Expanding Wave-Powered Propulsion to Canals
Wave surfing is a popular recreational activity at beaches international with surfers often travelling great distance to beaches where optimal waves occur. The surfing enthusiasts have their own weather experts who read developing weather patterns and often predict with great accuracy the locations of optimal ocean waves a few hours to a few days before the actually occur. Suitable surfing waves usually begin offshore within less than two kilometers of the coastline. The technology of riding ocean waves has transformed from a long and narrow surfboard to the shorter and wider modern surfboards.
The concept of using ocean waves as a source of propulsive energy began some 40 years ago as a parallel development to using wave energy for a variety of purposes. These purposes included pumping seawater to higher elevation for energy storage and to generate electric power. Such research and development is still ongoing at the present day. One experimental wave-powered small boat featured a flotation device secured ahead of the bow and attached to the boat by springs and levers. The relative pitching movements activated a submerged whale-like fluke that could propel the little boat at up to six knots velocity.
Other competing designs of wave powered small boats combined buoyant section linked by an articulation coupling with hydraulic pumping technology activating a propeller; except that people who are interested in wave powered boats seek minimal technical complexity. The fluke propelled boat combined a comparatively short articulated leading section attached to the submerged fluke, secured ahead of the bow of a much longer and heavier trailer section that involved minimal hydraulic drag. Experimental wave powered boats have sailed against rip currents, undertow currents and directly into prevailing winds that slowed the progress of wind powered sail boats.
Wave powered boats depend on the occurrence of winds blowing somewhere in the world to produce waves that will travel over very great distances. The market application for wave-powered boats may be limited to serving miniscule markets where boats may operate at low speed, such as carrying tourists on short-distance sightseeing trips.
However, wave propulsion may not be limited to the ocean. During the heyday of small canal boats that sailed along narrow canals in England, waves sometimes appeared on a canal and travelled for considerable distance before dissipating or being dissipated.
Waves along Canals
When a boat sailed along a narrow section of a canal at sufficient speed to produce a bow wave and then dropped its sailing speed, the bow wave would often continue to propagate along the canal over a distance several miles, or a comparatively greater distance than ocean coastal waves. These waves became known as travelling waves, except that they occurred at a time long prior to the appearance of surfing on oceanic coastal waves. The use of scale model technology could illustrate as to how to generate travelling waves along a canal.
A guide ramp would be installed at one end of a scale model ramp. A water-weighted hull that is slightly narrower that the model canal would be placed on the ramp and perpendicular to the canal. It would be allowed to rapidly descend and strike the water, broadside, to produce a wave on the water. As long as the canal is straight, the wave would travel along the canal. In large scale, surfers could ride the travelling canal wave over a considerable distance provided canal depth remained constant, with the option of a small boat riding the wave.
There are many old canals located in many parts of the world that at one time carried commerce and trade. In some cases, railway transportation captured that market while in other cases larger navigation canals were built parallel to the older canals. The absence of commercial traffic along these canals along with minimal recreational boat traffic provides opportunity to experiment with wave-powered propulsion, using travelling waves along canals. A specialized design of over-wide, height-extended stern section could ‘capture’ the wave energy to propel a boat carrying several passengers over an extended distance along the canal.
Travelling waves were first observed propagating along sections of the canals of the U.K. At the present day, it may be possible to generate such waves to propel surfboards and surf-boats over considerable distances along these canals. During the late 1950’s, the construction of the St Lawrence Seaway in North America brought larger ships on to the Great Lakes and made several older canals obsolete, except that some still carry seasonal recreational boat traffic. Travelling waves may be possible along some narrow streams and rivers that are free from boat traffic and where wave powered transportation may become possible.
Propulsion from a Series of Waves
A wave generator could produce a series of waves that will propagate along a canal to large wave-powered vessels that would convert the waves to propulsion, using any of a variety of water-wave-to-propulsion conversion technologies. One option would be an articulated section located at either the bow or the stern that would activate propulsion-fluke technology, or perhaps activate paddle wheels or propellers. Another option may involve small articulated sections attached to both the bow and stern of the larger vessel, with the technological means to convert water wave energy to propulsion energy.
The main section of the ferries may be of multi-hull design, perhaps parallel pairs of pontoons at the bow and stern to minimize pitching and rolling during wave conditions. Bidirectional ferry service may be possible over lengths of journeys that would exceed the distance capability of cable-pulled ferries. Along some recreational waterways, wave generators that receive energy from a local power grid could provide the wave energy required to propel wave-powered rental recreational boats that could operate along such waterways. Prior testing of wave-powered small boats indicates that they could sail along at speeds of up to six knots.
The plastics industry offers supersize bags made of heavy-gauge plastic that the energy industry is using to store compressed air under water. It is also possible to pump these bags with water to create a barrier in body of water. A series of parallel super-bags pumped with water and ballasted with rocks may be secured on the floor of along a large body of water to create an artificial canal capable of allowing the propagation of travelling waves. Bags pumped with air would be attached above the water-filled bags to form a canal along which waves may travel.
Artificial canals may be installed long a coastline, a riverbank or connect between an offshore island and a mainland to provide conduits for travelling waves capable of propelling small specialized vessels that carry small numbers of passengers, or even a specialized design of larger ferry. There may be scope to undertake further research into refining the concept of artificial canals or floating canals along which wave propelled transportation may become possible. Larger ferry vessels would convert multiple waves to propulsion while small vessels would ride the waves like an oceanic surfboard.
Along canals developed as conduits for waves, wave-powered vessels could operate quietly and free from carbon emissions. Purposefully generated choppy water at an enclosed or partially enclosed water recreation area could provide the energy to activate wave-powered small boats. Further research would be required to develop wave powered vessels along canals and channels.
The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.