RE: Driven: Porsche 911 GT3 R Hybrid drive
Discussion
Great little project, but what the article doesnt mention is the rather obvious downsides, namely;
1) every power "phase change" has an in-efficiency ascosiated with it, so wheels to generators 90%, generators to flywheel motor (via 2x inverters, 85%) motor to flywheel 90%, then, get the power back out to the wheels is all that in reverse, so overall efficiency is 0.9 x 0.85 x 0.9 x 0.9 x 0.85 x 0.9 which is only 47.4% efficiency.
2) the "flywheel" is a composite device, with integral magnets for the drive, it's v expensive as it spins at 60krpm
3) the flywheel resides in a vaccum containment chamber, that vacuum has to be maintained to prevent the flwheel from ablating
4) the flywheel is supported on magnetic bearings, these are not cheap
5)the specific energy density of the flywheel is classed as medium (specific power density is high however) but by the mass of the support systems is included, the specific energy density is similar to current battery technology
iirc, the current cost of the system is circa £500k......... (ok, there must be significant development overheads being recouped there, but it is a complex system
and finally
6) it pretty much is only competitive if the regulations effectively allow it to be a "loop hole", with racing minimum chassis masses and inlet restrictors, the hybrid system is artificially helped.
Having said all that, must have been a fun project to be involved with nevertheless!
1) every power "phase change" has an in-efficiency ascosiated with it, so wheels to generators 90%, generators to flywheel motor (via 2x inverters, 85%) motor to flywheel 90%, then, get the power back out to the wheels is all that in reverse, so overall efficiency is 0.9 x 0.85 x 0.9 x 0.9 x 0.85 x 0.9 which is only 47.4% efficiency.
2) the "flywheel" is a composite device, with integral magnets for the drive, it's v expensive as it spins at 60krpm
3) the flywheel resides in a vaccum containment chamber, that vacuum has to be maintained to prevent the flwheel from ablating
4) the flywheel is supported on magnetic bearings, these are not cheap
5)the specific energy density of the flywheel is classed as medium (specific power density is high however) but by the mass of the support systems is included, the specific energy density is similar to current battery technology
iirc, the current cost of the system is circa £500k......... (ok, there must be significant development overheads being recouped there, but it is a complex system
and finally
6) it pretty much is only competitive if the regulations effectively allow it to be a "loop hole", with racing minimum chassis masses and inlet restrictors, the hybrid system is artificially helped.
Having said all that, must have been a fun project to be involved with nevertheless!
Max_Torque said:
1) every power "phase change" has an in-efficiency ascosiated with it, so wheels to generators 90%, generators to flywheel motor (via 2x inverters, 85%) motor to flywheel 90%, then, get the power back out to the wheels is all that in reverse, so overall efficiency is 0.9 x 0.85 x 0.9 x 0.9 x 0.85 x 0.9 which is only 47.4% efficiency.
This- surely as the KE system that powers the electric motors uses what is essentially wasted energy, it's extremely efficient? Aren't most petrol engines only about 18-20% efficienty anyway?jamespink said:
Superb Porsche engineering designed to win major races and (without a dropped valve)would have done straight out of the box. Incredible achievement!
Not quite, the N24 was its 3rd race, it finished 5th and 3rd at the previous 2 VLN races I believeThough I agree about the engineering, expected to be at LM next year
What the efficiency reduction means is 2 things, you can only get back ~50% of the KE of your car at any given time, and the other ~50% generates heat, which needs to be removed from the hybrid system, and that takes extra complexity and weight. So, say you fill up with 100% energy (fuel tank) the IC engine then converts that into approx 20% KE, of which you hybrid system manages to recycle a total of 10% back into KE. Now, add the weight, complexity and cost, and it doesnt really add up
For ultimate fuel econmomy, 2 other factors should be noted, the best "recovery" of KE is not to brake at all, to put your car in neutral, shut off the engine and coast, this uses 100% of the cars intertial power! And, what you find, is the more economically someone drives, the more they do exactly this automatically.
and more importantly, the existing ECE drive cycle, over which road cars are tested, has it's greatest deceleration as the final part of the test. So, even if you can charge your flywheel up on this deccel, by the time of the next test (a mandated minimum 12hrs) the energy has been sigificantly depleted. (there are plans afoot to allow flywheel system to "precharge" the flyhweel before the test to the same value as it;s end condition, but this isnt currently ratified)
For these two reasons a road flywheel system is currently a no starter unfortunately.
For ultimate fuel econmomy, 2 other factors should be noted, the best "recovery" of KE is not to brake at all, to put your car in neutral, shut off the engine and coast, this uses 100% of the cars intertial power! And, what you find, is the more economically someone drives, the more they do exactly this automatically.
and more importantly, the existing ECE drive cycle, over which road cars are tested, has it's greatest deceleration as the final part of the test. So, even if you can charge your flywheel up on this deccel, by the time of the next test (a mandated minimum 12hrs) the energy has been sigificantly depleted. (there are plans afoot to allow flywheel system to "precharge" the flyhweel before the test to the same value as it;s end condition, but this isnt currently ratified)
For these two reasons a road flywheel system is currently a no starter unfortunately.
Edited by anonymous-user on Tuesday 6th July 22:14
oagent said:
Great idea on a track if the power overcomes the weight disadvantage and you lean hard on the anchors every 10 seconds to effectivly charge up your potential energy.
How would the system work on the road where corners are not so frequent, and 6 seconds of full power is less impressive. I would have to lean very hard on the breaks when commuting to work or on the motorway to generate enough energy to spin the flywheel up to 40k rpm. If I some how managed that, would the stored energy get me more than a mile driving sensibly? Probably not. Yet I would have to lug that extra 200kg round with me all the time.
This exact system wouldn't work on road cars - just like the Ceramic/Ceramic brakes and ridiculously hard compound tyres don't. If they fitted race car tyres on road cars we would all be weaving like maniacs trying to get heat in them before the first turning and our racing brakes wouldn't have enough heat in them to stop us at the first junction!! This system has probably been designed to benefit from the heaving braking and overtaking opportunities that present themselves on the circuit and the fact this can last a couple of laps further than a standard racecar gives great potential for events such as Le Mans. Could be a great way of making the diesel/petrol battle fairer by allowing the petrol cars to be fitted with these hybrid flywheels.....How would the system work on the road where corners are not so frequent, and 6 seconds of full power is less impressive. I would have to lean very hard on the breaks when commuting to work or on the motorway to generate enough energy to spin the flywheel up to 40k rpm. If I some how managed that, would the stored energy get me more than a mile driving sensibly? Probably not. Yet I would have to lug that extra 200kg round with me all the time.
We saw the Porsche running at Le Mans this year, along with other slightly less spectacular eco cars, as they were given two laps of the circuit, pre-race. Boy was it impressive, but more so was the Ferrari 599 XX hybrid, which looked and sounded magnificent. We were stood at Arnage as it thundered out of Indionapolis and down the short straight to Arnage corner. Certainly looked as quick as the GT 1 class cars.
I'm thinking that like most "F1" technology this will filter down to us minions on the street once the big boys get their heads around the economics of it all.
As long as the weight issues are dealt with I can see some sort of battery flywheel technology appearing in cars in the not so distant future.
I'm pretty sure that fly wheels have been used in trams etc for years' now.
Get the egg heads onto it and they will have it sorted in no time!
As long as the weight issues are dealt with I can see some sort of battery flywheel technology appearing in cars in the not so distant future.
I'm pretty sure that fly wheels have been used in trams etc for years' now.
Get the egg heads onto it and they will have it sorted in no time!
Max_Torque said:
For ultimate fuel econmomy, 2 other factors should be noted, the best "recovery" of KE is not to brake at all, to put your car in neutral, shut off the engine and coast, this uses 100% of the cars intertial power!
Which works brilliantly until you plough start into the back of a bus where you use 100% of your car KE to make your insurance quote next year very expensive indeed so i think that in stop start traffic i will prefer the hybrid thanks Munter said:
jamespink said:
Superb Porsche engineering designed to win major races
Superb Williams engineering designed to win GP races adapted for, and bolted into, a Porsche.
This system is very much realistic for use in road cars imho. The current manufacturing methods are no doubt prohibitive for mass production, but as with all things there will be developments in the processes which will resolve these issues. The technology itself is also a pretty good idea. A little bit more weight than a (current) battery pack, arguably easier to package, much lower lifecycle CO2 (as vehicles are starting to get measured in) than electric hybrids, no expensive 5/10yr battery replacements, fast re-charging in use etc. It's good to see Porsche using a racing program for such an interesting technology development program.
kambites said:
I know the recharge times are not comparable (yet), but it sounds like the flywheel is an awful lot heavier for the amount of energy it can store than a battery would be.
How much is the flywheel and how much is the additional electric motors/generators, driveshafts, cabling etc?jeremyc said:
What happens when you stop/turn off with a fully charged flywheel?
Does it keep spinning until the next time you use the car, or is there some way for the energy to be dissipated?
I doubt it's 100% efficient at storing the energy! I presume it'll be left to spin down in it's own time. Or to make it safe to work on it it'll have a way of "burning off" the energy.Does it keep spinning until the next time you use the car, or is there some way for the energy to be dissipated?
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