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Flywheel Energy Storage System for Rubber Tired Gantry Cranes

Vycon Energy has developed a flywheel energy storage technology for rubber tired gantry cranes (RTG) that can either be retrofit to existing RTG cranes or included as part of a new build.

Vycon
Components of a Vycon flywheel Click to enlarge.

RTG cranes are mobile equipment that load and unload containers onto trucks in a sea port terminal. Conventional RTG cranes are driven by electric motors powered by large on-board diesel generation sets. There are approximately 8,000 RTG cranes operating at sea ports around the world which contribute significantly to port emissions, as such they have become a testing ground for new hybrid technologies.

Flywheels provide significant fuel and emissions reductions via the capturing of braking energy generated when a container is lowered. The captured energy is then available to help hoist the next one. The Vycon REGEN flywheel energy system can be installed on any RTG crane, either retrofitted or as an option in manufacturing, to create a hybrid power system.

Compared to other energy storage technologies used on RTG cranes such as conventional batteries and ultracapacitors, flywheels do not require routine replacement and offer lower maintenance, higher tolerance for rapid cycling, and freedom from aging and environmental limitations.

The Vycon flywheel for the RTG crane consists of a 3-phase permanent magnet synchronous motor-generator connected to a 3-phase inverter. The flywheel spins in a vacuum, is levitated on active magnetic bearings, and stores 2.1 MJ (0.58 kWh) at 18 kRPM. The flywheel incorporates a high-speed motor controller design developed by University of Texas researcher Dr. Mark Flynn.

Vycon has tested the flywheel system on RTG cranes with the cooperation of Yantian International Container Terminal (YICT) and Hutchison Port Holdings. Among the test results:

  • The installation of the REGEN System on a conventional RTG provided a direct fuel savings of 8-15%.

  • By installing a lower output power genset in conjunction with the REGEN System (i.e., downsizing), additional fuel savings are realized during the idle periods. In the case of YICT, the ZPMC RTG crane was modified by replacing a 410 kW genset with a smaller 322 kW genset. The fuel savings increased to 32-38%. The smaller genset and flywheel energy storage device had no impact on performance and handling rates.

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