Author Topic: Steam turbine generator question  (Read 6845 times)

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tbfoster

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Steam turbine generator question
« on: June 07, 2013, 09:47:24 AM »
Nooob - please be gentle :)

After spending too much time reading about thermodynamics (way over my head) - I'm wondering why I haven't see a scaled down version of an industrial steam turbine?  Several solar plants use this type of technology and the components all "seem" to scale, but I've search many places and have yet to see someone do this.

It seems like with enough effort (and watching GreenPowerScience videos), that a small scale system could be built possibly circulating heated oil into a boiler and moving a steam turbine. 

So - everybody gets a free laugh and if someone could point me to a place I could read more about the subject, much appreciated :)

Thank you

madlabs

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Re: Steam turbine generator question
« Reply #1 on: June 07, 2013, 10:02:20 AM »
It could be done, but it is a tough nut to DIY. I fooled around a bit with concentrating light for hot water for my old hot tub and it ain't easy. I came to the conclusion that I would rather deal with regular thermal panels.

Also, I have dealt with steam just a tiny bit at the SF maritime museum and safely playing with steam is non-trivial.

Fun project though. I had a trough (reflective) that I also focused several mirrors and a fresnel lens that can melt a penny. I was cranking out some hot water! But the thought of auto tracking and focusing was too much for me. So I made a couple more regular thermal panels and spent time soaking in the tub instead.

JOnathan

tbfoster

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Re: Steam turbine generator question
« Reply #2 on: June 07, 2013, 10:16:58 AM »
Thanks for responding - that's helpful. 

I think I could track the sun as I've seen several do this with arduino and I can deal with the software side of things.  I'll have a lot more trouble with the things you've already done.

I can't come up with the math on this - 20 solar panels (estimated) only saves me about 50/month on electric - I'm not in the best area for solar panels.  So - I need to do a lot when I have sun and get above my net metering (LG&E) ceiling and steam is the only thing I can come up with.

Agree - it's above my capabilities now, but I'm going to try some things - if I have any success, I'll post.

Thanks again

bob g

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Re: Steam turbine generator question
« Reply #3 on: June 07, 2013, 11:08:45 AM »
i think it is the lack of suitably small surplus turbines that is the stumbling block

because such as system is quite an ambitious project for a diy'er, what with having to build the concentrating collectors, make them track the sun effectively, get the steam plumbed from the collector to the turbine, and hot water back again, and all the other related hardware and control issues, and the generation side of things it leaves one with little time or money to scratch build a turbine of suitable size.

one of the reasons the big scale systems work is government subsidies which are hundreds of millions of dollars, another is in systems that are privately developed the use of surplus turbines reduces the cost significantly

as an example there is a geothermal generator system in nevada (i don't recall where) they installed a GE turbine that was a used pullout from a ww2 destroyer. they did this in the mid 80's thinking the price for the turbine was cheap enough and they hoped it would last maybe 5 years before needing replacement.  some 30 years later the same turbine is till making power.

now instead of megawatt class turbines we could find mini turbines on the surplus market i think then we would see more of them being built into such systems for home use.

until such time one is on his own to engineer, design, fabricate and assemble such a turbine on his own, and that would be one hell of an undertaking in my opinion... however it would be cool as heck to see someone do it!

something in the back of my mind as a project turbine would be based on a rotary vane motor principle, much like an airtool motor.  i think one could build one using an alternator shaft as the main shaft of the turbine rotor, and make the motor diameter larger enough to run at a speed appropriate to the alternators needs. the sectional width could be maybe no more than a half inch or so and the turbine speed designed to operate under maybe 8krpm

personally i think such a project would be cool as hell, even though the possible high pitch screaming my neighbors dogs might take issue with?

bob g
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bob golding

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Re: Steam turbine generator question
« Reply #4 on: June 07, 2013, 01:30:31 PM »
to be efficient you need supereated steam at high temperatures and high pressure. not something you can safely do in a normal everyday workshop. then there is the problem of finding a suitable turbine.

you are talking expensive stainless alloy steel and some pretty fancy welding to hold it all together.

i once designed a rankine cycle engine using hot water and propane as the working fluid. never got around to building it,but i know someone who did and he said it worked fine. all off the shelf parts apart from a diaphagm which you need to buy. here is a link to his site. lots of fun stuff you CAN make at home.

http://www.packratworkshop.com/index.htm
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tbfoster

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Re: Steam turbine generator question
« Reply #5 on: June 07, 2013, 01:41:34 PM »
Thanks all, great feedback and thanks for being kind to the noob.  So nice to talk to peeps who have actually done things, really helps.  Have a good weekend!



electrondady1

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Re: Steam turbine generator question
« Reply #6 on: June 08, 2013, 09:53:24 AM »
would automotive turbo charger be of any use?

bob golding

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Re: Steam turbine generator question
« Reply #7 on: June 08, 2013, 02:10:02 PM »
you have the problem of keeping the bearings oiled. they need a constant pumped oil supply or they die very quickly. not a bad idea though. seems to bve going in the wrong direction to me though. i prefer low tech low speed reliable systems that dont need fancy bearings or  oil seals. cant beat the old volvo front stub axle for that. 
if i cant fix it i can fix it so it cant be fixed.

bob g

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Re: Steam turbine generator question
« Reply #8 on: June 08, 2013, 02:46:29 PM »
i guess efficiency is more important if you are making heat with a fuel source
however if you can make sufficient heat with a solar concentrator maybe you can deal with less efficiency?

iirc the geo thermal driven turbine i referenced earlier ran on around 50psi wet steam, certainly not the most desirable form of steam, and not the fluid for the turbine, but it was basically a free heat source and it worked out fine (likely still working out there).

personally i think this might be a really interesting project, one that might need a quite large collector to make a reasonable about of power, but nevertheless a cool project.

this is how i would approach the project

1. i would determine just how large a collector i would need to make enough steam at 50-100psi to make maybe 1000watts. (figuring in the end with all the other losses maybe i could get lucky and net a couple hundred watts to start with and work to improve that )

2. i would work with an automotive alternator, only because they are cheap and are built to take input rpm over a wide range and make power, this would negate the need for transmissions and their losses.

3. i would either use the tesla turbine design or the air vane motor design, and use the alternator shaft as the rotor shaft, therefore no coupling issues and a tightcompact package,  not unlike the hydro boys do things.

4. i would use a balmar controller, in lieu of the oem automotive regulator,  the idea being one could tailor the alternator to match the available power from the collector.

5. i would place the turbine assy at the base of the collector, no long pipe runs and therefore less heat losses to battle

maybe one starts by doing the research on the collector and determine its size requirment, then he builds a prototype turbine/alternator and tests it with air pressure
to determine how much air pressure @ X cfm to produce Y amount of watts electrical output, and tweaks the programming of the controller to optimize output to the input available.

then if the research tells you that a collector of perhaps 12ft diameter will produce the amount of steam required (volume and pressure) one could then couple the two (collector and turbine) and run a batch test to see if it really does work?  if it does as planned or acceptably so then you have to work out the plumbing, condenser, feedwater return pump, tracking mechanism etc, all of which will present their unique challenges i am sure, but at least you know or have a good idea that the thing will work when you are done?

me personally?  i would love to see it done! and i would get very excited to hear it run!

bob g
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
www.microcogen.info and a SOMRAD member

Dispatcherjinn

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Re: Steam turbine generator question
« Reply #9 on: June 08, 2013, 04:28:23 PM »
I took a brief shot at with a 15 foot die byrd AL dish and a very small iron gas bottle as the concentrator. In fact i was following some guys on here about it years ago. Good old 3M 77 and cheap emergency foiled blankets as the mirror. I got super saturated steam ok but the control valves were beyond me. The idea was to let it pulse in bursts and the vacuum from the past charge did at times recharge the concentrators with the next load. The last i did with the dish was just some solar distilling of water and transferring water 30 feet up as steam to condense supply water and some heat to the third floor.
  But there was plenty of buzz here ike all ready said about auto turbo changers and turbo type compressors and even conversions of IC motor to steam. I never followed the threads mush after that and began focusing more on destructive distillation ( Gasifycation )
  Should you want to do some digging deeper there is a steam club in Easton Maryland sadly now closed to the general public but you can make appointments or talk with there members. It is a impressive place and you assume your own safety now to visit but they even run gasifyers that long ago supplied many city's with the gas for mantel street lamps , cook stoves and dirty false fireplaces that gave heat in winter. Even Washington DC still has a few plants about and the terracotta piping under the side walks. Fuel-Trash !
  In retrospect I was on the wrong path believing i needed saturated super heated steam, That is great for tork but for electricity you shall feel the need for speed ! opps, to much TV lately !
  Might try here ? http://www.craftlister.com/E1539740

joestue

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Re: Steam turbine generator question
« Reply #10 on: June 08, 2013, 11:55:16 PM »
i've posted to this effect before but i'm too lazy to look up the posts and they probably aren't very readable anyway.

my math and back of napkin musings over the years basically point to the only micro turbine that is really doable is a radial inflow turbine using a mix of propane and butane as a heat fluid.
The liquid pump side of the rankine cycle system would need to be a very efficient bldc variable speed, i'm thinking piston pump.
a variable displacement hydraulic pump driven directly from the turbine would also suffice. (this is a low speed turbine, one third the specific speed of a steam system) (molecular weight of 44 instead of 18)
The electric generator needs to be able to be run as a motor, to start the system up.

Low temperature steam systems are essentially limited to like 3% thermodynamic efficiency on a really good day. an organic heat fluid should get you 5 times that regularly, with a theoretical efficiency limited by the time required for the boiler to corrode and fail at about 30%.
also, butane may break down into lighter weight compounds at its critical pressures and practical boiler temperatures very slowly, but fast enough that its going to raise the pressure on both sides of the turbine and reduce the efficiency.

i'd estimate you might need half a pound of propane per kilowatt.. and if the boiler fails you need to make sure the aluminium reflector dish can contain the flare (if it ignites) without lighting on fire.

in practice i was thinking the turbine, boiler, pump, and condenser would be mounted at the focal point of the concentrated reflector.
the condenser would be then water cooled, with water pumped through a loop to a truck radiator mounted behind the reflector.
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tbfoster

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Re: Steam turbine generator question
« Reply #11 on: June 10, 2013, 09:42:16 AM »
A couple of things based on all of this info.  I have a friend that can machine out an aluminum block as the base for the turbine.  Trial and error test turbine blades until I get the flow optimum.  Figuring this could handle more pressure than I'd ever want to put into it - reasonable?

Trying to figure out what a billet costs on another forum http://www.practicalmachinist.com/ - we'll see.

Thanks all - I'll try not to post here any more until I at least have a little something to show :)

bob golding

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Re: Steam turbine generator question
« Reply #12 on: June 10, 2013, 04:11:31 PM »
a tesla turbine would be a lot easier to machine. look at the tesla turbine yahoo group, if it is still active.
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bob g

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Re: Steam turbine generator question
« Reply #13 on: June 13, 2013, 05:44:59 PM »
i just saw a report on the turbine facility on history 2 this morning

the steam turbine came out of a ww2 destroyer and was repurposed in the early 80's in the "ORMAT" facility outside reno nevada

it has been running every since, producing power for 20k homes in the region

it runs on 400degree F steam at 55 psi and the turbine turns 4600rpm goes through a gear box to turn an alternator at 900rpm

in recent years they installed a second turbine to capture more of the waste heat and it makes a bit over 4 mwatts with a generator turning 1800rpm.

they expect the main turbine to run another 20-30 years!  not bad for a ww2 surplus pullout turbine.

the hot water is cooled and recycled back down a pipe into the thermal vent for reheating.

fwiw
400degree's is hot, but not horribly so... 55psi is certainly attainable, however getting a multistage turbine sized small enough is probably out of the question for most of us.

still a fascinating project

bob g
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
www.microcogen.info and a SOMRAD member

JW

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Re: Steam turbine generator question
« Reply #14 on: June 15, 2013, 04:27:44 PM »
For those who have decided an exhaust turbine would be a good expander, I appreciate the reaction (vs Impulse turbine)

If you are looking for a good source of "reaction turbine parts" they are no further than your local junkyard...

Buy a used automotive transmission torque convertor and cut it open around its radius and tell me what you find in  there :) 


JW

bob g

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Re: Steam turbine generator question
« Reply #15 on: June 15, 2013, 05:18:45 PM »
i have done not only just that but have  taken apart allison mt 40 and variants torque
converters which bolt together around the periphery.

years ago, after moving to the pacific nw, i always dreamed of buying a piece of mt ranier and tapping one of the streams that crash down the mountain side.

one of the turbines out of a torque converter ought to make some good power as a reaction unit in my opinion.

but sadly my dream never came true.

given enough steam and a small auto trans converter, and maybe something cool could be made to work.

bob g
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
www.microcogen.info and a SOMRAD member

JW

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Re: Steam turbine generator question
« Reply #16 on: June 15, 2013, 05:43:00 PM »
There is a HUGE devide between inpulse and reaction turbines.

To engage the turbine "like what your describing from the tourqe converter blading" you could use a series of small jet-nozzels 400psi or so. You would have to balance steam generator output using the nozzles, then just find your sweet spot,,,

Be very vibreation balence concerned of the impeller or blade is rotated. I' have seen blading sets with no loads to run away and cause a frag, keep it under load,


JW

mike_belben

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Re: Steam turbine generator question
« Reply #17 on: November 23, 2014, 09:44:05 AM »
I was hoping we could revisit this discussion on diy micro turbines from commonly available parts sourcing.

Suppose the steam were generated from a biomass furnace to make that end of it simple.  i have no comprehension at all of the math here.  What kind of power could one hope to generate from how many cords of wood or tons of chips, etc?  Steam fed to an automotive turbocharger coupled to an alternator.. Could it make substantial power or is one incandescent bulb going to stall the rotor?