Prospects for a Tug-pushed Cruise-Barge Tourist Ship

Several grand passenger liners sailed the world’s oceans during the early to mid 20th century, when the long-distance travel marker embraced the new generation of jet-powered passenger aircraft. A few passenger liners still plied a few long-distance sea routes during the 1960’s and into the early 1970’s. As the market for long-distance passenger maritime transportation declined, a new passenger maritime market emerged as vacationers set off on organized holiday cruises.

The long-distance maritime passenger ship industry had transformed itself from a passenger transportation service to a tourist service. However, the image of that industry has been marred in recent years by ship malfunctions and breakdowns. Fires have occurred in the engine rooms of several cruise ships over a period of several years, leaving the ships helplessly adrift. Recent events surrounding the Carnival Triumph provide a basis to explore possible alternative options in cruise ship design.

The earliest known sailing vessels were built to carry freight along rivers, to be pulled by a towrope connected to draft animals or to people walking on a path along a riverbank. Boats that were purposefully built to carry passengers were a spin-off from developments in maritime freight transport. At the present day, a large percentage of cruise ships sail at the same speeds as most cargo ships. There are cargo ships afloat today that are minus engines, fuel tanks and propellers. They are giant tug barges, a developing trend in maritime freight transportation.

Tug-Cruise-Barge Ship:

Based on precedent within the freight transportation sector, there is the option to remove engines and fuel tanks from a cruise ship to convert it into the giant passenger carrying tug barge. Such a conversion would provide additional space on board the barge from which to earn more revenue. Rebuilding the stern of the ship to include a V-notch stern would allow for a push tug to couple directly to the stern, possibly using a several tension cables to allow for relative pitch, roll, yaw plus lateral and vertical displacements. The V-notch structure may be built as an add-on extension.

An alternative remote-engine concept may combine azipod propulsion under the passenger section, with engines housed in a towed catamaran unit. Insulated electric power cables would connect between the power generating unit and the ship. Locating the engine remotely from the main ship would allow for easy removal and replacement of a malfunctioning engine. A cruise company may own one additional remote-engine unit (or push-tug) than its fleet of cruise-barges in any given geographic region, with the additional unit being rotated amongst the passenger ships on a regular schedule.

While the cruise-barges are at sea carrying tourists and earning revenue, one of the remote-engine units (or push tug) will be at the maintenance center for inspection and maintenance. The design concept would simultaneously reduce layover time at port for the cruise-barge while assuring greater long-term reliability for the power section. The additional revenue that a cruise ship company may earn from the additional space aboard a cruise barge would likely offset the added expense of an additional power unit in the fleet plus the time that a power unit will spend at a maintenance facility.

Renewable Energy at Sea:

The recent breakdown aboard the Carnival Triumph resulted in the absence of functioning water pumping and air conditioning systems. That breakdown provides opportunity to explore alternative strategies by which to operate a water system and cooling system aboard a stricken vessel. A range of new technology is available and can sustain a range of functions aboard both a stationary and also a towed vessel. Some of these technologies are spin-offs from the renewable energy sector. That sector has placed wind turbines at oceanic coastal locations and introduced ocean wave and ocean current conversion technologies to generate power for land-based use.

During 1928, the German physicist Anton Flettner sailed a windmill-powered boat across the Atlantic. Many windmill-powered boats sail on waterways around the world at the present day. The combination of onboard vertical-axis windmills and solar PV panels may generate electrical power aboard a ship, possibly to provide power for an LED-based ship lighting system, to recharge on-board batteries, operate LED-lights and even drive water pumps. Water pumps generally operate at very high efficiency and generally require very little energy to pump relative small amounts of water to higher elevation.

A series of large floatation units mounted at the end of retractable struts would protrude from sides of a stationary ship when lowered to the ocean. These units could convert energy from ocean waves to provide a measure of emergency power, including directly driving a piston-water-pump, refrigeration units and electrical generators. If the ship is equipped with frahm tanks, designers may install small turbines between the frahm tanks to perhaps generate sufficient electrical power to operate LED-lighting.

Towing/Pushing:
                       
There have been advances in small-scale water turbine technology that allow for the installation of such technology aboard cruise ships. Small-scale low-head water turbines installed in a duct could be build into the hull of a ship, to directly drive water pumps and also air conditioning machinery. While at port, power accessed from the grid would recharge onboard grid-scale storage batteries, sustaining interior lighting, operating water pumps as well as air conditioning and refrigeration systems.

Grid power and shore-based refrigeration technology may freeze a large block of ice housed inside an insulated compartment aboard ship, to provide for short-term air-conditioning and refrigeration requirements. As the ship leaves port, the onboard batteries would for operate onboard hotel power for some 20-minutes, until the ship approaches cruising speed when seawater would flow through the intakes of water turbines housed inside the hull. The intake duct cross-sectional area would decrease on the approach to the turbines, to increase water flow velocity and simultaneously raise efficiency and power output.

These water pumps may operate at 70% to as high as 90% conversion efficiency while driving water pumps and refrigeration units, operating at the same range of efficiency as engine-drive electrical generating systems. Large ship propellers also operate at the equivalent conversion efficiency of electrical generators while electric motors operate at equivalent efficiency as water turbines. As a result, hydraulic power conversion would be as efficient as electrical conversion, perhaps at lower cost. Aboard a tug-cruise-barge, railway-style multiple-unit control cables would link the bridge to the push tug.

Marketing a Tug-Cruise-Barge:

The cruise ship industry has in recent years gained much negative publicity due to a series of breakdowns that have occurred at various locations around the world. As a result, there may actually be a market niche for a tug-cruise-barge that includes some renewable energy technology that may maintain on-board hotel systems during a few scheduled hours of a simulated breakdown. The cruise ship industry is in the business of providing their guests with a memorable experience.

During a simulated breakdown, tourists may gain a sense of security and reassurance seeing some wave-driven, wind-powered and solar PV technology at work driving onboard water pumps, air conditioners and even generating electric power for an emergency LED lighting system. There may even be scope to use bio-fuel stoves and/or solar cookers to prepare one of the meals. A pleasant memory of a comfortable simulated breakdown at sea could create repeat customers.

Conclusions:

The initial success of tug-barges in freight transportation enhances prospects for similar success involving tug-cruise-barges carrying guests in the popular tourists regions around the world. A design of ship that remains inhabitable Designers may include multiple renewable energy technologies into a cruise-barge, to provide all or some of the power required by passenger section. When the cruise-barge is stationery, renewable energy technology would sustain multiple operations aboard ship. Designers may include multiple renewable energy technologies into a cruise-barge, to provide all or some of the power required by passenger section.

The conversion of an existing cruise ship into a tug-cruise-barge presents a formidable technical challenge. Precedents that involve oceanic tug-barges from the maritime freight sector may serve as the basis by which to convert a cruise ship into a cruise barge. The result could be the introduction of very unique form of maritime tourist technology into the Caribbean and Mediterranean Seas.

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Harry Valentine can be reached at [email protected] for any comments or questions. Also feel free to leave your thoughts on this editorial below in the comment section.