Flybrid Automotive already has a successful long-term relationship with Torotrak, which uses Flybrid’s flywheel module in its Mechanical Kinetic Energy Recovery System (M-KERS). M-KERS captures and stores energy that is otherwise lost during vehicle deceleration events.

As the vehicle slows, kinetic energy is recovered through the KERS continuously variable transmission (CVT) and stored by accelerating a mechanical flywheel. As the vehicle gathers speed, energy is released from the flywheel, via the KERS CVT, back into the driveline.

The full toroidal variator combined with a torque control operating strategy seamlessly transfers energy from the vehicle driveline to the flywheel during dynamic operation, when the speeds of both elements are changing independently. Torotrak’s variator reliably and naturally adopts the appropriate ratio, giving accurate control of the transmission torque and therefore precisely defining the energy flow.

M-KERS can recover up to 70% of braking energy for around a third the cost of battery electric hybrids, the company says.

As well as allowing us to accelerate the development of our M-KERS technology family, this acquisition will secure our access to what we believe is the most market-ready flywheel system available. We now have the complete skill set, development resources and low-volume manufacturing expertise needed to help vehicle manufacturers, across a wide range of applications, introduce a technology that will allow them to significantly reduce CO₂ emissions for a fraction of the cost and weight of conventional electric hybrids.

—Torotrak CEO, Jeremy Deering

Flybrid’s carbon fibre flywheel spins at up to 60,000 rpm in a near vacuum. Drive can be provided by the company’s CFT (clutched flywheel transmission) clutch-based transmission system or by Torotrak’s CVT (continuously variable transmission).

Flybird introduced the CFT in 2011 for the 100 kW Flybrid KERS for Le Mans 2011. The system uses a series of small clutches to transmit the drive between the flywheel and the main vehicle gearbox. Proven in motorsport applications such as LMP1 sportscar racing, CFT KERS can provide up to 100 kW and 540 kJ of storage in a system that has a full wet weight, including the electro-hydraulic control system, of less than 40 kg (88 lbs).

CFT KERS scales down very well so could open-up a new market for small, low-cost automotive hybrids. It’s a good fit with Torotrak’s CVT, which is ideal for higher power systems and is already central to several of our customer programs.

—John Hilton, Flybrid co-founder

Flybrid’s portfolio of development programmes includes Volvo Cars (which uses Torotrak’s CVT), Wrightbus, two manufacturers of off-highway vehicles and several motorsport constructors. Evaluation programs are ongoing with several other vehicle manufacturers across a wide range of sectors including passenger cars. Flybrid says that if these relationships continue to progress as planned, their technology could be specified for a production vehicle by 2016. Torotrak’s investment will provide additional resources to help secure this timing.

Deering sees these relationships as also offering considerable potential to extend the reach of Torotrak’s other technologies, particularly the company’s high-efficiency transmissions and low-cost, variable drive pressure charging system.

Hilton also sees synergies in technology and manufacturing.

Both technologies use high speed rotating assemblies of precision machined components and the electronic and hydraulic control systems are so similar that a single control unit can be used to control either product. These shared aspects will help the combined companies develop more quickly and at a lower cost than either party could on its own.

—John Hilton

Market prospects for flywheel hybridization. In an independent report on flywheel hybrid technologies, commissioned by Torotrak, Ricardo Strategic Consulting concluded that pure mechanical flywheel hybrids promise similar fuel economy and CO₂ benefits to electric hybrids but at around one third the cost.

The purely mechanical flywheel system eliminates the cost and price instability of exotic metals, the end-of-life costs of batteries, the need to train dealers and bodyshops to work safely with high voltages and several other significant penalties of traditional high-voltage solutions, the Ricardo report found. The report suggests that in the heavy duty commercial vehicle market, pure mechanical flywheel hybrids “appear to be one of the most cost-effective powertrain technologies for reducing CO₂.”

This view is supported by E4tech, an independent research consultancy specializing in sustainable energy and low carbon vehicles (advisors to the UK Government’s Department of Transport). Their research concludes that the Flybrid technology is well suited to the bus market, medium-volume market entry in the commercial vehicle market and to some sectors of passenger cars, saying that it can match or improve upon electric hybrid fuel economy improvements of at least 15%. Their view is that the considerably reduced costs would enable it to become an established low carbon technology ahead of likely fuel cell mass-market adoption.

In passenger car applications, pure mechanical flywheel hybrid technology could reduce emissions of CO₂ by up to 30 g/km at a cost of around £20 (US$30) per gram, says Ricardo. This compares favorably with their estimate of £20 - £45 (US$30 - $68) per gram for enhanced Internal combustion engine technologies and up to £90 (US$136) per gram for electric hybrids.

Passenger car manufacturers are now making decisions about which technology to invest in as they prepare for very challenging 2020 emissions targets in Europe and 2016 / 2025 fuel economy targets in the US. We believe that purely-mechanical flywheel hybrids can significantly cut the cost of compliance using modular technology that can be quickly integrated and doesn’t require any enabling investments or other technology steps.

—Jon Hilton

Torotrak expects the first application of pure-mechanical flywheel hybrid technology will be in the urban commercial vehicle market, where benefits are strongest and volumes can be managed through existing relationships. In the mid-sized UK bus market alone, there are 3,000 new vehicles each year and an existing fleet, with retrofit potential, of 50,000 vehicles. There are also substantial opportunities with other fleets that operate a stop-start drive cycle such as urban delivery vehicles and refuse vehicles.

In the passenger car sector, the Ricardo report forecasts penetration levels of 0.4% - 3.8% by 2020, offering potential volumes of up to four million units per year. As well as affordable hybrids, these could include high-performance cars where the ability to release energy very quickly (more quickly than batteries) provides an attractive, differentiating ‘press to pass’ function.

Torotrak’s Deering points out that the combination of the recent strengthening of the company’s high-precision manufacturing capability, together with joining forces with Flybrid’s own supply capability, means they can jointly support volumes from prototypes and fleet trials up to around 20,000 units a year, at which point the technology becomes attractive to global first tier partners.

Allison. Separately, Torotrak concluded negotiations, under a Licence and Exclusivity Agreement dated March 2009, with its licensee Allison Transmission, Inc., under which Allison will pay £6.0 million (US$9 million) for continued exclusivity to manufacture and sell Torotrak main drive transmissions in commercial vehicle market segments; this exclusivity excludes Torotrak’s other commercial vehicle licensees, Tata Motors and the European Truck and Bus manufacturer (ETBM).

Allison has also subscribed for an additional 8,248,434 new ordinary shares in Torotrak at a price of 30.255p per share, raising approximately £2.5 million (US$3.8 million).

Allison is committed to introducing fuel-efficient, emissions-reducing technologies and our licensing decision today with Torotrak reflects our determination to be a global leader in this field. We are pleased with Torotrak’s progression following the strategy announced in November 2012 and want to support the investment arrangements with Flybrid, which are forward-looking and offer good growth potential.

—Lawrence Dewey, Chairman, President and CEO of Allison

The next step in Allison’s programme is to focus on a final design to optimize performance, size and weight. Torotrak is taking responsibility for core component testing and to establish a fully conformed supply into the Allison program, helping to reduce lead times. Torotrak will also assist Allison with product design and validation process support in Europe.

Resources

• E4tech (2013) Kinetic energy recovery systems