Flysafe Project

The drive towards less polluting vehicles has led manufacturers to develop hybrid technologies (where internal combustion engines are combined with battery power) to significantly reduce the emissions of CO2 and other noxious gases in towns and cities.

To allow for the typical fluctuations in energy demand in hybrid vehicles, flywheels are often incorporated; their stored energy can be utilised to meet the transient power demands of the vehicle. The ideal flywheel material for use in hybrid vehicles has a high strength and low density. The high strength permits the flywheel to operate safely at high rotational speeds, which also maximises the stored energy. A low density allows the overall vehicle weight to remain low, whilst the flywheel design can optimise the rotational inertia for a given mass. Carbon fibre reinforced composite materials offer the optimum combination of properties for the application.

Flysafe brings together all three of the UK's leading developers of flywheel-hybrid systems, with a strong academic research base, to develop commonly applicable understanding, engineering processes and standards for the safety of high-speed flywheel energy storage systems. The project will research the fundamental mechanisms of composite flywheel failure, thus enhancing understanding and the development of standards, and accelerating market acceptance. Such understanding will also enable safe but lower cost systems, widening the potential market penetration of the technology. This understanding will be developed in an academic environment accessing world class knowledge in fracture mechanics and high speed imaging; industrial partners will in parallel research safety-critical system issues and implement their learning into engineering processes and joint work with the BSI on standards.

The objectives for the University of Brighton (UoB) and Imperial College London (ICL) are to:
> Analyse composite flywheels and simplified, but representative rimmed structures, to determine the maximum stresses under in-service rotational speeds (ICL)
> Develop a new experimental rig for characterising the failure of high-speed composite flywheels (UoB)
> Use high speed testing to determine the critical strain energy release rate, Gc, for the various composites, at the appropriate test speeds (ICL)
> Use a fracture mechanics approach to design the location and size of critical flaws to trigger component failures at predefined rotational speeds (ICL)
> Characterise the failure history from initiation to burst of a composite flywheel (UoB)
> Analyse the subsequent failures, the fracture mechanisms, and the distribution and momentum of debris for use by the industrial partners for the design and development of the containment systems (ICL)
> Create a phenomenological model that describes the failure of high-speed composite flywheels (UoB + ICL)

The research programme incorporates a number of activities with potential for green energy storage applications, new collaborations and training.

This will lead to
> removing market barriers to this hybrid technology being adopted,
> increasing the use of composite materials,
> improving the understanding of flywheel failures,
> improving manufacturing techniques (e.g. filament winding),
> reducing CO2 emissions,
> increasing market share and profit to UK industrial collaborators,
> developing new standards and
> training and enthusing the next generation of British engineers.