Generator PTO generator feedback

[SPYDERLK]

Just checked some dyno test on internet. Two wheel drive cars deliver about 7% less power to the road than the engine produces. It includes all transmision and differential gears and tire deformation and friction to the road. It might give you some idea about losses of generators with gearboxes. My guess is that the gearbox makes very little difference in efficiency. Probably the cooling fan uses more power that the gear. Look at it this way. If the gear would lose (all loses are turned into heat) let say 10% of engine power to deliver 10kW it would run red hot.

No. The air cooling and conduction to adjacent cooler parts is significant. The parts do not have to become incandescent to rid the heat. The fan wont require more than low fractional HP to remove a couple HP of heat if the gearbox is running at a delta of 50F or so [150F in 100F ambient air]. 2HP of heat is 1500W. The trouble with PTO driven gens is you lose about 10% getting the engine power to the driveshaft...and then another 10% in the 6:1 speed increase transmission of a 3600 rpm gen on a 540pto. This great speed increase is very inefficient because of the small driven gear.

And were not even talking yet about parasitic losses of the tractor hydraulic pump circulating uneeded fluid
larry

 

[BobRip]

Also, if you are running lightly loaded then you are rotating a much larger gearbox and oil pump than you need for that load.

 

[Redneck in training]

No. The air cooling and conduction to adjacent cooler parts is significant. The parts do not have to become incandescent to rid the heat. The fan wont require more than low fractional HP to remove a couple HP of heat if the gearbox is running at a delta of 50F or so [150F in 100F ambient air]. 2HP of heat is 1500W. The trouble with PTO driven gens is you lose about 10% getting the engine power to the driveshaft...and then another 10% in the 6:1 speed increase transmission of a 3600 rpm gen on a 540pto. This great speed increase is very inefficient because of the small driven gear.

And were not even talking yet about parasitic losses of the tractor hydraulic pump circulating uneeded fluid
larry

I agree that tractor engine runs unneeded load and has additional losses in the gears inside of the tractor. But I still think that the gearbox on the geny makes little difference in cost of operation. In bang/dollar, in spite of greater fuel consumption/kWh produced, PTO geny wins in most cases. I would argue that, considering the number of hours the geny will be running per year, it will take many years (not even counting maitenance cost) before the built in and PTO geny will achieve the same cost of operation. Perhaps never. The money saved is worth the inconvenience of the PTO geny. For many people buying PTO geny is the difference between not having geny at all. It is like NOT buying Porsche when Aveo would do.

 

[Soundguy]

So, to repeat: Just to be clear, you think these diesel engines might be throwing away 15 or 20% more fuel than a tractor engine?
larry

Which is it? 15% or 20%.. or neither.. do you have actual data to back up these friction losses you are quoting? Or actual fuel efficiency numbers based on load on that diesel genset we are talking about? So far.. I havn't seen any actual data posted.. that's why i said my opinion was reserved at this point, though I had my own personal doubts..

I've told you my position more than once now..multiple times.

I won't do so again. Nor will I bother reading or responding to your posts anymore.

Just to be clear..I'm adding you to my ignore list after this post... so later..

soundguy

 

[Soundguy]

Yep.. I agree.. considering buying a standalone unit you are buying an engine.. vs just a gen head.. dollar for dollar when you look at KW production.. it's hard to beat a pto gen in price efficiencey, especially when you look at the 10-15kw range units.

soundguy

The money saved is worth the inconvenience of the PTO geny. For many people buying PTO geny is the difference between not having geny at all. It is like NOT buying Porsche when Aveo would do.

 

[bucmeister]

The biggest issue for us "one tractor" guys is that tractors are designed to be monitored by the operator in the seat and are not set up for unattended operation, therefore they do not have the low oil, high temperature, or low hydraulic fluid safety shutdown features to protect the engine, transmission, and pump in case something unforeseen happens. Will something happen? Most likely not, however stuff does happen.

 

[Diamondpilot]

Well this was a timely debate. Last night at 11:15 our power went out. Just after my Colts won by the way and another good Indiana Boy by the way of Purdue got-r-done also. Either way I just went to bed. Had to be up at 5:45 for work. Well about 2 am I woke up and the house was getting cold and I was going to need a shower in the morning. Out to the barn and roll the Troy Built out, starts on the first pull, plug in the wire, throw the Hot Tub Breaker, then flip the 200 amp transfer switch. Off and running. Got back to bed and woke up to the alarm on my Cell Phone. Got my shower thanks to the genny running the well pump and noticed my farmer neighbors barn lot lights were on. Go down, throw the transfer switch, kick back on the hot tub, and roll it back in the barn. All in all it only ran for 4 hours but was much need.

Chris

 

[SPYDERLK]

Which is it? 15% or 20%.. or neither.. do you have actual data to back up these friction losses you are quoting? Or actual fuel efficiency numbers based on load on that diesel genset we are talking about? So far.. I havn't seen any actual data posted.. that's why i said my opinion was reserved at this point, though I had my own personal doubts..

I've told you my position more than once now..multiple times.

I won't do so again. Nor will I bother reading or responding to your posts anymore.

Just to be clear..I'm adding you to my ignore list after this post... so later..

soundguy

Good.

 

[tsteahr]

With the numbers being tossed about in this thread concerning gearbox losses, hydraulic losses, delta T, heat dissipated, etc, I think some reference-able information would be helpful.

Lets take a look a two losses. First gearbox losses then hydraulics and parasitic losses.

Referring to two accepted engineering design handbooks ("Machine Design Theory and Practice" by Deutschman and "Marks' Handbook for Mechanical Engineers") the accepted efficiency loss for a "typical manufacturing quality" gear mesh is 2%. Precision manufactured gear set loss is considered less than 1%. Using the 2% number, a PTO generator gear set transmitting approximately 10 KW will absorb (and have to dissipate) approximately 200 watts of energy. This heat will be dissipated through the gear case housing, the input and output shafts. I don't believe this is enough to power to make much of a delta T with the ambient air (a couple light bulbs - incandescent ones that is ).

Engine parasitic losses. All engines have parasitic losses resulting from accessories being driven (alternator, oil pump, etc) and internal losses such as windage. For that reason I don't think engine parasitic losses are very relevant to a standalone vs PTO comparison. Although I would agree engines can be designed to reduce parasitic losses (at a $ cost). What we are interested in is net engine HP.

What seems more relevant is the loss of power between the net engine output and the PTO output. The only info I have on hand for this comparison are the specs for the Massey GC2400/2600. Looking at the MF GC2400, the net engine power is 16.1 kW @2600 rpm. The PTO power is speced at 13.9 kW @ 2600 rpm (555 PTO rpm). So the power transmission loss from the engine output shaft to the PTO output shaft is 13.9/16.1 = 0.8634 or a loss of 13.66% (1-0.8634).

Therefore total transmission efficiency loss of this PTO driven setup is approximately 15.66% (13.66 + 2).

So if we look at a MF GC2400 running a 10KW PTO generator vs a 10KW standalone, the question becomes is the MF motor running at 2600 rpm 15.66% more fuel efficient than a standalone diesel running at 3600 rpm?

Well, the MF motor is clearly a "higher quality", higher cost motor running 1000 rpm slower. Does that make it 15% more fuel efficient? Unfortunately I don't have fuel consumption curves for any of these motors.

Can anyone add to this?

Edit: The MF numbers come from the '09 MF GC series Owner's Manual.

 

[SPYDERLK]

With the numbers being tossed about in this thread concerning gearbox losses, hydraulic losses, delta T, heat dissipated, etc, I think some reference-able information would be helpful.

Lets take a look a two losses. First gearbox losses then hydraulics and parasitic losses.

Referring to two accepted engineering design handbooks ("Machine Design Theory and Practice" by Deutschman and "Marks' Handbook for Mechanical Engineers") the accepted efficiency loss for a "typical manufacturing quality" gear mesh is 2%. Precision manufactured gear set loss is considered less than 1%. Using the 2% number, a PTO generator gear set transmitting approximately 10 KW will absorb (and have to dissipate) approximately 200 watts of energy. This heat will be dissipated through the gear case housing, the input and output shafts. I don't believe this is enough to power to make much of a delta T with the ambient air (a couple light bulbs - incandescent ones that is ).

Engine parasitic losses. All engines have parasitic losses resulting from accessories being driven (alternator, oil pump, etc) and internal losses such as windage. For that reason I don't think engine parasitic losses are very relevant to a standalone vs PTO comparison. Although I would agree engines can be designed to reduce parasitic losses (at a $ cost). What we are interested in is net engine HP.

What seems more relevant is the loss of power between the net engine output and the PTO output. The only info I have on hand for this comparison are the specs for the Massey GC2400/2600. Looking at the MF GC2400, the net engine power is 16.1 kW @2600 rpm. The PTO power is speced at 13.9 kW @ 2600 rpm (555 PTO rpm). So the power transmission loss from the engine output shaft to the PTO output shaft is 13.9/16.1 = 0.8634 or a loss of 13.66% (1-0.8634).

Therefore total transmission efficiency loss of this PTO driven setup is approximately 15.66% (13.66 + 2).

So if we look at a MF GC2400 running a 10KW PTO generator vs a 10KW standalone, the question becomes is the MF motor running at 2600 rpm 15.66% more fuel efficient than a standalone diesel running at 3600 rpm?

Well, the MF motor is clearly a "higher quality", higher cost motor running 1000 rpm slower. Does that make it 15% more fuel efficient? Unfortunately I don't have fuel consumption curves for any of these motors.

Can anyone add to this?

Edit: The MF numbers come from the '09 MF GC series Owner's Manual.

Yes. Ill have to subtract from it some tho. 1st bigger engines have more parasitic losses - more friction and pumping losses both in the cylinders and crankcase. Its a factor, but only a contributing one, as you say, less important than the power transfer losses
- Your gearset info is correct as far as it goes. What isnt said in your references is all the contributing parameters that are considered. To see only 2% loss in a gearset while seeing over 13% loss in a straight shot out the pto is fodder for quizzicality. I believe we would find that the 2% figure is possible only in a gearset in the 1:1 to 1:2 ratio range and that the gearset is being supplied perfect lubrication for it and its bearings. A light spray of oil is what is needed -too much and you add to losses. I can tell you from experience that my 12kW Northstar pto gen runs a very hot gearbox at just medium output - - the whole area in contact with the gearbox runs hot [front of gen and pto coupling] ... even after I broke it in and then switched to Mobil 1 gearoil. The issue?... 1:6 speed increase and more oil than needed. Badly non optimum...but the only help I could do is play with oiling and thats playing with fire if your not in a lab to exactly check effects real time.
My experience in testing heat input vs delta T in turbulent open air tells me this isnt a 2 or even 5% loss when I cant hold my hand on the gearbox of a gen outputting 4 or 5KW. Thats why I throw 10% in as a ballpark figure.
larry