A flywheel energy storage system (FESS) uses a high speed spinning mass (rotor) to store kinetic energy. The energy is input or output by a dual-direction motor/generator. To maintain it in a high efficiency, the flywheel works within a vacuum chamber. Active magnetic bearings (AMB) utilize magnetic force to support rotor's rotating shaft without mechanical friction. It also makes the rotor more dynamically controllable.A prototype of FESS with AMBs was developed. Dynamical model is obtained and analyzed for the rotor-bearing system. Control method is determined in accord with the dynamical characteristics of the flywheel. AMB's parameters are obtained by parameter identification. Influences of the magnetic force on the nutation and procession of the flywheel rotor, and of the controller to the stability of the dynamical system were analyzed.Experiment has been undertaken. The flywheel has steadily past through its flexible critical speed and reached to the rotating speed of 28500RPM. Maximum tip speed is 450m/s. Maximum electrical discharge power reaches 40W. Discharge duration is 100 minutes.
Large-scaled ZnO nanowires have been successfully synthesized by heating and evaporating zinc powders directly without the assistance of any catalysts or additives. We acquired disarrayed and arrayed ZnO nanowires respectively on Si(100) substrates and c-oriented ZnO thin film. The disarrayed ZnO nanowires are about 40nm in diameter and 10μm in length, evenly and randomly distributed on the substrate; while the arrayed nanowires are about 60nm in diameter and 3-4μm in length, well aligned along the normal direction of the substrate. XRD and TEM results reveal that in both kinds of the products, most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. During the growth process of arrayed ZnO nanowires, the c-oriented ZnO thin film control the growth direction. Photoluminescence spectrums were measured showing that both of the disarrayed and arrayed ZnO nanowires have a strong ultraviolet emission around 380nm. Such results suggest the synthesized ZnO nanowires, especially arrayed nanowires can be applied to excellent optoelectronic devices.
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