What ever happened to series hybrids?

[marjam]

Series hybrids were all the talk in the mid-nineties and Volvo had a car which used a turbine engine running at two different speeds to create the electricity for the traction motors. I know that fuel cell cars are basically series hybrids but they still seem years away. Was fuel economy the issue? How about small jet turbines or even steam turbines to create the electricity?

Is anyone familiar with the research in this area?

[richard schumacher]

Turbines are not very efficient unless they run at full power. Since the power required by a car varies a lot, making good use of a turbine requires a big battery for storing surplus power when the car's power demand is low ("load levelling").

Meanwhile, Toyota invented HSD, which makes excellent use of an internal combustion engine without using a very large battery. And now plug-in hybrids are on the horizon...

[clett]

Series-hybrids will make their big comeback when the batteries in PHEVs get bigger. About 70kW electrical output and 30 mile EV range, people will start thinking about switching to serial. But as Richard said, Toyota are continuing with a parallel arrangement for now while the Prius makes do with a small battery.

[kevinwhite]

<div class='quotetop'>QUOTE(clett @ Aug 14 2006, 12:54 PM) [snapback]303159[/snapback]</div>

Series-hybrids will make their big comeback when the batteries in PHEVs get bigger. About 70kW electrical output and 30 mile EV range, people will start thinking about switching to serial. But as Richard said, Toyota are continuing with a parallel arrangement for now while the Prius makes do with a small battery.
[/b]

Actually the Prius is a hybrid-hybrid in that it is a series hybrid at low speeds or high load situations such as hill climbing and a parallel hybrid at crusing speeds.

The amount of power transferred through MG1 to MG2 relative to the power transferred directly varies depending on the instantaneous power requirements.

Pure series hybrids require large motors and generators and suffer form the inefficiency of conversion - e.g. the motor/generators on Prius are about 90% efficient but put the two in series and you only get about 80% out of what you put in. the mechanical path is about 95% efficient so you get about 15% better economy at freeway speeds with the HSD than with a pure series hybrid.

kevin

[hampdenwireless]

<div class='quotetop'>QUOTE(marjam @ Aug 14 2006, 12:38 PM) [snapback]303027[/snapback]</div>

Series hybrids were all the talk in the mid-nineties and Volvo had a car which used a turbine engine running at two different speeds to create the electricity for the traction motors. I know that fuel cell cars are basically series hybrids but they still seem years away. Was fuel economy the issue? How about small jet turbines or even steam turbines to create the electricity?

Is anyone familiar with the research in this area?
[/b]

http://en.wikipedia.org/wiki/General_Motor...1_Series_Hybrid

60-100mpg

In the end I would rather have a plug in Prius even with less range, the EV1 has far less usable space then the Prius.

[marjam]

Thanks for the info. The Prius really is the best of both worlds. In a recent trip in mountainous areas I saw over 58 MPG in the mountains and many "full battery" meters. On the Interstates at 65MPH in hilly country I saw 54MPG. The Prius does make best use of the resources available to it and I have always gotten higher mileage on the highways than on my short commutes. It is a great car.

[buyaninsight]

<div class='quotetop'>QUOTE(richard schumacher @ Aug 14 2006, 02:56 PM) [snapback]303126[/snapback]</div>

Turbines are not very efficient unless they run at full power.
[/b]

WRONG

your thinking of maximum efficiency. and they are actually efficient elsewhere to. Ever notice the top speed of an aircraft and its cruising speed aren't the same thing?

it would probably be more efficient but turbines have serious draw backs. this was tried on semis in the 60-70 by international I believe. perfect usage right? long long periods of steady state cruising (just like a flight to tokyo) but they are very very precise to build and very expensive to maintain/fix. and while the motor/generator in the prius may be whatever efficient the loses in the drivetrain are more significant than quoted..and if an ICE operated at 90% efficiency you would be able to grab the exhaust while its running

[clett]

The peak thermal efficiency from a small turbine is too low - only about 25%.

This is because they suffer from heat loss and poor compression ratio. An ICE is able to achieve a much better compression ratio because the combustion area is sealed. There is no seal in a turbine, so only big (like powerplant) turbines can get reasonable compression ratio and hence up to 40% efficiency.

By comparison....

A typical gasoline ICE gets about 25% efficiency. (10:1 expansion ratio)
Prius "Atkinson" cycle ICE gets about 34% efficiency. (13:1 expansion ratio)
VW diesel engine ICE gets about 43% efficiency. (20:1 expansion ratio)

So in terms of thermal efficiency, a diesel engine is by far the best way to go.

There are some good 600 cc diesel units from Japan that, with some serious forced induction, could give say 80hp or so. This would be a tiny, light-weight unit with very high efficiency and more than enough power for a series-hybrid. Not much in the way of raw materials, so cheap too.

[molgrips]

Seems to me like diesel prius would be the way to go, at least for Europe where smog isn't such a big deal. I'm also guessing that the puff of smoke you see in some of the more powerful units is due to turbo lag (extra fuel goes in via the accelerator, but not enough air), so perhaps this could be cut down with an engine changing speed less rapidly (as could be managed with HSD). Or how about a supercharger, or electric turbo?

Then again, how about an Atkinson/Diesel engine? Is there a reason why this wouldn't work?

I had a great idea for a steam driven car that used mechanical heating of water to reclaim energy under braking. Go on, ask me about it

[donee]

<div class='quotetop'>QUOTE(clett @ Aug 16 2006, 06:33 AM) [snapback]303970[/snapback]</div>

The peak thermal efficiency from a small turbine is too low - only about 25%.

This is because they suffer from heat loss and poor compression ratio. An ICE is able to achieve a much better compression ratio because the combustion area is sealed. There is no seal in a turbine, so only big (like powerplant) turbines can get reasonable compression ratio and hence up to 40% efficiency.

By comparison....

A typical gasoline ICE gets about 25% efficiency. (10:1 expansion ratio)
Prius "Atkinson" cycle ICE gets about 34% efficiency. (13:1 expansion ratio)
VW diesel engine ICE gets about 43% efficiency. (20:1 expansion ratio)

So in terms of thermal efficiency, a diesel engine is by far the best way to go.

There are some good 600 cc diesel units from Japan that, with some serious forced induction, could give say 80hp or so. This would be a tiny, light-weight unit with very high efficiency and more than enough power for a series-hybrid. Not much in the way of raw materials, so cheap too.
[/b]

Hi Clett,

Thanks for all the electric battery stuff you have put on here and priusonline.

I am wondering what a electrically compounded turbo Atkinson engine would do? That is using a turbo on the exhaust to generate electricity for the drive battery. Might be some technical problems with magnets an high temps, but maybe not with the high expansion ratio engines. Have you run across any info on this?