Comment by donttrustatoms | Hacker News Reader

Comment by donttrustatoms | Hacker News Reader

Parent Full thread

I love that you bring up the global scale. It's in the global scale things sound daunting. But it's in the global scale that what is really important becomes clear.

Maybe the most important fact it all boils down to is energy density. Nuclear is literally millions of times more energy dense than any other energy source. Practically, that means millions of times less waste. (See let's talk about physics baby http://www.thingsworsethannuclearpower.com/2013/02/energyden... )

Envision a world powered entirely by coal. Not pretty. Entirely by solar? Appealing PR, but besides being not at all possible it has it's own immense ewaste issues and those never decay away and that waste certainly cannot produce energy. Entirely by hydro? That means destruction of perhaps the largest swaths of ecosystems in the world. Etc. Take any qualms about a globe powered by nuclear and then multiply it almost by millions of times for the other sources.

Land use is another huge factor. See this graphic for comparison. http://newenergyandfuel.com/wp-content/uploads/2010/06/LandU...

As far as security forces, etc, it wouldn't likely scale like that but let's assume it does. Are numbers like a million well paying jobs spread worldwide actually daunting? How many military folk end their service time in the US alone each year? I was an intern in the Office of the Secretary of Defense for Economics and Manpower so I should remember but I looked it up. There are hundreds of thousands of former service members looking for jobs each year. ( http://www.civilianjobs.com/careeradvice/related.aspx) Thats leaving out more than 6 billion in other people.

Net of total space requirements for a nuclear reactor site (and not counting processing or mining space), nuclear is only about 2-4x more dense than solar. That is, you could take a nuclear power plant site, remove the reactors, fill it with solar PV, and you'd have ~1/4 - 1/2 the energy output.

When you consider that solar energy can be co-sited with many other land-uses, the situation gets even better. Residential, commercial, or industrial buildings, highway rights-of-way (not on the freakin' roadways, but alongside), or of course, high-potential solar in desert or other largely empty space.

Coal fails for multiple reasons, including in the long term that there's simply not enough of it: the global R/P ratio is 113, that is, there are 113 years' supply at present rates of use. And that rate is increasing -- the R/P ratio has fallen from above 200 in 1993 to just over 100 in 2013. Source: BP Statistical Review of World Energy, June, 2014 http://bp.com/statisticalreview

Then there's that little issue about global warming.

Solar has markedly little waste issue. The life of PV panels is 20-25 years, they're comprised largely of silicon, and other materials can be recycled from them.

Total present US energy usage (not just electricity generation) could be provided from a region 233 miles on a side (54,400 mi^2). Via GNU units and some fairly standard values:

    You have: 100 quad / (1 kW/m^2 * 0.3 * 0.17 * 0.9 * 0.55 * 0.94 * 1 year )
    You want: mi^2
    	* 54397.603
    	/ 1.8383163e-05
    You have: sqrt(54397.603)
    You want: 
            Definition: 233.23294

Switch instead to solar thermal, and you're now free of virtually any

The more significant problem is that there are more humans, consuming more resources, by a long stretch, than the Earth can support. We might be able to provide for 3-4 billions sustainably, but at a standard of living equivalent to slums of Manilla, Kolkata, or the favellas of Rio. Or worse.

Or 500 million to 2 billion at a higher rate of resource consumption, though likely markedly lower than that of the present-day US.

The thing about those 1.8 million security forces is that they represent themselves a vast level of resource allocation that's not itself directly productive. It's an overhead that other energy systems don't require.

Your land-area charts mostly show that biofuels aren't viable. I don't disagree with that conclusion:

http://www.reddit.com/r/dredmorbius/comments/2cvap7/the_intr...

(More: http://www.reddit.com/r/dredmorbius/search?q=biofuels&restri...)

Note that the delta for nuclear and solar isn't particularly significant, again noting that solar power can be co-located with other land uses.

I'd also strongly suggest you actually read and view my references before responding, as several of these aspects are addressed. And you've wholly avoided addressing the large-scale, long-term, unavoidable systemic risks of nuclear.

Something to take note of.

Different types of energy production are useful for different roles.

Nuclear tends to fall into the category of base load - it costs (close enough to) just as much to run it at 5% capacity as at 100%.

Most traditional fossil-fuel steam turbines (coal, oil) have spin-up times on the order of several hours to a day. As such, they tend to be used to compensate for longer-timescale variations, but cannot really cope with very short term spikes.

There are fossil-fuel power stations with shorter lag times, but they tend to be relatively inefficient, and as such only get used for unexpected high loads.

Hydro is really good in a lot of ways, at least where hydro power stations can be built. The biggest reason is that it can be adjusted on really short timescales. Read: minutes or less. Longer lag time for larger power stations - the biggest limitation tends to be preventing cavitation and water hammer.

Solar and wind are both extremely variable, and unpredictably so (you can predict, but there is enough inaccuracy in the predictions that you cannot trust them). As such, they are practically useless without at least one of power storage, fast-responding power generation, or fast-acting power usage cuts when necessary. (Read: hydro or paying aluminum smelters to only run in the back shifts. (First thing that came to mind))

As there is no efficient and decently long-lasting power storage at grid scales (Vanadium-redox batteries are good, but have issues. Molten-salt storage leaks heat quickly. Etc.), effectively: you can forget about solar and wind for grid-scale power without hydro.

Nuclear power for everything is a waste unless society changes. And good luck with that.

Quite.

Hydro, hydro pumped storage, tidal impounds (essentially low-head but large-area reservoirs), and geothermal (wet field) are all highly dispatchable.

Solar thermal is expensive but among its benefits it has is a built-in storage capability. For most present plants that's only a few hours, but several days worth of banked heat might be viable.

There are a number of storage options, of which the prospect of synfuels, in particular seawater-based Fischer-Tropsch fuel synthesis, which as been studied by Brookhaven National Labs, MIT, and the US Naval Research Lab for over 50 years, looks fairly promising. It starts with hydrogen electrolysis, to which CO2 is added, sourced from seawater. Outputs are analogs of present day diesel, gasoline, natural gas, or other hydrocarbons. Most of the energy cost is in the electrolysis. Net energy return in terms of fuel is about 50-60%, round-trip net of generation would be fairly low (~20%), but the energy storage is very long-term stable, and dense by weight or volume (for liquids). We've got a lot of experience burning hydrocarbons, and these are carbon-neutral (the source CO2 comes from the present biosphere).

http://www.reddit.com/r/dredmorbius/comments/28nqoz/electric...

http://www.reddit.com/r/dredmorbius/comments/22k71x/us_navy_...

There's also work by some (including a recent video by Amory Lovins) suggesting that there are relatively modest requirements for dispatchable generation, though I suspect those are a tad optimistic.

http://www.engineering.com/ElectronicsDesign/ElectronicsDesi...

https://www.youtube.com/watch?v=MsgrahFln0s

Dispatchable. That's the term. Thanks.

The thing is, by the time you talk about the design lifetime power output of wind in particular, and couple in the 20% figure you quote for the round trip, one has to wonder if it is worth it.

It's a lot of metal (and in particular the "weirder" metals - rare-earths and the like) to smelt and move around to get a relatively small amount of power. And the increased power losses due to having to put them where the wind is. And the power cost of building the storage capability.

Synfuels are indeed interesting, for bunches of reasons, chief among them that they are the most power-dense storage solution we've got. Personally, it's about the best option for personal vehicles. Yeah, electric vehicles are neat, but they suffer from short ranges and long recharge times, as well as using bunches of relatively rare elements (and elements that are mined using techniques that are abysmal in environmental terms).

I've always thought of windpower as a weird kind of battery. You put all sorts of energy in upfront (manufacturing, installing, repairing) and get a trickle our for a long time.

There are better batteries...

There are a few people who've done calculations of the EROEI (energy returned on energy input) of various renewable energy technologies, most notably the guy who came up with the term, Charles A.S. Hall. I've had a few discussions with him on this.

Wind power has a modestly high EROEI, around 18. For solar PV, his numbers are far lower -- around 2.6. The problem comes in when you account for whether there's a minimum EROEI necessary to sustain an advanced civilization, and just what that might be. Hall's view is that it's around 6-10, after which you pretty much fall off a cliff -- you've got to get a sufficient return on your energy investment to make other economic activity possible.

For the synfuel path I discussed, the point is that there are a few things for which having hydrocarbons (liquid or gas) is really, really useful, and as I've noted elsewhere in this discussion, there's simply not enough net biological productivity ("photosynthetic ceiling" to use Jared Diamond's term, or HANNP, human appropriation of net primary productivity, another formulation) to provide fuels in the quantities humans are presently accustomed to -- some of the acreage requirement estimates get stunningly large and rapidly:

http://www.reddit.com/r/dredmorbius/comments/2cvap7/the_intr...

In particular (the table on that page is a bit prettier than it will appear here on HN):

    Crop        Yield (gal/acre-yr)     Acres required (millions)
    soybeans    50      5,670
    canola      100     2,835
    canola      300     945
    algae       1000    283
    algae (high est)    10,000  28

Note that total arable land in the US is about 410 million acres, and total land area of the US is 2.4 billion acres. You'd have to overplant the US twice to get enough fuel-from-crops via soybeans.

Note that "rare earths" aren't actually all that rare, though there are plenty of minerals which are limited in abundance:

http://www.reddit.com/r/dredmorbius/comments/267901/global_r...

As for synfuels: since you're converting surplus generating capacity, your marginal energy cost is nil. Even assuming you're building capacity specific to the need, what you're trading is a non-storable, non-mobile, non-dispatchable form of energy for one which has all of those properties. That can be a good trade.

The fact that it's a drop-in replacement for the existing energy system is an added bonus.

Will it work? I really don't know, though the answer to that question's been occupying me for some time.

Thanks for the detailed response!

If you're talking about an EROEI on wind of 18, and a 20% storage efficiency, that brings down the EROEI to 3.6. Probably more, as not all energy will pass through the storage. Still well below replacement. Or is that already factored into the EROEI? Does that include the unmetered power usage of windmills? If so: how? Does that factor in increased power-line losses, and the cost of building and maintaining those power lines? What are the details of the windmills measured? Is that real-world data, or simulations? If real-world, where?

I agree that current foodstuffs are not suitable for biodiesel. And raises food prices. But two things. One, I was talking about synthetic production. And two, that's assuming current plants. Personally, we shouldn't be looking at land-based solutions anyways. We already have space issues, at least at that scale. Look at sea-based ideas instead. Algae farming on megascales, that sort of thing. Much more efficient, much more land available, and can be situated closer to the equator.

I knew I shouldn't have just said "rare-earths and the like". I am aware that rare earths are a misnomer in general. Although... Neodymium isn't rare, but the bulk of the world's production thereof is in China. Has that energy cost been factored in? Much less the other costs? (Amount of radioactive release, etc.)

> As for synfuels: since you're converting surplus generating capacity, your marginal energy cost is nil.

Wrong. Your marginal energy cost is the cost of building and maintaining the plant and supporting infrastructure. And even just that may be less than unity overall. It may be useful, but I'd want to see the numbers.

As for the trade you mention ("Even assuming you're building capacity specific to the need, what you're trading is a non-storable, non-mobile, non-dispatchable form of energy for one which has all of those properties"), I agree partly, but the question remains: what energy input should we use? Is it worth it to build wind generators or solar power stations? Should we stick to nuclear? Or what?

Fundamentally, we currently have a couple of different energy sources. Geothermal, direct solar, indirect solar (wind, hydro), tidal, "biological solar", nuclear energy, and potentially fusion. Everything else is just energy storage. (Well, to be pedantic, so is fission and fusion, but by the time we're worrying about those running out we'll have worse issues.)

Current biological solar solutions are not exactly efficient. Your figures show direct solar isn't either. Wind is iffy for various reasons - maybe not insurmountable, but still. Geothermal is great, but only in limited areas. Same with hydro and tidal. Nuclear is great, but the political climate is rather iffy to put it mildly.

Taking a look at the full-cycle EROEI is something I'd like to do, but haven't. It's not necessary for any given element of a power cycle to be EROEI-positive. In fact any given energy transform will represent a net energy loss. But for the total effective cycle you've got to get more than you give. Note that at present agriculture in the US represents a 10:1 energy cost -- you get 1 unit of energy for every ten units of fossil-fuel energy you input. In Europe it's about a 1:5 ratio. Again, negative EROEI. The saving grace is that fossil fuel energy has such a high EROEI.

On marginal cost of energy: if the alternative is to discard the generating potential entirely, then the marginal cost is zero. If you're building excess capacity specifically to provide fuel synthesis capabilities, you do have real costs. The US Naval Research Lab's estimate is $3-6/gallon for aviation fuel, though I'm not sure if they assume a gratis reactor. I've specced out $9/gallon with solar input. Not cheap, but a long-term stable price, vs. constantly rising fossil fuel costs.

As for input energy: my assumption is generally for solar + wind -- they're simply the largest available long-term sustainable energy sources we've got (I've got my doubts on how long nuclear fuel will last, and terrestrial fusion's still unproven). The initial scheme for large-scale F-T synthesis was based on a presumption of nuclear energy input. M. King Hubbert proposed this in 1964, and the idea was picked up by Meyer Steinberg of BNL pretty much immediately. The initial proposal was that CO2 come from, e.g., limestone, but seawater was identified as a reservoir pretty early on. Steinberg's a nuclear engineer, and most of his work assumes nuclear power supplying electricity.

Incidentally: in a nuclear economy, you'd still need liquid fuels, though most proposals focus on hydrogen alone. Given difficulties with its chemistry, I doubt this will prove effective.

Compared with alternatives, I really see solar as the backbone of any future energy system. The only questions are how large the supported population will be, and how advanced its technology. Solar energy is what humans relied on before finding fossil fuels. And there's no assurance that we'll retain our present tech levels.

Nuclear's problems are not merely political, though that's a significant hurdle of its own.

NB: source of that land use chart:

http://www.lincolninst.edu/pubs/2036_Alternative-Energy-Sour...

http://newenergyandfuel.com/http:/newenergyandfuel/com/2010/...

http://www.cnet.com/news/figuring-land-use-into-renewable-en...

Reply on news.ycombinator.com