4 ms·

How do you interpret these numbers? If your point is that we can simply overprovision photovoltaik arrays by a factor of 6.67, then that would make solar the mo

by adwn 10mo ago

How do you interpret these numbers? If your point is that we can simply overprovision photovoltaik arrays by a factor of 6.67, then that would make solar the most expensive power generation method by far. And it only gets worse the more households transition to heatpumps, because the consumption in winter is so lopsided. For example, I heat my home with a heatpump, and I have 10 kWp of solar arrays on my roof. In the last week of July, we consumed 84 kWh and generated 230 kWh (273 %). In the last week of November, we consumed 341 khW and generated 40 kWh (11 %). This means we'd need roughly 10 times as much PV area to match demand (10 roofs?), and huge batteries because most of that consumption is in the evening, at night, and in the morning. Of course, utility-scale and residential solar behave a bit differently, and it becomes more complicated if wind is factored in. But it shows that you can't just overprovision PV a little to fix the main problem of solar power: that it is most abundant in summer, and most in demand in winter.

morsch 10mo ago
My point was really only that neither is solar what I'd consider negligible in winter, nor are there really weeks with no wind. Other than that, my interpretation is pretty much the same as yours. Above, I looked at the weekly min/max ratio. Of course the daily ratios are much higher, 1:60 for solar, and about 1:30 for wind. But wind and solar do have a useful anti-correlation: the ratio is "only" about 1:15 for combined solar+wind. Still high, but a huge improvement on both wind and solar individually. https://www.energy-charts.info/charts/energy/chart.htm?l=en&c=DE&interval=day&source=public&year=2025&legendItems=fw3w1 https://www.energy-charts.info/charts/energy/chart.htm?l=en&... In reality, the ratio is even higher since we routinely have to drop solar and turn off wind turbines when there is more production than demand (and I don't think that generation is reflected in the graph). Ie. the max is already a representation more of grid and demand than of production, and it'd make more sense to use the ratio of min:mean, so comparing what we expect PV+wind to produce on average with what they give on the worst day. That gets us a different, more favorable ratio: 195 TWh produced in 2025 so far, let's call it 550 GWh/day, giving a ratio of about 1:6.
- adwn 10mo ago
  Thank you for actually running the numbers. I think the data is quite convincing that overprovisioning won't be the solution to the seasonal storage problem, or at least not the major factor in it. Personally, I have high hopes for flow batteries. Increasing storage capacity is so easy with them, liquids can easily be stored for a long time, and it would even make long-distance transport by ship feasible. If only we can find a cheap, suitable electrolyte.
ZeroGravitas 10mo ago
This is just a slighty more sophisticated version of the "solar doesn't work at night" trope. The implications of bringing it up is that these silly hippies haven't even thought of this basic fact so how can we trust them with our energy system. Meanwhile, actual energy experts have been aware of the concept of winter for at least a few years now. If you want to critique their plans for dealing with it, you'd need to do more than point out the existence of winter as a gotcha.
- adwn 10mo ago
  I don't see you countering my argument, only attempting to ridicule it ("slighty more sophisticated", "trope", "these silly hippies", "been aware of the concept of winter", "existence of winter as a gotcha"). That sucks, man :-( > If you want to critique their plans for dealing with it […] There are many ideas for seasonal storage of PV-generated electricity, but so far there is no concrete plan that's both scalable to TWh levels and economically feasible. Here on HN, there's always someone who'll post the knee-jerk response of "just build more panels", without doing the simple and very obvious calculation that 5x to 10x overprovisioning would turn solar from one of the cheaper into the by far most expensive power generation method out there [1]. [1] Except for paying people to crank a generator by hand, although that might at least help with obesity rates.
  - dinfinity 10mo ago
    > 5x to 10x overprovisioning would turn solar from one of the cheaper into the by far most expensive power generation method out there. This is trivially false if the cost of solar generation (and battery storage) further drops by 5x to 10x. Additionally that implies the overprovisioned power is worthless in the summer, which does not have to be the case. It might make certain processes viable due to very low cost of energy during those months. Not trivial as those industries would have to leave the equipment using the power unused during winter months, but the economics could still work for certain cases. Some of the cases might even specifically be those that store energy for use in winter (although then we're not looking at the 'pure' overprovisioning solution anymore).

by adwn 10mo ago

morsch 10mo ago

My point was really only that neither is solar what I'd consider negligible in winter, nor are there really weeks with no wind. Other than that, my interpretation is pretty much the same as yours. Above, I looked at the weekly min/max ratio. Of course the daily ratios are much higher, 1:60 for solar, and about 1:30 for wind. But wind and solar do have a useful anti-correlation: the ratio is "only" about 1:15 for combined solar+wind. Still high, but a huge improvement on both wind and solar individually. https://www.energy-charts.info/charts/energy/chart.htm?l=en&c=DE&interval=day&source=public&year=2025&legendItems=fw3w1 https://www.energy-charts.info/charts/energy/chart.htm?l=en&... In reality, the ratio is even higher since we routinely have to drop solar and turn off wind turbines when there is more production than demand (and I don't think that generation is reflected in the graph). Ie. the max is already a representation more of grid and demand than of production, and it'd make more sense to use the ratio of min:mean, so comparing what we expect PV+wind to produce on average with what they give on the worst day. That gets us a different, more favorable ratio: 195 TWh produced in 2025 so far, let's call it 550 GWh/day, giving a ratio of about 1:6.

adwn 10mo ago
Thank you for actually running the numbers. I think the data is quite convincing that overprovisioning won't be the solution to the seasonal storage problem, or at least not the major factor in it. Personally, I have high hopes for flow batteries. Increasing storage capacity is so easy with them, liquids can easily be stored for a long time, and it would even make long-distance transport by ship feasible. If only we can find a cheap, suitable electrolyte.

ZeroGravitas 10mo ago

This is just a slighty more sophisticated version of the "solar doesn't work at night" trope. The implications of bringing it up is that these silly hippies haven't even thought of this basic fact so how can we trust them with our energy system. Meanwhile, actual energy experts have been aware of the concept of winter for at least a few years now. If you want to critique their plans for dealing with it, you'd need to do more than point out the existence of winter as a gotcha.

adwn 10mo ago
I don't see you countering my argument, only attempting to ridicule it ("slighty more sophisticated", "trope", "these silly hippies", "been aware of the concept of winter", "existence of winter as a gotcha"). That sucks, man :-( > If you want to critique their plans for dealing with it […] There are many ideas for seasonal storage of PV-generated electricity, but so far there is no concrete plan that's both scalable to TWh levels and economically feasible. Here on HN, there's always someone who'll post the knee-jerk response of "just build more panels", without doing the simple and very obvious calculation that 5x to 10x overprovisioning would turn solar from one of the cheaper into the by far most expensive power generation method out there [1]. [1] Except for paying people to crank a generator by hand, although that might at least help with obesity rates.
- dinfinity 10mo ago
  > 5x to 10x overprovisioning would turn solar from one of the cheaper into the by far most expensive power generation method out there. This is trivially false if the cost of solar generation (and battery storage) further drops by 5x to 10x. Additionally that implies the overprovisioned power is worthless in the summer, which does not have to be the case. It might make certain processes viable due to very low cost of energy during those months. Not trivial as those industries would have to leave the equipment using the power unused during winter months, but the economics could still work for certain cases. Some of the cases might even specifically be those that store energy for use in winter (although then we're not looking at the 'pure' overprovisioning solution anymore).