Diesel vs. propane
Diesel vs. propane
(OP)
I'm looking for case studies on propane vs. diesel costs in a standby power application of 15-25KW.
Obviously, the relative fuel costs will favor diesel, while the initial purchase & lower maint. costs favor propane. At some # of hours/year, the lines cross. My goal is get some numbers to figure out where that point is.
Obviously, the relative fuel costs will favor diesel, while the initial purchase & lower maint. costs favor propane. At some # of hours/year, the lines cross. My goal is get some numbers to figure out where that point is.





RE: Diesel vs. propane
Depending on the number of run hours anticipated I would ALWAYS go with propane. Both Diesel and Gasoline have horrid aging issues. If you keep either of those fuels around for a year they are greatly degraded and will eventually cause failures of different sorts. To prevent this you have to run them enough to consume the fuel or cycle the fuel out on a schedule, which is typically a stinky messy ordeal done only once...
If you never expect to run more than the size of a reasonable propane tank definitely go that route. If you can anticipate a multi-day - week operation go with a mixed fuel setup, gasoline and propane. Then as your projections and usages shape up during an emergency you can work on securing more propane or some gasoline in a timely manner.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Diesel vs. propane
Plus, they already have a menagerie of other equipment that uses Diesel; not just a tractor or 3, but also a road grader, full-size dozer, backhoe, etc. So
Plus, there seems to a good secondary market in Diesel generators; much less so in propane.
That is why I want to be able to put numbers to things; so we can look at the real costs, and then decide.
RE: Diesel vs. propane
When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge of it is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced it to the stage of science.
Sir William Thompson, Lord Kelvin (1824-1907)
RE: Diesel vs. propane
It's not the only consideration, though. Think about what happens when the tank runs empty. In the aftermath of Hurricane Rita it was impossible to get propane delivered into the hurricane zone in any quantity. A couple of drums of diesel fit in the bed of a pickup truck.
old field guy
RE: Diesel vs. propane
itsmoked has made some very valid points, but if that won't be an issue to you, diesel is your obvious choice.
I am potentially in the market for a stand-by generator, and it won't be diesel. It will be natural gas or propane. In other engine driven applications, I am a natural diesel fan and have owned my share of them. But not for one where the fuel has to be stored for long periods.
rmw
RE: Diesel vs. propane
Not at all. First off, it's not my call; I'm just getting options together. Second, I don't know the costs yet.
But it costs a bit to fill up a 1000g propane tank; so I think some due diligence is called for at this stage.
If there was natural gas; there'd be no discussion. Dual fuel from it or propane would win hands down. But he's as likely to get FIOS as that....i.e. not in his my lifetime or his.
Nod re: refuelling Afterwards. Post-911, the several server hotels in Lower Manhatten had a major problem getting refuelers to their buildings. Those shutdowns days later were the only Internet failures of any note. This is an earthquake and wildfire zone, just to make life interesting.
He will have smaller generators that run off gasoline, and maybe a PTO-driven one off the 'dozer. We'll see.
RE: Diesel vs. propane
Are we talking small enough that a tank such as a forklift tank is adequate, and thus its easy to deal with?
We've got an installation we inherited with a gas powered 300kW set, but theres been no designation of any sort of hazardous areas. I would have thought that compliance with the standards, at least in terms of regular inspections and so on would seriously sway the balance.
I'm in IEC land for reference, I have no knowledge of the NEC requirements.
RE: Diesel vs. propane
RE: Diesel vs. propane
I worked for an engine dealer for a number of years, at one time we had nearly 1000 standby generators under CSA's. Even though natural gas and propane units made up a fairly small percentage of the population, they had a larger number of failures and problems. I don't think a lower knowledge level was the issue since we had a large number of larger natural gas and some propane units in prime power and cogeneration service, and we serviced competitors units as well. We also did a fairly large number of NG pump units for irrigation, with far fewer problems than similar units in standby service.
Some issues from my experience,
SI engines suffered more problems from running at no or low loads, included plug fouling, fuel system problems and failures to start when commanded.
Found a large number of propane units had failed to start, either during regular testing or during an outage. Root cause, tank was empty. Hopefully fuel tank level monitoring has improved since then, but it was a big problem.
Propane vaporizers seemed to be problematic, one of our most frequent reasons for service call.
The governing systems provided, especially on auto-derived engines, seemed problematic, poor control of speed/Hz and erratic droop response, probably due to low cost. Hopefully newer engines use electronic governing or better mechanical governors. If it seems nit picky, most standby customers I dealt with wanted "utility like performance" from the cheapest standby they could buy.
I worked the aftermath of both the Northride and Oakland earthquakes, and a number of fires over the years, I'll second OldFieldGuys comment about diesel fuel in the back of a truck. Seen a propane tank during a wildfire? You may also be able to find someone from LA County Watewater to tell you about a small number of spectacular "launching" of pump houses that housed propane engine powered pumps. After that I was told they no longer considered propane as a suitable standby fuel.
Yup, diesel fuel does degrade during storage, seems the newer fuels do it faster, likely due to the fact that the sulphur probably helped combat biological growth and older fuels had lower levels of light ends. I would bet anyone can make a better case for one over the other based on his perspective.
But I think a small diesel, especially under the current HP limit for emissions regulations, with a simple robust fuel injection system and solid governing is going to be hard to beat for shear reliability. And I can't imagine anyone who buys the size units we are discussing is going to spend much on maintaining the units to assure most reliable operation.
my 2 cents worth.
Mike L.
RE: Diesel vs. propane
RE: Diesel vs. propane
I can't recall the last time a car did not start, save a dead battery or out of gas. Fuel injected/closed loop control have solved so many things, inc. fouled plugs, idle while cold, and oil dilution.
Have stationary powerplants been following along; or are they like GA aircraft engines, still using the finest WWII technology?
RE: Diesel vs. propane
Sometimes at remote job sites I run my truck long hours at idle to run my inverter for power, a newer Dodge Ram 1500 with a "modern" control system, guess what, after that kind of operation a couple times a week, it has problems too.
As for the technology, how many auto-derived industrial gas engines have the same level of ECU and controls as an automotive application? Likely not as much, since the industrial market is a lower much volume and automakers build overall system controls into the ECU, not just for the engines.
Sorry to seem blunt, but comparing a car engine to an engine in standby generator service is like comparing house wiring to an electrical distribution system at a large industrial facility, the general idea is the same, but the actual application, maintenance and equipment selection needs to be different, at least in my opinion.
Mike L
RE: Diesel vs. propane
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Diesel vs. propane
(Consider how well your '72 Dodge truck would run after idling for 6 hours....I used to work on police car radios, & long idling times were a major issue with the dept's...that and the stinking tiny MOPAR alternators of the era.)
I talked options with the owner. He's going to see if we can get outage stats from the utility. Neighbors estimate that they are black 75-100 hrs a year; unless there's been a quake, then all bets are off. Longest outage they've had was 8-10 days.
Their current fuel management scheme is take the empty 55g drum back to the farm supply, and get a new one. With a Diesel generator, he'd get a rack at least. I concur about fuel transfer schemes.
One possible Plan B is a PTO generator run by his new Kuboto L4400HST, but I have not found a 3-phase one of appropriate size. We're going to look at both fuel options for Plan A.
RE: Diesel vs. propane
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Diesel vs. propane
But the PTO solution gives us an alternative; one that burns Diesel.
And in theory, the priority 1 loads are within the envelope of the PV system. In other words, at during sunny days, we should need no IC engine going at all; or maybe for an hour.
The water tankage has 25' of head vs the house, so everything short of the showers will work regardless, albeit more slowly.
RE: Diesel vs. propane
The generator can shut down, and the P-1 house loads will stay up. Lower priority loads such as the freezer will drop off.
Thus you can refuel, and restart; or if need be, drive the tractor over and start up the PTO generator.
One of the TBD questions is how many minutes of batteries does the client want to buy.
Another one is: what kind of remote tank gauge technology can I use on Diesel or propane tanks? When I was in the pipeline business, the tankgauges were a major pain, and not to be trusted.
RE: Diesel vs. propane
Keith Cress
kcress - http://www.flaminsystems.com
RE: Diesel vs. propane
I'll need some Flo Control software http://tinyurl.com/2apww6p
RE: Diesel vs. propane
An interesting side issue may be the ability to determine the average specific gravity of the diesel fuel.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Diesel vs. propane
Re Plan B- 3 phase 25kw PTO generators are available, I had one until recently. If your tractor is used regularly, it should run when needed. If not, a neighbor may have one that does. Using the PTO set for home standby, it took about 20 minutes to get the power back on if I was not asleep at the time of the outage. The tractor governor has more droop than is ideal, but the result beat nothing by a large margin.
My "remote tank gauge" was watching the tractor guage over the first tankful, then pouring in 5 gallons every 6 hours thereafter. It isn't a good idea to let the tractor run unattended for long periods anyway.
RE: Diesel vs. propane
You may not have been exposed to the latest automotive style industrial engine. Currently, the NG and propane engine my company produce are EPA compliant. Becoming EPA compliant requires the use of an ECM with closed loop control and active sensor monitoring. We have a number of these units in the NG compression field. Some of these engines are only used at 3 to 6 month intervals when NG prices make it worthwhile.
Personally, I believe a diesel or SI engine would work great it just depends on the any constraints that effect the application.
RE: Diesel vs. propane
It seems they can run on a variety of fuels: diesel, kerosene, propane, natural gas etc.
http://www.capstoneturbine.com/prodsol/products/
No affiliation, but I find their products interesting.
Benta.
RE: Diesel vs. propane
A Kubota L4400HST is only 45hp. We build PTO that are 160kw three phase so it would not be difficult to find a PTO set that would exceed the power available from the Kubota.
RE: Diesel vs. propane
He has a Fiat [aka Italian Cat] dozer as well, but it does not have a matching PTO. I was thinking a hydraulic motor might work, but that's another issue.