, 20, 40 years? Hopefully not so much any longer. I firmly believe in the power of engineering research and given humanities history in solving engineering challenges, we will also solve this one. If we will end up with reliable long distance cables, or some form of energy storage I have no opinion on, only the future will tell us.
- mrfusion 7y ago
  I’ve never heard of it increasing exponentially. Also with very high voltage AC we can actually transmit quite far.
  - bluGill 7y ago
    With high voltage DC we can transmit farther then high voltage AC (for reasons I don't understand - ask a high voltage engineer), and it avoids all the phase problems with long distance AC.
    - mrfusion 7y ago
      I don’t understand how you change between voltages with dc? Is it as efficient as AC using transformers?
      - bluGill 7y ago
        Ask an electrical engineer not me. The basic idea is you go to high voltage DC at the generation end, run a long ways (across states), turn the DC to AC and then run that through a transformer. It isn't as efficient as a transformer, but it isn't far behind so you more than get it back by the smaller losses in transmission.
      - pjc50 7y ago
        Effectively a giant version of your laptop power supply. The conversion is not quite as efficient as a transformer, and certainly more expensive, but for long distances the whole system can be more efficient than AC. (The magic component is the "insulated gate bipolar transistor", sometimes using silicon carbide as the semiconducting element. These are capable of multi-kilovolt switching.)
    - gnode 7y ago
      Capacitance is a major reason; the capacitance of the very large line doesn't need to be charged and discharged at very high voltage 100 or 120 times a second (per half wave of 50 or 60Hz). Also, an X volts RMS AC line is 2.8X volts peak-to-peak. The peak voltage is limiting with regards to breakdown voltages, and so DC can reach a higher equivalent voltage on a line with the same maximum voltage.
- dgacmu 7y ago
  This is not correct. Resistive losses are linear with distance. There are some other issues such as getting out of phase, which can require a transformer (and its associated losses), but there's absolutely nothing exponential. For the basics: http://www.learnabout-electronics.org/Resistors/resistors_03.php http://www.learnabout-electronics.org/Resistors/resistors_03...
  - gnode 7y ago
    Naively that's true, but if you consider a distribution grid with a series of transmission line segments at a given voltage, after each segment the voltage is increased to normalise it to the target transmission voltage. Each stage results in a proportional loss of power transmitted, resulting in an exponential loss as distance increases. Achieving a linear transmission loss ignores bounds on the source voltage. In this case, you may as well choose a transmission voltage of infinity and say resistive losses are constant because current tends to zero.
    - dgacmu 7y ago
      No? If I lose a fixed percent at each stage, my losses as a function of distance are slightly sublinear. Ex: 10% per stage, I lose 10% at first loss, then 9%, and so on. Further, if I have intermediate transformers, my current on later segments is lower, which means that my resistive heating is lower, which means my resistance (and therefore loss) is lower.
      - gnode 7y ago
        Consider supplying a fixed amount of power P to a load. If each stage loses 10% of the power transmitted, after one stage you need to supply 1.1P, after the second stage, you must supply that power plus ten percent, and so on, so you need to supply 1.1^N P after N stages.
graycat 7y ago
> This is independent of the method of power generation. Nope: I'm SURE you can see this, wind comes and goes often just hourly. A coal plant commonly can go years without so much as a single flicker in the power output. The coal plant itself and its pile of coal out back are no doubt factors of 10 more reliable than wind or solar. You seem to be dreaming of renewables, at no matter what effort, e.g., superconducting long distance grid lines, molten salt storage, etc. WHY? A lot of nonsense, expensive, chancy, risky nonsense all due to some quasi-religion about CO2. The renewables proponents want to talk storage: Yes, storage would be crucial for much in renewables. But with coal, there's a really easy approach to storage -- just that pile of coal out back renewed occasionally by long coal trains such as Burlington Northern that Buffett invested in. Don't be fooled: It's all a swindle, about CO2, and some people are getting big bucks from this swindle.
- pintxo 7y ago
  The term we are talking about is called capacity factor [1]. According to this article, capacity factor for nuclear (no data for coal available) is ~0.9 vs .2-.4 (hydro), .47 (wind), .29 (solar) for renewables. So the difference in availability between current base load plants (nuclear) and renewables is somewhere between 3x (hydro, solar) and 2x (wind). I got it, that you do not buy into the co2 story, and it's everyones right to have their own opinions. But have you ever considered that there might be other factors which would make it possible for you to see renewables as a worthy alternative? Burning stuff [2,3] causes all sorts of effects on our environment, directly impacting health. [1] https://en.wikipedia.org/wiki/Capacity_factor https://en.wikipedia.org/wiki/Capacity_factor [2] https://toxtown.nlm.nih.gov/sources-of-exposure/power-plants https://toxtown.nlm.nih.gov/sources-of-exposure/power-plants [3] https://en.wikipedia.org/wiki/Great_Smog_of_London https://en.wikipedia.org/wiki/Great_Smog_of_London
  - graycat 7y ago
    > Burning stuff [2,3] causes all sorts of effects on our environment, directly impacting health. It can; apparently in the US long it did; but a lot of the dirt got cleaned up. E.g., can have clean air even in LA and NYC with lots of gasoline and Diesel power cars and trucks. And outside the top 50 or so US cities, car and truck exhaust is a problem not worth even talking about. E.g., coal needs to be cleaned up since it can put out sulfur, mercury, some radioactivity, etc. Some uses of coal in China and India might be causing significant to serious problems there. For some ugly problems, see the movie I referenced here: The movie shows some of what happens in Africa where they try to cook indoors by burning dried animal dung -- really bad, ugly medical problems. They would be much better off burning coal or using electricity from burning coal in a power plant.
makomk 7y ago
Building loads of independent power plants works for non-renewables because the availability of different power plants within the grid is uncorrelated. That isn't true for wind or solar. When the weather's unsuitable for wind or solar generation that means that all power plants in the region stop working, and because weather patterns can affect quite large geographic areas that can take out a huge swathe of power plants.

by pintxo 7y ago

gnode 7y ago

It is inefficient to distribute electricity over very long distances currently, and that inefficiency increases exponentially. Perhaps in the future a global electrical grid backed primarily with solar may be practical with superconducting transmission lines, but for now, generation is relatively local. While a fossil fuel or nuclear plant is not reliable, their unreliability is uncorrelated. Solar and wind have geographically correlated unreliability, which is a major problem. To make them practical, large scale energy storage is necessary. As energy storage is expensive, fossil fuel and nuclear redundant generation is going to be necessary for some time. Scaling demand could also help ease the problem. Electric storage heaters, aluminium smelters, and air conditioning for example can respond dynamically to supply through a real time market, or demand-side response agreement.

astrodust 7y ago
> It is inefficient to distribute electricity over very long distances currently... Québec built a 735kV AC very-long-haul transmission system in 1965 to address the efficiency concerns, carrying power over 1000km efficiently and reliably. That's almost the width of Texas. It's also been using renewable hydro-electric power.
pintxo 7y ago
True. Today, and probably in the next couple of years. But in 10, 20, 40 years? Hopefully not so much any longer. I firmly believe in the power of engineering research and given humanities history in solving engineering challenges, we will also solve this one. If we will end up with reliable long distance cables, or some form of energy storage I have no opinion on, only the future will tell us.
mrfusion 7y ago
I’ve never heard of it increasing exponentially. Also with very high voltage AC we can actually transmit quite far.
- bluGill 7y ago
  With high voltage DC we can transmit farther then high voltage AC (for reasons I don't understand - ask a high voltage engineer), and it avoids all the phase problems with long distance AC.
  - mrfusion 7y ago
    I don’t understand how you change between voltages with dc? Is it as efficient as AC using transformers?
    - bluGill 7y ago
      Ask an electrical engineer not me. The basic idea is you go to high voltage DC at the generation end, run a long ways (across states), turn the DC to AC and then run that through a transformer. It isn't as efficient as a transformer, but it isn't far behind so you more than get it back by the smaller losses in transmission.
    - pjc50 7y ago
      Effectively a giant version of your laptop power supply. The conversion is not quite as efficient as a transformer, and certainly more expensive, but for long distances the whole system can be more efficient than AC. (The magic component is the "insulated gate bipolar transistor", sometimes using silicon carbide as the semiconducting element. These are capable of multi-kilovolt switching.)
  - gnode 7y ago
    Capacitance is a major reason; the capacitance of the very large line doesn't need to be charged and discharged at very high voltage 100 or 120 times a second (per half wave of 50 or 60Hz). Also, an X volts RMS AC line is 2.8X volts peak-to-peak. The peak voltage is limiting with regards to breakdown voltages, and so DC can reach a higher equivalent voltage on a line with the same maximum voltage.
dgacmu 7y ago
This is not correct. Resistive losses are linear with distance. There are some other issues such as getting out of phase, which can require a transformer (and its associated losses), but there's absolutely nothing exponential. For the basics: http://www.learnabout-electronics.org/Resistors/resistors_03.php http://www.learnabout-electronics.org/Resistors/resistors_03...
- gnode 7y ago
  Naively that's true, but if you consider a distribution grid with a series of transmission line segments at a given voltage, after each segment the voltage is increased to normalise it to the target transmission voltage. Each stage results in a proportional loss of power transmitted, resulting in an exponential loss as distance increases. Achieving a linear transmission loss ignores bounds on the source voltage. In this case, you may as well choose a transmission voltage of infinity and say resistive losses are constant because current tends to zero.
  - dgacmu 7y ago
    No? If I lose a fixed percent at each stage, my losses as a function of distance are slightly sublinear. Ex: 10% per stage, I lose 10% at first loss, then 9%, and so on. Further, if I have intermediate transformers, my current on later segments is lower, which means that my resistive heating is lower, which means my resistance (and therefore loss) is lower.
    - gnode 7y ago
      Consider supplying a fixed amount of power P to a load. If each stage loses 10% of the power transmitted, after one stage you need to supply 1.1P, after the second stage, you must supply that power plus ten percent, and so on, so you need to supply 1.1^N P after N stages.

graycat 7y ago

> This is independent of the method of power generation. Nope: I'm SURE you can see this, wind comes and goes often just hourly. A coal plant commonly can go years without so much as a single flicker in the power output. The coal plant itself and its pile of coal out back are no doubt factors of 10 more reliable than wind or solar. You seem to be dreaming of renewables, at no matter what effort, e.g., superconducting long distance grid lines, molten salt storage, etc. WHY? A lot of nonsense, expensive, chancy, risky nonsense all due to some quasi-religion about CO2. The renewables proponents want to talk storage: Yes, storage would be crucial for much in renewables. But with coal, there's a really easy approach to storage -- just that pile of coal out back renewed occasionally by long coal trains such as Burlington Northern that Buffett invested in. Don't be fooled: It's all a swindle, about CO2, and some people are getting big bucks from this swindle.

pintxo 7y ago
The term we are talking about is called capacity factor [1]. According to this article, capacity factor for nuclear (no data for coal available) is ~0.9 vs .2-.4 (hydro), .47 (wind), .29 (solar) for renewables. So the difference in availability between current base load plants (nuclear) and renewables is somewhere between 3x (hydro, solar) and 2x (wind). I got it, that you do not buy into the co2 story, and it's everyones right to have their own opinions. But have you ever considered that there might be other factors which would make it possible for you to see renewables as a worthy alternative? Burning stuff [2,3] causes all sorts of effects on our environment, directly impacting health. [1] https://en.wikipedia.org/wiki/Capacity_factor https://en.wikipedia.org/wiki/Capacity_factor [2] https://toxtown.nlm.nih.gov/sources-of-exposure/power-plants https://toxtown.nlm.nih.gov/sources-of-exposure/power-plants [3] https://en.wikipedia.org/wiki/Great_Smog_of_London https://en.wikipedia.org/wiki/Great_Smog_of_London
- graycat 7y ago
  > Burning stuff [2,3] causes all sorts of effects on our environment, directly impacting health. It can; apparently in the US long it did; but a lot of the dirt got cleaned up. E.g., can have clean air even in LA and NYC with lots of gasoline and Diesel power cars and trucks. And outside the top 50 or so US cities, car and truck exhaust is a problem not worth even talking about. E.g., coal needs to be cleaned up since it can put out sulfur, mercury, some radioactivity, etc. Some uses of coal in China and India might be causing significant to serious problems there. For some ugly problems, see the movie I referenced here: The movie shows some of what happens in Africa where they try to cook indoors by burning dried animal dung -- really bad, ugly medical problems. They would be much better off burning coal or using electricity from burning coal in a power plant.

makomk 7y ago

Building loads of independent power plants works for non-renewables because the availability of different power plants within the grid is uncorrelated. That isn't true for wind or solar. When the weather's unsuitable for wind or solar generation that means that all power plants in the region stop working, and because weather patterns can affect quite large geographic areas that can take out a huge swathe of power plants.