[looping__lui]

What are you going to do at night, or in Germany when it’s cloudy and rainy for a month straight? I can show you my electricity consumption from my heat pump in the winter compared to the electricity my PV system produced. Hint: it doesn’t work. And batteries aren’t an option either, because I can’t generate any excess electricity during the day. Take a look at the Fraunhofer study.

[triceratops]

> And batteries aren’t an option either, because I can’t generate any excess electricity during the day

You can't generate excess electricity because you don't have enough land or rooftop (I mean maybe you do, I'm talking about the typical homeowner). Utilities can overbuild panels because they're extremely cheap.

LFP batteries have a self-discharge rate of 2-5% per month. Once they're cheap enough, over-building batteries to move summer sunshine into the winter months also becomes an option*. At $100/kwh, you could power Sweden 6 months a year for about $60bn (EDIT: $6tn, sorry) in batteries (yes labor and everything else will probably double that cost). And that doesn't even account for recent advances in sodium batteries, which reportedly bring that price down to $20/kwh

* (Any battery experts know why this might be wrong? I'm using basic arithmetic, not physics. That tells me a battery charged to 100% in July or August will still have > 70% charge left in December)

[looping__lui]

Germany would require a ballpark of 100 MILLION tons of Teslas Megapack grade batteries to run on battery for 2 weeks - which is even shorter than what we had to endure due to “Dunkelflauten”.

[triceratops]

Why would Germany need to run solely on battery for 2 weeks? Do you expect 2 weeks with 0 sun and wind all over continental Europe?

In any case, at $100/kwh, it would cost $250bn (EDIT: $25tn sorry) in batteries and maybe the same in installation costs to power Germany for 6 months a year. At the lower $20/kwh price tag it would be more like $5tn, compared to Germany's ~$4.5tn GDP. Over 10 years it could be done.

(And 6 months' storage is maybe too much anyway)

[looping__lui]

Because historically we had periods of a couple of days or weeks in a row where wind and solar were essentially non-existent:

https://www.tech-for-future.de/dunkelflaute/

[input_sh]

I mean not the whole Europe and this is obviously geography-dependent, but those "dark periods" are fairly common for Germany, as in there are weeks-long periods where Germany itself produces basically no electricity from wind or solar. In the most extreme case some years back, that "dark period" lasted almost two months.

This isn't to say they can't import it from elsewhere, they just can't make any of their own. Adding more capacity wouldn't do anything, it would take an incredible amount of batteries to handle the more extreme end of those "dark periods".

[triceratops]

But that's my point. It would cost 1 year's worth of German GDP in batteries to power Germany on batteries for 6 months. No one would ever need that much battery backup. And while it's a huge number, it's not an unfathomably huge number.

[looping__lui]

So, just jack up the debt from 60% of GDP to 160% for battery packs?

[looping__lui]

Yes, we had these scenarios of 2+ weeks w/o sufficient renewable energy source MULTIPLE times: Google “Dunkelflaute”.

[nicoburns]

Batteries are definitely an option for day -> night shifting. If not today, then soon, and without requiring and technological advances.

Seasonal or month-long periods of low-generation are another matter, and as-yet an unsolved problem. It may be that synthesizing fuels ends up being a sensible option here.

[jopsen]

Gas? Which you then only use 5-10% of the time.

At least that's what I hear people saying.

[looping__lui]

Well, you gonna pay for building gas power plants that never run? Customers will need to pay for gas power plants that cover the entire electricity need (read up on Fraunhofer on the thinking: https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p... ) . But that infrastructure will sit there idle most of the time. That’s not driving down electricity prices. And you’ll still end up with higher carbon emissions than France.

[toast0]

> Well, you gonna pay for building gas power plants that never run? Customers will need to pay for gas power plants that cover the entire electricity need

Paying for the plant but not having to pay for it to run most of the time is probably cheaper than having it running most of the time.

Maybe there's opportunities for net metering for customers with backup generators. At the right price per kWH, I would run my generator and feed into the grid... personally, my fuel cost is likely too high for that to make sense very often, but I think there's likely some hidden capacity there with the right incentives.

[looping__lui]

Take a look at this study: https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p...

Germany will require 100-150 GW capacity which cost about 1000 EUR/kW and would require an investment of 100+B EUR.

Electricity prices already skyrocketed in Germany and no end in sight.

Listen: I invested in PV, in low energy houses, in heat pumps - but the PV/wind strategy doesn’t work the way people would like them to in their ideology and Germany has proven that.

[toast0]

I think I'm more or less agreeing with you. You've got to build the gas plants (or something), for the dark and windless days of winter, right? That's going to be expensive, but PV/wind won't solve it, so you have to build it.

Now that you've built those plants, would you rather pay to operate them year round, or only when needed?

PV/wind won't help you reduce capex for winter, but it should reduce opex on gas. And that's something.

Spending capex on interconnections may reduce the total dispatchable capacity needed; if it's done carefully. Having more time zones in one grid helps because peaks correspond with time of day; having more latitude helps because day lengths and cloud cover varies. Having more of both helps because still air tends to be geographically bounded. But long distance transmission is expensive.

[looping__lui]

I’d rather build nuclear plants and not keep them entirely idle but forego the investment into additional PV and wind. Don’t get me wrong: when the sun shines and the wind blows we cover 100% of our need essentially. That’s great. But we can stop now. Because we produce too much on some days and put our grid at risk and we produce too little to often on others and put our grid at risk

[adgjlsfhk1]

Solar panels are cheap enough that it pays to have gas plants that never run.

[pfdietz]

One complements batteries with hydrogen (burned in turbines) or long term thermal storage.

Germany has plenty of salt formations for very cheap hydrogen storage, and there are no geographical constraints on thermal storage.

[looping__lui]

Tell the Fraunhofer about that.

[pfdietz]

I don't need to -- we can just look in that report you linked earlier (thanks!), on pages 5 and 6. They already know. They knew five years ago.

[looping__lui]

Yes, they mention hydrogen caverns and thermal storage on pp. 5–6 — but those are more theoretical potentials than real, scalable solutions today. That’s why even in Fraunhofer’s own scenarios we still see 500–750 GW of wind + PV (6–9× average load) and 100–150 GW gas backup on top. In practice, it’s the massive renewable overcapacity that smooths supply, with storage playing only a limited supporting role.

[pfdietz]

How are they not scalable? And realize that even in the fantasy of an all-nuclear world, electrolyzers are still required: they are needed to make the hydrogen that's the feedstock for synthesis of ammonia, without which world agricultural yield would be much lower.

Given that this all-nuclear world has electrolyzers, what then prevents these from being driven by renewables (perhaps buffered short term by batteries), and the hydrogen then stored (as has been done for decades in underground storage caverns, just like natural gas is stored)? And once that is done, what prevents some of that hydrogen from then being profitably used to drive turbines when electricity prices are high? Gas turbines burning hydrogen are nearly identical to ones burning natural gas (just minor differences in the combustors) and have been available industrially for decades.

Using reasonable projections for cost (some of which have already been superseded by lower figures), we can estimate the cost of providing synthetic baseload from wind/solar/storage in Europe, using historical weather data. It comes in cheaper than nuclear.

https://model.energy/