It's renewable in the sense that there's a massive geological reservoir which replenishes the uranium dissolved in the seawater. There's 4 billion tons dissolved right now in the ocean (enough to run 1,000 reactors for 100,000 years) but that is replaced as it's extracted. [1]

It's about as renewable as solar, which is to say, we will eventually run out - but at that point the heat death of the universe is a more pressing concern.

[1] https://cna.ca/2016/07/27/theres-uranium-seawater-renewable/

> It's about as renewable as solar, which is to say, we will eventually run out - but at that point the heat death of the universe is a more pressing concern.

Nitpicking:

The sun is expected to stop fusing helium in about 8x10^9 years [1]. The heat death will occur in around 1.7x10^106 years [2]. (if at all, there are some uncertainties around that)

Which means that while they are both far, the heat death as predicted is much much further than the other. In short, the heat death of the universe won't be a pressing concern at all when we run out of solar.

1: https://en.wikipedia.org/wiki/Black_dwarf#Future_of_the_Sun 2: https://en.wikipedia.org/wiki/Graphical_timeline_from_Big_Ba...

It’s oddly reassuring to know that we’ll actually have some time to stay a spacefaring civilization after the sun runs out.

I remember reading some time ago that after the Sun runs out there's only enough energy in a state fit for fusion for like one or two more generations of stars in the universe, and after that the universe will go dark forever.

That may be true, but it's worth noting that the length of a "generation" of stars varies wildly depending on the type of star. Stars like our Sun might only live 10 billion years or so, but red dwarfs live 100 billion years or more so we could presumably live around them long after all the Sun-like stars have burned out.

Can't we dump matter into black holes to draw things out for a while even after that?

From where are you getting the energy to do that?

If you have a bunch of matter (dead stars, planets, interstellar dust) is there some fundamental reason this can't be dumped into accretion disks, etc. in an energy-positive way?

I wonder, does the sun /have/ to run out? Could we find a bunch more hydrogen from outside the solar system and dump it into the sun to recharge it?

Proper management of star lifetime actually requires the opposite approach: subtract mass from the star, so that the star "core" where actual fusion happens can steadily mix with a larger fraction of the remaining mass. The harvested mass can then be stored away as gas-giant planets, and used for miscellaneous purposes.

This is fascinating. Do you have any recommendations for sources so I can learn more about megascale engineering projects to maximize the life of a star?

warning: Isaac Arthur is like crack to sci-fi/intellectuals.

binge at your own risk:

https://www.youtube.com/watch?v=pzuHxL5FD5U

Assuming we possesed that capability it seems like it would be simplet to build a dyson sphere around another star and setup shop on a nearby planet.

Stars fail when the elements in their cores stop releasing net energy when fused. This crossover occurs at iron. Adding more mass will just make it's death more violent.

Also the sun contains 99% of the mass of the solar system. The remaining 1% includes Jupiter. I'm not sure how much effect we can have when only leveraging 1% of 1% of the solar systems mass.

I also wonder how one removes mass from the sun. Its the biggest gravity well in the solar system and our biggest power source is the sun itself.

Star lifting seems plausible.

https://www.youtube.com/watch?v=pzuHxL5FD5U

Transform the mass into energy, and radiate it.

I suspect human will have LONG since destroyed themselves by the time the sun dies, probably before we're spacefaring and out of the solar system.

The distinction is that wind/solar arrive for free without any effort. That just isn't true of nuclear fuel. I don't think that is a problem particularly. More that "renewable" is the wrong word.

You have to build solar panels and wind turbines. Then have connecting service roads able to carry heavy equipment. Wash the panels frequently or watch their performance plummet. Grease moving parts to avoid friction losses. Maintain the rotor blades at the cost of significant downtimes. Replace everything after 20 years as that is their average lifespan. Deal with all poorly recyclable waste you have created. Overbuild all transmission lines by a wide margin, to compensate for the low density and intermittent nature of wind and solar. Accept that what could have been truly space reserved for wild nature is now used for low density energy farming. I really don't see how wind and solar are renewable in the true sense of the word. From an ecological perspective the point should be to use our resources efficiently so as to return large swaths of land to pristine nature. Currently you can do this two ways: one use high density technologies like nuclear, the other is to go extinct voluntarily. My choice was made after becoming a parent.

If we ran the entire world off of nuclear reactors, we could increase the energy we used and still not worry about exhausting the amount of uranium available to us. Proliferation would be a concern though.

That said, why would we run the entire world on nuclear, or go for a nuclear-only strategy when we also have solar and wind and geothermal and hydroelectric? For that matter, why should we exclude nuclear from the energy mix available to us?

Different sources of power have different properties with different tradeoffs, but if you can cover your bases with multiple types, why wouldn’t you?

Hydro is actually not a particularly good choice in most cases. Some hydro installations can actually produce just as much global warming impact as a fossil fuel plant (largely methane produced in the flooded area - which has a far greater impact than CO2; about 80X greater). They also have significant ecological impact that isn't usually accounted for in folks mental models. [1, 2] Hydro isn't really green energy.

Geothermal I think only works in some places without causing earthquakes. [3]

Wind and solar are good, though.

[1] https://www.science.org/content/article/hundreds-new-dams-co...

[2] https://www.utilitydive.com/news/hydropower-emissions-fossil...

[3] https://news.stanford.edu/2019/05/23/lessons-south-korea-sol...

The massive advantage of hydro is that it also serves as energy storage. Too much wind today? Just use the excess electricity to pump water back up

From a Californian perspective, hydro and geothermal are basically tapped as far as I know, in-State anyway. The plants that are operational already is about the extent of what we can probably build.

Actually something of a dream of mine is to see nuclear reactors eventually replace some of our dams, maybe restore some of the lakes and tributaries that have been lost, but presently new reactor construction is prohibited here per a ballot initiative from before I was born.

My larger point is that society is going to continue to demand increased electricity generation, which means new plants and installations. It’s one thing to want to replace existing installations but if you’re going to service future demand, then new sources of multiple types have to remain on the table. I would take nuclear over gas-fired plants, but I would take gas-fired plants over coal-fired plants.

> From a Californian perspective, hydro and geothermal are basically tapped as far as I know

For what I understand, the California State Water Project as visioned in the 1960s, had Stage I and Stage II. Only Stage I was built. Then from the 1980s onward, there was political opposition and Phase II was never started.

https://en.wikipedia.org/wiki/California_State_Water_Project...

True, but the Klamath River is in the grand scheme of things a fairly minor watershed in California. Some room for growth, but effectively tapped out as far as the major watersheds in the State go. We have just a lot of dams and we’re still importing more and more of our energy from other States as we make it harder to build plants here.

> Proliferation would be a concern though.

https://whatisnuclear.com/non-proliferation.html

Non-proliferation as a movement is only as strong a movement as nuclear-equipped nations are willing to enforce it. I’m not willing to hold up deploying reactors in the US over it, but proliferation is a legitimate concern.

I'm more concerned about global warming personally...

Really, this week? With nuclear war looming over us all?

Also lets put things in perspective, Global Warming means future generations will need to adapt to new weather patterns. Some animal and plant species will become extinct, others may thrive.

Nuclear war will end civilization and make many parts of the world completely uninhabitable.

> Really, this week? With nuclear war looming over us all?

Nuclear war has been looming over us all since 1949, this week is no different than last week or 10 years ago.

There is nothing we can do if Putin decides to push the button. The world as we know it ends at that point because the USA won't hesitate to answer with our own nukes, and I wouldn't have it any other way. I don't worry about things that I could never have any control over. I am worried about global warming per this conversation about energy sources that won't destroy human civilization via natural disasters.

I thought we were talking about proliferation of nuclear technology, and we _do_ have control over that.

What happens when every country has nuclear weapons at the ready and dictators in power? Pretty sure global warming (Climate change) won't be as disastrous as a nuclear winter.

I don't think the word "renewable" implies anything about effort involved?

Wind generators aren't free. Solar cells aren't free. And (even more importantly) backing storage for when the sun isn't shining and the wind isn't blowing is most definitely not free.

I don’t understand what you mean by “arrive for free”. We have to capture it. It is not free of any externalities.

You don’t have to produce/extract/manufacture anything to make the wind blow or the sun shine. We capture them as they are.

Edit: let’s see how many people will continue to ignore other comments to get the same point in I guess.

Why is that an important difference? To capture wind and solar you have to build turbines and solar panels which aren't free. You also have to have batteries to store them because of seasonal nature of these sources. You also need to transmit the energy thousands of miles through electrical grid because these sources of energy are limited to certain areas. Building the electrical grid itself just needs cutting out millions of more trees. So overall, the environmental impact of going full solar/wind would be worse than a combination of solar, wind, nuclear, and even maybe natural gas.

No one is denying you need those things. We’re talking about a specific step that doesn’t exist for solar/wind akin to being able to drink water you find vs. having to make it clean.

I understand what you are saying, and I'm saying it's a pointless argument which doesn't add any value to the discussion.

Duly noted.

You don't have to produce/extract/manufacture anything to make the ocean hold uranium for us.

You don't have to build anything to make uranium radiate.

That's a pointless argument and unrelated to "renewable", which means it won't get used up.

the solar panels and wires and plastic that hook these systems up to the grid/end-user require a lot of producing/extracting/manufacturing

We need tons of coal and plastics to capture the sun shine.

By that standard, solar isn’t renewable either, since the sun is decaying. Nuclear is renewable in human civilisation time scale.

Well it depends on the course of human civilisation. If we wipe ourselves out in WWIII then we won't run out of coal. If we continue to grow exponentially then we will quickly run out of solar.

By that definition I don't think there is such a thing as renewable yet considering you need storage/batteries for just about any "renewable" energy source out there. Energy will always cost us something imho.

One alternative approach to storage/batteries is trying to provide over 100% of the average daily demand of electricity. Excess electricity could be priced lower. Consumers & industries could use those cheaper hours for certain tasks. This is already done in many areas. Run your dishwasher, charge your car, etc. at night.

Which leads me to think storage/batteries is not the issue & that manufacturing, installation & infrastructure is. I also imagine getting land permits, regulations, politics, etc. is also a huge factor.

Are there any simulations done on actual historical weather data on how much you need for that to work.

I would be far less sceptical about massive deployment of renewables if somebody could point me to a study that shows: Given this grid, this amount of wind, solar and storage in that areas and the historical weather data of the last 30 years it would have resulted in this amount of overproduction, blackouts....

Not all energy uses can be shifted. IT infrastructure, the pumps delivering plumbing to your house, streetlights, HVAC, all needs to be running at all times. Furthermore, if shifting energy demand is the plan, then renewables need to factor in the cost of shifting that energy demand into the equation.

Gasification of woody biomass waste streams (walnut shells, wood chips, corn stover, bigasse) is quite renewable, and can be run 24/7 regardless of weather. The CO2 emmitted comes from the atmosphere and therefore is cyclical in nature (thus sustainable). If you take biochar into account the carbon generation is actually negative, as you have carbon left over that can be used for other things or put back into the soil in a form that is stable for thousands of years and beneficial to the soil quality for life.

Nothing is truly renewable as entropy gets us all in the end.

Now maybe someone or something will answer "The Last Question" one day and solve that problem. I wager we wont be around to see it.

By that logic, solar isn't renewable because it'll "run out" in 5 billion years.

Nuclear will run out much, much faster, though, particularly when it comes to uranium we actually know how to extract economically. People's proposals for things like extracting uranium from seawater have not even reached the prototyping stage--we don't even know if it's possible to do at the scale required to support modern civilization--but people are already willing to treat it as a done deal. It's one of the reasons I'm not nearly as enthusiastic about nuclear as many people here. For some reason, people seem very quick to point out at extremely minor problems with solar, which is technically pretty much already there and which we know can work, and has improved by leaps and bounds in a short amount of time, or argue that it can't work because of the storage problem (even though we already know how to build big batteries--pumped storage isn't sexy, but it works and can be produced at scale without requiring exotic materials or anything like that). But those same people are happy to use as-yet-unrealized technological leaps to deflect concerns about the sustainability and expense of nuclear power, even though nuclear power is a much older and better-understood technology and many of the breakthroughs being cited (like thorium breeder reactors etc.) have been studied and promised for decades without significant progress.

We know we could extract uranium from seawater. The prototypes would scale. The reason we don’t do that is that there is no economic reason to do that: it would be more expensive than mining, so why bother? However, even at that higher cost, it would still be plenty cheap enough to use in our power plants.

You complain about people overblowing a minor concern with solar, but you do the same with uranium extraction.

Also, I take issue with your suggestion that we can do pumped storage at scale: we can’t. There are not a lot of suitable sites for that: we either lack enough altitude delta, or lack water, or would have to flood huge swaths of land, often already more productively used. I like hydro, and I like pumped storage, but unlike nuclear, you can’t do it just about anywhere.

US is actually particularly lucky when it comes to hydro: most other countries are too flat, too dry, or too short on wastelands. Even if we could pull it off, most can’t, and they need power too.

Pumped storage can be constructed out of concrete. It's not necessary for there to be a preexisting basin. This isn't often done because there's not much demand for it and it's very expensive compared to fossil fuels (which pretty much everything is), but it is entirely industrially feasible and is still generally cheaper than any other kind of battery. I realize you are arguing that extracting uranium from seawater is in the same category, but it's not: there are no industrial scale mining operations extracting uranium from seawater, and there is no evidence that existing prototypes would scale up to global power requirements (in addition to the other issues mentioned by the neighboring comment).

> but it is entirely industrially feasible and is still generally cheaper than any other kind of battery.

Really? That sounds interesting. Can you send me some materials on this?

> there are no industrial scale mining operations extracting uranium from seawater, and there is no evidence that existing prototypes would scale up to global power requirements

This is true, but again, hardly relevant, because nobody really tried to do that at scale, as there is no good reason for it for as long as mined uranium is cheap.

If I remember correctly the tested uranyl ion collectors were not very specific and they concentrated other radioactive heavy elements to a dangerous degree for the lifeforms flowing through.

Pumped storage is simply a gravity battery. There are vertical gravity batteries that can be built anywhere. Basically they are giant cranes that lift heavy blocks high up. This is the storage component and requires electricity. When we need to drain electricity they move the high blocks to a lower elevation using the crane. This generates electricity. This seems like the perfect type of battery to me for urban cities with large towers already.

The sort of battery you describe is utterly non-viable. The amount of energy you can store with solid blocks is extremely small relative to the cost of the structure. Do the math. With 100 tons weight and 100 meters lift (an enormous structure) you get something like 1 (one) dollar worth of electricity, which is bupkis.

Pumped storage works, because it pumps absolutely enormous amounts of water. You can't handle comparable amounts of solid blocks similarly easily.

Sure, nuclear will run out much faster than the sun. But that "much faster" is still on the order of magnitude as the age of human civilization.

And no, pumped storage is nowhere near on the scale required to make renewables feasible. For example, the US uses about 500 GWh of electricity every hour, but only ~20GWh of pumped storage. The pumped storage facilities take about as long to build as nuclear power plants. Storage is also just one of the challenges to making renewables feasible. The fact that renewables are geographically dependent means we'll also have to make large expansions to transmission infrastructure [1].

1. https://www.vox.com/videos/22685707/climate-change-clean-ene...

> Sure, nuclear will run out much faster than the sun. But that "much faster" is still on the order of magnitude as the age of human civilization.

Not with what we actually know how to economically recover, AFAIK, though sources vary widely on such figures.

And yes, pumped storage takes a long time to build, but that is not a disadvantage compared to nuclear plants, as you note. Expanding transmission infrastructure also falls under the line of boring things we know how to do, if the political will is there. I am mostly just pointing out that while both require massive infrastructure investments, making nuclear truly sustainable relies essentially on speculative research in a way that solar + pumped storage does not. Plus, nuclear has other advantages (like being usable in deep space, under the ocean, etc.), which makes it feel a little wasteful to use for power generation on a planet bathed in sunlight. So I don't really understand the strong preference for nuclear that a lot of people seem to espouse.

Massive expansions of electricity transmission, and huge energy storage projects - several hundred times the size of what we have currently - cannot just be hand-waved away "boring things we know how to do". Hydroelectric storage is geographically limited, which leaves large areas without a storage solution. The strong preference for nuclear is because it avoid these difficulties which are typically ignored when renewable plans for decarbonization are proposed.

> Nuclear will run out much, much faster, though, particularly when it comes to uranium we actually know how to extract economically.

With breeder reactors there is enough economically usable fuel to last billions-with-a-b of years.

As I mentioned in my post, people are very quick to bring up breeder reactors, despite the fact that no commercial prototypes that can recycle fuel to that degree actually exist. I have nothing against nuclear power as a short-term stopgap to deal with climate change, but we should stick to technology that actually exists if we're talking about using it as a primary power source into the indefinite future.

There are no wind or solar installations that can come anywhere close to providing the base load power for the United States, either.

According to what I'm seeing, there are only 5 solar plants that produce > 1 GW in the entire world. 1 GW is very small by the standards of nuclear or even large hydro installations.

If electricity/m^2 or per site is your metric of choice, solar isn't going to do well. However, this is an uninteresting metric in a world with so much unused land, and with a technology that doesn't gain significant efficiency improvements from being deployed at a large farm vs. in smaller installations. I don't think anybody seriously disputes at this point that solar can generate enough electricity to power the world (with suitable investments in transmission infrastructure)--and at far lower prices than nuclear for the same amount of electricity. Storage is the problem proposals for significant portions of the grid being solar has to deal with.

> However, this is an uninteresting metric in a world with so much unused land

What do you suppose environmentalists are going to say when you start covering all that "unused land" (which they call "wilderness") with solar plants?

You're shifting goalposts here.

The technology you favor doesn't exist on the scale needed, any more than breeder reactors do. The French Superphénix experimental breeder reactor produced 1.2 GW of electricity, in 1985. That's more than any solar installation in the world except for one.

> What do you suppose environmentalists are going to say when you start covering all that "unused land" (which they call "wilderness") with solar plants?

Probably "wow, thanks for using all that desert?" The environmental argument against solar is by far the weakest out there given that literally every other alternative has substantially worse externalities (whether you think the risks of nuclear waste are worth it or not--I'd imagine most of us do--they obviously exist!). I'd actually go so far as to say that the vast majority of people who claim they are against large solar deployments for environmental reasons are arguing in bad faith.

I do not understand what you're saying as far as "scalability" required of solar farms. What challenges of scale do you think will exist? Solar does not have economies of scale in terms of deployment, only construction (and it is already cheap enough, without subsidies, to undercut fossil fuels in many countries). Deploying a large or small farm scales basically linearly in the number of solar panels, until it becomes such a large fraction of the grid that storage becomes a concern (which we are nowhere close to). This is not comparable to the obvious challenges of mining and processing enormous amounts of seawater (which takes a long time to mix thoroughly and for which we still don't have a good way of actually isolating the uranium) compared to small amounts.

Again, many informed people have issues with solar, but none of their issue is that it couldn't provide the power required. The reason there are not larger solar deployments is that people have not invested in larger solar farms, not that there is some scalability or economic limit; a large farm being a fraction of the size of some nuclear plants is pretty meaningless, considering that it costs proportionally less than the same nuclear plant (which is why I bought up square footage--because that's the only metric by which trying to argue that a single nuclear plant generating more electricity than a large solar farm actually means anything). There is absolutely no technical hurdle there, and frankly I can't really imagine what you think the technical hurdle would be.