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Methane/LOX Generator?

Posted by: jabowery - Wed Jul 01, 2009 10:25 pm
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Methane/LOX Generator? 
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Post Re: Methane/LOX Generator?   Posted on: Fri Jan 15, 2010 2:18 pm
yeah, off the shelf turbine/generators i've no doubt are big...lol
I've seen people build small jet engines using turbo chargers out of a car though. were they efficient?lol probably not considereing it was a slap together project, but it did work. I've also seen turbines about the size of an apple, granted neither of these were attached to a generator unit, and that micro trubine certainly would not be useful in this sense.

as for scale of my project.... at the moment its a hobby project i'm working on by myself. eventually, if i can get the space/help/funding, i'd like to build a prototype system. initially the goal would be able to convert the sewage waste of up to 20 people in a system that fits (not including the Algenol reactors) into no more than 2 standard shipping containers, and eventually smaller.
now how much fuel this will produce will depend on two factors, 1)the type of anaerobic digester for the sewage will determine the methane output, 2) the size of the algenol reactor will determine the amount of ethanol output.
Algenol claims their system will produce 6000 gallons per acre per year, and any initial prototypes will use far smaller reactors than that. At first, i wouldn't try to produce more ehtanol than i'd use in system. Now the amount of methane that will be produced, I've not determined yet. I'm still researching digester technology and methods. so far they seem pretty straight foward, though there have not been very many who have built them on a small scale. There is one company in India that I know about, though I cannot remember their name off hand.

I'm trying to design this system as if it were to be used on a moon/mars/station colony, attempting to make the system as 'clean' as possible, using no more energy than what it generates itself from the sewage inputs and solar engery to the algae, yet producing power, oxygen, water, and growing fertilizer while consuming CO2 and greywater. if it ends up producing only enough power to cover its own systems, then that is sufficient.
With that above goal being said, the most likely application will be for home/building use, as another tool to try and pull less and less from the environment. I figure if it could be used to help sustain life on an otherwise barren ecosystem with tight resource requirements, then it will be more than suited for terrestrial uses.
The technology and systems to build this system already exist and have been implemented in the field seperately for various industries. I've just taken them and combined them into a single concept.

Hope that answers the questions you had johno, though if you have more I'm more than happy to answer :)


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Post Re: Methane/LOX Generator?   Posted on: Fri Jan 15, 2010 9:03 pm
If you want to have a look at some micro turbine generators Capstone makes various sizes of MicroTurbines http://www.capstoneturbine.com/prodsol/products/index.asp.

If you want to get a prototype or proof-of-concept system running cheaply I would suggest that running the fuel gas into a mildly converted diesel or gasoline engine. http://en.wikipedia.org/wiki/Wood_gas.

Just my 2c.


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Post Re: Methane/LOX Generator?   Posted on: Sun Jan 17, 2010 1:09 am
ooo, that's right i had forgotten about capstone.
I remember seeing their company website several months ago when researching for a different project.
I plan on trying to contact them here soon for cost and performance numbers.
I saw an animation on their website detailing the operation of their turbines, and i think they are beautiful in their simplicity and ingenuity.

thank you for reminding me of them

Mike


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Post Re: Methane/LOX Generator?   Posted on: Sun Jan 17, 2010 8:45 pm
Aren't there fuel cells now that react methane with air (or presumably GOX)?

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Post Re: Methane/LOX Generator?   Posted on: Mon Jan 18, 2010 4:35 am
Lourens wrote:
Aren't there fuel cells now that react methane with air (or presumably GOX)?


If we're talking about departing from Armadillo's methane rocket engine, then its time to look at other options like hydrogen.

The RS-68 LOX/LH2 engine is .75/.4 more powerful than an SSME and costs only $14M. Each SSME generates more than 8GW of energy, so on a pure $/W basis the "primary mover" of the LOX/LH2 rocket engine system is around $0.001/W.

What is the installed cost per watt of fuel cells? The difference between that and $0.001/W is about what you have to work with to efficiently convert the kinetic energy of the RS-68 engine's exhaust into electricity.


Last edited by jabowery on Mon Jan 18, 2010 6:43 pm, edited 5 times in total.



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Post Re: Methane/LOX Generator?   Posted on: Mon Jan 18, 2010 5:51 pm
Mike,

I stumbled across this article while browsing today. http://www.farmideas.co.uk/custom.php?id=37
It's low on detail but you might get some ideas from it. There is a full report available from the website for a reasonable price.
It might be some use to you.

johno


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Post Re: Methane/LOX Generator?   Posted on: Tue Jan 19, 2010 2:24 am
Hey johno, thanks for the link.
I've heard of some guys in Connecticut who are doing something similar
http://www.cowpots.com/history.html

\I've already skimmed through the article you sent, and will try to go through it more in detail when i am a bit more awake,lol.
The digesters are one portion of the system that i've not fully investigated as of yet, though i know there are several ways of going about it.
I still need to contact Algenol and Capstone Turbines about cost and performance estimates.
And now that i think about it, i need to look into the department of energy and see if they give grants for this sort of thing.


Mike


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Post Re: Methane/LOX Generator?   Posted on: Sun Jan 31, 2010 11:53 am
jabowery wrote:
The RS-68 LOX/LH2 engine is .75/.4 more powerful than an SSME and costs only $14M. Each SSME generates more than 8GW of energy,


Problem is that their specific impulse is to brief to be practical. Yeah they can generate a lot of energy but they do it over such short periods of time there is no practical way of storing it to be used at a reasonable rate. Not only would your turbine need to be unobtainium, so would the energy storage flywheel it was attached to. And rockets are not fuel efficient enough to be used for primary power generation.

If you don't have very high power demands, have you looked at thermocouples? An array of thermocouples in the bell of the motor or the exhaust stream would produce "free" current and be solidstate and reasonablly maintinance free.


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Post Re: Methane/LOX Generator?   Posted on: Sun Jan 31, 2010 4:25 pm
JamesG wrote:
jabowery wrote:
The RS-68 LOX/LH2 engine is .75/.4 more powerful than an SSME and costs only $14M. Each SSME generates more than 8GW of energy,


Problem is that their specific impulse is to brief to be practical.


Re-engineering a rocket engine for stead-state ground-based operation -- where mass-minimization isn't the objective -- is relatively easy.

Quote:
If you don't have very high power demands..


The idea is for baseload electic generation and the last time I looked that was around 1000GW in the United States -- and growing.


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Post Re: Methane/LOX Generator?   Posted on: Mon Feb 01, 2010 2:05 pm
where exactly do you get that number?

think of things this way. You don't want centralized power generation. moving to decentralized power generation via a series of small, low maintenance facilities, individual solar and wind sites all contributing to the grid will both reduce the loads on a single point on the grid, allowing for simpler generation systems, as well as a more robust system overall. if one generation source goes down, there are plenty of other sources on teh grid that, under normal load conditions, would likely not be near their peak output, and therefore can take up the slack.

now, looking to using a small methane engine as a part of such a generation system would serve two purposes. one, transforming methane into CO2, which is easier to deal with and less harmful to the environment (if you buuy into the whole induced global warming thing). and two, uses an already plantiful, and very easily renewable resourse.

a turbine system being driven by a methane/O2 engine would not necessarily need to be built out of 'unobtanium'. if you are talking about using an 'overkill' engine, like the SSMEs, or an F-1, well then you would have an engineering challenge ahead of you. However if you think smaller, you can eliminate several problems.

Really, now that i think about it, the only reason to use a 'rocket engine' would be to get a certain level of combustion efficiency. you certainly dont need a bell, and the nozzly would be far different than if it was on a rocket engine. your mass flow rates, combustion rates, thermal outputs are all vastly different when using it as a power generator than as using it as a rocket. And therein is another reason I would look to Armadillo's engines, not only because of their small sixe, but also their relative simplicity. Why use a system that has complex putbomachinery attached to it with a shorter time between overhauls (or complete replacement) when a much simpler, and therefore more likely robust system, is available.

Even still, who says you would even have to drive a single turbine? Why not cluster 3 or 4 small centrifugal turbines in parrallel being fed by a single combustion chamber? You'd be dividing the heat, and flow among them, and as such reducing the loads on any single turbine. So long as your combustion cylce is tuned to match it.

Anywho, Excuse my ramblings, its a monday and a rather crappy one at that.
(I work for United Space Alliance at JSC as a par tof the shuttle program)

Mike


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Post Re: Methane/LOX Generator?   Posted on: Mon Feb 01, 2010 2:45 pm
MFL wrote:
where exactly do you get that number?


The DoE's Energy Information Agency says the total generating capacity of the US is 1,104,486MW with most of that being baseload.

But as I said earlier, carbon capture is a big motivator in future energy infrastructure, and that means you're going to be moving to electrified transport.

Quote:
You don't want centralized power generation.


That's one reason rocket engines are attractive: They're scalable and there are different scales that make sense for different areas. NYC isn't the same as Iowa (where I live).

Moreover, solar, wind etc. aren't baseload.

Quote:
now, looking to using a small methane engine as a part of such a generation system would serve two purposes. one, transforming methane into CO2


Which was among my originally stated goals.

Quote:
Really, now that i think about it, the only reason to use a 'rocket engine' would be to get a certain level of combustion efficiency...

Even still, who says you would even have to drive a single turbine? Why not cluster 3 or 4 small centrifugal turbines in parrallel being fed by a single combustion chamber? You'd be dividing the heat, and flow among them, and as such reducing the loads on any single turbine. So long as your combustion cylce is tuned to match it.

Anywho, Excuse my ramblings, its a monday and a rather crappy one at that.
(I work for United Space Alliance at JSC as a par tof the shuttle program)


Your comments indicate you need some rocket engine thermodynamics education to be a more effective contributor to the United Space Alliance at JSC. Take this last quoted block to a rocket engine guy there at JSC who can tell you why you're wrong (my prior comments already indicate it but from your comments in general you aren't paying attention). That's probably a guy you should establish a collegial relationship with.


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Post Re: Methane/LOX Generator?   Posted on: Mon Feb 01, 2010 2:58 pm
lol, if my job had anything to do with propulsion systems, then I would be embarrased by my current limited knowledge, however, I'm not, nor do i claim to be. I am an Electrical Engineer by trade, this is more of a hobby than anything.

my question about your load numbers wasn;t intended to come across as being combative, i really was curious as to your source for that number.

as for your prior comments, no i did not see them, there seems to be (or were) two converstions going on in this thread, so I did not pick up some of the details of the other.

When you say solar and wind are not 'base load' what is it you are refering to?


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Post Re: Methane/LOX Generator?   Posted on: Mon Feb 01, 2010 3:24 pm
MFL wrote:
When you say solar and wind are not 'base load' what is it you are refering to?


The Wikipedia article on baseload is adequate.


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Post Re: Methane/LOX Generator?   Posted on: Wed Feb 03, 2010 1:19 pm
Ok, yeah, I see what you mean by baseload capabilities, and i agree, Solar and wind are no where near consistent enough to supply base load.
there was a technology in development (been proven on a small scale) that would greatly improve the contributing capability or non baseload systems, though unfortunately I'm sure its many years off still. If I remember correctly it was a liquid metal/salt battery, that would allowed for grid sized storage capacity. I believe it was from out of MIT, but its been several months since i've seen the article. This is the closest i can find (http://en.wikipedia.org/wiki/Molten_metal_battery) similiar tech. But I digress.

The more i've been thinking about the use of rockets as a means of power generation, the more one thing keeps coming to mind. Other than physical configuration, how is this approach different than a gas turbine? granted, i understand there are many configurations for gas turbines, from the system that Capstone uses, to APUs in an aircraft, with extreme variations in complexity depending on the route you go. I guess I should ask what the benefit of using a rocket core based system would be over a simple gas tubine (like one of Capstones).


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Post Re: Methane/LOX Generator?   Posted on: Thu Feb 18, 2010 6:17 pm
You know, you might think about a 'tesla turbine' for that - it's much more efficient and can be made from ceramics so would be very heat tolerant.

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