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Old 07-13-2013, 02:19 AM   #201 (permalink)
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Originally Posted by IamIan View Post
Both systems have pros and cons ... neither is the best option for all situations ... pretending or claiming otherwise ... to me ... is just incorrect and too biased on one side.
Yep, agreed! All the range extending options for an EV discussed here have their pros & cons.

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Old 07-13-2013, 04:17 AM   #202 (permalink)
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Quote:
Originally Posted by IamIan View Post
Here I'll show you a few ... but there are others as well.

#1> Generator out-performs pusher.
Low SoC ... pull into rest stop to pee and eat ...

#2> Generator out-performs pusher.
Many Hours of Grid lock traffic on a 120+ degree day ... your EV as Air conditioning so you don't have a heat stroke ...

#3> Generator out-performs pusher.
House generator during a black out.
I'd add my biggest concern:

#4> Generator out-performs pusher.
In wet or otherwise limited traction conditions. Try to drive uphill with the pusher in rain or on dusty road...
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Old 07-14-2013, 01:35 PM   #203 (permalink)
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1. the pusher pushes regardless of the SOC. If you need to pass BSFC for more power in extreme circumstances then so what. No advantage of series here.

2. some measure of series when you add an alternator to pusher, can size for continuously running fans/compressors/lights, but pusher has most of the power go straight to the wheels. Series only has no measure of parallel, series loses.

3. It's a dessert topping, it's a floor cleaner, not relevant to the discussion of range extending, nor a typical situation requiring constant loss of efficiency. Not even sure the tzero generator makes 120v@60hz.

4. pusher = 4wd, series loses (and pusher has redundant powertrains)
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Old 07-14-2013, 02:42 PM   #204 (permalink)
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Quote:
Originally Posted by P-hack View Post
4. pusher = 4wd, series loses (and pusher has redundant powertrains)
4WD with two of the wheels aft of a flexible coupling, so what is that going to do on a slippery surface where there's little friction to resist sideways forces? Can you spell "jackknife"?
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Old 07-14-2013, 02:47 PM   #205 (permalink)
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@P-hack:
I don't know why you continue to try and defend the one sided biased ... any situation position ? ... it's incorrect.

Depending on the situation the pusher might be better ... and in different situations the generator will be better ... what is so bad about it depending on the situation?

Quote:
Originally Posted by P-hack View Post
1. the pusher pushes regardless of the SOC. If you need to pass BSFC for more power in extreme circumstances then so what. No advantage of series here.
As has been said.

Past a certain point in the BSFC the Pusher reaches a lower minimum efficiency from tank to road.

This is true to either more power or less power.

- - - - - -
as has also been said ... the inverse is a pro of the pusher ... it will have higher peak efficiency as the generator tops out sooner... but this does not remove the low efficiency situation from existence.

Quote:
Originally Posted by P-hack View Post
2. some measure of series when you add an alternator to pusher, can size for continuously running fans/compressors/lights, but pusher has most of the power go straight to the wheels. Series only has no measure of parallel, series loses.
Adding alternator to Pusher = Combined Pusher / Generator.

Thus it admits the situation where the generator is better than just the pusher.



( the guy in the 120+ degree hours of grid lock traffic will appreciate having the generator option for his Air Conditioning ... the guy next to him with only a pusher ( and no generator ) for his BEV doesn't have his and as he sweats into dehydration , will look enviously at the guy sitting comfortably with the generator. )

Quote:
Originally Posted by P-hack View Post
3. It's a dessert topping, it's a floor cleaner, not relevant to the discussion of range extending, nor a typical situation requiring constant loss of efficiency.
The current discussion left 'typical situation' when you went to the extreme of ... not in any situation ... post #198.

As long as you insist on trying to defend this absolute ... not in any situation ... position ... sorry , you're incorrect.

- - - - -
What is 'typical' will vary from person to person ... context to context ... and sense each does have pros and cons ... and sense neither one is the best in all cases ... depending on what that 'typical' is ... will determine which is the best fit ... it could be the pusher ... or it could be the generator.

Quote:
Originally Posted by P-hack View Post
Not even sure the tzero generator makes 120v@60hz.
It didn't ... it's generator was DC output.

But that doesn't effect the far more wide claim you made in Post #198 and continue to try and defend ... about what is ... inherent ... to the two systems ... DC output is not inherent to the generator ... it could have been wound as AC ... or I could already have DC appliances in my home to use the DC ... or I could use a DC-AC Inverter ... Those are all options that are not possible with just a stationary pusher... thus the pusher has less utility... and the generator will out perform it in that situation.

Quote:
Originally Posted by P-hack View Post
4. pusher = 4wd, series loses (and pusher has redundant powertrains)
All the wheel power the pusher makes will be limited to the friction it has from the 1,100 pound down force ... that was the weight of the pusher trailer referenced earlier in this thread.

The higher down force of the 3,100 pound BEV it is pushing will loose traction less than the 1,100 pound pusher trailer ... be it up hill or slippier surface ... As long as it is the Pusher that is doing the pushing ... zsnemeth is correct ... it's wheel will spin sooner than if wheels of the heavier BEV getting power from a 300 pound generator would.

- - - - -

#5> Pusher referenced = Increased Rolling Resistance
This does bring up another good point though ... the pusher trailer is heavier ... almost 4x heavier ... thus it will increase the net combined system rolling resistance more than the lighter generator would... thus more power will be needed to sustain any given speed , due to the increased rolling resistance.

In this case ... the proposed pusher would have about ~20% more rolling resistance... that might vary with other designs ... but it will be difficult to get the pusher weight bellow the generator ( without also picking up additional drive train losses as the pusher tries to deal with all vehicle speeds and loads. )

And if one tried to make the pusher trailer lighter to reduce this #5 con ... you only serve to increase the #4 con of having less down force for friction on pusher trailer wheels.
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Old 07-14-2013, 04:36 PM   #206 (permalink)
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Quote:
Originally Posted by IamIan View Post
@P-hack:
I don't know why you continue to try and defend the one sided biased ... any situation position ? ... it's incorrect.
I'm not saying pusher is better in terms of deflecting asteroids, or has more utility post apocalypse, I am talking about peak and overall efficiency, i.e. for long trips (or stop and go if designed for it). A good range extender should be treated like any other ecomod and get mpg similar to a vehicle with the same weight,rr,cda and why not enable hypermiling the pusher as the situation allows.

The auto-pushers are not examples of good ones in the efficiency sense, but they are superbly cost-effective and simple. But they are heavy and use oversized engines for the job of cruising, and etc. Since they are shortened cars (complete with alternator).

But the state of the art of electronics and motors and generators does not compare with mechanical linkages in terms of efficiently transmitting power to the wheels. Thus the more power flows directly to the wheels (efficiently) the more efficient the system. This is true at any reasonable speed. And a handful of gears is enough to keep the engine in the target efficiency rpm range, and the battery can load the engine while moving, again if that actually helps vs the losses "regen" incurs, the series is basically regen always except when demand = generator output.


Quote:
Originally Posted by IamIan View Post
Depending on the situation the pusher might be better ... and in different situations the generator will be better ... what is so bad about it depending on the situation?
Series only is good when stopped (taking a wiz), and that is basically idling, which is not a good efficiency strategy, ever.

Quote:
Originally Posted by IamIan View Post
Past a certain point in the BSFC the Pusher reaches a lower minimum efficiency from tank to road.
The options a generator has are to A. deplete the pack to keep the engine near bsfc, or B. go past bsfc (and upsize the generator). The pusher can also be locked via ratio/rpm selection and have the battery assist, or if the battery is dead as in your scenario, the pusher will have more power available beyond bsfc in a pinch. Peak bsfc is not peak horsepower, but we are talking about having let the pack run down completely. There is nothing inherently different about pusher vs generator except that a well engineered pusher has greater efficiency overall, not just peak.

Quote:
Originally Posted by IamIan View Post
This is true to either more power or less power.
true for the pusher as well as the generator, both have engine loading/unloading, rpm control strategy at their disposal.


Quote:
Originally Posted by IamIan View Post
Adding alternator to Pusher = Combined Pusher / Generator.

Thus it admits the situation where the generator is better than just the pusher.
I think some of both is best, but "mostly pusher" for efficiency. I'm kind of assuming that an EV with AC has electric AC and that a pusher (or generator) should handle lights/fans/whatnot. Of course the EV can work with the pusher and just use regen (hopefully efficient regen) to keep the battery from depleting completely. Some knowledge of your situation is essential for hypermiling such a system too. It is best to use what battery power you have even on a long trip, assuming you can recharge at your destination.

Quote:
Originally Posted by IamIan View Post
... it could be the pusher ... or it could be the generator.
I don't see how the generator is going to come out ahead in efficiency with so many losses in just getting the power to the wheels, and with no special techniques that are not also available to a pusher.


Quote:
Originally Posted by IamIan View Post
But that doesn't effect the far more wide claim you made in Post #198 and continue to try and defend
The situation is which is most efficient, that is all, which will turn the fuel in to miles covered being the best. Talking about powering a house isn't relevant. Because I can make up scenarios where you need to leave the house powered and leave with the car too.

Quote:
Originally Posted by IamIan View Post
All the wheel power the pusher makes will be limited to the friction it has from the 1,100 pound down force ... that was the weight of the pusher trailer referenced earlier in this thread.
Either way there will be more motive traction than a front wheel drive EV has by itself. But if you need more traction, spring load the pusher (or better yet, hydraulically add down force on demand), or move the weight forward (and add appropriate sway damping), or make it integral to the EV like putting a generator in the trunk.

Quote:
Originally Posted by IamIan View Post
The higher down force of the 3,100 pound BEV
you ignored some rather obvious solutions if it is even a problem for most people. Would like to focus on normal driving, not rock crawling either, like the 15,000 miles on roads that normal people use. Like so many SUVs that will never go offroad as much as my prius does. Determining "need" based on extremes is kinda futile. The t-zero is front wheel drive and would benefit from a push from the rear up this "slippery slope" anyway.

Quote:
Originally Posted by IamIan View Post
#5> Pusher referenced = Increased Rolling Resistance
This does bring up another good point though ... the pusher trailer is heavier
not an example of a good pusher for efficiency. A pusher that does not have all the efficiency losses of the generator system can have a smaller engine, and does not need a large generator (though a gearbox would be nice for efficiency at sub-hiway speeds), and it can carry less fuel for the same range.

Quote:
Originally Posted by IamIan View Post
In this case ... the proposed pusher
I'm not proposing that pusher except as a quick fix (though it is thoroughly robust and reliable), if you have a generator and charger and trailer laying about then why not try the generator approach? Some guys spent $75,000 on a generator powering a 1500lb $200,000 car and got 30-35mpg. Another guy spent a couple grand on a diesel rabbit pusher and got 25-30mpg behind a 3100lb rabbit.

I'm trying to comparing apples to apples, as well as one can, in terms of hypothetical innovative range extenders. Both can load/unload the engine with the battery, both have relatively independent speed vs rpm. Both are operated for maximum efficiency, both can downsize the engine. I don't see where the generator is going to be more efficient in locomotion, but lots of obvious cases where the pusher is.

Given how many EV's don't even have a gearbox, or even a neutral, I get the "dirty hands" feeling this must give you to even consider it, but physics are physics and our imaginations should not be limited by preconceptions.

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Old 07-14-2013, 05:53 PM   #207 (permalink)
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Quote:
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Determining "need" based on extremes is kinda futile.
Well said.
This is why we have people buying SUVs or pickup who drive around with empty beds on agressive AT tires who never go off road.
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Old 07-14-2013, 08:12 PM   #208 (permalink)
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Quote:
Originally Posted by P-hack View Post
But the state of the art of electronics and motors and generators does not compare with mechanical linkages in terms of efficiently transmitting power to the wheels.
You go too far again.

"does not compare" is correct ... but not in the way you think ... if we actually went "State of the Art" ... electronics , motors, and generators ... would trounce mechanical linkages in efficiency , power , size, weight.

My advise ... don't even open that "state of the art" door.

Quote:
Originally Posted by P-hack View Post
Series only is good when stopped (taking a wiz), and that is basically idling, which is not a good efficiency strategy, ever.
The "ever" part is going too far ... and is not correct.

Series vs Parallel is a whole other massive generalization , can of worms ... I suggest we stick with the more narrow ... pusher vs generator trailer currently being discussed.

Quote:
Originally Posted by P-hack View Post
There is nothing inherently different about pusher vs generator except that a well engineered pusher has greater efficiency overall, not just peak.
Still an incorrect over simplification.

Inherent Differences have been pointed out.

Errors of this overly broad claim have been pointed out.

Quote:
Originally Posted by P-hack View Post
I think some of both is best, but "mostly pusher" for efficiency. I'm kind of assuming that an EV with AC has electric AC and that a pusher (or generator) should handle lights/fans/whatnot. Of course the EV can work with the pusher and just use regen (hopefully efficient regen) to keep the battery from depleting completely. Some knowledge of your situation is essential for hypermiling such a system too. It is best to use what battery power you have even on a long trip, assuming you can recharge at your destination.

Holly crap ... progress

Quote:
Originally Posted by P-hack View Post
I don't see how the generator is going to come out ahead in efficiency with so many losses in just getting the power to the wheels, and with no special techniques that are not also available to a pusher.
I've already given you examples of it ... If something was not clear about them ask about it , and I will try and re-explain.

And ... there are techniques / options the generator has for efficiency that the pusher does not ... as I have already pointed out... if something about those was not clear ... ask, and I will try and re-explain.

Quote:
Originally Posted by P-hack View Post
The situation is which is most efficient, that is all, which will turn the fuel in to miles covered being the best. Talking about powering a house isn't relevant. Because I can make up scenarios where you need to leave the house powered and leave with the car too.

Give that man a cookie.
Situation determines which is the best fit.

Powering the house is 100% relevant if I ever want a generator to power my house... or work site power tools ... or a pizza oven at the beach ... etc.

Quote:
Originally Posted by P-hack View Post
Either way there will be more motive traction than a front wheel drive EV has by itself.
Situation dependent.

In the situation where the vehicle power can come from both the BEV and the trailer ... yes.

In the situation where the vehicle is being moved only by the power output from the trailer ... no.

In the situation where the Heavier BEV tires are not slipping but the lighter Pusher Trailer tires are slipping ... no.

etc.

Quote:
Originally Posted by P-hack View Post
But if you need more traction, spring load the pusher (or better yet, hydraulically add down force on demand), or move the weight forward (and add appropriate sway damping),
Action has opposite reaction.
The spring or hydraulics that pushes down the trailer will lift the rear wheels of the forward , being pushed by the same force ... lifting the point of connection is a VERY bad idea ... especially where that same point of connection can move side to side as a trailer connection does... this is very unsafe.( sway dampen or not)

Moving weight forward won't help ... the trailer's total weight is less ... it's tires will slip at less torque than the heavier BEV tires will.

Quote:
Originally Posted by P-hack View Post
or make it integral to the EV like putting a generator in the trunk.
If you are going to skip the trailer idea completely ... than sure you're a PHEV ... and that different situation then has a different result.

Quote:
Originally Posted by P-hack View Post
you ignored some rather obvious solutions if it is even a problem for most people. Would like to focus on normal driving, not rock crawling either, like the 15,000 miles on roads that normal people use. Like so many SUVs that will never go offroad as much as my prius does. Determining "need" based on extremes is kinda futile.
Another Cookie.
Situation matters ... if your situation doesn't need off road ... another vehicle without that feature may be a better fit for you... but if your situation does need off road ... then it does.

I am not determining need based on extremes ... I have consistently and repeatedly pointed that either the pusher or the generator could be the better fit depending on the situation ... you've been fighting against me on this... I refuse to go one sided biased either Always A , or Always B ... that would be incorrect.

Quote:
Originally Posted by P-hack View Post
not an example of a good pusher for efficiency. A pusher that does not have all the efficiency losses of the generator system can have a smaller engine, and does not need a large generator (though a gearbox would be nice for efficiency at sub-hiway speeds), and it can carry less fuel for the same range.
It was the example you were holding up... if you want to hold up an example of a better real world pusher ... go ahead, be my guest.

Nice theory. ... but unfortunately ... this comes back again ... depends on the situation... in some situations A > B ... others it's B>A .

Quote:
Originally Posted by P-hack View Post
I'm not proposing that pusher except as a quick fix (though it is thoroughly robust and reliable), if you have a generator and charger and trailer laying about then why not try the generator approach?


Quote:
Originally Posted by P-hack View Post
I'm trying to comparing apples to apples, as well as one can, in terms of hypothetical innovative range extenders. Both can load/unload the engine with the battery, both have relatively independent speed vs rpm. Both are operated for maximum efficiency, both can downsize the engine. I don't see where the generator is going to be more efficient in locomotion, but lots of obvious cases where the pusher is.
I've pointed some situations out for you already.

Quote:
Originally Posted by P-hack View Post
Given how many EV's don't even have a gearbox, or even a neutral, I get the "dirty hands" feeling this must give you to even consider it, but physics are physics and our imaginations should not be limited by preconceptions.
Many EVs don't even have gear boxes ... for a good reason.

The electric motors are not as negatively effected for efficiency and for power as ICE engines are ... as the wheel RPM and Torque changes.

I don't have any problem at all considering the pusher ... I have already posted several times ... there are situations where it will be the better option ... but I have refused to do is pretend it is one sided and always ___ is the better option ... it isn't.

Being aware of the pros and cons of both ... is the better option ... it allows the actual best device for the situation to be used... and not incorrectly assuming one is always better than the other.
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Old 07-14-2013, 09:50 PM   #209 (permalink)
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Quote:
Originally Posted by P-hack View Post
I'm not proposing that pusher except as a quick fix (though it is thoroughly robust and reliable), if you have a generator and charger and trailer laying about then why not try the generator approach? Some guys spent $75,000 on a generator powering a 1500lb $200,000 car and got 30-35mpg. Another guy spent a couple grand on a diesel rabbit pusher and got 25-30mpg behind a 3100lb rabbit.

I'm trying to comparing apples to apples, as well as one can, in terms of hypothetical innovative range extenders. Both can load/unload the engine with the battery, both have relatively independent speed vs rpm. Both are operated for maximum efficiency, both can downsize the engine. I don't see where the generator is going to be more efficient in locomotion, but lots of obvious cases where the pusher is.
Comparing a commercially built genset along with a very unique handmade (and therefore rather expensive) EV to a self-built pusher with a run-of-the-mill production car converted to EV does not strike me as "apples-to-apples". I suspect that there are several on this board that could build a genset trailer for a production car EV conversion which can be as efficient (if not more efficient) than the 500cc gasoline Kawasaki motorcycle engine used with the tzero EV. And if they're already going to be DIY'ing the solution, then certainly they could drive the motors directly from the generator, making pulse&glide an interesting variation from an ICE counterpart... pulse using electric power generated directly from the genset and then (when gliding (without regen)) the genset can be charging the batt pack. Any time one would leave the ICE in gear when coasting (for DFCO), the EV can be using regen plus the genset for charging. Maybe (?) not as efficient as the ICE pusher, but I believe the range of options are there, just as they are for a pusher. And of course, as noted by redpoint5, there's no reason the genset even needs to be on a trailer (depends on the owner's willingness to heft the components up to hitch height).

That's not to say a pusher couldn't also be improved over Mr. Sharkey's implementation. Right-sizing the engine, spring-loading the trailer to help with traction, making the trailer more aero and with lower rolling resistance, etc all could help in making that combination more efficient as well.

It really does depend on the EV owner's situation and skills (as IamIan implies); I'm not seeing the obvious advantage of efficiency between a well built (and therefore better than gasoline motorcycle engine) genset (which is integrated as well as possible into the EV) and a well built pusher (which is integrated as well as possible into the EV).
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Old 07-15-2013, 12:42 AM   #210 (permalink)
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I can't explain it any better, engine to wheels efficiency in the 90s (high 90s with some optimizing) for direct drive, with experienced hypermilers showing us how to get stellar mileage out of even a basic 5 speed taking full advantage of changes in situation. I can easily imagine a pusher trailer that can also be hypermiled or "right sized".

Show me the efficient generator trailer, not the pipe dream.

here is a modern tdi:


1. motors are not always at peak efficiency.
A. generally not efficient at slow speed, starting at about 0% efficient at very low rpm. No gear box means more time spent at low rpm, so lots of time at slow speeds the generator is at more of disadvantage since that is how the power flows to the wheels.

B. efficiency is still largely load dependent. Peaking around 90-95%

2. Controllers are not %100 efficient, say %90 (large heat sinks)

3. The generator has losses going from mechanical to electrical, like %80 efficient.

4. driveline losses, say %95 efficient.


These are just swags, but let me total them up for this example so we have at least a starting point. Lets say demand is optimal.

.95 * .90 * .80 * .95 = 0.65 efficient in steady state mode with optimum load.

compared to a tdi that is %95 efficient (assuming some effort in driveline optimization) at driving the wheels under optimum conditions.

Now if you want to use "peak bsfc" as your argument, we are assuming peak bsfc in both "pusher" and "generator" here.

But if the tdi direct drive has to "compete" with the generator, the "at the wheels" bsfc for the tdi is like 206 gm/kwh. Whereas the same efficient engine running a generator is like 301 gm/kwh.

So lets play the load the battery for peak bsfc game now, but first note that pretty much any operating condition above 3 bar will be to the advantage of the direct drive in this graph already.

5. lithium batteries are 80%-90% in charge/discharge efficient under optimal conditions.

6. Say you have a %90 efficient charger and bms, which is also dependent on state of charge and current.

So aside from the fact that you can't ever touch most of the bsfc graph with a generator in front of this tdi driving the wheels, you are looking at a generator efficiency of
.65 * .90 *.90 = 53% efficient when loading the generator for bsfc (assuming all the electrical are in a fairly optimal operating range). That is a wheel bsfc of 369, below the very bottom line on the bsfc chart.

Now you may take issue with the specific numbers here, but the point is clear, there are a lot of losses in the series proposal.

I have heard speculation about higher peak BSFC with rpm targeting but I have never seen any actual data, nor do I know that a cvt wouldn't still be more efficient than an "electronic torque converter" in maintaining target rpm.

Sending all your ICE power through a generator to drive your EV wheels certainly seems like an inefficient solution all around, and requires %54 more engine in steady state for the same power at the wheels in this example.

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