Hybrid cargo cranes for bulkers

09 Apr 2013
DNV’s Eirik Ovrum: “we have concluded that the payback time is less than a year”

DNV’s Eirik Ovrum: “we have concluded that the payback time is less than a year”

DNV and Bergen-based open hatch bulker operator Greig Star have unveiled the results of a joint study into the energy saving potential of a battery hybrid system for operating electric cargo cranes on the next-generation Greig bulkers.

The study concludes that the hybrid ship crane proposal can achieve a payback time of under one year, maybe less depending on fuel cost rises and the final cost of the battery pack, with fuel savings of around 30%. And, adds DNV, the resulting environmental benefits, which means that the project came within the remit of the joint industry project ‘Low Carbon Shipping’, funded by the Norwegian Research Council.

“Hybrid ships are similar to the better known hybrid cars, like the Toyota Prius, but have greater advantages. The payback time on additional investments is much less than the 10 years expected for a car,” says Eirik Ovrum, a researcher in DNV Research & Innovation. “In our project, we have concluded that the payback time is less than a year and that fuel consumption will be reduced by nearly one third.”

DNV has worked on hybrid ships and batteries for several years and is starting to see breakthrough results. In the recent collaboration with Grieg Star, the partners set out to simulate crane operations on one of Grieg Star’s open hatch vessels. The DNV simulation tool COSSMOS was used to model a conventional and a battery hybrid power production system on board the vessel. The simulation included four cranes using a conventional system of diesel generator sets to produce electric power while the hybrid system had a lithium-ion battery installed. Rather than the standard three diesel gensets, running inefficiently at low load most of the time, the hybrid system used just one genset, with a second for redundancy, running at optimum load, in combination with regenerative braking from the crane motor when the cargo is being lowered, to charge the Li-Ion battery pack which powers the cranes.

The combination of shipowner knowledge and a detailed simulation of the second-by-second ship operations showed that the battery hybrid cranes used 30% less fuel, could achieve annual savings of $110,000 and had less than a year’s payback time. New rules, tools and advisory services for battery-powered ships have already been developed by DNV.

“The uplifting results show that bringing batteries on board ships is not only a viable business operation, it is also good housekeeping. By reducing both energy consumption and emissions, we create a win-win situation for ship owners and the environment, an essential element of a sustainable business future,” says Jan Øivind Svardal, vice president newbuildings and projects of Grieg Star.

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