The problem with series hybrids

[cfg83]

dcb -

Originally Posted by dcb

I am really just saying that there are energy conversion losses from the ICE in a series hybrid that a parallel hybrid does not have to endure, and in the "range extender" mode these will be magnified.

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series gets the hype for convenience of implementation, you do not have to think about driveline issues, but there are real conversion losses which rarely get addressed and are presented as their optimal values when they are. if a motor is 80-90 % efficient, and a generator is 80%-90% you have a worst case of a %64 efficient ICE driveline and a best of .81 for series.

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I have no problem with that benefit. If this makes a series hybrid forward-compatible to different energy production/storage solutions, ICE or otherwise, then that's great. I like the idea of a factory being able to retool faster to take advantage of technology X. We can't get smaller engines in the USA, but I can imagine smaller and/or diesel implementations of the Volt when it is sold as an Opel Ampera.

Ha ha, it would make our lives easier when we want to swap in a Kubota diesel, .

CarloSW2

[user removed]

Q. MECH, assume you are operating a vehicle at a constant speed and load, with an ICE that has a 98% efficient transmission that is cheap and lightweight, and the engine is operating at bsfc. Lets assume a fairly clean design and the engine only needs to put out 15hp to cruise @55 mph.

It isn't directly relevant to the question, but this is where the bar for peak parallel/direct drive efficiency is at and these are not part of the variables for this question.

Can you give accurate assessments of how converting this relatively constant speed/load operation to a hydraulic will affect:
1. efficiency, in terms of how much power leaving the engine shaft gets to the wheels.
2. weight at the efficiency.
3. cost that weight/efficiency
4. additional space needed in cubic feet to house the components at that weight/cost/efficiency/no word games/ etc.

Also I would say the assume you have a hydraulic transformer in there (you neglected to mention its efficiency) if you wish to also claim the benefits of having a hydraulic system, but I don't care about storage right now, we will come to that, but it isn't a factor in extended constant load/speed operation.[/QUOTE]

Your example is a vehicle that requires 15 HP to maintain 55 MPH with 2% losses through the transmission, and the engine is operating at max BSFC.

Not sure any vehicle exists that meets that criteria, especially with 2% losses from engine to the tires, which reflects all losses. Maybe your word game?

Theoretical max efficiency for the hh would be 89% of the engine power to the wheels. Same for regeneration.

According to EPA and other sources the best powertrains (engine to tire) are about 85% give or take. In fact their web site quotes 70%.

Their figure is 18.2% of potential energy from engine and 12.6% of that available at the rear wheels, 30% losses, far different from 2%.

Weight at the efficiency. The Innas design is quoted as weight neutral. Mine is weight negative, meaning it would weigh less than what it is replacing. Not knowing the weight of your proposed configuration makes a direct comparison impossible. Best answer I can give you without specifics of your base design.

Same or less would be my rough answer without more details from you.

Cost that weight and efficiency?

In mass volume production on assemble line, half of the cost of the replaced and no longer necessary components.

Less volume than what is eliminated, probably 50% less.


http://www.fueleconomy.gov/FEG/atv.shtml

Show me a 2% loss powertrain, this link is 15 times greater losses than your quote.

regards
Mech

[dcb]

ok, so how much efficiency are we really talking about for hh transmission? if theoretical max is 89%, that is probably the unobtanium version that costs a bajillion dollars.

is it safe to say that after high pressure seals and internal leakage/etc that 80% is a more realistic?

how much does an 80% efficient hh cost initially and weigh that can transmit 15 hp on the output shaft?

[dcb]

Originally Posted by cfg83

I have no problem with that benefit.

I've described a parallel range extender attachment that slides into something like a tow receiver hitch on your ev, that has better peak efficiency by far than a series arrangement ever will. It certainly doesn't preclude us MODDERS from doing it with a diesel or whatever.

[user removed]

The cost to produce each wheel motor would be about the same as the cost of producing the brake assembly it replaces. Actual manufacturing costs in mass production on a dedicated assembly line $100 per unit.

That does not consider the cost of all the rest of the power train components that are eliminated, several hundred parts per vehicle. Costs, thousands of dollars.

A decent accumulator of 5 gallons capacity brand new is about 1k retail. Cost to manufacture is probably $300.

Low pressure accumulator is very low cost.

High strength seamless steel pipe with an 1/8 th inch wall thickness can handle almost 3000 PSI with ample reserve capacity. That's not very heavy parts in each wheel drive.
The drive pistons can also be hollow.

Now if you want to get expensive then make the accumulator 12,000 PSI, and the energy density increases by 400%, but it really is not necessary, cost effective, or a significant weight savings considering the weight of the whole vehicle.

In fact you could build the whole power train including a decent power engine and not weigh a lot more than the transmission and transfer case assembly on a Nissan D21 4 wheel drive pickup.

About 500 pounds for the complete power train including the brakes.

Here is a drawing from the as yet unpublished patent.

Notice the two bearings and the axle and hub. Those components are necessary even if it was just a trailer axle. The cylinders and pistons as well as the adjustable journal are the additional components that constitute the complete IVT wheel drive. External hydraulic actuation of the journal changes the stroke position.

This drive should approach 94% efficiency by itself, possibly higher, maybe even 97%. No way to tell until you have actually built and tested one.

Virginia Tech calculated the horsepower and torque at 35 HP and 380 pounds feet of torque, per wheel from 0 speed, comparable to an electric motor of substantial size.

regards
Mech

[dcb]

ok, my incongruity alarm just went off.

how did we go from 89% theoretical max efficiency to %94-%97? Are you mixing energy storage back in already when I'm trying to isolate the variables?

[user removed]

Originally Posted by dcb

ok, so how much efficiency are we really talking about for hh transmission? if theoretical max is 89%, that is probably the unobtanium version that costs a bajillion dollars.

is it safe to say that after high pressure seals and internal leakage/etc that 80% is a more realistic?

how much does an 80% efficient hh cost initially and weigh that can transmit 15 hp on the output shaft?

Transmission alone 93-95%. The 89% was wheel to accumulator back to wheel. Best accumulators are 99%.

95X99X95=89.3475%

Next energy told me anything above 80% was gravy, they were at 78% 3 years ago.

Efficiency would be highest from a dead stop and drop off slightly at higher speeds.

regards
Gary

[user removed]

Originally Posted by dcb

ok, my incongruity alarm just went off.

how did we go from 89% theoretical max efficiency to %94-%97? Are you mixing energy storage back in already when I'm trying to isolate the variables?

The 89% was wheel to accumulator and back to wheel. 3 steps including all compounding of losses.

Here is the EPA efficiency figures for the pump and motor. Not the same design, so I could not tell you my figures are absolute without testing of a functional prototype.

This is a wheel to wheel energy flow chart. I think its ten years old and the figures are averages over pump RPM ranges far higher than my setup would ever see unless the vehicle was going 180 MPH.

regards
Mech

[dcb]

allright, that pic describes something that would be ~87 efficient in a series role as a transmission, but doesn't include hydraulic "gear" ratio changes, which is why you would bother with anything but a chain and sprocket in the first place.

ok, so I haven't seen this exact picture anywhere yet (that's your job), but it sounds like you have for comparisons sake:

an ICE driving a constant volume pump

a high pressure accumulator

a low pressure accumulator

plumbing/hoses of sufficient diameter to not incur pressure drop (the fluid DOES flow in this system despite your previous statement that it doesnt, or else you need to draw a picture)

4 floaty cup glorified bent axis variable displacement motors, one at each wheel.

Is that correct so far?

[user removed]

Fluid does not flow unless work is being done. Fluid must flow for work to be done.
That is in my design.

The INNAS design does not have variable displacement in their wheel motor-pumps, so In THEIR design fluid always flows, even when no work is being done, so it should be less efficient.

Here is a pic of my functional (but fixed displacement) prototype running on 120 PSI shop air. You can see how fast it is spinning and my hand gives you an idea of the size.

http://www.youtube.com/user/Ride122609

I had it made from scratch. It normally has a cover that seals off the internals. You can see what it looks like if your freeze the video in the last couple of seconds, or just look at the other video where it spins slowly on the air in a small pancake compressor with the compressor shut off running only on the air reserve.

The details of the stroke adjustment feature are somewhat secret, until I can file provisional applications for any future improvements. If I disclose those future conceptional developments before filing a provisional application then they become a part of the public domain and I can never get them patented. That's the way patent law works, an it limits the extent of my disclosure.

regards
Mech