I am working on a grain storage and handling complex. Due to the demand charges the power company bill is obscene. Last month I paid $460. for $17 worth of electricity. Seasonal use facility, mostly September through December. Motor load will be a 60hp, 2x 30hp, and sometimes 1 or 2 20hp as well. All will start unloaded, and in sequence, never simultaneously. I have natural gas at the site, had a 10,000,000 btu burner previous, so am thinking of natural gas for power. It looks like natural gas is about 1/3 the price of diesel right now. So I am looking for a used generator in the 175 to 250 kw range, 480V 3 phase. What things do I need to know, any things to stay far away from, what would be good? Any knowledge or observations that could be helpful?
You are talking about 100HP of electrical load, The question is will the 30 HP be engaged before or after 2- 20HP motors. The inrush current can be 6 times the running amperage on 600 volt units. It would be just as high from what I know on 480 volt units. If the generator is too weak there could be issues. Lots will depend on if it is automatic load control or operator adjusted frequency. There is lots of things to consider when generators are being selected. Simon C
Forgot to mention that $1500 of electricity from Sept-Dec. is just small compared to a 250KW generator used. And used will mean some big dollars to repair at some point. Simon C
Electric company demand charge with new equipment will jump to $1,000 to $1500/month for a 12 month period, even with no electric usage. Actual power usage is small. I estimate 200-300 hours/year of run time.
Genny makes sense under those circumstances. Mom and Pop crushers run those kinds of sequenced loads. Might be nice to find one of those power trailers all set up and just make the few changes. I would think Tier 2 stuff out of California would be available now. For those kinds of hours I would get a diesel and not bother with the NG.
Today's prices for natural gas is $7.15/1,000ft3. 200kw full snort should be 2,583,000 btu/hr, or about $18.47/hr operating cost. Diesel, 14.5 gallon/hour. At $4.30/gallon, thats $62.35/hour. 200 hours, thats $8776 operating cost difference in favor of the natural gas.
Natty gas doesn't have the power of diesel for motors . Gas is good for light loads not motors . We do BIG gen sets and I only use cat . The one we just did in Oklahoma Was 3000 amps at 480 volt . The price of them will make you poop . They aint cheap not to mention the tornado requirements you will need to comply with . At 480 3 phase line to line voltage with all running you will need 261 kw . I know you say they will never all run together but I've done this far too long to believe you . Not calling you a lair just from past experiences this is what I learned . So 300 kw gen set new you are in the six figure range . 250 is the next size down and those can be towable . You would put quick disconnects on your electrical panel the genny already has them on it . We are a design build contractor that does lots of BIG gen sets . hope that helps .
Sept. thru December, might want to see if the heat thrown off can warm the shop as well.
Look at Gov Surplus, gen sets are something the Army likes to dispose of frequently. Here's a little one https://www.govplanet.com/jsp/s/ite...et&utm_medium=email&utm_campaign=GP-FA-061826 Joe H
Have to agree with size, the question is how much is the budget and what will you get for it? Simon C
You'd need to post up what you're checking out at auction or private sales to give you real world pros & cons (not links that would drive up the price, just model info). Nat Gas at that kW is going to chew through some fuel. You'd likely be looking mostly at a PSI 10L-T or 11L, or some older Big Cam Cummins with the gasser head. There are other engines ran, but I'm not at my laptop right now.
Generators are very expensive unless you are getting close to max load, consider your load requirements and I would size multiple generators so you are getting your bang for your buck, also consider getting drives for your motors although they probably would be too expensive, but you could use small single phase generators and it would be overall cheaper
My cousin had a 855 genny, irc he said it was 20 gal/hr diesel
We've dealt with some big crusher generators, and we actually just loaded up a big Cummins diesel a couple months ago. I think it was around $50,000 used. But the former owner had just put $25,000 into it with some repairs. It went to Louisiana. I'll try to find out what the kw was on that unit.
Here is one that seems to fit my requirements. https://www.machinerytrader.com/listing/for-sale/255972137/2002-spectrum-255-kw-stationary-generators-power-systems
That seems really cheap!
could work well in your application. Its a DD so if a twister gets it just follow the oil trail . it will be really loud but you can get sound damping for it . There is a company out of Washington state that does used and custom builds but I can't remember the name . I do know they stand behind what they sell if that helps .
Oh and one more thing . Don't matter the motor they all break . they do service and mantainance are key . the motor doesn't matter the brand its what it spins that is going to fail first .
Like New Detroit Diesel 16V71T 450KW Diesel Generator Set - Depco Power Systems www.depco.com No mufflers either!
I sell & install home standby generators. While I've been asked to price big machines, I've never sold one. I do from time to time work on them. Something to be VERY careful about is confirming you buy a machine you can configure to meet your power needs. Most large ones can be reconnected to choose your power choice, a few can't. I've gone to look at former military generators to find they are only 208/120. Others are 50 cycle, usually a manageable change. Motors & other magnetic machines depend on "magnetic choke" to limit current. An across the line starter sends power to the motor. Magnetic field builds from 0% to 100%. At the instant it starts your magnetic field is zero. Starting current may be 700% to 1200% of running current. If it overloads the engine, it may slow the generator, lowering frequency, and voltage, as current spikes. A variety of failures can occur. Soft starters, or VFD controls can help. Be very sure your generator is big enough.
On a note of the millitary gennys the 2 ive owned where able to be wired for 480.
From the Spec number, that should be basically a rebranded Kohler 250RZD/RZDB with a slightly reorganized DEC-3 16 Light Controller. Gen-end and controller parts are still all available through Kohler (or Rehko now). Also can updated to a Flight Systems controller pretty easily (or ordered as a plug and play through Davidson Sales).
Marshall, I don't find anything via gogl about flight systems controller or davidson sales. Is this something that would improve the responsiveness of the generator? Was Spectrum a reseller that is no longer around?
Interesting, I always thought KW is KW no matter the prime mover.
In the 10-30 KW ranges, the same machine might have a KW rating for natural gas, another for propane. Propane makes an engine more powerful than it'd be on natural gas. I think about 9% difference. I presume the gas fueled engines need to be bigger than diesels for the same KW rating.
According to the numbers I have available a natural gas powered genset in the 200-250 eKw output range will be anything from 20-40% less fuel efficient than the equivalent diesel-powered set, all other factors being equal. Maybe @Catsparky1 can shed more light. Diesel Generator Fuel Consumption Chart by kW | Gallons/Hour Fuel consumption charts for diesel generators 20 kW to 4000 kW. Gallons per hour at 25%, 50%, 75%, 100% load. Plan fuel tank sizing and operational costs. generatorsource.com
I wouldn't say that is necessarily the case. There will be ways of turning up the wick on any model of engine to make it produce the required power from an energy-poor fuel. All down to the control of fuelling and cramming sufficient air into it.
Either way, is not a 200 kw genset a 200 kw genset, regardless of prime mover ? and a 200 kw genset should run whatever loads up to 200 kw ? The local phone company had a large backup genset in the basement powered by a gas turbine.
I guess bigger was a poor choice of words. In Generac home standby machines the less costly models are the same machine, you only adjust the orfice from natural gas to propane. In some models they rate output lower for natural gas. Other models have an engine with adequate power to run the alternator at full rating.
Electrically I would agree with you, it’s simply the amount of fuel required to produce whatever quantity of power that comes out of the generator end.
Nige, I agree with you on the better thermal efficiency of diesel engines over natural gas. But I'm looking at the economic efficiency. Using the table you linked, (thanks for that) a 250kw at 75% load the cost per hour of the diesel would be $58.40 at $4.30/gallon. Natural gas would be $18.51 at $7.20/mcf. Based on Catsparky1 post, I think a 250 kw is probably a better choice than a 200 kw.
Based on your OP I also thought that. TBH if the right set came up for sale you could probably go as big as 300 eKW and still be winning. The load on it would be adequate to keep the engine clean internally. I've seen the results of too many sets that were run at very low loads and it's not pretty.
The engine is a DD 60 series not a screaming 2 stroke. Arguably one of the best engines ever made according to Truck Shop.
Sorry, I meant a Deep Sea controller retrofit, not Flight Systems. The Kohler DEC3 is a good controller, but when the boards start having issues they can be a pain to properly diagnose and are pricey to replace. Many elect to update to a newer controller and aftermarket AVR that's easy to plug into and program versus patching up peices at a time. Davidson Sales Co Davidson Sales Company is a factory representative, stocking distributor and manufacturer serving the power generation market. www.davidsonsales.com That unit was built by Kohler for MTU/Detroit Spectrum. I really don't know the history of their relationship. EDIT: Thank you Wikipedia "In 2000, DaimlerChrysler acquired the Detroit Diesel Corporation and placed its on-highway division under Daimler Trucks North America. The off-highway division was placed under MTU Friedrichshafen to form MTU America. Detroit Diesel branding has been maintained by DTNA and MTU America."
Bigger nat gas gensets are all the rage right now. Just look at Caterpillar's stock price over the last 18 months. Data centers are gobbling up everything they can get their hands on. A diesel genset will handle power spikes (transient loads) better than a nat gas engine, but power wise they will have the same rating. A 3512 B/C/E genset has the same power rating as its G3512 cousin. There is a guy in western Oklahoma that has some contract with major retailers like Wal Mart and often sells their emergency generators on Marketplace. Another suggestion would be to use a manual transfer switch on your install so if you ever need to go back to grid power, you can just pay the bill and have them set your meter. Just to give you a reference point, there is a 200kw diesel generator (200 hours), sound enclosure, and ASCO 300 auto transfer switch for sale near Tulsa, OK for $25,000.
Thanks everyone for their help and insight. I may not be much smarter, but I am less uneducated. In reading some specs I found the note "derate 7% per 1,000' elevation above 600'. (I am at 1300', so 5% derate.) Maximum rated altitude 5,000'." That is a far more severe altitude derate than I have encountered in other applications. ISTR we used to figure 4%/1000' for spark ignition non-forced induction, but there was a slightly offsetting vehicle drag reduction of 2%/1000'.
That’s fine, but do those same numbers hold true for a turbocharged engine which I assume it will be if you are looking at a 250eKW generator set.