Why did the flywheel hybrid system by no means catch on for highway automobiles?

Enlarge / Why did the flywheel hybrid by no means catch on for highway automobiles?

When a Pace community tv crew interviewed Margo T. Oge, then-director of the Environmental Safety Company’s Workplace of Transportation and Air High quality, throughout the 10-hour lengthy 2010 Petit Le Mans Sequence race at Highway Atlanta, Porsche’s experimental 911 GT3 R Hybrid race automobile held down a top-20 place within the 45-car subject.

The published crew took each alternative to name consideration to the presence of the brand new Porsche. Hybrid road automobiles had been turning into mainstream, and “highway relevance” was repeatedly cited by Oge together with vitality independence and low carbon emissions as EPA imperatives.

However, like its equally new Components One hybrid race automobile cousins, this particular 911 GT3 R was not a street-going hybrid. This was a “flywheel hybrid.” As an alternative of parallel gasoline engine/electrical motor drive techniques mixed with a battery, the 911 racer paired an inside combustion flat-six cylinder with an electro-mechanical flywheel vitality storage system.

Porsche motorsports engineers started researching hybrid techniques for racing in 2007. Across the identical time, F1 determined to combine hybrid tech. Beginning with the 2009 season, F1 allowed its groups to make use of delicate hybrid techniques referred to as kinetic vitality restoration techniques (KERS).

Most F1 groups developed KERS that used batteries, however the Williams F1 staff created an electromechanical flywheel system. Williams in the end didn’t race that system owing to Components One technical rules. (Apparently, Chrysler tried to construct a pure gasoline/flywheel hybrid race automobile for Le Mans 15 years earlier, however that program by no means made it to a race both.)

Nevertheless, Porsche finally licensed the idea from Williams Hybrid Energy and set about adapting it to endurance racing within the 911 GT3 R Hybrid. Audi, too, had a go along with a flywheel in its all-conquering R18 e-tron Quattro diesel-electric prototype. The Audi prototype used a system additional developed by UK automotive/aerospace provider, GKN, which acquired Williams Hybrid Energy in 2014. This flywheel hybrid racer gained dozens of races, together with the 24 Hours of Le Mans, outright, in 2012, 2013, and 2014.

Given these high-profile racing manufacturing unit applications nestled in F1 and sports activities automobile racing, many if not most informal observers anticipated flywheel hybrid expertise emigrate to manufacturing autos inside a couple of years.

That by no means occurred. How come?

A high-RPM booster

In easy phrases, an automotive flywheel hybrid system leverages energy from a mechanical flywheel motor to reinforce energy from an inside combustion engine for brief durations. Electrical motor/turbines positioned at a car’s wheels or axles produce electrical energy harvested from the kinetic vitality which is in any other case wasted as warmth when friction brakes decelerate the car.

However as an alternative of sending the vitality to a chemical battery for storage and redeployment, the electrical energy is used to drive a flywheel motor. Electrical vitality is transferred to rotating kinetic vitality by a novel magnetic materials (typically a magnetic powder) embedded inside the flywheel. The extra vitality utilized, the sooner it spins. (NB: that is completely different to the mechanical flywheel hybrid system that Nissan tried unsuccessfully to develop for its 2015 Le Mans racer.)

The mass of the flywheel and the rate at which it spins—usually from 25,000rpm as much as 55,000rpm or extra—decide the provision of vitality it could launch. To switch the kinetic vitality saved within the flywheel again into electrical vitality, the rotating magnetic subject generates a present within the reverse path (by inverting the polarity of the utilized voltage) and energy is delivered to the identical motor/turbines that harvested vitality throughout the unique braking occasion.

As famous, the motor turbines could also be positioned on the wheels. Alternately, a flywheel motor could also be linked to the engine driveshaft by way of a repeatedly variable transmission (CVT) or different coupler. When referred to as for, it {couples} with the driveshaft, taking the potential vitality from the flywheel and translating it to kinetic vitality propelling the driveshaft and drive wheels.

Flywheel motors have typically been in comparison with capacitors, able to rapidly storing and releasing vitality. Proponents cite weight, value, and environmental benefits over conventional chemical-battery hybrids.

Within the 911 GT3 R, the flywheel motor used a carbon fiber-composite flywheel with a 16-inch (406mm) diameter. Mounted in a carbon fiber field the place the passenger seat could be in a road-going 911, the flywheel motor acquired energy from, and despatched energy to, an 80hp (60kW) electrical motor/generator at every entrance wheel. The configuration allowed Porsche to include torque vectoring to enhance dealing with/traction when accelerating from nook apex out.

The flywheel motor in Porsche’s racer had a capability of 0.2kWh. It might ship 163hp (122kW) for as much as six seconds, providing enhance for acceleration—out of corners or for passing relying on how/when the motive force determined to use the additional energy by way of a steering wheel-mounted button.

The automobile had a complete system output of about 670hp (500kW) and weighed roughly 2,866lbs (1,300kg). The flywheel and help construction reportedly weighed round 103lbs (47kg), significantly lighter than a battery-electric hybrid setup. In all, the automobile weighed 230lbs (104kg) greater than the standard Porsche GT3 automobiles it shared the monitor with.

Porsche seen flywheel storage as extra sturdy than lithium-ion batteries within the excessive energy cost/discharge cycles of racing. Not like a battery, the flywheel motor was able to being absolutely charged (accelerated to its most pace) and discharged (decelerated to a close to cease) a number of occasions a minute with out adversarial impacts.

Due to its relative gasoline effectivity—if not outright pace—the 911 GT3 R Hybrid really led the 2010 Nurburgring 24 Hour race for eight hours earlier than dropping out. On the 2010 Petit Le Mans, the automobile in the end completed 18th, although attrition helped.

It raced once more in 2011 however was put apart thereafter as Porsche targeting its 919 Hybrid World Endurance Championship prototype racer.

Sluggish, not quick, vitality restoration & storage

The shift in Porsche’s racing dedication to the Le Mans-bound 919 Hybrid was partly linked to its up to date road-going supercar undertaking, in response to Daniel Armbruster, president and CEO of Porsche Motorsport North America.

“It was round that point that work was additionally already underway on the 918 Spyder plug-in hybrid tremendous sports activities automobile,” he remembers. “In each cases [919/918], it was discovered that lithium-ion batteries provided the perfect stability of vitality retention and energy supply for his or her respective functions.”

Regardless of its routine stop-start nature—and thus alternatives to reap regenerative braking vitality—road driving will not be characterised by the necessity to dash from nook apex to nook apex, braking and accelerating at most doable charges as in racing. The demand for fast, intensive vitality restoration and subsequent deployment is changed by a mandate for slower-paced electrical vitality technology and deployment, shifting the emphasis to vitality storage.

“The flywheel hybrid expertise within the 911 GT3 R Hybrid provided gasoline financial savings and due to this fact a lowered want for pit time versus the automobiles it competed towards,” Armbruster explains. “In racing functions, it is doable to make simpler use of a flywheel due to the frequent onerous braking and acceleration which might be each good matches for the short-term vitality storage skill and excessive output capability of that expertise.”

“However the expertise wasn’t with out challenges. On the whole, the flywheel doesn’t retailer a lot vitality, simply the braking vitality,” he says. “A battery is ready to obtain extremely secure, long-term vitality storage in a manner {that a} flywheel merely can’t match. For highway makes use of the place the power to drive on demand with out native emissions is necessary, as is turning into more and more the case in components of Europe, a battery-based answer is the perfect hybrid powertrain choice.”

Whereas the restricted storage capability of the flywheel hybrid sidelined the expertise for Porsche, Armbruster provides that, “There is no such thing as a denying that the 911 GT3 R Hybrid performed a pivotal function in proving that hybrid expertise had a house in high-performance sports activities automobile functions.”

Trying again to that point from the current day, Glen Pascoe, principal design engineer with Williams Superior Engineering (WAE), says that the fast seize and launch of vitality by flywheel motor techniques is healthier suited to peak cycle functions.

“Moreover city-center use, the responsibility cycle for a typical passenger automobile doesn’t swimsuit the repeated ‘start-stop’ nature that most accurately fits flywheel expertise,” says Pascoe. “The saved vitality in a flywheel is at all times depleting, in contrast to a chemical battery, which may maintain its state of cost over a really lengthy time period.”

On the buses

Williams’ primary flywheel hybrid idea did attain metropolis facilities in 2015 when GKN modified the system for London buses. GKN’s Gyrodrive flywheel hybrid system included a traction motor pushed from the car’s drive axle, an electrical flywheel, an inverter for the motor/flywheel unit, and an digital management system.

The system, and subsequent variations, have seen use in buses from UK producer Alexander Dennis in each single and double-decker bus fashions. Nevertheless, the Gyrodrive flywheel system was thought of too massive and costly for urban-use automobiles (taxis), which adopted varied battery methods.

Glen Pascoe says WAE will not be particularly refining any flywheel techniques at the moment however provides that “as we work throughout a variety of industries and look at the necessities of our purchasers intimately, this expertise could also be applicable for sure functions sooner or later.”

That would embody racing if racing collection/sanctioning our bodies allowed such gadgets although present curiosity seems to lie extra in hybrid battery and fast-charging growth. WAE is presently engaged in hydrogen gasoline cell growth for big mining vehicles utilizing regenerative braking in a lot the identical manner as with flywheel techniques.

Porsche Motorsport North America’s president says the corporate “is at all times evaluating which applied sciences supply the perfect answer for the present scenario,” not ruling out any single strategy.

Armbruster explains that Porsche’s technique “contains inside combustion powertrains, sporty plug-in hybrids and absolutely electrical autos… We’re additionally investigating the event of artificial fuels that supply an environmentally sound strategy to inside combustion autos which might be already on the highway.”

Sarcastically, the flywheel hybrids that the majority of us now encounter lie in autos we journey in (buses, trains, ships) moderately than drive. And static flywheel techniques are additionally beneath growth; in Germany, an organization referred to as Chakratec has simply put in a flywheel storage system at a Premier Inn in Leipzig, designed to handle peak masses for EV chargers.

However a few decade in the past flywheel-motor-augmented race automobiles led the Nurburgring 24 and competed credibly towards lighter GT3 automobiles. Additional funding might each lighten and doubtlessly enhance the vitality storage capability of such techniques, once more pairing drivers and flywheels in a sport that hardly ever throws every thing away.

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