Shape Optimization of Rotor of Flywheel Energy Storage System

Flywheel Energy Storage System (FESS) is an emerging technology with notable applications. To conduct analysis of flywheel?s rotors, cylindrical shape optimization considering steel material is an untapped research domain. This is the first-ever shape optimization study in which main focus is to des

Project Title

Project Area of Specialization

Mechanical Engineering

Project Summary

Flywheel Energy Storage System (FESS) is an emerging technology with notable applications. To conduct analysis of flywheel’s rotors, cylindrical shape optimization considering steel material is an untapped research domain. This is the first-ever shape optimization study in which main focus is to design and optimize shape of flywheel’s rotor with different combinations of radius and thickness by keeping constant rotational speed (50,000 rpm with one-hour retention time), energy storage capacity (50 kW) and material properties (steel).

Project Objectives

. To conduct analysis of flywheel’s rotors, cylindrical shape optimization considering steel material is an untapped research domain. This is the first-ever shape optimization study in which main focus is to design and optimize shape of flywheel’s rotor with different combinations of radius and thickness by keeping constant rotational speed (50,000 rpm with one-hour retention time), energy storage capacity (50 kW) and material properties (steel).

Project Implementation Method

A shape optimization analysis was performed for four different shapes (cylindrical, laval, conical and oval) to find most suitable for rotor design. The suitable combinations of rotor thickness and radius of the selected shape were determined for maximum energy storage value (180-190 MJ) within commercially available ranges (10-2080 mm and 30-600 mm). A static analysis was conducted to calculate stresses and deformations for these combinations and best ones were selected based on lowest values. The narrowed down limits of these values were used for second optimization to increase precision. The intersecting combinations of radius and thickness (when compared with stress and displacement) were used as input in third optimization. Four different cases were performed on the finest combination to introduce non-homogeneities in the homogenous model. The final model was obtained by converging dimensions from each case experiencing the least stress and displacement.

Benefits of the Project

. This is the first-ever shape optimization study in which main focus is to design and optimize shape of flywheel’s rotor with different combinations of radius and thickness by keeping constant rotational speed (50,000 rpm with one-hour retention time), energy storage capacity (50 kW) and material properties (steel).

Technical Details of Final Deliverable

The diameter (hub diameter) and outer (inner) thickness of converged model were 377.1 mm (90 mm) and 1022.7 mm (755.9 mm) respectively, the model was curved inward at 882.6 mm. The minimum stress and displacement observed for this model were 11.8 GPa and 5.09 mm respectively.

The study uses general static analysis in which aerodynamics, friction and vibrations were ignored. To improve results, an approach of using dynamic analysis (rotor balancing and aerodynamic system) and composite materials can be considered.