Choosing a good generator

Re: Choosing a good generator

Visit Bob Golding's microcogen forum. There's all kinds of people that do it.
http://www.microcogen.info/

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Chris

Re: Choosing a good generator

Roughly 30% thermal efficiency, 30% goes to cooling and lubrication systems, 40% goes out the exhaust.

Turbocharged engines can recover some of the exhaust heat loss and use it to improve thermal efficiency.
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Chris

Re: Choosing a good generator

When we got our Honda generator I was curious as to how it would compare against the LP fueled EcoGen. I ran it on a real-world battery charging job for 2.5 hours.

I don't have a good way to measure genset power production directly on a variable load (yet - I'd like to pick up an old utility kWh meter), but I can measure on the DC side going into the batteries with very good accuracy. I put 6.0 kWh into the batteries in 2.5 hours, which at 90% charging efficiency (estimated) I figured to be about 6.7 kWh at the genset. There was other loads on in the house at the same time, and I estimated those at about 370 watts ave for the 2.5 hour run, which would be another .9 kWh direct from the genset at Power Factor 1.0. That would be a total of 7.6 kWh produced by the genset over 2.5 hours, or roughly 3.04 kVA average output for the run.

The generator burned 141 ounces of 91 octane (non-ethanol blend) fuel for the 2.5 hour test. That figures out to a fuel consumption rate of .44 gal/hr. The BTU content of the fuel is about 114,500 BTU/gal, or 33.56 kWh/gal. So overall efficiency figured out to 20.6%.

That's about 3% better than the LP fueled EcoGen could do. Some diesels will achieve 3-4% better than that. But I was pretty happy with it.

I did some measured fuel consumption tests on various generators over a year ago. The inverter types (I tested both Honda and Yamaha) were invariably less efficient (~2%) than a conventional driving a fixed resistive load. I chose to use the resistive load for testing because it simulates battery charging during the bulk stage pretty well. And was a more controlled load than a real world battery charging job, so the different generators could be accurately compared.

Looking back in my test data, the Yamaha EF3000iES that I tested achieved a best efficiency of 13.5% @ 2.292 kVA output and 57,982.3 BTU.h input. I had also tested a Honda EM4000SX. The Honda was too big compared to the other generators I tested, so it could not reach anywhere close to its peak efficiency because it wasn't loaded heavily enough. But the Honda did 15.5% @ 2.292 kVA output and 50,324.3 BTU.h input.

Edit:
The data from my generator testing is attached for reference. The diesel Yanmar was the most efficient of the bunch overall. But the little high compression Champion generator could beat it. But here again, the Yanmar, like the big Honda, was operating at well below what it could achieve because it's a bigger generator. The Yanmar had incredible surge power, right on par with the big Honda. The cheap Chinese generators were pretty darn good overall - they're basically Honda clones. The inverter types were pretty good at lower loads. But when you add load to them they fall behind the conventional excited wound field generators.

I also tested each generator to see if it would produce its rated continuous power and rated surge capacity, although the results of that are not shown in this data. The Honda's, Yamaha and Yanmar all passed with flying colors. Neither of the Chinese generators (Champion and Generac) would produce rated power, nor rated surge. The Generac was close but no cigar. The Champion was woefully short by almost 1 kVA and was pretty much running at it's full maximum continuous output at 2,300 watts. Loaded any heavier and it had a lot of governor droop and wouldn't maintain either voltage or frequency. It was so bad that if I tried to increase load on it the voltage would drop as fast as the amperage would increase, with the net result that it didn't put out any more power.

Attachment not found.
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Chris

Re: Choosing a good generator

I'm of the school of thought that it's better to have two generators that run on different fuels than to have one that runs on multiple fuels. It not only provides multi-fuel capability, it also provides redundancy in the event one would fail.
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Chris

Re: Choosing a good generator

niel wrote: »

it seems to me that if your propane genny were to fail and all that's left is your gasoline genny and the gas stations have no power or gas, then you are still sunk. maybe for redundancy it would be good to have 2 gennies capable of multi fuels.

It comes down to "how much redundancy is enough?" One gasoline generator with a can of fuel will do for most power outages. If it gets to be armageddon it won't matter if you have ten thousand generators in varieties ranging from gasoline to multi-fuel to alcohol.

You can not plan for every possible contingency. All you can do is look at the history of your area and plan for what is the most likely catastrophe to strike.

Re: Choosing a good generator

niel wrote: »

it seems to me that if your propane genny were to fail and all that's left is your gasoline genny and the gas stations have no power or gas, then you are still sunk. maybe for redundancy it would be good to have 2 gennies capable of multi fuels.

I agree with 'coot here - your gasoline generator should be the primary. Gasoline generators are inherently more efficient than propane (except really exotic engines with high compression, modified valve and ignition timing, etc.). It's not too hard to have a full tank in the generator and an extra 10 gallons on hand for it. And if you have to you can siphon some gas out of your car or truck for it. It it fails or runs out gas, then break out the propane one.

If you run out of fuel for both, gasoline is going to be easier to find than LP gas. A gasoline engine will even run on moonshine (some of us have stills hid back in the woods) if you leave the choke on. LP won't.
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Chris

Re: Choosing a good generator

swmspam wrote: »

But that's why I'm looking at the Honda. Good engineering compensates for much of the fundamental inferiority of gasoline. But you pay for it.

Diesel fuel is currently 65 cents more/gallon than gasoline. The cost/kWh with diesels is too high because of that, even with their superior thermal efficiency. You might not have spark plugs or carbs. But you got injection pumps that are VERY sensitive to water and I've seen more than a few Yanmar and Hatz diesels with a seized pump plunger because of being fueled out of a can and water got in it. You can buy a whole Honda gasoline engine for what it costs for a new injection pump on a Yanmar or Hatz.

When you buy a Honda you pay extra for the reputation, reliability, engineering and dealer support. Something you don't get from most other companies.
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Chris

Re: Choosing a good generator

That's a cool comparison method! If I apply that same methodology to our EM4000SX I can buy 1163 gallons of fuel for that $4000 (at today's prices). That fuel would give us 2643 hours @ 3 kVA output (what I measured in my fuel comsumption test on it doing real world battery charging). That equates to 7929 kWh or right on 50 cent/kWh. To put that in perspective, that's a little over 3x what grid power costs (at today's prices in town).
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Chris

Re: Choosing a good generator

Sometimes the type of noise it makes is as much difference as a reading on a db meter too. An example is that the background noise in an urban environment can be as loud as a small generator, but a generator running will cause annoyance while the background noise doesn't.

I don't know about the EU2000 but the EU3000 makes more apparent noise at full load than my EM4000SX does. The specs show the EU3000 at 58 db(A) at rated load, and the EM4000SX at 71 db(A). But the 4000SX has more of a deep throated growl intermixed with a slight turbine whistle type sound to it while the EU3000 has a tinny-sounding, annoying, hammering at full load. The 4000SX is much more pleasing to listen to, making it seem quieter, because of the more steady muffled-sounding type deeper noise, while the higher pitched hammering of the little engine in the EU3000 is just plain annoying after awhile.

I attribute that to the fact that the little GX200 only develops 5.5 hp and it's operating at 85% of its max power output in the EU3000 at rated load of 2.8 kVA. The iGX270 in the 4000SX develops 8.8 hp (up from 8.5 in the old GX270), and is operating at 61% of its max rated output at 3.6 kVA. The harder a particular engine works, the more pronounced the "hammering" becomes on a single cylinder because of combustion noise and a sharper exhaust note.

I think the turbine-type sound from the iGX comes from its re-designed cooling blower that only requires 50% of the hp to run that the old GX had. Looking at it reminds me of a compressor wheel in a turbocharger. It's got smaller fins on the outside where they travel the fastest, and bigger fins in the middle where the fins have a lower tip speed. It also has a huge air intake screen over the flywheel and doesn't have an exposed recoil like the GX had.
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Chris

Re: Choosing a good generator

Well Tony, it might be kind of a bad deal (for you)

I had to do some welding on a wind turbine transmission case yesterday. I tried that generator on the welder to see if it would work. It makes it pop right up out of its chair, stand at attention and recognize that's it's got something hooked up to it. But it runs my Lincoln AC/DC 225 amp spark welder with no problems, with the welder set at Full Dawg.

So now I'm keeping it
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Chris