They aren't going away (hydraulic hybrids)

[IamIan]

Originally Posted by Old Mechanic

The principle benefits I see in a HH vehicle is weight (overall) cost, simplicity and reliability.

Perhaps ... I'll wait and see to see how it pans out over time ... it is still a bit early I think to call it one way or the other.

Remember ... this HH is not really in competition against other non-hybrids ... it is in competition against other types of hybrids ... including PHEVs ... which themselves also see many of the same benefits the HH has ... the HH is starting the race with the other hybrid tech options already having a significant head start on it.

Originally Posted by Old Mechanic

Va Tech did a lot of work looking at stresses and stress points. The found nothing significant which is the basis of the relaibility claim.

I think I have their final report on this cpu if you are interested. Its about 82 pages of information.

Yes I would be interested... thanks

As I've said:
"I don't think there will be an 'Achilles heel' , kind of major flaw ... I suspect if designed and built right , it will perform mostly as anticipated ... including all the benefits you've listed."

Meaning ... it is not about it being unreliable in an abstract ... but how reliable will it be compared to some other alternative ... for example an electric motor ... which a group of PHDs would look at and also tell you that the principle of the electric motor is very reliable , durable , has fewer moving parts than a ICE , etc ... both would be stamped as 'reliable' by the academic looking at them ... but that doesn't tell you how reliable they are compared to each other.

Also ... reliability is important ... but like most things ... it to eventually reaches a point of diminishing returns ... once it is reliable enough it might not be worth investing in a more reliable option ... is a MTBF of 1 million hours good enough? ... ie ~114 years of constant use ... is a MTBF of 1 billion hours ( ~114,000 years ) worth even 0.1% more cost/weight/volume/etc? ... probably not... even though it would be more reliable.

[NeilBlanchard]

The point about the hydraulic hybrid is that it avoids losses from braking, and returns that energy back to moving the car again. It effectively replaces the brakes, right? What it cannot do is also provide storage for energy that comes from outside the vehicle i.e. like the battery in an electric hybrid.

It is more efficient at regenerating energy than is an electric hybrid, but it is more limited in the amount of energy it can store. So, a hydraulic hybrid is not able to "double" as a second type of energy input i.e. a battery can be charged from an external source and increase the energy storage. Since electricity can come from several different sources i.e. from renewable energy and not just from fossil fuels, this is an important advantage.

Any advantage a hydraulic hybrid may have will be in the real world functionality over time. Does the accumulator hold up over a long enough time to be practical? Does the hydraulic fluid itself need to be replaced, or is it flammable, or caustic, or poisonous? Does it have enough storage capacity to allow the ICE to be smaller and more optimal because it gets assisted by the hydraulics?

We'll see when we have these cars on the road.

[IamIan]

Originally Posted by NeilBlanchard

What it cannot do is also provide storage for energy that comes from outside the vehicle i.e. like the battery in an electric hybrid.

welll .... it can actually be scaled into a Plug-HH ... where a external source of energy is used to charge a larger capacity accumulator , or other energy storage for it ... it would have issues , but it can be done.

For example AFAIK current storage tech would allow for up to about ~50wh/L energy per volume ... and ~130 wh/kg energy per weight... these are ok numbers ... will use more space than chemical energy based batteries to store the same amount of energy ... but the weight is on par with average modern batteries , but not as good as the best modern batteries.

It also isn't being mass produced like batteries are the world over for a wide variety of things... not that it couldn't be ... but it isn't ... the battery has a large established production and market head start on it.

Originally Posted by NeilBlanchard

It is more efficient at regenerating energy than is an electric hybrid

As I posted previously in this thread ... I don't agree with that over-generalization.

A specific HH design can be more or less cycle efficient than a specific HEV design ... the devil will be in the details of the two designs being compared ... and the conditions of the comparison ... It is not a given that the HH is more cycle efficient Mechanical back to mechanical cycle efficiency.

Originally Posted by NeilBlanchard

Any advantage a hydraulic hybrid may have will be in the real world functionality over time. Does the accumulator hold up over a long enough time to be practical? Does the hydraulic fluid itself need to be replaced, or is it flammable, or caustic, or poisonous? Does it have enough storage capacity to allow the ICE to be smaller and more optimal because it gets assisted by the hydraulics?

We'll see when we have these cars on the road.

[user removed]

These illustrations are from the 2006 EPA documents, 7 years old. They were the source of my statements about efficiency comparisons. Another it the efficiency is high enough to allow P&G of the accumulator versus P&G of the vehicle.

Remember Neil, the X prize rules outlawed any P&G tactics. I am talking about maintaining a constant vehicle speed while operating the engine intermittently, automatic constant speed P&G of the primary power source, with any fuel consumed at highest BSFC, which in one test on the euro cycle amounted to the engine running for only 11% of the test period.

Can any other vehicles do this today, regardless of their price? We are talking about the cheapest car you can buy not something costing over 100K.

Got your PM Ian. I'll try to get the doc to you, one way or the other it will be avaialble even if I have to stick it in an envelope and mail it to you.


regards
Mech

[IamIan]

Originally Posted by Old Mechanic

Can any other vehicles do this today, regardless of their price? We are talking about the cheapest car you can buy not something costing over 100K.

Yes , there are other methods / options, that also can do this function.

How the different methods will compare , is in the details of specific cases ... not all designs of any platform are equal ... not even two motors ( electric, ICE, or Hydraulic ) are equal in all aspects of $ , performance, etc.

A separate question about OEM on the market one can just walk in and buy vehicles would be different ... but AFAIK that criteria would also rule out the proposed In-Wheel HH.

Also 'the cheapest car you can buy' criteria , will rule out a lot of things ... including the proposed In-Wheel HH ... used beater cars can be bought VERY cheap.

Originally Posted by Old Mechanic

Got your PM Ian. I'll try to get the doc to you, one way or the other it will be avaialble even if I have to stick it in an envelope and mail it to you.

I got it.
Thanks much.

[NeilBlanchard]

So the hydraulics are primarily the transmission with a buffer, and regenerative braking, as well.

How long does the ICE need to run to recharge the accumulator? What about warm up time? If the ICE has just finished it's charging cycle, does it leave a little capacity for a potential use of the brakes? What if the accumulator is full, and there are no friction brakes in the car - how does it stop moving?

Is that how the PSA Peugeot Citroën and Bosch system works?

P.S. I'm not sure what the X-Prize rules have to do with this discussion?

[user removed]

http://www.innas.com/Assets/files/Hydrid%20brochure.pdf

I've posted this link several times before. It shows a comparison and explains the advantages, even allowing for a more efficient manual transmission.

How long the ice needs to run to fully recharge the accumulator depends on the load the vehicle is encountering Neil. Speed and grade both affect total load, while braking offers an opportunity to replensih the accumulator without fuel consumption or engine operation. The linked article mentioned 11% total engine run time in the vehcle during the run through the euro cycle. The engines efficiency was doubled compared to a normally operated manual transmission.

regards
Mech

[NeilBlanchard]

If the accumulator has no pressure, how long does the ICE have to run to fully pressurize it (while the car is sitting still)? If it is just minutes, then the ICE cannot warm up properly.

Can the ICE be sized to meet just the average load? In other words, the accumulator has to be large enough to meet the largest demand - say climbing a steep grade for longer than the ICE takes to pressurize it.

It doesn't look like the PSA Peugeot Citroën and Bosch system uses in-wheel hydraulic motors.

With in-wheel motors, there cannot be any gear changes, right? So, the faster you go, the faster the pressure is used, since the volume of hydraulic fluid used vs speed is constant?

[jamesqf]

Originally Posted by IamIan

welll .... it can actually be scaled into a Plug-HH ... where a external source of energy is used to charge a larger capacity accumulator , or other energy storage for it ... it would have issues , but it can be done.

Seems like you'd be getting rather Rube Goldbergish, though. Say I have solar panels on my roof, and want to charge my hybrid with them. Pretty easy with electricity, but with an HH you'd have to add something like an extra electric pump to the system, plus plumbing &c.

[user removed]

Neil, the linked INNAS vehicle uses fixed displacement in wheel drives and their "transformer" to proivde the pressure to the drives. Mine uses a variable stroke position from 0 stroke to the maximum of probably 3-4 inches depending on the wheels daimeter, larger daimeter=greater stroke. The "gear ratios" are the stroke position which can be adjusted at each wheel individually. Moving the journal distance A provides 2A stroke position change. The amount of fluid consumed is directly proportional to the stoke position. At 0 stroke there is no fluid movement which is the equivalent of neutral. When the stroke position is moved from 0 the fluid volume increases as the wheel provides power to the vehicle. To provide the same level of power as the accumulator pressure reserve is depleted the stoke position would be increased.
When the engine comes on to replenish the accumulator pressure, as the pressure rises the stroke position decreases to provide the exact same amount of power to the wheel.

Your point about fixed displacement drives using the same volume of fluid regardless of the load is valid, but if that was the case you would have no control of the power applied to the wheel and no way to regulate that power as accumulator pressure depleted.

Accumulators are never completely depleted, pressure wise, they will have around 1000 to 1500 PSI precharges and max pressures from 3-12K PSI. The EPA used 5k PSI accumulators in their calculations 7 years ago.

A bladder contained in a high pressure vessel is collapsed by hydraulic fluid, which can be biodegradable and non toxic. As the fluid volume increases the bladder collapses and compresses an inert gas. Life expectancy is considerable, usually measured in hundreds of thousands of cycles, and bladder replacement is all that is necessary to restore the accumulator to new condition as long as the containment vessel is not damaged.

The accumulator can dump its total charge in a matter of seconds at extremely high power levels, but when yo uare trying to move a vehicle that will not happen unless you are trying to smoke all 4 wheels (assuming one drive per wheel or one drive per 2 wheels).

Each drive operates independently of the other drives and in a 4 wheel drive configuration you just place two drives in the ) stroke position and they are basically freewheeling axles with no fluid consumed.

Braking means you use the "reverse" stroke position which also works as a reverse "gear".
Regeneration occurs when the stoke position is reversed in relation to the vehicles motion.

regards
Mech