[IamIan]

Originally Posted by NachtRitter

Honestly, I have no idea what you are trying to say here.

1 mile is not a specific amount of joules ... 1 mile going up hill is the same 1 mile distance as 1 mile going down hill ... but there is a massive difference in the joules of energy... 1 mile at 80MPH is not the same joules as 1 mile at 8MPH ... 1 mile at 50degrees F is not the same joules as 1 mile at 100 degrees F.

When the question is about efficiency ... MPG is a poor metric to use ... % in vs out ... is better.

If given all the various variables that change and effect the total sum number of joules to travel a given __ miles ... than that is the total joules needed to go that miles under those conditions ... if I get those joules from fuel to road at 30% efficiency ... that is better than 29% efficiency ... and it is better no matter what the joules are for the ___ Miles you traveled ... no matter how much the joules change per each individual mile.

Originally Posted by NachtRitter

There is no entirely off-the-shelf solution for either option.

Exactly.

Originally Posted by NachtRitter

Here, I'm not clear if we're talking about the same thing. You're saying that the generator can run at peak efficiency more often than the pusher can run at peak efficiency, right?

Not quiet.

I'm saying the situation will determine which one ... the pusher ... or the generator ... is able to net better efficiency levels.

The Pusher has a higher Peak Efficiency for part of it's BSFC operating range... If the situation allows the pusher to stay in that range ... than the pusher is more efficient.

If the situation forces the Pusher ICE into the part of it's operation that the Generator is more efficient ... than the generator is more efficient.

Which one is net more efficient will depend on the situation ... without knowing the situation ... you don't know the situation ... which would mean you can't know what which one pusher or generator is more net efficient.

Originally Posted by NachtRitter

To me that doesn't mean anything because the peak efficiency of a generator may not be as good as the peak efficiency of a pusher...

It isn't in the example at hand ... the pusher has a higher peak efficiency ... when the situation allows for it to operate in that range ... it is the more efficient option.

But ... without knowing the situation ... you can't know how often the pusher would be in what parts of it's efficiency band.

Originally Posted by NachtRitter

To me, the more efficient solution is the one that gets me farther on a gallon of diesel, and as I've shown, the diesel generators which can keep up with the EV's energy consumption at 65mph will get me only a fraction of the distance on a gallon of gasoline compared to the pusher.

Yes ... and that is one situation with that result.

A different situation gives a different result ... I prefer the situation I gave which uses the same ICE for both the pusher and the generator ... it is a more apples to apples comparison than using different ICEs.

Originally Posted by NachtRitter

Even if we where to assume that the exact same diesel engine, the VW TDI engine, is being used for the pusher as for the generator, I really do not know that the TDI has enough horsepower to run a 20+ kW electric generator, or that the TDI's peak efficiency RPM aligns with the electric generator's peak output rpm. For example, a 2-pole generator must run at 3600RPM to output 60Hz; a 4-pole generator must run at 1800RPM to output 60Hz. Neither of those RPMs fall in the TDI's peak efficiency spot on the BSFC chart.

Exactly.
That is the other part of the situation ... the components being used.

I already posted previously when using the crappy ,outdated , intentionally low efficient devices that P-Hack pulled numbers from thin air for ... that it makes for an entirely different situation.

Because he designed it to be significantly less efficient it would create a much larger gap between the Pusher and the Generator ... which would mean the operational situations would favor the pusher a larger % of the time.

But this equipment side of the ... situation ... is still part of my claim ... that which one is more efficient depends on the situation... not just that one is a pusher and the other a generator.

Originally Posted by NachtRitter

We also have to be talking about the same range extending capabilities for the generator as the pusher...

That is included.

Either the average joules output to the road can keep up with the average load or it can't ... true for either the generator or the pusher.

If either one can't than it is not keeping pace... true for either one.

When the situation allows for the Pusher to be a net of say 5% more efficient ... than it would allow for the pusher to apply 5% more joules toward travel than the generator ... If the joules per mile stays the same ... than that is 5% more distance.

Originally Posted by NachtRitter

As noted, even at peak efficiency, constant load, a typical off-the-shelf 20kW will consume more gph than the TDI pusher running at 65mph...

And as I wrote above:

#1> I preffer the more apples to apples comparison of using the same ICE for both the pusher and the generator.

#2> If you want off the shelf generator ... than for apples to apples ... show me the off the shelf pusher... as you posted before ... neither of these will be off the shelf devices ... as such I don't see the apples to apples for try to only require the generator to be off the shelf and not the pusher.

#3> The different situation you put together ... is a 100% valid justification for my position that the situation will determine the winner.

Originally Posted by NachtRitter

If you hook the genset directly to the motors (without the super-fancy customization mentioned by jamesqf) in order to bypass the battery charging losses, your genset load will vary (e.g. constant RPM, but varying torque) as the electric motor's load varies...

Nope ...

#1> The hit to efficiency for the electric motor to vary in load is much smaller ... than the hit for the ICE to vary in load ... which is an asset for the generator , not the pusher.

#2> The load doesn't have to vary if the surplus is cycled through the BEV battery ... which brings us back to the blue line on the BSFC ... to give us an idea of under what situations the pusher will be more efficient.

Originally Posted by NachtRitter

All I saw is that you pointed to a BSFC chart for a TDI... Not a BSFC chart for a generator (one which can compensate for the power consumed by the EV), and not a comparison of BSFC between the TDI and the generator.

It's included together as one ... and for a better apples to apples comparison it is the same ICE used in both cases.

See the red and blue lines indicating the transition points.

Originally Posted by NachtRitter

Generally, you can't run a generator at any RPM you choose; you have to run it at a specific RPM to get the specific AC frequency which means that the BSFC chart for an automotive engine is likely invalid for a generator engine.

Except getting a specific AC frequency directly from the generator is not needed... and motors can be wound differently ... but , that is why a motor controller is used ... to convert the electricity from form A to form B ... and the modern types of those electronics have high efficiency rates ... the Prius's goes over 99% efficiency.

The BSFC is 100% valid for any discussions about that engines efficiency... weather it is used for a generator or it is used for a pusher... the BSFC defies where that engine will be what % efficient from fuel to shaft.

Originally Posted by NachtRitter

As well, just looking at the BSFC chart does not tell the whole story...

Agreed.

We also need to know what the rest of the situation is... then we can see how the operation lines up with those BSFC points.

Originally Posted by NachtRitter

in order to get the whole story of how the gallon of fuel that you put into the generator (the energy input) gets converted to some distance traveled at 65mph (the energy output), you must include the vehicle... because that absolutely does matter. It's the same with the pusher...

65mph is NOT energy output ... 65MPH up hill or down hill ... head wind or tail wind ... 100C or 0C ... etc ... etc ... speed does not define energy.

Red added ... And that is exactly why you don't need to include the vehicle at all.

The vehicle that we would be connecting this trailer to ... be it pusher or generator ... that is the same vehicle ... it will have the same aerodynamics ... the same rolling resistance ... the same gravitational effects on hills ... etc.

Originally Posted by NachtRitter

ignoring the rest of the system makes the knowledge of how much power the pusher engine creates entirely useless information.

It wasn't ignored ... the relevant pieces were already included to get the red and blue lines.

Originally Posted by NachtRitter

On the other hand, I looked at how far each solution can take me on a gallon of fuel, and found no situation where a generator will take me further than a pusher... even assuming no efficiency-related modifications on the pusher and genset-specific modifications to the EV (such as modifying the charger to accept a 20kW charge vs 6.6kW). If you could point out any flaws in my approach, please do.

I already have pointed out several ... I'll give highlights again:

#1> Apples to Apples ICE.
#2> Apples to Apples , Off the shelf vs custom.
#3> BSFC efficiency areas previously indicated in red and blue.
#4> Leaf has OEM ability to take up to ~60kw fast charge rate.
#5> If doing custom already , OEM limits don't apply.
#6> x miles do not define the amount of energy ( without knowing the situation )
#7> Gallons/Hour limit for __ Hours doesn't tell you efficiency.
#8> MPG doesn't tell you efficiency.
#9> Transmissions have limits
#10> Magnitude of the effect Load Variation has on the Pusher vs the Generator.

Originally Posted by NachtRitter

I don't believe we know that the same ICE even has the ability to run an electric generator with sufficient output to offset the consumption of our sample EV at 65mph. I searched and found no examples of a 4cyl TDI being used in this way.

#1> These aren't Off the shelf options ... so it is unlikely to find previous examples from searches.

#2> That would entirely depend on the situation of that 65MPH... in order to know even what that converts to in terms of kw of power.

#3> The vehicle may not always be traveling at 65MPH ... like if it hits grid lock traffic.... again situation dependent.

#4> The BSFC can be used to calculate the power output at any point on that BSFC... The Power output gap for the generator will line up with the red and blue lines on the BSFC ... because they are based on % efficiency ... They can be equally used for kw of power or kwh of energy.

#5> If the ICE chosen is not able to output the desired power for both situations Pusher / Generator ... it would be best for a Apples to Apples comparison to look for a single ICE that can do that.

Originally Posted by NachtRitter

I haven't researched that, but it is a valid point. However, even in this case I do not believe we can assume that the genset wins.

Agreed ... and my point exactly.

I'm the one advocating for no default assumption of winner ... not the generator ... not the pusher.

My consistent position the whole time has been ... which one will win ... depends on the situation... for some reason people are arguing against that ... as if the situation makes no difference at all ... and that is known to be incorrect.

Originally Posted by NachtRitter

Yes, I mentioned that, and now we're talking about a generator that is twice as heavy as the pusher, consumes over two times as much fuel per mile, and costs in the range of 10x as much.

Only in the situation you described ... the heavier , more consumption , etc.

Not black and white in the situation I described.

Just like the intentionally low efficiency devices would give a different situation.

And ... all of that is exactly as I have been consistently claiming the whole time ... different situation will give different results.

Originally Posted by NachtRitter

Errr... I'm not sure I get your point... if you need 14kW real time and have only a 12kW generator, then you're drawing an extra 2kW from the batteries... so what?

I was actually pointing out the opposite ... 12 kw generator output ... 10kw load needed ... would result in 2kw to the batteries.

Two points:

#1> The amount going through the batteries does not have to be the amount used by the vehicle ... as was suggested in some other situations.

#2> the 10kw that don't cycle through the battery effect the efficiency burden of the Pusher ICE in order to be better ... see red and blue lines.

Originally Posted by NachtRitter

As I've pointed out many times, the Leaf consumes ~20kWH every hour (on average) when traveling at 65mph. If that's our baseline, and our goal is to extend the range of the EV as far as we want to go, then the generator must be sized to at least offset the consumption... so it has to be at least 20kW. A 20kW generator consumes more fuel per mile than the pusher... so in this situation, the genset still looses.

Yes exactly my point.

In that situation ... you outlined ... the pusher wins.
The pusher also wins with the intentionally low efficiency devices.
The pusher also wins if it can be operating the majority of the time inside the red on the BSFC.

And in a different situation ... as I described previously ... the generator wins.

Thus ... my position ... that which one will win ... depends on the situation.

Originally Posted by NachtRitter

So, still no situation in sight where the genset outperforms the pusher from an efficiency perspective.

Incorrect ... from a efficiency perceptive ... see previous red and blue on BSFC.

Originally Posted by NachtRitter

Pointing to the TDI BSFC chart doesn't give us a fuel tank to miles traveled number for either the pusher or the generator.

#1> It does actually tell you the areas of transition where the pusher is more efficient and where the generator is more efficient... see red and blue lines.

#2> The reason it doesn't give you a miles ... is because x miles by itself does not define a specific amount of energy.

#3> If you assume some specific situation ... that would give some specific amount of energy per mile ... as you did with your 20kwh@65MPH ... than you have the information needed to go between the BSFC and that assumed situation.

Originally Posted by NachtRitter

Saying that the pusher is "less efficient outside the blue area" of the BSFC chart doesn't tell me anything without knowing how that translates to number of miles traveled for that gallon of fuel...

#1> But it does clearly define what I was describing... and the points where the efficiency transition happens from pushed favored to generator favored.

#2> If you are able to define the situation of those miles ... than you are able to translate between the miles and the BSFC indication.

Originally Posted by NachtRitter

and that would be based on what percentage of time (or miles) you expect the pusher to be outside the blue area... and how that compares to a genset approach under the same conditions.

Exactly.

You would have to define the situation ... in order to know which one will net better efficiency.

Just because the pusher might have dipped outside the blue for 1 second or 1 minute ... does not mean it would net less efficient ... the situation would determine how far it dipped and for how long ... etc.

Originally Posted by NachtRitter

I ask again... is there a real world scenario you can provide where a genset outperforms a pusher? Painting lines on a BSFC chart does not give the whole picture, so pointing to it again won't answer the question.

We do need to look at the summary the red and blue lines show us on the BSFC in order to be able to predict the situations were the pusher would be more efficient ... or as you asked ... where the generator would be more efficient.

When we do that ... we see two gap trends... one based on RPM , the other based on load.

At lower RPMs ... under ~1,250 ... the Generator can pull ahead of the Pusher ... which in the real world would be times of either slow speed ... or times of pulling out from a stop ... like in stop and go traffic... exactly how slow would depend on the limits of the specific transmission used ... but that is the trend for RPM.

At Lower Torque ... under ~7 Bar ... the Generator can pull ahead of the Pusher ... which in the real world would be times of lower than peak load conditions ... cruising on flat level terrain , etc ... Exactly how fast would depend on other variables ... but that is the trend for torque.

If the situation allows for the pusher to stay in the red area enough ... it will be more efficient... if for example the power requirements are large enough to allow the pusher to stay in the red area allot.

Of course a different situation for the pusher or the generator devices , would change that ... as we saw with the different situation you pulled together ... or the different situation for the unusually low efficiency devices.

Are those situation trends sufficiently descriptive ??? or do you want to get into the specifics of:
aerodynamics, rolling resistance, gravitational incline, average driver dynamics, travel traffic patterns, weather patterns, etc... etc.