High-speed flywheel and motor drive operation for energy recovery in a mobile gantry crane

This paper describes the results of experimental testing using a high-speed permanent magnet synchronous machine and its motor drive designed to recover potential energy in mobile gantry crane applications. Rubber-Tired Gantry (RTG) cranes are commonly used in shipping ports around the world to move containers massing up to 40 metric tons. These cranes are mobile and derive their electrical power requirements for the hoist motor from a diesel engine and generator set rather than from the utility system. Because these cranes are independent of the utility system, energy regenerated via the hoist motor as a container is lowered to the ground is typically wasted as heat in dissipator resistors. This paper details the operation and experimental results of a novel long-life flywheel motor and its drive system which can capture the regenerated energy and provide it for subsequent container lifts. Such a flywheel system has proven to significantly reduce fuel usage and diesel engine emissions.