Parallel Hybrids

[NeilBlanchard]

The challenge with hydraulics is that it is a closed system - the only way to get energy into it is still with liquid fuel, and it still involves a heat engine; which are inherently inefficient.

Electricity is pure energy and it can come from renewable sources, external to the car and it is readily transferable. So while each system has challenges, electricity has several large advantages.

[P-hack]

The point is to have better regen. And hybrids are not required to be plug in, though you can add a battery and motor if you like, maybe the rear wheels regen electric too, but hydraulic should be primarily for braking if it works out.

Re capturing 80% would be huge, but I don't know what engineering compromises are in play with that figure.

[NeilBlanchard]

Having better coasting with no idling is more important to high efficiency. If you accelerate less, and then coast, and only use regen to slow down, then that is better overall.

The thing we are all most concerned about is the amount of energy we have to put into the car, right? If you put in electricity mainly, then that is good because it can come from renewable sources.

Unless you can pressurize the accumulator in an hydraulic hybrid and do that with renewable electricity, then you are forced to only use liquid fuels - and these by definition are limited to 25-35% efficiency.

[redpoint5]

While I'm not familiar with the construction of hydraulic systems, I don't see myself benefiting from them as much as other technologies because I rarely use my brakes, even in stop and go traffic.

Where the technology would shine is a system that Old Mech(?) describes that turns the ICE on and runs at most efficient BSFC charging the hydraulic system, and then shuts off while that system maintains speed.

The whole idea of hybrids is to minimize modes of operation that are non-ideal. Those modes for an ICE being idling, partial throttle, and open loop. Unfortunately, those modes are the large majority of what an ICE spends time doing.

[freebeard]

Originally Posted by P-hack

Re capturing 80% would be huge, but I don't know what engineering compromises are in play with that figure.

If you haven't yet, sit through

Edison 2's Oliver Kuttner's talk at Google

They won the X-Prize with an ICE. He covers your question a 3:00-5:00 (it's 30% of 80%), but it's all fascinating.

So, pure liquid fuel or pure electric. Hybrids are like E-85, as compared to a good idea. Having said that though, I'm partial to the Scuderi Engine.

Part of the deal is with an air tank in the interconnect passage you have an ICE, a Kinetic Energy recovery subsystem and a compressed air only mode for moving it ariound the yard or urban centers. Without a lot of added parts count.

[P-hack]

interesting to note that they did the generator series thing on an electric version and got 44 mpg, when they were getting 103-109,129 mpg in the gas version @ about 7:55. 44lb 2kw generator.

[IamIan]

Originally Posted by NeilBlanchard

Having better coasting with no idling is more important to high efficiency. If you accelerate less, and then coast, and only use regen to slow down, then that is better overall.

The only caveat I would add.
It is important to remember the source of the vehicles applied energy.

Coasting is not a source of energy ... it is consuming the kinetic energy that the engine / motor ... already applied to the vehicle to get it to any given speed / position.

The energy that the engine / motor applied to the vehicle to invest in that amount of kinetic energy / location ... that was done at some ___% efficiency of that motor / engine.

That initial __% of the motor/engine ... that applied the fuel energy to the vehicle ... is the max efficiency % ... all other down stream effects only reduce the final net vehicle __% ... to some value bellow that initial __% Motor/Engine conversion efficiency.

Coasting is useful ... As a Engine/Motor control strategy to avoid the low efficiency operating situations of that engine/motor.

But like everything else ... there are pros and cons.

Using coasting as a motor/engine efficiency optimization strategy means one is introducing variable vehicle speed into the equation ... and variable vehicle speed is a aerodynamic penalty... meaning it causes the vehicle to need more joules of energy ... to travel the same distance in otherwise the same conditions , average speed , weather , etc.

Thankfully ... at least for most ICE based designs ... there is a significant gap in the magnitude between ICE efficiency variation and the imposed aerodynamic penalty.

But ... you don't get something for nothing , with coasting ... so keeping in mind the pros and cons ... can be useful.

[P-hack]

being able to coast efficiently would be worth the (relatively simple) complexity it takes for me. But in most congested driving I find traffic more accepting of slower acceleration (whaddayagonnado?) than of slower deceleration, so more efficient regen is useful IMHO.

Also, not sure you noticed the relatively poor performance of the series generator there in my previous post there Ian/Neil. Same basic car, probably some extra weight in the electric version though, but still the gas version of the car simply crushes it MPG wise (44 mpg vs 100+mpg). Please take note, it is always nice to have real world examples.

[IamIan]

Originally Posted by P-hack

Also, not sure you noticed the relatively poor performance of the series generator there in my previous post there Ian/Neil. Same basic car, probably some extra weight in the electric version though, but still the gas version of the car simply crushes it MPG wise (44 mpg vs 100+mpg). Please take note, it is always nice to have real world examples.

Real world examples are nice.

Understanding why the real world example did what it did ... and didn't do what it didn't do ... is better... at least from my point of view.

In this case there are lots of very important pieces of data missing about the situations that produced the given results ... in order to get to the understand why level ... in order of importance magnitude for me:

#1> BSFC of the two completely different ICEs used... ideally with Average Operational ICE efficiency over the respective route... or the data that would allow that to be reconstructed.

#2> kwh/mile energy consumption for the routes ... or the data that would allow one to be able to reconstruct that.

- - - - - -

My biggest resistance is to any kind of absolute claims.

As the saying goes ... extraordinary claims require extraordinary proof ... and absolute claims are an order of magnitude above an extraordinary claim.

But that's just me.

I am neither pro , nor anti Series.
I am neither pro , nor anti Parallel.

- - - - - -

A side ... there are examples of a Gen-1 Insight getting over 160MPG for an entire tank of gasoline ... and there are examples of a Gen-1 insight getting 50MPG for an entire tank of gasoline ... both are real world examples ... it is when one understands why the 160 got 160 and why the 50 got 50 ... that why is better ... but that's just me.

[freebeard]

Originally Posted by P-hack

But in most congested driving I find traffic more accepting of slower acceleration (whaddayagonnado?) than of slower deceleration, so more efficient regen is useful IMHO.

^^Truth. I was a victim of road rage brought on by slow deceleration. A guy in a dirty black Jetta.

I tried to write a paragraph on hydraulics vs pneumatics but it turned to mush.

IamIan -- awesome screen name.

#1> Will you be looking into that?

#2> I understand Edison2 likes the EPA test cycle.