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Comment by dv_dt | Hacker News Reader

Why does the answer always reply with coal and oil instead of Renewables and storage?

Because we need truly fantastic levels of storage to make renewables even remotely feasible. The US has 8 seconds of battery storage, and ~4 minutes of hydroelectric storage. We need 12 hours of storage to get to 80% renewable generation, and 3 weeks of storage to get to 100% renewable generation [1]. And even if we did go this route, we'd still need to cover 3-5% of the landmass of the Earth with solar panels to achieve this.

1. https://pv-magazine-usa.com/2018/03/01/12-hours-energy-stora....

There have been many studies since 2018 that say areas where they previously thought it would be difficult to get to 80%, that would be perfectly feasible to get to 100% with near term technologies. See Austrailian grid analysis. The key difference is that the prices for both renewables and storage are far ahead of cost reduction estimates in previous forcasts.

Australia has vast tracts of cheap land and very good solar potential (close to equator, little cloud cover). They also have energy usage patterns that are amenable to solar, with ACs run during the day and little need for heating at night. Most countries do not share these characteristics.

And I'd still like to see what they have planned for energy storage. It likely still involves shifting demand (in other words, they can't actually fulfill demand and they have to tell people not to use electricity during certain times of day).

That seems to have improved greatly in a years time. The speed with which renewable sources come one line I think is surprising everyone.

https://www.pv-magazine.com/2020/08/31/renewables-improve-re...

For the last 40 years, that has been the actual alternative.

Can you imagine where we'd be if we had continued pursuing the nuclear future? A largely decarbonized grid, advanced reactor designs deployed, knock-on effects from plentiful power, etc. What would the CO2 levels look like now? But no, instead we're now at a crisis point...

If you’re German for one, then it’s justified, because Merkel has been shutting down nuclear plants which forced a switch back to more coal.

Then why isn't the argument that Germany should build more solar and wind generation? Nuclear plants take decades from start to finish - if they even finish in the West. Vs months to a few years for many renewable projects.

Because the plants are finished and working. They just shut them down.

Nuclear plants have a lifetime of 30ish years. Many are getting shutdown now because the first wave of builds was around 30-50 years ago. The risks of continuing to operate older designs gets higher if they're refurbished.

Sure, but newer designs were shut down too. I used to live basically next to one. It was in construction for years, very close to completion when Fukushima happened. It was definitely not a rational reaction to cancel that thing.

Becayse germany has been very rapidly ramping up wind and solar, and still they are struggling to replace the reactors. They have made no progress in decarbonising the grid because rhey've been replacing one zero-carbon source with another zero carbon source, instead of removing coal.

Germany has cut coal use in half since the wind-down of the nuclear fleet began. Please do not repeat misinformation.

And they would have cut it to zero by now if they left nuclear plants alone.

That is factully incorrect. Even if Germany had left nuclear on a level of 1995 and replaced aging plants with new plants of the same capcity the net nuclear output combined with renewables would not be enough to offset coal/gas/oil. See https://de.m.wikipedia.org/wiki/Stromerzeugung

This graph seems to show that coal would have been gone by now.

What I getting wrong?

That’s misinformation.

https://en.m.wikipedia.org/wiki/Energy_in_Germany

You can clearly see how coal is on the rise shortly after 2010. So it is factually true to say they switched back to coal. You would be correct to point out that coal use has gone down since, but not by half. Not even close.

Let’s use German industry data[1]

    Fuel        2010  2019  (TWH)
    Lignite    145.9 113.9
    Hard Coal  117.0  57.3
    Nuclear    140.6  75.1
    Renewables 105.2 244.3
    Natural Gas 89.3  91.0

That’s as of 9 months ago. Since Lignite generation dropped 22% in 2019 alone, and Anthracite 30%, we can expect it is even lower today. I make it about 35% by the 2010-2019 numbers, so true, not 50%, but it does in no way support any kind of statement that “coal use has gone up”. Just the opposite.

[1] https://ag-energiebilanzen.de/index.php?article_id=29&fileNa...

Your numbers also show that coal use went up by several TWh shortly after the Energiewende. I'll concur that the numbers improved much faster than I would have expected based on what I had in mind from previous years. But they still went up.

Anyone who describes the Energiewende nuclear draw down as having caused coal consumption to rise is propagating misinformation.

While there may be some small, tightly qualified way in which the statement can be twisted to be true the impression that is conveyed is one that is in conflict with the facts.

Misinformation often uses small truths to tell larger lies.

> Anyone who describes the Energiewende nuclear draw down as having caused coal consumption to rise is propagating misinformation.

Anyone who does that would be factually correct, as proven by your own numbers. And this accusation is especially ironic coming from someone who made a factually incorrect statement.

> there may be some small, tightly qualified way in which the statement can be twisted to be true

It was true for several years and for several TWh. It's not at all fair to call that "twisted and tightly qualified".

If you don't think so, note that from 2010 until now, the length of time in which coal use was elevated is about the same as the length of time where it decreased. So if my statement is twisted and tightly qualified, then so is your statement that coal use has been reduced by 35%. Not to mention your initial claim that it's been cut in half.

> the impression that is conveyed is one that is in conflict with the facts.

Since you insist, I'll amend my statement: getting out of nuclear forced an increase in coal use for several years.

But the main point remains untouched. From a climate standpoint, Germany would've been strictly better off with nuclear.

Because nobody has put forth any workable plan to provide the storage capacity needed to rely on solar or wind.

Because you cannot simply replace conventional rotational generators with inverters. The inertia of the turbomachinery smooths out fluctuations in the grid keeping it stable. Lots of details in [0].

So without lots of hydro or synchronous wind generation, there will always been a need for some kind of conventional generation to keep the grid stable.

0. https://www.renewableenergyworld.com/2019/10/25/grid-inertia...

I'm no expert, but I did find this[1] recent (May 2020) information posted by the U.S. National Renewable Energy Lab that indicates that non-inverted power sources (such as solar and wind) may be able to produce synthetic current frequency in order to maintain grid stability. This technology can be included within large-scale storage batteries.

In addition, these inertial techniques ('fast frequency response') are digital and as a result could provide lower-latency and higher-accuracy response compared to mechanical approaches.

If I understand that correctly, then eventually these approaches could phase out the need for rotational inertia (no pun intended).

[1] - https://www.nrel.gov/news/program/2020/inertia-and-the-power...

Edit: adding a useful quote from the linked report, below:

"In the United States, the Texas grid (the Electric Reliability Council of Texas, or ERCOT) is the smallest of three main grids. ERCOT’s relatively small size, combined with its large wind deployment, has required it to compensate for declining inertia by adopting several low-cost solutions, including allowing fast-responding noncritical loads to respond to changes in frequency. This has enabled ERCOT to achieve increasingly high instantaneous wind penetrations—reaching a record of 58% in 2019—while maintaining reliability."

If you're building a grid-scale battery storage system, isn't it a relatively straightforward engineering problem to emulate the inertia of a flywheel?

I would be much more concerned about batteries' ability to respond on the days/weeks/months scale than the milliseconds scale.

What challenges do you foresee in responding over days/weeks/months?

The challenge is just having enough raw capacity to meet demand using intermittent renewable sources. Weather varies on the scale of days/weeks, and winter is cold because of limited sunlight. What energy source will we use to stay warm all winter?

Make hydrogen, store it underground, and have enough combustion turbines available to back up the grid. A simple cycle combustion turbine power plant is about 5% of the cost of a nuclear power plant, per unit of power output.

That seems physically plausible, though it would be a lot easier if we could make methane efficiently, because we already have the infrastructure to transport and burn it.

The problem then is where do you get the carbon to make the methane. Ammonia might be a possibility, if it can be kept from escaping (toxic) or dissolving in underground water.

Yet another possibility is underground storage of high temperature heat, artificial geothermal, if you will. But it would have to be extractable with cheap equipment. Perhaps it could be used to superheat hydrogen for injection into those combustion turbines.

Making hydrogen via electrolysis is very lossy though.. it's only worth it if you have nothing else to burn the power on.

Or if you need a chemical energy store with very low $/kWh of storage capacity, for long term or rarely used storage. There, the efficiency penalty is much less important than it would be for rapidly cycling diurnal storage.

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