Composite Inertia Wheel Hub with Variable Stiffness
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Solution Overview
Problem
Current inertia wheels for energy storage have limitations in energy density due to high self-discharge and cost, particularly due to the use of carbon fibers, and face mechanical stress issues when increasing the internal diameter of the storage ring, leading to a suboptimal stored energy to weight ratio and restricted rotation speed.
Innovation Solution
A composite material inertia wheel design with a hub made of decreasing stiffness modulus from the central part to the rim, using draping and shaping of composite plies to position the storage material far from the axis of rotation, and a hub comprising a central body, disc, and rim with specific fiber orientations to manage radial and circumferential stiffness, allowing for increased energy storage capacity and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the internal diameter of the storage ring is increased to improve energy storage capacity, then the stored energy increases, but the mechanical strength of the hub connecting the ring deteriorates due to metal hubs reaching technological limits
Solution Approach 1:
The patent applies composite materials (carbon fiber reinforced polymer) to manufacture the hub, replacing traditional metal hubs. This composite construction provides superior strength-to-weight ratio and allows the hub to withstand the mechanical stresses generated by larger storage rings with increased internal diameters, thereby enabling higher energy storage capacity without compromising structural integrity.
Solution Approach 2:
The patent implements variable ply orientation and thickness distribution within the hub structure. Different regions of the hub have optimized fiber orientations (0°, 45°, 90°, -45° plies) and thicknesses tailored to local stress conditions, with higher stiffness requirements near the center and flexible transitions toward the rim, allowing the hub to accommodate larger storage rings while maintaining mechanical strength throughout.
2Weight of moving object
If carbon fiber composite materials are used to increase energy density, then the stored energy per unit weight increases, but the manufacturing cost increases
Solution Approach 1:
The patent optimizes the manufacturing parameters of the composite hub, including ply orientation angles, thickness distribution, and curing conditions, to achieve the required mechanical performance with minimized material usage. By carefully controlling these parameters, the design achieves high energy density while reducing the total amount of expensive carbon fiber material required, thereby lowering manufacturing costs.
Solution Approach 2:
The patent applies composite material technology selectively where it provides the most benefit - in the hub structure where high strength-to-weight ratio is critical - rather than using it throughout the entire flywheel system. This partial application of expensive composite materials optimizes the strength-to-weight ratio where needed while controlling overall manufacturing costs.
3Weight of moving object
If the storage material is positioned far from the axis of rotation to optimize energy density, then the stored energy per unit weight increases, but the mechanical stress on the hub increases
Solution Approach 1:
The patent implements a hub design with spatially varying properties, where the composite ply orientation and thickness are optimized for each radial position. The hub features a rigid central region for shaft connection that transitions through intermediate zones with varying stiffness to a more flexible peripheral region, allowing it to accommodate the high mechanical stresses generated by storage material positioned far from the axis while maintaining overall structural integrity.
Solution Approach 2:
The patent uses carbon fiber reinforced composite materials with tailored fiber orientations to create anisotropic mechanical properties in the hub. By orienting fibers in specific directions (0°, 45°, 90°, -45° plies), the hub achieves high circumferential and radial strength to withstand the increased mechanical stresses resulting from positioning storage material at larger radii for optimized energy density.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances the energy storage capacity per unit weight, achieving ratios of over 55 Wh/kg compared to the typical 40 Wh/kg, while mitigating mechanical stress and allowing higher rotation speeds by optimizing the placement and orientation of composite materials.
Implementation Method 1
the hub comprises a central part forming a hub body for connection with the shaft, a peripheral part forming a rim for connection with the storage ring and an intermediate part consisting of a disc between the hub body and the rim, the hub being made of composite material and has a decreasing stiffness modulus from the hub body towards the rim
Implementation Method 2
The hub is advantageously made by draping and shaping composite plies
Implementation Method 3
the rim is connected to the disc by a second curvature of same direction as the first curvature. Advantageously, the second curvature forms a flexible connection between the disk and the rim conferring a radial modulus of elasticity on the rim adapted to allow a deformation of the latter to follow the deformations of the storage ring in rotation
Implementation Method 4
the orientation of the fibers of the plies confers a circumferential modulus of elasticity on the rim adapted to allow a deformation of the latter to follow the deformations of the storage ring in rotation
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to an inertia wheel comprising a storage ring (1) and a hub (2) connecting the storage ring (1) to a rotation shaft (3) of the wheel, said hub (2) comprising a central part forming a hub body (2a) for connecting to the shaft (3), a peripheral part forming a rim (2c) for connecting to the storage ring and an intermediate part formed by a disk (2b) between the hub body and the rim. The inertia wheel is characterised in that the hub is made from a composite material and includes a module having a stiffness that decreases from the hub body to the rim. The invention also relates to the method for producing such an inertia wheel.