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Comment by DennisP | Hacker News Reader

That'd be great but the word "storage" does not appear in this article. For wind/solar to truly be cheaper than fossil, the cost of storing enough energy to get through a few windless nights has to be included.

Backing up by natural gas doesn't count; natural gas is a fossil fuel and if you take methane into account it might even be worse than coal.

Hydro and geothermal don't need storage but they're also geographically limited. We can't expand them arbitrarily the way we could expand wind/solar. This also means using hydro to store energy from wind/solar can only go so far.

None of this matters in the near term, since we can certainly expand wind/solar a lot before we run into problems. But over the next several decades we need to replace fossil entirely.

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This is inclusive of storage.

https://www.bloomberg.com/news/articles/2018-09-17/solar-wit...

https://www.bloomberg.com/news/articles/2018-02-12/a-powerfu...

https://www.greentechmedia.com/articles/read/an-interview-wi...

How much storage?

On a grid with natural gas backup, it's easy to throw in an hour's worth of battery storage to cover minor fluctuations, quote a price "with storage," but still rely on gas if the wind dies down over a large area for a couple days (which does happen).

"Bigger turbines will create more wind power, and the intermittency of both sources can be optimized with large-scale battery backup facilities."

Ok. How much intermittency can they handle?

I'm not talking about smoothing our minor variations in output. I'm talking about enough storage so you don't need fossil backup at all, even if the wind dies down over a large area for a couple days. Battery backup at that scale is not affordable with current technology, but that's what we'd need if we actually got rid of fossil.

Wind/Solar + storage already has actual bids coming in cheaper than coal:

https://www.vox.com/energy-and-environment/2018/1/16/1689559...

That article doesn't say how much storage they're bidding. Is it enough for an hour, or three days?

If you've got fossil backup, an hour is fine. If you don't, it's not.

You're conflating energy concepts "capacity" with "energy"

The grid can have wind/solar and fossil. Generation is dispatched in "merit order" -- when wind/solar is has a lower marginal cost, it will serve load. During other periods (like those windless nights), the fossil will still generate.

By 2050 or so, the grid can only have both if we accept disastrous levels of climate change. See the latest U.N. report that's been all over the news, e.g. here: https://www.cnn.com/2018/10/07/world/climate-change-new-ipcc...

> natural gas is a fossil fuel and if you take methane into account it might even be worse than coal

Huh? Natural gas only produces about half the CO2 per unit of energy that coal does.

I don't know about the claims re: methane and natural gas, but methane causes warming significantly worse per kg than CO2 does.

The point is that natural gas (also known as methane) can leak out into the environment during production and distribution, and methane is a very potent greenhouse gas, 30X as bad per mass.

So if burning methane only produces half the CO2 per unit of energy, but just 2% of it leaks into the atmosphere at any point in the production/distribution pipeline, then it's actually worse.

Methane has a relatively short half-life in the atmosphere, only 8.6 years, which means that over the long term it's not that potent a GHG versus long-lived CO2 (about 100 years, but it's complicated). The radiative forcing alone doesn't tell the whole story.

Yes but it's not only direct forcing over the long term that matters. Push the planet hard enough in the short term, and we'll kick off positive feedbacks that take things several degrees further with no more help from us. The exact threshold is unknown but it's thought to be about two degrees C over preindustrial.

Feedbacks depend on which model you use. Still, it's not particularly relevant to the question of slow methane leakage from a natural gas distribution system, which is what we're talking about.

Sure it's relevant. If we use twice as much methane this year, we'll probably have twice as much leakage, and that means twice as much climate impact from this year's methane over the next few decades.

The feedbacks depend on total temperature not atmospheric gas composition, so methane raising temperatures by X degrees isn't any worse than CO2 causing the same temperature rise, and methane will exit the atmosphere faster. That is, feedback is proportional to the time integral of warming, not the forcing!

Yeah fine but total warming over the next 25 years could well be sufficient to get us over the critical threshold, and methane does have a greater impact than CO2 over a period of 25 years.

> Push the planet hard enough in the short term, and we'll kick off positive feedbacks

Which have never actually been observed. The whole "positive feedbacks" thing is based on computer models which have been falsified by the actual data.

No, it's based on extensive geological evidence. See Hansen's book for details.

Besides that, it's based on the fact that we're already seeing things like polar ice melt and emissions from permafrost.

> No, it's based on extensive geological evidence.

We don't have accurate enough geological evidence to support the kinds of "positive feedback" claims that are being made. Hansen's book lays out a partisan case.

> we're already seeing things like polar ice melt and emissions from permafrost.

What were these things doing a thousand years ago? Five thousand years ago? Ten thousand years ago? We don't know. And that means we don't have the data to put what we're currently seeing in proper perspective. And nobody is claiming that we do: as I said, the claims of possible disaster based on positive feedback are based on models, not data. And the models have been falsified by the data.

I take it you've read his book then? Could you point out specifically what's wrong with his evidence?

It seemed pretty convincing to me, since there were multiple independent lines of evidence that all pointed to the same conclusion.

> I take it you've read his book then?

No, I've read scientific papers on the topic, his and others. I don't trust what is said in books on science for lay people; I've caught too many scientists misrepresenting the science when they write for lay people, because they know they can get away with it (and not just in climate science--I've caught physicists doing it about general relativity and basic QM, which are a lot more solidly nailed down by evidence and controlled experiments than climate science is).

Ok. Tell me something he gets wrong, and why it's wrong.

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