Flywheel

1 . A flywheel comprising

a plurality of discs arranged in a stack on a common axis, including at least first and second end discs at either end of the stack, in which each disc has substantially the same thickness across its full diameter, and in which each disc includes a disc surface within the stack, the disc surface including a central region on the common axis and a peripheral region disposed around the central region, the peripheral region being adjacent to a peripheral edge of the disc,

first and second plate members disposed at opposing ends of the stack, and

bonding means comprising bonding material or bonded interfaces between adjacent discs, in which the bonding means bonds only part of each disc surface within the stack to each neighbouring disc in the stack, including bonding together adjacent peripheral regions of neighbouring discs, and which bonds each of the first and second plate members respectively to the first and second end discs of the stack.

2 . A flywheel as claimed in claim 1 , in which the peripheral region of some or all of the discs is at least marginally thicker than the central region of those discs to space apart adjacent central regions of neighbouring pairs of those discs during flywheel rotation.

3 . A flywheel as claimed in claim 2 , in which a contact area between adjacent discs is less than 100% of the disc-facing area of a given disc.

4 . A flywheel as claimed in claim 1 , in which the peripheral region of each of the discs includes a substantially planar surface or landing on one or both sides of each disc, each substantially planar surface or landing being bonded to a corresponding substantially planar surface or landing in the peripheral region of a neighbouring disc.

5 . A flywheel as claimed in claim 1 , in which the bonding means includes or consists of annular-shaped bonded regions between each pair of neighbouring discs in the stack.

6 . A flywheel as claimed in claim 1 , in which one or more shims or landing elements are provided for some or all of the neighbouring pairs of discs in the stack.

7 . A flywheel as claimed in claim 6 , in which the or each shim or landing element is bonded to a pair of adjacent peripheral regions of a given pair of neighbouring pairs of discs, and adjacent central regions of those neighbouring pairs of discs are spaced apart.

8 . A flywheel as claimed in claim 6 , in which the or each shim is made of metal or metal alloy.

9 . A flywheel as claimed in claim 8 , in which the metal or metal alloy is or includes any of steel, aluminium or titanium.

10 . A flywheel as claimed in claim 6 , in which the bonding means includes or consists of annular-shaped bonded rejoins between each pair of neighboring discs in the stack, and in which the or each shim is substantially annular in shape.

11 . A flywheel as claimed in claim 1 , in which the flywheel does not include clamping means for clamping the discs in the stack together.

12 . A flywheel as claimed in claim 11 , in which the stack of discs does not accommodate any clamping elements extending between the plate members.

13 . A flywheel as claimed in claim 1 , in which the discs do not include disc apertures for a connection element.

14 . A flywheel as claimed in claim 1 , in which the plate members do not include one or more plate apertures for a connection element.

15 . A flywheel as claimed in claim 1 , in which the bonding means includes an adhesive or an epoxy resin for tolerating flywheel rotation.

16 . A flywheel assembly comprising one or more flywheels as claimed in claim 1 , the or each flywheel being mounted on or to a drive assembly for facilitating rotation of the or each flywheel for storing energy in or deploying energy from at least one of the flywheels.

17 . A flywheel as claimed in claim 1 , in which opposing central disc face regions of adjacent pairs of discs are not bonded together.