Making Jet Fuel From Seawater While at Sea • Hacker News Board

Re: Making Jet Fuel From Seawater While at Sea

#61

Post by sophacles » Sat, Sep 29, 2012, 4:19 PM UTC

Roritharr wrote: post #39

zmmz wrote: post #37

Earlier quoted context omitted.

It's not that simple: CO2 in atmosphere -> CO2 in water -> Ocean acidification[1] -> Change in ocean ecosystem The oceans absorb OC2 from the atmosphere, which you could argue is good, but it is not without consequences. Putting CO2 in the water moves the problem from having it in the atmosphere elsewhere, but it's still a problem. In some ways then, this can be seen as a good thing, because it is undoing the effects…

I'm not for putting more carbon into the oceans... just against taking the currently stored carbon out.

You only really have 2 choices here[1] (provided this gas-to-liquid thing pans out):

1. Take carbon out of the ground, where it is not active in any carbon system. Put it in the air, and ultimately the ocean. This releases more carbon into the whole system, and causes problems we all know about. It eventually goes to the water as the parent mentioned, with the acidification problem (s)he brought up. Adding ever more carbon to the system only adds to the total carbon load.

2. Take carbon out of the water, reduce acidification, albeit by transferring it to the air. This doesn't actually put new carbon in the system tho, so it has benefit.

However, the carbon put in the air with #2 is the same as traditional jet fuels from sources in the ground, so those effects cancel out as a consideration in our choice range.

Sure in a perfect world, we would find a way to start actively reducing the amount of carbon in circulation, however, to get there we have to find ways to stop adding new carbon to the system. This helps with that.

[1] I know there are lots of options we could consider, but I highly doubt any option that effectively translates to "have the military be less effective" will fly politically, so I am assuming that short-term achievable options have to have no negative effect from the military POV at minimum.

Re: Making Jet Fuel From Seawater While at Sea

#62

Post by sophacles » Sat, Sep 29, 2012, 4:23 PM UTC

dctoedt wrote: post #40

pixie_ wrote: post #5

Earlier quoted context omitted.

Yep, it's a pretty good use of 200MW of power when you're just sitting around in the ocean.

> when you're just sitting around in the ocean Watch any of the documentary series about life aboard an aircraft carrier [1] and you'll see that there's essentially no "just sitting around in the ocean." But your main point is still accurate: If there's power available, putting it to work making jet fuel might be a good trade-off for the additional drain on the nuclear fuel. [1] E.g., http://www.pbs.org/weta/carrier/

From friends and family in the navy: whenever you see a fleet or battle group "stationed" somewhere, it means they are basically doing right turns in the middle of the ocean (a joke being that someone has to balance the effect of all those left turning NASCAR races). While they are doing operations etc, a lot of this time is considered extremely boring, more so than even long voyages going somewhere. Further, they usually aren't going full speed, so to some extent they are "just sitting there", particularly in the effect that they aren't using the full output of their power systems - leaving lots of power and (if needed people time) available for fuel "creation".

Re: Making Jet Fuel From Seawater While at Sea

#63

Post by DennisP » Sat, Sep 29, 2012, 4:24 PM UTC

confluence wrote: post #48

jrabone wrote: post #46

Earlier quoted context omitted.

What? 10 years until battery technology has advanced to the point of parity? Gasoline has an energy density of 132 MJ/US gal, or say 1500 MJ on a full small tank. Modern engines hit 30% thermal efficiency, but then there are drive train losses etc, so I'll give you the 15% as an absolute worst case, AND give you a 100% efficient electric motor / drive train. Therefore your car needs to provide 225 MJ of stored energy…

I'm assuming nuclear fusion is viable with the development of the ITER and DEMO plants in the South of France. If they aren't viable - I'm calling time of death on the world.

Don't rest all your hopes on ITER. Alternative approaches that could well be cheaper and come to fruition a lot sooner include NIF/LIFE, polywell, focus fusion, General Fusion, Tri-Alpha, Helion, levitated dipole, petawatt picosecond laser fusion, and Sandia's new approach to magnetized inertial fusion.

If none of them work, advanced fission designs like LFTR or IFR could be almost as good, with better safety and a hundred times less nuclear waste than conventional reactors.

Re: Making Jet Fuel From Seawater While at Sea

#64

Post by dalke » Sat, Sep 29, 2012, 4:25 PM UTC

sophacles wrote: post #59

stcredzero wrote: post #54

Earlier quoted context omitted.

> That is incorrect. If the fusion source is compact, and can produce a lot of instantaneous electrical power, and is quick to throttle up and down, then a "Back to the Future"-style Mr. Fusion would be the best way to power cars. There's also safety to consider.

On top of that, reliability. To have a large plant with a high mechanical complexity which can justify dedicated maintenance workers to help manage complexity and the results of part wear etc is likely able to achieve the same or higher reliability than a backyard unit, in TCO terms anyway.

So I think you both agree with me that it's not necessarily the case that a hypothetical fusion power source or free energy source is best used to produce hydrocarbons for distribution and downstream use.

Regarding the comment of sophacles, power distribution is part of the economic factor. It may be that the central plant is much more reliable than a backyard plant, but the power grid - subject to thunderstorms, ice, tree falls, backhoes, curious squirrels, and so on - makes the overall power supply system less reliable than a backyard fusion plant.

Re: Making Jet Fuel From Seawater While at Sea

#65

Post by wpietri » Sat, Sep 29, 2012, 4:29 PM UTC

sien wrote: post #27

ta12121 wrote: post #20

Earlier quoted context omitted.

No. Electrolysing water to make H2 and extracting CO2 from the environment, and then synthesizing hydrocarbons from them, is extremely energy inefficient. Sure, theoretically, it can be done, and maybe one day it could even be done efficiently. But Tesla is making battery-electric cars that work today . The military does not care about efficiency because they have nuclear reactors on their ships and their goal is to…

If they can hit $3 / gallon why does it matter? Tesla's cars are wildly price inefficient because they cost $100K. For 10K you can get a decent car that has 4 times the range. http://en.wikipedia.org/wiki/Tesla_Roadster How many gallons of fuel can you get for 90K? They are nice toys for rich people. Perhaps there is a market for that. Good luck to them. But for mass transit unless you can get the price of the batter…

You're cheating.

Telsa, like many startups, is pursuing a low-volume, price-insensitive market first. That helps pay for all sorts of startup and R&D costs, and lets them work out issues before they scale. Their long-term goal is, per Wikipedia, "eventually mass producing fully electric cars at a price affordable to the average consumer".

There are several fully electric vehicles in production that cost $35k.

http://en.wikipedia.org/wiki/List_of_production_battery_elec...

They have a substantially lower cost of operation than gas-powered vehicles, so they are plausibly cheaper to operate over the lifetime of the car:

http://en.wikipedia.org/wiki/Nissan_Leaf#Operating_costs

And over the long term, expecting batteries to get better is a pretty good bet. Everybody from Apple to Toyota is eager for battery improvements.

Re: Making Jet Fuel From Seawater While at Sea

#66

Post by ta12121 » Sat, Sep 29, 2012, 4:39 PM UTC

danielharan wrote: post #53

ta12121 wrote: post #42

Earlier quoted context omitted.

$3 a gallon is what the fuel costs today when it comes straight out of the ground. Claiming to be able to build and run a nuclear reactor and then synthesize the fuel through multiple energy inefficient steps all for the same price is a pipe dream.

It's not competing against the price straight out of the ground; it's competing against fuel that's been refined and delivered to a moving ship somewhere potentially very far away. Instead of $3 a gallon, it could be up to 10X more.

The amount of energy needed to refine crude oil is much less than the energy it takes to synthesize it. Think about it: people refine the crude, transport it, and use the end product in an energy net positive manner. To synthesize hydrocarbon fuel, you need to put in at least the amount of energy you're going to store, and with current technology probably 2 times as much at least due to inefficiencies. Then you need to still account for building and running the nuclear reactor. Try to imagine the systems as a whole, the number of steps and losses at each step. The scheme does not make sense.

1) uranium -> nuclear power -> expensive synthesis -> local transport -> fuel

2) uranium -> nuclear power -> transmission lines -> charging batteries

3) crude oil -> refinement -> transport -> fuel

EDIT: Found a reference from another comment: http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process... It says that the input energy is 2-4 times the stored energy for synthesized hydrocarbon fuel.

Re: Making Jet Fuel From Seawater While at Sea

#67

Post by sophacles » Sat, Sep 29, 2012, 4:59 PM UTC

dalke wrote: post #64

sophacles wrote: post #59

Earlier quoted context omitted.

On top of that, reliability. To have a large plant with a high mechanical complexity which can justify dedicated maintenance workers to help manage complexity and the results of part wear etc is likely able to achieve the same or higher reliability than a backyard unit, in TCO terms anyway.

So I think you both agree with me that it's not necessarily the case that a hypothetical fusion power source or free energy source is best used to produce hydrocarbons for distribution and downstream use. Regarding the comment of sophacles, power distribution is part of the economic factor. It may be that the central plant is much more reliable than a backyard plant, but the power grid - subject to thunderstorms, ice…

No. I will agree that a distributed power system may provide overall reliability but this condition must be true:

There is still a grid. If my power source goes out, I want backup to come from other nearby sources - the timeline of power restoration from the current delivery system is on the order of minutes or hours for over 80% of outages, and on the order of a couple weeks for over 99% of the rest of outages. If my power plant breaks, I need restoration numbers that meet that. (additionally, I need plant repair bills to be lower than however much money having the backyard plant would save me. TCO considerations again).

Further, these two assumptions are built into your "better" assessment:

* It is cheaper to have a power plant in my back yard than buying it from the grid.

* The backyard source can be made safe.

Combining these two assumptions is a big deal. If both are true, I will agree that it is a good option (with the caveat listed above). However, there is a HUGE amount of R&D to get there, including a massive set of efficient production runs for parts to build all the systems to make it happen. The economics of this points to it not being likely that everyone has a backyard fusion plant.

It is far more likely to see big fusion plants in greater number scattered around the power grid to provide higher reliability in the cases of line loss etc. Further, with energy now being much, much cheaper to produce, you'll likely start seeing more reliable distribution channels for electrical power. Overhead lines would be reasonable to replace with underground ones, which are less efficient, but are also more reliable as they are less likely to be damaged in weather events. You'll also probably see a reduction in star-topology distribution - more redundancy in distribution paths, at the cost of some efficiency, because the complex equipment will be cheaper to manufacture (you know, because energy to do so will not factor into costs anymore).

Re: Making Jet Fuel From Seawater While at Sea

#68

Post by dalke » Sat, Sep 29, 2012, 6:03 PM UTC

sophacles wrote: post #67

dalke wrote: post #64

Earlier quoted context omitted.

So I think you both agree with me that it's not necessarily the case that a hypothetical fusion power source or free energy source is best used to produce hydrocarbons for distribution and downstream use. Regarding the comment of sophacles, power distribution is part of the economic factor. It may be that the central plant is much more reliable than a backyard plant, but the power grid - subject to thunderstorms, ice…

No. I will agree that a distributed power system may provide overall reliability but this condition must be true: There is still a grid. If my power source goes out, I want backup to come from other nearby sources - the timeline of power restoration from the current delivery system is on the order of minutes or hours for over 80% of outages, and on the order of a couple weeks for over 99% of the rest of outages. If m…

The original premise was already unrealistic. I made it even more unrealistic. If there is a "Mr. Fusion" device which can produce 1.21 GW, on-demand, safely, and it small and light enough to fit in your car, then there's no need for a grid. You would just have several of those devices in your house.

My hypothetical was to show that there could be cases where it does not make sense to use a Mr. Fusion type device to produce hydrocarbon fuel which is then used as the energy source. Everything I said takes place in the original fantasy world. Under the original premise -- "some grad student gets fusion going at a very low price" -- then it must be using some principle we haven't yet thought of. And with that premise in place, almost anything goes.

Once I put realism into place, then the original hypothetical is not sustainable. The long term solutions for real life are decreased energy use, fission, hypothetical fusion, and renewable. None of the last three can exist without a grid, at least for most people. The only way to be without a grid is greatly reduced power use, a less concentrated population, and switch to local renewable resources. That isn't going to happen.

Re: Making Jet Fuel From Seawater While at Sea

#69

Post by danielharan » Sun, Sep 30, 2012, 3:18 AM UTC

antidoh wrote: post #55

danielharan wrote: post #53

Earlier quoted context omitted.

It's not competing against the price straight out of the ground; it's competing against fuel that's been refined and delivered to a moving ship somewhere potentially very far away. Instead of $3 a gallon, it could be up to 10X more.

And, dollar cost of the fuel is not the only cost of maintaining a "long supply tail." There's also the dollar cost of all the ships and sailors on that tail, and there's the logistical opportunity costs: we have to protect that tail with military resources that might otherwise have gone to more directly military purposes, and the head of the tail (the military activity at the front) is held back and slowed down by a…

Exactly. Less replenishment means more flexibility.

Lots of people killed by IEDs on long supply lines in Afghanistan is an extreme example of the human and military costs. Some of those died to fuel A/C for uninsulated tents... madness.

Re: Making Jet Fuel From Seawater While at Sea

#70

Post by danielharan » Sun, Sep 30, 2012, 3:26 AM UTC

ta12121 wrote: post #66

danielharan wrote: post #53

Earlier quoted context omitted.

It's not competing against the price straight out of the ground; it's competing against fuel that's been refined and delivered to a moving ship somewhere potentially very far away. Instead of $3 a gallon, it could be up to 10X more.

The amount of energy needed to refine crude oil is much less than the energy it takes to synthesize it. Think about it: people refine the crude, transport it, and use the end product in an energy net positive manner. To synthesize hydrocarbon fuel, you need to put in at least the amount of energy you're going to store, and with current technology probably 2 times as much at least due to inefficiencies. Then you need…

Asking me to imagine a system as a whole doesn't prove your argument.

Instead of the energy system, consider the cost of military supply lines. There's more than the financial cost of delivery; long supply lines are vulnerable to attack and disruption. You don't need to imagine an example: consider IEDs in Afghanistan. Many of those were trucks delivering food and fuel to bases. Efficiency (i.e. insulating tents so less fuel is needed for A/C) results in less deliveries and less deaths.

The same principle applies at sea. Oil ships are a vulnerability and another thing to plan, as well as a major cost that can be more important than the energy efficiency issues.