Research: Double cycling could boost terminal efficiency, cut emissions

Research: Double cycling could boost terminal efficiency, cut emissions Marine terminals could double their gantry crane efficiency, save costs and conserve fuel by adopting a technique known as double cycling, according to two academic studies released this week.
   Dockside gantry cranes now perform one function at a time. First a vessel is unloaded of all its containers and then the process is reversed to fill the vessel with outbound containers. This means that half of a crane's cycle per container — after releasing the container and heading back for another — is done empty. Double cycling maximizes crane operation by assuring that a container is 'on the hook' anytime it moves. A double-cycling crane unloads a container on the dock and then picks up an outbound container at the dock to load on the vessel during its second half of the cycle.
   While not a new idea — more than 20 percent of terminals use the technique — the two studies, both co-written by Anne Goodchild of the University of Washington and Carlos Daganzo of the University of California at Berkeley, are the only scholarly publications on the technique.
   “Most of a port’s focus is on keeping that big crane working, but half the time the crane is not carrying anything,” said lead author Goodchild, a UW assistant professor of civil and environmental engineering. “Most people know what double cycling is. We wanted to demonstrate that it’s really not that complicated.”
   Goodchild said that while the system is more efficient, it has not been widely implemented over fears it would complicate port operations and create terminal logistics problems.
   The results of both studies suggest otherwise, according to the researchers. One study showed that double cycling would eliminate 20 percent of crane trips and shave 10 percent off the ship’s turnaround time. The second discovered that if a crane is loading and unloading goods simultaneously, the trucks that drive containers to the terminal storage areas can drop one outgoing container off and pick up one incoming container, resulting in the need for less trucks.
   Less trucks would also mean less emissions, according to Goodchild.
   “Anything that reduces the time in the port or the equipment used also reduces the per-container environmental cost,” Goodchild said. “And there’s a lot of pressure on ports right now to reduce their emissions.”
   The research was funded by the National Science Foundation, the University of California Transportation Center and the American Association of University Women.