[jansan]

This probably depends a lot on how close you are to the equator. Here in Germany output of solar in winter is negligible, and if there is no wind, which can happen for several consecutive weeks, we need a backup. No utilities company will build a fossil power plant that will be used only a few weeks per year, so our government will have to step in to make sure this happens.

On top of this you have very high costs for an increasingly complex grid, which needs to be built and then maintained. Prices will never again be as low as in the fossil/nuclear era.

[morsch]

Here are some numbers: January 2025, the output of solar was ~1500 GWh, it peaked in June at 10500 GWh. So the lowest output was about 15% of the maximum, this year.

https://www.energy-charts.info/charts/energy/chart.htm?l=en&...

https://www.energy-charts.info/charts/energy/chart.htm?l=en&...

Looking at wind, the ratio between min and max per week is about 1:5 (~1200 vs ~6000 GWh). Just as there is always some solar power generation, there is never no wind, though looking at those charts there were 4 weeks in the late summer of 2023 when production was low consecutively, between 700 and 1000 GWh.

[adwn]

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]

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&...

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]

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]

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]

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]

> 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).

[adwn]

> This is trivially false if the cost of solar generation (and battery storage) further drops by 5x to 10x.

That's a huge "if". The cost of PV panels has come down by a factor of 10 in the last 13 years or so, that's true. I doubt another 10x decrease is possible, because at some point you run into material costs.

But the real issue is that price of the panels themselves is already only about 35% of the total installation cost of utility-scale PV. This means that even if the panels were free, it would only reduce the cost by a factor of 1.5.

[adrianN]

What amounts to „concrete plan“? Right now we’re still in the state where building more generation is the best use of our money with batteries for load shifting a few hours ramping up. So it’s entirely expected that there is no infrastructure for seasonal storage yet. However the maths for storing energy as hydrogen and heat looks quite favorable and the necessary technology exists already.

[adwn]

"Concrete plan" means a technology which satisfies all of these requirements:

1) demonstrated ability in a utility-scale plant

2) already economically viable, or projected to be economically viable within 2 years by actual process engineers with experience in scaling up chemical/electrical plants to industrial size

Yes, that's hard to meet. But the thing is, we've seemingly heard of hundreds of revolutionary storage methods over the last decade, and so far nothing has come to fruition. That's because they were promised by researchers making breakthroughs in the lab, and forecasting orders of magnitude of cost reductions. They're doing great experimental work, but they lack the knowledge and experience to judge what it takes to go from lab result to utility-scale application.

[coryrc]

And this also leaves out all the heating power still consumed directly from fossil fuels. The gap is much larger.

This doesn't have have to be by switching consumption; using less is possible: Passivhaus is from Germany, after all. However, you can't do that and keep all your historical protections on buildings and layers-upon-layers of red tape on renovations.

[gpm]

> it peaked in June at 10500 GWh

And 8280 GWh the previous June for those wondering roughly how much of this was due to more solar panels being deployed.

[toomuchtodo]

For reference, Germany has ~101GW of solar capacity installed as of this comment (and is deploying ~2GW/month). 59% of Germany's electricity in 2024 came from renewable sources, up from 56% in 2023. I am curious to see how 2025 turns out, and therefore predict 2026 from planned renewables and battery storage projects.