5 ms·

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 ha

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.

fluoridation 4y ago
That's fine, and that's a metric that's worth considering, but you're not talking about the same kind of efficiency arcticbull was talking about. When someone says that "a solar panel is 20% efficient" what they mean is that, of the energy contained in the light that hits it, 20% of it is converted into electricity and the rest is converted into waste heat stored in the panel. Yes, if the panel hadn't been there 100% of that energy would have gone unused, but that's a different discussion. It doesn't make what arcticbull said false. Optimistically a new solar panel is 20% efficient, and that efficiency becomes worse with age.
- dpierce9 4y ago
  Articbull is saying nuclear is better than solar for the energy system. He bases this on a claim that solar panels are inefficient along a number of dimensions. Look at his actual comments, they aren’t narrowly related to lab or theoretical efficiency (he is making points about land use, death, etc). There is no real concept of physical inefficiency there is only relative efficiency. And relative efficiency of Rankine cycle prime movers vs semiconductors is not a strictly easy comparison. 20% of something free that would have been entirely wasted is different than 40% of something you have to find, dig out, transport, crush, then filter. I also didn’t say what he said about theoretical panel efficiency is wrong (except all his actual numbers were wrong until he edited them). I am broadly saying this point doesn’t support his conclusion. Edit: you are also wrong about what happens to the energy that hits the panel. Some light is reflected, a lot of light passes right through the panel. Further, panels are designed for particular wavelengths which is why multi gap panels have theoretical efficiencies higher than any thermal plant. And some is turned into heat. All of this would have happened had the panel not been there too except no usable electricity would be created.
  - fluoridation 4y ago
    > Look at his actual comments, they aren’t narrowly related to lab or theoretical efficiency (he is making points about land use, death, etc). I don't know about deaths, but the point about land use is related to theoretical efficiency. If an existing solar plant that is 20% was 100% efficient it could generate five times as much power in the same space, or generate the same power in a fifth of the land it currently uses. The land used by solar power plants is very relevant when considering its practical utility. > 20% of something free that would have been entirely wasted is different than 40% of something you have to find, dig out, transport, crush, then filter. It's not free, though, because those rooftop panels will lose efficiency over time. Eventually they will need to be replaced or they will generate so little power that they may as well not be there. Since they need to be replaced over time then harvesting that 20% of sunlight is no longer free, but carries an ongoing resource cost. Is that more or less than the cost of getting the same total energy from a nuclear power plant? > I am broadly saying this point doesn’t support his conclusion. The conclusion is that solar and wind can at best only complement nuclear, and this is supported by various points about the inefficiency of solar panels. Setting wind aside for the moment, why do you think the fact that solar panels are inefficient and degrade over time doesn't affect their viability as an alternative to nuclear power? Response to edit: I don't know whether the 20% figure counts in the theoretical 100% light that is reflected or unabsorbed. It seems to me that it shouldn't be counted, since if you're going to count light that couldn't have interacted with the cells anyway, then you may as well count light that hits the ground next to the panel, which would mean the panel is 0% efficient.
    - dpierce9 4y ago
      If nuclear plants were twice as efficient that would be great too. They aren’t. Land use isn’t relevant for rooftop solar. There is basically no opportunity cost. Everything becomes less efficient over time. Sunpower warranties their panels for a 20% decline in performance over 25 years. That means a 20% efficient panel is warrantied to be 16% efficient after 25 years in the field. To put that in perspective, panels made 15 years ago were around 16% efficient. There isn’t a cliff and they are still useful. Suppose you abandon the system for whatever reason. You go back to the steady state of not producing power on that site. There is again no cost. I am not saying nuclear is bad. I am outright rejecting the claim that solar panels are inefficient on any dimension that counts. I think this argument about degradation is beyond silly. I also think you are an astroturfing troll.

fluoridation 4y ago

That's fine, and that's a metric that's worth considering, but you're not talking about the same kind of efficiency arcticbull was talking about. When someone says that "a solar panel is 20% efficient" what they mean is that, of the energy contained in the light that hits it, 20% of it is converted into electricity and the rest is converted into waste heat stored in the panel. Yes, if the panel hadn't been there 100% of that energy would have gone unused, but that's a different discussion. It doesn't make what arcticbull said false. Optimistically a new solar panel is 20% efficient, and that efficiency becomes worse with age.

dpierce9 4y ago
Articbull is saying nuclear is better than solar for the energy system. He bases this on a claim that solar panels are inefficient along a number of dimensions. Look at his actual comments, they aren’t narrowly related to lab or theoretical efficiency (he is making points about land use, death, etc). There is no real concept of physical inefficiency there is only relative efficiency. And relative efficiency of Rankine cycle prime movers vs semiconductors is not a strictly easy comparison. 20% of something free that would have been entirely wasted is different than 40% of something you have to find, dig out, transport, crush, then filter. I also didn’t say what he said about theoretical panel efficiency is wrong (except all his actual numbers were wrong until he edited them). I am broadly saying this point doesn’t support his conclusion. Edit: you are also wrong about what happens to the energy that hits the panel. Some light is reflected, a lot of light passes right through the panel. Further, panels are designed for particular wavelengths which is why multi gap panels have theoretical efficiencies higher than any thermal plant. And some is turned into heat. All of this would have happened had the panel not been there too except no usable electricity would be created.
- fluoridation 4y ago
  > Look at his actual comments, they aren’t narrowly related to lab or theoretical efficiency (he is making points about land use, death, etc). I don't know about deaths, but the point about land use is related to theoretical efficiency. If an existing solar plant that is 20% was 100% efficient it could generate five times as much power in the same space, or generate the same power in a fifth of the land it currently uses. The land used by solar power plants is very relevant when considering its practical utility. > 20% of something free that would have been entirely wasted is different than 40% of something you have to find, dig out, transport, crush, then filter. It's not free, though, because those rooftop panels will lose efficiency over time. Eventually they will need to be replaced or they will generate so little power that they may as well not be there. Since they need to be replaced over time then harvesting that 20% of sunlight is no longer free, but carries an ongoing resource cost. Is that more or less than the cost of getting the same total energy from a nuclear power plant? > I am broadly saying this point doesn’t support his conclusion. The conclusion is that solar and wind can at best only complement nuclear, and this is supported by various points about the inefficiency of solar panels. Setting wind aside for the moment, why do you think the fact that solar panels are inefficient and degrade over time doesn't affect their viability as an alternative to nuclear power? Response to edit: I don't know whether the 20% figure counts in the theoretical 100% light that is reflected or unabsorbed. It seems to me that it shouldn't be counted, since if you're going to count light that couldn't have interacted with the cells anyway, then you may as well count light that hits the ground next to the panel, which would mean the panel is 0% efficient.
  - dpierce9 4y ago
    If nuclear plants were twice as efficient that would be great too. They aren’t. Land use isn’t relevant for rooftop solar. There is basically no opportunity cost. Everything becomes less efficient over time. Sunpower warranties their panels for a 20% decline in performance over 25 years. That means a 20% efficient panel is warrantied to be 16% efficient after 25 years in the field. To put that in perspective, panels made 15 years ago were around 16% efficient. There isn’t a cliff and they are still useful. Suppose you abandon the system for whatever reason. You go back to the steady state of not producing power on that site. There is again no cost. I am not saying nuclear is bad. I am outright rejecting the claim that solar panels are inefficient on any dimension that counts. I think this argument about degradation is beyond silly. I also think you are an astroturfing troll.