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> Are you saying it's cloudy for four months straight? No. But it's cloudy most of the time for four month straight (in average there's only 200 hours of sun b

> Are you saying it's cloudy for four months straight? No. But it's cloudy most of the time for four month straight (in average there's only 200 hours of sun between November and February in Copenhagen. Yes, you read it right, that's not even 2 hours per day in average!). > A detailed chart would be nice but a good starting point to imagine is 60-70 days that average 50% solar power and the rest of the year is full solar power minus a couple particularly bad days That's an insane assumption! An average of 50% solar power during the day is the higher bound of what you can expect in the middle of the Nevada desert! (Because you know, the sun rises and falls during the day, it's never going to give the full power during daytime). And because there's night half of the time in average, even in Nevada you end up with load factors around 25%! (Go check the figures!) In winter in Danemark, the situation is obviously far worse! A 2-5% load factor is to be expected depending on the weather. (Just check the live data: we're in April, it's 11am and solar panels are delivering just 10% of their power right now https://app.electricitymaps.com/map/zone/DK-DK1/live/fifteen_minutes https://app.electricitymaps.com/map/zone/DK-DK1/live/fifteen... ) > the 90% number isn't crazy. If this number doesn't sounds crazy to you, it's just because you're completely off in terms of orders of magnitude involved. 90% is likely achievable in southern US with great effort, lots of storage for night times and significant over-paneling, but it's pure science fiction in Denmark.

Dylan16807 6mo ago
> That's an insane assumption! [...] load factor No no no no, that line has nothing to do with load factor. I'm talking about half the kilowatts for the house coming from solar, and half coming from the grid. > Just check the live data There's no way those panels are optimally angled and out of shade if they're making that little. Are those panels installed in rows on the ground? Rows that are pretty close to each other? Panels on a roof, the steeper the better, will see a much higher load factor in winter. I'm other words, a home rooftop install will do much better in winter than a standard commercial install. That's a mixture of chance and optimizing for different things. A thought experiment: You have one big solar panel mounted very high, with a multi-axis aiming system that points it directly at the sun. Do you think the amount of power you can make is going to be that far off a linear relationship with the number of hours of daylight?
- littlestymaar 6mo ago
  > No no no no, that line has nothing to do with load factor. I'm talking about half the kilowatts for the house coming from solar, and half coming from the grid. Assuming consumption isn't correlated with sun hours, these are equivalent unless you over-panel. With a load factor of 5%, you need to over-panel 10x to achieve 50% of your energy supply (in fact it's more complex than this and you'll need even more of that but that's an OK simplifying assumption). > There's no way those panels are optimally angled and out of shade if they're making that little Those are commercial solar farms, optimally angled under the constraint that the cost must be reasonable. > A thought experiment: You have one big solar panel mounted very high, with a multi-axis aiming system that points it directly at the sun. Do you have an idea of how much it would cost?! With Materials + installation + maintenance, such a mechanism would dwarf the price of the panels. There's a reason we don't deploy those at scale in practice … > Do you think the amount of power you can make is going to be that far off a linear relationship with the number of hours of daylight? In a country where 80% of the winter is cloudy, it's going to be very far, yes. The 10% power happening right now is because it's cloudy (light clouds, no rain, but still). It peaked at 40% in recent days with proper sun, but it happened only a handful of times in the entire winter.
  - Dylan16807 6mo ago
    > These are equivalent unless you over-panel. I don't think so? If your Nevada desert load factor is 25%, then we're talking about it dropping to 12% or something. Unless I'm not understanding the way you're using those numbers. > unless you over-panel Some amount of over-paneling would be perfectly fine here. Not 10x, agreed. > Those are commercial solar farms, optimally angled under the constraint that the cost must be reasonable. They're optimized mostly for total power output, which affects things. And they don't have a free house to be mounted on. They're also not trying very hard to avoid shade. The commercial plant has to buy land for every panel, while a house has much more land than panels. That's a massive difference. When the sun is near the horizon, you want your rows of panels to be very far apart or at different heights. Which means: A commercial solar plant like one pictured in the article will have each panel shade most of the next row's panel when the sun is very low. To stop this effect, you need to put the rows super far apart, or put them at different heights (like on a roof). This means a home install could have 4x as much light hit each panel in the depths of winter. > Do you have an idea of how much it would cost?! It's a thought experiment. Don't worry about the cost of tracking. Because it turns out, a 60 degree angle that completely avoids shade is just as good. The key is avoiding shade. Commercial plants do not avoid shade. Rooftop installs do avoid shade (they won't be quite as tilted, but they'll still have a huge advantage). If you have a nice big yard you can also avoid shade. > The 10% load factor happening right now is because it's cloudy (light clouds, no rain, but still). It peaked at 40% in recent days with proper sun, but it happened only a handful of times in the entire winter. I think you didn't go through the full implications of this. It's mid-april. If it's cloudy this far from the depths of winter, that means needing more panels is much more of a year-round thing. Which means a household array needs to be bigger as a baseline. Which means it can tolerate more losses in the winter. The thing that would make 90% unreasonable is the difference between winter and non-winter power output. If spring and/or fall also require lots of panels, then 90% gets more realistic because expanding the system saves money for more months of the year.

Dylan16807 6mo ago

> That's an insane assumption! [...] load factor No no no no, that line has nothing to do with load factor. I'm talking about half the kilowatts for the house coming from solar, and half coming from the grid. > Just check the live data There's no way those panels are optimally angled and out of shade if they're making that little. Are those panels installed in rows on the ground? Rows that are pretty close to each other? Panels on a roof, the steeper the better, will see a much higher load factor in winter. I'm other words, a home rooftop install will do much better in winter than a standard commercial install. That's a mixture of chance and optimizing for different things. A thought experiment: You have one big solar panel mounted very high, with a multi-axis aiming system that points it directly at the sun. Do you think the amount of power you can make is going to be that far off a linear relationship with the number of hours of daylight?

littlestymaar 6mo ago
> No no no no, that line has nothing to do with load factor. I'm talking about half the kilowatts for the house coming from solar, and half coming from the grid. Assuming consumption isn't correlated with sun hours, these are equivalent unless you over-panel. With a load factor of 5%, you need to over-panel 10x to achieve 50% of your energy supply (in fact it's more complex than this and you'll need even more of that but that's an OK simplifying assumption). > There's no way those panels are optimally angled and out of shade if they're making that little Those are commercial solar farms, optimally angled under the constraint that the cost must be reasonable. > A thought experiment: You have one big solar panel mounted very high, with a multi-axis aiming system that points it directly at the sun. Do you have an idea of how much it would cost?! With Materials + installation + maintenance, such a mechanism would dwarf the price of the panels. There's a reason we don't deploy those at scale in practice … > Do you think the amount of power you can make is going to be that far off a linear relationship with the number of hours of daylight? In a country where 80% of the winter is cloudy, it's going to be very far, yes. The 10% power happening right now is because it's cloudy (light clouds, no rain, but still). It peaked at 40% in recent days with proper sun, but it happened only a handful of times in the entire winter.
- Dylan16807 6mo ago
  > These are equivalent unless you over-panel. I don't think so? If your Nevada desert load factor is 25%, then we're talking about it dropping to 12% or something. Unless I'm not understanding the way you're using those numbers. > unless you over-panel Some amount of over-paneling would be perfectly fine here. Not 10x, agreed. > Those are commercial solar farms, optimally angled under the constraint that the cost must be reasonable. They're optimized mostly for total power output, which affects things. And they don't have a free house to be mounted on. They're also not trying very hard to avoid shade. The commercial plant has to buy land for every panel, while a house has much more land than panels. That's a massive difference. When the sun is near the horizon, you want your rows of panels to be very far apart or at different heights. Which means: A commercial solar plant like one pictured in the article will have each panel shade most of the next row's panel when the sun is very low. To stop this effect, you need to put the rows super far apart, or put them at different heights (like on a roof). This means a home install could have 4x as much light hit each panel in the depths of winter. > Do you have an idea of how much it would cost?! It's a thought experiment. Don't worry about the cost of tracking. Because it turns out, a 60 degree angle that completely avoids shade is just as good. The key is avoiding shade. Commercial plants do not avoid shade. Rooftop installs do avoid shade (they won't be quite as tilted, but they'll still have a huge advantage). If you have a nice big yard you can also avoid shade. > The 10% load factor happening right now is because it's cloudy (light clouds, no rain, but still). It peaked at 40% in recent days with proper sun, but it happened only a handful of times in the entire winter. I think you didn't go through the full implications of this. It's mid-april. If it's cloudy this far from the depths of winter, that means needing more panels is much more of a year-round thing. Which means a household array needs to be bigger as a baseline. Which means it can tolerate more losses in the winter. The thing that would make 90% unreasonable is the difference between winter and non-winter power output. If spring and/or fall also require lots of panels, then 90% gets more realistic because expanding the system saves money for more months of the year.