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Ricardo reports significant efficiency advance in its Kinergy hermetically-sealed high-speed flywheel energy storage system; prospects for price-sensitive hybridization

22 August 2011

Kinergy
Exploded view of Kinergy high-speed flywheel prototype and magnetic gear system. Click to enlarge.

Ricardo reports that a significant improvement in the magnetic coupling and gearing system in its Kinergy hermetically-sealed high-speed flywheel energy storage device (earlier post) has now taken the system efficiency to better than that of a conventional geared-drive system.

The subject of nine Ricardo patent families in application, Kinergy is based on a high-speed carbon fibre flywheel operating within a hermetically sealed vacuum chamber at speeds of up to 60,000 rev/min. Unlike current devices in which energy is imported and exported via a drive shaft operating at flywheel speed, Kinergy transfers torque directly through its containment wall using a magnetic gearing and coupling system. This approach to high-speed flywheel technology offers the prospect of enabling the unit to be sealed for life, thus avoiding the need for high-speed seals and a vacuum pump, and hence reducing costs and maintenance requirements.

Kinergy2
Kinergy prototype prepared for testing. Click to enlarge.

The consequent weight and space saving potential provides for a competitive packaging envelope, while the ability of the efficient magnetic coupling to incorporate a high gear ratio makes the input and export of torque significantly more manageable than would be the case in a more conventional direct-driven high-speed flywheel design, Ricardo says.

This first Kinergy prototype has resulted from a fast-track engineering development process intended to deliver the unit that will be at the core of the Flybus high-speed flywheel mechanical hybrid powertrain demonstrator vehicle. (Earlier post.) Following precise balancing of the flywheel rotor during construction and assembly, the unit was installed on a specially constructed dynamometer for development testing.

Successive tests have been carried out at increasing speeds and compared with the results of engineering simulations of performance and efficiency. A major thrust of that development has been the elimination of stray magnetic losses in the coupling, and breakthroughs have been made that are critical to the success of the technology.

The 960kJ-rated Kinergy system provided for use on Flybus has been developed by Ricardo as part of its involvement in the KinerStor project, which also includes a longer term development process planned for completion towards the end of 2011. This work will focus on the further optimization of the Kinergy system, primarily integration with an improved continuously variable transmission, and with electrical power take-off devices for recharging vehicle batteries.

Also being explored are improvements to the design of the magnetic gearbox for better manufacturability and efficiency, and designs for improved component concepts including low loss magnetic bearings and lighter containment systems. The prototype Kinergy system—as delivered to the Flybus project—will be on display at the Ricardo and Torotrak booths at the Cenex LCV2011 event at Rockingham, UK, on 7-8 September 2011.

The efficiency improvements announced today represent a significant milestone in the development of this highly promising Ricardo patented energy storage technology. This next-generation, cost-effective, high energy density flywheel system technology genuinely moves the state of the art forward, offering the prospect of effective mechanical hybridization of low-carbon powertrain applications in all types of vehicles from passenger cars to high speed railway rolling stock.

— Nick Owen, project director for research and collaboration at Ricardo UK

Flybus and KinerStor. Ricardo is currently engaged in two research collaborations through which it is developing and refining its Kinergy high-speed flywheel technology. Each of these projects is supported by an investment from the UK Government-backed Technology Strategy Board with balancing resources provided by the respective research partners.

The first of these research collaborations—Flybus—involves the development of a Ricardo Kinergy flywheel energy storage device incorporating a Torotrak patented Continuously Variable Transmission (CVT) for installation in a demonstrator vehicle based on an Optare Solo commercial bus. The Flybus project is being led by Torotrak and includes partners Optare and Ricardo along with support from Allison Transmission.

The KinerStor project led by Ricardo comprises a consortium of industrial partners including CTG, JCB, Land Rover, SKF, Torotrak and Williams Hybrid Power. The project aims to demonstrate the potential of using high-speed flywheel technologies—including both Kinergy and competitor systems—in delivering hybrid systems with the potential for 30% fuel savings (and equivalent reductions in CO+ emissions) at an on-cost of below £1000 (US$1,600), thus enabling the mass-market uptake of hybrid vehicles in price-sensitive vehicle applications.

August 22, 2011 in Hybrids, Vehicle Systems | Permalink | Comments (24) | TrackBack (0)

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The make this unit more comparable unit batteries, would it be possible to use grid e-power to get the flywheel(s) to max speed just before leaving the house and get a few Km on flywheel power (if the stored energy is enough to do it)?

@Harvey - not a bad idea at all.

You could "precondition" the battery and oil+interior temperature from the mains - especially if you had predictable departure times. (it is already done in Alaska etc.)

In which case, you could oversize it and get more "kinetic" miles at low speed.
An induction charging connection could be used if we weren't transferring too much energy.

It does not matter how we do braking energy recovery (battery electric, hydraulic or kinetic) as long as we do it, OR prevent people driving too fast in built up areas (and you can guess how popular that would be).

HD, not sure of units(check me), but if 1 watt = Joule/sec, 960kJ = 128 hp for 1 second(750 W/s = 1hp).

While this isn't a long drive, having an extra 20 hp for six seconds whenever one accelerates would useful - esp. if it comes from wasted braking heat.

Maybe I missed a 0 (1280 hp)..

Flywheels are used as an alternative to capacitors, ie to provide a burst of power. They are high power density and low energy density so whether they are charged before leaving home from the mains is pretty irrelevant as the total energy is small.

One may be better off with recent super caps?

Maybe. But these flywheels are in the same energy-density league as recent ultracaps, so most of the useful distinction between them comes down to cost and cycle efficiency.

Given that batteries are the biggest cost and warranty headache in HEVs, adding flywheels as an alternative storage system can't do anything but speed adoption.

This is interesting stuff but if my math is correct 960 kJ is 0.27 kiloWatt-hours. That's about one fourth the energy storage in the battery of a Prius hybrid.

Super-Ultra Caps performance growth has been exceptional in the last 10 years. Another similar decade and they could reach or fly by most batteries and be worlds ahead of flywheels.

Their inherent capability to charge/recharge quickly a million+ times and retain their charge could make them the winner.

Parry People Movers uses large steel flywheels. ..HG..

@Eschewo
The Ni-Mh batteries in the Prius hybrid can only use a few per cent of the capacity (otherwise, battery life is compromised). Thus, one fourth of the energy is all that is needed in a hybrid application. If an all-electric range is desired, Li-ion batteries could be added at a (prohibitively high) extra cost. Significantly lower cost, higher efficiency and long life make flywheel hybrids an interesting alternative to conventional electric hybrids.

More to the point, the power density of the flywheel is a lot higher than the Prius battery.

@Engineer-Poet
Sure, this means that you can have all the benefits of a conventional electric hybrid (start-stop, peak-shaving, engine downsizing, regenerative braking, etc.) but at a lower cost and with lower vehicle mass. In fact, this is definitely a serious competitor to any other hybrid technology (electric, pneumatic or hydraulic).

They may lose some efficiency via the magnetic coupling but some is probably recovered, since the mechanical coupling and the vacuum pump is not needed and it is definitely more manageable as well as it provides simplification via the seal-for-life option. To me, the CVT seems to be the most critical component in the system. It has to provide a very wide gear ratio at high efficiency and, potentially, it may have some tribological issues to address.

This means more than peak-shaving; 960 kJ is on the order of the total kinetic energy of a 1500 kg car at freeway speeds. (I'm not sure if the 960 kJ unit is small enough for a passenger car; the Ricardo site buries details and has few internal links.) This could take up and return the full braking energy of a bus-sized vehicle from 30 kph or so and is not rate-limited by chemical reactions or diffusion.

The potential for fuel savings (or e.g. shifting a BEV from batteries specified for peak-power to average power requirements) is enormous. So is the potential for quiet; a sustainer engine on a bus wouldn't need to start until some distance from a bus stop, and would not need to run at high power except e.g. to climb hills.

Anyone know if gyroscopic effects from a flywheel affect vehicle handling?

Anytime someone gives you energy in kJ instead of kWh...that means they have really, really low energy.

It sounds a hell of a lot better to say 900kJ instead of .27kWh! Kind of like telling someone your car cost 1.2 million....yen! ROFLMAO

On the other hand, 960kJ (.27kWh) is almost exactly the energy needed to accelerate a 4,000lb vehicle from 0 to 70 mph. So it's very useful for regen breaking and acceleration, and that is what it was designed for.

DaveD, you said pretty much what was in my first sentence.

No, James, the gyroscopic effect won't be much. The angular momentum of a flywheel is Iω, but the kinetic energy is ½Iω². A flywheel spinning at 60,000 RPM (~6300 rad/sec) and storing 960 kJ has a peak angular momentum on the order of 300 Nmsec. Figure that the orientation will be vertical and cars usually stay pretty flat (roads don't do barrel rolls) and you can see that the forces won't be all that large even without gimbals.

EP,

Yeah, but you said kg. That confuses the hell out of all us poor US folks ROFL But I'll give you a pass this time because you said "freeway speeds" instead of 113kph!

Sorry, but I couldn't resist :-)

On a serious note, I can't find any real specs on it's size and weight. But at a cost of $1,600 it is way ahead of any package with this much storage built from supercaps today.

Of course, I haven't seen the specs on the new generation of supercaps coming out which are supposed to be between 15-20Wh/kg. But the price would have to come way down because today they are about $15/Wh. At that price, a 275Wh pack would cost over $4,000.

If they hit their targets to offer the next generation supercaps at the same price with 3x the energy density...then it gets interesting again.

But for now, this Ricardo flywheel system looks like the best on the horizon.

The complete Prius electric transaxle costs about $1500 (OEM), and that includes the battery, a transmission, alternator, starter and the differential. Plus the Prius does not use direct fuel injection or turbocharging.

Herm,

I'm sure that the Ricardo flywheel system (and supercaps as well) can also drop in cost quite a bit if they they are in volumes in the millions...as the Prius is today.

And flywheels (or supercaps) would clearly last the life of the car. The batteries of the Prius will probably have to be replaced if the car hangs around 17+ years as most cars do these days.

Prius batteries seem to be lasting a long time, I think the consensus in the forums is around 250k miles.. but lets not talk about Honda hybrids. Apparently both Ford and GM are also doing good engineering, and designing their batteries to last the life of the car. Hyundai engineers are boasting of very long lifes for their lithium-ion batteries.

I think the hybrid ship has sailed and it settled on electrics, plus it provides a path directly into the future.. BEVs.

If partial electric propulsion suddenly had to cover 50% of vehicles instead of 2%, battery production would have difficulty filling demand (due to raw materials if nothing else). Flywheels and supercaps use different materials and also have different capabilities; they charge and discharge much faster, so they are superior for stop-and-go operation or driving cycles with hard braking and acceleration. They'd have a place, at least for a while.

Electric hybrid manufacturing will be dominated by the Asian countries for a while to come, perhaps an equivalent mechanical solution could be done locally in the UK and the US.

"If partial electric propulsion suddenly had to cover 50% of vehicles instead of 2%, battery production would have difficulty filling demand "

Thats a strawman argument E-P.

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