The most recent generation of Siemens’ ECO-RTG system significantly improves the energy efficiency of these hybrid diesel-electric drives – mainly through enhancements to the control system. Simulation tools track a gantry crane’s energy requirements and apply sophisticated algorithms to optimize how it operates. The system also employs an equivalent consumption minimization strategy (ECMS) to determine the exact performance set points for the motor and the ultra capacitors and thus minimize fuel consumption. A control algorithm ensures that, when needed, as much power as possible is supplied from the ultracapacitors. It also ensures that the energy store in the capacitors is never fully depleted. This means that, across the crane’s operating cycle, a balance is maintained between the amount of energy drawn from the ultracapacitors and the amount of energy that is stored in them when braking and lowering loads.

Flexibly controlling the amount of energy supplied by the individual components enables the system’s efficiency to be optimized. If, for example, a crane is idling and only its auxiliary systems need power, the ultracapacitors can provide all of it, allowing the motor to be shut down. The ECO-RTG system’s new control functions and its ability to save braking energy in the ultracapacitors mean it can reduce its fuel requirements by more than 70 percent. The world’s four largest container terminal operators all use ECO-RTG from Siemens.