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Possible Future Propulsive Prospects for Oceanic Barge-Ships and Barges

By Harry Valentine 2013-01-16 15:59:00

The maritime industry has for many years sought methods by which to reduce the fuel consumption of ships, including a possible conversion to nuclear power. In recent years, companies such as NuScale Technologies and Toshiba have developed micro-nuclear power stations capable of delivering up to 10MW (13,500-Hp) of electrical power. Hyperion Technologies had earlier developed a micro reactor of 25MW (33,500-Hp). While several navies use uranium-based nuclear propulsion, the commercial maritime sector has so far not embraced this propulsive option.

Micro-nuclear technologies presently use uranium-based fuels. Research is underway in China involving the possible future use of low-radiation thorium-fluoride based fuel, while other research is underway in the USA involving possible radiation-free boron-fusion and lithium-fusion nuclear technology. The thorium-fluoride option produces minimal byproduct while fusion technology produces no radioactive byproduct. The use of alternative maritime propulsive energy may compliment other ongoing developments in multi-section ship technology.

Great Lakes Precedent:

A maritime development on North America’s upper Great Lakes provides possible opportunity to explore alternative maritime propulsive options, including micro nuclear power. One of the complaints of inland ships has been the volume of space occupied by the engine and fuel. It was the reason by schooners carried much of the shipping trade on the upper Great Lakes right up to the onset of WW2. Removing the engines and fuel tanks converted an inland ship to a barge with increased payload capacity that a tug pushes and navigates from the stern.

Tug Energy:

The tug could be modified to carry a spherical tank of compressed natural gas to operate its engine(s) on a lower priced fuel. A competing tug may store propulsive energy in grid-scale electrical batteries and be recharged from the power grid. Another tug technology may carry a heat-of-fusion thermal-battery of a molten mixture bauxite and cryolite from the aluminum industry to operate an externally heated, closed-cycle compressed-air turbine engine.

A single shore-based micro-nuclear technology could provide a thermal recharge and sustain the operation of a fleet of such tug units, plus other units that operate harbor service, ferry service and short-distance trans-lake services. It could also recharge a thermo-chemical energy storage system capable of providing propulsive power for extended voyages.

Oceanic Barge-Ship Option:

While there will be further need to develop the push-tug system for trans-oceanic service, there is the option of removing the diesel engines and fuel tanks from an oceanic diesel-electric ship to increase payload capacity. The unit may retain its azipod(s) and/or electrically driven propellers and tow a twin-hull, floating electrical generator. The backwash from the barge-ship’s main propeller(s) would be directed to flow between the twin hulls to reduce hydrodynamic drag. While the barge-ship is moored at dockside to transfer cargo, the floating electrical generator will be detached.

It may either move to a port-based service station for a recharge of energy, or be assigned to another barge-ship very shortly after its arrival at port. If the electrical generator requires an extended-duration recharge, it may remain at port while other identical unit is assigned to a freshly reloaded barge-ship. A ship that carries an onboard rechargeable propulsion system may need to remain at dockside during an extended duration recharge, occupying valuable space required to transfer cargo. By comparison, a barge-ship may occupy dockside space for a limited duration during an exchange of cargo, before being sent on its way with an available electrical generator.

Crew:

The navigation crew of a barge-ship would remain with the barge-ship at a port of call, while the crew of the electrical generator section would remain with that unit or be transferred to a different identical unit. Ship companies that operate frequent voyages between a given a few major ports may realize benefit from the operation of barge-ships capable of carrying additional payload. The frequency of ship arrival and departures would provide greater flexibility in scheduling the crew of barge-ships, some of whom would be responsible for ship navigation and others who oversee the energy storage and/or power generating section.

Super-Wide Tug:

An earlier commentary described a possible oceanic tug with propellers spaced at extreme width that push the backwash along the sides of the towed unit. It may either use either direct mechanically driven or electrically powered propellers, with the latter option may using any of rechargeable electrical energy storage or rechargeable thermal-storage technology, with optional micro-nuclear-based thermo-electric power. On some routes, the tug could be scheduled to do a rapid turnaround where it would leave with a newly laden oceanic barge very shortly arriving with a different laden barge.

Present technology restricts a tug to towing a Post-Panamax size barge across the ocean. Future innovation may develop technology whereby a tug may push and navigate an oceanic barge on an extended voyage, including through rough and stormy seas. Such future development would allow a diesel-powered tug with wide-spaced propellers to simultaneously tow a trailing barge with a semi-submerged telescopic coupling connecting between its bow, the tug and the stern of the leading barge, to minimize hydraulic drag and reduce fuel consumption. The towed unit may also be a barge-ship that receives some electrical propulsive power from the tug.

In Port:

A barge-ship towing a twin-hull electric generator could maneuver itself to dockside, using azipod and/or side thrusters. The electric generator may be detached by port tugs, refueled or recharged and then assigned to the same or another barge-ship. Port tugs would maneuver oceanic barges to from quayside after and before the barges are towed and/or pushed across the ocean by super-wide tugs.

Conclusions:

The precedent of removing engines from a ship and converting it into a tug-pushed barge has increased payload capacity and revenue earning potential while incurring minimal increase in operating costs. It may be possible to adapt that precedent to oceanic ships to increase revenue-earning payload while only marginally increasing long-term operating costs.

Harry Valentine can be reached at harrycv@hotmail.com.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.