RE: Lotus Unveils 'Range Extender'

[ctallchris]

Mr Whippy said:

ctallchris said:

Mr Whippy said:

How pointless.

Isn't it shown, in the 'real world', that a small diesel will blow these silly hybrid things into the weeds on efficiency?

Dave

Parallel hybrids yes

Serial hybrids absolutely not no way ever

http://karma.fiskerautomotive.com/

400 bhp hybrid with some insane economy figures

So what are the economy figures?

From what I have seen, a great deal of the apparent 'benefit' of a hybrid on paper is that it starts the relatively short CO2 cycle run on a full battery. That makes them appear great, and since manufacturers have targets around CO2, they make them.

In reality, are they actually much better, or are the 'economy figures' misleading due to benefits put on hybrids?

Dave

What economy do you want?

it's unrealistic to do mpg for a car that doesn't use fuel for the first 40 - 60 miles after you wake up in the morning having charged your car overnight. Over this distance it's infinite mpg because the engine doesn't start until it is needed.

Cost wise it cost's about 1/10 of the price of a petrol car over this distance.

My commute is 50 miles the longest distances i tend to drive at weekends are 20-30 miles out and the same back so for me for a week's use i might use 1-2 litres of petrol to get 370 miles this would cover 95% of my travel. When i get out on the motorway for the long haul two or three times a year even if it's less efficient than a diesel that's not where i spend my money on fuel.

If you're like me (which the majority of drivers are) this is not the kind of efficiency savings like you would see from switching from petrol to diesel this is closer to not having to pay for fuel.

[collateral]

I thought derv was more suited to generators - trains anyone?

[Ozzie Osmond]

I'm always mystified by this stuff.

Q. Which is going to be more economical and environmentally friendly?

a) a car with a small engine, or

b) a car with a small engine PLUS a battery pack, generator and auxiliary motors.

A. Sounds like a no-brainer to me.

[TTwiggy]

I look forward to the 'limited edition'...

[xyphod]

Diesel engines on trains drive the wheels directly.
Current High speed trains with electric motors and local generation use gas turbines.

I would however had thought that a really small Gas turbine would provide the same efficiency/weight/power as this little Lotus design.

[kambites]

collateral said:

I thought derv was more suited to generators - trains anyone?

I think the problem is that diesels are noisy. Basically, every now and then the engine fires up and immediately revs to peak efficiency (peak torque and WOT, near enough).

I suppose a diesel doing that would be impracticable simply due to NVH issues. A petrol engine designed purely to rev at that speed (hence with a very low compression ratio) will be quite refined.

[kambites]

Ozzie Osmond said:

I'm always mystified by this stuff.

Q. Which is going to be more economical and environmentally friendly?

a) a car with a small engine, or

b) a car with a small engine PLUS a battery pack, generator and auxiliary motors.

A. Sounds like a no-brainer to me.

Yes, the one with a battery by miles. These things are quite new technology and are already using half the fuel of a car driving the wheels directly. It may have a bit more weight to lug around, but running the engine optimally gives 40% chemical to kinetic efficiency rather than 15% efficiency from a direct drive system which makes up for a LOT of extra weight and manufacturing cost.

Direct drive hybrid systems like the Toyota and Honda systems are daft because they miss out of the biggest gain - the ability to run the engine efficiently. Range extender electric cars can be extremely economical.

Edited by kambites on Tuesday 8th September 14:56

[mybrainhurts]

Having read this story....

I must say....

Bah....

[Tony*T3]

kambites said:

collateral said:

I thought derv was more suited to generators - trains anyone?

I think the problem is that diesels are noisy. Basically, every now and then the engine fires up and immediately revs to peak efficiency (peak torque and WOT, near enough).

I suppose a diesel doing that would be impracticable simply due to NVH issues. A petrol engine designed purely to rev at that speed (hence with a very low compression ratio) will be quite refined.

noise and weight I would guess. Diesel engines are normally a large percentage heavier than petrol, are they not? Some petrol engines getting seriosuly good MPG now too, I guess running as maximum efficiency at all times means they return better MPG.

[ctallchris]

Ozzie Osmond said:

I'm always mystified by this stuff.

Q. Which is going to be more economical and environmentally friendly?

a) a car with a small engine, or

b) a car with a small engine PLUS a battery pack, generator and auxiliary motors.

A. Sounds like a no-brainer to me.

Petrol motor circo 25% efficient after 100 years of dev
(theoretical maximum circo 35%-40% )


Electric motors maximum efficiency 95%
(theorectical maximum 100%)

In parallel hybrids (prius / insight) savings are made by using excess energy made while the engine idles / from braking to move the car at low speeds (reduces losses due to use of clutch and inefficient gearing.

Serial hybrids are electric cars.

The motor comes in when they reach the end of their range and yes it will only be as efficient as a prius after that but for the first miles it is 95% efficient from the electricity it receives.

electric drive is just so much more efficient than any alternative even if you burnt petrol in a power station to get the energy out this can still be done with 80-90% efficiency.

For references and exact numbers check ont of the recent threads on electric cars.

forgive me for i am lazy

[julian64]

so lotus have just invented the lister diesel......

[otolith]

Ozzie Osmond said:

I'm always mystified by this stuff.

Q. Which is going to be more economical and environmentally friendly?

a) a car with a small engine, or

b) a car with a small engine PLUS a battery pack, generator and auxiliary motors.

A. Sounds like a no-brainer to me.

I think the principle is that the peak power demand (for acceleration) is so much higher than the continuous requirement (for cruising) that you can get an advantage by sizing the engine for a little over cruising demand and meeting the peak demand with the battery.

[Mr Will]

Ozzie Osmond said:

I'm always mystified by this stuff.

Q. Which is going to be more economical and environmentally friendly?

a) a car with a small engine, or

b) a car with a small engine PLUS a battery pack, generator and auxiliary motors.

A. Sounds like a no-brainer to me.

This is option c: a car with a battery pack, electric motors and a small generator which kicks in when the batteries run out. No engine involved!

Very different to the hybrids on our roads today and potentially significantly more efficient.

[collateral]

xyphod said:

Diesel engines on trains drive the wheels directly.
Current High speed trains with electric motors and local generation use gas turbines.

I would however had thought that a really small Gas turbine would provide the same efficiency/weight/power as this little Lotus design.

Ah thanks for clarifying

[DPX]

I will take one for my flymo

[leon9191]

ctallchris said:

jaik said:

How about a diesel serial hybrid then?

Because of this the extra cost of manufacturing a diesel engine will probably never be paid for by a slight gain in efficiency. Also as the torque no longer matters the benifits of the diesil falls further away from the petrol.

What torque becomes irrelevant when TURNING a generator? Er no I am pretty sure it still plays a role as the generator will put the engine under load while generating electricity.

I would imagine that the use of petrol over diesel is down to the fact that diesel is still seen as a dirty fuel (a misconception of course) and for something trying to sport “GREEN” credentials isn’t seen in the right light.

[kambites]

leon9191 said:

ctallchris said:

jaik said:

How about a diesel serial hybrid then?

Because of this the extra cost of manufacturing a diesel engine will probably never be paid for by a slight gain in efficiency. Also as the torque no longer matters the benifits of the diesil falls further away from the petrol.

What torque becomes irrelevant when TURNING a generator? Er no I am pretty sure it still plays a role as the generator will put the engine under load while generating electricity.

I would imagine that the use of petrol over diesel is down to the fact that diesel is still seen as a dirty fuel (a misconception of course) and for something trying to sport “GREEN” credentials isn’t seen in the right light.

Both the peak torque and the peak power of the petrol engine are irrelevant as long as it generates enough power at peak efficiency to keep the batteries topped up. Since it will presumably never rev above the point at which it generates peak efficiency (which is usually around peak torque), I'd imagine that it will be mapped for a lot of torque in comparison to a direct drive engine of the same capacity.

Diesels are more efficient than petrol engines, but IIRC only a couple of percent more efficient.

Edited by kambites on Tuesday 8th September 15:44

[ctallchris]

DPX said:

I will take one for my flymo

If your flymo a converted hovercraft? mine's 2000Watts 35000 watts seems pretty hardcore unless of course you intend to race it?

[Rich1973]

Slightly off topic but as someone brought it up above, diesel engines on trains do not drive the wheels. For locomotives they are attached directly to a generator which produced electric that powers traction motors attached to the wheels. It is partly true in the case of trains with no seperate locomotive which are hydraulic but is not powered directly from the engine. I am a car nut. Honest!!

[ctallchris]

Rich1973 said:

Slightly off topic but as someone brought it up above, diesel engines on trains do not drive the wheels. For locomotives they are attached directly to a generator which produced electric that powers traction motors attached to the wheels. It is partly true in the case of trains with no seperate locomotive which are hydraulic but is not powered directly from the engine. I am a car nut. Honest!!

Yup the reason they use diesel here is that those engines will run all the time and efficiency is key. A range extender runs only when the vehicle has exhauster it's range ergo cost / weight / size are more important than economy