High speed electromechanical flywheel design for rural electrification in Sub Saharan Africa

This paper presents the electromechanical flywheel energy storage system designed to enhance rural electrification in Sub-Saharan Africa. Most non-grid connected areas, mostly rural, are powered with solar home systems whose sustainability is limited by the short life span, low power density and low storage efficiency of the battery storage. The electromechanical flywheel rotor is made from glass fiber and epoxy composite and designed using novel shape profiles based on Berger, Porat and Stodola´s design. Dr. Stodola´s design utilizes a stress based solution by introducing a central hole for a shaft inclusion. An Axial flux brushless DC machine was considered because of the low cost, ease of construction and simple control. The system stores 1,080 kJ and supplies 100 W with an operating speed range of 8,000-25,000 rpm. Stress, modal and thermal analysis are performed on the flywheel system using finite elements and analytical methods. The brushless DC drive together with the DC-DC converter were constructed and tested. The various components were simulated, prototyped using locally available material and the results presented.