How big are the gyroscopic precessional forces?
Gyroscopic forces are proportional to rotational speed and inertia so although our flywheel speed is high our inertia is very low and consequently the forces are low. Even for a Formula One system the maximum torque experienced on the track is less than 130 NM.
Presumably the flywheel will slow down if the stored energy is not used?
The flywheel will slow down due to friction in the bearings and seals but because it runs in a vacuum the losses are low. Typically a Flybrid flywheel coasts down in about 25min. In most use cases the Flybrid system only needs to store the energy for a few seconds and therefore the coast down time is no concern for these applications.
How safe is a high speed flywheel?
Very safe. Flybrid take safety very seriously and have invented a special containment mechanism to help make sure that their system is safe.
The specific storage capacity (kJ/kg) of some batteries is much greater than that of even a high-speed flywheel so surely it will be less effective?
Whilst the usable flywheel storage capacity is less than some batteries all of it can be used at full power. The rated capacity of batteries can be misleading as they cannot deliver (or accept) anything like the rated power over the full depth of charge. They also have a very short life if you use all the storage capacity. Storage capacity is useless if you cannot charge it up and during typical vehicle usage the hybrid system is almost always power limited. Just think about how long you spend on the throttle compared to how long you spend on the brakes and you will immediately see that power during energy storage is THE limiting factor.
How environmentally friendly is this technology?
Very. The system is made entirely from conventional materials with the only exception being the carbon fibre wrap around the flywheel that holds it together at our very high speed. This makes it easy to produce and to recycle.