High-Speed Flywheel and Motor Drive Operation for Energy Recovery in a Mobile Gantry Crane

Abstract

Abstract-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.

Recording and analysing measurements from an RTG crane

“…Their ESS will be positioned on-board the RTG harvesting otherwise wasted energy during lowering of a container and using it to compensate the power demand of sequential lifts. The CRESS ESS is flywheel based, which has also been examined by Flynn et al [11,33]. Flywheels are not the only type of ESS technology being examined for this application, batteries and super capacitor based systems, as well as hybrid solutions are also under investigation and implementation [34][35][36].…”

Modeling Power Flow in a Hoist Motor of a Rubber-Tired Gantry Crane

“…Shipping ports are now considering reducing the energy consumption by increasing efficiency, improving operations, and recovering energy that is otherwise wasted. The hoist motor of a crane, with a power rating of up to 400 kW, accounts for the majority of the consumed energy and offers opportunities to recover potential energy when lowering a container [2]. Modelling the power flow of this element is crucial for increasing the efficiency and enabling the utilization of stored energy via a control methodology.…”

“…The geometry of hoisting cables has been primarily studied with the objective to reduce sway and oscillations, while the benefits are also found when modelling the power demand of a hoist motor. Accounting for non-parallel cables and the resulting change in power demand in steady state can expand the work done on RTG cranes, including the control of energy storage [8], [9], particularly in works that explicitly assume constant power demand in steady state [2], [10], [11]. Due to the unexpected increase in power demand during the constant speed phase, it is difficult to implement a control strategy designed specifically for cranes with parallel cables to cranes with non-parallel ones.…”

Flywheel Energy Storage for Automotive Applications

“…The fuel consumption was reduced by 21%, emissions of nitrous oxides by 26% and particulate emissions by 67%. It is also worth noticing that the number of cycles, 100,000-200,000 per year, would be hard to achieve with batteries, since their lifetime would be severely compromised [66,67].…”