Diesel vs Propane

[Cyrcle]

I'm researching my options for a backup generator. The biggest question at the moment is what fuel to use.

I like that propane stores very well and doesn't gel and burns nice and clean. We already have two 120 gallon propane tanks for heat and DHW.

I like the idea of being able to use WVO in a diesel.

I'd appreciate any comments from folks that have made a similar decision. Thanks!

[WindriderNM]

I have a 10 kw 18 hp diesel gen i use for backup and to run power tools.  It is a little hard to start when cold.
 Are you planing on using WVO or converting it to bio-diesel?
I am starting to collect part to make bio-diesel.

[DanG]

When I visited the Dans up above Fort Collins Colorado DanB's comment was "the mountains up here are littered with propane generators"....  as I was telling about the cell-phone tower station propane back-up DC generator I was driving on to Denver to pick up...

To get any conversion efficiency on propane you need go large, the mechanical losses on less than 4000w gen sets are proportionately huge.

If you do need just a small generator then converting a Honda Eu3000 is the most efficient bang for the buck - even that you can re-pipe the exhaust to salvage (co-generate) the waste heat from and really get impressive conversion numbers.

If you need 240VAC with some surge capacity bite the bullet up front and get diesel, don't turn this into a 12 vs. 24/48V food fight 

[Cyrcle]

Some more info-
I'd like to do it all-mechanical if possible. I want this sucker to keep running through an EMP-zombie situation  
I like the looks of the UtterPower PGM. Not sure how I would get both 120 and 230 out of it.

[WindriderNM]

http://cgi.ebay.com/10-HP-DIESEL-GENERATOR-KIT-5-6-6-5-Kw_W0QQitemZ190487535366QQcategoryZ106437QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D10%26pmod%3D190482130234%26ps%3D63%26clkid%3D6460511089371751509
I found this from another post on this site. it is $695

[bob g]

if i were to advise you, i would highly recommend a diesel engine setup to run in
dual fuel mode, with propane being the offset fuel and diesel as the pilot fuel.

the efficiency can be quite high, and the ability to run 100% diesel, veggie, or other
oils, or dual fuel mode with ~70-90% propane is certainly appealing.

the changeover is seamless as well, so if you run out of propane in the middle of a storm
the engine will continue to run on 100% diesel fuel.

most small diesels can run in dual fuel mode with no alteration to the governor, injection system or timing, all you need is a control valve and a way to meter in the propane into a mixer that is between the aircleaner and the intake port.

a dual fuel mode diesel is very near the same efficiency of a diesel, which is much higher than that of a typical propane fueled spark ignition engine.

for standby use, or backup use, an air cooled diesel might be preferable to a watercooled engine, however if you plan on using the engine for a few hours a week on a regular basis there is much to be said for a water cooled engine.

bob g

[Cyrcle]

Thanks for all the info everyone! I wasn't sure if I should put this in the newbie section, but I figured it fit better here.

I had no idea that propane could be run in a compression ignition engine! I did know that diesel performance engines will use it as a power booster, like gas engines can use nitrous oxide.

Can anyone recommend a small diesel engine? It seems like Listers are getting really rare. A VW diesel seems like an interesting option, but I wonder if it would be too big to be efficient at the relatively low power levels I need.

[WindriderNM]

The one on above feebay site might be OK. You can also check gov.and industrial auctions
I got a 18hp 10kw trailer mounted at a surplus auction for $75 with 10 gal tank full. All it needed was a fan and a battery.
I wired in 2 additional start and kill switches 1 the the house and 1 to the shop.
I have built most of my system with surplus stuff.

[Cyrcle]

I worry about parts availability for random surplus stuff. What's been your experience?

[Cyrcle]

I'm seeing various Yanmars for around $1000. Are they generally good for this use? Anybody know what RPM they like to run at?

[WindriderNM]

the one i have is a Yammer 18 hp. it works well
it runs at 1800 rpm with the pulleys that are on it
I am thinking about changing them for a lower engine rpm. i don't need 10kw of power.
parts are available for almost anything on the net now.
I got lucky the gen i got was made in a town about 30 mi from my home and there # and address was an the gen.

[peter altas]

LPG (propane). I have a 4.4kW Honda powered generator (GX 270) I converted to LPG with a kit from US Carburetion. It's hooked up to a 400L bulk tank. Starts simply first pull after a short primer press. It also runs perfectly on unleaded petrol, and if I so choose, I can retune the mixer to run on natural gas (tri fuel kit).

On propane, it burns really clean, no nasty exhaust smells like diesel and the oil stays really clean for much longer. Spark plug stays pretty clean for a while over running on petrol. I also like how, as a fuel, it doesn't need refilling by Jerry cans (which almost always I'd spill a bit), they come to me to refill, and if I don't need to use it, it doesn't degrade like petrol. Having a bulk tank also means I can decant and refill my 9kg BBQ bottles myself at a cheaper cost.

Next generator will be a key start yamaha inverter which they also sell the conversion kits for.

[ChrisOlson]

I'm researching my options for a backup generator. The biggest question at the moment is what fuel to use.

Our standby gen is auto-start (controlled by the master inverter) and diesel is not an option for us because even with pre-heat (which takes a lot of energy to keep a diesel warm enough to start at -30F) a diesel won't start reliably enough.  So we bought a LP-fueled Generac EcoGen and, unfortunately, ended up with the same problem anyway - it won't start and run at temps much below zero F.

When you live in a cold climate you can't waste too much power or time fiddling with pre-heating generators that won't start.  So we also bought a small gasoline fueled 3 kW Champion generator for standby use when it's really cold out.  We use the Champion in cold weather for emergency standby power and preheat power for the EcoGen to get it started.

Diesels are only practical if you live in a warm enough climate, or if you live in a cold place have the genset in a heated generator room so you can get it started.  Otherwise the energy consumption for pre-heating diesels in really cold weather does not justify the increased thermal efficiency of the diesel genset.  You will more than likely consume more energy keeping it warm so it'll start when needed than you will running it.  Diesels are great for prime power.  Not so great for standby.
--
Chris

[TimS]

Sure makes sense.  The only thing I would add is that at high elevations (I'm at about 7500 ft), diesel is more efficient than either propane or gasoline power, i.e. you may be rated at 8KW and only get 5 or so at elevation.  Correct me if I'm wrong, but that's the way it looks up here.
Tim

edit:
and yeah, the diesel pickup is a real pain in the butt at temps below about -15...

[ChrisOlson]

Sure makes sense.  The only thing I would add is that at high elevations (I'm at about 7500 ft), diesel is more efficient than either propane or gasoline power

No, that's not the case unless the diesel engine is turbocharged so it's altitude compensated.  The fuel rate of a mechanically injected, normally aspirated diesel is fixed at full power.  Being the rack position is controlled by the governor (and hence speed and load) the diesel will lose efficiency (and be de-rated on power) just as quick as a spark ignition engine as altitude increases.

Either one can be turbo or supercharged to compensate for altitude.  But turbocharging is more common with diesels than it is with spark ignition engines.
--
Chris

[TimS]

Thanks- I didn't know that.
Tim

[oztules]

"Sure makes sense.  The only thing I would add is that at high elevations (I'm at about 7500 ft), diesel is more efficient than either propane or gasoline power, i.e. you may be rated at 8KW and only get 5 or so at elevation.  Correct me if I'm wrong, but that's the way it looks up here.
Tim"

If thats an observation, then I'd stick with it.
I'm not sure Chris's explanation takes into account all of what happens.

True. Rack position is how much diesel is pushed into the cylinder. That will be proportionate to load.... but in a diesel, all the fuel will immolate on combustion.... regardless of the fuel air ratio. Every molecule of combustible material  will explode on the compression stroke... regardless of the ratio unless over rich .... and then because not enough oxidant is present.... hence no throttle butterfly.... no flame front to continue combustion from the spark to the entire cylinder.... At sea level it is very air rich (or fuel lean), so has more room for higher altitudes before degradation occurs.

In spark engines, it is the air fuel ratio that is responsible for the flame front combusting the fuel. This is dependent on the right ratios. At sea level this is perfect...... as we increase altitude, it will become richer to the point of cold burn (carburettored  aircraft have a lean burn control to allow for the higher altitudes.. higher you go, leaner you need to make it)

I would expect diesel to be better as you have observed, as it does not rely on fuel air mixture until the extreme of over rich.... if it did it would need a butterfly to control the air flow...... and I have never observed that.

Put simply, the gasoline engine with less molecules of air per cubic foot will have to add less fuel to keep the ratio perfect... so less energy... but unless it has injection, this engine will get richer.... injection will help to a point.


The diesel naturally runs fuel lean.... so if you need to add more to less air, you have more chance of combustion that is generating more energy..... and the throat is unrestricted... not like gasoline engines.


........oztules

[armadillo]

The problem with generators under 12 KW is limited availability of well designed new units.
Most are made in China and not worth bothering with at any price. The next category is high RPM units. Wall Street jerks discovered that you can take a 1800 RPM generator, increase the speed to 3600 RPM and double the KW output and thus the profit. These generators make more noise and wear out fast. Some do a better job of manufacturing them than others, the best ones being made by Honda. Be aware that no Honda is designed to run on propane and if you adapt it as such you void the warranty.
Personally I would not buy any new generator even if money were not an object.

For an off grid home, most generator use is in the winter. That said, ease of starting in cold weather is of paramount importance. Gasoline generators start easier than anything else in cold weather. Remember that propane displaces air and that means less oxygen in the combustion chamber. Also realize that propane is a very slow burning fuel and this makes it less suitable for high RPM engines.

In the 4 KW to 7 KW range, the best buy is an older used RV generator like an Onan or Kohler. These can be had for $300 to $800 on Craigslist. Most have low hours and will outlast any new generator 4 times over. Almost all the older ones run at 1800 RPM. Converting them to propane often doubles your investment and thus I have never been tempted.
Due to mergers and aquisitions, Onan is now run by Wall Street gentlemen who don't support their older and better lines of equipment. They are easy to do minor repairs on but when they need major repairs, it's time to get another one off Craigslist.

Some off gridders like myself have irrigation needs in the summer and something more efficient than gasoline and less of a fire hazard is called for to power a deep water well. Not much is available in new diesel generators. Avoid ones that run at any speed other than 1800 RPM. Some Japanese powered units like Isuzu and Kubota will run a long time ( maybe 7,000 hours) before needing an overhaul, but the highly touted 3 cylinder Kubotas are not designed to be overhauled.

Older diesels found on generators include Lister and few others. Older Listers were designed to run 20 to 30 thousand hours between overhauls!! I just rebuilt mine, most parts came from China, I suppose because Lister is now run by Wall Street types who don't support their older and better lines of engines. I'm a bit skeptical that it will run another 20,000 hours.
Most of these older Listers, unless you go back 50 years or more, are direct injection engines not suitable for biodiesel.
The whole biodiesel thing is more problematic than most people realize. Very few engines ever made are suited to run on it.

[ChrisOlson]

In spark engines, it is the air fuel ratio that is responsible for the flame front combusting the fuel.

This all depends on the type of combustion chamber used on a spark ignition engine - wedge, hemi or a derivative of one of those).  But even at "lean" conditions the air/fuel ratio of a spark ignition engine is slightly on the rich side of stoichiometric.  For full power air/fuel ratios it is extremely on the rich side of stoichiometric.

The typical passenger car engine will run air/fuel ratios from 11 or 12 to 1 at full power to 14 to 1 at "lean".  Ideal is 14.7:1 but few engines will actually create any real power at that air/fuel ratio.  Very high-performance gasoline burning racing engines that develop in excess of 2 hp/in³ of displacement in a naturally aspirated configuration will run air/fuel ratios as low as 8.5:1.

Extremely high-performance gasoline burning, supercharged competition engines, which you're only going to find in offshore power boats and racing aircraft are even more radical.  The Rolls-Royce Merlin V-1650's in the clipped wing P-51 Mustangs at Reno develop 7,500 hp at the prop shaft on 1,650 cubic inches.  They run at air/fuel ratios down to 6.3:1 with water injection at a 3:1 ratio with the fuel rate to control detonation.

Unlike the Otto Cycle, the Diesel Cycle is a true heat cycle.  Otto Cycle engines are pressure driven machines.  All you have to do is look at the stoichiometry for diesel fuel to see that at higher altitudes a diesel loses power just as fast as a spark engine, and it emits more particulates (smoke) and hydrocarbons from unburned fuel that gets blown up the stack.  Diesels respond particularly well to turbocharging because they can run at very lean air/fuel ratios approaching 100:1.  When you use turbo or supercharging with a spark engine, the fuel rate has to be increased with the air rate or it will detonate and destroy itself.

After working as an engineer for Cummins for 19 years I still have some of the testing data from the old normally aspirated gensets we used to build.  One example was the "250 Cummins" (NT250 Small Cam, which later became the NTC270).  At sea level it was rated at 250 hp @ 2,100 rpm, 219 hp @ 1,800 rpm on genset duty.  At 8,000 feet its rating was 182 hp @ 2,100 rpm, 160 hp @ 1,800 rpm on prime power genset duty.

The later NTC270 (which was turbocharged) had the same rating at sea level as at 8,000 feet.
--
Chris

[oztules]

Stoichiometric ratios are rooted in chemical equations and are simple ratio relationships.

If I looked at the number for diesel and petrol, they would be very similar, as will butane, and propane, bit higher for methane and ethane. If we get O-H groups in the fuel (ethanol etc) then we can come down to 9:1 from 15:1 for those without.

So it will be the other characteristics of the motor/ignition mode that will determine the usefulness or otherwise in different operating conditions.

If local agreement is that one is more suited than the other, you need to find why.



.................oztules

[ChrisOlson]

If local agreement is that one is more suited than the other, you need to find why.

It's my opinion that diesel power is well suited to prime power applications, and it's OK for standby power where the climate permits it, and/or you can afford the energy input required to keep a diesel warm enough to start in cold weather.

Gasoline gensets start the most reliably off all of them, in all temperatures even down to -30°F.

LP gas is somewhere in between.

What works for one person might not work for another.  For us, for instance, a gasoline genset is more energy efficient than a diesel.  Most of the hours on our genset are put on in the dead of winter when it is below zero F.  The energy input required for preheat to start a diesel at those temps simply does not pencil out.  Our little Champion generator started last winter at -36° with no pre-heat and absolutely no starting aid except the choke.

When it comes to gensets there is no such thing as "one fits all".
--
Chris

[oztules]

I live in absolute awe at you folks being able to even survive in those temps.

Whatever works best for you is the best for you.

I just can't imagine living at those temps, so can't begin to comment as to what is best in those circumstances.

If it works... do it.


..........oztules

[ChrisOlson]

There is nothing "in awe" about it.  We had an abnormally warm winter for the most part this year, with only about 10 days of really cold weather under 20 below.  Last year it never got warmer than -20F for a month straight in Jan/Feb.

When we tried to get our LP generator started we couldn't get enough pressure from the LP tank.  I put a black blanket over it to try to warm it but that didn't work.  I put two pans of burning charcoal under the LP tank and got it warm enough to get 25 lbs of pressure but the engine still wouldn't run.

When we got a bad vapor valve on a Anhydrous Ammonia tank we wait until the dead of winter when it gets really cold.  Then simply screw the vapor valve out and replace it with the tank full of NH₃.  If you tried that when it's warm out you'd have a disaster of Biblical Proportions and probably have to evacuate half the township.  At -40 the ammonia is safe and looks like water sitting there in the tank.   
--
Chris

[equiluxe]

I have been building diesel gensets for many years, what I have always recommended to people who want or need fast starting in very cold conditions is to mix the diesel with petrol and paraffin equal proportions. Then a good squirt of ether and if the engine is well maintained it will start first go with no problems even in arctic conditions.

[thirteen]

equiluxe
What is the smallest diesel engine generator you ever worked on or made? Just wondering.
As a side note I heat my house with wood and when I do my footing for under the sink in June I will put a 2 in plastic pipe back thru the wall and install a small fan that will take the warm air from the house and blow it on my generator when it gets cold and I need to start it. They have their own small room 4 X 6 ft. and an hour of warm air should take the chill off of the engine. I have two, one is gas, one is diesel. I got this well abused and well used diesel for $200.oo and all it needed was a clean fuel filter and I do not think it ever had it's oil changed. I had to drill a hole in the belly pan oil plug to get the oil to come out. If that was what was in it.(sludge)  I drilled out the old plug had a new oil plug welded back in.  It has around 8600 hrs on the hour meter and it doesn't work anymore. But it also does not like to start below 30F degrees. It is old and uses about quart of oil every 10 hrs of use.  But it runs good and I only use it off and on.  My neighbor used it last year when he rebuilt his barn. 

[equiluxe]

The smallest I have worked on is 0.9KVA the smallest set I have built is 1.5 KVA diesel and the biggest set I have built is 275 KVA but I have worked on an corrected bigger sets. 

[bob golding]

i use a mixture of 80% WVO and 20% RUG, gasoline, you need to add the RUG to the oil in a container with a tap near the bottom. about 2 inches up is ideal. pour the WVO in first. no need to filter it just strain it though a sieve. then add the RUG and leave it for a couple of weeks to settle. filter though a set of sock filters down to 1 micron add a drop of cetane improver. i use veggie boost, cant remember the chemical name for it. works fine on my 11 hp yanmar copy generator.

[allenbee]

Equiluxe ; You seem very talented and experienced .
I'm looking at different engines or ways - just to charge 12 v car batteries , for very basic 220 AC usage , through 300 W inverter - like light , cell charge and radio .                                   

What is the smallest most efficient diesel engine that will run a car alternator at minimum charging RPM ?

Do you sell them , or know where I can buy them ? 
IF.... this is the way to go .

[ChrisOlson]

Interesting - I recently got a 1B40 Hatz diesel given to me because it had a bad injection pump.  I fixed it with the idea of driving a modified car alternator with it in hot weather, feeding high voltage DC from it into a Classic controller to charge our battery bank.  I need it for "dog days" in summer where it gets really hot here and we sometimes want to run an AC unit to cool the house down so we can sleep.

I got the engine running and I'm pretty impressed with it.  It will drive a fairly large car alternator easily.  I have not checked it for fuel consumption yet, but I think it's pretty miserly on fuel.  It's about a 9.6 hp engine at our elevation here.
--
Chris

[Frank S]

You might look into the little single cylinder Wisconsin Robin diesels
 the little DY 23-2 is 4.8 HP or 3.5KW 230cc  you could probably run 2 ALts on one easy enough
The robin comes in 6 sizes up to 9.5 HP 7KW 412CC
http://www.clydepac.com/products/other-products/robin-diesel-engine.aspx

[ghurd]

Not so sure I'd put much thought into high efficiency.  It is a back-up gen.  And the power is not off all that long, per year?

How many hours was your gid down in the last 5 years, total?
10, 20, 50 hours?

"I like the idea of being able to use WVO in a diesel".
Yes, nice idea, but a lot of work too!

Propane gens may not be the best for somewhere like where the Das are.
I expect the cell companies excerise them very regularly, and did the math on costs.
And you already have propane available.
I'm just sayin'...

If the Zombies invade, fuel is gonna be hard to come by no matter what you choose.
G-

[BillBlake]

I'm researching my options for a backup generator. The biggest question at the moment is what fuel to use.

I like that propane stores very well and doesn't gel and burns nice and clean. We already have two 120 gallon propane tanks for heat and DHW.

I like the idea of being able to use WVO in a diesel.

I'd appreciate any comments from folks that have made a similar decision. Thanks!

Of course on a per gallon basis it's no secret that diesel fuel and kerosene can have approaching
50% more BTU's per gallon than propane. Did a Lot of looking into various fuels and what they could do years ago.
From a storage point of view my findings were different than most people because I recently
(8 months or so ago) used up the Last of my high-test (just before Katrina) Gasoline and it was still OK. It burnt like cheaper regular gas would.  No stabilizers - no nothing. Vent-less containers.
I know a lot of the old timers said - No Way. Too bad what they say.
Also have put some time in on various Kerosene and New (grow your own) Vegetable Oil experiments /  inventions. Like how to burn vegetable oil using a simple wick system if
anyone is interested.

Have some Kerosene in storage right now just to see what it does.
3 - 7 years old. One 6 gallon container is 14 years old. (Similar storage qualities to Diesel).
I was going to use the oldest of it to fire up some big brush piles last Fall. Put the flashlight to it and it still looked too clean to waste. Old stuff works great heating a well ventilated barn.
Perhaps my garage floors are magic or something.
It doesn't burn as clean or smell as good after X number of years but it still burns.
I have no idea why I have such extraordinary luck with storing fuels - just do.

Propane is super sweet if your money is right and I fool with it a little as well.
Valves REALLY Rusting shut after enough years can be a killer with propane if you don't take
proper care of business.
I know because of full tanks a customer gave me.

As far as 'outside the box' stuff Cords of Firewood (at least 160 gallons of Oil, or More, equivalent for a righteous cord) properly hidden and properly stored to run a small steam generator is very hard to compete with for people that have the resources.

For heat Corn Pellet stoves are Incredible if you can come up with the 2/3 of an acre in corn for
the average home set-up. There is a huge disparity in how much electric you will need to run the auger, blower, controls, etc. depending on who built it.
Wonder if anyone has started to use Corn in a semi-automated steam power generator set-up?

For decades some people have filtered large volumes of the Air Going OUTSIDE from
Indoor Grow rooms.  (Leave it to the Chinese to retail huge filters cheap.)
 
Solar Systems and Wind Energy was always a big deal but never the Star of some shows only because they were looking for ways to generate power without saying 'Hey Look at me'.
'Put me on the Google Satellite Map high dollar List'.
I need the attention.

Of coarse in some areas huge arrays of solar panels are nothing. Where I live if anything ever
went wrong I suspect a truck with a few Troops in it would be pulling up for the
eminent domain "Save the Children's 'Donation' in short order.

Far fetched? Not according to the top experts testifying to Congress.
I'm not hung up on any of that stuff but I am well aware of the game. I wrote some of it with
home built emergency preparedness air & water purification systems, etc. in the past.

With the recent talk at OtherPower about some of the local thugs being afraid that you might have 'a little something' in South Africa it got me thinking of the old 'Incognito Power Gang' again.

That Multi-million dollar Charity installation Allen stayed at for a while down in the middle of the Legendary Zulu stronghold area of South Africa looks like it's out in the middle of thousands of acres of farm land.

Excellent Google Earth scope job of what they have and don't have down there.

It's about 5 miles to the DVD rental store in Camperdown that I figured was probably around someplace. However they have DSTV beaming Satellite TV and the latest Movies right into the place so there is no need to burn gas for video's - if your happening. 
Chances are they have all kinds of little goodies from the hill and dale down there.

Bill Blake

[Kingfish]

    Hi all , I just joined this forum. Thanks Bill Blake for the link.

I thought long and hard about the choice between Propane and diesel. Yes diesel gives you the most power for the dollar. Gasoline second and propane last.  All proven truths.  Yes  a skilled guy can make his own veg. oil from squeezing seeds or boiling down some pig fat, etc. etc.   TOO MUCH TROUBLE FOR ME.

  Propane sits in the tank for as long as I need it. Keep the valves working by opening them once in a while. Test for leaks. I went with Propane because I can fill my 500 gallon tank with 400 gallons and not worry about it.  I had a line tee installed so I can also run on 20,40 or 100 pound cylinders. Generator is an 8000 watt  Generac Guardian series . It is quiet, smooth and will start at 5 below zero. We test fire the unit every other month.  ZERO PROBLEMS.  In my world I have too much other things to worry about then treating old fuel, stabilizers, water in my tanks etc.  For long term storage Propane has no equal in a stored fuel.  Natural gas would be even better but we do not have access to a gas line so its moot for me. We have four 100 pound cylinders and half a dozen 20 pounders to go with the 500 gallon tank. 80% is considered full in the big tank. This means we have just over 500 gallons total dedicated to the Generac. Used wisely this will last a long long time.

  I agree with Bill Blake about Wood.  I have been heating with straight wood now for 3 years. I live in Lower Michigan so I am surrounded by literally thousands of acres of federal forest lands loaded with standing dead and down Oak trees.  The permits cost 20 dollars per 5 cord. I used 4.5 cord last year.  Wood is my greatest asset here. 

  I met Old Bill over at Survival Monkey on a thread where we were discussing batteries. He steered me to a nice website where it seems some of the best batteries in the USA are built. Thanks Bill!!!   Now charging this future battery bank is going to require some real thought .  Do I use propane? Or should I go to wood?  I guess Im going to have to open a new thread on this . Kingfish