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.
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.
Rooftop solar is more expensive than solar farms. There's nothing free in putting a solar panel on a roof. (Which is a pity because it means that if your country doesn't have a desert, the economically optimal way of installing solar panels is deforestation, but that's the world we live in…).
> Because it turns out, a 60 degree angle that completely avoids shade is just as good
Not at all…
The sun isn't just going up and down you know, it also circles from east to West…
> They're also not trying very hard to avoid shade. […] When the sun is near the horizon, you want your rows of panels to be very far apart or at different heights.
> 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.
I'm sorry but this is utter bullshit. The commercial plants do avoid shade as much as possible because shade destroy efficiency (one cell being shaded criples the output of the entire row…).
They don't care about shade when the sun is low because when the sun is low the incidence angle is terrible in the first place. You want your average panel directed south (or north in the southern hemisphere), when the sun is low, it's going to be completely in the East or completely in the West, and you care about the cosine of your incidence angle, which means the output is going to be near zero even without any shade whatsoever.
> 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.
Of course clouds are a year-round thing, what do you think… But sunny days are still much more frequent in summer.
> Which means a household array needs to be bigger as a baseline
Yes, but that's over-paneling…
> 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.
Sigh… Over-paneling 10x isn't going to be more worth it just because in spring and winter you need 5x. That's a nonsensical argument…
I'm sorry but you obviously have no idea about any of these things, I can only invite you to document yourself better at this point, because you're just pilling up crazy takes on top of crazy takes here.
> The sun isn't just going up and down you know it also circles from east to West…
Over a narrow range in winter. You get good coverage from pointing very south and avoiding shade.
> I'm sorry but this is utter bullshit. The commercial plants do avoid shade as much as possible because shade destroy efficiency
They do not avoid it "as much as possible". The panels are shading each other in that very photo, and that photo wasn't taken at the crack of dawn.
It's basic trigonometry. Narrow spacing needs the sun to get pretty high before shading stops. A roof install never shades itself. The difference matters.
> They don't care about shade when the sun is low because when the sun is low the incidence angle is terrible in the first place.
Wrong answer. Those panels are plenty tilted for low incidence sunlight. The ones in front will make plenty of power in the winter. But the ones behind them won't.
The limiter is the price of land. If land was free I guarantee they would spread them out more.
And a home install doesn't have this specific issue.
> Yes, but that's over-paneling…
No it's not! If you need it for most of the year it's not "over"!
> Sigh… Over-paneling 10x isn't going to be more worth it just because in spring and winter you need 5x. That's a nonsensical argument…
If you need 5x or more for half the year, you calculated "x" wrong. Your math is what's nonsense here.
You haven't linked the photo…
> It's basic trigonometry. Narrow spacing needs the sun to get pretty high before shading stops.
Of course it's “basic trigonometry”… It doesn't matter if the panels are shaded when the incidence angle is high anyway!
> The limiter is the price of land. If land was free I guarantee they would spread them out more.
They wouldn't, they'd just put more panels on a bigger surface. And again, industrial actors are maximizing the economic output they can make. Whatever decision you take at your level, it's going to be more expensive than what they are doing, and more efficient.
> No it's not! If you need it for most of the year it's not "over"
Yes it is… By definition you are over-paneling if your peak production is higher than what you use. This threshold is important because cost calculations only works when you haven't reached that yet!
> If you need 5x or more for half the year, you calculated "x" wrong. Your math is what's nonsense here.
X is the value for which the cost/MWh makes sense. The further you got from there, the bigger fraction of the power is unexploited and the higher the cost per unit of useful electricity rises.
I didn't invent these concepts or these calculations, those are standards when talking about solar.
The one at the top of the article.
> They wouldn't, they'd just put more panels on a bigger surface.
Given a specific budget they can only buy so many panels. Free land would change the tradeoffs.
> And again, industrial actors are maximizing the economic output they can make.
Based on current costs. Change the costs and the methods change too.
> Whatever decision you take at your level, it's going to be more expensive than what they are doing, and more efficient.
No. I already have the land and the house. That means most efficient for me is different.
I don't want to waste any more of our time arguing about how to define X so I'll skip the rest.
Where did you get your morning shade fixation from?
I got this "fixation" by doing the math to figure out why panels do so badly when there's still seven and a half hours of daylight.
The insolation per square meter of ground is very low when the sun is near the horizon. But the insolation of a flat surface at 60 degrees of tilt is still pretty good. If you avoid shade.
Please tell me you have no disagreements with that. It's basic math.
So as you said with basic panels "one cell being shaded criples the output of the entire row". Normal commercial installs don't try to capture the morning sun. But in the middle of winter in Denmark the "morning" sun is basically all you have access to.
You said "They don't care about shade when the sun is low because when the sun is low the incidence angle is terrible in the first place."
If you tilt really far and avoid shade, you counteract the bad incidence angle. A single square meter of panel can absorb the light that would have hit 6 square meters of ground.
I'm not aware of any desert in Denmark…
But you say the design is driven by lack of space, then why do they use the same design in deserts?! That's my question. Denmark doesn't have much free space, but Sweden do, land is cheap in many places there, yet the Swede don't design their plant differently.
> Normal commercial installs don't try to capture the morning sun. But in the middle of winter in Denmark the "morning" sun is basically all you have access to.
And yet you insist commercial plants don't do that? Why? Are they stupid?
> If you tilt really far and avoid shade, you counteract the bad incidence angle.
Only the vertical angle, not the horizontal one… And again it makes no sense to optimize for winter morning sun when there's only 2 hours of sunlight per day in average during winter…
You could set up a football field of our perfectly optimized morning sun solar panels, plus the same for evening sun, and you'd still have failed to power a house for the full month between January and February where the sun often don't show up once, and in that time span you've already exceeded the 10% non-solar budget in that mental exercise…
Right! A lack of places with such super free land that also have horrible sun angles.
> But you say the design is driven by lack of space, then why do they use the same design in deserts?!
The desert builds don't have to deal with the same horrible sun angles.
But whatever, I might be wrong on what they would do with free land. That was a guess, I admit it. That guess was to illustrate my point about angles. It's not a critical part of my argument.
It's a fact that solar panels on a roof avoid the shading problem, while a normal commercial layout does not. Pure mathematics.
> Only the vertical angle, not the horizontal one…
The horizontal angle doesn't change very much. If you point flat 50-60 degrees south (the year-round optimal angle for Denmark) you will get a significant amount of sun no matter the season if you avoid shade. Winter sun is less than average but it's close to 50%, not 5%.
> And again it makes no sense to optimize for winter morning sun when there's only 2 hours of sunlight per day in average during winter…
That's so close to understanding my argument!
Commercial plants don't bother. They're not optimal for winter. But if you build on a slanted roof you get that optimization for free. So a home install actually becomes better than a commercial install for this specific use case.
But it's not 2 hours of significant light, it's more than that. Clouds don't make the sun useless.
> where the sun often don't show up once
Nah.
Yes the range reduces in winter especially when you go north, but you still get at least 45° of incidence angle in the best case scenario.
> Winter sun is less than average but it's close to 50%, not 5%.
How can it be 50% when the sun is beyond the horizon for 17 hours straight?! For some reason you obsess with shade, but disregard the most important one: the one caused by earth moving in front of the sun (also called “night”)…
> That's so close to understanding my argument!
> Commercial plants don't bother. They're not optimal for winter
I see what you mean, but plants optimize for electricity value, not rough output, and electricity is more expensive in winter, if they could get good yields at that period, they would actually make more money than the one they get by selling excess electricity in summer…
> But it's not 2 hours of significant light, it's more than that. Clouds don't make the sun useless.
For regular solar panels, they pretty much do, especially in the north (because the cloud layer is effectively much thicker due to the high sunlight incidence angle). Amorphous panels have better performance in these scenarios but it's still far from good, especially if you tilt them heavily to face the sun as these panels need to be facing the sky to get as much diffuse daylight as possible.
As a result, the sunny hours, even though rare, are going to dwarf the others in electricity production, even if there's few of them.
But if you believe you can sustain 90% of your electricity consumption from solar in Denmark, go ahead, I'm not going to convince you otherwise and I'll have no guilt if you lose your shirt in the process.