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

Re: Making Jet Fuel From Seawater While at Sea

#71

Post by jnw2 » Sun, Sep 30, 2012, 3:34 AM UTC

ChuckMcM wrote: post #24

jnw2 wrote: post #15

Earlier quoted context omitted.

http://en.wikipedia.org/wiki/USS_Gerald_R._Ford_(CVN-78) notes that ``Unfortunately the power limitations for the Nimitz class make the installation of the recently developed [Electromagnetic Aircraft Launch System] impossible.'', which seems to indicate that existing nuclear powered aircraft carriers don't always have large amounts of electricity to spare. However, more electricity will be available on future aircra…

If you look at the power requirements for the EMALs system you will see why a Nimitz class carrier can't power it. Not only is it a crapload of power, its needed all at once. The JP4 from Seawater project can run at much lower powers and for long periods of time.

http://en.wikipedia.org/wiki/A1B_reactor indicates that there's 300 MW per reactor on the Ford class, and two reactors, so maybe 600 MW total, although I'm not sure if that's the output of the steam powered electrical generators, or if it's the theoretical amount of energy in the steam coming out of the reactor.

http://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equiv... says the EPA figures 33.7 kwH is the same as a gallon of gasoline, and there's enough slop in estimating how much power a carrier will have left over for making jet fuel that the error in pretending that jet fuel is the same amount of energy per gallon as gasoline is probably noise.

Other commenters are saying that synthetic fuel is going to take 2-4 times as much energy as the synthetic fuel stores, so let's assume roughly 100 kwH to make a gallon of jet fuel.

That suggests that 600 MW total power might be able to make as much as 6000 gallons per hour if people are happy to leave the carrier drifting with no lights and all its defensive equipment turned off. If the carrier is carrying 75+ planes, that suggests it can make less than 100 gallons an hour per plane. The Google Search summary of http://www.google.com/url?q=http://wiki.answers.com/Q/What_i... says a Gulfstream III consumes 568 gallons per hour. A supersonic fighter jet probably consumes somewhat more, and that leaves me wondering if a Ford class reactor is going to be able to produce enough jet fuel for an active fleet of fighter jets. Certainly, the planes don't fly 24 hours a day, but this estimate suggests that the carrier's reactors might not even have enough left over power to make enough jet fuel to have the average plane on board flying one hour out of 24.

Re: Making Jet Fuel From Seawater While at Sea

#72

Post by jnw2 » Sun, Sep 30, 2012, 3:38 AM UTC

jrabone wrote: post #43

ChuckMcM wrote: post #24

Earlier quoted context omitted.

If you look at the power requirements for the EMALs system you will see why a Nimitz class carrier can't power it. Not only is it a crapload of power, its needed all at once. The JP4 from Seawater project can run at much lower powers and for long periods of time.

And in fact, here is another illustration of just how hard it is to replace conventional energy storage systems with electricity. High pressure steam stores an enormous amount of energy. EMALs effectively uses 4 flywheels as rotational energy stores, suggesting battery / supercap technology just isn't viable. It does have an efficiency advantage over steam though.

I bet batteries don't tend to like going from full to empty in the time it takes to launch a plane.

I wouldn't be surprised if later in the Ford class's life, we do see supercapacitors taking over.

Re: Making Jet Fuel From Seawater While at Sea

#73

Post by jnw2 » Sun, Sep 30, 2012, 3:42 AM 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…

Mass transit has some advantages with predictable trip lengths: no transit agency is going to insist that they need a bus that can go 200 miles on a charge if their average bus only travels 50 miles each morning. Meanwhile, the average consumer ``needs'' car with a battery that is several times what their 99th percentile trip length is.

Re: Making Jet Fuel From Seawater While at Sea

#74

Post by jnw2 » Sun, Sep 30, 2012, 3:48 AM 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…

Several strings of solar panels + lithium ion batteries might very well be cheaper than paying your local electric monopoly for transmission line capacity in 20 years. And if the non-redundant parts (the inverter, perhaps) fail, it might not be all that different from your water heater failing today.

(Although if we had that technology in cheap enough form, some of the major loads in your house may switch to DC to avoid conversion losses to AC, since solar panels and batteries are both inherently DC technologies, and that might make the inverter less important.)

Re: Making Jet Fuel From Seawater While at Sea

#75

Post by ta12121 » Sun, Sep 30, 2012, 4:03 AM UTC

danielharan wrote: post #70

ta12121 wrote: post #66

Earlier quoted context omitted.

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 l…

I missed the part where you brought the argument back to the military. Yes, it makes sense for the military, as I acknowledged in my original post. The Parent, however was claiming that electric cars for general use are made moot by this technology, which is certainly not the case.

Re: Making Jet Fuel From Seawater While at Sea

#76

Post by pdonis » Sun, Sep 30, 2012, 6:08 AM UTC

jnw2 wrote: post #15

ChuckMcM wrote: post #10

Earlier quoted context omitted.

That is exactly why its such a big deal. Current jet fuel costs over $8/gal delivered. It costs so much because even if it comes out of the refinery at San Diego at $2/gal it has to be loaded into an oiler [1] and then driven out to sea where the carrier task group is. If you're on a nuclear powered aircraft carrier you have plenty of electricity so this is a pretty huge win. Of course an alternative way to make this…

http://en.wikipedia.org/wiki/USS_Gerald_R._Ford_(CVN-78) notes that ``Unfortunately the power limitations for the Nimitz class make the installation of the recently developed [Electromagnetic Aircraft Launch System] impossible.'', which seems to indicate that existing nuclear powered aircraft carriers don't always have large amounts of electricity to spare. However, more electricity will be available on future aircra…

> existing nuclear powered aircraft carriers don't always have large amounts of electricity to spare

The limitation isn't the nuclear reactors, it's the electrical generators, which are only sized to make a small fraction of the total power the reactors are capable of. Most of the reactor power is for moving the ship, not making electricity.

Re: Making Jet Fuel From Seawater While at Sea

#77

Post by pdonis » Sun, Sep 30, 2012, 6:11 AM UTC

jnw2 wrote: post #71

ChuckMcM wrote: post #24

Earlier quoted context omitted.

If you look at the power requirements for the EMALs system you will see why a Nimitz class carrier can't power it. Not only is it a crapload of power, its needed all at once. The JP4 from Seawater project can run at much lower powers and for long periods of time.

http://en.wikipedia.org/wiki/A1B_reactor indicates that there's 300 MW per reactor on the Ford class, and two reactors, so maybe 600 MW total, although I'm not sure if that's the output of the steam powered electrical generators, or if it's the theoretical amount of energy in the steam coming out of the reactor. http://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equiv... says the EPA figures 33.7 kwH is the same…

> 600 MW total, although I'm not sure if that's the output of the steam powered electrical generators, or if it's the theoretical amount of energy in the steam coming out of the reactor

It's the latter. Most of that power goes to moving the ship, not making electricity.

Re: Making Jet Fuel From Seawater While at Sea

#78

Post by dalke » Sun, Sep 30, 2012, 8:56 AM UTC

jnw2 wrote: post #74

sophacles wrote: post #67

Earlier quoted context omitted.

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…

Several strings of solar panels + lithium ion batteries might very well be cheaper than paying your local electric monopoly for transmission line capacity in 20 years. And if the non-redundant parts (the inverter, perhaps) fail, it might not be all that different from your water heater failing today. (Although if we had that technology in cheap enough form, some of the major loads in your house may switch to DC to av…

There will still be a grid. The scenario you mention will be useful for some, but assuming $80/month for electricity over a paid-for grid vs. $10,000 for installation of cheap solar panels+batteries gives a pay-off time of about 10 years. (Currently solar water heaters cost about $5,000, so the best is 5 years.)

I don't think most will be willing to take that capital investment.

It would be interesting to see how distributed solar compares to grid-based distribution in the face of large disasters like a hurricane or ice storm. Especially if the power lines were underground. I assume that those with damaged panels would quickly look for replacements, causing an instant demand and price spike. While the large electricity companies would have stockpiled reserves and have agreements already in place to handle the short-term demand. I don't know how this would affect the overall long-term costs.

Re: Making Jet Fuel From Seawater While at Sea

#79

Post by jrabone » Sun, Sep 30, 2012, 10:37 AM UTC

jnw2 wrote: post #72

jrabone wrote: post #43

Earlier quoted context omitted.

And in fact, here is another illustration of just how hard it is to replace conventional energy storage systems with electricity. High pressure steam stores an enormous amount of energy. EMALs effectively uses 4 flywheels as rotational energy stores, suggesting battery / supercap technology just isn't viable. It does have an efficiency advantage over steam though.

I bet batteries don't tend to like going from full to empty in the time it takes to launch a plane. I wouldn't be surprised if later in the Ford class's life, we do see supercapacitors taking over.

No, I expect they'd need to be specially designed for it, with a number of compromises (gas venting/replenishment) along the way.

Battery technologies tend to have a limiting internal resistance that determines the maximum discharge rate, although in many cases the maximum SAFE discharge rate is much lower - traditional lead acid will allow you draw so much current that the plates buckle and the acid boils...

It's all down to the chemistry, and every technology has different characteristics and weaknesses - for example, any secondary cell involving nickel or zinc has to deal with the tendency of these metals to grow dendrites when plating out of solution (ie. the recharge case) - this is what bursts a regular AA cell if you try to recharge it using DC. There are simple workarounds, and although the regular dry cell design is not optimal for recharging it can be done. It also causes the memory effect in NiCd cells, and explains why they can sometimes be recovered with a large pulse of charging current (local melting of the dendrites).

Re: Making Jet Fuel From Seawater While at Sea

#80

Post by jrabone » Sun, Sep 30, 2012, 10:48 AM UTC

jnw2 wrote: post #74

sophacles wrote: post #67

Earlier quoted context omitted.

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…

Several strings of solar panels + lithium ion batteries might very well be cheaper than paying your local electric monopoly for transmission line capacity in 20 years. And if the non-redundant parts (the inverter, perhaps) fail, it might not be all that different from your water heater failing today. (Although if we had that technology in cheap enough form, some of the major loads in your house may switch to DC to av…

I don't think you necessarily need Li-ion for that - in my experience lead acid works well enough in the domestic case, is a lot cheaper and probably safer (although hydrogen venting is perhaps an issue).

I built a little mixed DC (lighting) + AC (1kW inverter) system out in the garden (far enough from the flat that running a cable would be a nightmare of planning permissions & digging trenches).

Since it's for intermittent use the panel is tiny (50W Kyocera) compared to the battery (110 Ah 'leisure') & inverter (1kW true sine), and it works just fine even here at 53 deg latitude. It would scale up for the entire house quite well, were it not for the fact that it's a four-in-a-block with a communal roof, and 1/2 loft space unusable due to loft conversion.