Xtrac Proposes Applications of Flywheel Kinetic Energy Recovery Systems for Road Cars
11 June 2008
Xtrac CVT variator for F1. Click to enlarge. |
Transmission technology specialist Xtrac says the flywheel kinetic energy recovery systems (KERS) currently being developed for Formula One (earlier post) could be applied to road vehicles in a number of ways.
Xtrac’s role in designing, developing and integrating the mechanical KERS system for F1 with partners Flybrid and Torotrak is to provide the toroidal continuously variable transmission (CVT) between the flywheel and the vehicle powertrain.
Complementing its work in F1, Xtrac is also a partner in a new project to develop a flywheel hybrid system for premium cars. Xtrac forms part of a consortium supported by the UK government’s Technology Strategy Board, which recently announced funding of £23 million for 16 innovative low carbon vehicle development projects. (Earlier post.)
The flywheel hybrid project will involve the design and development of a mechanical KERS system for use in a premium segment passenger car as an alternative solution to other hybrid systems and to prove its effectiveness and viability for production. Jaguar is leading the project, which will be carried out by a consortium made up of Flybrid Systems, Ford, Prodrive, Ricardo, Torotrak and Xtrac.
By providing an additional boost of power, the F1 technology is particularly relevant to the trend to fit cars with smaller engines in pursuit of better fuel efficiency and lower CO2 output.
The technical challenge with engine downsizing is compensating for the loss of engine torque and driveability, which can be restored by applying flywheel technology. It is also possible that a mechanical KERS system could be used as a range extender in a battery electric hybrid vehicle or even to power vehicle auxiliaries.
All are potential applications of the technology, subject to the size of the flywheel, compactness of the system and vehicle packaging requirements. These are all resolvable technical issues. The intent of the KERS technology in F1 is to consider energy recovery, storage and discharge, and to demonstrate that technology in a novel and effective way.
—Adrian Moore, Xtrac technical director
The energy recovery rate and storage requirements of a flywheel for a road car could be considerably less than that required in F1 where the energy which can be recovered from 5g braking is significant. As the flywheel is required to be charged, some preliminary motion may be required; though road cars could store energy in the flywheel directly from the engine, which is not currently permissible under F1 regulations. Road driving conditions also vary from the stop-start conditions experienced in a town environment to constant speed cruising found on motorways.
Although still maturing, KERS has stimulated the introduction of radical new technologies to F1 and ultimately to other engineering sectors. The mechanical-based concept offers one such solution and indeed could offer significant energy efficient benefits to the driveline of both race and road vehicles.
—Adrian Moore
Moore is presenting a paper outlining the design and development of the CVT used in the Flybrid F1 system this week at the Global Powertrain Congress being held in Vaals in the Netherlands.
This would be great for all the saps that continue to drive SUV's. The extra weight of the SUV would mean recovery quite a lot of energy. Ekinetic = (1/2) M * V * V.
I would guess that the SUV fuel economy would jump significantly if these systems could be made cheap enough.
Posted by: | 11 June 2008 at 09:42 AM
A nice heavy flywheel to make the SUV go faster?
This has a marginal application to store breaking energy for re-acceleration, but expecting to store large amounts of energy in a flywheel is pie in the sky.
Posted by: | 11 June 2008 at 09:58 AM
Before you "poo-poo" the idea for a flywheel based energy storage conversion of an SUV, consider that the same result from a generator->battery->motor in a mild hybrid approach may weigh more (electric motors and battery weight).
Posted by: NCyder | 11 June 2008 at 10:11 AM
I agree, my engineering brain just cannot see this being efficient enough, besides increasing mass ruins agility, handling, braking and put more wear on components.
Posted by: | 11 June 2008 at 10:13 AM
A flywheel has a significantly higher power per weight ratio than a Li-ion battery and still reaches about half the energy density of a Li-ion battery.
Posted by: | 11 June 2008 at 10:16 AM
For short high power delivery at low cost and complication, flywheels are very very good. Flywheels are used in every gasoline and diesel engine to even the torque between piston strokes. Very small engines will give high efficiency, and combined with moderate flywheels they will also give high acceleration. Regenerative energy savings can improve economy also.
See Parry People Movers for flywheels in actual use in trolleys...HG...
Posted by: Henry Gibson | 11 June 2008 at 10:50 AM
Flywheel energy storage is a good alternative to battery in HEV...for a HFV (Hybrid Flywheel Vehicle, shall we?), especially given the fact that battery still will not last the entire life of the HEV and must be replaced for a hefty sum of money. Furthermore, the recent shortage of lanthanum has restricted battery production for the Prius' NiMh battery.
Given the low energy storage capacity of flywheel but very rapid discharge of power, a small battery pack (~0.3kwh, instead of 1.3kwh as in the Prius) can provide additional energy reserve for stop-start function and energy recuperation. Since this small battery pack is used much less often, it will last longer, or if not, it will be much cheaper to replace. This will give us a HEFV (Hybrid Electric Flywheel Vehicle) :)
The beauty of a HEFV is in cost and weight saving, when the flywheel and the starter-generator motor can be combined into one unit. Thus, we have a flywheel-starter-generator-motor (FSGM) all-in-one unit capable of provide direct power to accelerate the vehicle via a torotrak or Xtrak transmission. Then, when the FSGM reaches its maximum rated rpm, the stator coil will be closed, providing current to charge the battery while keeping its rpm within safe limit.
How's that for a super-duper IMA, Honda engineers? The problem with Honda's hybrid is the low recuperative potential and weak power of the IMA due to the drag of the engine and small size of the motor and battery. Using a FSGM coupled with Xtrak, we will have phenomenon acceleration, like a drag racer from 0-60 mph, along with complete recuperative braking due to the phenomenon power absorption of the FSGM unit...an engine-off driving mode using both the mechanical power of the flywheel and the electrical power of the battery...all for a lower acquisition cost and long-term cost than a comparable Toyota's HSD.
Posted by: Roger Pham | 11 June 2008 at 12:39 PM
Roger, that sounds like a cool design, but where is the hydrogen? :)
Posted by: Bob Bastard | 12 June 2008 at 12:57 PM
How about combining the engine and flywheel like in the Gnome radial aircraft engine:-)
Posted by: RetroJoe | 13 June 2008 at 09:47 AM
Joe,
Mr. Gary Greenwell from Virginia Tech has invented such a concept that he called RIDE. Look in the following link for details and ensuing extended discussion:
http://www.greencarcongress.com/2006/05/concept_modifie.html
Posted by: Roger Pham | 14 June 2008 at 09:24 AM
I seem to recall that a flywheel system was being tes ted on Britain's rail system. Wouldn't a constant stop- and-go application on a petrol or diesel powered vehicle yield the shortest payback time?
Posted by: ken | 17 June 2008 at 12:48 PM
UltraBattery based on the new FireFly Lead Acid
and flywheel tech for energy recovery and a controler
thats massed manufactured and a simpler modular EV design seems very possible.
Wonder how many miles you could get out of it?
Posted by: Bob | 19 June 2008 at 01:34 PM
Could using a compressor to store compressed air during breaking then use the compressed air somehow to accelerate the vehicle be an alternative that was lighter but just as efficient?
Posted by: andyvancleve | 26 July 2008 at 08:49 AM