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Improvements in fuel economy of up to 22.4 percent on the ARTEMIS test cycle (pdf), which represents typical real-world usage, have been demonstrated by a research vehicle fitted with a flywheel hybrid system that includes stop-start technology.

Developed by a consortium of British firms as part of the UK government-backed Flywheel Hybrid System for Premium Vehicles (FHSPV) program, the mechanically-driven flywheel system delivers a claimed 80 horsepower of recovered energy from its self-contained hybrid module.

The consortium says mechanical hybrids solve many of the challenges associated with electrified vehicles. The firms claim the flywheel setup eliminates cost, weight, packaging and recycling issues associated with the batteries in conventional hybrids. Prodrive's head of vehicle engineering, David Hemming, states:
The research shows the potential of mechanical hybrids as an affordable alternative to battery hybrids. Both the fuel economy results and the driveability are impressive, even with early-stage calibrations and no other design optimization.
The FHSPV vehicle recovers energy via its rear differential and continuously variable transmission and routes that juice into a flywheel. When the driver reapplies the accelerator pedal, the CVT transfers energy back to the wheels. The flywheel and its associated drive system are installed adjacent to the rear axle, in a space normally occupied by the spare tire. The whole system reportedly weighs in at less than 176 pounds.

Designed by Flybrid Systems, the flywheel is constructed from carbon composite and operates in a partial vacuum, allowing it to spin at up to 60,000 rpm. The CVT is built by transmission experts Xtrac and Torotrak. Engineering consultants Prodrive and Ricardo handle the system's configuration and integration and automakers Jaguar, Land Rover and Ford pitched in to develop the FHSPV.
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FLYWHEEL HYBRID VEHICLE DELIVERS UP TO 22.4% FUEL ECONOMY IMPROVEMENT

Improvements in fuel economy of up to 22.4 percent (in the new ARTEMIS test cycle, which represents typical real-world usage today) have been demonstrated by a research vehicle fitted with a flywheel hybrid system including stop-start. Developed by a consortium of British companies as part of the Government-supported Flywheel Hybrid System for Premium Vehicles (FHSPV) programme, the mechanically-driven flywheel system delivers up to 80bhp (82PS, 60kW) of recovered energy from a self-contained hybrid module.

In the industry-standard NEDC cycle, the flywheel hybrid including stop-start achieved an 11.9 percent improvement.

The consortium believes that mechanical hybrids solve many of the challenges associated with electric hybrids. There is no inefficient conversion of energy from kinetic to electrical to chemical and back. And the cost, weight, packaging and recycling issues associated with batteries are also eliminated.

"The research shows the potential of mechanical hybrids as an affordable alternative to battery hybrids," confirms Prodrive's head of vehicle engineering, David Hemming. "Both the fuel economy results and the driveability are impressive, even with early-stage calibrations and no other design optimisation."

The FHSPV engineering development vehicle recovers energy via the rear differential through a continuously variable transmission (CVT) into a high-speed flywheel. When the driver reapplies the accelerator, the CVT smoothly transfers the energy back to the wheels. The flywheel and its drive system are installed adjacent to the rear axle, in the space normally occupied by the spare wheel and the whole system weighs 80 kg. Minimal body and packaging changes were required to integrate the system. There is no change to the driveline configuration.

Designed by Flybrid Systems, the flywheel is constructed from carbon composite and operates in a partial vacuum, allowing it to spin at up to 60,000rpm. The CVT, which manages the flywheel's speed and the flow of energy in each direction, has been built by precision-engineering firm Xtrac using proven traction drive technology from Torotrak.

Automotive technology specialist Prodrive is responsible for the system's configuration and integration into the vehicle. Prodrive also developed the system's complex control strategy and software including preliminary calibrations. Ricardo and Ford provided specialist expertise around alternative technologies and applications.

"There is growing support for flywheel hybrid systems across the industry, fundamentally driven by affordability," said Torotrak CEO Dick Elsy. "From Torotrak's work in this market, the directional costs of the system look to be less than half of the cost of equivalent battery/electric hybrids. A mechanical hybrid with stop/start, at a transaction price that makes sense, has significant potential for widespread application in the drive to reduce CO2."

ABOUT THE TECHNOLOGY STRATEGY BOARD:

The Technology Strategy Board (which part-funded this programme) is a business-led executive non-departmental public body, established by the government. Its role is to promote and support research into, and development and exploitation of, technology and innovation for the benefit of UK business, in order to increase economic growth and improve the quality of life. It is sponsored by the Department for Business, Innovation and Skills (BIS). For further information please visit www.innovateuk.org


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    • 1 Second Ago
  • 61 Comments
      Arun Murali
      • 3 Years Ago
      The question is how cheap. I certainly dont think having a second transmission is going to be cheap. I am sure in 2-3 years the premium for Hybrids are going to be only $1500-1700 over their standard counter parts and they can deliver over 50% improvement in efficiency in city and highway. So if this has to have some acceptance as cheap then it has to cost about $500-600 a piece at the best. Add this and the start-stop system together, you might really save some fuel. The other thing is most cars today does not have a rear axle, so they must be talking about 4x4 or trucks or a few luxury cars. If not, can you install this thing in one of the rear wheels, without the axle. I have been thinking of a cheap hybrid solutions for long and the best I could come up was this http://arunmur.blogspot.com/2011/09/cheapest-possible-hybrid-design-idea.html
      Larry
      • 3 Years Ago
      This basic system was developed at the Johns Hopkins Univ. Applied Physics Lab a couple of decades ago. As non-classified work, the JHU Magazine ran a story on it. The APL being a joint Navy-JHU facility also does classified work, indeed, it created the proximity fuse for Navy flak shells used in WW2. The original test vehicle got ~100 miles per charge which they figured would increase 50% with regenerative brakes.
      2 Wheeled Menace
      • 3 Years Ago
      Very interesting.. this could be easy to mass implement... but the fuel economy improvement seems like a wild claim. Maybe there's an improvement in city stop and go, but otherwise.. i do doubt it
        • 3 Years Ago
        @2 Wheeled Menace
        Check out the pdf on the Artemis test cycle. It sounds solid to me. Of course you don't gain in highway cruising, but the cycles take account of that to average it for typical driving. The high efficiency is because you are keeping kinetic energy in the same state, not altering it to electricity, storing it in a battery or capacitor, and then re-converting it to kinetic energy again. The gains would still apply to electric vehicles. If you are using batteries rather than capacitors to store the energy the relatively low power density as opposed to energy density of the batteries also mean that a lot of the energy does not even make it to the battery, so again the efficiency is improved.
          2 Wheeled Menace
          • 3 Years Ago
          They should be equal to the loss from the battery to the controller - 3 phase DC to DC + PWM action and current limiting certainly incur about ~10% loss. Yes, there is lithium titanate, but so far what i have seen has very wHr/KG ( about 100 or so? ), and weak discharge ratings ( under 5C i think? ). This means that you will need a large battery and can't use a smaller one.. and there has been no talk of the cost of those batteries either. Capacitors would be great! apparently they have low energy storage though, and eat up a lot of space. It would be a dream to have all the best worlds with a battery. With a battery that could suck in >20C, you may not even need mechanical brakes anymore and the EV could be even simpler..... well, a man can dream ;)
          2 Wheeled Menace
          • 3 Years Ago
          Good points David. Esp. about the braking thing - the charge rate on modern lithium batteries is still very low, and braking will produce more energy than the car uses to accelerate. A lot of energy is indeed still wasted in friction. Until we have batteries that can charge at 5C-15C with no major shortening of the lifespan of the battery, a flywheel system such as this would be helpful even on electric cars.
          • 3 Years Ago
          2WM: Lithium titanate can handle 15A discharge and 10C charge rates: http://www.toshiba.com/ind/data/tag_files/SCiB_Brochure_5383.pdf For their latest 100Wh/kg is about right. Toshiba reckon their batteries are in the same ball-park for costs as conventional lithium ones. Altairnano are much dearer.
          skierpage
          • 3 Years Ago
          A 1500 kg car traveling at 30 mph has only 50 Watt·hrs of kinetic energy. If it decelerates in 5 seconds to 0, the rate at which work is performed is 36 kW. Air and road resistance slows down the car and generation isn't 100% efficient, so say 30 kW is available for 5 seconds. It seems hybrid car packs only have to get a little bigger to handle that easily (and a bigger battery pack is good if it's powering a motor in a CVT that permits the ICE to run at optimum load more often). Yahoo Answers says a Prius owner says the current Prius brakes most efficiently at 60A or 16 kW, so it seems Toyota is willing to recharge that NiMH pack at 10 C for a few seconds. (Disclaimer: "Math is hard" -- Barbie) @2 Wheeled Menace, braking *never* produces more energy than the car uses to accelerate. On this planet we obey the laws of physics! :-)
          Larry
          • 3 Years Ago
          David, the flywheel is electrically driven, regenerative brakes would convert the vehicle's kinetic energy to electrical to power the flywheel so yes there would be line loses but at least 50% of the kinetic energy is conserved for reuse. Friction losses by the flywheel itself are minimal due to the high vaccuum, ~10-8th Torr and magnetic bearings.
          • 3 Years Ago
          2WM A lithium titanate battery has those specifications, but you still loose energy by transforming to and from kinetic energy. I don't know how significant those losses are. By and large, maybe the obvious way to go is to use batteries/capacitors on electric cars, and maybe flywheels on mechanical or hybrid cars.
        Dave D
        • 3 Years Ago
        @2 Wheeled Menace
        I've been scouring the web trying to find a flywheel company who will give real numbers on their efficiency and it's about impossible. I've found a couple of white papers by flywheel manufacturers who claim to be 5-10% "more efficient than battery systems". But they ignore supercaps so I'm sure that must not be a good comparison for them LOL I've also found some white papers from government studies where they claim "the fuel economy improvements are 10%-15% higher with a ultracapacitor system than the same weight of batteries due to the higher efficiency of the ultracapacitors". http://spinnovation.com/sn/Batteries/Batteries_and_Ultracapacitors_for_Electric_Hybrid_and_Fuel_Cell_Vehicles.pdf Of course, they're comparing the effect on MPG which is the real goal and we're talking about the efficiency of the flywheel compared to batteries compared to ultra/supercaps. That efficiency of the storage device is not linear with the MPG improvements so it's a bit of a red herring. (think about it, flywheel systems claim to be somewhere between 80-90% efficient, but they can only help about 22% on a heavily weighted city driving type drive cycle. So how much of a MPG difference will a small change in storage unit efficiency have on the overall system then??? Not much....They'll all be somewhere between 20-23% improvement on this drive cycle. So it really comes down to which one will have the cost advantage over the next 5 years.
      Spec
      • 3 Years Ago
      22% . . . nice. But I wonder if the mechanical complexity is worth it?
      King George
      • 3 Years Ago
      Plug-in hybrid wins. You can plug in your Prius, charge it in the garage over night. Save money on gas.
        joemca9529
        • 3 Years Ago
        @King George
        joeMac You know "king George", you and everyone else talks about recharging batteries as though it doesn't cost anything. There is no free lunch unfortunately
      George Krpan
      • 3 Years Ago
      The world uses 82.77 million barrels a day. 22% is 18.21 million bbls. Tha'ts nearly what the US uses per day. While we are still using oil, this will save a lot of oil. It's cheaper than hybrids and needs no filthy batteries.
      Smith Jim
      • 3 Years Ago
      Energy and power are two completely different things. 60 kW is the power output and NOT the amount of energy that can be stored in this flywheel. The amount of energy stored is about 0.11 kW-hr. (http://www.flybridsystems.com/F1System.html To convert kiloJoules to kiloWatt-hours divide by 3600) That's about 1/5 of the energy storage in a Honda Insight and about 1/10 as much energy storage of the Toyota Prius. Flywheel energy storage sounds interesting but not very practical.
        • 3 Years Ago
        @Smith Jim
        They are not meant to run the car on, but to conserve braking energy. That is why capacitors if you are going to go the electric route are better than batteries as their power density is higher. You don't need high energy density.
        Ford Future
        • 3 Years Ago
        @Smith Jim
        With so little energy capacity what is it going do to for you? You get a 10 feet acceleration boost and then that's it? Battery Hybrids can climb small hills with electric assist.
          • 3 Years Ago
          @Ford Future
          Nah, I ain't an engineer, so I will screw up the figures if I try to quote them, but the energy in a 'braking event' or in an 'acceleration event' only lasts a few seconds, and the energy requirements are surprisingly modest. You only need to store one of them.
          • 3 Years Ago
          @Ford Future
          Oh, for an edit function! The bottom line is that you can pretty much trust the Artemis cycle figures, and flywheel storage in city driving is going to make you good energy savings.
        Larry
        • 3 Years Ago
        @Smith Jim
        Reread the article, the flywheel storage capacity is 80 KW-Hrs which is 40 minutes charging time on 120 VAC if it uses direct power transfer, an intervening stepdown power supply would of course waste energy as heat and lengthen charging time. 80 KW-Hrs was also the capacity of the car/system developed by JHU decades ago. Only difference is this system is a hybrid not a pure electric car.
          Richard
          • 6 Months Ago
          @Larry
          No, that is just completely wrong. - Engineer
      • 3 Years Ago
      Why do you suppose it is that one no longer reads of innovation by U.S. auto companies?
      Peter
      • 3 Years Ago
      *up to means on the city cycle, which is fine, it will give economies there where small diesels and other ICE have particular trouble The weight advantage is not insignificant - the Sonata Hybrid is 320 lb surplus of battery + electrics with a 40hp electric motor mind you this (KERS) can be expensive, and it is noted that it is being developed for premium cars.
      krisztiant
      • 3 Years Ago
      Like everything, flywheel has lots of pros and cons. In this case (for Premium Vehicles) the most significant advantage: the flywheel doesn't require any structural changes to existing vehicles and also lighter than battery tech, so easy and cost effective to implement, but delivers a significant improvement in fuel economy (especially in urban environment).
        Dave D
        • 3 Years Ago
        @krisztiant
        Actually, the weight, and subsequent energy density of the flywheel system is surprisingly bad. It would only take 18kg of Ioxus supercaps to hold that same amount of energy. http://www.ioxus.com/documents/5000FPrismaticDataSheetRev12132010.pdf You'd also have to add the weight of the motor, but one of the Remy's gives you 110hp and it only weighs 33.5kg. So we're talking about 51kg (113lbs) and you'd get 110 hp compared to the 80 from this flywheel unit. The real difference is going to come down to which one is cheaper between the flywheels+CVT transmission or supercaps+electric motor. They will both give you about the same result in mpg gains on the drive cycle.
          krisztiant
          • 3 Years Ago
          @Dave D
          Dave D, I think they are simply playing the CAFE / EURO 6 game, with the lowest possible investment. Press release: "The research shows the potential of mechanical hybrids as an affordable alternative to battery hybrids," Emphasis on affordable. Also: “…the cost, weight, packaging and recycling issues associated with batteries are also eliminated. “ About the technology strategy board: “The Technology Strategy Board… is a business-led executive non-departmental public body, established by the government.” So it’s more of a “business-led” project, than a “technology-led”. Flywheel cons: they, of course, didn't mention any limitations, like e.g. energy storage time. „Flywheel energy storage systems using mechanical bearings can lose 20% to 50% of their energy in 2 hours”. So after some hours of spinning during parking - or even riding on highway - the flywheel loses most - or all - of its energy. It’s no problem at racing, but in everyday usage, it is. (F1 also uses mainly battery). The future is definitely the more and more electric and less and less mechanical solution.
          Dave D
          • 3 Years Ago
          @Dave D
          krisztiant, I didn't realize the flywheel systems lost that much energy over time. I guess it's a fairly low energy, high power system for stop start applications so it's not a show stopper, but certainly not a good feature either. Like you, I think the electric systems will win out in the long run. I think batteries or supercaps (some of the new ones coming out have energy densities on the order of 100-150Wh/kg and will hopefully be on the market in a couple of years), will gain the advantage of mass production and then it will be game over. And it ties too much into the production of EVs/PHEVs as well. I could be wrong, but it seems that path is the most likely to me.
          King George
          • 3 Years Ago
          @Dave D
          Good point. The patents been taken by the Japs already. And a electric hybrid system is complex, involving 3 motors. So the Brits need a cheap alternative that will buy time, and comply with Euro 6.
          krisztiant
          • 6 Months Ago
          @Dave D
          David, That's why the article title - i.e. flywheel hybrid - a little bit misleading, as it is clearly a flywheel KERS (which otherwise loses its energy after some ours) and not a hybrid. It is also very clear from the press release: the Technology Strategy Board did not choose the flywheel (over the battery), due to its technological supremacy, but because lower cost and weight. Thus, it can be a good solution in existing premium gas guzzlers to - cost effectively - improve city fuel economy (as flywheel KERS), but this system is nowhere near as efficient, as any full-blown hybrid system (which otherwise cost much more).
          • 3 Years Ago
          @Dave D
          kristiant: Loosing the energy over 2 hours has almost no effect on overall efficiency, as the energy in any one braking event is not that great. The point is that the savings are made in lots of braking events in city traffic.
        guyverfanboy
        • 3 Years Ago
        @krisztiant
        This would be good to see Porsches, Ferraris and whatnot.
      • 3 Years Ago
      Might be worth a try for the cars that aren't micro hybrids yet. Mechanical hybrid is easier to apply, but results to breakdown if not used and maintained properly. Full hybrids still have their edge on batteries and ultracapacitors.
        krisztiant
        • 6 Months Ago
        This system is rather a Kinetic Energy Recovery Systems (KERS) than a hybrid, as it simply recuperates some break energy and then helps the vehicle to accelerate while its energy lasts. This does improve fuel economy in cities (which is good), but it is far from a full-blown hybrid system (which naturally much more expensive too).
      Ladson
      • 3 Years Ago
      This is a nice mechanical engineering experiment; but, it makes little sense to produce the product;...why? because they have no future; don't forget the country has a goal to become independent of foreign oil and dirty air. Building gasoline and diesel cars will never do that. It would be better to bring all those electric cars experiments the auto makers have complete up to the next level; put them into production and not some far out mechanical experiment using fly wheels. This idea has been around almost as long as electric cars; but, has never proven to be viable....forgetaboutit!
        • 3 Years Ago
        @Ladson
        The product has no future because 'the country' has a different goal? Which country is that, and is it the only one in the world, with no production or consumption occurring elsewhere? :-0
        2 Wheeled Menace
        • 3 Years Ago
        @Ladson
        Sometimes you have to accept the lesser evil. We do this every 4 years when we vote so you should be used to it :) Not everyone can afford a $30k electric car. A 22% improvement in fuel economy is not a small drop in the bucket. And why not use oil as efficiently as possible while we still have it anyway?
          Joeviocoe
          • 6 Months Ago
          @2 Wheeled Menace
          Mock Mook, Yes, subsidies ARE unsustainable. But that is why they are designed to phase out as the market for EVs grows and is able to stand on its own. Yeah, a lot of the time subsidies that are designed to go away, never do (Oil/Gas and Ethanol)! But as long as we make good on growing the market, EVs won't need subsidies soon enough. Nissan is actually banking on the fact that they will be able to drop the Leaf price when the subsidies disappear (after 200,000 Leafs sold) so that the cost to buyers is about the same as it is now. --------------------- BTW, every credible study out there shows that MILLIONS of EVs can be on the road without building a single new power plant or running additional HV power lines. Yeah, about 47% of the fuel might be dirty coal (IF, and ONLY IF EVs are sold evenly throughout the US population, which they are not). The majority of EVs will be sold and used in states with cleaner energy profiles. Either way, Oil is both dirty and mostly imported.... while coal is 100% domestic. And a single stationary coal plant is still MUCH cleaner than thousands of gasoline burning cars. The rest of the 53% of our electric power comes from Natural Gas, Nuclear, and renewables. And depending on the state you live in, it could be VERY different.
          • 6 Months Ago
          @2 Wheeled Menace
          Ladson, you do realize that the $12,500 in government rebates to make a Leaf competitive is an "unsustainable environment" right? BTW, where are all the new power plants and electric power lines going to come from? Where is the fuel for all those power plants going to come from?
          Ladson
          • 6 Months Ago
          @2 Wheeled Menace
          Yes 2 Wheel, you're right...the Congress is like a circus, every four years we get a new set of clowns. And, I agree $30k is too much; however, I did receive $12,500 rebates and Fed credits for my Leaf and is the only reason I could afford it. I think as soon as electric cars reach the tipping point, we will see the prices go down...bound to happen; buying oil from enemy states and paying $4 for gasoline cannot continue to without continuing economic damage to our country. I would like to see the auto makers provide a mix during this pre-period before electric cars take over the roads. How about NatGas, Bioalcohol, Biodiesel?; smaller and lighter four cylinder cars?
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