[Koromix]

Photovoltaic capacity is expected to be around 4674 GW in 2050 (currently around 150, I think) [1]. Let's be optimistic and say it'll actually be around 20000 GW, just for the fun of it, and let's ignore all of the variability problems that solar poses.

Considering that PV's capacity factor is around 15%, that's around 26 PWh of annual (electric) energy production, around 50% of the electrical energy we use up in a year today, nevermind what we will actually need in 2050 thanks to the neverending growth we're apparently trying to go for.

IIRC, electricity represents 20-25% of our civilization's energy use mix, so solar should solve around 10-15% of our needs in 2050 under extremely optimistic assumptions and ignoring ALL of the variability, energy grid, energy storage, solar panel production issues, none of which are minor limitations.

2050 is around 10 years beyond the date we need to be carbon neutral to stay below 2°C [2], if we were to peak in 2020 and quickly ramp down our emissions. It's 20 years too late in business as usual scenarios.

[1] http://www.iea.org/publications/freepublications/publication... [2] http://www.realclimate.org/index.php/archives/2017/06/why-gl...

[ghouse]

"Considering that PV's capacity factor is around 15%"

In the SW United States, capacity factor for a ground-mounted system utilizing a single-axis tracker is between 28% and 35%.

Source: I am a developer of utility-scale PV power plants.

[toomuchtodo]

Looking for an apprentice? I'd love to shift from tech ops/security architecture into developing renewables at scale.

[philipkglass]

15% capacity factor is reasonable for rooftop, but utility scale PV in the United States was at 27% last year: https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...

Emissions are pretty obviously not going to peak by 2020, unless there's some sort of civilization-smashing catastrophe in the next few years. Large scale active carbon dioxide removal measures will be needed later, or natural processes will eventually restore the pre-industrial equilibrium over ~100,000 years. We're not going to stay in the "safe" zone below 2 degrees. Reducing future emissions is necessary but not sufficient. I say this as someone who fully wishes that humans had cut emissions quickly enough to render active CDR measures unnecessary, but recognizes that we did not act in time.

[Koromix]

27% is better, though from a quick look it applies only to the US, and in Europe it looks closer to 15%. I need to take time tomorrow to find good sources on this.

I'm not convinced by carbon storage, though I don't know enough about it to be sure. It is my understanding that it is either energy-hungry (so useless because we don't and likely won't have enough carbon-neutral energy surplus) or pretty slow (also useless). And completely unproven at large or even moderate scales, too.

[philipkglass]

Germany has the most PV installed of any European country. Utility scale PV facilities in Germany may reach only 10% capacity factor. But most of the world's present and future electricity demand centers are significantly closer to the equator than Germany is.

"Carbon storage" would normally refer to physically sequestering purified carbon dioxide or other carbon bearing compounds. I agree that storage of that type is not practical.

Enhanced silicate weathering is IMO the process with the best prospects for large scale atmospheric carbon dioxide removal. It is relatively slow but the thermodynamics are favorable and the kinetics are still orders of magnitude faster than waiting for unaided nature to restore the pre-industrial equilibrium. Enhanced weathering CDR just accelerates the kinetics of the natural chemical reaction that turns alkaline silicate rocks and CO2 into silica and alkaline carbonates. Doing it on a scale large enough to make a difference would be a gargantuan undertaking, of course, because the scale of the problem is also gargantuan.

[Koromix]

That's interesting, thanks for the information, I'll probably spend a good portion of tomorrow reading up on this. Geoengineering is scary.

Honestly, I am extremely pessimistic about mankind's ability to work on such a scale. Too many people seem to assume global warming is still a far-off problem, and that for some reason humanity is destined to "progress" forever, even though we know of many civilizations that have collapsed before ours.

I'd just like more people to grasp the dire reality of the situation, and stop assuming that somehow technology and/or progress will save us no matter what.

[icebraining]

I don't get it, what's your argument? Yes, at the pace we're building them, PV is not sufficient. Guess what, the exact same fact is true of nuclear. All that establishes is that we must invest more, it doesn't say in what we should invest.

[Koromix]

It was an answer to parent's "It's simply a matter of scaling up." comment.

I agree with you that the exact same fact is true of nuclear. And wind too, while we're at it.

I don't think there's a way out of it: our technological civilization lives WAY WAY beyond its means, and that is made possible only by burning through fossil fuels, among many other non-renewable resources. When that dries up (economically speaking) or enough ecosystems have been damaged, our civilization will most likely fall apart. It'll be a slow and ugly process, it'll happen over decades, and it's already under way.

Renewables would have been great in a simpler and slower world. Hopefully, that's how the next global (if any) civilization goes in a few hundred or thousand years.

[sqeaky]

It seems to me that people don't stop a behavior just because its unsustainable. They only seem to stop a bad behavior entirely when the market provides a less harmful alternative and its costs approximately the same amount or much less.

Whale oil and ambergris where replaced by Fossil fuels.

Ivory for billiard balls was replaced by plastic.

Cigarettes are being replaced by vaping.

Look at the amount of people skipping out on bike helmets and car safety belts. People don't do it even when there is literally no downside and it could literally save their life.

The pace of the world is here to stay, people will just figure out how to sustain it with new stuff. There might a turbine in every backyard, I don't know what the solution will look like. But the extinction of several whale species wasn't enough to put lamplighters out of business coal and transmission lines did and the world got ever faster.

[Koromix]

"The pace of the world is here to stay, people will just figure out how to sustain it with new stuff".

I don't know how you can think that. The pace of our world requires incredibly huge amounts of energy, which we get from finite fossil fuels. Either they become economically unavailable or climate change becomes so severe that we can't use what remains in the ground. Oil companies don't go to ultra-deep water wells and shale gas just because they are evil money-eating bastards (which is the prevalent narrative). They exploit these economically mediocre sources for the same reason garbage starts to look appealing when you are starved: you are hungry and the good food has run out.

Too many people assume that technology alone is what has allowed us to reach 7.5 billion people. This misses a significant piece of the puzzle, because in reality it's fossil-fuel powered technology. It's a crucial distinction, as shiny but empty trucks and tractors won't help you feed billions of people. Without fossil fuels we have no realistic idea how to feed that many people. So we'll probably continue burning them as long as we can, because the alternative (mass starvation) is even worse.

If we were a rational species, we could fix all of it. We'd massively slow down our economies, have very few kids for some time to reduce our population to more sustainable levels, rely on local food, stop traveling all the time, and so on. Doing it smart, we could reach a relatively slower but very nice and sustainable way of life, augmented by sparse but useful technology. Something a lot more sustainable that the Rude Goldbergian machine we call "modern life".

Since we're not rational and obviously won't do the smart thing, instead it'll degenerate to resource wars (over food, water, gas, etc.) and massive refugee crises way beyond what we're already seeing. Our civilization will stumble from one crisis to the next, blaming this or that ethnic group for what is happening, each time cobbling a half-solution together that seems to work for a time, but gradually it will sched most of the modern things we currently take for granted.

The myth of humanity going from caves to space is just that, a myth. In the real world, countless civilizations have risen and fallen, gaining and then losing most of their culture and scientific knowledge in the process. We've done it bigger than anyone before due to fossil fuels, which for a limited time have replaced our need for human and animal labor, but it is unsustainable and soon it will go away. Human ingeniosity plays a small part in the real story of our world.

The real story is that nature has kindly stored millions years worth of solar energy as fossil fuels and we've gotten so drunk on it for 200 years that we've started to think that we've mastered the universe, with soon to come galactic civilization, godlike AI and the end of death itself. The hangover is not going to be fun for a lot of people, and these delusions will not survive it.

[sqeaky]

People thought that the pace of the world couldn't get faster when everyone had horses. They had no distinct concept of energy and now we know nuclear energy is possible.

You see what exists and presume it is all that can exist. You are limited and whether or not it is rational human ingenuity is not limited. Only those civilizations that slowed down as you advocate "failed", and even then they still innovated just in different ways.

You are wrong because you make the same argument as people of yesteryear and they were wrong for reasons unknowable to them but obvious to us now. The future is unknowable to us but it should be obvious that some group of people will do better with some technology or process that seems obvious to them.

[Koromix]

Past civilizations did not fail because they slowed down. They slowed down while they were failing. I mean, this is what failing is. They failed at getting enough food and energy to feed their growing population, they failed at managing their growing social and technological complexity. The "people of yesteryear" you reference may have been wrong, until now, for our civilization. But it turns out these people also existed in failed civilizations and guess what, then they were right. Read "The Collapse of Complex Societies" by Joseph Tainter, it's a great book and it makes much more compelling arguments than I ever could about this subject.

Human ingenuity is definitely limited. There are levels of complexity we probably won't manage to get past. More importantly, physical laws have limits, and these are not negotiable. For example, we very probably won't ever get beyond the speed of light. We won't produce energy from nothing. We won't cancel gravity. We won't stop heat death. We won't travel in time. We won't teleport, or beam up as they say. We know that with a relatively high degree of certainty because science has progressed a lot, so we know a lot more about what this universe can do for us, but also about what it cannot do. This is not comparable to a few centuries (or even decades) ago, because then we knew a lot less about both.

We've got 20 years to address climate change and fossil fuel shortage, probably less, before they become catastrophic. There are reasons to think it may already be too late without active measures (carbon capture and so on). 20 years is less than the time it takes to go from brand new technology (let alone lab experiments) to widespread commercial use, which means that technologies that don't yet exist are of no use to address this problem, and that rules out fusion (which hasn't even proven it can produce more power than it consumes, let alone at economically viable scales), among others. I'd say thorium-based fission plants are the only semi-viable bet if we want to continue BAU, because uranium is probably a dead end (there's just not that much that can be exploited with an EROEI > 1).

Note that this is only the energy problem. We also need to deal with over-population, climate change, sea level rise, resource depletion, soil loss, aquifer depletion, species extinction, collapsed fisheries, ocean acidification and so on. At the same time, and at a time when our political institutions are reaching unparalleled levels of passivity and incompetence. If we solve all these problems, remember that our economists and leaders still insist on the need of exponential growth on a finite planet, which means it would soon prove not enough and the new problems we'd face would be even worse.

If you are part of the people who think we're destined to a Star Trek future, I can imagine that the thought of collapse can be painful to you. It used to pain me a lot, but now I'm okay with it. I'd prefer for our civilization to survive, but like with terminal illness, there comes a time when acceptance becomes the only good option.

Our civilization will fail, but eventually the biosphere will recover (though with the amount of damage we do, it'll take more time than with past collapses). Then life will go on for about 500M-1B years, after that it'll be toast and it will most likely be over for life in this corner of the galaxy.