Flywheel claimed to be more efficient than geared drives

Ricardo has announced that its Kinergy flywheel energy storage system is more efficient than a conventional geared drive.

The company said in a statement that it has achieved this via a significant improvement in the magnetic coupling and gearing system of Kinergy, a hermetically sealed, high-speed flywheel energy storage device.

Kinergy is based on a high-speed carbon-fibre flywheel, operating within a sealed vacuum chamber at speeds of up to 60,000rev/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 enables the unit to be sealed for life, negating the need for high-speed seals and a vacuum pump, which in turn reduces costs and maintenance requirements.

According to Ricardo, 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 more manageable than would be the case in a more conventional direct-driven high-speed flywheel design.

This first Kinergy prototype has resulted from an 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. The Flybus project began in 2009, with the aim of demonstrating a viable alternative to battery-based hybrid buses.

‘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 hybridisation of low-carbon powertrain applications in all types of vehicles, from passenger cars to high-speed railway rolling stock,’ said Nick Owen, project director for research and collaboration at Ricardo UK.