Maintenance Free Flywheel Energy Storage System for Wind Turbine Application Using Magnetic Bearing

Abstract

Among the renewable resources wind energy contributes the major share of generating power compared to solar energy and biogas. But due to fluctuation of wind speed and due to other internal problems in wind generators, quality of the electricity produced does not meet the required standards. The fluctuations can remain from few seconds to few hours in the system. The present trend is that the fluctuations in hours are taken care of by diesel generator while fluctuations in seconds to minutes are taken care of by lead acid batteries. But the response time of lead acid batteries are low due to their chemical reactions process to generate the power with limited cycle of operation. Therefore, an alternate energy storage system is required to maintain the quality of power produced in small durations. The application of flywheel energy storage system (FESS) is proposed to be a viable solution under these conditions wherein the excess energy from wind generator is given to the motor/generator of FESS that rotates the flywheel and consequently the energy gets stored in it in form of mechanical energy so that it can be utilized during power fluctuations. However, the performance of the FESS is mainly dependent on the power losses of the bearing on which it is mounted. The present research work proposes the use of a magnetic bearing to support the flywheel which eliminates the contact between the journal and bearing and minimizes the power loss.