It shows nuclear lifetime emissions are lower than solar, but I think this report excludes the carbon footprint in manufacturing/recycling the renewables.
[outdated] You might be misinterpreting that report slightly - it estimates that all renewables -- with the exception of utility-scale solar -- currently emit fewer lifetime emissions than nuclear.
Digging into why utility-scale solar is currently an exception, one potentially relevant factor is that utility-scale solar is working through some regulatory and infrastructure obstacles[1] as it scales up.
[outdated] That said, I couldn't see any indication that manufacturing solar panels themselves is an issue. If residential solar has lower lifecycle emissions, then I wonder why the panel manufacturing would be a problem. Do you have any more information on that?
Edit: noting that first and third paragraphs are outdated following edits to parent comment
Self-reply: d'oh, I may have misinterpreted on this too; the data in the report is a little more complex.
I was comparing the 'max' lifetime estimates per-source (the third value in the column) rather than the medians (second value).
Using the medians, wind is cleanest, followed by nuclear, followed by solar. I'd encourage anyone interested to read the linked report to confirm their understanding.
It'd be nice to find trends over time to see whether these estimates (and thus the overall ordering) is likely to remain stable, or whether recent developments may change the situation.
yeah, thanks for this, and sorry for edits, I need to search for a good reference on manufacturing/recycling emissions for renewables, i think the report either excludes or underestimates the bootstrapping and maintenance carbon footprint. I got my original info from a professor in nuclear engineering program years ago, I wish I still had the notes.
All good, and no problem - I try to follow a mostly-append-only commenting approach where possible, hence the edit notes.
Glad to read what you find; I think some of these figures may also be due for updates given the latest updates around small modular reactors -- and no doubt renewable tech continues to advance too.
Seems like a boot strapping problem to me. If we create enough solar/wind energy then we can devote some of that energy back to production of materials used to produce solar panels.
I'll bite: the energy density of sunlight on average is something like 1.4 kW/m^2
If you put down a square meter of solar panel, weigh it and run it for an hour to get an equivalent wh/kg and compare to almost any other energy source (except maybe wind?) you will find it to be complete garbage.
The only thing solar has going for it is it's free, basically no waste products and you can find it literally anywhere on the surface of the earth.
The energy density of sunlight itself is energy available per kg of mass-energy. That mass-energy can be totally converted to usable energy, unlike nuclear reactions or chemical fuels.
Of course, what this shows is that energy density, as was being used, is a silly metric. By that I mean that it's useful for d--- measuring contests, but not for making any actual decision about what technology to choose.
It seems you've written c² in units of Wh/kg? But the fact that per arbitrary mass, you can theoretically get more energetic reactions than by fission or even fusion doesn't mean comparing the productivity of fission to oil is silly. The issue is realistic ways of efficiently liberating and harnessing energy from matter.
One better than fusion not impossible option is carefully feeding small black holes and extracting their huge output of energy. The feedstock for the black hole might even be lifted from the sun. In the meantime, fission is a productive and practical option to add to the energy mix that will more than serve until we've worked out fusion.
One place I think I agree with you is that phrasing it as energy density, rather than focusing on efficiency of a given unit of mass or fuel at yielding energy can be a bit obscuring. That is, it's better to focus on sustainability of fuel source. Energy density (J/m^3 and J/kg, specific energy) are units more appropriate for talking about energy storage and bombs.
You're comparing the wrong things. Those weights are of energy stored, but with light it is in motion. Maybe if you manage to get some light stuck in a crystal we can have a meaningful comparison.
Are there any details on how much processing you need to get uranium from the ore? My intuition is that it is a lot harder to get to uranium fuel from the ore compared coal and oil.
And there's 2 million more oil/coal on earth than uranium, quantity wise?
Don't get me wrong, being an informed human being, I'm obviously pro-nuclear but if humanity main energy source become uranium then we will note have enough by the end of the century, at least by the current estimate (more funding will enable to find more uranium but it is an unknown which imply an existential risk).
The solution would be thorium based nuclear reactors which would feed humanity for at least a millennium! But by design they must be less cost effective (how much?) and needs R&D funding today.
Both uranium breeders and thorium breeders offer truly inexhaustible energy for humanity. Especially uranium, which is available in seawater at astronomical scale, and which replenishes first through runoff and then through plate tectonics.
We'll run out of nuclear fission fuel roughly when we run out of nuclear fusion fuel in the sun (i.e. when the sun burns out).
2. Sunlight can't be measured by kilos, so it can't be compared against.
3. Sunlight is the consequence of the sun's nuclear reactions. So fusion nuclear energy might be comparable, but until then, fission is as close as we get.
If you have an idealized mirrored box, and add some light to the inside, that will increase the inertia of the box. So in that sense the light has mass.
by weight nuclear has 2 million times the energy of coal or oil.
(and I think coal might have more radioactivity by energy)