Using Water Power to Propel Free Barges Through Navigation Locks
While there is economic merit to sailing extended length barge trains along inland waterways, the cost of lengthening navigation locks can be prohibitive. It may be possible to use water power to transit non-powered sections of a barge train through navigation locks.
The ability to sail barge trains along inland waterways provides a nation with a low cost method of moving massive volumes of bulk cargo. While river transportation may be slower then road or railway transportation, it is very cost competitive with these modes. On the American inland waterway system between New Orleans and Memphis, tugs move flotillas of coupled river barges. Upon arrival at Memphis, barges of 35-foot beam and 200-foot length headed to inland destinations are assembled into tows of three abreast (105 feet) and up to five lengthwise to fit into a lock of 110 feet width by 1,200 feet length.
While a single tug could propel and navigate a tow of barges arranged three abreast by eight lengthwise along sections of the American inland waterway to the north of Memphis, the tow would need to be split into two sections to transit through navigation locks. A single tug would incur an extended delay to transit each section of an extended length tow through the locks. While carrying a micro-tug on deck to be deployed to transit navigation locks is an option, there may also be scope to modify navigation locks to propel a barge through the locks.
Modifying the Locks
When a tug pushing an extended length of barge tow arrives at navigation locks, the tug may push half of the tow into the lock, uncouple it and reverse the rear half of the tow out of the lock. The lock gates would close and the forward section of barge tow would change elevation. Modifications to navigation locks would include high-volume water pumps, overhead water storage tanks and additional water pipes that extend far upstream and downstream of the navigation lock area. After the forward section of barge tow has changed elevation, lock exit doors would open.
For upstream sailing, water from either high volume water pumps or from overhead tanks would rapidly enter the lock behind the barge, or at furthest distance from the open lock doors, to briefly create a powerful water current capable of propelling the barge forward and outside of the lock. The rearmost barges would need to be coupled abreast so as to occupy maximum allowable vessel width in the lock, with optional spring loaded hinged flaps located under and at the sides of the barges to be deployed at locks to reduce water leakage area and to assure propulsion.
Research and Testing
The option of pumping water into a navigation lock behind a vessel stern to generate propulsion will require further research, testing, evaluation and refinement at a university or college hydraulics laboratory where construction and testing of scale models may proceed. The hydraulic approach would likely move heavy non-powered vessels from a lock rather than pulling a vessel using the combination of a steel towing cable, pulley and winch mechanism that would be suitable for lighter weight vessels. Restraining cables would stop and hold the barge just beyond the lock doors to allow for door closure and post-transit assembly recoupling.
Either high powered water pumps or an overhead tank could provide the surge of water required behind the stern of a barge to accelerate it from the lock, with the option of a bank of ultra-capacitors providing the needed surge of electric power required to activate the pumps. The refilling of the overhead tank could occur over an extended time period, using solar PV energy, wind power or off-peak electric power to pump water to high elevation. There may be scope to use overhead tank water for purposes other than just providing energy to propel a barge from a lock.
Reducing Water Usage
There would be a need to economize on water usage when sections of extended length barge transit through navigation locks. Pumping water would be the option at locations where side reservoirs would be impractical. For sailing downstream, water from an overhead tank may flow through venturi pumps installed at lock upper level to initially transfer a large volume of water to the upper reservoir as water level in the lock drops. While having no moving parts and being maintenance free, a series of different venturi pumps would activate in response to rising water elevation in the lock.
For upstream sailing, upstream water may flow through venturi pumps installed at downstream elevation, to transfer some downstream water into the lock, raising water elevation while reducing water consumption. A series of different sizes of venturi pumps would be required to respond to changes in elevation. At around 60 percent of the difference between lower and upper elevation after venturi pump performance declines, water from an overhead tank could then flow through the lower level venturi pumps to continue pumping downstream water into the lock to further raise its elevation while economizing on water usage.
The availability any of an overhead water tank, high-volume water pumps or a mini-tug at each navigation lock requires a certain sailing frequency of extended length barge trains to assure viability. There is also the option of an extended length tug-barge assembly carrying a mini-tug on deck and lowered into the water upon arrival at each navigation lock, to propel a section of the barge assembly at low speed through the navigation lock. When extended-length vessel sailing frequency exceeds the number of navigation locks, a tug, water pumps or overhead water tank at each lock becomes feasible.
Operation of extended length tug-barges along an inland waterway network requires low-cost methods of moving barges through locks. At certain height differences across the lock, sailing downstream would involve water being flowed from upstream (higher elevation) to behind the barge stern in the lower elevation lock, to produce propulsive water current. Upstream sailing would require either assistance from a tug, water pumps or overhead water tank to produce propulsive water current to move the barge from the lock. The initial stages of extended length tug-barge operation would require the assemble carry or tow a mini-tug.
Great Lakes Locks
The close proximity of Welland Canal to ports of Hamilton ON, Toronto ON and Erie PA assures possible of arranging to assure the availability of a tug ahead of arrival of an extended length vessel. There may also be scope at Welland Canal for innovative use of water pipes to transfer bursts of water from higher elevation, including an overhead tank at Port Colborne to low elevation locks to propel non-powered barges upstream through locks. For sailing downstream, water flowing from higher elevation into the stern end of a lower elevation lock would propel a barge from a lock.
At the Soo Locks, mostly eastbound vessels are heavily laden with bulk payload that includes ore and agricultural grains. Based on research undertaken several years ago at University of Michigan and precedent of large tug-barges sailing on the Upper Great Lakes, there may be scope to develop a 600-foot length tug-ship capable of pushing and navigating a barge of 1,000-foot length, with both units built to 105-foot beam. The assembly would be uncoupled to transit the Soo Locks, with either water pumps or overhead water tanks providing water current to propel upstream bound barges from the locks.
When transporting agricultural payload, there may be scope near Port Colborne for a ship-to-ship transfer of payload from large Upper Great Lakes vessel to a Seaway beam and draft extended length barge train. The Seaway barge train would sail to the Lower St Lawrence River, uncoupling at Seaway locks where water flowed from higher elevation could propel the non-powered barge out of each lock, with a water pump perhaps being required at the Iroquois lock. For American grain, a 500-foot tug-ship could push a 700-foot barge while a tug pushing barges of 400-foot and 700-foot would carry Canadian grain.
During the early stages of extended length tug-barge operation, low frequency of sailing would require that a mini-tug either be towed or carried on deck and deployed at each navigation lock to slowly push a section of the barge assembly. Camera technology would assist pilots in guiding vessel movement. The mini-tug length would coincide with the depth of the U-shaped or V-shaped indentation built into the stern of the leading barge. An increase in the sailing frequency of extended length coupled vessels would warrant modifications at each lock to transit sections of such vessels.
As vessel size increases, the transportation cost per ton and/or per container decreases. The option of being able to sail extended length coupled vessels along inland waterways offers the possible reductions in per ton and/or per container transportation cost. Waterways with the fewest navigation locks would offer the greatest gains in vessel productivity, as could be the case for extended length coupled vessels sailing between Lake Superior and any of Lakes Michigan, Huron or Erie. The prospect of more competitively priced transportation rates could attract more tonnage to move on water than by road or rail.
The ability to sail extended length coupled vessels along navigable inland waterways has the potential to make inland waterway transportation more cost competitive. While carrying a micro-tug or mini-tug on board, to be deployed at navigation locks is a lock transit option, an increase in the sailing frequency of extended length coupled vessels would warrant implementing modifications at navigation locks to transit non-powered sections of the extended length vessels. Depending on the Great Lakes shipping industry, the single navigation lock between Lakes Superior and Huron may be a possible candidate for such modification.
The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.