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I'm really confused why you don't follow my argument. Suppose instead of $50 for a 1% efficient goop, my goop only cost $1 but was only 0.1% efficient. That i

I'm really confused why you don't follow my argument. Suppose instead of $50 for a 1% efficient goop, my goop only cost $1 but was only 0.1% efficient. That is five times more efficient per dollar but reduces your yield by 10x! Do you see why nobody who wanted any appreciable amount of solar energy would put my "$1 for a roof's worth of 0.1% efficient solar collection" on their roof? They would naturally choose the "$50 for a roof's worth of 1% efficient solar collection" goop over that one (if those two were the only two choices), even though it's 5x worse per kilowatt-hour? I hope this explains what I'm talking about. A lot of people want more than 0.1% efficiency because they'd like to collect more energy than that...

sbierwagen 9y ago
I follow your argument, I just don't think it matches reality. In any system analysis, you have to consider all the relevant factors. If you wave away important factors for the sake of argument, you get the wrong answers, and end up in long arguments on internet forums, repeating yourself a lot. Let's game out some scenarios using your numbers. The choices are between a $1 array that gives 100 watt-hours, ($0.01/Wh) or a $50 array that gives 1000 watt-hours. ($0.05/Wh) Rooftop solar, grid power is $0.001/Wh: You don't buy either array, since neither is cheaper than grid. This is true for most of the industrialized world. Rooftop solar, grid power is $0.025/Wh: You buy the 100 watt-hour array, since the power it produces is cheaper than grid power. You don't care about total wattage, since you can get all the watts you want from the grid. This is true of places where either electricity is expensive, or PV is subsidized. (Hawaii, Germany, etc) Rooftop solar, grid power is $0.1/Wh: You do buy the 1000 watt-hour array, since it saves you from having to buy expensive grid watt-hours. There is no place on Earth where grid power is more expensive than both single-crystal and multijunction PV. Rooftop solar, offgrid: Here you do strongly care about array output... but you're only offgrid in very rural locations, where land is cheap. In practice, off grid solar is never limited to just rooftops! If you need more watt-hours, you build bigger arrays, rather than paying five times as much per panel. Space: You need every milliwatthour, and each gram of spacecraft costs hundreds of dollars anyway, so multijunction PV suddenly becomes price competitive.
- logicallee 9y ago
  your own third scenario analysis shows (grid power $0.1/Wh), if all rooftop options are cheaper than grid, a worse $/KWh would be chosen as long as it saved reliance on the grid. You left something out of your analysis: people can have an ethical reason to assign a cost of $0.1/Wh to grid power, because they consider environmental externalities they're not paying for, to be something they actually are paying for. If forced to, they may use the grid, but they might treat its cost higher than the listed cost. You've summarized things well in your second sentence: "In any system analysis, you have to consider all the relevant factors." As both your and my analysis show, it is not simply the dollar per kilowatt-hour that informs purchase decisions. If a certain cheap solar array manufacturing process was extremely toxic to the environment, the environmentalist might not buy it at any price. it's a complicated, not simple analysis.

sbierwagen 9y ago

I follow your argument, I just don't think it matches reality. In any system analysis, you have to consider all the relevant factors. If you wave away important factors for the sake of argument, you get the wrong answers, and end up in long arguments on internet forums, repeating yourself a lot. Let's game out some scenarios using your numbers. The choices are between a $1 array that gives 100 watt-hours, ($0.01/Wh) or a $50 array that gives 1000 watt-hours. ($0.05/Wh) Rooftop solar, grid power is $0.001/Wh: You don't buy either array, since neither is cheaper than grid. This is true for most of the industrialized world. Rooftop solar, grid power is $0.025/Wh: You buy the 100 watt-hour array, since the power it produces is cheaper than grid power. You don't care about total wattage, since you can get all the watts you want from the grid. This is true of places where either electricity is expensive, or PV is subsidized. (Hawaii, Germany, etc) Rooftop solar, grid power is $0.1/Wh: You do buy the 1000 watt-hour array, since it saves you from having to buy expensive grid watt-hours. There is no place on Earth where grid power is more expensive than both single-crystal and multijunction PV. Rooftop solar, offgrid: Here you do strongly care about array output... but you're only offgrid in very rural locations, where land is cheap. In practice, off grid solar is never limited to just rooftops! If you need more watt-hours, you build bigger arrays, rather than paying five times as much per panel. Space: You need every milliwatthour, and each gram of spacecraft costs hundreds of dollars anyway, so multijunction PV suddenly becomes price competitive.

logicallee 9y ago
your own third scenario analysis shows (grid power $0.1/Wh), if all rooftop options are cheaper than grid, a worse $/KWh would be chosen as long as it saved reliance on the grid. You left something out of your analysis: people can have an ethical reason to assign a cost of $0.1/Wh to grid power, because they consider environmental externalities they're not paying for, to be something they actually are paying for. If forced to, they may use the grid, but they might treat its cost higher than the listed cost. You've summarized things well in your second sentence: "In any system analysis, you have to consider all the relevant factors." As both your and my analysis show, it is not simply the dollar per kilowatt-hour that informs purchase decisions. If a certain cheap solar array manufacturing process was extremely toxic to the environment, the environmentalist might not buy it at any price. it's a complicated, not simple analysis.