4 ms·

You might want to try reading the whole post and further editing. And you should consider avoiding all the weird scaling and working in units of energy. For ex

by amluto 2y ago

You might want to try reading the whole post and further editing. And you should consider avoiding all the weird scaling and working in units of energy. For example: > ~65 kilowatts provided per dead bird. This is incoherent. BTW, Wikipedia says the annual net output is 856 GWh, so it’s 143 MWh per bird killed. You’ve forgotten about capacity factor.

foxglacier 2y ago
It's mind-boggling how consistently almost everyone is confused about energy and power units and makes meaningless calculations and claims. People make this kind of mistake pretty much every time there's an energy story. Journalists too. It is confusing but a little red flag appears in my head whenever I try to do this kind of math. It would be nice if we used energy as the main unit and energy/time for power like in SI. Rates seem to be more intuitive than integrals.
- Terr_ 2y ago
  IMO the number one biggest contributor to this problem is "watt hours", it a cursed unit, a name which sows confusion. Even if it were named nonsense like "floops", the world would become a better clearer place. It automatically sounds as if it involves watts, hours, or even watts per hour, but it's actually none of those things. It's just (joules * 3600), where that fixed multiplier comes from a quirk of history in how we subdivided our clocks. My advice? Whenever you see it, replace it with "jumbojoules", as in "I used 87 kilo-jumbojoules running that appliance this month."
Terr_ 2y ago
You misunderstand, the two hypothetical power plants have an equivalent instantaneous power output in watts. It does not matter how long you choose to sit around staring at them, they're doing their steady-state thing in the background, forever. It doesn't matter to them whether the next calculation involves a halfday or a fortnight. The "year" aspect comes into play for taking "solar-fried birds per year" (given to us) and "coal burned per year" (calculated from wattage) and then canceling out the year, leaving us with "solar-fried birds per coal". > you should consider avoiding all the weird scaling and working in units of energy [...] the annual net output is 856 GWh You're the one doing weird stuff here: Even as you say to use units of energy, you are actually using a unit of power, since "annually" means per-year! Choosing to use cursed units (1 watt-hours vs 3600 joules) just makes it even harder to realize what's going on because the word "hour" is hanging out there as a red-herring. > capacity factor Fair enough, I inserted Wikipedia's value for planned/rated level of operation, rather than the much-reduced level it was actually operating under for various reasons.
- mlyle 2y ago
  > You misunderstand, the two hypothetical power plants have an equivalent instantaneous power output in watts. Yes, but they have different capacity factors. That is, the solar plant is not producing power at night, but your calculation gives it credit for it. It's best to just keep sane units; e.g. say this plant generates 3 petajoules each year, and kills 6000 birds/year, so it kills one bird per 500 gigajoules. A coal plant is about 33% efficient, and coal has about 30MJ/kg of specific energy; so we get about 10MJ of electrical energy/kg. So each 50,000 kg of coal mined and burnt would produce the same amount of energy that Ivanpah does between killing birds.
- amluto 2y ago
  > It does not matter how long you choose to sit around staring at them, they're doing their steady-state thing in the background, forever. This is simply not true. Very few power plants work like that, and Ivanpah is definitely an exception. (This is why the capacity factor isn’t 100%.) > > capacity factor > Fair enough, I inserted Wikipedia's value for planned/rated level of operation, rather than the much-reduced level it was actually operating under for various reasons. No, and you might consider reading the article on capacity factor (and don’t stop at the first paragraph - read the section on renewables). If you put 1kW of solar panels on your roof, you are not getting 1kW times 1 year of energy every year — not even close. And you are replying to my objection to: > ~65 kilowatts provided per dead bird. If Ivanpah could kill a bird, once, to produce 65 kW forever, that would be an unbelievably good tradeoff. But, of course, that’s not what Ivanpah does, and saying that years somehow enter the mix later on doesn’t make this statement any more coherent.
  - amluto 2y ago
    > Very few power plants work like that, and Ivanpah is definitely an exception. I meant definitely not an exception.
  - Terr_ 2y ago
    > > napkin math > Very few power plants work like that And most "napkin math" refers to a simplified calculation with rough guesses made in an impromptu or amateur fashion, like using a pen to write with no options nearby except a disposable paper napkin. > > canceling out the year > If Ivanpah could kill a bird, once, to produce 65 kW forever The context is to get ratios between (A) scope/benefit as indicated by wattage and (B) birds-deaths, and (C) coal-used. If you double the activity of each plant, you can expect one to double the fried-birds, and the other to double the coal-needed. It feels like I'm comparing dollars-costs of running electric versus gasoline engines of the same "horsepower", and you're unsatisfied because "a gallon of gasoline can't burn forever."

by amluto 2y ago

foxglacier 2y ago

It's mind-boggling how consistently almost everyone is confused about energy and power units and makes meaningless calculations and claims. People make this kind of mistake pretty much every time there's an energy story. Journalists too. It is confusing but a little red flag appears in my head whenever I try to do this kind of math. It would be nice if we used energy as the main unit and energy/time for power like in SI. Rates seem to be more intuitive than integrals.

Terr_ 2y ago
IMO the number one biggest contributor to this problem is "watt hours", it a cursed unit, a name which sows confusion. Even if it were named nonsense like "floops", the world would become a better clearer place. It automatically sounds as if it involves watts, hours, or even watts per hour, but it's actually none of those things. It's just (joules * 3600), where that fixed multiplier comes from a quirk of history in how we subdivided our clocks. My advice? Whenever you see it, replace it with "jumbojoules", as in "I used 87 kilo-jumbojoules running that appliance this month."

Terr_ 2y ago

You misunderstand, the two hypothetical power plants have an equivalent instantaneous power output in watts. It does not matter how long you choose to sit around staring at them, they're doing their steady-state thing in the background, forever. It doesn't matter to them whether the next calculation involves a halfday or a fortnight. The "year" aspect comes into play for taking "solar-fried birds per year" (given to us) and "coal burned per year" (calculated from wattage) and then canceling out the year, leaving us with "solar-fried birds per coal". > you should consider avoiding all the weird scaling and working in units of energy [...] the annual net output is 856 GWh You're the one doing weird stuff here: Even as you say to use units of energy, you are actually using a unit of power, since "annually" means per-year! Choosing to use cursed units (1 watt-hours vs 3600 joules) just makes it even harder to realize what's going on because the word "hour" is hanging out there as a red-herring. > capacity factor Fair enough, I inserted Wikipedia's value for planned/rated level of operation, rather than the much-reduced level it was actually operating under for various reasons.

mlyle 2y ago
> You misunderstand, the two hypothetical power plants have an equivalent instantaneous power output in watts. Yes, but they have different capacity factors. That is, the solar plant is not producing power at night, but your calculation gives it credit for it. It's best to just keep sane units; e.g. say this plant generates 3 petajoules each year, and kills 6000 birds/year, so it kills one bird per 500 gigajoules. A coal plant is about 33% efficient, and coal has about 30MJ/kg of specific energy; so we get about 10MJ of electrical energy/kg. So each 50,000 kg of coal mined and burnt would produce the same amount of energy that Ivanpah does between killing birds.
amluto 2y ago
> It does not matter how long you choose to sit around staring at them, they're doing their steady-state thing in the background, forever. This is simply not true. Very few power plants work like that, and Ivanpah is definitely an exception. (This is why the capacity factor isn’t 100%.) > > capacity factor > Fair enough, I inserted Wikipedia's value for planned/rated level of operation, rather than the much-reduced level it was actually operating under for various reasons. No, and you might consider reading the article on capacity factor (and don’t stop at the first paragraph - read the section on renewables). If you put 1kW of solar panels on your roof, you are not getting 1kW times 1 year of energy every year — not even close. And you are replying to my objection to: > ~65 kilowatts provided per dead bird. If Ivanpah could kill a bird, once, to produce 65 kW forever, that would be an unbelievably good tradeoff. But, of course, that’s not what Ivanpah does, and saying that years somehow enter the mix later on doesn’t make this statement any more coherent.
- amluto 2y ago
  > Very few power plants work like that, and Ivanpah is definitely an exception. I meant definitely not an exception.
- Terr_ 2y ago
  > > napkin math > Very few power plants work like that And most "napkin math" refers to a simplified calculation with rough guesses made in an impromptu or amateur fashion, like using a pen to write with no options nearby except a disposable paper napkin. > > canceling out the year > If Ivanpah could kill a bird, once, to produce 65 kW forever The context is to get ratios between (A) scope/benefit as indicated by wattage and (B) birds-deaths, and (C) coal-used. If you double the activity of each plant, you can expect one to double the fried-birds, and the other to double the coal-needed. It feels like I'm comparing dollars-costs of running electric versus gasoline engines of the same "horsepower", and you're unsatisfied because "a gallon of gasoline can't burn forever."