KERS and Aero Engines ?

[ZULU1]

I have been watching progress with interest of the KERS (Kinetic energy recovery system) hyprid drive system that Formula 1 manufacturers have been developing, today we saw the first practical demonstration with Lewis Hamilton winning in Hungary.

A question has to be asked as its proven to be of value "It works" and KTM have used it with illegal success last year in a 125cc machine. Why not use it in light aircraft ?

Now as a hybrid drive is little affected by altitude (electrically it is but not so large losses) then this could be useful for a Gauteng take off and a VP prop (this would be a necessity to turn the power into thrust) on a hot and humid day or if cruising and a requirement is for extra power. Whatever reason.

As the technologies are developing rapidly and the Formula 1 weights are about 25 kgs for 60 hp, sure the power is generated by braking; but a wind up mechanism before take off possibly?

An example would maybe an extra 10 hp on take off with a 912, but it would be a genuine power addition and not a altitude reduced power input and for little weight addition and also "for free".

The software and technology (thats the easy bit) has been developed as an example for the Thielert diesel engine using a one lever control system, now there is no reason why this could not be interfaced into a similar system, adjusting pitch, then unleashing the KERS at the required moment, then in cruise would be regenerated back to the system after the prop is re pitched. I see the entire system being totally automatic and the pilot would not possibly notice the additional control interface ?

This subject warrants further thought, we have plenty of Engineers on this forum to discuss the matter further and maybe it could get somewhere ?

Grostek, Morph, Dark Helmet (software) I expect some form of reply...

zulu1

[justin.schoeman]

Firstly - thanks for ruining the GP for me - I am only watching it when I get home!



Kidding.

Anyway. That 80hp boost is for 8 seconds!

Here is a table of typical power densities (from http://www.allaboutbatteries.com/Battery-Energy.html):

Battery
Type Cost
$ per Wh Wh/kg Joules/kg Wh/liter
Lead-acid $0.17 41 146,000 100
Alkaline long-life $0.19 110 400,000 320
Carbon-zinc $0.31 36 130,000 92
NiMH $0.99 95 340,000 300
NiCad $1.50 39 140,000 140
Lithium-ion $4.27 128 460,000 230

With LiIon batteries, you get 128 Watts per hour per kilogram, so that is around 2hp for 5 minutes per kg. (I used 5 minutes because this is often used as the max performance duration limit for engines.) So for your 10hp, you would need 5kg of batteries. A motor/generator for this power output would weigh in at around 1kg. Support electronics can probably also budget around 1kg.

So for a 7kg weight penalty, you can get a 10hp/5 minute boost. Technically it is no problem to build. Electronics are fairly simple. Add a failsafe cut-off to disconnect the coils, and there should not be any safety issues.

I would guestimate the component costs at around R20k.

Don't see why it can't be done?

[grostek]

Hi All,

KERS is fine but why does a designer have to add weight to get more power to give extra performance, at a cost, and this power is available in 5 minute units (or whatever increments you choose to use) at a time.

In aviation there is no free lunch to be had. any changes to a basic design will have a knock on effect.

Surely the whole system should be analysed, ie Airframe, engine, propeller

Airframe,
Drag reduction, Counter sunk rivets, Fairings, Gap seals. Weight reduction by material substitution in specific areas.Improved wing design, improved Flap designs to lower stall speeds. Adapting the Krueger Flap (Nose Flap) to LSA type aircraft like Steve Wittman already did in the 1940 something on his Buttercup.

Engine Better design,Fuel Injection systems for improved economy,Optimising exhaust systems for best gas removal.
Better ignition systems.
Having said that the Rotax is probably the most refined aero engine available and delivers the best HP per weight ratio, (Around 0.87Kg/KW) In addition it has good TBO figures. This points the way to go using watercooled engines. Aircooled engines are just to fickle and relatively speaking inefficient with around 0.5Kg/KW.

Propeller
VP propellers are the way to go, fixed pitch is good for one speed at one specific rpm.Yes I know fixed pitch props from people like Pieter de Necker are better than most but fact is a VP prop will be even better yet.

All of this comes at a cost, putting it beyond the reach of 95% of "the man in the street" who wants to fly.

LSA manufacturers and Kit Manufacturers will try to give as much of that 95% as possible what they want, and that means relatively uncomplicated aircraft and kits that can be mass produced and still give the manufacturers an adquate return on investment. Please bear in mind that the relatively low volumes of aircraft and kits produced make the initial purchase price seem very expensive. (Vans has produced some thing like 12000 kits in his time and if we compare that to a car manufacturer like Volkswagen in the EU they produce something like 800 POLO's per DAY and that is what makes cars cheap.

So what does that leave us with? Build our own? modify an existing design? Start with a clean sheet of paper?

The answer will be different for each and every one of us.

I think Zulu1's ideas have merit, but also feel that much the same can be achieved by simpler methods.
If we wait long enough bike and car engines may in future become available with such systems and that will save us all a lot of development work, not to mention the money that private development costs.

Overall I say lets pick up the ball that Zulu1 has passed and run with it we may very well end up with an affordable low weight system.

Finally the best weight reduction that can be performed is by reducing our body mass, that will give instant performance gains and not only while sitting in an aircraft.
As an example For my weight I should be 2.5meters tall.

Kind regards,

Gunter Rostek

[ZULU1]

Gunther and Stephen, I think that MB will be having a technical meeting first thing this morning !! Formula 1 threw the KERS ball at manufacturers for lets call it "eco reasons" with a opportunity to add power (only 6 secs). All engine manufacturers saw an opportunity and most (as yet) failed. Each went their own way, super caps, flywheels and so on. Anyway I see MB now attacking a KERS weight reduction programme now which is my interest for aero engines.

The efficiency factors that Gunther suggests have been around since PR spitfires in WW2 and yes I agree its the logical way to go, and we are watching a live demo with Mike and James in the Sling, good stuff. 19 ltrs per hour with a tonne of aerie, not shabby !!

What we are all really angling for is a efficient, cost effective, lightweight alternative engine. Now if we see projects, Boet has the Yaris, Oupa G the BMW and its derivatives. A lot of activity is happening behind the scenes. I have a Daihatsu Sirion which is a twin cam 16 valve 61 kw motor and you can buy a whole car for R79k. So its a matter of time before someone comes up with a suitable alternative...Junkers had a aero engine, two stroke diesel in the 30s which worked, with modern technologies and materials why should two stroke diesel be confined to big ships and generators. And you can start them backwards !!

Thats why I started this thread...the forum needs it.

Paul

[grostek]

Hi Paul,

Listened to an interview with Norbert Haug of mercedes yesterday 10 mins after Hamiltons win. This was on german TV RTL and he was asked if KERS is now a priortity for Mercedes and he said

"We were surprised that the system functioned so much better than the oppositions"
and he also said that this was probably a once off win for KERS because Mercedes did not expect another win for the rest of the season.
He then went on to say that KERS would probably not be in any F1 car next season.

Please bear in mind he might be bluffing, to confuse the opposition. Time will tell.

As for a more affordable alternative engine, any development to reduce costs for Joe Public is to be applauded.

The prices being bandied bout for the BMW conversion are also over R120,000 or ut another way close to Jabiru 2200 engines, which incedently seem to be lighter than a 100Hp BMW coversion.

The work Boet plans to do with his conversion is at the early days stage and we will have to see what final price emerges.

2 stroke Diesels would have superior power to weight ratios but the question is are any such engines in production in the 100Hp class that would be candidates for conversion.
I like the idea of a 2 stroke diesel delivering high torque at low revs which would mean low specific fuel consumption and no need for a reduction drive.

[justin.schoeman]

I have been seeing some very surprising results recently on the AeroVee (direct drive 80hp VW conversion) mailing list. First flight for a skyranger this weekend, and performance figures were very similar to a 80hp Rotax.

Seems as people begin to understand propeller choice and cooling better, the VW becomes an option for more and more airframes. I get the distinct impression that the AeroVee would work quite well on the BB and other similar planes. Seems to give similar performance to a 85hp Jabiru, but at 1/2 the price.

I really think this could become (again) the definitive homebuilder's engine.

Another nice one I saw (was it on microlighters), was going to the other (i.e. non Rotax) snow mobile engines for conversions. Like the Yamaha Genesis 120hp. Very light 4 stroke, 4 cylinder. Complete conversion for around R60k (for 120hp!).

[ystervark7]

Yes we live in interesting times. I have also looked at the Yamaha snowmobile engine and agree that it that it looks like an excellent engine, the only problem is that we do not have snow, so no snow mobiles. Does somebody know if we will be able to import one at a reasonable price?

Locally the Yamaha VX jetski engines are an option but you might have to make some changes to the cooling system since the Yamaha sucks its water in directly. The 120HP engine is a 4-cylinder 4 stroke engine and the complete Jetski is about 100k new. It would be interesting to see how much a second hand engine cost?

The Skidoo jetski engine (made by rotax) is another options suggested by Charl. I understand that they have a radiator so that makes it somewhat easier. To my knowledge they are not readily available? If you can get one cheaply let me know.

I have looked at the automotive engines including the Metro Geo and the Yaris. I am not convinced that they are suitable for airplanes. Go Boet, if it is a great success I might still put one in my plane

For the record the BMW engine is about R90000-100000 is you add up the gearbox, exhaust, cooling system, fuel system, etc. I think that this can be reduced significantly if you can build it with a belt drive since the gearbox is the most expensive part. I know of al least 2 people who are looking at this and I hope to try it myself sometime next year. (For the record I am involved with oupa-G's BMW so I am somewhat biased but try to keep an open mind)

[grostek]

Have had a look atthe dieselis again, This is a French project using the opel Corsa Motor.

http://membres.lycos.fr/dieselis/

Herewith Pasted

DIESELIS

Diesel powered prototype aircraft



For a long time and with a few exceptions, light aircraft engines are special gas engine that are powerful and light but very expensive.

On the other side, car engines, built in mass production, take advantage of top-level technical research. Over time, diesel engines have gained more and more power, thanks to turbochargers and intercoolers, and have become lighter.

The "Dieselis" is a prototype aircraft with a diesel engine that is based at the Brest-Guipavas airport (France). It's an amateur-built two seater that was specially designed to use this type of engine and to challenge the popular notion that the diesel was "too heavy for an airplane". It has been built by two members of the Brest flying club, Paul Lucas for design and wood work, and Serge Pennec for the engine and metal work. The configuration is classic tractor, a low wing monoplane with a front position engine, in order to not take any risks with the airframe, beyond the difficulties and uncertainties that the engine might pose.

ENGINE TYPE

The engine chosen for this prototype needed to be reasonably powerful ( at least 65 hp) and not too heavy. The European market offers many choices, particularly in the two liters range. After having considered many engines between 1500 cc and 1900 cc, and eliminating the heaviest and the least powerful, three possible candidates emerged : Peugeot/Citroen, VW and Opel. Serge choosed the 1.5 l turbo, 67 hp used on the Opel Corsa. A year was needed to ready the engine for the plane and perform static tests, two and a half years to design and build the airframe. The prototype made its first flight at the end of september 1998, registred as F-PTDI, TDI signifying Turbo Diesel Injection. Since this date, the Dieselis has flown more than 500 flying hours without a problem. (july 2000)

To achieve this project, there were two essential characteristics to consider : the heavy weight of he engine, and the low amount of power for a two seater.

WEIGHT

The stripped engine (cast iron block) weighs 105 kg as compared to 60 kg for a Rotax 912 or 75 kg for a typical VW type engine. With the accessories installed on the engine, the weight goes up to 135 kg which results in an additional 50 kg to the aircraft empty weight.

POWER

The Opel factory technical data for the turbo engine without an intercooler indicates 67 hp at 4600 rpm, and a maximum torque of 123 Nm around 2600 / 2800 rpm. The power curve is that of a typical diesel, very flat at its maximum : the engine produces 63 hp at 3600 rpm, and there are only 4 hp more to be gained in the last 1000 rpm. The intercooler, by cooling the intake air, should augment the power by 8 -10 %. These DIN figures include the accessories and are thus more stringent than the SAE norm.

WEIGHT/POWER RATIO

This ratio seems unfavorable at first glance: we are dealing with about 2 kg per hp. What is the overall impact of this weight on performance? To find out, we could make acomparison with a VW conversion engine, weighing 78 kg that produces 76 hp at 2900 rpm, about 1 kg per hp, so at first glance two times better than the diesel.

In flight at 2400 m, the normally aspirated VW loses about 25 % of its power, peaking it at 57 hp. Considering the higher speed and the smaller diameter of the VW propeller, the larger and less stramlined cowling needed for the VW and its cooling drag, we believe the performance will be reduced down by another 10 % to 52 hp.Also, because of the drop in propeller efficiency and the lower performance of the engine, the amount of fuel to take along for the same range is 75 kg instead of 50. All things considered, we come out with 103 kg for 52 hp, or about 2 kg/hp, same as the diesel.

In the end, the weight/power ratio of the VW isn't better in cruise and at altitude. It wouldn't be the same if this engine was equipped with a turbo and a reduction drive but its weight (and its price) would go up at the same time.

THE ENGINE

Originally used on the Opel Corsa, it is actually a japanese engine produced by Isuzu, a world leader in diesel engine technology and a GM partner. The cylinder capacity is1500cc. There is also a 1700 cc version, 82 hp, same weight, on the Astra and Vectra. The block is cast iron wich explains the heavy weight ot the engine.

To reduce weight, the exhaust manifold was redone in stainless tubing obtained for a farm milk cooler since the original was also cast iron.

The turbo is the original factory unit. The turbo pressure is limited to 600 g.

A single exhaust pipe is fitted to the turbo outlet. The intercooler ( a radiator to cool the heated air from the turbo exit) has a section of 260 x 100 and is attached to the firewall. The carefully shaped NACA style intercooler intake duct is built into the side of the carbon fiber cowling and seals against the intercooler periphery. The intercooler exit ramp is integrated into the firewall and fuselage, conveniently located over the leading edge ot the wing in a low pressure zone.

The engine does not have an air intake filter. Passage through the turbo (thermal and compression exchange) raises the temperature of the incoming air about 60° in a climb. At the exit of the intercooler, the difference between the outside air is only 20° in a climb, and only 10° in cruise. The aluminium intake manifold is what is left of a stock part since we've greatly modified the shape, as well as removing excess weight. Lightweight tubes adjacent to the firewall connect the manifold to the intercooler.

The original starter (5 kg) is fed by a 30 amp-hour battery. For cold engine start conditions a plug-in external battery is utilized. The engine mount is a cradle type made of 16 and 20 mm high tensile tubing. Four silentblocks are located at crankshaft level below the propeller centerline.

TRANSMISSION

A custom redrive was designed to reduce the propeller sped and raise the centerline ot the propeller. It is a non-slip cog belt type. An industriel elastomeric coupling is installed between the lightened flywheel and the redrive. It's principal purpose is to handle any misalignment between the two assemblies. The belt is a Gates Poly Chain GT, 62 mm wide, 8 mm spacing. The manufacturer indicates its rating to be as high as 71 hp at 4000 rpm for industrial applications. The custom sprockets are made of hard anodized aluminium in accordance with Gates tooth profiles. The propeller centerline is 24 cm above the crankshaft. The sprocket assembly turns in a cage formed by two 8 mm aluminium support plates. These are spaced apart by two 8 mm U channels, press formed plates which were subsequently machined to maintain paralell conditions. The redrive cage is mounted 5 cm from the engine block by 6 tubular standoffs.

The propeller shaft turns on two bearings in a lengthened support made of machined aluminium.

The propeler flange extends 15 cm in front of the reduction drive to streamline the front of the cowling. The propeller shaft assembly has provisions to adjust belt tension. The weight of the redrive is 14 kg. The reduction ratio is 48/80, that is 1/1.66 or 60 percent. In cruise, between 2800/3200 rpm, the propeller turns at less than 1900 rpm, instead of at 2800 rpm, common for a direct drive engine.

COOLING

The coolant radiator is the same as found on the car, 650 x 265 mm size, 17 dcm2 area, quite a large piece to try and fit under the front cowling. We solved the problem by putting it behind the seats under the rear package shelf, which then permitted us to move back the CG, but which obligated us to install a "central heating" system in the plane. The total weight of the radiator, hoses, expansion reservoir and radiator fluid (7.5 liters) is 13 kg. The advantage in having the radiator in the rear is the available space to install a divergent/convergent ductwork for cooling efficiency and drag reduction. The intake is through a flush NACA inlet under the fuselage in a positive pressure area. The entry section measures 250 x 65 mm, that is 1.7 dcm2. The exit (like on the P-51 mustang) has a moveable flap to adjust the airflow and thus the coolant temperature. The adjustable flap makes a 10° difference. Because of the engine to radiator distance, the thermostat was removed to increase coolant circulation speed.

The water temperature is about 80° during climb, 70° in level flight, and 60° in descent. As on many auto engines, the oil is cooled in an exchanger, with the water circuit located at the base of the oil filter.

COWLING

The engine cowling is made up of three parts. The bottom part of the cowling is permanently attached to the engine mount. The left and right upper cowling pieces are hinged together at the upper centerline and attached to the firewall and lower cowling by Dzus fasteners for quick servicing. The cowling was formed from carbon fiber/epoxy over a male plaster mold shaped appropriatly with the engine and spinner in place. The cowling weighs 3.3 kg.

The engine compartment is cooled by a scoop under the cowling directed toward the hottest zones which are the intake manifold and the turbo. The heated air exit is made on top of the cowling (and not under as is so often done, since it is more advantageous to use the low pressure present during the climb on top of the cowling to help evacuate the heat).

PROPELLER

The relatively large 1.76 m diameter of the propeller is appropriate for the engine's power, thanks to the reduction drive and the diesel's high torque at low RPMs. The settings for the propeller sections were established for a speed about 170 km/h. The prop was built of soft wood and composite, four plies of unidirectional carbon fibers were applied with epoxy resin. First, two plies were placed at +/-30 degrees for torsional stiffness. Two plies were then added at 0 degree for bending strength, resulting in a finished weight of 3.2 kg.

The considerable propeller disk area and the small required power (less than 30 HP during cruise) produce a small prop loading favorable to efficiency. The narrowness of the engine block permits the streamlining of the cowling behind the propeller. The performance figures show the efficiency of the propeller to be at least 0.85. The propeller match seems good but the payoff is due to the torque curve of the diesel (the torque increases when the speed decreases, see curves) which makes this match particularly easy.

The takeoff thrust is pretty high for the power; the rate of climb is 5.0 m/s instead of 2.5 to 3.0 m/s for directly driven planes of comparable weight and power. Thanks to the lower prop rotation speed there is little noise on the ground or in flight. The 290 mm diameter spinner is made from carbon/kevlar and weighs 290 grammes.

These people wanted a cheaper, reliable, mass produced base engine to convert for a 2 seater that would give reasonable speed and range.

It is interesting to see the reasoning behind the project and what appeals to me is the 500 trouble free hours that the engine/airframe combination had done at the time of this article. The engine/airframe cobination probably has more hours now.

Notice how the 1.7L engine has more power for the same weight and if I am not mistaken the 1.7L engine is or was readily available in SA.

To do the same thing in SA, they have shown a methodology that can be sucessfully copied, and if possible even improved on.

Kind regards,

Gunter Rostek.

[grostek]

Here are some links to pics of the 1.7l Dieselis conversion

http://dieselis001.canalblog.com/albums ... index.html

http://dieselis001.canalblog.com/albums ... index.html

http://dieselis001.canalblog.com/

and here the whole reasoning and planning of the project.

http://membres.lycos.fr/dieselis/gb2.htm

Kind regards

Gunter Rostek.

[thermalator]

I would say KERS has zero applicability in aviation

KERS is all about storing energy that would otherwise be wasted in the brake cooling systems

[justin.schoeman]

Speak of the devil!

http://www.avweb.com/eletter/archives/a ... tml#200862

HYBRID ENGINE CONCEPT FROM FLIGHT DESIGN
Flight Design, GmbH, is developing from a standard Rotax 914 engine, an electric augmented powerplant that will produce an extra 40 hp for short (less than three minute) bursts of power. The company has "specifically developed for this task" an electric motor that is coupled to the prop hub through a belt drive. The goal of the concept is to produce an engine capable of fulfilling the role of a 160- to 180-hp normally aspirated engine without the larger engine's emissions. Mated to the turbocharged Rotax, the Hybrid Concept Engine will not readily lose power at altitude, flying efficiently in cruise, while enjoying the electric motor's extra boost during takeoff and initial climb. Batteries for the unit are based on Lithium Iron Phosphate chemistry and are quick-chargeable. Operation of the engine is designed for one-lever control, with a controller module selecting thrust from the electric motor only when the reciprocating engine is operating at more than 90 percent above available power. Otherwise, the reciprocating engine works to recharge the motor's batteries in flight, which causes "negligible" resistance on the crankshaft, according to the company. More...

[ZULU1]

The KZN coast has been internet less in the last three days and just caught up. So I wasnt far wrong with my thoughts on KERS. Its quite interesting that totally unknown to me that this had already been developed. However I would imagine a hybrid Rotary-KERS would be a very compact package and possibly they would be able to utilise something similar to a Ward Leonard control system in a hybrid drive type arrangement or a variation of the same type. (Ward Leonard systems were the fore runners of SCR and Oulton drives and used in lifts, trains, boats, submarines etc.) Studied them years ago at the Naval college in Devonport. But somewhere in there possibly lies an answer..Maybe drive a hydraulic motor instead of a reduction box re drive assembly ?? This would allow a motor C of G to suit the aerie, and the hydraulics could also be used to pitch the prop, control would be easy and the torque would be awesome ? Possibly use a constant loss oil lubricated rotary motor for the hydraulic source ?? Alleviates a sump.

Anyway, The question is how do they wind up the "KERS" power ? Maybe by pitching the prop no thrust pre take off, similar to charging a capacitor, maybe in Engine warm up phase, then unleashing the motor on take off run, that would be brilliant for a Gyro. Also in a Gyro the rotor head could also re generate the power back to the system.

Gunther I think the Thiellert diesel was a Isuzu 1,7 diesel with new castings and so on.

There are some interesting possibilities and warrant some debate.

Paul

[thermalator]

There are some interesting possibilities and warrant some debate.

That's the spirit.

When I say zero applicability I mean: Most aircraft take off at 100% power & cruise @ 75%. SO this is postulating - store some energy during runnup, take off @ 125% & cruise @ 100%. I just don't want to fly it. It will also use more fuel than a larger engine would.

Aviation always seems to attract the weird designs & self exciting dynamo's. Not to mention those inventors just in it for the "Funding magnet" aspect.

I would be more impressed if someone used a Rotax 914 with a turbo compound energy recovery system or even a combined cycle heat recovery system (like BMW has)

[grostek]

There are some interesting possibilities and warrant some debate.

Paul

Hi Paul,

Have a look at this article, the thing that caught my eye was ----Flywheel 64,000RPM and all running in a Vacuum.

http://www.racecar-engineering.com/arti ... ybrid.html

They are two ex Renault engineers seem to have come up with a marketable system.

Kind regards,

Gunter Rostek

[grostek]

Hi Paul Have just found some readers comments at the bottom of this page makes interesting reading.

http://www.racecar-engineering.com/arti ... ybrid.html

Kind Regards,

Gunter Rostek.

Reader comments
Add your comments
April 30 13:51
JudebertSomething like this could be very useful in electric vehicles. Instead of complicating the controller by adding extra silicon to turn the motor into a generator, we could just hook one of these flywheels to the output shaft. It would be a lot more efficient than converting kinetic energy to electric energy and back again, too.
May 30 09:12
JamesThis is all very well, and environmentally friendly but does it not worry people that F1 is now moving away from what it's meant to be? Ever since it began it has been 4 wheels and an internal combustion engine, with a gearbox in it. Recent additions such as traction control and ABS, although banned, were only driver aids and didn't really affect the performance. Electronic gearboxes and clutches again didn't change anything, they just made the sport safer and faster! So why do we have to settle for watching hybrid rubbish come 2013?? If I wanted to do that i'd watch the "Toyota Prius" grand prix... not F1, the pinicale of racing engineering. The noises and smells make it what it is, and 22 cars polluting isn't going to make any difference in the grand scheme of things. o well
July 09 12:44
PrimozA few years back i read in a chemistry notebook that a normal Nascar race pllotes the air more than one of our thermo electric plants burning lignite in a year.

Now as for F1, i see where you are going, but a lot of F1 techonologies are vecoming available in road cars (use of CF, TC, ABS, electronic suspension), making for a better, safer ride. So KERS would be a usable thing, expensive at first but F1 teams have the money and experimental knowledge, to do it. Once thoroughly tested, it can be adapted to road cars. And with todays fuel prices, every bit of energy saved is a good thing. I still hate priuses and diesels though.
July 23 14:47
svoburnerMmmmm, the flywheel can store 60Kw, that equates to 60,000J for one second. Premium petrol has an average energy content of 39.5MJ / ltr. So, 60KJ is the same as burning 39.5MJ / ltr / 60KJ = 0.00151ltr.... so the energy stored in the flywheel is the equivalent to burning 1.5ml of petrol...... is this worth it? Bearing in mind the energy required to manufacture the flywheel system.
These calculations make some assumptions, the main one being that a petrol engine would not be able to extract 39.5MJ as mechanical energy from a litre of petrol.
60Kw (for one second) sounds a lot, but it would only supply a 3Kw electric heater for 20secs.

September 23 03:03
REESRaceing continues to be the crucible of performance inovation. This may be the most exciting development we've seen in 20+years (on demand torque!). This technology will translate into performance as well as efficiency.
January 06 12:34
Belattisvoburner, Flywheel doesnt store 60KW (power) but 60KW during 7 secods (energy) twice a lap. Thats 60KJ/s * 2 * 7s = 840KJ. If a liter of fuel has got your claimed 39.5MJ / ltr the energy stored in the flywheel is the equivalent to burning 0.021 liters per lap. Multiply that 70 times for the whole race and you have got 1.47 ltr.
I heard more developed rear axle KERS will supply 200KW during 7 seconds. That would be almost 5 liters for the race (and half a second less in pitstop)