6 ms·

This is some bad reasoning. Solar efficiency is very different from say engine efficiency. A very efficient combustion engine is 35% efficient meaning it wastes

This is some bad reasoning. Solar efficiency is very different from say engine efficiency. A very efficient combustion engine is 35% efficient meaning it wastes 65% of the energy in the input fuel. Solar panels don’t waste sunlight and have no input costs. Rooftop solar turns 20% of something that would have been 100% wasted into high grade energy. A very efficient coal power plant is 45% efficient before transmission losses. That means more than half the energy in the coal is wasted. Solar wastes nothing. Your numbers on solar panel degradation are also incorrect based on my experience in the industry. They do degrade but not at that at 7+% per year for ten years. Edit: corrected degradation amount

arcticbull 4y ago
> Solar panels don’t waste sunlight and have no input costs. Not exactly, the point is that building and installing solar panels consumes resources and physical space. A solar plant with 100% efficient panels is 1/10th the size of today's solar plant, and as I mentioned, to generate comparable amounts of power to conventional sources requires huge amounts of landmass. Plus input materials. And it has to be replaced every 20 years. > Rooftop solar turns 20% of something that would have been 100% wasted into high grade energy. Not 20%, right, closer to 15%. Rooftop solar also kills about 10X as many people per generated TWh (0.44-0.83 people per TWh) as compared to nuclear power (0.04 people per TWh) - due to installation. [1] I'm not advocating for coal of course, but it's wrong to say solar wastes nothing. There's input materials, plastics, silicon - all sorts of toxic chemicals - and generates tons and tons of e-waste that we don't really have a plan for right now. [2] > Your numbers on solar panel degradation are also incorrect based on my experience in the industry. They do degrade but not at that at 2% per year for ten years. As I mentioned, the degradation rate is highest in the first year, I said 2.5%, but then it drops off to about 0.5% in subsequent years. The data comes from an NREL analytical review. [3] NOTE: I edited the number to more generously assume the 0.5%-1% degradation was not in percent efficiency but rather in percent capacity - which is 1/5th as much, to your point. [1] https://www.nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html https://www.nextbigfuture.com/2011/03/deaths-per-twh-by-ener... [2] https://www.wired.com/story/solar-panels-are-starting-to-die-leaving-behind-toxic-trash/ https://www.wired.com/story/solar-panels-are-starting-to-die... [3] https://www.nrel.gov/docs/fy12osti/51664.pdf https://www.nrel.gov/docs/fy12osti/51664.pdf
- dpierce9 4y ago
  Not sure why I am responding since you moved the goal posts from operating efficiency to lifecycle efficiency but even there you are wrong. To your point re: land use, this is why I said rooftop solar. The roof is already there, the structure is already there, there is zero additional land use and very little opportunity cost for the space. Further, the land use for coal is much broader than the plant area because of mining, transit, and waste heat management. There was a recent post on HN comparing total land usage by prime mover. Solar is only deadlier per unit than coal if you ignore substantial local health effects that aren’t priced in.[0] Your implied rate of degradation to go from 20-10 is more than 7%. Even 15-10 is more than 2.5% and again that is an absurd number that contradicts observed performance. You misunderstand what degradation means in this context, to your point. [0] https://surgery.duke.edu/news/despite-studies-health-effects-coal-burning-power-plants-remain-unknown https://surgery.duke.edu/news/despite-studies-health-effects...
  - arcticbull 4y ago
    I never said anything about coal, and I updated the degradation numbers per your suggestion, but the degradation numbers themselves come from NREL. I think you're confusing the derating due to temperature with degradation. They are additive.
    - dpierce9 4y ago
      Panel temps go up and down depending on time, date, location, and weather. On cool, sunny spring days you can see panels produce more than they are rated. You can’t simply apply a fixed worst-case derate for all time to all panels regardless of installation details. Further, the derates are not additive, they are multiplicative. (A a 20% panel which has degraded in lab efficiency by 10% operating at 90% thermal efficiency is running at 16.2% efficient compared to 18% for a non-degraded panel). Nothing you have said, however, addresses my first and principal point which is that operational efficiency has a different meaning for solar when compared to anything that has non-free inputs. Efficiency is outputs/inputs. One way to look at it is [energy out]/[energy hitting panel]. That is 20% for a solar plant, 45% for an nuclear analogue. Another, financial way is [value of output]/[cost of inputs]. This is infinity for solar setting aside fixed/financing costs and quite finite for nuclear using the same assumptions.
fluoridation 4y ago
>Solar efficiency is very different from say engine efficiency. A very efficient combustion engine is 35% efficient meaning it wastes 65% of the energy in the input fuel. Solar panels don’t waste sunlight and have no input costs. They're exactly the same kinds of waste. A 35% efficient IC engine wastes 65% of the energy in the fuel heating itself up. A 20% efficient photovoltaic cell wastes 80% of the energy in the light heating itself up.
- shmeeed 4y ago
  This argument only stood if the fuel for the IC engine were raining from heaven for free and would go 100% to waste if not burned, and if the combustion process itself produced no other waste than heat, both of which are obviously not true. You have to consider /all/ inputs and outputs for any honest assessment of efficiency. Yes, I am aware solar cells need to be manufactured, producing waste in the process. Still, the same applies for all alternatives, neither fossil nor nuclear plants grow on trees.
  - fluoridation 4y ago
    That's not what "efficiency" means, though. The efficiency of a power source is the ratio between the actually generated work and the work that could theoretically be generated. I don't know if the metric you're referencing has a name but let's call it "greenness". arcticbull's argument was that solar panels are inefficient at converting light into electricity, not that they're ungreen. dpierce9 tried to reframe the discussion from efficiency into greenness for no apparent reason.
    - dpierce9 4y ago
      My argument has nothing to do with ‘greenness’. What I am talking about already has a name: marginal productivity or marginal efficiency. My point is if you have to dig and burn 2.5 rocks to get 1 rocks worth of energy you are really concerned with that ratio for a whole host of reasons and affects everything you do (it is one reason why coal plants are huge for instance). Now say you can get a rocks worth of energy with no rocks to dig and burn. Of course you still want to get the most amount of energy and there is an upper limit to how much you can collect but you no longer think about it in terms of the number of rocks you have to dig out and burn. That is a huge difference.

arcticbull 4y ago

> Solar panels don’t waste sunlight and have no input costs. Not exactly, the point is that building and installing solar panels consumes resources and physical space. A solar plant with 100% efficient panels is 1/10th the size of today's solar plant, and as I mentioned, to generate comparable amounts of power to conventional sources requires huge amounts of landmass. Plus input materials. And it has to be replaced every 20 years. > Rooftop solar turns 20% of something that would have been 100% wasted into high grade energy. Not 20%, right, closer to 15%. Rooftop solar also kills about 10X as many people per generated TWh (0.44-0.83 people per TWh) as compared to nuclear power (0.04 people per TWh) - due to installation. [1] I'm not advocating for coal of course, but it's wrong to say solar wastes nothing. There's input materials, plastics, silicon - all sorts of toxic chemicals - and generates tons and tons of e-waste that we don't really have a plan for right now. [2] > Your numbers on solar panel degradation are also incorrect based on my experience in the industry. They do degrade but not at that at 2% per year for ten years. As I mentioned, the degradation rate is highest in the first year, I said 2.5%, but then it drops off to about 0.5% in subsequent years. The data comes from an NREL analytical review. [3] NOTE: I edited the number to more generously assume the 0.5%-1% degradation was not in percent efficiency but rather in percent capacity - which is 1/5th as much, to your point. [1] https://www.nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html https://www.nextbigfuture.com/2011/03/deaths-per-twh-by-ener... [2] https://www.wired.com/story/solar-panels-are-starting-to-die-leaving-behind-toxic-trash/ https://www.wired.com/story/solar-panels-are-starting-to-die... [3] https://www.nrel.gov/docs/fy12osti/51664.pdf https://www.nrel.gov/docs/fy12osti/51664.pdf

dpierce9 4y ago
Not sure why I am responding since you moved the goal posts from operating efficiency to lifecycle efficiency but even there you are wrong. To your point re: land use, this is why I said rooftop solar. The roof is already there, the structure is already there, there is zero additional land use and very little opportunity cost for the space. Further, the land use for coal is much broader than the plant area because of mining, transit, and waste heat management. There was a recent post on HN comparing total land usage by prime mover. Solar is only deadlier per unit than coal if you ignore substantial local health effects that aren’t priced in.[0] Your implied rate of degradation to go from 20-10 is more than 7%. Even 15-10 is more than 2.5% and again that is an absurd number that contradicts observed performance. You misunderstand what degradation means in this context, to your point. [0] https://surgery.duke.edu/news/despite-studies-health-effects-coal-burning-power-plants-remain-unknown https://surgery.duke.edu/news/despite-studies-health-effects...
- arcticbull 4y ago
  I never said anything about coal, and I updated the degradation numbers per your suggestion, but the degradation numbers themselves come from NREL. I think you're confusing the derating due to temperature with degradation. They are additive.
  - dpierce9 4y ago
    Panel temps go up and down depending on time, date, location, and weather. On cool, sunny spring days you can see panels produce more than they are rated. You can’t simply apply a fixed worst-case derate for all time to all panels regardless of installation details. Further, the derates are not additive, they are multiplicative. (A a 20% panel which has degraded in lab efficiency by 10% operating at 90% thermal efficiency is running at 16.2% efficient compared to 18% for a non-degraded panel). Nothing you have said, however, addresses my first and principal point which is that operational efficiency has a different meaning for solar when compared to anything that has non-free inputs. Efficiency is outputs/inputs. One way to look at it is [energy out]/[energy hitting panel]. That is 20% for a solar plant, 45% for an nuclear analogue. Another, financial way is [value of output]/[cost of inputs]. This is infinity for solar setting aside fixed/financing costs and quite finite for nuclear using the same assumptions.

fluoridation 4y ago

>Solar efficiency is very different from say engine efficiency. A very efficient combustion engine is 35% efficient meaning it wastes 65% of the energy in the input fuel. Solar panels don’t waste sunlight and have no input costs. They're exactly the same kinds of waste. A 35% efficient IC engine wastes 65% of the energy in the fuel heating itself up. A 20% efficient photovoltaic cell wastes 80% of the energy in the light heating itself up.

shmeeed 4y ago
This argument only stood if the fuel for the IC engine were raining from heaven for free and would go 100% to waste if not burned, and if the combustion process itself produced no other waste than heat, both of which are obviously not true. You have to consider /all/ inputs and outputs for any honest assessment of efficiency. Yes, I am aware solar cells need to be manufactured, producing waste in the process. Still, the same applies for all alternatives, neither fossil nor nuclear plants grow on trees.
- fluoridation 4y ago
  That's not what "efficiency" means, though. The efficiency of a power source is the ratio between the actually generated work and the work that could theoretically be generated. I don't know if the metric you're referencing has a name but let's call it "greenness". arcticbull's argument was that solar panels are inefficient at converting light into electricity, not that they're ungreen. dpierce9 tried to reframe the discussion from efficiency into greenness for no apparent reason.
  - dpierce9 4y ago
    My argument has nothing to do with ‘greenness’. What I am talking about already has a name: marginal productivity or marginal efficiency. My point is if you have to dig and burn 2.5 rocks to get 1 rocks worth of energy you are really concerned with that ratio for a whole host of reasons and affects everything you do (it is one reason why coal plants are huge for instance). Now say you can get a rocks worth of energy with no rocks to dig and burn. Of course you still want to get the most amount of energy and there is an upper limit to how much you can collect but you no longer think about it in terms of the number of rocks you have to dig out and burn. That is a huge difference.