some incredible bsfc numbers...

[glort]

The problem is not so much with the numbers as it is your attitude.
You carried on like an arse when simple and civil questions were asked with no animosity at all.

[mobile_bob]

Chris

first of all you did not mention that you set the support control to 3kva
you just mentioned that you loaded it to 3.04kva and burned x amount of fuel in an hour.

from that one could reasonably conclude there is a problem with the number reported. it is apparent now, looking back, that the generator was either lightly loaded while running that hour or the load dropped off for a significant amount of time.

now had you clearly stated that you set a support control to a specific number, i agree, there would be no way to construe any bsfc number from that. actually one could not construe any useful info from that other than the engine ran an hour and consumed x amount of fuel doing so.

when the question was asked, it was asked civilly and with due sincerity, because it just didn't feel right at the time.  time was not taken initially to do the calculations to determine how far things were off, so therefore a question was asked.

had the time been taken to do the calculations it would have been apparent from the start that the reported numbers (as presented were definitely flawed) and another explanation would have been sought, such as did the OP mean he actually loaded the engine to 3.04kva or did he mean he set the limit to 3.04kva?

however it never got there because rather than being civil the OP decided to get knotted up and give a lesson in "diesel 101" which comes off as being not only condescending but downright arrogant and combative.

you see the thing is, we here are used to sparring vigorously at times over all manner of questions, and yes sometimes it gets tedious, sometimes it gets a little heated but we generally always treat each other with respect and work hard to answer anyone's questions. that is how we all learn as a group.

no one walks on water here, we all learn from each other, and we all are constantly on the lookout for projects from all over the planet that might further our understanding and our goals of increased efficiency.  (perhaps) unlike the otherpower forum we do understand the need for a generator and also understand that if one is going to accept a generator as one of lifes realities we ought to work and strive to make it a productive and efficient as we can.

lastly, yes some of us get knotted up over reported bsfc numbers or numbers that are reported that appear to be something a newbie might consider bsfc numbers, because...  they mislead folks into thinking the impossible is possible with the result being folks spending time and hard earned money tracking down and buying something that will never in a million years produce those results.   you know how it goes with windpower and some of the claimed output from some of the oem's out there, like honeywells joke... the only way that machine will ever attain the advertised output is in a cat 5 hurricane which isn't very useful for 99.999% of those that would buy one.

just my take on the subject
ymmv and all that.

your friend
bob g

[ChrisOlson]

The problem is not so much with the numbers as it is your attitude.
You carried on like an arse when simple and civil questions were asked with no animosity at all.

Yessir, you are correct.  I did not wish the thread to be turned into a discussion of BSFC when I had intended it to outline the use of one of the smallest 120/240 diesel generators that exist for off-grid prime power during bad RE generating times.  And when it did, I sent a request to the moderators to remove it.  Eventually I would've had some hard data on operating cost per kWh of electricity produced, directly to loads vs producing that same electricity by digging into the battery bank and then being forced to recharge the bank with a standby unit.

And I do believe I can beat the "traditional" method of off-grid standby power with a small prime power unit running several hours for several days during bad RE production.  That's what the thread was about.  And prior to doing that I needed to establish some baselines on how the little unit is going to perform on the grid input of my XW inverter to find out if it's even going to work.

It was my thread and when people failed to take the hint that I do not wish it hijacked with some rant that does not apply, I do mess around, nor do I mince words.  I requested that the moderators remove it.  Then I saw that Bob G brought the topic over here - again presenting the same inaccurate information.  Anybody that has developed BSFC curves knows that you use a dyno with fuel flow equipment to do it, and that it is only done for a specific fuel.  It is a measure of combustion efficiency.  A diesel, being a true heat engine, can vary by up 10% just by changing the fuel.  And that's why trying to apply BSFC values to a generator test, especially when the kWh output of the generator head was not even measured nor is the efficiency of the gen head known, is so pointless that it's pretty much beyond belief.  It could have been running at 50% load for part of the test, for pete's sake.  I don't know because it wasn't measured - I only know what I set the peak load to.  It was not the purpose.  And when someone fails to take the hint that it was not the purpose, well, I'll call 'em an idiot right to their face.

If that's being an arse, then that's what I am.
--
Chris

[ChrisOlson]

first of all you did not mention that you set the support control to 3kva
you just mentioned that you loaded it to 3.04kva and burned x amount of fuel in an hour.

Actually I set the support level to 3,050 volt-amp.  But as I stated several times, it was NOT a fuel consumption test for BSFC.  I did NOT measure kWh output of the gen head, even.  It was a simple test to determine how long it's going to run on a tank of fuel doing the job it will normally do in an off-grid prime power application.  I did some rough figuring based on what I suspect things are running at, and arrived at the conclusion that the little engine is roughly 30% efficient, which is not too bad for a little diesel.  At least as compared to gas engines in the 5 hp range - most of those are hard pressed to make 20% thermal efficiency as they run ridiculously low compression ratios.

Had I said I measured the watt-hours at "blah" for the hour, and it burned "x" amount of fuel for the hour, THEN you would have something to go on.  But that's not what I said.  By setting the load to 3.05 kVA you ASSUMED that was the constant load.  I assumed that anybody that knows how the XW inverter works would not assume such a thing.
--
Chris

[mobile_bob]

ok Chris, its game on my friend
you aren't in the otherpower sandbox now.

you relating a question to being a rant is typical of your behavior when pushed into a corner
i know you are far more intelligent than needing to resort to ridicule rather than reason.  that is a lazy man's way out of a difficult conversation.

much like "jane you ignorant slut"  didn't advance akroids characters intelligence, it did however entertain the viewers,,, no one is entertained by that behavior here.

you have made a few more assertions i would like to address

in working with this class of engine driven generators, particularly single cylinder diesels of the less than 20kva class you will never see a difference in bsfc of 10% by the use of differing pump diesel fuels... even fortifying diesel with motor oil and effectively increasing the btu value with a 50/50 mix will rarely change the numbers by even as much as 5% points in overall efficiency.

your number were not off by just a measly 10%, had that been the case there would have been no questions asked, what you reported was your setup was 35% plus more efficient than the best of breed in its class... or viewed from the other side the best of breed will consume 50% more than  your unit...  that is just way outside reality.

nobody highjacked your thread/topic, although yes you were asked questions, questions which according to the rules of the forum are fair to ask i might add.  it would have been so easy for you to have stepped up and clarified your reporting at the time, all you would have had to do was state that it was not a constant load applied, but rather as you state now, that it was the upper limit that was set.  why you chose not to rectify that i will leave to the readers to conclude on their own,  i won't tell you what i think the reason was.

you can call me an idiot if you like, you can call me anything you like, i really don't care one way or the other, whatever you call me i have been called worse ( i do have an exwife).

if you want to post the project here that will be fine, if not, i am not sure we have anything else to talk about in regard to this topic.

sincerely
bob g

[mobile_bob]

chris

how can you conclude anything other than the engine ran for an hour and burned x amount of fuel

we certainly cannot conclude the engine/generator is 30% efficient!

its doubtful as hell the engine is even close to that on its own, let alone driving a generator
and taken as overall efficiency,  where it will be fighting like hell to achieve much over 25% overall.  my bet is it won't even do that.

you said that you stated all along that it wasn't a fuel consumption test?  bullcrap!

it wasn't until you got pushed on the issue, and pushed only after you took your condescending position, and was presented with the math showing this was not possible that you first mentioned this was not a fuel consumption test.

it  wasn't  until after that, that you stated that it was a limit set and not a load that you initially reported.

you are one slippery dude when it comes to the details, are you sure you wouldn't consider running for office?  i think you would fit in real well in DC.



bob g

[mobile_bob]

one more thing comes to mind Chris

in my initial questioning of your report, i stated having an issue with your numbers
and asked you clearly that perhaps i was missing something, or misread something?
and asked for clarification if that was the case.

do you recall that?

do you remember me stating that i had been sick and had just had a molar removed and was on percocet, so maybe i misread something, and asked for clarification?

do you recall that?

that would have been the time to add all the details that are just now coming out, had you responded to that, perhaps we wouldn't be talking about it now?

bob g

[ChrisOlson]

Bob, and all - this gets to the meat of the topic of the thread I started on Fieldlines.  I has nothing to do with BSFC, etc..  All you can do is very rough figuring without a real dynamometer on any of this.  And at best, that's what it is - rough.  I do not wish to get into an argument over the details here, any more than I did there.

But I have to inform you, Bob, that changing fuels varies a diesel's performance by even more than 10%, depending on what you use.  Mobile engines don't achieve anywhere near the efficiencies of stationary and marine engines on heavy fuel oils, even though identical combustion chamber designs can be used in both.  And some (like the Cummins QSK) are designed for both fuels.  Operating a diesel on #4 vs 70% 20 micron coal slurry yields a difference in thermal performance approaching 50% with the identical combustion chamber.

The entire topic was about believing that the traditional method of applying off-grid standby power is flawed, and it is flawed due to manufacturers of inverters putting battery chargers in them so AC generators can be used for charging batteries.  Due to that fact, it has become the defacto-standard way of recovering during periods of poor RE production.  I believe using a small genset that is properly sized to the normal loads, and using it to power those loads directly, is more efficient that digging into the bank and then recharging it with an AC generator and inverter/charger, or using a DC charger.

But that topic got lost in the heat of the moment, and this is probably not the forum to present such a thing anymore than Fieldlines is not the proper forum to get into a big argument over BSFC.
--
Chris

[mobile_bob]

Chris stated

"The entire topic was about believing that the traditional method of applying off-grid standby power is flawed, and it is flawed due to manufacturers of inverters putting battery chargers in them so AC generators can be used for charging batteries.  Due to that fact, it has become the defacto-standard way of recovering during periods of poor RE production.  I believe using a small genset that is properly sized to the normal loads, and using it to power those loads directly, is more efficient that digging into the bank and then recharging it with an AC generator and inverter/charger, or using a DC charger."

i think that is a very constructive position/hypothesis, one you would find much agreement on here i suspect.
it has long been my belief that manufactures of offgrid stuff make things they think will sell to a more or less ignorant or better put, ill informed buying public, with the efficiencies be damned.
i think you will find lots of dicussion on this very topic and maybe even some useful information too, and if you like we are always welcoming of more information in that direction.

as for not being able to do more than rough approximation or estimation without a dyno, we could argue that if you like,  i would direct you to read more here and i think you will see how we have gotten over that hurdle to a surprising level of accuracy.  genheads and load banks make pretty good dyno's and the math proofs will support this assertion.

as for heavy oils, bunker or coal slurries, we aren't likely to use them for small engine's even if they were widely available.  as for higher efficiencies with their use in stationary engine's with the same combustion chamber designs... size in this case is the predominate factor, larger cylinders and longer strokes are able to recover and convert more btu's to useable rotational power and that is predominately why they can be a bit over 50% efficient. 

anyway we use pump diesel fuels for the most part and always for testing around here, and engine's of similar design, size and speed will produce bsfc numbers very close to one another, generally all within 5% from worst to best.

there as you know are other factors such as temperature and barometric pressure,  luckily for me and my testing which was done for the most part in the winter months at about 300ft above sea level, my ambient temperatures were always very near 70deg F in the shop.  all my test sheets noted ambient temperatures, baro pressure, humidity, where i got the fuel (which btw i bought in large enough quantities so that comparative test of differing components could be done without fear of skewing by virtue of differing fuels), etc.

it was never my intention to get into an argument over exact bsfc numbers with you with that particular engine combination, it just seemed a bit too good, and i thought maybe even though not likely that good it would in any case be enough better to warrant further investigation here.

like i have said on otherpower, this forum is populated by some of the best at finding information, obscure engine's, parts and just about anything a guy would want or need.  much like a vacuum cleaner we go to whatever lengths necessary to suck up information where ever we can find it.

and yes we (ok, maybe i got a mouse in my pocket) can be quite anal about the details! 

bob g

[ChrisOlson]

i think that is a very constructive position/hypothesis, one you would find much agreement on here i suspect.

The thing is, nobody that I know does this, though.  Short of a few that run co-gen units.  Why?  I think it's all mind-set.  Off-grid folks tend to have the belief that running a generator is "bad".  You're supposed to use wind, solar, hydro, etc., and running a generator is like a "sin".  But it's not, IMHO.  Most off-grid folks make the mistake of buying a generator that's way too big and then they can't afford to run it because it's maybe 50% larger than needed for charging batteries, and WAY bigger than needed for normal loads.

So I intend to pursue my theory that a small generator can be used more efficiently by passing power from it direct to loads rather that using the batteries for bad RE production times, and then having to "catch up" by using a generator to recharge them.

as for heavy oils, bunker or coal slurries

Heavy oils are very good.  Coal slurry is terrible.  It takes roughly 2 BTU's of input using coal slurry for every 1 BTU of input using heavy oil to get the same power output.  We certified some K engines back in the 80's for coal slurry for mining operations.  But the market was not big enough to justify the engineering cost and it eventually became a dead issue.  Now, with all the talk of "alternative fuels" it's being revisited as the best thing since sliced bread.  But the engineers of today must've forgotten the lessons we learned 30 years ago.

anyway we use pump diesel fuels for the most part and always for testing around here, and engine's of similar design, size and speed will produce bsfc numbers very close to one another, generally all within 5% from worst to best.

Basically, that's because pump fuels don't vary by more than 5% on energy content, usually.  BSFC numbers are established by manufacturers normally based on straight #2 fuel with a cetane number of 40, in whatever version the EPA considers acceptable at the time.  In real life, premium fuels with a cetane number of 48 or better will yield better thermal performance than the baseline test fuels, usually by 3-5%.

You stated earlier:
we certainly cannot conclude the engine/generator is 30% efficient!

I didn't say this.  I said the little engine is roughly 30% thermally efficient, based on some quick calcs in my head.  Not the engine/generator combination.  Efficiency is given by 1/(BSFC × 0.0119531) using a baseline #2 fuel with 0.0119531 kWh/g energy content.  This even agrees with the manufacturer's publish BSFC numbers on the little Robin, assuming the engine is running at about 80% rated power with the gen head at full rated output, so the real shaft power is only going to be around 4.5 hp @ 1,100 ft elevation without manifold pressure compensation via a turbocharger.

I was happy with this, as most gasoline engines in the same size class are going to be in the 20% thermally efficient range.  That just meant to me that I had made a good choice for my off-grid prime power project.

You can get more efficient engines.  But few of those engine/generator combinations will produce stable enough power for a XW inverter's AC1 input.  This little Robin does.  But it took some tweaking to get the torque rise up and prevent loss of freq during overload so the inverter wouldn't disqualify it.  And the injector opening pressure was too low, as it was misfiring at high idle no-load.  So I took that apart and shimmed it for 195 kg/cm² opening pressure, and then it ran perfect.  It was deliberately set to the low side of the spec at the factory to start the injection event sooner - main due to a design flaw in the timing advance not providing enough advance for a high-speed engine.  But with a little wear on the nozzle tip after 500 hours the performance of the engine degrades due to a poor spray pattern, without shimming it up.

So I think it will work for my intended purpose, and be efficient enough to achieve my intended goal.
--
Chris

[Ronmar]

Chris, if your original post wasn't about fuel consumption, then what was it about?  Because quite frankly I know if I am off grid, the ammount of fuel I consume to make a given ammount of electrical power is VITALLY important to my bottom line...  It may indeed be more efficient to power loads directly at times as opposed to taking it from the batteries and having to replace it with all the associated losses. But again, the efficiency of such a path comes down to fuel burnt...  If you were not interested in talking fuel consumption, then you shouldn't have posted an outlandish fuel burnt to power generated number. 

I will be the first to admit I make mistakes.  One of the reasons I post here is as a sounding board, as there are a whole lot of years of combined corporate knowledge here to use as a sounding board. 

SO man up and recount. (It burnt X ammount of fuel in an hour, but I don't have an accurate measurement of the load yet)... or put up the SPECIFICS of a good solid test to support your claims.  Dont divert/deflet with "it had nothing to do with BSFC"  Because you posted load and fuel burnt figures, so it had EVERYTHING to do with BSFC.  I would  take a stab that if you had posted NO fuel consumption figures in your original posting, that would have been one of the very first questions posted in response...

Personally I value mistakes and honesty far more than argued BS.  At least if you are making mistakes(best teacher I know:)) and recognizing them as such, then you are at least capable of learning something...

Best of luck to you.

[ChrisOlson]

I got my new powerhouse built and the Robin installed in it.  Although not done insulating it yet and our Honda EM4000SX goes in there too.  Plus have to bury electrical service and control wires for gen auto-start to the building yet.  Just using a 200 foot 10 AWG generator cord at present.

Since this generator is for prime power during bad RE times, or heavy continuous load times, I decided to make a 24 hour run with it to see how it does.  I ran it from 6:00 PM yesterday to 6:00 PM today.  I shut down my wind turbines but left the solar arrays operating, and disabled the charger in the XW6048.  So all the generator powered was our normal loads for the 24 hours.  Which is easy to measure because I got an old utility kWh meter on the XW that keeps track of our daily power consumption.  I set the load on the generator set to 3.05 kVA (13 amps) in the XW's Gen Support menu.

We used 36 kWh during the 24 hours and the Robin burned 5.3 gallons of fuel - the fuel measured with the meter on the 125 gallon fuel tank in the back of my service truck.  The tank on it only holds about 3.5 gallons so I had to refuel it this morning after breakfast.  The numbers are a little skewed because several times the loads exceeded what the Robin can put out for power so the XW assisted it from RE power using Gen Support.  But again, this is NOT a BSFC test!  It's a 24 hour run with the generator on prime power duty to see what it's going to do when we need to run it in the winter for several days at a time.

This is the powerhouse:



This is the generator inside it, running



This is the load on it at the time I took the photos:



This is a short video of it operating inside the powerhouse on its 24 hour test run

Chris, if your original post wasn't about fuel consumption, then what was it about?

It was about using this little generator for prime power when we want to run our AC unit in the summer, or get bad RE production in winter.  I was curious to see what it burns in an hour to decide if it's worth it to install an external fuel tank when I built my new powerhouse where it's installed now.  I burn over 60,000 gallons of diesel fuel in my equipment and semis in a year's time.  So whether this thing burns 2cc/hr or 2 gallons/hr, it don't matter.  The one and only thing I wanted to know about fuel consumption is how many times I have to refuel it per day if it runs for several days at a time.  Like I said before, how the hell that got misconstrued into BSFC from a post on another forum is beyond my wildest imagination.
--
Chris

[Dualfuel]

I read something on this thread that startled me...the idea of wanting to run a generator instead of using battery power. Wow! I got tinnitus from living next to a generator in Iraq. Yup, lived next to it for a year...right next door. Like 20 feet away. Before that I listened to commo tracks running all night because their batteries could not keep the radios going plus start the tracks...or the military standard engines running to power the radios.
When I went off grid, it was because I couldn't pay the bill...so I had to have a generator, or a truck running, sometimes a junk minivan full of sulfated batteries...but there was hardly ever an real peace or silence if there was something that needed doing.
Now that I have some dough for infrastructure, I bought lots of solar panels, and lots of batteries...I bought silence. I also bought simplicity...my 8 year old can start the inverter and check the bank voltage...
The reason inverters charge batteries when you pull the rope on the generator, is so the bank gets charged from incidental use of the generator...an example is watching Youtube all night on the computer, then starting the Honda in the morning to run the drip coffee maker, while the Magnum pumps 103 amps into the bank. This feature is a natural progression away from running a generator all the time for a small load, to the blissful silence of a battery bank and an off grid lifestyle.
I don't believe anymore that these things were built for idiots...I think they were built for people who do not worship engines. I am the only one around here that can start my stuff, and judging by the fan in the cooling door of the generator house, Chris will be the only one starting the Robin, (what happens when someone else forgets to open the door and start the fan?). Its those details that these other people don't think of.

[millman56]

One benefit of tinnitus is that once you`ve got it all generators/engines/wives make the same ringing noise even when switched off.   

Mark.

[ChrisOlson]

I read something on this thread that startled me...the idea of wanting to run a generator instead of using battery power.

We've been living off-grid here since June 2002.  What's startling is the cost of batteries.  They're the most expensive component of an off-grid power system.  We got $9000 in our Surrettes and they're good for about 1700 cycles.  That means if you cycle them every day the cost per year in batteries alone is about $1,800, or about $150/month.  Using the battery power is fine as long as they're charged by RE sources of power.  But when the weather don't cooperate and you have to charge a sacked bank with a generator you're throwing good money after bad.

We use 30+ kWh/day here and our bank can store 28 kWh down to 50% SOC.  During the days in winter when we only get 3 kWh in a day from solar and wind, I can buy a lot of damn diesel fuel for a little prime power diesel generator that's properly matched to normal loads compared to what it costs to cycle those batteries and then burn the fuel anyway to recharge them.  Using the small diesel prime power generator lets the batteries float during those times instead of using up cycles, and basically I can run that Robin diesel 24 hours a day, 10 days out of a month for less money than it costs us long term to cycle the batteries every day for the month.

Off-grid living is expensive - WAAY more expensive than even buying power off the grid for 30 cents/kWh.  Many people have a misconception about that because they think we don't have a utility bill.  Well, I got news for ya' buddy - the utility bill is a lot cheaper than what it costs us to keep the lights on.  But we also like where we live and 11 years ago there was no way in hell I was going to pay the utility company $168,000 to run powerlines to our place.

So this is all about reducing the expense in batteries over the long term.
--
Chris