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Author Topic: Engine for natural gas generator  (Read 24679 times)

Procrustes

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Re: Engine for natural gas generator
« Reply #30 on: September 10, 2006, 10:04:56 PM »
There are many aftermarket auto cruise controls that use a magnetic driveline sensor.

If you are going to retain the electric starter for your engine, and alternator, battery, etc,  you will have the DC power necessary to operate the cruise control.

Cheap, simple, and effective.

Now that is a good idea.  They're dirt cheap on Ebay.  Thanks very much.

rcavictim

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Re: Engine for natural gas generator
« Reply #31 on: September 10, 2006, 10:29:52 PM »
Procrustes,

Just occured to me to ask WHY are you going to the trouble of making a power plant to run on natural gas from scratch?  Seems to me it would be easier to start with a power plant made to run on gasoline, and you ought to be able to get one of those for cheap since nobody in his right mind is gonna pay money for one.  Stationary prime power plants that run on gasoline are virtually impossible to sell nowadays because of the cost of petrol.  Diesel is the new only game in town and those are worth money.  If you are in the small niche market that wants to run on gaseous fuel then you are in an interesting position of advantage from a hardware cost, but not for a fuel cost however.

As an aside it is fine to think of using natural gas to power a standby power plant if you already have the gas being delivered for say home heating, but consider that when TSHTF, not only will you be without utility power, your natural gas pressure will also be zero.  Then a diesel that can run on just about anything resembling oil including hot bacon grease will be your salvation.
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
- 1966, Petter PJ-1, 5 kW air cooled diesel standby lighting plant
-DIY JD175A, minimum fuel research genset.
-Changfa 1115
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Rtqii

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Re: Engine for natural gas generator
« Reply #32 on: September 10, 2006, 11:52:28 PM »
As an aside it is fine to think of using natural gas to power a standby power plant if you already have the gas being delivered for say home heating, but consider that when TSHTF, not only will you be without utility power, your natural gas pressure will also be zero.  Then a diesel that can run on just about anything resembling oil including hot bacon grease will be your salvation.

I don't know where he is at... But where I used to live in the central midwest the government and gas companies sold everyone 10 years ago on natural gas as the cheap, abundant, clean energy of the future.

Well... The future is coming to light and the only truth is that natural gas burns pretty clean, all the rest was a pack of lies.  The last two winters natural gas prices went so high that it was cheaper to go to the Salvation Army and Goodwill and get old clothes to burn for heat (think I am kidding?).

It won't be long and natural gas consumers will be dependant on LNG shipped by bulbious tankers from the Mideast.

The supply system will not collaspe for some years... Think about the state of mind in your typical blinder wearing suburban resident when there is little or no gas pressure regardless of cost. Something like that would break the back of the American myth and the Fascists in control of U.S. politics will expand their World War before they admit truth. They will blame anybody and everybody before they will admit fault or take responsibility... It's lies they tell.

However... In the short and mid term, natural gas powered electrical generation does have advantages... You don't have to bunker fuel, the gas supply is independant of electrical mains for the most part, and the technology required is inexpensive and all off the shelf.  LNG starts getting less and less efficient because of the expense in compressing it and the transportation costs, but as long as the fuel cycle is not dependant upon imported compressed gas it's pretty efficient...

europachris

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Re: Engine for natural gas generator
« Reply #33 on: September 11, 2006, 12:39:18 AM »
Natural gas engines have the added benefit of renewable fuels, like diesels.  If you have enough garbage or poop (and who doesn't?) you can build a digester and make your own methane. 

That doesn't help the average suburbanite, but if you're off-grid or a farmer, you could be set up well for biogas production.  I'd rather do that than try to make biodiesel.  End benefit is after gas production, the sludge is used for fertilizer, completing the loop of events.

chris

Procrustes

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Re: Engine for natural gas generator
« Reply #34 on: September 11, 2006, 03:12:14 AM »
About choosing NG: it's for backup power so I'm not thinking much about the cost of fuel.  I'm somewhat remote and my road floods out and snows out.  The power goes out for days at a time every two or three years.  As rtgii said, with NG you don't have to store your fuel.  The only reason I have NG is that I happen to be on a trunk line.

I've spent some time studying generators on Ebay and I've seldom if ever seen a big gasoline-only one.  Lots of the NG ones are tri-fuel: gas, NG, LP.   A low-hours Onan 35kW sold recently with an inline 6 setup for NG for around $1,600, but it was too far away.

The gas-only ones are usually 3600rpm screamers, portable, and air cooled.

aqmxv

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Re: Engine for natural gas generator
« Reply #35 on: September 11, 2006, 04:25:32 AM »
Costing:  Corvair engines are sturdier than T1 VW engines, so are actually commoner on the ground as good, used runners than the VWs.  If you want to go the VW route, you'll probably end up either buying a crate engine, or somebody's fresh rebuild.  There just aren't many ready-to-run used engines sitting around anymore.  Complete stock VW rebuilds go for about $2k. Longblocks are about a grand.  Runner-used?  No idea.

You can get a plain-jane runner 2-carb corvair engine most days for $500-800.  You may have to hunt a little.  A lot of engines are "as removed" and may or may not be runners.  If you offer the corvair-enthusiast owner a little cash, he'll probably hook the thing up to a battery and test-run it for you.  If I were shopping for such an engine, I'd pick a powerglide motor, since you know it's never been over-revved, and "performance oriented" drivers tended not to buy automatics.  You're lucky that you don't want a "high-performance" engine.  They're considerably pricier and rarer as runners unless rebuilt.

If you get a good-used engine, you'll want to reseal it to keep the oil in.  Not a big deal - about four hours if you have the engine bare on the bench.  You'll have to take the carburetors off anyway, and strip out any mouse nests on top of the engine while you're there.

If you can find a cheap 20 KW methane-fueled Onan, I'd go that route just because it's the whole deal in a turnkey package.  If you can't, I'd look closely at something like this.  But then I have four corvair engines stored here and there in various conditions...
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rcavictim

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Re: Engine for natural gas generator
« Reply #36 on: September 11, 2006, 04:40:20 AM »


I've spent some time studying generators on Ebay and I've seldom if ever seen a big gasoline-only one.  Lots of the NG ones are tri-fuel: gas, NG, LP.   A low-hours Onan 35kW sold recently with an inline 6 setup for NG for around $1,600, but it was too far away.

That`s the sort of thing to look for!



The gas-only ones are usually 3600rpm screamers, portable, and air cooled.

I don`t consider those any more than short lived, noisy toys so they don`t enter into serious discussions about generators.  If it is good enough to make reliable prime power spinning 1800 RPM or less I consider that a good candidate for standby service.
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
- 1966, Petter PJ-1, 5 kW air cooled diesel standby lighting plant
-DIY JD175A, minimum fuel research genset.
-Changfa 1115
-6 HP Launtop air cooled diesel
-Want Lister 6/1
-Large DIY VAWT nearing completion

Procrustes

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Re: Engine for natural gas generator
« Reply #37 on: September 11, 2006, 06:00:42 AM »
rcavictim -- here she is, or was:

http://cgi.ebay.com/Onan-35KW-Natural-Gas-Propane-Generator-and-Trailer_W0QQitemZ160024793860QQihZ006QQcategoryZ106437QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

200 hours!  A solid purchase.

Incidentally I read elsewhere that there are Onan 45kW powered by Ford 300 i-6's.

rcavictim

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Re: Engine for natural gas generator
« Reply #38 on: September 11, 2006, 06:41:29 AM »
rcavictim -- here she is, or was:

http://cgi.ebay.com/Onan-35KW-Natural-Gas-Propane-Generator-and-Trailer_W0QQitemZ160024793860QQihZ006QQcategoryZ106437QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

200 hours!  A solid purchase.

Incidentally I read elsewhere that there are Onan 45kW powered by Ford 300 i-6's.

That looks a bit like my 15 kW, 18.75 kVA gasoline Onan plant.  The control panel on the ebay one is missing.  I`m using mine to power my big 3-phase Miller arc welder lately building my wind turbine, or was until the starter motor totally self destructed.  Must fix that soon.  Since then I was extremely fortunate to be able to borrow a almost new Lincoln Commander 250, welding machine. Has just 86 hours on it and the last 6 are mine.  Two cylinder Winsconsin air cooled gasoline engine.  Powerful machine but thirsty!

Too bad it isn`t easy to post pictures here.  I`d show you my Onan.
« Last Edit: September 14, 2006, 02:02:05 AM by rcavictim »
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
- 1966, Petter PJ-1, 5 kW air cooled diesel standby lighting plant
-DIY JD175A, minimum fuel research genset.
-Changfa 1115
-6 HP Launtop air cooled diesel
-Want Lister 6/1
-Large DIY VAWT nearing completion

aqmxv

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Re: Engine for natural gas generator
« Reply #39 on: September 11, 2006, 04:27:10 PM »
That 45 KW Onan looks a little big to economically feed, unless you really *need* 45 KW.  OTOH, bet that Ford will run forever on methane. 

I have an Onan, too, but it's a little smaller - the K450 gasoline single-phase with the carry handle on top.  I did some measurement and found that it actually will sustain about 950 W load - no idea where they came up with a 450 watt continuous rating.  Say what you will about 3600 RPM screamers, it's been awfully convenient to have something luggable to run a power tool here or there.  Used it to cut body panels off a junked car in somebody's back forty once, for instance.  Gets about 12 hours runtime out of 1/2 gallon of gasoline.  Got it for nothing from a guy who didn't know how to clean carburetor jets.

When Hurricane Fran blew through Raleigh, it was the only power in the neighborhood the following night.  It ran a TV, VCR, light, and box fan, which made us feel like we were the Ritz-Carlton Fuquay-Varina in comparison to the neighbors moping around by candlelight listening to their battery op AM radios.

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bitsnpieces1

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Re: Engine for natural gas generator
« Reply #40 on: September 13, 2006, 02:44:14 PM »
  I have NO interest in the following site other than drooling every time I check it out. 

  As long as you're looking at gas/NG/LP types you might want to check out   "COLEMANS.COM"  for their mil surp generators.  They tend to have a good line of gasoline and diesel gensets from 1.5kw up to 60-100kw.  The 7.5kw diesel and up appear to be 1800rpm.  Don't know where the break is for the gas type.  Probably all 3600rpm.  Most are aircooled; gas models should be fairly easily converted to LP/NG operation, just need to switch carbs.  Heavily built, ratings are for continuous power for 8 hrs at a time.  ie: solid 1.5kw continuously for 8 hrs., no up and down, probably = to about 3kw if up and down loading. 
Lister Petter AC1, Listeroid 12/1, Briggs & Stratton ZZ, various US Mil. surplus engines. Crosley (American) 4cyl marine engine(26hp).

aqmxv

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Re: Engine for natural gas generator
« Reply #41 on: September 14, 2006, 12:39:02 AM »
The mil-spec generators are truly overbuilt monsters.  They'll generally deliver 1.5 times their rated capacity continuously for a long, long time indeed.  They're all (up to really large sizes, anyway) 1800 RPM.

As you may know, the US military decided to go with one fuel for everything from aircraft carriers to camp stoves.  USAF calls it JP8.  It's a kerosene relative, so all the newer generators are diesel powered regardless of size.  You've spec'd natural gas as your backup generator fuel of choice.  While you could use the natural gas as a makeup fuel for a diesel generator, it makes more sense to go with otto cycle instead of diesel.

The good news is that essentially all of the gasoline-powered predecessors to the new, small diesel generators are out there to be had for very reasonable prices.  The bad news is that the military went diesel on pretty much everything above about 20 KW a long time ago (probably before 1960).

The biggest Mil-Spec gasoline generator I know of is 15 KW.  Coleman's will sell it to you for a mere $3K.  The commoner MEP-017A 5KW gas generators show up regularly on govliquidation.com quite cheaply, as you'd expect.  Coleman's wants $1K.   I don't know how common the 15 KW jobs are, and have no idea what they cost if not sold with guarantees, etc.


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timgunn1962

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Re: Engine for natural gas generator
« Reply #42 on: September 20, 2006, 01:19:30 PM »
I'm in the UK with 50 Hz mains. We used to run a converted 260 cid Ford inline six on landfill gas. It made 60 kW max at 1500RPM and ran 24/7/52 for almost 4 years (33000 hours). It only got removed because we installed a much bigger unit. I'd guess you would probably need something around the 120 cid, 2 Litre mark. A converted Gasoline set would be a good option. The biggest problem I could foresee is mating it up with the alternator. If you can get hold of a gasoline generator of about the right size, most of the work is already done. The next biggest problem is the governor system. Again, this is side-stepped by using a gasoline generator. Our set was a Diesel engine, converted to spark ignition. I assume this was at least partly because it was easy to mate the engine to an alternator with off-the-shelf parts.

I know Volkswagen were selling small industrial diesel engines quite aggressively in Europe a few years back. I think they were basically Golf/Rabbit engines so the bits needed to fit an alternator may be available. I can't be any help on US domestic engines, I'm afraid.

Next problem is the carburettor or gas mixer. Our Ford set used an Impco for a while and it worked pretty well. It did not cope well with the varying gas quality from the landfill, so was changed at around 20000 hours for a too-complicated system. We had a couple of converted Deutz engines running on landfill gas, too. These had the most elegant and effective gas mixer I have ever seen. Armed with a small lathe, one could be made in a weekend by the average home machinist. I have no drawings or photos but could scan and email a (very) rough sketch, if you are interested.

You will need to check out your local requirements for gas safety systems. Here we have to fit dual, approved solenoid valves in the supply line. Above some line size, a test unit needs to be used which opens the upstream valve, closes it, waits a few seconds, checks there is still pressure between the valves, opens the downstream valve, closes it, waits a few more seconds and then checks there is no pressure between the valves. If all is well, it opens both valves and feeds gas to the engine.

You may find the cost of the gas supply train and its control are the biggest obstacle you face, especially if you have to buy new.

It is worth checking the gas spec with your supply company. Particularly the limits on "Methane Number". This is a measure of the detonation resistance of gaseous fuels, just as Octane Number is for liquid fuels. Gas from different sources can have very different methane numbers. In the UK, we have North Sea gas, formed at high temperature and almost pure methane, Methane Number near 100. When this runs out, we will need to import gas from wherever we can get it. I have seen specs for Eastern European Natural Gas with a Methane Number as low as 45. Formed at lower temperatures, this has significant amounts of Nitrogen, ethane and ethylene. It probably also has some propane and perhaps some butane in. Generators optimized for North Sea gas are likely to start falling off their perches if fed with something with a MN of 45. Realistically, it's not likely to be a problem, but I'd try to cover all the bases before taking on a big project.

Procrustes

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Re: Engine for natural gas generator
« Reply #43 on: September 20, 2006, 06:33:17 PM »
Thanks for your help timgunn1962.  60kW for 33,000 hours continuous is outstanding.

That's an excellent idea about the two solenoid valves and pressure switches.  Clearly that's the best way to know if a valve has failed.  That's going to add quite a bit of cost.  Maybe I'll use a manual valve plus a solenoid.  Come to think of it, I believe the automotive propane kits require a single solenoid here in the US.  I wonder how likely it is for a normally closed solenoid valve to stick open.

I agree that a smaller engine would be more efficient, but I already bought a Chrysler slant six 255ci [edit - I meant 225ci].  I chose this one because it's well known for its reliability and easy to work on.  Also I got the k-frame, radiator, muffler, alternator, exhaust, etc so I already have a leg up on fabricating the frame.

I'm going to build the governor.  I've long wanted to build an embedded controller, and it looks not too bad judging from similar projects on the web.  I'll probably use one of these: http://www.bdmicro.com/compare/.  The linear actuator to drive the throttle seems reasonably easy to set up.  I cannot however find a linear actuator that is small enough.  Most of them are too strong for moving a throttle arm.  I'm unsure how to approach the speed sensor.  The type that counts flywheel teeth is said to be somewhat fallible.  The type that monitors frequency from the gen head is ideal except that it doesn't work until the gen head comes on line.

The fuel system will consist of an Impco 55 series carb, which is a perfect size: 70hp, 115cfm.  The engine will require about 100cfm when turning at 1800rpm, so I should get good response.  I hope I don't end up ditching the Impco like you did.  The carb is about $115, and then I need a regulator for $50, and then there's the fuel lines, brackets, gewgaws and gimcracks.  I'm impressed that you made your own carb.  Alas I have no possibility of making one with a lathe.  I'd still like to see the sketch though if it's not too much work on your part.  The problem with Impco is basically finding one the right cfm with the correct bolt holes and draft orientation.

I agree that I would have been better off buying a complete unit.  However a man's gotta do what a man's gotta do.  Anyway I think I'll end up saving some money if I count my time at zero.  We'll see just how many parts I end up ordering.

I'll probably need a beefy starter too.  I don't know how long the stock one will last turning over a big gen head.

Thanks again for your help.

Fixed incorrect engine ci
« Last Edit: September 20, 2006, 08:28:42 PM by Procrustes »

aqmxv

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Re: Engine for natural gas generator
« Reply #44 on: September 20, 2006, 07:33:36 PM »
You don't have to use a linear actuator.  I'd probably use a rotary actuator (stepper motor) with a pulley and cable.  You can get the cables and pulleys out of the junkyard for nearly nothing - anytyhing with fuel injection uses a single throttle body with cable-and-pulley control.  Another option would be a model airplane servo.  attatch with a spring and put a solenoid opposite for a force-close emergency shutoff.

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